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The  present  day  motor  car. 


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BEN  G.  ELLIOTT,  M.  E. 





BEN  G.  ELLIOTT,  M.  E. 






239  WEST  39TH  STREET.    NEW  YORK 

a  &  8  BOUVERIE  ST.,  E.  C. 


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Copyright,  1915,  1919,  by  the 
McGraw-Hill  Book  Company,  Inc. 

First  Edition 
Fourteen  Impressions 

Second  Edition 
First  Impression,  August,  1919 

Total  Issue,  38,500 

TUX    HAI'LK     l'XKHH    VOMK    1»  X 

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OCT  U  919 


The  developments  in  automobile  practice  since  the  first  edition  of 
The  Gasoline  Automobile  have  necessitated  some  changes  and  revisions 
in  this  edition.  The  entire  book  has  been  completely  rewritten  and  en- 
larged. Much  new  illustrative  material  has  been  added.  The  number 
of  chapters  has  been  increased  from  ten  to  sixteen.  Complete  chapters 
are  now  given  on  "Chassis  and  Running  Gear,"  "Clutches  and  Trans- 
missions," "Rear  Axles  and  Differentials,"  while  entirely  new  chapters 
on  "Principles  of  Electricity  and  Magnetism,"  " The  Automobile  Storage 
Battery,"  and  "Wheels,  Rims  and  Tires,"  have  been  added. 

No  attempt  has  been  made  to  cover  all  makes  and  models  of  cars 
and  apparatus,  but  the  purpose  of  offering  instruction  on  the  fundamental 
principles  of  automobile  design,  construction,  and  operation  has  been 
adhered  to  as  far  as  possible. 

Mr.  Earl  L.  Consoliver,  Assistant  Professor  of  Mechanical  Engineer- 
ing, has  acted  as  co-author,  taking  the  place  of  Mr.  George  W.  Hobbs. 

Ben.  G.  Elliott. 
The  University  op  Wisconsin, 
Madison,  Wisconsin, 
July,  1919. 


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The  purpose  of  this  book  is  admirably  expressed  in  the  following 
quotation  taken  from  the  Buick  instruction  book:  "To  derive  the  greatest 
amount  of  satisfaction  and  pleasure  from  the  use  of  his  car  the  driver 
should  have  a  complete  understanding  of  the  mechanical  principles  under- 
lying its  operation.  Merely  knowing  which  pedal  to  press  or  which  lever 
to  pull  is  not  enough.  The  really  competent  driver  should  understand 
what  happens  in  the  various  parts  of  the  car's  mechanism  when  he  presses 
the  pedal  or  pulls  the  lever.  He  should  know  the  cause  as  well  as  the 

When  we  consider  the  complexity  of  modern  automobiles  from  a 
mechanical  standpoint,  with  the  duties  that  are  required  of  them,  to- 
gether with  the  fact  that  the  great  majority  of  them  are  operated  by  men 
with  little  or  no  experience  in  the  handling  of  machinery,  the  automobile 
stands  as  one  of  the  most  remarkable  machines  that  the  ingenuity  of 
man  has  ever  produced.  The  operating  expense  of  the  automobile 
has  already  assumed  a  large  place  in  the  budget  of  the  American  people. 
Although  it  is  so  built  that  the  owner  may  secure  good  service  from  his 
automobile  with  very  little  knowledge  of  its  construction,  still  it  is 
evident  that  an  intimate  acquaintance  with  its  details  should  enable  him 
to  secure  better  service  at  less  expense  and  at  the  same  time  to  prolong 
the  useful  life  of  the  car. 

It  is  with  the  hope  of  increasing  the  pleasure  of  automobile  owner- 
ship and  reducing  the  trouble  and  expense  of  operation  that  this  book  is 
offered.  It  is  planned  primarily  for  use  in  the  University  Extension 
work  in  Wisconsin,  for  the  instruction  of  those  who  drive,  repair,  sell, 
or  otherwise  have  to  do  with  motor  cars.  It  is  largely  the  outgrowth 
of  a  series  of  lectures  on  the  subject  which  were  given  in  twenty-three 
cities  of  Wisconsin  during  the  past  winter. 

The  thanks  of  the  authors  are  especially  due  to  Mr.  M.  E.  Faber  of 

the  C.  A.  Shaler  Co.  for  assistance  in  preparing  the  section  dealing  with 

tire  troubles,  to  Prof.  Earle  B.  Norris  for  much  of  the  chapter  on  Engines 

and  for  editing  the  manuscript  and  reading  the  proof,  and  to  the  many 

manufacturers  who  have  liberally  assisted  in  the  preparation  of  the  work 

by  supplying  their  cuts  and  other  material. 

G.  W.  H. 
Madison,  Wis., 
Sept.  15,  1915. 

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The  Automobile 

Art.  Page 

1.  The  steam  propelled  car 1 

2.  The  electric  car 1 

3.  The  gasoline  car 4 

4.  The  gasoline-electric  car 4 

5.  Types  of  cars 5 

6.  Passenger  car  bodies  .    : 5 

7.  Automobile  bodies 8 

8.  Commercial  cars 9 

9.  General  principles  of  automobile  construction 12 

10.  Control  systems 16 

The  Automobile  Engine 

11.  The  gasoline  engine 17 

12.  Cycles 17 

13.  The  four-stroke  cycle 18 

14.  The  two-stroke  cycle 20 

15.  The  order  of  events  in  four-stroke  engines 20 

16.  The  mechanism  of  four-stroke  engines 21 

17.  Pistons  and  piston  rings 22 

18.  Connecting  rods 24 

19.  The  crankshaft 25 

20.  The  flywheel 25 

21.  Valves 25 

22.  Valve  operating  mechanism 27 

23.  Valve  opening  and  closing 29 

24.  Half-time  gears. 29 

25.  The  Knight  engine. 30 

26.  The  fuel  charge 31 

27.  Ignition 31 

28.  The  muffler 33 

29.  Cylinder  cooling 33 

30.  Piston  displacement 34 

31.  Clearance  and  compression 34 

32.  Horsepower  of  engines 34 

33.  Derivation  of  the  S.  A.  E.  horsepower  formula 35 


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Automobile  Power  Plants 
Art.  Paob 

34.  Multi-cylinder  engines 37 

35.  Modern  automobile  power  plants 38 

36.  Power  plant  support 39 

37.  Four-cylinder  power  plants 39 

38.  Ford  power  plant 39 

39.  White  four-cylinder  engine 40 

40.  Duesenberg  engine 43 

41.  Guy  rotary  valve  engine 43 

42.  Six-cylinder  power  plants 44 

43.  Marmon  power  plant 44 

44.  Franklin  air  cooled  engine 47 

45.  The  Hall-Scott  engine 47 

46.  Chandler  six  power  plant 48 

47.  Constructional  features  of  four-  and  six-cylinder  engines 48 

48.  Six-cylinder  crankshafts 50 

49.  Camshafts 53 

50.  Eight-  and  twelve-cylinder  power  plants 53 

51.  Cadillac  eight-cylinder  engine 54 

52.  The  Oldsmobile  eight-cylinder  engine 56 

53.  King  eight-cylinder  engine 57 

54.  Knight  eight-cylinder  engine 58 

55.  Firing  order  of  eight-cylinder  engines 58 

56.  Determining  firing  order  of  eight-cylinder  engine 60 

57.  Packard  twelve-cylinder  engine 60 

58.  National  twelve-cylinder  engine 60 

59.  Pathfinder  twelve-cylinder  engine 62 

60.  Firing  order  of  twelve-cylinder  engines 63 



61.  Hydrocarbon  oils 65 

62.  Refining  of  petroleum 65 

63.  Gasoline 67 

64.  Principles  of  vaporization 68 

65.  Testing  gasoline 68 

66.  Kerosene  and  alcohol 70 

67.  Heating  value  of  fuelo 70 

68.  Gasoline  and  air  mixtures 70 

69.  Principles  of  carburetor  construction 71 

70.  Auxiliary  air  valves 72 

71.  Air  valve  dashpots 74 

72.  Float  chambers  and  floats 74 

73.  Metering  pins 74 

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Abt.  pAai5 

74.  Operating  conditions  of  the  carburetor 74 

75.  Schebler  model  L  carburetor 75 

76.  Schebler  model  R  carburetor 77 

77.  Marvel  carburetor 79 

78.  Bayfield  model  G  carburetor 81 

79.  The  Holley  model  H  carburetor 84 

80.  Holley  model  G  carburetor 86 

81.  Kingston  model  L  carburetor 87 

82.  The  Tillotson  carburetor 88 

83.  Zenith  model  L  carburetor 90 

84.  Stewart  model  25  carburetor 91 

85.  Stromberg  plain  tube  carburetor 92 

86.  Stromberg  model  H  carburetor 96 

87.  The  Hudson  carburetor 98 

88.  Cadillac  carburetor 98 

89.  Packard  carburetor 98 

90.  General  suggestions  on  carburetor  adjustment  and  operation 99 

91.  Intake  manifolds 100 

92.  Carburetor  control  methods 101 

93.  The  gasoline  feed  system 101 

94.  Care  of  gasoline 105 

Engine  Lubricating  and  Cooling 

95.  Lubrication  and  friction 107 

96.  Lubricants  and  lubrication 107 

97.  Test  of  lubricating  oils 108 

98.  Gas  engine  cylinder  oil 109 

99.  Systems  of  engine  lubrication 110 

100.  Full  splash  system  of  lubrication Ill 

101.  Splash  system  with  circulating  pump 112 

102.  Pressure  feed  and  splash  lubrication 114 

103.  Pressure  feed  system 114 

104.  Pull  pressure  or  forced  feed  system 116 

105.  Oil  pumps 116 

106.  Engine  lubrication  in  general 118 

107.  Cylinder  cooling 118 

108.  Thermosyphon  cooling  system 120 

109.  Pump  or  forced  system  of  water  circulation 121 

110.  Packard  cooling  system 122 

111.  Cadillac  cooling  system 123 

112.  Air  cooling 125 

113.  Radiators 126 

114.  Temperature  indicators 127 

115.  Cooling  solutions  for  winter  use 127 

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Principles  op  Electricity  and  Magnetism 

Art.  Pack 

116.  Electricity • 131 

117.  Conductors  and  non-conductors 131 

118.  Hydraulic  analogy  of  electric  current 132 

119.  Resistance 132 

120.  Relation  between  current,  voltage,  and  resistance 133 

121.  Electrical  power 134 

122.  Effects  of  electric  current 134 

123.  The  dry  cell 135 

124.  The  storage  battery 136 

125.  Wiring  of  ignition  batteries 137 

125.  Magnetism 139 

127.  Natural  and  artificial  magnets 139 

128.  Magnetic  and  non-magnetic  metals 139 

129.  The  poles  of  a  magnet 140 

130.  The  magnetic  field 141 

131.  Electromagnetism 142 

132.  The  electromagnet 143 

133.  To  determine  the  polarity  of  an  electromagnet 144 

134.  Electromagnetic  induction            144 

135.  The  right-hand  rule 146 

Battery  Ignition  Systems 

136.  Automobile  ignition 147 

137.  The  low^tension  coil  for  make-and-break  ignition 147 

138.  The  induction  coil 148 

139.  The  safety  gap 151 

140.  The  condenser 151 

141.  The  vibrating  induction  coil 153 

142.  The  three  terminal  coil 154 

143.  The  vibrating  type  ignition  system 154 

144.  Timers 155 

145.  Spark  plugs      156 

146.  Spark  plug  testing 158 

147.  Typical  battery  ignition  system 159 

148.  The  distributor 160 

149.  The  ignition  resistance  unit 160 

150.  Spark  advance  and  retard 161 

151.  Automatic  spark  advance 162 

152.  The  Atwater-Kent  ignition  system — open  circuit  type 163 

153.  The  Atwater-Kent  ignition  system,  Type  CC 167 

154.  The  Connecticut  battery  ignition  system 169 

155.  The  Remy  ignition  system 174 

156.  The  Remy-Liberty  ignition  breaker  for  U.  S.  Military  Truck 178 

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Art.  Page 

157.  The  North  East  ignition  system • 178 

158.  The  Delco  ignition  system 181 

159.  Delco  ignition  breakers  for  eight-  and  twelve-cylinder  engines 184 

160.  Timing  battery  ignition  with  the  engine 185 

161.  Care  of  battery  ignition  system 186 

Magnetos  and  Magneto  Ignition 

162.  Magneto  classification 187 

163.  Magneto  magnets 187 

164.  lines  of  force 188 

165.  Types  of  magnets • 188 

166.  Mechanical  generation  of  current 189 

167.  Low-  and  high-tension  magnetos 190 

168.  Armature  and  inductor  type  magnetos 191 

169.  Current  wave  from  a  shuttle- wound  armature 191 

170.  Low-tension  magneto  ignition  system  with  interrupted  primary  current .    .  193 

171.  Low-tension  magneto  ignition  system  with  interrupted  shunt  current  .    .    .  194 

172.  Dual  ignition  systems 196 

173.  Splitdorf  low-tension  dual  ignition  system  with  type  T  magneto 197 

174.  Remy  inductor  type  magneto 198 

175.  The  Ford  ignition  system 202 

176.  The  high-tension  magneto 205 

177.  The  Bosch  high-tension  magneto 205 

178.  The  Bosch  high-tension  dual  system 215 

179.  The  Bosch  high-tension  magneto,  type  NU4 217 

180.  The  Eisemann  high-tension  magneto,  type  G4 220 

181.  The  Eisemann  high-tension  dual  magneto,  type  GR4 225 

182.  Timing  of  the  Eisemann  magneto  to  the  engine  for  variable  spark   ....  227 

183.  The  Dixie  magneto 229 

184.  General  instruction  for  high-tension  magneto  care  and  maintenance    .    .    .  233 


The  Automobile  Storage  Battery 

185.  Function  of  the  battery 237 

186.  Construction 237 

187.  The  plates 238 

188.  Positive  and  negative  groups 238 

189.  Elements 238 

190.  Separators 239 

191.  The  electrolyte 242 

192.  Jars  and  covers 242 

193.  Cell  arrangement 243 

194.  Battery  box 243 

195.  Markings  of  the  battery 244 

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Art.  Paob 

196.  Voltage  of  the  battery 244 

197.  Battery  capacity 244 

198.  Principle  of  operation 245 

199.  Effect  of  overcharging 245 

200.  Effect  of  undercharging 245 

201.  Heat  formed  on  charge  and  discharge 246 

202.  Evaporation  of  water 246 

203.  Necessity  of  adding  pure  water 247 

204.  Cause  of  specific  gravity  change  .    » 247 

205.  The  hydrometer 247 

206.  Hydrometer  readings 248 

207.  Variation  in  cell  readings 248 

208.  Variation  in  hydrometer  readings  caused  by  temperature 249 

209.  Freezing  temperature  of  the  battery 250 

210.  Results  of  freezing 251 

211.  Battery  charging 252 

212.  Detailed  instruction  for  charging  batteries 254 

213.  Battery  testing  with  the  voltmeter 255 

214.  Sulphation 256 

215.  Effect  of  overfilling 257 

216.  Corroded  terminals 258 

217.  Disintegrated  and  buckled  plates 258 

218.  Sediment 260 

219.  Conditions  causing  the  battery  to  run  down 260 

Starting  and  Lighting  Systems 

220.  Automobile  starters 263 

221.  Mechanical  starters 263 

222.  Air  starters 263 

223.  Acetylene  starters 263 

224.  Electric  starters 264 

225.  Hydraulic  analogy  of  an  electric  starting  and  lighting  system 266 

226.  Generator  drives 268 

227.  Starting  motor  drives 270 

228.  The  bendix  drive 273 

229.  Motor-generator  drives 275 

230.  Construction  of  the  dynamo 277 

231.  The  simple  alternating-current  generator 280 

232.  The  simple  direct-current  generator 281 

233.  The  simple  direct-current  motor 282 

234.  The  shunt-wound  generator 284 

235.  Conditions  which  prevent  a  generator  from  building  up 286 

236.  Types  of  field  winding 287 

237.  The  reverse  current  cut-out 28t 

238.  Regulation  of  the  generator 29( 

239.  Generator  regulation  through  reverse  series  field  winding 291 

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Abt.  Paqb 

240.  Current  regulation  of  the  generator  through  vibrating  type  relay 293 

241.  Voltage  regulation  of  the  generator  through  vibrating  type  relay     ....  295 

242.  Combined  current  and  voltage  regulation  of  the  generator  through  vibrating 
type  relay 297 

243.  The  Ward  Leonard  automatic  controller 298 

244.  Third  brush  regulation 300 

245.  Characteristics  of  third  brush  regulation 304 

246.  The  Remy  generator  with  thermostatic  control 304 

247.  The  Remy  starting  and  lighting  system  with  relay  regulation 307 

248.  The  Bijur  generator  with  constant  voltage  regulation 310 

249.  The  Westinghouse  starting  and  lighting  system— voltage  regulator  type.    .  311 

250.  The  Westinghouse  starting  and  lighting  system — third  brush  type  ....  315 

251.  The  North  East  starting  and  lighting  system  on  the  Dodge  car 318 

252.  The  Delco  single-unit  starting,  lighting,  and  ignition  system  on  the  Buick  .  322 

253.  The  Delco  two-unit  starting,  lighting,  and  ignition  system  on  the  Olds- 
mobile  Eight 327 

254.  Delco-Iiberty  lighting  system  on  U.  S.  standardised  military  truck — class  B.  330 

255.  The  "  F.  A.  Liberty  "  Ford  starting  and  lighting  system 334 

256.  Automobile  lamps  and  reflectors 338 

257.  Care  of  starting  and  lighting  apparatus 340 

The  Automobile  Chassis  and  Running  Gear 

258.  General  arrangement  of  chassis 343 

259.  Frames 343 

260.  Springs  and  spring  suspension 345 

261.  Unsprung  weight 355 

262.  The  front  axle 356 

263.  Steering  system 357 

264.  Steering  gear 358 

265.  Brakes 360 

266.  Transmission  brake 363 

267.  Effectiveness  of  brakes 363 

268.  Antifriction  bearings 364 

Clutches  and  Transmissions 

269.  The  automobile  clutch 367 

270.  The  cone  clutch 367 

271.  The  disc  clutch 371 

272.  Operation  of  clutch    .......................  375 

273.  Change  gear  sets 375 

274.  Operation  of  the  gear  set  ......................  378 

275.  lubrication  of  the  transmission    ...................  379 

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xviii  CONTENTS 

Art.  Page 

276.  Gear  shift  levers 379 

277.  Location  of  transmission 380 

278.  The  planetary  transmission 380 

279.  Operation  of  planetary  transmission 383 

280.  Universal  joints  and  propeller  shaft 386 

281.  Lubrication  of  universal  joints 387 

282.  Flexible  couplings 387 

283.  Propeller  shaft 387 

Rear  Axles  and  Differentials 

284.  Final  drives 389 

285.  Bearings  for  final  drive 391 

286.  Types  of  rear  axles 391 

287.  Simple  live  rear  axle 392 

288.  Semi-floating  rear  axles 392 

289.  Three-quarter  floating  axle 394 

290.  Full-floating  rear  axle 396 

291.  The  differential 396 

292.  M.  &  S.  differential  or  Powrlok 398 

293.  Lubrication  of  rear  axle  and  differential 400 

294.  The  torque  arm 400 

295.  Strut  rods 402 


Wheels,  Rims,  and  Tires 

296.  Wheels  .    . 403 

297.  Wooden  wheels 404 

298.  Wire  wheels 405 

299.  Other  types  of  wheels 406 

300.  Rims  .    . 407 

301.  Removal  of  demountable  rims 410 

302.  Types  of  tires 411 

303.  Construction  of  tires 412 

304.  Proper  use  and  care  of  tires 415 

305.  Proper  inflation 415 

306.  Tires  of  proper  size 417 

307.  Care  in  application  of  tires  to  rims 418 

308.  Rim  irregularities 418 

309.  Flat  tires 418 

310.  Fabric  bruises 419 

311.  Improper  braking 419 

312.  Tight  chains 420 

313.  Wear  of  tire  by  parts  of  car 421 

314.  Alignment  of  wheels 421 

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Abt.  Paoe 

315.  Ruts  and  car  tracks 421 

316.  Neglected  injuries 422 

317.  Oil  on  tires .422 

318.  light  and  heat 422 

319.  Fast  driving 422 

320.  Poorly  made  repairs 423 

321.  Tire  powder 423 

322.  Inserting  inner  tubes 424 

323.  Care  of  spare  tubes 424 

324.  Leaky  air  valves 425 

325.  Tire  fillers 425 

326.  Tire  protectors ^ 425 

327.  Spare  casings 425 

328.  Care  of  tires — car  in  storage 425 

329.  Repair  of  tires.    .' 426 

Automobile  Troubles  and  Remedies 

330.  Classification  of  troubles 427 

331.  Power  plant  troubles 427 

332.  Mechanical  troubles  in  engine 431 

333.  Carburetion  troubles 437 

334.  Ignition  troubles 438 

335.  Starting  troubles 444 

336.  Lighting  troubles 445 

337.  Lubricating  and  cooling  troubles 448 

338.  Transmission  troubles 450 

339.  Chassis  troubles 450 

Operation  and  Care 

340.  Preparations  for  starting 453 

341.  Starting  the  engine  with  the  electric  starter 455 

342.  Cranking  by  hand 455 

343.  How  to  drive 456 

344.  Use  of  the  brakes 457 

345.  Speeding 458 

346.  Speedometers 459 

347.  Care  in  driving 459 

348.  Driving  in  city  traffic 460 

349.  Skidding 461 

350.  Knowing  the  car 463 

351.  The  spring  overhauling 463 

352.  Washing  the  car 465 

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Art.  Paqb 

353.  Care  of  the  top 466 

354.  Cleaning  the  reflectors 466 

355.  Care  of  tires 466 

356.  Figuring  speeds 468 

357.  Insurance 469 

358.  Interstate  regulations 469 

359.  Canadian  regulations 470 

360.  Touring  helps.     Route  books 471 

361.  Cost  records 471 

Index 475 

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Automobiles  may  be  classified  according  to  the  type  of  power  plant 
used,  as  steam,  electric,  gasoline,  and  gasoline-electric;  or  they  may  be 
divided  into  two  classes  according  to  use,  as  passenger  cars  and  com- 
mercial cars. 

1.  The  Steam  Propelled  Car. — The  steam  engine,  when  used  on  an 
automobile,  has  the  advantage  of  being  very  flexible.  All  operations 
such  as  starting,  stopping,  reversing,  and  acquiring  changes  of  speed 
can  be  done  directly  through  the  throttle  on  the  steering  wheel.  By 
opening  or  closing  the  throttle,  more  steam  or  less  steam  is  supplied  to 
the  engine,  and  the  power  is  increased  or  decreased  in  proportion.  When 
the  car  is  climbing  a  hill,  it  is  necessary  only  to  give  the  engine  more 
steam.  This  results  in  more  power  being  delivered.  The  fact  that  the 
steam  engine  is  able  to  start  under  load  eliminates  the  clutch  and  also 
the  transmission  or  change  speed  gears,  the  engine  being  connected 
directly  to  the  rear  axle.  The  arrangement  of  the  parts  on  the  Doble 
steam  car  is  illustrated  in  Fig.  1. 

The  disadvantage  of  the  steam  propelled  car  is  that  it  sometimes 
requires  considerable  time  to  raise  the  steam  pressure  before  starting. 
This  is  especially  true  if  the  boiler  has  been  allowed  to  cool  off.  If 
it  is  desired  to  keep  the  steam  pressure  up  so  that  the  car  can  be  started 
without  loss  of  time,  a  pilot  light  must  be  kept  burning  under  the  boiler 
at  all  times.  The  steam  pressure  carried  is  very  high,  and  this  means 
that  constant  care  and  attention  must  be  given  to  the  boiler  and  its 
accessories.  The  steam  car  requires  that  the  boiler  be  filled  with  water 
for  making  steam  every  150  to  250  miles.  Kerosene  is  generally  used 
for  heating  the  boiler. 

2.  The  Electric  Car. — The  advantages  of  the  electric  car  are  similar 
to  those  of  the  steam  car.  The  electric  motor  is  very  flexible  in  operation 
and  can  be  operated  entirely  by  the  control  levers.  By  supplying 
more  current  or  less  current  to  the  motor  the  power  is  increased  or  de- 
creased accordingly.  The  electric  car  is  especially  adapted  to  the  use 
of  women  and  children  in  cities.  It  is  an  easy  riding  car,  clean,  and 
runs  quietly. 


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tlOTOR  dc  FAN'" 

















Fio.  1. — Chassis  of  Doble  steam  car. 

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The  disadvantages  are  that  it  is  not  suitable  for  long  drives,  heavy 
roads,  or  hilly  country.  On  one  charge  of  the  battery  the  average  car 
will  run  from  100  to  150  miles,  depending  on  the  speed  of  the  car  and 
the  condition  of  the  roads.  If  the  car  is  run  at  high  speed,  the  battery 
will  not  drive  the  car  as  far  as  it  will  when  running  at  a  moderate  rate. 
This  car  is  also  limited  to  localities  where  there  are  ample  facilities  for 
charging  the  storage  batteries. 

3.  The  Gasoline  Car. — The  gasoline  engine  is  very  economical  as  an 
automobile  power  plant.  After  being  started,  it  has  great  flexibility. 
It  is  especially  adapted  for  touring  purposes  and  does  not  require  any 
great  attention  from  the  operator.  The  average  car  carries  enough 
fuel  to  run  it  200  to  400  miles.  It  is  then  necessary  to  refill  the  gaso- 
line tank.  Occasionally,  a  quart  or  two  of  water  should  be  put  into  the 
.  radiator.  With  proper  care,  the  engine  will  run  as  long  as  the  gasoline 
supply  and  the  electrical  system  hold  out. 

The  disadvantages  of  the  gasoline  engine  as  compared  with  those  of 

the  steam  engine  or  electric  motor  are,  first,  the  gasoline  engine  is  not 

self -starting;  and,  second,  it  lacks  overload  capacity.     On  account  of 

these  two  factors  some  method  of  changing  the  speed  ratio  of  the  engine 

to  the  rear  wheels  is  necessary  in  order  to  acquire  extra  power  for  start- 

ii  ig  the  car,  for  climbing  hills,  for  heavy  roads,  and  also  for  reversing 

tlK  ^  car»  as  *^e  ordinary  four-stroke  automobile  engine  is  not  reversible. 

The    Qosoline  engine  will  not  start  under  load.     This  necessitates  the  use 

of  a  c  lutch,  so  that  the  engine  can  be  started  and  speeded  up  before  any 

load  is    thrown  on.     Apparently,  there  are  a  great  many  disadvantages 

to  the  g  vsoline  engine  but  in  reality  they  are  very  few,  for  with  the  proper 

handling    °f  the  spark  and  throttle  control  levers  it  is  not  necessary  to 

keep  chan  ^g  gears  continually.     The  gear  shifting  lever  need  not  be 

used  excep  f'  f°r  starting,  stopping,  hill  climbing  in  congested  districts, 

and  on  bad  .  toads. 

The  ad va*  stages  of  the  gasoline  engine  for  use  on  an  automobile  are 
so  numerous  tl  ^  it  is  universally  used  for  driving  pleasure  and  com- 
mercial cars.     1  \ure  2  is  a  plan  view  of  a  modern  gasoline  driven 


4.  The  Gasolint  Velectric  Car. — The  gasoline-electric  or  the  dual- 
power  car  is  driven  h,  Y  a  combination  of  a  gasoline  engine  and  an  electric 
motor.  This  arrange.  Xient,  illustrated  in  Fig.  3,  gives  the  advantages 
of  both  the  gasoline  car  #nd  the  electric  car.  The  electric  motor  is  con- 
nected directly  to  the  ^Vopeller  shaft  running  to  the  rear  axle.  By 
means  of  a  magnetic  clui^h,  the  gasoline  engine  can  be  connected  to 
the  shaft  of  the  motor.  there  are  no  change  gears  or  transmission. 
The  car  is  started  by  the  e  Vctric  motor,  and,  after  a  certain  speed  is 
attained,  the  engine  may  be  started  by  a  magnetic  clutch.     Power  for 

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running  may  be  obtained  either  from  the  electric  motor  and  batteries, 
from  the  engine  alone,  or  from  both. 

6.  Types  of  Cars. — In  general,  there  are  two  types  of  motor  cars — 
passenger  cars  and  commercial  cars — the  names  indicating  the  use  for 
which  each  type  is  intended.  The  parts  of  the  passenger  and  commercial 
car  are  similar  except  that  in  the  passenger  car  the  construction  is 
lighter  than  in  the  commercial  car.  In  the  passenger  car  everything  is 
planned  for  comfort  and  speed,  while  the  commercial  car  is  built  for 
heavy  loads  and  is  generally  intended  to  be  driven  at  lower  speeds. 

6,  Passenger  Car  Bodies. — The  principal  types  of  bodies  for  passen- 
ger cars  are  the  roadster,  the  touring  car,  the  coupS,  the  sedan,  the  limou- 
sine, and  the  town  car.    These  are  shown  in  Fig.  4. 






Fia.  3. — Chassis  of  dual  power  car. 

The  roadster  body  is  open  and  usually  has  one  seat  for  either  two  or 
three  persons.  Occasionally,  both  front  and  rear  seats  are  provided, 
increasing  the  seating  capacity  to  four.  In  this  case,  the  front  seat  is 
divided  by  an  aisle  which  furnishes  the  entrance  from  the  front  doors 
to  the  rear  seat.  The  name  doverleaf  is  sometimes  given  to  this  type  of 
roadster  body.  The  seating  arrangement  of  the  Chandler  four-pas- 
senger roadster  is  seen  in  Fig.  5. 

In  the  touring  car  body,  which  is  also  open,  rear  seats  with  separate 
rear  doors  are  provided.  The  seating  capacity  is  for  five  or  even  seven, 
in  which  case  two  additional  folding  seats,  in  front  of  the  rear  seat,  are 
provided.  In  some  cases  only  rear  doors  are  provided,  the  entrance  to 
the  front  seats  being  through  the  aisle.  Figure  6  illustrates  a  seven- 
passenger  touring  car  with  the  two  auxiliary  folding  seats  in  front  of 
the  rear  seat. 

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The  coupS  is  similar  to  the  roadster  excepting  that  it  is  enclosed  and 
inside  operated.  It  has  seating  capacity  for  two  or  three,  and  quite 
often  a  small  seat  which  faces  backward  provides  for  another  passenger. 
When  a  coup6  is  provided  with  a  detachable  top  or  sides  as  in  Fig.  7, 
it  gives  all  the  advantages  of  an  open  roadster.  Such  a  coup6  is  some- 
times called  a  convertible  coup6  or  cabriolet 

The  sedan  is  practically  an  enclosed  touring  body.  It  may  be  of 
the  single  or  two  door  type.     If  of  the  single  door  type,  the  front  seat 


Touring  car. 



Limousine.  Town  car. 

Fig.  4. — Types  of  passenger  car  bodies. 

is  divided  by  an  aisle  to  furnish  an  entrance.  In  some  types  of  sedan 
bodies,  the  sides  can  be  removed  during  summer  use,  giving  practically 
all  the  advantages  of  an  open  touring  body.  A  double  door  sedan  is 
illustrated  in  Fig.  8. 

The  limousine  is  a  closed  body,  seating  three  to  seven  persons, 
with  the  driver's  seat  in  front  covered  with  a  top.     If  the  driver's  seat  is 

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Fiq.  5. — Seating  arrangement  of  Chandler  four  passenger  roadster. 

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open  and  not  covered,  the  body  is  called  a  brougham  or  town  car.  If  on 
either  a  limousine  or  town  car,  arrangements  are  provided  for  throwing 
open  the  housing  of  the  rear  seat,  Fig.  9,  the  body  is  called  a  landauht. 

Fia.  6. — Seven  passenger  touring  car  with  auxiliary  rear  seats. 

7.  Automobile  Bodies. — Automobile  bodies  are  usually  made  of 
pressed  steel,  combining  both  strength  and  lightness,  and  built  up  on 
wooden  frames,  as  indicated  in  Figs.  10  and  11.     Some  bodies  are  built 

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of  sheet  aluminum  which  is  considerably  lighter  than  the  other  metals, 
but  is  more  costly  and  is  not  so  serviceable  as  the  pressed  steel. 

8.  Commercial  Cars. — Commercial  cars  are  built  for  light,  medium, 
or  heavy  duty.     They  are  usually  classified  as  delivery  cars  and  trucks. 

Fig.  7. — Convertible  coup6  body. 

The  delivery  cars  are  lighter  and  are  usually  driven  at  higher  speeds 
than  the  trucks,  which  are  for  heavier  and  slower  service.  Some  typical 
commercial  cars  are  illustrated  in  Fig.  12.    Commercial  cars  are  built 

Fig.  8. — Double  door  sedan  body. 

on  the  same  fundamental  principles  as  passenger  cars,  but  the  construc- 
tion is  heavier  and  more  sturdy.     In  a  great  many  cases,  passenger  cars 

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Fiq.  9. — Limousine — Landaulet  body. 

Fio.  10. — Wooden  frame  for  automobile  body. 

Fiq.  11. — Pressed  metal  automobile  body. 

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Ford  light  truck  chassis. 

Kissel  medium  truck. 

Packard  heavy  truck. 
Fiq.  12. — Typical  types  of  commercial  cars. 

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are  converted  for  commercial  use  by  putting  on  a  body  adapted  for 
commercial  purposes. 

9.  General  Principles  of  Automobile  Construction. — The  two  prin- 
cipal divisions  of  an  automobile  are  the  body  and  the  chassis.  The 
chassis  includes  all  parts,  with  the  exception  of  the  body  and  its  im- 
mediate attachments.  The  frame,  springs,  axles,  wheels,  steering  gear, 
power  plant,  clutch,  transmission  system,  and  control  apparatus  go  to  make 
up  the  automobile  chassis.  These  parts  are  fully  illustrated  in  Figs.  2 
and  13. 

Frame. — The  frame  may  be  called  the  foundation  of  the  automobile 
because  it  furnishes  the  support  for  the  body,  engine,  transmission 
system,  etc.  It  must  be  strong,  light,  and  at  the  same  time  not  too 
rigid.  It  is  desirable  to  have  the  frame  as  long  as  possible  as  this  in- 
creases the  wheel  base,  giving  an  easier  riding  car.  The  wheel  base  is 
the  distance  measured  between  the  centers  of  a  front  and  rear  wheel. 
Frames  are  usually  made  of  steel  although  some  wooden  frames  are  used. 

Springs. — As  on  any  type  of  vehicle,  springs  must  be  provided  to 
take  the  jars  and  bumps,  due  to  rough  roads,  and  to  make  an  easy 
riding  car.  Springs  of  the  laminated  leaf  type  are  attached  to  the  frame, 
providing  a  flexible  connection  between  the  frame  and  the  front  and  rear 
axles.  In  most  cases  four  springs  are  used,  but  on  some  of  the  lighter  cars 
only  two  springs,  one  front  and  one  rear,  are  provided. 

Front  Axle. — The  front  axle  which  carries  the  weight  of  the  front  of 
the  car  is  generally  of  the  solid  type  and  is  attached  directly  to  the  front 
springs.  Unlike  the  front  axle  on  a  wagon  or  carriage,  the  front  axle  on 
an  automobile  does  not  turn  on  a  fifth  wheel  for  the  purpose  of  steering, 
but  is  fixed  to  the  springs.  Movable  spindles,  which  carry  the  wheels, 
are  provided  on  the  axle  ends  for  the  purpose  of  steering.  These  spindles 
are  tied  together  by  a  rod  so  that  they  move  both  wheels  in  the  same 
direction  when  the  car  is  being  turned.  The  steering  of  the  car  is  done 
by  the  steering  wheel  and  its  connection  to  the  front  wheels,  as  indicated 
in  Fig.  14.  The  front  wheels  support  the  weight  of  the  front  of  the  car 
and  serve  for  steering  purposes  but  in  most  cases  do  not  assist  in  driving 
the  car. 

Power  Plant. — The  power  for  driving  an  automobile  is  furnished  by 
the  engiqf  which  is  supported  on  the  front  of  the  frame.  In  some  cases 
a  sub-frame,  attached  to  the  main  frame,  supports  the  engine,  which  is 
placed  parallel  to  the  sides  of  the  frame.  Most  of  the  engine  auxiliaries 
are  placed  either  on  or  very  near  to  the  engine  itself.  The  radiator  is 
supported  on  the  frame  in  front  of  the  engine.  The  gasoline  tank,  in 
which  the  fuel  is  carried,  is  placed  either  at  the  extreme  rear  of  the  frame, 
or  above  and  close  to  the  engine,  such  as  under  the  front  seat. 

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Clutch. — It  is  sometimes  necessary  that  the  engine  be  run  when  the 
car  is  not  moving,  so  a  device  has  been  provided  to  disconnect  the  engine 
from  the  car  driving  mechanism.  This  device  is  called  the  clutch.  If  a 
clutch  were  not  provided  it  would  be  necessary  to  stop  the  engine  every 
time  the  car  stopped.  It  would  also  be  impossible  to  start  or  run  the 
engine  without  having  the  car  move.  The  power  from  the  engine  is 
delivered  through  the  clutch  to  the  change  gears,  or  transmission,  as  it  is 
usually  called. 

Change  Gears  or  Transmission. — The  transmission  is  a  system  of 
gears  which  makes  it  possible  to  change  the  speed  ratio  of  the  engine 
and  the  car.     When  the  car  is  being  started,  or,  when  going  up  steep 



Fiq.  14. — Method  of  steering  an  automobile. 

hills,  it  is  necessary  that  the  engine  run  comparatively  fast  with  respect 
to  the  car.  After  the  car  has  gotten  up  speed,  the  engine  can  be  run 
slower  with  respect  to  the  car  speed.  The  change  gears  also  furnish  the 
means  for  reversing  the  direction  of  the  car.  The  change  gears  are 
usually  placed  at  the  front  of  the  propeller  shaft,  but  occasionally  are 
found  at  the  back  of  the  propeller  shaft,  near  the  rear  axle.  From  the 
transmission  or  change  gears  the  power  from  the  engine  goes  to  the  pro- 
peller shaft,  which  revolves  and  delivers  the  power  back  to  the  rear  axle. 
On  account  of  the  fact  that  the  propeller  shaft  does  not  run  in  a  straight 
line  with  the  engine  shaft,  a  flexible  coupling,  usually  a  universal  joint, 
is  used  to  transmit  the  power  at  an  angle  to  the  rear  axle. 

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Rear  Axle. — The  power  is  delivered  by  the  propeller  shaft  to  the 
rear  axle,  which  turns  in  its  housing.  The  axle  is  divided  in  the  center, 
each  half  being  fastened  to  one  of  the  rear  wheels.  The  power  is  de- 
livered' through  the  axle  to  the  two  rear  wheels.     This  type  of  axle, 

Fio.  15. — Live  type  of  rear  automobile  axle. 

Fig.  15,  in  which  the  power  is  transmitted  by  a  divided  shaft  revolving 
inside  a  housing,  is  called  a  live  axle. 

Differential. — 1^  is  sometimes  necessary,  as  when  turning  a  corner, 
that  one  rear  wheel  turn  faster  than  the  other  one.     In  order  to  accom- 



StAvK*  ohmi  r*(Mft 


Fio.  16. — Left-hand  drive,  center  control. 

plish  this,  the  differential  is  placed  between  the  two  halves  of  the  rear 
axle.  The  use  of  the  differential  permits  each  rear  wheel  to  be  fastened 
to  the  rear  axle  and  at  the  same  time  move  at  different  speeds  while 
delivering  power: 

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Wheels. — Automobile  wheels  are  of  either  the  wooden  or  wire  type. 
Both  of  these  types  carry  a  rim  on  which  is  fitted  a  pneumatic  tire  filled 
with  high  pressure  air.  The  tire  serves  as  a  good  shock  absorber  and 
eliminates  a  large  part  of  the  road  jars  before  they  reach  the  mechanism 
of  the  car.  The  distance  measured  between  the  two  front  wheels  or  the 
two  rear  wheels  is  called  the  tread  of  the  car.  It  is  usually  standard, 
being  56  in.  The  rear  wheels,  being  the  driving  wheels,  are  equipped 
with  brakes  so  that  the  car  may  be  stopped  or  slowed  down  very  quickly. 
Usually  two  sets  are  provided,  one  for  ordinary  service  called  service 
brakes,  and  the  other  for  emergency  purposes  called  emergency  brakes. 
Both  sets  of  brakes  are  controlled  from  the  driver's  seat. 

Fio.  17. — Right-hand  drive  with  right  control. 

10.  Control  Systems. — The  seat  for  the  person  driving  an  automobile 
is  generally  on  the  left  side,  although  the  right-hand  drive,  formerly 
used  to  a  large  extent,  is  still  in  use.  With  the  left  drive,  Fig.  16,  the 
control  levers  for  the  change  gears  and  the  emergency  brake  are  near  the 
center,  being  within  ready  reach  of  the  driver's  right  hand.  The  clutch 
pedal  and  service  brake  pedal  are  on  the  left,  so  as  to  be  operated  by  the 
driver's  feet.  With  the  right-hand  drive,  Fig.  17,  the  steering  wheel  and 
foot  pedals  are  placed  on  the  right  of  the  car,  with  the  control  levers  to 
the  right  of  the  driver,  when  seated. 

The  following  chapters  will  treat  in  detail  the  various  parts  of  th€ 
automobile,  their  construction,  and  methods  of  operation. 

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11.  The  Gasoline  Engine. — Practically  all  gasoline  engines  are 
driven  by  explosions  which  take  place  within  the  cylinder  of  the  engine 
and  drive  the  piston,  thus  causing  rotation  of  the  revolving  parts  of 
the  engine.  These  explosions  are  in  a  way  very  similar  to  the  explosions 
of  gunpowder  or  dynamite.  When  a  charge  of  gunpowder  is  fired  in  a 
cannon  or  gun,  the  gunpowder  burns  and  produces  gases  which  expand 
and  exert  a  tremendous  pressure  on  the  shell  and  force  it  from  the  gun. 

Practically  any  substance  that  will  burn  can  be  exploded  if  under 
the  proper  conditions.  An  explosion  is  merely  the  burning  of  some 
material  almost  instantaneously,  resulting  in  a  great  amount  of  heat 
being  generated  all  at  once.  When  any  substance  burns,  it  unites 
rapidly  with  oxygen  from  the  air.  In  order  to  have  an  explosion,  it 
is  necessary  to  have  the  fuel  very  finely  divided  and  carefully  mixed 
with  air,  so  that  the  burning  can  be  very  rapid.  Then,  if  the  fuel 
is  ignited,  by  an  electric  spark  or  any  other  means,  the  flame  instantly 
spreads  throughout  the  mixture  and  an  explosion  occurs.  In  a  gasoline 
engine,  gasoline  vapor  mixed  carefully  with  air  is  taken  in.  This  mixture 
is  then  exploded  inside  the  cylinder  of  the  engine.  The  force  of  this 
explosion  drives  the  piston,  and  the  motion  is  transmitted  through  the 
connecting  rod  to  the  crank.  To  make  the  process  continuous  and  keep 
the  engine  going,  it  is  necessary  to*  automatically  get  rid  of  the  burnt 
gases  from  the  previous  explosion  and  to  get  a  fresh  charge  into  the 
cylinder  ready  for  the  next  explosion.  This  process  must  be  carried  out 
regularly  by  the  engine,  in  order  to  keep  it  running. 

12.  Cycles. — There  are  two  principal  systems  in  use  for  carrying 
out  the  series  of  operations  necessary  for  getting  a  fresh  charge  of  gas 
into  the  cylinder,  exploding  it,  and  getting  the  burnt  gases  out  of  the 
cylinder  again.  These  systems,  or  rather  the  series  of  operations,  are 
called  cycles,  and  the  engines  are  named  according  to  the  number  of 
strokes  it  takes  to  complete  a  cycle.  These  two  cycles,  or  systems  of 
strokes,  are  the  four-stroke  cycle  and  the  two-stroke  cycle. 

It  must  be  remembered  that  a  cycle  refers  to  the  series  of  operations 

the  engine  goes  through.     In  the  four-stroke  cycle  it  requires  four 

strokes  or  two  revolutions  to  complete  the  cycle.     In  the  two-stroke 

cycle,  two  strokes  or  one  revolution  are  necessary.     Many  people  leave 

2  17 

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out  the  word  stroke  and  talk  of  four-cycle  engines  and  two-cycle  engines. 
This  causes  the  misunderstanding  that  many  people  have  as  to  just  what 
a  cycle  really  is.  A  better  way  is  to  call  them  four-stroke  engines  and 
two-stroke  engines.  • 

13.  The  Four-stroke  Cycle. — Figures  18,  19,  20,  and  21  show  an 
engine  which  operates  according  to  the  four-stroke  cycle.  The  engine 
shown  here  is  a  vertical  engine,  that  is,  the  cylinder  is  placed  above  the 
crankshaft  (instead  of  being  at  one  side)  and  the  piston  moves  up  and 
down  in  the  cylinders.  This  is  the  prevailing  form  for  automobile 

Any  engine  consists  of  four  principal  parts:  the  cylinder,  which  is 
stationary  and  in  which  the  explosion  occurs;  the  piston,  which  moves 
within  the  cylinder  and  receives  the  force  of  the  explosion;  the  connecting 
rod,  which  takes  the  force  from  the  piston  and  transmits  it  to  the  crank; 
and  the  crank,  which  revolves  and  receives  the  force  of  the  explosion  as 
the  piston  goes  in  one  direction,  and  which  then  shoves  the  piston  back 
to  its  starting  point.  When  the  piston  is  at  the  top  end  of  its  stroke, 
and  the  engine  crank  also  in  its  extreme  upper  position,  the  engine  is 
said  to  be  on  its  upper  dead  center.  When  the  piston  and  crank  are  in 
the  extreme  lower  positions,  the  engine  is  on  lower  dead  center.  A  four- 
stroke  engine  has  a  number  of  other  minor  parts,  the  uses  of  which  wW 
be  brought  out  later. 

This  engine  uses  four  strokes  of  the  piston  to  complete  the  series 
of  operations  from  one  explosion  to  the  next,  and  is,  therefore,  said 
to  operate  on  the  four-stroke  cycle,  or  it  is  said  to  be  a  four-stroke  en- 
gine. The  first  illustration,  Fig.  18,  shows  the  engine  just  beginning 
to  draw  in  a  mixture  of  gas  and  air  through  the  inlet  or  intake  valve. 
This  is  continued  until  the  piston  gets  down  to  the  bottom  of  the  stroke, 
and  the  cylinder  is  full  of  this  explosive  mixture.  This  operation  is  called 
the  suction  stroke.  Then  the  valves  are  shut,  as  in  Fig.  19,  and  the  piston 
is  forced  back  to  its  top  position.  This  squeezes  or  compresses  the  gas 
into  the  space  left  in  the  top  of  the  cylinder.  This  process  of  compressing 
the  gas  is  called  the  compression  stroke.  After  the  piston  gets  to  the  top, 
the  gases  are  ignited  or  set  fire  to  and  burn  so  quickly  that  an  explosion 
results  and  the  piston  is  driven  down  again,  as  in  Fig.  20.  This  is  called 
the  expansion  or  working  stroke.  When  the  piston  reaches  the  bottom 
of  the  stroke,  the  exhaust  valve  is  opened,  and  while  the  piston  is  return- 
ing to  the  top  position  it  forces  out  through  this  valve  the  burned  gases 
which  occupy  the  cylinder  space.  This  is  the  exhaust  stroke.  The  engine 
is  now  ready  to  repeat  this  series  of  operations.  A  stroke  means  the 
motion  of  the  piston  from  either  end  of  the  cylinder  to  the  other  end. 
Consequently,  there  are  four  strokes  in  the  cycle  of  operations  of  this 
engine,  and  we,  therefore,  call  it  a  four-stroke  engine. 

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Suction   Stroke 

Fiq.  18. 

Compression  Stroke 

Fiq.  19. 

Working  .Stroke 

Fig.  20. 

Exhaust  Stroke 

Fiq.  21. 

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14.  The  Two-stroke  Cycle. — The  two-stroke  cycle  engine,  Figs.  22 
and  23,  completes  the  cycle  of  events,  suction,  compression,  explosion, 
and  exhaust,  in  two  strokes  of  the  piston  instead  of  four.  The  engine, 
instead  of  having  valves,  as  in  the  four-stroke  cycle  type,  has  exhaust 
and  intake  ports,  or  openings,  cast  in  the  sides  of  the  cylinders.  These 
ports  are  uncovered  by  the  piston  as  it  moves  up  and  down  in  the  cylinder. 
During  the  power  stroke  of  the  piston,  the  fuel  for  the  succeeding  charge 
is  partially  compressed  in  the  engine  crank  case.  When  the  piston  is 
nearing  the  end  of  its  power  stroke,  it  uncovers  the  exhaust  port,  permit- 
ting the  burned  gases  to  escape;  shortly  after,  the  intake  port  is  uncovered 
and  the  partially  compressed  charge  from  the  crank  case  rushes  into  the 
cylinder.    On  the  return  stroke  of  the  piston,  the  intake  and  the  exhaust 

Spark    fQug 

Exhaust  Port 
Transfer   fhrt 
Check  Valve  (Open) 

Transfer  Port 

Check   Valve  (Oastd) 

Fio.  22. 

Fio.  23. 

Fios.  22  and  23. — Two-port,  two-stroke  engine 

ports  are  closed,  and  the  gases  are  compressed  for  the  following  power 
stroke.  The  two-stroke  cycle  engine  for  automobile  use  has  been 
practically  discarded. 

15.  The  Order  of  Events  in  Four-stroke  Engines. — The  periods  in 
the  four-stroke  cycle  are  represented  on  the  diagram  of  Fig.  24.  This 
figure  represents  the  two  revolutions  of  a  four-stroke  cycle  so  as  to  show 
the  crank  positions  when  the  different  events  occur.  The  diagram  is 
drawn  for  a  vertical  engine  with  the  crank  revolving  to  the  right.  This 
is  the  direction  of  rotation  of  an  automobile  engine  to  a  person  standing 
in  front  of  the  car  looking  toward  the  engine. 

Let  it  be  assumed  that  the  engine  piston  has  reached  the  top  of  the 
stroke  and  has  started  back  on  the  return  stroke.  The  crank  of  the 
engine  will  also  be  moving  down  until  at  point  A  when  the  crank  angle 

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will  be  around  10°,  the  inlet  valve  opens.  From  A  to  B  the  suction 
stroke  of  the  piston  takes  place,  the  inlet  valve  closing  about  20°  to  30° 
past  the  lower  dead  center.  The  inlet  valve  has  thus  been  open  180°  to 
200°.  From  crank  position  at  B  to  crank  position  at  C,  the  gas  is  com- 
pressed, both  valves  being  closed.  From  5°  to  10°  before  the  upper  dead 
center  is  reached,  the  gas  is  ignited  and  the  burning  or  combustion  occurs 
from  the  crank  position  at  C  to  the  crank  position  at  D,  or  during  a  period 
of  from  5°  to  10°.  The  full  force  of  the  explosion  is  exerted  just  as  the 
crank  passes  the  upper  dead  center  and  the  piston  begins  to  descend. 
From  crank  position  at  D  to  that  at  E,  the  expansion  of  the  gases  takes 
place.     At  E,  which  is  from  30°  to  45°  before  lower  dead  center,  the 





Fio.  24. — Order  of  events  in  the  four-stroke  cycle. 

exhaust  valve  opens  permitting  the  gases  to  be  exhausted  while  the 
crank  is  moving  from  E  around  to  F  where  the  exhaust  valve  closes  a 
few  degrees  past  the  upper  dead  center.  One  complete  cycle  has  now 
been  completed. 

16,  The  Mechanism  of  Four-stroke  Engines. — The  details  and  the 
mechanism  of  a  four-stroke  automobile  engine  with  four  cylinders  are 
shown  in  Figs.  25  and  26.  The  cylinders  are  cast  in  one  piece  from  grey 
iron,  which  is  the  usual  material  for  cylinders.  The  grey  iron  flows 
easily  when  being  cast,  is  easy  to  machine,  and  presents  a  good  wearing 
surface  to  the  pistons.  The  water  jacket  around  the  cylinder  is  generally 
made  a  part  of  the  cylinder  casting,  although  some  jackets  have  been 
made  of  copper  and  put  on  around  the  cylinder  casting.    The  design  of 

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the  water  jacket  is  very  important  as  sufficient  cooling  surface  must  be 
provided  and  all  pockets  where  steam  might  collect  must  be  avoided. 


WRIST  PIN  ^  ^^flonA           M 

COOLING,    H  ~**i*&jj 

SPACE    ^M 



\               ^ 

- 1 




I!  J  ~~        j 



Fio.  25. — Continental  four  cylinder  engine. 

The  cylinder  head  can  be  either  cast  solid  with  the  cylinder  as  in  Fig. 
26,  or  cast  singly  and  made  removable,  being  fitted  to  the  cylinder  by 
means  of  a  gasket  or  a  ground  joint.    The  removable  head  provides  easy 

access  to  the  cylinder  for  working  pur- 
poses. The  cylinder  is  made  smooth 
inside  by  being  bored  out  and  is  usually 
ground  to  size  with  a  grinding  wheel. 
The  inside  diameter  of  the  cylinder  is 
spoken  of  as  the  bore  of  the  engine. 


.  WH7W  SfiA££ 

Fio.  26. — Continental  Model  N  auto- 
mobile engine. 


Concentric  piston  ring.       Eccentric  piston  ring. 
Fio.  27. — Types  of  piston  rings. 

17.  Pistons  and  Piston  Rings. — The  pistons  which  receive  the  force 
of  the  explosion  and  expansion  and  transmit  the  motion  to  the  connecting 
rod  and  crank  are  commonly  made  of  soft  grey  cast  iron,  although  some 

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pistons  of  aluminum  and  also  of  an  aluminum  alloy  called  lynite  are 
being  used.  The  aluminum  and  alloy  pistons  have  the  advantage  of 
being  light,  and  it  is  also  claimed  that  they  radiate  heat  much  faster  than 
cast  iron.  Being  lighter  than  cast  iron,  the  aluminum  or  alloy  piston  is 
easier  to  move  up  and  down  in  the  cylinder.  The  expansion  of  these 
pistons  is  more  than  for  cast  iron  and,  consequently,  a  greater  clearance 
must  be  provided  when  being  fitted  to  the  cylinders. 

The  pistons  are  turned  and  ground  so  that  they  will  be  a  few  thou- 
sandths of  an  inch  smaller  in  diameter  than  the  cylinder  in  order  that  there 
will  be  a  good  sliding  fit  without  undue  friction.    The  pistons  are  made 

Fiq.  28. — Types  of  piston  rings  and  ring  joints. 

gas  tight  by  means  of  cast-iron  piston  rings  placed  in  grooves  around  the 
body  of  the  piston.  Ordinarily,  three  rings,  placed  in  the  piston  above 
the  wrist  pin,  are  used.  In  some  cases  an  oil  groove  is  also  cut  in  the 
piston  below  the  rings  to  improve  the  lubrication  between  the  piston 
and  the  cylinder  walls. 

Piston  rings  are  of  two  general  types,  the  concentric  and  eccentric, 
the  difference  being  shown  in  Fig.  27.  The  concentric  rings  are  of  uni- 
form thickness,  while  the  eccentric  rings  are  considerably  thicker  on  the 
side  opposite  the  opening.  It  is  impossible  with  a  concentric  ring  to 
get  a  uniform  bearing  pressure  between  ring  and  cylinder  wall,  but  with 
an  eccentric  ring,  this  is  accomplished.  In  addition  to  these  types  of 
one  piece  rings,  numerous  patented  and  two  piece  rings  have  been  devised 

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so  as  to  get  the  advantages  both  of  the  concentric  and  eccentric  types. 
Figure  28  illustrates  several  types  of  these  patented  piston  rings  and  also 
several  piston  ring  joints. 

The  pistons  used  in  automobile  engines  are  of  the  trunk  type,  explo- 
sions taking  place  on  one  end  only.  The  other  end  is  open  and  allows 
for  the  movement  of  the  connecting  rod.  The  length  of  the  piston  is 
usually  134  times  the  diameter.  The  head  of  the  piston  is  commonly 
made  flat,  although  occasionally  pistons  with  slightly  concave  or  convex 
heads  are  used. 

18.  Connecting  Rods. — The  connecting  rod  may  be  either  a  forging  or 
a  steel  casting  and  may  be  either  solid  or  of  I-beam  section  as  shown  in 



Fig.  29. — Piston,  connecting  rod  and  parts. 

Fig.  29.  The  connecting  rod  is  under  compression  at  all  times  and  the 
I-beam  section  is  the  best  for  withstanding  the  tendency  of  the  rod  to 
bend.  The  connecting  rod  is  attached  to  the  piston  by  means  of  a  steel 
wrist  pin.  This  pin  may  be  clamped  either  to  the  connecting  rod  end 
and  turn  on  a  bearing  in  the  piston,  or  it  may  be  clamped  to  the  piston 
bosses  and  the  connecting  rod  turn  on  the  fixed  pin  as  in  Fig.  25.  The 
bearing  in  the  small  end  of  the  connecting  rod  is  usually  a  bronze  bush- 
ing forced  into  the  rod  and  then  bored  or  reamed  to  size.  The  wrist  pin 
is  usually  made  hollow  in  order  to  reduce  the  weight  and  to  increase  the 
outside  bearing  surface. 

The  lower  end  of  the  connecting  rod  turns  on  the  crankshaft.     One- 
half  of  the  bearing  is  generally  found  in  the  rod  itself,  the  other  half  being 

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held  and  supported  by  the  cap  which  is  bolted  to  the  rod.  By  adjusting 
these  bolts,  the  wear  on  the  bearing  can  be  taken  up  from  time  to  time. 
The  shims  are  very  thin  pieces  which  are  placed  between  the  halves  of  the 
connecting  rod  bearing  when  the  halves  are  tightened  together  by  the 
bolts.  As  the  bearing  wears  it  may  be  taken  up  by  removing  some  of  the 
shims  and  then  tightening  the  bolts.  The  bearing  on  the  lower  end  of 
the  connecting  rod  may  be  entirely  of  bronze  or  may  be  a  babbitted 
bearing  backed  up  by  bronze.  The  babbitted  bearing  is  much  softer 
than  the  bronze  and  is  much  easier  to  fit.  It  wears  more  quickly  than 
a  bronze  bearing  and,  consequently,  needs  to  be  adjusted  oftener.  Al- 
though the  bronze  bearing  is  more  difficult  to  fit,  it  wears  longer  and 
needs  less  attention.  Either  type  of  bearing  must  have  a  little  side  play 
on  the  crank  pin  in  order  to  prevent  heating.  The  length  of  the  con- 
necting rod  is  from  2  to  2*4  times  the  stroke  of  the  engine.  It  is 
desirable  to  have  it  as  long  as  possible. 

19.  The  Crankshaft — The  crankshaft  turns  the  reciprocating  motion 
of  the  piston  and  connecting  rod  into  a  circular  motion.  The  length  of 
crank  or  the  distance  from  the  center  of  the  crank  pin  to  the  center  of 
the  main  bearing  is  one-half  the  stroke  of  the  piston,  the  stroke  being  the 
distance  the  piston  moves  in  one  direction  in  the  cylinder.  A  long  stroke 
engine  is  one  on  which  the  stroke  is  over  1%  times  the  cylinder  bore. 
The  longer  the  piston  stroke  is,  the  longer  the  engine  crank  must  be. 

When  the  crankshaft  is  running  at  high  speeds,  there  are  unbalanced 
forces  set  up  and  these  tend  to  shake  and  jar  the  engine.  To  prevent 
this,  many  schemes  have  been  devised  for  balancing  these  forces  when 
running.    These  will  be  taken  up  under  multi-cylinder  crankshafts. 

20.  The  Flywheel. — The  purpose  of  the  flywheel  is  to  keep  the  engine 
running  from  one  power  stroke  to  another.  In  a  single  cylinder  engine, 
power  is  being  delivered  by  the  piston  and  connecting  rod  only  about  one- 
quarter  of  the  time.  Part  of  this  power  is  stored  in  the  flywheel  and 
given  back  to  the  crankshaft  and  piston,  during  the  other  three-quarters 
of  the  time.  It  can  easily  be  seen  that  a  single  cylinder  engine  requires  a 
heavier  flywheel  than  a  four-cylinder  engine  of  the  same  cylinder  size. 
As  the  number  of  cylinders  is  increased,  the  weight  and  size  of  the  flywheel 
can  be  reduced.  In  a  great  many  automobile  engines  the  flywheel  and 
clutch  are  built  together  as  a  small  unit.* 

21.  Valves. — It  is  necessary  in  a  four-stroke  gas  engine  that  provision 
be  made  for  getting  fresh  gases  into  the  cylinder  and  for  getting  the  burnt 
gases  out.  This  is  done  by  the  use  of  valves,  two  of  which  are  provided 
for  each  cylinder.  One  of  these,  the  intake  valve,  provides  the  opening 
for  getting  the  gases  in  and  the  other,  the  exhaust  valve,  provides  the 
exhaust  opening  from  the  cylinder.    In  Fig.  25,  the  intake  and  exhaust 

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valves  with  the  operating  mechanism  are  illustrated.    An  end  view  of  a 
similar  mechahism  is  shown  in  Fig.  26. 

The  prevailing  type  of  valve  is  called  the  poppet  mushroom  valve — 
poppet  from  its  operation,  and  mushroom  from  its  shape.  The  valve 
seat  upon  which  the  valve  closes  is  generally  found  in  the  cylinder  casting 

Fig.  30. — Forms  of  poppet  mushroom  valves. 

itself,  although  removable  valve  cages  which  carry  the  seat  are  sometimes 
used.    The  common  forms  of  valves  are  shown  in  Fig.  30. 

The  best  materials  for  valve  heads  are  cast  iron,  nickel  steel,  and 
tungsten  steel.  Cast  iron  is  very  cheap,  easily  worked,  and  stands  corro- 
sion well.  It  is  weak,  however,  and  a  heavier  weight  is,  therefore,  required 
than  with  other  materials.     This  weight  is  especially  objectionable  for 

Cast  iron. 
Fia.  31. — Effect  of  pitting  on  tungsten  and  cast-iron  valves. 

high  speed  engines.  Nickel  steel  is  strong,  non-corrosive,  and  has  a  very 
low  coefficient  of  heat  expansion.  Hence,  it  does  not  warp  so  readily  as 
other  metals.  It  is  rather  expensive  and  when  used  is  generally  electri- 
cally welded  to  a  carbon-steel  valve  stem.  Tungsten  steel  is  very  hard 
and  will  stand  high  temperatures  without  pitting.  Figure  31  shows  the 
relative  effect  of  pitting  on  a  cast-iron  valve  and  a  tungsten  steel  valve 
after  the  same  use  on  an  engine.    The  tungsten  valve  has  a  smooth, 

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tight  seat,  while  the  cast-iron  valve  seat  is  pitted  and  worn.  Cast-iron 
valve  heads  can  be  screwed  on  a  steel  stem  as  in  Fig.  30J?,  the  stem  being 
riveted  to  prevent  loosening.  Figure  30C  shows  a  common  European 
form  for  valves  which  is  being  rapidly  adopted  here.  The  curvature 
underneath  gives  the  gases  a  smooth  passage  without  any  of  the  whirling 
eddies  that  occur  under  the  ordinary  valve. 

The  valve  seats  are  usually  beveled  at  an  angle  of  45°,  as  shown, 
though  flat  valves  with  flat  seats  are  occasionally  used.  The  valves  must 
be  large  enough  to  let  the  gases  in  and  out  of  the  cylinders  freely.  If 
they  are  too  small  they  will  cut  down  the  power  of  the  engine  by  not 
permitting  it  to  get  a  full  charge.  The  valves  usually  measure  from  one- 
third  to  one-half  of  the  cylinder  diameter.  Valve  diameters  are  usually 
measured  by  the  opening  in  the  valve  seat  (see  dimension  marked  d  in 
Fig.  30.4).  The  diameter  of  the  inlet  and  exhaust  pipes  should  at  least 
equal  this  valve  diameter  and  should  be  larger  if  possible. 

The  valve  lift,  or  the  distance  the  valve  opens,  should,  when  possible, 
be  sufficient  to  give  the  gases  as  large  a  passage  between  the  valve  and 
seat  as  they  have  through  the  opening  d,  Fig.  30A.  For  a  flat  valve  seat 
this  would  require  a  lift  of  one-fourth  of  the  valve  diameter.  With  a 
beveled  seat,  the  gases  pass  through  an  opening  in  the  shape  of  a  conical 
ring  having  a  width  of  passage  equal  to  A,  Fig.  30A.  To  have  the  neces- 
sary passage  area,  the  lift  h  of  the  valve  should  be  about  three-tenths  of 
the  diameter.  In  most  stationary  engines  this  lift  can  be  given  the  valve, 
but  in  high-speed  automobile  engines  it  would  be  too  noisy.  This  lift 
would  cause  pounding  and  wear  on  the  cams.  It  would  require  very  stiff 
springs  to  make  the  valves  follow  the  cams  in  closing  and  would  be  very 
hard  on  the  valve  seats  and  stems.  For  automobile  engines  the  valves 
are  made  as  large  as  possible  and  the  lift  is  limited  to  from  *Ke  to  ^  in. 

Any  valve  needs  regrinding  into  its  seat  occasionally  with  oil  and 
emery  or  ground  glass.  Exhaust  valves  require  this  more  often  than 
inlet  valves,  as  they  become  warped  and  pitted  by  the  hot  gases.  After  a 
valve  is  ground  in,  the  push  rods  should  be  readjusted,  as  the  grinding 
will  lower  the  valve  and  reduce  the  clearance  in  the  valve  motion. 

The  engine  in  Fig.  26  has  the  valve  seat  on  the  engine  casting  and, 
consequently,  the  valve  and  its  seat  cannot  be  removed  for  grinding. 
With  valves  in  the  head,  the  valve  and  seat  are  built  into  a  cage  which 
may  be  removed  from  the  engine  when  it  becomes  necessary  to  grind  the 

22.  Valve  Operating  Mechanism. — The  form  of  mechanism  for  operat- 
ing the  valves  depends  somewhat  on  the  valve  arrangement.  The  valve 
arrangement,  in  turn,  is  determined  by  the  shape  of  the  cylinder  head. 
The  usual  head  arrangement,  in  turn,  is  determined  by  the  shape  of  the 
cylinder  head.    The  usual  head  arrangements,  illustrated  in  Fig.  32,  are 

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named  from  the  shape  of  the  combustion  space  and  the  cylinder.  The 
T-head  permits  of  large  valves  and  low  lifts.  It  requires  two  valve 
operating  mechanisms  and  two  camshafts,  one  on  each  side  of  the  engine. 




I-HeacL  L-Head.  T-Head. 

Fig.  32. — Arrangement  of  valves  on  engine  cylinders. 

The  L-head  with  both  valves  on  one  side  requires  only  one  camshaft. 
The  L-head  does  not  present  as  much  cooling  surface  to  the  combustion 
chamber  and  is,  therefore,  a  little  more  economical  in  fuel  than  the  T-head 






Fiq.  33. — Valve  operating  mechanism  on  Ford  car. 

arrangement.  The  l-head  arrangement  has  come  into  quite  popular  use 
because  it  gives  a  short,  quick  passage  into  the  combustion  chamber  and 
also  a  simple  compact  combustion  chamber  with  a  minimum  loss  of  heat 

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to  the  cooling  water.  The  valve  in  the  head  arrangement  requires  that 
the  motion  of  the  push  rod  be  reversed  in  order  to  operate  the  valves 
properly.  This  is  accomplished  by  means  of  a  rocker  arm.  Both  valves 
are  operated  by  one  camshaft.  With  a  T-  or  an  L-head  valve  arrange- 
ment, the  operation  of  the  valves  is  simplified. 

The  valves  are  operated  as  illustrated  in  Fig.  33  by  two  push  rods, 
one  for  each  valve.  These  push  rods  receive  their  motion  from  the  cams. 
On  the  lower  ends  of  these  rods  are  rollers  or  followers,  and  these  roll  or 
slide  on  the  cams  on  the  camshaft.  These  cams  each  have  a  hump  or 
projection  on  about  one-fourth  of  their  circumference.  When  one  of 
these  strikes  the  roller  or  follower  it  raises  it  up,  and  this  motion  is  trans- 
mitted through  the  push  rod  to  the  valve.  After  the  projection  of  the 
cam  has  passed  under  the  roller,  the  valve  spring  will  close  the  valve 
and  force  the  push  rod  back  to  the  original  position.  In  order  to  allow 
for  expansion  and  to  provide  for  certain  adjustments  in  the  opening  and 
closing  of  the  valve,  there  is  always  a  small  clearance  between  the  push 
rod  and  its  follower  when  the  valve  is  on  its  seat. 

23.  Valve  Opening  and  Closing. — The  exhaust  valve  of  an  engine 
opens  on  an  average  of  about  45°  before  the  end  of  the  stroke,  in  order 
that  the  pressure  may  be  reduced  to  atmospheric  by  the  end  of  the  power 
stroke,  and  also  that  there  will  be  no  back  pressure  during  the  exhaust 
stroke  following.  At  the  end  of  the  exhaust  stroke,  the  exhaust  valve 
should  remain  open  while  the  crank  is  passing  the  center  so  that  any 
pressure  remaining  in  the  cylinder  may  have  time  to  be  reduced  to 
atmospheric.  The  exhaust  valve  usually  closes  from  5°  to  10°  late 
(past  dead  center),  having  been  open  from  230°  to  235°. 

The  inlet  valve  very  seldom  opens  before  the  exhaust  closes.  Most 
manufacturers  do  not  open  the  inlet  until  the  exhaust  closes,  for  fear  of 
back-firing,  although  there  is  little  danger  of  this  except  with  slow- 
burning  mixtures.  The  inlet  valve  opens,  on  an  average,  10°  late 
(after  center).  At  the  end  of  the  suction  stroke  there  is  still  a  slight 
vacuum  in  the  cylinder  and  the  inlet  is  kept  open  for  a  few  degrees  past 
center  to  allow  this  to  fill  up  and  get  the  greatest  possible  quantity  of 
gas  into  the  cylinder.  On  an  average,  the  inlet  valve  closes  about  35° 
late,  depending  on  the  piston  speed  of  the  engine.  The  inlet  valve  thus 
remains  open  about  205°. 

24.  Half-time  Gears. — Since  the  valves  on  an  engine  open  and  close 
but  once  in  two  revolutions,  the  engine  must  be  arranged  so  that  the 
cams  on  the  camshaft  come  around  and  strike  the  cam  followers  only 
once  in  two  revolutions  of  the  engine  crank.  To  do  this,  the  arrangement 
is  to  put  a  gear  on  the  crankshaft  and  have  this  drive  another  gear, 
twice  as  large,  on  the  camshaft.    In  this  way  the  camshaft  will  run  at 

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just  half  the  speed  of  the  crankshaft.    These  gears  are  called  half-time 

Plain  spur  gears  with  straight  teeth,  or  helical  gears  with  teeth  at 
an  angle,  are  the  usual  type  of  half-time  gears.  In  some  cases  the  posi- 
tive connection  between  gears  is  furnished  by  a  chain  drive  similar  to 
that  on  a  bicycle.  The  plain  spur  timing  gears,  together  with  the  cam- 
shaft and  valves  on  the  Ford  car,  are  shown  in  Fig.  33.  The  helical 
timing  gears  in  the  Case  engine  are  illustrated  in  Fig.  34  and  the  silent 
chain  drive  in  Fig.  35.  Difficulty  is  sometimes  experienced  with  the 
plain  spur  gear  on  account  of  the 
lost  motion  due  to  wear,  and  with 
the  chain  drive  due  to  an  increase 
in  length .  These  difficulties  have 
to  a  large  extent  been  overcome 
by  the  use  of  the  helical  gears. 

Fig.  34. — Helical  timing  gears. 

Fio.  35. — Silent  chain  camshaft  drive. 

25.  The  Knight  Engine. — The  Knight  engine  is  built  on  the  principle 
of  the  four-stroke  cycle,  but  the  usual  poppet  valves  have  been  replaced, 
by  two  concentric  sleeves  which  slide  up  and  down  between  the  piston 
and  cylinder  walls.  Certain  slots  in  these  sleeves  register  with  one  an- 
other at  proper  intervals,  producing  direct  openings  into  the  combustiQn 
chamber  from  the  exhaust  and  inlet  ports.  The  construction  of  the 
Willys-Knight  motor  is  illustrated  in  Fig.  36,  which  shows  the  general 
arrangement  of  the  parts  and  their  nomenclature. 

It  will  be  noted  that  the  sleeves  are  independently  operated  by 
small  connecting  rods  working  from  an  eccentric  or  small  crankshaft 
running  lengthwise  of  the  motor.  This  eccentric  shaft  is  positively 
driven  by  a  silent  chain  at  one-half  the  speed  of  the  crankshaft.  The 
eccentric  pin  operating  the  inner  sleeve  is  given  a  certain  lead  or  advance 

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over  the  pin  operating  the  outer  sleeve.  This  lead,  together  with  the 
rotation  of  the  eccentric  shaft  at  half  the  crankshaft  speed,  produces  the 
valve  action  illustrated  in  Fig.  37,  which  shows  the  relative  positions  of 
the  pistons,  sleeves,  and  cylinder  ports  at  various  points  in  the  rotation 
of  the  crankshaft. 

The  advantage  of  the  sliding  sleeves  over  the  usual  valve  type  is 
that  they  are  practically  noiseless  in  operation.    It  is  also  possible  to 

Spark  plug 

Exhaust  manifold 

Intake  manifold 


Piston  connecting  rod 


Outer  sleeve 

Inner  sleeve 

Connecting  rod,  to 
operate  outer  sleeve 

Connecting  rod,  to 
operate  inner  sleeve 

Eccentric  shaft 

Fig.  36. — Cylinder  on  Willys-Knight  engine. 

have  larger  openings  and  ports  into  the  cylinder,  thereby  insuring  a  full 
charge  of  fuel  to  the  cylinders  at  all  engine  speeds. 

26.  The  Fuel  Charge. — When  the  inlet  valve  opens,  the  suction  of 
the  piston  moving  downward  draws  a  charge  of  fuel  into  the  cylinder.  To 
evaporate  the  gasoline  and  mix  this  gasoline  vapor  with  the  proper 
amount  of  air  is  the  function  of  the  carburetor  which  is  treated  in  detail 
in  one  of  the  following  chapters. 

27.  Ignition. — In  order  to  cause  the  explosion  within  the  cylinder, 
some  means  must  be  provided  for  igniting  the  charge  of  gas.    This  is 

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usually  done  by  causing  an  electric  spark  to  pass  between  two  points 
within  the  cylinders.  This  spark  sets  fire  to  the  mixture  and  the  ex- 
plosion follows. 

There  are  two  general  methods  of  electric  ignition.     One  of  these  is 
called  the  make-and-break  system  because  it  requires  moving  parts  inside 

v  "H  < 

Intake  stroke. 

Intake  ports  open. 
Exhaust  ports  closed. 

Compression  stroke. 

All  ports  closed  and  sealed  by  ring 
in  cylinder  head. 

Power  stroke. 

All   ports   closed  and  protected   by 
ring  in  cylinder  head. 

Exhaust  stroke. 

Intake  ports  closed. 
Exhaust  ports  open. 

Fig.  37. — Valve  events  in  Willys-Knight  engine. 

the  cylinder  to  make  an  electric  circuit,  and  then  break  it  quickly  so 
that  a  spark  will  occur  inside  the  cylinder.  The  other  system  is  called 
the  jump-spark  system.  This  is  the  system  used  in  automobiles.  In 
this  system  there  are  no  moving  parts  which  have  to  pass  through  the 

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cylinder  wall.  The  spark  coil  or  magneto  makes  a  current  powerful 
enough  to  jump  between  two  fixed  points  inside  the  cylinder.  The  com- 
plete details  of  these  systems  of  ignition  will  be  taken  up  in  a  later 

28.  The  Muffler. — When  the  exhaust  valve  of  an  engine  opens  at 
the  end  of  the  expansion  stroke  the  pressure  of  the  gas  inside  the  cylinder 
is  still  about  50  or  60  lb.  per  square  inch.  The  valve  must  open  and 
let  this  pressure  out  before  the  piston  starts  back,  or  else  the  back  pres- 
sure will  tend  to  stop  the  engine.  The  valve  is  opened  quickly,  and 
the  high  pressure,  being  suddenly  released  into  the  exhaust  pipe,  causes 
the  sharp  sound  which  is  heard  when  an  engine  exhausts.  This  sound  is 
not  the  sound  of  the  explosion,  as  is  commonly  supposed.    The  real  ex- 



^  W      -—_  — 

Fio.  38. — Typical  muffler. 

plosion  takes  place  a  little  before  this  sound  and  can  be  heard  only  as 
a  dull  thump  inside  the  cylinder.  The  explosion  occurs  at  the  beginning 
of  the  working  stroke,  while  the  sound  that  we  hear  in  the  exhaust  comes 
at  the  end  of  the  stroke.  In  order  to  prevent  this  sudden  exhaust  from 
causing  too  great  a  noise  it  is  customary  to  have  a  muffler.  A  muffler, 
Fig.  38,  is  a  chamber  in  the  exhaust  pipe  which  receives  the  exhaust 
gases  from  the  engine  an4  expands  them  gradually  into  the  outside  air, 
thus  preventing  a  loud  noise.  * 

The  use  of  a  muffler  causes  a  slight  reduction  in  the  power  of  the  engine 
because  the  pressure  against  which  the  gases  must  exhaust  in  the  exhaust 
manifold  is  increased.  A  cut-out  which  permits  the  exhaust  gases  to 
expand  directly  into  the  air  without  going  through  the  muffler  can  be 
used  wherever  the  noise  is  not  objectionable  nor  the  use  of  the  cut-out 
prohibited  by  law. 

29.  Cylinder  Cooling. — When  an  explosion  occurs  inside  the  cylinder 
of  an  engine,  the  gases  on  the  inside  reach  a  temperature  somewhere 
around  3000°.  The  walls  of  the  cylinder  are,  of  course,  exposed  to  this 
high  heat  and  would  get  red  hot  very  quickly  if  there  was  not  some  way 
of  keeping  them  cool.  The  polished  surface  upon  which  the  piston 
slides  would  be  spoiled  very  quickly.  The  most  common  way  of  keeping 
the  cylinder  cool  is  by  the  use  of  water.  The  arrangement  for  this  is 
shown  on  the  engines  illustrated  in  this  chapter.    Surrounding  the  cylin- 


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der  ia  a  jacket  with  a  space  between  for  the  cooling  water.  By  keeping  a 
supply  of  water  passing  through  this  space,  the  cylinder  can  be  kept 
cool  enough  for  the  operation  of  the  engine.  The  cylinder  head  is  also 
cast  with  a  double  wall,  especially  around  the  valves,  so  that  these  parts 
will  also  be  kept  cool.  The  cooling  fluid  used  is  generally  water,  although 
sometimes  special  anti-freezing  solutions  are  used  where  there  is  danger 
of  the  engine  freezing.  Water  should  not  be  allowed  to  remain  in  the 
jacket  of  an  engine  over  night  if  there  is  danger  of  a  frost,  as  the  freezing 
of  the  water  will  crack  the  cylinder.  When  the  supply  of  water  is  limited, 
as  in  an  automobile,  the  water  is  cooled  in  a  radiator  or  system  of  pipes, 
and  used  over  again.  The  water  is  kept  in  circulation  by  a  pump  or  by 
the  thermosyphon  system  and  the  hot  water  cooled  by  the  air  passing 
over  the  radiator. 

30.  Piston  Displacement. — This  refers  to  the  space  swept  through  by 
the  piston  in  going  from  one  end  of  the  stroke  to  the  other.  It  is  given 
this  name  because,  as  the  piston  moves  through  its  stroke,  it  will  either 
draw  in  or  force  out  that  volume  of  air  or  gas.  The  piston  displacement 
is  calculated  by  multiplying  the  length  of  stroke  by  the  area  of  a  circle 
whose/  diameter  is  the  inside  diameter  of  the  cylinder.  For  example,  a 
3J^-in.  by  5-in.  engine  (this  means  3J^-in.  inside  cylinder  diameter  and 
5-in.  stroke)  would  have  a  piston  displacement  as  follows: 

The  area  of  a  3^-in.  circle  is  0.7864  X  3}i  X  3H  =  9.621  sq.  in. 

The  piston  displacement  is  5  times  this,  or  48.105  cu.  in. 

The  clearance  of  such  an  engine  would  be  from  24  to  30  per  cent,  of 
this.  If  we  suppose  that  it  is  25  per  cent.,  then  the  actual  space  which 
must  be  left  for  the  clearance  will  be  48.105  X  0.25  =  12.026  cu.  in. 

31.  Clearance  and  Compression. — It  was  discovered  by  some  of  the 
early  inventors  of  gas  engines  that  compressing  a  gaseous  mixture  causes 
it  to  gftfe  a  much  more  powerful  explosion.  Consequently,  all  gas  engines 
draw  in  a  full  cylinder  charge  of  gas  and  air,  and  then  compress  this 
back  into  a  space  left  at  the  upper  or  rear  end  of  the  cylinder.  This 
space,  which  is  left  for  the  gas  to  occupy  when  the  piston  is  at  the  top 
end  of  its  stroke,  is  called  the  clearance  space  or  combustion  chamber. 
The  amount  of  this  clearance  space  in  relation  to  the  whole  cylinder 
volume  determines  just  how  much  the  gas  is  compressed.  It  has  been 
found  from  experience  that  different  kinds  of  gases  require  different 
amounts  of  compression  and,  therefore,  the  clearance  space  is  made 
different  for  different  fuels.  The  clearance  is  generally  spoken  of  as 
being  a  certain  per  cent  of  the  piston  displacement,  varying  from  24  to  30 
per  cent,  for  automobile  engines. 

32.  Horse  Power  of  Engines. — The  horse  power  of  an  engine  is  the 
measure  of  the  rate  at  which  it  can  do  work.  One  horse  power  is  a 
rate  of  33,000  ft.-lb.  a  minute.    There  are  two  ways  of  measuring  engine 

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power.  We  can  determine  the  power  developed  by  the  explosions  in  the 
cylinder,  in  which  case  we  have  what  is  called  the  indicated  horse  power 
(i.hp.) ;  or  we  can  attach  a  brake  to  the  flywheel  and  measure  the  power 
which  the  engine  actually  delivers.  This  is  called  the  brake  horse  power 
(b.hp.).  Engines  are  usually  rated  by  their  brake  horse  power  because 
that  is  what  they  are  actually  capable  of  delivering.  The  brake  horse 
power  of  an  automobile  engine  will  usually  be  from  70  to  85  per  cent,  of 
its  indicated  horse  power,  the  loss  being  that  consumed  in  the  engine 

There  are  a  number  of  quick  rules  for  estimating  the  power  of  engines 
according  to  their  cylinder  dimensions  and  the  speed.  Those  most  used 
for  four-stroke  engines  are  given  below.  The  simplest  of  these  and  the 
one  most  used  is  known  as  the  S. A.E.  formula  or  Society  of  Automotive 
Engineers  formula. 

33.  Derivation  of  the  S.A.E.  Horse  Power  Formula. — The  indicated 
horse  power  of  a  single-cylinder,  four-stroke  engine  is  equal  to  the  mean 
effective  pressure,  P,  acting  throughout  the  working  stroke,  times  the 
area  of  the  piston,  A,  in  square  inches,  times  one-quarter  the  piston  speed, 
S,  divided  by  33,000,  thus: 

thp'     33,000  X  4 

Multiplying  this  by  the  number  of  cylinders,  N,  gives  the  indicated 
horse  power  for  an  engine  of  the  given  number  of  cylinders,  and  further 
multiplying  by  the  mechanical  efficiency  of  the  engine,  E}  gives  the  brake 
horse  power. 

Therefore,  the  complete  equation  for  brake  horse  power  reads: 

b.hp.  = 

33,000  X  4 

The  S.A.E.  formula  assumes  that  all  motor  car  engines  will  deliver 

or  should  deliver  their  rated  power  at  a  piston  speed  of  1000  ft.  per 

minute;  that  the  mean  effective  pressure  in  such  engine  cylinders  will 

average  90  lb.  per  square  inch;  and  that  the  mechanical  efficiency  will 

r<-  average  75  per  cent. 

Substituting  these  values  in  the  above  brake  horse  power  equation, 
and  substituting  for  A  its  equivalent,  0.7854D2,  the  equation  reads: 

90  X  0.7854D2  X  1000  XNX  0.75 
bMp'~  33,000X4 

and  combining  the  numerical  values  it  reduces  to: 

b.hp.  = 


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To  make  it  simpler,  the  denominator  has  been  changed  to  2.5  without 
materially  changing  the  results. 

The  formula  can  be  simplified,  however,  for  ordinary  use  by  consider- 
ing the  number  of  cylinders;  thus  for  the  usual  four-,  six-,  and  eight- 
cylinder  engines  it  becomes: 

1.6  D1  =  hp.  for  all  four-cylinder  motors. 

2.4  D*  =  hp.  for  all  six-cylinder  motors. 

3.2  D*  =  hp.  for  all  eight-cylinder  motors. 

4.8  D*  =  hp.  for  all  twelve-cylinder  motors. 

The  S.A.E.  formula  comes  very  close  to  the  actual  horse  power  de- 
livered by  most  automobile  engines  at  the  piston  speed  of  1000  ft.  per 
minute.  However,  at  the  present  time,  most  of  the  engines  will  deliver 
the  maximum  power  at  speeds  higher  than  this,  usually  around  1500 
ft.  per  minute.  As  a  result,  the  power  which  the  engines  are  capable 
of  delivering  is  greater  than  that  given  by  the  S.A.E.  formula.  The 
formula  will  serve,  however,  as  a  means  of  comparing  engines  on  a  uniform 

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34.  Multi-cylinder  Engines. — The  first  automobile  power  plant  con- 
sisted of  a  one-cylinder  engine  which  gave  power  impulses  at  regular 
intervals  of  time  for  the  propulsion  of  the  car.  Naturally  it  operated  in 
a  jerky  manner  and  with  considerable  noise,  due  to  the  size  of  the  cylinder 
and  the  time  between  power  impulses.    These  disadvantages  led  to  the 



4  Cylinders 



1  iil 




«Cy Undid 

Fig.  39. — Power  diagrams. 

adoption  of  the  two-,  four-,  and  six-cylinder  engines;  and  even  the  eight- 
and  twelve-cylinder  engines  have  come  into  general  use  as  automobile 
power  plants. 

In  Fig.  39  can  be  seen  one  of  the  distinct  advantages  of  the  multi- 
cylinder  engine  for  motor  car  purposes.    The  length  of  the  diagram  rep- 


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resents  two  revolutions  of  the  engine  crankshaft  or  one  complete  cycle 
of  the  engine.  The  curved  line  acefg  represents  the  variations  in  the 
power  from  a  single  cylinder.  The  line  bh  represents  uniform  power 
requirement  of  the  car.  When  the  power  curve  goes  above  bh  the  engine 
speeds  up  and  the  surplus  power  is  thus  stored  in  the  flywheel;  when  the 
curve  goes  below  bh  the  flywheel  gives  up  power  and  the  engine  slows 

As  the  number  of  cylinders  increases,  the  power  impulses  increase 
in  frequency,  the  average  power  is  greater,  and  above  four  cylinders  there 
is  no  period  during  which  some  cylinder  is  not  delivering  power.  This 
means  that  in  a  six-,  eight-,  or  twelve-cylinder  car,  there  is  no  time  during 
which  the  flywheel  must  supply  all  the  power  required  by  the  car. 

The  multi-cylinder  engine,  therefore,  furnishes  practically  a  con- 
tinuous flow  of  power  to  the  car  with  little  vibration.  The  increase  in 
the  number  of  cylinders  has  a  tendency  to  reduce  the  size  of  each  cylinder 
and  this  combined  with  the  steady  operation  of  the  engine,  makes  the 
automobile  engine  a  very  quiet,  smooth  running,  power  plant  unit. 

35.  Modern  Automobile  Power  Plants. — The  automobile  power 
plant  includes  the  engine  and  all  auxiliaries  necessary  for  the  production 
of  power.  The  transmission  system  includes  the  mechanism  necessary 
for  taking  that  power  furnished  by  the  engine  and  transmitting  it  to 
the  rear  wheels.  In  most  cases,  the  power  plant  includes  the  engine  and 
its  component  parts  such  as  the  carburetor;  starting,  lighting,  and 
ignition  equipment;  cooling  and  lubricating  systems;  etc.  When  the 
unit  power  plant  is  used,  it  includes,  in  addition  to  the  engine  and  its 
essential  component  parts,  the  clutch  and  the  change  gears. 

It  should  be  understood  that  in  the  case  of  a  four-cycle  engine,  all 
the  cylinders  must  fire  in  two  complete  revolutions  of  the  crankshaft 
regardless  of  the  number  of  cylinders.  For  example,  in  a  four-cylinder 
engine  there  are  two  power  impulses  per  revolution  of  the  crankshaft, 
while  in  an  eight-  or  twelve-cylinder  engine,  there  are  four  or  six  power 
impulses  per  revolution,  respectively. 

The  use  of  the  four-cylinder  engine  as  an  automobile  power  plant 
has  been  slowly  giving  away  in  part  with  the  adoption  of  the  engine  with 
six,  eight,  and  twelve  cylinders.  In  general,  the  gasoline  consumption 
per  unit  of  power  increases  with  the  number  of  cylinders,  so  from  the 
standpoint  of  fuel  consumption  alone,  the  four-cylinder  engine  has  the 
advantage.  Due  to  the  increased  number  of  power  impulses  per  revolu- 
tion, the  six-cylinder  engine  gives  a  much  better  balance  to  the  crankshaft, 
thereby  cutting  down  the  vibration  on  the  car.  The  car  equipped  with 
a  six-,  eight-,  or  twelve-cylinder  engine  is  more  flexible  in  operation  and 
can  be  run  under  all  conditions  with  less  frequent  changing  of  gears. 
The  four-  and  six-cylinder  engines  are  built  with  cylinders  vertical, 

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while  the  eight-cylinder  engine  consists  of  two  blocks  of  four  cylinders 
each,  placed  in  the  form  of  a  V  with  an  angle  of  90°.  The  crankshaft  is 
essentially  the  same  as  used  for  a  four-cylinder  engine.  In  the  twelve- 
cylinder  engine,  the  angle  of  the  V  is  60°,  the  crankshaft  being  like  that 
of  the  six-cylinder  engine.  As  a  general  rule,  the  bore  of  the  cylinders  in 
the  eight  and  twelve  is  less  than  in  the  four  and  six.  The  power  impulses 
come  closer  together  giving  a  smoother  running  and  more  flexible  engine* 
In  numbering  the  pistons  or  cylinders  of  a  four-  or  six-cylinder  engine, 
the  first  or  number  one  cylinder  is  the  one  next  to  the  radiator  or  the 
front  of  the  engine. 

36.  Power  Plant  Support — The  power  plant  of  an  automobile  is 
placed  near  the  front  and  is  supported  by  the  frame  of  the  car.  The 
engine  crank  case  is  designed  so  that  it  is  supported  on  the  frame  at 
four  points  or  is  designed  to  be  supported  at  only  three  points.  When 
three  point  support  is  used,  the  engine  is  carried  on  the  frame  by  one 
point  at  the  front  and  two  at  the  back,  or  by  two  points  at  the  front  and 
one  at  the  back.  The  three  point  support  has  the  distinct  advantage 
that  no  strain  or  stress  will  be  thrown  on  the  engine  shaft  or  bearings, 
if  the  side  of  the  car  frame  be  twisted  or  sprung.  In  some  cases  a  sub- 
frame  built  inside  of  the  main  car  frame  serves  to  carry  the  power  plant 
of  the  car. 

37.  Four-cylinder  Power  Plants. — The  Dodge  four-cylinder  engine, 
Fig.  40,  shows  the  cylinders  cast  en  bloc  with  the  cylinder  head  removable. 
The  block  casting  permits  a  short,  compact,  and  rigid  engine.  Although 
it  is  cheaper  in  the  first  cost,  the  cost  of  replacing  in  case  of  a  damaged 
cylinder  is  higher  than  with  cylinders  cast  singly  or  in  pairs.  The 
cylinder  diameter  is  3%  in.  and  the  stroke  4J£  in.  The  piston  displace- 
ment is  212  cu.  in.    The  engine  is  rated  at  24  horse  power. 

The  L-head  valve  arrangement  is  shown  with  both  inlet  and  exhaust 
valves  operated  by  one  camshaft.  .The  camshaft  which  is  made  with 
the  cams  solid  on  the  shaft  is  driven  by  helical  gears,  which  prevent  the 
backlash  or  lost  motion  which  is  sometimes  found  when  plain  spur  gears 
are  used. 

The  pistons  are  of  cast  iron  and  are  fitted  with  three  rings  above  the 
wrist  pin.  The  connecting  rod  is  of  I-section.  At  its  upper  end  its 
bearing  is  on  the  hollow  wrist  pin  which  is  prevented  from  turning  in 
the  piston  bosses  by  means  of  the  cap  screw  shown.  The  crankshaft  has 
the  conventional  three  main  bearings. 

38.  Ford  Power  Plant. — The  Ford  unit  power  plant  with  three  point 
support  is  shown  in  section  in  Fig.  41,  with  all  parts  fully  designated. 
The  cylinders  with  the  water  jackets  and  upper  half  of  the  crank  case 
are  cast  en  bloc.  The  cylinder  head  being  removable  permits  easy  access 
to  the  cylinders  and  valves.    The  crankshaft,  camshaft,  and  the  con- 

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necting  rods  are  made  from  a  special  vanadium  steel  permitting  a  light 
construction  which  at  the  same  time  retains  its  strength.  The  piston 
has  three  rings,  two  near  the  top  and  one  at  the  bottom.  The  crankshaft 
has  the  customary  three  main  bearings.  The  camshaft  is  driven  by  plain 
spur  gears,  as  indicated.  The  magneto,  transmission  gears,  and  clutch- 
ing arrangement  are  of  considerable  interest  and  will  be  discussed  later 
under  the  proper  headings.  The  cylinders  are  3%  in.  by  4  in.,  and  the 
engine  is  rated  at  22.5  horse  power. 

39.  White  Four-cylinder  Engine. — The  four-cylinder  engine  used  in 
the  Wliite  car  presents  some  extraordinary  features  as  may  be  seen  from 







Fig.  40. — Dodge  four-cylinder  engine. 

Figs.  42  and  43.  Instead  of  only  one  intake  and  one  exhaust  valve  for 
each  cylinder,  two  are  provided.  This  arrangement  gives  an  unusually 
large  and  desirable  area  for  getting  the  gases  into  and  out  of  the  cylinders 
quickly.  The  T-head  valve  arrangement  requires  the  use  of  two  cam- 
shafts which  are  driven  by  helical  gears. 

The  cylinder  size  is  comparatively  large  for  a  four-cylinder  engine, 
434  in-  by  b%  in.  When  an  engine  with  a  large  cylinder  is  run  at  high 
speed  and,  consequently,  high '  piston  speed,  it  is  often  impossible  for  a 
full  charge  of  gas  to  get  into  the  cylinder.  This  cuts  down  the  power  and 
efficiency.    With  the  exceptionally  large  valve  area  provided  by  double 

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In  ml  hi 

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Fia.  42. — Top  view  of  cylinders  and  valves  on  White  16  valve  four-cylinder  engine. 

Fio.  4&. — Crank  case  and  camshafts  on  White  16  valve  four-cylinder  engine. 

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valves,  the  large  cylinders  can  be  run  at  high  speed  without  cutting  down 
the  charge  of  gas  to  the  cylinders. 

40.  Duesenberg  Engine. — The  Duesenberg  automobile  engine,  Fig. 
44,  is  provided  with  horizontal  valves  which  are  placed  in  the  cylinder 
head.  These  valves  are  operated  by  a  side  lever  which  transmits  the 
motion  directly  from  the  cam.  The  horse  power  varies  from  35  at  1000 
r.p.m.  to  80  at  2100  r.p.m.  The  weight  of  this  motor  is  about  490  lb. 
The  piston  carries  one  piston  ring  of  triple  construction.  The  connect- 
ing rods  are  of  I-section  and  are  clamped  to  the  piston  pins,  the  bearing 
being  in  the  piston  bosses.    The  crankshaft  has  only  two  main  bearings. 

Fio.  44. — Duesenberg  four-cylinder  engine. 

The  cylinders  are  cast  en  bloc,  an  unusually  large  cooling  space  being 
provided.  This  engine  being  of  the  high-speed  type  is  commonly  used 
for  racing  purposes. 

41.  Guy  Rotary  Valve  Engine. — The  rotary  valves  of  the  Guy  engine 
used  on  the  Hackett  car  are  illustrated  in  Figs.  45  and  46.  These  rotary 
valves  are  driven  by  spur  gears  which  in  turn  are  driven  by  one  small 
master  gear.  The  valves  rotate  at  one-eighth  crankshaft  speed  and  give 
four  intake  openings  and  four  exhaust  passages  for  each  of  the  four  cylin- 
ders. The  special  claim  made  for  this  type  of  valve  is  that  it  provides  an 
unusually  large  valve  opening  while  giving  all  the  advantages  of  a  valve 
in  the  head  engine. 

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42.  Six-cylinder  Power  Plants. — The  Case  six-cylinder  power  plant 
is  shown  in  Fig.  47.  The  cylinders  are  of  the  L-head  type  cast  en  bloc. 
The  push  rods  and  tapered  valve  springs  can  be  clearly  seen.  The  cam- 
shaft is  driven  from  the  crankshaft  by  helical,  gears.  The  small  helical 
gear  at  the  left  drives  the  centrifugal  pump  which  circulates  the  cooling 

Fio.  45. — Top  view  of  cylinders  showiDg  rotary  valves. 

water,  and  also  the  generator  which  furnishes  the  current  for  charging  the 
batteries  and  for  ignition.  The  water  jacket  is  cast  integral  with  the 
cylinder  casting.  The  cylinder  head  is  not  removable  but  is  cast  with 
the  cylinders.  The  horse  power  is  approximately  30  and  the  cylinders 
are  3J^-in.  bore  by  5J4-i&-  stroke. 

Fio.  46. — Bottom  view  of  cyliDder  head  for  rotary  valve  engine. 

43.  Marmon  Power  Plant. — The  Marmon  power  plant  shown  in 
Fig.  48  is  characterized  by  the  extensive  use  of  aluminum  in  its  construc- 
tion. The  upper  half  of  the  crank  case,  the  cylinder  retainers,  and  the 
water  jackets  are  cast  in  one  piece  of  aluminum  as  illustrated  in  Fig.  49. 
The  cylinder  sleeves,  Fig.  50,  are  separate,  being  made  of  cast  iron  and  set 

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Fig.  47.— Case  continental  six  engine. 

Fig.  48. — Marmon  six-cylinder  power  plant. 

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into  the  aluminum  retainers.     The  cylinder  head  or  firing  head  is  of  cast 
iron  and  is  bolted  to  the  top  of  the  aluminum  cylinder  casting.     The 

Fiq.  49. — Aluminum  cylinder  casting  on  Marmon  engine. 

Fig.  50. — Removable  cylinder  liners  on  Marmon  engine. 

valves  are  placed  in  the  head  and  are  operated  by  overhead  valve  rocker 
arms.  An  aluminum  cover  fastens  over  the  valve  mechanism.  The 
total  weight  of  the  engine  with  the  aluminum  castings  is  about  650  lb. 

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The  cylinders  are  3%-in.  bore  and  5j^-in.  stroke.  The  pistons  of  cast 
aluminum  alloy  parry  four  piston  rings  as  shown.  The  bottom  ring  serves 
as  an  oil  wiper. 

44.  Franklin  Air  Cooled  Engine. — The  Franklin  engine,  Fig.   51, 
represents  a  very  interesting  and  unique  design,  having  overhead  valves 


Fig.  51. — The  Franklin  air-cooled  engine. 

and  air  cooling.  The  cylinders  are  cast  singly  and  each  is  air  cooled  by 
a  system  of  cast  ribs,  doing  away  with  the  water  jackets  around  the 
cylinders.  The  air  is  drawn  downward  around  the  cylinder  ribs  by  the 
suction  of  the  flywheel  fan. 

Fig.  52. — Hall-Scott  aviation  type  automobile  engine. 

46.  The  Hall-Scott  Engine. — The  Hall-Scott  aviation  type  engine, 
Figs.  52  and  53,  has  the  cylinders  cast  singly  of  grey  and  Swedish  iron. 
The  valves  are  operated  by  an  overhead  camshaft,  as  indicated.  Special 
attention  has  been  given  to  cooling  this  engine  as  it  has  been  designed  for 

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high  powers  and  speeds.    The  weight  is  565  lb.  and  gives  125  horse  power 
at  1300  r.p.m.    The  cylinders  are  5-in.  bore  and  7-in.  stroke. 

46.  Chandler  Six  Power  Plant. — The  casting  of  engine  cylinders  in 
pairs  of  three  is  illustrated  on  the  Chandler  engine,  Fig.  54.  This  engine 
is  of  the  Lr-head  type.  The  camshaft  is  driven  by  means  of  a  silent  chain. 
This  type  of  camshaft  drive  is  not  so  positive  as  a  gear  drive.    Any  play 

due  to  wear,  etc.  must  be  taken  up 
immediately  in  order  to  keep  the 
valves  in  time. 

47.  Constructional  Features  of 
Four-  and  Six-cylinder  Engines. — 
The  essential  differences  of  construc- 
tion on  the  various  four- and  six-cylin- 
der engines,  outside  of  the  methods 
of  cylinder  construction  and  valve  ar- 
rangement, consist  mostly  in  the  con- 
struction and  arrangement  of  the  cam- 
and  crankshafts.  Figure  55  is  a  con- 
ventional four-cylinder  crankshaft, 
shown  with  connecting  rods  and  pis- 
tons attached.  No  attempt  has  been 
made  to  counterbalance  this  shaft. 
There  are  three  main  bearings,  as  in- 
dicated. As  is  customary  in  a  four- 
cylinder  engine,  the  connecting  rod 
bearings  are  all  in  the  same  plane, 
bearing  Nos.  1  and  4,  the  two  end 
bearings,  being  just  180°  from  Nos.  2 
and  3,  the  two  center  bearings.  This 
means  that  the  No.  1  piston  and  the 
No.  4  piston  are  in  the  same  position 
in  the  cylinders  at  the  same  time. 
Likewise,  No.  2  and  No.  3  are  in  the 
same  position.  If  No.  1  piston  is  on 
the  compression  stroke,  No.  4  must  necessarily  be  on  the  exhaust  stroke 
and  Nos.  2  and  3  on  the  suction  and  explosion  strokes.  On  account 
of  the  arrangement  of  the  cranks  on  the  shaft,  the  order  of  firing  in  a 
four-cylinder  engine  must  be  in  the  order  1,  3,  4,  2,  or  1,  2,  4,  3. 

On  account  of  the  fact  that  a  crankshaft,  such  as  shown  in  Fig.  55, 
is  very  unbalanced  and  produces  excessive  vibration  on  the  engine  and 
car,  many  methods  of  counterbalancing  four-cylinder  crankshafts  are  in 
use.  In  the  crankshaft  shown  in  Fig.  56,  counterweights  have  been 
placed  opposite  the  crank  bearings  to  overcome  the  unbalanced  forces. 


53. — Section  of  Hall-Scott  aviation 
type  automobile  engine. 

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Only  one  counterweight  is  used  for  two  center  cranks.  Another  method 
of  attaching  the  counterweights  is  shown  in  Fig.  57.  Two  sets  of  weights 
serve  to  counterbalance  the  entire  shaft. 

Cooung  WVre« 




Fig.  54. — Chandler  six-cylinder  engine. 

4/  'b 

Fig.  55. — Three-bearing,  four-cylinder  crankshaft. 

The  conventional  four-cylinder  crankshaft  has  three  main  bearings 
as  in  Fig.  55.  The  center  bearing  does  away  with  the  tendency  of  the 
shaft  to  spring.     In  some  cases,  as  in  Fig.  56,  only  two  main  bearings 


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are  used.  The  crankshafts  are  made  in  one  piece,  although  when  it  is 
desired  to  use  ball  bearings  on  the  crank  and  main  bearings,  the  shaft  is 
built  up.     This  practice,  however,  is  rare. 

48,  Six-cylinder  Crankshafts. — There  are  two  ways  in  which  cranks 
on  a  six-cylinder  crankshaft  are  arranged.  The  sketches  in  Fig.  58  show 
this  essential  difference.  Starting  with  crank  1  up,  as  shown,  crank 
2  may  be  either  120°  to  the  right  or  left.  Crank  3  is  then  120°  beyond 
crank  2.     In  either  case,  cranks  1  and  6,  2  and  5,  3  and  4  are  in  the  same 


Flo.  56. — Four-cylinder  counterbalanced  crankshaft. 

plane  and  in  similar  positions.  A  crankshaft  is  either  right  or  left,  de- 
pending upon  whether  cranks  3  and  4  are  120°  to  the  right  or  left  of  cranks 
1  and  6,  when  the  latter  af  e  vertical.  Figure  58-4  represents  a  right  crank 
and  Fig.  582?  a  left  crank,  the  flywheel  being  at  the  far  end  of  the  shaft. 
As  each  cylinder  fires  once  in  two  revolutions  of  the  crankshaft,  there 
are,  consequently,  three  explosions  per  revolution  or  one  every  one-third 
revolution  of  a  six-cylinder  crank. 

Ordinarily,  a  six-cylinder  crankshaft  has  three  main  bearings  as  in 
Fig.  59.     In  some  cases,  four  main  bearings,  as  shown  in  Fig.  60,  may  be 


Fig.  57. — Counterbalance  weights  on  a  four-cylinder  crankshaft. 

used,  or  seven  as  in  the  case  of  the  Hall-Scott  airplane  engine,  the  crank- 
shaft of  which  is  illustrated  in  Fig.  61.  Only  in  rare  cases  has  a  six- 
cylinder  crank  been  constructed  with  two  main  bearings.  Without 
one  or  more  center  bearings  the  shaft  would  spring  unless  it  were  made 
unusually  heavy  and  strong. 

The  six-cylinder  crankshaft,  on  account  of  the  number  and  arrange- 
ment of  the  cranks,  is  naturally  much  better  balanced  than  a  four- 
cylinder  crankshaft.     The  power  impulses  come  oftener;  consequently, 

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l?e    \ 


e*5  5*4 


3*4  2+S  8 

Flo.  58. — Methods  of  crank  arrangement  for  six-cylinder  engine. 

Flo.  69. — Chandler  six-cylinder  crankshaft  with  three  main  bearings. 

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the  unbalanced  forces  are  not  so  evident.  By  the  proper  distribution  of 
the  weight,  it  is  possible  to  give  a  fairly  well  balanced  crankshaft  without 
the  addition  of  counterbalance  weights. 

The  crank  shown  in  Fig.  59  is  a  right  crank  while  that  in  Fig.  61  is  a 
left  crank.  The  only  essential  difference  is  that  in  one  case  the  flywheel 
is  on  one  end  of  the  crank,  while  in  the  other  it  is  placed  on  the  opposite 







Shaft  sbar 


Fio.  60. — Four-bearing,  six-cylinder  crankshaft. 

end.  The  crank  arrangement  determines  the  order  in  which  the  cylinder 
can  fire;  assuming  that  the  direction  of  rotation  is  the  same  in  each  case. 
Referring  to  Fig.  58 A,  the  crank  arrangements  for  the  crank  of  Fig.  59 
are  seen.  Obviously,  pistons  1  and  6,  2  and  5,  and  3  and  4  will  be  in  the 
same  respective  positions  in  their  cylinders  at  the  same  time.  If  pistons 
1,  2,  or  3  are  on  the  suction  stroke,  then  pistons  6,  5,  or  4  will  be  on  the 

Fio.  61. — Hall-Scott  crank  case  with  seven  main  bearings. 

expansion  stroke.  If  i,  2,  or  3  are  on  the  compression,  then  6,  5,  or  4 
will  be  on  the  exhaust.  It  is  also  evident  that  the  cylinders  can  fire  only 
in  certain  definite  orders.  For  instance,  the  right  crank  in  Fig.  5SA 
might  fire  1,  5,  3,  6,  2,  4,  or  1,  2,  3,  6,  5,  4,  or  1,  5,  4,  6,  2,  3,  or  1,  2,  4„6, 
5,  3.  The  first  order  given,  1,  5,  3,  6,  2,  4,  is  the  b^st  and  most  usual 
firing  order,  because  the  power  impulses  are  better  distributed  along  the 

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The  left  crank,  Fig.  58B,  corresponds  to  the  crank  positions  shown  in 
Fig.  61.  The  firing  order  might  be  1,  3,  5,  6,  4,  2,  or  1,  4,  5,  6, 3, 2,  or 
1,  3,  2,  6, 4, 5,  or  1, 4, 2, 6, 3, 5.  The  last  order,  1, 4, 2, 6, 3, 5,  is  the  best 
order  for  the  reason  given  above. 

49.  Camshafts. — In  Figs.  62  and  63  are  illustrated  the  two  general 
methods  of  camshaft  construction.  Figure  62  is  a  one-piece  camshaft, 
the  cams  and  shaft  being  made  of  one  solid  bar  of  steel.  This  is  the  more 
common  method  of  construction.  The  assembled  camshaft,  Fig.  63,  on 
which  the  individual  cams  are  pinned  or  keyed,  is  used  at  present  in  very 

Fio.  62. — One-piece  camshaft. 

few  cases.  The  objection  to  this  type  of  shaft  is  that  the  cams  may 
become  loose  on  the  shaft  and  give  considerable  trouble.  It  has  the 
advantage  that  the  cams  can  be  replaced  after  considerable  wear.  For 
an  L-head  engine,  a  single  camshaft  on  one  side  of  the  engine  carries  both 
inlet  and  exhaust  cams.  For  a  T-head  engine,  however,  one  camshaft 
carries  the  inlet  cams  on  one  side  of  the  engine  and  another  shaft  carries 
the  exhaust  cams  on  the  other  side. 

The  camshafts  are  driven  at  one-half  crankshaft  speed.     The  drive 
may  be  either  by  a  silent  chain,  such  as  shown  on  the  Chandler,  Fig.  54, 

Assembled  camshaft. 

by  spur  gears,  such  as  on  the  Ford,  Fig.  41,  or  by  helical  gears,  such  as  on 
the  Case  engine  shown  in  Fig.  47. 

60.  Eight-  and  Twelve-cylinder  Power  Plants. — In  the  four-cylinder 
engine  there  is  a  power  impulse  every  one-half  revolution,  but  during  a 
small  interval  at  the  end  of  each  power  stroke,  no  power  is  being  delivered 
by  the  engine.  This  means  short  periods  in  the  operation  of  the  engine 
in  which  the  flywheel  must  supply  all  the  power.  In  the  six-cylinder 
engine,  there  is  a  power  stroke  every  one-third  revolution  and,  as  a  result, 

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there  is  an  overlapping  and  a  more  continuous  flow  of  power,  Fig.  39. 
The  power  impulses  come  oftener  and,  consequently,  the  vibration  is 
reduced.  The  same  effect  is  carried  further  in  the  eight-cylinder  engine 
which  gives  a  power  stroke  every  one-fourth  revolution  and  in  the  twelve- 
cylinder  engine  where  the  power  strokes  come  one-sixth  of  a  revolution 
apart.  The  parts  are  considerably  lighter  and  this  aids  in  reducing  the 
vibration.  The  eight-  and  twelve-cylinder  engines  are  built  in  the  V-type. 
This  method  of  construction  adds  to  the  smoothness  of  operation. 

51.  Cadillac  Eight-cylinder  Engine. — Figure  64  is  a  front  end  view 
of  the  Cadillac  eight-cylinder  engine.  The  cylinders  are  arranged  in 
blocks  of  four  each,  placed  in  a  V-shape  at  an  angle  of  90°.     A  cross 

Pio.  64. — Cadillac  eight-cylinder  engine.  r 

section  of  two  opposite  cylinders  is  shown  in  Fig.  65.  The  engine  is  of 
the  L-head  type  with  the  valves  on  the  inside  of  the  V.  The  cylinder 
heads  are  removable,  permitting  access  to  the  valves.  One  camshaft 
placed  directly  above  the  crankshaft  operates  all  of  the  sixteen  valves 
by  means  of  the  rockers  as  shown.  Eight  cams  serve  to  operate  the  six- 
teen valves,  as  one  cam  operates  a  valve  in  each  cylinder  block.  The 
camshaft  is  carried  by  five  bearings  and  has  a  silent  chain  drive  as  shown 
in  Fig.  64. 

The  crankshaft  is  like  a  conventional  four-cylinder  shaft  with  three 
main  bearings.  There  are  only  four  crank  pins,  and  two  connecting  rods, 
one  from  each  side  of  the  engine,  bearing  on  the  same  crank,  Fig.  66. 

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One  of  the  rods,  Fig.  67,  is  forked,  while  the  other  is  perfectly  straight, 
fitting  in  between  the  forks  of  the  other.    The  split  bearing  shown  at  the 




Fia.  65. — Sectional  view  of  Cadillac  eight-cylinder  engine. 

right  fits  directly  over  the  pin.     The  forked  rod  fits  over  this  bearing 
and  is  pinned  to  it  so  that  the  rod  and  bearing  work  together.     The  other 

Fig.  66. — Cadillac  crankshaft,  piston,  and  connecting  rod  assembly. 

rod  fits  over  the  center  surface  of  the  bearing  and  runs  on  it.     This 
arrangement  permits  the  length  of  the  crankshaft  to  be  no  greater  than 

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in  a  four-cylinder  engine.  On  some  eight-cylinder  engines,  one  cylinder 
block  is  sometimes  set  ahead  of  the  other  so  that  the  connecting  rods 
from  opposite  cylinders  can  turn  side  by  side  on  the  same  crank  pin. 

Fiq.  67. — A  pair  of  Cadillac  connecting  rods. 

The  horse  power  rating  of  the  Cadillac  eight  is  31.25  according  to  the 
S.A.E.  formula.  On  dynamometer  test,  however,  it  has  developed  70 
horse  power  at  a  speed  of  2400  r.p.m. 

52.  The  Oldsmobile  Eight-cylinder  Engine. — The  cylinder  block 
castings  of  the  Oldsmobile  eight-cylinder  engine  are  shown  in  Fig.  68. 

Fio.  68. — Cylinder  blocks  of  Oldsmobile  eight-cylinder  engine. 

The  cylinder  heads  are  cast  separately  and  made  removable  for  inspec- 
tion of  the  valves  and  the  inside  of  the  cylinders.  The  two  cylinder 
blocks  are  clamped  together  by  bolts,  giving  a  very  compact  and  sturdy 
construction.     The  connecting  rods,  Fig.  69,  are  arranged  in  pairs,  one 

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rod  of  each  pair  being  straight  and  the  other  forked  as  shown.  Both 
rods  fit  on  the  bearing  shown.  This  bearing  is  of  bronze,  lined  on  the 
inside  with  babbitt.  The  crankshaft  is  of  the  four-cylinder  type  with 
only  two  main  bearings. 

Fio.  69. — Oldsmobile  connecting  rods  and  crankshaft. 

63.  King  Eight-cylinder  Engine. — In  the  King  eight-cylinder  engine, 
Figs.  70  and  71,  the  cylinder  blocks  are  staggered,  the  left  block  being 
slightly  ahead  of  the  right  one  so  as  to  permit  the  use  of  straight  connect- 

Fia.  70. — King  eight-cylinder  engine. 

ing  rods,  turning  side  by  side  on  the  same  crank  pin  as  indicated.  The 
cylinder  and  heads  are  cast  in  one  piece,  caps  being  provided  for  removing 
the  valves,  which  are  inclined  to  the  cylinder  as  indicated.    The  sixteen 

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valves  are  operated  by  a  single  camshaft  driven  by  a  silent  chain.  The 
camshaft  is  of  the  solid  type  with  the  sixteen  cams  integral  with  the  shaft. 
The  crankshaft  has  three  main  bearings  which  are  unusually  long.  It 
is  hollow  so  as  to  provide  forced  lubrication  to  all  crank  and  main  bearings. 
54.  Knight  Eight-cylinder  Engine. — The  Knight  engine  is  also  built 
in  the  eight-cylinder  type  as  shown  in  Fig.  72.  The  sliding  sleeves  are 
operated  by  small  connecting  rods  which  turn  on  a  small  crank  or  cam- 
shaft. The  use  of  the  sliding  sleeves  gives  the  advantages  of  a  valve  in 
the  head  motor,  at  the  same  time  using  eight  cylinders.  The  intake 
parts  are  inside  of  the  V,  and  the  exhaust  parts  on  the  outside  lead  to 
separate  exhaust  pipes.     The  combination  of  the  sliding  sleeves  and  the 

Fiq.  71. — Sectioned  view  of  King  eight-cylinder  engine. 

eight  cylinders  gives  an  exceptionally  smooth  running  engine  with  very 
little  vibration. 

55.  Firing  Order  of  Eight-cylinder  Engines. — The  cylinders  of  an 
eight-cylinder  engine  are  generally  numbered  as  shown  in  Fig.  73,  the 
right  and  left  blocks  being  numbered  from  the  radiator  to  the  back.  The 
possible  firing  orders  of  each  block  are  the  same  as  in  a  four-cylinder 
engine.  It  will  be  noticed  that  on  account  of  the  cylinder  blocks  being 
placed  at  an  angle  of  90°,  that  when  the  pistons  of  cylinders  XL  and  AL 
are  at  the  top  of  the  stroke,  pistons  2L  and  3L  are  at  the  bottom  of  the 
stroke  and  all  the  pistons  of  the  right  block  are  at  the  middle  of  the 
stroke,  two  of  them  moving  towards  the  top  and  the  other  two  towards 
the  bottom.    This  means  that  the  power  impulses  will  be  90°  apart,  and 

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that  the  firing  will  alternate  from  one  side  to  the  other.     Although  it  is 
possible  to  have  four  firing  orders  for  an  eight-cylinder  engine,  two  of  these 

Fig.  72. — Eight-cylinder  Knight  type  engine. 

|  RADIATOR      |  |     RAPIATO^H    I    RADIATOR  1  I    RADIATOR"! 
LEFT  *1«HT         UfT  ftl«riV         LIFT  gjgHT         LEFT  RIGHT 

































A  B  C  D 

Fio.  73. — Methods  of  numbering  the  cylinders  on  an  eight-cylinder  engine. 

are  practically  never  used.     Both  cylinder  blocks  usually  fire  in  the 
1, 3, 4,  2  order  or  the  1,  2,  4,  3  order.    If  in  the  1,  3,  4, 2  order,  the  firing 

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order  for  the  engine  is  1L,  2ft,  3L,  lft,  4L,  3ft,  2L,  4ft,  as  shown  on  Fig. 
73 A.  If  the  1,  2,  4,  3  order  is  used  the  engine  fires  LL,  3ft,  2L,  lft, 4L, 
2ft,  3L,  4ft,  as  on  Fig.  734. 

The  system  of  numbering  the  cylinders  is  not  always  as  shown  in 
Fig.  73ii.  The  cylinders  may  be  numbered  in  the  order  of  firing  as  on 
the  Cadillac,  Fig.  73B,  or  as  on  the  Cole  car,  Fig.  73C,  where  the  cylinders 
are  numbered  1,  2,  3,  4,  on  the  right  side,  beginning  at  the  radiator,  and 
5,  6,  7,  8,  on  the  left  side,  also  beginning  at  the  radiator.  The  order  of 
firing  on  the  Cadillac  corresponds  to  the  order  previously  given,  LL,  2R, 
3L,  lft,  4L,  3ft,  2L,  4ft.  The  firing  order  on  the  Cole  is  1,  8,  3,  6,  4,  5,  2, 
7,  as  in  Fig.  73C,  which  is  the  same  order  as  on  the  Cadillac.  The  num- 
bering and  order  of  firing  on  the  Oldsmobile,  and  King  eight  are  the  same 
as  on  the  Cole  car,  Fig.  73C 

66.  Determining  Firing  Order  of  Eight-cylinder  Engine. — If  it  be- 
comes necessary  to  determine  the  firing  order  of  an  eight-cylinder  engine, 
it  can  be  easily  done  by  assuming  that  the  cylinders  are  numbered  as  in- 
dicated in  Fig.  73D.  The  firing  order  for  the  right  block  is  determined 
by  cranking  the  engine  so  that  cylinder  No.  1  is  on  compression.  By 
further  cranking  it  can  be  determined  whether  cylinder  No.  2  or  cylinder 
No.  3  is  next  on  compression.  If  No.  1  is  followed  by  No.  2,  the  firing 
order  for  the  block  will  be  1, 2, 4,  3;  if  No.  1  is  followed  by  No.  3,  the  order 
will  be  1,  3,  4,  2.  The  firing  order  of  the  engine  can  then  be  determined 
by  starting  with  right  cylinder  No.  1,  following  this  with  the  left  cylinder 
No.  1,  and  then  by  ft2,  L2,  ft4,  L4,  ft3,  L3,  if  the  firing  order  of  the  block 
is  1,  2,  4,  3.  If  the  firing  order  of  the  block  is  1,  3,  4,  2,  then  the  order 
for  the  engine  will  be  ftl,  LI,  ft3,  L3,  ft4,  L4,  ft2,  L2. 

67.  Packard  Twelve-cylinder  Engine. — The  twelve-cylinder  engine 
used  on  the  Packard  car  is  shown  in  Figs.  74  and  75.  The  twelve  cylinders 
are  cast  in  two  blocks  of  six  each,  arranged  in  a  V  with  an  included  angle 
of  60°.  The  left  block  of  cylinders  is  set  ahead  of  the  right  one  by  1J£  in. 
in  order  to  permit  the  lower  end  of  the  connecting  rods  of  opposing  cylin- 
ders to  be  placed  side  by  side  on  the  same  crank  pin.  This  arrangement 
permits  the  use  of  a  single  camshaft  with  a  separate  cam  for  each  valve, 
making  24  cams  on  the  camshaft.  A  silent  chain  drives  the  camshaft 
which  is  placed  directly  above  the  crankshaft.  The  cylinders  are  3-in. 
bore  by  5-in.  stroke  with  L-head  valve  arrangement.  The  exhaust  mani- 
folds from  the  two  blocks  are  joined  near  the  rear  of  the  engine,  and  the 
exhaust  gases  are  led  to  the  muffler  placed  along  the  left  side  of  the 
frame.  The  crankshaft  is'  of  the  conventional  six-cylinder  type  with 
three  main  bearings.  The  engine  is  built  into  a  single  unit  with  the  clutch 
and  transmission. 

68.  National  Twelve-cylinder  Engine. — On  the  National  twelve-cyl- 
inder engine,  Fig.  76,  the  valves  are  placed  on  the  outside  of  the  V  instead 

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Fia.  74. — Packard  twelve-cylinder  engine. 

J^^^^                                                                          _^t^ 


3f                      ^fl    mmam 

/  fmT 

Will*  it 


mm       ml'  i  m    3 

Flo.  75. — Packard  twelve-cylinder  engine  in  car. 

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of  on  the  inside.  The  cylinders  are  set  exactly  opposite,  forked  connect- 
ing rod  ends  permitting  both  rods  to  bear  on  the  one  crank  pin.  The 
cylinder  heads  are  made  removable,  permitting  easy  access  to  the  cylinder 
and  valves.  A  separate  camshaft  is  provided  for  each  cylinder  block 
with  a  separate  cam  for  each  valve.  The  intake  manifolds  are  sur- 
rounded by  the  hot  water  connection  at  the  top  of  the  cylinders.  The 
intake  passages  leading  to  the  valves  are  cast  integral  with  the  cylinders. 
Each  set  of  cylinders  has  its  own  exhaust  manifold  pipe  and  muffler. 

Fio.  76. — Details  of  construction  on  National  twelve-cylinder  engine. 

The  crankshaft  is  of  the  conventional  six-cylinder  type  with  three  main 
bearings.  The  cylinders  are  2%-in.  bore  by  4%-in.  stroke  with  a  total 
piston  displacement  of  370  cu.  in.  The  horse  power  according  to  the 
S.A.E.  formula  is  39.7  but  on  dynamometer  test  77  horse  power  have 
been  delivered. 

69.  Pathfinder  Twelve-cylinder  Engine. — The  Pathfinder  twelve-cyl- 
inder engine,  Fig.  77,  has  its  cylinders  cast  in  blocks  of  three  instead  of 
six  as  is  customary.  The  head  for  each  side  of  the  engine  is  cast  in  one 
piece  with  the  intake  manifold  and  water  outlet  integral  for  each  set  of 

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six  cylinders.  The  right  set  of  cylinders  is  placed  1  J£  in.  ahead  of  the 
left  on  account  of  the  connecting  rods.  The  valves  are  placed  in  the 
head  and  are  operated  through  rocker  arms  at  the  top  of  the  motor  head. 
One  camshaft  placed  above  the  crankshaft  serves  all  of  the  24  valves. 
The  motor  is  built  as  a  unit  with  the  clutch  and  transmission  and  has 
three  point  suspension. 

Fiq.  77. — Twelve-cylinder  engine  in  Pathfinder. 

60.  Firing  Order  of  Twelve-cylinder  Engines. — The  several  methods 
of  numbering  the  cylinders  on  a  twelve-cylinder  engine  are  shown  in 
Fig.  78.  The  firing  order  in  each  block  is  similar  to  that  in  a  six-cylinder 
engine  and  is  usually  1,  5,  3,  6,  2,  4  or  1,  4,  2,  6,  3,  5  with  the  cylinders 
numbered  as  iu  Fig.  78-4,  the  impulses  alternating  from  one  side  to 

On  the  Packard  engine,  numbered  as  in  Fig.  78-4,  the  firing  order  is 
1R,  6L,  4i2,  3L,  2R,  5L,  QR,  LL,  3#,  4L,  5#,  2L,  corresponding  to  a  firing 
order  for  each  block  of  1,  4,  2,  6,  3,  5.    On  the  Pathfinder,  numbered  as 

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in  Fig.  78C,  the  firing  order  is  1/J,  1L,  4iJ,  4L,  2/2,  2L,  6/2,  6L,  3/2,  3L, 
5/2,  5L.    This  is  the  same  order  as  is  used  on  the  Packard. 

With  cylinders  numbered  as  in  Fig.  785,  the  order  of  firing  for  the 
National  twelve  is  1,  12,  9,  4-,  5,  8,  11,  2,  3,  10,  7,  6.  This  corresponds 
to  an  order  of  1,  5,  3,  6,  2,  4,  for  each  block  numbered  as  in  Fig.  78 A.' 













































Fiq.  78. — Numbering  of  cylinders  on  twelve-cylinder  engines. 

A  power  impulse  comes  every  60°  or  %  revolution  of  the  crankshaft. 
Two  and  sometimes  three  power  impulses  are  effective  on  the  crankshaft 
at  the  same  time,  thus  insuring  a  steady  flow  of  power  from  the  engine. 

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One  of  the  most  important  operations  in  a  gas  engine  is  that  of  get- 
ting an  explosive  charge  inside  of  the  engine  cylinders  at  the  proper 
time.  This  explosive  mixture  is  formed  by  the  thorough  mixing  of  air 
and  a  gas  formed  by  the  evaporation  of  a  volatile  liquid  fuel,  usually 
gasoline.  The  process  of  vaporizing  the  liquid  fuel  and  mixing  it  with 
the  proper  amount  of  air  is  called  carburetion,  and  the  device  for  doing 
this  is  called  a  carburetor. 

61.  Hydrocarbon  Oils. — Most  of  the  liquid  fuels  are  known  as  hydro- 
carbon  oils  because  they  come  from  crude  mineral  oil  containing  as  its 
principal  parts,  hydrogen  and  carbon.  Crude  oil  contains  about  85  per 
cent,  carbon  and  15  per  cent,  hydrogen  by  weight.  One  of  the  hydro- 
carbon fuels,  viz.,  alcohol,  is  not  of  mineral  derivation,  but  is  made  by 
the  distillation  of  vegetable  matter. 

The  crude  oil  or  petroleum  from  which  the  hydrocarbon  fuels  are 
made  is  found  in  natural  deposits  several  hundred  feet  below  the  surface 
of  the  earth.  In  some  places  it  is  necessary  to  pump  the  oil  out,  while 
in  others  it  is  forced  out  by  natural  gas  pressure.  Most  of  the  crude  oils 
found  in  the  United  States  comes  from  Pennsylvania,  Ohio,  Illinois,  Kan- 
sas, Texas,  Oklahoma,  and  California.  These  crude  oils  are  of  two  gen- 
eral types,  that  coming  from  Texas,  Oklahoma,  and  California  having 
what  is  known  as  an  asphalt  base,  and  that  from  Pennsylvania  and  Ohio 
having  a  paraffin  base.  Crude  oil  having  an  asphalt  base  is  a  heavy, 
dark  liquid,  which,  when  distilled,  leaves  a  black,  tarry  residue.  Crude 
oil  having  a  paraffin  base  is  much  lighter  in  weight  and  color  and,  when 
distilled,  leaves  a  residue  from  which  is  made  the  white  paraffin  or  wax 
with  which  everyone  is  familiar.  Gasoline  made  from  crude  oil  with  a 
paraffin  base  was  formerly  supposed  to  be  of  a  higher  grade  than  that 
from  an  asphalt  base,  but  with  the  modern  processes  of  refining,  the  gaso- 
line from  either  kind  of  crude  oil  gives  equally  good  results. 

62.  Refining  of  Petroleum. — The  crude  oil  or  petroleum  is  heated  in 
large  retorts  or  stills,  provided  with  accurate  temperature  recording 
devices.  A  typical  refining  still  is  shown  in  Fig.  79.  When  the  tempera- 
ture in  the  still  has  reached  about  100°F.  vapor  begins  to  rise  from  the 
oil.  This  vapor  is  collected  from  the  top  of  the  still  and  condensed  in 
cooling  coils,  from  which  the  liquid  is  collected  in  tanks.    As  the  tem- 

5  65 

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perature  in  the  still  rises,  the  vapor  becomes  heavier  and,  when  con- 
densed, forms  the  heavier  and  less  volatile  liquids  which  are  collected 

Fig.  79. — Still  for  the  refining  of  crude  petroleum. 

in  other  tanks  as  illustrated.     The  following  table  gives,  approximately, 
the  products  of  this  method  of  distillation: 

Temperature  in  the  retort 

Kind  of  oil  after  condensing 
the  vapor 

Percentage  by  weight 

100°F.  to  125°F. 

125°F.  to  350°F. 

Over  360°F. 

Gasoline  distillate  (Highly 
volatile  oils,  as  gasoline, 
benzine,  and  naphtha) 

Illuminating  oil  distillate 
(Kerosene  and  light  lubri- 
cating oils) 

Gas  oil  and  lubricating  dis- 

(Heavy  oils,  paraffin  wax, 
and  residue) 

10  to  15  per  cent. 

65  to  75  per  cent. 

15  to  20  per  cent. 

It  will  be  noticed  that  there  is  from  three  to  five  times  as  much  kerosene 
and  light  lubricating  oils  produced  as  there  is  gasoline.  This  part  of  the 
refining  process  is  called  separation  into  groups  because  the  more  volatile 
portions  of  the  crude  oil  are  separated  from  the  less  volatile  portions. 
The  light  or  more  volatile  portions,  like  gasoline,  vaporize  very  easily 
but  the  less  volatile  and  heavy  portions  are  vaporized  with  difficulty. 
As  can  be  seen,  these  several  portions  are  grouped  according  to  beginning 
and  end  boiling  points.  The  groups  from  which  gasoline  is  made  are 
the  gasoline  distillate  and  illuminating  oil  distillate. 

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These  two  groups  are  then  redistilled,  as  shown  in  Fig.  80.  The 
gasoline  distillate  or  crude  gasoline,  after  being  treated  in  the  agitator, 
goes  into  a  steam  still  where  it  is  divided  into  the  various  grades  of 
gasoline  having  different  boiling  points  and  volatility. 

63.  Gasoline. — Gasoline,  as  used  for  automobiles,  is  a  physical 
mixture  of  hydrocarbon  oils  which  can  be  vaporized  to  form  an  explosive 
mixture.  Gasoline  is  classified  either  as  straight-run,  cracked,  or  casing- 
head,  according  to  the  method  by  which  it  is  obtained.  Straight-run 
gasoline  is  the  first  product  of  distillation  of  the  crude  oil.  It  is  distilled 
between  the  boiling  points  of  approximately  100°F.  and  125°F.  Casing- 
head  gasoline  is  made  by  compressing  and  liquefying  certain  gases  coming 
from  oil  wells.  The  liquid  is  then  distilled  under  pressure  giving  very 
light  and  volatile  gasoline  which  is  usually  mixed  or  blended  with  that 
of  another  quality  for  market   purposes.     The   casing-head  gasoline 

Fio.  80. — Redistilling  of  crude  gasoline  into  various  grades. 

is  hardly  ever  used  as  it  comes  from  the  still  because,  on  account  of 
its  volatility,  too  much  of  it  evaporates  in  handling.  Cracked  gasoline 
is  that  made  by  breaking  up  or  cracking  the  high  boiling  point  prod- 
ucts obtained  by  the  first  distillation  of  the  crude  oil.  The  cracking 
is  done  by  redistilling  under  heat  and  pressure.  The  Burton  process 
used  by  the  Standard  Oil  Company  and  the  Ritmann  process  are  both 
cracking  processes.  A  large  proportion  of  market  gasoline  consists  of 
mixtures  or  blends  of  the  above  qualities  of  gasoline.  The  blending 
is  done  so  as  to  insure  vaporization  in  the  carburetor.  The  blends  are 
usually  about  equal  in  fuel  value  and  are  usually  heavier  and  less  volatile 
in  summer  than  in  winter. 

Gasoline  satisfactory  for  automobile  use  should  be  volatile  enough 
so  that  the  engine  can  be  easily  started  under  ordinary  conditions. 
This  means  that  if  the  gasoline  is  blended  it  should  contain  some  low 
boiling  point  product  which  will  vaporize  first  for  starting  purposes. 

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If  the  blend  contains  very  heavy  products  with  high  boiling  points,  it 
is  possible  that  it  may  not  even  vaporize  in  the  engine  cylinder  but 
will  be  partially  burned  leaving  an  excessive  carbon  deposit.  It  is, 
therefore,  desirable  to  have  the  initial  and  end  boiling  points  of  the 
gasoline  or  gasoline '  blend  as  low  as  possible.  Less  trouble  is  usually 
found  with  straight-run  gasoline  than  with  the  blended  fuel,  but  in  order 
to  conserve  the  straight-run,  which  is  limited  in  quantity,  it  is  usually 
blended  with  low  volatile  gasoline. 

64.  Principles  of  Vaporization. — Before  an  explosive  mixture  can  be 
formed,  the  liquid  fuel  must  first  be  atomized  or  vaporized  and  then 
mixed  with  the  proper  amount  of  air  to  burn  it.  As  we  know,  it  requires 
heat  to  change  water  into  steam  or  vapor.  If  the  water  is  out  in  the 
open,  it  will  evaporate  rapidly,  or  boil  if  heated  to  a  temperature  of 
212°F.  Likewise,  in  order  to  change  a  liquid  fuel  into  a  gas  or  a  vapor, 
it  is  necessary  that  heat  be  added  to  it,  but  the  temperature  at  which 
this  heat  must  be  added  is  different  for  different  fuels.  For  instance, 
gasoline  will  evaporate  under  the  usual  atmospheric  pressure  and  tem- 
perature, and  will,  in  some  cases,  evaporate  at  lower  temperatures. 
This  can  be  tested  by  exposing  a  dish  of  gasoline  to  the  air.  In  a  short 
time,  the  liquid  will  have  evaporated.  That  heat  has  been  absorbed 
can  be  verified  by  feeling  the  dish  before  it  is  filled  and  again  after 
evaporation  has  been  taking  place.  Consequently,  we  see  that  heat  is 
necessary  before  a  liquid  fuel  can  be  vaporized. 

Kerosene  and  alcohol,  on  the  other  hand,  will  not  evaporate  until 
heat  is  added  from  an  external  source  at  a  higher  temperature,  the 
same  as  is  done  when  steam  is  made  from  water.  This  explains  the 
difficulty  of  evaporating  these  fuels  for  use  in  a  gas  engine. 

From  the  above  considerations,  some  general  principles  of  vaporiza- 
tion cau  be  stated : 

1.  The  heavier  a  liquid  and  the  higher  its  boiling  point,  the  harder 
it  will  be  to  vaporize;  for  example,  kerosene  as  compared  with  gasoline. 

2.  A  liquid  fuel  will  vaporize  easier  and  faster  under  suction,  or 
reduction  of  pressure,  than  under  pressure;  for  example,  gasoline  is  more 
difficult  to  vaporize  at  low  than  at  high  altitudes. 

3.  The  closer  the  temperature  of  a  liquid  fuel  is  to  its  boiling  point, 
the  easier  and  faster  it  will  vaporize;  for  example,  gasoline  will  vaporize 
more  readily  in  summer  than  in  winter. 

66.  Testing  Gasoline. — Gasoline  is  usually  spoken  of  as  high  or 
low  test.  By  reference  to  the  principles  of  vaporization,  we  see  that 
the  heavier  a  liquid,  the  more  difficult  it  is  to  evaporate.  This  prin- 
ciple explains  the  basis  of  the  Baume  test.  A  hydrometer  such  as  shown 
in  Fig.  81  is  graduated  in  degrees,  the  numbers  reading  from  the  bottom 
up.    These  degrees  have  nothing  to  do  with  the  thermometer  degrees, 

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but  are  named  after  Baumg,  who  originated  the  idea.  When  the  hydrom- 
eter is  placed  in  a  quantity  of  gasoline,  it  will  sink  to  a  depth  corre- 
sponding to  the  density  of  the  liquid.  It  will  sink  deeper  in  a  light 
gasoline  than  in  a  heavy  one.  The  deeper  the  hydrometer  sinks,  the 
higher  the  scale  reading  will  be.  This  scale,  usually  reading  from  45° 
to  95°  Baum6,  indicates  in  a  very  indirect  way  the  ease  and  rapidity  with 
which  the  gasoline  or  fuel  will  evaporate.  It  is  not  a  direct  nor  an 
absolute  test  unless  the  exact  nature  and  the  boiling  points  of  the  gaso- 
line are  known.  For  most  pur- 
poses, it  serves  as  a  guide  as  to  the 
way  the  gasoline  will  act  in  service. ' 

The  commercial  gasoline  of  to- 
day has  a  Baum6  test  of  from 
56°  to  65°,  the  high  test  being 
in  the  neighborhood  of  65°  and 
the  low  test  in  the  neighborhood 
of  66°.  For  summer  use,  the  low 
test  or  heavier  gasoline  can  be 
used  because  it  will  evaporate  with 
comparative  ease  at  the  usual 
summer  temperatures,  but  for 
winter  use  the  high  test  or  light 
gasoline  is  to  be  preferred  because 
it  will  evaporate  more  easily  at  the 
low  temperatures. 

Occasionally,  a  low  grade,  im- 
pure gasoline  is  sold  which  lacks 
sufficient  refinement  and  purifica- 
tion, the  sulphur  and  other  impuri- 
ties not  having  been  eliminated. 
The  use  of  this  may  result  in  car- 
bon deposits  in  the  cylinders.  A 
gasoline  that  readily  carbonizes 
should  be  avoided  and  a  higher 
grade  used.     A  simple  test  can  be 

made  by  burning  some  of  the  gasoline  in  a  porcelain  dish  or  crucible. 
If  the  residue  is  slight,  with  practically  no  deposit  on  the  bottom,  the 
gasoline  is  comparatively  good.  If  the  residue  is  of  a  heavy  black 
nature,  the  gasoline  is  of  low  quality  and  will  not  give  satisfactory  service. 

The  best  tests  for  practical  purposes  can  be  determined  from  the 
service  of  the  car.  With  proper  carburetor  adjustments,  the  engine 
should  start  easily,  should  give  a  maximum  number  of  miles  per  gallon, 


Kerosene  Gasoline 

81. — Baume  hydrometer  in  kerosene 
and  gasoline. 

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and  should  leave  the  cylinders  comparatively  free  from  carbon  deposits. 
No  gasoline  should  be  found  in  the  lubricating  oil  of  the  crank  case. 

66.  Kerosene  and  Alcohol. — Kerosene  and  alcohol  are  not  used  to 
any  great  extent  in  automobiles  on  account  of  the  fact  that  both  are 
extremely  hard  to  vaporize.  Several  more  or  less  successful  devices  have 
been  tried  for  using  kerosene,  but  the  varying  speed&and  loads  of  the 
automobile  engine  make  the  problem  of  controlling  the  heat  very  difficult. 
The  price  of  gasoline  and  the  prospects  for  a  greater  increase  in  the 
supply  make  it  unlikely  that  any  great  development  in  the  use  of  kerosene 
or  alcohol  will  take  place.  Consequently,  the  discussion  will  deal  only 
with  gasoline  and  its  vaporization. 

67.  Heating  Value  of  Fuels. — The  heating  value,  or  the  amount  of 
heat  energy  contained  in  a  liquid  fuel,  is  given  in  British  thermal  units 
per  pound;  a  British  thermal  unit,  or  a  B.t.u., being  the  quantity  of  heat 
energy  required  to  raise  the  temperature  of  1  lb.  of  water  1°  on  the  Fahren- 
heit scale.  The  following  table  gives  the  heating  values  of  the  common 

Gasoline 18,000  to  19,500  B.t.u.  per  pound. 

Kerosene  about 20,000  B.t.u.  per  pound. 

Alcohol  (grain)  about. .  10,000  B.t.u.  per  pound, 

(wood)  about. .  7,500  B.t.u.  per  pound. 

Inasmuch  as  the  heavier  fuel  contains  more  pounds  per  gallon,  and  as 
gasoline  and  kerosene  are  sold  by  the  gallon,  a  gallon  of  heavy  or  low 
test  gasoline  or  of  kerosene  contains  slightly  more  energy  than  a  gallon 
of  light,  or  high  test  gasoline. 

68.  Gasoline  and  Air  Mixtures. — It  is  necessary  when  gasoline  is 
vaporized  or  atomized  that  the  vapor  be  mixed  with  the  proper  amount  of 
air  to  form  an  explosive  mixture.  The  air  supplies  the  oxygen  necessary 
for  combustion.  If  too  little  air  is  furnished,  there  will  not  be  enough 
oxygen  to  burn  the  carbon  and  hydrogen  in  the  fuel,  and  the  fuel  will  be 
wasted  as  will  be  indicated  by  the  black  smoke  coming  from  the  exhaust. 
If  less  than  7  parts  by  weight  of  air  are  furnished  to  1  part  by  weight  of 
gasoline  the  mixture  will  not  be  combustible.  If  too  much  air  is  fur- 
nished, the  mixture  will  be  weak  in  fuel,  giving  a  very  slow  combustion. 
This  results  in  lost  power.  A  weak  mixture,  or  an  excess  of  air,  is  indi- 
cated by  back-firing  through  the  carburetor.  The  mixture  becomes 
non-combustible  if  more  than  20  parts  of  air  by  weight  are  furnished  to  1 
part  of  gasoline  by  weight.  On  an  average,  a  proportion  of  15  parts  of 
air  by  weight  to  1  part  of  gasoline  by  weight  will  give  the  best  results. 

The  burning  or  exploding  of  a  fuel  charge  of  the  proper  proportions 
gives  out  a  blue  color  such  as  is  found  in  the  flame  of  a  properly  adjusted 
gas  stove.  Too  much  air  gives  a  white  flame,  and  too  much  fuel  gives  a 
reddish  flame. 

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A  definite  mixture  of  gasoline  vapor  and  air  is  necessary  for  the  most 
efficient  operation  of  a  gasoline  engine.  The  function  of  the  carburetor 
is  to  take  the  gasoline,  vaporize  or  atomize  it,  and  furnish  the  proper 
mixture  of  vapor  and  air  to  the  cylinder  under  all  conditions  of  tempera- 
ture, speed,  load,  power,  and  varying  atmosphere. 

69.  Principles  of  Carburetor  Construction. — Most  of  the  modern  types 
of  carburetors  are  of  the  spray  or  nozzle  type,  in  which  a  jet  of  atomized 
gasoline  is  sprayed  from  a  nozzle  into  a  current  of  air  to  form  an  ex- 
plosive mixture.  Figure  82  illustrates  a  very  elementary  spray  or 
nozzle  type  carburetor.  The  gasoline  supply  tank  is  placed  below  the 
carburetor  and  the  gasoline  is  pumped  up  through  the  supply  pipe  to  the 
supply  chamber  C  The  overflow  pipe  maintains  the  level  of  the  liquid 
at  a  constant  height.    The  standpipe  or  nozzle  T  is  connected  with  the 

from  ptffTh 

F/oat  chamber 


to  tank 


A  PiP* 

Fig.  82.  Fio.  83. 

Figs.  82  and  83. — Elementary  types  of  carburetors. 

supply  chamber  C  by  means  of  the  connection  N,  the  flow  being  regulated 
by  the  needle  valve  S.  The  gasoline  level  in  the  standpipe  or  nozzle  T  is 
always  just  below  the  tip  or  end  of  the  nozzle.  The  flange  B  is  fastened 
to  the  intake  passage  of  the  engine.  With  the  intake  valve  open,  the 
suction  of  the  piston  causes  a  rapid  flow  of  air  through  the  air  opening  A 
upward  past  the  nozzle,  drawing  a  spray  of  gasoline  into  the  air.  The 
air  and  gasoline  vapor  form  the  explosive  mixture  for  the  engine  cylinder. 

The  butterfly  valve  D  in  the  air  passage  is  for  the  purpose  of  in- 
creasing the  suction  on  the  gasoline  in  the  nozzle  T  when  the  engine 
is  being  started  and  the  suction  is  low.  This  valve  should  then  be 
completely  or  partially  closed.  When  the  engine  is  running,  the  valve 
D  should  be  wide  open,  in  order  to  admit  sufficient  air  to  the  cylinders. 
This  valve  is  sometimes  called  the  choke  valve. 

The  gasoline  supply  is  regulated  by  adjusting  the  needle  valve  S. 
This  simple  type  of  carburetor  can  be  used  only  on  constant  speed 
engines,  the  reason  for  which  will  be  seen  later. 

Figure  83  shows  another  elementary  type  of  carburetor  which  illus- 

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trates  the  application  of  two  modern  ideas.  In  this  carburetor,  the  gaso- 
line supply  is  maintained  at  a  constant  level  in  the  supply  or  float  chamber 
by  means  of  a  hollow  metal  float  operating  a  ball  valve.  This  arrange- 
ment requires  that  the  gasoline  supply  tank  be  placed  above  the  carburetor 
or  that  some  other  means  be  provided  for  supplying  the  gasoline  to  the 
float  chamber.  It  will  also  be  noticed  that  the  passage  surrounding  the 
standpipe  or  spray  nozzle  is  contracted,  giving  the  inside  surface  a  convex 
shape.  This  is  the  application  of  the  well-known  Venturi  tube  principle. 
By  contracting  the  section  near  the  opening  of  the  nozzle  the  velocity 
of  the  air  and,  consequently,  the  suction  at  that  point  are  increased,  thus 
making  it  much  easier  for  the  gasoline  to  be  taken  up,  and  greatly  facili- 
tating the  starting  of  an  engine  when  the  suction  is  low. 

The  gasoline  needle  valve  is  placed  in  the  nozzle  and  the  flow  of  gaso- 
line is  regulated  from  below.  In  many  of  the  more  modern  carburetors 
this  needle  valve  is  adjusted  automatically,  opening  and  closing  accord- 
ing to  the  demand.    It  is  then  called  a  metering  pin. 

70.  Auxiliary  Air  Valves. — If  the  carburetor  in  Fig.  82,  or  the  one  in 
Fig.  83,  be  put  on  a  variable  speed  engine  such  as  used  on  an  automobile 
and  the  adjustment  made  by  regulating  the  needle  valve  so  that  the 
mixture  proportions  of  gasoline  and  air  are  correct  at  low  speed,  and 
the  engine  should  then  be  speeded  up,  black  smoke  would  come  from  the 
exhaust,  indicating  an  excess  of  gasoline  in  the  mixture.  This  would  be 
due  to  the  fact  that  under  the  increased  suction,  due  to  the  higher  speeds 
of  the  enginfe  and  piston,  the  air  drawn  in  past  the  gasoline  nozzle  expands 
and  increases  in  volume  and  velocity  faster  than  it  increases  in  weight. 
This  means  that  at  high  engine  speeds  and  under  the  consequent  increased 
suction,  too  much  gasoline  is  supplied  for  the  amount  of  air  drawn  in. 
In  order  to  keep  the  mixture  of  the  proper  proportions  at  all  speeds  of  the 
engine,  it  is  necessary  to  have  an  auxiliary  air  entrance  such  as  indicated 
at  X  in  Fig.  84  to  admit  an  additional  amount  of  air  at  the  higher  engine 
speeds,  or  some  other  method  of  automatically  regulating  the  proportion 
of  air  and  gasoline  must  be  provided.  This  auxiliary  air  entrance  is  usu- 
ally in  the  form  of  a  mushroom  valve  controlled  by  a  spring,  the  tension 
on  which  can  be  changed  to  control  its  opening  and  closing.  For  low 
speed  adjustments  the  gasoline  needle  valve  is  used,  and  for  high  speed 
adjustments  the  auxiliary  air  valve  is  used.  That  is,  when  the  engine  is 
running  at  low  speed,  the  air  is  taken  in  through  the  ordinary  air  opening 
A  shown  below  the  valve  in  Fig.  84.  The  mixture  is  then  proportioned 
by  regulating  the  gasoline  needle  valve  NV.  When  the  engine  speeds  up 
and  the  suction  is  increased,  the  auxiliary  air  valve  X  in  Fig.  84  comes 
into  action  and  by  opening  furnishes  more  air.  If  it  is  found  that  the 
mixture  at  high  speeds  is  too  rich,  that  is,  if  there  is  too  much  fuel  for  the 
air  furnished,  it  indicates  that  the  tension  on  the  valve  spring  is  too  great, 

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which  prevents  the  valve  from  opening  to  admit  sufficient  air.  By 
reducing  the  tension,  the  valve  opens  wider,  letting  in  sufficient  air  to 
keep  the  mixture  uniform.  If  the  mixture  is  too  weak  at  high  speeds, 
the  spring  tension  is  too  weak,  admitting  an  excess  of  air.  The  spring 
should  be  tightened  so  as  to  permit  less  air  to  enter,  and  to  increase  the 
suction  on  the  gasoline. 

It  has  been  found  that  if  the  auxiliary  air  valve  be  provided  with 
a  straight  coil  spring  there  will  be  considerable  difficulty  in  keeping 
the  mixture  of  the  proper  proportions.  The  tendency  is  for  too  much 
air  to  be  supplied  at  high  speed  and  open  throttle.  This  objection  has 
been  met  by  the  use  of  a  tapered  coil  spring  such  as  S,  in  Fig.  84,  instead 
of  a  straight  one.  The  tapered  spring  is  better  because  it  prevents  the 
air  valve  from  opening  too  wide  and  furnishing  too  much  air  on  open 
throttle.     In  some  cases,  two  coil  springs  are  used  on  the  auxiliary 

Fig.  84.  Fio.  85. 

Figs.  84  and  85. — Typical  variable  speed  carburetors 

air  valve.  One  of  these  regulates  the  air  opening  at  medium  speed  and 
the  other  comes  into  play  at  high  speed  to  prevent  the  valve  from  opening 
too  wide. 

Numerous  other  ways  have  been  devised  for  supplying  the  auxiliary 
air.  A  series  of  weighted  balls,  B,  B,  B}  Fig.  85,  rise  and  admit  the 
auxiliary  air  at  various  engine  speeds.  The  weights  of  these  balls  have 
been  determined  by  experiment  and  no  method  of  adjustment  is  provided. 
The  reed  air  .passage  on  the  Tillotson  carburetor,  Fig.  104,  and  the 
flat  hinged  valve  on  the  Marvel,  Fig.  93,  illustrate  other  methods  of  auxil- 
iary air  supply. 

In  many  of  the  modern  carburetors  a  secondary  gasoline  jet  or  nozzle 
furnishes  a  small  amount  of  fuel  to  the  auxiliary  air,  making  it  a  very 
lean  mixture.  This  secondary  jet  may  be  either  of  the  metering  pin 
type  as  on  the  Rayfield,  Fig.  95,  in  which  a  certain  opening  of  the  air 
valve  automatically  opens  the  metering  nozzle,  or,  it  may  be  of  the 
suction  type,  as  on  the  Marvel,  Fig.  93,  in  which  a  certain  engine  speed 
produces  sufficient  suction  to  draw  the  gasoline  out  in  a  finely  atomized 

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condition.  By  thus  supplying  a  small  amount  of  fuel  to  the  auxiliary  air, 
the  tendency  of  the  mixture  to  thin  out  at  high  speeds  is  avoided.  The 
high  speed  power  demands  may  also  be  taken  care  of. 

71.  Air  Valve  Dashpots. — With  the  mushroom  type  air  valve  there  is 
occasionally  considerable  fluttering  of  the  valve  and  also  excessive  noise 
of  the  valve  when  it  closes  on  its  seat.  This  is  overcome  by  providing 
a  dashpot,  usually  filled  with  gasoline,  which  prevents  the  excessive 
fluttering  and  noise  of  the  valve.  The  Stromberg  carburetor,  Fig.  112, 
and  the  Ray  field,  Fig.  95,  are  provided  with  dashpots  on  the  air  valve. 

72.  Float  Chambers  and  Floats. — Float  chambers  may  be  eccentric, 
as  in  Fig.  83,  in  which  case  the  chamber  is  placed  at  the  side  of  the  carbu- 
retor, or  concentric  in  which  the  chamber  is  built  central  with  the  carbu- 
retor body  as  in  Fig.  84  or  86.  The  floats  which  regulate  the  height  of 
fuel  in  the  chamber  may  be  either  of  hollow  metal  as  in  Fig.  83  or  solid  of 
cork  as  in  Figs.  84  and  85.  The  hollow  metal  float  must  be  air-tight 
in  order  to  prevent  it  from  filling  with  gasoline.  The  cork  float  is  usually 
coated  with  shellac  to  form  a  water-tight  covering.  This  keeps  the 
float  from  becoming  water-logged  and,  consequently,  useless. 

73.  Metering  Pins. — In  some  types  of  carburetors  the  opening  of  the 
gasoline  nozzle  or  jet  is  fixed  and  cannot  be  regulated.  In  other  types, 
the  gasoline  supply  is  regulated  by  a  valve  such  as  shown  in  Fig.  83 
and  also  in  Fig.  85.  In  some  cases,  arrangements  are  made  for  auto- 
matically opening  and  closing  this  pin  valve  which  is  called  the  metering 
pin.  It  may  be  operated  by  the  throttle,  as  on  the  Schebler  L,  Fig.  89, 
by  the  auxiliary  air  valve,  or  by  an  adjustment  on  the  dash  under  the 
control  of  the  driver. 

74.  Operating  Conditions  of  the  Carburetor. — Formerly,  when  gaso- 
line was  of  higher  grade  and  the  engines  of  lower  speed,  the  problem  of 
carburetion  was  simple,  but  with  the  necessary  use  of  lower  grade  fuel  and 
the  higher  speed  and  power  of  the  engines,  the  problem  of  satisfactory 
carburetion  is  a  very  important  and  difficult  one.  The  higher  grade 
fuels  would  evaporate  easily  and  there  was  little  danger  of  the  vapor 
condensing  after  it  left  the  carburetor.  The  adoption  of  lower  grade 
and  blended  fuels  made  it  necessary  to  provide  means  for  easily  vaporiz- 
ing or  atomizing  these  and  also  to  prevent  condensation  after  leaving 
the  carburetor.  The  usual  way  of  doing  this  is  to  furnish  external  heat 
to  the  carburetor  and  intake  manifolc^  leading  to  the  cylinders  and  also 
to  heat  the  incoming  air  and  the  gasoline.  Some  decided  improvements 
in  the  design  of  the  manifold  have  also  helped  in  the  prevention  of 

Figures  92  and  94  illustrate  typical  methods  of  heating  the  air  going 
into  the  carburetor.  The  air  is  taken  from  a  stove  surrounding  the 
exhaust  pipe  and  goes  through  a  flexible  connection  to  the  carburetor. 

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A  regulating  valve  placed  near  the  carburetor  can  be  adjusted  when  it  is 
necessary  to  regulate  the  temperature  by  taking  air  from  the  outside. 
The  carburetor  body  is  sometimes  jacketed,  and,  either  part  of 
the  exhaust  gases  as  in  the  Marvel,  Fig.  93,  or  part  of  the  cooling  water 
from  the  engine,  is  used  to  heat  the  carburetor  body.  This  method 
heats  the  gasoline  as  well  as  the  air.  In  other  cases  the  entire  intake 
manifold  is  kept  hot  by  passing  the  exhaust  gases  through  a  jacket  sur- 
rounding it.  This  prevents  the  usual  condensation  which  tends  to  take 
place.     An  electric  heating  unit,  Figs.  86  and  87,  has  also  been  used  in 

the  float  chamber  to  keep  the  gasoline  warm 
•ui  to  insure  complete  vaporization. 
*    If  the  explosive  mixture  going  into  the 
cylinder  be  heated  too  much,  it  is  expanded 

¥iq.  86. — Electrical  heating 
unit  for  carburetor  bowl. 

Fiq.  87. — Connections  for  electrical  heater  for 

so  that  a  full  charge  cannot  get  into  the  cylinder  and,  consequently, 
the  power  of  the  engine  is  reduced.  The  fuel  and  the  air  should  be 
heated  just  enough  to  insure  vaporization  and  to  prevent  condensation. 
Beyond  this  there  is  no  advantage  in  heating  the  fuel  charge. 

Various  methods  of  providing  efficient  carburetion  are  employed  in 
the  numerous  types  of  modern  carburetors.  These  methods  of  construc- 
tion and  operation  are  described  and  illustrated  for  the  following  typical 

\  76.  Schebler  Model  L  Carburetor. — The  Model  L  carburetor,  Figs. 
88\nd  89,  is  of  the  lift-needle  or  metering  pin  type  and  is  so  designed 
that  the  amount  of  fuel  entering  the  motor  is  controlled  by  means  of  a 
raised  needle  working  automatically  with  the  throttle.  The  flow  of  gaso- 
line can  be  adjusted  for  closed,  intermediate,  or  open  throttle  positions, 
each  adjustment  being  independent  and  not  affecting  either  of  the  others. 
This  carburetor  has  an  automatic  air  valve,  shown  at  the  left  in  Fig.  89. 
At  high  speeds  or  heavy  loads,  the  suction  raises  this  valve  and  admits 
an  extra  supply  of  air.  The  opening  of  the  throttle  for  high  speed  or  a 
heavy  pull  raises  the  needle  valve  and  increases  the  supply  of  gasoline 
to  correspond  with  the  increased  air  supply. 

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The  Model  L  is  furnished  with  a  warm  air  connection  from  around 
the  exhaust  manifold  leading  into  the  primary  air  opening  at  the  base  of 
the  carburetor,  as  shown  in  Fig.  92. 

This  carburetor,  as  illustrated  in  Fig.  89,  is  equipped  with  a  dash- 
control  to  the  air  valve  spring,  this  being 
adjusted  by  a  lever  which  is  controlled  by 
a  handle  on  the  dashboard  or  steering  post 
of  the  car.  Three  types  of  these  air  con- 
trols are  illustrated  in  Fig.  90. 

The  Schebler  L  is  also  built  with  a  dash- 
pot  on  the  air  valve  to  prevent  the  unsteady 
action  of  the  valve  and  give  a  smooth  and 
satisfactory  operation  of  the  engine. 

Adjusting  Schebler  Model  L  Carburetor. — 

The  carburetor  should  be  connected  to  ihe 

intake  manifold  so  that  it  is  located  below 

the  bottom  of  the  gasoline  tank  a  sufficient 

distance  to  be  filled  by  gravity  flow  under 

all  running  conditions.     Where  pressure  feed  is  used,  it  is  unnecessary 

to  locate  the  carburetor  below  the  gasoline  tank;  also,  when  pressure  is 

used,  it  is  never  advisable  to  carry  over  2  lb. 

Fio.  88. — Schebler  Model  L 

Fio.  89. — Section  of  Schebler  Model  L  carburetor. 

Before  adjusting  the  carburetor  it  is  necessary  that  the  ignition  be 
properly  timed;  that  there  is  a  good  hot  spark  at  each  plug;  that  the 
valves  are  properly  timed  and  seated;  and  that  all  connections  between 
the  intake  valves  and  the  carburetor  are  tight.     The  carburetor  should 

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be  adjusted  to  the  engine  under  normal  running  temperature,  and  not  to 
a  cold  engine. 

In  setting  the  carburetor,  the  auxiliary  air  valve  is  first  adjusted  so 
that  it  seats  lightly  but  firmly.  The  handle  on  the  dash  control  should 
be  set  in  the  center  of  the  dashboard  adjuster,  and  with  this  setting  of  the 
handle,  the  tension  on  the  air  valve  should  be  light  yet  firm.  The  needle 
valve  should  be  closed  by  turning  the  adjustment  screw  to  the  right.  It 
is  then  turned  to  the  left  about  four  or  five  times  and  the  carburetor 
primed  or  flushed  by  pulling  up  the  priming  lever  and  holding  it  up  for 
about  5  seconds.  The  throttle  is  opened  about  one-third  and  the  engine 
started.  After  closing  the  throttle  slightly,  and  retarding  the  spark,  the 
throttle  lever  screw  and  the  needle  valve  adjusting  screw  are  adjusted 
so  that  the  motor  runs  at  the  desired  speed  and  hits  on  all  cylinders. 
This  is  the  low  speed  adjustment. 

After  getting  a  good  adjustment  with  the  engine  running,  the  needle 
valve  adjustment  should  not  be  changed  again.     The  intermediate  and 

Fia.  90. — Dashboard  and  steering  column  controls  for  Schebler  carburetor. 

high  speed  adjustments  are  made  on  the  dials.  The  pointer  on  the  right 
or  intermediate  dial  should  be  set  about  halfway  between  figures  1  and  3. 
The  spark  should  be  advanced  and  the  throttle  opened  so  that  the  roller 
on  the  track  running  below  the  dials  is  in  line  with  the  first  dial.  If  the 
engine  back-fires,  with  the  throttle  in  this  position  and  the  spark  ad- 
vanced, the  indicator  or  pointer  should  be  turned  a  little  more  toward 
figure  3;  if  the  mixture  is  too  rich,  the  indicator  should  be  turned  back, 
or  toward  figure  1,  until  the  engine  is  running  properly  with  the  throttle 
in  intermediate  speed  position.  For  high  speed  adjustment  the  throttle 
is  opened  wide  and  the  adjustment  made  for  high  speed  on  the  second  dial 
in  the  same  manner  as  the  adjustment  for  intermediate  speed  on  the  first 

76.  Schebler  Model  R  Carburetor.— The  Schebler  Model  R  carbu- 
retor, Fig.  91,  is  of  the  single-jet  raised-needle  type,  automatic  in  action. 
The  air  valve  controls  the  lift  of  the  needle  valve  so  as  to  proportion  or 
meter  automatically  the?  amount  of  gasoline  and  air  at  all  speeds. 

The  Model  R  carburetor  is  designed  with  separate  adjustments  for 
both  low  and  high  speeds.     As  the  speed  of  the  motor  increases,  the  air 

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valve  opens,  raising  the  gasoline  needle  and  thus  automatically  increasing 
the  amount  of  fuel.  The  low  speed  adjustment  is  made  by  turning  the 
air  valve  cap  A,  which,  through  a  lever,  regulates  the  height  of  the  needle 
valve  E  and,  consequently,  the  flow  of  gasoline  from  the  nozzle.  The 
screw  F  regulates  the  tension  on  the  air  valve  spring  and  gives  the  ad- 
justment for  high  speed. 

The  Model  R  carburetor  is  equipped  with  an  eccentric  near  the  top 
of  the  metering  pin.  This  eccentric  is  controlled  by  the  outside  crank 
lever  B  which  in  turn  is  operated  either  from  the  steering  column  or  from 
the  dash.    The  eccentric  raises  or  lowers  the  needle  valve  according  to 

Fiq.  91. — Schebler  Model  R  carburetor. 

the  position  of  B  which  is  under  the  control  of  the  driver.  The  needle 
can  be  raised  by  adjusting  the  dash  control  and  an  extremely  rich  mix- 
ture furnished  for  starting  and  for  heating  up  the  engine  in  cold  weather. 
A  choke  valve  is  placed  in  the  air  bend. 

The  Model  R  carburetor  must  be  installed  with  either  steering  or 
dash  control,  in  order  to  insure  proper  performance  under  all  weather 
conditions.  It  is  also  absolutely  necessary  to  apply  heat  at  low  engine 
speeds  to  insure  proper  vaporization  of  the  fuel.  A  hot  air  drum  and 
tubing  running  from  the  exhaust  manifold  to  the  carburetor  are  used  as 
illustrated  in  Fig.  92. 

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Adjusting  Schebler  Model  R  Carburetor. — The  crank  lever  B,  Fig.  91, 
should  be  attached  to  the  steering  column  or  dash  control,  so  that  when 
boss  D  of  lever  B  is  against  stop  C,  the  handle  on  the  steering  column  or 
dash  control  will  register  lean  or  air.  Fig.  90.  This  is  the  proper  running 
position  for  lever  B. 

To  adjust  the  carburetor,  turn  the  air  valve  cap  A  to  the  right  until 
it  stops,  then  turn  it  to  the  left  one  complete  turn.  To  start  the  engine, 
open  the  throttle  about  one-eighth  or  one-quarter  way.  When  the  en- 
gine is  started,  let  it  run  till  it  is  warmed,  then  turn  the  air  valve  cap  A 
to  the  left  until  the  engine  fires  perfectly.  Advance  the  spark  three- 
quarters  of  the  way  on  the  quadrant;  then  if  the  engine  back-fires  on 
quick  acceleration,  turn  the  adjusting  screw  F  up  (which  increases  the 
tension  on  the  air  valve  spring)  until  acceleration  is  satisfactory.  Turn- 
ing the  air  valve  cap  A  to  the 
right  lifts  the  needle  E  out  of 
the  nozzle  and  enriches  the 
mixture;  turning  it  to  the  left 
lowers  the  needle  into  the 
nozzle  and  makes  the  mixture 

When  the  engine  is  cold  or 
the  car  has  been  standing, 
move  the  steering  column,  or 
dash  control  lever,  toward 
gas  or  rich.  This  operates 
the  crank  lever  B  and  lifts  the 
needle  E  out  of  the  gasoline 
nozzle,  giving  a  rich  mixture 
for  starting.  As  the  engine  warms  up,  the  control  lever  should  gradu- 
ally be  moved  back  toward  air  or  lean  to  obtain  best  running  condi- 
tions, until  the  engine  has  reached  normal  temperature.  When  this  tem- 
perature is  reached,  the  control  lever  should  be  at  air  or  lean.  For  best 
economy,  the  slow  speed  adjustment  should  be  made  as  lean  as  possible. 

77.  Marvel  Carburetor. — The  Marvel  carburetor,  shown  in  Fig.  93, 
is  of  the  double  nozzle  type,  the  high  speed  nozzle  coming  into  action  at 
high  engine  speeds.  At  low  speeds,  all  the  air  is  drawn  through  the 
Venturi  tube,  where  it  takes  up  gasoline  from  the  primary  nozzle.  The 
flow  from  the  primary  nozzle  is  controlled  by  the  adjusting  screw  A. 
At  high  speeds,  after  the  air  has  passed  the  choke  damper,  it  divides, 
part  of  it  going  through  the  Venturi  tube  around  the  low  speed  spray 
nozzle,  and  the  remainder  passing  to  one  side  and  opening  the  auxiliary 
air  valve  against  the  pressure  of  its  spring.  The  auxiliary  or  high  speed 
spray  nozzle  is  placed  near  the  top  of  the  auxiliary  air  valve. 

Fig.  92. — Hot  air  connection  for  Schebler 

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The  rush  of  air  through  the  Venturi  tube  picks  up  and  atomizes  the 
gasoline  from  the  low  speed  nozzle  and  carries  it  in  suspension  past  the 
throttle  end  to  the  cylinders.  When  the  suction  at  the  auxiliary  air 
valve  has  increased  sufficiently  to  open  this  valve  and  create  a  high  air 

Hot  air  jacket 

~Arr  intake 
■  Choke  dofhper 
Verituri  tube 

Weedk  vohe 

Fio.  93. — The  Marvel  Model  E  carburetor. 

velocity  at  this  point,  gasoline  is  also  picked  up  from  the  high  speed 
nozzle  and  carried  to  the  cylinders. 

The  choke  damper  in  the  air  inlet  is  used  only  for  starting  the  motor, 
by  partially  shutting  off  the  air  supply  and  forcing  the  engine  to  draw  in 
a  rich  mixture. 


Ms  \ 




^^_.                 ^-^^— 

Fia.  94. — Hot  air  and  heating  connections  for  Marvel  carburetor. 

•  To  the  throttle  is  connected  a  hot  air  damper,  which,  when  open, 
allows  the  exhaust  gas  from  the  engine  to  flow  through  a  cored  passage 
around  the  throttle,  where  it  maintains  the  proper  temperature  for  the 
mixture  of  gasoline  and  air.     As  the  throttle  is  opened,  the  hot  air  damper 

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is  closed.  A  tube  connects  this  cored  passage  with  another  which  sur- 
rounds the  Venturi  tube  and  spray  nozzle.  Figure  94  shows  this  hot  air 
tube  which  is  screwed  into  the  exhaust  manifold.  When  the  exhaust  pipe 
stove  is  used  to  heat  the  carburetor  air,  a  shutter  is  used  near  the  car- 
buretor to  regulat  the  temperature  according  to  weather  conditions. 
This  shutter  is  regulated  by  hand  from  the  instrument  board  on  the  dash. 

Adjusting  Marvel  Carburetor. — The  needle  valve  A  should  be  turned 
to  the  right  until  it  is  completely  closed,  and  the  air  adjustment  B  three 
complete  turns  to  the  right.  Then  the  needle  valve  A  is  opened  one 
complete  turn  to  the  left.  The  engine  is  started  with  the  air  regulator  at 
hot  until  the  engine  is  warmed  up.  The  spark  lever  should  be  fully  re- 
tarded after  which  the  gasoline  adjustment  A  should  be  turned  to  the 
right  (closed)  until  the  engine  runs  smoothly. 

After  the  motor  has  warmed  up,  turn  the  air  valve  adjusting  screw 
B  to  the  left,  a  little,  at  a  time,  until  the  motor  begins  to  slow  down. 
This  indicates  that  the  air  valve  spring  *is  too  loose.  Turn  it  back  to 
the  right  just  enough  to  make  the  motor  run  well. 

To  test  the  adjustment;  advance  the  spark  and  open  the  throttle 
quickly.  The  motor  should  take  hold  instantly  and  speed  up  at  once. 
The  best  adjustment  is  obtained  when  the  gasoline  adjustment  is  tinned 
as  far  as  possible  to  the  right  and  the  air  adjustment  as  far  as  possible  to 
•  the  left.  With  this  setting  the  engine  should  idle  smoothly  and  accel- 
erate quickly. 

78.  Rayfield  Model  G  Carburetor.— This  carburetor  illustrated  in 
Figs.  95  and  97  has  two  gasoline  jets  and  three  air  entrances,  two  of 
which  are  auxiliary  air  inlets  into  the  mixing  chamber.  There  are  no 
air  valve  adjustments,  but  two  gasoline  adjustments,  a  low  speed  adjust- 
ment and  a  high  speed  adjustment,  are  provided. 

At  low  speeds,  air  is  drawn  into  the  mixing  chamber  through  the 
constant  air  opening,  Fig.  95.  This  air  passes  around  the  nozzle  and  picks 
up  the  gasoline  which  leaves  the  spray  nozzle  in  the  form  of  a  spray. 
When  the  speed  increases,  the  upper  automatic  air  valve  opens,  admitting 
more  air.  The  movement  of  the  air  valve  causes  the  metering  pin  to 
open  the  metering  pin  nozzle*  This  furnishes  additional  fuel  to  the  charge. 
The  lower  air  valve  opens  and  closes  with  the  main  or  upper  automatic  air 
valve,  giving  a  greater  volume  of  air  in  proportion  to  the  greater  amount 
of  gasoline  to  be  vaporized.  At  high  engine  speeds,  or  when  the  throttle 
is  fully  opened,  the  engine  requires  more  gas  and,  consequently,  a  greater 
volume  of  air  to  vaporize  the  gasoline  which  comes  through  the  spray 
nozzles.  At  low  engine  speeds,  less  gas  is  required  and,  consequently, 
less  air  is  necessary  to  vaporize  the  gasoline. 

The  upper  automatic  air  valve  is  controlled  by  the  tension  on  the  coil 
spring.     The  bottom  end  of  the  valve  stem  carries  a  dashpot  filled  with 


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gasoline.  This  dashpot  prevents  fluttering  of  the  air  valves  and  also 
acts  to  force  the  gasoline  out  of  both  gasoline  nozzles  when  the  throttle 
is  suddenly  opened  and  quick  acceleration  is  desired. 

Fia.  95. — Section  of  Rayfield  Model  G  carburetor. 

The  method  of  applying  heat  to  the  Rayfield  Model  G  is  illustrated 
in  Fig.  96.  The  upper  water  connection  on  the  carburetor  is  run  to  B 
where  the  temperature  of  the  engine  cooling  water  is  highest.     The 

Fig.  96. — Connections  for  supplying  heat  to  Rayfield  Model  G  carburetor. 

bottom  water  connection  is  run  from  the  carburetor  to  the  suction  side  of 
the  water  pump  at  A.     These  connections  provide  a  constant  circulation 

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of  hot  water  through  the  jackets  on  the  carburetor.  The  constant  air 
opening  is  connected  by  a  flexible  tubing  to  stove  F  which  is  placed  around 
the  exhaust  pipe  at  G.  The  dash  control  wire  is  connected  through 
bracket  J  to  arm  H ,  Fig.  97,  the  movement  of  which  opens  or  closes  the 
primary  gasoline  jet.     A  priming  wire  is  also  run  to  G,  the  priming  lever. 



Fio.  97. — Rayfield  Model  G  carburetor. 

Adjusting  Rayfield  Model  G  Carburetor. — With  the  throttle  closed  and 
the  dash  control  down  in  run  position,  Fig.  98,  close  the  nozzle  needle  by 
turning  the  low  speed  adjustment,  Fig.  97,  to  the  left  until  U  slightly  leaves 
contact  with  the  regulating  cam  M  and  then  turn  to  the  right  about  three 
complete  turns.  Open  the  throttle 
not  more  than  one-quarter.  Prime 
the  carburetor  by  pulling  steadily 
a  few  seconds  on  the  priming  lever 
G.  Start  the  engine  and  allow  it  to 
run  until  warmed  up.  Then  with 
retarded  spark  close  the  throttle 
until  the  motor  runs  slowly  with- 
out stopping.  Now,  with  the 
motor  thoroughly  warm,  make  the 
final  low  speed  adjustment  ty  turning  the  low  speed  screw  to  the  left 
until  the  engine  slows  down.  Then  turn  it  to  the  right  a  notch  at  a 
time  until  the  engine  idles  smoothly. 

To  make  the  high  speed  adjustment,  advance  the  spark  one-quarter. 
Open  the  throttle  rather  quickly.  Should  the  motor  back-fire  it  indicates 
a  lean  mixture.     Correct  this  by  turning  the  high  speed  adjusting  screw  to 

Fiq.  98. — Dash  control  handle  for  Rayfield 

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the  right  about  one  notch  at  a  time,  until  the  throttle  can  be  opened 
quickly  without  back-firing.  If  loading  (choking)  is  experienced  when 
running  under  heavy  load  with  the  throttle  wide  open,  it  indicates  too  rich 
a  mixture.  This  can  be  overcome  by  turning  the  high  speed  adjustment 
to  the  left. 

V  79.  Holley  Model  H  Carburetor. — Before  the  gasoline  enters  the 
float  chamber  of  this  carburetor,  Fig.  99,  it  passes  a  strainer  disc  A  which 
removes  all  foreign  matter  that  might  interfere  with  the  seating  of  the 
float  valve  B  under  the  action  of  the  cork  float  C.    The  gasoline  passes 

from  the  float  chamber  D 
into  the  nozzle  well  E  through 
a  passage  F  drilled  through 
the  wall  separating  D  and  E. 
From  the  nozzle  Well,  the  fuel 
enters  the  cup  G  through  the 
opening  H,  and  rises  past  the 
needle  valve  I  to  a  level 
which  partially  submerges  the 
lower  end  of  the  small  tube  J 
which  has  its  outlet  K  at  the 
edge  of  the  throttle  disc. 

Cranking  the  engine,  with 
the  throttle  kept  nearly  closed, 
causes  a  very  rapid  flow  of  air 
through  the  tube  J  and  its 
calibrated  throttling  plug  K. 
With  the  engine  at  rest  the 
lower  end  of  this  tube  is 
partially  submerged  in  fuel. 
Therefore,  the  act  of  cranking 
automatically  primes  the 
engine.  With  the  engine 
turning  over  under  its  own 
power,  the  flow  through  the  tube  J  takes  place  at  very  high  velocity, 
causing  the  fuel,  entering  the  tube  with  the  air,  to  be  thoroughly 
atomized  upon  its  exit  from  the  small  opening  at  the  throttle  edge. 
This  tube  is  called  the  low  speed  tube,  because  for  starting  and  idle 
running,  all  of  the  fuel  and  most  of  the  air  in  the  working  mixture  are 
taken  through  it. 

As  the  throttle  opening  is  increased  beyond  that  needed  for  idling  of 
the  motor,  a  considerable  volume  of  air  is  drawn  down  around  the  outside 
of  the  strangling  tube  L  and  then  upward  through  this  tube.  In  its 
passage  into  the  strangling  tube,  the  air  is  made  to  assume  an  annular, 

Fiq.  99. — Holley  Model  H  carburetor. 

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converging  stream  form  so  that  the  point  in  its  flow  at  which  it  attains 
its  highest  velocity  is  in  the  immediate  neighborhood  of  the  upper  end  of 
the  standpipe  M .  The  velocity  of  air  flow  being  highest  at  the  upper  or 
outlet  end  of  the  standpipe,  the  pressure  in  the  air  stream  is  lowest  at  the 
same  point.  For  this  reason,  there  is  a  pressure  difference  between  the 
top  and  bottom  openings  of  the  pipe  M ,  thus  causing  air  to  flow  through 
it  from  bottom  to  top,  the  air  passing  downward  through  the  openings  N 
in  the  bridge  supporting  the  standpipe  and  then  up  through  the  standpipe. 

100. — Temperature  regulator  used  with  Holley  carburetor. 

With  a  very  small  throttle  opening,  the  action  through  the  standpipe 
keeps  the  nozzle  cup  thoroughly  cleaned  out,  the  fuel  being  carried  directly 
from  the  needle  opening  into  the  entrance  of  the  standpipe.  To  secure 
the  best  vaporization  of  the  fuel,  the  passage  through  the  standpipe  is 
given  an  aspirator  form,  which  further  increases  the  velocity  of  flow 
through  it  and  insures  the  best  possible  mixing  of  the  fuel  with  the  air. 
A  further  point  is  that  the  vaporized  discharge  from  the  standpipe  enters 

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the  main  air  stream  at  the  point  at  which  the  latter  attains  its  highest 
velocity  and  lowest  pressure. 

The  Holley  temperature  regulator  is  shown  in  Fig.  100.  Hot  air  is 
taken  from  around  the  exhaust  manifold  to  the  carburetor  through  a 
flexible  coupling.  The  regulator  is  under  the  control  of  the  dash  adjust- 
ment which  can  be  made  according  to  conditions. 

There  is  but  one  adjustment,  that  of  the  needle  valve  J.  The  effect 
of  a  change  in  its  setting  is  manifest  over  the  whole  range  of  the  engine. 

80.  Holley  Model  G  Carburetor. — This  carburetor,  Fig.  101,  is  a 
special  design  for  Ford  cars.  The  operation  is  the  same  as  the  regular 
Model  H  already  illustrated  and  described.    The  chief  differences  are 

Fig.  101. — Holley  Model  G  carburetor. 

structural  ones  providing  a  horizontal  instead  of  a  vertical  outlet,  a 
needle  valve  controlled  from  above  instead  of  from  below,  and  a  simpli- 
fication of  design  to  secure  compactness. 

The  gasoline  from  the  float  chamber  passes  through  the  ports  E  to 
the  nozzle  orifice,  in  which  is  located  the  pointed  end  of  the  needle  F. 
The  ports  E  are  well  above  the  bottom  of  the  float  chamber,  so  that,  even 
should  water  or  other  foreign  matter  enter  the  float  chamber,  it  would 
have  to  be  present  in  very  considerable  quantity  before  it  could  inter- 
fere with  the  operation  of  the  carburetor.  A  drain  valve  D  is  provided 
for  the  purpose  of  drawing  off  whatever  sediment  or  water  may  accumu- 
late in  the  float  chamber. 

The  float  level  is  set  so  that  the  gasoline  rises  past  the  needle  valve 

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F  and  fills  the  cup  G  sufficiently  to  submerge  the  lower  end  of  the  small 
tube  H .  Drilled  passages  in  the  casting  communicate  the  upper  end  of 
this  tube  with  an  outlet  at  the  edge  of  the  throttle  disc.  The  tube  and 
passage  give  the  starting  and  idling  actions,  ad  described  in  connection 
with  the  Holley  Model  H.  The  lever  L  operates  the  throttle  in  the  mix- 
ture outlet.  A  larger  disc  with  its  lever  S  forms  a  spring-returned  choke 
valve  in  the  air  intake  for  starting  in  extremely  cold  weather. 

The  dash  adjustment  consists  of  a  handle  or  small  thumb  wheel 
attached  to  a  rod  by  which  the  needle  valve  F  may  be  opened  or  closed. 
The  Holley  temperature  regulator  may  also  be  used  with  this  carburetor. 

81.  Kingston  Model  L  Carburetor. — Figure  102  show  the  construc- 
tion of  this  carburetor  which  has  been  designed  especially  for  Ford  cars. 
Gasoline  enters  the  carburetor  from  the  tank  at  the  connection  A  and 
is  maintaiaed  at  a  constant  level,  by 
means  of  the  float.    A  pool  of  gasoline 
forms  in  the  base  of  the  U-shaped  mixing 
chamber  and  is  always  present  when  the 
engine  is  not  running.     This  aids   in 
positive    starting.      When    the   engine 
starts,  this  pool  is  quickly  lowered  to 
the  point  of  adjustment  of  the  needle 
valve  and  continues  to  feed  from  this 
point  till  the  motor  is  stopped. 

When  the  motor  is  running  slowly, 
the   weighted    ball   air  valve   B  rests 

,.   i  Al  ..  x       ii       •  -a  Fig.  102.— Kingston  Model  L 

lightly  on  its  seat,  allowing  no  air  to  carburetor. 

pass  through;  consequently,  all  the  air 

must  pass  through  the  low  speed  mixing  tube  C.    Due  to  the  lower  end 

of  this  tube  being  close  to  the  spray  nozzle  and  all  the  low  speed  air 

having  to  pass  this  point,  the  atomized  gasoline  drawn  from  nozzle  D 

becomes  thoroughly  mixed  with  air  in  its  upward  course  and  is  carried  in 

this  state  to  the  engine. 

When  the  throttle  is  opened  slowly,  the  air  valve  B  gradually  leaves 
its  seat,  permitting  an  extra  air  supply  to  enter  and  compensate  for  the 
increased  flow  of  gasoline  produced  by  the  greater  suction  of  the 
motor.  In  this  carburetor  the  extra  amount  of  gasoline  for  the  start- 
ing and  warming  up  period  can  be  obtained  by  opening  the  needle  valve 
from  the  dash  or  by  the  use  of  the  choke  throttle  E  placed  in  the  air 

When  starting  with  a  cold  motor,  this  choke  throttle  should  be  closed. 
This  cuts  off  nearly  all  the  air  supply  and  produces  a  very  strong  suction 
at  the  spray  nozzle,  which  causes  the  gasoline  to  fill  the  jet  and  be  carried 
with  the  incoming  air  to  the  cylinders. 

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A  drain  cock  G  is  placed  at  the  lowest  point  in  the  bowl  and  should  be 
opened  from  time  to  time  to  discharge  all  water  and  foreign  matter. 

Adjusting  Kingston  Model  L  Carburetor. — The  throttle  should  be 
opened  about  five  or  six  notches  of  the  quadrant  on  the  steering  post  and 
the  Spark  fully  retarded.  The  needle  valve  binder  nut  on  the  carburetor 
should  be  loosened  until  the  needle  valve  turns  easily.  The  needle  valve 
is  then  turned  (with  dash  adjustment)  until  it  seats  lightly.  It  should 
be  opened  one  complete  turn.  This  will  be  slightly  more  than  necessary 
but  will  assist  in  easy  starting. 

The  engine  is  started  and  the  throttle  opened  or  closed  until  the 
engine  runs  at  fair  speed.  It  should  be  run  long  enough  to  warm  up  to 
service  conditions.  Then,  for  purposes  of  adjustment,  the  throttle  must 
be  closed  until  the  engine  runs  at  the  desired  idling  speed.  This  can  be 
controlled  by  adjusting  the  stop  screw  in  the  throttle  lever. 

The  lieedle  valve  should  then  be  closed  until  the  motor  begins  to  lose 
speed,  thus  indicating  a  weak  or  lean  mixture.  The  valve  should  now  be 
opened  very  slowly  until  the  motor  attains  its  best  and  most  positive 
speed.  This  completes  the  adjustment.  The  throttle  should  be  closed 
until  the  engine  rims  slowly,  and  then  opened  quickly.  The  engine  should 
respond  strongly  and  quickly.  If  the  acceleration  is  slightly  weak  or 
sluggish,  a  slight  adjustment  of  the  needle  valve  may  be  advisable  to 
correct  this  condition.  With  the  adjustments  completed,  the  binder 
nut  should  be  tightened  until  the  needle  valve  turns  hard. 

82.  Tillotson  Carburetor. — This  carburetor,  Fig.  103,  embodies  a 
unique  method  of  regulating  the  air  supply.  This  regulation,  being 
entirely  automatic,  the  only  other  adjustment  is  the  gasoline  needle 
valve.  The  air  supply  comes  through  the  air  opening  at  the  top  and  is 
drawn  through  the  V  shaped  passage  formed  by  the  steel  reeds,  the  exact 
construction  of  which  may  be  clearly  understood  from  Figs.  104  and  105. 
The  two  steel  reeds  form  an  air  passage  which  is  really  an  automatic 
adjustable  Venturi  tube.  When  the  engine  is  still  or  running  slowly,  the 
reeds  bear  against  the  side  of  the  primary  gasoline  nozzle.  As  the  engine 
speeds  up  and  the  suction  increases,  the  mouth  of  the  V  opens,  giving  a 
greater  air  passage  and  at  the  same  time  producing  the  maximum  air 
velocity  past  the  gasoline  nozzle.  Figure  104  represents  the  various 
positions  of  the  two  reeds  as  the  mouth  of  the  V  opens. 

Provision  is  also  made  for  a  small  jet  of  air  to  pass  up  through  the 
primary  nozzle  from  the  bottom.  This  air  atomizes  the  charge  of 
gasoline  thoroughly  and  sprays  it  into  the  main  charge  of  air  coming 
through  the  reed  opening. 

The  secondary  gasoline  jet  coming  up  from  the  float  chamber  between 
the  reeds  also  supplies  gasoline  to  the  incoming  air  when  the  engine 

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speed  is  high,  and  the  suction  at  the  large  part  of  the  Venturi  is  sufficient 
to  draw  the  gasoline  out  of  the  secondary  jet. 

Fig.  103.— Tillotson  Model  B  carburetor. 

Fig.  104. — Steel  reed  air  valve  on  Tillotson  carburetor. 

Adjusting  Tillotson  Carburetor. — There  is  only  one  adjustment  to 
make,  that  of  the  gasoline  supply  for  the  primary  nozzle.     The  engine 

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should  be  thoroughly  wanned  up  and  the  spark  control  lever  retarded  to  a 
position  approximately  one-third  of  the  way  upon  the  quadrant.  The 
throttle  is  then  adjusted  ntil  the  engine  is  turning  at  a  speed  equivalent 
to  approximately  15  miles  per  hour  on  the  road.  Then  the  gasoline  needle 
valve  is  turned  to  the  right  until  the  engine  starts  to  misfire.  The  valve 
should  be  opened  slightly  until  the  motor  is  firing  regularly.  Then  the 
engine  should  be  suddenly  accelerated  by  opening  the  throttle  to  the 

extent  of  its  travel.  If  there  is  any  back- 
fire, or  spitting  back,  through  the  car- 
buretor, the  adjusting  valve  must  be 
opened  still  farther,  until  when  suddenly 
accelerated  the  engine  picks  up  and  fires 
with  regularity. 

This  is,  theoretically,  the  proper  car- 
buretor adjustment.  It  is  not  the  most 
economical  adjustment.  Under  certain 
conditions  of  travel  it  will  be  found  that 
the  motor  will  fire  regularly  and  develop 
maximum  power  with  the  carburetor  ad- 
justed to  a  point  at  which  this  back-firing 
will  occur  when  the  motor  is  suddenly 
accelerated.  If  constant  high  speed  of  the 
motor  is  to  be  maintained,  the  latter  ad- 
justment will  be  entirely  satisfactory. 

83,  Zenith  Model  L  Carburetor.— This 
carburetor,  shown  in  Fig.  106,  differs  from 
most  conventional  types  in  the  absence  of 
auxiliary  air  valves.  It  is  a  fixed  adjust- 
ment carburetor,  and  has  as  its  particular 
feature  the  compound  nozzle,  invented  by 
Baverly.  The  compound  nozzle  has  an 
inner  nozzle,  the  gasoline  for  which  is 
furnished  direct  from  the  float  chamber. 
The  amount  of  gasoline  leaving  this 
nozzle  would  make  the  mixture  too  rich 
at  high  speeds.  To  compensate  for  this  rich  mixture,  the  compensat- 
ing nozzle  surrounding  the  main  or  inner  nozzle  furnishes  a  mixture 
too  weak  at  high  speeds.  This  is  because  the  gasoline  feed  to  this  jet 
is  constructed  so  as  to  be  constant  at  all  speeds.  When  the  engine 
speeds  up,  the  amount  of  air  increases  and  the  compensating  mixture 
is  a  weak  one.  This  answers  the  purpose  of  the  auxiliary  air  valve  on 
other  types  of  carburetors  and'  keeps  the  mixture  of  constant  proper- 


Fio.  105. — Primary  fuel  nozzle 
and  air  valve  on  Tillotoon  carbu- 

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tions.     By  a  proper  selection  of  the  two  nozzles  a  well  balanced  mixture 
can  be  secured  through  the  entire  range. 

In  addition  to  the  compound  nozzle,  the  Zenith  is  equipped  with  a 
starting  and  idling  well.  This  well  terminates  in  a  priming  hole  at  the 
edge  of  the  butterfly  valve,  where  the  suction  is  greatest  when  the  valve 
is  slightly  open.  The  gasoline  is  drawn  up  by  the  suction  at  the  priming 
hole  and,  being  mixed  with  the  air  rushing  by  the  butterfly,  gives  a  rich 
slow  speed  mixture.  This  slow  speed  mixture  is  regulated  by  the  regu- 
lating screw,  which  admits  air  to 
the  priming  well.  At  higher 
speeds,  with  the  butterfly  valve 
opened,  the  priming  well  ceases  to 
operate  and  the  compound  nozzle 
drains  the  well  and  compensates 
for  any  engine  speed. 

84.  Stewart  Model  25  Carbu- 
retor.— This  carburetor,  which  is 
manufactured  by  the  Detroit 
Lubricator  Company,  involves  an'i 
interesting  principle  of  operation. 
Figure  107  is  a  sectioned  view  of 
this  carburetor  and  shows  the  posi- 
tion of  the  air  valve  with  the 
engine  running  and  air  and  gaso- 
line being  admitted. 

With  the  engine  at  rest  and  no 
air  passing  through  the  carburetor, 
the  air  valve  A  rests  on  the  seat 
B,  closing  the  main  air  passage. 

The  gasoline  rises  to  a  height  of  about  1%  in.  below  the  top  of  the  cen- 
tral aspirating  tube  L.  As  soon  as  the  engine  starts,  a  partial  vacuum 
is  formed  above  the  air  valve,  causing  it  to  lift  from  its  seat  and  admit 
air,  at  the  same  time  gasoline  is  being  drawn  up  through  the  aspirating 
tube  L.  The  lower  end  of  the  air  valve  extends  down  into  the  gasoline 
and  around  the  metering  pin  P.  Due  to  the  decreasing  diameter  of 
this  pin,  the  higher  the  air  valve  is  lifted  the  larger  the  opening  into  the 
tube  L  will  be,  and  the  more  gasoline  there  will  be  drawn  up.  The 
upper  end  of  the  air  valve  measures  the  air;  the  lower  end  measures  the 
gasoline;  therefore,  as  the  suction  varies,  the  air  valve  moves  up  or 
down  and  the  volume  of  air  and  the  amount  of  gasoline  admitted  to  the 
Trirring  chamber  increase  or  decrease  in  the  same  ratio.  Most  of  the 
air  passing  through  the  carburetor  goes  through  the  air  passages,  as 
indicated  by  the  black  arrows.    A  small  amount  is  drawn  through  the 

Fig.  106. — Zenith  Model  L  carburetor. 

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drilled  holes  HH  and  past  the  end  of  the  tube  L.  The  flared  end  of 
this  tube  deflects  the  air  through  a  small  annulus,  thereby  increasing 
the  velocity  of  air  at  this  point  so  as  to  aid  in  atomizing  the  fuel. 

The  air  valve  is  restrained  from  any  tendency  to  flutter,  caused 
by  the  intermittent  suction  of  the  cylinders,  by  the  dashpot  D.  Due 
to  the  greater  inertia  of  the  gasoline  and  because  it  flows  comparatively 
slowly  through  the  small  opening  and  into  the  dashpot,  the  air  valve  can 
rise  or  fall  only  as  liquid  is  expelled  or  admitted.  Thus  the  air  valve  is 
held  steady.  The  Stewart  carburetors  have  but  one  adjustment,  which 
raises  or  lowers  the  metering  pin,  thereby  decreasing  or  increasing  the 

Fig.  107. — Stewart  Model  25  carburetor. 

amount  of  gasoline  admitted  to  the  mixing  chamber.  The  correct 
position  of  the  metering  pin  is  determined  with  the  motor  running  at 
idling  speed.  This  adjustment  may  be  manipulated  at  the  dash  to 
compensate  for  extreme  changes  in  atmospheric  temperatures  and  for 
use  in  starting  in  cold  weather. 

85.  Stromberg  Plain  Tube  Carburetor. — In  the  Stromberg  plain  tube 
carburetor,  Figs.  108  and  109,  both  the  gasoline  and  the  air  openings  are 
fixed  in  size.  The  gasoline  is  metered  automatically  by  the  suction  of  the 
air  past  the  gasoline  jets.  The  flow  of  gasoline  from  the  float  chamber 
is  regulated  by  the  high  speed  adjustment  needle  A}  Fig.  109,  the  gasoline 
flowing  past  the  high  speed  needle  seat  through  the  opening  F  either  to  the 
accelerating  well  or  to  the  idling  tube,  through  the  opening  at  J.     With 

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the  engine  not  running,  the  gasoline  rises  in  the  accelerating  well,  idling 
tube,  and  air  bleeder  to  the  same  height  as  in  the  float  chamber. 

The  air  bleeder  G,  Figs.  109  and  110,  is  for  the  purpose  of  admitting 
air  through  the  openings  D  into  the  gasoline  channel  where  it  breaks  up 
the  gasoline  charge  and  carries  it  through  a  number  of  openings  E  into 
the  charge  of  air  going  through  the  small  Venturi  tube.  By  admitting 
this  small  amount  of  air  into  the  gasoline  before  it  is  sprayed  into  the  air 
current,  it  is  possible  to  break  down  the  surface  tension  of  the  liquid  and 
to  break  up  the  gasoline  into  a  finely  divided  mist.  This  insures  that  the 
fuel  is  completely  atomized. 







With  Motor  it  Ratf 





Fig.  108. — Strom  berg  plain  tube  carburetor. 

Surrounding  the  main  gasoline  passage  is  the  circular  chamber  M  or 
accelerating  well.  The  purpose  of  this  chamber  is  to  furnish  the  extra 
amount  of  gasoline  needed  when  the  throttle  is  suddenly  opened  and  the 
mixture  must  be  somewhat  richer.  When  the  engine  is  running  at  slow 
speed  or  slowing  down,  this  accelerating  well  fills  with  gasoline.  If  the 
throttle  is  suddenly  opened  and  the  engine  speeds  up,  the  gasoline  from 
this  well  flows  through  openings  H,  Fig.  109,  to  join  the  gasoline  coming 
from  the  float  chamber.  This  doubles  the  normal  rate  of  fuel  supply. 
The  amount  and  rate  of  discharge  from  the  well  are  determined  by  the 
size  and  number  of  holes  in  the  side  of  the  well. 

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In  the  center  of  the  main  gasoline  passage  is  found  the  idling  tube 
through  which  the  gasoline  is  furnished  to  the  cylinder  when  the  engine  is 
idling  and  the  throttle  is  practically  closed.  Air  is  drawn  into  the  idling 
tube  through  the  small  opening  under  control  of  screw  B  and  its  needle 
valve  near  the  top  of  the  large  Venturi  tube.  This  air  being  regulated 
by  B  goes  through  the  gasoline  which  it  atomizes  and  sprays  out  into  the 
carburetor  through  K  above  the  throttle  valve.  By  means  of  B,  the  idle 
adjustment  needle,  the  amount  of  air  is  regulated  and  the  idling  mixture 
is  correctly  proportioned. 

Fig.  109. — Sectioned  view  Strom  berg  plain  tube  carburetor. 

As  the  throttle  is  slightly  opened  from  the  idling  position  a  suction 
is  created  on  the  throat  of  the  small  Venturi  tube  as  well  as  on  the  idling 
jet.  When  idling,  the  suction  is  greater  at  the  idling  jet,  and  when  the 
throttle  is  open  the  suction  is  greater  at  the  small  Venturi  tube.  At 
some  intermediate  position  of  the  throttle  there  is  a  time  when  the  action 
at  the  idle  jet  is  equal  to  that  at  the  small  Venturi,  and  at  this  particular 
time  gasoline  will  go  both  ways  to  the  cylinders.  This  condition  lasts 
but  a  very  short  time  because  as  the  throttle  is  opened  wider,  the  suction 
at  the  small  Venturi  tube  rapidly  becomes  greater  than  that  at  the  idling 
jet.  The  result  is  that  the  idling  tube  and  idling  jet  are  thrown  entirely 
out  of  action,  the  level  of  the  gasoline  in  the  idling  tube  dropping  when 

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the  throttle  is  open,  in  which  case  all  of  the  gasoline  enters  the  manifold 
by  way  of  the  holes  in  the  small  Venturi  tube. 

Adjusting  Stronzberg  Plain  Tube  Carburetor. — The  high  and  low  speed 
adjusting  screws,  A  and  J3,  Fig.  109,  should  be  completely  turned  down 
so  that  the  needle  valves  just  touch  their  respective  seats.  The  high 
speed  adjustment  A  should  be  unscrewed  about  3  turns  off  the  seat,  and 
the  low  speed  adjusting  screw  B  turned  anti-clockwise  about  1^  turns 
off  its  seat.  These  settings  are  merely  to  be  taken  as  a  starting  point, 
because  there  is  hardly  any  question  but  that  the  engine  will  start  easily 
with  these  settings,  provided  a  spark  is  available  and  other  things  are  in 
proper  condition. 

To  make  the  high  speed  adjustment,  the  spark  is  advanced  to  the 
position  for  normal  running  and  the  gas  lever  on  the  steering  wheel  quad- 
rant set  to  a  position  corresponding  to  an  engine  speed  of  approximately 
750  r.p.m.  The  high  speed  screw  A  is  gradu- 
ally turned  down  (clockwise)  notch  by  notch, 
until  a  slowing  down  of  the  engine  is  ob- 
served. The  same  screw  should  then  be 
turned  up  or  opened  (anti-clockwise)  until 
the  engine  runs  at  the  highest  rate  of  speed 
for  that  particular  setting  of  the  throttle. 

To  make  the  idling  adjustment  on  Bf  re- 
tard the  spark  fully  and  close  the  throttle  as 

far   as  possible  without  causing  the  motor  tO  Fig.   HO.-— Air   bleeder   on 

come  to  a  stop.  If  upon  idling,  the  motor  ^rmberg  plain  tube  "^ 
tends  to  load,  it  is  an  indication  that  the  mix- 
ture is  too  rich  and,  therefore,  the  low  speed  adjusting  screw  B  should 
be  turned  away  from  the  seat  (anti-clockwise),  thereby  permitting  the 
entrance  of  more  air  into  the  idling  mixture.  The  low  speed  adjustment 
is  best  made  by  carefully  observing  the  smoothness  with  which  the  motor 
revolves  when  idling,  and  can  be  properly  obtained  by  turning  the  screw 
B  up  or  down,  notch  by  notch,  until  the  best  idling  prevails.  It  is  safe 
to  say  that  the  best  idling  results  will  exist  when  the  screw  B  is  not  much 
more  or  less  than  1%  turns  off  the  seat. 

After  satisfactory  adjustments  have  been  made  with  the  car  station- 
ary, it  is  advisable  to  take  the  car  out  on  the  road  for  further  observation 
and  finer  adjustment.  If  upon  rather  sudden  opening  of  the  throttle, 
the  motor  back-fires,  it  is  an  indication  that  the  high  speed  mixture  is 
too  lean  and  in  this  case  the  adjusting  screw  A  should  be  opened  one  notch 
at  a  time  until  the  tendency  to  back-fire  ceases.  On  the  other  hand,  if 
when  running  along  with  open  throttle  the  engine  rolls  or  loads 7  it  is  an 
indication  that  the  mixture  is  too  rich.  This  is  overcome  by  turning  the 
high  speed  screw  A  down  (clockwise)  until  this  loading  is  eliminated. 

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The  Strorriberg  Economizer. — It  has  been  found  that  a  richer  mixture 
is  needed  for  power  at  wide  open  throttle  than  for  ordinary  pleasure  car 
driving  at  nearly  closed  throttle.  With  a  carburetor  giving  a  single  mix- 
ture proportion  under  all  conditions,  the  best  pulling  power  can  be  ob- 
tained only  with  a  considerable  waste  of  fuel  during  ordinary  closed 
throttle  driving.  The  operation  of  an  engine  at  wide  open  throttle  is 
very  much  more  sensitive  to  low  temperatures  than  at  closed  throttle. 
In  addition,  many  drivers  set  the  mixture  unduly  rich  in  the  winter 

The  Stromberg  economizer,  Fig.  Ill,  which  graduates  the  gasoline 
adjustment  to  best  efficiency  for  each  throttle  position,  has  been  devel- 
oped for  use  on  Stromberg  carburetors.  The  high  speed  gasoline  needle 
A  is  held  by  the  nut  N  which  is  supported  on  the  lever  arm  M  at  closed 
and  open  throttle.     The  proper  needle  adjustment  for  wide  open  throttle 

Fig.   111. — Economizer  on  Stromberg  carburetor. 

is  thus  obtained  with  the  nut  N.  But  with  the  throttle  in  ordinary 
driving  positions,  ranging  from  15  to  40  miles  per  hour,  the  roller  P  drops 
into  the  cam  notch  0  which  permits  the  lever  arm  to  drop  free,  so  that 
the  high  speed  nut  is  then  supported  upon  the  economizer  nut  R.  This 
lowers  the  high  speed  needle  into  its  orifice,  and  partially  cuts  off  the 
gasoline  for  these  speeds.  The  amount  of  drop  can  be  regulated  by  the 
pointer  L  which  gives  a  special  adjustment  for  the  greatest  possible 
economy  for  these  speeds.  This  does  not  interfere  with  the  maximum 
power  adjustment. 

86.  Stromberg  Model  H  Carburetor. — The  Stromberg  Model  H  car- 
buretor, Fig.  112,  is  of  the  double-jet  type  with  two  adjustments,  one 
for  high  and  one  for  low  speed,  both  working  on  the  gasoline  supply. 

The  gasoline  level  in  the  glass  float  chamber  is  regulated  by  the  hol- 
low metal  float.  The  fuel  for  low  speed  is  furnished  by  the  spray  nozzle 
in  the  Venturi  tube,  through  which  the  low  speed  air  passes.     At  high 

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speed,  the  auxiliary  air  comes  through  the  auxiliary  air  valve,  which  in 
turn  automatically  regulates  the  gasoline  flow  from  the  auxiliary  gasoline 
valve.  This  supplies  the  extra  gasoline  for  high  speed  and  heavy  duty 

The  dashpot  with  the  piston  riding  in  gasoline  prevents  all  fluttering 
of  the  air  valve  on  its  seat,  when  opening  and  closing. 


AunuuK  MaoLwricauMMUCMNtiisu 


Fiq.  112. — Stromberg  Model  H  carburetor. 

This  type  of  carburetor  is  fitted  with  a  strangling  or  choke  valve  in 
the  primary  air  inlet,  for  starting  in  cold  weather.  This  assists  in  the 
vaporization  of  the  gasoline  by  increasing  the  suction  on  the  liquid. 

The  spring  tension  on  the  air  valve  and  auxiliary  needle  valve  is  con- 
trolled either  from  the  dash  or  from  the  steering  post,  depending  upon 
the  style  of  control  installed.  This  permits  adjustment  to  be  made 
in  order  to  compensate  for  varying  conditions  of  weather,  fuel,  and 


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87.  Hudson  Carburetor. — The  Hudson  carburetor.  Fig.  113,  is  of  the 
metering  pin  type.  The  amount  of  gasoline  furnished  to  the  mixture 
depends  upon  the  height  of  the  metering  pin,  which,  as  will  be  noticed, 
has  a  tapering  V  groove.  When  the  engine  speeds  up  and  the  suction 
is  increased,  the  piston  in  the  air  chamber  raises  the  pin,  permitting  a 
greater  amount  of  gasoline  to  be  taken  up  by  the  incoming  air.  The 
raising  and  lowering  of  the  piston  also  increases  or  decreases  the  amount 
of  air  going  through  the  carburetor.  In  order  to  regulate  the  gasoline 
supply  from  the  steering  wheel,  a  sliding  sleeve  on  the  bottom  of  the 
metering  pin  can  be  raised  or  lowered  by  means  of  the  feed  regulator 
lever,  which  is  under  control  from  the  steering  wheel  or  dash. 

«-«      i    ;» M 

ttCTIOKM       VIEW 

Fio.  113. — Hudson  carburetor. 

88.  Cadillac  Carburetor. — Several  novel  features  are  found  on  the 
Cadillac  carburetor,  Fig.  114.  The  gasoline  supply  is  through  a  nozzle 
or  standpipe  placed  at  the  throat  of  a  Venturi  tube.  The  primary  air  is 
taken  in  through  an  opening  on  the  side  of  the  carburetor  as  indicated. 
The  auxiliary  air  valve  consists  of  a  hinged  shutter  controlled  by  a  coil 

The  throttle  pump  shown  is  controlled  by  the  movement  of  the 
throttle  valve..  Its  purpose  is  to  force  gasoline  through  the  spray  nozzle 
when  the  throttle  is  opened  suddenly  and  the  engine  speeds  up  quickly. 
When  the  throttle  is  opened  slowly,  the  throttle  pump  has  little  or  no 
effect  upon  the  gasoline  in  the  nozzle. 

89.  Packard  Carburetor. — This  carburetor,  Fig.  115,  is  of  the  con- 
ventional auxiliary  air  valve  type.    The  primary  air  supply  at  the  left 

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of  the  carburetor  furnishes  the  air  at  low  speeds.  This  air  current  picks 
up  the  gasoline  from  the  standpipe.  When  the  engine  speed  and  the 
suction  are  increased,  the  auxiliary  air  valve  opens  and  supplies  the  addi- 





Fia.  114. — Section  of  Cadillac  carburetor. 

tional  air  needed.  The  opening  and  closing  of  this  valve  is  regulated  by 
the  tension  on  its  two  springs.  This  tension  is  adjusted  by  two  cams 
underneath  the  springs.    Connections  to  these  cams  are  made  on  the  con- 

Fig.   115. — Packard  carburetor. 

trol  board  so  that  the  adjustment  can  be  made  from  the  driver's  seat. 
This  is  the  only  adjustment  to  be  made. 

90.  General  Suggestions  on  Carburetor  Adjustment  and  Operation. — 
It  is  obviously  impossible  to  give  detailed  instructions  which  will  answer 

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for  all  types  of  carburetors,  but  there  are  certain  fundamental  principles 
which  apply  to  the  adjustment  of  all  types. 

There  are  numerous  troubles  coining  from  an  engine  01  its  auxiliaries 
which  apparently  indicate  the  carburetor  is  at  fault.  These  troubles 
must  be  remedied  before  any  adjustment  on  the  carburetor  can  be  satis- 
factorily made.  It  must  be  ascertained  if  a  good  spark  occurs  in  the 
cylinder  at  the  proper  time;  if  each  cylinder  has  the  proper  compression; 
if  the  intake  manifold  or  connections  are  free  from  air  leaks;  and  if  gaso- 
line is  being  furnished  to  the  carburetor. 

The  engine  must  be  warmed  to  normal  running  conditions  before  any 
adjustments  are  attempted.  The  engine  should  be  run  idle  with  the 
spark  retarded  and  the  throttle  open  so  that  the  speed  of  the  car  will  be 
around  15  miles  per  hour.  The  low  speed  adjustment,  usually  on  the 
gasoline,  is  made  so  that  the  engine  hits  smoothly  and  regularly  after 
which  the  spark  is  advanced  and  the  engine  speeded  up.  The  high  speed 
adjustment,  usually  on  the  auxiliary  air,  is  then  made.  With  the  engine 
running  slowly  the  throttle  should  be  opened  quickly  to  give  the  engine 
a  rapid  acceleration.  The  engine  should  pick  up  quickly  and  fire  uni- 
formly. If  upon  opening  the  throttle  the  engine  back-fires  or  spits  back, 
the  mixture  is  weak  and  the  gasoline  adjustment  should  be  made  to  pro- 
vide more  fuel.  If  the  engine  is  to  be  run  at  practically  constant  speed 
and  there  is  little  need  of  quick  acceleration,  the  most  economical  adjust- 
ment will  be  one  which  back-fires  occasionally  on  rapid  acceleration.  A 
loading  upon  accelerating  indicates  too  rich  a  mixture. 

A  rich  mixture  is  indicated  by  the  overheating  of  the  cylinders,  waste 
of  fuel,  choking  of  the  engine,  misfiring  at  low  speeds,  and  by  a  heavy 
black  exhaust  smoke  with  a  very  disagreeable  odor.  A  weak  mixture 
manifests  itself  by  back-firing  through  the  carburetor  and  by  loss  of 
power.  A  back-fire  is  caused  by  the  fresh  charge  of  mixture  entering  the 
cylinder  and  coming  in  contact  with  the  slow  burning  charge  in  the  cyl- 
inder. With  the  intake  valve  open,  the  force  of  the  explosion  comes 
back  through  the  carburetor.  A  proper  mixture  will  give  little  or  no 
smoke  at  the  exhaust.  Blue  smoke  is  caused  by  the  burning  of  excess 
lubricating  oil  and  has  no  relation  to  the  quality  of  the  mixture. 

The  common  carburetor  troubles  and  remedies  will  be  taken  up  fully 
in  Chapter  XV. 

91.  Intake  Manifolds. — The  tendency  in  present  engine  design  is  to 
make  the  intake  manifold  of  such  shape  and  proportions  that  the  path 
from  the  carburetor  to  the  engine  cylinders  will  be  as  short  and  as  smooth 
as  possible.  Being  close  to  the  cylinders,  the  manifold  as  well  as  the 
carburetor  is  heated,  and  this  greatly  aids  the  vaporization  of  the  gaso- 
line. A  short  straight  manifold  gives  the  gas  very  little  chance  to  con- 
dense between  the  carburetor  and  the  cylinders.    It  is  also  desirable  to 

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have  the  distance  from  the  carburetor  to  each  of  the  different  cylinders 
the  same.  This  insures  the  same  amount  of  mixture  to  each  cylinder. 
On  some  engines,  where  the  cylinders  are  cast  en  bloc,  the  manifold  is 
cored  out  in  the  casting,  giving  a  short,  smooth  passage  for  the  fuel  charge. 
It  is  necessary  then  merely  to  attach  the  carburetor  to  the  cylinder 

Several  methods  of  casting  the  intake  manifold  to  insure  vaporization 
of  the  fuel  have  been  used.  The  exhaust  and  intake  manifolds  have  been 
combined  so  that  the  heat  from  the  exhaust  can  assist  in  the  vaporization 
of  the  fuel  in  the  intake  manifold.  The  Wilmo  manifold,  Fig.  116,  is 
such  a  combination,  in  which  the  exhaust  and  intake  manifolds  are 
divided  by  a  thin  wall.  The  high  temperature  of  the  exhaust  increases 
the  temperature  of  the  intake  manifold  and  insures  vaporization  of  the 
fuel.  Other  methods  such  as  casting  the  exhaust  manifold  around  the 
intake  manifold,  and  also  of  providing  hot  spots  in  the  intake  manifold, 

Fig.  116. — Wilmo  manifold. 

have  been  designed  to  insure  vaporization  and  prevent  condensation  of 
the  fuel. 

92.  Carburetor  Control  Methods. — The  carburetor  is  controlled  from 
the  driver's  seat.  The  hand  throttle  on  the  steering  post  regulates  the 
amount  of  mixture  to  the  cylinders,  thereby  regulating  the  engine  and 
car  speed.  In  conjunction  with  the  throttle  connection  is  the  accelerator 
on  the  toe-board.  This  permits  the  throttle  to  be  opened  by  the  foot, 
independently  of  the  hand  lever.  The  accelerator  must  be  held  open  by 
the  pressure  of  the  foot.  As  soon  as  the  pressure  is  removed  from  it,  the 
throttle  closes  to  the  point  set  by  the  hand  lever.  The  air  and  gasoline 
adjustment  can  usually  be  made  from  the  dash  of  the  car. 

93.  The  Gasoline  Feed  System. — There  are  numerous  systems  for 
feeding  the  gasoline  to  the  carburetor  from  the  gasoline  tank,  which 
may  be  placed  at  the  rear  of  the  frame,  in  the  cowl,  or  under  the  seat. 
These  feed  systems  are  classified  as  gravity,  pressure,  and  vacuum 

The  Gravity  Feed  System. — In  the  gravity  system  of  gasoline  feed,  the 
fuel  flows  to  the  carburetor  by  gravity  alone.    The  tank  may  be  placed 

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either  under  the  seat  or  in  the  cowl.  If  under  the  seat,  there  is  the  dis- 
advantage of  having  to  remove  the  cushions  before  being  able  to  fill  the 
tank.    There  is  also  the  possibility  in  some  cases  that  the  tank  will 

Fig.  117.— Typical  gravity  feed  system  with  supply  tank  in  cowl. 

become  lower  than  the  carburetor,  when  going  up  hill,  and,  consequently 
the  gasoline  will  not  flow  to  the  carburetor.  Both  of  these  disadvantages 
are  done  away  with  by  placing  the  tank  in  the  cowl.    In  either  case, 

iupply  tank  under  front  seat. 

Fio.  118. — Gasoline  supply  system  on  Ford 

however,  the  pressure  on  the  carburetor  float  valve  varies  as  the  level  in 
the  tank  varies.  When  filling  the  tank,  any  gasoline  which  spills  or 
leaks,  either  falls  around  the  seat,  in  the  car,  or  on  the  engine.     The 

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advantage  of  the  gravity  system  is  that  it  is  simple  and  always  ready. 
Figure  117  shows  a  typical  gravity  system  with  the  tank  in  the  cowl. 
The  float  operates  the  gasoline  indicator,  which  is  placed  on  the 
dash.  Figure  118  shows  the  gravity  tank  placed  under  the  seat  of  the 
Ford  car. 

The  Pressure  Feed  System. — When  the  gasoline  tank  is  placed  at  the 
rear  of  the  frame,  it  is  obviously  impossible  to  use  the  gravity  system. 
The  gasoline  may  be  forced  to  the  carburetor  by  putting  a  pressure  in 
the  gasoline  tank.  This  pressure  is  maintained  by  a  small  air  pump 
operated  by  the  engine,  or  by  a  hand  pump,  or  both.  After  filling  the 
tank,  a  hand  pump  is  used  to  get  up  pressure  until  the  engine  has  been 

Fig  119. — Pressure  system  of  gasoline  feed  as  used  on  Packard  car. 

started.  A  safety  valve  in  the  pressure  system  keeps  the  pressure  from 
getting  too  high.  The  particular  advantage  of  this  type  of  feed  system 
is  that  gasoline  feeds  to  the  carburetor  regardless  of  the  position  of  the 
car.  As  in  the  gravity  system,  the  pressure  on  the  float  valve  is  liable 
to  vary.  The  filler  cap  is  placed  away  from  the  engine  and  passengers, 
and  gasoline  may  be  put  in  without  disturbance.  A  typical  pressure 
feed  system  is  illustrated  in  Fig.  119. 

The  Vacuum  Feed  System. — Several  systems  have  been  developed  in 
which  the  gasoline  is  transferred  from  the  main  tank  at  the  rear  of  the 
car  by  a  vacuum  or  suction  to  a  small  auxiliary  tank  near  the  engine. 
From  this  small  tank  the  gasoline  flows  by  gravity  to  the  carburetor. 
Figures  120  and  121  show  the  installation  of  the  Stewart  vacuum  system 
in  a  car,  and  Fig.  122  indicates  the  construction  of  the  auxiliary  vacuum 

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This  system  comprises  a  small  round  tank,  mounted  on  the  engine 
side  of  the  dash.  This  tank  is  divided  into  two  chambers,  upper  and 
lower.  The  upper  chamber  is  connected  by  a  pipe  to  the  intake  manifold, 
while  another  pipe  connects  it  with  the  main  gasoline  tank.  The  lower 
chamber  is  connected  with  the  carburetor. 

Fig.  120. — The  Stewart  vacuum  feed  system. 

The  intake  strokes  of  the  motor  create  a  vacuum  in  the  upper  chamber 
of  the  tank,  and  this  vacuum  draws  gasoline  from  the  supply  tank.  As 
the  gasoline  flows  into  this  upper  chamber,  it  raises  a  float  valve.  When 
this  float  valve  reaches  a  certain  height,  it  automatically  shuts  off  the 
vacuum  valve  and  opens  an  atmospheric  valve,  which  lets  the  gasoline 

Fig.  121. — Under  the  hood. — The  Stewart  vacuum  feed  system. 

flow  down  into  the  lower  chamber.  The  float  in  the  upper  chamber 
drops  as  the  gasoline  flows  out,  and  when  it  reaches  a  certain  point,  it  in 
turn  reopens  the  vacuum  valve,  and  the  process  of  refilling  the  upper 
chamber  begins  again.  The  same  processes  are  repeated  continuously 
and  automatically.  The  lower  chamber  is  always  open  to  the  atmosphere 
so  that  the  gasoline  always  flows  to  the  carburetor  as  required  and  with  an 
even  pressure. 

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The  gasoline  always  remaining  in  the  tank  gets  some  heat  from  the 
engine  and  thereby  aids  carburetion;  it  also  makes  starting  easier,  by 
reason  of  supplying  warm  gasoline  to  the 
carburetor.  The  lower  chamber  of  the  tank 
is  constructed  as  a  filter  and  prevents  any 
water  or  sediment,  that  may  be  in  the  gaso- 
line, from  passing  into  the  carburetor.  A 
petcock,  in  the  bottom  of  the  tank,  permits 
drawing  this  sediment  off  and  also  allows  the 
drawing  of  gasoline,  if  required  for  priming 
or  cleaning  purposes. 

94.  Care  of  Gasoline. — Gasoline,  being  a 
volatile  liquid,  is  very  dangerous  if  not  prop- 
erly handled,  but  if  proper  care  and  attention 
are  given  to  it  there  should  be  no  danger 
whatever.  It  should  never  be  exposed  in  a 
closed  room  as  it  will  evaporate,  mix  with 
the  air,  and  form  a  very  explosive  mixture. 
Open  lights  should  always  be  kept  away 
from  gasoline.  When  it  is  necessary  to 
handle  gasoline  at  night,  it  should  be  done 
with  an  electric  light.  Do  not  under  any  con- 
dition use  an  open  light 

In  putting  out  a  gasoline  fire,  water  will 
only  spread  the  fire,  as  the  gasoline,  being 
lighter  than  water,  floats  on  it.  The  only 
successful  method  of  extinguishing  a  gasoline 
fire  is  to  smother  it,  either  by  sand,  or  a 
blanket,  or  by  the  gases  from  a  fire  extin- 

The  exhaust  gases  from  a  gasoline  engine  are  very  deadly.  Do  not 
breathe  them  for  any  length  of  time.  If  it  becomes  necessary  to  run  your 
engine  in  a  small  garage  with  the  doors  closed,  arrangement  should  be 
made  to  pipe  the  exhaust  to  the  outside  air. 

Fig.  122. — Stewart  vacuum 

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95.  Lubrication  and  Friction. — The  purpose  of  lubrication  is  to  reduce 
the  friction  between  moving  surfaces.  If  parts  rubbing  on  each  other 
are  not  separated  by  a  film  of  lubricant,  the  surfaces  will  rub  and  rapidly 
wear  away.  Friction  is  a  force  that  tends  to  retard  or  to  stop  the  motion 
of  one  surface  over  another.  The  f rictional  force  depends  on  the  nature 
of  the  surface,  and  also  on  the  kind  of  material.  The  rougher  the  surface 
and  the  softer  the  material,  the  greater  the  friction;  while  the  harder  the 
material  and  the  smoother  the  surface,  the  less  the  friction.  The  more 
friction  there  is,  the  greater  the  loss  of  power,  as  it  requires  power  to  over- 
come friction.  A  great  amount  of  friction  is  necessary  in  certain  parts 
of  the  car  such  as  in  the  brakes,  the  clutch,  and  the  outer  surface  of  the 
tires  in  order  that  they  be  efficient.  On  the  other  hand,  it  is  essential 
that  all  friction  possible  be  eliminated  from  the  bearings  and  pistons 
in  order  to  have  as  little  of  the  engine  power  lost  as  possible.  It  is  im- 
possible to  eliminate  the  friction  entirely,  but  with  the  proper  use  of  a 
suitable  lubricant,  the  loss  due  to  friction  can  be  reduced  to  a  minimum. 
The  principal  parts  of  the  engine  needing  lubrication  in  order  to  prevent 
friction  are  the  main  crankshaft  bearings,  connecting  rod  bearings,  wrist  pin 
in  the  piston,  camshaft  bearings,  half-time  gears,  pistons,  and  cylinder  walls. 

96.  Lubricants  and  Lubrication. — Lubricants  are  used  in  the  following 
three  forms:  fluid  oils,  such  as  gas  engine  cylinder  oil;  semisolids,  such 
as  soft  grease;  and  solids,  suchas  graphite.  These  forms  are  used  accord- 
ing to  the  condition  and  nature  of  the  surfaces  to  be  lubricated,  although 
on  automobile  engines,  lubricants  in  the  fluid  form  are  almost  universally 

There  are  three  general  sources  of  lubricants:  animal  oils,  such  as 
lard  and  fish  oils;  vegetable  oils,  such  as  olive,  castor,  and  linseed  oils;  and 
mineral  oils  which  are  secured  from  petroleum.  The  lubricants  of  mineral 
derivation  are  generally  used  for  gas  engine  lubrication  because  they 
serve  the  purpose  better,  are  more  plentiful,  and  are  cheaper. 

A  lubricant  must  be  of  such  character  and  quality  that  it  will  not 
break  up  or  decompose  at  the  temperature  under  which  it  will  work.  If 
a  lubricant  for  an  engine  cylinder  decomposes  at  a  temperature  lower 
than  that  in  the  cylinder,  it  will  be  useless  for  lubrication  and  the  cylinder 
walls  will  be  cut.  The  lubricant  must  also  have  sufficient  body  to  with- 
stand the  pressure  subjected  to  it  and  should  also  be  free  from  acids  in 
order  to  prevent  the  eating  away  and  etching  of  the  rubbing  surfaces. 


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97.  Test  of  Lubricating  Oils. — The  following  tests  are  made  to  deter- 
mine the  qualities  of  lubricating  oils: 

Viscosity. — Viscosity  is  the  property  of  a  liquid  by  which  it  has  a 
tendency  to  resist  flowing.    A  liquid  like  molasses  will  flow  less  readily 


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Fiq.  123. — Determining  viscosity  of  lubricating  oil.    (The  Tide  Water  Oil  Company.) 

Fig.  124. — Determination  of  flash  and  fire  point  of  lubricating  oil.     (The  Tide  Water  OH 


than  a  liquid  like  gasoline  and,  consequently,  is  said  to  have  a  higher 
viscosity.  Oils  are  tested  for  viscosity  by  putting  them  in  a  container 
called  a  viscosimeter,  Fig.  123,  and  allowing  them  to  flow  through  a  small 

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opening.  The  oil  that  flows  the  fastest  has  the  least  viscosity.  It  is 
necessary  to  use  oil  with  less  viscosity  on  some  parts  of  an  automobile 
than  on  other  parts.  Tight  fitting  bearings  should  use  oil  with  low  vis- 
cosity, while  meshed  gears  should  have  semi-solid  lubricants  with  high 
viscosity  because  the  pressure  on  the  rubbing  surface  is  very  high. 

Flash  and  Fire  Point. — The  flash  point  is  the  temperature  at  which, 
if  an  oil  be  heated  and  a  flame  held  over  the  surface  as  in  Fig.  124,  the 
vapor  rising  from  the  oil  will  burst  into  flame,  but  will  not  continue  to 
burn.  A  thermometer  is  placed  in  the  oil  bath  and  the  temperature  taken 
at  this  point.    The  fire  test  is  a  continuation  of  the  flash  point  test;  that 

Fio.  125.— Cold  teat  for  lubricating  oil.     (The  Tide  Water  Oil  Company.) 

is,  the  temperature  at  which  the  vapor  which  rises  from  the  oil  will  con- 
tinue burning,  and  not  merely  flash  for  a  second. 

Cold  Test. — The  cold  test,  Fig.  125,  indicates  the  temperature  at  which 
the  oil  hardens,  or  becomes  so  stiff  as  not  to  flow.  Good  cylinder  oil 
should  not  become  so  stiff  as  to  prevent  its  reaching  the  desired  points 
at  zero  temperature. 

Acid  Test. — A  simple  method  to  test  for  acid  is  to  dissolve  a  little 
of  the  oil  in  warm  alcohol  and  then  dip  a  piece  of  blue  litmus  paper  in  the 
solution.  If  there  is  any  acid  present,  the  paper  will  turn  red.  The 
litmus  paper  can  be  obtained  at  any  drug  store. 

98.  Gas  Engine  Cylinder  Oil. — The  oil  to  be  used  for  cylinder  lubrica- 
tion must  be  of  mineral  derivation.  Animal  and  vegetable  oils  decompose 
and  become  gummy  when  used  under  cylinder  conditions. 

Cylinder  oils  are  classified  in  three  grades:  light,  medium,  and  heavy. 
Light  cylinder  oil  looks  something  like  the  ordinary  machine  oil,  but 
has  a  higher  viscosity.    The  medium  is  somewhat  heavier  than  the  light, 

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and  might  be  compared  to  warm  maple  syrup.  Light  and  medium  oils 
should  be  used  only  on  engines  which  have  close-fitting  pistons.  The 
heavy  oil  is  used  in  air-cooled  engines  and  in  engines  that  have  loose 
pistons  or  that  become  too  hot  to  use  the  lighter  grade  of  oil. 

A  gcjbd  gas  engine  cylinder  oil  should  have  a  flash  point  not  under 
400°F.  and  a  fire  test  of  over  500°F.  so  that  it  will  not  break  down  and  give 
off  inflammable  gases  at  low  temperatures.  Its  viscosity  should  be  such 
that  it  will  retain  its  body  and  not  become  so  thin  as  to  be  worthless  as  a 
lubricant  at  high  temperatures.  It  should,  however,  be  thin  enough  so  as 
to  flow  quickly  over  the  cylinder  walls.  It  should  have  sufficient  body 
to  maintain  a  positive  film  between  piston  and  cylinder,  to  prevent 
leakage,  yet  should  not  be  so  heavy  as  to  retard  the  free  motion  of  the 
piston  and  rings.  It  should  also  be  free  from  acids  or  any  form  of 
vegetable  or  animal  matter  and  should  not  leave  a  carbon  deposit  in  the 
cylinder.  The  cold  test  must  be  low  enough  so  that  the  oil  will  flow  at  a 
low  temperature.  A  large  majority  of  the  cylinder  oils  sold  on  the 
market,  under  the  well-known  trade  names,  meet  all  of  the  necessary 
requirements  and  may  be  safely  used. 

99.  Systems  of  Engine  Lubrication. — The  purpose  of  a  lubricating 
system  is  to  provide  a  film  of  lubricant  between  all  rubbing,  moving,  and 
bearing  surfaces  in  order  to  prevent  undue  friction  and  wear  on  these 
surfaces.  The  main  and  crank  pins  of  the  crankshaft  turn  in  bearings 
on  the  crank  case  and  connecting  rods  and  at  the  same  time  sustain  the 
force  of  the  explosion  in  the  cylinders.  If  the  rubbing  surfaces  were  not 
separated  by  a  film  of  oil,  the  bearings  would  become  hot,  would  cause 
excessive  loss  of  power,  and  would  probably  seize  the  pins.  Proper 
lubrication  will  reduce  the  frictional  loss  to  a  minimum  and  will  carry 
away  any  excess  heat  which  would  cause  the  bearings  to  heat. 

A  similar  condition  exists  in  the  cylinders  where  the  pistons  are 
constantly  moving  up  and  down.  A  film  of  oil  on  the  cylinder  wall  pre- 
vents undue  friction  and  excessive  heating  which  might  cause  the  pistons 
to  stick.  This  film  can  be  maintained  by  a  light  oil  as  well  as  a  heavy 
oil,  if  other  conditions  are  such  that  it  can  be  used.  The  fuel  conditions 
have  considerable  to  do  with  the  lubrication  of  the  cylinder,  for,  if  any 
liquid  gets  into  or  condenses  in  the  cylinder,  the  lubricating  oil  will 
be  washed  down  into  the  crank  case.  This  is  particularly  true  when 
heavy  fuels,  which  are  hard  to  vaporize,  are  used. 

There  are  three  principles  used  in  providing  suitable  lubrication 
for  the  various  parts  of  the  automobile  engine.  The  oil  may  be  placed 
in  the  crank  case  and  be  splashed  by  the  revolving  cranks  to  the  parts 
to  be  lubricated,  or  a  pump  may  be  provided  to  pump  the  oil  from  the 
bottom  part  of  the  crank  case  to  a  point  above  the  part  to  be  lubricated 
to  which  the  oil  flows  by  gravity.     A  pump  may  also  be  used  to  pump 

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the  oil  under  pressure  to  the  parts  to  be  lubricated.  All  the  modern 
lubricating  systems  are  based  upon  one  or  a  combination  of  the  above 
principles.  In  general,  the  systems  may  be  classified  under  the  following 

1.  Full  splash. 

2.  Splash  with  circulating  pump. 

3.  Pressure  feed  with  splash. 

4.  Pressure  or  forced. 

5.  Full  pressure  or  forced  feed. 

100.  Full  Splash  System  of  Lubrication. — The  full  splash  system  is 
used  in  the  Ford  engine,  as  shown  in  Fig.  126.  The  oil  is  poured  directly 
into  the  crank  case  through  the  breather  pipe  until  it  comes  above  the 
lower  oil  cock.    The  level  of  the  oil  should  be  maintained  somewhere 




Fio.  126. — Full  splash  lubricating  system  on  Ford  car. 

between  the  two  oil  cocks.  The  flywheel  runs  in  the  oil,  picking  some  of 
it  up  and  throwing  it  off  by  centrifugal  force.  Some  of  the  oil  is  caught 
in  the  oil  cup  and  is  carried  through  the  crank  case  oil  tube  indicated  to 
the  front  end  of  the  crank  case  where  it  lubricates  the  timing  gears.  As 
the  oil  flows  back  to  the  rear  part  of  the  crank  case,  it  fills  the  small 
wells  in  the  crank  case  under  each  connecting  rod.  As  the  connecting 
rods  come  around,  a  small  spoon  or  dipper  on  the  bottom  scoops  up  the 
oil,  so  that  there  is  a  regular  shower  of  oil  all  the  time.  The  pistons, 
cylinder  walls,  and  bearings  are  lubricated  in  this  manner  and  the  oil  is 
kept  in  continuous  circulation.  All  parts  of  the  clutch  and  transmission 
are  lubricated  in  the  same  manner  as  the  engine. 

The  oil  level  should  never  get  below  the  lower  oil  cock  and  never 
above  the  upper  oil  cock.  The  level  of  the  oil  should  never  be  tested 
when  the  engine  is  running. 

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101.  Splash  System  with  Circulating  Pump. — A  combination  splash 
and  circulating  pump  feed  system  is  used  on  the  Dodge  car,  as  illustrated 
in  Fig.  127.  The  oil  is  poured  into  the  crank  case  through  the  breather 
pipe  on  the  left  side  of  the  engine.  The  oil  is  carried  in  the  oil  pan  at  the 
bottom  of  the  crank  case.  It  is  drawn  through  the  oil  strainer  by  the 
oil  pump  which  consists  of  two  vanes  and  an  impeller  driven  by  a  vertical 
shaft*  The  oil  is  forced  by  the  pump  into  the  oil  feed  pipe  which  supplies 
oil  through  holes  into  pockets  from  which  the  camshaft  bearings  are 
lubricated.  The  crankshaft  bearings  are  furnished  with  oil  through  oil 
pockets  which  are  in  turn  supplied  from  the  camshaft  bearing  pockets 
through  passages  cast  in  the  cylinder  block.    Openings  in  the  oil  feed 












Fig.  127. — Splash  and.  circulating  pump  lubricating  system  on  Dodge  car. 

pipe  allow  oil  to  fill  the  four  pockets  in  the  oil  pan  from  which  the  con- 
necting rods,  pistons  and  cylinder  walls,  cams,  etc.,  are  lubricated  by 
splash.  All  the  overflow  oil  goes  to  the  bottom  of  the  oil  pan  from, 
where  it  is  drawn  and  recirculated  by  the  oil  pump.  The  oil  gauge 
on  the  dashboard  indicates  the  pressure  under  which  the  oil  is  being 
fed  to  the  bearings.  A  slight  pressure  should  be  indicated  on  the  gauge 
when  the  car  speed  is  from  15  to  25  miles  per  hour.  Otherwise  there 
is  trouble  in  the  oiling  system. 

Some  combination  splash  systems  with  circulating  pump  use  the 
pump  merely  for  the  purpose  of  circulating  the  oil  from  the  oil  pan  to  the 
splash  troughs  below  the  connecting  rods.  The  circulation  is  usually 
through  a  sight  feed  on  the  dash  so  that  the  driver  may  know  whether  or 

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not  the  system  is  operating  properly.  This  system  as  used  on  the  Over- 
land car  is  illustrated  in  Fig.  128.  The  oil  reservoir  is  located  in  the 
bottom  of  the  crank  case  and  is  filled  through  the  combination  breather 
pipe  and  oil  filler  on  the  right  side  of  the  engine.  The  glass  gauge  on  the 
side  of  the  crank  case  close  to  the  breather  pipe  indicates  the  oil  level. 
The  oil  pump,  which  is  located  in  the  rear  of  the  crank  case,  is  driven 
from  the  camshaft.  The  oil  is  drawn  from  the  base  and,  after  passing 
through  a  strainer,  runs  through  a  sight  feed  on  the  dash,  from  where  it 
runs  into  the  troughs  and  is  splashed  onto  the  bearing  surfaces. 

Fio.  128. — Overland  splash  system  with  circulating  pump. 

The  wrist  pin  is  lubricated  from  the  cylinder  walls,  through  the 
opening  in  the  piston  through  which  the  wrist  pin  is  inserted,  as  well 
as  through  a  slot  cut  into  the  connecting  rod  over  the  wrist  pin  bush- 
ing. The  lubricant  circulates  freely  through  the  system  as  long  as 
the  small  wheel  in  the  dash  sight  feed  revolves.  But  as  soon  as  the 
wheel  stops  or  the  sight  feed  glass  shows  clear,  this  is  an  indication 
that  the  oil  supply  is  exhausted  or  that  there  is  an  obstruction  in  the 
circulation  of  the  oil.  In  some  types  of  splash  lubricating  systems  with 
circulating  pump,  the  sight  feed  on  the  dash  is  not  provided,  the  oil 
merely  being  circulated  between  the  oil  pan  or  pump  and  the  troughs 
below  the  connecting  rods. 

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102.  Pressure  Feed  and  Splash  Lubrication. — The  oil  pump  is  some- 
times used  for  furnishing  oil  under  pressure  to  all  of  the  parts  to  be 
lubricated,  with  the  exception  of  the  pistons  and  cylinder  walls.  These 
are  lubricated  by  the  oil  thrown  up  from  the  overflow  of  the  connecting 
rod  bearings.  The  pressure  feed  and  splash  system  of  lubrication  used 
on  the  Willys-Knight  four-cylinder  engine  is  shown  in  Fig.  129.  The 
sliding  sleeves_and  pistons  are  lubricated  by  the  splash  from  the  connect- 
ing rods. 

103.  Pressure  Feed  System. — The  pressure  feed  system  as  used  on  the 
Cadillac  Eight  is  shown  in  Fig.  130.  A  gear  pump  C  located  at  the  for- 
ward end  of  the  motor  and  driven  from  the  crankshaft  takes  the  oil  up 

Fia.  129. — Pressure  feed  and  splash  lubricating  system  on  Willys-Knight  engine. 

from  the  oil  pan  A  in  the  lower  part  of  the  crank  case  and  forces  it  through 
a  reservoir  pipe  D  running  along  the  inside  of  the  crank  case.  From  pipe 
D  leads  run  to  each  of  the  main  bearings.  The  crankshaft  and  webs 
are  drilled  and  oil  is  forced  from  the  main  bearings  to  the  connecting  rod 
bearings  through  the  drilled  holes.  The  forward  and  rear  main  bearings 
supply  the  rod  bearings  nearest  them,  while  the  center  main  bearing  takes 
care  of  the  rod  bearings  on  either  side  of  it.  The  oil  is  then  forced  from 
the  main  reservoir  pipe  up  to  the  relief  valve  M ,  which  maintains  a  uni- 
form pressure  above  certain  speeds,  and  overflows  from  this  valve  to  a 
pipe  R  running  parallel  with  the  camshaft  but  above  it.  Leads  from 
this  latter  pipe  carry  lubricating  oil  by  gravity  to  the  camshaft  bearings 
and  front  end  chains.  Pistons,  cylinders,  and  piston  pins  are  lubricated 
by  the  oil  thrown  from  the  lower  ends  of  the  connecting  rods. 

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A  gauge  indicating  the  level  of  the  oil  is  attached  to  the  upper  cover 
of  the  crank  case.  Whenever  the  indicator  reaches  the  space  marked 
fill,  oil  should  be  added  until  the  indicator  returns  to  full.  A  filling  hole 
is  provided  on  the  fanshaft  housing  just  forward  of  the  distributor.  If 
the  hand  on  the  pressure  gauge  on  the  cowl  vibrates  or  returns  to  zero 
on  the  dial  when  the  engine  is  running,  it  indicates  that  the  oil  level  is 
very  low.  Should  this  occur  through  neglect  to  add  oil  at  the  proper 
time,  the  engine  should  immediately  be  stopped  and  sufficient  oil  added 
to  bring  the  pointer  up  to  the  top  of  the  gauge  before  the  engine  is  again 

Fig.  130. — Pressure  lubricating  system  used  on  Cadillac  car. 

The  forced  feed  or  pressure  system  as  used  by  the  Wisconsin  Motor 
Manufacturing  Company  is  shown  in  Fig.  131.  The  oil  is  carried  in  an 
independent  chamber  at  the  bottom  of  the  crank  case,  and  the  connecting 
rods  are  not  allowed  to  dip  into  this,  thus  preventing  the  oil  from  being 
whipped  to  a  froth,  and  preserving  its  viscosity. 

The  oil  is  pumped  by  means  of  a  gear  pump,  located  at  the  lowest 
point  of  the  oil  reservoir,  into  a  main  duct  which  is  cast  integral  with  the 
crank  case.  From  this  duct,  the  oil  is  distributed  to  the  main  bearings 
by  means  of  other  ducts,  drilled  into  the  crank  webs.  From  the  main 
bearings  it  is  forced  through  drilled  passages  to  the  connecting  rod  bear- 
ings, and  also  a  sufficient  amount  of  oil  is  forced  out  of  the  ends  of  the 

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bearings  to  lubricate  the  pistons,  piston  pins,  and  camshafts.  A  separate 
lead  runs  directly  over  the  timing  gears,  and  all  oil  is  thoroughly  filtered 
before  it  is  pumped  over  again.  An  oil  gauge  indicates,  by  means  of  a 
ball  and  float,  the  exact  amount  of  oil  contained  in  the  reservoir.  Dis- 
tinct marks  on  the  glass  gauge  show  the  high  and  low  mark.     If  the  oil 

level  is  maintained  between  these 
two  levels  no  burnt  oil  smoke  will 
be  emitted,  and  the  spark  plugs  will 
not  be  fouled. 

The  pressure  of  the  oil  increases 
with  the  speed  of  the  motor,  so  the 
faster  the  engine  is  run  the  more  oil 
will  be  forced  to  it.  The  location  of 
the  oil  reservoir  permits  the  proper 
cooling  of  the  oil,  thus  minimizing  the 
danger  of  burning  out  bearings. 

104.  Full  Pressure  or  Forced 
Feed  System. — In  this  system,  as 
shown  in  Fig.  132,  the  oil  is  forced 
by  pressure  to  all  parts  to  be  lubri- 
cated, including  the  wrist  pins  and 
pistons.  Oil  is  carried  up  the  side  of 
|  the  connecting  rods  through  a  small 
I  pipe  which  is  fed  from  the  connect- 
ing rod  bearing  on  the  crankshaft. 
Besides  lubricating  the  wrist  pin, 
the  oil  flows  out  onto  the  cylinder 
walls  and  provides  lubrication  for 
the  pistojis. 

106.  Oil  Pumps. — The  oil  pump 
used  may  be  either  of  the  enclosed 
gear  type  or  of  the  piston  type.  A 
gear  type  of  oil  pump  is  illustrated 
in  Fig.  133.  The  two  gears  are  en- 
closed in  a  close  fitting  housing  and 
are  driven  from  the  camshaft  as  in- 
dicated. As  the  gears  turn,  the  oil 
is  taken  into  the  spaces  between  the 
teeth  and  carried  around  to  the  out- 
let where  the  action  of  the  teeth  meshing  together  squeezes  the  oil  out  of 
the  spaces  and  forces  it  to  flow  out  of  the  pump.  The  oil  pump  is 
driven  either  from  the  crankshaft  of  the  engine  or  from  the  camshaft. 

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The  camshaft  drive  to  the  gear  pump  used  on  the  Buick  is  illustrated  in 
Fig.  134. 

The  piston  oil  pump  is  very  much  like  an  ordinary  bicycle  pump  in 
principle.     The  oil  is  taken  into  the  oil  cylinder  on  the  suction  stroke  of 

Fig.  132. — Full  pressure  system  of  lubrication  on  Pierce  Arrow  car. 

the  oil  piston,  through  a  ball  valve.  On  the  return  stroke  of  the  piston, 
the  ball  valve  is  closed  and  the  oil  is  forced  out  into  the  oiling  system. 
Usually  some  method  is  provided  for  regulating  the  oil  pressure  when  the 
engine  speed  is  high.     This  is  done  by  putting  a  relief  valve  into  the  oil 

coNwecrtoN  ro 


Pt/M*>  HO&StMG 


Fio.  133. — Gear  type  of  oil  pump. 

pipe  line,  or  by  regulating  the  stroke  of  the  oil  pump  piston.  The  piston 
pump  and  pressure  regulating  device  used  on  the  Hudson  car  is  shown 
in  Fig.  136.    The  plunger  piston  is  driven  by  the  cam  shown.    The 

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plunger  is,  however,  under  the  control  of  another  eccentric  which  is  in 
connection  with  the  throttle  of  the  engine.  When  the  engine  speed  is 
low,  the  eccentric  holds  the  plunger  in,  permitting  it  to  make  a  very- 
short  stroke  when  the  cam  comes  around.  As  the  engine  speeds  up, 
the  eccentric  is  shifted  by  opening  the  throttle.  This  permits  a  longer 
stroke  of  the  plunger. 

106.  Engine  Lubrication  in  General. — The  proper  lubrication  of  the 
automobile,  especially  the  engine,  is  one  of  the  most  important  items  in 
its  operation.  Poor  lubrication  may  be  the  source  of  continual  trouble 
and  expense,  and  may  cause  considerable  damage  to  the  engine  parts, 

while  good  lubrication  permits  the  engine 
to  run  efficiently  without  undue  friction 
or  wear  on  its  parts. 

As  mentioned  before,  only  the  best 
lubricants  obtainable  should  be  used  for 
the  lubrication  of  an  automobile  engine. 
It  is  better  to  follow  the  manufacturer's 
instructions  in  regard  to  the  kind  of  oil  to 
use.  The  various  automobile  companies 
run  extensive  tests  and  find  out  the  best 
oil  for  their  particular  type  of  engine.  A 
poor  lubricant  should  never  be  used.  "  Its 
first  cost  may  be  less  but  it  is  more  ex- 
pensive in  the  end,  due  to  worn-out  bear- 
ings and  scored  cylinders. 

Excess  lubrication  in  the  cylinders  will 
produce  carbon  deposits  and  dirty  spark 
plugs.  It  may  also  cause  the  piston  rings 
to  gum  up  and  stick.  Excess  lubrication 
can  be  detected  by  the  color  of  the  ex- 
haust which  will  have  a  bluish  tinge,  or 
it  may  be  detected  by  a  sticky  black 
coating  on  the  spark  plugs. 
When  an  engine  has  a  tendency  to  lose  compression,  due  to  slightly 
worn  pistons  and  cylinders,  it  may  be  desirable  to  use  a  heavier  lubricating 
oil  for  the  cylinder  lubrication.  This  will  maintain  a  better  seal  between 
the  pistons  and  the  cylinder  walls  and  will  tend  to  prevent  the  loss  of 

107.  Cylinder  Cooling. — When  an  explosion  occurs  inside  the  cylinder 
of  a  gas  engine,  the  gases  on  the  inside  reach  a  temperature  of  from  2000° 
to  3000°F.  The  walls  of  the  cylinder  are,  of  course,  exposed  to  this 
high  heat  and  would  get  red  hot  very  quickly  if  there  was  not  some  way 
of  keeping  them  cool.     The  polished  surface  upon  which  the  piston  slides 



^Spiral  drive 
from  cam 





Gear  oil 

Pio.  134. — Oil  pump  drive  on 
Buick  engine. 

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would  be  spoiled  very  quickly  and  lubrication  prevented  because  of  the 
high  temperature  burning  up  the  lubricating  oil.  The  most  common 
way  of  keeping  a  cylinder  cool  is  by  the  use  of  water.  A  metal  jacket 
surrounds  the  cylinder  and  provides  a  space  for.  the  cooling  water  By 
keeping  a  supply  of  water  passing  through  this  space,  thevcylinder  can 


r.   *l»vOwfr>  WIO, 

•  •not.  in  my  cowTitet  in 

ILOW   g^CKO    POkiT.Qfti       MIOM    lOltD   POSITION 

IK  ntunvoiff 

Fig.  135. — Piston  type  of  oil  pump  on  Hudson  car. 

be  kept  cool  enough  for  the  efficient  operation  of  the  engine.  The  cylin- 
der head  is  also  cast  with  a  double  wall,  especially  around  the  valves, 
80  that  these  parts  are  also  cooled  by  the  circulating  water. 

There  are  two  general  methods  of  keeping  the  cylinders  cool  by  the 
use  of  circulating  water  or  other  cooling  liquid.  These  are  the  ihermo- 
typhon  and  the  forced  or  pump  circulation. 

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108.  Thermosyphon  Cooling  System. — In  any  type  of  cooling  system 
using  water,  the  cylinders  are  surrounded  by  a  water  jacket  through  which 
the  water  circulates.  The  top  of  the  water  space  is  connected  by  a  rubber 
hose  to  the  top  of  the  radiator,  and  the  bottom  of  the  water  space  to  the 
bottom  of  the  radiator.  The  water,  being  heated  by  the  engine  cylinder, 
goes  to  the  radiator  at  the  front  of  the  car  where  it  is  cooled  and  returned 
to  the  engine  for  use  again. 

The  circulation  of  the  water  in  the  thermosyphon  system  is  based  on 
the  fact  that  cold  water  is  heavier  than  hot  water,  and,  consequently, 
the  water  heated  in  the  cylinder  jackets  rises  and  goes  over  into  the  top 
part  of  the  radiator.  The  water  is  cooled  while  passing  down  through 
the  radiator  and  flows  from  the  lower  portion  of  the  radiator  back  to 
the  engine  cylinder  jackets.    The  rate  at  which  the  water  circulates  is 

Fio.  136.— Overland  thermosyphon  cooling  system. 

increased  or  decreased  with  every  increase  or  decrease  in  jacket  tempera- 
ture. Circulation  is  automatically  maintained  as  long  as  the  engine  is 
hot  and  there  is  enough  water  in  the  radiator  to  insure  that  the  return 
connection  from  the  cylinder  to  the  radiator  also  contains  water.  This 
means  that  the  radiator  must  be  kept  practically  full  all  the  time,  or 
there  will  be  no  circulation  and  the  water  will  merely  boil  away.  A  fan 
placed  in  front  of  the  engine  draws  air  through  the  radiator  and  cools 
the  water  as  it  passes  down  through  the  radiator. 

The  thermosyphon  cooling  system  o£  the  Overland  car  is  illustrated 
in  Fig.  136.  The  water  enters  the  cylinder  jackets  A,  and  upon  becoming 
heated  by  the  explosions  within  the  cylinders,  expands  and,  becoming 
lighter  than  the  cooler  water,  rises  to  the  top.  It  then  enters  the  pipe  D 
and  passes  into  the  radiator  at  F,  where  it  is  brought  into  contact  with 

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a  large  cooling  surface  Ey  in  the  form  of  the  cellular  radiator.  On  being 
cooled  and  thereby  contracting  and  becoming  heavier,  the  water  sinks 
again  to  the  bottom  of  the  cooling  system,  to  enter  the  cylinders  once 
more  and  to  repeat  its  circulation.  The  cooling  action  is  further  in- 
creased by  a  belt-driven  f aji  which  draws  air  through  the  radiator  spaces. 
The  cooling  system  on  the  Ford,  Fig.  137,  is  also  of  the  thermosyphon 
type.  The  arrows  indicate  the  path  of  the  cooling  water  through  the 
engine  cylinders  and  radiator. 

Fio.  137. — Ford  cooling  system* 

109.  Pump  or  Forced  System  of  Water  Circulation. — The  thermo- 
syphon system  of  water  circulation  depends  upon  the  temperature  dif- 
ference between  the  water  in  the  cylinder  jackets  and  in  the  radiator. 
This  circulation  is  not  so  definite  or  positive  as  in  a  pump  system  where 
a  water  pump  is  used  to  maintain  the  water  circulation.  The  pump  is 
usually  driven  by  the  engine,  and,  if  the  engine  is  running,  the  water  is 
circulating  regardless  of  water  temperatures.  Figure  138  illustrates  a 
typical  pump  or  forced  system  of  water  circulation.  The  centrifugal 
pump  placed  at  the  front  of  the  engine  keeps  the  water  in  constant  cir- 
culation while  the  engine  is  running.  From  the  pump  the  water  is  driven 
into  the  cylinder  water  jacket,  directly  at  the  valve  seats,  where  perfect 
cooling  is  needed  most.  Here  it  absorbs  the  heat  and  goes  on  to  the  upper 
cylinder  connection  and  thence  to  the  radiator.  In  the  radiator  D  the 
water  percolates  slowly  down  through  many  fine  tubes  F  and  is  cooled 

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by  the  air  rushing  between  the  fins  surrounding  the  tubes  and  thence 
returns  to  the  pump.  The  fan  on  the  front  of  the  engine  is  driven  from 
the  crankshaft  and  draws  the  air  through  the  radiator,  thus  facilitating 
the  cooling  operation.  This  radiator  is  a  standard  design  of  tubular 
radiator.  The  pump,  which  is  of  the  centrifugal  type,  requires  no  atten- 
tion other  than  to  see  that  it  does  not  become  choked  by  using  dirty 
water.  There  is  a  packing  nut  on  the  shaft  which  should  be  repacked 
if  the  pump  should  ever  leak  around  the  shaft  entrance.  This  can  be 
done  very  easily  by  turning  off  the  packing  nut,  removing  the  old  packing, 

Fio.  138. — Pump  or  forced  system  of  water  circulation. 

rewinding  the  shaft  with  a  few  inches  of  well  graphited  packing,  and 
tightening  up  the  packing  nut.  The  packing  should  be  wound  on  in  the 
same  direction  as  the  nut  is  turned  to  tighten  it. 

110.  Packard  Cooling  System. — The  circulation  in  the  cooling  system 
of  the  Packard  Twin  Six,  Fig.  139,  is  maintained  by  a  double  impeller 
centrifugal  pump.  This  pump  takes  the  water  from  the  bottom  of  the 
radiator  and  forces  it  through  each  of  the  cylinder  block  water  jackets. 
The  outlet  from  the  cylinder  jackets  is  through  the  cored  water  passage 
surrounding  the  gas  intake  header,  which  connects  the  cylinder  blocks, 
and  then  to  the  top  of  the  radiator. 

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A  thermostat,  located  at  the  top  connection  of  the  radiator,  by-passes 
the  water  coming  from  the  cylinders  to  the  inlet  side  of  the  pump  until 
it  has  reached  the  proper  temperature  for  the  efficient  running  of  the 
engine.  When  the  water  is  cold,  the  thermostat  valve  is  closed  and  the 
by-pass  to  the  water  pump  is  open,  allowing  the  water  to  circulate 
through  the  cylinder  jackets  and  back  to  the  pump  without  going  through 
the  radiator.  As  the  water  becomes  heated,  the  expansion  of  the  ther- 
mostat opens  the  radiator  valve  and  closes  the  by-pass  to  the  pump, 
making  it  necessary  for  all  of  the  water  to  go  through  the  radiator. 








.  A 








by-pass  con- 
necting rad- 
iator inlet  & 
outlet  tube 

Pio.  139. — Packard  cooling  system. 

The  radiator  is  of  the  flat  ribbon  tube  type.  A  vent  pipe  extending 
from  the  lower  left  corner  of  the  radiator  to  the  filler  cap  carries  off  any 
surplus  water  or  steam  which  may  be  formed. 

111.  Cadillac  Cooling  System. — The  cooling  system  on  the  Cadillac 
Eight,  Fig.  140,  is  also  of  the  forced  circulating  type.  The  radiator  is  of 
the  tubular  and  plate  type,  with  a  rotating  fan  mounted  on  the  forward 
end  of  the  generator  driving  shaft,  the  latter  being  driven  by  a  silent 
chain  from  the  camshaft.  Each  set  of  cylinders  is  cooled  separately. 
There  are  two  centrifugal  water  pumps,  one  on  each  side  of  the  forward 
end  of  the  engine.  These  are  driven  by  a  transverse  shaft  which  is 
driven  by  spiral  gears  from  the  crankshaft.  Within  each  pump  housing, 
is  a  Sylphon  thermostat,  Fig.  141,  which  controls  the  flow  of  water  be- 
tween the  radiator  and  the  pump. 

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When  the  temperature  of  the  cooling  water  drops  below  a  predeter- 
mined temperature,  the  thermostats  contract  and  close  the  valves  be- 

Fiq.  140.— Cooling  system  on  Cadillac  eight. 

tween  the  pump  and  radiator.     The  water  is  then  circulated  only  through 
the  cylinder  blocks  and  the  water  jacket  on  the  intake  manifold.     When 

the  thermostats  are  closed,  none  of  the 
water  circulates  through  the  radiator  but 
as  the  temperature  of  the  water  rises, 
the  thermostats  expand,  thereby  gradually 
opening  the  valves,  permitting  the  water 
to  circulate  through  the  radiator. 

The  advantage  in  this  method  of  con- 
trol is  that,  in  starting  with  a  cold  en- 
gine, the  engine  is  brought  to  a  point  of 
highest  efficiency,  in  so  far  as  temperature 
is  concerned,  much  more  quickly  than  if 
it  were  necessary  to  heat  the  entire 
volume  of  water  before  reaching  that 
efficiency.  With  the  usual  water  circulat- 
ing system,  the  highest  efficiency  of  the 
engine  is  not  reached  in  extremely  cold 
Fio.  hi.— Cadillac  water  pump      weather.    An    engine   uses    its  gasoline 

showing  sylpbon  thermostat.  .     ,.  ,  ... 

most    economically  when   it  is  running 
rather  warm;  but  with  a  radiator  which  is  adequate  to  prevent  over- 

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heating  in  hot  weather,  the  cooling  is  too  great  for  best  economy  in  ex- 
tremely cold  weather. 

The  thermostat  is  simply  a  small  accordion  shaped  copper  tube 
containing  a  liquid  which  when  heated  changes  to  a  gas  and  expands. 
This  thermostat  is  in  connection  with  a  valve  B,  Fig.  141,  so  that,  when 
it  expands,  it  raises  the  valve  from  its  seat,  this  valve  controlling  the 
flow  of  water  from  the  radiator  to  the  pump.  A  by-pass  C  connects 
with  the  water  jacket  of  the  engine,  and,  when  the  engine  is  started, 
the  water  is  naturally  cold.  Therefore,  the  thermostat  is  contracted 
and  its  valve  is  seated.  Thus  the  radiator  water  is  shut  off,  the  cir- 
culation being  simply  to  the  water  jackets  of  the  cylinders  from  which 
some  water  is  by-passed  through  the  carburetor  jacket  and  pipe  D  and 
some  returns  direct  to  the  pump  through  hose  C.  There  is  only  a  small 
part  of  the  water  circulating,  and  when  this  heats  up,  the  thermostat 
begins  to  expand  and  lifts  its  valve  from  its  seat,  permitting  the  water 
in  the  radiator  to  flow  into  the  system.  This  action  continues  back  and 
forth  and  keeps  the  water  temperature  nearly  constant. 

Cadillac  Condenser. — The  Cadillac  system  employs  a  condenser  for 
the  purpose  of  preventing  the  loss  of  the  cooling  fluid  by  evaporation 
when  an  alcohol  solution  is  used.  The  condenser  is  placed  under  the 
front  floor  boards  and  is  connected  to  the  overflow  pipe  of  the  radiator 
by  a  pipe  S,  Fig.  140.  The  vapor  given  off  from  the  hot  cooling  liquid 
in  the  radiator  passes  through  the  overflow  tube  to  the  condenser  where 
it  is  condensed  by  coming  into  contact  with  the  liquid.  When  the  engine 
is  stopped,  the  liquid  in  the  radiator  contracts  and  the  vapor  condenses, 
resulting  in  a  vacuum  in  the  top  part  of  the  radiator.  This  vacuum 
allows  the  pressure  of  the  atmosphere  on  vent  V,  Fig.  140,  and  this  forces 
the  liquid  out  of  the  condenser  back  to  the  radiator.  In  order  for  the 
condenser  to  operate  properly,  the  radiator  cap  must  make  an  air  tight 

112»  Air  Cooling. — The  Franklin  engine,  shown  in  Fig.  142,  uses  an  air 
cooling  system.  The  individual  cylinders  are  each  provided  with  52 
vertical  steel  flanges  projecting  from  their  periphery.  The  flanges  on 
each  cylinder  are  surrounded  by  sheet  aluminum  jackets  which  form 
passages  for  the  air.  These  jackets  or  sleeves  form  a  connection  with  a 
sheet  metal  deck  which  divides,  horizontally,  the  space  under  the 
hood.  The  flywheel  is  provided  with  a  number  of  curved  blades  so  that 
it  has  a  blower  effect  whenever  the  engine  is  running.  This  forms  a 
partial  vacuum  which  sucks  air  into  the  space  underneath  the  hood 
through  the  grilled  opening  in  front.  This  air  passes  in  uniform  quan- 
tities down  through  the  individual  jackets  on  each  cylinder  into  the  com- 
partment below  the  engine  deck  and  then  out  through  the  fan  blades. 
The  fan  is  incorporated  in  the  flywheel  and  driven  directly  by  the  engine, 

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so  a  steady  stream  of  fresh  air  is  being  continually  drawn  down  over  the 
cylinders  as  long  as  the  engine  is  running.  As  there  is  no  cooling  action 
when  the  hood  is  raised,  the  engine  should  never  be  run  for  more  than  a 
few  minutes  with  the  hood  raised. 

113.  Radiators. — The  cooling  water  after  being  heated  in  the  water 
jackets  of  the  engine  enters  the  radiator  at  the  top,  and,  as  it  is  cooled  by 
the  air  rushing  through  the  openings  in  the  radiator,  it  slowly  descends 
down  through  the  radiator  to  the  bottom.  The  rate  and  effectiveness  of 
the  cooling  action  depend  somewhat  upon  the  type  of  radiator.  There 
are  two  general  types  of  radiators,  the  tubular,  and  the  cellular  or  honey- 

Fia.  142. — Franklin  air  cooling  system. 

The  tubular  radiator  consists  of  a  series  of  tubes  placed  either  hori- 
zontally, vertically,  or  at  an  angle.  The  vertical  placing  of  the  tubes, 
as  shown  in  Fig.  138,  is  the  usual  method.  Fins  placed  around  the  tubes 
assist  in  carrying  away  the  heat  and  cooling  the  water. 

The  cellular  radiator  consists  of  a  number  of  short  cells  or  tubes 
arranged  so  that  the  water  passes  around  the  outside  while  the  air  rushes 
through  the  inside.  The  cellular  radiator  is  more  costly  to  manufacture 
but  gives  correspondingly  more  effective  cooling,  because  the  water  flows 
in  thin  flat  streams  instead  of  a  comparatively  large  round  stream  as  in 
most  of  the  tubular  radiators.  Some  radiators  are  built  which  resemble 
both  the  tubular  and  cellular  types.  Thin  flat  tubes  run  from  the  top  to 
the  bottom  of  the  radiator  in  a  zigzag  path,  giving  a  cellular  or  honey- 
comb appearance. 

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Radiator  Shutters. — With  the  general  use  of  automobiles  in  the  winter 
time,  several  schemes  have  been  adopted  to  regulate  the  amount  of  air 
drawn  through  the  radiator  by  the.  fan.  Covers  are  used  which  partially 
cover  the  front  of  the  radiator  and  allow  the  cold  outside  air  to  pass 
through  only  asmail  partof  the  radiator.  An;adjustable shutter, Fig.  143, 
under  the  control  of  the  driver  is  also  employed  for  this  purpose.  When 
the  car  is  running,  the  shutter  can  be  adjusted  according  to  the  outside 
temperature,  and,  when  the  car  is  left  standing,  the  shutter  can  be  closed 
to  assist  in  keeping  the  cooling  water  warm  enough  to  insure  starting 
and  prevent  freezing. 

Fig.  143. — Adjustable  shutter  for  radiator. 

Fig.  144. — Boyce  moto-meter. 

114.  Temperature  Indicators. — If  for  any  reason  the  cooling  system 
should  not  operate  properly,  it  is  very  possible  that  the  engine  will 
become  overheated  and  may  possibly  stop.  This  usually  results  from  a 
loose  or  broken  fan  belt,  leaky  radiator  or  connections,  obstructions  in 
radiator  or  connections,  or  from  a  defective  pump.  In  turn,  the  cooling 
system  may  be  working  properly,  but  the  engine  may  overheat  causing 
the  temperature  of  the  cooling  water  to  become  excessive.  In  order 
that  the  driver  may  be  able  to  know  just  how  the  engine  and  cooling 
system  are  working,  a  temperature  indicator  may  be  placed  on  the  radia- 
tor cap.  Figure  144  illustrates  the  Boyce  Moto-Meter  which  indicates  at 
all  times  the  exact  operating  conditions  of  the  engine  and  cooling  system. 
A  temperature  indicator  is  very  desirable  on  a  car  because  it  will  warn 
the  driver  of  coming  trouble  before  serious  damage  results. 

115.  Cooling  Solutions  for  Winter  Use. — In  climates  where  the  tem- 
perature does  not  go  below  a  dangerous  freezing  point,  the  cooling  medium 
used  is  water;  but  in  cold  regions,  where  cars  are  run  a  good  deal  in  the 

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winter,  it  is  necessary  to  use  some  kind  of  anti-freezing  solution.     The 
ideal  requirements  for  an  anti-freezing  compound  are  as  follows: 

1.  It  should  have  no  harmful  effect  on  any  part  of  the  circuit  with 
which  it  comes  into   contact. 

2.  It  should  be  easily  dissolved  or  combined  with  water. 

3.  It  should   be   reasonably   cheap. 

4.  It  should  not  waste  away  by  evaporation,  that  is,  its  boiling  point 
should  be  as  high  as  that  of  water. 

5.  It  should  not  deposit  any  foreign  matter  in  the  jackets  or  pipes. 
The  principal  materials  used  are:  (1)  oil;  (2)  glycerine;  (3)  calcium 

chloride;  (4)  alcohol;  (5)  mixture  of  alcohol  and  glycerine;  (6)  kerosene. 

Oil  has  the  advantage  of  a  very  high  boiling  point  so  it  does  not  waste 
away,  but  it  has  the  disadvantage  that  it  does  not  make  a  good  mixture 
with  water.  It  will  not  absorb  heat  so  rapidly  as  water  and  also  has  a 
lower  heat  coefficient,  that  is,  it  takes  less  heat  to  raise  the  temperature 
of  a  certain  amount  of  oil  one  degree,  than  it  does  the  same  amount  of 
water.  Oil  cannot  be  used  where  there  is  any  rubber  in  the  circuit.  The 
oil  causes  the  rubber  to  deteriorate  rapidly. 

The  disadvantages  of  using  glycerine  are  similar  to  those  of  oil, 
but  the  most  important  is  sure  destruction  to  the  rubber  connection. 
Glycerine  is  also  liable  to  contain  free  acids,  and  is  quite  expensive. 

Calcium  chloride  jnakes  a  very  good  solution  with  water,  the  freezing 
point  depending  upon  the  proportion  used.  The  general  solution  is  to 
use  5  lb.  of  the  salt  to  1  gal.  of  water.  This  solution  will  stand  39° 
below  zero  before  freezing.  It  has  the  disadvantage  of  being  very  apt 
to  cause  electrolytic  action  where  two  metals  are*  joined  together.  Cal- 
cium chloride  is  derived  from  hydrochloric  acid,  and  is  liable  to  contain 
free  acids,  which  attack  metal  very  rapidly.  Calcium  chloride  has  the 
same  appearance  as  chloride  of  lime,  but  has  a  somewhat  different  chemi- 
cal composition.  Only  pure  calcium  chloride  should  ever  be  used.  The 
commercial  chloride  of  lime  sets  up  electrolytic  action.  The  solution 
may  be  tested  for  acid  by  dipping  a  piece  of  blue  litmus  paper  in  it.  If 
there  is  any  acid  present,  the  paper  will  turn  red.  As  the  water  is  evapo- 
rated in  the  radiator,  there  will  be  a  crust  formed  on  the  inside  of  the 
jacket,  and  also  in  the  pipes.  This  crust  has  a  tendency  to  clog  up  the 
system  and  prevent  circulation.  The  rate  at  which  these  deposits 
occur  depends  on  the  strength  of  the  solution. 

Denatured  alcohol  is  the  best  substance  to  use  as  a  non-freezing 
solution,  as  it  has  no  destructive  action  whatever  on  either  metal  or 
rubber,  makes  no  deposits,  and  never  causes  electrolytic  action.  A  solu- 
tion of  50  per  cent,  water  and  50  per  cent,  alcohol  will  stand  about 
32°  below  zero.  The  only  disadvantage  is  that  it  evaporates  more 
readily  than  the  water,  so  that  when  adding  new  solution,  more  alcohol 

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than  water  must  be  added  in  order  to  keep  the  solution  of  the  same 
strength.  The  combination  of  alcohol,  glycerine,  and  water  seems  to 
give  very  good  results.  In  this  combination,  equal  parts  of  alcohol  and 
glycerine  are  used.  The  alcohol  has  a  tendency  to  overcome  the  de- 
structive action  of  the  glycerine  on  the  rubber  connections,  and  the 
glycerine  keeps  the  alcohol  from  evaporating  too  rapidly.  The  freezing 
point  depends  on  the  strength  of  the  solution.  A  solution  of  60  per  cent, 
water  and  20  per  cent,  each  of  alcohol  and  glycerine,  freezes  at  24°  below 
zero.  The  proportions  must  be  governed  by  the  locality  in  which 
they  are  used. 

There  are  also  numerous  anti-freezing  compounds  on  the  market. 
These  are  generally  put  up  from  some  of  the  materials  mentioned. 

In  the  following  tables  are  shown  the  temperatures  at  which  some  of 
the  well-known  anti-freezing  solutions  will  freeze.  The  different  localities 
and  different  altitudes  require  different  solutions.  Every  person  should 
be  able  to  select  a  solution  in  the  right  proportion,  to  avoid  having  any 
trouble  in  the  coldest  possible  weather  likely  to  be  experienced  in  the 
home  location. 

Freezing  Points  of  Calcium  Chloride  Solutions 

Per  cent,  by  volume  of  calcium  chloride 

Specific  gravity  of  solution 

Freezing  point 












-  9°F. 










The  specific  gravity  is  given  to  be  used  as  a  check  on  the  proportions. 

Freezing  Points  of  Denatured  Alcohol  Mixed  with  Water 

Per  cent,  by  volume  of  alcohol 

Specific  gravity  of  solution 

Freezing  point 









-  1°F. 













If  wood  alcohol  be  used  instead  of  denatured  alcohol,  slightly  lower  temperatures 
can  be  reached  with  the  same  proportions  of  alcohol  and  water. 

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Freezing  Points  or  Alcohol  and  Glycerine  Mixed  with  Water 

Alcohol  and  glycerine,  per  cent. 

Water,  per 


Freezing  point 









-  5°F. 













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116.  Electricity. — Probably  no  other  factcr  has  played  a  more  im- 
portant part  in  making  possible  the  modern  gasoline  automobile  with  its 
four-,  six-,  eight-,  or  twelve-cylinder  engine,  than  has  electricity  in  its 
many  applications.  It  may  be  said  that  the  development  of  the  auto- 
mobile power  planth  as  been  controlled  largely  by  the  development  of 
the  electrical  ignition  equipment  upon  which  the  engine  depends  for  its 
operation.  Besides  using  electricity  for  igniting  the  fuel  charge  within 
the  engine  cylinders,  it  is  also  called  upon  to  start  the  engine,  furnish  the 
light,  operate  the  horn  and,  in  some  instances,  to  shift  the  gears  of  the 
transmission.  The  indispensable  usefulness  of  electricity  in  the  auto- 
mobile field  is  evidenced  by  the  fact  that  all  makes  of  passenger  auto- 
mobiles, as  well  as  many  trucks  and  tractors,  are  now  completely  equipped 
with  an  electric  starting,  lighting,  and  ignition  system. 

Since  the  operation  of  the  automobile  depends  so  greatly  on  the 
successful  operation  of  its  electrical  equipment,  it  is  very  necessary 
to  have  a  clear  understanding  of  the  fundamental  electrical  and  electro- 
magnetic principles  governing  the  construction  and  operation  of  the 
electrical  equipment  used,  in  order  that  it  may  be  operated  and  repaired 

The  exact  nature  of  electricity  is  not  known;  but  its  effects,  the 
laws  governing  its  action,  and  the  methods  of  controlling  and  using  it  in 
doing  various  kinds  of  work  are  well  understood.  Two  general  methods 
are  employed  in  generating  electrical  energy  on  the  automobile.  One 
of  these  is  chemical  action,  which  is  the  fundamental  principle  of  the 
battery,  while  the  other  is  the  conversion  of  mechanical  energy  into 
electrical  energy  through  electromagnetic  induction,  the  method  em- 
ployed in  the  magneto  and  generator. 

117.  Conductors  and  Non-conductors. — All  substances  conduct  elec- 
tricity to  some  extent;  some  much  better  than  others.  There  is  no 
known  substance  which  does  not  offer  some  resistance  to  the  flow  of 
electrical  current  through  it.  Substances  such  as  silver,  copper,  etc., 
which  offer  a  comparatively  low  resistance  are  known  as  conductors, 
while  substances  such  as  porcelain,  glass,  fiber,  etc.,  which  offer  a  high 
resistance  to  the  passage  of  electrical  current  are  known  as  non-conductors 
or  insulators.    A  liquid  which  offers  a  comparatively  low  resistance  is 


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known  as  an  electrolyte,  while  a  liquid  that  offers  a  high' resistance  is 
termed  a  non-electrolyte. 

118.  Hydraulic  Analogy  of  Electric  Current. — An  electric  current 
flowing  through  a  wire  may  be  compared  to  the  flow  of  water  through 
a  pipe  line.  As  the  water  flows  through  the  pipe  due  to  pressure  from 
a  pump  or  a  difference  in  water  level,  such  as  from  A  to  B  in  Fig.  145, 

—  XJ 



Fig.  145. — Hydraulic  analogy  of  electrical  current. 

so  electrical  current  will  flow  through  a  conductor  due  to  an  electrical 
pressure  or  potential  created  by  a  battery  or  mechanically  driven  gen- 
erator. The  current  flows  through  the  circuit  from  the  high  potential 
or  positive  (+)  terminal  to  the  low  potential  or  negative  (— )  terminal, 
as  shown  by  the  arrows  in  Fig.  146.  In  the  case  of  the  water,  however, 
the  pressure  causing  it  to  flow  is  measured  in  pounds  per  square  inch 

and  the  rate  of  flow  in  gallons 
per  unit  of  time,  while  in  the 
electrical  circuit  the  pressure  or 
electromotive  force  is  measured  in 
units  called  volts,  and  the  rate  of 
current  flow  in  amperes. 

119.  Resistance. — The  oppo- 
sition that  a  substance  offers  to 
the  passage  of  an  electric  current 
through  it  is  called  its  resistance, 
and  the  unit  of  this  electrical  re- 
sistance is  called  the  ohm.  The 
ohm  may  be  defined  as  the  resis- 
tance offered  by  a  circuit  to  1  ampere  of  current  flowing  under  a  pres- 
sure of  1  volt.  Resistance  of  a  circuit  may  be  compared  to  the  friction 
which  a  pipe  offers  to  the  flow  of  a  liquid,  in  that,  electrical  resistance 
depends  upon  the  size,  length,  material,  and  temperature  of  the  wire,  just 
as  the  flow  of  any  liquid  is  resisted  by  friction  which  in  turn  depends 
upon  the  size,  length,  and  shape  of  the  conducting  pipe  as  well  as  upon 
the  temperature  of  the  liquid.  Thus  the  resistance  of  a  conductor  or 
wire  will  decrease  by  increasing  its  cross  sectional  area,  and  will  in- 
crease by  simply  increasing  its  length.     In  both  cases,  the  current  which 

Fig.  146. — Battery  electrical  circuit. 

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will  flow  at  a  certain  voltage  will  increase  or  decrease  as  the  resistance 
changes.  In  fact,  the  resistance  is  directly  proportional  to  the  length 
of  a  conductor  and  inversely  proportional  to  its  cross  sectional  area. 
This  is  true  only  in  case  the  temperature  does  not  change,  since  it  has 
been  found  that  in  the  case  of  most  metal  conductors  an  increase  in 
temperature  is  accompanied  by  an  increase  in  resistance,  while  in  the 
case  of  insulating  materials,  carbon  and  various  electrolytic  solutions, 
an  increase  in  temperature  is  accompanied  by  a  decrease  in  resistance. 
120.  Relation  between  Current,  Voltage,  and  Resistance. — Ohm  dis- 
covered that  in  the  case  of  circuits  which  carry  current  continuously  in  one 
direction  (known  as  direct-current  circuits),  a  definite  relation  exists 
between  the  current  flowing,  the  voltage,  and  the  resistance  of  the 
circuit.     This  relation  is  known  as  Ohm's  law,  namely:  The  electric 


TERMINALS--^  A^  i, 


SOURCE  OF  v  -  *  ' 

Fig.  147. — Method  of  connecting  ammeter  and  voltmeter  on  electrical  circuit. 

current  in  a  conductor  equals  the  voltage  applied  to  the  conductor  divided  by 
the  resistance  of  the  conductor.  This  law  may  be  simply  stated:  Current 
=  voltage  -s-  resistance. 

Or,  stating  the  same  thing  in  another  way: 

(1)  Amperes  =  Volts  -*-  Ohms 

(2)  Volts       =  Amperes  X  Ohms 

(3)  Ohms      =  Volts  -£-  Amperes 

These  rules  may  also  be  expressed  in  more  convenient  formulas: 

Namely:    (1)  To  find  Current,  I  =  ^  •    (2)  To  find  Voltage,  E  =  I  X  R. 

(3)  To  find  Resistancef  R  =  -j  in  which  J  =  the  current  in  amperes,  E  = 

the  voltage,  and  R  =»  the  resistance  in  ohms. 

Thus  if  two  things  are  known  regarding  a  circuit  such  as,  the  voltage 
and  resistance,  or  the  current  and  resistance,  or  the  voltage  and  current 
the  exact  relation  between  voltage,  current,  and  resistance  can  be  readily 
calculated  by  applying  the  proper  formula. 

The  voltage  and  current  in  a  circuit  can  be  readily  measured  by 
connecting  a  voltmeter  and  ammeter  as  shown  in  Fig.  147.    The  voltmeter 

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is  an  instrument  for  measuring  the  electrical  pressure  in  volts  and  is 
connected  across  the  source  of  current  supply  which  in  Fig.  147  is  repre- 
sented by  terminals  A  (+)  and  B  (— ).  The  ammeter  is  an  instrument 
for  measuring  the  current  flow  in  amperes  and  is  connected  in  the  circuit 
so  that  all  the  current  flowing  in  the  circuit  passes  through  the  instru- 
ment. As  there  is  no  instrument  for  measuring  directly  the  electrical 
resistance  of  a  circuit,  it  must  be  calculated  by  first  measuring  the  voltage 
and  current  and  dividing  the  voltage  in  volts  by  the  current  in  amperes  as 
in  formula  (3).  Consequently,  if  a  wire  consists  of  such  material,  size, 
length,  and  temperature  as  to  offer  1  ohm  resistance,  the  voltage  re- 
quired to  force  1  ampere  through  it  must  be  1  volt.  The  volt  or  unit  of 
electrical  pressure,  then,  may  be  defined  as  the  pressure  required  to  force 
one  ampere  of  current  through  a  circuit  having  one  ohm  resistance. 

121  Electrical  Power. — The  unit  of  electrical  power  is  the  watt.  It  is 
defined  as  the  rate  at  which  work  is  performed  by  1  ampere  of  current 
flowing  through  a  circuit  under  1  volt  pressure.  Expressing  this  as  a 

(4)  P  =  I  X  E 

in  which  J  =  the  current  in  amperes,  E  =  the  voltage,  in  volts,  and  P  = 
the  power  in  watts. 

As  an  example:  The  electrical  energy  or  work  required  of  a  6  volt 
battery  in  supplying  a  current  of  2  amperes  to  the  primary  ignition  cir- 
cuit would  be  6  X  2  =  12  watts.  The  watt  is  too  small  a  unit  for  con- 
venient use  in  many  cases  so  that  the  kilowatt  (kw.)  or  1000  watts  is 
frequently  used. 

Other  factors  which  the  reader  should  become  familiar  with  are: 

1  Horse  Power  (Hp.)  =  746  watts  or  .746  kilowatt. 
1  kilowatt  =  1.34  Horse  Power. 

1  kilowatt  of  power  used  for  1  hour  =  1  kilowatt-hour. 
1  ampere  of  current  for  1  hour  =  1  ampere-hour. 

122.  Effects  of  Electric  Current. — Experiments  have  shown  that 
electric  current  in  flowing  through  certain  circuits  produces  various 
physical,  chemical,  and  magnetic  changes  or  effects.  On  the  automobile, 
these  effects  include  (1)  heat  and  light,  as  witnessed  in  the  glow  of  the 
lamp  filaments;  (2)  chemical  action,  which  is  the  principle  of  the  storage 
battery;  and  (3)  magnetism,  upon  which  the  induction  coil,  magneto, 
generator,  and  starting  motor  depend  for  their  operation. 

Heat  is  developed  in  any  conductor  through  which  electricity  flows. 
The  temperature  of  the  conductor,  consequently,  is  raised.  The  heat 
represents  the  loss  due  to  the  overcoming  of  the  resistance  by  the  current. 
The  amount  of  heat  developed  is  often  very  small  and  is  not  noticeable. 

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148. — Chemical  effect  of  electrical  current. 

Fuses  burn  Out  because  of  the  heat  developed  in  them  by  the  current. 
When  the  current  becomes  excessive  the  fuse  wire  melts  and  opens  the 
circuit,  protecting  it  from  possible  damage.  Incandescent  lamps  produce 
light  because  their  filaments  are  heated  by  the  passage  of  an  electric 

The  chemical  action  due  to  electric  current  may  be  illustrated,  as  in 
Fig.  148,  by  submerging  the  ends  of  two  wires,  connected  to  battery 
terminals,  in  a  glass  of  water  in  which  a  little  salt  has  been  dissolved. 
The  current  in  passing  through 
the  water  will  liberate  a  gas  in 
the  form  of  fine  bubbles  which 
it  will  be  noticed  rise  particu-  / 
larly  around  the  negative  ter-  > 
minaL  This  simple  test  is  very 
valuable  to  remember  as  a  means 
of  determining  the  positive  and 
negative  of  two  direct-current 
leads.  It  is  also  valuable  in 
distinguishing  between  alternating  and  direct  current,  since  alternating 
current  will  cause  bubbles  to  collect  equally  around  both  terminals. 

The  magnetic  effect  of  electric  current  can  be  readily  noticed  by  send- 
ing battery  current  through  an  insulated  wire  wound  on  an  iron  bar  as 
shown  in  Fig.  149,  and  noting  the  attraction  which  the  iron  will  then 
have  for  other  pieces  of  iron.    The  iron  bar  is  now  said  to  contain  magnet- 
ism which,  as  will  be  shown 
later,  has  a  definite  rela- 
tion to  the  direction  of  the 

123.  The  Dry  Cell.— 
The  first  necessary  part  of 
an  electric  ignition  system 
is  a  source  of  current.  For 
this  purpose  either  a  bat- 
tery, a  generator,  or  a  mag- 
neto can  be  used.  In  a  battery  ignition  system,  the  current  is  supplied 
by  either  dry  batteries  or  a  storage  battery  in  combination  with  a  gener- 
ator that  is  driven  by  the  engine. 

The  dry  cell  has  been  a  common  source  of  current  for  ignition  pur- 
poses but  is  now  being  supplanted  by  the  storage  battery.  The  dry  cell 
is  especially  adaptable  for  ignition  systems  of  the  open  circuit  type  such 
as  certain  models  of  the  Atwater-Kent  system  where  the  current  demand 
is  small.  Figure  150  shows  a  section  of  a  commercial  dry  cell.  It  con- 
sists of  a  cylindrical  zinc  shell  or  can  around  the  inside  of  which  has  been 





Fio.  149. — Magnetic  effect  of  electrical  current. 

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placed  a  piece  of  absorbent  paper  saturated  with  salammoniac  and  zinc 
chloride  dissolved  in  water.  The  zinc  shell  forms  the  negative  terminal 
of  the  battery,  and  the  carbon  element  down  through  the  center  of  the 
cell  forms  the  positive  .terminal.  The  space  between  the  absorbent  paper 
and  the  carbon  is  filled  with  a  mixture  of  powdered  carbon  and  manganese 
dioxide  which  acts  as  a. depolarizing  agent.  Polarization  refers  to  the 
accumulation  of  hydrogen  gas  bubbles  around  the  carbon  or  positive  ter- 
minal of  the  cell  upon  rapid  current  discharge.  The  gas  tends  to  insulate 
the  carbon  stick,  thereby  increasing  the  internal  resistance  and  diminish- 
ing the  current  output.  The  voltage  of  a  dry  cell  is  about  1.5  volts. 
The  maximum  current  or  amperage  of  a  new  cell  ranges  from  20  to  35 
amperes,  depending  upon  the  size  of  the  cell  and  the  temperature.  A 
dry  cell  giving  more  than  25  to  30  amperes  will  probably  polarize  rapidly. 
Nearly  all  American  dry  cells  are  2}i  in.  in  diameter  and  6  in.  high.    The 

Fig.  160. — The  dry  cell. 

top  is  sealed  with  a  special  compound  to  make  it  water-tight.  The  entire 
cell,  except  the  top,  is  wrapped  with  pasteboard  to  prevent  the  zinc 
making  contact  with  other  zinc  cans  in  the  set.  The  dry  ceU  always 
gives  out  direct  current.  Its  capacity  and  its  life  depend  on  the  way  it  is 
used,  both  being  greater  when  it  is  used  intermittently.  Cells  not  in  use 
should  be  stored  in  a  cool  dry  place  to  prevent  rapid  deterioration. 

124.  The  Storage  Battery. — Although  the  storage  battery  will  be  dis- 
cussed in  Chapter  IX,  a  brief  description  is  given  here  in  order  to  bring 
out  clearly  its  function  as  a  source  of  electrical  energy  on  the  automobile. 
A  storage  cell,  Fig.  151,  consists  of  two  sets  of  lead  plates,  positive  and 
negative,  placed  in  an  acid  proof  jar  containing  a  solution  of  sulphuric 

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acid  and  water.  Each  plate  consists  of  a  grid  or  framework  composed  of 
lead  and  antimony,  the  openings  of  which  are  pasted  full  of  a  lead  com- 
pound, known  as  active  material.  Two  or  more  plates  of  the  same  kind 
connected  to  a  common  terminal  form  a  group. 

In  the  positive  group,  the  active  material  is  lead  peroxide,  character- 
ized by  its  chocolate  brown  color,  while  in  the  plates  of  the  negative 
group  it  consists  of  finely  divided  sponge  lead  (pure  lead)  and  is  greyish 
in  color.  The  positive  and  negative  groups  are  placed  in  the  cell  so  that 
the  positive  and  negative  plates  alternate  and  are  insulated  from  each 
other  by  separators  of  specially  treated  wood  or  threaded  rubber.  By 
passing  direct  current  through  the  cell,  sending  it  in  at  the  positive  and  out 

Bvttpty  T€ffinui  twwttc 
■irt  «  hrw  *f  fvtc  ftn 

toll*  CwragiMtf  Swbct 

Ht«t(  nun— |»rr  |*  M4 
HI  •rrfiwcni  frws  »J»ir» 

Fig.  151. — Section  of  storage  cell. 

at  the  negative  terminals,  the  plates  undergo  an  electrochemical  change 
known  as  charging.  When  the  battery  is  used  or  discharged  the  chemical 
change  is  reversed  and  the  plates  tend  to  return  to  their  original  state, 
giving  off  current  as  they  do  so.  The  current  thus  produced  is  a  direct 
current.  It  leaves  the  battery  at  the  positive  terminal  and  returns  to  the 
negative.  A  single  storage  cell  consists  of  one  positive  and  one  negative 
set  of  plates,  and  gives,  when  fully  charged,  a  pressure  of  about  2  volts. 
Its  current  capacity  depends  upon  the  size  and  number  of  plates  in  the 

126.  Wiring  of  Ignition  Batteries. — When  current  for  ignition  is  sup- 
plied by  a  storage  battery  the  voltage  may  be  either  6  or  12  volts.  This 
voltage  is  fixed  by  the  design  of  the  starting  and  lighting  system  which  is 

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usually  of  the  sarpe  voltage  as  the  ignition  and  which  operates  off  of  the 
same  battery.  The  battery  may  vary  in  size  from  60  to  130  ampere-hour 
capacity,  depending  upon  the  requirements  of  the  starting  and  lighting 
system.     Since  one  storage  cell  gives  only  2  volts,  in  a  6  volt  battery  the 









12  Volts 

Fio.  152. — Cell  connections  for  a  six 
volt  storage  battery. 

Fio.  153. — Cell  connections  for  a 
twelve  volt  storage  battery. 

proper  voltage  is  obtained  by  connecting  3  cells  in  series,  that  is,  con- 
necting the  Positive  (+)  terminal  of  one  cell  to  the  Negative  (— )  of  the 
next  as  shown  in  Fig.  152.  In  like  manner,  a  12  volt  storage  battery 
must  have  6  cells  connected  in  series  as  in  Fig.  153. 

fit^y^y®^    &&Q 

S  Dry  cells  in  series 

Fio.  154. 

S  Dry  cells  in  parallel 
Fio.  155. 

When  dry  cells  are  used  for  ignition,  two  methods  of  connecting 
several  cells  may  be  resorted  to  in  order  to  raise  the  voltage  and  amperage 
to  the  proper  amount,  namely,  through  series  or  parallel  connection.  The 
series  method  of  connection  is  shown  in  Fig.  154  in  which  the  carbon  or 

Positive  of  one  cell  is  connected  to  the  zinc 

or  Negative  of  the  next,  leaving  one  carbon 

and  one  zinc  free  for  connection.     Thus 

the  current  has  to  pass  through  the  entire 

set  of  cells  to  complete  its  circuit.     This 

method    increases   the  voltage  as  many 

times  as  there  are  cells.     The  five  cells  of 

Fig.   154  each  give  about  1.5  volts  and 

will,  when  connected  in  series,  furnish  a 

current  at  5  X  1.5,  or  1%  volts  pressure.     The  current  output  is  equal 

to  the  current  of  one  cell,  or  about  20  amperes.     If  all  the  carbons  are 

connected  and  all  the  zincs  fastened  together,  as  shown  in  Fig.  155, 

/S  cells  in  multiple  scries  arronyement 
Fio.  156. 

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the  connection  is  known  as  parallel.  The  resultant  voltage  equals  the 
voltage  of  one  cell,  and  the  current  output  equals  the  current  output  of 
one  cell  mutiplied  by  the  total  number  of  cells.  For  example,  the  current 
output  of  five  cells  connected  in  parallel  would  be  5  X  20  or  100  amperes 
and  the  voltage  would  be  1J^  volts.  Therefore,  to  increase  voltage,  con- 
nect the  cells  in  series,  and  to  increase  current  output  connect  them  in 

Where  the  current  demand  is  small  or  not  continuous,  five  cells 
connected  in  series  may  be  used.  This  arrangement  gives  7}£  volts  and 
20  amperes  and  is  suitable  for  single  cylinder  engines  or  for  starting  en- 
gines of  two  or  more  cylinders  where  a  magneto  is  used  after  the  engine 
is  in  operation.  It  is  also  suitable  for  battery  ignition  systems  of  the 
open  circuit  type,  such  as  certain  models  of  the  Atwater-Kent. 

When  the  amount  of  current  required  is  great  and  a  storage  battery 
is  not  available,  the  multiple  series  connection  may  be  used.  It  is  suitable 
for  engines  of  two  or  more  cylinders  and  for  continuous  service.  This 
arrangement  consists  of  parallel  groups  of  as  many  cells  in  a  series  as  may 
be  required  for  the  service.  Figure  156  shows  an  arrangement  with  three 
parallel  sets,  each  having  five  cells  connected  in  series.  This  arrange- 
ment provides  for  an  amperage  of  about  60  at  7}>i  volts. 

126.  Magnetism. — That  property  of  certain  substances  to  attract 
and  repel  other  materials  is  called  magnetism.  It  is  not  known  precisely 
what  magnetism  is  any  more  than  the  exact  nature  of  electricity  is  known. 
But  the  rules  governing  it  have  been  well  established.  Electricity  and 
magnetism  are  entirely  different  although  they  are  very  closely  related. 

127.  Natural  and  Artificial  Magnets. — Magnetism  and  its  properties 
were  first  made  known  to  man  near  the  town  of  Magnesia,  in  Asia,  where 
an  iron  ore  was  found  that  possessed  a  remarkably  attractive  power  for 
iron.  This  attractive  power  was  called  magnetism,  and  a  piece  of  ore 
having  this  power  was  termed  a  magnet.  The  ore  itself  has  since  been 
named  magnetite  and  lodestone  and  is  the  only  form  of  natural  magnet 
known.  It  is  not  in  such  form  as  to  be  of  commercial  value,  consequently 
the  magnets  which  will  be  considered  are  manufactured  and  are  known 
as  artificial  magnets. 

128.  Magnetic  and  Non-magnetic  Metals. — Only  certain  substances, 
chiefly  iron  and  steel  or  alloys  containing  the  same,  show  magnetic  prop- 
erties. Metals  such  as  brass,  copper,  aluminum,  or  zinc  which  do  not 
contain  iron  and  which  are  not  susceptible  to  magnetism  are  called  non- 
magnetic metals. 

Soft  iron,  after  being  magnetized,  loses  its  magnetism  readily  as  soon 
as  the  magnetizing  force  is  removed,  and  is  called  a  temporary  magnet. 
A  bar  of  hardened  steel  after  being  magnetized  will,  with  proper  treatment, 
remain  magnetized  indefinitely  and  is  called  a  permanent  magnet.     For 

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this  reason,  temporary  magnets,  such  as  used  in  the  cores  of  induction 
coils,  are  made  of  soft  iron — usually  a  bundle  of  soft  iron  wire — while  per- 
manent magnets,  such  as  the  magnets  of  a  magneto,  are  made  of  either 
hardened  nickel,  chrome,  or  tungsten  steel. 

129.  The  Poles  of  a  Magnet — Certain  parts  of  a  magnet  possess  the 
power  of  attracting  iron  to  a  much  greater  extent  than  other  parts.    These 

parts  are  called  the  poles.  In  a  bar 
magnet  the  strength  is  greatest  at  the 
ends,  consequently  the  ends  form  the 
poles.  These  poles  are  designated 
North  and  South  according  to  their 
magnetic  influence  on  other  mag- 
nets, and  according  to  the  direction 
of  magnetism. 

It  is  generally  understood  that 
magnetism  acts  in  the  nature  of  a 
stream  or  current.  This  flow  of  mag- 
netism is  termed  magnetic  flux  and 
is  conventionally  represented  by  lines 
of  force  which  always  flow  out  of  the 
North  pole  of  a  magnet  and  around 
into  the  South  pole,  forming  a  complete  circuit.  The  reason  for  this  is 
readily  seen  by  placing  a  piece  of  paper  over  a  bar  magnet  and  sprin- 
kling iron  filings  over  the  paper.  The  action  of  the  magnetic  force  will 
arrange  the  filings  in  lines  running  from  one  end  of  the  magnet  around  to 

Fig.   157. — Field  of  a  bar  magnet  as 
shown  by  iron  filings. 

Fig.  158. — Lines  of  force  around  bar  and  horseshoe  magnets. 

the  other  end  as  shown  in  Fig.  157.    These  lines  of  force  may  also  be 
illustrated  graphically  as  shown  in  Fig.  158. 

When  two  magnets  are  brought  together,  it  is  found  that  the  North 
pole  of  one  attracts  the  South  pole  of  the  other,  and  that  two  like  poles, 
either  North  and  North  or  South  and  South,  repel  each  other.  Magnetic 
attraction  and  repulsion  are  shown  by  dipping  two  common  magneto 

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magnets  in  iron  filings  and  noting  the  formation  of  the  filings  when  the 
poles  of  the  two  magnets  are  brought  together.  With  the  North  and 
South  poles  brought  together,  as  in  Fig.  159,  the  iron  filings  will  form  in 
metallic  strings  between  the  poles  thus  showing  magnetic  attraction. 
With  the  like  poles  brought  together,  as  in  Fig.  160,  the  filings  will  have 



Fio.  159. — Magnetic  attraction  of 
unlike  poles. 

Fig.  160. — Magnetic  repulsion  of  like 

the  appearance  of  two  jets  of  water  being  forced  against  each  other, 
and  will  show  repulsion.  In  each  case  the  iron  filings  plainly  indicate 
the  path  of  the  magnetic  circuit  which  is  flowing  within  the  magnet 
from  the  South  (S)  to  the  North  (N)  pole  and  through  the  space  between 
the  poles  from  the  North  (N)  to  the  South  (S). 



Fig.  161. — Use  of  compass  to  determine  magnetic  polarity. 

130.  The  Magnetic  Field. — The  zone  surrounding  a  magnet  through 
which  the  magnetism  flows  from  the  North  pole  to  the  South  pole  is 
known  as  its  magnetic  field.  The  strength  of  this  field  depends  upon  the 
number  of  magnetic  lines  of  force  per  square  inch  of  the  magnet  poles  and 
is  usually  measured  in  pounds  pull  per  unit  area  of  the  pole. 

The  polarity  of  a  magnet  and  the  direction  of  its  magnetic  field 

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may  be  determined  by  using  a  compass  as  shown  in  Fig.  161.  The  North 
end  of  the  compass  needle  (the  end  which  naturally  points  toward  the 
geographical  North  pole)  will  always  point  in  the  direction  of  the  magnetic 
field  which  is  towards  the  South  pole  of  the  magnet.  Likewise,  the 
South  end  of  the  compass  needle  will  point  towards  the  North  pole  of 
the  magnet. 

131.  Electromagnetism. — Magnetism  which  is  produced  by  an  electric 
current  is  called  electromagnetism.    Experiments  show  that  a  wire  or  any 

(A)  (B)     SIDE  VIEW  (O 


Fjq.  162. — Magnetic  lines  of  force  about  a  straight  conductor  carrying  current. 

other  form  of  conductor  which  carries  an  electric  current  will  have  a  magnetic 
field  set  up  around  it  in  a  right-handed  direction  to  the  current  and  proper" 
tional  in  strength  to  the  amount  of  current  flowing.  This  fact  constitutes 
the  basis  for  the  relation  between  electricity  and  magnetism.  The  mag- 
netic field  thus  produced  is  arranged  in  concentric  circles  around  the 
wire,  as  in  Fig.  162,  and,  like  the  field  of  a  magnet,  its  direction  can  be 
determined  by  a  pocket  compass.  The  magnetic  needle,  if  held  above 
or  below  a  wire  carrying  a  direct  current,  will  turn  crosswise  of  the  wire, 

Fig.  163. — Deflection  of  a  compass  needle  when  near  a  conductor  carrying  a  current. 

as  in  Fig.  163,  with  the  North  end  of  the  compass  pointing  around  the 
wire  in  the  direction  of  the  magnetic  field.  Thus  by  determining  the 
direction  of  magnetic  field  around  the  wire,  the  direction  of  current 
flowing  in  the  wire  may  also  be  determined. 

If  the  wire  is  coiled  into  a  loop,  as  in  Fig.  164,  it  will  be  found  that 
the  lines  of  force  all  enter  the  same  face  of  the  loop  and  come  out  of 
the  other  face.     If  two  loops  are  placed  close  together,  as  in  Fig.  165,  the 

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(P^  fe\  /£V 
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lines  of  force  will  join  and  go  around  the  two  wires  together  instead  of 
around  each  one  alone.  The  same  is  also  true  of  the  lines  of  force  sur- 
rounding two  parallel  wires  placed 
close  together  in  which  both  wires 
are  carrying  current  in  the  same 
direction.  If  a  number  of  turns  of 
insulated  wire  are  wound  into  a  coil 
or  solenoid,  as  in  Fig.  136,  nearly 
all  the  lines  of  force  will  enter  one 
end  of  the  coil,  pass  through  it,  leave 
the  opposite  end,  and  return  outside 
of  the  coil  to  the  starting  point. 
Thus  a  solenoid  or  coil  carrying  an 
electric  current  has  the  same  char- 
acter of  magnetic  field  as  a  bar  mag-  Flo  164._Magnetic  field  produced  by 
net  having  a  North  pole  where  the  current  in  a  single  loop. 

#^-  *-.    \H 

Piq.  165. — Magnetic  lines  of  force  around  two  adjoining  loops  carrying  current  in  the  same 


lines  of  force  leave  the  coil  and  a  South  pole  where  the  lines  of  force 
enter  the  coil,  and  may  be  considered  an  electromagnet. 

Fio.  166. — Lines  of  force  through  a  coil  or  solenoid. 

132.  The  Electromagnet. — An  electromagnet  made  as  just  described 
is  not  very  strong,  but  may  be  made  so  by  inserting  a  core  of  soft  iron  or 

Digitized  by  LiOOQ IC 



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steel,  as  in  Fig.  167.  The  iron  has  the  property  of  conducting  magnetic 
lines  much  more  readily  than  air;  hence,  a  solenoid  with  an  iron  core 
will  have  a  much  greater  strength  than  a  simple  solenoid  without  a  core. 
The  strength  of  the  electromagnet  may  also  be  increased  by  in- 
creasing either  the  amount  of  current  flowing  through  the  winding 
or  the  number  of  turns  in  the  coil,  or  both.  In  fact,  the  magnetic  pull 
of  the  core  will  depend  not  only  on  the  size  and  length  of  the  core  but 
on  the  number  of  amperes  multiplied  by  the  number  of  turns  in  the  wind- 
^•— -^^.^  ln&  or  the  total  number  of 

ampere-turns  producing  the 
magnetism.  Thus,  in  Pig. 
167,  if  the  coil  consists  of  10 
turns  of  wire  through  which 
a  current  of  8  amperes  is 
flowing  the  magnetic  pull  of 
the  core  will  be  due  to  10  X 
8  or  80  ampere-turns. 
133.  To  Determine  the  Polarity  of  an  Electromagnet — A  simple, 
method  for  determining  the  polarity  of  an  electromagnet,  if  the  direction 
of  current  is  known,  is  to  grasp  the  coil  in  the  right  hand  with  the  fingers 
pointing  around  the  core  in  the  same  direction  as  the  current  flowing  in 
the  winding.  With  the  hand  in  this  position,  the  thumb  will  naturally 
point  in  the  direction  of  the  magnetic  lines  of  force  or  along  the  core  to 
the  North  pole. 

The  polarity  of  such  an  electromagnet  may  also  be  quickly  determined 
by  holding  a  compass  near  its  poles.  The  North  end  of  the  needle  will 
point  to  the  South  pole  of  the  magnet  as  already  illustrated  in  Fig.  161. 

Fig.  167. — The  electromagnet. 

Direction  of  Current 

Direction  of 
Magnetic  Field 


Fig.   168. — Relation  between  direction  of  current  and  magnetic  field. 

134.  Electromagnetic  Induction* — It  was  found  in  the  preceding 
paragraphs  that  a  current  flowing  in  a  conductor  produced  a  magnetic 
field  which  was  set  up  around  the  conductor  in  a  right-handed  direction 
to  the  flow  of  current,  as  shown  in  Fig.  162.  It  will  also  be  found  that 
if  a  magnetic  field  is  set  up  around  a  conductor  an  electric  current 
will  be  caused  to  flow  in  the  conductor  and  that  the  same  relation  exists 
between  the  direction  of  current  flow  and  the  magnetic  field.  This 
relation  is  shown  very  clearly  in  Fig.  168,  in  which  the  forward  travel 

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of  the  screw  represents  the  direction  of  current,  and  the  rotation  of  the 
screwdriver,  the  direction  of  magnetism. 

The  process  of  generating  a  current  in  this  manner  is  known  as 
induction,  and  the  current  thus  produced  is  called  an  induced  current. 
If  the  current  is  generated  by  magnetism  alternating  in  direction,  the 
induced  current  will  also  be  alternating  in  direction,  with  as  many 
reversals  through  the  wire  per  second,  as  there  are  reversals  of  magnetism. 
Such  a  current  is  dialled  alternating  current  and  is  usually  abbreviated  A.C. 

A  magnetic  field  may  be  set  up  around  a  wire  by  either  cutting 
a  magnetic  field  with  a  wire,  such  as  rotating  an  armature  of  a  magneto 
or  generator  in  a  magnetic  field,  or  by  cutting  the  wire  or  coil  of  wire 

Fig.  169. — Principle  of  electromagnetic  induction. 

with  a  rapidly  moving  magnetic  field  as  found  in  the  inductor  type 
magneto  and  induction  coil. 

The  method  by  which  a  magnetic  field  is  set  up  around  a  conductor 
and  the  relative  direction  of  the  induced  current  are  illustrated  by  Fig. 
169 A,  B,  and  C,  in  which  N  and  S  represent  North  and  South  poles  of 
a  magnet  and  W  a  wire  cutting  through  the  magnetic  field  between  N 
and  S  in  a  downward  direction.  The  magnetic  lines  of  force  between  N 
and  S  cause  an  attraction  between  the  two  poles,  like  that  of  many 
rubber  bands  under  tension.  The  rubber  bands  if  intercepted  by  a 
moving  wire  will  be  crowded  ahead  as  indicated  in  Fig.  169B.  In  a 
similar  way,  the  magnetic  lines  of  force  will  be  distorted  by  the  moving 
wire  as  shown  in  Fig,  169C    It  will  be  noted  that  the  distorted  lines  of 


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force  crowding  ahead  of  the  moving  conductor  or  wire  create  a  field  of 
greater  intensity  on  one  side  of  the  conductor  than  on  the  other.  This 
will  have  the  effect  of  setting  up  a  magnetic  whirl  around  the  conductor 
in  an  anti-clockwise  direction  thereby  inducing  a  voltage  and  current 
in  the  conductor  as  indicated  by  the  arrow.  This  whirl  of  magnetic 
lines  may  be  likened  in  direction  to  a  whirlpool  caused  by  water  turning 


Fig.  170. — Water  analogy  of  magnetic  whirl 
around  a  conductor. 

Fio.  171. — Magnetic  lines  of 
force  cutting  a  conductor. 



a  sharp  bend  in  a  creek,  as  in  Fig.  170,  in  which  the  water  corresponds 
to  the  magnetic  lines  of  force. 

In  this  example,  the  field  was  considered  stationary  and  the  wire 
movable.  If  the  wire  should  be  stationary  and  the  magnetic  lines  made 
to  cut  the  wire  as  in  Fig.  171,  the  effect  would  be  the  same,  resulting  in 
a  current,  and  voltage  being  induced  in  the  wire.  In  either  case,  the 
current  will  be  set  up  in  the  wire  in  a  direction  which  depends  upon  the 

direction  of  the  magnetic  lines  between 
the  poles  and  upon  the  direction  at 
which  the  wire  cuts  the  magnetic  lines 
of  force.  The  voltage  thus  produced 
is  proportional  in  strength  to  the  re- 
sistance of  the  wire,  to  the  strength 
of  the  magnetic  field,  and  to  the  speed 
at  which  the  magnetic  lines  of  force 
are  cut. 

135.  The  Right-hand  Rule. — An 
easy  way  to  determine  the  relation  be- 
tween the  induced  current,  the  direction 
of  magnetism,  and  the  motion  of  the  wire  through  the  magnetic  field, 
is  by  holding  the  thumb  and  first  two  fingers  of  the  right  hand  at  right 
angles  as  shown  in  Fig.  172.  If  the  thumb  is  made  to  point  in  the 
direction  of  the  magnetic  field,  and  the  second  finger  in  a  direction  cor- 
responding to  the  relative  motion  of  the  conductor,  the  first  finger  will 
point  along  the  conductor  in  the  direction  of  the  induced  current. 


Fio.  172. — Right-hand  three-finger 
rule  for  determining  direction  of  in- 
duced current. 

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136.  Automobile  Ignition. — All  automobile  engines  depend  upon  some 
form  of  electric  ignition  for  igniting  the  fuel  charge  within  the  engine 
cylinders  by  means  of  a  spark.  To  accomplish  this,  two  methods  of 
electric  ignition  may  be  used;  namely,  the  make-and-break  or  the  jump- 
spark  method. 

In  the  make-and-break  method  of  ignition,  an  electric  current  of  low 
voltage,  furnished  either  by  a  battery  or  a  magneto,  is  made  and  broken 
by  a  contact  mechanism  known  as  an  igniter,  the  contact  points  of  which 
extend  into  the  combustion  chamber  of  the  engine  cylinder.  The  spark 
for  ignition  occurs  at  the  instant  the  contact  opens,  and  is  caused  by  the 
sudden  stoppage  of  the  electric  current  in  combination  with  the  action 
of  a  coil  connected  in  the  circuit. 

In  the  jump-spark  ignition  system,  current  is  derived  either  from  a 
battery  or  a  magneto,  but  is  first  transformed  from  low  voltage  to  high 
voltage,  whereupon  it  is  made  to  jump  the  points  of  a  spark  plug  inside 
the  cylinder,  the  spark  thus  created  setting  fire  to  the  combustible  gases. 

The  make-and-break  method  of  ignition  on  the  automobile  has  given 
way  entirely  to  the  jump-spark  method  on  account  of  the  greater  sim- 
plicity and  many  advantages  of  the  latter,  but,  owing  to  the  similarity 
in  the  action  of  the  ignition  coils  used  in  both  systems,  the  operation  of 
the  make-and-break  coil  should  be  well  understood. 

137.  The  Low  Tension  Coil  for  Make-and-break  Ignition. — The  coil 
used  for  make-and-break  ignition  is  very  simple  in  construction  in  that 
it  consists  of  a  single  winding  of  insulated  wire  wound  on  a  soft  iron  core 
as  shown  in  Fig.  173.  The  core  is  usually  made  of  a  bundle  of  soft  iron 
wire  so  that  it  will  magnetize  and  demagnetize  rapidly.  Such  a  coil  is 
usually  termed  a  kick  coil  for  the  reason  that,  if  a  current  through  the 
coil  is  suddenly  interrupted  by  breaking  the  circuit,  a  flashy  spark  of 
considerable  intensity  or  kick  will  occur  at  the  point  of  breaking.  The 
spark  thus  produced  occurs  between  the  igniter  points  inside  the  cylinder 
and  is  made  use  of  in  igniting  the  fuel  charge. 

The  large  flashy  spark  which  occurs  at  the  point  of  current  interrup- 
tion is  due  to  the  induction  of  a  voltage  and  a  current  in  the  winding 
of  the  coil  by  the  collapsing  lines  of  force  when  the  circuit  is  broken. 
A  study  of  Fig.  173  will  show  that  the  magnetic  lines  of  force,  upon  the 


Digitized  by 




demagnetizing  of  the  core,  will  move  rapidly  toward-  the  core  and  cut 
each  turn  of  wire  much  the  same  as  in  Fig.  171.  This  cutting  of  the  wire 
by  the  lines  of  force  will  set  up  a  whirl  of  magnetic  lines  around  each  turn 
of  wire  and  will  induce  a  voltage  in  the  coil  in  the  same  direction  as  the 
original  current  from  the  batteries.  This  induced  or  kick  voltage  of  the 
coil  is  in  series  with  the  battery  voltage  and  often  reaches  200  to  300 
volts,  depending  on  the  design  and  size  of  the  coil.  Such  a  voltage  is 
sufficient  to  break  down  for  an  instant  the  resistance  of  the  air  gap  when 
the  circuit  is  broken,  thus  permitting  the  induced  current  to  flow  across 
the  gap  and  create  a  very  hot,  yellow,  flashy  spark. 

-4T    ^    3    -2    3    ■Jt/v«i«* 
jndll  of  Iron  >#iRt/V//'i 

i  jl  O  <Pundlc  of  Iron  >&\Rt&//J 


Fiq.  173. — Principle  of  the  low-tension  coil. 

The  action  of  a  hick  coil  may  be  compared  to  some  extent  to  the  water 
hammer  in  a  water  pipe.  If  the  valve  is  closed  suddenly  when  the  water 
is  flowing,  the  momentum  of  the  water  in  motion  will  produce  a  terrific 
blow  on  the  valve,  known  as  water  hammer.  The  instantaneous  pres- 
sure produced  by  the  water  hammer  may  be  several  times  that  of  the 
ordinary  pressure  of  the  water  which  set  up  the  motion  when  the  valve 
was  open. 

138.  The  Induction  Coil. — When  the  current  for  automobile  ignition 
is  derived  from  either  the  dry  battery,  storage  battery,  low-tension  magneto, 
or  generator,  the  voltage,  which  usually  ranges  from  6  to  12  volts,  is  too 
low  to  jump  the  gap  between  the  spark  plug  points  inside  of  the  engine 
cylinder.    Consequently,  the  low  voltage  current  must  be  transformed 

Digitized  by  LiOOQ IC 



to  a  current  of  high  voltage  by  a  special  transformer  known  as  an  in- 
duction coil.  Induction  coils  may  be  of  either  the  vibrating  or  non- 
vibrating  type,  but  in  either  case  the  general  construction  and  principle 
of  operation  are  the  same.  The  chief  difference  is  that  the  vibrating  type 
coil  operates  with  a  timer  and  gives  a  shower  of  sparks  at  the  plug,  while 
the  non-vibrating  type  operates  with  a  breaker  and  gives  a  single  spark 
at  the  plug.    The  non-vibrating  coil  is  the  most  popular  for  automobile 

.ignition.  Its  application  to  a  jump-spark  ignition  system  is  illustrated 
in  Fig.  174. 

The  induction  coil  consists  essentially  of  a  primary  and  a  secondary 
winding  both  wound  on  the  same  core  of  soft  iron  wire.    This  core  is 

'  usually  about  J^  in.  to  %  in.  in  diameter  and  5  to  6  in.  long.    The  wires 



Fig.  174. — Jump-spark  ignition  with  breaker  and  non-vibrating  coil. 

in  the  core  are  annealed  to  make  them  as  soft  as  possible  so  that  the  core 
will  magnetize  and  demagnetize  rapidly. 

The  primary  winding  which  is  connected  to  the  source  of  current 
supply  consists  usually  of  several  layers  of  insulated  copper  wire,  ranging 
in  size  from  No.  16  to  No.  20  B.  &  S.  gauge.  The  wire  is  wound  around 
the  core  so  as  to  make  it  an  electromagnet.  The  insulation  on  the  wire 
usually  consists  of  layers  of  cotton  fiber,  though  in  some  cases  an  enamel 
insulation  is  used. 

The  secondary  or  high-tension  winding,  to  which  the  spark  plug  is 
connected,  is  wound  outside  of  the  primary  coil  and  is  made  up  of  several 
thousand  turns  of  enameled  or  silk  covered  copper  wire,  usually  about 
No.  36  B.  &  S.  gauge.    This  winding  is  sometimes  made  up  of  many 

Digitized  by 



layers  each  running  the  entire  length  of  the  coil,  the  layers  being  insulated 
from  each  other  by  paraffin  wax  paper.  Another  type  of  construction 
is  where  the  winding  is  made  up  of  several  narroV  spools  or  "pancakes" 
assembled  over  the  primary  coil  with  suitable  insulation  between.  The 
adjacent  ends  of  these  pancake  coils  are  connected  so  that  their  windings 
are  in  series.  To  safeguard  against  the  winding  becoming  short  circuited 
through  moisture,  the  entire  coil  is  usually  imbedded  in  paraffin,  or  some 
other  insulating  and  moisture-proof  compound. 

Figure  174  shows  a  circuit  diagram  of  a  simple  ignition  system  for  a 
single  cylinder  four-cycle  engine.  The  induction  coil  is  of  the"  non- 
vibrating  type  operating  with  a  breaker  for  making  and  breaking  the  pri- 
mary current.  It  will  be  noticed  that  a  condenser  is  connected  across 
the  breaker  contact  points.  This  is  to  protect  the  points  against  pitting 
and  to  assist  the  primary  coil  in  inducing  a  high  voltage  in  the  secondary 
winding.  (The  operation  of  the  condenser  will  be  taken  up  later.)  The 
breaker  points  are  normally  held  closed  by  spring  tension  and  open  only 
when  the  lobe  of  the  cam  lifts  the  movable  contact  arm.  This  cam  is 
driven  by  the  engine  and  rotates,  at  one-half  crankshaft  speed  in  order  to 
produce  one  spark  in  two  revolutions  of  the  crankshaft.  The  cam  must 
be  timed  with  the  engine  so  that  the  spark  will  occur  when  the  piston  is 
nearing  the  end  of  its  compression  stroke. 

When  the  switch  is  turned  on  and  the  cam  is  in  such  a  position  that 
the  breaker  contacts  are  closed,  current  flows  through  the  primary  circuity 
from  the  positive  (+)  terminal  of  the  dry  cells,  through  the  switch  and 
primary  winding  of  the  coil  (magnetizing  the  core  as  indicated)  to  the 
insulated  terminal  of  the  breaker.  It  crosses  the  breaker  contacts  and" 
passes  through  the  contact  arm  to  the  ground,  returning  through  the 
ground  to  the  negative  (— )  grounded  terminal  of  the  dry  cells,  thus  com- 
pleting the  circuit.  (A  ground  circuit  is  that,  part  of  the  circuit  in  which 
current  travels  through  the  engine  and  chassis  frame,  the  frame  or  ground 
acting  as  a  conductor  the  same  as  one  wire.)  When  the  primary  current 
is  interrupted  by  the  cam  lobe  lifting  the  breaker  contact  arm  and  sepa- 
rating the  contact  points,  the  core  demagnetizes  causing  the  magnetic 
lines  of  force  to  collapse  cutting  each  turn  of  the  primary  and  secondary 
wtnding.  This  sudden  collapse  of  the  magnetic  lines  induces  a  current 
in  both  windings,  causing  it  to  flow  around  the  core  in  the  same  direction 
.as  the  original  battery  current.  By  having  several  thousand  turns  of 
very  fine  wire  in  the  secondary  winding,  sufficiently  high  voltage  will  be 
induced  in  the  secondary  circuit  to  force  a  current  to  jump  across  the 
spark-plug  points,  thus  completing  the  circuit  and  giving  the  desired  igni- 
tion spark  within  the  cylinder.  The  path  followed  by  the  secondary 
current,  as  shown  by  the  arrows,  leads  from  one  end  of  the  secondary 
winding  to  the  spark  plug  terminal,  through  the  insulated  electrode  of  the 

Digitized  by 



plug,  jumping  the  gap  between  the  plug  points  to  the  engine  frame  and 
returning  through  the  engine  frame  to  the  other  end  of  the  secondary 
winding.  It  will  be  seen  that  the  primary  winding  and  its  current  are 
used  for  magnetizing  the  core.  The  current  which  is  induced  in  the 
secondary  coil  when  the  primary  circuit  is  broken  is  that  used  for  the 
ignition  spark. 

A  voltage  will  be  induced  in  the  secondary  winding  while  the  core  is 
being  magnetized  as  well  as  when  it  is  being  demagnetized,  but,  owing  to 
the  fact  that  the  core  magnetizes  much  slower  than  it  demagnetizes,  the 
induced  voltage  at  this  time  is  negligible.  When  the  primary  circuit  is 
broken,  the  core,  assisted  by  condenser  action,  demagnetizes  very  rapidly 
and  induces  a  current  of  very  high  voltage  in  the  secondary  winding.  The 
voltage  thus  produced  is  usually  from  10,000  to  20,000  volts. 

139.  The  Safety  Gap, — A  gap  of  j^e  to  %  in.,  known  as  a  safety  gap, 
is  usually  provided  across  the  ends  of  the  secondary  winding  of  most 
coils  such  as  shown  in  Fig.  174.  Its  purpose  is  to  provide  a  by-pass  for 
the  high  voltage  current  in  case  a  spark  plug  lead  should  become  discon- 
nected and  the  secondary  circuit  opened,  or  in  case  the  spark  plug  points 
should  become  too  far  apart  for  the  spark  to  jump.  In  case  a  break 
should  occur  in  the  secondary  circuit,  which  offers  more  resistance  to  the 
high-tension  current  than  the  resistance  across  the  safety  gap,  the  spark 
will  jump  the  safety  gap,  thereby  safeguarding  the  coil  against  any  ex- 
rasive  voltage  which  might  puncture  the  insulation  and  cause  short 

140.  The  Condenser. — The  action  of  the  primary  circuit  is  similar 
to  that  of  the  kick  coil  in  a  make-and-break  ignition  system  and  the 
same  kind  of  a  flashy  spark  which  occurred  between  the  igniter  points 
will  also  occur  at  the  interrupter  points  when  the  primary  circuit  is  broken. 
In  the  jump-spark  ignition  system  this  spark  is  prevented  and  the  action 
of  the  coil  greatly  improved  by  the  use  of  a  condenser.  The  condenser 
consists  of  two  folded  strips  of  tin  foil  insulated  from  each  other  by  other 
stripe  of  paraffined  paper,  each  strip  of  tin  foil  being  provided  with  a 
terminal.  The  two  condenser  terminals  are  connected  to  the  interrupter 
terminals  as  shown  in  the  circuit  diagrams  of  Figs.  174  and  175.  The  con- 
denser may  be  mounted  either  in  the  breaker  head  or  in  the  coil  housing. 
There  is  no  electric  circuit  through  a  good  condenser.  If  any  current  does 
pass  through,  the  condenser  is  short  circuited  and  must  be  replaced. 
The  condenser  has  the  property  of  being  able  to  absorb  and  discharge 
an  electrical  charge,  and  it  is  this  characteristic  which  makes  its  use 
essential  to  jump-spark  ignition. 

Referring  to  Fig.  175,  the  operation  of  the  condenser  is  as  follows: 
When  the  break  of  the  primary  circuit  occurs,  the  induced  surge  of  cur- 
rent in  the  primary,  which  is  in  the  same  direction  as  the  original  battery 

Digitized  by  LiOOQ IC 



current  and  which  would  otherwise  cause  an  arcing  of  the  contact  points, 
rushes  into  the  condenser  and  charges  it.    The  side  of  the  condenser  which 

Induction  Coil 



Primary  Winding 

Fig.  175. — Operation  of  the  condenser. 

Contact  Rwnts 
Melo  Normally  CloslcA 
Jhrolkjh  Spring Tcns»on/ 

receives  the  surge  is  temporarily  charged  positive  and  the  other  side  nega- 
tive.    Instantly,  the  condenser  discharges  back  through  the  primary 

winding  and  battery  in  the 
opposite  direction  in  an  at- 
tempt to  equalize  the  poten- 
tial of  the  two  sides.  As 
this  backward  surge  is  oppo- 
site in  direction  to  the  origi- 
nal magnetizing  current,  it 
assists  in  quickly  reducing 
the  magnetism  of  the  core  to 
zero,  thus  aiding  in  securing 
the  maximum  voltage  in  the 
secondary  winding.  In 
reality,  the  current  surges  or 
oscillates  to  and  fro  from  the 
condenser  before  it  finally 
dies  out.  The  initial  con- 
denser discharge  is  repre- 
sented by  the  crooked  arrows. 
The  action  of  the  condenser  may  be  compared  to  that  of  the  flexible 
diaphragm  shown  in  Fig.  176.     When  the  valve  is  closed,  suddenly 

Pi  Ft  Coil 

Flcxisle  Diaphragm 

Fia.  176. — Water  analogy  explaining  action  of 

Digitized  by 




cutting  off  the  flow  of  water  from  B  through  the  coil  of  pipe  into  A,  the 
water  will  depress  the  diaphragm  for  an  instant  due  to  the  momentum 
attained  by  the  water.  The  diaphragm  will  then  rebound  immediately 
forcing  a  surge  of  water  back  through  the  pipe  into  B;  in  fact,  the  water 
will  surge  back  and  forth  several  times  before  it  finally  comes  to  a  stand- 
still. This  surging  action  of  the  water  is  similar  to  the  surging  of  the 
electric  current  of  the  condenser. 

141.  The   Vibrating   Induction   Coil. — The   vibrating   coil   ignition 
system  differs  from  the  non-vibrating  type  chiefly  in  the  addition  of  a 





Fig.  177. — Jump-spark  ignition  system  with  vibrating  coil  and  timer. 

vibrator  to  the  coil  and  the  employment  of  a  timer  instead  of  a  breaker 
for  opening  and  closing  the  primary  circuit.  The  essential  parts  of  the 
coil  are;  a  core  of  soft  iron  wire,  a  primary  winding  of  coarse  insulated 
copper  wire,  a  secondary  winding  of  fine  insulated  copper  wire,  a  condenser , 
and  a  vibrator. 

In  Fig.  177  is  shown  a  circuit  diagram  of  a  simple  jump-spark  ignition 
system  with  a  vibrating  coil.  There  are  two  separate  and  distinct  elec- 
trical circuits,  namely,  the  primary  and  secondary  circuits  the  same  as 
in  the  non-vibrating  system.  The  primary  or  battery  circuit  includes 
the  battery,  the  switch,  the  vibrator,  the  primary  winding  of  the  coil,  the 
timer,  and  the  condenser.  The  condenser  is  connected  across  the 
vibrator  points.  The  secondary  circuit  contains  the  fine  or  secondary 
winding  of  the  coil  and  the  spark  plug.  When  the  primary  circuit  is 
completed  at  the  timer  (which  is  usually  driven  by  the  camshaft  of  the 

Digitized  by 




engine),  current  will  flow  from  the  battery  through  the  primary  winding 
of  the  coil  in  the  direction  indicated  by  the  arrows.  The  core  of  the  coil 
thus  becomes  magnetized  and  as  long  as  the  current  flows  this  core  will 
have  the  properties  of  a  magnet.  The  core  exerts  a  pull  on  the  iron  disc 
or  armcUure  attached  to  the  end  of  the  vibrator  and  in  so  doing  separates 
the  contact  point  on  the  vibrator  from  the  stationary  contact.  This 
breaks  the  primary  circuit  and  the  current  ceases  to  flow.  The  core, 
therefore,  loses  its  magnetism  and  the  vibrator  returns  to  its  former 
position.  In  so  doing,  it  reestablishes  the  primary  circuit  and  the 
action  is  repeated.  Thus,  as  long  as  the  primary  circuit  is  closed  by  the 
roller  making  contact  with  the  segment  of  the  timer,  the  vibrator  will 
vibrate  rapidly  similar  to  the  vibrator  of  an  ordinary  electric  doorbell. 

Each  time  the  vibrator  opens,  breaking  the  primary  circuit,  the 
magnetic  field  dies  away  very  quickly  followed  by  a  high-tension  spark 

at  the  plug.    The  flashy  spark 






which  would  naturally  occur 
at  the  vibrator  points  is 
wiped  out  by  the  condenser 
which  is  connected  across  the 
points.  Since  the  vibrator 
makes  and  breaks  many 
times  on  each  contact  of  the 
timer,  a  shower  of  sparks  is 
delivered  at  the  plug.  These 
sparks  begin  at  the  instant 
the  contact  is  made  and  last 
throughout  the  period  of 
timer  contact. 

142.  The  Three  Terminal 
Coil. — Many  of  the  coils  used 
on  automobile  ignition  sys- 
tems have  only  three  termi- 
nals instead  of  four.  Figure  178  shows  a  typical  three  terminal  coil  such 
as  is  used  on  the  Ford  car.  One  end  of  the  secondary  winding  is  joined 
to  one  end  of  the  primary,  and  the  junction  connected  to  one  of  the  ter- 
minal binding  posts  which  in  turn  leads  to  the  ground  through  the  pri- 
mary wiring.  The  other  end  of  the  secondary  leads  out  of  the  coil  to 
the  spark  plug. 

143.  The  Vibrating  Type  Ignition  System.— Where  vibrating  coils  are 
used  for  ignition  on  a  multiple  cylinder  engine,  it  is  customary  to  use 
a  coil  for  each  cylinder.  These  coils  are  usually  enclosed  in  an  upright 
box  as  shown  in  Fig.  179,  which  is  a  coil-set  for  a  four-cylinder  engine. 
The  box  is  fitted  with  interchangeable  slip-type  coil  units  such  as  shown 

Fig.  178. 


— Ford  (K-W)  induction  coil,  showing 
typical  three  terminal  coil. 

Digitized  by 




in  Kg.  178.  The  connections  for  these  coils  are  made  by  contact  springs 
in  the  coil  box  bearing  on  the  metal 
contacts  of  the  coil  as  shown  in  Fig. 
180.  This  makes  it  possible  to  re- 
move any  of  the  coils  without  discon- 
necting any  of  the  wiring.  The 
switch  on  the  front  of  the  box  per- 
mits the  primary  current  to  be  used 
from  either  a  battery  or  low-tension 
magneto.  This  system  may  also  be 
used  with  two  independent  batteries, 
one  being  held  in  reserve. 

Figure  180  shows  the  circuit  dia- 
gram of  a  vibrating  coil  ignition  sys- 
tem for  a  four-cylinder  engine  using 
either  dry  batteries  or  low-tension 
magneto  as  the  source  of  current 
supply.  This  is  similar  to  the  Ford 
system  of  ignition  which  will  be  taken  up  in  the  next  chapter. 

Fio.  179. — Pfanstiehl  four-cylinder 


W1N0ING    0R0UND) 

Fio.  180. — Diagram  of  four-cylinder  vibrating  coil  ignition  system. 

144,  Timers. — The  timer  may  be  defined  as  a  revolving  switch  for 
the  purpose  of  connecting  the  source  of  primary  current  supply  to  the 

Digitized  by 




proper  coil  at  the  proper  time.  It  is,  consequently,  always  placed  in  the 
primary  circuit.  The  timer  used  on  the  Ford  engine  is  shown  in  Fig.  181. 
The  inside  or  rotating  part  is  fastened  to,  and  rotates  with,  the  camshaft. 
When  the  roller  comes  into  contact  with  one  of  the  four  terminals  on  the 
housing,  the  primary  circuit  is  completed  through  the  coil  connected  to 

Pull  Rod  Connection 


Thumb  Nut 

Contact  Poim 
Roller  Ann 

Engine  Cover 

Fio.  181.— The  Ford  timer. 

that  terminal,  causing  its  vibrator  to  operate  and  a  series  of  sparks  to 
occur  in  rapid  succession  at  the  plug.  The  housing  of  the  timer  does  not 
turn  with  the  camshaft,  but  can  be  shifted  forward  or  backward  in 
respect  to  the  camshaft  and  roller  either  to  advance  or  retard  the  time 
of  the  spark. 

Binding    posts 

l    CLtCTfiOOtS 

Comical  Type 

•v    SV»HIN« 



Fio.   182. — Construction  of  typical  spark  plugs. 

-  The  timers  for  six-  and  eight-cylinder  engines  are  similar  to  the  above 
but  have  six  or  eight  insulated  terminals  instead  of  four  equally  spaced 
in  the  housing. 

s  145.  Spark  Plugs. — The  spark  plug  consists  of  two  terminals  fastened 
together,  but  insulated  from  each  other,  and  the  whole  screwed  into  the 

Digitized  by 




cylinder.  Figure  182  illustrates  the  internal  construction  of  typical 
plugs.  The  center  terminal  is  insulated  from  the  rest  of  the  plug  and  the 
other  terminal.    The  insulation  between  the  center  electrode  and  the 

Fiq.  183.— Types  of  spark  plugs. 

body  of  a  plug  is  usually  either  of  porcelain  or  of  mica.  The  outside 
terminal  is  in  contact  with  the  engine  cylinder  and  is,  consequently, 
grounded.     The  only  way  the  current  can  get  from  one  terminal  to  ffie 

Digitized  by 




other  is  across  the  air  gap  between  them.  The  gap  between  points  for 
battery  ignition  systems  on  the  average  automobile  engine  of  normal 
compression  up  to  80  lb.  should  be  about  J^2  in.,  or  the  thickness  of 
a  smooth  dime.  On  engines  of  higher  compression  the  points  should  be 
set  a  trifle  closer  to  compensate  for  the  increase  in  resistance  across  the 
plug  points  caused  by  the  high  compression. 

Figure  183  shows  a  few  of  the  many  types  of  spark  plugs  now  in  use. 
Although  the  designs  vary  a  great  deal  to  suit  different  conditions  the 
purpose  of  each  is  the  same,  namely,  to  ignite  the  charge  within  the 
cylinder.  One  of  the  important  factors  in  the  operation  of  a  spark  plug 
is  its  proper  installation  in  the  cylinder  or  cylinder  head.  Figure  184 
shows  proper  and  improper  methods  of  installing  spark  plugs. 

Corrcct  Incorrect 

Fio.  184. — Correct  and  incorrect  methods  of  installing  spark  plugs. 

146.  Spark  Plug  Testing. — The  porcelain  of  a  spark  plug  may  become 
cracked  due  to  the  intense  heat  or  to  accident.  The  plug  is  then  usually 
short  circuited  and  no  spark  is  produced  in  the  cylinder.  A  broken  por- 
celain can  sometimes  be  detected  by  a  grating  sound  when  an  effort  is 
made  with  the  fingers  to  wiggle  the  porcelain  of  the  plug  before  it  is  re- 
moved from  the  cylinder.  The  plug  may  also  become  short  circuited 
through  carbon  or  oil  deposits  between  the  plug  points. 

The  spark  plug  which  seems  to  spark  properly  when  tried  out  on  a 
cylinder  block  may  fail  entirely  inside  the  cylinder  because  of  the  greater 
resistance  the  spark  encounters  under  the  compression  pressure.  Con- 
sequently, the  most  satisfactory  way  to  test  a  plug  is  to  test  it  under 
operating  conditions.  To  determine  which  cylinder  is  missing  fire,  the 
plugs  may  be  short  circuited  one  or  more  at  a  time,  with  the  engine  run- 
ning, by  holding  a  screwdriver  or  hammer  head  from  the  plug  terminal 
to  th^  engine  frame,  or  the  wires  may  be  detached  from  the  spark  plug, 
one  6r  more  at  a  time,  and  the  change  in  engine  power  noted.  If  the 
plug  ha§  not  been  operating  there  will  be  no  change  in  engine  power, 
but  if  the  engine  shows  a  material  loss  of  power,  it  indicates  that  the  plug 
has  been  operating  satisfactorily.    Also,  the  priming  cups  may  be  opened 

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one  at  a  time  and  the  issuing  flame  watched.  A  hot  flame  should  issue 
with  each  explosion  of  the  cylinder. 

A  sooty,  oily  appearance  of  the  spark  plug  points  when  removed  from 
the  cylinder  also  indicates  that  the  plug  has  not  been  working  properly. 
A  white  or  yellowish  white  clean  dry  appearance  of  the  porcelain  indi- 
cates that  the  cylinder  has  been  firing.  Probably  the  most  satisfactory 
method  of  testing  a  spark  plug  is  to  exchange  plugs  between  the  cylinders 
or  to  try  out  a  plug  which  is  known  to  be  good  in  the  cylinder  which  is 

If  the  plug  is  not  to  be  taken  apart  it  can  be  cleaned  with  a  brush 
and  gasoline.  If  it  is  taken  apart  the  porcelain  may  be  cleaned  without 
scratching  it  by  using  water  and  a  little  road  dust.  If  emery  cloth  were 
used,  the  porcelain  would  be  scratched.  Figure  185  shows  the  Champion 
spark  plug  cleaner  which  screws  onto  the  plug.  The  container  is  filled 
with  gasoline  and  upon  being  shaken,  the  needles  in  combination  with 
the  gasoline  remove  any  carbon  deposit  that  may  be  on  the  plug.  y 

mCUm^r  fluforf     Pick  wy  GAtm 

Fig.  185. — Champion  spark-plug  cleaner. 

It  is  important  that  all  the  plugs  in  the  engine  be  set  with  the  same 
gap.  If  the  gap  is  over  3^2  hi-  or  -030  in.,  the  cylinders  are  liable  to 
misfire  on  a  hard  pull.  If  the  gap  is  set  much  closer  than  .020  in.,  the 
cylinders  will  probably  miss  when  the  engine  is  running  idle. 

147.  Typical  Battery  Ignition  System. — The  main  parts  of  a  modern 
automobile  battery  ignition  system  are:  the  storage  battery,  high-tension 
non-vibrating  coil,  breaker,  and  distributor.  The  battery  is  the  source  of 
the  electric  current.  The  breaker  and  distributor  are  usually  combined  in 
one  unit  driven  by  the  same  shaft  from  the  engine.  Figure  186  shows  a 
circuit  diagram  of  a  typical  battery  ignition  system  for  a  four-cylinder 
engine.  The  distributor  unit  contains  the  breaker  points  which  make 
and  break  the  primary  current,  and  also  the  distributor  which  directs 
the  high-tension  current  to  the  individual  cylinders  in  their  proper  firing 
order.  The  breaker  points  are  two  small  contact  pieces,  usually  tungsteij 
or  platinum,  one  stationary  and  the  other  one  on  a  movable  arm.  The 
points  are  normally  held  closed  by  spring  tension.  A  small  cam  with  as 
many  lobes  as  there  are  cylinders,  revolves  and  separates  the  two  points 
about  ^4  in.,  interrupting  the  current  in  the  primary  winding  of  the  coil 
every  time  a  spark  is  required  at  one  of  the  plugs.    The  points  are  made 

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of  tungsten  alloy  or  platinum  to  withstand  pitting  due  to  the  sparking 
between  them  as  the  points  separate.  To  prevent  this  sparking  a  con- 
denser connected  across  the  two  contacts  is  used  to  absorb  the  surplus 
current  that  would  have  a  tendency  to  keep  on  flowing  after  the  circuit 
is  broken. 

148.  The  Distributor. — The  distributing  arm  for  the  high-tension 
current  is  in  the  head  of  the  distributor  and  connects  the  center  terminal, 
or  high-tension  lead  from  the  coil,  with  the  contacts  leading  to  the  indi- 
vidual spark  plugs,  there  being  as  many  contacts  as  there  are  cylinders. 
The  bodies  of  the  distributor  head  and  arm  are  molded  of  a  very  high  re- 
sistant insulating  material  known  as  bakelite  and  designed  to  be  as  water 
and  dust  proof  as  possible. 


GaouNDTnnoutM  enow*  mo  cm*  frami 

Fio.  186. — Diagram  of  typical  battery  ignition  system. 

149.  The  Ignition  Resistance  Unit — The  ignition  resistance  unit 
which  is  found  on  many  storage  battery  ignition  systems  and  which  is 
shown  in  Fig.  186  is  for  the  purpose  of  protecting  the  coil  winding  from 
overheating  and  the  battery  from  excessive  discharge  in  case  the  switch 
is  left  on  with  the  engine  not  running  and  breaker  points  closed.  It  also 
assists  in  equalizing  the  intensity  of  the  secondary  spark  at  high  and  low 
engine  speeds.  It  consists  usually  of  a  number  of  turns  of  special  iron 
resistance  wire,  similar  to  that  in  an  electric  toaster.  The  resistance  of 
this  unit  is  considerably  more  than  that  of  the  primary  winding  of  the 
ignition  coil. 

If  the  switch  is  left  on,  the  resistance  of  the  iron  wire  increases  gradu- 

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ally  with  increase  in  temperature,  due  to  the  primary  current,  until  the 
wire  begins  to  turn  to  a  cherry  red  when  the  resistance  takes  a  sudden  rise. 
This  causes  the  current  discharge  from  the  battery  through  the  primary 
winding  to  decrease,  thus  protecting  the  coil  against  possible  damage 
from  overheating,  and  the  battery  against  rapid  discharge.  It  will  also 
be  found  that  at  low  engine  speed  the  temperature  of  the  resistance  wire 
will  be  lower  than  at  high  speed,  partly  due  to  the  longer  period  during 
which  the  contacts  are  closed,  and  partly  to  the  impedance  or  opposition 
exerted  by  the  coil  against  being  magnetized  rapidly.  This  opposition 
will  increase  more  and  more  with  increase  in  engine  speed.  The  period  of 
time  which  the  primary  current  has  for  magnetizing  the  core  will  decrease 
in  proportion  to  the  increase  in  engine  speeds.  The  breaker  will  then  have 
the  tendency  to  interrupt  the  primary  current  before  the  core  is  fully 
magnetized,  thus  decreasing  the  intensity  of  the  secondary  spark. .  This 
is  counteracted  by  the  decrease  in  resistance  of  the  resistance  unit  which 
permits  a  large  momentary  flow  of  current  through  the  primary  winding 
when  the  breaker  points  are  closed.  By  controlling  the  primary  current, 
the  intensity  of  the  secondary  voltage  is  thus  equalized  at  high  and  low 
engine  speeds. 

160.  Spark  Advance  and  Retard. — On  a  variable  speed  gasoline  engine 
it  is  very  essential  that  the  time  at  which  the  spark  occurs  in  the  cylinder 
be  changed  according  to  the  engine  speed,  since  it  takes  a  certain  length 
of  time  for  the  explosion  to  take  place  regardless  of  the  engine  speed. 
When  the  engine  speed  is  high,  the  spark  must  occur  before  the  piston 
reaches  dead  center  in  order  to  have  the  full  force  of  the  explosion  exerted 
when  the  piston  has  just  passed  the  center  position.  When  the  engine 
speed  is  slow,  the  spark  can  occur  later  and  the  force  of  the  explosion  will 
be  exerted  just  after  dead  center.  It  is  necessary  when  starting  the 
engine  that  the  spark  occur  when  a  piston  is  approximately  on  dead  center. 
When  the  engine  must  start  on  ignition  from  a  high-tension  magneto, 
the  spark  can  occur  slightly  before  dead  center.  This  is  especially 
true  when  an  electric  starter  is  used,  on  account  of  the  high  cranking 

These  various  considerations  demand  that  the  position  of  the  spark 
be  made  variable.  This  is  usually  done  by  shifting  the  timer,  or  inter- 
rupter housing,  causing  the  break  of  the  primary  current  (and,  conse- 
quently, the  spark  in  the  cylinder)  to  occur  earlier  or  later.  The  position 
of  the  spark  in  most  cases  is  governed  by  the  spark  control  lever  on  the 
steering  wheel.  In  starting  the  engine,  the  spark  should  be  retarded  so 
that  it  will  not  occur  until  the  piston  is  starting  on  its  downward  stroke. 
The  spark  should  then  be  advanced  as  the  engine  increases  its  speed.  If 
the  spark  is  too  far  advanced,  there  will  be  a  decided  knock  in  the 

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161.  Automatic  Spark  Advance. — In  several  modern  ignition  systems, 
means  are  provided  by  which  the  position  of  the  spark  is  advanced  and 
retarded  automatically  with  the  changes  in  engine  speed.  The  purpose 
of  this  is  to  relieve  the  driver  of  the  responsibility  and  uncertainty  of 
correctly  gauging  the  proper  position  for  setting  the  spark  control  lever 
during  normal  driving  speeds.  Figure  187  shows  the  Delco  ignition 
breaker  and  automatic  spark  advance  mechanism  as  used  on  the  Hudson 

As  can  be  seen  from  the  figure  the  automatic  advance  mechanism  is  in 
the  form  of  a  revolving  weight  type  governor  mounted  on  the  timer  shaft 
below  the  interrupter  cam.  The  weights  are  carried  by  a  ring  which  is 
mounted  on  a  short  hollow  shaft  integral  with  the  cam.  Above  the  cam 
is  mounted  the  distributor  arm  or  rotor  which  rotates  with  it.  The 
entire  mechanism  is  arranged  so  that,  as  the  engine  speeds  up  and  the 




■  *-■       DISTRIBUTOR    ROTOR 











View    of  Breaker    Mechanism 
with  Distributor  Rotor  Removed 

Vie.w   showing  Automatic 
Spark  Advance  Mechanism 

Fio.  187. — Delco  battery  ignition  unit  on  Hudson  Super-Six  showing  breaker  and  auto- 
matic spark  advance  mechanism. 

weights  spread  outward  against  the  resistance  of  the  spring,  the  ring  and 
cam  are  shifted  in  a  forward  direction  in  respect  to  the  timer  shaft.  This 
has  the  effect  of  advancing  the  spark  automatically  to  the  correct  position 
in  proportion  to  the  engine  speed.  As  the  engine  speed  decreases,  the 
springs  pull  the  weights  inward  and  the  spark  is  automatically  retarded. 
The  manual  spark  advance  lever  is  connected  to  the  spark  control 
lever  on  the  steering  wheel  and  is  for  the  purpose  of  securing  proper  timing 
and  hand  control  of  the  spark  under  various  conditions,  such  as  starting, 
difference  in  gasoline,  variable  weather  conditions,  and  at  extremely  high 
speeds  requiring  spark  advance  beyond  the  automatic  advance  range. 

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Other  types  of  automatic  spark  advance  mechanism  will  be  discussed  in 
connection  with  the  system  on  which  it  is  used. 

162.  The  Atwater-Kent  Ignition  System — Open  Circuit  Type. — The 
Atwater-Kent  battery  ignition  systems  include  two  principal  types,  the 
open  circuit  type  in  which  the  interrupter  points  are  normally  open,  and 
the  closed  circuit  type  in  which  the  interrupter  points  are  normally 

A  typical  example  of  the  open  circuited  type  Atwater-Kent  system 
which  has  been  widely  used  is  known  as  type  lf-2,  the  unisparker  of  which 
is  shown  in  Fig.  188.     The  principal  parts  of  the  system  consist  of: 

1.  The  unisparker,  which  combines  the  special  form  of  contact  maker, 
which  is  the  chief  feature  of  this  system,  with  a  high-tension  distributor. 

2.  The  coil}  which  consists  of  a  simple 
primary  and  secondary  winding,  with  con- 
denser— all  imbedded  in  a  special  insulating 
compound.  The  coil  has  no  vibrators  or 
other  moving  parts,  this  function  being  per- 
formed by  the  contact  maker. 

3.  The  ignition  switch,  which  reverses  the 
direction  of  the  primary  current  across  the 
interrupter  points  each  time  the  switch  is 
turned  on.  This  is  called  a  polarity  chang- 
ing type  switch. 

The  unisparker  is  connected  to  the  ordi- 
nary timer  shaft  of  the  engine.  The  dome- 
shaped  cover  contains  the  primary  contact 
maker  and  the  secondary  distributor,  as  well 
as  the  spark  advance  mechanism.  Figure  189 
shows  an  exploded  view  of  this  construction. 
An  important  feature  of  the  contact  maker  is 

that  the  length  of  contact  is  absolutely  independent  of  the  engine 
speed,  and  as  strong  a  spark  is  produced  when  the  engine  is  cranked  as 
when  it  runs  at  normal  or  even  at  racing  speed.  The  length  of  con- 
tact is  constant  and  not  greater  at  any  speed  than  is  necessary  to  insure 
the  magnetic  field  of  the  coil  being  built  up  to  its  full  strength. 

The  action  of  the  contact  mechanism  is  shown  in  Fig.  190.  The  four 
views  show  the  movement  described  in  producing  one  spark.  The  prin- 
cipal moving  parts  are:  the  hardened  steel  rotating  shaft  in  the  center 
with  as  many  notches  as  there  are  cylinders,  the  lifter,  the  latch,  and  the 
contact  spring.  The  contact  points  are  normally  open.  The  contact 
is  made  and  broken  by  the  action  of  the  lifter  spring  in  drawing  the  lifter 
back;  or  after  it  has  become  unhooked  from  the  notched  shaft.  When 
the  lifter  is  pulled  forward  by  the  notched  shaft  it  does  not  touch  the 


Fio.  188.— Atwater-Kent  Uni- 
sparker, Type  K-2. 

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latch.  It  is  pulled  forward  until  it  reaches  a  point  where  it  unhooks 
from  the  notched  shaft  and  is  then  pulled  back  by  the  lifter  spring,  strik- 
ing the  latch  as  it  returns.  The  latch  being  struck  by  the  lifter,  presses 
against  the  contact  spring  and  closes  the  points  for  a  brief  instant  opening 










*&M  BLOCn 




Pio.  189. — Construction  of  Atwater-Kent  ignition  unit.  Type  K-2. 

immediately  after  the  lifter  passes.  With  the  latch  and  lifter  having 
returned  to  their  original  position  the  mechanism  is  again  ready  to  repeat 
the  same  operation  for  producing  the  next  spark.     The  spring  action 

(B)1^  (CX^WM  (Of 



Fio.  190. — Operation  of  Atwater-Kent  contact  mechanism  for  Type  K-2  ignition  system. 

makes  the  speed  of  the  break  independent  of  the  speed  of  the  engine. 
It  also  makes  the  time  of  contact  uniform,  and  since  the  period  of  contact 
is  so  brief,  the  system  draws  the  least  possible  current  from  the  batteries. 
This  makes  it  particularly  adapted  for  use  with  dry  cells. 

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la  Fig.  191  a  complete  wiring  diagram  of  the  Atwater-Kent  system, 
Type  K-2,  is  shown.  The  switch  is  of  the  polarity  changing  type  which 
reverses  the  direction  of  current  across  the  interrupter  points  each  time 
the  switch  is  turned  on.     The  switch  has  two  positions  off  and  on. 

One  time  when  the  switch  is  on,  terminal  B  is  connected  to  S,  and 
B'  to  S'.  The  next  time  it  is  turned  on,  by  turning  the  switch  another 
quarter  turn  in  the  same  direction,  the  connection  is  reversed,  connecting 
B  to  S',  and  B'  to  S.  This  reverses  the  direction  of  the  primary  current 
through  the  unisparker.  The  purpose  of  this  is  to  equalize  the  transfer 
of  metal  produced  by  the  action  of  the  spark  at  the  point  of  contact, 
thereby  decreasing  the  wear  and  increasing  the  life  of  the  points. 






Fio.  191. — Wiring  diagram  for  Atwater-Kent  ignition  system,  Type  K-2. 

Contact  Point  Adjustment. — The  normal  gap  between  the  contact 
points  is  from  .010  in.  to  .012  in. — never  closer.  When  the  gap  be- 
comes too  wide,  due  to  wear,  the  engine  will  be  hard  to  start  and  will 
fire  irregularly.  The  head  of  the  contact  screw,  Fig.  191,  is  set  up  against 
several  thin  washers.  A  sufficient  number  of  these  washers  should  be 
removed  to  give  the  correct  gap  when  the  screw  is  set  up  tightly. 

The  contact  points  are  made  of  purest  tungsten,  which  is  many  times 
harder  than  platinum. 

When  contact  points  are  working  properly,  small  particles  of  tungsten 
are  carried  from  one  point  to  the  other,  sometimes  forming  a  rough  sur- 
face, characterized  by  a  dark  grey  color.  The  rough  surface  does  not 
in  any  way  affect  the  proper  working  of  the  points,  owing  to  the  fact 
that  the  rough  surfaces  fit  into  each  other  perfectly.     However,  when  it 

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becomes  necessary  to  take  up  the  distance  between  these  points,  due  to 
natural  wear,  it  is  advisable  to  remove  both  contact  screw  and  spring 
contact  arm,  and  dress  down  the  high  spots  with  a  new  fine  file.  This 
makes  it  possible  to  obtain  a  more  accurate  adjustment  and  eliminates 
any  danger  of  any  high  points  on  the  two  contacts  touching  when  the 
system  is  at  rest. 

Automatic  Spark  Advance. — Figure  192  shows  the  centrifugal  governor 
which  advances  the  spark  as  the  speed  increases.  The  rotating  shaft  is 
divided,  and  as  the  governor  weights  expand  they  rotate  the  upper  part 
of  the  shaft  forward  in  its  own  direction  of  rotation,  thus  making  and 
breaking  contact  earlier  than  at  slow  speed. 

Timing  the  Spark. — Since  the  type,  K-2,  is  not  generally  used  with 
a  spark  control  lever  it  should  be  installed  so  as  to  allow  a  small  amount 

Motor  stopped  or  running  slowly.  Motor  at  high  speed. 

Fia.  102. — Atwater-Kent  automatic  spark  advance  mechanism. 

of  angular  movement  for  the  initial  timing  adjustment.  In  other  words, 
the  socket  into  which  the  unisparker  fits  should  be  provided  with  a  clamp 
which  will  permit  the  unisparker  to  be  turned  and  locked  rigidly  in  any 
given  position. 

In  timing,  the  piston  in  No.  1  cylinder  should  be  raised  to  upper  dead 
center,  between  compression  and  power  strokes.  The  clamp  which  holds 
the  unisparker  should  be  loosened  and  the  unisparker  should  be  slowly 
and  carefully  turned  backward  or  counterclockwise  (opposite  in  direc- 
tion to  the  rotation  of  the  timer  shaft)  until  a  click  is  heard.  This  click 
occurs  at  the  exact  instant  of  the  spark.  At  this  point,  the  unisparker 
should  be  clamped  and  care  taken  not  to  change  its  position.  The  dis- 
tributor head  which  fits  only  in  the  one  position  should  now  be  removed 
and  the  position  of  the  distributor  block  on  the  end  of  the  shaft  noted. 

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The  terminal  to  which  it  points  should  be  connected  to  No.  1  cylinder. 
The  other  cylinders  in  their  proper  order  of  firing  are  then  connected  to 
the  other  terminals  in  turn.     When  these  connections  are  made,  the 
direction  of  rotation  of  the  timer  shaft  must 
be  kept  in  mind. 

When  timed  in  this  manner,  the  spark  oc- 
curs exactly  on  center  when  the  engine  is  < 
turned  over  slowly.  At  cranking  speeds,  the 
governor  automatically  retards  the  spark  for 
safe  starting,  and,  as  the  speed  increases,  the 
spark  is  automatically  advanced,  thus  re- 
quiring no  attention  on  the  part  of  the  driver. ' 

Among  the   particular  features    of    this  Fio.  iya.— Atwater-Kent  fgni- 
system  are:  timg  of  closed  primary  circuit  is         tion  unit»  Tyv*  cc* 
independent  of  engine  speed;  speed  of  break 

is  independent  of  engine  speed;  circuit  cannot  be  closed  when  engine  is 
stopped;  battery  consumption  is  reduced  to  a  minimum;  the  spark  is 
uniform  in  all  cylinders  and  is  independent  of  engine  speed. 

Pro.  194. — Atwater-Kent  system  mounted  on  Maxwell  engine. 

163.  The  Atwater-Kent  Ignition  System,  Type  CC. — This  system  dif- 
fers from  other  Atwater-Kent  models  in  that  it  operates  on  the  closed 
circuit  principle.    It  was  developed  for  use  on  cars  equipped  with  a  start- 

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ing  and  lighting  system  and  is  intended  to  operate  on  current  from  a  stor- 
age battery.  It  consists  of  a  breaker  and  distributor  unit  mounted  with 
a  non-vibrating  coil  on  a  base  as  shown  in  Fig.  193.  This  unit  has  the 
same  general  dimensions  as  the  standard  high-tension  magneto  and  is 
driven  in  the  same  manner.  For  this  reason  it  is  termed  a  magneto 
replacement  unit.  Figure  194  shows  this  Atwater-Kent  installation  on 
the  Maxwell  engine. 

The  principal  feature  of  the  system  lies  in  the  design  of  the  breaker 
mechanism  which  is  shown  in  Fig.  195.  The  contact  maker  consists  of 
an  exceedingly  light  steel  contact  arm,  the  end  of  which  rests  lightly  on 
a  hardened  steel  cam  which  rotates  one-half  as  fast  as  the  engine  crank- 
shaft. For  use  on  four-cylinder  engines,  the  cam  has  four  lobes  which 
open  the  contact  points  four  times  for  each  revolution  of  the  timer  shaft 
or  twice  for  each  revolution  of  the  engine  crankshaft.  Each  time  the 
contact  points  are  opened,  the  primary  circuit  of  the  ignition  system  is 

Fia.  195. — Atwater-Kent  breaker 
mechanism,  Type  CC. 

Fia.  106. — Construction  of  Atwater- 
Kent  distributor  head,  Type  CC, 

interrupted,  thus  producing  a  discharge  of  secondary  high-tension  cur- 
rent at  one  of  the  spark  plugs.  The  normal  gap  between  the  breaker 
points  should  not  be  less  than  .005  in.  nor  more  than  .008  in.  The 
standard  setting  is  .006  in.  This  is  about  the  thickness  of  two  pages 
of  this  book. 

The  distributor  head,  a  section  of  which  is  shown  in  Fig.  196,  forms 
the  top  of  the  contact  maker.  Each  spark  plug  wire  terminates  in  an 
electrode  which  passes  through  the  distributor  cap  and  a  rotating  distribur 
tor  block  which  takes  the  high-tension  current  from  the  center  terminal 
of  the  distributor  and  distributes  it  to  the  plugs  in  the  proper  firing  order. 
The  distributor  block  just  clears  the  distributor  points  without  actually 
touching.  The  high-tension  current  jumps  this  small  gap  without  appre- 
ciable loss.    The  secondary  spark  occurs  when  the  contacts  separate. 

Another  feature  is  that  the  condenser  is  mounted  directly  on  the 
contact  maker  instead  of  in  the  coil.  This  greatly  simplifies  the  entire 
ignition  system  and  increases  the  life  of  the  contacts. 

Digitized  by  LiOOQ IC 



In  Fig.  197  is  shown  a  complete  circuit  diagram  of  the  usual  type 
CC  installation.     In  some  cases  the  ignition  switch  may  be  combined  with 










Fio.  197.r— Wiring  diagram  of  Atwater-Kent  ignition  system,  Type  CC. 

the  lighting  switch.  With  the  type  of  switch  shown,  the  primary  circuit 
is  complete  when  the  ignition  button  is 
pushed  in,  the  arrows  indicating  the  path 
of  the  current.  A  resistance  unit  is 
mounted  in  the  top  of  the  coil  to  provide 
protection  to  the  coil  and  battery  in 
case  the  switch  is  left  on.  It  also  assists 
in  equalizing  the  secondary  spark  at  high 
and  low  engine  speeds,  as  previously  ex- 

154.  The  Connecticut  Battery  Igni- 
tion System.— The  principal  parts  of  this 
system  consist  of  an  igniter ,  a  non-vibrat- 
ing induction  coil,  and  a  switch  as  shown 
in  Figs.  198,  199,  and  200. 

The  igniter,  details  of  which  are  shown 
in  Figs.  201  and  202,  operates  on  the 
closed  circuit  principle,  the  primary  cir- 
cuit being  interrupted  or  broken,  and  the 
secondary  spark  produced  when  the  lobes 
of  the  cam  strike  the  roller  of  the  contact  arm.    The  cam  has  as  many 

Fio.  198. — Connecticut  igniter, 
Model  16C. 

Digitized  by 




lobes  as  there  are  cylinders  and  rotates  at  one-half  crankshaft  speed. 
The  distributor  arm,  which  directs  the  secondary  current  to  the  various 
plugs  in  their  proper  order  of  firing,  is  carried  above  the  cam  on  the 
upper  end  of  the  same  shaft.     In  most  installations,    the   igniter  is 



'     l^^^P^^/ »  ^1 


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^  1) 

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FiQ.  199. — Connecticut  coil  showing  spark  gap  and  connections. 

mounted  on  the  side  of  the  engine  and  is  driven  through  spiral  gears 
from  one  end  of  the  generator  shaft. 

The  coil  which  also  houses  the  condenser  is  mounted  close  to  the 
igniter  on  the  engine  frame,  or  on  top  of  the  generator,  and  is  connected 

Fig.  200. — Front  and  rear  views  Connecticut  combination  lighting  and  ignition 
switch.  Type  H-MD. 

to  the  breaker  by  short  flexible  leads.  One  side  of  the  condenser,  as 
well  as  one  side  of  the  primary  and  secondary  winding,  is  grounded 
through  the  brass  strip  on  the  side  of  the  coil  to  the  coil  base  and  engine 
frame.     The  condenser,  although  mounted  in  the  coil,  is  connected  across 

Digitized  by  LiOOQ IC 



the  interrupter  points  through  the  two  short  leads  which  connect  the  coil 
with  the  igniter.  Its  purpose  is  to  protect  the  points  against  pitting, 
as  previously  explained. 

Fxo.  201. — Connecticut  igniter  with  distributor  head  removed  showing  breaker 
mechanism,  Models  16  and  16C. 

Fig.  202. — Connecticut  igniter  with  distributor  head  removed  showing  breaker  mechanism 


A  complete- circuit  diagram  of  the  Connecticut  system  is  shown  in 
Fig.  203.  The  automatic  switch  of  this  system,  as  shown  in  Figs.  203 
and  204,  is  a  feature  unique  in  ignition  apparatus  and  is  used  only  on 
Connecticut  systems.     Its  function  is  to  open  the  switch,  should  the 

Digitized  by 




primary  circuit  be  closed  an  unusual  length  of  time,  as  in  the  case  of 
a  car  being  left  with  the  switch  on  and  the  engine  stopped.  This  will 
prevent  the  draining  of  batteries  and  overheating  of  the  coil.     When  the 



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*i°*TAT        £6391 




Fio.  203. — Wiring  diagram  of  Connecticut  battery  ignition  system. 

ignition  button  (the  left-hand  button  to  the  driver)  is  pushed  in,  the 
primary  current  from  the  battery  completes  its  circuit  as  indicated. 
From  the  positive  battery  terminal,  the  current  flows  to  the  switch 

Fio.  204. — Internal  view  of  Connecticut  automatic  ignition  switch. 

terminal  B,  then  through  the  switch  contacts  and  resistance  element 
to  switch  terminal  C,  which  is  connected  to  terminal  C  on  ooil.     The 

Digitized  by  LiOOQ IC 


current  now  flows  through  the  primary  winding  of  the  coil  to  the  station- 
ary side  of  the  igniter,  across  the  breaker  points  to  the  grounded  terminal 
of  the  coil,  returning  to  the  negative  terminal  of  the  battery  through  the 
ground.  The  current  induced  in  the  secondary  winding  of  the  coil  flows 
from  the  secondary  winding  to  the  center  of  the  distributor,  through  the 
distributor  arm  to  the  spark  plug,  across  the  plug,  and  back  to  the 
grounded  coil  terminal.  The  ignition  is  turned  off  by  simply  pushing  in 
the  off  button.  It  will  be  noted  that  a  spark  gap  is  provided  to  protect 
the  secondary  winding  from  the  destructive  action  of  the  high  voltage, 
in  case  a  plug  terminal  should  become  disconnected,  so  that  the  high- 
tension  current  cannot  take  its  regular  path.  The  safety  gap  is  in  a 
mica  tube  inaccessible  to  vapor  o*  fumes.  It  is  conveniently  arranged 
for  observation  in  cases  of  misfiring  cylinders. 

A  study  of  Fig.  203  will  also  show  the  principles  of  the  automatic 
switch  mechanism.  When  the  switch  is  left  on  and  the  current  flows 
continuously  through  the  resistance  unit  surrounding  the  thermostat  arm, 
the  resistance  unit  will  heat,  causing  the  thermostat  arm  to  bend  suffi- 
ciently to  close  the  contacts  E.  This  will  complete  a  circuit  from  the 
battery  through  the  winding  of  the  electromagnet,  causing  the  arm  F  to 
vibrate  rapidly.  The  end  of  arm  F  upon  striking  the  lever  G,  automat- 
ically releases  the  switch  button.  The  thermostat  can  be  adjusted  to 
operate  at  any  time  from  30  seconds  to  4  minutes.  This  adjustment  is 
made  after  the  engine  stops,  by  varying  the  gap  of  the  contacts  E.  The 
normal  setting  is  to  release  in  about  three-quarters  of  a  minute. 

The  breaker  mechanism  is  very  simple  as  Figs.  202  and  203  show. 
In  operation,  the  rotation  of  the  cam  C  causes  it  to  touch  the  fiber  roller 
R  in  the  arm  A,  thus  separating  the  contacts.  The  arm  is  returned  to 
its  normal  position  by  a  spring.  The  contacts  should  be  adjusted  to 
open  .020  in. 

The  breaker  mechanism  is  mounted  on  a  plate  which  rests,  in  the 
casing  and  is  held  in  place  by  a  spring  ring  and  also  by  a  solid  ring,  the 
latter  being  held  by  two  screws  as  shown  in  Fig.  202.  The  advance  lever 
engages  a  pin  on  the  breaker  plate,  the  whole  plate  being  advanced 
around  the  shaft  to  advance  the  time  of  ignition. 

Inasmuch  as  the  system  operates  on  the  closed  circuit  principle, 
the  maximum  time  is  allowed  for  the  complete  magnetization  of  the 
induction  coil.  The  intensity  of  the  sparks  produced  at  the  plugs  depends 
upon  this  magnetization.  It  follows  that  the  slower  the  speed  of  the 
engine  the  greater  will  be  the  magnetization  of  the  core  and  the  greater 
the  spark  intensity.  However,  this  is  partly  counteracted  by  the  action 
of  the  resistance  unit  surrounding  the  thermostat.  The  resistance  unit 
tends  to  equalize  the  intensity  of  the  secondary  spark  at  high  and  low 
engine  speeds  in  the  same  way  as  the  resistance  units  on  other  systems. 

Digitized  by 




166.  The  Remy  Ignition  System. — The  Remy  battery  ignition  system 
which  is  of  the  high-tension  distributor  type  consists  principally  of 
a  vertical  breaker  unit,  Fig.  205;  a  non-vibrating  coil,  a  typical  design 
of  which  is  shown  in  Fig.  206;  and  a  switch  which  may  be  of  either  the 


01  DtS7R.'3U. 




Fio.  205. — Remy  battery 
ignition  breaker  and  distrib- 
utor unit. 

Fig.  206. — Remy  induction   coil — two  primary  terminal 

plain  or  polarity  changing  type.     The  ignition  switch  is  often  combined 
with  the  lighting  switch. 

One  type  of  Remy  ignition  system  which  has  been  used  very  exten- 
sively is  that  shown  in  Fig.  207.     In  this  system  the  breaker  is  driven 




Fia.  207. — Remy  ignition  type  generator. 

from  the  generator  shaft  through  spiral  gears  and  the  coil  is  mounted 
close  by  on  the  generator  frame.  The  coil  is  supported  by  a  special 
bracket  which  also  serves  to  ground  one  side  of  both  the  primary  and 
secondary  windings.     The  breaker  operates  on  the  closed  circuit  principle 

Digitized  by 




and  is  very  simple  in  construction  as  may  be  seen  from  Fig.  208.  The 
interrupter  comprises  two  contact  points  of  platinum-iridium  or  tungsten, 
usually  the  latter,  one  being  stationary  while  the  other  is  carried  at  the 
free  end  of  a  pivoted  lever  which  bears  against  the  rotating  steel  cam. 
The  cam  has  accurately  ground  corners  (one  for  each  cylinder)  which 
bear  against  the  fiber  block  on  the  lever  in  rotation  and  cause  the  contact 
points  to  open  and  close  at  correct  intervals.  The  cam  has  as  many 
lobes  as  there  are  engine  cylinders  and  is,  therefore,  driven  at  one-half, 
crankshaft  speed.  The  high-tension  current  is  distributed  to  the  spark 
plug  leads  by  a  distributor  brush  which  is  carried  above  the  cam  but  does 
not  touch  the  pins  in  the  distributor  head. 

The  distributor  brush  also  carries  the  safety  gap  which  is  a  gap 
of  %  in.  between  the  distributing  segment  and  the  bottom  plate  which  is 
grounded  upon  the  shaft.  This  provides  a  safety  gap  across  which  the 
spark  can  discharge  in  case  any  of  the  connections  from  the  distributor 




Fio.  208. — Remy  breaker  and  distributor. 

to  the  spark  plugs  should  become  broken.  The  destruction  of  the  coil 
windings  due  to  excessive  voltage  is  thus  prevented.  The  safety 
gap  should  not  be  less  than  1^^2  in-  as  the  spark  might  then  discharge 
across  it  instead  of  across  the  spark  plug  gap,  when  the  plug  is  under 

Some  of  the  distributor  units  are  equipped  with  an  automatic  spark 
advance  in  which  the  governor  mechanism  is  mounted  in  the  housing 
below  the  cam.  The  advance  of  the  spark  is  provided  by  the  revolving 
weights  which  spread  more  and  more  due  to  centrifugal  force  and  shift 
the  cam  in  an  advance  direction.  As  the  engine  slows  down  the  cam  is 
shifted  in  the  reverse  direction  and  the  spark  is  retarded. 

Two  types  of  coils  are  used.  One  has  two  primary  terminals  on  top, 
as  shown  in  Fig.  206,  in  which  case  the  coil  operates  with  a  simple  switch 
of  the  on  and  off  type,  while  the  other  has  three  primary  terminals  on 
top  as  shown  in  Fig.  207  and  operates  with  a  four-terminal  switch  of 
the  polarity  changing  type.     In  both  cases  the  condenser  is  placed  in- 

Digitized  by 




side  the  coil  housing  and  a  resistance  unit  is  mounted  on  top  for  con- 
trolling the  primary  current.  Figure  209  shows  a  typical  wiring  diagram 
of  the  Remy  system  using  a  two  terminal  coil,  and  Fig.  210  shows  a 
typical  wiring  diagram  of  the  system  using  the  three  terminal  coil. 



— •         M 







Fig.  209. — Wiring  diagram  for  Remy  battery  ignition  system  using  two  primary  terminal 


The  purpose  of  the  polarity  changing  type  switch  is  to  reverse  the 
direction  of  current  flow  across  the  breaker  points  each  time  the  ignition 
is  used.  It  is  absolutely  necessary  that  the  ignition  switch  be  placed 
in  the  off  position  when  the  engine  is  not  running.  If  it  is  left  in  the 
on  position,  current  from  the  storage  battery  will  discharge  through 





Fig.  210. — Wiring  diagram  for  Remy  battery  ignition  system  using  three  primary  terminal 


the  ignition  coil.  If  this  discharge  continues,  the  battery  will  be  ex- 
hausted. To  aid  in  preventing  theft  or  unauthorized  use,  the  operator 
should  remove  the  switch  key  when  leaving  the  car. 

Adjustment  of  Contact  Points. — Contact  points  should  have  a  maxi- 
mum opening  of  .020  in.  to  .025  in.  or  the  thickness  of  the  gauge  which 

Digitized  by  LiOOQ IC 


is  on  the  side  of  the  wrench  furnished  for  adjusting  the  contact  point 
opening.  It  is  recommended  that  an  inspection  of  the  points  be  made 
every  1000  miles.  If  the  points  are  found,  to  be  worn  unevenly  or  are 
dirty,  they  may  be  cleaned  by  passing  a  fine  flat  file,  or  preferably  a 
piece  of  No.  00  sandpaper,  between  them.  When  the  contacts  are 
properly  fitted  they  should  make  clean  square  contact  as  shown  by  A 
in  Fig.  211.  Adjustment  of  the  gap  between  the  contacts  is  made  by 
loosening  the  lock  nut  with  the  wrench  furnished,  turning  the  adjusting 
screw,  and  then  locking  the  nut  again.  These  contact  points  should  not 
be  oiled.  A  slight  trace  of  vaseline  placed  on  the  fiber  block  or  on  the 
cam  every  1000  miles  will  keep  the  cam  from  rusting. 

Timing  Ignition  to  the  Engine. — The  proper  time  of  opening  the  breaker 
contact  points  relative  to  the  travel  of  the  piston  is  determined  as  follows: 
The  distributor  advance  lever  is  pushed  back  to  full  retard  position.  The 
engine  is  brought  to  dead  center  position  with  No.  1  piston  at  the  top  of 
its     compression    stroke.      Dead 

center  is  accurately  indicated  when  Cornet  /ncomct 

the  line  U.D.C.  on  the  flywheel  is 
opposite  the  corresponding  prick  A- 
punch  mark  or  ind&tor  on  the 
engine  frame.  I^0K  position  of 
the  flywheel,  the  jfctons  in  both 
of  the  cylinders  indicated  by  the 
numerals  after  U.D.C.  will  be  at    _ 

-i      .  »,i  w     .      i  -r»     i    ij.  **o.  211. — Correct  and  incorrect  shapes  for 

the  top  Of  the  Stroke.      By  holding  battery  breaker  contact  points. 

the  finger  over  the  open  petcock 

as  the  engine  is  turned  in  the  proper  direction  of  rotation  the  cylinder 
on  compression  can  be  determined.  The  breaker  contact  points  should 
just  be  starting  to  separate  (the  flywheel  being  turned  in  the  direction 
of  rotation  past  dead-center  position)  for  a  six-cylinder  engine,  or  from 
1  in.  to  1%  in.  (as  measured  on  flywheel)  past  dead  center  for  a  four- 
cylinder  engine. 

If  it  is  found  necessary  to  readjust  the  timing,  the  distributor  arm 
(which  has  an  arrow  on  it)  should  be  removed  and  the  nut  which  holds 
the  cam  in  place  unscrewed.  The  cam  can  be  loosened  by  giving  it  a 
sharp  rap  to  release  it  from  the  tapered  part  of  the  shaft  on  which  it  fits 
snugly.  The  cam  should  then  be  turned  to  obtain  the  proper  time  of 
opening  the  contact  points,  noting  that  the  cam  strikes  the  fiber  in  the 
proper  direction  of  rotation.  The  cam  should  be  rapped  down  in  place 
and  the  nut  tightened  to  keep  the  cam  from  slipping. 

Oiling. — The  grease  cup  below  the  distributor  head  should  be  kept 
full  of  medium  grease,  and  should  be  given  two  turns  to  the  right  every 
500  miles,  so  as  to  force  a  little  grease  into  the  bearing. 


Digitized  by 




Spark  Plugs. — Failure  of  spark  is  sometimes  due  to  the  spark  plug 
gap  inside  the  cylinder  becoming  clogged  with  carbon  or  oil.  This 
gap  should  measure  .025  in.  to  .030  in.  or  the  thickness  of  the  gauge 
supplied  by  the  manufacturer. 

166.  The  Remy-Liberty  Ignition  Breaker  for  U.  S.  Military  Truck.— 
The  special  battery  ignition  breaker  manufactured  by  the  Remy  Electric 
Company  for  the  U.  S.  Standardized  Military  truck  Class  B  is  shown  in 
Figs.  212  and  213.  The  breaker  is  of  the  closed-circuit  type  and  operates 
with  a  plain  non-vibrating  coil.  Both  breaker  and  coil  are  mounted  on 
the  left  side  of  the  engine  in  front  of  the  water  pump.  The  coil  is  de- 
signed so  that  a  resistance  unit  is  not  used  in  the  primary  circuit.    The 


\     JMAt 




Fia.  212. — Remy-Liberty  battery  ignition  unit  for  U,  S.  Military  truck,  Class  B. 

condenser  is  mounted  inside  the  distributor  head  where  it  is  very  acces- 
sible. Another  feature  is  that  the  breaker  mechanism  is  mounted  on  a 
plate  separate  from  the  main  distributor  body.  This  permits  the  ad- 
vancing and  retarding  of  the  spark  by  simply  shifting  the  breaker  mechan- 
ism around  the  cam  instead  of  shifting  the  entire  head,  thus  avoiding 
the  bending  of  the  wiring.  The  operation  and  adjustment  of  the  system 
are  identical  with  other  systems  of  the  closed-circuit  type. 

167.  The  North  East  Ignition  System. — The  installation  and  wiring  of 
the  North  East  battery  ignition  system  as  used  on  the  Dodge  car  is  shown 
in  Fig.  214.     The  ignition  unit,  Fig.  215,  is  virtually  a  magneto  replace- 

Digitized  by 




ment  outfit,  being  driven  the  same  as  a  magneto.  This  unit  comprises 
an  induction  coil,  a  breaker  of  the  closed-circuit  type,  a  condenser  mounted 
in  the  breaker  housing,  and  an  automatic  spark  advance  mechanism.    The 





(ADJ.  70  OPEN '0.0/7. 
7V  0.022  OF  AN  INCH) 




Fig.  213. — Construction  of  Remy-Liberty  battery  ignition  unit  for  U.  S.  Military  truck, 

*  Class  B. 

latter  is  shown  separately  in  Fig.  216.     Either  one  of  two  types  of  breaker 
is  used.     In  one  type  the  terminals  of  the  breaker  are  both  insulated  and 









Fio.  214. — Installation  and  wiring  of  North  East  ignition  system  on  Dodge. 

the  system  operates  with  a  polarity  changing  type  switch.  In  the 
other  type,  Fig.  217,  one  breaker  terminal  is  grounded  and  the  system 
operates  with  a  simple  key  switch. 

Digitized  by  LiOOQ IC 



The  principle  of  the  system  as  well  as  the  method  of  ignition  timing 
is  very  similar  to  that  in  other  systems  of  the  closed-circuit  type.  To 
time  ignition  the  cam  is  loosened  and  the  time  of  contact  break  is  ad- 
justed by  shifting  the  cam  so  that  the  points  are  on  the  verge  of  separat- 
ing (if  the  cam  were  turned  forward)  with  No.  1  piston  about  J^  in.  to 
%  in.  (as  measured  on  the  rim  of  the  flywheel)  past  upper  dead-center 





Fiq.  215. — North  East-ignition  unit. 

A  good  way  to  check  the  time  of  contact  break  is  with  a  test  lamp, 
connected  as  shown  in  Fig.  218.  After  the  ignition  switch  is  turned 
on,  the  engine  should  be  turned  over  slowly  by  hand.  The  light  will 
flash  on  and  off,  depending  upon  whether  the  contacts  are  open  or  closed. 





Fiq.  216. — North  East  automatic  spark  advance  mechanism. 

The  instant  the  points  separate  the  lamp  will  light.  The  light  should 
occur  (with  the  above  setting)  when  the  dead-center  mark  on  the  flywheel 
is  %  in.  to  Y±  in.  past  dead-center  position.  The  time  of  contact  opening 
should  be  the  same  for  each  cylinder.  The  points  should  be  adjusted 
to  separate  .020  in. 

Digitized  by 



168.  The  Delco  Ignition  System. — Many  types  of  Delco  ignition 
equipment  are  in  use.  A  few  of  these  are  shown  in  Fig.  219.  The 
varied  designs  are  due  not  so  much  to  the  principle  involved,  as  this 
is  practically  the  same  in  all  models,  but  to  the  many  individual  ignition 
requirements  of  the  four-,  six-,  eight-,  or  twelve-cylinder  engine  on  which 
they  are  used. 




CONDENSER^  .  .y^flL 

NUT                    ffitt-g 


5    W 





Fig.  217. — North  East  breaker  and  distributor. 

The  distributor  and  breaker  unit  is  usually  carried  on  the  front  end  of 
the  generator  and  driven  at  one-half  crankshaft  speed  by  the  same  shaft 
which  drives  the  generator.  The  distributor  consists  of  a  cap  or  head  of 
insulating  material  with  one  high-tension  contact  in  the  center  and  simi- 
lar contacts,  as  many  as  there  are  cylinders,  spaced  equidistant  about 
the  center.     The  distributor  arm  or  rotor  carries  a  contact  button  which 






Fio.  21S. — Method  of  connecting  test  lamp  to  check  time  of  contact  opening. 

makes  continuous  contact  with  the  head  and  serves  to  direct  the  second- 
ary current  to  the  proper  spark  plug. 

Beneath  the  distributor  head  and  the  rotor  is  the  breaker,  Fig.  220, 
which  is  piovided  with  a  timing  adjusting  screw  in  the  center  of  the  shaft. 
The  loosening  of  this  screw  allows  the  cam  to  be  turned  in  either  direction 
to  secure  the  proper  timing..    The  breaker  operates  on  the  closed  cir- 

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cuit  principle  and  the  spark  occurs  at  the  instant  the  timer  contacts 
open.     The  adjustment  screw  must  always  be  screwed  down  tight  after 

J      the  cam  is  adjusted. 

^*  The  distributor  is  equipped  with  both  manual  and  automatic  spark 
control.     The  manual  control  is  linked  up  with  the  spark  lever  on  the 

Packard.  Cadillac. 

Fiq.  219. — Types  of  Delco  ignition  equipment. 


steering  wheel  sector.  This  is  for  the  purpose  of  securing  the  proper 
retard  of  the  ignition  for  the  starting  operation  and  very  slow  idling 
speeds,  and  to  secure  the  proper  advance  required  for  maximum  power 
at  very  low  engine  speeds  over  which  the  automatic  feature  has  no 

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The  automatic  spark  advance  mechanism  is  located  in  the  lower  part 
of  the  breaker  housing.  This  mechanism  is  for  the  purpose  of  securing 
the  additional  advance  that  is  required  to  give  the  best  operating  condi- 



TO     SPARK  Pl.U« 3 

,    |    ,         i 







open  oie'To  our 


Fio.  220. — Wiring  diagram  for  typical  Delco  ignition  system  for  four-  and  six-cylinder 


tions  of  the  engine  at  the  higher  engine  speeds.  This  feature  makes  it 
unnecessary  to  manipulate  the  spark  lever  for  ordinary  varying  engine 
speeds  in  order  to  secure  the  best  performance  of  the  engine. 

221. — Typical  1917  Delco  ignition  type  generators. 

The  ignition  coil  is  usually  mounted  on  top  of  the  generator  as  shown 
in  Pig.  221.  It  will  be  noticed  that  an  ignition  resistance  unit  is  mounted 
on  one  end,  and  that  the  condenser  is  placed  in  the  bottom  of  the  coil 
with  one  side  grounded.    The  switch  button  next  to  the  ammeter,  Figs. 

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200  and  221,  controls  both  the  ignition  circuit  and  the  circuit  between 
the  generator  and  the  storage  battery.  It  connects  the  three  contacts 
numbered  (2),  (4),  and  (3)  in  the  circuit  diagram.  The  second  button 
from  the  ammeter  controls  the  cowl  and  tail  light;  the  third  button  con- 

6108ED  CAM,     ^K 
PR/MARY                   -  V*   — — 
TERMINAL                      ^^%TC\* 



k  V               SCREW 






Fro.  222. — Deloo  breaker  mechanism  used  on  Cadillac  Eight,  Model  57. 

.  trols  the  headlight  bright;  and  the  button  on  the  extreme  left  controls  the 
headlight  dim.  The  starting  and  lighting  features  of  the  Delco  system 
will  be  taken  up  in  the  chapter  on  starting  and  lighting  systems. 












Fio.  223. — Delco  breaker  mechanism  used  on  Packard  twin  six. 

159.  Delco  Ignition  Breakers  for  Eight-  and  Twelve-cylinder  Engines. 

— The  breaker  of  the  Delco  equipment  as  used  on  the  Cadillac  "Eight" 
is  shown  in  Fig.  222  and  that  used  on  the  Packard  "Twin  Six"  in  Fig. 
223.  These  are  typical  of  the  many  designs  of  breakers  for  eight-  and 
twelve-cylinder  engines. 

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On  the  Cadillac  breaker,  the  cam  has  eight  lobes  and  operates  two 
contact  breakers  at  one-half  crankshaft  speed.  These  breakers  are 
connected  in  parallel,  and  are  timed  to  open  and  close  at  the  same  time. 
The  object  is  to  distribute  over  two  sets  the  current  which  would  other- 
wise pass  through  one.  This  greatly  reduces  the  wear  and  burning  of  the 
points.  In  order  to  accomplish  this,  both  sets  of  contact  points  should 
be  adjusted  exactly  the  same,  namely,  to  open  .020  in. 

On  the  Packard  unit,  there  are  two  low-tension  circuits  and  two 
distributors.  A  separate  breaker,  coil,  condenser,  and  distributor  serve 
each  set  of  six  cylinder.  The  breaker  mechanism  consists  of  a  separate 
set  of  circuit-breaker  points  for  each  low-tension  circuit.  These  are 
operated  by  a  single  three-lobed  cam  mounted  on  the  top  of  a  vertical 
shaft  which  is  driven  at  crankshaft  speed.  This  causes  each  low-tension 
circuit  to  be  broken  three  times  during  each  revolution  of  the  crank- 
shaft, thus  providing  the  six  necessary  sparks  for  each  revolution  of  the 

160.  Timing  Battery  Ignition  with  the  Engine. — The  details  con- 
nected with  ignition  timing  depend  somewhat  on  the  make  and  type  of 
system  and  also  on  the  type  of  engine.  The  general  principles,  however, 
are  the  same.  The  following  rules  for  timing  a  four-cylinder  engine, 
with  minor  modifications  to  suit  certain  individual  conditions,  will  apply 
generally  to  all  systems  of  the  vertical  unit  closed-circuit  type  having 
an  adjustable  cam. 

1.  Place  the  spark  lever  on  the  steering  wheel  in  the  fully  retarded 
position,  making  sure  that  the  interrupter  timer  lever  is  fully  retarded 
and  that  all  play  in  the  connecting  mechanism  from  spark  lever  to  timer 
has  been  taken  up. 

2.  With  the  pet  cocks  open  or  the  spark  plugs  removed,  turn  the 
engine  over  slowly  by  hand.  After  noting  the  firing  order,  either  by 
testing  the  order  of  compression  or  by  watching  the  operation  of  the 
valves,  turn  the  engine  until  the  dead-center  mark  on  the  flywheel  for 
No.  1  and  4  cylinders  (D.C.  1-4)  is  about  1  in.  past  dead-center  posi- 
tion with  No.  1  cylinder  (the  cylinder  next  to  the  radiator)  on  the  upper 
end  of  its  compression  stroke.  (One  inch  measured  on  the  rim  of  a  163^ 
in.  flywheel  measures  off  about  seven  degrees  of  the  crank  angle.)  In  a 
four-cylinder  engine,  the  exhaust  valve  in  No.  4  cylinder  should  be  just 
closed  with  this  setting. 

3.  Remove  the  distributor  head  and  loosen  the  timing  adjusting  screw 
or  nut  in  the  center  of  the  timer  shaft.  Turn  the  breaker  cam  so  that  the 
distributor  brush  or  button  will  be  in  the  position  under  No.  1  high- 
tension  terminal  when  the  distributor  head  is  fastened  in  the  proper 
position.  In  this  position,  adjust  the  breaker  cam  carefully  so  that  when 
the  distributor  arm  is  rocked  forward,  taking  up  the  slack  in  the  gears, 

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the  contacts  will  be  opened  by  the  breaker  cam,  and,  when  the  arm  is 
rocked  backward,  the  contacts  will  just  close. 

4.  Tighten  the  adjustment  screw  or  nut  securely  and  replace  the 
distributor  arm  and  head.  The  head  should  be  properly  located  by  the 
locating  tongue  and  the  hold-down  clip.  The  distributor  should  be  wired 
to  the  plugs  in  the  proper  order  of  firing,  beginning  with  No.  1  and  pro- 
ceeding around  the  distributor  head  in  the  direction  of  breaker  rotation. 
N*§1.  Care  of  Battery  Ignition  Systems. — General  rules  which  will 
provide  proper  care  and  insure  long  life  to  practically  all  types  and 
makes  of  battery  ignition  systems  are  as  follows: 

Contact  Points  and  Distributor. — The  distributor  cap  should  be  re- 
moved and  the  contact  points  inspected  every  1000  to  1600  miles.  If 
found  dirty  or  uneven  and  pitted,  a  fine  flat  file,  or  preferably  a  piece  of 
No.  00  sandpaper,  should  be  passed  between  them.  The  contact  points 
have  a  standard  opening  of  .017  to  .020  in. 

The  Distributor. — The  distributor  cap  will  require  no  attention  except 
to  wipe  out  from  time  to  time  any  dust  which  may  accumulate.  This 
may  be  done  by  using  a  rag  moistened  with  gasoline. 

Oiling. — Each  bearing  of  the  breaker  distributor  unit  should  be  given 
a  few  drops  of  clean  cylinder  oil  every  1000  miles.  Oil  is  much  cheaper 
than  new  bearings. 

Every  1000  to  1500  miles  a  slight  trace  of  clean  oil  or  grease  placed 
on  the  fiber  block  or  on  the  steel  cam  will  keep  the  cam  from  rusting. 
The  contact  points  should  not  be  oiled. 

Wiring. — Once  or  twice  each  season  all  wiring,  especially  the  high- 
tension  cables,  should  be  thoroughly  inspected  and  all  wires  with  worn 
or  cracked  insulation  replaced  with  new.  All  terminals  should  be  kept 
tight.  Care  should  be  taken  that  each  secondary  wire  is  kept  free  from 
oil  and  well  supported  so  that  there  is  no  rubbing  contact  with  the  engine 
frame.    Short  circuits  and  misfiring  of  the  engine  are  thus  avoided. 

Spark  Plugs. — Failure  of  ignition  is  usually  due  to  dirty  spark  plugs. 
When  the  engine  does  not  fire  regularly,  the  plugs  should  be  examined, 
and,  if  found  to  be  sooted,  they  should  be  cleaned  by  scraping  off  the 
carbon  and  washing  them  in  gasoline.  The  opening  of  the  plug  gap 
should  measure  .025  to  .030  in.,  or  the  thickness  of  a  worn  dime.  After 
the  plugs  have  been  replaced  in  the  cylinder,  the  porcelains  should  be 
examined  to  be  sure  that  they  are  not  cracked. 

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162.  Magneto  Classification. — The  magneto  which  is  used  very 
extensively  for  ignition  purposes  on  automobiles,  trucks,  and  tractors, 
consists  essentially  of  two  parts,  a  magnet  type  frame  for  supplying  the 
magnetic  field  and  an  armature  which  carries  the  winding  and  which 
usually  must  revolve  in  this  magnetic  field  in  order  to  generate  a  current. 
The  magneto  is  built  in  two  general  types  according  to  the  methods 
employed  for  generating  the  current,  namely,  the  armature  wound  or 
H-type  and  the  inductor  type.  In  the  armature  wound  type  the  winding 
generates  current  by  revolving 
in,  and  cutting,  the  magnetic 
field.  In  the  inductor  type,  the 
winding  in  which  the  current 
is  generated  is  stationary  and 
the  current  is  generated  by  the 
reversal  of  the  magnetism 
through  the  coil  and  the  cutting 
of  the  winding  by  the  lines  of 
force.  The  magneto  may  also 
be  classified  either  as  high  or 
low  tension,  according  to  the 
voltage  of  the  current  which  it 
generates.  Both  the  high-  and 
low-tension  magnetos  may  be 
constructed  on  either  the  arma- 
ture  wound  or  inductor  principle. 

163.  Magneto  Magnets. — It  is  a  well-known  fact  that  either  in  a 
bar  magnet  or  in  a  magnet  bent  in  the  shape  of  a  horseshoe,  as  in  Fig. 
224,  the  magnetism  (that  invisible  force  which  attracts  and  repels  iron 
or  steel)  is  concentrated  near  the  ends,  as  indicated  by  the  bunches  of 
iron  filings  at  the  ends  of  the  magnets.  One  end  of  the  magnet  is  called 
the  North  or  N-pole,  and  the  other  the  South  or  S-pole.  The  difference 
between  the  two  poles  can  be  seen  by  placing  two  like  poles  and  again 
two  unlike  poles  together;  it  will  be  found  that  the  like  poles  repel  each 
other  and  the  unlike  poles  attract  each  other.  This  is  the  fundamental 
law  of  magnetism. 


Fig.  224. — Bar  and  horseshoe  magnets. 

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164.  Lines  of  Force. — If  a  horseshoe  magnet  be  placed  on  its  side,  as 
shown  in  Fig.  225 A,  with  a  piece  of  paper  over  it,  and  iron  filings  sprinkled 
over  the  paper,  it  will  be  found  that  the  filings  arrange  themselves  in 
well-defined  lines.  This  arrangement  indicates  that  there  is  a  magnetic 
force  acting  between  the  two  poles  of  the  magnet.  The  influence  which 
two  horseshoe  magnets  (such  as  used  on  magnetos)  have  on  each  other 
when  laid  side  by  side  is  clearly  shown  in  Fig.  225,  B  and  C.  In  Fig.  225B 
two  magnets  are  arranged  in  a  vertical  position  to  show  the  magnetic 
flux  between  the  pole  ends  when  properly  assembled;  while  at  C,  Fig. 
225,  the  magnets  are  incorrectly  assembled,  the  north  end  of  one  magnet 
lying  next  to  the  south  end  of  the  other,  thereby  greatly  reducing  the 
number  of  lines  of  force  that  would  be  cut  by  an  armature  rotating 

■  >  ■  i 

&  lii 

Fiq.  225. — Magnetic  field  shown  by  iron  filings. 

between  the  poles.  In  placing  the  magnets  on  a  magneto,  great  care 
must  be  taken  to  get  all  the  north  poles  together  and  all  the  south  poles 
together.  An  easy  way  to  make  sure  of  this,  before  putting  the  magnets 
on  the  magneto,  is  to  lay  the  magnets  together  so  that  the  poles  will 
repel  each  other. 

165.  Types  of  Magnets. — In  some  types  of  magnetos,  compound  per- 
manent magnets  are  used.  A  compound  magnet  is  one  built  up  of  several 
simple  magnets  arranged  with  like  poles  together,  as  shown  in  Fig. 
226.  It  has  been  found  that  a  compound  magnet  is  usually  stronger 
than  a  simple  magnet  of  the  same  size,  and  more  desirable.  The  number 
of  magnets  required  to  produce  the  desired  magnetic  field  strength  de- 
pends to  a  great  extent  on  both  the  kind  and  quality  of  the  steel  used  in 
the  magnets.  At  the  present  time,  chrome  or  tungsten  steel  is  most 
generally  used,  so  that  two  magnets  arranged  as  shown  in  Fig.  2262?  are 
usually  found  sufficient.  It  is  generally  recognized  that  the  magnetic 
pull  of  each  magnet  should  be  such  as  to  sustain  a  weight  of  at  least  15 
lb.  in  order  to  give  satisfactory  service. 

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166.  Mechanical  Generation  of  Current. — It  has  been  found  that  if 
a  wire  be  moved  across  the  magnetic  field  between  the  poles  of  a  magnet 
so  as  to  cut  the  lines  of  force  there  will  be  an  electric  current  generated 

Simple  magnet 

Double  magnet 
Fio.  226. 

Compound  magnet 

in  the  wire.     If  the  wire  should  then  be  moved  across  the  lines  of  force 

in  the  opposite  direction  the  current  would  again  flow  in  the  wire  but 

in  the  opposite  direction.     The  exact  reason  for  the  generation  of  current 

is  unknown,  but  it  is  a  well-known 

fact  that  cutting  magnetic  lines  of 

force  by  moving  a  wire  across  them 

will   generate   current   in   the   wire. 

The  process  of  generating  a  current  in 

this  manner  is  known  as  induction, 

and   the   current   thus   produced    is 

termed  an  induced  current. 

The  fact  that  current  can  be 
generated  through  induction  is  made 
use  of  in  the  magneto  generator,  an 
elementary  type  of  which  is  shown  in 
Fig.  227.  The  wire  is  formed  in  the 
shape  of  a  rectangle  and  arranged  to 
rotate  between  the  pole  pieces  of  the 
magnet.  If  the  ends  of  the  wire  are 
connected  to  a  measuring  instrument, 
a  current  of  electricity  will  be  found 
to  flow  out  of  one  end  of  the  wire 
and  into  the  other  end,  as  the  wire 

is  revolved.     In   the   position   shown,   with    the   loop   rotating   in  a 
clockwise  direction,  the  current  flows  out  at  B  and  in  at  A.     If  the  loop 


Fig.  227. — Mechanical  generation  of 

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of  wire  is  turned  through  a  complete  revolution,  it  will  be  found  that  the 
current  generated  will  alternate  in  direction,  making  one  complete  rever- 
sal in  one  revolution  of  the  wire.  This  is  due  to  the  wire  cutting  the 
magnetism  first  in  one  direction,  then  the  other.  When  the  wire  is 
cutting  the  lines  of  force  at  right  angles,  the  voltage  is  the  maximum,  and 
it  is  at  this  period  of  rotation  that  the  current  is  best  for  ignition  purposes. 
This  condition  occurs  twice  during  a  complete  revolution  of  the  loop  of 
wire.  The  position  for  maximum  induced  voltage  is  at  A-B,  while  the 
position  for  no  induced  voltage  is  at  A'-B'.  In  this  position  the  wire  is 
traveling  parallel  to  the  magnetism  and  is  not  cutting  lines  of  force. 
After  passing  the  vertical  position,  the  side  of  the  loop  A  will  cut  the 
magnetic  lines  of  force  in  the  opposite  direction,  causing  the  induced 
current  in  the  wire  to  reverse,  flowing  out  at  A  instead  of  B. 

In  the  actual  magneto,  instead  of  only  one  turn  of  wire,  a  great  many 
turns  of  wire  are  wound  in  the  shape  of  a  coil  around  a  piece  of  laminated 

Fio.  228. — Flow  of  magnetic  field  through  H-type  armature. 

iron,  called  the  armature  core.  This  coil  is  caused  to  rotate  between  the 
magnetic  poles.  This  rotation  of  the  coil  generates  a  current  in  it. 
Figure  228  illustrates  the  change  and  cutting  of  the  magnetic  lines  of 
force  during  one  complete  revolution  of  the  armature.  By  using  the 
laminated  iron  armature  core,  the  strength  of  the  magnetism  flowing  be- 
tween the  poles  of  the  magnet  is  increased,  thus  increasing  the  number 
of  lines  of  force  that  are  cut  by  the  coils  of  wire. 

167.  Low-and  High-tension  Magnetos. — A  low-tension  type  of  mag- 
neto is  one  which  delivers  current  of  a  low  voltage.  This  current  must 
be  converted  to  the  necessary  high  voltage  for  ignition  by  an  external 
induction  or  transformer  coil.  The  armature  contains  only  a  primary 
winding,  while  the  transformer  coil  has  the  usual  primary  and  secondary 

A  high-tension  magneto  delivers  current  from  the  armature  at  suffi- 
ciently high  voltage  for  ignition,  without  the  use  of  an  external  transformer 
coil.    The  high-tenfcion  current  is  generated  by  the  combined  action  of 

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two  windings  on  the  armature  of  the  magneto,  one  a  primary  winding, 
and  the  other  a  secondary  winding.  The  armature  assembly  also  con- 
tains a  condenser.  The  true  high-tension  magneto  must  not  be  confused 
with  the  so-called  high-tension  magneto  in  which  the  armature  current  is 
transformed  by  a  coil  placed  in  the  top  of  the  magneto,  instead  of  out- 
side as  is  done  in  the  low-tension  type.  The  coil  is  contained  in  the 
magneto  assembly  merely  for  convenience,  but  this  does  not  make  it  a 
high-tension  magneto  in  the  correct  sense  of  the  term. 

168.  Armature  and  Inductor  Type  Magnetos. — An  armature  or 
shuttle-wound  type  magneto  is  one  in  which  the  lines  of  force  are  cut  by 
means  of  a  coil  of  wire  wound  on  an  armature  or  shuttle  rotating  between 
the  magnetic  pole  pieces,  as  just  described.  It  may  be  of  either  the 
high-  or  low-tension  type. 

In  an  inductor  type  magneto,  the  coil  of  wire  is  stationary.  The 
cutting  of  the  lines  of  force  by  the  stationary  coil  is  caused  by  a  revolving 
inductor.  Since  the  coil  in  which  the  current  is  generated  is  stationary, 
this  avoids  the  necessity  of  having  sliding  contacts  and  brushes  in  order 
to  connect  the  coil  with  the  external  circuit.  The  inductor-type  magneto 
may  also  be  either  low  or  high  tension.  The  constructional  features 
of  these  two  general  types  will  be  pointed  out  in  considering  the  several 
types  of  modern  magnetos. 

169.  Current  Wave  from  a  Shuttle-wound  Armature. — Figure  229 
shows  a  typical  curve  of  the  current  generated  in  the  winding  of  a  shuttle- 
wound  armature  as  it  turns  through  one  revolution.  In  Fig.  230  are 
shown  the  positions  of  the  armature  corresponding  to  the  points,  A,  B, 
C,  Dy  and  E  of  Fig.  229.  In  position  A  the  flux  is  passing  through  the 
armature  in  one  direction,  while  in  position  E,  after  turning  180°,  the 
flux  is  in  the  other  direction,  because  the  armature  has  turned  around. 
During  the  remainder  of  the  revolution,  from  position  E  around  to  posi- 
tion A,  the  current  generated  will  be  opposite  in  direction  to  that  gen- 
erated during  the  first  half  of  the  revolution.  The  current  generated 
during  the  first  half  of  the  revolution  is  shown  in  Fig.  229  by  the  height  of 
the  curve  above  the  base  line,  while  that  generated  during  the  second 
half  is  shown  below  the  line. 

The  exact  positions  of  the  armature  at  which  the  strongest  electrical 
impulse  can  be  obtained,  and  also  the  shape  of  the  current  wave,  depend 
upon  the  shape  and  construction  of  the  pole  pieces  and  armature  core, 
as  well  as  upon  the  speed  of  rotation  and  the  strength  of  the  magnets. 
Any  change  in  one  of  these  factors  will  produce  a  change  in  the  electric 
pressure  at  the  terminals  of  the  armature  winding. 

Most  magnetos  that  are  run  at  variable  speeds  are  constructed  so 
that  a  strong  current  can  be  produced  throughout  a  considerable  range 
of  position  of  the  armature.     This  is  done  to  allow  for  the  advance  and 

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retard  of  ignition  relative  to  the  position  of  the  pistons,  as  well  as  to 
allow  for  the  lag  of  the  current  in  the  armature  with  regard  to  the  position 
of  the  armature  at  the  instant  of  maximum  impulse  or  voltage.  This 
current  lag  for  the  speeds  in  usual  practice  is  small,  so  that  in  general 
the  positions  of  the  armature  for  the  maximum  current  are  about  as 
indicated  in  Figs.  229  and  230. 

It  is  evident  from  the  current  wave  diagram  of  Fig.  229  that,  whatever 
the  system  of  ignition  with  which  a  low-tension  magneto  is  used,  the 

Fig.  229. — Typical  curve  of  current  from  shuttle  armature. 

best  spark  will  be  produced  only  during  the  angle  of  rotation  in  which 
the  current  generated  is  at  or  near  its  maximum.  When  the  armature 
is  in  position  C,  Fig.  230,  the  current  is  at  its  maximum  and  the  spark 
will  be  strongest.  As  the  armature  rotates  from  position  C  to  D  the 
curve,  Fig.  229,  decreases  $lowly  in  height;  hence,  during  this  period  the 
current  produced  is  most  favorable  for  ignition  purposes.  Position  C 
would  correspond  to  extreme  advance  and  D  to  extreme  retard  for  this 


B-65'  C-86*  D-186' 

Fig.  230. — Armature  positions  of  Fig.  229. 

!-  lso- 

magneto,  giving  a  spark  range  of  about  40°  of  armature  rotation.  It  is 
evident  from  the  shape  of  the  curve  that  a  position  of  advance  beyond 
C  or  of  retard  beyond  D  would  give  a  spark  too  weak  for  ignition  purposes 
or  no  spark  at  all.  This  shows  the  necessity  of  having  an  alternating 
current  magneto  gear-driven  from  the  engine  shaft,  so  that  the  armature 
will  always  be  in  the  proper  position  with  relation  to  the  engine  pistons. 
The  curve  of  Fig.  229  also  shows  that  there  are  two  points  in  a  revolution 
of  this  type  of  armature  during  which  a  spark  can  be  obtained,  namely, 

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between  C  and  D  as  just  mentioned  and  at  a  similar  position  180°  later, 
when  the  current  is  in  the  other  direction.  Consequently,  the  magneto 
with  an  H-type  or  shuttle-wound  armature,  ordinarily  used  for  automo- 
bile ignition,  gives  two  sparks  per  revolution  of  its  armature.  Because 
of  this,  the  armature  speed  of  a  magneto  must  have  a  definite  relation 
to  the  number  of  cylinders  of  the  engine.  In  a  four-cylinder  four-stroke 
engine  the  armature  must  revolve  at  crankshaft  speed  in  order  to  pro- 
duce four  sparks  during  two  revolutions  of  the  engine  crankshaft.  On  a 
six-cylinder  four-stroke  engine  the  armature  must  make  three  revolu- 
tions during  two  revolutions  of  the  crankshaft,  or  it  must  turn  at  one 
and  one-half  times  crankshaft  speed. 


"iJ  [h  w  rJ 

tstributor  T_ 

(on  Magneto! ' 

Fig.  231. — Low-tension  magneto  ignition  system  with  interrupted  primary  current. 

170.  Low-tension  Magneto  Ignition  System  with  Interrupted  Primary 
Current — In  this  type  of  ignition  system,  the  current  is  supplied  at  low 
voltage  by  a  low-tension  magneto  and  is  stepped  up  to  a  high  voltage  by 
an  induction  coil  similar  to  the  non-vibrating  coil  used  with  a  battery 
ignition  system.  The  mechanical  interrupter  for  the  primary  or  low- 
tension  current,  and  the  distributor  for  the  high-tension  current,  are 
provided  on  the  magneto.  Figure  231  shows  this  system  in  its  simplest 
form.  A  magneto  with  a  shuttle-wound  armature  is  shown,  although  a 
magneto  of  the  inductor  type  could  be  used  as  well.  One  end  of  the  arma- 
ture winding  is  grounded  to  the  metal  of  the  armature  as  is  usual  in  mag- 
neto construction.  The  current  is  collected  from  the  other  end  of  the 
winding  by  a  collector  ring  and  brush  which  are  not  shown.    The  inter- 


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rupter  is  shown  separate,  but  it  is  always  mounted  on  the  magneto  shaft 
so  that  the  time  of  opening  the  circuit  is  in  proper  time  with  the  period 
of  greatest  current  flow  in  the  armature  winding.  Assuming  the  inter- 
rupter contacts  to  be  closed,  the  low-tension  current  generated  in  the 
armature  winding  flows  through  the  switch  and  the  primary  winding  of 
the  coil  and  through  the  interrupter  to  the  ground  (on  the  armature 
shaft)  and  back  into  the  armature  winding.  During  the  next  half  revolu- 
tion of  the  armature,  the  current  in  the  circuit  is  in  the  reverse  direction. 
At  the  desired  time  for  the  spark,  which  must  be  during  the  period  of 
maximum  current  flow,  the  primary  circuit  is  broken  at  the  interrupter. 
This  is  caused  by  the  high  point  of  the  cam  raising  the  interrupter  lever 
from  its  contact  with  the  fixed  contact  point.  A  condenser  placed  in 
parallel  with  the  interrupter  absorbs  the  induced  current  in  the  primary 
winding,  caused  by  this  sudden  interruption  of  the  current  flow,  and 
assists  in  rapidly  breaking  down  the  magnetism  of  the  coil  core,  in  the 
same  manner  as  in  a  battery  ignition  system.  By  this  action,  a  high- 
tension  current  is  induced  in  the  fine  secondary  winding  of  the  coil.  The 
distributor,  which  is  mounted  on  the  magneto,  receives  this  current  at 
its  central  connection  and  directs  it  to  the  proper  plugs. 

The  secondary  winding  of  the  coil,  as  shown,  is  entirely  separate 
from  the  primary  and  has  its  own  ground  connection.  This  is  not  neces- 
sary, as  the  two  coils  could  be  connected  at  their  upper  ends  and  the  sec- 
ondary ground  be  made  through  the  armature  to  the  grounded  end  of 
that  winding.  The  connection  to  the  distributor  would  then  be  made 
from  the  other  end  of  the  secondary  winding. 

Instead  of  having  the  switch  in  series  with  the  armature,  and  the 
circuit  through  the  coil  and  interrupter,  so  that  opening  the  switch 
breaks  the  circuit,  the  switch  connection  might  be  from  the  insulated 
side  of  the  circuit  to  the  ground.  In  this  case  the  circuit  would  be  through 
the  coil  and  interrupter  when  the  switch  was  open.  When  the  switch 
was  closed,  the  current  would  have  a  permanent  and  easy  path  to  the 
ground  and  back  into  the  armature,  so  that  practically  no  current  would 
flow  through  the  coil  and  interrupter.  In  this  case,  closing  the  switch 
would  ground  the  primary  current  so  that  the  coil  would  become  inopera- 
tive and  ignition  would  cease. 

The  interrupter  cam  has  two  lobes  corresponding  to  the  two  current 
waves  produced  per  revolution  in  the  shuttle  type  of  armature  and  also 
in  some  magnetos  of  the  inductor  type.  This  arrangement  is  used  when 
the  number  of  cylinders  is  such  that  each  current  wave  can  be  used  for 
the  production  of  a  spark  and  is  common  for  four-  and  six-cylinder 

171.  Low-tension  Magneto  Ignition  System  with  Interrupted  Shunt 
Current. — The  interrupter  in  this  system  is  not  in  series  with  the  circuit 

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through  the  primary  winding  of  the  coil,  but  is  in  a  shunt  or  cross  con- 
nection as  shown  in  Fig.  232.  This  system  is  the  one  commonly  used 
when  a  low-tension  magneto  is  employed  for  ignition.  The  primary 
current  has  two  possible  paths,  either  through  the  interrupter,  if  that  is 
closed,  or  through  the  primary  winding  of  the  coil.  The  current  naturally 
takes  the  easy  path  through  the  interrupter,  when  that  is  closed,  there 
being  practically  no  current  through  the  coil  at  this  time.  When  the 
magneto  armature  reaches  the  desired  position  for  the  spark,  which  is  at 
some  point  during  the  period  of  maximum  current  flow,  the  interrupter 
is  opened.  This  sudden  interruption  of  the  current  through  the  shunt 
circuit,  combined  with  the  action  of  the  condenser,  produces  an  induced 

Spark  Plugs 

llj  N4 


(on  Mognetpf 

Fio.  232. — Low-tension  magneto  ignition  system  with  interrupted  shunt  current. 

current  in  the  armature  circuit,  and  this,  having  no  other  path,  rushes 
instantly  through  the  primary  winding  of  the  coil.  This  sudden  current 
through  the  primary  winding  induces  a  powerful  momentary  voltage  in 
the  secondary  winding,  and  this  voltage  is  used  for  the  production  of  the 
spark  at  the  plugs. 

It  will  be  noted  that  the  spark  from  this  type  of  magneto  is  produced 
by  the  building  up  of  the  magnetic  field  of  the  coil  instead  of  by  the  break- 
ing down  of  the  field  as  in  the  interrupted  primary  system  previously 
described.  For  this  reason,  and  also  because  of  the  resemblance  of  its 
action  to  that  of  the  ordinary  transformer,  the  coil  is  sometimes  called 
a  transformer  coil.    An  induced  voltage  is  created  in  the  secondary  of  any 

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coil  when  the  magnetic  field  is  built  up  as  well  as  when  it  is  broken  down. 
In  battery  ignition  systems,  however,  the  action  of  building  up  is  com- 
paratively slow,  and  the  induced  current  is,  therefore,  not  of  sufficient 
voltage  to  be  used.  In  the  interrupted  shunt-type  magneto,  the  coil 
winding  of  the  armature,  coupled  with  a  condenser  of  proper  capacity, 
produces  on  the  break  of  the  shunt  circuit  by  the  interrupter,  an  impulse 
of  current  of  sufficient  power  to  magnetize  the  coil  very  rapidly  and  to 
give  the  desired  induced  voltage  in  the  secondary  winding. 

After  the  armature  has  passed  the  position  of  maximum  current,  the 
interrupter  is  closed  and  the  armature  again  has  the  easy  shunt  path 
through  which  to  build  up  its  current  when  it  again  rotates  into  the 
position  of  maximum  current. 

As  shown  in  the  diagram  of  Fig.  232  the  coil  has  a  common  ground 
connection  for  the  two  windings,  making  three  terminal  connections  for 
the  coil.  The  switch  and  coil  are  usually  mounted  as  a  unit  on  the  dash. 
The  collector  brush  on  the  magneto  is  connected  to  the  switch  on  the  coil. 
There  is  also  a  connection  from  the  switch  in  the  coil  back  to  the  insulated 
contact  point  on  the  interrupter  and  another  connection  from  the  primary 
winding  of  the  coil  back  to  a  grounded  binding  post  on  the  magneto  frame. 
The  secondary  terminal  of  the  coil  is  connected  to  the  central  post  on  the 
distributor.  This  makes  four  connections  when  the  switch  is  on  the  coil, 
although  there  are  really  only  three  coil  connections.  When  a  battery  is 
used  for  starting  purposes,  another  connection  is  added  to  the  switch,  and 
sometimes  two  if  the  one  side  of  the  battery  is  not  grounded  directly. 

The  condenser  may  be  placed  either  in  the  coil  box  or  may  be  built  in 
the  magneto.  The  switch  may  be  placed  in  series  with  the  connection 
from  the  armature  to  the  coil  and  interrupter,  as  shown,  or  it  may  be 
arranged  to  ground  the  armature  current  permanently  so  as  to  short- 
circuit  the  current  from  the  coil  and  interrupter,  thus  rendering  them 
inoperative.  In  this  latter  connection,  closing  the  switch  cuts  off  the 
ignition  current,  while  opening  the  switch  permits  the  ignition  to  operate. 
A  safety  gap  is  also  provided,  either  at  the  coil  or  at  the  magneto. 

172.  Dual  Ignition  Systems. — The  majority  of  the  low-tension  magne- 
tos of  the  type  just  described  are  provided  with  an  arrangement  for  using 
battery  current  for  starting  purposes  when  the  magneto  current  is  small, 
due  to  the  low  rotative  speeds.  The  batteries  can  also  be  used  for  con- 
tinuous running  in  cases  of  emergency,  although  the  life  of  the  batteries 
in  this  case  is  usually  short  because  of  the  long  contact  at  the  interrupter, 
which  wastes  the  battery  current.  The  connections  at  the  switch  are 
usually  made  so  that  when  the  battery  is  used,  the  interrupter  is  in  series 
between  the  battery  and  the  coil;  then  the  spark  is  induced  by  the  inter- 
ruption of  the  battery  current  through  the  coil.  In  some  of  the  dual 
systems,  the  switch  is  provided  with  a  push-button  operating  a  vibrator 

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or  interrupter  in  the  battery  circuit,  so  that  a  spark  can  be  produced 
without  turning  the  engine.  This  enables  the  operator  to  start  the  engine 
on  the  spark  if  there  is  an  explosive  charge  in  the  cylinder. 

173.  Splitdorf  Low-tension  Dual  Ignition  System  with  Type  T  Mag- 
neto.— The  Splitdorf  low-tension  magneto  ignition  system  is  a  typical 
dual  ignition  system  of  the  interrupted  shunt  current  type.  Figure  233 
shows  the  model  T  magneto  and  Fig.  234  the  circuit  wiring  of  this  mag- 
neto with  the  typical  box-type  induction  coil  which  is  mounted  on  the 
dash.  The  magneto  is  of  the  wound  type  having  a  single 
winding.  The  switch  on  the  coil  box  has  three  positions,  "Off,"  "Bat- 
tery," and  "Magneto."  The  figure  shows  the  switch  dotted  in  on  the 
"Magneto"  position.  The  armature  current  is  led  from  the  collector 
brush  A,  which  is  mounted  in  the  breaker  cap  and  which  rubs  on  an  in- 
sulated button  on  the  end  of  the 
armature  shaft  extending  through 
the  cam,  to  the  coil  box  terminal  A 
and  to  the  lower  right  switch  button, 
as  indicated  by  the  arrows.  From 
there,  the  current  has  two  paths  back 
to  the  magneto  ground.  One  path  is 
by  the  way  of  No.  2  terminal  over  the 
breaker  points  which  are  normally 
closed;  the  other,  through  the  primary 
winding  of  the  coil  to  the  grounded 
No.  3  magneto  terminals.  With  the 
contacts  closed,  practically  all  of  the 
primary  current  will  flow  across  the 
breaker  points,  owing  to  the  fact 
that  the  resistance  is  much  less  than 
that  through  the  primary  coil  wind- 
ing. When  the  points  open,  this  path  is  broken  and  there  will  be  a 
sudden  rush  of  current  through  the  primary  winding  of  the  coil.  The 
action  of  the  primary  current  combined  with  the  discharge  from  the 
condenser  induces  a  high-tension  current  in  the  secondary  winding  of 
the  coil.  This  high-tension  current  is  directed  to  the  proper  plug  by 
the  distributor  on  the  magneto.  A  safety  gap  is  provided  on  the  top 
of  the  coil  box. 

With  the  switch  on  the  "Battery"  position  the  magneto  is  disconnected 
and  the  dry  cells  connected  to  the  primary  circuit.  It  will  be  found 
that  when  operating  on  the  battery,  the  coil  and  breaker  are  in  series 
and  the  system  operated  as  an  interrupted  primary  current  system.  The 
secondary  circuit  will  be  the  same  as  when  operating  on  the  magneto, 
namely,  from  the  high-tension  terminal  on  the  coil  to  the  distributor,  to 

Fig.  233. — Splitdorf  low-tension 
magneto,  Model  T. 

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the  plug,  to  the  ground  and  returning  to  the  secondary  winding  over  the 
primary  wire  connected  to  No.  3  grounded  terminal. 

The  condenser  is  mounted  in  the  coil  and  is  connected  so  as  to  protect 
both  the  magneto  interrupter  points  and  the  push-button  contacts  on 
the  switch. 

The  push-button  contacts  are  in  the  primary  circuit  in  series  with  the 
coil,  and  are  normally  closed.  When  the  switch  is  thrown  on  "Battery" 
position  and  the  breaker  points  are  closed  (which  they  normally  are)  the 
primary  circuit  will  be  completed  and  the  coil  magnetized  by  current  from 
the  dry  cells.     If  the  push-button  is  pressed  and  the  contacts  opened, 






Fig.  234. — Wiring  diagram  of  Splitdorf  low-tension  dual  ignition  system. 

the  primary  current  will  be  interrupted,  causing  a  sudden  demagnetizing 
of  the  coil  and  creating  a  secondary  spark  in  the  cylinder  which  is  lined 
up  to  fire  in  accordance  with  the  position  of  the  distributor  arm.  If  the 
cylinder  should  contain  a  combustible  mixture,  it  is  possible  that  a  spark 
caused  in  this  manner  would  ignite  the  mixture  and  create  sufficient 
explosion  pressure  to  kick  the  engine  over,  causing  it  to  start  without  the 
usual  cranking. 

174.  Remy  Inductor  Type  Magneto. — The  Remy  Magneto  Model 
RL,  as  shown  in  Fig.  235,  is  a  typical  low-tension  magneto  of  the  inductor 
type.     Figure  236  shows  the  inductor  and  coil,  while  Fig.  237  shows  the 

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coil  and  the  shaft  in  their  places  with  respect  to  the  pole  pieces,  the 
magnets  and  the  shaft  bearings  having  been  removed.  The  two  wing- 
shaped  inductors  are  mounted  on  a  steel  shaft  and  are  revolved  on  either 
side  of  the  stationary  coil.  Figure 
238  shows  the  path  of  the  magnetism 
during  one  complete  revolution  of  the 

When  the  inductors  are  in  the 
horizontal  position,  the  flux  enters 
one  inductor,  makes  a  right-angled 
turn,  passes  along  the  shaft  and 
through  the  coil  to  the  other  induc- 
tor and  then  to  the  other  pole  piece. 
In  this  position,  the  same  condition 
exists  as  when  an  armature  of  a 
shuttle  type  is  in  the  horizontal  posi- 
tion. When  the  inductors  are  re- 
volved to  the  vertical  position,  the 
flux  passes  from  one  pole  piece  di- 
rectly across  through  the  inductors  to 
the  other  pole  piece,  and  there  is  no  flux  through  the  coil.  This  change, 
therefore,  produces  a  voltage  in  the  coil  winding.  The  outer  ends  of 
the  inductors  are  of  such  length  that  when  they  are  in  the  vertical  posi- 
tion, they  offer  a  direct  path  from  one  pole  to  the  other,  but  when  they 
are  horizontal,  the  flux  must  enter  the  one  inductor,  pass  through  the 
center  of  the  coil,  and  out  through  the  other  inductor. 

Fiq.  235. — Remy  magneto,  Model  RL 

-Remy  inductors  and  stationary  coil. 

Fig.  237. — Remy  inductor  shaft  and 
coil  assembled  in  pole  pieces  and  base. 

This  magneto  will  produce  two  current  waves  per  revolution  in  the 
same  manner  as  the  shuttle  type.  The  current  produced  is  also  an 
alternating  current,  as  the  direction  of  the  flux  through  the  coil  is  reversed 
each  180°  of  revolution  of  the  shaft.  Due  to  the  design  of  the  parts,  the 
current  wave  has  an  abrupt  rise  and  fall  with  an  almost  flat  top,  making 

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possible  a  large  timing  range  (35°)  with  practically  the  same  intensity 
of  spark.    This  magneto  is  used  for  jump-epark  ignition,  the  low-tension 

A  B  C  D  E 

Fio.  238. — Path  of  magnetic  flux  through  Remy  inductor  during  one  revolution. 

current  generated  in  the  coil  being  used  with  a  circuit  breaker  and  a  step- 
up  transformer  coil.     The  secondary  current  from  the  transformer  is  led 

IX  Itetav  KkM  wHk  tlput  Xrtutad  • 
▲4ju*  *•  OMtert  ttaNv  «rt  a  |«*  B 

Fig.  239. — Circuit  breaker  of  Remy  magneto. 

to  a  distributor  on  the  magneto  and  is  there  distributed  to  the  different 
plugs  of  the  engine.     The  circuit  breaker,  Fig.  239,  is  mounted  on  the 

magneto  and  operated  by  a  cam  on 

the  end  of  the  armature  shaft,   the 

^M  ^k  cam   being  mounted  so  as  to  break 

M  ■  the  circuit  in  proper  relation  to  the 

position  of  the  armature  for  maximum 

^^^^1  current.      The   condenser,   Fig.   240, 

^^^^T      "*^^^  is  mounted  in  the  arch  of  the  mag- 

Ip^P     nets  and  is  connected  directly  across 

the  breaker  points. 

Figure  241  shows  an  external 
wiring  diagram  of  the  model  RL  mag- 
neto with  type  LE  switch  and  coil,  while  Fig.  242  shows  a  diagram  of  the 
internal  circuits.     The  lettering  on  the  coil — Y,  R,  and  G — indicates  the 

Fig.  240. — Condenser  for  Remy  Model 
RL  magneto. 

Digitized  by  LiOOQ IC 



color  of  the  wire  intended  by  the  manufacturer  to  be  connected  to  that 
terminal.  The  wiring  from  the  coil  to  the  magneto  is  connected  as 

Fiq.  241. — External  wiring  diagram  of  Remy  magneto,  Type  RL. 

Red  (R)  wire  goes  to  ground  binding  post  on  timer  end  bearing. 
Yellow  (Y)  wire  goes  to  contact  screw  post  on  circuit  breaker. 
Green  (G)  wire  goes  to  insulated  screw  post  on  the  timer  end  bearing. 




■  AT     Mir     CONTACTS 

BAT.  MAG.  Chormaily  WO() 







Fiq.  242. — Internal  circuit  diagram  of  Remy  magneto,  Type  RL. 

Timing. — For  timing  this  magneto,  turn  the  engine  over  by  crank 
until  No.  1  piston  reaches  top  dead  center  on  compression  stroke. 
Press  in  on  the  timing  button  at  the  top  of  the  distributor  and  turn  the 
magneto  shaft  until  the  plunger  of  the  timing  button  is  felt  to  drop  into 

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the  recess  on  the  distributor  gear.  With  the  magneto  in  this  position 
couple  it  to  the  engine.  Pay  no  attention  to  the  circuit  breaker  when 
coupling  or  setting  gears,  as  the  breaker  is  automatically  brought  into 
the  correct  position,  and  the  distributor  segment  is  in  contact  with  No.  1 
terminal.     This  No.  1  terminal  is  plainly  marked  on  the  distributor. 

175.  The  Ford  Ignition  System. — The  Ford  magneto  may  be  classed 
as  a  high-frequency,  alternating-current  magneto  of  the  inductor  type. 
It  serves  merely  as  the  source  of  primary  current  for  an  ordinary  vibra- 
ting-coil  type  of  ignition  system.  The  construction  of  the  magneto  is 
shown  in  Figs.  243  and  244,  while  the  wiring  diagram  is  shown  in 
Fig.  245. 

Magneto  Coil  Spool 

Copper  Wire  — 

End  of  Ribbon  1 
Grounded  Here  f 

To  Coil 

Magneto  Coil  Support 

Fig.  243. — The  Ford  magneto. 

The  stationary  and  revolving  elements  are  interchanged  from  the 
customary  relation.  The  armature  coils  are  stationary  and  the  magnets 
revolve.  The  armature  consists  of  16  coils  which  are  attached  to  a 
stationary  supporting  disc  in  the  flywheel  housing.  An  equal  number  of 
permanent  magnets  of  the  horseshoe  or  V  type  are  secured  to  the  flywheel 
through  non-magnetic  studs.  The  magnets  revolve  with  the  flywheel  at 
a  distance  of  J-^2  ln-  from  the  coils.  The  North  poles  of  two  adjacent 
magnets  are  fastened  together,  likewise  the  next  pair  of  South  poles. 
When  a  pair  of  North  poles  is  in  front  of  the  core  of  one  of  the  coils,  the 
magnetic  flux  will  flow  in  through  the  core,  through  the  supporting  coil 
plate,  and  out  through  the  core  of  the  adjacent  coils  to  the  South  poles 

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as  shown  in  Fig.  244.  When  the  flywheel  makes  Ke  revolution  this 
flow  is  reversed.  Thus,  16  current  waves  are  generated  per  revolution  of 
the  flywheel.  The  coils  are  all  connected  in  series  with  one  end  of  the 
winding  grounded  and  the  other  end  connected  to  an  insulated  binding 
post  on  the  top  of  the  flywheel  housing.  This  post  is  connected  through 
the  switch  to  all  four  induction  coils  by  means  of  a  contact  plate  in  the 
bottom  of  the  coil  box  as  was  shown  in  Fig.  180,  Chapter  VII.  The  other 
ends  of  these  coils  are  connected  to  the  four  posts  of  the  timer  mounted 
on  the  front  end  of  the  camshaft.  Since  one  end  of  the  magneto  winding 
is  grounded,  and  since  the  timer  completes  the  circuit  to  the  ground  from 
each  induction  coil  in  proper  order,  it  follows  that  the  magneto  current 
will  pass  through  whichever  induction  coil  is  grounded  at  the  timer. 
The  induction  coils  are  of  the  ordinary  double  wound  induction  t^pe 
with  vibrators  to  interrupt  the  primary  current  from  the  magneto.     A 


FlYWHEEl.    HOUSING         ' 


>W  *CA»  CNO  OC 

Fig.  244. — Diagram  showing  scheme  of  Ford  magneto. 

diagram  of  the  Hienze-Ford  coil  is  shown  in  Fig.  246.  The  secondary  of 
each  coil  has  a  direct  connection  to  the  plug  of  one  of  the  cylinders  with 
a  grounded  return. 

This  magneto  is  quite  unlike  those  previously  described  in  that  the 
current  waves  are  of  high  frequency  and  are  not  all  used  for  ignition. 
The  magneto  itself  does  not  have  to  be  timed  to  the  engine.  The  alter- 
nations of  the  magneto  current  are  frequent  enough  to  cause  only  a 
slight  variation  in  the  instant  of  ignition  as  affected  by  the  periods  of  no . 
current.  The  length  of  contact  in  the  timer  is  sufficient  to  overlap  from 
one  current  wave  to  the  next.  In  case  the  magnet  is  in  a  position  where 
no  current  is  generated  when  the  timer  first  makes  contact,  there  will  be 
a  lag  of  a  very  few  degrees  in  the  spark  until  the  magneto  has  turned  into 
a  position  where  it  will  generate  sufficient  current  to  operate  the  coil. 

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Due  to  the  shape  of  the  current  waves,  the  greatest  possible  lag  due  to  this 
cause  is  probably  not  more  than  5°  on  the  engine  crankshaft. 

176.  The  High-tension  Magneto. — Under  the  name  of  High-tension 
Magneto  are  included  all  magnetos  which  generate,  directly  in  the  mag- 
neto winding,  a  current  of  sufficiently 
high  voltage  for  jump-spark  ignition  with- 
out the  aid  of  a  separate  induction  coil. 
The  magneto  winding  contains  both  a 
primary  and  secondary  winding,  similar 
to  the  winding  of  a  non-vibrating  type  in- 
duction coil,  instead  of  the  usual  single 
winding  found  in  the  low-tension  magneto. 
In  the  high-tension  magneto  is  also  incor- 
porated the  interrupter,  distributor,  and 
condenser,  so  that  the  magneto  contains 
within  itself  all  the  essentials  of  a  complete 
ignition  system,  the  only  necessary  out- 
side parts  being  the  spark  plugs  and  the 
This  applies  to  both  the  armature  wound 



j[*0*  maghcto 
7m*u  switch. 

Fig.  246. — Diagram  of  Ford- 
Heinse  induction  coil. 

magneto  controlling  switch. 

and  the  inductor  type  of  magneto. 

177.  The  Bosch  High-tension  Magneto. — The  Bosch  Magneto,  Figs. 
247  and  248,  is  a  typical  high-tension  magneto  of  the  armature  wound 


Fio.  247. — Bosch  high-tension  magneto  installation  on  M  arm  on  engine. 

type.  The  armature  or  rotating  element,  Fig.  249,  is  mounted  on  ball 
bearings  supported  in  the  end  housings  and  rotates  between  the  magnet 
pole  pieces  shown  in  Fig.  250.     The  armature,  a  cross  section  of  which 

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«ETA(NIN8   5P»H' 




'  fi  MM  MM 





Fig.  248. — View  of  driving  end  of  Bosch  high-tension  magneto. 






Fig.  249. — View  of  armature  of  Bosch  DU4  high-tension  magnetos  showing  ball  bearings 
on  armature  shaft  and  pinion  that  drives  distributor  gear. 






Fiq.  250. — Magneto  and  pole  pieces  of  Bosch  magneto. 

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is  shown  in  Fig.  251,  consists  of  a  soft  iron  core,  a  primary  winding  of 
comparatively  few  turns  of  coarse  wire,  a  secondary  winding  of  many 
turns  of  fine  wire  wound  on  the  outside  of  the  primary,  and  a  condenser. 
The  condenser,  Fig.  252,  is  mounted  in  one  end  of  the  armature  housing 
and  connected  so  as  to  protect  the  interrupter  points,  the  interrupter  or 




Fiq.  251. — Cross-sectional  view  of  Bosch  high-tension  magneto  armature. 

circuit  breaker  being  mounted  on  one  end  of  the  armature  shaft  and 
revolving  with  it.  The  cams  for  actuating  the  interrupter  points  are  on 
the  inside  of  the  interrupter  housing.  This  arrangement  is  the  reverse  of 
that  of  the  usual  low-tension  magneto  which  has  the  cam  on  the  armature 




Fig.  252. — Condenser  of  Bosch  DU4  high- tension  magneto. 

shaft  and  the  interrupter  in  the  housing.  By  having  the  interrupter, 
condenser,  and  primary  winding  all  on  the  armature,  the  entire  primary 
circuit  is  thus  contained  in  the  armature,  forming  a  very  compact  and 
efficient  unit.  One  end  of  the  primary  winding  is  grounded  on  the 
armature  core,  and  the  live  end  brought  out  to  a  circuit-breaking  device. 

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The  grounded  end  of  the  secondary  winding  is  connected  to  the  live  end 
of  the  primary  winding  so  that  one  is  a  continuation  of  the  other.  The 
magneto  armature  core  is  grounded  to  the  magneto  base  by  the  ground 
brush  shown  in  Pig.  253. 





Fia.   253. — Bottom  view  of  magneto  base  plate  showing  ground  brush. 

During  certain  portions  of  the  rotation  of  the  armature  the  primary 
circuit  is  closed,  and  the  variations  in  magnetic  flux  have  the  effect  of 
inducing  an  electric  current  in  the  winding.  When  the  current  reaches 
a  maximum,  which  will  occur  twice  during  each  rotation  of  the  armature, 
the  primary  circuit  is  broken,  and  the  resulting  armature  reactions 
produce  a  high-tension  current  of 
extreme  intensity  in  the  secondary 
winding.  This  current  is  trans- 
mitted to  the  distributor  by  means 
of  which  it  passes  to  the  spark  plugs 
in  the  cylinders  in  their  proper  order 
of  firing. 

The  Bosch  DU4  high-tension 
magneto  is  shown  in  Fig.  254,  while 
a  longitudinal  section  and  the  rear 
view  with  the  breaker  cover  removed 
are  shown  in  Fig.  255.  Figure  256 
is  a  circuit  diagram  for  the  magneto. 

Magneto  Interrupter. — The  mag- 
neto interrupter  mechanism  is 
mounted  on  a  circular  disc  which  is  held  rigid  to  the  armature  shaft 
by  the  interrupter  fastening  screw.  The  relative  position  of  the  inter- 
rupter to  the  armature  is  fixed  by  a  keyway  in  the  end  of  the  armature 
shaft  which  is  taper  bored.  As  may  be  seen  in  Fig.  256,  the  fastening 
screw  also  forms  the  electrical  connection  between  the  stationary  (insul- 
ated) half  of  the  interrupter  and  the  primary  winding  of  the  armature. 


Fiq.  264. — Bosch    high-tension    magneto, 
Type  DU4. 

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This  fastening  screw  also  makes  connection  with  the  insulated  terminal 
of  the  condenser,  the  other  terminal  of  which  is  grounded  as  are  also 
one  end  of  the  primary  winding  and  the  movable  contact  arm  of  the 

Twice  during  each  revolution  of  the  armature,  the  primary  circuit 
closes  and  opens,  this  being  caused  by  the  fiber  block  on  the  interrupter 
lever  striking  the  two  steel  cams  on  the  inside  of  the  interrupter  housing. 
When  the  interrupter  is  not  being  acted  upon  by  the  cams,  the  interrupter 
points  are  normally  held  closed  by  spring  tension,  consequently  the 

Longitudinal  section. 

1.  Brass  plate  for  connecting  the  end  of  the 
primary  winding. 

2.  Fastening  screw  for  magneto  interrupter. 

3.  Contact  block  for  magneto  interrupter. 

4.  Magneto  interrupter  disc. 

5.  Long  platinum  screw. 

6.  Short  platinum  screw. 

7.  Flat  spring  for  magneto  interrupter  lever  8. 

8.  Magneto  interrupter  lever. 

9.  Condenser. 

10.  Collector  ring. 

11.  Carbon  brush. 

12.  Brush  holder  for  same. 

13.  Terminal  piece  for  conducting  bar  14. 

14.  Conducting  bar. 

Rear  end  interrupter  cover  removed. 

15.  Distributor  brush  holder. 

16.  Distributor  carbon  brush. 

17.  Distributor  plate. 

18.  Central  distributor  contact. 
10.  Brass  segment. 

20.  Knurled  nut  on  terminal  stud. 

21.  Steel  segment. 

22.  Dust  cover. 

24.  Knurled  nut  on  grounding  terminal  stud. 

25.  Holding  spring  for  distributor  plate  17. 
116b.  Interrupter  housing  and  timing  arm. 

117.  Cover  for  interrupter  housing. 

118.  Conducting  spring  for  grounding  terminal  stud. 

119.  Holding  spring  for  interrupter  housing  cover. 

Fig.  255. — Construction  of  Bosch  high-tension  magneto,  Type  DU4. 

primary  circuit  is  also  closed.  It  is  very  important  in  this  type  of  in- 
terrupter that  the  interrupter  lever  unit  be  very  accurately  balanced  on 
its  pivot  to  insure  proper  optening  and  closing  of  the  points  at  high  rotat- 
ing speeds.  The  interrupter  points  are  made  of  platinum  and  should 
be  adjusted  to  open  .012  in.  to  .015  in.  on  engines  of  normal 

Principle  of  Operation. — The  function  of  the  interrupter  or  breaker 
is  to  interrupt  the  circuit  of  the  primary  winding  of  the  armature  when  a 
high-tension  spark  is  to  occur  at  the  plug,  the  action  in  the  armature 
being  similar  to  that  of  an  induction  coil.     This  interruption  must  take 


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1    ui  ou 

w  D  - 

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place  when  the  flow  of  current  through  the  primary  winding  is  at  or  near 
its  TnAYiTniiin  value,  which  occurs  \yiien  the  armature  core  is  approxi- 
mately in  a  vertical  position,  as  shown  in  Fig.  256,  the  same  as  in  the 
low-tension  magneto.  In  this  position  the  corner  of  the  armature  is 
just  leaving  the  corner  of  the  pole  pi<ce  and  the  winding  is  cutting  the 
greatest  number  of  magnetic  lines  of  iiOrce.  In  Bosch  magnetos,  having 
a  variable  spark  advance,  the  interrt^>ter  points  are  timed  to  open  when 
the  corner  of  the  armature  has  left*l\e  corner  of  the  pole  piece  about 
He  »*•>  with  *he  interrupter  housing  in  full  advance  position.  The 
timing  lever  may  be  advanced  aba  it  35°;  then,  when  the  interrupter 
housing  is  fully  retarded,  the  armj1"  ire  has  passed  the  pole  piece  about 
%  in.     Thus  the  best  spark  is  obt^.ned  with  the  interrupter  in  full  ad- 

A  B  c 

Fio.  257. — Distribution  of  magnetic  flux  through  magneto  armature  core  for  various 


vance  position,  which  is  the  normal  operating  position  at  high  engine 

Figure  257  A,  Bf  and  C  shows  the  distribution  of  the  magnetic  flux 
through  the  armature  core  for  various  armature  positions.  Owing  to 
the  rotation  of  both  primary  and  secondary  windings  of  the  armature  and 
the  consequent  cutting  of  the  magnetic  lines  of  force  by  both  windings, 
a  voltage  is  generated  in  both  the  primary  and  secondary  circuits  pro- 
portional to  the  number  of  turns  in  the  two  windings.  During  the  period 
of  rotation,  when  the  magnetic  field  is  passing  through  the  armature 
core,  the  interrupter  points  are  closed,  thus  completing  (by  short- 
circuiting)  the  circuit  through  the  primary  winding.  The  current  thus 
generated  in  the  primary  winding  will  flow  around  the  core,  causing  the 
core  to  become  magnetized  in  a  cross  direction  as  shown  in  Fig.  258. 
At  approximately  the  instant  when  the  generated  voltage  is  greatest, 
the  interrupter  breaks  the  primary  circuit  thus  permitting  the  armature 

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core  to  demagnetize  instantly.  IJiis  causes  a  high  voltage  to  be  induced 
in  the  secondary  winding  in  the  s&me  direction  as  the  generated  voltage. 
The  induced  current  produced  by  the  interruption  of  the  primary  circuit 
lasts  a  very  short  interval  of  time  art  1,  if  acting  alone,  would  produce  but  a 
single  flash  at  the  spark  plug.  H  ^wever,  owing  to  the  revolving  of  the 
secondary  winding  in  the  magnetic  field,  a  more  continuous  current  of 
not  so  high  a  voltage  is  generatecT  This  generated  voltage  alone  is  not 
sufficient  to  break  down  the  resistance  of  the  gap  in  the  spark  plug,  but 
at  the  instant  the  primary  circuit  I  interrupted,  the  induced  current  is 
sufficient  to  break  down  this  resis^  nee  and  then  the  somewhat  lower 
voltage  of  the  generated  current  is  a"T  le  to  cross  the  gap,  thus  producing 








Fig.  258. — Diagram  showing  armature  cross-magnetisation  due  to  current  generated  in 
primary  and  secondary  winding. 

not  an  instantaneous  flash  but  a  hot  flame  which  lasts  for  a  considerable 
period  of  armature  rotation. 

Condenser. — The  condenser,  as  in  all  high-tension  armature-type 
magnetos,  is  located  in  one  end  of  the  armature.  It  is  connected  in 
parallel  with  the  primary  winding  and  the  interrupter  circuit.  As  stated 
previously,  the  purpose  of  the  condenser  is  to  absorb  the  induced  charge 
in  the  primary  winding  and  prevent  the  discharge  of  this  current  across 
the  interrupter  points.  The  charge  in  the  condenser  surges  back  into 
the  primary  winding  in  the  opposite  direction  to  that  of  the  primary  cur- 
rent, thereby  causing  a  more  rapid  demagnetization  of  the  armature 
and,  consequently,  producing  a  higher  voltage  in  the  secondary  winding 
than  would  otherwise  be  obtained. 

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In  the  diagram  shown  in  Fig.  256,  it  will  be  seen  that  one  end  of  the 
secondary  winding  is  connected  to  the  insulated  end  of  the  primary 
winding  so  that  the  one  forms  a  continuation  of  the  other.  The  other  end 
of  the  secondary  winding  leads  to  the  collector  ring  or  slip  ring  on  which 
slides  a  carbon  brush,  insulated  from  the  magneto  frame.  The  secondary 
current  is  conducted  from  the  brush  to  the  center  distributor  contact 
and  from  there  through  the  carbon  brush,  carried  on  the  distributor 
gear  wheel,  to  the  various  cable  connections  and  spark  plugs  in  their 
proper  order  of  firing.  After  jumping  the  spark-plug  points,  the  current 
then  returns  through  the  engine  frame  and  the  ground  brush  in  the  base 
of  the  magneto,  Pigs.  250  and  253,  to  the  armature  core  and  back  to  the 
beginning  of  the  secondary  winding.  As  in  the  low-tension  armature 
type  of  magneto,  there  are  two  sparks  produced  per  revolution  of  the 
armature.  The  distributor  is,  therefore,  similar  to  that  found  on  the 
low-tension  magneto  and  is  driven  at  similar  speeds.  The  only  difference 
is  that  the  secondary  current  is  received  direct  from  the  armature  instead 
of  being  brought  back  to  the  distributor  from  a  transformer  coil.  The 
distributor  has  as  many  segments  as  there  are  engine  cylinders  and  is 
driven  at  one-half  the  speed  of  the  crankshaft.  For  a  four-cylinder  engine 
the  distributor  has  four  segments  and  is  driven  at  one-half  the  speed  of  the 
armature.  For  a  six-cylinder  engine  there  are  six  segments,  and  the 
distributor  arm  is  driven  at  one-third  the  speed  of  the  armature. 
The  relations  of  magneto  speeds  to  engine  speeds  are  also  the  same 
as  for  the  armature  type  of  low-tension  magnetos.  For  a  four-cylinder 
four-stroke  engine  the  armature  revolves  at  crankshaft  speed.  For 
a  six-cylinder  four-stroke  engine  the  armature  revolves  at  one  and 
one-half  times  crankshaft  speed.  Likewise,  for  an  eight-  or  twelve- 
cylinder  engine  a  magneto  of  this  type  must  be  driven  at  twice  or  three 
times  crankshaft  speed,  respectively,  in  order  to  produce  the  required 
number  of  sparks  per  revolution  of  the  engine. 

Care  should  be  taken  in  assembling  the  magneto  to  get  the  distributor 
gear  timed  correctly  with  the  armature  so  that  the  distributor  brush  will 
be  in  proper  alignment  with  the  distributor  head  segment  when  the  inter- 
rupter points  open  with  the  breaker  housing  in  either  the  advance  or 
retard  positions.  On  full  advance  position  the  distributor  brush  should 
be  moving  on  to  the  distributor  head  segment  when  the  interrupter 
contacts  open,  and  should  be  leaving  the  same  segment  when  the  contacts 
open  with  breaker  housing  shifted  to  full  retard  position.  Figure  259 
Bhows  the  punch  markings  on  the  distributor  gears  for  the  purpose  of 
timing  the  distributor  with  the  armature.  For  a  magneto  having  clock- 
wise direction  of  rotation,  the  punch  mark  C  on  the  distributor  gear 
should  mesh  with  the  punch  mark  on  the  armature  gear,  while  in  the 
case  of  a  magneto  with  anti-clockwise  rotation,  the  gears  should  be 

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meshed  so  that  punch  mark  A  will  mesh  with  the  punch  mark  on  the 
armature.  The  direction  of  armature  rotation  is  usually  indicated  by 
an  arrow  stamped  on  the  magneto  housing  near  the  driving  end  of  the 
armature  shaft. 

The  Safety  Spark  Gap. — In  order  to  protect  the  insulation  of  the 
armature  and  of  the  current-conducting  parts  against  excessive  voltage, 
a  safety  spark  gap  of  about  *Ke  in-  is  provided  as  shown  in  Fig.  256.  The 
current  will  pass  through  this  gap  in  case  a  cable  connection  to  one  of  the 
spark  plugs  becomes  disconnected  while  the  magneto  is  in  operation,  or 
if  the  electrodes  on  the  spark  plugs  are  too  far  apart.    The  secondary 
















Fig.  259. — Bosch  distributor  gears  showing  markings  for  timing  distributor  with  armature. 

current  should  not  be  permitted  to  jump  the  safety  gap  for  any  length  of 
time,  as  the  continued  discharge  of  the  current  over  the  safety  gap  is  liable 
to  damage  the  magneto  winding  and  condenser. 

The  Magneto  Grounding  Suritch.-^In  order  to  cut  off  the  ignition 
without  damaging  the  windings,  the  primary  current  must  be  short- 
circuited  so  that  it  will  not  be  interrupted  when  the  interrupter  points 
open.  This  is  arranged  for  by  connecting  a  wire  from  the  insulated 
terminal  on  the  breaker  cover,  to  a  simple  ground  switch  which  has  two 
terminals,  one  of  which  connects  to  the  engine  or  chassis  frame.  The 
terminal  on  the  breaker  cover  is  connected  by  a  brush  to  the  insulated 
half  of  the  interrupter,  so  that  when  the  switch  is  closed,  the  primary 
current  is  short-circuited  through  the  switch  and  ground  and  the  magneto 
ceases  to  generate  sufficient  voltage  in  the  secondary  winding  to  jump 
the  spark  plug  points,  thus  preventing  ignition. 

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178.  The  Bosch  High-tension  Dual  System. — In  the  Bosch  high- 
tension  dual  ignition  system,  the  standard  type  of  Bosch  magneto  is  used 
with  the  application  of  two  timers  or  interrupters.  The  parts  of  the 
regular  current  interrupter  are  carried  on  a  disc  that  is  attached  to  the 
armature  and  revolve  with  it,  the  rollers  or  segments  that  serve  as  cams 
being  supported  on  the  interrupter  housing.  In  addition,  the  magneto 
is  provided  with  a  steel  cam  which  is  built  into  the  interrupter  disc  and 
has  two  projections.  This  cam  acts  on  a  lever  supported  by  the  interrup- 
ter housing,  the  lever  being  connected  in  the  battery  circuit  so  that  it 




Fig.  260. — Bosch  dual  magneto  showing  magneto  interrupter  and  battery  timer. 

serves  as  a  timer  to  control  the  flow  of  battery  current.  These  parts 
may  be  seen  in  Fig.  260.  A  non-vibrating  transformer  coil  is  used  with 
the  battery  current  to  produce  the  necessary  voltage. 

It  is  obvious  that  the  sparking  current  from  the  battery  and  from  the 
magneto  cannot  be  led  to  the  spark  plugs  at  the  same  time,  so  a  further 
change  from  the  magneto  of  the  independent  form  is  found  in  the  removal 
of  the  direct  connection  between  the  collecting  ring  and  the  distributor. 
The  collecting  ring  brush  shown  in  Fig.  261  as  No.  3  is  connected  to  the 
switch,  and  a  second  wire  leads  from  the  switch  to  the  central  terminal 
on  the  distributor.     When  running  on  the  magneto,  the  sparking  current 

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that  is  induced  in  the  secondary  armature  winding  flows  to  the  distributor 
by  way  of  the  switch  contacts.  When  running  on  the  battery,  the  primary 
circuit  of  the  magneto  is  grounded,  and  there  is,  therefore,  no  production 
of  sparking  current  by  the  magneto;  it  is,  then,  the  sparking  current  from 
the  coil  that  flows  to  the  central  distributor  connection.  It  will  thus  be 
seen  that  the  only  parts  of  the  magneto  and  battery  circuits  used  in 
common  are  the  distributor  and  the  spark  plugs. 

The  Bosch  Dual  Coil. — The  Bosch  dual  coil  used  in  the  dual  system 
consists  of  a  cylindrical  housing  bearing  a  brass  casting,  the  flange  of 
which  serves  to  attach  the  coil  to  a  dashboard  or  other  part.  The  coil  is 
provided  with  a  key  and  lock,  by  which  the  switch  may  be  locked  when 

Fig.  261. — Wiring  diagram  for  Bosch  dual  ignition  system. 

in  the  "off"  position.  This  is  a  point  of  great  advantage,  as  it  makes  it 
unlikely  that  the  switch  will  be  left  thrown  to  the  battery  position  when 
the  engine  is  brought  to  a  stop.  The  absence  of  such  an  attachment  is 
responsible  in  a  large  measure  for  the  accidental  running  down  of  the 
battery.  This  locking  device  also  prevents  the  unauthorized  operation 
of  the  engine.  The  parts  of  the  coil  are  shown  in  Fig.  262.  In  addition 
to  the  housing  and  end  plate,  they  consist  of  the  coil  itself,  the  stationary 
switch  plate,  and  the  connection  protector. 

When  the  engine  is  running  on  battery  ignition,  a  single  contact 
spark  is  secured  at  the  instant  when  the  battery  interrupter  breaks  its 
circuit,  and  the  intensity  of  this  spark  permits  efficient  operation  of  the- 
engine  on  the  battery  system. 

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Starting  on  the  Spark. — For  the  purpose  of  starting  on  the  spark,  a 
vibrator  may  be  cut  into  the  coil  circuits  by  turning  the  button  that  is 
seen  on  the  coil  body  in  Figs.  261  and  262.  Normally,  this  vibrator  is 
out  of  circuit,  but  the  turning  of  the  button  places  it  in  the  battery 
primary  circuit.     A  vibrator  spark  of  high  frequency  is  thus  produced. 

It  will  be  found  that  the  distributor  on  the  magneto  is  then  in  such 
a  position  that  this  vibrator  spark  is  produced  at  the  spark  plug  of  the 
cylinder  that  is  performing  the  power  stroke.  If  a  combustible  mixture 
is  present  in  this  cylinder,  ignition  will  result  and  the  engine  will  start. 

Connections. — In  the  wiring  diagram  of  this  system,  as  shown  in  Fig. 
261,  it  will  be  noted  that  while  the  independent  magneto  requires  but  one 
switch  wire  in  addition  to  the  cables  between  the  distributor  and  spark 
plugs,  the  dual  system  requires  four  connections  between  the  magneto 

Fiq.  262.— Parts  of  Bosch  dual  coil. 

and  the  switch;  two  of  these  are  high  tension  and  consist  of  wire  No.  3 
by  which  the  high-tension  current  from  the  magneto  is  led  to  the  switch 
contact,  and  wire  No.  4  by  which  the  high-tension  current  from  either 
magneto  or  coil  goes  to  the  distributor.  Wire  No.  1  is  low  tension,  and 
conducts  the  battery  current  from  the  primary  winding  of  the  coil  to  the 
battery  interrupter.  Low-tension  "wire  No.  2  is  the  grounding  wire  by 
which  the  primary  circuit  of  the  magneto  is  grounded  when  the  switch  is 
thrown  to  the  "Off"  or  to  the  "Battery"  position.  Wire  No.  5  leads 
from  the  negative  terminal  of  the  battery  to  the  coil,  and  the  positive 
terminal  of  the  battery  is  grounded  by  wire  No.  7;  a  second  ground  wire 
No.  6  is  connected  to  the  coil  terminal. 

179.  The  Bosch  High-tension  Magneto,  Type  NU4. — The  Bosch 
magneto,  type  NU4,  Fig.  263,  is  of  the  high-tension,  armature  wound 
type  and  is  suitable  only  for  four-cylinder,  four-cycle  engines  of  the 
automobile  type,  rated  at  or  under  30  horse  power.     A  distinct  feature  of 

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this  magneto  is  the  absence  of  the  usual  gear-driven  distributor,  this 
being  incorporated  in  the  form  of  a  double  high-tension  slip  ring  mounted 
on  one  end  of  the  armature  shaft  as  shown  in  Fig.  264.  The  magneto 
interrupter,  Fig.  265,  is  the  same  as  that  used  in  the  ordinary  Bosch 
independent  high-tension  magneto. 

Fig.  263.  FiQ.  264, 

Fio.  263. — Bosch  high-tension  magneto,  Type  NU4. 

Fio.  264. — Distributor  on  Bosch  "NU4"  magneto  showing  position  of  the  carbon 
brushes  with  relation  to  the  slip  ring. 

A  circuit  diagram  of  this  magneto  is  shown  in  Fig.  266.  It  will  be 
noted  that  the  circuit  of  the  primary  winding  is  the  same  as  for  the  Bosch 
DU4  shown  in  Fig.  256.  The  secondary  winding,  however,  is  not  con- 
nected to  the  primary,  its  two  ends  being  connected  to  the  two  metal 
segments  in  the  slip  ring  mounted  on  the  armature  just  inside  of  the 

265.— Interrupter  end  of  Bosch  "NU4"  magneto. 

driving  shaft  end  plate  of  the  magneto.  The  slip  ring  has  two  grooves, 
each  containing  one  of  the  two  metal  segments.  These  segments  are 
set  diametrically  opposite  on  the  armature  shaft,  that  is,  180°  apart,  and 
insulated  from  each  other  as  well  as  from  the  armature  core  and  magneto 

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The  four  slip  ring  brushes  which  collect  the  secondary  current  are 
supported  by  two  double  brush  holders,  one  on  each  side  of  the  driving 
shaft  end  plate,  each  holder  carrying  two  brushes  arranged  so  that  each 
brush  bears  against  the  slip  ring  in  a  separate  groove.  Upon  rotation 
of  the  armature,  the  metal  segment  in  one  slip  ring  groove  makes  contact 
with  a  brush  on  one  side  of  the  magneto  at  the  same  instant  that  the 
metal  segment  in  the  other  slip  ring  groove  comes  into  contact  with  a 
brush  on  the  opposite  side  of  the  magneto.  The  marks  "1"  and  "2" 
appearing  in  white  on  both  brush  holders  indicate  pairs  of  brushes  receiv- 









266. — Circuit  diagram  of  Bosch  "NU4"  high-tension  magneto. 

ing  simultaneous  contact,  those  marked  "1"  constituting  one  pair,  and 
those  marked  "2,"  the  other. 

From  the  wiring  diagram  it  is  important  to  note  that  as  two  of  the 
four  slip  ring  brushes  make  contact  simultaneously  and  each  is  connected 
by  cable  to  the  spark  plug  in  one  of  the  cylinders,  the  secondary  circuit 
always  includes  two  plugs,  and  the  spark  occurs  in  two  cylinders  at  the 
same  time,  namely,  cylinders  Nos.  1  and  4  or  2  and  3.  Only  one  of  these 
sparks,  if  properly  timed,  will  cause  ignition,  since  in  a  four-cylinder 
engine,  when  No.  1  cylinder  is  under  compression  ready  for  ignition,  No.  4 
piston  is  finishing  its  exhaust  stroke  and  the  cylinder  contains  nothing 
but  burned  exhaust  gases.  The  same  relation  exists  when  each  cylinder  is 
ready  for  ignition,  the  other  cylinder  in  which  the  spark  occurs  containing 
non-combustible  exhaust  gases.  Care  should  be  taken  in  timing  this 
type  of  magneto  so  that  when  fully  retarded  the  spark  will  not  occur  in 

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the  dead  cylinder  after  the  intake  valve  has  opened,  which  is  usually  a 
crank  angle  of  about  8°  to  10°  past  upper  dead  center.  The  platinum 
interrupter  points  should  be  adjusted  to  open  0.015  in.  while  the  spark 
plugs  should  be  adjusted  to  a  gap  of  .020  to  .030  in.,  or  the  thickness  of  a 
worn  dime. 

180.  The  Eisemann  High-tension  Magneto,  Type  G4. — The  Eise- 
mann  high-tension  magneto,  type  G4,  Fig.  267,  is  typical  of  the  various 
models  of  the  Eisemann  magneto.  It  is  made  in  two  types  known  as 
G4,  I  Edition,  and  G4,  II  Edition.  The  principal  differences  between 
the  two  models  are  in  the  design  of  the  interrupter  mechanism  and  in  the 
construction  of  the  armature  housing. 

In  the  type  G4, 1  Edition,  shown  in  Fig.  268,  the  movable  contact  of 
the  interrupter  is  carried  on  a  flat  spring  instead  of  on  the  usual  rocking 
type  lever.  The  interrupter  points  are  actuated  by  this  spring  striking 
the  two  fiber  cams  on  either  side  of  the  center  part  of  the  timing  lever 

Fiq.  267. — Eisemann  high-tension  magneto,  Type  G4 — II  Edition. 

body.  The  fixed  end  of  the  spring  is  grounded  to  the  magneto  frame 
through  a  grounding  brush  which  bears  on  the  inside  of  the  timing  lever 
body.  In  this  type  of  magneto  the  interrupter  platinum  points  may  be 
adjusted  without  removing  the  timer  body,  as  shown  in  Fig.  269.  In 
the  type  G4,  II  Edition,  the  usual  form  of  rocking  type  interrupter  is 
used,  in  which  the  interrupter  lever  is  actuated  by  two  steel  segments 
or  cams  mounted  on  the  inside  of  the  timing  lever  body,  as  shown  in 
Fig.  270.  The  platinum  contacts  in  both  types  of  magnetos  should  be 
adjusted  to  open  .13  to  .17  in. 

The  armature  housing  or  frame  of  the  type  G4,  II  Edition,  consists  of 
the  unit-cast  construction  shown  in  Fig.  271,  whereas  the  I  Edition  hous- 
ing is  built  up  of  several  parts  screwed  together.  This  unit-casting  is 
extremely  rigid,  thus  positively  eliminating  all  danger  of  loosened  screws 

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-        SETTING  SCREW 





Ito.  268. — Principal  parts  of  Eisemann  high-tension  magneto,  Type  G4 — I  Edition. 

ft®.  269. 

— Eisemann  magneto,  Type  G4 — I  Edition,  with  distributor  removed  showing 
setting  marks  for  timing,  also  method  of  adjusting  interrupter  contacts. 

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or  end  plates,  due  to  vibration  or  accidental  twisting.  Another  advan- 
tage of  the  unit-casting  is  the  absence  of  any  joints.  Consequently,  an 
absolutely  water-,  oil-,  and  dust-tight  protection  is  provided  for  the  vital 
elements,  such  as  the  winding  and  the  condenser.  The  unit-casting  can 
be  bored  out  and  machined  all  in  one  piece,  and  also  because  of  its  rigidity, 
it  is  possible  to  better  maintain  the  running  clearance  between  the  arma- 
ture and  the  poles  of  the  magnets.  This  tends  to  give  increased  magnetic 
efficiency,  and,  as  a  result,  a  much  hotter  spark. 

The  Armature. — The  armature  used  in  the  Eisemann  magneto  is  shown 
in  Fig.  272.-   The  armature  which  carries  the  winding  is  of  the  H-  shaped 

•istrirrtor  rim 


irdicator  rout 



•ATM  r.vivir  ERR 

«A0ft£fO  CRIIKf 
■If  MER  MINT* 

IMIH6  lit ER  RMf 

Fig.  270. — Principal  parts  of  Eisemann  high-tension  magneto,  Type  G4 — II  Edition. 

type,  similar  to  that  shown  in  Fig.  251.  On  this  core  are  wound  a  few 
layers  of  medium-sized  copper  wire,  the  beginning  end  of  which  is  grounded 
to  the  armature  core.  The  other  end  of  the  wire  is  connected  through 
the  interrupter  fastening  screw  to  the  insulated  contact  of  the  breaker 
mechanism.  Over  this  primary  winding  is  the  secondary  winding  con- 
sisting of  many  turns  of  very  fine  copper  wire,  the  wire  itself  being  in- 
sulated its  entire  length  and  the  layers  carefully  insulated  from  each 
other.  A  circuit  diagram  of  the  Eisemann,  type  G4,  I  Edition,  is  shown 
in  Fig.  273.  It  will  be  noted  that  the  beginning  of  the  secondary  is 
connected  directly  to  the  end  of  the  primary  winding  and  the  end  is  led 
to  the  collector  ring  which  is  mounted  on  the  same  end  of  the  armature 

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as  the  interrupter.     The  condenser,  which  is  connected  so  as  to  protect 
the  interrupter  points,  is  mounted  in  the  other  end  of  the  armature. 

Pole  Pieces. — One  of  the  distinct  features  of  the  Eisemann  magneto 
is  the  shape  of  the  pole  pieces,  which  are  wedge-shaped  as  shown  in  Fig. 
274.     These  wedge-shaped  pole  pieces  cause  the  magnetic  lines  of  force 

Fig.  271. — Frame  casting  for  Eisemann  magneto,  Type  G4 — II  Edition. 

to  flow  from  the  extremities  of  the  pole  pieces  toward  the  center  of  the 
core.  All  of  the  magnetic  lines  of  force  are  thus  forced  through  the  wind- 
ing of  the  armature  and  are  not  diffused  as  in  the  case  of  the  straight  pole 
pieces  which  are  most  commonly  used.  The  wedge-shaped  pole  pieces 
also  prolong  the  duration  of  maximum  current  in  the  primary  winding, 




Fiq    272. — Armature  for  Eisemann  magneto. 

when  the  corner  of  the  armature  passes  the  pole  pieces,  thus  increasing 
the  angle  of  spark  range  and  permitting  a  hotter  spark  with  breaker  in 
retard  position.  The  armature  which  is  always  overlapped  by  the  pole 
pieces  acts  as  a  keeper  to  the  magnets,  thereby  aiding  in  preventing  de- 
magnetization which  is  common  to  magnetos  with  straight  pole  pieces. 

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These  pole  pieces  greatly  reduce  the  wear  on  the  coupling  or  gear  which 
drives  the  magneto,  by  preventing  the  sudden  breaking  of  the  magnetic 
field.    This  feature  also  aids  in  making  the  magneto  gears  noiseless. 












Fig.  273. — Circuit  diagram  of  Eiaemann  high-tension  magneto,  Type  G4 — I  Edition. 

The  Distributor. — By  placing  the  collector  ring  on  the  same  end  of 
the  magneto  as  the  distributor  head,  the  necessity  of  carrying  the  high- 
tension  current  around  the  magneto  by  means  of  brushes  and  conductors 

FiG.  274. — Diagram  showing  the  wedges-haped  pole  pieces  used  on  Eisemann  magnetos. 

is  done  away  with.  Instead,  a  brush  in  the  distributor  plate,  carried 
straight  down  to  a  contact  with  the  collector  ring,  is  used  and  in  this 
manner  the  high-tension  current  is  carried  directly  to  the  center  brush  in 
the  distributor  plate.    This  center  brush  in  turn  makes  contact  with  the 

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metal  insert  of  the  distributor  disc.  This  disc  is  attached  to  the  distribu- 
tor gear  and,  consequently,  rotates  with  it,  so  that  the  metal  insert 
makes  contact  in  rotation  with  each  of  the  outside  carbons  of  the  distribu- 
tor plate,  whence  the  current  is  led  to  the  spark  plugs  by  the  high- 
tension  cables. 

The  safety  spark  gap  is  located  in  the  breaker  end  of  the  magneto 
instead  of  in  the  arch  of  the  magnets,  as  in  the  usual  armature  wound  type 
magneto.  It  consists  of  a  gap  of  about  JKe  *n-  between  the  collector  ring 
and  the  point  of  a  screw  placed  in  the  armature  housing,  immediately 
behind  the  breaker.  Its  purpose  is  to  provide  a  by-pass  for  the  high- 
tension  current  in  case  a  spark-plug  cable  should  become  disconnected  or 
broken,  thereby  protecting  the  winding  and  other  high-tension  insulation 
against  possible  injury. 

181.  The  Eisemann  High-tension  Dual  Magneto,  Type  GR4. — The 
Eisemann  high-tension  dual  magneto,  known  as  type  GR4,  II  Edition, 
is  shown  in  Figs.  275  and  276.  It  is 
used  in  conjunction  with  a  battery 
(either  dry  cells  or  storage  battery) 
and  either  the  DC  or  the  DCR  type 
coil  shown  in  Fig.  277. 

The  primary  purpose  of  this  sys- 
tem is  to  give  two  sources  of  ignition 
(magneto  and  battery)  using  one  dis- 
tributor and  one  set  of  spark  plugs. 
The  arrangement  consists  essentially 
of  a  direct  high-tension  magneto, 
used  in  conjunction  with  a  combined 
transformer  coil  and  switch  which 
can  be  mounted  on  the  dash.  This 
transformer  coil  is  used  only  in  connection  with  the  battery,  whereas  the 
switch  is  used  in  common  with  both  the  battery  and  the  magneto. 

The  magneto,  as  may  be  seen  from  Fig.  276,  is  practically  the  same  as 
the  type  G4  independent  magneto  with  two  exceptions,  the  timing  arm 
is  equipped  with  an  extra  separate  contact  breaker  for  the  battery  current, 
and  the  distributor  is  modified  to  permit  of  its  electrical  separation  from 
the  magneto  armature,  when  distributing  the  battery  high-tension 

This  magneto  may  be  used  with  equally  good  results  with  either  of  the 
Eisemann  dash  coils,  type  DC  or  type  DCR,  Fig.  277.  The  coils 
differ  only  in  the  arrangement  for  starting  on  the  spark,  the  DC  having 
a  push-button  giving  a  single  spark,  provided  the  engine  happens  to 
stand  with  the  battery  breaker  open;  whereas  the  DCR  has  a  mechan- 

Fio.      275. — Eisemann     high-tension 
dual  magneto,   Type  GR4 — II   Edition. 


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Fio.  276. — Principal  parts  of    Eisemann   high-tension   dual  magneto,    Type    GR4 — II 


Type  "  D.C.R."  coil.  Type  "  D.C."  coil." 

Fia.  277. — Dash  coil  and  switch  units  for  Eisemann  high-tension  dual  magneto,  Type 


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ical  ratchet  device,  delivering  a  shower  of  sparks  regardless  of  the  crank 
position  of  the  engine. 

A  rapid  back  and  forth  motion  of  the  starting  handle  on  the  front  of 
the  DCR  coil  causes  the  toothed  ratchet  in  the  center  to  oscillate  the 
lever  B,  Fig.  278,  which,  in  turn,  makes  contact  alternately  at  C  and 
D.  If  the  switch  is  on  battery  position  and  the  battery  breaker 
points  in  the  magneto  are  closed,  as  they  normally  are,  a  rapid  sequence 
of  sparks  will  occur  at  the  plugs.  This  shower  of  sparks  is  much  more 
effective  for  starting  on  compression  than  a  single  spark. 

A  circuit  diagram  of  the  system,  including  the  coil  connections  for  the 
different  switch  positions,  is  shown  in  Fig.  279.  As  may  be  seen,  the 
battery  breaker  operates  in  much 
the  same  manner  as  the  corre- 
sponding part  on  the  magneto.  It 
is  actuated  mechanically  by  two 
polished  steel  cams  attached  to 
the  magneto  breaker,  but  is  en- 
tirely separate,  electrically,  from 
it.  Like  the  magneto  breaker,  the 
battery  breaker  causes  the  spark 
to  occur  at  the  instant  of  separa- 
tion of  the  contact  points.  For 
practical  reasons,  this  interruption 
is  timed  to  take  place  10  degrees 
later  than  the  magneto,  but  is, 
naturally,  subject  to  the  same  de- 
gree of  advance  and  retard,  being 
mounted  in  the  same  timing  lever 
body.  Both  breakers  are  pro- 
tected by  the  same  waterproof  cap,  and  are  easily  exposed  to  view. 

Both  sets  of  contact  points  should  be  adjusted  to  open  from  .012  in. 
to  .014  in.  The  distributor  is  the  same  as  the  G4  except  that  there  is 
no  connection  between  the  lower  carbon  (collector)  brush  and  the  center 
one.  Cables  lead  from  each  of  these  brushes  to  the  switch  portion  of 
the  coil,  enabling  the  center  brush  to  be  connected  to  the  lower  one  when 
running  on  the  magneto,  or  to  the  coil  when  running  on  the  battery. 

If  for  any  reason  it  is  desired  to  operate  the  magneto  without  the 
coil  and  switch  unit,  it  may  be  operated  as  an  independent  high-tension 
magneto,  the  same  as  the  type  G4,  by  connecting  the  cables  marked 
H  and  KM  on  the  distributor  head,  thus  making  a  direct  path  for  the 
high-tension  current  from  the  collector  ring  to  the  distributor. 

182.  Timing  of  the  Eisemann  Magneto  to  the  Engine  for  Variable 
Spark. — As  the  spark  occurs  when  the  primary  circuit  is  broken  by  the 

Fio.  278.— Type  "DCR"  coil  with  front 
plate  removed  showing  mechanism  for  start- 
ing on  the  spark. 

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opening  of  the  platinum  contacts  on  the  breaker  mechanism,  it  is  neces- 
sary that  the  magneto  be  so  timed  that  at  full  retard  position  of  the  timing 
lever  body  the  platinum  contacts  just  begin  to  open  when  the  respective 
piston  of  the  engine  has  reached  its  highest  point  on  the  compression 
stroke.  The  engine  should  be  turned  by  hand  until  piston  of  No.  1 
cylinder  is  on  dead  center  (firing  point).  The  distributor  plate  should 
then  be  removed  from  the  magneto  and  the  driving  shaft  turned  until 
the  setting  mark  on  the  distributor  disc  is  in  line  with  the  setting  screw 
as  shown  in  Figs.  268,  270,  and  276.  (For  a  magneto  rotating  clockwise, 
setting  mark  R  is  used,  and  for  anti-clockwise  setting  mark  L  is 
used.)  With  the  armature  in  this  position  and  the  timing  lever  body 
fully  retarded,  the  platinum  contacts  of  the  magneto  breaker  are  just 
opening,  and  the  metal  insert  of  the  distri- 
butor disc  is  in  connection  with  the  car- 
bon distributor  brush  for  No.  1  cylinder. 
The  driving  medium  must  now  be  fixed 
to  the  armature  shaft  without  disturbing 
the  position  of  the  latter,  and  the  cables 
connected  to  the  plugs  in  their  proper 
order  of  firing. 

It  has  been  found  advisable  in  prac- 
tice to  time  the  battery  spark  slightly 
later  than  that  of  the  magneto  itself. 
For  this  reason  the  battery  breaker  on 
the  Eisemann  dual  type  magneto  is  per- 
manently arranged  to  open  10°  later  than  Fio.  280.— The    Dixie    high-tension 

the  magneto  breaker,  although  subject  to  magneto,  Model  46. 

the  same  degree  of  advance  and  retard. 

183.  The  Dixie  Magneto. — The  Dixie  high-tension  magneto,  Fig.  280, 
differs  widely  from  the  usual  armature  wound  type  in  that  the  winding 
does  not  rotate.  In  this  respect  it  is  virtually  an  inductor  type  magneto, 
operating  on  what  is  known  as  the  "  Mason  Principle."  The  construction 
and  general  arrangement  of  the  various  parts  are  shown  in  Fig.  281, 
which  is  a  front  view  with  the  distributor  block  and  breaker  cover  re- 
moved ;  and  in  Fig.  282  which  is  a  side  view  with  the  cover  and  one  magnet 
withdrawn.    The  magnets  and  rotating  element  are  shown- in  Fig.  283. 

It  will  be  noted  that  the  magneto  consists  principally  of  a  pair  of 
magnets,  a  rotor,  a  field  structure,  a  winding,  an  interrupter,  and  a  con- 
denser. The  rotor,  Fig.  284,  consists  of  two  revolving  wings,  N  and 
S9  separated  by  a  bronze  center  piece,  B.  The  ends  of  the  wings  are 
brought  into  contact  with  the  poles  of  the  magnets  as  shown  in  Fig. 
283,  and,  therefore,  bear  the  same  polarity  of  magnetism  as  the  poles  of 
the  magnets  with  which  they  are  in  contact.    This  polarity  of  the  wings 

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is  always  the  same,  as  there  is  no  reversal  of  magnetism  through  them. 
The  rotor  is  surrounded  by  a  field  structure  which  carries  laminated  pole 
extensions,  on  which  the  winding  with  its  laminated  core  is  mounted. 
The  grinding  contains  both  primary  and  secondary  windings.  As  the 
rotor  revolves,  it  causes  the  magnetic  flux  to  flow  back  and  forth  through 
the  core  of  the  winding,  first  in  one  direction  and  then  in  the  other, 
according  to  the  position  of  the  rotor  in  relation  to  the  poles  of  the  field 
structure  as  shown  in  Figs.  285,  286,  287,  and  288.     Figure  286  shows  the 

9.  Ground  spring. 

10.  Thumb  nut  for  ground  stud. 

11.  Lock  washer  for  ground  stud  nut. 

12.  Washer  for  ground  stud. 

13.  Cam. 

14.  Distributor  block. 

15.  Thumb  nut  for  distributor  block. 

16.  Breaker  base. 

17.  Breaker  bar  spring. 

Front  view  of  Dixie  magneto  with  distributor  head  and  breaker  dover 

1.  Distributor  gear. 

2.  Distributor  disc. 

3.  Finger  spring  for  breaker  bar. 

4.  Cam  screw. 

5.  Breaker  bar  with  platinum  point. 

6.  Contact  screw  bracket   with  insu- 
lating bushings. 

7.  Platinum  contact  screw. 

8.  Breaker  cover. 

Fig.  281 

rotor  in  such  a  position  that  the  flux  flows  from  wing  N  through 
the  core  C  and  back  to  wing  S  of  the  rotor.  Figure  288  shows  the 
flux  flowing  in  the  reverse  direction. 

The  greatest  intensity  in  the  primary  circuit  occurs  when  the  rate  of 
change  of  the  flux  or  magnetic  lines  of  force  through  the  core  is  a  maxi- 
mum. This  occurs  when  the  rotor  is  in  the  position  shown  in  Fig.  287, 
where  the  rotor  wings  have  just  reversed  the  direction  of  flux  through 
the  core,  the  gap  between  the  trailing  wing  corner  and  pole  piece  being 
from  .015  in.  to  .035  in.,  preferably  .020  in.     Consequently,  the  inter- 

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rupter  contact  points  should  be  adj  usted  to  break  the  primary  circuit  when 
the  rotor  is  in  this  position.  A  circuit  diagram  of  the  magneto  is  shown 
in  Fig.  289  from  which  it  will  be  seen  that  the  primary  circuit  is  of  the 
interrupted  primary  current  type.  The  breaking  of  the  primary  circuit 
induces  a  high-voltage  current  in  the  secondary  winding,  this  current 

1.  Condenser. 

2.  Magnet. 

3.  Gap  protector. 

4.  Oil  hole  cover,  front. 

5.  Stud  for  distributor  block. 

6.  Clamp  for  distributor  block. 

7.  Thumb  nut  for  distributor  block. 

8.  Hexagonal  nut  for  grounding  stud. 

9.  Thumb  nut  for  grounding  stud. 

10.  Grounding  stud. 

11.  8ereir  and  washer  for  fastening  breaker. 

12.  Screw  and  washer  for  fastening  condenser  and 

primary  lead  to  winding. 

13.  Screw  and  washer  for  fastening  primary  lead 

tube  clamp. 

14.  Primary  lead  tube. 

15.  Primary  lead  tube  clamp. 

16.  Screw  and  washer  for  fastening  grounded  clip 

to  pole  structure. 

17.  Rotor  shaft. 

18.  Drive  key. 

19.  Back  plate. 

20.  Oil  hole  cover,  back. 

21.  Grounding  clip. 

22.  Screw  and  washer  for  fastening  grounding  clip 

to  winding. 

23.  Winding. 

24.  Screw  and  washer  for  fastening   winding  to 

pole  structure. 

Fio.  282. — Side  view  of  Dixie  magneto  with  cover  and  one  magnet  removed. 

being  directed  to  the  proper  plug  by  a  distributor  driven  by  a  gear  on  the 
rotor  shaft.  The  condenser,  one  terminal  of  which  is  connected  to  the 
insulated  end  of  the  primary  coil  and  the  other  grounded  to  the  magneto 
frame,  is  mounted  on  the  top  of  the  coil. 

One  of  the  outstanding  features  of  the  Dixie  magneto  is  the  shifting 
of  the  pole  pieces  with  the  timing  lever,  upon  advancing  and  retarding 

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Fio.  283. — Rotor  and  magneto  for 
Dixie  magneto. 

the  spark.  This  permits  the  breaker  to  interrupt  the  primary  circuit  at 
all  times  when  the  primary  current  is  flowing  at  its  maximum,  thus 
causing  a  spark  of  maximum  intensity  at  all  positions  of  the  breaker. 

Since  the  coil  windings  are  not  on  a  revolving  armature,  the  interrupter 
is  built  like  that  for  a  low-tension  magneto,  that  is,  the  interrupter 
mechanism  is  mounted  on  the  interrupter  housing  and  the  cam  is  revolved 
with  the  rotor  shaft.    This  construction  permits  the  adjusting  of  the 

contact  points  with  the  engine  and 
magneto  running.  The  contacts  are 
made  of  platinum  and  should  be  ad- 
justed to  open  .020  in.  This  adjust- 
ment can  be  made  with  a  screwdriver 
by  turning  the  stationary  contact 

Magneto  Switch. — Extending 
through  the  magneto  breaker  cover 
is  an  insulated  terminal  which  is  con- 
nected to  the  insulated  end  of  the 
magneto  primary  winding.  This  ter- 
minal is  also  connected  to  a  grounding 
switch  by  which  the  primary  winding 
can  be  grounded  or  short-circuited,  and  ignition  prevented.  The  Dixie 
magneto  switch  is  shown  in  Fig.  290.  The  wire  leading  from  the  mag- 
neto must  be  attached  to  one  of  the  terminals  on  the  back  of  the  switch 
and  the  other  terminal  grounded.  The  ignition  is  locked  when  the  switch 
lever  is  in  the  "off  "  position.  When  in  this  position  the  switch  lever  can 
be  taken  out,  preventing  the  operation  of  the  magneto. 

Timing. — The  method  of  tim- 
ing the  Dixie  magneto  with  the 
engine  is  similar  to  the  timing 
of  other  types  of  high-tension 
magnetos.  The  crank  of  the  en- 
gine should  be  turned  until  one 
of  the  pistons,  preferably  that  of 
cylinder  No.  1,  is  on  upper  dead-center  position  at  the  end  of  the  com- 
pression stroke.  With  the  timing  lever  in  full  retard  position,  the 
driving  shaft  of  the  magneto  should  be  rotated  in  the  direction  in  which 
it  will  be  driven.  The  circuit  breaker  should  be  closely  observed,  and, 
when  the  platinum  contact  points  are  about  to  separate,  the  drive  gear 
or  coupling  should  be  secured  to  the  drive  shaft  of  the  magneto.  Care 
should  be  taken  that  the  position  of  the  magneto  shaft  is  not  altered  when 
the  nut  is  tightened  to  secure  the  gear  or  coupling.  After  this  is  done, 
the  magneto  should  be  secured  to  its  base.     The  distributor  block  should 





Fig.  284. — Rotating  element  in  Dixie 

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then  be  removed  to  determine  which  terminal  of  the  block  is  in  contact 
-with  the  bronze  sector  of  the  distributor  disc.  The  terminal  found  in 
contact  should  be  wired  to  the  cable  leading  to  No.  1  cylinder,  and  the 





Fig.  285.  Fig.  286.  Fig.  287.  Fio.  288. 

Figs.  285  to  288. — Showing  the  principle  of  the  Dixie  magneto. 

remaining  cables  to  the  remaining  cylinders  in  accordance  to  their 
sequence  of  firing,  remembering  that  the  distributor  runs  the  opposite 
direction  from  the  rotor  of  the  magneto. 



A    1 













Fig.  289. — Circuit  diagram  of  Dixie  high-tension  magneto,  Model  46. 

184.  General  Instruction  for  High-tension  Magneto  Care  and  Main- 
tenance.— To  insure  proper  working  of  the  magneto,  periodic  inspection 
and  attention  are  very  essential. 

Oiling. — A  few  drops  of  light,  clean,  high-grade  oil  should  be  injected 

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into  every  oil  hole  each  1000  miles  of  travel.    Too  much  oil  should  not 
be  used. 

Distributor  Block. — The  distributor  block  should  be  removed  every 
2000  miles  and-  cloaned  so  as  to  remove  any  carbon  deposit  caused  by 
the  wearing  of  the  brushes.  This  may  be  done  with  a  soft  cloth  moistened 
with  gasoline.  The  gasoline  should  be  allowed  to  dry  up  thoroughly 
before  the  engine  is  started.  The  same  attention  should  be  given  the 
high-tension  slip  ring  on  the  armature.  The  distributor  and  slip  ring 
brushes  should  be  inspected  to  make  sure  that  they  are  not  stuck  in 
their  holders  and  that  the  springs  have  the  proper  tension. 

Interrupter. — The  contact  points  of  the  interrupter  should  be  exam- 
ined every  1000  to  1500  miles  to  see  that  they  are  clean  and  have  the 
right  point  opening.    If  they  are  dirty  or  badly  pitted  and  uneven  they 

should  be  cleaned  by  passing  a  thin  fine  file  or 
a  piece  of  No.  00  sandpaper  between  them. 
The  contacts  must  not  be  filed  unless  absolutely 
necessary.  The  contacts  should  make  square 
contact  across  their  entire  contact  surface. 

The  contact  points  have  a  standard  open- 
ing of  .012  to  .020  in.  Usually  an  adjust- 
ing wrench,  which  has  a  gauge  to  measure 
the  proper  point  opening,  is  furnished  with 
the  magneto. 

A  slight  trace  of  clean  oil  or  grease  put  on 
the  fiber  block  of  the  interrupter  lever,  or  on 
the  steel  cam,  every  1000  to  1500  miles,  will 
prevent  the  cam  from  rusting.  The  contact 
points  must  never  be  oiled. 

Wiring. — The  wiring  should  be  examined 
carefully  at  least  once  each  year.  If  cables  are  cracked  or  worn,  they 
should  be  replaced.     All  connections  must  be  kept  clean  and  tight. 

Spark  Plugs. — Failure  of  ignition  is  usually  due  to  dirty  spark  plugs. 
When  the  engine  does  not  fire  regularly,  the  plugs  should  be  examined, 
and  if  found  to  be  sooted  they  should  be  cleaned  by  scraping  off  the 
carbon  and  washing  them  in  gasoline.  The  opening  of  the  plug  gap 
should  measure  .025  to  .030  in.  After  the  plugs  have  been  replaced 
in  the  cylinders,  they  should  be  examined  to  make  sure  that  none  of  the 
porcelains  have  cracked. 

Testing  the  Magneto. — If  the  engine  fires  irregularly,  indicating  poor 
ignition,  the  magneto  may  be  tested  by  resting  a  screwdriver  on  the 
magneto  housing  and  holding  it  about  %  to  %  in.  from  the  high-tension 
collector  ring  or  collector  ring  brush  terminal.  If  upon  rotating  the 
armature,  a  spark  jumps  across  the  gap,  it  shows  that  the  trouble  does 

^^^^"n  t^  ■»■  l^^B 






Mb      h3 


Fig.  290. — Dixie  magneto 

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not  lie  in  the  magneto,  but  in  some  other  part  of  the  engine,  possibly 
the  carburetor  or  gasoline  system. 

Magnets. — A  remagnetization  of  the  magnets  will  be.  necessary  only 
when  they  have  been  taken  away  from  the  magneto  and* allowed  to  remain 
a  long  time  without  the  ends  being  connected  with  a  piece  of  soft  iron 
known  as  a  keeper.  Demagnetization  of  the  magnets  will  also  occur  if  the 
armature  is  taken  out  from  between  the  pole  pieces  without  a  conducting 
bar  of  iron  being  first  laid  across  both  poles.  This  conducting  bar 
should  be  placed  on  the  poles  before  the  armature  is  entirely  removed 
and  should  remain  until  the  armature  is  again  placed  between  the  pole 
pieces.  The  magnets,  after  being  taken  down,  are  often  put  back  in  the 
wrong  position  and  in  this  way  the  magnetic  power  is  neutralized.  To 
prevent  this  mistake  the  magnets  are  usually  marked,  the  North  pole 
being  designated  by  the  letter  N  stamped  in  the  magnet.  When  replac- 
ing magnets,  care  should  be  taken  to  place  the  like  poles  on  the  same 

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186.  Function  of  the  Battery. — The  storage  battery  on  the  automobile 
may  be  considered  the  heart  of  the  entire  electrical  system.  Its  function 
may  be  compared  to  that  of  the  storage  tank  or  reservoir  in  the  typical 
waterworks  system  of  the  modern  small  town.  The  reservoir  corresponds 
to  the  storage  battery,  the  pump  to  the  generator,  and  the  water  mains 
to  the  wiring  of  the  car.  When  the  generator  produces  more  current 
than  is  consumed  by  the  ignition,  lamps,  or  other  electrical  accessories, 
the  surplus  current  passes  through  the  battery,  causing  it  to  take  on  an 
electrical  charge,  that  is,  to  store  up  energy  as  ordinarily  understood. 
When  the  engine  is  at  a  standstill  and  the  generator  is  not  running,  or  if 
the  engine  is  not  driving  the  generator 
fast  enough  to  produce  the  required 
amount  of  current,  the  battery  supply 
may  be  drawn  upon  for  cranking  the 
engine,  operating  the  lights,  supplying 
ignition,  operating  the  horn,  or  perform- 
ing any  other  service  for  which  the 
electrical  system  may  be  designed. 

The  cause  of  most  battery  troubles 
is  due  to  improper  care  of  the  battery 
and  misuse  of  the  electrical  equipment 
on  the  part  of  the  user,  chiefly  because 
he  does  not  understand  the  principles 
involved.  It  is,  therefore,  the  purpose  of 
this  chapter  to  remove,  as  far  as  possible,  the  mystery  surrounding  the 
storage  battery  and  to  explain  its  construction,  operation,  care,  and 
troubles  in  as  clear  and  concise  a  manner  as  possible. 

186.  Construction. — The  storage  battery,  Fig.  291,  as  used  for 
starting,  lighting,  and  ignition  purposes  consists  of  three  or  more  cells, 
depending  upon  the  voltage  desired.  Each  cell  has  an  electric  pressure 
of  about  two  volts.  A  battery  of  three  cells  connected  in  series  is  known 
as  a  6-t>oft  battery  and  one  of  six  cells  in  series  is  known  as  a  12-twft 
battery.  Each  cell  consists  of  a  hard  rubber  jar  in  which  is  placed  two 
kinds  of  lead  plates  known  as  positive  and  negative.  These  plates  are 
insulated  from  each  other  by  suitable  separators  and  are  submerged  in  a 


Fio.   291. — 6-volt  automobile 
storage  battery. 

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solution  of  sulphuric  acid  and  water.    Typical  cell  construction  is  shown 
in  Figs.  292  and  151. 

187.  The  Plates. — The  grid,  or  framework  of  the  plate,  is  cast  from 
an  alloy  of  lead  and  antimony  and  is  similar  in  appearance  to  a  coarse 
wire  netting  or  filigree  work  as  shown  in  Fig.  293.  '  The  open  spaces 

Fig.  292. — Construction  and  internal  arrangement  of  typical  storage  battery  cell. 

are  pressed  full  of  a  putty-like  paste  or  compound  known  as  active  mate- 
rial consisting  chiefly  of  oxides  of  lead.  When  dry,  this  active  material 
becomes  hard  like  cement.  The  plates  are  then  put  through  an  electro- 
chemical process  which  converts  the  active  material  of  the  positive  plates 
into  brown  peroxide  of  lead,  Fig.  294,  and  that  of  the  negative  plates 

into  a  grey  spongy  metallic  lead  as 
in  Fig.  295.  This  process  is  known 
as  forming  the  plates. 

188.  Positive  and  Negative 
Groups. — Af ter  the  positive  and  nega- 
tive plates  have  been  formed,  they 
are  built  into  positive  or  negative 
groups  as  in  Fig.  296.  The  positive 
group  consists  of  one  or  more  positive 
plates  burned  to  a  connecting  strap, 
and  the  negative  group  of  two  or 
more  negative  plates  connected  to  a 
similar  connecting  strap.  To  each 
strap  is  attached  a  post  which  is  used  to  make  electrical  connection 
between  two  adjoining  groups  or  to  the  starting  and  lighting  system. 

189.  Elements. — An  element,  as  shown  in  Fig.  297,  consists  of  a  posi- 
tive and  a  negative  group,  together  with  the  separators.  The  negative 
group  always  has  one  more  plate  than  the  positive  group  as  shown  in 
Fig.  298.     For  example,  a  three-plate  element  would  have  one  positive 








Fio.  293. — Types  of  battery  plate  grids. 

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and  two  negative  plates  and  a  five-plate  element  would  have  two 
positive  and  three  negative  plates.  This  is  true  regardless  of  the 
number  of  plates  in  the  element. 

The  plates  are  burned  to  the  connecting  straps,  usually  by  a  hydrogen 
or  oxy-acetylene  flame,  so  that  the  plates  and  strap  form  one  unit.    The 

Fio.  294. — Positive  plate. 

Fio.  295. — Negative  plate. 

plates  are  so  arranged  that  when  the  element  is  assembled,  each  positive 
plate  surface  is  adjacent  to  a  negative  plate  surface,  the  distance  between 
these  surfaces  being  from  %  2  to  %  in.  The  positive  and  negative  sur- 
faces are  kept  apart  by  insulators  known  as  separators. 

190.  Separators. — The  separators  play  a  very  important  part  in  the 
life  and  operation  of  the  battery,  since  they  insulate  the  positive  and 

Fio.  296.— Battery  group. 

Fio.  297.— Battery  element. 

negative  plates  from  each  other  and  prevent  short  circuits  between  them. 
If  the  separators  become  cracked,  or  damaged  in  any  other  way,  per- 
mitting electrical  contact  between  the  plates,  the  battery  will  discharge 
and  may  ultimately  become  useless.  Two  principal  kinds  of  separators 
are  used,  namely,  wood  and  threaded  rubber. 

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The  wood  separator,  Fig.  299,  is  made  of  specially  selected  wood, 
usually  basswood  or  cypress,  and  is  chemically  treated  to  remove  the 
acetic  acid  and  other  impurities  which  are  always  in  the  wood  and  which 
are  harmful  to  the  battery.  This  chemical  treatment  also  makes  the 
wood  porous,  and  thus  allows  ready  diffusion  of  the  electrolyte  through 

Fig.  298. — Positive  and  negative  group. 

the  separator  pores  upon  the  charging  and  discharging  of  the  battery. 
The  separators  are  grooved  on  one  side.  When  the  separators  are  in- 
stalled, this  grooved  side  should  be  placed  next  to  the  positive  plate 
with  the  grooves  running  vertical  as  in  Fig.  300.  The  purpose  of  these 
grooves  is  to  permit  the  gas  which  accumulates  around  the  positive  plate, 
which  is  the  most  active  plate,  to  escape 
freely  to  the  surface.  The  grooves 
also  provide  a  passageway  for  any 
active  material,  which  may  free  itself 
from  the  plate,  to  fall  to  the  sediment 
space  below. 




Fio.  299. — Wood  separator. 


300. — Inserting  separators  in  battery 

The  threaded  rubber  separator,  Fig.  301,  is  manufactured  by  the 
Willard  Storage  Battery  Company  and  is  used  exclusively  on  the  Willard 
battery.  From  Fig.  302,  which  shows  a  magnified  view  of  this  separator, 
it  will  be  seen  that  the  threads  run  through  the  separator  at  right  angles 
to  the  surface.     According  to  the  manufacturers,  there  are  196,000  of 

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these  threads  per  square  inch.    The  theory  is  that  each  thread  acts 
as  a  wick  between  the  positive  and  negative  plates.    The  separator  is 

Fro.  301. — Willard  threaded  rubber  separator. 

1  ***!<++  m  ******  + 

*  «r   v    *    « 

fC  «fc  «<*»  <<?»  ^  *lt    ,»    . 

Fio.  302. — Microscopic  section  of  Willard  threaded  rubber  separator. 

thus  rendered  porous  due  to  the  capillary  attraction  of  the  threads. 
Another  feature  of  this  separator  is  that  it  does  not  carbonize  and  crack 


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upon  drying  out  as  does  the  wood.  On  this  account  the  life  of  the  sepa- 
rator and  battery  is  greatly  increased.  The  threaded  rubber  separator 
has  corrugations  which  correspond  to  the  grooves  of  the  wood  separator 
and  should  be  installed  in  a  similar  manner  with  the  corrugations  running 

191.  The  Electrolyte. — The  electrolyte,  as  used  in  all  types  of  auto- 
mobile lead  storage  batteries,  consists  of  a  mixture  of  chemically  pure 

sulphuric  acid  (H2S04)  and  distilled  water, 
the  proportion  being  about  1  part  of  acid 
to  3  parts  of  water  by  volume.  The  pro- 
portion of  water  and  acid  is  such  that  the 
density  of  the  solution  will  have  a  specific 
gravity  of  1.300  at  70°F. 

Specific  Gravity. — By  specific  gravity 
is  meant  the  relative  weight  of  any  sub- 
stance compared  with  the  weight  of  an 
equal  volume  of  pure  water.    Pure  water 

has  a  specific  gravity  of  1,  usually  written  1.000  and  spoken  of  as  (en 

hundred.    One  pound  of  water  has  a  volume  of  approximately  one  pint. 

An  equal  volume  of  chemically  pure  sulphuric  acid  weighs  1.835  lbs. 

It,  therefore,  has  a  specific  gravity  of  1.835  and  is  spoken  of  as  eighteen 


192.  Jars  and  Covers. — The  jars  forming  the  cells,  Fig.  303  and  Fig. 
304,  are  made  of  hard  rubber,  designed  to  resist  both  the  action  of  the 

Fio.  303.— Rubber  jars. 




Fio.  304. — Cut  away  section  of  storage  cell  showing  sediment  space  below  the  plates. 

electrolyte  and  mechanical  strains.  Bridged  supports,  Fig.  304,  are 
molded  in  the  bottom  of  each  cell  to  hold  the  plates  and  separators  off 
the  bottom  thus  forming  a  sediment  chamber  for  catching  the  accumu- 
lation of  any  active  material  which  may  free  itself  from  the  plates. 

The  cover,  Fig.  305,  is  of  hard  rubber  with  an  opening  in  the  center 
for  the  vent  cap  and  an  opening  on  each  side  for  the  connecting  posts  of 

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the  positive  and  negative  groups,  which  are  known  as  terminals.    The 
cover  also  provides  an  expansion  chamber  for  the  electrolyte. 

193.  Cell  Arrangement. — A  complete  cell  consists  of  tl^e  rubber  jar, 
the  element  in  the  jar  resting  on  the  bridges,  the  electrolyte  covering 
the  element,  and  the  cover  which  is  carefully 
sealed  to  the  jar  with  sealing  compound. 

The  complete  battery  consists  of  the 
desired  number  of  cells  assembled  in  a 
wooden  case,  the  cells  being  connected  in 
accordance  with  the  requirements  of  the 
starting  and  lighting  system  with  which 
the  battery  is  to  be  used, 
trated  in  Fig.  306. 

194L  Battery  Box. — The  battery  box  is  made  of  hard  wood  thoroughly 
coated  with  an  acid-proof  paint.  The  cells  are  usually  sealed  in  place 
by  pouring  a  sealing  pitch-compound  over  the  entire  top.     This  prevents 

Fio.  305. — Cover  for  battery  cell. 

Some  of  these  various  connections  are  illus- 

Fig.  306. — Typical  cell  arrangements  for  starting  and  lighting  batteries. 

any  vibration  of  the  jars  and  renders  the  tops  of  the  cells  dirt  and  leak 
proof.  In  some  cases,  where  specially  designed  covers  are  used,  only  the 
individual  cell  tops  are  sealed.  This  adds  greatly  to  the  ease  with  which 
the  battery  can  be  taken  apart. 

It  is  absolutely  essential  that  the  battery  be  securely  held  in  position 

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on  the  car.  For  this  purpose,  brackets  which  fit  on  the  battery  case 
are  often  used.  The  battery  is  usually  made  fast  to  the  car  by  means 
of  bolts  engaging  the  hold-down  clips. 

195.  Markings  of  the  Battery. — For  convenience  in  connecting  up 
the  battery,  the  terminals  are  ordinarily  marked  either  with  Pos  (+), 
(plus  sign)  or  a  red  fiber  sleeve  on  the  positive  post  and  with  Neg  or 
( — )  (negative  sign)  on  the  negative  post.  This  marking  is  in  accordance 
with  the  way  the  battery  discharges,  the  current  leaving  the  positive 
terminal  ahd  returning  to  the  negative. 

It  is  also  customary  among  battery  manufacturers  to  make  the  posi- 
tive cable  connection  larger  than  the  negative.  If  the  terminals  are  not 
marked,  the  polarity  can  be  readily  determined  by  attaching  a  wire  lead 
to  each  terminal  and  inserting  the  two  free  ends  in  a  glass  of  salt  water  or 
battery  electrolyte,  whereupon  gas  bubbles  (hydrogen)  will  be  noticed 
to  form  around  the  negative  lead,  as  in  Fig.  307. 


Gas  Dufi5LC3  Around 
NeoATivL  Terminal 

Salt  Water  or 
Cattcry  Electrolyte 

Fio.  307. — Method  of  determining  polarity  of  storage  battery  terminals. 

196,  Voltage  of  the  Battery. — Each  cell,  after  being  properly  charged, 
gives  approximately  two  volts  with  a  current  capacity  corresponding  to 
the  size  of  the  plates  and  the  total  number  of  square  inches  of  free  active 
material  in  them.  Consequently,  when  several  cells  are  connected  in 
series,  that  is,  the  terminals  connected  positive  to  negative,  the  same 
as  in  connecting  dry  cells  for  ignition,  the  total  voltage  across  the  battery 
terminals  will  be  the  added  voltage  of  all  the  cells,  while  the  current 
capacity  will  be  the  same  as  the  current  from  one  cell.  For  example, 
across  a  3-cell  battery,  the  voltage  is  6  volts  and  across  a  6-cell  battery  the 
voltage  is  12  volts.  It  will  be  found  later  that  the  voltage  varies 
slightly  with  the  condition  of  charge  and  the  temperature. 

197.  Battery  Capacity. — The  capacity  of  a  battery  is  measured  in 
ampere-hours.  This  is  determined  by  multiplying  the  number  of  amperes 
by  the  number  of  hours  during  which  the  battery  is  capable  of  discharg- 
ing at  a  given  rate.  For  example,  a  battery  that  will  deliver  10  amperes 
for  10  hours  is  said  to  have  a  capacity  of  100  ampere-hours  at  the  10- 
ampere  discharge  rate.  However,  one  of  the  inherent  characteristics 
of  a  storage  battery  is  that  its  ampere-hour  capacity  is  dependent  upon 
the  rate  of  discharge.    The  lower  the  rate  of  discharge  the  greater  the 

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ampere-hour  capacity  will  be.  The  same  battery  that  has  a  capacity 
of  100  ampere-hours  at  the  10-ampere  discharge  rate  will  have  a  capacity 
in  excess  of  100  ampere-hours  at  a  5-ampere  rate,  that  is,  it  will  deliver 
5  amperes  for  more  than  20  hours.  On  the  other  hand,  the  battery  would 
not  discharge  100  amperes  for  1  hour  since  the  efficiency  of  the  battery 
drops  when  discharging  at  a  rate  higher  than  that  specified  by  the  manu- 
facturer.   This  rating  is  usually  found  on  the  name  plate  of  the  battery. 

198.  Principle  of  Operation. — When  the  cell  is  fully  charged  the 
electrolyte  has  a  density,  or  specific  gravity,  of  1.275  to  1.300;  the  active 
material  on  the  positive  plates  being  peroxide  of  lead  and  on  the  negative 
plates  pure  spongy  metallic  lead.  The  pressure  between  the  positive  and 
negative  groups  is  about  two  volts,  and  if  these  groups  are  connected  to- 
gether through  an  electric  conductor,  such  as  an  electric  lamp  or  a  motor, 
current  will  flow  between  them,  discharging  the  cell.  During  the  dis- 
charge a  chemical  action  takes  place  which  converts  both  the  lead  per- 
oxide on  the  positive  plates  and  the  pure  spongy  metallic  lead  on  the 
negative  plates  to  sulphate  of  lead.  This  chemical  change  removes  sul- 
phur from  the  acid,  thereby  lowering  the  specific  gravity  or  density  of  the 
solution.  When  the  cell  is  considered  completely  discharged  its  density 
is  1.160  or  below,  and  its  voltage  about  1.8  volts  or  loss. 

When  current  is  sent  through  the  cell  in  an  opposite,  or  charging, 
direction  a  chemical  action  occurs,  precisely  the  reverse  of  that  on  dis- 
charge. The  action  of  the  charging  current  removes  the  sulphur  from 
the  plates,  changing  the  lead  sulphate  on  the  positive  plates  back  to  lead 
peroxide,  and  that  on  the  negative  plates  to  pure  spongy  metallic  lead. 
Inasmuch  as  the  sulphur  returns  to  the  solution,  this  solution  becomes 
more  dense,  and  when  the  cell  is  fully  charged  the  solution  reaches  its 
original  density  of  1.275  to  1.300. 

199.  Effect  of  Overcharging. — As  above  stated,  the  charging  current 
changes  the  plates  back  to  their  original  chemical  formation.  When  the 
element  is  completely  charged,  the  charging  current  can  do  no  more  useful 
work;  consequently,  its  only  effect  is  to  convert  particles  of  water  in  the 
electrolyte  to  hydrogen  and  oxygen  gas  which  bubble  up  violently  and 
indicates  that  the  battery  is  nearing  a  full  state  of  charge. 

200.  Effect  of  Undercharging. — If  the  element  does  not  receive 
sufficient  charge,  the  sulphate  may  harden  to  such  an  extent  as  to  be 
very  difficult  to  remove  from  the  plates.  Furthermore,  if  the  battery 
is  allowed  to  remain  in  an  uncharged  condition,  a  denser  and  harder 
sulphate  which  is  even  more  difficult  to  remove  will  form  on  the  plates. 
This  hardening  of  the  sulphate  takes  place  to  some  extent  even  when 
the  battery  is  considered  fully  charged.  It  is  advisable,  therefore, 
to  charge  the  battery  immediately  after  a  discharge,  and  about  once  a 
month  when  idle,  even  though  it  be  fully  charged. 

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201.  Heat  Formed  on  Charge  and  Discharge. — When  the  element  is 
charged  or  discharged,  the  chemical  reactions  due  to  the  passage  of  the 
current  through  the  electrolyte  cause  heat  to  be  formed.  This  heat  does 
not  become  injurious  until  the  temperature  rises  to  about  105°F.,  and 
it  may  rise  to  110°F.  or  even  higher  for  a  brief  period  of  time  without 
injury  to  the  plates.  It  is  not  considered  advisable,  however,  to  charge 
a  battery  for  any  length  of  time  after  the  temperature  has  risen  to  105°F. 
The  battery  should  be  taken  off  charge  and  allowed  to  cool  or  the  charg- 
ing rate  reduced. 

202.  Evaporation  of  Water. — The  water  in  the  electrolyte  slowly 
evaporates  due  to  heat  formed  on  charge  and  discharge  and  also  due  to 

gassing  on  overcharge.  The  sulphuric 
acid,  however,  does  not  evaporate, 
and,  consequently,  the  solution  be- 
comes denser.  This  loss  of  water  due 
to  evaporation  must,  therefore,  be 
made  up  by  adding  only  pure  water. 
The  amount  of  evaporation  will  de- 
pend on  the  temperature  and  on  the 
amount  of  work  done  by  the  battery, 
and  is  a  varying  quantity;  but  a  safe 
rule  to  follow  is  to  replace  the  water, 
lost  by  evaporation,  every  week  in 
summer  and  every  two  weeks  in 
winter,  during  ordinary  use  of  the 
car.  If  the  car  is  out  of  service, 
water  should  be  added  once  every 
two  weeks  in  summer  and  once  a 
month  in  winter  before  it  is  given  a 
refreshing  charge.  During  cross-country  touring  it  is  good  practice  to 
add  distilled  water  every  200  miles  of  travel  or  once  a  day.  The  hydrom- 
eter syringe  may  be  used  for  adding  the  water.  Enough  water  should 
be  added  to  keep  the  level  of  the  electrolyte  at  all  times  up  to  the  bottom 
of  the  inside  cover,  or  %  to  J^  in.  above  the  tops  of  the  plates,  as  shown  in 
Fig.  308.  The  cells  should  never  be  filled  above  this  level.  The  electro- 
lyte expands  when  charging,  due  both  to  increase  in  temperature  and  to 
the  gas  bubbles  which  rise  from  the  plates,  therefore  space  must  be 
allowed  for  expansion.  The  battery  if  filled  too  full  will  run  over, 
resulting,  not  only  in  loss  of  electrolyte,  but  in  the  eating  away  of  the 
battery  box  and  in  the  serious  corrosion  of  the  battery  terminals  and 
connectors.  Short  circuits  may  also  result  from  the  film  of  electrolyte 
on  the  top  of  the  battery. 


308. — Section  of  storage  cell  show- 
ing proper  level  of  electrolyte. 

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203.  Necessity  of  Adding  Pure  Water. — Only  absolutely  pure  water, 
such  as  distilled  water,  should  be  used  in  filling  the  battery.  Distilled 
water  is  obtained  by  boiling  water,  catching  the  steam  that  comes  off, 
and  condensing  it  into  a  liquid.  Distilled  water  can  usually  be  obtained 
at  any  drug  store  or  garage  and  must  be  kept  in  an  acid-proof  vessel. 
A  common  way  of  storing  it  is  in  a  glass  bottle  or  jug.  Water  which  has 
merely  been  boiled  should  not  be  used.  If  distilled  water  is  hard  to 
obtain,  melted  artificial  ice,  or  filtered  rain  water  which  has  not  come 
into  contact  with  iron  pipes  or  tin  roofs,  may  be  used.  A  common  way 
of  collecting  the  latter  is  to  catch  the  rain  directly  in  an  earthenware 
jar  set  out  after  it  has  been  raining  for  about  5  or  10  minutes.  This  is 
to  insure  that  there  are  no  impurities  in  the  form  of 

gases  and  small  solid  particles  taken  into  the  water 
on  its  journey  from  the  clouds.  The  use  of  spring, 
river,  hydrant,  or  well  water  should  also  be  avoided 
as  these  are  liable  to  contain  iron  or  other  substances 
detrimental  to  the  life  of  the  battery. 

204.  Cause  of  Specific  Gravity  Change.— The 
specific  gravity  of  the  electrolyte  in  a  fully  charged 
battery  should  be  .between  1.275  and  1.300.  This 
specific  gravity  becomes  lower  as  the  battery  be- 
comes discharged.  At  the  same  time  that  the  bat- 
tery discharges  its  current,  the  acid  which  is  in  the 
electrolyte,  leaves  the  water  and  goes  into  the  plates, 
thus  lowering  the  specific  gravity  of  the  solution. 
Then,  upon  charging  the  battery,  the  acid  is  driven 
out  of  the  plates  back  into  solution  witji  the  water, 
causing  the  specific  gravity  to  rise.  The  amount 
of  specific  gravity  change  is  directly  proportional  to 
the  state  of  charge  of  the  battery,  so,  by  merely  test-  Fiq.  309.— Hydrom- 
ing  the  gravity  of  the  electrolyte,  the    exact  state        eter  syringe. 

of  charge  of  the  battery  can  at  once  be  determined. 

,  205.  The  Hydrometer. — A  convenient  way  of  testing  the  specific 
gravity  of  the  electrolyte  is  by  the  hydrometer  syringe,  as  shown  in  Fig. 
309.  This  instrument  consists  of  a  large  glass  tube  syringe  within 
which  is  a  small  elongated  glass  hydrometer  float  with  a  vertical  cylinder 
graduated  from  1.100  to  1.300.  The  rubber  bulb  at  the  top  is  used  to 
draw  the  liquid  into  the  instrument.  Normally,  the  hydrometer  rests 
on  the  bottom,  but  as  soon  as  a  liquid  with  a  specific  gravity  greater 
than  water  is  drawn  into  the  syringe,  the  hydrometer  floats  at  a  depth 
according  to  the  specific  gravity  of  the  liquid.  The  graduation  on  the 
scale  in  line  with  the  surface  of  the  electrolyte  is  the  reading  of  the  specific 
gravity  of  the  solution.     For  convenience,  its  reading  is  spoken  of  as 

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being  1160,  1200,  1280,  1300,  etc.,  instead  of  1.15,  1.2,  1.28,  and  1.3 
which  is  of  course  correct.  The  hydrometer  syringe  is  also  used  for 
adding  water  to  the  cells. 

206.  Hydrometer  Readings. — Before  taking  a  hydrometer  reading, 
the  top  of  the  battery  should  be  cleaned  off  carefully  before  removing  the 
vent  caps  or  plugs.  This  is  to  prevent  dirt  or  other  injurious  substances 
from  getting  inside  the  cell.  .The  rubber  bulb  is  squeezed  and  the  tube 
of  the  syringe  inserted  into  the  cell  until  it  rests  on  top  of  the  plates. 
The  pressure  on  the  bulb  is  now  released  until  enough  electrolyte  is 
drawn  up  into  the  tube  to  float  the  hydrometer  freely.  The  line  on  the 
hydrometer  on  a  level  with  the  surface  of  the  liquid  is  the  specific  gravity 
reading.  The  hydrometer  must  be  held  steady  so  that  neither  the  float 
nor  the  liquid  moves  while  taking  a  reading.  Care  must  be  taken  that 
the  float  does  not  cling  to  the  side  of  the  syringe.  After  the  reading  has 
been  taken  the  liquid  should  be  returned  to  the  cell  from  which  it  was 

If  there  is  not  enough  electrolyte  in  the  cell  to  permit  a  hydrometer 
reading  to  be  taken,  pure  distilled  water  must  first  be  added  until  the 
electrolyte  is  up  to  the  proper  level.  A  hydibmeter  reading  taken  directly 
after  adding  distilled  water  is  of  no  value  as  the  water  will  remain  at 
the  top  of  the  cell.  The  battery  must  then  be  charged  for  at  least  one-half 
hour,  either  by  driving  the  car  or  by  letting  the  engine  run  idle.  This 
mixes  the  water  thoroughly  with  the  electrolyte.  Hydrometer  readings 
must  be  taken  for  all  cells  as  described  above,  since  they  are  not  connected 

Specific  gravity  readings  from  1.275  to  1.300  indicate  that  the 
battery  is  fully  charged.  Specific  gravity  readings  between  1.200  and 
1.225  indicate  that  the  battery  is  more  than  half  discharged,  and  starter 
and  lamps  should  be  used  sparingly  until  the  battery  is  again  fully  charged. 
Specific  gravity  readings  between  1.150  and  1.200  indicate  that  the  battery 
is  Hearing  a  discharged  condition  and  immediate  charging  is  necessary, 
otherwise  serious  damage  will  result.  Below  1.150  the  battery  is  prac- 
tically discharged  and  an  effort  should  be  made  immediately  to  bring  it 
back  to  a  charged  condition  by  means  of  the  generator  on  the  car;  If 
this  cannot  be  done,  the  battery  must  be  removed  from  the  car  and 
charged  from  an  outside  source. 

207.  Variation  in  Cell  Readings. — If  the  specific  gravity  in  any  cell 
tests  more  than  25  points  lower  than  the  other  cells  in  a  battery,  it  is 
an  indication  that  this  cell  is  out  of  order.  One  reading  to  determine 
the  specific  gravity  of  a  cell  is  not  sufficient.  Several  readings  should 
be  taken  and  the  average  determined.  Variation  in  cell  readings  may  be 
due  to  short  circuits  inside  the  cell;  putting  too  much  water  in  the  cell 

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causing  the  electrolyte  to  overflow;  or  to  loss  of  electrolyte  due  to  a 
cracked  or  leaky  jar. 

Low  specific  gravity  in  one  or  more  cells  can  very  often  be  brought 
up  by  driving  the  car  (using  starter  and  lights  sparingly),  or  charging 
by  means  of  the  generator  with  the  engine  running  idle  in  which  case 
readings  ought  to  be  taken  at  frequent  intervals.  If  the  specific  gravity 
in  any  cell  does  not  come  up  to  at  least  1.260  after  the  other  cell  readings 
indicate  that  the  battery  is  fully  charged,  it  is  an  indication  that  the  low 
cell  is  in  need  of  internal  adjustment.  This  can  only  be  done  by  an 
experienced  battery  repair  man.  Most  battery  troubles  can  be  traced  to 
the  electrolyte  becoming  too  low  in  the  cells.  The  effect  of  this  is  to 
weaken  the  battery,  thus  permitting  it  to  be  more  easily  discharged,  and 
frequently  causing  harmful  sulphation  of  the  plates  and  injury  to  the 
separators.  This  may  allow  the  plates  to  come  together,  causing  internal 
short  circuits.  It  is  very  important,  therefore,  that  pure  distilled  water 
be  added  regularly  to  all  cells  in  order  to  keep  the  electrolyte  up  to  the 
level  specified  by  the  manufacturer.* 

If  the  battery  does  not  regain  its  full  power  and  efficiency  within 
one  or  two  days,  after  continuous  charging  on  the  car,  as  explained 
above,  it  is  an  indication  that  the  battery  is  badly  sulphated,  or  has  some 
other  internal  trouble.  It  should  receive  immediate  attention  from  a 
competent  battery  man,  otherwise  the  battery  may  be  entirely  ruined. 
A  frequent  cause  for  the  electrolyte  being  low  in  one  or  more  cells  is  the 
presence  of  a  cracked  or  leaky  jar.  If  one  cell  needs  more  frequent 
addition  of  water  than  the  other  cells,  it  is  a  good  indication  that  the  jar 
leaks.  This  condition  calls  for  immediate  action,  as  the  trouble  can 
very  easily  be  corrected  if  the  battery  is  taken  to  a  service  station  at 
once  and  a  new  jar  installed.  If  the  cracked  or  leaky  jar  is  not  immedi- 
ately replaced,  the  cell  will  be  totally  ruined  and  very  likely  the  entire 
battery  seriously  damaged.  Jars  are  frequently  broken  due  to  the 
battery  hold-downs  coming  loose,  allowing  the  battery  to  jolt  around; 
or  to  freezing  of  the  electrolyte  in  cold  weather. 

206.  Variation  in  Hydrometer  Readings  Caused  by  Temperature. — 
All  the  definite  figures  given  in  hydrometer  readings  are  based  on  the 
normal  temperature  of  70°F.  for  the  electrolyte.  This  refers  strictly  to 
the  temperature  of  the  liquid  itself,  and  not  to  the  temperature  of  the 
surrounding  atmosphere.  The  weather  might  be  freezing  cold,  and  yet 
the  temperature  of  the  liquid  solution  in  the  battery  might  be  normal  or 
above,  either  from  the  heat  of  the  engine  or  because  the  battery  was 
being  vigorously  charged. 

A  special  inexpensive  battery  thermometer  is  needed  to  take 
the  temperature  of  a  battery.  The  thermometer  is  inserted  through  the 
vent  plug-hole  into  the  liquid,  in  the  same  way  as  a  hydrometer.    The 

Digitized  by  LiOOQ IC 



rule  in  making  temperature  correction  is  that  for  every  3°  above  70°F., 
0.001  be  added  to  the  hydrometer  reading;  and  for  every  3°  below  70°F., 
0.001  be  subtracted  from  the  observed  reading.  For  example:  The 
temperature  at  end  of  charge  is  120°F.  and  the  observed  gravity  reading 
is  1.260.    The  corrected  reading  is  determined  as  follows: 

Corrected  reading 

120°  -       70°  =     50° 

60    -s-        3    =      17    (approx.) 

17    X  0.001    =0.017 
1.260  +  0.017   =1.277 

If  the  reading  at  0°F.  is  1.210,  then 

Corrected  reading: 

70°  -        0°  -      70° 

70    ^       3    =      23 

23    X  0.001    =0.023 

1.210    -  0.023  =  1.187 

From  the  above  it  can  be  seen  that  temperature  must  be  taken  into 
consideration,  otherwise  the  hydrometer  reading  will  be  misleading.  It  is 
usually  unnecessary  to  make  allowance  for  temperature  variations,  but 
it  is  well  to  bear  them  in  mind,  particularly  in  the  case  of  a  battery  which 
has  been  giving  trouble. 

Another  thing  to  remember  in  this  connection  is  that,  in  hot  weather, 
if  the  temperature  of  the  liquid  is  more  than  20  degrees  in  excess  of  the 
temperature  of  its  immediate  surroundings,  it  indicates  that  the  battery 
is  possibly  being  overcharged  or  being  charged  at  too  high  a  rate,  or  is 
in  a  bad  condition.  This,  however,  cannot  be  given  as  a  positive  rule. 
In  theory,  the  temperature  of  the  liquid  in  a  battery  should  never  exceed 
105°F.,  as  high  temperatures  have  an  injurious  effect  and  tend  to 
shorten  the  life  of  the  battery;  but  as  long  as  batteries  are  carried  in 
locations  subjected  to  engine  heat,  and  used  on  automobiles  in  hot  cli- 
mates, ideal  conditions  do  not  exist  and  the  battery  must  get  along  as  well 
as  it  can. 

209.  Freezing  Temperature  of  the  Battery. — The  following  table  gives 
the  state  of  charge  and  the  freezing  temperatures  of  the  storage  battery 
at  different  specific  gravities. 

Specific  gravity 

Condition  of  battery 

Freesing  point  in  degree* 

1.275  to  1.300 




1.120  or  below 

Fully  charged 
%  charged 
\i  charged 
y±  charged 
Completely  discharged 

90  degrees  below  zero 

60  degrees  below  zero 

20  degrees  below  zero 


20  degrees  above  zero 

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It  will  be  noted  that  the  freezing  point  of  electrolyte  depends  upon 
its  specific  gravity  and  the  condition  of  battery  charge.  Therefore,  to 
prevent  a  battery  from  freezing,  it  should  be  kept  in  a  fully  charged 

If  it  becomes  necessary  to  add  water  to  the  battery  in  cold  weather, 
this  should  be  done  just  before  running  the  engine.  In  very  cold  weather, 
however,  it  is  better  to  start  the  engine  and  have  the  battery  charging 
before  the  water  is  added.  This  is  done  because  water,  being  lighter  than 
electrolyte,  remains  on  the  surface  of  the  liquid  in  the  cells  until  circulated 
and  mixed  by  the  charging  current.    If  water  .is  added,  therefore,  and 

Fio.  310. — Effect  of  freezing  on  battery 

Fio.  311. — Cracked  battery  jar  due  to 

the  battery  allowed  to  stand  for  a  time  without  charging,  there  is  a 
possibility  of  freezing  the  water  on  the  surface  of  the  solution. 

210.  Results  of  Freezing. — The  results  of  a  frozen  battery  can  be 
seen  in  Figs.  310  and  311.  Owing  to  the  discharged  condition  nearly  all 
the  acid  has  entered  the  plates,  leaving  water,  with  only  a  small  propor- 
tion of  acid,  surrounding  them.  The  result  is  that  the  water  froze  at 
quite  a  high  temperature,  and  as  it  froze  the  little  particles  of  ice  ex- 
panded, loosened  the  material,  and  even  cracked  the  grids  containing  it. 
As  soon  as  a  charge  is  given  a  frozen  battery,  the  grids  expand  and  the 
loosened  material  drops  to  the  bottom,  leaving  the  grids  exposed  as  shown 
in  the  illustration.    The  whole  battery  becomes  disintegrated  simply 

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due  to  the  fact  that  it  was  attacked  by  cold  while  in  a  discharged 

The  battery  should  be  fully  charged  when  it  is  put  away  for  the  winter 
and  should  be  given  an  additional  charge  every  three  or  four  weeks 
to  bring  it  up  to  its  proper  gravity  reading.  If  the  car  is  put  away  for 
the  winter  and  charging  is  neglected,  a  battery  that  readily  starts  the 
engine  in  the  fall  may  be  nothing  but  a  container  and  a  mass  of  muddy, 
disintegrated  material  in  the  spring. 

211.  Battery  Charging. — When  batteries  are  charged  from  an  outside 
source,  only  Uirect  current  should  be  used.  It.  is  not  possible  to  charge 
batteries  from  an  alternating  current  supply  without  apparatus  to  convert 
it  into  direct  current — either  a  motor-generator  or  rectifier. 

In  charging,  the  positive  wire  of  the  charging  circuit  must  always  be 
connected  to  the  positive  (+)  terminal  of  the  battery.  If  this  is  reversed, 
serious  injury  may  result  to  the  battery.     The  charging  wires  may  be 



Fia.  312. — Charging  batteries  from  110-volt  D.C.  supply,  using  rheostat  for  resistance. 

tested  for  polarity  either  by  using  a  voltmeter  or  by  immersing  the  ends 
of  the  wires  in  a  glass  of  water  to  which  a  few  drops  of  acid  or  a  little  salt 
have  been  added,  when  excessive  bubbles  will  form  on  the  negative  wire. 
In  charging  from  a  110-volt  direct-current  supply  it  is  necessary 
to  introduce  either  a  rheostat  (an  adjustable  resistance  unit),  Fig.  312, 
or  a  bank  of  lamps  in  series  with  the  battery  in  order  to  regulate  the 
flow  of  charging  current.  When  using  a  lamp  bank  as  in  Fig.  313,  to 
regulate  the  rate  of  current,  110-volt,  32  c.p.  carbon  filament  lamps  should 
be  used,  connected  in  parallel  with  each  other,  and  the  combination  in 
series  with  the  battery.  With  this  arrangement,  each  lamp  will  allow 
about  one  ampere  of  charging  current  to  pass  through  the  battery  so 
that  the  number  of  lamps  in  use  will  be  approximately  equal  to  the 
number  of  amperes  of  current  to  be  used  in  charging.    The  charging 

Digitized  by  LiOOQ IC 



rate  may  be  adjusted  by  turning  the  lights  off  or  on,  or  by  moving  the 
rheostat  handle  until  the  ammeter  shows  the  proper  reading. 

Where  more  than  one  battery  is  to  be  charged  at  a  time,  the  batteries 
should  be  connected  in  series;  that  is,  the  positive  terminal  of  one  battery 
should  be  connected  to  the  negative  terminal  of  the  adjoining  battery. 
Rubber-covered  copper  wire  (No.  14  or  larger)  cut  in  lengths  of  about 
18  in.  should  be  used  to  connect  batteries  in  this  manner.  The  wire 
is  connected  to  the  terminals,  either  by  clips  attached  to  the  ends  of  the 
wires,  or  by  twisting  the  wire  around  the  terminals.  Care  should  be 
taken  to  see  that  a  good  contact  is  made  without  damaging  the  terminals. 

The  total  voltage  of  a  combination  of  batteries  is  the  sum  of  all  the 
cells  in  the  circuit  multiplied  by  the  voltage  of  each  cell  (2  volts).  In 
charging  batteries,  each  cell  requires  2.5  volts;  therefore,  care  should  be 
taken  that  the  total  voltage  required  for  charging  all  the  cells  does  not 

110  V.-D.C  SUPPLY 






Fig.  313. — Charging  batteries  from  110-volt  D.C.  supply,  using  lamps  for  resistance.* 

equal  the  operating  voltage  of  the  generator.  Should  the  total  voltage  of 
the  cells,  while  on  charge,  equal  the  voltage  of  the  generator,  no  current 
will  pass  through  the  batteries.  Should  the  total  voltage  of  the  cells 
exceed  the  voltage  of  the  generator,  the  batteries  will  discharge  them- 
selves through  the  generator.  When  charging  several  batteries  in  series, 
care  should  be  taken  to  see  that  the  charging  rate  does  not  exceed  the 
maximum  rate  of  the  battery  requiring  the  lowest  charging  current. 

The  charging  rate  of  most  batteries  is  marked  on  the  name  plate,  in 
fact,  usually  two  rates,  the  start  and  finish  rates,  are  given.  The  reason 
for  this  is  that  it  is  much  better  for  the  battery  if  the  charging  rate  is 
reduced  when  approaching  a  full  state  of  charge,  to  avoid  excessive 
heating  and  evaporation  of  the  electrolyte.  If  the  charging  rates  are 
not  marked  on  the  battery,  a  safe  charging  rate  at  the  start  would  be 
about  10  per  cent,  of  the  rated  ampere-hour  capacity,  and  5  per  cent,  of 

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this  rating  to  finish ;  for  example,  in  the  case  of  an  80  ampere-hour  battery, 
the  charging  rate^t  the  start  should  be  10  per  cent,  of  80  or  8  amperes, 
and  at  the  finish  5  per  cent,  of  80  or  4  amperes.  If- the  ampere-hour 
capacity  is  not  known,  the  charging  rate  at  the  start  may  be  8  to  10  am- 
peres, but  should  be  reduced  to  a  lower  rate  if  any  of  the  cells  show  signs 
of  heating. 

212.  Detailed  Instruction  for  Charging  Batteries. — Before  placing  the 
battery  on  charge,  or  removing  the  vent  plugs  (or  caps),  the  top  should 
be  thoroughly  cleaned  off  to  prevent  any  dirt  or  impurities  from  falling 
into  the  cells.  If  any  of  the  cells  or  outside  battery  parts  are  corroded, 
the  corrosion  should  be  cleaned  off  with  a  solution  of  ordinary  washing 
soda  and  water,  applied  with  a  clean  cloth  or  sponge.  The  vent  plugs 
(or  caps)  are  now  removed  and  should  not  be  replaced  until  the  battery  is 
removed  from  the  charging  circuit,  unless  a  special  type  of  filler  tube, 
which  requires  the  plug  to  remain  in  place  while  the  battery  is  charging, 
is  used.  In  this  case,  the  plug  is  removed  only  when  it  is  necessary  to 
take  a  hydrometer  reading  or  add  distilled  water.  Distilled  water  should 
be  added  to  all  cells  in  sufficient  quantities  to  bring  the  electrolyte  up 
to  the  proper  level,  which  in  most  batteries  is  one-half  inch  above  the 
top  of  the  plates. 

The  battery  is  placed  on  charge  at  the  start  rate  specified  on  the  name 
plate  and  the  voltage  of  each  cell  tested  immediately.  The  voltage  and 
hydrometer  readings  of  each  cell  should  be  made  every  hour.  The 
charge  at  the  start  rate  should  continue  until  one  or  more  of  the  cells  are 
gassing  vigorously  and  the  voltage  of  each  cell  reads  2.4  or  higher. 
The  charging  rate  should  then  be  reduced  to  the  finish  rate  and 
charging  continued  at  this  rate  until  the  battery  is  fully  charged. 

A  battery  is  fully  charged  when,  with  the  current  flowing  at  the 
finish  rate,  all  cells  are  gassing  vigorously;  the  voltage  and  specific  gravity 
of  each  cell  have  stopped  rising  and  have  been  constant  for  one  hour; 
the  voltage  reading  is  2.4  or  higher  per  cell  on  charge;  and  the  specific 
gravity  of  each  cell  tests  between  1.275  and  1.300. 

Although  it  is  always  advisable  to  use  a  voltmeter  in  battery  charging 
it  is  not  absolutely  essential.  When  a  voltmeter  is  not  used,  the  start 
rate  should  be  continued  until  the  battery  is  gassing  vigorously.  The 
rate  should  then  be  reduced  to  the  finish  rate  and  charging  continued 
until  the  specific  gravity  of  all  cells  has  stopped  rising  and  remains  con- 
stant for  one  hour.  If  the  specific  gravity  rises  above  1.300  while  the 
battery  is  on  charge,  part  of  the  electrolyte  should  be  drawn  from  the 
cells  and  enough  distilled  water  added  to  reduce  the  specific  gravity  to 
1.285.  If,  on  the  other  hand,  the  specific  gravity  will  not  come  up  to 
1.275  by  continuous  charging  it  indicates  that  there  is  insufficient  acid 
in  the  electrolyte.    The  specific  gravity  should  be  corrected  by  removing 

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some  of  the  electrolyte  from  the  defective  cell  and  replacing  it  with  a  like 
amount  of  electrolyte  of  1.350  to  1.400  sp.  gr.  Pure  acid  should  never 
be  added  to  a  battery  as  it  will  gas  and  heat  violently  and  will  damage 
the  plates  and  separators.  Figure  314  shows  the  effect  on  wood  sepa- 
rators by  filling  the  cell  with  pure  acid  solution.  After  the  specific 
gravity  has  been  adjusted,  the  battery  should  remain  on  charge  for  at 
least  one  hour.  The  voltage  at  the  completion  of  charge  should  be  about 
2.5  volts  for  each  cell  but  this  will  immediately  drop  to  approximately 
2.2  volts  per  cell  making  the  voltage  of  a  fully  charged  three-cell  battery 
about  6.6  volts.  The  voltage,  however,  will  vary  slightly  with  the 


Us  •  11 



*   r 

&    <%  ... 

* ~        .^* 

Pia.  314. — Effect  of  strong  electrolyte  on  wood  separator. 

Caution. — Care  should  be  taken  to  keep  open  flames  away  from  a 
battery  which  is  or  has  been  charging  or  discharging.  The  gas  which 
accumulates  in  the  cells,  due  to  the  chemical  action,  is  combustible  and 
may  cause  sufficient  explosion  to  wreck  the  battery  and  injure  the 

After  the  battery  has  been  removed  from  the  charging  line,  the  vent 
caps  should  be  screwed  tightly  into  place  and  the  battery  top  and  con- 
necting terminals  cleaned  with  either  soda  solution  or  ammonia  water. 
To  prevent  corrosion  of  the  battery  terminals,  they  should  be  greased 
with  a  light  coat  of  vaseline  or  soft  grease. 

213.  Battery  Testing  with  the  Voltmeter.— The  chief  use  of  the  volt- 
meter is  to  determine  the  positive  and  negative  terminals  of  the  cells 
and  the  individual  cell  voltages  on  charge  and  discharge.  A  convenient 
instrument  to  use  is  a  low-reading  voltmeter  having  a  scale  from  0  to 
3  volts.    The  leads  should  be  equipped  with  sharp  prods.    These  prods 

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are  pressed  into  the  terminals  of  each  cell  until  a  good  connection  is  made. 
When  the  voltmeter  reads  in  the  right  direction,  the  terminal  of  the  cell 
connected  with  the  plus  or  positive  voltmeter  lead  is  the  positive  terminal. 
The  positive  terminal  of  one  cell  should  be  connected  to  the  negative 
terminal  of  the  next  cell.  If  this  has  not  been  done,  the  cells  are  not 
assembled  correctly  in  the  battery  case  and  they  should  be  reassembled. 
A  fully  charged  cell  while  on  charge  should  read  from  2.4  to  2.6  volts, 
depending  on  the  age  of  the  battery  and  the  amount  of  charging  current 
flowing  through  the  battery.  It  should  read  about  1.8  volts  when  nearly 
discharged  with  the  battery  discharging  at  a  current  of  about  5  amperes. 
When  a  cell  is  floating  (neither  charging  nor  discharging)  the  voltage 
should  be  about  2.1  to  2.2. 

Fio.  315. — Sulphation  of  battery  plates 
due  to  undercharging. 

Fio.  316. — Sulphation  due  to  underfilling 
of  battery. 

214.  Sulphation. — It  was  found  that  upon  the  discharge  of  the  bat- 
tery, the  plates  were  acted  upon  by  the  sulphuric  acid  in  the  electrolyte, 
converting  the  lead  peroxide  of  the  positives  and  the  pure  spongy  metallic 
lead  of  the  negatives  into  a  lead  sulphate,  which  upon  charging  is  again 
converted  back  into  its  original  form.  When  the  plates  are  permitted  to 
remain  in  a  discharged  condition,  the  lead  sulphate  grows  into  a  hard, 
white,  crystalline  formation,  which  closes  up  the  pores  and  destroys  the 
active  area  of  the  plates.  This  formation  is  known  as  sulphation. 
Figure  315  shows  a  positive  group  of  a  battery  with  wood  separators 
that  has  been  operated  in  a  partially  discharged  condition  for  some  length 
of  time.     The  white  area  on  the  plate  indicates  the  sulphation. 

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Sulphation  is  also  caused  by  low  electrolyte  or  because  the  cell  has 
not  been  filled  with  water.  If  water  is  not  added  at  regular  intervals  to 
replace  loss  through  evaporation,  the  electrolyte  level  will  soon  fall  below 
the  plate  tops,  causing  that  portion  of  the  plates  which  is  exposed  to  the 
air  to  sulphate  rapidly.  Figure  316  shows  a  sulphated  condition  of  plates 
after  a  few  months1  use  (or  rather  misuse)  produced  by  a  lack  of  water  and 
by  allowing  the  solution  to  become  low  and  not  cover  the  plates.  A  hard 
white  sulphate  has  formed  on  the  top  half  of  the  plates.  It  is  difficult 
and  sometimes  impossible  to  even  charge  and  bring  back  to  a  normal 
condition  a  plate  that  has  dried  out  and  become  hard.  The  concentrated 
condition  of  the  electrolyte  (only  the  water  evaporates)  is  also  injurious  to 
the  lower  half  of  the  plates  and  separators.    Sulphate  is  a  non-conductor 

Fio.  317. — Effect  of  overfilling  the  battery. 

of  electricity,  therefore  it  is  quite  destructive  to  the  activity  of  the  plates 
and  reduces  materially  the  ampere-hour  capacity  of  the  battery.  For 
example,  the  capacity  of  a  100  ampere-hour  battery  in  which  one-half 
of  the  plate  area  is  sealed  up  by  sulphation  would  be  reduced  approxi- 
mately 50  per  cent,  and  would  be  capable  of  no  more  work  than  a  battery 
of  50  ampere-hour  capacity.  Sulphation  can  be  removed  if  not  too  bad 
only  by  prolonged  charging  at  a  very  slow  rate,  usually  the  finish  rate 
for  the  battery.  It  may  require  charging  for  several  days  to  restore  it 
to  a  fully  charged  condition. 

In  order  to  prevent  sulphation,  the  battery  should  be  kept  charged  and 
the  plates  well  covered  with  electrolyte. 

215.  Effect  of  Overfilling. — The  effect  of  overfilling  a  battery  is  well 
illustrated  by  Fig.  317.    The  battery  should  be  filled  with  water  up  to 


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the  bottom  of  the  cover  tube,  or  %  in.  to  %  in.  above  the  top  of  the 
plates.  If  it  is  filled  above  this  point  it  will  run  over  upon  charging, 
due  to  the  lack  of  space  for  expansion.  This  will  result  in  a  loss  of  the 
electrolyte  and  an  eating  away  of  the  battery  box,  as  indicated.  The 
electrolyte  may  also  get  into  the  metal  case  and  eat  out  the  bottom. 

216.  Corroded  Terminals. — Frequently,  the  terminals  and  connectors 
will  be  found  covered  with  a  greenish  deposit.  This  is  a  corrosion  due 
to  the  acid  fumes  which  are  constantly  passing  off  from  the  cells  and 
attacking  the  metal  connectors.  Figure  318  shows  a  cable  terminal  badly 
corroded  by  the  splashing  or  spraying  of  electrolyte  on  the  bare  cable 
wires  where  insulation  has  been  stripped  off. 

The  eating  action  may  be  stopped  and  all  corrosion  removed  by 
soaking  the  parts  in  a  solution  of  bicarbonate  of  soda  (common  baking 
soda)  or  ammonia  and  brushing  them  with  a  stiff  brush  after  which  they 
should  be  wiped  dry.  Further  corrosion  will  be  prevented  by  covering 
the  parts  with  a  light  coat  of  vaseline  or  cup  grease. 

Fig.  318. — Effect  of  corrosion  on  battery  cable  terminals. 

217.  Disintegrated  and  Buckled  Plates. — Overheating  of  the  plates, 
through  excessive  charging  or  discharging,  causes  them  to  warp  or 
buckle.  It  also  causes  disintegration  of  the  active  material,  especially 
in  the  positive  plates.  Figure  319  shows  what  continuous  overcharging 
does  to  the  positive  plates.  It  softens  up  the  material  and  causes  the 
battery  to  give  unusually  high  capacity  for  a  short  time.  The  material 
then  begins  to  disintegrate  and  fall  out.  The  effect  is  about  the  same  as 
freezing.  In  order  to  determine  which  condition  has  existed,  it  should 
be  remembered  that  overheating  usually  blackens  and  softens  the  wood 

A  plate  is  especially  liable  to  buckle  when  in  a  sulphated  condition, 
if  discharged  or  charged  at  a  high  rate.  The  sulphated  portion  of  the 
plate  does  not  expand  at  the  same  rate  as  the  active  area,  thus  causing 
unusual  expansion  and  a  warping,  sometimes  cracking,  of  the  grid. 
A  group  which  has  been  allowed  to  stand  discharged  at  a  low  point  for  some 
time,  then  charged  at  a  high  rate  to  restore  its  energy,  is  shown  in  Fig. 
320.     On  account  of  the  hardness  of  the  plates  and  the  extra  resistance 

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of  the  sulphate  formed  during  the  excessively  low  period  of  discharge,  the 
plates  become  very  hot  and  being  only  slightly  flexible  or  elastic,  warp 
or  buckle  when  expanded  by  heat.  This  illustration,  Fig.  320,  shows  the 
difference  between  a  cell  continuously  overcharged  and  one  which  has 
been  allowed  to  discharge  and  become  hard.  Buckling  also  causes  a 
breaking  down  of  the  separators  and  often  results  in  cracking  the  jar, 
as  in  Fig.  321,  with  a  loss  of  the  electrolyte. 

To  avoid  overheating  and  buckling  of   the   plates,    the   following 
precautions  should  be  taken: 

Fio.  319. — Effect  on  battery  plates  of 
continuous  overheating. 

Fio.  320.— Buckled  battery  plates. 

1.  Prevent  sulphation  through  keeping  battery  charged  and  properly 

2.  Make  sure  that  the  generator  is  adjusted  to  charge  the  battery 
at  the  proper  rate. 

3.  Do  not  operate  the  starting  motor  excessively. 

4.  Do  not  propel  the  car  with  the  starter. 

5.  Watch  the  battery  temperature  in  hot  weather,  and  when  touring. 
If  the  top  connectors  feel  warm  to  the  hand,  drive  with  the  headlights 
on  to  cut  down  the  charging  rate. 

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218.  Sediment — When  a  battery  is  used,  a  deposit  known  as  sedi- 
ment collects  in  the  bottom  of  the  jars,  due  to  the  gradual  wearing  away 
of  the  active  material  in  the  plates.  Figure  322  shows  a  worn-out  plate 
from  which  practically  all  the  active  material  has  fallen.  In  time,  this 
sediment  may  fill  up  the  sediment  or  mud  space,  causing  a  phort-circuiting 
of  the  bottom  of  the  plates.  In  this  event,  the  cell  must  be  dismantled 
and  the  sediment  removed.  Broken  down  insulation  due  to  high  sedi- 
ment or  defective  separators  is  indicated  by  the  inability  of  a  cell  to 
hold  a  charge  on  open  circuit.    Other  indications  of  broken   down 




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Fig.  321. — Cracked  jar  due  to 
buckled  plates. 

Fio.  322. — A  worn-out  battery  -plate  show- 
ing the  active  material  fallen  out  and  the  grid 

insulators  are:  undue  heating  of  the  cells  upon  charging,  little  or  no 
voltage  or  gravity  rise  after  a  prolonged  charge,  and  the  impossibility 
of  making  the  cells  gas  properly.  Such  a  cell  is  considered  dead  and  can 
be  remedied  only  by  dismantling  and  rebuilding  the  battery.  This  is  a 
job  which  should  be  undertaken  only  by  an  experienced  battery  repair- 
man, as  it  involves  lead  burning  with  either  a  hydrogen  or  oxy-acetylene 
flame,  an  art  in  itself,  requiring  special  lead  burning  equipment  and  much 

219.  Conditions  Causing  the  Battery  to  Run  Down. — It  is  impossible 
to  include  here  all  the  conditions  which  may  cause  the  battery  in  the 
electrical  system  to  run  down,  since  many  of  the  causes  may  be  due  to 
faults  in  the  starting  and  generating  system.  However,  a  few  of  the 
most  important  causes  are  given  to  assist  in  diagnosing  battery  trouble 
on  the  automobile. 

A  discharged  or  weak  condition  of  the  battery,  which  is  indicated 

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by  a  loss  in  cranking  power  of  the  starter,  dim  lights,  low  specific  gravity, 
etc.,  may  be  attributed  to  one  of  the  following  causes: 

1.  Generator  either  not  charging  battery  or  charging  at  insufficient 

2.  Battery  plates  not  kept  properly  covered  with  electrolyte,  causing 
sulphation  of  the  plates. 

3.  Drain  on  battery  dye  to  excessive  lamp  load  or  too  many  electrical 
accessories  not  intended  for  the  battery. 

4.  Engine  not  driven  fast  enough  to  charge  at  sufficient  rate. 

5.  Too  much  night  driving  with  full  lamp  load  on. 

6.  Excessive  use  of  the  starting  motor;  starting  switch  sticking. 

7.  Electrical  cut-out  not  operating  properly. 

8.  Battery  ignition  switch  left  "on"  with  engine  not  running. 

9.  Cracked  jar  causing  loss  of  electrolyte. 

10.  Broken  down  battery  insulation  due  to  high  sediment  or  defective 

11.  Loose  generators,  cut-out,  or  battery  connections. 

12.  Corroded  battery  terminals. 

13.  Overfilling,  causing  loss  of  electrolyte  and  short  circuits. 

14.  Use  of  impure  water  for  filling. 

15.  Battery  too  small  to  meet  requirements  of  the  system. 

16.  Short  circuits  in  the  electrical  wiring. 

17.  Grounded  generator  or  motor  armature  winding. 

18.  Battery  freezing. 

19.  Plates  broken  loose  from  terminal  or  connector. 

20.  Battery  plates  worn  out. 

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220.  Automobile  Starters. — Devices  for  starting  automobile  engines 
may  be  classified  into  four  general  types,  according  to  the  source  of 
energy  for  turning  the  engine  crankshaft  until  the  engine  operates  under 
its  own  power.  These  four  general  types  are;  mechanical  starters,  air 
starters,  acetylene  starters,  and  electric  starters. 

221.  Mechanical  Starters. — Mechanical  starters  include  the  various 
types  of  hand-cranking  devices  and  springs.  The  disadvantage  of  the 
hand-cranking  starter  is  that  it  requires  a  certain  amount  of  human 
power.  The  only  advantage  is  that  the  driver  usually  does  not  have  to 
leave  his  seat  to  crank  the  engine.  One  type  of  mechanical  starter  is 
the  spring  starter.  It  is  capable  of  giving  the  engine  a  few  revolutions 
only,  and  if  the  engine  does  not  start  then  it  becomes  necessary  for  the 
driver  to  wind  up  the  spring,  which  is  a  rather  tiresome  operation.  If 
the  engine  starts,  there  is  an  automatic  device  by  which  the  spring  is 
wound  up  by  the  engine. 

222.  Air  Starters. — In  the  air  starters,  the  air  is  pumped  into  a  storage 
tank  to  about  150  lb.  pressure.  The  engine  is  started  either  by  admitting 
air  into  the  combustion  chamber  or  by  cranking  it  by  means  of  a  com- 
pressed-air motor.  In  the  first  method,  the  pipe  leading  from  the  tank 
goes  to  an  air  distributor  which  is  driven  by  the  engine,  the  air  being 
directed  to  the  various  cylinders  in  accordance  to  their  firing  order. 
The  air  enters  each  cylinder  when  it  is  on  its  working  stroke,  at  which 
time  all  the  valves  are  closed.  The  method  of  starting  by  air  has  the 
disadvantage  that  the  air  is  liable  to  cool  the  cylinders  sufficient  to 
prevent  proper  starting  of  the  regular  engine  cycle  on  account  of  the 
fuel  charge  condensing  on  the  cool  cylinder  walls.  Another  disadvantage 
in  using  air  for  starting  is  the  difficulty  in  preventing  air  leaks,  since  the 
system  is  necessarily  under  comparatively  high  pressure  and  subject 
to  continuous  vibration. 

223.  Acetylene  Starters. — Some  manufacturers  have  equipped  their 
machines  with  a  device  for  starting  with  acetylene  gas.  This  gas  is  very 
explosive  and  will  ignite  readily  under  almost  any  condition.  These 
engines  are  equipped  with  valves  and  tubes  from  the  acetylene  lighting 
system  so  that  the  driver  can  inject  a  small  quantity  of  acetylene  gas 
into  the  cylinder.  The  engine  will  then  be  practically  sure  of  starting 
on  the  spark. 


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224.  Electric  Starters. — The  mechanical,  air,  and  acetylene  starters 
have  practically  been  discarded  in  favor  of  the  electric  starter  which  is 
now  universally  used  and  is  furnished  as  standard  equipment  by  the 
manufacturer  on  all  makes  of  passenger  cars  and  on  a  large  percentage 
of  trucks.  The  electric  starter  is  in  the  form  of  a  low-voltage  direct- 
current  motor.  The  current  for  operating  this  motor  is  supplied  by  a 
storage  battery  which  also  furnishes  the  current  for  the  lighting  system 
and,  in  many  cases,  for  the  ignition. 

The  typical  electric  starting  and  lighting  system  consists  essentially 
of  the  following  component  parts: 

1.  A  direct-current  starting  motor  which  will  operate  on  current  from 
the  storage  battery  for  cranking  the  engine. 

2.  A  storage  battery  for  supplying  current  when  the  generator  is  not 
running  or  is  not  running  fast  enough  to  generate  the  required  amount 
of  current. 

3.  A  direct-current  generator  for  keeping  the  battery  charged. 
Electric  starting  and  lighting  systems  may  be  divided  into  two  general 

classes  according  to  the  number  of  machines  required  to  perform  the 
generating  and  cranking  operations,  namely,  the  single-unit  and  two-unit 
systems.  In  the  single-unit  system  the  generator  and  starting  motor 
are  both  combined  into  one  machine  known  as  a  " motor-generator' '  or 
"starter-generator."  In  this  system  the  machine  operates  as  a  motor 
using  current  from  the  battery  for  cranking  the  engine,  and  converts 
itself  automatically  into  a  generator  to  charge  the  battery  when  it  is 
driven  by  the  engine.  In  the  two-unit  or  "double-unit"  system  the 
generator  and  starting  motor  are  separate  and  comprise  two  independent 
machines.  In  this  type  of  system  the  generator  is  driven  continuously 
by  the  engine,  while  the  starting  motor  is  normally  disconnected  from  the 
engine  through  its  driving  mechanism  and  operates  only  when  the  engine 
is  to  be  cranked  and  the  starting  switch  is  closed.  A  wiring  diagram  and 
installation  of  a  typical  two-unit  system  are  shown  in  Fig.  323.  From 
this  diagram  it  will  be  noticed  that  the  current  for  the  ignition,  horn, 
lights,  starting  motor,  etc.,  returns  to  the  battery  through  the  ground 
or  frame  of  the  car,  instead  of  by  a  separate  wire.  An  electric  system 
employing  this  method  of  wiring  is  termed  a  single-wire  grounded  system. 
This  method  of  car  wiring,  in  preference  to  the  two-wire  method,  is  used 
by  practically  all  automobile  manufacturers,  since  the  use  of  the  frame  as 
one  wire  greatly  simplifies  both  the  wiring  of  the  car  and  in  many  cases 
the  construction  of  the  starting  and  lighting  apparatus. 

The  voltage  at  which  the  system  operates  is  usually  6  volts  although 
in  some  installations,  12  volts  are  used.  In  many  of  the  first  systems 
brought  out,  a  double  voltage  or  split  battery  was  used  such  as  the  6  volt 
-12  volt,  12  volt-24  volt,  and  the  6  volt-24  volt  types.    The  cells  of 

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the  battery  were  divided  into  two  groups  connected  normally  in  parallel 
giving  the  lower  voltage  when  being  charged  and  for  operating  the 
lights,  but  connected  in  series  with  the  starting  switch  closed,  to 
give  the  higher  voltage  for  operating  the  starting  motor.  However, 
owing  to  the  many  disadvantages  of  the  double  voltage  system  it  has 
been  practically  discarded  in  favor  of  the  single  6-volt  system  using  a 
3-cell  battery.  The  voltage  of  the  system  can  readily  be  determined  by 
looking  at  the  storage  battery,  since  a  6-volt  system  uses  a  3-cell  battery 
and  a  12-volt  system  a  6-cell  battery. 

225.  Hydraulic  Analogy  of  an  Electric  Starting  and  Lighting  System. 
— The  operation  and  function  of  the  different  parts  of  a  starting  and  light- 

MtAO  •IDE     OMH  AND 

LWHT3      LIGHTS   AND         OTHER 


Fig.  324. — Hydraulic  analogy  of  electric  starting  and  lighting  syBtem. 

ing  system  may  be  compared  to  the  operation  of  a  small  waterworks 
system  such  as  is  commonly  used  in  small  towns  or  private  residences. 
This  hydraulic  analogy  is  shown  in  Fig.  324. 

Such  a  water  system  usually  comprises  a  motor-driven  pump,  con- 
nected by  a  main  line  to  the  various  outlets,  and  a  tank  or  reservoir 
placed  at  a  height  which  will  give  the  desired  head  or  pressure. 

The  pressure  tank  or  reservoir  is  provided  with  a  regulator,  usually 
of  the  float  type,  adapted  to  indicate  the  amount  of  water  in  the  reservoir 
and  to  shut  off  or  reduce  automatically  the  power  of  the  pump  when  the 
water  has  reached  a  certain  predetermined  level.  This  regulation  may 
be  accomplished  by  connecting  a  float  regulator  to  a  switch  or  rheostat 

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(adjustable  resistance)  in  the  main  circuit  of  the  motor  which  drives  the 
pump  so  that  the  speed  of  the  motor  and  the  output  of  the  pump  will  be 
regulated  in  accordance  with  the  quantity  of  water  being  drawn  from  the 
system.  If  the  quantity  of  water  drawn  from  the  system  is  in  excess  of 
the  quantity  supplied  by  the  pump  at  a  given  speed,  the  reservoir  will 
supply  the  difference,  and  when  the  level  of  the  water  falls  to  a  certain 
point,  the  motor  will  be  caused  to  run  faster,  thus  making  up  for  the 
greater  demand. 

A  check  valve  is  placed  in  the  main  line  between  the  pump  and  the 
reservoir.  The  purpose  of  this  is  to  prevent  the  backward  flow  of  water 
into  the  pump  in  case  the  pressure  due  to  the  water  in  the  reservoir 
exceeds  that  of  the  pump  or  in  case  the  pump  is  stopped. 

The  reservoir  in  the  water  system  corresponds  to  the  storage  battery 
in  the  starting  and  lighting  system,  the  pump  to  the  generator  which  is 
driven  by  the  engine,  the  float  regulating  device  to  the  regulating  relay 
for  controlling  generator  output,  and  the  check  valve  to  the  cut-out  of 
the  electric  system.     The  meter  registers  the  amount  of  water  either 
pumped  into  or  discharged  from  the  reservoir  and  corresponds  to  the 
ammeter,  Fig.  323,  connected  in  the  generator  charging  circuit.     When 
the  current  output  of  the  generator  exceeds  the  amount  required  by  the 
lights,  ignition,  etc.,  the  excess  current  will  flow  through  the  battery  in  a 
charging   direction   so   that   the  ammeter  will  show   "charge."    For 
example,  if  the  lamps  require  8  amperes  and  the  generator  output  is 
12  amperes,  the  ammeter  will  show  4  amperes  charge.     On  the  other 
hand,  if  the  generator  is  only  supplying  8  amperes,  the  same  as  required 
by  the  lights,  the  battery  will  neither  charge  nor  discharge  and  the 
ammeter  will  read  zero.    But  if  the  generator  produces  less  than  that 
required  by  the  lights,  say  only  5  amperes,  the  battery  will  supply  the 
amount  which  the  generator  is  deficient  and  the  ammeter  will  show  3 
amperes  discharge.     It  will  be  noticed  in  the  diagram  that  the  current 
for  the  starting  motor  will  not  pass  through  the  ammeter,  since  the  motor 
requires  a  very  large  current  which  may  be  sufficient  to  burn  out  the  instru- 
ment.    Providing  the  lamps  are  of  the  proper  size,  the  generator  output 
should  be  so  regulated  that  at  normal  driving  speeds,  with  all  lights  and 
ignition  turned  on,  there  will  be  at  least  3  or  4  amperes  charging  the  battery. 
This  is  necssary  to  compensate  for  the  current  used  periodically  by  the 
starting  motor  and  horn  and  in  order  to  keep  the  battery  fully  charged. 
By  making  a  few  minor  changes,  such  as  forming  a  by-pass  around 
the  check  valve,  the  analogy  of  Fig.  324  will  apply  equally  well  to  the 
single-unit  system,  in  which  case  the  pump  will  act  as  a  water  motor 
when  the  valve  in  the  by-pass  is  opened  and  the  water  discharged  through 
it  from  the  reservoir.     The  pump  now  corresponds  in  action  to  the  motor- 
generator,  and  the  valve  in  the  by-pass  to  the  starting  switch,  which, 

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by  short-circuiting  the  cut-out,  permits  the  battery  to  discharge  through 
the  motor. 

With  this  connection,  it  will  be  noted  that  the  ammeter  must  now 
carry  the  starting  current.  Since  the  starting  current  is  usually  more 
than  the  ammeter  is  designed  to  carry,  the  ammeter  must  either  be  elimi- 
nated or  replaced  by  a  battery  indicator  capable  of  carrying  a  large  current. 
The  battery  indicator  does  not  register  the  number  of  amperes  flowing 
but  merely  indicates  which  way  the  current  is  flowing  through  the  battery. 
It  is  usually  referred  to  as  the  C.  O.  D.  indicator;  due  to  the  fact  that 
it  has  three  readings,  "charge,"  "off,"  and  "discharge." 

226.  Generator  Drives. — The  method  of  mounting  and  driving  the 
generator  depends  to  a  large  extent  upon  whether  the  engine  has  four, 
six,  eight,  or  twelve  cylinders.     For  this  reason,  it  is  more  or  less  of 

Fio.  325. — Westinghouse  generator  installation  on  Case-Continental  Six  engine. 

an  individual  problem  on  the  different  makes  of  cars.  In  the  two-unit 
system,  which  is  the  type  now  most  commonly  used,  the  generator  is 
usually  mounted  on  the  side  of  the  engine  and  driven  1  to  1%  times  crank- 
shaft speed.  The  method  of  drive  may  be  by  belt,  silent  chain,  or  gears, 
the  gear  drive  being  the  most  popular  method.  One  typical  generator 
mounting  is  that  shown  in  Fig.  325,  in  which  is  shown  the  installation 
of  the  Westinghouse  generator  on  the  Case-Continental  Six  engine.  The 
generator  is  supported  by  a  bracket  on  the  upper  half  of  the  crank  case 
and  is  driven  by  a  coupling  on  the  rear  end  of  the  pump  shaft  which  is 
driven  through  gears  from  the  crankshaft  at  1^  times  crankshaft  speed. 
By  mounting  the  generator  in  this  manner  it  is  possible  to  remove  it 

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without  disturbing  other  parts  of  the  engine.  The  flexible  coupling  in- 
sures proper  driving  of  the  generator,  although  it  may  not  be  in  exact 
alignment  with  the  driving  shaft. 

Another  method  of  supporting  the  generator  is  to  provide  it  with 
flanges,  as  shown  in  Fig.  326.     The  generator  flanges  are  bolted  directly 

Fio.  326. — Westinghouse  generator  with  flange  mounting. 

to  the  timing  gear  housing.  The  pinion  on  the  generator  armature  shaft 
meshes  directly  with  one  of  the  timing  gears,  thus  eliminating  the  drive 
shaft  and  coupling.  This  method  of  installation  gives  a  very  rigid  mount- 
ing, insures  perfect  alignment  of  the  bearings,  and  makes  the  generator 
very  accessible  in  case  it  is  to  be  removed  for  repair. 



Fio.  327. — Installation  of  Delco  starting,  lighting,  and  ignition  equipment  on  Nash  Six. 

The  method  of  mounting  the  Delco  electrical  equipment  on  the  Nash 
Six  is  shown  in  Fig.  327.  The  generator  is  mounted  on  the  front  of  the 
cylinder  casting,  being  fastened  by  machine  studs  passing  through  the 
flanges  of  the  generator  frame.     The  fan  and  the  pulley,  for  driving  both 

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the  fan  and  the  generator,  are  mounted  upon  the  forward  end  of  the 
generator  shaft.  The  generator  is  driven  by  a  V  belt  from  the  pulley 
on  the  forward  end  of  the  crankshaft  at  approximately  1H  times  crank- 

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Fig.  328. — Westinghouse  starting  motor  installation  on  Case- Continental  Six  engine. 

shaft  speed.    The  oblong  holes  in  the  flanges  through  which  the  studs 
pass  permit  adjusting  of  the  belt  tension. 

227.  Starting  Motor  Drives. — The  starting  motor  is  usually  mounted 
on  the  side  of  the  engine  by  means  of  a  bracket  or  flange  connection  to 


snirrtn  torh 


Fig.  329. — Sliding  pinion  type  of  motor  drive. 

the  cylinder  casting,  similar  to  the  generator  mounting.  Typical  instal- 
lations are  shown  in  Figs.  327  and  328.  In  Fig.  327,  the  rear  end  of 
the  starting  motor  casting  has  a  machined  neck  which  fits  into  a  cylin- 

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drical  hole  in  the  flywheel  housing,  the  motor  being  held  in  place  by  a 
single  set  screw.  The  starting  motor  may  drive  the  engine  through  a 
silent  chain  and  overrunning  clutch,  or  by  a  pinion  attached  to  the 
motor  armature  shaft  which  is  brought  into  mesh  with  teeth  cut  on  the 
rim  of  the  flywheel.  The  latter  method  has  many  advantages  and  is 
used  almost  universally  on  two-unit  systems,  while  the  chain  drive  is 
used  more  extensively  on  single-unit  systems. 

There  are  three  principal  methods  of  connecting  the  motor  to  the 
flywheel:  (1)  the  sliding  pinion  type,  Fig.  329,  in  Which  a  pinion  is  shifted 
by  the  operator  as  the  starting  switch  is  closed,  the  operation  of  which 


tmvme^ms  cow* 

B/LUSH  ffOt&ffi 

POt£  Pf£Cf 
"f/iU0  CO/l 

TT-1      STApTffi  * 

A/M6  G£A# 

Fig.  330. — Sectional  views  of  Bosch  starting  motor  with  magnetically  shifted  armature 
for  engaging  pinion  with  flywheel,  (A)  showing  pinion  out  of  engagement  and  (B)  showing 
pinion  engaged. 

depends  more  or  less  on  the  skill  of  the  operator;  (2)  the  magnetic  type, 
Pig.  330,  in  which  the  entire  armature  is  automatically  shifted  by  mag- 
netism pulling  the  pinion  into  mesh;  and  (3)  the  Bendix  drive,  Fig.  331, 
which  is  automatic  and  which  requires  very  little  attention  and  skill  on 
the  part  of  the  operator.  The  last  method  is  used  on  practically  all 
makes  of  cars  equipped  with  the  two-unit  system. 

The  gear  reduction  obtained  through  the  flywheel  type  starter  with 
single  reduction  is  usually  about  11  or  12  to  1,  that  is,  the  speed  of  the 
motor  armature  is  11  or  12  times  that  of  the  flywheel.  With  the  single 
reduction,  the  pinion  gear  on  the  armature  shaft  meshes  directly  with 
the  gear  teeth  on  the  flywheel,  as  in  Figs.  323,  330,  and  331.     In  some 

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cases,  however,  a  double  reduction  is  used  in  which  the  gear  ratio  may 
be  as  high  as  25  or  even  40  to  1.  With  the  double  reduction,  as  shown 
in  Fig.  332,  the  pinion  gear  A  on  the  armature  shaft  does  not  mesh 
directly  with  the  teeth  on  the  flywheel  but  with  an  intermediate  gear  B 

Fig.  331. — Starting  motors  with  inboard  (upper)  and  outboard  (Lower)  Bendix  drives. 

which  in  turn  drives  the  flywheel  driving  pinion.  The  double  reduction 
drive  permits  the  use  of  a  very  small  starting  motor  running  at  high 
speed  but  it  has  the  disadvantage  of  being  more  complicated  than  the 
drive  mechanism  of  the  single  reduction  type. 

Fig.  332. — Wagner  starting  motor  with  double  reduction  drive. 

Owing  to  the  high  gear  ratio  between  the  starting  motor  and  the 
engine,  in  all  starters  of  the  flywheel  type,  some  provision  must  be  made 
to  prevent  the  engine  from  driving  the  motor  at  excessively  high  speeds 
when  the  engine  starts  under  its  own  power.  In  starters  having  the  slid- 
ing pinion  type  of  drive,  as  shown  in  Fig.  329,  this  is  taken  care  of  by  an 
overrunning   clutch   incorporated  in  the  intermediate  gear  which  slips 

Digitized  by  LiOOQ IC 


when  the  flywheel  tends  to  drive  the  starting  motor.  Figure  333  shows 
the  construction  of  a  typical  overrunning  clutch.  In  starters  with  either 
the  magnetic  or  Bendix  type  of  drive  the  driving  pinion  is  automatically 
thrown  out  of  mesh  with  the  flywheel  gear  as  the  engine  speeds  up  under 
its  own  power. 

228.  The  Bendix  Drive. — The  automatic  screw  pinion  shift  mechan- 
ism, known  as  the  Bendix  drive,  Fig.  331,  is  built  in  two  distinct  styles, 
the  inboard  type  in  which  the  pinion  shifts  toward  the  motor  to  engage 
with  the  flywheel,  and  the  outboard  type  in  which  the  pinion  shifts  away 
from  the  motor.  The  outboard  type  requires  a  third  bearing  to  support 
the  outer  end  of  the  shaft. 

Fig.  333. — Gray  and  Davis  overrunning  clutch. 

The  construction  of  the  inboard  type  is  shown  in  Fig.  334.  Mounted 
en  the  extended  armature  shaft  is  a  sleeve  having  screw  threads  (usually 
a  triple  thread)  with  stops  at  each  end  to  limit  the  lengthwise  travel  of 
the  pinion,  which,  having  corresponding  internal  threads,  is  mounted  on 
this  sleeve.  This  pinion  is  weighted  on  one  side.  The  sleeve  is  connected 
to  the  motor  armature  shaft  through  a  coil  spring  attached  to  a  collar 
pinned  to  the  armature  shaft.  The  same  method  of  construction  is 
used  in  the  outboard  type. 

The  operation  of  the  Bendix  drive  is  shown  in  Figs.  335  and  336. 
Normally,  the  pinion  is  out  of  mesh  and  entirely  away  from  the  flywheel 
gear.  When  the  starting  switch  is  closed  and  the  full  battery  voltage  is 
impressed  on  the  motor  the  armature  immediately  starts  to  rotate  at 
high  speed.  The  pinion  gear  being  weighted  on  one  side  and  having 
internal  screw  threads,  will  not  rotate  immediately  with  the  shaft  but, 
due  to  its  inertia,  will  run  forward  on  the  revolving  screw  sleeve  until  it 
meets  or  meshes  with  the  flywheel  gear.     If  the  teeth  of  the  pinion  and 


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flywheel  meet  instead  of  meshing,  the  spring  will  allow  the  pinion  to 
revolve  until  it  meshes  with  the  flywheel.  When  the  pinion  is  fully 
meshed  with  the  flywheel  teeth,  the  spring  compresses,  and  the  pinion  is 
then  driven  by  the  motor  through  the  spring  and  turns  the  engine  over. 



Fio.  334. — Construction  of  Eclipse-Bendir  drive. 




STOR         \ 


Fig.  335. — Typical  outboard  Bendix  drive  installation. 

The  spring  acts  as  a  cushion  while  cranking  the  engine  against  compres- 
sion. It  also  breaks  the  severity  of  the  shock  on  the  teeth  when  the 
gears  mesh,  and  in  case  of  back-fire.  When  the  engine  fires  and  runs  on 
its  own  power,  the  flywheel  drives  this  pinion  at  a  higher  speed  than  the 

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armature,  causing  the  pinion  to  be  turned  in  the  opposite  direction  on  the 
screw  and  to  automatically  demesh  from  the  flywheel.  This  prevents  the 
engine  from  driving  the  starting  motor.  The  centrifugal  effect  of 
the  weight  on  one  side  of  the  pinion,  when  automatically  demeshed  from 
the  flywheel,  holds  the  pinion  to  the  sleeve  in  a  demeshed  position  until  the 
starting    switch    is    opened  and  the  motor  armature  comes  to  rest. 

Fro.  336. — Operation  of  Bendix  drive  inboard  type. 

Among  the  chief  advantages  claimed  for  this  type  of  motor  drive  are: 

1.  Simplicity  of  construction. 

2.  Mechanism  automatic  in  operation,  requiring  no  skill  from  the 

3.  High  cranking  speed,  owing  to  the  fact  that  the  starting  motor 
is  permitted  to  attain  full  speed  before  the  load  is  applied. 



Fro.  337. — North  East  starter-generator  on  Dodge  oar. 

4.  The  engine  is  given  a  high  "break  away"  cranking  torque,  thus 
requiring  the  minimum  amount  of  cranking  and  minimizing  the  demand 
on  the  battery. 

5.  Better  carburetion  and  easier  starting  in  cold  weather. 

229.  Motor-generator  Drives. — The  North  East  starter-generator 
installation  on  the  Dodge  car,  Fig.  337,  and  the  Dyneto  installation  on 

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the  Franklin  car,  Fig.  338,  are  typical  installations  of  single-unit  systems 
in  which  the  motor-generator  is  driven  by  a  silent  chain  from  the  crank- 
shaft. The  gear  ratio  in  these  installations  is  usually  2%  or  3  to  1  so  that 
the  armature  speed  is  2%  or  3  times  the  crankshaft  speed  when  operating 

Fio.  338. — Dyneto  motor-generator  installation  on  Franklin  engine  showing  chain  drive. 

either  as  a  generator  or  as  a  motor.  No  overrunning  clutch  is  used. 
Although  the  chain  runs  in  oil,  it  will  gradually  lengthen  through  wear 
and  must  be  adjusted  from  time  to  time  to  prevent  noise  and  "climbing" 
of  the  sprockets.     In  the  North  East  system  on  the  Dodge,  provision  is 






Fiq.  339. — Delco  motor-generator  installation  on  Buick  showing  separate  generator  and 

motor  drives. 

made  for  adjusting  the  chain  by  an  eccentric  adjusting  ring  on  the  for- 
ward end  of  the  starter-generator  where  its  frame  extends  through  the 
timing  gear  housing.  By  turning  the  eccentric  ring,  the  starter-generator 
can  be  moved  farther  away  or  closer  to  the  engine  until  the  required 

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chain  adjustment  is  obtained.  The  chain  should  be  adjusted  so  that  it 
has  an  up  and  down  movement  of  about  %  in.  In  the  Dyneto  system, 
similar  adjustment  may  be  made  by  loosening  the  three  screws  A  and 
backing  out  the  adjusting  set  screw  B  (not  shown  in  cut)  until  it  forces 
the  starter  away  from  the  engine  base  and  gives  the  chain  the  proper 

The  Delco  motor-generator,  Fig.  339,  differs  from  other  types  in 
that  it  has  a  generator  drive  independent  of  the  motor  drive.  As  a 
generator,  the  armature  is  driven  from  the  front  end  at  1  or  1^  times 
crankshaft  speed  through  an  overrunning  clutch  on  the  rear  end  of  the 
pump  shaft,  but  when  operating  as  a  starting  motor  the  rear  end  of  the 
armature  is  connected  to  the  engine  through  gears  meshed  with  the 


Fiq.  340. — Westinghouse  2-pole  square  type  generator  with  field  winding  on  one  polo. 

rim  of  the  flywheel,  the  cranking  gear  ratio  being  usually  about  25 
to  1.  This  change  in  gear  ratio  is  permitted  by  the  slipping  of  the  over- 
running clutch  in  the  generator  drive  end.  Another  overrunning  clutch 
is  provided  in  the  idler  of  the  motor  drive  gears,  to  prevent  the  flywheel 
from  driving  the  armature  through  the  starter  drive  when  the  engine 
speeds  up  under  its  own  power. 

230.  Construction  of  the  Dynamo. — The  dynamo  is  an  electric  machine 
which  by  the  principle  of  electromagnetic  induction  may  be  used  for  the 
conversion  of  either  electrical  energy  into  mechanical  energy  or  mechan- 
ical energy  into  electrical  energy.  When  the  dynamo  is  used  for  convert- 
ing electrical  energy  into  mechanical  energy,  it  is  called  a  motor,  and 
when  it  is  used  for  converting  mechanical  energy  into  electrical  energy  it 
is  called  a  generator.  Likewise,  when  a  dynamo  is  used  both  as  a  genera- 
tor and  as  a  motor,  such  as  in  the  case  of  the  single-unit  system  on  the 
automobile,  the  dynamo  is  usually  termed  a  motor-generator. 

The   component  parts  of  the  automobile  generator  are  shown  in' 

Digitized  by  LiOOQ IC 



Figs.  340,  341,  342,  and  343  and  consist  essentially  of  an  armature,  a 
field  frame,  field  coils,  and  brushes.  The  construction  differs  materially 
from  the  magneto  since  the  generator  operates  in  conjunction  with  the 
storage  battery  and  must  generate  direct  current.  It  must  also  be 
designed  to  permit  regulation  of  the  generator  output  at  high  engine 

Fig.  341. — Westinghouse  4-pole  square  type  generator  with  field  winding  on  2  poles. 

speeds,  which  is  unnecessary  in  the  magneto  used  for  ignition  purposes. 
Instead  of  using  permanent  magnets  for  producing  the  magnetic  field 
of  the  generator,  the  field  is  produced  by  electromagnets  or  "poles" 
magnetized  by  field  winding  or  field  coils  through  which  direct  current  is 




Fig.  342. — Westinghouse  4-pole  round  type  generator  with  field  winding  on  each  pole. 

made  to  flow.  The  field  frame  may  be  either  an  iron  or  steel  casting 
or  it  may  be  made  up  of  a  short  piece  of  4  in.  to  6  in.  steel  tubing  in 
which  poles  of  soft  iron  are  held  in  place  by  machine  screws.  The  frame 
may  have  two,  four,  or  six  poles,  although  the  two-  and  four-pole  frames 
are  the  most  common.     Figure  344  shows  several  types  of  dynamo  frames 

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most  commonly  used  and  the  magnetic  field  circuits  in  each.     It  will  be 
noticed  that  in  some  types  the  field  winding  is  wound  on  each  pole  while  in 

*  CUT  OUT 



Fio.  343. — Parts  of  Gray  &  Davis  generator. 

Field  coils 







^ ^ 


F  G 

Fio.  344. — Types  of  dynamo  field  frames. 

others  there  is  but  one  field  coil  to  two  poles.  In  the  latter  case,  the  manu- 
facturer puts  more  winding  in  a  single  field  coil  instead  of  distributing  it  in 
smaller  coils  on  all  poles.     It  will  also  be  noticed  that  in  the  two-pole 

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type  frame  the  magnetic  field  flows  directly  across  the  armature,  while 
in  the  four-  and  six-pole  types  each  magnetic  circuit  cuts  through  only 
a  portion  of  the  armature  core.  For  this  reason  the  armature  must  be 
constructed  in  accordance  with  the  number  of  field  poles,  since  it  is  the 
cutting  of  the  magnetic  field  by  the  winding  on  the  armature  in  passing 
the  pole  pieces  which  enables  the  generator  to  generate  current  when 
the  armature  is  rotated.  The  current  is  collected  from  the  armature 
coils  by  the  brushes — usually  carbon — which  make  rubbing  contact  on 
the  commutator.  The  commutator  consists  of  a  series  of  insulated  copper 
segments  mounted  on  one  end  of  the  armature,  each  segment  connecting 
to  one  or  more  armature  coils.  The  commutator  also  serves  to  convert 
the  alternating  current,  as  generated  in  the  armature  coils,  into  direct 
current  to  make  it  suitable  for  battery  charging  purposes. 


-J  / 

f  eE» 

•     \    '' 

_^      *  V 

-Z   M  c 



^\  5 





Fig.  345. — Principle  of  simple  alternating  current  generator. 

231.  The  Simple  Alternating  Current  Generator. — It  has  been  found 
that  if  a  single  loop  of  wire  is  revolved  in  the  magnetic  field  between  a 
North  pole  and  a  South  pole,  there  will  be  an  electrical  pressure  induced 
in  the  two  sides  of  the  loop;  also,  that  the  voltage  and  current  induced 
will  be  in  definite  relation  to  the  direction  of  magnetism  and  the  direction 
of  rotation.  If  the  terminals  of  the  loop  are  connected  to  two  metal 
collector  rings,  such  as  A  and  B,  Fig.  345,  upon  which  brushes  rest,  this 
induced  electrical  pressure  will  cause  a  current  to  flow  through  any 
external  circuit  which  may  be  connected  across  the  two  brushes. 

If  the  loop  be  rotated  through  a  complete  revolution,  sides  A  and  B 
will  cut  magnetic  lines  of  force  first  in  one  direction,  then  in  the  other, 
thereby  inducing  an  alternating  voltage  across  the  brushes  and  causing 
an  alternating  current  to  flow  through  the  external  circuit.     As  a  study 

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of  Fig.  345^4  and  B  will  show,  the  current  will  make  one  complete  re- 
versal in  one  revolution  of  the  loop.  The  value  of  the  current  during 
one  complete  revolution  of  the  loop  may  be  represented  graphically  by 
the  curve  shown  in  Fig.  346,  known  as  the  sine  curve.  The  highest  and 
lowest  points  of  the  curve  represent  the  current  at  its  maximum  value, 
which  is  reached  when  the  loop  is  in  a  horizontal  position. 

Fio.  346. — Current  wave  from  simple  alternating  current  generator. 

232.  The  Simple  Direct-current  Generator. — The  alternating  current 
produced  in  the  loop  may  be  converted  into  direct  current  in  the  external 
circuit  by  replacing  the  two  collector  rings  with  a  simple  two-segment 
commutator,  as  shown  in  Fig.  347.  The  two  segments  of  the  commutator 
are  connected  to  the  two  ends  of  the  loop  but  insulated  from  each  other. 


SI  *       ■     ■  ■■ 

\X \  '' 

i&- 4' 







Fio.  347. — Principle  of  simple  direct-current  generator. 

The  only  connection  between  the  commutator  segments  besides  through 
the  armature  loop  is  through  the  brushes  and  the  external  circuit.  The 
brushes  remain  stationary  and  make  rubbing  contact  first  with  one 
segment  and  then  with  the  other,  as  the  commutator  and  loop  rotate  as 
a  unit.     With  this  arrangement  it  will  be  noted  that  as  fast  as  the  loop 

Digitized  by  LiOOQ IC 



turns  over  and  as  fast  as  the  induced  voltage  reverses  in  the  loop,  the 
segments  change  connection  with  the  brushes  and  the  current  is  made  to 
flow  each  time  through  the  external  circuit  in  the  same  direction.  The 
current  thus  obtained  is  direct  current  and  may  be  graphically  represented 
as  in  Fig.  348.  Comparing  Fig.  348  with  Fig.  346,  it  will  be  noted  that 
the  chief  accomplishment  has  been  to  direct  both  impulses  of  current  in 
the  same  direction. 



Fig.  348. — Current  wave  from  simple  direct-current  generator. 

Such  a  direct-current  generator,  constructed  with  an  armature  of 
a  single  winding  of  one  or  more  turns,  would  be  very  inefficient  and  un«- 
satisfactory  in  that  the  current  would  pulsate  in  value.  To  overcome 
this  trouble,  the  armature  core,  which  is  in  the  form  of  a  laminated  iron 
cylinder,  is  wound  with  a  great  many  coils  equally  spaced  around  its 

c  _ 


Fia.  349. — Principle  of  the  direct-current  motor. 

circumference,  each  coil  being  connected  to  segments  in  the  commutator. 
These  coils  are  connected  so  that  the  current  impulse  of  one  coil  overlaps 
the  current  impulse  of  the  next,  much  the  same  as  the  overlapping  of 
the  power  impulses  in  an  8-  or  12-cylinder  engine.  The  result  is  practically 
a  continuous  steady  flow  of  current. 

233.  The  Simple  Direct-current  Motor. — A  direct-current  motor  is  a 
dynamo  which  will  run  as  a  motor  on  direct  current.     If  the  brushes  of 

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the  simple  generator  shown  in  Fig.  347  are  connected  to  a  battery  and 
current  permitted  to  flow  through  the  loop  of  wire  as  shown  in  Fig.  349, 
the  loop  of  wire  will  rotate  as  a  motor  in  the  direction  indicated  by  the 
arrow.  Briefly,  the  cause  of  this  rotation  may  be  explained  as  being  due 
to  the  repulsion  between  the  field  magnetism  and  the  magnetic  field  (set 
up  around  the  loop  of  wire)  produced  by  the  current  flowing  in  the  wire. 
In  Fig.  350  is  shown  a  simple  experiment  from  which  may  be  readily 



S        1 

Vn  VflVn  !  pulsion 






Fiq.  350. — Experiment  showing  the  relation  between  direction  of  magnetism,  direction  of 
current,  and  the  direction  of  wire. 

determined  the  direction  of  this  repulsion  in  relation  to  the  direction 
of  current  and  magnetism.  If  the  magnet  is  placed  so  that  the  North 
(N)  pole  is  above  the  wire  (W)  and  current  is  sent  through  the  loop  of 
wire,  in  at  E  and  out  at  F  as  shown,  the  wire  will  be  repulsed  to  the  posi- 
tion Wi.  The  repulsion  is  caused  by  all  of  the  magnetic  lines  of  force 
tending  to  flow  around  the  conductor  in  the  same  direction  and  the  con- 
sequent distortion  and  crowding  of  the  magnetic  lines  on  one  side  of  the 

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conductor  more  than  on  the  other.  This  results  in  a  repulsion  of  the  con- 
ductor as  shown  in  Fig.  3502?.  On  the  other  hand,  if  the  magnet  is 
reversed,  thus  reversing  the  magnetism,  but  the  direction  of  current  is 
unchanged,  the  magnetic  lines  of  force  will  crowd  to  the  other  side  of  the 
conductor  and  it  will  be  repelled  in  the  opposite  direction  as  shown  in 
Fig.  350C  and  the  wire  will  be  repulsed  to  the  position  W2,  Fig.  350A. 
The  same  action  would  result  if  the  current  were  reversed  instead  of  the 
magnetism.  Thus,  in  Fig.  349-4.,  owing  to  the  current  flowing  in  the 
two  sides  of  the  loop  A  and  B  in  reverse  directions  and  the  consequent 
field  distortion  as  shown  in  Fig.  349J5,  A  will  be  repulsed  upward  and 
B  downward  and  the  loop  will  rotate  m  a  clockwise  direction. 

Fig.  351. — Parts  of  Westinghousc  starting  motor,  mechanical  pinion  shift  type. 

In  practice,  such  as  in  the  starting  motor  shown  in  Fig.  351,  the  motor 
armature  has  many  armature  coils  equally  spaced  around  the  entire 
circumference  of  the  armature  core,  each  of  which  carries  current  and, 
consequently,  exerts  a  force  to  rotate  the  armature  as  it  passes  the  pole 
pieces.  The  result  is  a  comparatively  high  turning  power  or  torque  which 
if  applied  through  suitable  gear  reduction  is  sufficient  to  crank  the  engine. 

234.  The  Shunt-wound  Generator. — In  all  generators  and  motors 
now  used  as  standard  equipment  on  the  automobile,  the  magnetic  field 
is  produced  by  a  field  winding  of  either  the  shunt  or  series  type,  or  a  com- 
bination of  the  two.  The  shunt  type  of  field  winding  is  particularly 
adapted  to  the  generator,  while  the  series  type  is  especially  adapted  to 
the  starting  motor. 

In  the  shunt-wound  generator,  the  field  winding  is  connected  across 
the  brushes  of  the  generator  as  in  Fig.  352,  so  that  about  8  to  12  per  cent, 
of  the  total  current  generated  by  the  armature  is  shunted  through  the 
field  coils  for  producing  the  field  magnetism.     In  the  series  type  of  wind- 

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ing,  Fig.  353,  all  the  current  which  flows  through  the  armature  must  also 
flow  through  the  field  winding. 

If  a  generator  field  frame  should  be  tested  with  a  magnetic  compass  it 
will  be  found  that  the  frame  will  show  North  and  South  magnetic  polarity 






Fio.  352. — Principle  of  shunt-wound  generator. 

at  the  pole  pieces,  even  with  the  generator  dismantled.  This  magnetism 
is  known  as  residual  magnetism.  It  is  simply  the  magnetism  which 
remains  in  the  pole  pieces  and  frame  after  the  field  magnetizing  current 
has  died  out.  The  direction  of 
this  magnetism  will  always  be  in 
the  same  direction  as  the  field 
through  the  poles,  when  they 
were  last  magnetized.  Thus  the 
generator  frame  may  be  given 
residual  magnetism  by  simply 
sending  direct  current  through 
the  shunt  field  winding  from 
either  a  storage  battery,  or  a  set 
of  dry  cells.  The  residual  mag- 
netism may  be  reversed  by  re- 
versing the  direction  of  the 
magnetizing  current. 

In  Pig.  352,  which  represents 
a  shunt-wound  generator,  one  armature  coil  only,  of  the  simplest  type,  is 
shown,  although  the  armature  may  be  considered  as  being  wound  full  of 
similar  coils  distributed  at  equal  intervals  around  the  armature,  each  coil 
being  connected  to  the  commutator  the  same  as  the  one  shown.  Such 
an  armature  is  called  a  drum  wound,  open-circuited,  2-pole  type  arma- 
ture. The  open-circuited  type  armature,  however,  is  no  longer  used 
for  automobile  generators,  having  been  replaced  by  the  closed-circuit 

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type.  The  principle  of  operation,  however,  is  the  same  and  much  more 
easily  understood. 

The  principle  of  operation  of  a  shunt-wound  generator  is  as  follows: 
In  Fig.  352  let  it  be  assumed  that  the  armature  rotates  in  a  clockwise 
direction  as  indicated  by  the  arrow,  and  that  (n)  and  (s),  marked  on  the 
pole  pieces,  represent  the  direction  of  residual  magnetism  which  is  across 
the  armature  from  left  to  right.  When  the  armature  is  rotated,  the 
armature  coils,  cutting  the  weak  magnetic  field  produced  by  the  residual 
magnetism,  will  set  up  a  slight  voltage  across  the  brushes,  usually  1  to 
13^  volts,  making  the  upper  brush  positive  and  the  lower  brush  negative. 
This  voltage  is  sufficient  to  overcome  the  resistance  in  the  shunt-field 
winding  connected  across  the  two  brushes,  thereby  causing  a  current  to 
flow  from  the  positive  (+)  brush  through  the  field  winding  around  the 
pole  pieces  to  the  negative  (— )  brush.  If  the  magnetic  effect  of  this 
field  current  is  in  the  same  direction  as  the  residual  magnetism  (as  in  our 
example)  the  pole  strength  will  be  increased  and  tliis  in  turn  will  increase 
the  magnetic  flux  through  the  armature.  Since  the  armature  coils  will 
then  be  permitted  to  cut  more  magnetic  lines  of  force  per  revolution, 
the  voltage  across  the  brushes  will  also  be  increased.  An  increase  in 
brush  voltage  increases  the  field  strength  which  in  turn  increases  arma- 
ture output.  Thus  the  armature  voltage  helps  the  field  and  the  field 
helps  the  armature  voltage  until  the  generator  reaches  its  normal 
operating  voltage.  This  process,  which  all  automobile  generators 
must  go  through  in  producing  a  voltage,  is  called  the  "building  up"  of 
the  generator. 

235.  Conditions  Which  Prevent  a  Generator  from  Building  Up. — 
From  the  foregoing  it  will  be  noted  that  several  conditions  are  necessary 
to  permit  the  generator  to  build  up  a  voltage.  Two  of  the  most  im- 
portant requirements  are  that  the  field  frame  have  residual  magnetism 
as  a  foundation  on  which  to  build,  and  that  the  direction  of  the  current 
in  each  field  coil  be  in  such  direction  around  the  pole  that  the  field  current 
will  produce  magnetism  to  assist  this  residual  magnetism.  Otherwise, 
the  voltage  cannot  build  up  higher  than  that  produced  by  the  residual 
magnetism.  Other  common  conditions  which  prevent  the  generator 
from  building  up  are: 

1.  Reversed  direction  of  armature  rotation. 

2.  Open  in  shunt  field  circuit  due  to:  blown  fuse,  broken  wire,  loose 
connection,  etc. 

3.  Heavy  short  circuit  across  the  main  brushes. 

4.  Brushes  worn,  broken,  or  sticking  in  their  holders. 

5.  Weak  spring  tension  on  brushes. 

6.  Dirty  commutator  or  high  mica  preventing  the  brushes  making 
proper  contact. 

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7.  Short-circuited,  open,  or  grounded  field  coils. 

8.  Short-circuited,  open,  or  grounded  armature  coils. 

9.  Field  coils  opposed  on  two  pole  generator. 

10.  Brushes  in  wrong  position  on  the  commutator. 
236.  Types  of  Field  Winding. — Various  methods  may  be  used  in 
winding  the  field  poles  of  a  dynamo  to  suit  the  purpose  for  which  it  is 



E«tE5  FltLD, 
tjl        SHUNT   riCLo\ 

(C)  cumVlative  compound  wound 






Fig.  354. — Types  of  dynamo  field  windings. 

to  be  used.  Figure  354  shows  the  different  ways  in  which  the  shunt  and 
series  field  may  be  connected  on  the  same  type  of  frame,  the  markings 
and  arrows  referring  in  each  case  to  the  dynamo  when  operating  as  a 
generator.    These  markings  do  not  represent  the  conditions  when  current 

Digitized  by  LiOOQ IC 


is  sent  through  the  machine  causing  the  dynamo  to  operate  as  a  motor. 
The  small  diagram  to  the  right  of  each  main  sketch  is  the  conventional 
way  of"  indicating  briefly  that  particular  type  of  D.  C.  dynamo.  By 
applying  the  right-hand  rule  for  determining  the  magnetic  polarity  of 
an  electromagnet  (as  given  in  Chapter  VI)  it  will  be  seen  that  in  Fig.  354, 
C  and  D,  the  shunt  and  series  winding,  create  magnetism  in  the  same 
direction,  while  in  E  and  F  the  magnetism  produced  by  a  current  flowing 
in  the  series  field  winding  will  oppose  that  produced  by  the  shunt  winding. 
When  a  shunt  and  series  winding  operate  to  create  magnetism  in  the 
same  direction  they  are  said  to  be  cumulative  wound,  and  when  they 
operate  to  oppose  each  other  they  are  said  to  be  differentially  wound. 
The  shunt  field  may  be  connected  either  inside  or  outside  of  the  series 
field  winding.  When  it  is  connected  inside,  as  in  C  and  E,  it  is  known 
as  a  short  shunt  connection,  and  when  it  is  connected  outside  the  series 
as  in  D  and  Ff  it  is  known  as  a  long  shunt  connection.  The  principle 
of  each  is  very  similar,  the  difference  being  that  in  the  long  shunt  con- 
nection the  shunt-field  current  must  pass  through  both  the  shunt  and 
series  field  coils  to  complete  its  circuit. 

In  practice,  types  C  and  D  are  not  used  on  the  automobile,  owing 
to  the  fact  that  any  increase  in  armature  speed  and  output  would  increase 
the  field  strength,  causing  an  overloading  of  the  generator.  The  simple 
shunt  type  of  winding  used  in  conjunction  with  a  suitable  regulator  is 
the  type  of  field  winding  chiefly  used  for  the  generator,  while  the  series 
type  of  winding  is  used  in  the  starting  motor,  owing  to  the  fact  that  all 
the  current  through  the  armature  must  flow  through  the  field  winding 
thus  giving  the  motor  the  greatest  possible  cranking  power.  Types 
E  and  F  are  used  in  both  generators  and  motor-generators.  This  type 
of  winding  is  particularly  adapted  for  motor-generators  since  the  windings 
operate  differentially,  the  series  bucking  the  shunt,  for  regulating  pur- 
poses when  operating  as  a  generator,  and  cumulative,  the  series  helping 
the  shunt,  when  current  is  sent  through  the  machine  in  the  reverse  direc- 
tion when  operating  as  a  starting  motor.  This  action  is  possible,  due  to 
the  fact  that  the  current  will  reverse  in  the  series  winding  and  not  in 
the  shunt  winding,  if  the  current  is  reversed  through  the  dynamo,  as  a 
study  of  the  figures  will  show.  In  a  generator  of  the  differential  wound 
type,  the  series  winding,  which  is  commonly  known  as  reverse  series  or 
bucking  series,  is  used  only  for  regulating  purposes,  the  shunt  winding 
being  the  prevailing  winding  and  controlling  the  direction  of  magnetism. 
The  shunt  winding  is  distinguished  from  the  series  winding  since  it  con- 
sists of  a  large  number  of  turns  of  comparatively  small  wire,  while  the 
series  winding  consists  of  a  comparatively  few  turns  of  large  wire.-  Both 
windings  are  well  insulated  and  in  some  cases  impregnated  with  a  spe- 
cial compound  to  make  them  water  and  oil  proof. 

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237.  The  Reverse  Current  Cut-out — The  reverse  current  relay  or 
cutout  is  an  automatic  electromagnetic  switch  connected  in  the  battery 
charging  circuit  between  the  generator  and  the  storage  battery  of  the 
electric  system.  Its  function  is  to  connect  automatically  the  generator 
to  the  battery  when  the  voltage  of  the  generator  is  sufficient  to  charge 
the  battery  and  to  disconnect  the  two  when  the  generator  is  not  running 
or  when  its  voltage  falls  below  that  of  the  battery  to  prevent  the  battery 
discharging  through  the  generator  windings.  In  these  respects  the  action 
of  the  cut-out  is  very  similar  to  that  of  the  check  valve  connected  between 
the  pump  and  the  reservoir  as  shown  in  Fig.  324. 

A  circuit  diagram  of  a  typical  cut-out  is  shown  in  Fig.  355,  in  which  it 
is  shown  connected  with  a  differentially  wound  generator  and  a  6-volt 
storage  battery.     As  will  be  noted  from  the  diagram,  tjie  cut-out  con- 


\  CUT*  OUT  ■fWM*      cu-juouti 

cuwuntcou.     c?2IfCTy        ^Snmt^et 

(Hf  AVY  WINPNM)        *■**>    f         s' 







Fio.  355. — Wiring  diagram  of  a  typical  reverse  current  cut-out. 

8ist8  of  an  iron  core,  a  fine  shunt  winding  known  as  a  voltage  coil,  a  heavy 
series  winding  known  as  a  current  coil,  and  a  set  of  contacts.  One  of  the  con- 
tacts is  carried  on  one  end  of  an  iron  contact  arm  that  is  mounted  close  to 
but  held  apart  from  the  core,  by  spring  tension.  The  contact  points  are 
thus  held  normally  open  and  are  closed  only  when  the  magnetic  pull  of 
the  core  on  the  contact  arm  is  sufficient  to  overcome  the  tension  of  the 
spring.  The  spring  is  adjusted  so  that  the  contacts  will  close  when  the 
voltage  of  the  generator  has  reached  from  6H  to  7  volts  in  a  6-volt  system 
or  13  to  14  volts  in  a  12-volt  system.  These  voltages  are  usually  at- 
tained, causing  the  cut-out  to  close  at  a  car  speed  of  from  8  to  10  miles 
per  hour  on  direct  drive. 

The  voltage  coil,  which  consists  of  many  turns  of  a  fine  winding,  is  con- 
nected across  the  generator  terminals  so  as  to  receive  the  full  voltage  of 
the  generator.    When  the  generator  attains  a  speed  at  which  it  develops 


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approximately  7  volts  the  core  is  sufficiently  magnetized  to  overcome 
the  spring  tension  and  to  close  the  cut-out  contacts.  This  completes 
the  circuit  between  the  generator  and  the  battery.  Since  the  voltage 
of  the  generator  at  this  time  is  higher  than  the  voltage  of  the  battery  a 
charging  current  will  flow  from  the  positive  (+)  terminal  of  the  genera- 
tor, through  the  current  coil  and  contacts  of  the  cut-out,  through  the 
cells  of  the  battery  from  positive  (+)  to  negative  (— )  returning  through 
the  ground  to  the  negative  terminal  of  the  generator.  It  will  be  noticed 
that  the  charging  current  flowing  through  the  current  coil  flows  around 
the  core  and  creates  a  magnetic  effect  in  the  core  in  the  same  direction 
as  that  produced  by  the  voltage  coil.  This  greatly  increases  the  mag- 
netic pull  on  the  contact  arm  and  holds  the  contacts  firmly  closed. 

When  the  speed  of  the  generator  is  decreased  to  a  value  at  which  its 
voltage  is  lower  than  that  of  the  battery,  that  is,  below  6  volts,  or  when 
the  generator  is  at  rest,  a  momentary  discharge  of  the  battery  through 
the  current  coil  takes  place  in  the  reverse  direction  to  the  voltage  coil 
and  the  core  is  demagnetized.  The  instant  the  core  demagnetizes,  the 
spring,  which  is  under  tension,  pulls  the  contact  arm  away  from  the  core 
and  opens  the  circuit.  The  cut-out  should  be  adjusted  to  open  when  the 
discharge  current,  as  indicated  by  the  ammeter,  is  between  zero  and  2 
amperes,  preferably  as  near  zero  as  possible  to  prevent  flashing  of  the 
contact  points. 

The  ammeter  is  usually  connected  as  shown  so  that  it  will  register 
the  amount  of  current  either  charging  or  discharging  from  the  battery. 
The  car  speed  at  which  the  cut-out  opens  should  be  2  to  3  miles  per  hour 
below  tjie  closing  speed.  These  speeds  may  be  determined  by  increasing 
and  decreasing  the  speed  of  the  car  gradually  and  noting  the  readings 
of  the  speedometer  when  the  ammeter  first  shows  charge  and  again  when 
it  returns  to  zero.  Another  method  of  determining  whether  the  cut-out 
is  closing  properly,  if  the  car  is  not  running,  is  to  start  the  engine,  turn 
on  the  headlights,  and  watch  the  brilliancy  of  the  headlights  as  the  engine 
is  gradually  increased  in  speed.-  In  most  cases,  as  soon  as  the  engine 
reaches  a  speed  of  600  to  800  revolutions  per  minute  (corresponding  to 
a  driving  speed  of  8  to  10  M.P.H.),  it  will  be  noticed  that  the  lights 
brighten  up.  This  sudden  increase  in  brilliancy  will  occur  at  the  instant 
the  cut-out  closes  and  is  due  to  the  increased  voltage  impressed  across  the 
lamps,  namely,  from  7  to  7)4  volts  instead  of  6  volts  when  the  generator 
is  connected  to  the  battery  and  the  lamp  circuit. 

238.  Regulation  of  the  Generator. — Owing  to  the  fact  that  all  genera- 
tors used  on  the  automobile  have  the  characteristic  of  increasing  in 
voltage  and  current  output  with  increase  in  engine  speed,  some  method 
of  generator  regulation  is  necessary  to  protect  the  generator  windings 
and  brushes  against  excessive  current*  overload  and  the  battery  from 

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overcharge.  Several  methods  of  regulation  are  possible  such  as:  (1) 
controlling  the  speed  of  the  armature  through  mechanical  governors, 

(2)  controlling  the  strength  of  the  field  current  which  in  turn  controls 
the  strength  of  the  field  magnetism  cut  by  the  armature  windings,  and 

(3)  controlling  the  current  output  by  a  mechanically  operated  rheostat 
(adjustable  resistance  unit)  placed  in  series  with  the  battery,  the  resist- 
ance of  the  battery  charging  circuit  being  increased  or  decreased  as  the 
armature  speed  increases  or  decreases.  The  first  and  third  methods  have 
not  proved  satisfactory  so  that  the  various  methods  of  regulation  now 
in  use  all  operate  on  the  principle  of  controlling  the  field  magnetism — 
decreasing  the  field  strength  as  the  armature  speed  increases,  thus  striv- 
ing to  hold  the  generator  output  constant. 

Regulation  of  the  field  magnetism  may  be  effected  in  three  principal 

1.  Through  reverse  series  (differential)  field  winding  in  which  a  series 
winding  opposes  the  shunt  winding  more  and  more  as  the  generator  speed 
and  output  increase. 

2.  A  vibrating  type  relay  in  which  a  resistance  unit  is  cut  in  and  out 
of  the  shunt-field  circuit  to  obtain  either  current  or  voltage  regulation, 
or  both. 

3.  The  third  brush  principle  of  regulation,  which  depends  upon  the 
reactions  that  take  place  in  the  armature  and  the  resulting  distortion 
of  the  path  of  field  magnetism  through  the  armature,  as  the  generator 
increases  in  speed  and  current  output. ' 

239.  Generator  Regulation  through  Reverse  Series  Field  Winding. 
—The  reverse  series  or  bucking  field  method  of  generator  regulation  is 
one  of  the  simplest  methods  in  use  from  the  standpoint  of  construction 
and  operation.  It  is  simple,  in  view  of  the  fact  that  the  regulation  is 
taken  care  of  by  the  inherent  action  of  the  field  winding  which  does  not 
involve  any  wearing  or  moving  parts,  and  requires  no  adjustment.  Two 
typical  methods  of  connecting  the  shunt  and  series  field  windings  to 
obtain  this  regulation  were  shown  in  Fig.  354J?  and  F,  Fig.  3542?  showing 
the  short  shunt  and  Fig.  354^  showing  the  long  shunt  method  of  connect- 
ing the  windings.  The  principle  of  each,  however,  is  very  similar,  the 
difference  being  that  in  the  long  shunt  connection  the  shunt-field  current 
must  pass  through  both  the  shunt  and  series  field  coils  to  complete  its 

A  typical  application  of  the  reverse  series  method  of  generator  regu- 
lation is  found  in  the  Auto-Lite  two-pole  laminated  frame  type  generator 
Bhown  in  Fig.  356.  From  the  diagram,  Fig.  357,  it  will  be  noted  that  the 
field  winding  is  of  the  long  shunt  type  in  that  one  end  of  the  shunt  wind- 
ing is  connected  at  the  outer  end  of  the  series.  The  circuits  of  the  cut- 
out relay  will  be  found  similar  to  those  described  for  Fig.  355. 

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Referring  to  Fig.  357,  the  principle  of  operation  is  as  follows:  As  the 
generator  builds  up  a  voltage,  two  circuits  are  established  between  the 
brushes,  one  through  the  shunt  field  winding,  magnetizing  the  field  frame 
North  and  South  as  shown,  the  other  through  the  voltage  coil  winding  of 

the  cut-out  relay.  Both  of  these  cir- 
cuits lead  through  the  series  field 
winding  and  complete  their  circuits 
as  indicated  by  the  arrows  in  the 
diagram.  At  the  speed  at  which  the 
cut-out  closes,  connecting  the  genera- 
tor with  the  battery,  the  generator 
voltage  is  only  slightly  above  that  of 
the  battery  and  a  small  current  will 
flow  through  the  battery  in  the  charg- 
ing direction.  The  path  of  this  cur- 
rent is  from  the  positive  (+)  brush 
through  the  reverse  series  field  wind- 
ing, over  the  cut-out  contacts  through 
the  current  coil,  through  the  ammeter  and  battery  from  positive  (+)  to 
negative  (  — )  returning  through  the  ground  to  the  negative  (  — )  brush 
of  the  generator.  As  this  charging  current  flows  through  the  reverse 
series  fieM  winding  in  a  reverse  direction  to  the  current  flowing  in  the 

Fig.  366. — Auto-lite  generator, 
Model  G. 



(mounted  either  on  6ene**tor 

TO  CLOSE  AT  &£  TO  7  VOLTS) 

Fio.  357. — Circuit  diagram  of  auto-lite  generator  and  cut-out  relay  showing  reverse 
series  field  method  of  generator  regulation. 

shunt  winding,  a  demagnetizing  force  is  produced  in  the  field  frame 
which  increases  with  increase  in  generator  speed  and  current  output  to 
the  battery.  The  result  is  a  weakening  of  the  field  magnetism  as  the 
armature  speed  increases,  so  that,  after  the  maximum  desired  charging 

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rate  is  reached,  which  is  usually  12  to  14  amperes  at  18  to  20  miles  per 
hour,  the  current  output  of  the  generator  will  never  exceed  the  predeter- 
mined amount  even  though  the  generator  is  driven  at  a  very  high  rate 
of  speed. 

It  will  be  noted  that  the  regulation  depends  upon  the  current  flow- 
ing in  the  reverse  series  winding.  Consequently,  since  this  regulating 
current  constitutes  the  current  supplied  by  the  generator  to  the  battery 
and  the  lighting  system  (in  case  the  lights  should  be  turned  on),  it  is  very 
essential  that  an  open-circuit  does  not  occur  in  the  battery  charging  cir- 
cuit, otherwise  the  charging  current  will  be  obstructed  and  the  regulation 
of  the  generator  destroyed.  Precautions,  therefore,  must  be  taken*8t  all 
times  to  see  that:  the  cut-out  closes  properly;  the  connections  of  the  gen- 
erator, cut-out,  and  ammeter  are  clean  and  tight;  and  that  the  battery 
terminals  are  always  tight  and  free  from  corrosion.  If  such  an  open- 
circuit  should  occur  in  the  charging  circuit  destroying  generator  regu- 
lation, the  voltage  will  become  excessive,  usually  resulting  in  damage  to 
the  field  and  armature  winding,  also  the  winding  of  the  cut-out.  In  case 
the  open  in  the  circuit  exists  at  either  of  the  battery  terminals,  the  lights 
may  also  be  burned  out  if  they  were  turned  on  with  the  generator  run- 
ning at  speed  above  15  to  18  miles  per  hour  or  above  the  speed  at  which 
regulation  should  begin.  If  for  any  reason  the  car  is  to  be  operated  with 
the  battery  disconnected,  the  system  should  be  protected  by  connecting 
a  piece  of  copper  wire  across  the  two  generator  terminals.  This  short-  * 
circuits  the  brushes  through  the  reverse  series  winding  and  prevents  the 
generator  from  building  up  a  voltage. 

240.  Current  Regulation  of  the  Generator  through  Vibrating  Type 
Relay. — A  circuit  diagram  of  a  typical  vibrating  type  regulator  used  for 
obtaining  constant  current  regulation  of  the  generator  is  shown  in  Fig. 
358.  As  may  be  seen  from  the  diagram,  the  regulating  relay  consists 
of  a  soft  iron  core,  around  which  is  wound  a  single  winding;  a  current 
coil  of  heavy  wire;  a  set  of  regulator  contact  points,  held  normally  closed 
by  spring  tension;  and  a  resistance  unit,  which  is  connected  across  the 
two  regulator  contact  points. 

The  purpose  of  this  regulating  relay  is  to  control  the  current  output 
of  the  generator,  as  the  generator  speed  increases,  by  means  of  cutting  a 
resistance  intermittently  in  and  out  of  the  shunt-field  circuit  as  the  regu- 
lator points  open  and  close,  due  to  the  varying  magnetic  pull  of  the  core. 
The  resistance  unit  is  connected  in  the  shunt-field  circuit  but  is  normally 
short-circuited  by  the  regulator  contacts,  one  of  which  is  mounted  on  a 
soft  iron  contact  arm  to  which  is  attached  the  spring  for  holding  the  points 
in  contact.  When  driven  by  the  engine,  the  generator  builds  up  as  a 
simple  shunt-wound  generator,  the  shunt-field  current  flowing  as  indicated 
from  the  positive  (+)  brush  through  the  contact  points,  through  the 

Digitized  by 




field  winding  to  the  negative  (— )  brush.  When  the  speed  and  voltage 
of  the  generator  are  sufficiently  increased. to  cause  the  cut-out  to  close, 
thus  completing  the  battery  charging  circuit,  the  generator  will  begin 
to  charge  the  battery,  the  charging  current  flowing  through  the  regulator 
winding.  This  current  flowing  through  the  regulator  winding  will  mag- 
netize the  core  which  in  turn  exerts  a  magnetic  pull  on  the  regulator  con- 
tact arm  tending  to  pull  the  contacts  apart.  When  this  current — the 
armature  current — becomes  a  certain  amount  (usually  in  practice  10 
amperes)  the  core  becomes  sufficiently  magnetized  to  attract  the  contact 
arm,  overcoming  the  pull  of  the  regulator  spring.  This  separates  the 
contact  points,  and  the  resistance  unit  is  inserted  in  series  with  the  shunt- 
field  winding  causing  the  field  strength  to  weaken.  This  causes  the 
armature  voltage  to  drop  and,  consequently,  the  charging  current  to 
decrease.     When  the  current  decreases  to  a  predetermined  amount  (say 






NCSISURCt  £j    ft 

(contact*  nomhauy  clomo 

eoi  VWUfTC  AT  If  TOItKtK 
IMS  (CACHED  10  TO  *  AMM) 



Fio.  358. — Circuit  diagram  of  typical  vibrating  type  regulator  to  obtain  constant  current 

regulation  of  the  generator. 

9  amperes)  the  current  coil  does  not  magnetize  the  core  sufficiently  to 
overcome  the  pull  of  the  spring,  thus  allowing  the  spring  to  close  the  con- 
tacts. With  the  contacts  closed,  the  resistance  unit  is  once  more  short- 
circuited  and  the  full  field  strength  is  restored,  causing  the  charging 
current  to  again  increase.  Under  operating  condition,  the  contact  arm 
vibrates  automatically  and  rapidly  at  such  a  rate  as  to  keep  the  generator 
output  constant. 

As  a  result,  the  generator  will  never  charge  the  battery  above  a 
predetermined  amount  (10  amperes)  no  matter  how  high  the  speed  of 
the  car,  but  at  all  speeds  greater  than  a  predetermined  speed  (about  15 
miles  per  hour  in  practice)  the  generator  will  produce  a  substantially 
constant  current.  This  will  be  true  regardless  of  whether  the  battery 
is  fully  charged  or  completely  discharged. 

Digitized  by 




Such  a  method  of  generator  regulation  is  termed  current  regulation 
since  the  current  output  of  the  generator  is  made  use  of  in  regulating 
itself.  It  is,  therefore,  very  important  that  no  opens  occur  in  the  charging 
circuit,  since  there  would  then  be  no  current  flowing  through  the  current 
coil  to  operate  the  vibrating  points  and  all  regulation  of  the  generator 
would  be  destroyed.  Consequently,  to  operate  a  car  equipped  with  this 
type  system  with  the  battery  disconnected  the  field  wire  should  be  dis- 
connected, thereby  preventing  the  generator  from  building  up  a  voltage. 
As  in  the  case  of  all  systems  controlled  by  a  vibrating  type  relay,  the 
charging  rate  of  the  generator  is  very  easily  adjusted.  To  increase  the 
maximum  charging  rate,  the  spring  tension  should  be  increased  slightly, 
and  to  decrease  the  maximum  charging  rate,  the  spring  tension  should 
be  decreased,  caution  being  taken  that  the  generator  does  not  become 
overloaded.  Adjustments  should  be  made  only  by  a  competent  mechanic 
who  is  experienced  in  starting  and  lighting  repairing. 



^rrr^M^.       SYSTEM 
.  -  l-OUT  POIHT5  r-f»j 

>0*MAU.Y  own)  t        VJ^ 



359. — Circuit  diagram  of  typical  vibrating  type  regulator  to  obtain  constant  voltage 
regulation  of  the  generator. 

241.  Voltage  Regulation  of  the  Generator  through  Vibrating  Type 
Relay. — A  circuit  diagram  of  a  typical  vibrating  type  regulator  to  obtain 
constant  voltage  regulation  of  the  generator  is  shown  in  Fig.  359.  Al- 
though the  construction  of  the  relay  does  not  differ  widely  from  that  of 
the  current  type  regulator,  as  the  diagram  shows,  the  principle  is  some- 
what different  in  that  in  this  system  the  voltage  of  the  generator  is  auto- 
matically regulated  instead  of  its  current  output,  as  with  the  current 
type  regulator.  As  may  be  seen  in  comparing  Fig.  358  with  Fig.  359, 
the  principal  difference  in  the  two  relays  is  in  the  winding  of  the  core. 
In  the  voltage-type  regulator  the  charging  current  does  not  flow  through 
the  regulator  winding.  The  winding  of  the  core  consists  of  a  voltage 
coil  of  fine  wire,  the  two  ends  of  which  are  connected  across  the  generator 
brushes  and  in  parallel  with  the  battery  instead  of  in  series  with  it  as  in 

Digitized  by  CjOOQ IC 


the  case  of  the  current-type  regulator.  The  core,  regulator  points,  and 
resistance  unit,  however,  are  practically  the  same. 

The  current  flowing  in  the  voltage  coil  and  the  resulting  magnetic 
pull  of  the  core  on  the  regulator  contact  points  will  depend  upon  the 
voltage  developed  by  the  generator.  In  the  case  of  a  6-volt  system  the 
regulator  is  usually  adjusted  to  hold  the  generator  voltage  constant  at 
7.75  volts.  With  increasing  generator  speed  the  voltage  will  tend  to  rise 
above  7.75.  If,  however,  this  value  is  exceeded  by  a  very  small  amount, 
the  increased  magnetic  pull  of  the  core  on  the  contact  arm,  due  to  current 
flowing  in  the  voltage  coil,  will  overcome  the  spring  pull  and  the  contact 
arm  will  be  drawn  toward  the  core,  thus  opening  the  contacts  and 
inserting  the  resistance  in  the  generator  field  circuit.  The  added  resist- 
ance in  the  field  circuit  decreases  the  current  in  the  field  winding,  and  the 
voltage  developed  by  the  armature  tends  to  drop  below  the  normal  value 
of  7.75  volts. 

If  the  voltage  drops  slightly  below  the  normal,  the  pull  of  the  spring 
on  the  regulator  contact  arm  predominates  and  the  arm  moves  away 
from  the  core  and  closes  the  contacts  which  short-circuits  the  resistance 
unit  and  permits  the  field  current  to  increase.  This  cycle  of  operation 
is  repeated  rapidly  and  maintains  the  generator  voltage  constant  at  all 
speeds  above  the  critical  value  at  which  it  develops  7.75  volts  with  the 
resistance  cut-out  of  the  field  circuit.  In  this  type  system  it  is  possible 
to  operate  the  lamps  off  of  the  generator  with  the  battery  disconnected 
without  danger  of  burning  out  the  bulbs,  since  the  generator  is  regulated 
to  maintain  a  constant  voltage  even  though  an  open  should  occur  in  the 
charging  circuit. 

It  is  obvious  that  increasing  the  tension  of  the  regulator  spring  will 
increase  the  constant  voltage  which  the  generator  will  maintain.  Under 
no  circumstances  should  the  regulator  spring  tension  be  increased  in  an 
attempt  to  have  the  generator  charge  at  a  higher  rate  at  low  speed.  The 
generator  cannot  begin  to  charge  until  the  cut-out  closes,  and  the  closing 
of  the  cut-out  is  independent  of  the  action  of  the  regulator.  The  cut-out 
closes  after  the  generator  reaches  a  speed  at  which  it  develops  6.5  to  7 
volts,  and  no  adjustment  of  the  regulator  or  cut-out  can  change  the  speed 
characteristics  of  the  generator.  Increasing  the  tension  of  the  regulator 
spring  so  that  the  generator  will  develop  a  constant  voltage  in  excess  of 
7.75  volts  will  result  in  excessive  current  to  the  battery,  overcharging 
it  or  causing  the  generator  to  overheat  with  the  possibility  of  burning 
it  out. 

Characteristics  of  Voltage  Regulation. — With  the  constant  voltage-type 
generator  the  amount  of  current  generated  depends  upon  the  state  of 
charge  of  the  storage  battery  and  the  amount  of  lamp  load  in  use.  After 
the  generator  reaches  a  speed  at  which  it  develops  its  normal  voltage, 

Digitized  by 



there  will  be  no  further  increase  in  voltage  with  increasing  speed;  the 
voltage  will  be  maintained  constant  at  all  loads,  and  at  all  higher  speeds. 

The  voltage,  measured  across  the  terminals  of  the  storage  battery,  is 
variable  and  depends  upon  the  state  of  charge  of  the  battery.  With  a 
discharged  battery  the  voltage  is  a  minimum,  and  the  voltage  increases 
in  value  as  the  charge  proceeds. 

During  the  time  the  generator  is  connected  to  the  battery,  the  dif- 
ference in  pressure  between  the  two  is  the  pressure  available  for  sending 
current  into  the  battery;  thus,  if  the  battery  voltage  is  6.2  and  the  genera- 
tor voltage  7.75,  the  pressure  available  for  sending  current  through  the 
battery  will  be  1.55  volts.  In  the  case  of  a  discharged  battery,  the  dif- 
ference in  pressure  between  the  generator  and  battery  will  be  relatively 
great  so  that  a  comparatively  high  charging  current  will  pass  from  the 
generator  to  the  battery.  As  the  charge  proceeds  the  voltage  of  the 
battery  increases  so  that  the  difference  in  pressure  between  generator 
and  battery  is  continually  diminishing.  With  a  fully  charged  battery 
its  pressure  is  very  nearly  equal  to  that  of  the  generator,  and  the  difference 
between  the  two  is  small.  As  this  small  difference  in  pressure  is  all  that 
is  available  for  sending  current  into  the  battery,  the  charging  current 
will  be  small.  The  current  generated,  therefore,  is  variable  and  is  inde- 
pendent of  speed.  The  charging  current  tapers  from  a  maximum  in 
practice,  usually  15  to  20  amperes  to  a  discharged  battery,  to  a  minimum 
usually  4  to  6  amperes  in  the  case  of  a  fully  charged  battery. 

242.  Combined  Current  and  Voltage  Regulation  of  the  Generator 
through  Vibrating  Type  Relay. — The  circuit  diagram  of  a  typical  vibrat- 
ing type  relay  for  the  purpose  of  obtaining  both  constant  current  and 
voltage  regulation  of  the  generator,  is  shown  in  Fig.  360.  As  will  be  read- 
ily seen  in  comparing  this  diagram  with  the  two  regulator  diagrams  shown 
in  Fig.  358  and  Fig.  359,  the  winding  of  the  relay  is  merely  a  combination 
of  the  other  two,  the  core  being  wound  with  both  a  current  and  a  voltage 
winding.  This  construction  permits  of  the  combining  of  the  cut-out 
and  regulator  into  a  single  relay.  As  shown,  the  cut-out  points  are 
mounted  on  one  end  of  the  core,  while  the  regulating  points  are  mounted 
on  the  other  end,  the  two  sets  of  contacts  being  operated  by  independent 

The  operation  of  the  regulating  part  of  this  relay  is  practically  the 
same  as  that  of  the  voltage-type  regulator  with  the  exception  that  in 
addition  to  the  controlling  of  the  generator  voltage,  as  effected  by  the 
voltage  winding,  the  generator  current  output  is  also  controlled  by  the 
charging  current  flowing  through  the  current  coil.  It  will  be  noted  from 
the  diagram  that  both  windings  carry  current  around  the  core  in  the  same 
direction,  and  the  magnetizing  force  of  both  assist  each  other  in  operating 
both  the  regulator  and  the  cut-out  contact  points. 

Digitized  by 




By  combining  the  current  and  voltage  windings  in  this  manner, 
combined  characteristics  of  both  the  constant  current  and  constant  volt- 
age methods  of  regulation  are  partly  attained.  Proper  functioning  of  the 
relay,  however,  depends  upon  the  combined  effect  of  both  windings; 
consequently,  if  for  any  reason  the  cut-out  points  do  not  close  to  make 
proper  contact,  or  an  open  should  occur  at  some  other  point  in  the  charg- 
ing circuit,  such  as  due  to  a  burned  out  ammeter  or  corroded  battery 
terminal,  no  current  will  flow  through  the  current  coil,  thus  leaving  the 
generator  to  depend  entirely  on  the  voltage  winding  for  regulation.  The 
generator  voltage  will,  in  this  event,  operate  somewhat  higher  than  normal 
when  the  car  is  driven  at  high  speeds  and  if  continued  may  cause  damage 
to  the  regulator  and  generator  windings.  On  the  other  hand,  if  the 
voltage  winding  should  become  broken  or  disconnected,  the  cut-out 





Fig.  360. — Circuit  diagram  of  typical  combination  vibrating  type  regulator  and  out-out 
to  obtain  constant  current  and  voltage. regulation  of  the  generator. 

cannot  close  and  entire  regulation  of  the  generator  is  destroyed.  Pre- 
cautions should  be  taken,  therefore,  to  prevent  such  opens  occurring  in 
both  the  voltage  coil  and  charging  circuits,  otherwise  possible  damage 
may  result  through  burning  out  of  the  generator  and  regulator  windings. 
As  a  safeguard  in  case  the  car  is  to  be  operated  with  the  storage  battery 
removed,  the  shunt  field  wire  connection  to  the  regulator  should  be  disn 
connected,  thereby  preventing  the  generator  from  building  up.  In 
many  installations,  the  regulator  is  mounted  on  top  of  the  generator 
frame  in  which  event  it  is  often  more  convenient  to  remove  the  entire 
regulator  during  the  period  which  the  battery  is  disconnected  and  replace 
it  when  the  battery  is  again  installed. 

243.  The  Ward  Leonard  Automatic  Controller. — The  Ward  Leonard 
automatic  controller  type  CC,  Fig.  361,  is  a  typical  vibrating  type  regu- 
lator and  cut-out  by  which  both  the  voltage  and  current  output  of  the 

Digitized  by 




generator  are  controlled.  The  wiring  diagram  of  the  controller  is  shown 
in  Fig.  362.  The  voltage  coil  winding  is  represented  by  N,  the  current 
coil  by  F,  the  cut-out  contact  by  D,  the  regulator  contact  by  E,  and  the 
resistance  unit  by  M . 

Fig.  361. — Ward  Leonard  automatic  controller,  Type  CC. 

When  the  generator  is  driven  at  a  speed  sufficient  to  close  the  cut-out 
and  charge  the  battery,  the  current  output  of  the  generator  passes 
through  the  current  coil  F.  This  is  in  the  same  direction  around  the 
core  as  the  current  flowing  in  the  voltage  winding.     When  the  charging 


Fig.  362. — Wiring  diagram  of  Ward  Leonard  controller,  Typo  CC. 

rate  reaches  10  amperes,  the  magnetic  pull  of  the  core  is  sufficient  to 
attract  the  arm  H  and  separate  the  regulator  contacts  EE}  thereby  in- 
serting the  resistance  M  in  series  with  the  shunt  field.     This  weakens  the 

Digitized  by  LiOOQ IC 


field  and  reduces  the  generator  voltage  and  current  output.  When  the 
current  decreases  to,  say  9  amperes,  the  coil  F  is  not  strong  enough  to 
hold  the  arm  H  against  the  action  of  the  spring  J  and  the  contact  at  E 
is  made  again,  short-circuiting  the  resistance  M.  This  increases  the 
field  strength  and  the  generator  output  tends  to  increase,  but  when  it 
is  increased  to  10  amperes  the  contacts  E  open  again,  inserting  the  re- 
sistance M.  This  same  cycle  of  operations  of  inserting  and  short-cir- 
cuiting the  resistance  M  keeps  occurring  as  the  generator  speed  is  in- 
creased. Under  operating  conditions,  the  arm  H  vibrates  automatically 
and  rapidly  at  such  a  rate  as  to  keep  the  voltage  and  current  output  of 
the  generator  constant  when  the  engine  is  running  at  a  fair  speed. 

244.  Third  Brush  Regulation. — The  intermediate  or  third  brush 
principle  of  generator  regulation  depends  entirely  for  its  operation  upon 
the  reactions  which  exist  in  the  armature  when  it  is  rotated  and  generates 
a  current.  Consequently,  in  order  to  understand  the  principle  of  third 
brush  regulation,  the  causes  of  these  armature  reactions  must  first  be 
thoroughly  understood. 

It  has  been  found  that  when  the  armature  is  made  to  rotate  between 
the  pole  pieces,  causing  the  various  armature  coils  to  cut  the  magnetic 
lines  of  force,  the  side  of  each  armature  loop  which  cuts  in  front  of  the 
North  pole  will  induce  a  voltage  in  one  direction,  while  the  opposite  side 
of  the  same  loop  cutting  in  front  of  the  South  pole  will  induce  a  voltage 
in  the  opposite  direction  with  respect  to  the  armature  and  pole  pieces. 
In  Fig.  363  let  the  small  circles  (shown  equally  spaced  around  the  cir- 
cumference of  the  armature)  represent  so  many  armature  coils,  each 
coil  being  connected  to  the  commutator  segments  in  such  a  way  that  when 
the  armature  is  rotated  in  the  clockwise  direction  the  upper  brush  will 
become  positive  (+)  and  the  lower  brush  negative  (  — )  polarity.  With 
the  armature  rotating  in  this  direction,  the  current  induced  in  each  coil 
as  it  passes  in  front  of  the  North  pole  will  be  generated  to  flow  in  or  away 
from  the  reader,  while,  in  front  of  the  South  pole,  the  current  will  be  gener- 
ated to  flow  out  or  toward  the  reader.  The  direction  of  the  current 
flowing  in  each  coil  generating  is  indicated  by  either  a  cross  (+)  or  a  dot 
(.),  depending  upon  whether  the  current  is  leading  away  from  or  toward 
the  reader.  The  cross  and  dot  represent  the  tail  and  point,  respectively, 
of  an  arrow  pointing  in  the  direction  of  current  and  should  not  be  confused 
with  the  plus  (+)  and  minus  (  — )  signs  representing  positive  and  negative 

When  the  armature  is  delivering  current  to  an  external  circuit,  such 
as  the  battery  and  lighting  system,  the  effect  of  the  current  flowing  in 
different  general  directions  in  the  armature  coils  on  opposite  sides  of  the 
armature,  will  be  to  magnetize  the  armature  in  a  cross  direction,  thus 
making  one  side  of  the  armature  core  north  and  the  other  south.    This 

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effect  is  much  the  same  as  if  a  wire  were  wound  on  an  iron  cylinder  and  a 
current  passed  through  it  as  shown  in  Fig.  364A.  In  the  armature,  this 
cross  magnetizing  force  will  be  through  the  armature  and  pole  pieces  at 
right  angles  to  the  magnetic  field  produced  by  the  field  winding  as  shown 

Fio.  363. — Distribution  of  magnetic  flux  through  generator  armature  at  low  speed. 

in  Fig.  3642?.  By  a  study  of  thi3  figure  it  will  be  seen  that  at  the  lower 
corner  «of  the  north  pole  piece  and  at  the  upper  corner  of  the  south  pole 
piece  the  magnetic  lines  of  the  two  fields  are  in  opposite  direction,  while 
at  the  upper  corner  of  the  north  pole  piece  and  at  the  lower  south  pole 
piece  the  magnetic  lines  are  in  the  same  direction.     This  will  cause  a 



Fig.  364. — Cross  magnetisation  of  generator  armature  due  to  generated  current. 

reaction  between  the  two  magnetic  fields  resulting  in  the  magnetic  lines 
being  crowded  to  the  trailing  corners  of  the  poles,  thus  distorting  the 
general  path  of  the  magnetic  flux  across  the  armature  as  shown  in  Fig. 
365.     The  amount  of  this  field  distortion  will  depend  upon  the  speed  of 

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the  armature  and  the  strength  of  the  current — the  battery  charqpng  and 
lighting  current — flowing  in  the  armature  winding.  Owing  to  the  shift- 
ing of  the  magnetic  flux  and  the  consequent  shifting  of  the  points  of 
maximum  voltage  on  the  commutator,  the  brushes  should  be  set  slightly 

Fig.  365. — Distortion  of  magnetic  flux  through  generator  armature  due  to  speed  of  rota- 
tion and  armature  current. 

ahead,  as  shown,  to  have  them  in  the  best  running  position  at  the  normal 
operating  speeds  of  the  armature. 

Principle  of  Third  Brush  Regulation. — The  wiring  and  arrangement 
of  brushes  for  a  typical  2-pole  third  brush  type  generator  are  shown  in 






Fiq.  366. — Diagram  showing  principle  of  third  brush  regulation. 

Fig.  366.  A  and  B  represent  the  main  brushes  which  connect  to  the 
storage  battery  and  lighting  system,  and  C  the  third  brush,  which  con- 
nects only  to  one  end  of  the  shunt-field  winding.  The  dotted  loops  con- 
necting the  commutator  segments  represent  the  various  armature  coils 

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(which  are  also  represented  by  the  circles),  while  the  arrow  on  each  loop 
indicates  the  direction  of  the  induced  current  in  the  loop. 

When  the  generator  is  running  at  low  speed  and  little  or  no  current 
is  flowing  in  the  armature  winding,  the  magnetic  field  produced  by  the 
field  winding  is  approximately  straight  through  the  armature  from  one 
pole  piece  to  the  other,  and  the  voltage  generated  by  each  armature  coil 
is  practically  uniform  during  the  time  the  coil  is  under  the  pole  pieces. 
In  a  generator  of  the  6-volt  type,  in  which  7  to  7%  volts  are  actually 
generated  between  the  main  brushes  when  charging  the  battery,  it  is 
evident  that  with  the  third  brush  in  the  position  shown,  approximately 
5  volts  would  be  generated  between  B  and  the  third  brush  Cf  since  these 
brushes  span  only  this  relative  proportion  of  the  commutator  segments 
and,  consequently,  collect  only  a  part  of  the  total  voltage  generated.  In 
respect  to  B,  the  third  brush  C  is  of  positive  polarity,  so  that  if  one  end 
of  the  shunt-field  winding  is  connected  to  C  and  the  other  end  to  B,  the 
field  current  will  flow  from  C  through  the  winding  to  B  as  indicated 
by  the  arrows,  the  voltage  being  approximately  5  volts  when  the  full 
voltage  is  7. 

As  the  generator  speed  and  charging  rate  increase,  the  charging 
current  flowing  through  the  armature  winding  produces  a  cross-magnetic 
field  in  the  direction  of  the  arrow  G.  This  distorts  the  magnetic  field  * 
produced  by  the  shunt-field  winding,  so  that  instead  of  the  magnetism 
being  equally  distributed  under  the  pole  pieces,  it  becomes  denser  in  the 
pole  tips  marked  D  and  E  and  weaker  in  the  other  pole  tips.  With  this 
distortion  of  the  magnetic  field,  the  armature  coils  no  longer  generate  an 
equal  voltage  while  passing  under  the  different  parts  of  the  pole.  Al- 
though the  voltage  across  the  main  brushes  A  and  B  remains  near  7  to  7^ 
volts,  the  greater  part  of  this  voltage  is  generated  by  the  coils  which 
connect  to  the  commutator  between  brushes  C  and  Af  as  these  coils  are 
cutting  the  denser  magnetic  field  and  the  coils  which  connect  to  the 
commutator  between  the  brushes  B  and  C  are  for  the  most  of  the  time 
in  the  region  of  the  weak  field,  thus  generating  a  lower  voltage.  The 
result  is  a  dropping  off  of  the  voltage  across  brushes  B  and  C  as  the  speed 
and  charging  rate  increase.  Since  the  voltage  of  these  brushes  is  the 
same  as  that  applied  to  the  shunt-field  winding,  it  is  apparent  that  the 
field  strength  is  weakened.  As  this  drop  in  field  voltage  takes  place  more 
and  more  as  the  speed  of  the  generator  increases,  the  result  will  be  an 
automatic  regulation  of  the  current  output. 

Adjusting  Charging  Rate. — In  most  generators  having  third  brush 
regulation,  provision  is  made  for  changing  the  maximum  charging  rate 
to  suit  the  conditions  under  which  the  generator  is  operated.  This 
can  be  accomplished  by  moving  the  position  of  the  third  brush  on  the 
commutator.    Moving  this  brush  in  the  direction  of  armature  rotation 

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increases  the  output  of  the  generator,  while  moving  it  in  the  opposite 
direction  decreases  the  output.  Whenever  this  brush  is  moved  in  either 
direction,  care  should  be  taken  to  see  that  it  makes  perfect  contact  with 
the  commutator.  Usually  it  should  be  seated  to  the  commutator  by 
drawing  a  piece  of  fine  sandpaper  between  the  brush  and  the  commutator, 
with  the  sand  side  next  to  the  brush.  If  this  is  not  done,  the  brush  will 
seat  imperfectly  and  the  charging  rate  may  increase  when  the  brush 
seats  properly  through  wear.  Whenever  the  charging  rate  is  increased, 
after  the  brush  is  properly  seated,  the  maximum  charging  rate  should  be 
noted.  This  should  be  done  by  slowly  speeding  up  the  engine  and  noting 
the  highest  reading  on  the  ammeter.  In  most  cases  it  should  not  exceed 
15  to  16  amperes. 

245.  Characteristics  of  Third  Brush  Regulation. — One  of  the  out- 
standing characteristics  of  generators  with  third  brush  regulation  is  that 
the  charging  rate  of  the  generator  will  increase  gradually  with  increase  in 
speed,  up  to  a  car  speed  usually  of  25  to  30  M.P.H.,  after  which  the  charg- 
ing rate  will  fall  off  as  the  speed  continues  to  increase,  so  that  at  speeds 
of  40  to  50  miles  per  hour  the  charging  rate  will  be  approximately  \i  of 
its  maximum  value.  This  is  an  advantage  in  that  the  maximum  charging 
rate  is  obtained  at  normal  driving  speeds,  while  at  high  speed,  such  as 
during  cross-country  touring,  when  the  starter  and  lights  are  seldom  used, 
the  decreased  charging  rate  tends  to  prevent  overcharging  of  the  battery 
and  overheating  of  the  generator. 

Since  third  brush  type  generators  depend  upon  the  charging  current 
flowing  through  the  armature  winding  to  produce  the  field  distortion 
necessary  for  regulation,  it  is  obvious  that  the  generator  is  of  the  current 
regulated  type  and  must,  therefore,  have  a  complete  charging  circuit 
available  through  the.  battery  at  all  times.  In  this  respect,  it  is  like  the 
other  methods  of  regulators  already  discussed,  with  the  exception  of  the 
voltage  type.  Consequently,  the  same  precautions  are  recommended  in 
keeping  the  battery  terminals  clean  and  tight. 

To  operate  the  car  with  the  battery  disconnected,  care  should  be 
taken  to  see  that  the  generator  does  not  build  up  a  voltage.  This  may 
be  done,  usually,  either  by  grounding  the  main  generator  terminal  or  by 
removing  the  shunt-field  fuse. 

246.  The  Remy  Generator  with  Thermostatic  Control — The  Remy 
generator,  Fig.  367  and  Fig.  368,  is  a  6-volt  two-pole  generator  in  which  the 
regulation  is  by  the  third  brush  principle,  supplemented  by  a  thermostat 
mounted  in  the  generator  housing.  The  cut-out,  Fig.  369,  is  mounted 
either  on  the  brush  cap  or  on  the  generator  frame,  as  may  be  seen  in  Figs. 
367  and  368.  The  thermostat,  Fig.  370,  is  composed  of  a  resistance  unit, 
two  silver  contact  points,  and  a  spring  blade  at  one  end  of  which  is 
mounted  one  of  the  contact  points.    The  blade  is  made  of  a  strip  of 

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spring  brass  welded  to  a  strip  of  nickel  steel,  a  combination  which  warps 
at  its  free  end,  when  heated,  due  to  the  greater  expansion  of  the  brass 
side.    The  spring  tension  is  fixed  so  that  it  holds  the  two  contacts  firmly 




Fio.  367. — Remy  generator,  Model  234A. 

COVET?  s 



Pig.  368.— Remy  generator,  Model  257A. 

Fig.  369. — Remy  cut-out  for  generator,  Model  234A. 

together  at  low  temperatures,  but  as  soon  as  the  temperature  rises  to 

approximately  175°  F.,  the  blade  bends  and  separates  the  contacts. 

The  thermostat  is  mounted  above  the  commutator,  on  the  same  plate 


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with  the  brush  rigging,  as  shown  in  Fig.  371.  It  is  connected  in  the 
shunt-field  circuit  as  shown  in  Fig.  372,  so  that  when  the  thermostat 
contacts  are  closed,  full-field  current  passes  through  them  and  permits 
full  current  output  from  the  generator.  After  the  engine  has  been  run 
for  a  sufficient  time  for  the  normally  high  charging  rate  to  heat  up  the 
generator  and  battery,  the  thermostat  points  open,  due  to  the  bending  of 









Fio.  370. — Thermostatic  control  device  for  Remy  generator. 

the  thermostat  blade,  thus  causing  the  resistance  to  be  inserted  in  the 
shunt-field  circuit,  as  shown  in  Fig.  370,  and  reducing  the  current  output. 
The  generator  current  outputs,  with  the  contacts  closed  and  open,  are 
shown  by  the  two  curves  in  Fig.  373,  from  which  it  will  be  seen  that  the 
charging  rate  reduces  approximately  J^  when  the  thermostat  is  opened. 




Fig.  371. — Method  of  mounting  Remy  thermostat. 

The  chief  advantages  of  the  thermostatic  control  are  that  it  gives  a 
larger  battery  charging  rate  in  cold  weather,  when  the  efficiency  of  the 
battery  is  lower  than  in  warm  weather,  and  also  a  larger  charging  rate 
when  the  car  is  being  driven  intermittently  and  the  demands  on  the 
battery  are  greater,  caused  by  the  frequent  use  of  the  starting  motor. 
In  summer  it  also  prevents  the  generator  and  battery  from  overheating, 

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by  the  reduction  in  the  charging  rate,  when  the  temperature  rises  and 
the  thermostat  opens. 










GROUND  if- 




CLOSED-OPEN  AT  175  F.) 







Fw.  372. — Circuit  diagram  of  Remy  generator  and  cut-out  with  thermostatic  field  control, 

Model  234A. 

247.  The  Remy  Starting  and  Lighting  System  with  Relay  Regulation. 

—The  Remy  starting  and  lighting  system  used  on  the  Velie,  Model  22  as 
shown  in  Fig.  374  is  a  typical  2-unit  system  of  the  single-wire  grounded 






Fw.  373. — Curves  showing  relative  charging  rates  of  Remy  generator  with  thermostat 

closed  and  open. 

type.    The  generator  is  regulated  by  a  vibrating  type  relay  mounted  on 
one  end  of  the  generator  frame. 

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A  circuit  diagram  of  the  generator,  regulator,  and  cut-out  relay  is 
shown  in  Fig.  375.  As  will  be  seen  from  the  diagram,  the  regulator  and 
cut-out  comprise  two  independent  relays  mounted  side  by  side. 










The  regulator  consists  of  an  electromagnet;  an  arm  operating  on 
hardened  bronze  pivots;  two  sets  of  contact  points  held  normally  closed; 
and  a  resistance  unit.     The  contact  points  are  of  silver  and  the  two  on 

Digitized  by  VjOOQlC 



the  arm  are  mounted  upon  springs.  The  cut-out  is  of  similar  construc- 
tion, with  the  exception  that  a  single  set  of  contacts  is  used,  the  points 
of  which  are  held  normally  open.  It  will  be  seen  that  the  regulator  core 
has  a  single  winding — a  current  coil — while  the  cut-out  has  the  usual  vol- 
tage and  current  windings. 

When  the  engine,  and,  consequently,  the  generator,  are  running  fast 
enough  to  produce  sufficient  voltage  for  battery  charging,  the  cut-out 
closes  through  the  action  of  the  voltage  coil  and  connects  the  generator 
with  the  battery,  the  charging  current  flowing  through  the  current  coils 
of  both  the  cut-out  and  regulator  in  series.  When  the  generator  is 
running  at  a  speed  lower  than  that  required  for  maximum  output, 




Pio.  375. — Internal  circuit  diagram  of  Remy  generator  with  relay  regulator. 

the  regulator  contact  points  are  held  together  by  a  spring  under  the  con- 
tact arm  and  the  current  supplied  to  the  generator  field  passes  directly 
through  both  of  these  points  in  series.  As  soon,  however,  as  the  speed  of 
the  generator  tends  to  cause  its  output  to  rise  above  the  maximum  value 
predetermined,  the  charging  current,  which  is  flowing  through  the  cur- 
rent coil  on  the  regulator  core,  magnetizes  the  core  to  such  an  extent  that 
it  pulls  the  arm  down.  This  pulls  the  contact  points  apart,  forcing  the 
field  current  (which  has  heretofore  been  passing  through  these  points) 
to  pass  through  the  resistance  unit.  The  added  resistance  in  the  field 
circuit  decreases  the  field  current  and  in  turn  decreases  the  output  of  the 
generator.     This  naturally  reduces  the  energizing  effect  of  the  electromag- 

Digitized  by  LiOOQ IC 



net,  permitting  the  spring  to  force  the  contact  points  together  again, 
thereby  cutting  the  resistance  out  of  the  field  circuit.  The  generator 
output  immediately  starts  to  build  up  again  and  the  operation  previously 
described  is  repeated.  A  continuous  repetition  of  this  operation  sends 
a  pulsating  current  to  the  generator  field  and  holds  the  output  of  the 
generator  at  practically  a  constant  value.  Thus  it  will  be  seen  that  the 
regulator  is  of  the  constant  current  type  as  previously  illustrated  in  Fig. 

For  the  purpose  of  protecting  the  generator,  a  readily  accessible  fuse 
is  fitted  to  the  relay-regulator  base.  In  case  the  battery  should  become 
disconnected,  either  through  accident  or  neglect,  this  fuse  will  burn  out, 





Fia.  376. — Bijur  constant  voltage  generator  and  regulator. 

opening  the  shunt  field  and  rendering  the  generator  inoperative  and 
damage  proof. 

248.  The  Bijur  Generator  with  Constant  Voltage  Regulation.— The 
Bijur  constant  voltage  type  generator,  Fig.  376,  is  a  practical  application 
of  the  constant  voltage  method  of  regulation  as  previously  explained. 
The  circuit  wiring  diagram  of  the  generator,  regulator,  and  cut-out  is 
shown  in  Fig.  377.  The  cut-out,  voltage  regulating  unit,  and  resistance 
unit  are  fastened  on  a  fiber  board  as  a  unit  and  mounted  in  an  aluminum 
box  which  fits  on  top  of  the  generator.  The  box  is  provided  with  three 
split  connecting  pins  which  fit  into  three  receptacles  in  the  generator  so 
that  the  mechanical  act  of  putting  the  regulator  box  in  place  on  the  genera- 
tor makes  all  of  the  necessary  electrical  connections  between  the  generator 
and  the  cut-out  and  regulating  mechanism.     In  addition  to  the  regulator 

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box  being  held  in  place  on  the  generator  by  its  connecting  pins,  there  is 
a  knurled  screw  passing  through  the  box  to  the  machine. 

As  may  be  seen  in  Fig.  376  and  Fig.  377,  connection  from  the  generator 
to  the  battery  is  made  through  a  wire  and  plug  which  fits  into  the  recep- 
tacle at  one  end  of  the  relay  box.  In  this  receptacle  there  are  two  spring 
plungers  which  make  contact  with  two  contacts  mounted  in  the  dis- 
connecting plug.  The  plug  is  designed  so  that  it  can  be  rotated  through 
a  small  angle  after  it  is  in  place,  for  the  purpose  of  reversing  the  connec- 
tions of  the  contacts.  By  reversing  the  plug,  the  generator  polarity 
is  also  caused  to  reverse,  which  in  turn  reverses  the  polarity  of  the  regula- 
tion vibrating  points.  The  purpose  of  this  is  to  equalize  any  transfer 
of  metal  on  the  regulator  p'oints,  thereby  decreasing  their  tendency  to 




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spm*»l     T 


cut-out  coirn 

frtOHHALL/  OPCli 





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Fio.  377. — Wiring  diagram  of  Bijur  voltage  regulator  and  generator. 

pit  and,  consequently,  greatly  increasing  the  life  and  efficiency  of  the 
regulator.  It  is  recommended  that  this  disconnecting  plug  be  reversed 
to  reverse  the  generator  polarity  about  every  500  miles  of  travel.  By 
merely  reversing  the  plug,  the  polarity  of  the  generator  will  reverse 
automatically  when  the  engine  is  started. 

249.  The  Westinghouse  Starting  and  Lighting  System — Voltage 
Regulator  Type. — The  Westinghouse  generator  No.  400,  Fig.  378, 
together  with  the  regulator,  Fig.  379,  is  typical  of  the  Westinghouse 
equipment  of  the  relay  regulated  type  installed  on  1916  and  1917  cars. 
The  construction  of  this  generator  was  shown  in  Fig.  342.  A  complete 
wiring  diagram  showing  a  typical  installation  of  this  type  system  is 
shown  in  Fig*  380  in  which  is  shown  the  starting,  lighting,  and  ignition 
wiring  for  the  Glide  "six-40." 

Digitized  by  LiOOQ IC 


As  may  be  seen  from  the  circuit  diagram  of  the  generator  and  relay 
shown  in  Fig.  381,  the  relay  performs  two  functions:  (1)  that  of  a  cut-out 
which  automatically  connects  and  disconnects  the  generator  from  the 
battery  when  the  generator  is  driven,  respectively,  above  or  below  a 
predetermined  speed;  and  (2)  that  of  an  "automatic  voltage  regulator" 
which,  after  the  cut-out  has  connected  the  generator  circuit  to  the 
battery,  automatically  keeps  the  generator  voltage  at  a  predetermined 
value.  Bach  function  of  the  relay  is  performed  by  its  individual  element; 
however,  the  successful  operation  of  the  regulating  function  depends  upon 
the  proper  operation  of  the  cut-out.  The  core  of  the  relay  is  of  the  "  three- 
legged  "  or  W  type,  which  has  two  magnetic  circuits,  one  for  operating 
the  cut-out  contact  arm,  the  other  for  operating  the  regulator  points. 





Fio.  378.  Fio.  379. 

Fio.  378. — Westinghouse  generator,  Type  400,  with  vertical  ignition  unit. 
Fio.  379. — Westinghouse  voltage  regulator  for  separate  mounting. 

CutrovJL. — When  the  generator  is  being  operated  at  a  speed  below  the 
predetermined  "cut-in"  speed,  the  contacts  of  the  cut-out  are  open, 
the  voltage  of  the  generator  being  below  that  of  the  battery.  When  the 
generator  speed  reaches  the  "cut-in"  speed  these  contacts  are  closed, 
connecting  the  generator  to  the  battery  circuit.  The  "cut-in"  speed 
varies  from  5  to  10  miles  per  hour  on  igh  gear,  depending  upon  the 
gear  ratio  and  wheel  diameter  of  the  particular  car. 

The  "cut-in"  speed  of  the  generator  can  be  observed  by  running  the 
car,  allowing  it  to  increase  in  speed  slowly,  and  observing  on  the  speed- 
ometer the  speed  at  which  the  car  is  running  when  the  cut-out  contacts 
close,  which  is  indicated  by  a  slight  movement  of  the  ammeter  needle 
toward  the  "charge"  side. 

The  relay  is  constructed  so  that  the  cut-out  operates  to  disconnect 
the  generator  from  the  battery  circuit  at  a  speed  slightly  below  the 
"cut-in"  speed.     This  enables  the  cut-out  portion  of  the  relay  to  keep 

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the  circuit  closed,  instead  of  continuously  opening  and  closing  it  when  the 
car  is  being  run  at  speeds  close  to  the  " cut-in"  speed.  This  discon- 
necting of  the  generator  from  the  battery  circuit,  when  the  generator 
voltage  is  below  the  battery  voltage,  insures  that  the  battery  will  not 
be  discharged  through  the  generator. 

Regulator. — As  will  be  seen  from  the  diagram,  the  regulator  is  of  the 
combined  current  and  voltage  regulating  type.  The  shunt  field  of  the 
generator  is  connected  by  a  wire  to  the  middle  terminal  F  on  the  relay, 





RESISTANCE  UNIT         or/ 




%?mLD-l       REGULATOR  AND 

•       CUT-OUT  RELAY         AMMETER 









Fio.  381. — Circuit  diagram  of  Westinghouse,  Type  400  generator,  with  voltage  regulator. 

the  field  circuit  being  completed  through  this  wire,  the  regulator  contact 
points,  and  the  wire  which  connects  to  terminal  A  — . 

When  the  generator  is  operating  below  "cut-in"  speed,  the  regulator 
contacts  are  closed,  and  remain  closed,  short-circuiting  the  resistance 
unit  until  the  generator  armature  is  revolved  at  a  speed  sufficient  to 
produce  the  maximum  charging  rate  set  for  the  battery.  When,  due 
to  the  increased  speed  and  current  output  of  the  generator,  the  voltage 
and  current  tend  to  exceed  the  value  for  which  the  regulator  is  set,  the 
strength  of  the  magnetic  circuit  through  the  regulating  side  of  the  relay 
will  be  increased  by  the  action  of  the  voltage  and  current  coils  sufficient 
to  attract  the  regulator  contact  arm,  pulling  the  contacts  open.     This 

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cuts  the  regulating  resistance  into  the  shunt-field  circuit  and  reduces  the 
field  strength  which  in  turn  causes  a  momentary  drop  in  voltage  so  that 
the  contacts  close  again.  This  opening  and  closing  of  the  contacts  is 
continuous  and  so  rapid  as  to  be  imperceptible  to  the  eye,  and  to  hold  the 
voltage  and  current  fairly  constant. 

The  maximum  current  output  of  the  generator  can  be  increased  or 
decreased  by  increasing  or  decreasing  the  spring  tension  on  the  regulator 
points.  This  may  be  done  by  turning  the  regulator  adjusting  screw 
on  the  top  of  the  relay  shown  in  Figs.  379  and  381.  Care  should  be  taken 
in  making  this  adjustment  to  make  sure  that  the  generator  does  not 
become  overloaded.  The  usual  maximum  charging  rate  for  this  genera- 
tor should  be  fixed  to  not  exceed  10  to  12  amoeres. 

Pio.  382. — Typical  Westinghouse  third-brush  type  generator.  (A)  generator  Model  No. 
250;  (B)  generator  Model  No.  760  with  vertical  ignition  unit  for  cradle  mounting;  and  (C) 
generator  Model  760  for  flange  mounting. 

260.  The  Westinghouse  Starting  and  Lighting  System — Third  Brush 

Type.  Generators. — Several  models  of  Westinghouse  Third  Brush  type 
generators  are  shown  in  Fig.  382.  These  generators  are  four-pole  shunt 
wound  with  Third  Brush  regulation.  In  A,  which  shows  the  generator, 
model  No.  450,  the  construction  is  very  similar  to  that  of  the  No.  400 
generator,  Fig.  378,  the  construction  of  which  was  shown  in  Fig.  342. 
B  and  C  illustrate  the  types  known  as  No.  760. 

The  type  No.  760  generator  is  the  one  more  widely  used.  It  is  fur- 
nished either  with  or  without  the  ignition  unit  carrying  bracket  and  for 
either  flange  or  cradle  mounting.     The  cut-out  is  mounted  either  separate 

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from  the  generator  or  inside  the  generator  frame.     When  located  inside 
the  generator,  it  is  mounted  on  the  end  bracket  which  supports  the  brush 

Fig.  383.- 

-Brackets  for  Westinghouse  Third-brush  generator,  with  self-contained  cut-out 
(right)  and  with  separately-mounted  cut-out  (left). 

rigging,  as  shown  in  Pig.  383.  The  operation  of  the  generator  is  the 
same  as  that  previously  explained  for  generators  having  Third  Brush 

Fig.  384. — Westinghouse  starting  motor  with  automatic  electromagnetic  pinion  shift. 

Starting  Motors. — Westinghouse  starting  motors  are  made  in  two 
general  types:  (1)  with  mechanical  pinion  shift  as  shown  in  Figs.  331 

SMin*      HUSHING 

Fia.  385. — Parts  of  Westinghouse  starting  motor  with  electromagnetic  pinion  shift. 

and  351;  and  (2)  with  automatic  electromagnetic  pinion  shift,  as  shown 
in  Figs.  384  and  385.  The  first  type  is  the  more  commonly  used.  Its 
operation  is  the  same  as  previously  explained  for  starting  motors  equipped 

Digitized  by  LiOOQ IC 



with  the  Bendix  drive.    Construction  of  the  Westinghouse  starting 
switch  is  shown  in  Fig.  386. 

The  starting  motor  of  the  electromagnetic  pinion  shift  type  is  com- 
posed of  three  principal  parts  as  shown  in  Fig.  385:  the  stationary  parts, 
or  field;  the  rotating  parts,  or  armature  and  shaft;  and  the  shifting  mag- 

f biffing  Magnet    Storting  Motor 
%—mK=  p,nwn 

Fio.  386. — Westinghouse  starting  switch,  foot  operated  type. 

net.  The  armature  is  mounted  on  a  hollow  shaft,  on  the  end  of  which  is 
mounted  a  splined  pinion  which  drives  the  flywheel.  This  pinion  is  made 
to  slide  along  the  shaft  by  a  shifting  rod  which  is  attached  to  the  pinion 
and  passes  through  the  hollow  shaft.  The  other  end  of  this  shifting  rod 
acts  as  the  core  of  the  shifting  magnet.  When  the  motor  armature  is 
not  revolving,  a  return  spring  holds  the  pinion 
at  the  end  of  the  shaft  and  clear  of  the  fly- 
wheel gear.  A  diagram  of  this  type  of 
starter  is  shown  in  Fig.  387.  As  shown  in 
the  diagram,  when  the  starting  switch  is 
closed  a  circuit  is  complete  from  the  posi- 
tive (+)  terminal  of  the  battery,  through 
the  "ground"  or  frame  of  the  car,  through 
the  series  field,  armature,  and  shifting  mag- 
net, through  the  starting  switch  to  the  nega- 
tive (— )  terminal  of  the  battery.  The  start- 
ing motors  used  in  this  application  are  of 
the  series  type;  that  is,  the  field  is  connected 
in  series  with  the  armature  so  that  all  the 
current  flowing  through  the  one  also  flows 

through  the  other.  One  of  the  characteristics  of  this  kind  of  motor  is 
that  the  amount  of  current  flowing  through  it  is  proportional  to  the 
amount  of  energy  it  develops. 

When  the  starting  switch  is  closed,  current  flows  through  the  circuit 
as  outlined,  causing  the  armature,  the  shaft,  and  the  pinion  to  rotate. 
The  motor  requires  a  high  current  at  the  instant  it  starts  from  rest. 

Fig.  387.  — Diagram  of 
Westinghouse  starting  motor  for 
automatic  electromagnetic 
pinion  shift  shown  in  Fig.  384. 

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This  high  current  through  the  shifting  magnet  magnetizes  it  sufficiently 
to  overcome  the  force  of  the  return  spring,  and,  therefore,  draws  the  shift- 
ing rod  through  the  shaft,  thus  sliding  the  pinion  into  mesh  with  the  gears 
on  the  flywheel.    The  teeth  on  the  flywheel  and  the  pinion  are  cut  diag- 

Fia.  388. — North  Eaet  starter  generator. 
Model  G. 

Fig.  389. — North  East  combined  start- 
ing switch  and  reverse-current  cut-out. 
Type  8100. 

onally  so  that  they  mesh  very  easily.  As  soon  as  the  pinion  meshes 
with  the  flywheel  gear,  the  current  required  to  turn  the  engine  over  is 
enough  to  hold  the  pinion  in  mesh  until  the  engine  fires.     When  the  engine 

picks  up,  it  soon  runs  at  higher 
speed  than  that  of  the  motor. 

When  the  engine  speeds  up  so 
that  its  speed  approaches  the  no- 
load  speed  of  the  motor,  the  cur- 
rent in  the  latter  falls  off  so  that 
the  pull  of  the  shifting  magnet  is 
less  than  that  of  the  return 
spring,  which,  therefore,  throws 
the  pinion  to  its  original  position 
clear  of  the  flywheel.  The  motor 
will  continue  to  revolve,  without 
load,  however,  until  the  starting 
switch  is  opened  or  released;  but 
the  pinion  remains  out  of  mesh, 
because  the  current  required  to 
turn  the  motor  armature  over  is 
not  enough  to  energize  the  shifting  magnet  sufficiently  to  pull  the 
pinion  back  into  mesh  against  the  force  of  the  return  spring. 

251.  The  North  East  Starting  and  Lighting  System  on  the  Dodge  Car. 
— The  North  East  Starting  and  Lighting  system  on  the  Dodge  Broth- 
ers Motor  Car  comprises  the  North  East,  Model  G,  starter-generator, 

Fig.  390. — Battery  indicator. 

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dWin  QV3M  J.H9I* 

*W*-I  0V3M  uri 

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Fig.  388,  and  the  combined  starting  switch  and  reverse  current  cut-out, 
as  shown  in  Fig.  389,  together  with  the  following  accessory  parts  not 
of  North  East  manufacture:  the  storage  battery;  the  charging  indicator, 
Fig.  390;  the  lighting  (and  ignition)  switch;  the  head-lamps,  dash-lamp, 
and  tail-lamp;  and  the  necessary  cables  for  completing  the  electrical 
connections  between  these  several  elements  of  the  system. 



CUT-OUT  ^4 




Fio.  392.- 

(12  VOLT) 

-Circuit  diagram  of  North  East  starter-generator,  Model  G  and  reverse  current 

The  starter-generator  serves  to  start  the  engine  and  to  provide  current 
for  the  lamps  and  other  electrical  accessories  as  well  as  for  the  ignition 
system.  The  battery  acts  as  the  source  of  current  while  the  engine  u 
not  in  operation  or  is  running  slowly,  but  at  all  engine  speeds  above  350 
r.p.m.  the  starter-generator  converts  automatically  into  a  generator  and 
supplies  current  to  the  entire  electrical  system. 

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In  Fig.  391  is  shown  a  complete  wiring  diagram  of  the  car,  and  in 
Fig.  392  the  circuit  wiring  of  the  starter-generator  and  reverse  current 
cut-out.  In  these  diagrams  the  starting  circuit  is  represented  by  the 
very  heavy  cables;  the  charging  circuit,  where  it  does  not  coincide  with 
the  starting  circuit,  by  the  cables  of  medium  weight;  and  the  lighting 
and  the  ignition  circuits  by  the  lightweight  cables. 

As  will  be  seen  from  the  diagram,  the  starting  circuit  extends  from  the 
positive  terminal  of  the  battery  through  the  starting  switch,  through  the 
starter-generator  armature  and  field  coils,  back  to  the  negative  terminal 
of  the  battery  by  way  of  the  grounded  negative  starter-generator  termi- 
nal, the  car  frame,  and  the  battery  ground  connection.  The  charging 
circuit  is  identical  with  the  starting  circuit,  except  at  the  starting  switch, 

Fig.  393. — Readings  of  battery  indicator. 

where  instead  of  passing  from  one  switch  terminal  to  the  other  through 
the  switch  contacts,  it  extends  through  a  parallel  path  which  includes 
the  reverse  current  cut-out  and  the  charging  indicator.  The  cable 
leading  to  the  lighting  and  ignition  switch  is  attached  to  the  positive 
terminal  of  the  indicator.  From  this  switch  the  lighting  and  the  ignition 
circuits  become  distinct;  and  each,  after  passing  through  its  proper  course, 
reaches  the  car  frame  and  returns  through  it  to  the  source  of  supply. 
Owing  to  the  fact  that  the  charging  circuit  does  not  coincide  entirely 
with  the  starting  circuit,  either  an  ammeter  or  a  battery  indicator  of 
the  C.  O.  D.  type  may  be  used.  This  indicator  reads  " Charge,"  "OB," 
or  "Discharge"  as  shown  in  Fig.  393,  depending  upon  whether  the 
battery  is  being  charged  or  discharged. 

The  starter-generator  is  mounted  on  the  left-hand  side  of  the  engine 


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by  means  of  an  adjustable  support  and  a  clamping-strap  and  runs  at 
three  times  engine  speed,  being  driven  directly  from  the  crankshaft 
through  a  silent  chain  drive.  The  dynamo,  being  a  single-unit  machine, 
employs  but  one  armature  with  only  one  commutator;  one  set  of  field 
windings;  and  one  set  of  brushes  for  the  performance  of  all  of  its  functions, 
both  as  a  starter  and  as  a  generator.  The  dynamo  operates  at  12  volts, 
when  operating  both  as  a  motor  and  as  a  generator. 

As  may  be  seen  from  Fig.  392,  the  dynamo,  while  starting  the  engine, 
acts  as  a  cumulative  compound-wound  motor;  but  while  serving  as  a  gen- 
erator operates  as  a  differentially  compound-wound  machine.  Generator 
regulation  is  effected  by  the  Third  Brush  principle  in  combination  with 
the  differential  influence  of  the  series  field  upon  the  shunt  field. 

When  the  dynamo  is  driven  as  a  generator,  the  armature  normally 
begins  to  deliver  current  to  the  battery  when  the  car  speed  is  approxi- 
mately 10  miles  per  hour.  From  this  point  on,  the  charging  rate  rises 
rapidly  with  increasing  speed  until  the  standard  maximum  rate  of  6  am- 
peres is  reached  at  a  car  speed  of  16  to  17  miles  per  hour.  From  this 
speed  to  20  or  21  miles  per  hour  the  rate  remains  practically  constant; 
but  above  21  miles  per  hour  it  decreases  gradually  until  at  the  upper 
speed  limit  of  the  engine  it  may  become  as  low  as  3  amperes.  Since 
generator  regulation  is  taken  care  of  by  the  Third  Brush  principle  in 
combination  with  the  differential  effect  of  the  series  field  upon  the  shunt 
field,  the  charging  current  may  be  adjusted  by  shifting  the  third  brush. 
This  can  be  done  with  a  screwdriver,  by  turning  the  special  adjusting 
screw  in  the  brush  end  cap. 

Without  exception,  all  of  the  connections  of  the  starting  and  lighting 
system  must  be  made  exactly  as  indicated  in  the  diagrams,  if  satisfac- 
tory results  are  to  be  obtained  from  this  equipment.  Special  care  should 
be  taken  to  see  that  the  ground  wire  on  the  cut-out  makes  good  connec- 
tion at  all  times,  as  an  open  at  this  point  would  prevent  the  cut-out  from 
closing.  The  shunt  field  is  provided  with  a  fuse  which  should  be  removed 
in  case  the  car  is  to  be  operated  with  the  battery  disconnected. 

262.  The  Delco  Single-unit  Starting,  Lighting,  and  Ignition  System 
on  the  Buick. — The  principal  parts  of  the  Delco  starting,  lighting,  and 
ignition  system  used  on  the  Buick  "six"  consists  of  the  motor-generator 
Fig.  394,  the  combination  lighting  and  ignition  switch,  Fig.  395,  and  a 
6-volt  storage  battery. 

The  motor-generator  is  mounted  on  the  right  side  of  the  engine  and 
is  arranged  so  that  the  extension  of  the  water  pump  shaft  drives  the 
armature  through  an  overrunning  clutch  whenever  the  engine  is  in 
operation.  At  the  rear  of  the  motor-generator  are  the  starting  gears, 
as  shown  in  Fig.  396.  These  are  assembled  in  the  bell  housing  covering 
the  flywheel,  and  are  for  the  purpose  of  making  connection  between  the 

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armature  shaft  and  the  flywheel  for  the  cranking  operation.  An  over- 
running clutch,  Fig.  396,  is  built  in  the  largest  of  these  gears,  to  prevent 
driving  of  the  armature  from  the  flywheel  end. 

The  armature  in  the  Delco  motor-generator  differs  from  the  usual 
form  of  construction  in  that  it  is  double  wound,  having  two  separate 
windings  and  commutators,  one  being  for  th$  motor,  the  other  for  the 
generator.  The  brushes  are  so  arranged  on  the  two  commutators,  as 
shown  in  Fig.  397,  that  when  the  starting  pedal  is  pushed  down  and  the 
motor-generator  is  being  used  to  crank  the  engine,  both  of  the  motor 
brushes  make  contact  with  the  motor  commutator,  while  at  the  same  time 
one  of  the  generator  brushes  is  lifted  off.     However,  when  the  starting 






Fio.  394. — Delco  motor-generator  for  Buick  "six.' 

pedal  is  released,  one  of  the  starting  brushes  is  automatically  raised  and 
the  lifted  generator  brush  dropped  to  make  contact  with  its  commutator, 
thus  permitting  the  dynamo  to  operate  as  a  generator.  The  generator 
output  is  regulated  by  the  Third  Brush  principle. 

The  system  has  no  cut-out  as  is  usually  found  in  most  systems,  the 
closing  and  opening  of  the  charging  circuit  being  taken  care  of  by  the 
turning  on  and  off  of  the  ignition  button.  A  circuit  diagram  of  the  sys- 
tem is  shown  in  Fig.  398.  As  will  be  seen,  the  combination  switch 
controls  the  lighting  and  ignition  circuits,  and  the  circuit  between  the 
generator  and  the  storage  battery.  The  button  on  the  extreme  left 
of  the  switch  controls  the  main  head  lights;  the  second  button  controls 
the  auxiliary  head  lights;  the  third  button  controls  the  rear  and  cowl 

Digitized  by  LiOOQ IC 



lights;  while  the  fourth  button,  marked  "IGN,"  controls  both  the 
ignition  circuit  and  the  circuit  between  the  generator  and  storage  battery. 
By  controlling  the  latter  circuit,  the  combination  switch  thus  performs 
the  function  of  an  automatic  cut-out  as  is  commonly  used  for  this  pur- 
pose. For  this  reason,  the  "  IGN  "  button  should  not  be  left  in  the  "on" 
position  when  the  engine  .is  not  running. 

On  the  back  of  the  combination  switch 
is  located  the  circuit  breaker  which  takes 
the  place  of  fuses.  This  is  a  protective  de- 
vice which  prevents  excessive  discharging  of 
the  storage  battery,  or  damage  to  the  switch 
or  light  wires  in  the  event  of  a  ground  on 
any  of  these  wires.  All  of  the  current  for 
the  lights  is  conducted  through  the  circuit 
breaker.  Whenever  an  excessive  current  flows  through  the  circuit 
breaker,  it  opens  the  circuit  intermittently,  causing  a  clicking  sound. 
This  will  continue  until  the  ground  is  removed,  or  the  switch  is  operated 
to  open  the  circuit  on  the  grounded  wire.  When  the  ground  is  removed, 
the  circuit  is  restored  automatically,  there  being  nothing  to  replace  as  is 
the  case  with  fuses. 

Fig.    395. — Delco    combination 
ignition  and  Ughting  switch. 

ing  Gear 

Shifting  Rod 



Fig.  396. — Starting  gears  and  overrunning  clutch  on  Deloo  motor-generator. 

The  numbers  on  the  switch  terminals  correspond  with  the  numbers 
on  the  circuit  diagram,  thus  making  it  comparatively  easy  to  connect  up 
this  switch  if  for  any  reason  it  has  been  disconnected.  Referring  to 
Figs.  394,  397,  and  398,  the  motor  generator  performs  three  operations 
as  follows: 

(A)  Motoring  the  Generator. — This  operation  is  necessary  in  order 
that  the  starting  gears  may  be  brought  in  mesh  with  the  small  gear 

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on  the  armature  shaft  and  with  the  teeth  on  the  flywheel.  This  takes 
place  whenever  the  ignition  button  on  the  combination  switch  is  pulled 
out.  This  button  completes  the  circuit  from  the  storage  battery  to  the 
generator  windings  and  allows  current  to  be  discharged  from  the  storage 
battery  through  the  shunt-field  winding  and  the  generator  windings  on 
the  armature,  thus  causing  the  armature  to  revolve  slowly. 

(B)  Cranking  Operation. — The  cranking  operation  is  performed  when 
the  starting  gears  are  brought  fully  in  mesh  and  the  motor  brush  makes 
contact  with  the  commutator.  This  is  arranged  so  that  the  starting 
gears  are  fully  in  mesh  before  the  motor  brush  makes  contact  on  the  com- 
mutator. Since  considerable  power  is  required  for  the  cranking  opera- 
tion, a  heavy  discharge  from  the  storage  battery  is  necessary.     The 



Fio.  397. — End  view  of  Delco  motor-generator  showing  brush  arrangement. 

cranking  circuit  is  made  up  of  heavy  copper  cable  and  the  motor  brushes 
and  motor  windings  are  designed  to  operate  with  a  large  current.  For 
this  reason,  there  must  be  no  loose  or  poor  connections  in  this  circuit. 
All  battery  connections,  motor  connections,  and  motor  brushes  must 
make  good  electrical  contact. 

(C)  Generating  Electrical  Energy. — After  the  cranking  operation 
is  completed,  the  starting  pedal  is  returned  by  a  spring.  This  disconnects 
the  starting  gears,  raises  the  motor  brush,  and  allows  the  generator  brush 
to  make  contact  with  the  commutator  while  the  armature  is  driven  by  the 
extension  of  the  pump  shaft.     At  very  low  engine  speeds,  the  voltage 

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generated  is  not  sufficient  to  overcome  the  voltage  of  the  storage  battery 
and  a  small  amount  of  current  may  be  discharged  from  the  battery 
through  the  generator  winding;  but  this  amount  is  very  small.  At  all 
normal  engine  speeds  the  voltage  of  the  generator  exceeds  that  of  the 
storage  battery,  and  current  is  either  charged  into  the  storage  battery 
or  is  used  directly  for  lights,  horn,  and  ignition. 

The  ammeter  on  the  combination  switch  is  for  the  purpose  of  indicat- 
ing the  amount  of  current  that  is  being  charged  into  the  storage  battery 
or  discharged  from  it,  with  the  exception  of  the  cranking  current. 

The  generator  commences  to  charge  the  battery  at  engine  speeds 
corresponding  to  7  miles  per  hour  on  high  gear,  providing  no  current 
is  being  used  for  lights.  The  output  of  the  generator  increases  up  to 
approximately  25  miles  per  hour,  and  at  the  higher  speeds  the  output 
is  decreased.    This  characteristic  is  due  to  the  Third  Brush  principle 

Fio.  390. — Deloo  generator  and  ignition  unit  for  Oldsmobile  Eight. 

of  regulation  employed.  The  maximum  charging  rate  usually  should  be 
about  16  amperes. 

263.  The  Delco  Two-unit  Starting,  Lighting,  and  Ignition  System  on 
the  Oldsmobile  Eight. — The  starting  and  lighting  system  as  equipped 
on  the  Oldsmobile  Eight,  model  45A,  is  a  typical  Delco  system  of  the 
two-unit  type.  It  consists  of  a  generator  and  ignition  unit,  Fig.  399; 
a  starting  motor,  Fig.  400;  a  combination  ignition  and  lighting  switch, 
Fig.  395  (same  as  used  on  the  Buick  "six") ;  a  starting  switch,  Fig.  401; 
and  a  6-volt  storage  battery.  The  external  wiring  of  the  car  is  shown 
in  Kg.  402. 

The  generator  with  the  ignition  unit  is  mounted  between  the  cylinders 
in  front  of  the  carburetor  and  is  driven  by  the  fan  belt  as  shown  in  Fig. 
403.    The  starting  motor  is  located  back  of  the  flywheel  on  the  lower 

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right  side,  the  drive  between  the  starting  motor  and  the  flywheel  being 
by  means  of  the  Bendix  drive. 

Like  the  single-unit  system,  no  reverse  current  cut-out  is  used,  the 
closing  and  opening  of  the  charging  circuit  being  controlled  by  the  igni- 
tion button  as  may  be  seen  from  the  circuit  diagram  in  Fig.  404.    It 


Fio.  400. — Deloo  starting  motor  for  Old smo bile  Eight. 

will  also  be  seen  that  the  lighting  circuits  are  protected  by  a  circuit 
breaker  the  same  as  on  the  Buick,  instead  of  fuses.  The  generator  is 
of  the  two-pole  shunt-wound  type  regulated  by  the  Third  Brush  method 
of  field  control.  By  this  manner  of  regulation  it  is  possible  to  obtain  the 
highest  charging  rate  between  15  to  25  miles  per  hour.    The  maximum 



Fio.  401. — Delco  starting  switch. 

charging  rate  should  be  about  15  amperes  at  20  miles  per  hour  on  high 
gear.  If  the  ammeter  indicates  an  appreciably  higher  charge  than 
this,  the  charging  rate  should  be  adjusted  by  shifting  the  third  brush 
slightly  in  the  opposite  direction  to  armature  rotation.  In  case  such 
an  adjustment  is  made,  care  should  be  taken  to  make  sure  that  the 
third  brush  makes  perfect  fit  with  the  commutator.  The  arrangement 
of  the  brushes  is  shown  in  Fig.  405. 

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It  will  be  noted  in  the  circuit  diagram  of  the  starting  motor,  Kg. 
404,  that  each  of  the  four  field  coils  is  connected  in  parallel  with  another 
field  coil,  each  pair  being  in  series  with  the  armature  winding.  The 
winding  of  the  motor  is  such  that  the  armature  is  in  the  circuit  between 
the  two  pairs  of  field  windings.  The  starting  circuit  is  shown  by  the 
heavy  black  lines  in  the  diagrams.  Care  should  be  taken  to  see  that 
the  battery  terminals  are  kept  free  from  corrosion  at  all  times  to  insure 
proper  operation  of  the  starter. 

264.  Delco-Liberty  Lighting  System  on  U.  S.  Standardized  Military 
Truck,  Class  B. — The  special  Delco  generator  used  on  the  U.  S.  Stand- 
ardized Military  Truck,  Liberty — Class  B,  is  shown  in  Fig.  406.  The 
generator  is  mounted  in  a  housing  on  the  right  side  of  the  crank  case, 

Fig.  403. — Delco  generator  installation  on  Oldsmobile  eight-cylinder  engine,  Mode)  45A. 

and#is  held  in  place  by  a  large  set  screw  through  the  top  of  the  housing, 
the  armature  being  driven  from  the  rear  end  of  the  governor  shaft 
through  an  Oldham  coupling.  A  complete  wiring  diagram  of  the  truck 
is  shown  in  Fig.  407. 

As  may  be  seen  from  the  diagram,  the  current  output  of  the  generator 
is  regulated  by  the  Third  Brush  method.  The  generator  starts  charging 
at  low  speed,  and  the  output  increases  with  speed  until  a  maximum 
output  is  reached,  when  it  starts  to  decrease.  The  maximum  output, 
as  indicated  by  the  ammeter  on  the  dash,  should  be  10  to  13  amperes, 
with  all  the  lights  turned  off.  If  it  is  considerably  higher  than  this, 
or  if  it  is  so  low  that  the  battery  does  not  get  sufficient  charge,  the  output 
may  be  adjusted.  This  may  be  done  by  loosening  the  three  screws 
in  the  small  circular  plate  on  the  commutator  end  of  the  generator,  as 
shown  in  Fig.  406,  and  shifting  the  third  brush.  To  raise  the  output, 
this  plate,  which  connects  with  the  third  brush,  should  be  rotated  slightly 

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in  a  clockwise  direction  (same  as  armature  rotation),  and  to  lower  the  out- 
put the  plate  should  be  rotated  slightly  in  a  counterclockwise  direction. 
This  system  contains  no  reverse  current  cut-out,  this  function  being 
provided  for  by  the  ignition  switch.     The  generator  is  driven  by  an  Old- 








Fio.  405. — Arrangement  of  brushes  on  Delco  generator  used  on  Oldsmobile  Eight. 

ham  or  double  cross-type  coupling  which  contains  a  ratchet  clutch. 
When  the  ignition  switch  is  turned  on  while  the  engine  is  still,  the  gen- 
erator, being  connected  to  the  battery,  starts  to  run  as  a  shunt-wound 
motor  and  draws  a  small  amount  of  current  from  the  battery.  As  the 
generator  revolves,  the  clutch  ratchet  operates  and  a  clicking  noise  is 




Fio.  406. — Delco  generator  for  Liberty-Class  B,  military  truck. 

heard.  This  is  an  indication  that  the  generator  is  functioning  properly. 
It  is  also  a  warning  that  the  ignition  switch  is  "  On,"  and  unless  the  driver 
is  about  to  crank  the  engine,  the  switch  should  be  turned  "Off." 

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The  ignition  and  lighting  switch  contain,  besides  the  two  switches, 
an  ammeter,  a  circuit  breaker,  and  an  instrument  lamp,  as  shown  in  Fig. 

Ignition  TSmtch. — The  ignition  switch  has  one  "Off"  and  one  "On" 
position  and  controls  both  of  the  ignition  systems.  In  the  "Off" posi- 
tion the  magneto  is  grounded  and  the  generator  and  battery  ignition  are 
disconnected  from  the  battery.  In  the  "On"  position  the  battery  is 
connected  to  the  generator,  and  the  battery  and  magneto  ignition  systems 
both  operate  simultaneously. 

The  ignition  switch  should  always  be  turned  off  unless  the  truck 
is  to  be  operated.  If  the  switch  is  allowed  to  remain  "On"  with  the 
engine  not  running,  the  battery  will  become  discharged  after  several 
hours,  and  starting  will  be  very  difficult. 

Lighting  Suritch. — The  lighting  switch  has  three  positions: 

First  position:  Lights  the  danger  zone  or  side  lamps. 

Second  position:  Lights  the  side,  instrument  and  tail  lamps. 

Third  position:  Lights  the  head,  instrument  and  tail  lamps.  This 
order  was  reversed  on  some  of  the  first  trucks. 

Instrument  Lamp. — The  instrument  lamp  is  provided  with  inner  and 
outer  covers  which  are  removable  for  replacement  of  the  bulb.  The  outer 
cover  is  arranged  so  that  it  may  be  rotated  until  the  light  is  entirely 
shut  off. 

Ammeter. — The  ammeter  always  indicates  the  actual  current  going 
into  the  battery  or  being  taken  out  of  it. 

Circuit  Breaker. — The  circuit  breaker  which  is  mounted  on  the  back 
of  the  switch  is  connected  in  the  lighting  circuit.  When  a  ground  occurs 
on  the  lighting  circuit,  the  circuit  breaker  operates  with  a  buzzing  or 
rattling  noise  until  the  cause  of  the  trouble  is  removed.  The  circuit 
breaker  also  greatly  reduces  the  discharge  current  caused  by  the  ground 
or  short-circuit  and  prevents  the  wires  from  burning  and  the  battery 
from  becoming  quickly  discharged. 

255.  The  "F.  A."  Liberty  Ford  Starting  and  Lighting  System.— The 
"F.  A."  Liberty  starting  and  lighting  system  installed  on  Ford  sedans 
and  coupelets  consists  of  a  starting  motor,  a  generator,  a  charging 
indicator  or  ammeter,  a  combination  ignition  and  lighting  switch  and 
the  lights,  together  with  the  necessary  wiring  and  connections.  The  top 
view  of  the  Ford  engine  showing  the  generator  and  motor  installation 
is  shown  in  Fig.  408. 

Starting  Motor. — The  starting  motor,  Fig.  409,  is  a  typical  4-pole 
series  wound  6-volt  motor,  mounted  on  the  left-hand  side  of  the  engine 
and  bolted  to  the  transmission  cover.  When  in  operation,  the  pinion 
of  the  Bendix  drive  shaft  meshes  with  the  teeth  on  the  flywheel,  thus 
turning  the  crankshaft  over. 

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Generator. — The  generator,  Fig.  410,  is  a  6-volt,  4-pole,  Third  Brush 
type  of  generator  mounted  on  the  right-hand  side  of  the  engine  and  bolted 





Pio.  408. — Top  view  of  Ford  engine  showing  installation  of  Liberty  generator  and  starting 





Fig.  409. — "F.  A."  Liberty  starting  motor  for  Ford  car. 




Fio.  410.— "F.  A."  Liberty  generator  for  Ford  car. 

to  the  cylinder  front  end  cover.     It  is  driven  by  the  pinion  of  the  armature 
shaft  meshing 'with  the  large  timing  gear.     The  charging  rate  of  the 

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generator  is  set  so  as  to  "cut-in"  at  engine  speeds  corresponding  to  10 
M.P.H.  and  reaches  a  maximum  charging  rate  at  20  M.P.H.  At 
higher  speeds,  the  charging  rate  will  taper  off — a  characteristic  of  Third 
Brush  regulation.  The  closing  and  opening  of  the  charging  circuit  at 
suitable  speeds  is  accomplished  by  the  reverse  current  cut-out  relay, 
which  is  mounted  on  the  back  of  the  dash. 

Lighting  System. — The  lighting  system  consists  of  two  headlights  and 
a  tail-light  all  operated  by  a  combination  lighting  and  ignition  switch 
located  on  the  instrument  board.  The  lighting  system  is  of  the  ground 
return  type,  the  car  frame  serving  as  a  return  path  for  the  current  from 
the  lamps  to  the  negative  terminal  of  the  battery.  All  of  the  lamp  bulbs 
are  connected  in  parallel  so  that  the  burning  out  or  removal  of  any  one 
of  them  will  not  affect  the  other.  The  wiring  diagram,  Fig.  411,  shows 
the  different  circuits  and  the  course  of  the  current. 

Ammeter. — The  charging  indicator  or  ammeter,  Fig.  412,  is  located  on 
the  instrument  board.  This  indicator  registers  " charge"  when  the  gen- 
erator is  charging  the  battery,  and 
"discharge"  when  the  lights  are  burn- 
ing and  the  motor  not  running  above  10 
M.P.H.  At  an  engine  speed  of  15 
M.P.H.  or  more  the  indicator  should 
show  a  reading  of  from  10  to  12  am- 
peres with  the  lights  off  and  from  4  to 
6  amperes  with  the  lights  on  bright. 

Lubrication. — The  starting  motor  is 
lubricated  by  the  Ford  splash  system, 
the  same  as  the  engine  and  trans- 
mission. The  generator  is  lubricated 
by  a  splash  of  oil  from  the  timing  gears. 
In  addition,  an  oil  cup  is  located  at  the 
end  of  the  generator  housing.     A  few 

drops  of  oil  should  be  applied  every  two  weeks  or  about  once  each  500 
to  1000  miles  of  travel. 

Operating  the  Car  with  Battery  Removed. — If  for  any  reason  the  engine 
is  to  be  run  with  the  generator  disconnected  from  the  battery,  as  on  a 
block  test,  make  sure  that  a  copper  wire  is  connected  between  the  terminal 
on  top  of  the  generator  and  one  of  the  valve  cover  stud  nuts.  This 
"shorts"  the  main  brushes  and  prevents  the  generator  from  building  up 
a  voltage.  Failure  to  do  this  when  running  the  engine  with  the  generator 
disconnected  from  the  battery  will  no  doubt  result  in  serious  injury  to 
the  generator  field  and  armature  windings. 

Caution. — Care  should  be  taken  to  prevent  an  accidental  short  circuit 
between  the  battery  terminal  No.  3  and  the  magneto  terminal  No.  2  on 


Fio.  412. — Dash  type  ammeter  as 
used  on  Ford  car. 

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the  terminal  block  located  on  the  back  of  the  dash.  Since  the  introduction 
of  a  battery  current  into  the  magneto  winding  may  discharge  the  magnets, 
the  positive  wire  should  be  disconnected  from  the  battery  whenever 
repairing  is  necessary  in  the  ignition  system  or  car  wiring.  The  end  of 
this  wire  should  be  wound  with  tape  to  prevent  its  coming  into  contact 
with  the  ignition  system  or  metal  parts  of  the  car. 

266.  Automobile  Lamps  and  Reflectors. — Headlight  Focusing. — In  all 
automobile  electric  headlights  having  a  parabolic  shaped  reflector, 
there  is  a  theoretical  point  of  focus  from  which  any  light  rays  will  be 
reflected  in  parallel  rays  directly  ahead  of  the  lamp  reflector.  Con- 
sequently, to  secure  the  best  lighting  results  the  bulb  filament  should 

,  be  located  at  this  focal  point.  To 
accomplish  this,  all  head  lamps  are 
equipped  with  some  method  of  focus 
adjustment,  one  common  type  being 
that  shown  in  Fig.  413. 

In  focusing  a  lamp  it  is  necessary 
to  move  the  lamp  bulb  forward  or 
backward  to  a  point  where  the  re- 
flected rays  give  the  desired  lighting 
effect.  To  do  this,  it  is  usually  neces- 
sary to  open  the  front  of  the  lamp 
and  either  remove  the  reflector  and 
adjust  the  bulb  from  the  back  of  the 
reflector,  or,  in  the  type  shown, 
merely  turn  the  adjusting  screw  at 
the  top  of  the  reflector.  By  turning 
the  screw  to  the  right  the  bulb  will 
be  moved  toward  the  reflector,  while 
by  turning  the  screw  to  the  left  the 
bulb  will  be  moved  away  from  the 
One  lamp  at  a  time  should  be  focused,  the  other  being  covered  in 
order  that  the  rays  of  one  shall  not  interfere  with  the  rays  of  the  other. 
The  best  place  to  focus  the  lamps  is  on  a  dark  road.  A  good  plan  is  to 
first  focus  the  reflected  light  into  a  small  ray  or  pencil  beam,  then  align 
this  beam  properly  with  the  road  by  resetting  the  lamp  supports,  making 
sure  that  the  car  is  pointed  so  that  the  light  will  project  straight  ahead, 
as  desired  under  ordinary  driving  conditions.  In  most  states,  the  dim- 
ming laws  require  that  with  the  car  on  the  level,  the  reflected  beam  of 
light  from  either  lamp  should  not  rise  more  than  42  in.  from  the  ground 
at  a  point  75  ft.  in  front  of  the  car. 

Lamp  focus  adjustment  may  also  be  accomplished  by  placing  the  car 

Fio.  413. — Sectional  view  of  head  lamp 
showing  lamp  focusing  adjustment. 

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in  a  level  position  where  the  light  can  be  projected  on  a  wall  50  to  100  ft. 
from  the  car.  With  the  car  in  this  position,  the  lamp  bulb  should  be 
moved  forward  or  backward  until  the  light  on  the  wall  indicates  the 
greatest  brilliancy,  and  free  from  dark  spots  or  rings. 

In  replacing  lamp  bulbs,  care  should  be  taken  to  replace  them  with 
bulbs  of  the  proper  voltage  and  of  no  higher  current  consumption  than 
intended  for  the  system.  This  is  to  prevent  an  excessive  load  on  the 
battery  and  generator.  The  current  consumption  of  Mazda  lamps  for 
automobiles  is  as  follows: 

Candle-power 1J£ 

Current  in  amperes 0. 25 

Watts 1.5 

From  the  table  it  will  be  noted  that  the  power  consumption  of  headlight 
bulbs  is  one  watt  per  candle-power. 

Dimming. — The  devices  commonly  employed  to  meet  non-glare  re- 
quirements usually  make  use  of  one  of  the  following  principles:  (1) 
reducing  the  amount  of  light  at  its 
source  either  by  means  of  a  resistance 
unit  or  by  connecting  the  headlights 
in  series;  (2)  diffusion  or  spreading 
of  the  pencil  rays  through  special 
lenses;  (3)  deflection  of  the  pencil 
rays  below  the  level  at  which  the 
glare  is  objectionable  by  means  of 
special  lenses  or  reflectors;  (4)  auxil- 
iary small  bulbs  placed  in  the  head- 
light out  of  focus;  and  (5)  tilting  the 
headlight  reflector. 

In  Fig.  414  is  shown  a  cross  sec- 
tion view  of  the  reflector  tilting  type 
of  headlight  used  on  the  Cadillac 
Eight.  The  reflectors  in  the  head- 
lamps are  pivoted  so  that  they  may 
be  tilted,  being  controlled  by  a  lever 
on  the  steering  column.  When  the 
road  is  clear  and  the  illumination  of 
the  distant  road  is  desired,  the  re- 
flectors are  adjusted  to  direct  the  light  straight  ahead.  When  a  vehicle, 
traveling  in  the  opposite  direction  approaches,  the  reflectors  are  tilted 
down  by  simply  raising  a  small  lever  on  the  steering  column,  thus  deflect- 
ing the  rays  below  the  level  of  vision  of  the  occupants  of  the  approach- 
ing car,  and  increasing  the  illumination  directly  in  front  of  the  car, 
where  it  is  most  needed. 

Fio.  414. — Section  of  head-lamp  used 
on  Cadillac  Eight  showing  method  of  tilt- 
ing reflector  for  dimming. 

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Cleaning  Reflectors.— When  lamp  reflectors  become  tarnished,  great 
care  should  be  taken  in  cleaning  them  to  prevent  scratching  of  the  reflect- 
ing surface.  The  reflector,  being  plated  with  pure  silver  and  being  very 
highly  polished,  is  very  easily  scratched  unless  great  care  is  exercised, 
even  if  cleaned  with  soft  material.  If  reflectors  have  become  dull  from 
long  service,  they  can  be  polished  by  using  a  clean  chamois  and  rouge  or 
crocus  such  as  is  used  by  jewelers  for  cleaning  watches.  The  chamois 
should  be  soft  and  free  from  dust,  and  should  not  be  used  for  any  other 
purpose.  To  polish  the  reflector,  the  chamois  and  rouge,  dampened  with 
alcohol,  should  be  used  first  to  remove  any  spots  or  heavy  tarnish.  The 
reflector  should  then  be  wiped  off  using  a  second  piece  of  chamois  with 
dry  rouge.     This  will  give  a  very  high  finish.     The  polishing  should  be 

done  in  a  rotary  motion,  as  indicated 
by  the  arrows  in  Fig.  415,  to  avoid 
leaving  marks  on  the  reflector.  The 
fingers  should  not  come  in  contact 
with  the  reflecting  surface. 

257.  Care  of  Starting  and  Light- 
ing Apparatus. — In  order  to  procure 
the  best  results  from  any  mechanical 
or  electrical  device,  it  is  important 
that  it  be  properly  installed,  prop- 
erly operated,  and  reasonably  well 
cared  for.  The  automobile  owner  and 
mechanic  can  eliminate  many  of  the 
Fio.  415.— Method  oTdeaning  head-  common  starting  and  lighting  troubles 
lamp  reflectors.  by  an  occasional  inspection  of    the 

different  equipment,  and  seeing    to 
it  that  all  parts  are  working  properly. 

Lubrication. — In  practically  all  starting  motors  and  generators,  the 
bearings,  which  are  usually  of  the  anti-friction  type — either  ball  bearings 
or  roller  bearings — are  provided  with  an  oiler  for  lubrication  of  the  bear- 
ings. The  lubrication  required  by  the  different  systems  varies  with  the 
type  of  bearing  used;  however,  a  general  practice  which  may  be  followed 
is  to  oil  each  bearing  of  the  generator  with  5  or  6  drops  of  light  high-grade 
oil  every  2  weeks  or  every  500  to  1000  miles  of  travel,  and  the  starting 
motor,  about  once  each  two  months  of  service.  Care  should  be  taken  not 
to  over-oil  or  to  get  oil  on  the  commutator  and  brushes. 

Commutator  and  Brushes. — A  removable  band  which  provides  access 
to  the  commutator  and  brushes  is  usually  placed  around  the  commutator 
end  of  the  generator.  Inspection  of  these  parts  every  2500  to  3000 
miles  should  be  sufficient.  The  commutator  wears  naturally  to  a  brown- 
ish surface  in  normal  use,  but  if  it  appears  black  or  scored,  the  surface 

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should  be  smoothed  with  a  piece  of  fine  No.  00  sandpaper.  Never  use 
emery  doth  for  this  purpose.  Care  should  be  taken  to  blow  out  all  the 
dust,  also  to  see  that  the  brushes  move  freely  in  their  pivots  or  holders 
so  that  the  spring  tension  holds  them  in  good  contact  with  the  commu- 
tator. When  replacing  the  cover,  care  should  be  taken  to  have  the  ends 
of  the  band  come  over  a  solid  part  of  the  generator  frame  to  close  the  gap 
and  exclude  all  dirt,  water,  and  oil  from  the  commutator  and  brushes. 
When  new  brushes  are  to  be  installed,  they  should  be  made  to  fit  perfectly 
on  the  commutator.  It  is  always  a  good  policy  to  use  only  the  brushes 
sent  out  by  the  manufacturer  of  the  machine. 

Wiring. — All  wiring  should  be  inspected  several  times  each  season 
to  see  that  all  terminals  are  tight  and  that  all  wires  are  perfectly  insulated 
and  not  in  rubbing  contact  with  the  car  frame  or  any  moving  parts,  as  the 
continuous  vibration  and  rubbing  will  wear  the  insulation  away,  causing 
harmful  "grounds"  and  short  circuits.  One  of  the  most  important  pre- 
cautions to  take  is  to  keep  the  battery  terminals  free  from  corrosion,  and 

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The  automobile  chassis  includes  all  parts  of  the  car  with  the  exception 
of  the  body  and  its  immediate  accessories.  These  parts  are  the  frame, 
springs,  axles,  steering  gear,  wheels,  brakes,  transmission  system,  and  the 
power  plant  with  its  accessories.  Figure  416  is  a  plan  view  of  the  Stude- 
baker  Six  chassis  with  all  of  the  principal  parts  indicated,  and  Fig.  417 
is  a  section  view  of  the  Packard  Twin  Six  chassis. 

268.  General  Arrangement  of  Chassis. — The  power  plant  of  an  auto- 
mobile is  placed  at  the  front  of  the  car  and  is  supported  on  cross  members 
between  the  two  sides  of  the  car  frame.  On  the  Studebaker  car,  Fig. 
416,  a  sub-frame  for  the  purpose  of  supporting  the  rear  of  the  power  plant, 
the  clutch,  and  the  transmission  gears  has  been  built  in.  The  power 
plant  is  supported  at  four  points,  two  at  the  front  and  two  at  the  back 
of  the  engine.  On  the  Mitchell  car,  Fig.  418,  the  engine  is  supported 
at  only  three  points  as  indicated.  The  advantage  of  the  three-point 
support  is  that  the  engine  bearings  are  relieved  of  any  stress  or  strain 
caused  by  the  engine  crankshaft  being  thrown  out  of  alignment  with  the 
rest  of  the  mechanism,  if  the  frame  of  the  car  should  be  sprung  or  twisted. 

The  power  plant,  clutch,  and  transmission  gears  of  the  Cadillac  Eight, 
Fig.  419,  are  built  into  one  unit  called  a  unit  power  plant.  This  is  sup- 
ported at  one  point  in  front  and  two  in  the  rear,  thus  giving  the  three- 
point  support. 

The  change  gears  or  transmission  may  be  contained  as  a  unit  with  the 
power  plant  as  in  Fig.  419,  they  may  be  carried  amidship  as  on  the  Mit- 
chell, Fig.  418  and  the  Pierce  Arrow,  Fig.  420,  or  they  may  be  placed 
just  in  front  of  the  rear  axle  as  on  the  Briscoe,  Fig.  421.  One  objection 
to  placing  the  transmission  in  front  of  the  rear  axle  is  that  the  gears  are 
subjected  to  the  continual  jolting  and  jarring  due  to  the  rear  wheels  pass- 
ing over  rough  roads.  The  most  desirable  location  for  the  transmission 
is  as  a  unit  with  the  power  plant  as  in  Fig.  419,  or  amidship  as  in  Fig. 

269.  Frames. — The  frame  is  a  most  important  part  of  the  car  due 
to  the  fact  that  it  supports  the  power  plant,  transmission  mechanism, 
etc.  Consequently,  it  must  be  exceptionally  strong  and  at  the  same  time 
not  too  heavy.  The  frame  is  made  of  pressed  channel-section  steel  such 
as  illustrated  in  Fig.  422.    It  is  made  much  deeper  at  the  center  than  at 


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Fio.  416. — Chassis  of  Studebaker  Six. 

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the  ends  in  order  to  withstand  the  greater  bending  stresses.  The  kick-up 
at  the  rear  is  for  the  purpose  of  lowering  the  center  of  gravity  of  the  car 
and  also  for  allowing  greater  spring  action  on  the  rear  springs.  The 
frame  is  narrowed  at  the  front  in  order  to  permit  a  shorter  turning  radius 
when  steering. 

The  side  members  of  the  frame  may  be  straight  and  parallel  as  on  the 
Ford  car,  Fig.  423,  or  the  straight  members  may  be  tapered  toward  the 
front  as  in  Fig.  421.  By  tapering  the  frame  at  the  front,  it  is  possible  to 
have  a  shorter  turning  radius  for  the  car.  The  taper  also  permits  the  use 
of  a  wider  body  on  the  frame.  This  gives  a  greater  seating  capacity  with 
more  room.  Many  frames,  as  in  Fig.  420,  have  the  side  members  straight 
and  parallel  up  to  a  certain  point  where  the  frame  is  suddenly  narrowed. 

Fig.  417. — Sectional  view  of  Packard  Twin  Six  car. 

Another  shape  of  frame  is  that  of  the  Studebaker  Six,  Fig.  416,  on  which 
the  frame  has  a  long  taper  near  the  center. 

In  rare  cases,  frames  have  been  constructed  of  wood  instead  of  metal. 
The  wooden  frames  may  be  either  of  solid  timber  or  of  laminated  strips 
glued  together  and  sometimes  reinforced  by  steel  strips.  The  wood 
frame  is  very  strong  and  light  and  does  not  transmit  so  much  vibration 
as  the  steel  frame.  A  frame  made  of  second-growth  ash  and  used  on  the 
Franklin  car  is  shown  in  Fig.  424. 

260.  Springs  and  Spring  Suspension. — The  frame  of  the  automobile 
is  supported  on  laminated  leaf  springs  which  are  directly  attached  to  the 
axles.  The  springs  under  the  frame  must  be  gradual  and  easy  in  their 
action,  and  this  is  why  the  laminated  leaf  springs  are  used.  Coil  springs 
are  used  only  in  places  where  a  great  deal  of  strength  is  needed  in  a  small 
space  and  where  quick  action  is  required. 

Laminated  leaf  springs  are  built  up  of  a  series  of  flat  steel  plates  of 

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variable  lengths  which  are  placed  one  on  top  of  the  other  as  shown  in 
Fig.  425,  the  longest  being  on  the  concave  side  of  the  spring.     The  spring 

Fio.  418.— The  Mitchell  cl 

leaves  are  carefully  hardened  and  tempered.     The  leaves  are  held  to- 
gether by  spring  clips  or  a  center  bolt.     The  ends  of  the  long  leaves  are 

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bent  around  to  form  eyes  by  which  the  spring  can  be  fastened  either  to 
the  frame  or  to  another  spring.  The  springs  are  attached  to  the  axles  by 
means  of  clips  and  spring  blocks  which  are  held  down  on  the  spring  seats 
of  the  axle. 










Fio.  419. — Cadillac  Eight  chassis. 

The  shape  of  a  spring  is  a  very  important  item.  The  main  or  long 
leaf  (sometimes  called  the  master  leaf)  should  be  comparatively  flat, 
as  this  is  its  natural  position  and  can  better  take  care  of  road  jars  and 
shocks.     The  ideal  spring  is  one  having  long,  thin,  and  flat  leaves. 

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Fia.  420. — Pierce  Arrow  chassis. 

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Fig.  421. — Chassis  of  Briscoe  car. 

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Fiq.  422. — Channel  steel  frame  used  on  the  Case  Six. 

■A   • 


i  ift-=^M84 


T*fy — <w  > 



JJ                r«»T  y\ 



BSSBBi  * 

Fio.  423. — Chassis  of  Ford,  Model  T. 

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As  the  spring  is  depressed,  the  leaves  slide  on  one  another.     On  ac- 
count of  this  fact,  some  provision  must  be  made  for  lubricating  the  leaf 

Fio.  424. — Franklin  wood  frame. 

surfaces.     This  is  usually  done  by  forcing  grease  into  specially  cut  ways 
by  means  of  a  compression  grease  cup. 

Rebound  Clip  Spring 

I  Bushing    \     Clip  Bolt  Clip  Cup  Retainer 

Fio.  425. — Laminated  leaf  spring. 

Leaf  springs  are  built  into  the  following  forms  for  automobile  use: 
cantilever,  double  cantilever,  semi-cantilever  or  quarter  elliptic,  semi-elliptic, 
three-quarter  elliptic,  full-elliptic,  platform,  and  double  compounded  elliptic. 

mi        L^fl£ 

Fio.  426. — Cantilever  rear  spring. 

Cantilever  Spring. — The  cantilever  spring  as  shown  in  Fig.  426  is 
fastened  by  shackles  to  the  frame  at  one  end  and  the  center.     The  other 

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end  carries  the  axle.  This  type  of  spring  reduces  the  vibration  on  the 
car  body  because  most  of  the  vibration  and  jar  coming  from  the  axle  is 
taken  up  by  the  springboard  action  of  the  back  of  the  spring.  It  is 
extensively  used  as  a  rear  spring.  _ 

Semi-cantilever  Spring. — Another  type  of  cantilever  spring,  Fig.  427, 
consists  of  one-half  of  a  semi-elliptic  spring,  which  has  a  single  rigid  fas- 

Fia.  427. — Semi-cantilever  rear  spring. 

tening  to  the  frame.  It  permits  very  little  side  sway  and  is  not  quite  so 
springy  in  its  action  as  a  true  cantilever.  This  type  is  sometimes  called 
a  quarter-elliptic  or  eeminxintilever,  and  lias  been  used  for  both  front  and 
rear  suspension. 

Double  Cantilever  Spring. — The  double  cantilever  spring  consists  of 
two  single  cantilever  springs  arranged  as  in  Fig.  428.    By  using  two 

Fig.  428. — Double  cantilever  rear  spring. 

springs,  each  may  be  made  lighter  and  longer,  giving  an  easy  riding  car. 
The  springs,  as  attached  to  the  rear  axle,  furnish  a  good  method  for 
taking  care  of  the  torque  or  the  tendency  of  the  rear  axle  housing  to 
turn  over. 

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Semi-elliptic  Spring. — The  semi-elliptic  spring  has  its  center  fastened 
to  the  axle,  while  the  two  ends  support  the  frame.  This  type  of  spring 
is  generally  used  to  support  the  front  end  of  the  car,  because  it  has  the 
least  amount  of  side  sway.  Since  the  front  axle  is  used  for  steering  pur- 
poses, a  great  amount  of  flexibility  is  not  desired.  Figure  422  illustrates 
the  use  of  the  semi-elliptic  spring  for  both  front  and  rear  suspension. 

Three-quarter  Elliptic  Spring. — The  three-quarter  elliptic  spring,  Fig. 
429,  consists  of  a  semi-elliptic  member  to  one  end  of  which  is  shackled  a 
quarter-elliptic  member.  This  type  of  spring  is  fastened  to  the  frame  at 
one  end  of  the  semi-elliptic  and  at  the  free  end  of  the  quarter-elliptic. 
The  spring  is  attached  to  the  axle  housing  at  the  center  of  the  lower 
member.  The  three-quarter  type  of  spring  is  generally  used  at  the  rear 
of  the  car.  The  semi-elliptic  member  is  quite  long,  giving  an  easy  riding 
car.  When  used,  the  three-quarter  elliptic  permits  of  greater  side  sway 
than  with  either  a  cantilever  or  semi-elliptic. 

Fia.  429. — Three-quarter  elliptic  spring. 

Full-elliptic  Spring. — The  full-elliptic  spring  consists  of  two  sem'- 
elliptic  springs  connected  at  the  ends.  The  spring  is  supported  on  the 
axle  at  the  center  of  one  semi-elliptic  and  it  carries  the  load  at  the  middle 
of  the  other.  When  used,  it  is  generally  employed  as  a  rear  spring.  Only 
occasionally  it  is  found  as  a  front  spring.  The  full-elliptic  spring  is  very 
flexible  and  easy  riding,  but  it  has  the  disadvantage  of  permitting  exces- 
sive side  sway.  The  Franklin  car  uses  this  type  of  spring  for  both  rear 
and  front  suspension. 

Platform  Spring. — The  platform  spring,  Fig.  430,  consists  of  three 
semi-elliptic  springs  shackled  together.  Two  of  the  members  are  parallel 
to  the  sides  of  the  car  and  the  third  is  inverted  and  is  parallel  to  the  cross 
members.  The  car  frame  is  attached  to  the  front  end  of  the  side  members 
and  to  the  middle  of  the  cross  member.  The  middle  of  the  side  member 
rests  on  the  spring  seats.  The  advantage  of  this  spring  suspension  is 
that  whenever  one  rear  wheel  encounters  an  obstruction  or  goes  into  a 


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hole,  the  spring  action  is  taken  care  of  by  all  three  members.    Ordinarily, 
this  action  would  be  taken  by  the  one  spring  on  the  same  side  of  the  car 

±ia.  430. — Platform  type  of  spring  suspension. 

as  the  wheel.     This  equalization  of  spring  action  is  also  evident  when  the 
car  goes  around  a  sharp  corner  very  quickly. 

Double    Compounded    Elliptic    Spring. — The    double    compounded 
elliptic  spring  is  made  up  of  two  long  semi-elliptic  springs  fastened 

Fig.  431. — Double  compounded  elliptic  spring. 

together  at  the  center  as  shown  in  Fig.  431.  The  ends  of  the  upper  spring 
are  fastened  to  the  frame  and  the  lower  spring  is  shackled  to  the  rear 
axle  housing.     This  type  of  spring  permits  the  use  of  exceptionally  long 

Fiq.  432. — Underslung  suspension. 

leaves.  It  is  used  only  as  a  rear  spring,  and  being  set  back  of  the  rear 
axle  gives  the  effect  of  an  increased  wheel  base.  It  also  reduces  the  side 
sway  and  twist  on  the  car. 

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Spring  Suspension  with  Underslung  Frame. — In  most  cases  the  frame 

of  the  car  is  placed  above  the  springs  so  as  to  ride  on  them.  This  is 
called  the  overhung  method  of  suspension.  When  the  frame  is  placed 
below  the  springs  so  that  it  is  hung  from  them,  as  in  Fig.  432,  the  term 
underslung  is  given  to  this  method  of  suspension. 

^  Steering  Wheel 

'Steering  Post 

I     ^Steering  Mechanism 

Tjfer      V                  .Drag  Link 



- — — ^^   *-'  r^?^1 

^ — — ---—  _ 




Fio.  433. — Case  front  axle  and  steering  gear. 

The  underslung  suspension  permits  the  use  of  long  springs  with  the 
leaves  flat.  In  addition,  the  center  of  gravity  of  the  car  is  lowered, 
bringing  the  frame  members  close  to  the  ground,  consequently  larger 
wheels  can  be  used  than  with  an  overhung  frame. 

261.  Unsprung  Weight. — It  is  obviously  impossible  to  have  the  entire 
weight  of  the  car  supported  on  the  springs.  The  weight  of  the  wheels, 
rims,  tires,  and  in  many  cases  the  rear  axle  is  not  supported  on  the  springs. 

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This  weight  is  usually  termed  unsprung  weight.  The  car  with  the  least 
amount  of  unsprung  weight  will  have  less  wear  and  tear  in  the  tires.  The 
unsprung  weight  on  any  car  should  be  kept  down  to  a  minimum. 

262.  The  Front  Axle. — The  important  function  of  the  front  axle  is  to 
carry  the  weight  of  the  front  end  of  the  car.  A  typical  front  axle  assem- 
bled with  the  steering  mechanism  is  shown  in  Fig.  433.  The  front  axle  is 
commonly  of  the  I-beam  type  with  either  a  straight  or  dropped  center. 

Left  King! 
Rn— I       Yoke: 




Right  King 

Pin— I       RtftiT 




Left;  ^ 

Knuckle  ^— x>«— ^     . 
,        <J^***^>TZttm  Ball 




^vI-Beam  FftONT  AxlejBv^ight 
-^^  Steering 

Fiq.  434. — I-Beam  front  axle. 

The  I-beam  centers  are  made  either  of  drop  forgings  or  of  cast  steel  and 
are  heat  treated  to  do  away  with  brittleness  and  to  give  strength  and 
toughness.  The  axle  yokes  are  forged  or  cast  integral  with  the  axle 
center.  The  various  parts  of  a  typical  I-beam  front  axle  are  indicated 
in  Fig.  434. 

Fig.  435. — Tubular  type  of  front  axle. 

It  is  desirable  to  have  the  front  axle  as  low  as  possible  and  yet  keep 
the  proper  road  clearance.  The  lower  the  axle  can  be  swung,  the  lower 
the  center  of  gravity  of  the  car  will  be.  The  road  clearance  or  the  height 
of  the  front  axle  from  the  ground  is  usually  about  10  in. 

The  tubular  type  of  front  axle  construction,  such  as  shown  in  Fig. 
435,  is  made  from  the  best  high-grade  seamless  steel  tubing.  The  yokes 
are  either  pinned  or  brazed  on  the  ends  of  the  tubes.  This  type  of  axle  is 
used  very  little. 

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263.  Steering  System. — The  steering  system  of  the  Cadillac  car,  Fig. 
436,  illustrates  the  method  used  for  steering  an  automobile.  This  is 
accomplished  by  having  the  two  front  wheels  mounted  on  movable 
knuckles  which  turn  in  the  yokes  at  the  ends  of  the  front  axle.  These 
knuckles  are  held  in  the  yokes  by  kingbolts  or  pins  keyed  to  the  knuckles. 
The  kingbolt  is  held  in  place  by  a  nut  which  is  held  from  coming  off  by  a 
cotter  pin. 

The  front  wheels  are  carried  on  the  spindles  of  the  knuckle,  and  run 
on  taper  roller  bearings.  The  spindles  are  set  so  that  the  front  wheels 
have  a  camber  of  about  2  in.,  that  is,  the  tops  of  the  wheels  are  about 
2  in.  farther  apart  than  the  bottoms  of  the  wheels.    This  is  to  conform 






Fia.  436. — Cadillac  steering  gear. 

to  the  crown  of  the  road  and  to  bring  the  point  of  contact  between  the 
tire  and  the  road  in  line  with  the  kingbolt. 

The  knuckles  are  free  to  turn  in  the  axle  yokes  about  35°  either  way 
from  the  center  line  of  the  axle  so  as  to  allow  the  wheels  to  follow  a  curve 
when  turning.  Between  the  under  side  of  the  top  arm  of  the  axle  yoke 
and  the  top  of  the  knuckle,  a  taper  roller  bearing  is  found.  This  is  to 
take  the  end  thrust  of  the  bearing  between  the  knuckle  and  the  yoke. 

The  angle  through  which  the  knuckles  can  turn  on  the  king  pin 
determines  the  turning  radius  of  the  car.  The  turning  radius  is  one-half 
the  diameter  of  the  smallest  circle  it  is  possible  to  make  with  the  wheels 
of  the  car  as  in  Fig.  437.    In  order  to  have  a  short  turning  radius,  it  is 

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necessary  that  the  knuckle  angle  be  as  large  as  possible  and  that  the  frame 
be  narrowed  so  as  not  to  interfere  with  the  turning  of  the  wheels. 

The  steering  arms  which  are  usually  f  orgings  are  keyed  into  the  steer- 
ing knuckles  as  indicated.  The  left  steering  knuckle  carries  two  arms 
and  the  right  steering  knuckle  one  arm.  If  the  car  has  a  right-hand 
drive,  these  are  reversed. 

In  order  that  the  front  wheels  may  turn  together,  the  two  steering 
knuckles  are  connected,  as  shown,  by  a  tie  rod.  This  locks  the  front 
wheels  together.  The  tie  rod  may  be  either  in  front  or  in  back  of  the 
axle.  The  safest  location  is  back  of  the  axle.  The  steering  arm  on 
the  left  knuckle  is  connected  by  the  drag  link  to  the  pitman  arm  of  the 
steering  gear.  It  is  through  this  pitman  arm  that  the  movement  of 
the  steering  wheel  is  transmitted  to  the  steering  knuckles  and  the  front 

Fig.  437. — Turning  radius  of  car. 

264u  Steering  Gear. — There  are  two  general  types  of  non-reversible 
steering  gear  mechanism:  the  worm  and  gear  and  the  dovble^worm.  In 
the  worm-and-gear  type,  shown  in  Fig.  438,  the  worm  is  fastened  to  the 
bottom  of  the  steering  tube  which  is  turned  by  the  steering  wheel.  Mesh- 
ing with  this  worm  is  the  worm  wheel  which  carries  the  steering  lever  or 
pitman  arm.  This  arm  is  connected  to  the  drag  link  which  operates  the 
steering  knuckle.  The  worm-and-gear  type  of  steering  mechanism  is 
non-reversible  because  the  jarring  of  the  front  wheels  on  rough  roads  can- 
not be  transmitted  back  to  turn  the  steering  wheel,  although  the  move- 
ments of  the  steering  wheel  are  readily  transmitted  to  the  front  wheels. 
This  fact  makes  the  mechanism  non-reversible  in  action. 

A  modification  of  the  worm-and-gear  *type  steering  gear  is  the  worm 
and  sector  gear  shown  in  Fig.  439.  This  is  essentially  the  same  as  the 
worm  and  gear  but  instead  of  having  a  full  worm  gear  meshing  with  the 
worm  only  a  part  of  a  gear  or  a  sector  is  provided.  Some  manufacturers 
claim  an  advantage  in  the  worm-and-gear  type  over  the  worm  and  sector 
type  in  that  by  changing  the  position  of  the  gear,  practically  new  teeth 
can  be  had  to  take  the  place  of  those  which  have  been  worn. 

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'-^ — - 






^^^                       MO««* 




Fio.  438. — Worm  and  wheel  steering  gear. 

Fig.  439. — Worm  and  sector  steering  gear. 

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The  double-worm  steering  gear,  illustrated  in  Fig.  440,  has  a  double- 
threaded  worm  F  fastened  to  the  bottom  of  the  steering  tube.  The 
worm  meshes  with  two  half-nuts  (?,  one  with  a  right-hand  and  the  other 
a  left-hand  thread.  Two  rollers  Hf  which  are  attached  to  the  yoke 
that  operates  the  pitman  arm  or  steering  lever,  bear  against  the  lower 
ends  of  the  half-nuts.  When  the  handwheel  is  turned,  the  tube  and  worm 
turn  in  the  same  direction.  This  causes  one  half-nut  to  descend  and  the 
other  to  rise.  This  pushes  the  one  roller  down  and  lets  the  other  rise. 
The  yoke  is  given  the  same  motion  and  transmits  it  to  the  pitman  arm 
which  pushes  or  pulls  on  the  drag  link,  turning  the  knuckle  and  wheels. 
This  type  of  steering  gear  is  also  non-reversible. 

Fia.  440. — Double-worm  steering  gear. 

265.  Brakes. — Brakes  for  the  purpose  of  retarding  or  stopping  the  car 
are  usually  placed  so  as  to  operate  on  the  rear  wheels.  Each  rear  wheel 
carries  a  brake  drum,  a  typical  example  of  which  is  shown  in  Fig.  441. 
The  rear  axle  housing  carries  two  bands,  one  which  fits  inside  of  the  drum 
and  the  other  on  the  outside.  By  contracting  the  outside  band,  causing 
it  to  squeeze  the  outside  of  the  drum,  or  by  expanding  the  inside  band, 
causing  it  to  press  out  on  the  inside  of  the  drum,  the  motion  of  the  wheel 
is  retarded  or  stopped.  This  type  of  brake  is  called  an  irdernaLexternal 
brake  because  the  braking  effect  is  on  both  the  outside  and  inside  of  the 

Usually,  the  external  or  contracting  brakes  are  connected  by  means  of 
brake  rods  to  the  brake  pedal  in  front  of  the  driver's  seat.     They  thus 

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become  the  service  brakes  for  ordinary  braking  work.  The  internal  or 
expanding  brake  bands  are  connected  to  the  emergency  brake  lever  and 
act  as  brakes  for  emergency  purposes.  The  external-internal  braking 
system  on  the  Cadillac  car  is  shown  in  Fig.  442. 

Fto.  441. — Rear  wheel  showing  brake  drum. 



^              BAND  FOR 

EMERGENCY           !     ^  s^ 
BRAKE  LEVER     \/^m 


^^F*  /^-n** 

^      ^^P^^^B 










)A  L 

Fig.  442. — Braking  system  on  Cadillac  Eight. 

All  brake  bands  are  faced  on  the  rubbing  side  with  an  asbestos  or 
similar  friction  material  capable  of  standing  a  great  amount  of  wear  and 
not  easily  burned  out.  After  considerable  service  this  lining  must  be 
renewed  to  insure  perfect  braking  action. 

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Two  other  arrangements  of  brake  bands  and  drums  are  shown  in  Figs. 
443  and  444. 

service  saakk 








Fzq.  443. — Double  internal  brake  with  single  drum. 





Fra.  444. — Double  internal  brake  with  two  drums. 

In  the  double  internal  brake  only  one  wide  drum  is  used.  Both  bands 
are  of  the  expanding  type,  the  outside  one  serving  as  the  emergency  and 
the  inside  one  as  the  service  brake.    The  mechanism  for  expanding  the 

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drums  is  clearly  illustrated.  It  is  known  as  the  cam  type.  With  the 
double  internal  brake,  Fig.  444,  two  drums,  a  large  one  and  small  one, 
are  used.  The  brakes  are  of  the  expanding  type,  the  large  one  being 
the  service  brake  and  the  small  one  the  emergency  brake. 



Fiq.  445. — Brake  on  transmission. 

266.  Transmission  Brake. — Some  cars  have  in  addition  to  the  brakes 
on  the  rear  wheels,  a  brake  acting  on  the  transmission  or  propeller  shaft 

Fia.  446. — Types  of  antifriction  bearings. 

as  shown  in  Fig.  445.    The  transmission  brake  is  used  for  emergency 
purposes  and  is  used  on  cars  of  the  heavy  type. 

267.  Effectiveness  of  Brakes. — With  the  brakes  of  proper  design  and 
in  good  working  condition,  they  should  be  able  to  stop  a  car  within  the 

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distances  given  in  the  following  table.    The  table  has  been  worked  out 
on  the  basis  of  good  average  road  conditions. 

Speed  of  car 
Mfle«  per  hour 

Distance  in  feet  within  which  brakes 
should  stop  car 

















268.  Antifriction   Bearings. — In   order  that  the  lubrication  of  the 
bearings  on  the  automobile  chassis  may  be  reduced  to  a  minimum,  anti- 
friction bearings  are  used  at  the  important 
a  points  where  bearings  of  the  ordinary  rubbing 

type  would  not  be  practical  on  account  of  the 
excessive  wear  which  would  occur.  Bearings 
of  the  rubbing  type  also  require  extraordi- 
nary care  and  attention  to  insure  that  proper 
lubrication  is  being  furnished.  Antifriction 
bearings  when  once  fitted  and  installed  re- 
quire little  attention  and  practically  no  lubri- 
cation. They  are,  consequently,  well  adapted 
for  use  at  the  important  bearing  points  on 
the  automobile  chassis. 

Antifriction  bearings  are  of  two  general 
types:  ball  bearings  and  roller  bearings.  The 
adaptations  of  these  two  types  of  bearings  to 
automobile  use  are  illustrated  in  Fig.  446. 
In  all  antifriction  bearings  the  balls  or  rollers 
are  held  between  the  outer  and  inner  races. 
The  design  and  construction  of  the  races  and 
the  arrangement  of  the  bearings  determine  the  service  for  which  any 
particular  bearing  may  be  used.  The  annular  type  of  ball  bearing  is 
designed  to  carry  a  radial  load  or  thrust  but  is  not  well  adapted  to 
carry  an  end  load  or  thrust.  An  end  load  or  thrust  is  in  a  direction 
along  the  axis  of  the  shaft  passing  through  the  inner  race  while  a 
radial  load  or  thrust  is  directly  down  on  the  bearing  in  a  direction  at 
right  angles  to  the  axis  or  shaft.     The  cup-and-cone  ball  bearing  can 

Fig.  447.— Hyatt  roller 

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cany  an  end  as  well  as  a  radial 
load  by  having  the  races  con- 
structed as  shown.  The  plain  roller 
bearing  is  especially  well  adapted 
to  carry  a  radial  load,  in  fact  its 
carrying  capacity  is  greater  than 
the  annular  ball  bearings  having 
the  ball  diameter  same  as  the  roller 
diameter.  The  plain  roller  bearing 
obviously  is  unable  to  carry  an  end 
load.  When  an  end  load  must  be 
taken  a  special  thrust  ball  bearing 
with  side  races  is  used.  The  taper 
roller  bearing  can  support  an  end 
as  well  as  a  radial  load,  and  for 
this  reason  is  used  extensively. 

The  Hyatt  roller  bearing,  Fig. 
447,  uses  a  hollow  spiral  roller. 
This  construction  gives  a  certain 
springy  action  which  is  not  found 
in  the  plain  solid  roller.  The 
rollers  are  self  cleaning  and  any 
dirt  or  grit  is  carried  away  by  the 
spiral  openings.  This  Rearing  can- 
not sustain  an  axial  load.  When 
used  at  a  point  where  there  is  an 
end  load,  a  thrust  bearing  must 
also  be  used. 

Figure  448  indicates  the  various 
places  on  the  chassis  where  anti- 
friction bearings  are  used.  The 
most  important  of  these  are;  front 
wheels,  steering  knuckles,  change 
gears,  rear  end  of  propeller  shaft, 
differential,  and  rear  wheels. 

Fig.  448. — Antifriction  bearings  on  chassis. 

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The  power  generated  by  the  automobile  engine  is  delivered  to  the 
rear  wheels  through  the  power  transmission  system.  This  system  com- 
prises, as  may  be  seen  from  Figs.  449A  and  B,  the  clutch,  change  gears, 
universal  joints,  propeller  shaft,  differential,  and  rear  axle. 

269.  The  Automobile  Clutch. — The  gasoline  automobile  engine  must 
be  set  in  motion  by  external  means  before  it  can  take  up  its  cycle  and 
generate  power.  This  fact  prevents  it  from  being  started  under  load 
and,  consequently,  means  must  be  provided  for  disconnecting  the  engine 
from  the  rest  of  the  power  transmission  system  before  the  load  is  thrown 
on.  The  device  by  which  this  is  done  is  called  the  clutch.  There  are  in 
use  at  the  present  time  two  general  types  of  clutches,  the  cone  clutch  and 
the  disc  clutch. 

270.  The  Cone  Clutch. — The  principle  of  the  cone  clutch  is  illustrated 
by  the  sketches  in  Fig.  450.  The  engine  flywheel  is  turned  out  so  that 
the  inside  of  the  rim  has  a  taper  of  from  10°  to  12°,  and  the  pressed  steel 
or  aluminum  cone  of  the  clutch  fits  into  this  tapered  ring.  This  cone  is 
held  tightly  in  the  flywheel  by  springs,  and  when  it  is  desired  to  release 
the  clutch  or  disconnect  the  engine,  the  foot  clutch  pedal  is  pressed 
down  and  the  two  parts  of  the  clutch  disengaged.  A  brake  operating 
on  the  rear  end  of  the  cone  sleeve  prevents  it  from  revolving  after  dis- 
engagement. The  cone  is  faced  with  some  frictional  facing  such  as 
leather  or  asbestos.  Spring  inserts  placed  under  the  friction  material 
of  the  cone  allow  gradual  engagement  of  the  chitch  and  insure  the  release 
of  the  cone  from  the  flywheel. 

A  typical  cone  clutch  is  illustrated  in  Fig.  451.  It  consists  of  a 
leather-faced  aluminum  cone  which  fits  inside  the  tapered  rim  of  the 
flywheel,  and  is  held  by  four  springs  carried  on  a  spider.  The  aluminum 
cone  is  mounted  on  a  steel  sleeve  which  slides  back  and  forth  on  the  clutch 
gear  shaft  and  disengages  or  engages  the  cone  with  the  flywheel.  A 
grooved  ring  at  the  rear  end  of  the  sleeve  connects  the  clutch  to  the  clutch 
pedal.  A  small  brake,  attached  to  the  transmission  case,  serves  to  keep 
the  clutch  from  spinning  after  it  is  released.  Four  small  spring  plungers, 
located  under  the  leather,  force  it  out  at  four  points  and  prevent  grabbing 
when  the  clutch  is  let  in. 


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Pressure  on  the  clutch  foot  pedal  is  transmitted  by  a  connecting  link, 
to  the  yoke  operating  on  the  clutch  release  ring  which  pulls  the  clutch 

Clutch  *IN 

Fiq.  460. — Principle  of  core  clutch. 

back  out  of  engagement  with  the  flywheel.     The  small  brake  now  holds 
the  clutch  stationary,  while  the  clutch  spider  and  springs  continue  to 


Clutch   leather 

Clutch   cone -\ 

Clutch  release 

cose  - 

Clutch  qear--*\ 
shaft J 

Clutch  brake -* 

Clutch  thrust  bearing 

Clutch   spring 

I  Crank  shaft 


fta.  461. — Typical  cone  clutch. 

run  with  the  flywheel  until  the  clutch  is  again  engaged.     When  in  full 
engagement,  the  clutch  and  flywheel  turn  as  a  unit,  transmitting  the 

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power  through  the  change  gears  to  the  rear  axle.  There  are  no 
adjustments  to  be  made  on  this  clutch.  When  the  facing  on  the  cone 
becomes  so  worn  that  the  clutch  does  not  operate  satisfactorily,  it  is 
necessary  to  put  on  a  new  facing. 

The  cone  clutch  with  leather  facing  generally  runs  dry,  that  is,  it 
does  not  run  in  an  oil  bath.  The  leather  facing  must  be  prevented  from 
becoming  hard  by  dressing  it  with  neats-foot  or  castor  oil  which  will 
keep  it  soft  and  pliable.  Continued  use  of  the  clutch  causes  the  leather  to 
become  hard.  If  the  clutch  slips  on  account  of  oil  or  grease  getting  on  the 
leather  facing,  the  leather  should  be  cleaned  with  gasoline  and  a  small 
amount  of  finely  ground  fuller's  earth,  which  is  an  earthy  substance  resem- 
bling clay,  placed  on  it.  Although  the  cone  clutch  with  an  asbestos  or 
fabric  facing  usually  runs  dry,  some  types  are  run  in  an  oil  bath.  If  the 
oil  becomes  thick  and  gummy,  causing  the  clutch  to  stick,  it  should  be 
thoroughly  cleaned  out  with  kerosene  and  new  oil  put  in. 

Fiq.  452. — Cone  clutch  with  spring  inserts  on  flywheel. 

A  cone  clutch  with  spring  plungers  on  the  flywheel  instead  of  on  the 
cone  is  shown  in  Fig.  452.  The  facing  is  on  the  cone  and  while  being 
engaged  the  plungers  prevent  the  cone  from  grabbing.  These  plungers 
also  prevent  sticking  when  the  clutch  is  being  released. 

271.  The  Disc  Clutch. — The  disc  clutch  consists  of  a  series  of  flat 
friction  plates  or  discs  held  together  by  a  spring  as  illustrated  in  Fig. 
453.  Each  alternate  plate  or  disc  is  attached  to  the  flywheel  and  these 
drive  the  other  plates  which  have  a  connection  to  the  change  gear  set. 
The  power  is  transmitted  through  frictional  contact  of  the  sides  of  the 
plates.  This  type  of  clutch  gives  a  large  frictional  surface  with  a  com- 
paratively small  clutch  diameter,  while  on  the  cone  clutch,  the  diameter 
must  necessarily  be  large  in  order  to  give  the  necessary  frictional  surface. 
The  disc  clutch  may  use  as  few  as  three  plates  or  it  may  use  a  great  many. 

The  disc  clutch  may  also  be  run  dry,  in  which  case  it  is  called  a  dry 
plate  clutch,  or  it  may  be  run  in  an  oil  bath,  when  it  is  called  a  wet  plate 

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Fia,  453. — Dry-plate  typo  of  clutch. 

Fig.  454. — Borg  and  Beck  single  plate  dry-disc  clutch. 

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The  Borg  and  Beck  type  of  single  plate  dry  disc  clutch  is  illustrated  in 
Fig.  454.  The  casing  of  the  clutch  is  cast  with  the  flywheel  to  which  is  also 
directly  attached  the  two  asbestos  friction  rings.  The  friction  ring  on 
the  side  of  the  plate  away  from  the  flywheel  is  carried  by  a  thrust  ring 
which  receives  the  thrust  of  the  coil  clutch  spring  through  a  bell  crank 
lever.  When  the  clutch  is  in,  the  single  plate  is  held  between  the  two 
friction  rings,  locking  the  whole  mechanism  which  then  turns  with  the 
flywheel.  When  the  clutch  is  released  by  the  foot  pedal,  the  pressure  of 
the  friction  rings  on  the  plate  is  released  and  the  spinning  of  the  plate 
is  prevented  by  the  clutch  brake.     When  released,  all  parts  of  the  clutch, 








Fig.  455. — Dodge  multiple-disc  dry-plate  clutch  and  transmission. 

with  the  exception  of  the  plate,  its  shaft,  and  the  brake  collar,  continue 
to  turn  with  the  flywheel.  It  is  very  necessary  that  the  clutch  release 
bearing  be  well  lubricated,  as  this  bearing  carries  a  heavy  load  when  the 
clutch  is  released. 

The  multiple-disc  dry-plate  clutch  used  on  the  Dodge  car,  Fig.  455, 
consists  of  seven  discs  held  together  by  a  heavy  coiled  spring.  Four  of 
the  discs  are  carried  on  the  flywheel  by  six  pins,  and  the  other  three  are 
carried  by  three  pins  riveted  to  the  clutch  spider  which  is  keyed  on  the 
clutch  shaft.  The  four  driving  discs  on  the  flywheel  are  faced  with  a  wire 
woven  asbestos  fabric,  while  the  three  driven  discs  are  plain.  The  clutch 
is  released  by  pushing  on  the  left  foot  pedal.     This  presses  the  clutch 

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release  yoke  against  the  clutch  release  which  forces  the  clutch  hub  and 
pressure  plate  back.  This  releases  the  spring  pressure  from  the  clutch 
disc,  allowing  the  driving  discs  to  turn  free  from  the  driven  ones.  The 
clutch  release  is  lubricated  through  the  clutch  release  grease  tube  shown. 
The  Cadillac  multiple-disc  dry-plate  clutch,  Fig.  456,  has  nine  plain 
steel-driven  discs  and  eight  driving  steel  discs  faced  on  both  sides  with 
an  asbestos  friction  fabric.  By  attaching  the  friction  material  to  the 
driving  discs  rather  than  to  the  driven  discs,  unnecessary  and  undesirable 
weight  is  thereby  avoided  in  the  latter,  thus  decreasing  the  tendency  to 


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Fig.  456. — Cadillac  clutch  and  transmission. 

spin  when  the  clutch  is  released.  A  coil  spring  under  300  lb.  com- 
pression furnishes  the  pressure  for  forcing  the  driving  and  the  driven 
discs  tightly  together.  This  spring  is  held  within  the  clutch  hub,  the 
splines  on  which  are  a  sliding  fit  in  the  keyways  ant  in  the  driven  discs. 
The  clutch  is  released  by  pressure  on  the  clutch  peo^;  the  leverage  being 
compounded  to  produce  the  desired  result.  \ 

The  wet-plate  clutch  is  constructed  on  the  samA  general  principles 
as  the  dry-plate  clutch.  The  essential  difference  in  Operation  is  that  it 
runs  in  a  bath  of  oil  or  lubricating  oil  mixed  with  kefosene.  When  the 
clutch  is  released,  an  oil  film  covers  the  entire  surf ac  J  of  the  plates,  and, 

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when  the  clutch  is  thrown  in,  this  film  of  oil  is  gradually  squeezed  out, 
permitting  a  very  easy  and  gradual  engagement.  In  the  winter  time, 
the  oil  may  get  unusually  heavy  thus  preventing  quick  engagement  of 
the  clutch.  This  can  be  overcome  by  thinning  the  clutch  oil  with 

In  some  types  of  plate  clutches,  the  plates  are  punched  and  cork 
inserts  are  pressed  into  the  holes.  These  inserts  permit  an  easy  and 
gradual  engagement  of  the  clutch  even  if  the  plates  should  become 
coated  with  oil. 

272.  Operation  of  Clutch. — When  the  car  is  started,  the  clutch 
being  out,  the  gears  should  be  shifted  into  low  and  the  engine  speeded 
up  but  not  raced.  The  clutch  should  then  be  let  in  gradually  by  releas- 
ing the  pressure  of  the  foot  on  the  foot  pedal.  It  is  not  desirable  to  slip 
the  clutch  any  more  than  necessary  as  this  means  excessive  wear  on  the 
clutch  parts.  It  is  the  practice  of  some  drivers  to  keep  a  light  pressure 
with  the  foot  on  the  clutch  pedal  at  all  times.  This  results  in  a  more  or 
less  slipping  of  the  clutch  and  a  consequent  extra  wear  on  the  clutch  parts. 

273.  Change  Gear  Sets. — The  change  gear  set  or  the  transmission  as 
it  is  customarily  called  is  for  the  purpose  of  permitting  different  speed 
ratios  between  the  engine  and  the  rear  wheels  of  the  car.  When  the  car 
is  being  started  from  rest,  it  is  necessary  to  have  considerable  power 
delivered  to  the  rear  wheels  which  are  moving  at  slow  speed.  If  it  was 
necessary  to  also  run  the  engine  at  slow  speed  while  starting  the  car, 
very  little  power  would  be  delivered  to  the  rear  wheels,  because  the  auto- 
mobile engine  does  not  deliver  its  maximum  power  at  slow  speed.  It 
might  be  possible  to  speed  up  the  engine  and  then  endeavor  to  start  the 
car  by  throwing  in  the  clutch,  but  this  would  result  in  the  slowing  down 
and  perhaps  stopping  of  the  engine  when  the  heavy  load  was  suddenly 
thrown  on.  The  change  gears  make  it  possible  to  change  the  speed 
ratios  of  the  engine  and  rear  wheels  so  that  when  the  car  is  being  started, 
the  engine  can  be  run  fairly  fast  and  yet  be  able  to  pick  up  the  load  which 
comes  to  it  through  the  gears  of  the  transmission. 

The  change  gear  transmission  used  on  the  Cadillac  is  illustrated  in 
Fig.  456.  The  teeth  of  the  driving  gear  are  cut  on  the  end  of  the  clutch 
shaft  which  turns  when  the  clutch  is  engaged,  but  remains  stationary 
when  the  clutch  is  out.  The  countershaft  carries  four  gears  which  are 
fixed  to  the  shaft  and  revolve  with  it.  The  main  shaft  of  the  trans- 
mission fits  into  the  clutch  shaft  and  is  supported  by  the  roller  bearings 
shown.  The  transmission  shaft  carries  two  sliding  gears  which  can  slide 
along  the  shaft  but  which  cannot  turn  unless  the  shaft  also  turns.  This 
shaft  is  connected  to  the  propeller  shaft  leading  to  the  rear  axle.  The 
shifting  of  these  gears  along  the  shaft  is  done  through  the  gear  shift 

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lever  which  controls  the  two  gear  yokes  on  the  gears.  Figure  457  indi- 
cates the  various  positions  of  this  lever. 

The  driving  gear  on  the  clutch  shaft  and  the  large  gear  on  the  counter- 
shaft are  always  in  mesh.  This  means  that  whenever  the  clutch  is  in, 
the  driving  gear  and  also  the  four  gears  on  the  countershaft  will  be 
turning.  The  countershaft  gears  will  be  turning  in  the  opposite  direction 
to  the  driving  gear.  In  the  position  shown  the  gears  are  out  of  mesh  and 
are  said  to  be  in  neutral  and  even  though  the  clutch  were  in,  no  motion 
would  be  given  to  the  main  shaft  of  the  transmission.  The  countershaft 
and  gears  would  be  turning  idle. 

If  the  gear  shift  lever  be  pulled  to  the  position  indicated  under  low, 
gear  G  will  be  meshed  with  gear  H  on  the  countershaft.  Power  will 
then  be  transmitted  as  indicated  by  the  arrows  under  first  speed,  in  Fig. 
458,  which  represents  a  similar  change  gear  set.  When  in  low,  the  clutch 
shaft  turns  from  2^£  to  3  times  as  fast  as  the  transmission  shaft  which 




Fio.  457. — Positions  of  gear  shift  lever  for  transmission  speed. 

drives  the  propeller  shaft  leading  to  the  rear  axle.  The  exact  speed  ratio 
depends  upon  the  number  of  teeth  in  the  gears. 

If  the  car  is  running  in  low  gear,  the  gear  shift  lever,  by  first  releasing 
the  clutch,  can  be  shifted  from  the  low  to  the  intermediate  position, 
Fig.  457.  This  will  shift  gear  G  out  of  mesh  with  gear  H  and  put  gear 
F  into  mesh  with  gear  I.  After  engaging  the  clutch  again  the  power  is 
transmitted  as  indicated  by  arrows  under  second  speed,  Fig.  458.  It  will 
be  noticed  that  gear  F  is  smaller  than  gear  G  and  that  gear  I  is  larger  than 
gear  H .  For  this  reason  the  transmission  shaft  runs  faster  in  comparison 
to  the  countershaft  than  in  low  speed.  The  clutch  shaft  and  also  the 
engine  now  turns  only  about  1.75  times  the  speed  of  the  propeller  shaft. 

By  releasing  the  clutch  and  changing  the  lever  from  the  intermediate 
to  the  high  position,  gears  B  and  F  are  locked  together  by  side  or  clutch 
teeth,  as  in  Fig.  458,  or  by  the  meshing  of  the  teeth  of  a  small  geariT, 
attached  to  gear  B,  into  internal  teeth  cut  in  F.     When  in  this  position, 

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Fia.  458. — Positions  of  gears  in  three-speed-and-reverse  gear  set. 

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the  engine  and  propeller  shaft  turn  at  the  same  speed,  the  power  being 
transmitted  directly  through  gears  B  and  F.  The  countershaft  merely 
runs  idle.  This  is  the  running  position  for  the  gears  and  they  need  only  be 
shifted  when  it  is  desired  to  stop,  reverse,  go  up  a  hill,  or  accelerate  after 
the  car  has  been  running  very  slowly. 

The  car  can  be  reversed  after  being  brought  to  a  stop  by  shifting  the 
gear  lever  first  into  the  neutral  and  then  into  the  reverse  position,  Fig. 
457.  This  brings  gear  G  into  mesh  with  the  reverse  idler  gear  L  shown  in 
Fig.  458.  This  idler  gear  now  being  in  mesh  with  both  gears  G  and  J, 
these  revolve  in  the  same  direction.  This  means  that  G  and,  conse- 
quently, the  propeller  shaft  revolve  opposite  in  direction  to  the  gear  B 
and  to  the  engine.  The  speed  ratio  of  the  engine  and  propeller  shaft 
on  reverse  gear  is  about  3.5  to  1. 

This  type  of  transmission  is  called  a  selective  sliding  gear  set  because 
it  is  mechanically  possible  to  shift  immediately  from  one  gear  position 
to  any  other  position.  In  some  types  of  gear  sets,  it  i$  mechanically 
possible  to  change  gears  only  in  a  definite  order,  that  is,  reverse,  neutral, 
low,  intermediate,  and  high,  and  back  in  the  same  order,  rhis  type  is 
called  a  progressive  transmission.  It  is  not  used  to  any  extent  because  of 
the  almost  universal  adoption  of  the  selective  transmission  in  which  it  is 
possible  to  select  the  gear  position  at  will. 

In  a  few  cases,  more  than  three  forward  speeds  are  provided  for  in 
the  transmission.  Instead  of  having  only  &  first,  second,  and  third  speed, 
a  fourth  speed  is  added.  The  direct  drive  is  on  fourth  speed.  The  four 
speeds  are  usually  found  only  on  large  heavy  cars  where  it  is  thought 
three  speeds  are  not  adequate. 

274.  Operation  of  the  Gear  Set — In  order  to  operate  a  car  properly, 
considerable  skill  in  handling  the  engine,  clutch,  and  change  gears  is 
necessary.  The  engine  having  been  started  with  the  change  gears  in 
neutral,  the  clutch  must  be  disengaged  before  the  gears  can  be  shifted 
into  low.  After  the  gears  are  in  mesh,  the  clutch  must  be  let  in  gradually 
in  order  to  prevent  stalling  or  killing  of  the  engine.  While  the  clutch  is 
being  engaged,  the  engine  should  be  speeded  up  to  assist  in  accelerating 
the  car.  The  engine  should  not  be  raced  nor  the  clutch  slipped  for  any 
considerable  time  as  this  will  result  in  excessive  wear.  In  changing 
from  low  to  intermediate  or  from  intermediate  to  high,  the  clutch  must 
be  released  before  the  shift  to  the  higher  gear  is  made.  It  is  often  found 
that  a  pause  in  neutral  when  shifting  gears  will  assist  in  meshing  the 
gears  without  grinding  or  clashing.  It  may  be  found  advisable  to  slow 
down  the  engine  slightly  while  shifting  gears,  and  to  open  the  throttle 
just  as  soon  as  the  clutch  is  in. 

When  it  becomes  necessary  to  change  from  a  high  to  the  next  lower 
gear  this  can  be  accomplished  by  releasing  the  clutch,  shifting  to  neutral, 

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speeding  up  the  engine  somewhat,  and  then  putting  the  gears  into  the 
next  lower  position.  The  aim  is  to  have  the  gears  revolving  at  the  same 
speed  so  that  they  will  mesh  easily.  In  shifting  the  gears  into  reverse,  it 
is  necessary  that  the  car  first  be  brought  to  a 
stop.  The  shift  into  reverse  gear  sfiould  never  be 
made  with  the  car  moving  forward 

276.  Lubrication  of  the  Transmission. — The 
change  gears  should  work  preferably  in  a  soft 
gear  grease  or  heavy  oil.  A  graphite  grease  has 
also  been  used  for  this  purpose.  The  lubricant 
should  follow  the  gear  teeth  when  operating  and 
should  never  become  hard  enough  to  resist  flow- 
ing. It  should  be  thoroughly  cleaned  out  and 
replaced  about  every  2000  miles  of  service. 

276,  Gear  Shift  Levers. — The  type  of  gear 
shift  lever  illustrated  in  Figs.  455  and  456  is  of  the  ball-and-socket  type 
while  that  in  Fig.  459  is  of  the  gate  type.  The  positions  of  the  shift  lever 
for  the  different  gears  are  not  the  same  for  all  make3  cf  ball-and-socket  or 

Fig.  459. — Gate  type  of 
gear  shift  lever. 

Fig.  460. — Positions  of  gear  shift  lever  on  Dodge  car. 

gate-type  levers.  The  lever  positions  for  the  transmission  in  Fig.  455 
correspond  to  Fig.  460  while  those  shown  in  Fig.  461  are  just  opposite. 
Both  arrangements  are  used  extensively. 

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277.  Location  of  Transmission. — The  transmission  may  be  built  into 

a  unit  power  plant  with  the  engine,  may  be  placed  independent  of  and 

immediately  back  of  the  engine,  may  be  midway 

REVERSE        jJ^jMATE  ketween  the  engine  and  rear  axle,  or  may  be  placed 

\  NEUrRALfd 
iLil yfe~ — »*» 

at  the  rear  axle.  When  the  unit  power  plant  is 
used,  universal  joints,  one  at  the  front  and  one 
at  the  rear  of  the  propeller  shaft,  are  used.  If  the 
gears  are  placed  separate  just  back  of  the  engine, 
only  one  universal  joint  need  be  used.  One  objec- 
tion to  placing  the  gears  at  the  rear  axle  is  that 
the  transmission  is  subjected  to  all  of  the  jars  and 
jolts  from  the  rear  axle  when  the  car  is  running 
over  rough  roads  or  other  rough  places. 

278.  The  Planetary  Transmission. — The  plane- 
£f  tary  transmission,  as  used  on  the  Ford  car,  com- 
bines the  clutch  and  change  gears  into  a  single  com- 
pact unit.     It  provides  two  forward  speeds  and  a 
reverse.     The  gears  are  not  shifted  for  the  different 
speeds  as  in  a  sliding-gear  transmission   but  re- 
main meshed  together.     The  planetary  transmission  is  so  named  be- 
cause certain  gears  called  the  planet  gears  revolve  about  other  gears 

Fig.  461. — Positions 
of  gear  shift  lever  for 
Overland  car. 








Fiq.  462. — The  Ford  planetary  transmission. 

called  the  sun  gears  just  as  the  planets  revolve  about  the  sun.     An 
assembled  view  of  the  planetary  transmission  is  shown  in  Fig.  462,  a 

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sectioned  view  in  Fig.  463,  and  a  view  of  the  disassembled  parts  in  Fig. 

Fig.  40;i. —  Internal  construct  ion  of  planetary  transmission. 

DRIVING       Y 



Fig.  464. — Disassembled  view  of  Ford  planetary  transmission. 

The  engine  flywheel  A  carries  the  shaft  B  and  also  the  three  pins 
D  spaced  equally  around  the  flywheel  and  fixed  to  it.  The  triple  gears 
fit  over  these  pins.    The  triple  gears  consist  of  three  gears:  E  with  27 

•  Digitized  by  LiOOQ IC 



teeth;  F  with  33  teeth;  and  G  with  24  teeth.    These  three" gears  are 
pinned  together  and  turn  as  a  unit  on  pins  D. 

Gear  K  with  27  teeth  fits  over  the  shaft  B  and  meshes  with  the  three 
gears  E  of  the  triple  gears.  All  four  of  these  gears  (E,  E,  E,  K)  have  the 
same  number  of  teeth  (27).  The  brake  drum  T  which  carries  the  sleeve 
N  fits  over  shaft  B,  and  the  gear  K  is  keyed  to  sleeve  N.  Brake  drum  S 
is  attached  securely  to  sleeve  0  which  has  cut  on  its  end  the  gear  /  of 
21  teeth.  .  This  gear  L  meshes  with  all  three  gears  F  which  have  33  teeth 
each.  Gear  L  is  smaller  than  the  gears  F  by  12  teeth.  The  drum  R  with 
its  attached  gear  M  slips  over  sleeve  0,  and  gear  M  of  30  teeth  meshes 
with  all  the  gears  G  with  24  teeth  each.  Gear  M  is  larger  than  gear  G 
by  6  teeth. 

Fiq.  465. — Ford  control  showing  hand  lever  for  operating  clutch  stop. 

The  brake  drum  T  houses  the  disc  clutch  of  the  transmission.  Every 
other  disc  F,  Fig.  463,  is  attached  to  the  drum  T  which  in  turn  carries 
the  sleeve  N  and  the  gear  K.  The  alternate  clutch  discs  U  are  carried  by 
the  spider  V  fastened  to  shaft  B  which  turns  with  the  flywheel.  The 
drum  T  is  fastened  to  the  driving  plate  which  is  keyed  to  the  propeller 
shaft  C.  This  driving  plate  has  three  clutch  fingers  X  which,  because  of 
the  pressure  exerted  on  them  by  the  clutch  shift  and  spring  W,  force  the 
plates  Y  and  U  together,  thus  engaging  the  clutch.  The  clutch  spring 
W  is  held  on  the  shaft  C  by  the  clutch  spring  stop. 

By  referring  to  Fig.  462  the  construction  and  placing  of  the  operating 
bands,  pedals,  and  levers  can  be  seen.  Pedal  R  and  its  connections  make 
it  possible  to  tighten  the  friction  band  around  the  drum  R.  Likewise, 
pedals  S  and  T  cause  the  bands  S  and  T  to  be  tightened  around  the  drums 
S  and  T.    A  connection  is  made  between  the  pedal  S  and  the  clutch 

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shift  ring  so  that  when  clutch  pedal  S  is  pushed  down,  the  shift  ring 
compresses  the  spring  W  and  releases  the  clutch  plates.  The  clutch 
stop,  Fig.  462,  is  under  the  control  of  the  driver  through  the  hand  lever 
in  the  car  and  holds  the  clutch  out  when  the  hand  lever,  Fig.  465,  is  in  an 
upright  position.  This  throws  the  stop  immediately  under  the  clutch 
lever  screw. 

279.  Operation  of  Planetary  Transmission. — When  the  engine  is  not 
running  and  the  car  is  still,  the  hand  lever  is  in  the  upright  position  with 
the  stop  immediately  under  the  dutch  lever  screw,  thus  preventing  the 
disc  clutch  from  being  engaged.  With  this  position  of  the  hand  lever 
the  clutch  pedal  S  is  held  in  the  neutral  position  between  its  extreme 
forward  and  extreme  backward  positions.  Under  these  conditions,  the 
clutch  band  S  cannot  be  tightened  around  the  drum  S. 

After  the  engine  is  started,  the  flywheel  causes  the  shaft  B,  the  spider 
V,  and  the  plates  U  to  revolve  in  the  same  direction  and  at  the  same 
speed  as  the  engine.  The  triple  gears  are  carried  around  by  the  pins  D. 
Gear  K  being  fastened  to  sleeve  N  and  to  drum  T  is  held  stationary 
because  drum  T  is  attached  to  the  driving  plate  which  is  keyed  to  the 
propeller  shaft  C.  This  throws  the  resistance  of  the  car  on  gear  K  and 
holds  it  stationary,  because  in  order  for  K  to  revolve,  the  shaft  C  must 
also  revolve  and  the  car  must  move.  Gears  E  being  meshed  with  gear 
K  must  revolve  on  pins  D  as  will  also  the  gears  F  and  Gf  these  three 
(E,  F,  G)  being  fastened  together.  Gears  F  and  G  revolving  on  pins 
D  mesh  with  gears  L  and  M .  These  gears  L  and  M  are  free  to  turn 
because  they  are  attached  to  drums  R  and  S  which  are  free  to  move 
inside  of  the  bands  around  them,  and  revolve  in  a  direction  opposite 
to  the  flywheel  of  the  engine. 

Low  Gear. — Preparations  for  starting  the  car  are  made  by  first  throw- 
ing the  hand  lever,  Fig.  465,  forward  and  also  by  preventing  the  clutch 
pedal  from  coming  back  by  holding  it  in  neutral  position  with  the  foot. 
The  disc  clutch  is  still  disengaged.  By  pushing  the  clutch  pedal  full 
forward  the  band  S  grips  the  drum  S  tightly  and  prevents  it  from  re- 
volving. This  drum  S  (now  held  stationary)  being  connected  to  sleeve 
O  prevents  gear  L  with  21  teeth  from  turning  and,  consequently,  it  is 
held  stationary.  The  flywheel  revolving,  causes  the  pins  D  to  revolve 
in  a  circle.  The  fact  that  gear  L  with  21  teeth  is  held  stationary  causes 
gears  F  with  33  teeth  each  to  turn  about  pins  D  as  axes.  By  referring  to 
Fig.  466  the  relative  motion  of  these  gears  can  be  seen.  Gear  L  with  21 
teeth  is  held  stationary  while  the  flywheel  causes  pins  D  to  move  in  a 
circle.  This  causes  gears  F  to  revolve  on  pins  D.  Only  one  of  the  F 
gears  is  shown  as  the  action  of  the  other  two  is  identical.  Let  it  be  as- 
sumed that  gear  F  is  vertically  above  gear  L  as  shown  and  that  the  fly- 
wheel causes  pin  D  to  move  through  90°  or  one-quarter  of  a  revolution. 

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This  means  that  gear  F  has  revolved  on  pin  D  the  part  of  a  revolution 

corresponding  to  one-quarter  of  the  number  of  teeth  on  gear  L  or  5)^ 

teeth.    Gear  F  has  33  teeth  so  in  position  (2)  gear  F  has  turned  on  D 

5  25 
only  -j^T-  or  a  little  less  than  %  of  a  revolution.    In  position  (3)  gear  F 

has  made  slightly  less  than  %  revolution  on  D;  in  position  (4)  slightly 
less  than  \i  revolution;  and  when  the  flywheel  has  made  one  complete 
revolution,  gear  F  has  made  only  2^3  or  about  %  of  a  revolution  on 
pin  D.  In  other  words,  F  is  turning  on  D  about  %  as  fast  as  the  engine 
flywheel  and  in  the  same  direction.  Practically,  this  means  that  in 
relation  to  the  flywheel,  gear  F  has  been  turned  backward  on  D  about  % 
revolution,  each  time  the  flywheel  revolves  once.  Gear  E  being  fastened 
to  F  also  must  turn  back  on  D  about  J^  revolution  for  each  revolution 

of  the  flywheel.  If  gears  E,  Fig.  463, 
with  27  teeth  are  turned  back  on  D 
\i  revolution  for  each  revolution  of 
the  flywheel,  gear  K  with  the  same 
number  of  teeth  must  be  moved 
around  in  the  direction  of  the  fly- 
wheel %  revolution,  or  ^  as  fast  as 
the  flywheel.  Gear  K  being  attached 
to  the  drive  shaft  C  through  sleeve  N, 
drum  r,  and  the  driving  plate,  causes 
the  propeller  shaft  of  the  car  to  re- 
volve at  approximately  J^  engine 
speed  and  in  the  same  direction.  This 
is  the  method  of  operation  when  in 
low  gear. 

High  Gear. — After  the  car  is  under  way,  the  transmission  can  be 
put  in  high  gear  by  removing  the  pressure  from  the  clutch  pedal,  thus 
allowing  it  to  come  into  its  full  backward  position.  This  releases  the 
low-speed  brake  band  S  and  also  throws  the  disc  clutch  in.  If  the  hand 
lever  in  the  car  had  not  been  thrown  forward,  the  stop  would  have  pre- 
vented the  clutch  from  being  engaged.  When  in  high  gear,  all  the  bands 
are  loose  on  the  drums  and  they  are  free  to  revolve.  The  flywheel 
drives  the  triple  gears  E,  F,  G,  through  the  pins  D.  The  triple  gears 
cannot  revolve  on  the  pins  D  because  triple  gears  J?  are  in  mesh  with  K 
which  has  a  direct  connection  with  the  propeller  shaft  C  because  the 
clutch  is  in.  This  means  that  the  entire  mechanism  (planetary  gears, 
sun  gears,  drums,  and  clutch)  is  locked  together  and  turns  as  a  single 
unit  in  the  same  direction  and  at  the  same  speed  as  the  engine.  The 
propeller  shaft  and  engine  also  turn  at  the  same  speed. 

Reverse  Speed. — Before  the  transmission  can  be  thrown  into  reverse 

Fio.  466. — Relative  motion  of  planetary 
gear  F  and  sun  gear  L  on  slow  speed. 

Digitized  by  LiOOQ IC 



gear,  the  clutch  pedal  must  be  held  in  neutral  position  by  the  foot,  or 
the  hand  lever  must  be  in  its  vertical  position  which  would  also  hold  the 
clutch  pedal  in  neutral  and  hold  the  clutch  in  the  disengaged  or  out 
position.  All  bands  are  free  on  the  drums.  By  pushing  the  reverse' 
pedal  R  full  forward,  the  band  R  grips  the  drum  R  and  causes  it  and  the 
gear  M,  to  which  the  drum  is  attached,  to  be  held  stationary.  The 
flywheel  causes  the  triple  gears  to  revolve  with  it  and  also  causes  gears 
G  with  24  teeth  each  to  turn  on  pins  D,  in  mesh  with  gear  M  of  30  teeth. 
The  condition  now  is  as  shown  in  Fig.  467.  Gear  G  with  24  teeth  is 
meshed  with  gear  M ,  30  teeth  (held  stationary)  and  is  turning  on  it  in 
the  same  direction  as  the  flywheel.  When  pin  D  has  moved  through 
90°,  or  one-quarter  revolution,  gear  G  has  turned  on  pin  D  that  part  of 
a  revolution  corresponding  to  one- 
quarter  of  the  teeth  on  M  or  7  J^  teeth. 

Gear  G  has  thus  turned  on 

D  & 


Fig.  467. — Relative  motions  of  plane- 
tary gear  G  and  sun  gear  M  on  reverse 

or  about  %  revolution.  When  the 
flywheel  has  completed  %  revolution, 
gear  G  has  completed  about  %  revolu- 
tion on  D,  and  when  one  complete 
revolution  has  been  completed  by  the 
flywheel,  gear  G  has  turned  about  8%4 
or  1  V£  times  on  its  pin  D.  Practically, 
this  means  that  in  relation  to  the  fly- 
wheel, gear  G  is  moved  ahead  }£ 
revolution  for  each  turn  of  the  fly- 
wheel. It  can  be  seen  from  Fig.  463 
that  if  gears  G  be  turned  ahead  or  in 
the  direction  of  the  flywheel,  gears  E  must  also  be  turned  ahead.  This 
results  in  gear  K  being  driven  in  the  opposite  direction  to  gears  E  and  also 
to  the  flywheel,  at  practically  34  engine  speed.  The  power  is  trans- 
mitted through  sleeve  N,  drum  T,  and  the  driving  plate  to  the  propeller 
shaft  C. 

The  brake  pedal  when  pushed  down  causes  the  brake  band  to  tighten 
on  drum  T.  This  acts  as  a  service  brake  for  the  car.  The  service 
brake  shoulcl  never  be  applied  while  the  car  is  in  full  slow,  full  high  gear, 
or  full  reverse,  as  this  causes  undue  wear  and  strain  on  the  parts.  The 
reverse  pedal  should  never  be  pressed  down  unless  the  clutch  pedal  is  in 
neutral,  as  this  will  result  in  a  serious  damage  to  the  transmission. 

Advantages  of  Planetary  Gearing. — The  advantages  of  this  type  of 
transmission  are  that  it  is  compact,  can  be  controlled  by  the  feet,  and 
that  the  gears  are  always  in  mesh  and  need  not  be  shifted  at  any  time. 
The  planetary  gearing  is  extremely  noisy  when  running  in  low  gear  and 


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reverse,  as  all  of  the  gears  are  turning.  When  in  high  gear  all  the  gears 
turn  as  a  unit,  giving  a  quiet  running  and  compact  mechanism.  It  is 
almost  impossible  to  have  more  than  two  speeds  forward  with  this  type 
'  of  transmission  on  account  of  the  complexity  of  the  gearing.  This  limits 
its  use  to  small  and  light  cars. 

280.  Universal  Joints  and  Propeller   Shaft. — In  transmitting  the 
power  from  the  engine  or  transmission  to  the  rear  axle,  it  is  necessary 

couture  gwvensAL-joiMT 

Fig.  468. — Propeller  shaft  with  two  universal  joints. 

that  some  kind  of  a  flexible  connection  be  used  because  the  propeller 
shaft  is  usually  not  in  a  straight  line  with  the  crankshaft  of  the  engine. 
The  rear  axle  is  placed  lower  than  the  engine  and  this  means  that  power 
must  be  transmitted  at  an  angle  to  the  rear  axle.  This  is  made  possible 
by  the  use  of  one  or  more  universal  joints,  Fig.  468,  which  are  practically 
double-hinged  joints.  A  universal  joint  consists  of  two  yokes  or  forks 
both  hinged  to  a  crosspiece  of  block  between  them  as  in  Fig.  469.     Each 

Fig    469. — Blood  universal  joint. 

Fig.  470. — Thermoid  flexible  con- 
nection on  Crow  Elkhart  car. 

yoke  then  has  a  hinged  motion  at  right  angles  to  the  other  yoke.  By  the 
use  of  a  universal  joint,  power  can  be  transmitted  at  any  angular  direction 
with  a  very  small  loss  of  efficiency. 

One,  two,  or  three  universal  joints  may  be  used  in  the  transmission 
system.  With  a  unit  power  plant,  it  is  customary  to  use  two,  one  at  each 
end  of  the  propeller  shaft,  although  in  some  cases  only  one  at  the  front 
of  the  shaft  is  used.  The  exact  number  depends  upon  the  arrangement 
of  the  transmission  and  propeller  shaft. 

Digitized  by 




In  addition,  the  universal  joint  takes  care  of  the  jars  and  shocks  from 
the  rear  axle  which  tend  to  throw  the  propeller  shaft  out  of  line.  Without 
these  flexible  connections,  it  would  be  impossible  to  have  a  spring  action 
between  the  rear  axle,  and  the  engine  and  transmission  of  the  car. 

Fio.  471. — Hollow  propeller  shaft. 

281.  Lubrication  of  Universal  Joints. — The  universal  joints  are 
either  run  open,  or  are  encased  in  a  leather  cover  strapped  around  the 
joint.  With  the  open  type,  the  cross  pins  are  usually  lubricated  with 
grease   cups,   while  in  the   closed   type  the 

leather  cover  is  filled  with  a  grease  which 
surrounds  and  lubricates  the  pins. 

282.  Flexible  Couplings. — The  usual  type 
of  universal  joint  is  sometimes  replaced  by 
the  use  of  a  flexible  connection,  as  shown  in 
Fig.  470.  The  angular  movement  permitted 
by  this  connection  is  due  to  the  flexibility  of 
the  leather  or  fabric  discs  in  the  connection. 
The  use  of  the  flexible  type  of  universal  con- 
nection is  becoming  more  general,  although  it 
is  not  generally  considered  so  satisfactory  as 
the  usual  type  of  universal  joint. 

283.  Propeller  Shaft.— The  propeller  or 
drive  shaft  may  be  either  of  the  solid  or  of 
the  hollow  tube  type  as  in  Fig.  471.  The 
hollow  tube  type  gives  a  maximum  of  strength 
with  a  minimum  weight.  The  propeller  shaft 
may  run  open  or  it  may  be  enclosed  in  a  hous- 
ing which  keeps  it  away  from  dirt  and  possible 
damage.     Figure  472  shows  the  trunnion  joint 

connection  at  the  front  of  the  casing  surrounding  the  solid  propeller 
shaft  used  on  the  Paige  car.  Such  a  casing  around  the  propeller  shaft 
also  helps  to  take  care  of  the  torque  action  of  the  rear  axle. 

Fio.  472.— Trunnion  joint 
connection  at  front  of  propeller 
shaft  casing  on  Paige  car. 

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Digitized  by 




The  power  delivered  by  the  engine  through  the  clutch  and  trans- 
mission gears  to  the  propeller  shaft  is  made  available  at  the  two  rear 
wheels  by  transmitting  it  through  the  rear  axle.  The  general  method  of 
doing  this  is  illustrated  in  Fig.  473.  The  power  is  delivered  to  the  rear 
axle  by  the  final  drive,  which  consists  of  two  gears.  The  small  gear  is 
fastened  to  the  propeller  shaft  and  is  called  the  driving  pinion.  The 
large  one  is  fastened  to  the  rear  axle  and  is  called  the  ring  gear.  The 
power  is  transmitted  from  the  propeller  shaft  to  the  rear  axle  through 

JD*J(/5T/MG  Mt/T  I  OCK- 




I Q/rf£RENTfAl  tt0i/S/W6 

swi£  s/fs?rr 

Fia.  473. — Live  type  of  rear  axle. 

the  driving  pinion  which  drives  the  ring  gear  and,  consequently,  the 
rear  axle. 

284.  Final  Drives. — Three  types  of  gearing  have  been  employed  for 
the  final  drive  between  the  propeller  shaft  and  the  rear  axle.  These 
are  the  bevel,  spiral-bevel,  and  worm  gearing. 

The  bevel  gear  final  drive,  Fig.  474,  consists  of  two  plain  bevel  gears 
with  straight  teeth,  meshing  together  and  changing  the  direction  of  the 
power  through  a  right  angle  from  the  propeller  shaft  to  the  rear  axle. 
The  size  of  these  gears  and  the  number  of  teeth  in  each  regulate  the  speed 
ratio  of  the  propeller  shaft  and  the  rear  axle.  This  ratio  is  usually 
such  that  the  propeller  shaft  will  make  from  3  to  5  revolutions  to  one 
of  the  rear  axle.  The  number  of  teeth  on  one  of  the  gears  is  usually  odd, 
such  as  21  or  23,  while  the  number  on  the  other  is  usually  even,  such 


Digitized  by 




as  60  or  62.  By  this  arrangement,  the  odd  tooth,  which  is  called  the 
hunting  tooth,  meshes  at  times  with  all  of  the  teeth  on  the  other  gear, 
thus  causing  the  same  amount  of  wear  on  all  teeth  of  the  two  gears.  The 
straight  tooth  bevel  gears  have  the  disadvantage  that  there  is  sometimes 
considerable  lost  motion  or  backlash  between  the  teeth  causing  them  to 
be  very  noisy.  This  difficulty  has  been  overcome  to  a  large  extent  in 
the  spiral-bevel  type  of  final  drive. 

A  final  drive  using  spiral-bevel  gears  with  the  spiral  or  curved  teeth 
is  illustrated  in  Fig.  475.  The  spiral-bevel  gearing  gives  a  more  continu- 
ous contact  between  the  teeth,  and  prevents  the  possibility  of  the  exces- 
sive backlash  or  lost  motion,  which  is  sometimes  found  between  plain 





Fia.  474. — Bevel  gear  final  drive. 

bevel  gear3  after  considerable  use.  The  spiral-bevel  final  drive  is  quiet 
when  operating  and  in  general  is  more  satisfactory  than  the  plain  spiral 
gear  drive. 

The  worm  type  of  final  drive  employs  a  worm  for  driving  the  worn 
gear  on  the  rear  axle.  This  worm  may  be  placed  either  above  or  below  the 
worm  gear.  Figure  476  illustrates  a  worm  drive  with  the  worm  placed 
above  the  gear.  This  type  of  final  drive  is  very  quiet  running  and  effi- 
cient, but  requires  very  good  lubrication  because  of  the  constant  sliding 
action  between  the  worm  and  gear.  One  of  the  two  should  run  in  an  oil 
bath.  The  worm  is  usually  made  of  steel  and  the  gear  of  bronze  in  order 
to  keep  down  excessive  friction  and  wear.  The  worm  final  drive  permit* 
a  very  large  speed  reduction  and  is,  consequently,  well  adapted  to  truck 

'  Digitized  by  LiOOQ IC 



and  other  slow  speed  heavy  service.    Figure  477  is  a  view  of  the  worm 
final  drive  used  on  the  Ford  Model  T  Truck. 

286.  Bearings  for  Final  Drive. — On  account  of  the  fact  that  there  is 
a  thrust  between  the  gear  teeth,  tending  to  separate  them,  it  is  necessary 
that  proper  bearings  be  provided  to  take  up  the  thrust  and  at  the  same 
time  hold  the  gears  in  place.  Usually  the  bearings  are  of  the  ball  or 
tapered  roller  type  because  these  can  sustain  both  the  end  and  side  thrusts 
which  come  on  the  gears.    A  plain  roller  bearing  alone  could  not  answer 

the  purpose  because  it  cannot  withstand 
both  a  thrust  along  its  axis  and  one  at 
right  angles  to  it.  In  the  bevel  gear  drive 
of  Fig.  474,  the  thrust  is  taken  care  of  by 
ball  bearings.  These  prevent  both  end  and 
side  movement  of  the  driving  pinion  and 
the  bevel  gear.  The  use  of  tapered  roller 
bearings  is  illustrated  in  Fig.  475.    Being 



Fio.  475. — Spiral-bevel  gear  type 
of  final  drive. 

Fio.  476. — Worm  type  of  final  drive. 

tapered,  they  give  all  the  advantages  of  a  roller  bearing  and  also  the 
feature  of  a  ball  bearing  in  being  able  to  carry  an  end  thrust  as  well 
as  a  side  pressure. 

286.  Types  of  Rear  Axles. — There  are  two  general  types  of  rear 
axles,  the  dead  rear  axle  and  the  live  rear  axle.  The  dead  rear  axle  is 
similar  to  that  used  on  wagons  and  buggies.  It  is  made  solid  with  the 
wheels  turning  on  spindles  on  the  axle  end.  This  type  of  axle  is  used 
only  on  heavy  trucks  and  other  commercial  cars  where  it  is  necessary  to 
have  a  solid  construction  and  at  the  same  time  provide  for  a  large  reduc- 
tion in  speed. 

Digitized  by 




In  the  live  type  of  rear  axle,  the  axle  proper  turns  inside  of  a  sta- 
tionary housing  and  transmits  the  power  to  the  rear  wheels  to  which  the 
axle  is  attached.  The  axle  housing  supplies  the  bearing  for  the  wheels 
and  axle  and  also  supports  the  car  through  the  springs.  The  main  func- 
tion of  the  live  axle  is  to  transmit  power  and  not  to  support  the  weight 
of  the  car  as  in  the  dead  axle.  The  live  axle  is  divided  in  the  center,  each 
half  being  fastened  to  one  of  the  rear  wheels.  Live  rear  axles  are  classified 
according  to  the  method  of  construction,  as  simple,  semi-floating,  three- 
quarter  floating,  and  full  floating. 

287.  Simple  Live  Rear  Axle. — The  simple  live  rear  axle,  in  addition 
to  transmitting  the  power  to  the  rear  wheels,  also  supports  the  entire 
weight  of  the  rear  of  the  car.  The  rear  axle  used  on  the  Ford  car,  Fig. 
478,  illustrates  a  typical  simple  axle.     The  axle  shaft  is  carried  both  at 

Fio.  477. — Worm  final  drive  on  Ford  Model  T  truck. 

the  center  and  at  the  wheel  ends  by  roller  bearings  which-  in  turn  are 
supported  by  the  axle  housing.  The  rear  wheels  are  keyed  to  the  axle 
shafts  as  shown.  The  entire  weight  of  the  rear  of  the  car  is  carried  on  the 
axle  shaft  which  also  revolves  and  transmits  the  power  to  the  wheels. 
Any  stress  due  to  the  skidding  of  the  car  or  the  wobbling  of  the  wheels 
must  also  be  taken  care  of  by  the  axle  shaft.  The  side  thrust  of  the 
driving  pinion  is  taken  care  of  by  the  straight  roller  bearings,  while  ball 
bearings  support  the  end  thrust.  The  end  thrust  of  each  half  of  the  axle 
shaft  is  taken  care  of  by  the  three  metal  thrust  washers.  The  straight 
tooth  bevel  gear  final  drive  is  employed  with  this  axle. 

288.  Semi-floating  Rear  Axles. — The  essential  difference  between  a 
simple  live  axle  and  one  of  the  semi-floating  type,  Fig.  479,  is  in  the  fact 

Digitized  by 




that  in  the  latter  type,  the  inner  bearings,  supporting  the  axle  housing  and, 
consequently,  considerable  weight,  are  carried  on  an  extension  of  the 
differential  case,  instead  of  being  carried  by  the  axle  shaft  itself.     This 

I'1  . 




relieves  the  shaft  of  considerable  stress  due  to  the  weight  carried.    The 
wheels  are  keyed  to  the  axle  as  in  the  simple  type  and  the  outer  bearings 

Digitized  by 




are  also  on  the  shafts.  This  throws  the  stress,  due  to  skidding  and 
turning  corners,  on  the  axle.  If  an  axle  shaft  should  break  or  twist  off 
the  wheel  would  come  off.  It  is  impossible  to  remove  the  axle  shaft 
with  the  wheel  on  the  car. 






:bevel  ring 


Fio.  479. — Studebaker  semi-floating  rear  axle. 

289.  Three-quarter  Floating  Axle. — In  this  type  of  axle,  an  outer  end 
of  which  is  shown  in  Fig.  480,  the  wheel  is  supported  by  a  single  bearing 
carried  on  the  axle  housing.     This  bearing  is  placed  directly  under  the 

480. — Outer  end  of  three-quarter  floating  axle. 

center  of  the  wheel  thus  relieving  the  axle  shaft  of  all  stress  due  to  the 
weight  of  the  car.  The  wheel  is  keyed  onto  the  shaft  as  in  the  simple  and 
semi-floating  types.  On  account  of  this  rigid  connection  between  the 
axle  shaft  and  wheel,  and  also  because  the  wheel  is  supported  by  a  single 

Digitized  by 




bearing,  the  stresses  and  strains  due  to  a  possible  side  movement  of  the 
wheel,  or  due  to  distortion  from  a  bent  housing,  are  still  thrown  on  the 
axle  shaft.  Although  the  shaft  carries  no  part  of  the  weight  of  the  car, 
yet  it  is  still  subject  to  many  bending  and  twisting  strains.     If  the  axle 

Fia.  481. — Full  floating  rear  axles. 

shaft  should  break  on  either  a  simple,  semi-floating,  or  three-quarter 
type  of  axle,  the  wheel  can  come  off  and  let  the  car  drop.  This  can  be 
prevented  only  by  the  full-floating  construction. 

Digitized  by 



290.  Full-floating  Rear  Axle. — In  this  type  of  construction,  as  illus- 
trated in  Fig.  481,  the  wheels  are  carried  by  a  double  ball  or  roller 
bearing  on  the  axle  housing  in  such  a  way  as  to  retain  the  wheel  on  the 
housing  regardless  of  what  may  happen  to  the  axle  shaft.  The  axle  shaft 
has  only  to  transmit  the  power  and  is  not  subject  to  the  stresses  and 
strains  due  to  skidding  and  turning  corners.  These  are  taken  care  of  by 
the  axle  housing.  The  live  shaft  can  be  removed  and  replaced  without 
taking  the  wheel  off  or  disturbing  the  differential.  The  inner  end  of 
the  axle  shaft  is  grooved  and  fits  into  corresponding  grooves  in  the  dif- 
ferential. The  shaft  is  removed  by  removing  the  hub  cap  and  sliding 
the  shaft  out.  Some  types  of  axles  are  called  full-floating  when  the  wheel 
is  carried  by  two  bearings  on  the  housing  and  when  the  wheel  is  keyed 
onto  the  axle  shaft.  Strictly  speaking,  an  axle  is  not  full  floating  if  the 
wheel  is  keyed  onto  the  shaft,  as  there  is  still  the  possibility  of  stress  and 
strain  being  thrown  on  the  shaft  by  a  distortion  of  the  housing,  resulting 
in  a  slight  side  movement  or  wobbling  of  the  wheel.    A  true  full-floating 

Full  Fleeting  Axle  Shift 


Fixed  Huh  AxU  Shalt 

Fig.  482. — Axle  shaft  for  full-floating  and  fixed  hub  rear  axles. 

axle  is  one  in  which  the  connection  between  the  wheel  and  axle  housing 
is  made  by  a  toothed  clutch  on  the  axle  which  fits  into  the  toothed  opening 
on  the  hub  of  the  wheel.  This  permits  a  certain  amount  of  side  play 
and  relieves  the  shaft  from  any  stress  or  strain,  if  the  axle  housing  should 
become  bent.  If  the  connection  between  the  rear  wheel  and  axle  is  not 
such  that  a  certain  amount  of  side  action  can  be  taken  care  of  without 
throwing  a  stress  and  strain  on  the  shaft,  it  cannot  be  classified  as  a  full- 
floating  axle.  Axle  shafts  for  both  the  full-floating  and  the  fixed  hub 
types  of  rear  axle  are  shown  in  Fig.  482.  If  an  axle  is  of  the  fixed  hub 
type,  it  cannot  possibly  be  full-floating. 

291.  The  Differential. — The  halves  of  the  rear  axle  are  connected  at 
the  center  through  a  gear  mechanism  called  the  differential.  The  use 
of  the  differential  is  necessary  in  order  that  one  rear  wheel  may  turn  faster 
than  the  other  when  the  car  is  turning  a  corner  and  when  the  outside  rear 
wheel  must  travel  a  greater  distance  than  the  inside  one. 

Each  end  of  the  axle  shaft  fits  into  a  bevel  gear,  as  indicated  in  Figs. 
483  and  484.  These  gears,  called  differential  gears,  face  each  other  and 
mesh  with  smaller  bevel  gears  carried  on  a  spider  and  known  as  differ- 

Digitized  by 






'IF.  StfAFT 

Fio.  483.— Differential  gear. 


GP  ?  — *    //     GEAP 




d/ff/pent/al  sp/dep 


rASF   (/FED 


Fig.  484. — Parte  of  differential  gear. 

Digitized  by  LiOOQ IC 


ential  pinions.  The  number  of  these  differential  pinions  varies  from  two 
to  four,  depending  upon  the  design.  The  spider  carrying  the  pinions 
is  held  by  the  differential  case  which  also  keeps  the  differential  gears  in 
mesh  with  the  differential  pinions.  The  differential  case  is  attached  to 
the  bevel  ring  or  ring  gear  and  revolves  with  it.  The  power  goes  from  the 
driving  pinion  to  the  bevel  ring  which  causes  the  spider  carrying  the  differ- 
ential pinions  to  also  revolve  with  it.  The  power  is  transmitted  to  the 
axle  shafts  through  the  differential  pinions  and  gears.  With  equal  resist- 
ance on  each  wheel,  the  differential  pinions  cause  the  differential  gears 
and,  consequently,  the  axles,  to  revolve  at  the  same  speed.  With  the 
same  amount  of  power  being  delivered  to  each  wheel  there  is  no  motion 
of  the  teeth  of  the  differential  pinions  over  the  teeth  of  the  differential 

When  the  car  turns  a  corner,  one  rear  wheel  must  obviously  turn  faster 
than  the  other.  Consequently,  there  will  be  a  movement  of  the  dif- 
ferential pinions  around  their  own  axes  and  this  action  will  cause  one 
half  of  the  axle  to  turn  ahead  of  the  other,  or  one  rear  wheel  to  revolve 
faster  than  the  other  wheel.  Any  movement  of  the  differential  pinions 
on  their  own  axes  will  accelerate  the  movement  of  one  half  of  the  axle 
and  retard  the  movement  of  the  other  half. 

If  the  condition  of  the  road  or  ground  over  which  the  car  is  being 
driven  is  such  that  it  is  impossible  for  one  of  the  rear  wheels  to  get  a 
footing  and  it  spins,  it  is  then  impossible  to  start  the  car  as  there  will  be 
no  traction  for  the  other  wheel.  It  will  remain  still,  while  all  the  power 
will  go  toward  spinning  the  one  wheel.  In  some  cases  a  special  dif- 
ferential lock  for  locking  the  differential  has  been  installed.  Special 
differentials  have  been  designed  with  the  purpose  in  mind  of  preventing 
stalling,  due  to  a  lack  of  traction  on  one  wheel,  but  their  application  so 
far  has  been  limited. 

Differentials  using  types  of  gearing  different  from  the  bevel  gears 
have  been  used  in  some  cases.  The  spur  gear  differential  employs  spur 
gears  instead  of  bevel  gears  for  obtaining  the  differential  or  compensating 
action  between  the  axle  shafts.  It  is  used  very  little  at  the  present  time. 
The  bevel  gear  differential  is  used  almost  universally. 

292.  M  &  S  Differential  or  Powrlok. — As  previously  explained,  the 
main  difficulty  encountered  with  the  bevel-gear  type  of  differential  is 
that  when  one  rear  wheel  slips  or  spins,  due  to  a  muddy  or  wet  road  sur- 
face, the  entire  power  of  the  engine  goes  to  spinning  this  one  wheel.  This 
means  that  there  is  no  power  delivered  to  the  other  wheel  and,  conse- 
quently, the  car  cannot  be  started  as  long  as  the  one  wheel  spins.  This 
difficulty  has  been  avoided  in  the  M  &  S  Differential  or  Powrlok  which  is 
shown  in  Fig3.  485  and  486. 

The  fundamental  principle  of  this  differential  is  the  same  as  in  the 

Digitized  by 




bevel-gear  type.  The  construction,  however,  is  somewhat  different.  In- 
stead of  using  bevel  gears,  helical  (commonly  called  spiral)  gears  with 
45°  angles  are  provided.  The  differential  housing  H  carries  the  spider 
P  on  which  are  mounted  the  four  differential  helical  gears  C.  The 
crown  gears  A  and  A l  are  fastened  to  the  rear  axle  shafts  which  in  turn 
drive  the  two  rear  wheels.  The  differ- 
ential housing  also  carries  the  worm 
gears  B  which  have  their  axes  at  right 
angles  to  the  axes  of  the  differential 
gears  C.  When  the  differential  is  as- 
sembled the  gears  mesh  as  indicated 
in  Fig.  485. 

When  the  road  resistance  on  each 
rear  wheel  is  the  same,  the  entire 
differential  revolves  as  a  unit  in  ex- 
actly the  same  way  as  the  bevel-gear 
differential.  The  helical  gears  have 
no  motion  on  each  other  and  the 
power  is  equally  distributed  to  each 

wheel.  If  one  rear  wheel  should  lose  its  traction  on  the  road  and  start 
to  slip,  there  is  no  tendency  for  it  to  spin  and  take  the  entire  power  of 
the  engine  because  gears  B  are  unable,  on  account  of  the  angle  of  the 
teeth,  to  drive  gears  A.  Consequently,  there  is  no  differential  action 
and  the  axle  turns  as  if  solid,  and  delivers  power  to  both  rear  wheels. 

P.         C 









c"    "p 

Fia.  485. — M  and  a  differential. 

Fig.  486. — Construction  of  M  and  S  differential. 

There  is,  therefore,  no  possibility  of  stalling  the  car  as  long  as  one  wheel 
has  traction  on  the  road. 

When  turning  corners,  the  M  &  S  Differential  or  Powrlok  gives  the 
same  differential  action  as  a  bevel-gear  differential.  This  is  made  pos- 
sible because  gears  A  can  drive  gears  B  when  one  wheel  has  a  tendency 

Digitized  by 



to  move  faster  or  slower  than  the  other  wheel.  This  differential  action 
takes  place  whether  the  car  is  going  ahead  or  in  the  reversed  direction. 
293.  Lubrication  of  Rear  Axle  and  Differential. — It  is  very  essential 
that  effective  lubrication  should  be  provided  for  the  differential,  axle,  and 
wheel  bearings.  These  are  lubricated  by  a  semi-solid  grease  which  is 
carried  in  the  differential  housing.  The  differential  and  axle  housings 
are  not  usually  oil-tight  and  a  fluid  oil  cannot  be  used  to  advantage. 
In  addition,  the  semi-solid  lubricant  reduces  the  noise  and  prevents 
excessive  wear  on  the  gear  teeth.  Lubrication  through  grease  cups  is 
also  provided  for  various  parts  of  the  axle.  The  differential  should  be 
filled  to  the  level  of  the  filling  hole  every  2000  miles  the  car  is  run.  The 
wheel  bearing  at  the  axle  ends  should  be  thoroughly  cleaned  and  repacked 
with  the  proper  lubricant  every  season  and  also  every  2000  miles  of 
travel.     In  a  great  many  cases  an  oil  hole  is  provided  on  the  wheel  hub 

Cfatch  pedol 


\  \     ^'Un/versaf  tents  \      Cfutch 

Rear  ox/e  bousing  ^Torston  rods  Transmission  qeor  rasa 

Fig.  487. — Automobile  power  transmission  system  with  torsion  rods  for  taking  the  torque. 

so  that  a  little  oil  can  be  put  in  whenever  the  car  is  oiled.  This  oil 
keeps  the  grease  soft  and  in  good  workable  condition. 

294.  The  Torque  Arm. — When  the  brakes  are  used  in  stopping  the  car, 
the  brakes,  being  carried  by  the  rear  axle  housing,  tend  to  carry  this 
housing  around  with  the  wheels.  Likewise,  the  action  of  the  propeller 
shaft  and  the  bevel  or  spiral  pinion  in  driving  the  rear  axles  tend  to  turn 
the  axle  housing  over  backward  with  the  same  force  that  is  exerted 
on  the  bevel  ring.  This  tendency  of  the  axle  housing  to  turn  over,  due 
to  the  action  of  the  propeller  shaft,  is  greater  when  the  car  is  being  started, 
or  when  the  car  suddenly  runs  into  sand  or  mud,  where  the  resistance 
to  be  overcome  is  greater.  This  twisting  action  or  torque  must  be  taken 
care  of  in  some  way  in  order  to  prevent  the  axle  housing  from  turning 

This  torque  can  be  taken  by  torsion  rods,  Fig.  487,  running  to  the 

Digitized  by 




top  and  bottom  of  the  rear  axle  housing,  or  by  a  single  bar  called  a  torque 
arm.  Figures  488  and  489  illustrates  two  typical  types  of  torque  arms. 
With  the  use  of  a  torque  arm,  it  is  possible  to  have  the  propeller  shaft 
run  open  without  a  housing,  as  the  torque  or  twisting  effect  is  taken 
by  the  arm.     If  the  propeller  shaft  is  enclosed  by  a  housing,  and  this 

Fia.  488. — Torque  arm  on  Packard  Twin  Six. 

housing  takes  care  of  the  torque,  the  housing  is  called  a  torque  tube  or 
third  member  of  the  rear  axle  system.  When  a  torque  tube  is  used,  it  is 
not  necessary  that  a  universal  joint  be  used  at  the  rear  of  the  propeller 
shaft.  It  should  be  understood  that  whenever  the  torque  is  taken  by 
a  torque  tube,  by  torsion  rods,  or  a  torque  arm,  that  these  members  assist 

Fiq.  489. — Westcott  double  tubular  torque  arm. 

materially  in  driving  the  car,  as  one  end  is  attached  to  the  frame  of  the 
car  and  the  other  to  the  rear  axle. 

It  is  the  practice  of  a  great  many  designers  not  to  provide  separate 
means  for  taking  care  of  the  torque  but  to  depend  upon  the  rear  springs 
to  do  this  as  well  as  to  drive  the  car.    When  this  is  done  and  the  rear 


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axle  drives  the  car  through-  the  rear  springs,  it  is  designated   as    the 
"Hotchkiss  Drive.' ' 

295.  Strut  Rods. — In  order  to  assist  in  preserving  the  alignment 
of  the  rear  wheels,  or  to  keep  one  wheel  from  getting  ahead  of  the  other, 
strut  rods  are  fastened  to  the  brake  flanges  or  spring  seats  and  extend 

Fig.  490. — Strut  rods  and  torque  tube  on  Marmon  car. 

to  the  front  of  the  torque  tube  as  in  Fig.  490  or  to  some  other  part  of  the 
car  frame.  In  addition  to  keeping  the  wheels  in  alignment,  the  stmt 
rods  may  also  assist  in  taking  up  some  of  the  torque  action  of  the  rear 

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The  wheels,  rims,  and  tires  of  an  automobile  are  among  its  most 
important  parts.  The  rear  wheels,  in  addition  to  supporting  a  large 
part  of  the  weight,  transmit  the  power  and  drive  the  car.  The  front 
wheels  carry  the  weight  of  the  front  of  the  car  and  also  serve  to  guide  or 
steer  the  car  in  the  proper  direction.  The  pneumatic  tire,  which  is 
universally  used  on  automobile  wheels,  is  responsible  for  most  of  the 
present-day  comfort  and  easy-riding 
qualities  of  the  modern  passenger 
cars.  A  great  part  of  the  expense  in 
operating  a  car  is  the  money  spent  for 
tires.  If  tires  are  purchased  and  used 
with  the  proper  care,  the  wear  and  mile- 
age obtained  from  them  can  be  a  maxi- 
mum and  the  expense  can  be  reduced 
to  a  minimum.  On  the  other  hand, 
poor  judgment  in  buying,  and  hard 
treatment  in  use,  may  be  responsible 
for  a  great  deal  of  unnecessary  grief, 
trouble,  and  expense  on  the  part  of 
the  car  owner  or  driver. 

296.  Wheels. — The  wheels  of  an 
automobile  are  light  but  strong.  They 
must  transmit  the  driving  power  from 
the  rear  axle  to  the  rear  tires,  and  at 
the  same  time  resist  the  terrific  side 
strains  caused  by  skidding  and  turning 
corners  rapidly. 

The  general  arrangement  of  the 
wheel,  rim,  and  tire  is  shown  in  Fig.  491.  The  wheel  proper  may  be 
made  of  wood,  of  metal  with  wire  spokes,  or  of  light  pressed  steel.  A 
felloe  which  may  be  of  wood  or  steel  fits  over  the  ends  of  the  spokes 
and  holds  them  together. 

The  rim  which  carries  the  tire  may  be  fixed 'permanently  on  the  wheel 
or  it  may  be  made  removable,  in  which  case  the  tire  and  rim  are  removed 
together.    After  the  tire  and  rim  are  removed  from  the  wheel,  the  tire 



Flo.  491. — Arrangement  of  wheel, 
rim,  and  tire. 

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can  be  taken  off  the  rim  by  prying  one  of  the  beads  over  the  side  of  the 
rim,  if  it  is  a  solid  one-piece  rim.  If  the  rim  is  built  so  that  the  tire 
may  be  easily  removed,  due  to  some  special  constructional  feature  of 
the  rim,  the  name  detachable  is  applied  to  the  rim. 

297.  Wooden  Wheels. — Automobile  wheels  made  of  wood  are  copied 
after  the  wheels  used  on  artillery  buggies  and  are  called  artillery  wheels. 
The  spokes  are  mitered  and  wedged  together  at  the  center  as  shown  in 
Fig.  492,  and  are  held  at  the  center  by  the  flanges  of  the  hub  plates  on 
each  side  of  the  wheel.  The  hub  plates  are  held  together  by  bolts. 
The  holes  for  these  bolts  are  in  the  spokes  near  the  center  of  the  wheel. 
Second  growth  hickory  is  the  best  wood  for  wheels,  but  it  is  becoming 
so  scarce  and  expensive  that  the  medium  and  lower-priced  wheels  are 
sometimes  made  from  oak  or  some  other  kind  of  wood. 

The  outside  ends  of  the  wooden  spokes  are  held  by  a  band  called  the 
felloe.    The  felloe  may  be  either  a  wooden  band  as  in  Fig.  492  or  a  steel 

band,  Fig.  491.  The  wooden  felloe  is 
made  by  steaming  and  bending  special 
pieces  of  stock  to  the  correct  curvature 
and  fitting  two  such  pieces  together  over 
the  spokes.  A  steel  band  is  shrunk  over 
the  wooden  felloe  to  hold  the  assembled 
parts  together.  Steel  felloes  are  of 
channel  section  and  are  usually  made  in 
one  piece. 

With  ordinary  care,  a  well-made 
artillery  wheel  usually  causes  no  trouble. 
The  spokes  may  loosen  and  squeak  dur- 
ing a  long  spell  of  dry  weather,  especially 
if  the  car  is  seldom  washed.  This  con- 
dition is  aggravating  not  only  to  the  oc- 
cupants of  the  car:  b|it  is  apt  to  cause  distortion  of  the  felloe  and  undue 
wear  of  the  tire.  This  should  be  attended  to  at  once  as  wooden  wheels 
run  with  loose  spokes  have  very  short  periods  of  usefulness.  If  the  rim 
used  on  the  wheel  is  of  the  demountable  type,  the  wedges  which  hold 
the  rim  in  place  may  also  become  loose  and  cause  a  squeaking  noise. 
They  may  become  so  worn  that  it  will  be  impossible  to  tighten  them 
and  new  wedges  will  be  required.  In  some  cases  the  wheel  itself  is  de- 
formed as  a  result  of  loose  wedges.  If  some  of  the  wedges  are  tightened 
more  than  others,  the  body  of  the  wheel  may  be  slightly  deformed. 
For  this  reason  the  wedges  should  be  tightened  uniformly. 

When  repair  work  is  needed  on  wooden  wheels,  it  should  be  put  in  the 
hands  of  an  expert.  Only  a  person  who  is  well  acquainted  with  the 
manufacture  of  wooden  wheels  can  replace  a  broken  spoke  or  take  the 

Fio.  492. — Wooden  artillery 
wheel  with  wooden  felloe  and  de- 
mountable rim. 

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squeak  out  of  the  wheel  without  distorting  it.  When  a  good  thorough 
washing  will  not  remove  the  squeak,  it  generally  means  that  it  has  been 
neglected  too  long. 

298.  Wire  Wheels. — While  the  artillery  type  of  wheel  has  been  the 
most  commonly  used,  the  wire  wheel  is  gradually  gaining  favor  for  pas- 
senger cars.  Wire  wheels  are  lighter  and  readily  demountable,  which 
simplifies  tire  changing.  The  heat  developed  in  the  tire  is  conducted 
from  it  to  the  hub  of  the  wheel  more  readily  in  a  wire  wheel  than  in  a 
wooden  wheel.  This  is  true  especially  if  the  car  speed  and  road  friction 
are  such  that  the  tire  temperature  is  unusually  high.  The  small  diameter 
of  the  spokes  of  a  wire  wheel  give  easier  access  to  the  brakes  for  the  pur- 
pose of  adjustment.  Some  wire  wheels  have  demountable  rims  30  that 
the  wheels  need  not  be  removed  for 
changing  tires.  A  wire  wheel  with 
demountable  rim  is  shown  in  Fig. 

One  disadvantage  of  wire  wheels 
is  that  they  are  somewhat  difficult 
to  keep  clean.  The  spokes  are  also 
easily  injured  when  run  in  deep, 
hard  ruts  and  when  they  come  in 
contact  with  other  objects.  In  re- 
placing damaged  spokes,  the  hub  end 
fits  through  the  hub  plate.  The 
other  end  is  threaded  and  fits 
through  the  felloe.  The  adjustment 
is  made  by  tightening  the  nut  on 
the  threaded  end.  It  is  very  im- 
portant when  replacing  wire  spokes  that  they  be  tightened  the  same 
amount  in  order  to  prevent  the  rim  from  being  pulled  out  of  true. 

The  wire  wheels  are  very  easily  applied  and  removed  by  means 
of  locking  devices.  The  wheels  are  applied  so  that  if  the  locking  device 
should  fail  the  forward  motion  of  the  car  would  still  tend  to  keep  them  on. 
An  automobile  is  run  in  reverse  comparatively  little,  so  for  safety  the 
wheels  are  applied  on  the  right  side  of  the  car  with  right-handed  screws 
and  on  the  left  side  with  left-handed  screws. 

One  particular  claim  of  the  manufacturers  of  wire  wheels  is  that  they 
are  easier  on  the  car  and  occupants,  as  more  of  the  jolts  are  absorbed  by 
the  wheel  body.  The  wire  wheels  are  built  so  that  the  weight  of  the  car 
is  supported  by  the  spokes  above  the  hub  in  tension,  while  other  types 
of  wheels  support  the  load  below  the  hub  in  compression.  The  compres- 
sive support  is  direct  from  the  road  to  the  hub,  while  the  stress  in  a 
wire  wheel  is  spread  over  the  entire  tire  and  rim  to  the  upper  spokes  of 


493. — Wire  wheel  with  demountable 

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the  wheel.  Because  of  this,  more  of  the  shocks  and  jolts  are  absorbed 
by  the  wire  wheels,  consequently  are  not  transmitted  to  the  car  itself 
and  its  occupants.  This  added  resilience  is  another  fact  that  assists 
in  giving  greater  tire  mileage. 

The  two  types  of  spoke  lacing  now  in  general  use  are  shown  in  Fig.  494. 
The  relative  strength  of  any  two  wire  wheels  cannot  be  determined  en- 
tirely from  the  number  of  spokes  used.  Much  depends  on  the  distri- 
bution of  the  stress  and  the  relative  strength  of  the  steel  used  in  the 
spokes  of  the  different  wheels. 

Fig.  494. — Methods  of  spoke 
lacing  on  wire  wheels. 

Fio.  495. — Section  of  pressed 
steel  wheel. 

299.  Other  Types  of  Wheels. — In  Europe,  because  of  scarcity  of 
wood,  a  form  of  pressed  steel  wheel  has  become  very  popular.  The  hubs, 
felloes,  and  spokes  are  stamped  in  halves.  The  halves  are  welded  to- 
gether so  as  to  resemble  the  artillery  form  of  wooden  wheel.  When 
painted,  a  close  inspection  is  needed  to  tell  the  difference.  These  wheels 
are  generally  made  demountable  like  wire  wheels  in  order  to  make  tire 
changing  easy.  They  can  be  made  as  cheaply  as  the  wooden  wheel  and 
much  lighter. 

Wheels  of  thin  discs  of  pressed  steel,  as  shown  in  Fig.*  495,  are  being 
used  on  some  of  the  higher-priced  and  heavier  passenger  cars.  These 
wheels  are  strong  and  durable  and  are  also  very  easy  to  keep  clean. 

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Wheels  made  of  cast  steel  are  popular  for  trucks  but  it  is  difficult  to  manu- 
facture them  light  enough  for  passenger  cars. 

300.  Rims. — Rims  for  securing  tires  to  the  wheels  of  automobiles 
may  be  divided  into  three  types;  clincher ,  quick  detachable,  and  demount- 
able. A  combination  of  the  quick  detachable  and  demountable  types  is 
also  used  extensively. 

The  Clincher  One-piece  Rim. — The  clincher  one-piece  rim,  Fig.  496, 
is  made  in  one  piece  with  a  pocket  at  each  side  for  the  clincher  bead  of  the 
tire.  Such  a  rim  can  be  made  removable  from 
the  wheel  or  can  be  fastened  permanently  to  it  as 
in  the  case  of  the  Ford  rim  and  wheel.  This  type 
of  rim  is  considered  the  cheapest  to  manufacture 
but  it  is  difficult  to  remove  the  tire.  It  is  made 
practically  the  same  for  wooden  and  wire  wheels. 
Wire  wheels,  of  course,  have  the  advantage  of  Fio.  496.— Section  of  one- 
being  easily  demountable.  In  the  case  of  a  punc-  piece  °  nc  er  nm* 
ture  or  a  blow-out,  a  wheel  can  be  replaced  by  one  with  a  tire  already 

Figure  497  illustrates  the  method  of  removing  a  tire  from  a  clincher 
rim.  The  wheel  should  first  be  jacked  up  off  the  road  or  floor.  After 
removing  the  valve  cap  and  lock  nut,  the  valve  stem  should  be  pushed 
in  until  it  is  flu3h  with  the  rim,  and  the  shoe  or  bead  of  the  tire  then  loos- 

Seoond  Position 
of  Tiro  Tool 

Run  Tool 

Around  Edge 

of  Rim 

Fiq.  497. — Method  of  removing  tire  from  clincher  rim. 

ened  by  working  the  tire  with  the  hands.  A  tire  tool  should  be  inserted 
under  the  bead  as  shown  in  the  first  position.  Great  care  must  be  taken 
to  see  that  the  inner  tube  is  not  pinched  by  the  tire  tool.  A  second  tire 
tool  should  then  be  inserted  and  used  to  work  the  bead  over  the  rim  as  in 
position  three.  Either  one  or  both  tools  may  be  used  in  doing  the  work 
shown  in  position  four.    The  casing  should  then  be  moved  so  that  the 

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inner  bead  is  nearer  the  outside  edge  of  the  rim.  The  inner  tube  may 
now  be  removed  without  pinching  at  any  point.  In  removing  the  inner 
tube  the  start  should  be  made  diametrically  opposite  the  position  of  the 
valve  stem,  and  finally  the  stem  itself  lifted  from  its  hole  in  the  felloe. 

\   rh 
Demountabk  rim 


roggk  ""* 

Fe/lot  band 
Dtmountabk  rim 

%hmpino  fa/r 

Fia.  498. — Demountable  clincher  rim. 

The  clincher  rim  may  also  be  made  demountable,  as  illustrated  in 
Fig.  498.  After  the  rim  and  tire  are  removed  from  the  wheel,  the  method 
of  getting  the  tire  off  the  rim  is  the  same  as  with  the  clincher  rim  which 
is  fixed  on  the  wheel. 

Quick  Detachable  or  Q.  D.  Rims. — A  quick  detachable  rim  is  con- 
structed with  a  removable  ring  on  one  side,  Fig.  499,  so  that  the  tire  can 

Fio.  499. — Quick  detachable  rim  with 
removable  ring. 

Fio.  500. — Inserting  tool  to  remove 
ring  on  quick  detachable  rim. 

be  removed  from  it  very  easily.  This  outside  retaining  ring  is  split 
and  a  place  provided  for  inserting  a  tool  so  that  one  end  may  be  pried 
up  as  in  Fig.  500.  The  entire  ring  is  then  removed,  and  the  deflated  tire 
taken  off. 

Quick  detachable  rims  are  manufactured  in  three  types;  the  quick 
detachable  clincher,  the  quick  detachable  straight  sidef  and  the  quick  de- 

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tachable  universal.  The  quick  detachable  clincher  is  a  combination 
clincher  and  detachable  rim,  as  shown  in  Fig.  501.  This  is  an  uncommon 
type  of  rim.  It  is  usually  demountable  as  well  as  detachable,  in  which 
case  it  is  called  the  Q.  D.  demountable  clincher  rim. 

The  quick  detachable  straight  side  rim  differs  from  the  clincher  rim 
in  that  the  sides  of  the  rim  are  made  straight  to  fit  the  straight  side  type 

Fiq.  501. — Quick  detachable  clincher 
rim  which  is  also  demountable. 

Fiq.  502. — Detachable  straight  side 
rim  also  demountable. 

of  tire,  as  in  Fig.  502.  The  demountable  and  detachable  features  are  the 
same  as  for  a  clincher  rim.  Figure  503  illustrates  a  detachable  straight 
side  rim  which  is  not  demountable. 

The  side  rings  of  the  universal  type  of  rim  are  made  reversible  as  in 
Fig.  504  so  that  a  tire  of  either  the  clincher  or  of  the  straight  side  type  may 

Fiq.  503. — Detachable  straight  side 
rim  which  is  not  demountable. 

Fiq.  504. — Quick  detachable 
universal  rim. 

be  used.     In  addition  to  being  detachable,  these  rims  are  usually  made 

Demountable  Rims. — A  rim  is  demountable  when  provision  is  made  for 
removing  the  rim,  together  with  the  tire,  from  the  wheel  easily  and  quickly. 
This  feature  is  very  desirable  as  it  permits  a  quick  change  of  tires  in  case 

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of  a  puncture  or  a  blow-out.  A  fully  inflated  tire  may  be  carried  on  an 
extra  rim  which  can  be  placed  on  the  wheel  in  case  of  emergency. 

Demountable  rims  are  held  on  the  wheel  either  by  a  special  locking 
device  as  in  Fig.  498,  or  by  wedges  placed  around  the  circumference  of 
the  wheel.  The  locking  device  in  Fig.  498  locks  the  rim  on  the  wheel 
at  a  single  point.  When  the  toggle  nut  of  the  locking  device  is  in  its 
lowest  position,  the  clamping  ring  is  drawn  down  into  the  groove  and  the 
rim  is  released.  By  screwing  the  toggle  nut  up,  the  rim  becomes  locked 
on  the  wheel.  Various  forms  of  wedges  are  illustrated  in  Figs.  501  and 
502.  These  wedges  or  clamps  may  be  held  either  by  a  nut  fitting  over 
a  stud  or  by  a  bolt  extending  entirely  through  the  rim. 

The  demountable  rims  are  either  of  the  one-piece  clincher  or  of  the 
detachable  type.  All  types  of  quick  detachable  rims  may  be  made 
demountable.     They  would  then  be  called  Q.  D.  demountable  rims.     The 

Fio.  505. — Split-band  type  of  demountable  rim. 

split-band  type  of  demountable  rim,  as  shown  in  Fig.  505,  is  also  used. 
The  rim  may  be  removed  from  the  tire,  by  unlocking  the  ends. 

301.  Removal  of  Demountable  Rims. — When  it  is  necessary  to  re- 
move a  tire,. all  the  clamps  or  wedges  under  the  demountable  rim,  except 
the  two  nearest  the  valve  stem,  are  loosened  with  the  brace  as  shown  in 
Fig.  506.  This  should  be  done  before  jacking  up  the  wheel.  (The  weight 
of  the  car  holds  the  wheel  steady  for  this  work.)  The  wedges  are  turned 
out  of  the  way  and  should  be  fastened.  The  wheel  should  be  raised  from 
the  ground  with  the  jack  and  the  tire  tool  inserted  between  the  rim  and 
the  felloe  on  the  side  of  the  wheel  opposite  the  valve  stem,  as  shown  in 
Fig.  507.  The  rim  can  be  pried  off  the  wheel  at  this  point.  By  having 
the  valve  stem  at  the  lowest  point,  the  rim  can  be  slipped  off  the  wheel 
without  lifting  it.  Just  the  reverse  is  done  when  the  rim  and  tire  are 
put  on  the  wheel. 

The  operations  for  removing  a  split-band  type  of  rim  from  the  tire 
are  shown  in  Fig.  508.  The  rim  and  tire  are  put  flat  on  the  ground  and 
the  anchor  plate  which  holds  the  two  ends  of  the  rim  together  is  removed. 
The  long  side  of  the  end  containing  the  valve  stem  should  be  up.     (The 

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cut  in  the  rim  is  slanting.)  One  end  of  a  tire  tool  is  inserted  near  the 
cut  under  the  bead  of  the  tire  at  that  end  of  the  rim  which  does  not  con- 
tain the  valve  stem.  The  other  end  is  forced  downward  and  toward  the 
center  of  the  rim.  This  forces  the  end  of  the  rim  out  of  the  tire.  The 
tire  tool  is  then  removed  and  inserted  about  6  in.  farther  from  the  cut, 
on  the  same  side,  and  the  operation  repeated.  The  tire  and  the  rim 
must  now  be  turned  completely  over.  The  free  end  of  the  rim  may  be 
taken  hold  of  with  both  hands,  and  by  holding  the  tire  flat  on  the  ground 
with  one  foot,  the  rim  may  be  pulled  out  entirely.  In  putting  the  tire 
back  on  the  rim  the  operation  is  reversed,  in  which  case  care  must  be 
taken  that  both  beads  of  the  tire  are  properly  seated  in  the  rim.  The  tire 
tool  may  be  used  if  the  beads  are  too  stiff  to  work  by  hand.     The  end  of 

Fig.  606. — Loosening  wedges  before  re-  Fio.  507. — Inserting  tool  for  removal 

moving  demountable  rim.  of  demountable  rim. 

the  rim  should  not  be  slipped  into  place  until  the  rest  of  it  is  properly 

Care  of  Rims. — All  rims  should  be  inspected  frequently  to  see  if  they 
are  rusting.  If  rust  has  started,  it  should  be  removed  carefully  with 
a  sharp  tool,  the  spot  smoothed  with  emery,  and  rim  paint  used.  This  is 
very  necessary  in  order  to  save  the  tires. 

302.  Types  of  Tires. — Automobile  tires  may  be  divided  into  two  kinds: 
pneumatic  and  solid  or  cushion.  Pneumatic  tires  are  universally  used  for 
passenger  carrying  cars.  They  may  be  divided  into  three  types  from  the 
standpoint  of  construction:  fabric,  cord,  and  fabric  cord.  They  may  also 
be  classified  according  to  the  type  of  rims  for  which  intended,  as,  clincher, 
quick  detachable  clincher,  and  straight  side,  as  shown  in  Fig.  509.  The 
regular  clincher  tire  differs  from  the  Q.  D.  clincher  in  only  one  respect. 
The  beads  of  the  regular  clincher  type  are  filled  with  rubber  composition 

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and  are  very  flexible  so  as  to  be  easy  to  remove.  The  Q.  D.  clincher  beads 
have  a  core  of  many  turns  of  piano  wire  surrounded  by  the  same  compo- 
sition, which  gives  a  stronger  and  stiffer  bead  than  that  of  the  regular 
clincher  type.     Straight  side  tires  have  the  beads  constructed  in  a  simi- 

Fiq.  508. — Operations  in  the  removal  ofjgplifc-band  type  of  rim  from  tire. 

lar  manner.  As  the  names  signify,  each  of  these  tires  fits  into  a  rim  of 
its  own  particular  type,  and  should  never  be  placed  in  any  other  kind  of  a 
rim.  Straight  side  tires  are  believed  to  be  more  durable  and  stronger  and 
are  recommended  as  a  standard  by  the  Society  of  Automotive  Engineers 
for  all  sizes  larger  than  30  in: 

Quick  detachable 



Fiq.  509. — Types  of  tires. 

Straight  side. 

303.  Construction  of  Tires. — Figures  510  and  511  illustrate  the  con- 
struction of  fabric  tires.  Several  layers  of  heavy  canvas  (friction  fabric) 
are  wound  around  two  circular  braids  of  piano  wire  (beads)  into  the  shape 
of  a  tire.    A  thin  layer  of  rubber  gum  is  placed  between  all  layers  of  the 

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fabric.    The  canvas  used  in  the  construction  of  these  tires  is  prepared  by 
forcing  rubber  composition  into  the  meshes  of  the  cloth.    Five  or  six 







Pra.  510. — Construction  of  J.  and  D.  fabric  tire. 

f  Tread 

7th  Ply 
©tti  Ply 
5-th  Ply 
■4+ii  Ply 
3rd  Ply 
pEnd  Ply 
Mst  Ply 

Fiq.  511. — Construction  of  Quaker  City  fabric  tire. 

layers  of  this  fabric  wound  in  this  manner  form  the  carcass  around  which 
the  cushion  is  built.     This  cushion  is  an  extra  thickness  of  compounded 

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rubber  held  in  place  by  a  double  layer  of  canvas  which  is  called  the  breaker 
strip.  Outside  of  this  is  the  tread  which  comes  in  contact  with  the  road 
and,  consequently,  takes  the  wear.  There  is  also  a  thin  layer  of  rubber 
over  the  sides.  This  whole  structure  is  then  vulcanized  or  baked  into  a 
solid  unit.  Great  care  and  considerable  experience  are  needed  in  this 
operation  as  too  much  vulcanizing  will  make  the  rubber  hard  and  brittle, 
while  too  little  vulcanizing  will  leave  it  too  soft  to  resist  wear. 

The  fabric  is  laid  with  the  threads  on  a  bias  of  45°.  This  is  done 
so  that  in  case  of  rupture  the  break  will  not  run  the  entire  circumference 
of  the  tire.  The  layers  of  thread  running  one  way  bend  on  the  layers 
running  the  other,  causing  the  fabric  to  wear  and  the  threads  to  break. 
This  is  one  disadvantage  of  fabric  tires. 

In  cord  tires,  layers  of  cord  instead  of  fabric  are  wound  on  the  tire 
on  a  bias  of  45°  as  shown  in  Fig.  512.  On  account  of  the  fact  that  the 
cords  in  any  one  layer  are  parallel  to  each  other  there  is  no  bending  of 

Fiq.  512. — Internal  construction  of  cord  tires. 

one  over  the  other  as  in  the  case  of  the  threads  on  the  fabric  tire.  Adja- 
cent layers  of  cord  are  laid  with  the  cords  at  an  angle  of  90°  to  each  other. 
There  are  usually  two  to  five  layers  of  cord,  depending  upon  the  size  of 
the  cord.  Otherwise,  construction  is  the  same  as  of  fabric  tires.  There 
is  less  internal  heat  generated  because  there  is  not  the  continual  rubbing 
of  the  threads  upon  one  another.  A  stiffer  carcass  is  the  result  of  this 
cord  construction.  The  better  riding  qualities  of  cord  tires  are  due  chiefly 
to  this  fact  as  the  tires  will  carry  the  given  load  with  less  air  pressure  and, 
consequently,  with  more  resilience.  The  air  pressure  in  a  cord  tire 
should  be  about  10  per  cent,  less  than  the  air  pressure  in  a  fabric  tire  of 
the  same  size,  carrying  the  same  load.  This  is  due  to  the  increased 
resiliency  of  cord  tires.  A  car  fitted  with  cord  tires  will  invariably  coast 
farther  down  a  hill  than  the  same  car  fitted  with  fabric  tires.  Cord 
tires  give  the  best  possible  service  with  moderate  upkeep  cost  and 
economy  of  power. 

Fabric  cord  tires  are  constructed  of  about  the  same  number  of  layers 

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as  fabric  tires.  Heavy  cords  are  used  in  one  direction,  while  threads  are 
used  at  right  angles  to  the  cords.  These  threads  are  woven  in  with  the 
cords  and  hold  them  together  as  in  a  piece  of  fabric.  In  the  layers  of 
fabric  cord  there  is  not  the  tendency  to  wrinkle  that  there  is  in  the  layers 
of  fabric.  The  strain  is  carried  better  in  each  layer  of  fabric  cord  by  the 
heavy  cords  running  in  only  one  direction  than  in  tires  of  fabric  construc- 
tion.   In  other  respects,  the  construction  is  similar  to  cord  tires. 

Cord  tires  and  fabric  cord  tires  are  much  harder  to  repair  than  fabrie 
tires,  and  the  first  cost  is  greater. 

The  side  walls  in  all  pneumatic  tires  must  be  thin  and  elastic  as  the 
greatest  strains  occur  there.  If  the  side  walls  were  as  heavily  reinforced 
as  the  tread,  the  constant  stretching  would  cause  the  fabric  to  break  and 
the  rubber  to  crack,  the  cushioning  effect  of  the  tire  would  be  impaired 
and  the  car  would  ride  much  harder. 

Inner  tubes  are  simply  air-tight  bags  of  compounded  rubber  with 
mechanical  one-way  air  valves.  They  are  very  carefully  made  and  if 
properly  used  should  give  long  wear  and  service. 

304.  Proper  Use  and  Care  of  Tires. — One  of  the  most  important  prob- 
lems in  the  care  and  operation  of  an  automobile  is  that  of  giving  the 
proper  care  and  attention  to  the  tires.  This  is  important  because  tires 
are  one  of  the  chief  items  of  expense.  The  cost  per  mile  for  tires  alone  can 
be  reduced  considerably  with  just  a  little  extra  attention  and  care  on  the 
part  of  the  owner.  Tire  troubles  come  mainly  through  neglect  and  can 
be  avoided  in  most  cases.  Some  of  the  things  which  should  be  given 
special  attention  are: 

1.  Proper  inflation  of  tires.  13.  Oil  on  tires. 

2.  Tires  of  proper  size.  14.  Light  and  heat  on  tires. 

3.  Care  in  application  of  tires  to       15.  Fast  driving. 

rims.  16.  Poorly  made  repairs. 

4.  Rim  irregularities.  17.  Tire  powder. 

5.  Flat  tires.  18.  Inserting  inner  tubes. 

6.  Fabric  bruises.  19.  Care  of  spare  tubes. 

7.  Improper  braking.  20.  Leaky  air  valves. 

8.  Tight  chains.  21.  Tire  fillers. 

9.  Wear  of  tire  by  parts  of  car.        22.  Tire  protectors. 

10.  Alignment  of  wheels.  23.  Spare  casings. 

11.  Ruts  and  car  tracks.  24.  Care  of  tires — car  in  stor- 

12.  Neglected  injuries.  age. 

305.  Proper  Inflation. — No  exact  rule  can  be  given  for  the  proper 
inflation  of  tires  as  the  strength  of  tires  of  the  same  size,  as  made  by  dif- 
ferent manufacturers,  will  vary  considerably.    The  best  rule  to  follow 

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is  to  use  the  pressure  recommended  by  the  manufacturer  of  the  tire. 
This  pressure  has  been  determined  by  test  and  experience.  It  will 
average  about  20  lb.  per  inch  of  cross-section  of  the  tire  for  the  rear 
tires  with  possibly  a  slightly  lower  pressure  for  the  front  tires.  The 
front  wheels  generally  support  less  weight  and  can  of  tenbe  run  at  lower 

It  is  impossible  to  guess  at  the  correct  pressure  in  a  tire.  A  pressure 
gauge  should  always  be  used  as  it  will  indicate  the  correct  pressure. 
These  gauges  are  simple,  are  not  expensive,  and  save  many  times  their 

Over  one-half  of  the  failure  of  tires  to  give  the  proper  mileage  is 
due  to  under-inflation.  It  is  not  generally  known  in  this  connection 
that  over  60  per  cent,  of  the  total  loss  of 
power  between  the  engine  and  the  road  is 
consumed  by  the  tires  in  internal  friction, 
and  that  under-inflation  of  the  tires  may 
cause  as  high  as  25  per  cent,  increase  in  the 

Piq.  513. — Condition  of  tire  when  under- 

Fio.  514. — Breaking  down  of  side 
walla  due  to  under-inflation. 

power  necessary  to  drive  a  car.  It  is,  therefore,  advisable  to  keep  the 
tires  properly  inflated  to  save  gasoline  as  well  as  to  save  the  tires. 

The  inflation  pressure  should  be  practically  the  same  in  summer  as  in 
winter.  The  heat  from  the  road,  together  with  the  greater  heat  gen- 
erated in  an  under-inflated  tire,  destroys  the  casing  much  more  rapidly 
than  if  the  tire  were  properly  inflated.  The  increased  pressure  in  a  tire 
due  to  hot  weather  is  negligible  as  compared  with  the  inflation  pressure. 

The  excessive  strain  on  the  side  walls  of  a  casing,  due  to  the  bending 
when  it  is  under-inflated,  causes  heat  to  be  generated  and  the  layers  of 
fabric  to  try  to  slide  over  one  another.  Eventually,  this  strain  causes  a 
separation  or  breaking  of  the  binding  between  the  layers  of  fabric  and 
rapid  deterioration  of  the  tire.  A  break  in  the  fabric  may  result  from 
crossing  tracks  or  hitting  a  stone  when  a  tire  is  under-inflated  because 
of  the  excessive  strain,     A  blow-out  may  possibly  follow.     The  distor- 

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tion  of  an  under-inflated  tire  is  shown  in  Fig.  513  and  the  consequent 
breaking  down  of  the  side  walls  in  Fig.  514.  The  result  of  under-inflation 
on  the  outside  of  the  casing  is  illustrated  in  Fig.  515.  The  tires  should 
always  be  inflated  to  the  proper  pressure  and  this  should  never  be  per- 
mitted to  decrease  more  than  20  per  cent. 

306.  Tires  of  •Proper  Size* — Overloading  tires  has  exactly  the  same 
effect  as  under-inflation.  The  table  below  gives  the  maximum  allowable 
load  for  the  different  sizes  of  tires. 

Site  of  tires 

Load  per  wheel  in 

Sise  of  tires 

Load  per  wheel  in 

2J4  in.  all  diara. 


30  X  4  in. 


3  in.  all  diam. 


32  X  4  in. 


28  X  3H  in. 


34  X  4  in. 


30  X  3M  in. 


36  X  4  in. 


32  X  SH  in. 


32  X  4^  in. 


34  X  ZM  in. 


34  X  4^  in. 


36  X  3^  in. 


36  X  4H  in. 



All  5  in. 

1000  or  over 

Most  cars  are  fitted  with  regular  size  tires  at  the  factory  so  that  the 
tires  may  be  replaced  with  their  over-sizes,  when  necessary.  Even  when 
cars  are  not  overloaded  at  any  time  many  owners  prefer  to  use  over-size 
tires  on  account  of  their  greater  strength,  the  lessened  vibration,  and 
greater  tire  mileage.  A  comparison  of  the  regular  with  its  over-size 
to  fit  the  same  rim  is  shown  in  Fig.  516.  The  following  table  gives 
the  common  sizes  in  regular  tires  and  their  corresponding  over-size: 

Regular  sise  tire 

Over-sise  tire 

30  X  3 

31  X  SH 

30  XSH 

31  X  4 

32  XSH 

33  X4 

32  X  4 

33  X4K 

34  X  4 

35  X4% 

34  X4H 

35  X  5 

36  X« 

37  X  5 

36  X  5 

37  X5H 

If  it  is  thought  that  over-size  tires  are  needed,  this  may  be  determined 
by  the  use  of  large  platform  scales.  (The  ground  surrounding  the  scales 
should  be  level  and  even  with  them.)  The  car  should  be  placed  so  that 
the  front  wheels  rest  on  the  platform.  The  middle  of  the  car  should  be 
over  the  edge  of  the  scales.  With  the  car  in  this  position  and  fully 
loaded  the  reading  of  the  scales  should  be  taken.    This  weight  divided 


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by  two  gives  the  weight  supported  by  each  tire.     The  car  should  now 

be  driven  across  the  scales  and  a  reading  taken  for  the  rear  wheels  in  the 

same  manner. 

307.  Care  in  Application  of  Tires  to  Rims. — Tires  of  the  clincher 

type  cannot  be  fitted  to  straight  side  rims  nor  can  straight  side  tires 
be  fitted  to  clincher  or  Q.  D.  clincher  rims.  If  uni- 
versal rims  are  used  care  should  be  taken  that  the  side 
rings  are  properly  placed  for  the  type  Qf  tire  being 

308.  Rim  Irregularities. — Dented,  irregular,  and 
rusted  rims  are  commonly  the  causes  of  cutting  the 
beads  of  tires.  If  irregularities  are  not  removed  from 
the  rims,  new  tires  will  wear  very  quickly  and  have  very 
short  lives.  All  rust  should  be  carefully  removed  with 
emery  cloth,  and  some  preservative  like  rim  paint  used. 

309.  Flat  Tires. — When  a  tire  goes  flat  overnight 
(or  shortly  after  being  properly  inflated)  it  is  almost 
always  due  to  a  loose  or  leaky  air  valve.  In  this  case 
the  tube  should  be  removed  and  the  nut  at  the  base 
of  the  valve  stem  tightened  or  the  valve  cap  removed 
and  reversed  so  as  to  tighten  the  valve  itself.  It  may 
be  found  that  an  entirely  new  valve  is  needed.     In  the 

Fio.  515. — Result  of 
u  rider-inflation. 

Fig.  516. — Regular  and  over-size  tires  on  same  rim. 

case  of  a  puncture,  the  tire  will  generally  go  flat  while  the  car  is  run- 
ning. An  experienced  driver  will  immediately  notice  the  difficulty  in 
steering.  The  car  should  not  be  run  on  a  flat  tire.  It  should  be 
stopped  and  temporary  or  permanent  repairs  made  before  the  tire  is 
completely  ruined.  Rim  cutting  and  broken  side  walls  result  from 
running  on  flat  tires. 

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810,  Fabric  Bruises. — Tire  bruises  are,  perhaps,  harder  to  avoid  than 
any  other  tire  troubles.  While  it  is  impossible  to  avoid  every  rock  or 
obstruction  in  the  road,  it  is  possible  to  avoid  backing  into  curbs  and  fast 
driving  over  tracks,  which  are  very  common  causes  of  fabric  bruises. 
Many  drivers  also  run  the  front  wheels  against  a  curb,  when  the  brakes 
are  not  working  properly,  and  do  not  try  to  dodge  deep  holes  in  the 

A  break  in  the  fabric  can  be  noticed  on  the  inside  of  the  casing  shown 
in  Fig.  517.     It  was  caused  by  a  severe  blow  received  by  the  tire.     The 

Fiq.  617. — Broken  fabric. 

fabric  of  a  tire  may  give  way  under  such  a  blow  although  no  permanent 
mark  may  be  left  on  the  outside.  This  does  not  indicate  that  the  tire 
was  defective  in  any  way,  but  usually  indicates  carelessness  on  the  part 
of  the  driver.  Such  a  bruise  may  be  given  to  the  tire  weeks  before  the 
blow-out  occurs.  The  blow-out  may  happen  while  the  car  is  left  standing 
at  the  curb  or  in  the  garage.  Such  a  fabric  bruise  has  even  been  known  to 
pinch  the  inner  tube  so  as  to  cause  a  slow  leak. 

311.  Improper  Braking. — No  one  would  expect  to  use  a  sharp  file  on 
one  spot  of  a  tire  for  any  length  of  time  without  doing  it  permanent  in- 
jury, and  yet  this  practically  happens  when  the  brakes  are  used  to  keep 

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the  wheels  from  turning  before  the  car  stops.  The  wheels  of  a  moving 
car  should  never  be  stopped  suddenly  with  the  brakes  while  the  car  is  in 
motion,  except  in  case  of  great  danger.  The  roadbed  makes  an  excellent 
file,  and  the  pressure  between  the  road  and  the  tire  makes  the  filing  action 
exceedingly  severe.  Figure  518  shows  the  effect  on  a  tire  caused  by  lock- 
mg  the  wheels  with  the  brakes  and  of  sliding  the  tire  over  the  pavement 
or  road.  It  is  inexcusable  for  any 
other  cause  than  an  emergency  and 
is  a  very  expensive  practice. 

312.  Tight  Chains.— Anti-skid 
devices  of  all  kinds  are  severe  on 
tires.  Chains  should  always  be 
put  on  a  car  so  that  they  are  loose 

Fiq.  518. — Scraped  tire  due  to 
improper  use  of  brakes. 

Fia.  519. — Tire  injured  by  chains. 

enough  to  creep  around  the  tire  and  not  wear  the  same  spots.  They  should 
not  be  so  loose  as  to  be  noisy.  Any  anti-skid  device  that  is  fastened  to 
the  spokes  should  not  be  used.  Figure  519  shows  the  result  of  using  tight 
chains  on  a  tire.  In  this  case  the  chains  could  not  shift  around  the  tire 
and,  consequently,  the  wear  came  on  the  same  spot.  Mudhooks  may  be 
used  in  getting  a  car  out  of  very  muddy  holes  and  out  of  deep  snow. 
They  should  be  removed  as  soon  as  possible.  Under  no  condition  should 
chains  or  any  other  similar  device  be  used  any  longer  than  is  absolutely 

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necessary.    They  must  be  used  occasionally,  but  they  are  extremely 
hard  on  tires. 

313.  Wear  of  Tire  by  Parts  of  Car. — Care  should  be  taken  to  see  that 
no  projections  from  the  car  touch  the  tires;  that  the  fenders  are  not  bent 
so  as  to  wear  on  the  tires;  that  the  car  is  not  so  over- 
loaded that  any  part  of  the  car  will  scrape  the  tires;  and 
also  that  the  springs  or  spring  clips  are  not  broken. 
These  things  cause  unnecessary  wear  on  the  tires  and 
unnecessary  expense.  There  should  be  enough  clear- 
ance between  the  bumpers  and  the  tires  to  prevent  rub- 
bing. This  rubbing  is  more  liable  to  occur  when  over- 
size tires  are  used-  Sharp  turns  may  cause  tires  to 
come  into  contact  with  or  to  rub  against  some  spring 
shackle  or  bolt.  Rapid  wear  of  tires  is  sometimes  caused 
in  this  manner. 

314.  Alignment  of  Wheels. — A  large  part  of  front 
wheel  tire  trouble  is  due  to  faulty  alignment  of  the 
wheels.  (This  may  be  caused  by  a  bent  axle,  steerjng 
rod,  or  knuckle;  or  by  loose  or  crooked  demountable 
rims.)  If  the  front  wheels  are  out  of  alignment  the  tires 
will  undergo  a  grinding  action  as  they  pass  over  the  road. 
This  action  is  very  destructive  to  the  treads  and  should 
not  be  permitted  to  continue.  Figure  520  shows  the  re- 
sult of  this  filing  action  of  the  roadbed  caused  by  wheels 
being  out  of  alignment.  Rear  wheels,  as  a  rule,  do  not 
get  out  of  alignment  as  frequently  as  the  front  ones. 
The  alignment  of  the  wheels  can  be  checked  by  measur- 
ing the  distances  between  the  felloes  of  the  wheels  in 
front  of  the  axle  and  then  behind  the  axle.  All  measure- 
ments should  be  taken  at  the  same  height  from  the 
ground,  preferably  at  the  same  height  as  the  axle.  The 
measurement  in  front  of  the  front  axle  should  not  exceed 
the  measurement  behind  the  front  axle  by  more  than  % 
to  %  in.  There  should  be  no  difference  in  the  measure- 
ments at  the  rear  wheels. 

315.  Ruts  and  Car  Tracks. — The  result  of  driving 
a  car  in  ruts  is  shown  in  Fig.  521.    The  side  walls  are 

purposely  made  the  thinnest  part  of  the  tire  and  yet  many  drivers  often 
drive  in  ruts  because  it  is  a  trifle  easier  than  to  keep  out  of  them.  The 
fabric  soon  becomes  worn  and  weakened  from  wear,  and  dampness  may 
get  to  the  fabric  and  rot  it.  The  result  is  the  same  when  the  sides  of  a 
tire  are  scraped  against  curbstones.  Running  in  car  tracks  causes  a 
similar  condition  nearer  the  tread. 

Fig.  520. — 
The  result  of 
poor  wheel  align- 

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316.  Neglected  Injuries. — It  is  expensive  to  repair  neglected  cuts  and 
oftentimes  they  cannot  be  repaired  at  all.  A  little  attention  given  to  the 
tires  each  day  will  save  much  tire  expense.  Tacks,  nails,  and  glass  may 
be  easily  removed  if  attended  to  daily,  and  the  holes  may  be  plugged 
before  they  enlarge  and  moisture  penetrates  to  the  fabric.  In  the  case 
of  a  large  cut,  rubber  may  be  applied  and  a  small  vulcanizer  used  to  do  the 
repair  work.    Fewer  tire  cuts  will  result  if  a  driver  will  always  slightly 

accelerate  the  car  so  as  to  coast  over  loose 
crushed  stone  and  similar  surfaces. 

When  cuts  are  neglected  the  elasticity  of 
the  rubber  allows  them  to  expand  under  the 
weight  of  the  car;  sand,  mjid,  and  water  are 
forced  into  them  and  they  keep  growing  larger. 
Moisture  gets  to  the  fabric  causing  it  to  de- 
teriorate rapidly.  With  each  revolution  more 
foreign  matter  accumulates  which  finally  causes 
a  mud-boil.  Either  a  complete  separation 
from  the  tread  or  a  blow-out  is  the  result. 

317.  Oil  on  Tires. — Quite  often  a  car  is 
left  standing  in  puddles  of  oil  in  a  garage. 
This  should  never  be  done  as  oil  softens  the 
rubber  causing  it  to  wear  just  as  though  it 
had  been  improperly  cured.  Most  of  the 
damage  from  oil  is  probably  due  to  grease 
working  from  the  brake  drums  to  the  side 
walls  of  the  tires.  This  should  be  looked  for 
as  it  can  be  easily  removed  by  a  cloth  damp- 
ened with  gasoline  before  damage  results.  Oil 
may  cause  a  separation  between  the  layers  of 
fabric  and  at  the  same  time  damage  the  fabric 

318.  Light  and  Heat — Extra  casings 
should  be  protected  from  the  light  by  being 
well  wrapped  and  spare  casings  should  be  kept 

in  a  dark,  cool,  dry  place  whenever  possible,  or  the  tires  will  not  give  the 
expected  mileage.  Rubber  bands,  as  commonly  used  in  office  work,  be- 
come old  and  so  brittle  that  they  will  break  if  used.  Tires  also  slowly 
deteriorate  whether  they  are  used  or  not.  Both  light  and  heat  make 
this  deterioration  more  rapid. 

319,  Fast  Driving. — During  a  600-mile  race  on  a  speedway,  a  car  may 
use  from  8  to  10  of  the  best  obtainable  casings  any  one  of  which  could 
ordinarily  be  used  in  running  6000  miles.  The  filing  action  of  the  road 
on  tires  is  very  destructive  when  speeding.     Each  time  a  wheel  leaves  the 

Fio.  521. — Rut-worn  tire. 

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ground  and  comes  to  earth  again,  there  is  this  filing  action.  In  turning 
corners  at  a  high  rate  of  speed  the  strain  on  the  side  walls  is  excessive, 
and  is  very  apt  to  cause  trouble.  When  driving  20  to  25  miles  per  hour 
little  trouble  should  be  experienced.  When  a  car  is  driven  at  a  greater 
speed  the  tires  will  give  less  mileage. 

320.  Poorly  Made  Repairs. — The  pressure  in  a  tire  is  so  great  that  all 
repairs  must  be  well  made  in  order  to  be  effective.  This  is  especially 
true  of  repairs  for  blow-outs.  Figure  522  shows  a  tire  that  blew  out  due 
to  defective  repairs.  Originally,  it  had  a  small  cut  clear  through  the  cas- 
ing.   The  inside  patch  was  not  applied  properly  and  did  more  harm  than 

Fio.  522. — Blow-out  from  ineffective  repairs. 

good.  As  shown  in  the  figure,  the  pressure  forced  the  patch  through  the 
hole,  wedging  the  fabric  apart,  and  causing  it  to  break  from  bead  to  bead. 
The  inside  view  shows  the  patch  pulled  away  from  its  original  position 
and  forced  through  the  break.  This  condition  is  the  result  of  defective 
repairing.  An  inside  protection  patch,  used  with  an  outside  emergency 
band,  should  be  used  until  permanent  repairs  can  be  made  to  take  the 
strain  at  the  weakened  point. 

321.  Tire  Powder. — When  an  inner  tube  is  inserted  in  a  casing  it 
should  be  perfectly  dry,  and  the  casing  prepared  by  dusting  lightly  with 

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powdered  soapstone,  sometimes  called  French  chalk,  or  talcum,  or  with 
powdered  mica.  This  serves  as  a  lubricant  and  keeps  the  tube  from 
sticking  to  the  casing  or  from  chafing.  Too  much  powder  should  not 
be  used  as  it  may  collect  in  lumps  and  the  resulting  pressure  and  chafing 
damage  the  inner  tube. 

322.  Inserting  Inner  Tubes. — When  an  inner  tube  is  inserted  in  the 
casing  it  should  not  be  allowed  to  wrinkle.  It  should  be  slightly  inflated 
and  care  taken  to  see  that  it  does  not  get  pinched  under  the  beads  or  by 
an  inner  shoe  if  one  is  used.  The  flaps  should  be  properly  placed,  the 
one  containing  the  larger  hole  on  top,  and  care  taken  to  see  that  they  do 
not  slip  around  the  casing  as  this  causes  chafing  of  the  inner  wall  and 
often  results  in  worn  fabric. 

After  a  tire  is  punctured,  the  inside  of  the  casing  should  be  examined 
before  the  repaired  tube  or  a  new  one  is  put  in.  If  a  tack  or  piece  of 
glass  is  visible  on  the  inside  of  the  casing  it  should  be  removed.  Road- 
side repairs  of  the  casing,  due  to  such  injuries,  are  not  usually  necessary, 

Fiq.  523. — Proper  method  of  folding  inner  tube. 

but  the  cut  should  be  repaired  as  soon  as  possible.  A  spare  tube  should 
be  inserted  if  there  is  one  and  the  damaged  one  repaired  later  by  vul- 
canizing. If  the  damaged  one  must  be  used,  a  vulcanized  repair  is 
preferable.  It  may  be  repaired  temporarily  with  a  patch.  The  patch 
should  be  removed  later  for  a  vulcanized  repair,  as  tubes  patched  with 
cement  seldom  last  as  long. 

323.  Care  of  Spare  Tubes. — Spare  tubes  deteriorate  the  same  as 
casings.  Much  can  be  done  to  lengthen  the  life  of  spare  inner  tubes 
by  keeping  them  properly  folded  in  an  oil-proof,  dust-proof,  and  light-- 
proof bag  when  not  in  use.  They  are  easily  injured  and  heavy  articles 
should#not  be  placed  near  them  or  thrown  on  them.  A  little  care  given 
to  them  will  save  much  trouble  and  expense. 

In  rolling  a  spare  tube,  the  valve  should  be  removed  and  all  the  air 
forced  out.  The  valve  should  then  be  replaced  so  that  no  more  air  can 
enter.  The  valve  stem  should  be  covered  with  a  piece  of  chamois  skin 
or  cloth.  The  tube  should  be  laid  out  flat  with  the  valve  stem  up  as 
shown  in  Fig.  523.  Each  end  should  be  folded  over  so  that  it  almost  meets 
the  other  at  the  valve  stem.  The  tube  should  then  be  folded  at  the 
valve  stem  with  the  stem  on  the  inside  of  the  fold.  The  roll  should  be 
fastened  or  tied  rather  loosely  with  broad  tape  so  as  not  to  injure  the 
tube.    It  should  then  be  placed  in  a  bag. 

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324.  Leaky  Air  Valves. — Leaky  air  valves  may  be  easily  discovered 
the  same  as  punctures.  Bubbles  rising  from  the  valves  when  the  tube, 
slightly  inflated,  is  immersed  in  water,  indicate  that  the  air  valve  is 
leaking.  This  is  a  common  source  of  tire  trouble  and  may  be  repaired 
in  some  cases  by  simply  tightening  the  valve  or  the  nut  at  the  base  of 
the  valve  stem.  An  entire  new  valve  stem  or  a  new  valve  maybe 

326.  Tire  Fillers. — A  common  question  is  "Do  tire  fillers  mend  cuts 
and  keep  the  tires  in  good  condition?"  They  may  mend  cuts  but  their 
use  cannot  be  recommended.  The  opinions  of  two  leading  manufac- 
turers of  tires  in  regard  to  tire  fillers  follow: 

1.  Avoid  the  use  of  any  substitute  for  air.  Our  guarantee  is  with- 
drawn when  substitutes  are  used. 

2.  Tire  manufacturers  waive  the  guarantee  and  responsibility  for 
tires  when  a  substitute  for  air  is  used.  Car  manufacturers  discourage 
excess  weight  on  wheels. 

Tire  fillers  which  fill  the  tires  completely  are  added  weights  which 
reduce  the  resiliency.  No  filler  can  be  as  resilient  as  air.  A  puncture 
cure  or  filler  that  does  not  fill  a  tire  completely  is  an  unbalanced  weight 
that  will  distort  the  tire  in  time  and  tend  to  shorten  its  life  rather  than 
preserve  it.  Besides,  puncture  cures  do  not  mend  cuts  from  the  outside 
and  a  permanent  injury  may  be  done  to  the  casing  before  the  inside  is 
punctured  at  all. 

326.  Tire  Protectors. — Reliners,  inside  protectors,  and  tread  attach- 
ments add  extra  weight,  cause  additional  heat  by  friction  between  sur- 
faces, and  interfere  with  the  radiation  of  such  heat.  If  reliners  are  made 
of  flexible  material  and  are  well  constructed,  they  are  good  things  to 
use  in  old  casings.  They  protect  the  inner  tubes  and  make  it  possible  to 
secure  much  greater  mileage  from  them.  Reliners  should  never  be  used 
in  new  tires  as  they  tend  to  flatten  them  just  as  they  are  flattened  by 

327.  Spare  Casings. — Spare  casings  should  never  be  carried  so  that 
oil  or  water  can  collect  in  the  supports.  If  they  are  tied  or  strapped 
tightly  with  anything  narrow  the  jolting  of  the  car  will  cause  the  straps 
to  cut  the  tire  through  natural  wear.  As  mentioned  before,  they  should 
be  protected  from  light  and  heat  as  much  as  possible. 

328.  Care  of  Tires — Car  in  Storage. — Casings  and  tubes  should  be 
removed  from  the  rims  when  a  car  is  in  storage  and  placed  in  a  cool,  dark, 
dry  place.  If  the  car  is  out  of  use  temporarily,  it  should  be  jacked  up 
so  that  no  weight  rests  on  the  tires.  If  the  car  is  not  to  be  used  for  some 
time,  even  though  it  is  not  put  away  for  an  entire  season,  it  is  best  to 
remove  the  tires  and  examine  the  rims  for  rust.  The  casings  and  tubes 
should  also  be  protected  from  dust  and  dirt. 

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329.  Repair  of  Tires. — Tire  repairs,  except  for  minor  cuts  and  punc- 
tures, should  usually  be  made  by  an  expert  tire  repairman.  A  car  owner 
or  driver  should,  however,  become  familiar  with  the  processes  and 
operations  that  are  used  in  repairing  and  vulcanizing  casings  and  tubes. 
Every  large  tire  company  publishes  a  complete  booklet  on  repairing 
and  vulcanizing  tires  which  if  studied  carefully  will  give  all  the  necessary 
information  on  these  subjects.  A  small  vulcanizer  for  home  use  is  better 
than  one  for  roadside  repairs.  Roadside  repairs  can  seldom  be  made  as 
they  should  be. 

Important  Points  about  Tires — 

1.  Keep  tires  inflated  to  the  proper  pressure. 

2.  Never  rim  the  car  on  a  flat  tire. 

3.  Do  not  jam  on  the  brakes  so  as  to  keep  the  wheels  from  turning. 

4.  Avoid  skidding. 

5.  Keep  out  of  ruts  and  car  tracks,  and  do  not  scrape  sides  of  tires 
against  curbs. 

6.  Avoid  sharp  obstructions.  Do  not  run  tires  against  curbs.  Go 
over  bumps  and  car  tracks  slowly. 

7.  Apply  chains  in  proper  Way  but  do  not  use  them  for  a  time  longer 
than  necessary. 

8.  Keep  the  front  wheels  in  proper  alignment. 

9.  Repair  small  cuts  promptly. 

10.  Insert  inner  tubes  with  care.     Do  not  use  too  much  talc  or  lubri- 

11.  Keep  tires  free  from  oil  and  grease. 

12.  Keep  rims  free  from  irregularities  and  rust. 

13.  Carry  spare  casing  and  tube  in  bag. 

14.  Never  use  substitutes  for  air. 

15.  Buy  good  tires  and  give  them  the  best  possible  care. 

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330.  Classification  of  Troubles. — The  manufacturers  of  automobiles 
are  constantly  striving  to  simplify  the  design  and  construction  of  all  parts 
in  order  to  reduce  the  number  of  troubles  which  are  a  constant  source  of 
worry  to  the  automobile  owner  and  driver.  They  have  been  quite 
successful  in  reducing  troubles  to  a  minimum;  as  a  matter  of  fact,  the 
possible  troubles  on  the  modern  car  are  now  few  in  number  compared  with 
those  of  not  a  great  many  years  ago.  The  troubles  now  commonly 
experienced  are  those  inherent  in  every  man-made  machine  which  is 
subject  to  the  wear  and  tear  of  everyday  use. 

It  is  obviously  impossible,  in  many  cases,  to  give  a  direct  statement  of 
a  cure  for  all  of  the  various  symptoms  which  are  likely  at  some  time  or 
other  to  confront  the  motorist,  as  some  symptoms  may  be  due  to  one  or 
more  of  several  different  causes.  All  that  can  be  done  is  to  offer  a  few 
general  suggestions  which  will  assist  him  to  diagnose  his  own  specific 
troubles  and  apply  the  proper  remedy. 

The  automobile  is  a  fine  piece  of  machinery  and  the  service  from  it 
will  depend  upon  the  care  and  attention  given  to  it.  Many  of  the 
troubles  on  the  modern  automobile  are  due  to  uncalled  for  adjustments 
and  investigations  by  the  motorist.  Although  good  care  and  attention 
must  be  given  in  order  to  get  efficient  service,  it  is  good  policy  to  leave 
well  enough  alone  and  not  do  any  unnecessary  tampering,  nor  try  to 
improve  upon  the  operation  or  construction  as  planned  by  the 

The  more  common  motor-car  troubles  may  be  divided  into  the  follow- 
ing general  headings: 

i  .  ii  in 

Power  plant  troubles  Transmission  troubles  Chassis  troubles 

*  (a)  Mechanical  parts  of  engine       (a)  Clutch  (a)  Wheel  hubs 

(6)  Carburetting  and  gasoline  (6)  Change  gears  (6)  Steering  gear 

(c)  Ignition  (c)  Differential  (c)  Brakes 

(d)  Lubricating  and  cooling  (d)  Rear  axle  (d)  Springs 

(e)  Starting  and  lighting  (e)  Tires 

331.  Power  Plant  Troubles. — Any  derangement  in  the  power  plant 
will  show  itself  by  one  of  the  following  symptoms.     Under  each  symptom 


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is  given  the  common  causes  with  a  reference  to  the  discussion  on  the 

1.  Engine  Jails  to  start 

(a)  Poor  compression.    See  Art.  332a. 

(6)  Engine  cylinder  flooded.     See  Art.  333e. 

(c)  Carburetor  adjustment  not  right.     See  Art.  333. 

(d)  Water  in  gasoline.     See  Art.  333?. 

(e)  Dirt  in  gasoline.     See  Art.  333k 
(/)  Carburetor  frozen.    See  Art.  333?. 

(g)  Carburetor  throttle  lever  disconnected. 
(h)  Out  of  gasoline, 
(t)  Engine  too  cold.     See  Art,  333/. 
(j)  Ignition  switch  off. 
(k)  Foul  or  broken  plugs.     See  Art.  3346. 
(I)  Weak  batteries  or  magneto.     See  Art.  334&,  I,  and  m. 
(m)  Loose  or  corroded  battery  terminal.     See  Art.  334J. 
(n)  Vibrators  not  properly  adjusted.     See  Art.  334#. 
(o)  Wiring  system  out  of  order.     See  Art.  334c. 
(p)  Ignition  not  timed  properly.     See  Art.  334,;. 
(q)  Cylinders  not  wired  in  proper  order  of  firing, 
(r)  Defective  condenser.     See  Art.  334e. 
(s)  Resistance  unit  burned  out.     See  Art.  334/. 

2.  Engine  misses  at  low  speeds 

(a)  Poor  compression.     See  Art.  332  a. 

(6)  Mixture  too  lean  or  too  rich.     See  Art.  333a  and  6. 

(c)  Carburetor  not  suitable  for  the  kind  of  fuel  used. 

(d)  Spark  plug  gap  too  wide.     See  Art.  3346. 

(c)  Spark  plug  cable  not  connected  or  short-circuited.     See  Art.  334c 

CO  Dirty  interrupter.     See  Art.  334d  and  m. 

(g)  Dirty  or  defective  spark  plug.     See  Art.  3346. 

(h)  Vibrator  not  properly  adjusted.    See  Art.  334#. 

(t)  Weak  magneto  magnets.     See  Art.  334m. 

3.  Engine  misses  at  high  speeds 

(a)  Carburetor  not  set  for  this  speed.     See  Art.  333. 
(6)  Bad  spark  plug.     See  Art.  3346. 

(c)  Spark  plug  gap  too  wide.     See  Art.  3346. 

(d)  Weak  valve  spring.     See  Art.  332c. 

(c)  Timer  or  breaker  contact  imperfect.     See  Art.  334t. 

(/)  Interrupter  contacts  adjusted  to  open  too  far.    See  Art.  334d  and  m. 

(g)  Vibrator  points  dirty  or  burned.    See  Art.  334j?. 

(h)  Defective  condenser.     See  Art.  334c. 

(t)  Ignition  timed  too  late.    See  Art.  Z34j. 

(j)  Weak  interrupter  spring. 

4.  Engine  misses  at  all  speeds 

(a)  Carburetor  not  properly  adjusted.     See  Art.  333. 
(6)  Carburetor  not  suitable  for  kind  of  fuel  used. 

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(c)  Dirty  or  broken  plug.    See  Art.  3346. 

(d)  Spark  plug  gap  not  right.    See  Art.  3346. 
(«)  Poor  compression.     See  Art.  332a. 

if)  Bent  or  worn  valve  stem.    See  Art.  332c  and  d. 
(g)  Leak  in  intake  manifold. 

(h)  Valve  tappets  adjusted  too  close.    See  Art.  332c. 
(i)  Broken  piston  rings  or  scored  cylinder.    See  Art.  332c. 
(j)  Valves  not  timed  properly.    See  Art.  332d. 
(k)  Loose  or  broken  terminals.    See  Art.  334c. 
(0  Weak  batteries  or  magneto.    See  Art.  334/:,  /,  and  m. 
(m)  Defective  wiring.     See  Art.  334c. 
(n)  Coil  not  properly  adjusted.     See  Art.  334p. 

(o)  Interrupter  not  adjusted  to  proper  opening.     See  Art.  334d  and  m. 
(p)  Defective  condenser.     See  Art.  334c. 
(q)  Weak  interrupter  spring, 
(r)  Wrong  type  of  ignition  coil  used. 
(«)  Ignition  improperly  timed.     See  Art.  33^;. 
(t)  Cracked  distributor  head.    See  Art.  334c. 
(u)  Safety  gap  too  small. 
(v)  Gasoline  feed  stopped  up.    See  Art.  333A. 
(w)  Needle  valve  bent  or  stuck, 
(x)  Water  in  gasoline, 
(y)  Poor  water  circulation.     See  Art.  3376. 
(z)  Excessive  lubrication.     See  Art.  337a. 

5.  Engine  overheat* 

(a)  Lack  of  proper  water  circulation.     See  Art.  3376. 
(6)  Lack  of  proper  lubrication.     See  Art.  337a. 

(c)  Slipping  fan  belt  or  bent  fan  blades.     See  Art.  3376. 

(d)  Too  rich  a  mixture.     See  Art.  333a. 
(c)  A  weak  mixture.     See  Art.  3336. 

(J)  Running  with  spark  retarded.     See  Art.  334;. 
(?)  Ignition  timed  too  late.     See  Art.  334.;. 
{h)  Carbon  deposit  in  cylinders.     See  Art.  332/. 
(t)  Broken  water  pump.     See  Art.  3376. 
(/)  Water  too  low  in  radiator.     See  Art.  3376. 
(k)  Radiator  too  small. 
(0  Frozen  radiator.     See  Art.  3376. 
(m)  Brakes  dragging.     See  Art.  339c. 
(n)  Choked  muffler. 

0.  Engine  stops 

(a)  Gasoline  tank  empty. 

(6)  Water  in  gasoline.     See  Art.  333?. 

(c)  Sediment  in  gasoline.     See  Art.  333/i. 

(d)  Carburetor  flooded.     See  Art.  333d. 

(e)  Lack  of  pressure  on  gasoline  tank.     See  Art.  333i. 
(/)  Carburetor  throttle  control  rod  disconnected. 

(g)  Overheating  due  to  poor  circulation  or  lack  of  lubrication.     See  Art.  337. 

(h)  Excessive  lubrication.     See  Art.  337a. 

(t)  Short-circuiting  of  wires  or  terminals.     See  Art.  334c. 

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(j)  Disconnected  or  broken  wires.    See  Art.  334c  and  h. 
(k)  Defective  condenser.     See  Art.  334e. 
(0  Wet  batteries  or  magneto.     See  Art.  334A;. 

7.  Engine  knocks 

(a)  Carbon  deposits  in  cylinder  and  on  piston  heads.     See  Art.  332/. 
(6)  Spark  too  far  advanced.     See  Art.  334j. 

(c)  Running  motor  slow  when  pulling  heavy  load  on  direct  drive. 

(d)  Faulty,  lubrication.     See  Art.  337a. 

(e)  Engine  overheated.     See  Art.  331-5. 

if)  Loose  connecting-rod  bearings.     Sec  Art.  332y. 
(g)  Loose  piston.    See  Art.  332e. 
(h)  Loose  flywheel. 

(t)  Loose  crankshaft  bearings.     See  Art  332y. 
(j)  Valves  not  timed  properly.    See  Art.  332d. 
(k)  Compression  too  high.     See  Art.  332a. 
(I)  Operating  on  wrong  kind  of  fuel  for  carburetor, 
(m)  Improper  spark-plug  installation.     See  Art.  146. 

8.  Engine  trill  not  stop 

(a)  Short-circuit  in  switoh. 

(6)  Magneto  ground  may  be  disconnected. 

(c)  Overheating  and  carbon  deposits.     See  Art.  332/. 

9.  Lack  of  power 

(a)  Poor  compression.     See  Art.  332a. 

(6)  Too  weak  or  too  rich  a  mixture.     See  Art.  333a  and  b. 

(c)  Operating  in  high  altitudes. 

(d)  Weak  spark.    See  Art.  334c. 

(e)  Ignition  timed  too  late.     See  Art.  334?. 

(/)  Running  with  spark  retarded.     See  Art.  334j. 
(g)  Valves  not  timed  properly.     See  Art.  332d. 
(h)  Valve  tappets  not  adjusted  properly.    See  Art.  332c. 
(i)  Valves  not  seating  properly.     See  Art.  3326. 
(J)  Lack  of  lubrication.     See  Art.  337a. 
(k)  Lack  of  cooling  water.     See  Art.  3376. 
(/)  Lack  of  gasoline. 
(m)  Dragging  brakes.     See  Art.  339c. 
(n)  Slipping  clutch.     See  Art.  338a. 
(o)  Plat  tires, 
(p)  Choked  muffler  causing  back  pressures. 

10.  Back-firing  through  carburetor 

(a)  Improper  needle  valve  adjustment.     See  Art.  3336. 
(6)  Dirt  in  gasoline  passage  or  nozzle.     See  Art.  333A. 

(c)  Inlet  valve  not  closing  properly.     See  Art.  332d 

(d)  Excessive  temperature  of  the  hot-water  jacket  of  the  carburetor,  especially 
in  hot  weather.  This  can  be  remedied  by  shutting  off  the  water  from  the 
carburetor  jacket  and  cutting  off  the  hot  air  supply. 

(c)  Spark  retarded  too  far.     See  Art/  334j. 

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11.  Firing  in  muffler 

(a)  Weak    mixture,    slow    burning   exhaust,  igniting  unburned  charge  from 
previous  miss.    See  Art.  3336. 

(b)  Exhaust  valves  not  closing  properly.     See  Art.  332d. 

(c)  Valves  out  of  time.     See  Art.  333d. 

(d)  Too  rich  a  gasoline  mixture.     See  Art.  333a. 

(e)  Occasional  misfiring  of  a  cylinder.     See  Art.  334a. 

12.  Starter  will  not  operate 

See  starting  troubles,  Art.  335. 

332.  Mechanical    Troubles    in    Engine,     (a)  Poor    Compression. — 
*  Poor  compression  is  one  of  the  common  causes  for  lack  of  power.     Unless 


Insulation   worn  off, 
cable  not  attached 


Broken,  fouled,  hose, 
gap  too  wide  ***n^ 


^  Loose 

Pitted  with  sediment 

I  Loose 

Pitted,  scored.      *"- 
covered  with  carbon 


Not  tight 


Bent,  stuck 

Too  weak  broken, 
out  ofpfoce 

To  much  or  too  little         I        M  VALVE 

Disconnected  from 
throttle  valve  rod 

Soaked  or  logged 

Stem  bent  seat 

leaks,  va/ve  stuck  v      l  AUXILIARY 
on  seat  lA/R  VALVE  . 

VALVE  /        - 

Bent  or  stutk  ■ 

CAM''  J 

Contour  worn      / 

Gears  not  meshed 

Loose,  broken, 

Worn,  too  loose, 
out  of  round 


Worn,  loose 


Scored,   worn 





Contact  potnts  not 
property  adjusted 

Worn,  out  of 

Loose,  worn 


Bearings  worn 

Fig.  524. — Chart  showing  location  of  common  mechanical  troubles  of  engines. 

the  compression  pressure  is  high  enough,  the  explosion  will  be  lacking 
in  force  and  the  engine  will  be  weak.  The  engine  can  be  turned  by  hand, 
with  the  ignition  off,  throttle  open,  and  the  compression  noted  in  each 
cylinder,  or  a  more  accurate  way  is  to  remove  the  spark  plug  and  screw  in 
a  small  pressure  gauge,  which  should  show  from  60  to  80  lb.  at  the  end  of 
the  compression  stroke,  depending  on  the  make  of  engine.    Loss  of  corn- 

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pression  is  commonly  due  to  leaky  or  improperly  seated  valves,  or  to  leaky 
joints.  Leaky  thread  joints,  valve  caps,  or  cracks  in  cylinder  are  com- 
mon causes  for  loss  of  compression.  These  can  be  detected  by  a  hissing 
sound  or,  if  the  suspected  leak  is  covered  with  gasoline  or  oil,  the  leak 
will  show  itself  by  a  bubbling  through  the  oil.  If  the  trouble  cannot 
be  located  in  this  manner,  attention  should  be  given  to  the  valves. 

As  a  rule,  the  intake  valve  requires  less  attention  than  the  exhaust 
valve,  because  the  former  comes  into  contact  "with  the  cool,  fresh  fuel 
charges,  whereas  the  latter  is  apt  to  become  fouled  and  burnt  by  the  hot 
and  dirty  exhaust  gases.  A  frequent  cause  of  leaky  valves  is  carbon 
deposit  on  the  valve  seats.  These  deposits  prevent  the  proper  seating 
of  the  valves.     The  remedy  is  to  clean  and  grind  them. 

(6)  Grinding  Valves. — There  are  several  good  grinding  compounds 
on  the  market.     It  is  advisable  to  use  a  coarse  grade  in  the  first  operation 

and  then  to  finish  off  with  a  finer  one 
to  give  a  polished  surface.  A  very 
good  homemade  mixture  is  obtained  by 
making  a  thin  paste  of  a  couple  of 
?** ,,  tablespoouf  uls  of  kerosene,  a  few  drops 
|  of  oil,  and  enough  fine  emery  flour  to 
thicken  to  the  consistency  of  paste. 

The  valve  spring  must  be  removed 
so  that  the  valve  may  be  lifted  and 
turned.  A  moderate  coating  of  the 
paste  is  applied  to  the  bevel  face  of  the 
valve.  The  valve  is  next  rotated  back 
and  forth  until  the  entire  bearing  sur- 
face is  polished  bright  and  smooth  the 
full  width  of  the  face.  The  valve  should  never  be  turned  the  whole 
way  round  but  rotated  back  and  forth  not  over  a  quarter  turn  under 
light  pressure.  It  should  be  lifted  frequently  and  turned  halfway  round 
before  being  replaced  on  the  seat  again.  This  method  distributes  the 
friction  evenly  and  eliminates  the  possibility  of  the  emery  scoring  the 
valve  seat.  If  no  valve  grinding  tool  is  available,  the  use  of  a  car- 
penter's brace  or  bitstock  is  recommended,  as  a  much  smoother  move- 
ment is  thus  obtained  than  by  using  a  screwdriver.  The  use  of  this 
method,  recommended  by  the  Overland  Company,  is  shown  in  Fig.  525. 
After  grinding  to  a  good  clean  seat  entirely  free  from  spots  or  pits, 
wash  the  valve,  valve  seat,  and  guide  thoroughly  in  gasoline.  If  the 
stem  is  rough  or  gummy,  smooth  it  up  with  emery  cloth,  but  clean  it 
afterward  before  replacing  it  in  the  guide.  To  test  the  effectiveness  of 
your  work,  mark  the  valve  seat  in  several  places  with  a  lead  pencil 

Fig.  525. — Valve  grinding. 

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and  turn  the  valve  around  a  few  times.  If  the  marks  are  entirely  rubbed 
off,  the  work  may  be  considered  well  done. 

(c)  Valve  Adjustment. — Poor  adjustments  of  the  valve  operating  mech- 
anism may  cause  poor  compression,  even  if  the  valve  seats  have  been 
properly  ground  in.  The  valve  spring  may  be  broken  or  too  weak  to  close 
the  valve  on  its  seat  in  the  proper  time.  Sticking  of  the  valves  when  open 
may  also  be  the  cause  of  low  compression. 

The  clearance  between  the  valve  stem  and  push  rod  may  be  the  cause 
of  considerable  trouble.     This  clearance  is  usually  about  the  thickness  of 

Voire  Spring  - 

Spring  Dm 

Adjusting  Sere- 

Gun  Shaft 

Fig.  526. — Adjustment  of  push  rod  clearance. 

a  thin  visiting  card,  the  exact  amount  being  somewhat  different  for  dif- 
ferent cars,  but  never  over  3^2  *n- 

If  this  clearance  for  the  intake  valve  is  too  great,  the  lift  is  reduced, 
thus  preventing  the  proper  charge  from  getting  into  the  cylinder.  If 
the  exhaust  valve  lift  is  reduced  in  the  same  way,  it  will  be  more  difficult 
for  the  exhaust  gases  to  escape.     Too  much  clearance  also  changes  the 


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time  of  valve  opening  and  closing,  causing  the  valves  to  open  late  and 
close  early.  If,  on  the  other  hand,  this  clearance  is  too  small  or  entirely- 
absent,  the  valve  will  open  early  and  close  late,  or  will  not  close  on  its 
seat  at  all. 

As  the  valve  seats  are  lowered  by  continual  grinding,  the  clearance 
is  gradually  changed.  For  the  proper  operation  of  the  valves,  careful 
attention  should  be  given  to  this  clearance  space.  Figure  526  illustrates 
the  clearance  adjustment  on  the  Overland  car. 

A  weak  spring  on  the  exhaust  valve  may  have  a  marked  effect  on  the 
operation  of  the  engine.  The  exhaust  valve  will  then  open  on  the  suc- 
tion stroke  and  burnt  gases  will  again  be  drawn  into  the  cylinder. 

(d)  Valve  Timing. — It  is  essential  that  the  valves  be  properly  timed 
or  set,  in  order  to  have  the  engine  operate  properly.     The  valves  are 

set  at  the  factory  and  the  necessity  for 
adjusting  the  timing  comes  as  the  re- 
sult of  wear  on  the  valve  seats,  stems, 
rods,  cams,  half-time  gears,  or  by  im- 
proper replacement  of  any  of  these 
parts.  If  the  camshaft  has  been  re- 
moved, care  must  be  taken  to  mesh 
the  gears  properly  when  replacing  it. 
The  gears  are  marked  so  that  replace- 
ment is  not  difficult-  The  proper 
method  of  replacing  the  gears  on  the 
Ford  engine  is  shown  in  Fig.  527.  It 
will  be  noticed  that  there  is  a  prick 
punch  mark  on  one  tooth  of  the  pinion 
and  a  corresponding  mark  on  the  large 
gear.  Before  taking  a  camshaft  out, 
Fig.  527. — Ford  camshaft  setting,  an  examination  should  be  made  and  if 
showing  marked   tooth  and  space  on  the  gears  are  not  so  marked  it  should 

be  done  before  they  are  disturbed. 
If  the  clearances  are  properly  adjusted  for  the  push  rods  and  valve 
stems  and  if  the  timing  gears  are  properly  meshed,  the  valves  should  be 
correctly  timed,  making  allowance  for  wear  on  the  cam  faces.  On  most 
engines  the  positions  at  which  the  valves  start  to  open  and  close  are 
marked  on  the  circumference  of  the  flywheel.  These  points  should  be 
opposite  the  pointer,  usually  at  the  top  of  the  case,  when  the  valves 
start  to  open. and  close.  This  time  can  be  determined  by  the  use  of  a 
thin  sheet  of  tissue  paper.  By  placing  a  piece  of  the  paper  in  the  clear- 
ance space  between  the  push  rod  and  valve  stem,  one  can  tell  when  the 
valve  opens  or  closes. 

Valve  setting  is  an  adjustment  that  should  be  made  by  an  experienced 

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mechanic  or  one  thoroughly  familiar  with  the  principles  of  the  four- 
stroke  engine.  The  different  makers  have  found  by  trial  the  settings 
that  will  give  the  best  result  with  their  engines  and  cars.  These  settings 
differ  somewhat  according  to  different  conditions.  If  they  are  not 
marked  on  the  flywheel,  they  should  be  obtained  from  the  manufacturer. 

Figure  528  shows  the  approximate  crank  and  piston  positions  for  the 
valve  events.  The  inlet  may  open  anywhere  from  top  center  to  20° 
of  flywheel  motion  after  center.  The  inlet  closes  from  25°  to  50°  past 
lower  center.  The  exhaust  opens  35°  to  60°  before  lower  center  and 
closes  from  top  center  to  15°  past  center. 

(e)  Loose  Piston  or  Scored  Cylinder  Walls. — A  loose  piston  or  scored 
cylinder  walls  will  cause  a  marked  loss  of  compression.  If  the  piston  is 
not  too  loose,    slightly  larger  rings  may  be  put  on.     Sometimes  the 

Inlet  closes.  Exhaust  opens. 

Fig.  528. — Valve  setting  diagram. 

Exhaust  closes. 

blowing  can  be  remedied  by  using  a  heavier  cylinder  oil.  This  will,  to 
some  extent,  remedy  the  trouble  caused  by  scored  cylinder  walls, 
although  if  too  badly  cut,  they  must  be  rebored  and  new  pistons  and  rings 
fitted  in.     Again,  this  is  the  work  of  an  experienced  mechanic. 

(/)  Carbon  Deposits  in  Cylinder. — After  the  engine  has  been  run  for 
some  time,  carbon  deposits  are  liable  to  collect  in  the  cylinder  and  on  the 
pistons,  especially  if  too  much  lubricating  oil  or  gasoline  has  been  used. 
The  carbon  deposit  resulting  from  too  much  lubricating  oil  is  a  sticky 
substance,  while  that  from  too  much  gasoline  is  hard,  dry,  and  brittle. 
These  deposits,  if  allowed  to  collect,  become  hot  from  the  heat  of 
explosion,  and  may  cause  preignition  of  the  fresh  charge  of  gas. 

The  best  methods  of  removing  carbon  deposit  are  to  scrape  it  out 
or  to  burn  it  out  by  means  of  an  oxygen  flame.  The  latter  method  is 
quicker  and  by  far  the  more  convenient.  For  an  engine  with  a  non- 
detachable  cylinder  head  the  following  method  is  recommended  by  the 
Overland  Company  for  the  removal  of  carbon  by  scraping: 

To  scrape  the  cylinders,  remove  both  inlet  and  exhaust  valve  caps, 

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Fig.  529,  and  turn  the  motor  over  until  the  pistons  of  two  cylinders  are 
at  their  top  centers.  The  scraping  off  of  the  deposit  is  done  by  means  of 
tools  of  different  shapes,  the  tools  being  bent  so  as  to  reach  the  piston 
head  and  the  sides  and  tops  of  the  cylinders.  Scrape  all  loose  carbon 
over  to  the  exhaust  valve  and  when  through,  turn  the  motor  until  the 
exhaust  valve  lifts  when  the  carbon  may  be  scraped  past  the  valve  and 
into  the  exhaust  passage,  whence  it  will  be  blown  out.  To  do  a  good 
job,  brush  the  surface  clean  and  make  sure  that  no  carbon  becomes 
lodged  between  the  exhaust  valve  and  its  seat.  Finally  wash  with 

In  replacing  the  cylinder  plugs  over  the  valves,  put  graphite  grease 
around  the  threads;  this  will  make  a  compression-tight  joint  and  also 

make  it  easier  to  remove  the  plugs  the 
next  time.  Likewise,  be  sure  to  replace 
the  copper  gaskets  under  the  plugs. 

It  is  an  excellent  plan  to  remove  the 
carbon  and  to  grind  in  the  valves  at  the 
same  time. 

Kerosene  may  also  be  used  for  the  re- 
moval of  carbon  from  the  cylinders.     Two 
or  three  tablespoonf uls  should  be  poured 
through    the    priming    cocks    while    the 
engine    is    warm.     The    kerosene   has  a 
strong    solvent    action   on   any   gummy 
binding    material    in    the   carbon.     The 
kerosene   can  be  spread  over  the  entire 
cylinder  by  cranking  the  engine  a  few 
times  around.    Some  motorists  inject  the 
kerosene  through  the  air  valve  of  the  car- 
buretor just  before  the  engine  is  stopped, 
preparatory  to  putting  the  car  away.     Kerosene  will  not  remove  a  hard 
carbon  deposit  but  it  will  prevent  it  from  forming  if  used  regularly, 
about  once  a  week. 

Running  the  engine  on  alcohol  for  a  few  minutes  is  another  device 
that  is  sometimes  used  for  burning  out  carbon  deposits. 

(g)  Bearing  Troubles. — The  common  bearing  troubles  are  those  caused 
by  the  bearings  becoming  worn  and  loose,  with  a  consequent  knocking. 
Faulty  lubrication,  clogged  oil  pipes  and  oil  holes,  and  dirty  oil  are  the 
main  causes  of  warm  or  hot  bearings.  The  bearings  which  are  most 
liable  to  give  trouble  are  the  wrist  pin  bearings,  the  connecting-rod  bear- 
ings, and  che  main  crank  bearings.  After  a  bearing  has  been  excessively 
hot,  it  should  be  refitted  by  a  mechanic.  A  loose  bearing  can  be  tightened 
on  the  pin  by  removing  the  liners  or  shims,  or  by  refitting  it. 

Fig.  529. — Scraping  the  cylinders. 

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333.  Carburetion  Troubles. — Improper  mixture  is  the  common  source 
of  carburetor  troubles.  An  improper  mixture  is  either  too  rich,  that  is, 
too  much  gasoline  in  proportion  to  the  air,  or  too  weak,  that  is,  too  much 
air  in  proportion  to  the  gasoline. 

(a)  Mixture  too  Rich. — A  rich  mixture  can  be  detected  by  black 
smoke  coming  from  the  muffler,  and  by  overheating  and  missing  of  the 
engine.  Not  only  is  fuel  wasted,  but  the  cylinders  become  fouled  and 
carbonized.  A  mixture  which  is  too  rich  at  slow  speeds  can  be  corrected 
by  cutting  down  on  the  gasoline,  and  at  high  speeds  by  increasing  the 
auxiliary  air.  An  auxiliary  air  spring  which  sticks,  a  restricted  air  opening, 
or  a  flooded  carburetor  will  cause  an  over-rich  mixture. 

(b)  Mixture  too  Weak. — A  weak  mixture  can  be  detected  by  back- 
firing through  the  carburetor  and  by  occasional  muffler  explosions.  A 
weak  mixture,  being  a  slow-burning  mixture,  is  still  burning  when  the 
intake  valve  opens  for  the  following  charge.  This  permits  the  flame  to 
shoot  back  through  the  manifold  ihto  the  carburetor.  A  weak  mixture 
gjiould  not  be  confused  with  an  improperly  timed  intake  valve  which 
opens  before  the  burning  charge  has  been  exhausted.  If  the  intake 
valve  has  a  weak  spring,  which  does  not  close  the  valve  properly,  it  may 
permit  back-firing  through  the  carburetor.  The  back-firing  caused 
through  valve  trouble  is  usually  more  violent  than  back-firing  due  to  a 
weak  mixture.  A  weak  mixture  at  low  speeds  is  caused  generally  by 
too  little  gasoline  and  at  high  speeds  by  too  much  auxiliary  air.  The 
carburetor  should  be  adjusted  accordingly. 

Air  leaks  in  the  manifold  connections  will  dilute  the  mixture  with 
air  and  cause  a  weak  mixture  and  back-firing.  These  leaks  should  be 
closed  before  the  carburetor  adjustments  are  made. 

A  stuck  or  bent  or  obstructed  gasoline  needle  valve  may  cause  a  weak 
mixture  by  shutting  off  the  supply  of  gasoline.     The  remedy  is  obvious. 

(c)  Color  of  Explosive  Flame. — By  opening  the  priming  cocks  on  the 
cylinders,  the  color  of  explosive  flame  can  be  seen  as  it  issues  from  the 
cocks.  A  blue  flame  indicates  a  perfect  mixture,  a  red  flame  indicates 
an  excess  of  gasoline,  and  a  white  flame  indicates  an  excess  of  air. 

(d)  Flooded  Carburetor. — If  the  carburetor  float  becomes  gasoline 
soaked  or  filled  with  gasoline,  it  will  not  shut  off  the  gasoline  float  valve 
and  the  carburetor  float  chamber  will  become  filled  with  gasoline.  The 
remedy  is  to  take  the  float  out  and  if  it  is  made  of  cork,  have  it  dried  out, 
painted  with  shellac,  and  baked.  If  of  the  hollow  metal  type  it  should 
be  emptied  and  the  hole  soldered.  A  small  particle  of  dirt  under  the 
float  valve  will  also  cause  the  carburetor  to  become  flooded. 

(e)  Flooded  Cylinder. — If  the  engine  has  been  cranked  for  some  little 
time  and  too  much  gasoline  has  been  sucked  into  the  cylinders,  the  cylin- 
ders become  flooded  with  almost  pure  gasoline  which  condenses  in  the 

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cold  cylinders.  This  charge  will  not  explode.  The  remedy  is  to  open 
the  priming  cocks  and  crank  the  engine  until  the  over-rich  mixture  has 
been  expelled  or  diluted.  After  the  priming  cocks  are  closed,  the  engine 
can  usually  be  started.  Flooding  of  the  engine  may  also  be  caused  by 
priming  the  cylinders  with  too  much  gasoline.  It  sometimes  happens 
that  a  flooded  engine  can  be  started  without  difficulty  after  standing  for 
several  hours,  the  excess  gasoline  having  evaporated  in  the  meantime. 

(/)  Cold  Weather  Starting. — In  cold  weather,  when  the  engine  is 
stiff  and  the  gasoline  is  hard  to  evaporate,  it  is  desirable  to  inject  a  little 
warm  or  high  test  gasoline  into  each  cylinder  through  the  priming  cocks. 
The  carburetor  may  also  be  heated  by  the  application  of  warm  cloths. 
The  priming  gasoline  can  be  heated  to  advantage  by  placing  a  bottle  of 
it  in  a  pan  of  Jiot  water. 

(g)  Frozen  Carburetor. — If  there  is  water  in  the  gasoline  this  water 
may  be  frozen  in  the  carburetor.  The  water,  being  heavier  than  the 
gasoline,  sinks  to  the  bottom  where  it  may  freeze  in  cold  weather.  To 
remedy  this  trouble  apply  hot  cloths  to  the  parts  affected.  Never  use  a 
torch  or  flame  of  any  sort  around  the  carburetor. 

(h)  Feed  System  Stopped  Up. — If,  after  priming,  the  engine  starts 
and  suddenly  dies  down,  the  gasoline  supply  may  be  exhausted,  the  feed 
pipe  may  be  clogged,  or  a  piece  of  dirt  may  have  worked  into  the  needle 
valve.-  If  there  is  a  supply  of  gasoline  and  the  trouble  is  found  to  be  due 
to  dirt  in  the  feed  system,  the  feed  pipe  may  be  disconnected  and  the  dirt 
blown  out.  A  particle  of  dirt  in  the  needle  valve  may  be  removed  by 
screwing  the  valve  shut  and  then  opening  it  the  proper  amount.  This 
trouble  and  also  the  one  due  to  water  in  the  gasoline  can  be  prevented  by 
straining  the  gasoline  through  a  chamois  skin  before  putting  it  into  the 
main  tank. 

(i)  Loss  of  Pressure  on  Gasoline  Tank. — It  sometimes  happens  that 
if  a  pressure  gasoline  system  is  used,  the  pressure  becomes  too  low  to 
force  the  gasoline  from  the  main  tank  to  the  auxiliary  tank.  This  causes 
a  lack  of  fuel  at  the  carburetor.  A  hand  pump  is  usually  furnished  for 
increasing  this  air  pressure  on  the  tank. 

If  the  car  is  equipped  with  a  gravity  feed  system,  the  gasoline  may 
fail  to  run  to  the  carburetor  when  ascending  a  steep  hill.  It  sometimes 
becomes  necessary  to  back  the  car  uphill,  in  which  case  the  gasoline  will 
run  to  the  carburetor  without  difficulty. 

(j)  Water  Logged  Carburetor. — It  sometimes  happens  that  the  car- 
buretor becomes  loaded  with  water,  due  to  the  fact  that  the  water  can 
neither  evaporate  nor  get  out.  This  water  prevents  the  gasoline  from 
getting  in.     The  water  should  be  drained  from  the  carburetor  drain  cock. 

334.  Ignition  Troubles. — Misfiring  or  " missing"  of  the  engine  may  be 
caused  from  faulty  ignition,  a  faulty  carburetor,  or  from  the  valves  operat- 

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ing  improperly.  Missing  which  occurs  with  some  regularity  may  usually 
be  attributed  to  faulty  ignition  or  valve  operation.  Very  irregular 
missing  is  usually  caused  by  faulty  carburetor,  but  may  result  from  dirty 
breaker  points  or  some  other  fault  in  the  ignition  system. 

(a)  Locating  a  Misfiring  Cylinder. — To  detect  and  correct  faulty  igni- 
tion, the  cylinder  at  fault  must  first  be  located.  This  may  easily  be 
done  with  the  engine  running  by  short-circuiting  the  spark  plug  or  bridg- 
ing between  the  engine  cylinder  and  spark-plug  terminal  with  either  a 
hammer  head  or  a  screwdriver  which  has  a  wooden  handle  as  shown  in 
Fig.  530.  If,  in  testing  the  various  spark  plugs,  one  is  found  which,  when 
short-circuited,  does  not  affect  the  operation  of  the  engine,  it  is  in  all 
probability  the  one  at  fault.  The 
trouble  may  be  either  in  the  ignition 
apparatus  or  in  the  spark  plug  itself. 

Another  convenient  method  of 
locating  a  misfiring  cylinder  on  engines 
having  vibrating  coil  ignition,  such 
as  the  Ford,  is  to  run  the  engine  first 
on  one  cylinder  then  another  by  hold- 
ing down  all  of  the  vibrators  except 
the  one  connected  to  the  cylinder 
under  test.  The  engine  should  run 
idle  on  any  one  of  the  cylinders  and 
should  show  approximately  the  same  *»■  ^-^ZVL^***  a  ^ 
power  from  each. 

(b)  Defective  Spark  Plugs. — The  most  common  fault  found  in  the 
spark  plug  is  carbonizing  or  sooting,  which  results  in  short-circuiting 
the  high-tension  current  so  that,  instead  of  jumping  between  the  points 
or  electrodes  of  the  plugs  in  the  combustion  chamber,  it  passes  through 
the  carbon  accumulation  directly  to  the  metallic  shell.  The  plug  should 
be  removed,  and  if  there  is  evidence  that  it  is  short-circuited  the  carbon 
accumulation  should  be  removed.  This  may  be  done  by  first  scraping 
off  the  carbon  and  then  washing  the  plug  with  gasoline  and  a  stiff  brush. 
Inspect  the  plug  carefully  to  determine  whether  or  not  the  porcelain  has 
become  cracked  or  damaged  in  any  way.  Next  determine  if  the  gap  or 
distance  between  the  electrodes  is  correct.  This  gap  should  be  between 
.025  to  .030  i}/±§  to  y$2  in)>  about  3  thicknesses  of  an  ordinary  U.  S. 
post  card.  If  this  gap  is  found  incorrect,  the  electrode  that  is  attached 
to  the  shell  may  be  bent  until  proper  adjustment  is  secured.  A  worn 
dime  is  a  good  gauge  to  use  for  setting  this  gap. 

The  porcelain  of  the  plug  may  be  cracked  in  such  a  manner  that  it 
will  not  show  upon  casual  inspection,  but  it  may  be  detected  as  follows: 
If  the  plug  is  screwed  into  the  cylinder  and  some  pressure  is  brought  to 

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bear  against  the  upper  part  of  the  plug  with  the  finger,  grating  or  grind- 
ing will  sometimes  be  heard  and  a  very  small  motion  will  be  felt.  The 
high-tension  current  will  often  bridge  the  gap  between  the  center  elec- 
trode and  the  shell  through  a  crack  in  the  porcelain,  instead  of  jumping 
across  the  space  intervening  between  the  electrodes  or  points  of  the  plug. 
The  spark  plug  may  be  tested  by  removing  it  from  the  cylinder  and  laying 
it  upon  the  cylinder  block.  The  engine  should  be  turned  over  by  hand 
and  observations  made  as  to  whether  a  spark  jumps  between  the  elec- 
trodes. The  plug  should,  of  course,  be  laid  on  the  cylinder  block  so 
that  no  part  of  the  plug,  save  the  shell,  will  touch  the  cylinder  block. 
This,  however,  is  not  a  positive  test,  as  the  spark  may  sometimes  jump 
the  gap  between  the  points  of  the  plug  and  yet  be  at  fault,  owing  to  the 
fact  that  under  compression  the  resistance  is  greatly  increased  between 
the  plug  electrodes.  The  spark  may  jump  this  gap  in  the  open  air  and 
yet  not  pass  under  the  conditions  of  operation  in  the  cylinder. 

A  positive  test  for  the  plug  is  to  replace  it  with  one  that  is  known  to 
be  perfect.  If  the  condition  of  operation  is  improved  the  original  plug 
is  unquestionably  at  fault. 

(c)  Defective  Wiring  and  Ignition  Apparatus. — If  the  plugs  are  found  in 
good  order,  and  yet  one  or  more  cylinders  continue  to  misfire,  the  trouble 
may  be  due  to  a  lack  of  secondary  current  in  the  wire  connected  to  the 
plug.  The  trouble  can  be  located  when  the  engine  is  running,  or  being 
cranked,  by  detaching  the  wire  from  the  plug  and  holding  the  end  about 
%  to  34  m-  irom  the  plug  binding  terminal  or  cylinder  head.  If  the 
secondary  current  is  being  distributed  properly  to  the  cylinder  in  question, 
a  spark  will  occur  at  the  gap.  If  there  is  no  spark  across  the  gap  and 
there  is  regular  sparking  at  the  other  plugs,  the  trouble  is  undoubtedly 
due  to  defective  high-tension  wiring,  cracked  distributor  head,  or  poor 
timer  contact. 

If  the  rubber  covering  or  insulation  on  the  spark-plug  .wires  is  chafed 
or  cut  through,  allowing  the  conductor  to  touch  or  nearly  touch  any 
metal  part  of  the  car,  the  current  will  be  short-circuited  and  will  not  jump 
the  gap  in  the  plugs.  It  is  not  necessary  that  this  insulation  be  worn 
down  to  the  metal  of  the  conductor.  If  a  sharp  snapping  is  heard  when 
the  engine  is  running  under  a  heavy  pull  it  is  evidence  of  a  short-circuit 
from  the  high-tension  conductor  to  the  frame.  The  fault  will  usually 
be  found  due  to  imperfect  insulation  of  the  spark-plug  wires,  or  a  wire 
loose  from  the  spark-plug  terminal.  The  only  satisfactory  remedy  for 
cracked  insulation  is  to  replace  the  wiring  with  new. 

Irregular  misfiring  of  all  cylinders  may  be  due  to  defective  primary 
wiring,  discharged  battery,  weak  magneto,  corroded  or  loose  battery 
connections,  improper  adjustment  of  vibrator  or  interrupter  contact 
points,  or  defective  condenser. 

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(d)  Battery  Ignition  Breaker. — A  common  cause  of  irregular  misfiring, 
when  ignition  is  from  a  battery  high-tension  distributor  unit,  is  improper 
make-and-break  of  the  primary  circuit  by  the  contact  points.  In  a 
majority  of  the  various  systems  employed,  the  contact  points  are  made 
of  tungsten  and  normally  held  closed  by  spring  tension,  the  spark  occur- 
ring the  instant  the  primary  circuit  is  broken  by  the  cam  lobe  bearing 
against  the  contact  arm.  The  contact  points  have  a  standard  opening 
of  .17  to  .020  in.,  about  the  thickness  of  two  U.  S.  postcards.  If  found 
dirty  or  uneven  and  pitted,  they  should  be  cleaned  by  passing  a  fine  flat 
file,  or  preferably  a  piece  of  No.  00  sandpaper,  between  them. 

(e)  Defective  Condenser. — A  defective  condenser  is  indicated  by  seri- 
ous sparking  and  rapid  burning  of  the  interrupter  or  vibrator  contact 
points,  also  by  the  inability  of  the  coil  to  produce  a  hot  secondary  spark 
when  the  primary  circuit  is  interrupted.  If  these  conditions  exist, 
the  condenser  is  probably  either  punctured  (insulation  between  tinfoil 
layers  destroyed)  or  open-circuited.  The  best  remedy  is  to  replace  the 
condenser,  or  unit  in  which  it  is  contained,  with  another  that  is  known  to 
be  good.  If  the  condenser  is  mounted  inside  the  coil,  the  entire  coil 
usually  must  be  replaced.  However,  when  the  condenser  is  mounted  in 
the  breaker  housing  it  can  usually  be  replaced  without  disturbing  the 
other  parts  of  the  system.  The  action  of  a  good  condenser  results  in 
intensifying  the  secondary  current  nearly  25  times  and  preventing  an 
arc  at  the  breaker  points  when  they  are  separated. 

(J)  The  Resistance  Unit. — In  many  battery  ignition  systems,  a  re- 
sistance unit  is  placed  in  the  primary  circuit  to  protect  the  coil  and  bat- 
tery in  case  the  ignition  switch  is  left  on,  and  to  aid  in  equalizing  the 
intensity  of  the  secondary  spark  at  high  and  low  engine  speeds.  In 
case  the  resistance  unit  should  burn  out,  or,  for  any  other  reason  become 
open-circuited,  the  primary  circuit  is  opened  and  no  current  can  be  ob- 
tained at  any  of  the  plugs.  This  resistance  unit  consists  of  a  small  coil 
of  iron  wire  and  is  usually  placed  either  on  the  coil  or  on  the  breaker 
housing.  In  case  this  resistance  unit  should  be  burned  out  or  accidentally 
broken,  the  terminals  may  be  temporarily  short-circuited  with  a  piece  of 
wire  to  relieve  an  emergency,  but  in  all  such  coxes  the  resistance  unit  must 
be  replaced  with  another  of  the  same  kind  as  soon  as  possible.  Continued 
operation  without  it  will  result  in  serious  burning  of  the  interrupter 
points  and  may  cause  injury  to  the  coil  and  condenser. 

(g)  Coil  Adjustments. — A  frequent  cause  of  no  current  at  the  plug 
is  due  to  coil  trouble,  especially  where  a  vibrating  coil  is  used  for  each 
cylinder.  When  the  vibrator  points  become  pitted,  out  of  line,  or  burned, 
good  contact  is  impossible.  The  tension  on  the  vibrator  spring  may  also 
become  changed,  permitting  the  coil  to  consume  too  much  or  too  little 

Digitized  by  LiOOQ IC 


In  the  case  of  burned  or  pitted  points,  they  should  be  either  filed  flat 
with  a  thin  smooth  file,  or  preferably  a  piece  of  No.  00  sandpaper  passed 
between  them.  In  either  case  the  points  should  be  shaped  so  as  to  meet 
each  other  squarely. 

If  it  becomes  necessary  to  adjust  the  tension  on  the  vibrators,  the 
tension  should  be  entirely  taken  off  and  gradually  increased  until  the 
engine  runs  satisfactorily  under  all  load  conditions  with  the  coil  consum- 
ing as  little  current  as  possible.  It  is  very  important  to  have  all  the 
units  adjusted  alike.  This  can  be  easily  done  after  a  little  experience. 
The  most  accurate  method  of  coil  adjustment  is  with  a  coil  current  indi- 
cator by  which  the  amount  of  current  consumed  is  measured.  Coils 
are  built  to  consume  about  %  to  1)4  amp.;  consequently,  the  tension 
should  be  adjusted  so  that  the  current  consumption  of  each  coil  is  not 
much  greater  than  this  amount. 

(A)  Breakdown  of  Coil  Wiring  or  Insulation. — If  no  current  is  ob- 
tained in  the  secondary  circuit  of  a  coil  when  the  vibrator  is  working  as  it 
should,  the  trouble  is  probably  due  to  either  a  broken  wire  or  punctured 
insulation  inside  of  the  coil.  It  sometimes  happens  that  the  binding 
post  wires  become  loose  from  the  post  just  inside  of  the  coil.  If  only  a 
slight  spark  can  be  obtained,  the  insulation  on  the  inside  wire  may  be 
broken  down,  thus  causing  a  short-circuit  of  the  current.  Obviously, 
there  is  no  remedy  but  to  replace  the  coil.  Moisture  in  the  coil  may  also 
cause  it  to  become  short-circuited.  In  this  event  the  coil  should  be 
thoroughly  dried  out  before  it  is  put  back  into  service. 

(i)  Timers. — Trouble  in  the  timer  is  usually  due  to  oil,  water,  or  dirt 
which  has  gotten  into  the  housing,  causing  either  a  short-circuit  or  poor 
contact.  This  foreign  matter  should  be  cleaned  out  of  the  timer  in  order 
to  permit  it  to  give  good  service.  After  a  time,  the  contact  segments  in 
the  timer  become  worn  and  irregular,  causing  misfiring  at  high  speed. 
In  this  event,  it  will  be  necessary  to  supply  a  new  timer. 

(j)  Improper  Spark  Timing. — If  the  engine  kicks  back  after  cranking, 
the  spark  is  too  far  advanced  and  should  be  retarded  so  that  it  will  not 
occur  until  the  piston  has  passed  the  dead  center.  The  tendency  of  an 
early  spark  on  starting  is  to  cause  the  engine  to  start  backward.  Too 
early  a  spark  at  low  speeds  will  make  the  engine  knock  and  will  cause  the 
car  to  jerk. 

A  retarded  spark  causes  the  engine  to  overheat  and  lose  considerable 
of  its  power.  There  is  no  advantage  in  retarding  the  spark  past  center, 
even  in  starting.  When  the  engine  is  running,  the  spark  should  be  ad- 
vanced in  proportion  to  the  speed.  With  the  spark  control  lever  fully 
retarded,  the  interrupter  points  should  be  timed  to  open  (thus  causing  the 
spark)  when  the  respective  pistons  are  on  upper  dead  center  at  the  end 
of  their  compression  strokes. 

Digitized  by 



On  cars  equipped  with  automatic  spark  advance,  the  troubles  due 
to  early  and  late  spark  are  seldom  experienced,  providing  the  original 
timing  of  the  spark  was  correctly  made.  Preignition  from  other  causes, 
however,  may  occur  with  either  type  of  spark  advance. 

(A:)  Dry  Batteries. — Weak  or  exhausted  batteries  are  a  common  source 
of  trouble.  If  the  batteries  are  suspected,  they  should  be  tested  with  a 
small  ammeter.  If  any  one  of  the  dry  cells  shows  less  than  6  amp.,  it 
should  be  taken  out  and  replaced  with  a  new  one.  One  weak  cell  will 
interfere  greatly  with  the  operation  of  the  others  in  the  set.  Occasionally, 
a  weak  dry  cell  can  be  livened  up  temporarily  by  boring  a  small  hole 
through  the  top  and  pouring  in  a  small  quantity  of  water,  or  better  still, 
vinegar.     The  effect,  however,  is  only  temporary. 

A  dry  battery  should  always  be  kept  perfectly  dry.  If  it  becomes 
wet  on  the  outside,  there  is  a  tendency  for  the  battery  to  be  short-cir- 
cuited and  exhaust  itself.  This  is  true  especially  if  water  is  spilled  on 
the  top  of  the  battery  between  the  terminals. 

(I)  Storage  Batteries. — If  the  storage  battery  appears  dead,  or  shows 
lack  of  energy,  it  may  be  due  to  one  of  the  following  causes:  (a)  dis- 
charged; (b)  electrolyte  in  the  jars  too  low;  (c)  specific  gravity  of 
electrolyte  too  low;  (d)  plates  sulphated;  (e)  corroded  terminals;  (/) 
battery  terminal  broken  loose  from  the  plates;  or  (g)  broken  down 
insulation.  These  troubles  are  fully  treated  in  the  chapter  on  Storage 

If  the  same  battery  is  used  for  starting  and  also  for  ignition  and  the 
battery  has  very  little  charge,  the  battery  may  not  be  strong  enough  to 
produce  a  spark  at  the  same  time  that  the  starting  motor  is  drawing 
current  to  turn  the  engine  over.  In  this  case  the  engine  will  generally 
start  if  cranked  by  hand. 

(m)  Magneto  Troubles. — If  the  ignition  trouble  has  been  located  in 
the  magneto  side  of  the  ignition  system  and  the  plugs  and  wiring  system 
have  been  found  in  good  working  order,  attention  should  be  turned  to  the 
magneto  itself.  The  distributor  plate  should  be  thoroughly  cleaned  with 
a  cloth  moistened  with  gasoline,  to  rerfiove  any  foreign  matter  such  as  oil 
and  carbon  dust  which  may  have  collected.  It  should  then  be  deter- 
mined whether  or  not  the  magneto  is  generating  current.  To  make  this 
test,  first  disconnect  the  magneto  grounding,  then,  with  either  the  spark- 
plug cables  disconnected  from  the  plugs  or  with  the  distributor  block 
removed,  rest,  a  screwdriver  on  the  magneto  frame,  holding  the  point  of  it 
from  \&  to  y±  in.  from  either  the  collector  ring  or  slipring  brush  terminal, 
and  watch  for  the  spark  to  jump  this  gap.  If  no  spark  appears  the 
trouble  is  in  the  magneto  itself. 

The  contact  points  may  be  pitted  or  burned  or  may  not  have  the 
proper  adjustment.     The  correct  opening  of  the  magneto  interrupter 

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points  is  from  .012  to  .020  (approx.  ^4)  in.  If  they  are  set  too  close, 
excessive  arcing  will  occur  and  the  points  will  burn,  and  cause  weak 
spark  at  high  speeds.  If  set  too  wide,  the  result  will  be  burning  of  the 
points  and  weak  or  no  spark  at  high  engine  speeds,  in  which  case 
the  primary  winding  does  not  have  time  to  "build  up,"  thus  decreasing 
the  strength  of  the  spark.  If  the  interrupter  points  are  found  dirty  or 
badly  pitted  and  uneven,  they  may  be  cleaned  by  passing  a  thin  flat  file 
or  a  piece  of  No.  00  sandpaper  between  them. 

The  contacts  should  not  be  filed  unless  absolutely  necessary. 

The  carbon  or  collector  brushes  may  be  dirty  or  worn.  They  should 
be'cleaned,  or  if  badly  worn,  replaced  with  new  brushes,  making  sure  that 
each  brush  has  the  proper  spring  tension. 

It  occasionally  happens  that  the  magnets  become  weak  or  demag- 
netized or  they  may  be  placed  on  the  magneto  in  the  wrong  position. 
If  weak  or  demagnetized,  they  should  be  remagnetized  before  being 
replaced.  Care  should  be  exercised  in  getting  the  like  poles  of  the 
magnets  on  the  same  side  of  the  magneto.  Most  magnets  are  marked 
with  an  N,  indicating  the  North  pole. 

(n)  Premature  Ignition. — Premature  ignition  or  preignition  is  caused 
by  particles  of  carbon,  sharp  corners,  etc.,  becoming  incandescent  from 
the  heat  of  explosion  and  igniting  the  charge  on  the  compression  stroke 
before  the  spark  occurs.  Preignition  occurs  generally  when  the  engine 
is  laboring  under  a  heavy  load  at  slow  speed  such  as  when  going  up  a 
steep  hill  on  high  gear.  Any  engine  will  have  premature  ignition  if  it 
becomes  excessively  hot  under  low  speed  and  heavy  load,  but  the  tend- 
ency to  preignite  is  much  more  marked  if  the  cylinder  is  full  of  carbon 
deposits.  These  carbon  deposits  should  be  cleaned  out  as  explained 
before.  Preignition  may  also  be  due  to  improper  spark-plug  installation 
such  as  using  a  plug  which  extends  too  far  into  the  cylinder  head  and 
which  is  not  properly  cooled. 

336.  Starting  Troubles. — If  the  starting  motor  fails  to  start  at  all 
when  the  starting  switch  or  pedal  is  pressed  down  as  far  as  it  will  go,  the 
trouble  may  be  tested  out  as  follows: 

(a)  With  a  low  reading  voltmeter  connected  across  the  battery  ter- 
minals, note  the  voltage  reading  while  the  starting  switch  is  closed  tem- 
porarily. If  the  voltmeter  indicates  less  than  4%  volts  (for  a  6-volt 
battery)  the  electrical  supply  is  defective.    This  in  turn  may  be  due  to: 

(a-1)  Battery  nm  down  or  battery  solution  low.  The  remedy  is  to 
fill  the  cells  with  distilled  water  to  the  proper  level,  and  recharge. 

(a-2)  Battery  defective.  This  is  possible  if  the  battery  has  been 
operated  for  considerable  periods  in  a  nearly  discharged  condition  or 
with  plates  exposed  above  the  solution.  The  only  remedy  is  to  repair 
the  battery. 

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(a-3)  Loose,  rusty,  or  corroded  connections  at  the  battery  terminals 
or  battery  ground  connections.  To  prevent  corrosion,  clean  the  terminals 
thoroughly  with  either  ammonia  or  soda  solution  and  cover  the  parts 
with  a  light  coating  of  vaseline  or  cup  grease. 

(o-4)  Heavy  short-circuit  in  the  starting  circuit.  This  may  be  due  to 
heavy  short  circuit  in  starting  motor  field  or  armature  winding,  or  acci- 
dental ground  at  the  brush  connectors  or  motor  or  starting  switch 

(6)  If  voltmeter  indicates  more  than  4%  volts  as  in  (a) : 

(6-1)  The  starting  switch  pedal  connections  and  adjustments  should 
be  examined  to  see  that  they  have  not  worked  loose  in  such  a  way  that 
the  switch  will  not  close.  This  can  be  readily  checked,  when  the  starting 
switch  is  pushed  down,  by  temporarily  bridging  across  the  switch  ter- 
minals with  a  pair  of  pliers  or  a  heavy  copper  wire.  If,  then,  the  motor 
does  not  start  or  attempt  to  start,  the  fault  is  not  in  the  switch. 

(6-2)  A  broken  wire  or  loose  connection  should  then  be  looked  for  in 
the  circuit  from  battery  to  starting  switch;  from  switch  to  starting  motor; 
from  motor  to  ground;  and  from  battery  to  ground. 

(6-3)  Next,  the  brushes  and  commutator  should  be  examined  to  see 
that  they  are  in  good  condition,  not  sticky  with  oil,  and  that  the  brushes 
are  making  contact  with  the  commutator  with  the  proper  spring  tension. 
If  the  commutator  is  black  and  pitted  it  should  be  cleaned  by  holding 
a  piece  of  No.  00  sandpaper  (do  not  use  emery  cloth)  next  to  the  com- 
mutator segments  when  the  armature  is  rotated  by  hand.  Any  dirt 
or  oil  found  on  the  commutator  or  brushes  should  be  cleaned  off  by  using 
a  lintless  cloth  moistened  with  gasoline. 

(c)  If,  in  the  flywheel  type  starter  with  Bendix  drive,  the  motor 
spins  but  does  not  crank  the  engine,  the  pinion  may  fit  too  tight  on  its 
shaft,  the  threads  may  be  clogged,  the  pinion  shift  spring  may  be  broken, 
or  there  may  be  some  teeth  broken  off  in  the  flywheel  gear.  In  the  case 
of  motor-generators,  the  trouble  may  be  in  a  broken  chain,  broken  driving 
gear,  or  a  slipping  over-running  clutch. 

If  the  motor  rotates  until  the  pinion  meshes  with  the  flywheel  and 
then  stops  rotating,  the  engine  or  some  of  its  auxiliary  parts  may  not 
be  moving  freely  due  to:  improper  lubrication,  binding  of  the  bearings 
and  pistons,  etc.,  or  the  battery  may  be  discharged  or  of  too  small  a 
capacity  for  the  engine. 

(d)  If  the  starting  motor  continues  to  run  after  the  starting  switch 
pedal  is  released,  the  starting  switch  spring  should  be  examined  to  see 
if  it  has  proper  tension  to  return  the  parts  positively  and  fully  to  the 
"open"  position. 

336.  Lighting  Troubles. — When  trouble  arises  in  the  lighting  system 
it  should  be  located  and  corrected  at  once  to  prevent  possible  damage  to 

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other  parts  of  the  electric  system.  The  reason  for  this  is,  not  that  a 
burned  out  Jamp  in  itself  will  be  injurious  to  the  system,  but  because  oft- 
times  the  real  trouble  causing  the  lamp  to  burn  out  is  in  the  battery  or 
generating  system,  which,  if  neglected,  may  prove  more  disastrous  than 
the  mere  burning  out  of  the  lamp.  This  is  especially  true  on  systems  in 
which  the  generator