Engineering Library
Geo. B. Selden in his "Benzhe Bu^gy.
The present day motor Jar.
(Frontispiece)
ENGINEERING EDUCATION SERIES
THE GASOLINE AUTOMOBILE
PREPARED IN THE
EXTENSION DIVISION OF THE UNIVERSITY OF WISCONSIN
BY
GEORGE W. IJOBBS, B. S.
FORMERLY INSTRUCTOR IN MECHANICAL ENGINEERING
IN THE UNIVERSITY EXTENSION DIVISION
THE UNIVERSITY OF WISCONSIN
AND
BEN G. ELLIOTT, M. E.
FORMERLY ASSOCIATE PROFESSOR OF MECHANICAL ENGINEERING THE UNIVERSITY OF NEBRASKA
SECOND EDITION
COMPLETELY REVISED AND REWRITTEN
SECOND IMPRESSION
BY
BEN G. ELLIOTT, M. E.
PROFESSOR OF MECHANICAL ENGINEERING THE UNIVERSITY OF WISCONSIN
AND
EARL L. CONSOLIVER, M. E.
ASSISTANT PROFESSOR OF MECHANICAL ENGINEERING THE UNIVERSITY OF WISCONSIN
McGRAW-HILL BOOK COMPANY, INC.
239 WEST 39TH STREET. NEW YORK
LONDON: HILL PUBLISHING CO., LTD. 6 & 8 BOUVERIE ST., B. C.
1919
Engineeri Library
neering
COPYRIGHT, 1915, 1919, BY THE McGRAw-HiLL BOOK COMPANY, INC.
FIRST EDITION FOURTEEN IMPRESSIONS
SECOND EDITION
FIRST IMPRESSION, AUGUST, 1919 SECOND IMPRESSION, SEPTEMBER, 1919
TOTAL ISSUE, 43,500
THE MAPLE PRESS TORK PA
PREFACE TO SECOND EDITION
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 OF WISCONSIN, ^MADISON, WISCONSIN, July, 1919.
vii
PREFACE TO FIRST EDITION
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 result."
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.
ix
CONTENTS
CHAPTER I
THE AUTOMOBILE ART. PAGE
1. The steam propelled car 1
2. The electric car ...... iff 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 r"T 9
9. General principles of automobile construction : . . . 12
10. Control systems 16
CHAPTER II THE AUTOMOBILE ENGINE
11. The gasoline engine . 17
12. Cycles 17
13. The four-stroke cycle 18
14. The two-stroke cycle T~ 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 i 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
xi
xii CONTENTS
CHAPTER III
AtTTO MOBILE POWER PLANTS ART. PAGE
34. Multi-cylinder engines . . 37
35. Modern automobile power plants 38
36. Power plant support f 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 . . . v-^ . 54
52. The Oldsmobile eight-cylinder engine 7 . . 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
CHAPTER IV FUELS AND CARBURETTING SYSTEMS
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 fuels 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
CONTENTS xiii
ART. PAGE
74. Operating conditions of the carburetor 74
75. Schebler model L carburetor 75
76. Schebler model R carburetor 77
77. Marvel carburetor 79
78. Rayfield 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
CHAPTER V
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. Full 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 327
xiv CONTENTS
CHAPTER VI
PRINCIPLES OF ELECTRICITY AND MAGNETISM
ART. PAGE
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 . • >. V *.r. ' 134
123. The dry cell ......... . ........... 9 135
124. The storage battery ......'......-...... 136
125. Wiring of ignition batteries . . . . .... . 137
126. Magnetism 139
127. Natural and artificial magnets 139
128. Magnetic and non-magnetic metals 139
129. The poles of a magnet \ . . . V 10. .^ . 140
130. The magnetic field . ^fk. 141
131. Electrom agnetism ....;.......... jff. . 142
132. The electromagnet ; . . 143
133. To determine the polarity of an electromagnet . . ^ . . 144
134. Electromagnetic induction 144
135. The right-hand rule 146
CHAPTER VII 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. Sparkplugs . 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 . iv. . . 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 . . . "1 . 169
155. The Remy ignition system 174
156. The Remy-Liberty ignition breaker for U. S. Military Truck 178
CONTENTS xv
ART. pAGB
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
CHAPTER VIII 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 . . . ; m 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
CHAPTER IX 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
xvi CONTENTS
ART. PAGE
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
205. 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 jj^ .. ... , . . . 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
CHAPTER X 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 289
238. Regulation of the generator 290
239. Generator regulation through reverse series field winding 291
CONTENTS xvii
ART. PAGE
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-Liberty lighting system on U. S. standardized 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
CHAPTER XI THE AUTOMOBILE CHASSIS AND RUNNING GEAR
258. General arrangement of chassis 343
259. Frames 343
260. Springs and spring suspension 345
261. Unsprung weight 7—. 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
CHAPTER XII 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
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
CHAPTER XIII 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 . . .f •-.-» . . . , 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 . . , . . :>>T . ..,..,..,.... 400
295. Strut rods. . 402
CHAPTER XIV
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 1 ...... 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 ..J. •. 421
314. Alignment of wheels 421
CONTENTS xix
ART. PAGE
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
CHAPTER XV 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
CHAPTER XVI 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
xx CONTENTS
ART. PAGE
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
THE GASOLINE AUTOMOBILE
CHAPTER I THE AUTOMOBILE
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. ' = i ...... .%•••«•
THE GASOLINE AUTOMOBILE
rtOTOR & FAN'"
THROTTLE VALVE--
HAND BRAKE -^
/GN/T/ON AND-- L/GHT/NG SWITCH
CYL/NDERS —
CRANK CASE
AND DIFFERENTIAL
HOUSING
BRAKE COOLING"" FLANGES
CONDENSER
STEAS1 GENERATOR
-SERVICE BRAKE -WATER TANK
-THROTTLE CONTROL
FRONT END ENGINE SUPPORT
PUMPS
ELECTRIC MOTOR GENERATOR
^KEROSENE TANK
FIG. 1. — Chassis of Doble steam car.
THE AUTOMOBILE
4 THE GASOLINE AUTOMOBILE
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- ing the car, for climbing hills, for heavy roads, and also for reversing the car, as the ordinary four-stroke automobile engine is not reversible. The gasoline engine will not start under load. This necessitates the use of a clutch, 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 gasoline engine but in reality they are very few, for with the proper handling of the spark and throttle control levers it is not necessary to keep changing gears continually. The gear shifting lever need not be used except for starting, stopping, hill climbing in congested districts, and on bad roads.
The advantages of the gasoline engine for use on an automobile are so numerous that it is universally used for driving pleasure and com- mercial cars. Figure 2 is a plan view of a modern gasoline driven automobile.
4. The Gasoline-electric Car. — The gasoline-electric or the dual- power car is driven by a combination of a gasoline engine and an electric motor. This arrangement, illustrated in Fig. 3, gives the advantages of both the gasoline car and the. electric car. The electric motor is con- nected directly to the propeller shaft running to the rear axle. By means of a magnetic clutch, 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 electric motor, and, after a certain speed is attained, the engine may be started by a magnetic clutch. Power for
THE AUTOMOBILE
running may be obtained either from the electric motor and batteries, from the engine alone, or from both.
5. 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 coupe, the sedan, the limou- sine, and the town car. These are shown in Fig. 4.
MAGNETIC CLUTCH,
PROPELLER
SHAFT
STORAGE BATTERIES
FIG. 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 cloverleaf 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.
6
THE GASOLINE AUTOMOBILE
The coupe 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 coupe* is provided with a detachable top or sides as in Fig. 7, it gives all the advantages of an open roadster. Such a coupe* is some- times called a convertible coupe 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
Roadster.
Touring car.
Coupe.
Sedan.
Limousine. Town car.
FIG. 1 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
THE AUTOMOBILE
FIG. 5. — Seating arrangement of Chandler four passenger roadster.
8
THE GASOLINE AUTOMOBILE
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 landaulet.
FIG. 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
THE AUTOMOBILE 9
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
10
THE GASOLINE AUTOMOBILE
FIG. 9. — Limousine — Landaulet body.
FIG. 10. — Wooden frame for automobile body.
FIG. 11. — Pressed metal automobile body.
THE AUTOMOBILE
11
Ford light truck chassis.
Kissel medium truck.
Packard heavy truck. JFio. 12. — Typical types of commercial cars.
12 THE GASOLINE A UTOMOBILE
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 engine 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.
THE AUTOMOBILE
13
14 THE GASOLINE AUTOMOBILE
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
STEERING WHEEL
STEERING COLUMN
'STEERING KNUCKLE ^ SOL ID FRONT AXLE
FIG. 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.
THE AUTOMOBILE
15
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,
FIG. 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. — It is sometimes necessary, as when turning a corner, that one rear wheel turn faster than the other one. In order to accom-
SPARK CONTROL LEVER
THROTTLE
IGNITION SWITCH
LIGHT SWITCH
SPEEDOMETER
COMPARTMENT
CLUTCH PEDAL
ACCELERATOR PEDAL
SERVICE BRAKE PEOAt
EMERGENCY BRAKE LEVER CONTROL LEVER
FIG. 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.
16 THE GASOLINE AUTOMOBILE
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.
FIG. 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 the automobile, their construction, and methods of operation.
CHAPTER II THE AUTOMOBILE ENGINE
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
18 THE GASOLINE AUTOMOBILE
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 engines.
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 wi]l 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.
THE AUTOMOBILE ENGINE
19
SPAftK INLET VALVE
JACKET
COOLING
SUCTION STROKE
FIG. 18.
COMPRESSION STROKE
FIG. 19.
WORKING STROKE
FIG. 20.
EXHAUST STROKE
FIG. 21.
20
THE GASOLINE AUTOMOBILE
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 unco vered 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 Plug
Exhaust Port Transfer Part /Check Valve (Open) Carburetor
/Deflector
Transfer Port
Check Valve (Closed)
FIG. 22. FIG. 23.
FIGS. 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
THE AUTOMOBILE ENGINE
21
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 Z>, 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
UPPER DEAD CENTER
COMBUSTION
LOWER DEAD CENTER
FIG. 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
22
THE GASOLINE AUTOMOBILE
the water jacket is very important as sufficient cooling surface must be provided and all pockets where steam might collect must be avoided.
VALVE SPRINGS WRIST PIN,
COOLING, SPACE
FLYWHEEL
VALVES
Jm
MAIN BEARING
MAIN BEARING
FIG. 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.
oo
Concentric piston ring. Eccentric piston ring.
FIG. 26. — Continental Model N auto- FIG. 27. — Types of piston rings,
mobile engine.
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
THE AUTOMOBILE ENGINE
23
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
FIG. 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
24
THE GASOLINE AUTOMOBILE
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 \y± 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
CONNECTING ROD SHIMS ' Jfc ,1^ CAP
WRIST PIN
BEARING
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
THE AUTOMOBILE ENGINE 25
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 2J^ 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 1J^ 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
26
THE GASOLINE AUTOMOBILE
valves wiih the operating mechanism are illustrated. An end view of a similar mechanism 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
B
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
Tungsten. A
Cast iron. B
FIG. 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,
THE AUTOMOBILE ENGINE 27
tight seat, while the cast-iron valve seat is pitted and worn. Cast-iron vrlve heads can be screwed on a steel stem as in Fig. 3QB, 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 h, Fig. 3QA. 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 %Q to J/£ 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 valves.
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
28
THE GASOLINE AUTOMOBILE
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-Head. 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
VALVES
CRANK SHAFT
FIG. 33. — Valve operating mechanism on Ford car.
arrangement. The I-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
THE AUTOMOBILE ENGINE 29
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 recefl^^ir 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 camshltft.J, 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
30
THE GASOLINE AUTOMOBILE
just half the speed of the crankshaft. These gears are called half-time gears.
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.
FIG. 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 combustion 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
THE AUTOMOBILE ENGINE
31
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
Piston connecting rod
Crankshaft
Outer sleeve
Inner sleeve
Connecting rod, to operate outer sleeve
Connecting rod, to operate inner sleeve
Eccentric shaft
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
32
THE GASOLINE AUTOMOBILE
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
Intake stroke.
Intake ports open. Exhaust ports closed.
Compression stroke.
All ports closed and sealed by ring in cylinder head.
Power stroke. Exhaust stroke.
Intake ports closed. Exhaust ports open.
FIG. 37. — Valve events in Willys-Knight engine.
All ports closed and protected by ring in cylinder head.
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
THE AUTOMOBILE ENGINE
33
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 chapter.
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 Ib. 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-
FIG. 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 and 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-
34 THE GASOLINE AUTOMOBILE
der is 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 3^-in. by 5-in. engine (this means SJ-^-in. inside cylinder diameter and 5-in. stroke) would have a piston displacement as follows:
The area of a 3^-in. circle is 0.7854 X 3^ X 3^ = 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 give 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
THE AUTOMOBILE ENGINE 35
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 mechanism.
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:
PAS "*p'~ 33,000X4
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:
PASNE
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 Ib. per square inch; and that the mechanical efficiency will 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 p' 33,000 X 4
and combining the numerical values it reduces to:
36 THE GASOLINE AUTOMOBILE
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 D2 = hp. for all four-cylinder motors.
2.4 D2 = hp. for all six-cylinder motors.
3.2 D2 = hp. for all eight-cylinder motors.
4.8 D2 = 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 basis.
CHAPTER III AUTOMOBILE POWER PLANTS
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
1 Cylinder
2 Cylinders
4 Cylinders
6 Cylinders
8 Cylinders
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-
37
38 THE GASOLINE AUTOMOBILE
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 down.
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,
AUTOMOBILE POWER PLANTS 39
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 4J4 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-
40
THE GASOLINE AUTOMOBILE
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 White car presents some extraordinary features as may be seen from
REMOVABLE CYLINDER HEAD
WATER COOLING WRIST PIN^ SPACE,
INTAKE VALVE
-CAM SHAFT
CLUTCH.
MAIN BEARING
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, 4J4 in. by 5% 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
A UTOMOBILE POWER PLANTS
41
iiiJii
42
THE GASOLINE A UTOMOBILE
FIG. 42. — Top view of cylinders and valves on White 16 valve four-cylinder engine.
FIG. 43. — Crank case and camshafts on White 16 valve four-cylinder engine.
AUTOMOBILE POWER PLANTS
43
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 Ib. 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.
FIG. 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.
44
THE GASOLINE AUTOMOBILE
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
FIG. 45. — Top view of cylinders showing 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 5^-in. stroke.
FIG. 46. — Bottom view of cylinder 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
AUTOMOBILE POWER PLANTS
45
FIG. 47. — Case continental six engine.
FIG. 48. — Marmon six-cylinder power plant.
46
THE GASOLINE AUTOMOBILE
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
ALUMINUM /'COVER
FIG. 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 Ib.
AUTOMOBILE POWER PLANTS
47
The cylinders are 3%-in. bore and 5j£-in. stroke. The pistons of cast aluminum alloy carry 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
Overhead- va/ves
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.
45. 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
48
THE GASOLINE AUTOMOBILE
high powers and speeds. The weight is 565 Ib. 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 L-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.
FIG. 53. — Section of Hall-Scott aviation
type automobile engine. 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.
AUTOMOBILE POWER PLANTS
49
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.
EXHAUST
MANIFOLD
COOLING WATC.R OUTLET
GeNERATOf
FIG. 54. — Chandler six-cylinder engine.
Afa/n
bear/nos .- ^ J|
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
50 THE GASOLINE AUTOMOBILE
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
FIG. 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 are vertical. Figure 58 A represents a right crank and Fig. 58B a left cra.nk, 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,
AUTOMOBILE POWER PLANTS
51
2+5
3+4 2+5 B
FIG. 58. — Methods of cra,nk arrangement ior six-cylinder engine.
MAIN BEARING
FIQ. 59. — Chandler six-cylinder crankshaft with three main bearings.
52
THE GASOLINE AUTOMOBILE
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
FLY WHEEL.
Pf-STON R!NS
N^ SHAFT BEARING- CONNECTING WOO BETARfNtf
CRANK SHAFT
CRANK
SHAFT G»M?
FIG. 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
FIG. 61. — Hall-Scott cranlc 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. 58A 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 best and most usual firing order, because the power impulses are better distributed along the crank.
AUTOMOBILE POWER PLANTS 53
The left crank, Fig. 58J5, 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
FIG. 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,
FIG. 63. — 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,
54
THE GASOLINE AUTOMOBILE
theie 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
FIG. 64. — Cadillac eight-cylinder engine.
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.
AUTOMOBILE POWER PLANTS
55
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
FIG. 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
56
THE GASOLINE AUTOMOBILE
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.
FIG. 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.
FIG. 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
AUTOMOBILE POWER PLANTS
57
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.
FIG. 69. — Oldsmobile connecting rods and crankshaft.
53. 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-
FIG. 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
58
THE GASOLINE AUTOMOBILE
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
FIG. 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 1L and 4L 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
AUTOMOBILE POWER PLANTS
59
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
\nr Yin
FIG. 72. — Eight-cylinder Knight type engine.
1 RADIATOR RADIATOR | RADIATOR | I RADIATOR
LEFT RIGHT LEFT RIGHT LEFT RIGHT LEFT RIGHT
©
(D
: .A B C D
FIG. 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
60 THE GASOLINE AUTOMOBILE
crder for the engine is 1L, 2R, 3L, 1R, 4L, 3R, 2L, 4R, as shown on Fig. 73A. If the 1, 2, 4, 3 order is used the engine fires LL, 3R, 2L, 1R, 4L, 272, 3L, 4R, as on Fig. 73 A.
The system of numbering the cylinders is not always as shown in Fig. 73 A. The cylinders may be numbered in the order of firing as on the Cadillac, Fig. 73B, or as on the Cole car, Fig. 73 C, 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, 1L, 2R, 3L, IR, 4L, 3R, 2L, 4R. The firing order on the Cole is 1, 8, 3, 6, 4, 5, 2, 7, as in Fig. 73 C, 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. 73 C.
56. 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 R2, L2, R4, L4, #3, 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 Rl, LI, #3, L3, R4, L4, R2, L2.
57. 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.
58. National Twelve -cylinder Engine. — On the National twelve-cyl- inder engine, Fig. 76, the valves are placed on the outside of the V instead
AUTOMOBILE POWER PLANTS
61
FIG. 74. — Packard twelve-cylinder engine.
FIG. 75. — Packard twelve-cylinder engine in car.
62
THE GASOLINE AUTOMOBILE
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 afc 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.
FIG. 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.
59. 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
AUTOMOBILE POWER PLANTS
63
six cylinders. The right set of cylinders is placed 1^ 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.
FIG. 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 in Fig. 78 A, the impulses alternating from one side to another.
On the Packard engine, numbered as in Fig. 78A, the firing order is 1R, 6£, 4#, 3L, 2R, 5L, 6R, IL, 3R, 4L, 5R, 2L, corresponding to a firing order for each block of 1, 4, 2, 6, 3, 5. On the Pathfinder, numbered as
64
THE GASOLINE AUTOMOBILE
in Fig. 78C, the firing order is 1#, 1L, 4R, 4L, 2R, 2L, 6R, 6L, 3#, 3L, 5R, 5L. This is the same order as is used on the Packard.
With cylinders numbered as in Fig. 78B, 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. 7SA.
I RADIATOR | | RADIATOR | | RADIATOR!
LEFT RIGHT LEFT RIGHT LEFT RK3HT
(g) Q>
© ®
@ (D
A 6 C
FIG. 78. — Numbering of cylinders on twelve-cylinder engines.
A power impulse comes every 60d 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.
CHAPTER IV FUELS AND CARBURETTING SYSTEMS
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
66
THE GASOLINE AUTOMOBILE
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 350°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- tillate
(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.
FUELS AND CARBURETTING SYSTEMS
67
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
FIG. 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 Ritmarin 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.
68 THE GASOLINE AUTOMOBILE
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 can 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.
65. 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,
FUELS AND CARBURETTING SYSTEMS
69
but are named after Baume", 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° Baume", 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 Baume* test of from 56° to 65°, the high test being in the neighborhood of 65° and the low test in the neighborhood of 56°. 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 n ..
. Kerosene Gasoline
gasoline that readily carbonizes ^ 81._Baume hydrometer in kerosene
should be avoided and a higher and gasoline,
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,
70 THE GASOLINE AUTOMOBILE
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 speeds^ 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 Ib. of water 1° on the Fahren- heit scale. The following table gives the heating values of the common fuels :
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.
FUELS AND CARBURETTING SYSTEMS
71
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 pum.
r~foaf chamber
Butterfly /throH/e
FIG. 82. FIG. 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 che 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-
72 THE GASOLINE AUTOMOBILE
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 engine 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,
FUELS AND CARBURETTING SYSTEMS 73
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 $, 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. FIG. 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
74 THE GASOLINE AUTOMOBILE
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 85. 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 manifold 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 condensation.
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.
FUELS AND CARBURETTING SYSTEMS
75
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 nd to insure complete vaporization.
If the explosive mixture going into the cylinder be heated too much, it is expanded
FIG. 86. — Electrical heating unit for carburetor bowl.
FIG. 87. — Connections for electrical heater for carburetor.
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 carburetors.
75. Schebler Model L Carburetor.— The Model L carburetor, Figs. 88 and 89, is of the lift-weedle 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.
76
THE GASOLINE AUTOMOBILE
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 the 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 Ib.
FIG. 88.— Schebler Model L carburetor.
FIG. 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
FUELS AND CARBURETTING SYSTEMS 77
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
FIG. 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 dial.
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
78
THE GASOLINE AUTOMOBILE
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
FIG. 91.— §chebler 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.
FUELS AND CARBURETTING SYSTEMS
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 lean.
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 carburetor.
80
THE GASOLINE AUTOMOBILE
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 Mix/no chamber *
A/'r adjusting screw \
y \
Hot air damper
ffW*' a/r -^ intake
r valve sprav nozzle
•4—A/r intake -Choke damper -Venturi tube
valve
FIG. 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.
FIG. 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
FUELS AND CARBURETTING SYSTEMS 81
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 turned 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 t-he 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
82
THE GASOLINE AUTOMOBILE
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.
FIG. 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
FUELS AND CARBURETTING SYSTEMS
83
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.
HIGH SPEED ADJUSTMENT
TURN TO RIGHT FOR, MORE GAS
GASOLINE INTAKE
CONNECTION
SPEED ADJUSTMENT
TUR.N 10 R.IGHTFORMORE GAS
FIG. 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
FIG. 98.— Dash control handle for Rayfield carburetor.
motor thoroughly warm, make the
final low speed adjustment by 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
84
THE GASOLINE AUTOMOBILE
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.
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 / 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 / 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,
FIG. 99. — Holley Model H carburetor.
FUELS AND CARBURETTING SYSTEMS
85
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.
FIG. 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
86 THE GASOLINE AUTOMOBILE
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 I. 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
FUELS AND CARBURETTING SYSTEMS
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, as described in connection with the Holley Model H. The leve^^oDfcrates the throttle in the mix- ture outlet. A larger disc with its Ijdl Kms a spring-returned choke valve in the air intake for starting^! BPety cold weather.
The dash adjustment consistSMpfandle or small thumb wheel attached to a rod by which the needlevalve 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 maintained 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 lightly -on its seat, allowing no air to 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 passage.
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.
FIG. 102. — Kingston Model L carburetor.
88 THE GASOLINE AUTOMOBILE
A drain cock G is placed at the lowest point in the bowl and should be opened from tune to tinr 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 needle 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 runs 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
FUELS AND CARBURETTING SYSTEMS
89
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
90
THE GASOLINE AUTOMOBILE
should be thoroughly warmed 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-
FIG. 105. — Primary fuel nozzle and air valve on Tillotson carbu- retor.
FUELS AND CARBURETTING SYSTEMS
91
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 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 1J^ 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 mixing 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.
92 THE GASOLINE AUTOMOBILE
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
FUELS AND CARBURETTING SYSTEMS
93
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.
^CARBURETOR FIANCE
LARGE VENTURI
.THROTTLE VALVE
THROTTLE STEM OR SHAFT
THE STROMBERG
PLAIN TUBE CARBURETOR
With Motor at Rert
IDLE DISCHARGE JET IDLE ADJUSTMENT 'NEEDLE HIGH SPEED ADJUSTMENT NEEDLE I fg± >X FLOAT NEEDLE
,„,,_ . BIL — N
FLOAT
GASOLfNE1 CONNECTJOM
DRAIN PLUG
FIG. 108. — Stromberg 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.
94 THE GASOLINE AUTOMOBILE
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 tithe 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 Stromberg 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
FUELS AND CARBURETTING SYSTEMS 95
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 Stromberg Plain Tube Carburetor. — The high and low speed adjusting screws, A and B, 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 1J^ 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 B, re- tard the spark fully and close the throttle as far as possible without causing the motor to FIG. no.— Air bleeder on come to a stop. If upon idling, the motor ^0°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 jevolves 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, 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.
96
THE GASOLINE AUTOMOBILE
The Stromberg 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 months.
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
M
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
FUELS AND CARBVRETTING SYSTEMS
97
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
service.
The dashpot with the piston riding in gasoline prevents all fluttering of the air valve on its seat, when opening and closing.
AIR VALVE CMC SCREW
MIXTURE REOULATOP TUBE HOLOCR • SC8EW
AUXILIARY GASOLINE NEEDLE VALVE (COMPLETE)
AUMLARY 6ASOUNE NEEDLE VALVC AOJOSTiC LEWW AUXILIARY GASOLINE NEEDLE VALVE LOCK LEVER:
AUXILIARY 6ASOLINC NEEDLE VALVE SCAT DASH POT PISTON WASHER
AUXILIARY GASOLINE WELL PLUS
GASOLINE WELL PLUG CASKET PRIMARY NOZZLE NEEDLE VALVE (COMPUTE)
FIG. 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 operation.
98
THE GASOLINE AUTOMOBILE
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.
*ND FEED REGULATOR IN PHfKTOM
FIG. 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 spring.
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
FUELS AND CARBURETTING SYSTEMS
99
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-
-THROTTLE
GASOLl NE INLET NEEDLE VALVE
AUXILIARY A/R
VALVE SPRING
FIG. 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
100 THE GASOLINE AUTOMOBILE
for all types of carburetors, but there are certain fundamental principles which apply to the adjustment of all types.
There are numerous troubles coming 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 cy Under 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 ate 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
FUELS AND CARBURETTING SYSTEMS 101
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 casting.
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
102
THE GASOLINE AUTOMOBILE
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,
FIG. 118. — Gasoline supply system on Ford car — supply tank under front seat.
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
FUELS AND CARBURETTING SYSTEMS 103
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
GASOLINE /NO/CATOR
ON DASH HAND AIR PUMP
/ ON DASH 1
CARBURETOR^
6A5OU PIPE
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 tank.
104
THE GASOLINE AUTOMOBILE
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.
FUELS AND CARBURETTING SYSTEMS
105
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- guisher.
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 tank.
CHAPTER V ENGINE LUBRICATION AND COOLING
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 frictional 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; semi-solids, such as soft grease; and solids, such as 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 used.
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.
107
108
THE GASOLINE AUTOMOBILE
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
FIG. 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 Oil
Company.)
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
ENGINE LUBRICATION AND COOLING 109
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
FIG. 125. — Cold test 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,
110 THE GASOLINE AUTOMOBILE
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 good 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
ENGINE LUBRICATION AND COOLING 111
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 headings :
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
OIL CUP
?/L PUT 'N HERE
UPPER . \
COCK ^ I CRANK CASE Oil TUBE
LOWER OIL"
COCK
FIG. 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.
112
THE GASOLINE AUTOMOBILE
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
,,0/L PRESSURE GAGE
PUflP TO GAGE 0/L TUBE
OIL FEED PiPE
i
VL LEVEL INDICATOR BUTTON
OIL TUBE ELBOW
0/L PUflP
OIL
GEAR CASE- 0/L OVERFLOW
CONNECTING ROD OIL DIPPER
PUfJP putlPTOENGtNE-%
PUflP TO ENGINE OIL TUBE OIL TUBE
STRAINER OIL PUHP SHAFT
OIL PAN OIL STRAINER RESERVOIR
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