PART VII. FARM EQUIPMENT AND MACHINERY 



EXERCISE 92 

 THE GAS ENGINE AND AUTOMOBILE 



Inlet 

 valve 



Spark ^ 



plug 



Exhaust, 

 valve 



Suction of the mixture of air and gas through inlet valve takes place during the com- 

 plete outward stroke of the piston, the exhaust valve being closed 



Inlet 

 valve 



Spark 



plug 



Exhaust 

 valve 



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Fig. 145. Compression stroke 



Statement. There is no machine that has been so widely and rapidly introduced on the 

 farm as the gas engine. Probably no other machine can be put to so many uses or can save so 



much human energy. 



Object. To study the important 

 parts of a four-stroke-cycle gasoline 

 engine, its operation, and the essen- 

 tial parts of an automobile. 



Materials . Gasoline engine and an 

 automobile which may be examined. 



Directions. 1. Examine a gas 

 engine and learn the function and 

 location of the following parts : fuel 

 tank, fuel-regulating valve, carbu- 

 retor, inlet valve, exhaust valve, igni- 

 tion system, engine cylinder, piston, 

 connecting rod, crank, crank shaft, 

 flywheel, valve gear shaft, two-to- 

 one gears, governor, cylinder jacket, 

 cooling system, lubricators. 



Explain in writing the action of 

 the four-stroke-cycle gasoline engine, 

 indicating the function of each of the 

 above parts. 



2. Before attempting to start the 

 engine examine the fuel supply, try 

 out the ignition system, see that the 

 lubricators are working properly, 

 retard the spark to the starting posi- 

 tion, open the fuel-regulating valve, 

 and crank the engine, always pulling 

 upon the crank. As soon as the en- 

 gine picks up adjust the fuel valve 

 for best fuel economy and advance 

 the spark to the running position. 

 Stop and start the engine until you 

 are familiar with the operation. Ex- 

 plain in writing causes for a gasoline 



On the return stroke of the piston both valves remain closed and the mixture of air and 

 gas is compressed between the piston and the closed end of the cylinder 



Inlet 



valve ' 



Spark 

 plug 



Exhaust 

 valve 



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Fig. 146. Ignition and explosion 



Just before the compression stroke is completed the compressed mixture is ignited by 

 a spark and rapid combustion or explosion takes place 



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Spark 

 plug 



Exhaust 

 valve 



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Fig. 147. Explosion or power stroke 



The increased pressure within the cylinder due to rapid combustion of the mixture 



drives the piston on its second forward stroke. This is the only stroke in the cycle in 



which power is generated. Both valves remain closed during this stroke 



engine's failing to start. Give directions in writing for operating gasoline engines. 



3. Examine an automobile and learn the location and function of the following parts : motor, 

 clutch, transmission gearing, differential, universal joint, steering system, control system, service 



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