452 



THE ESSENTIALS OF AGRICULTURE 



used successfully as a fuel for this type of engine, but it is too 

 expensive in comparison with gasoline and kerosene. 



In order that the greatest energy of the fuel may be secured 

 in gas engines and oil engines, the fuel must be mixed with 



FIG. 226. Essential parts of a gasoline engine 



The gasoline from the tank V passes through the strainer Z, where the impurities are 

 deposited, then through the gasoline-regulating valve N to the mixer, or carburetor x. 

 The air through the air-regulating valve A enters the same carburetor and is thoroughly 

 mixed with the gasoline. The mixture of air and gasoline enters the engine cylinder 

 C through the inlet valve / as the piston P moves to the right on the outward stroke. 

 Under the influence of the flywheel F, the piston returns, compressing the mixture 

 between the piston and the closed end of the cylinder, with all the valves closed. 

 Just before this return stroke of the piston is completed the mixture is ignited by an 

 electric spark at the spark plug U and rapid burning, or explosion, of the mixture takes 

 place. The high pressure developed by this explosion drives the piston forward on its 

 power stroke, all valves still remaining closed. Near the end of the power stroke, the 

 exhaust valve E opens and the " burned gases " begin to rush out. The return of the 

 piston clears the cylinder of the burned gases. The sliding motion of the piston is 

 changed into a rotary motion at the shaft S by the connecting rod D and the crank K. 

 The shaft, while driving the machinery to which it is connected, also gives motion 

 through the two gears G, to the exhaust-valve lift rod L. The spark for igniting the 

 mixture is produced at the spark plug by the electrical batteries B, the timer T com- 

 pleting the electric circuit at the proper time 



air in certain definite proportions before it enters the engine 

 cylinder. This can be accomplished only when the fuel is in 

 the gaseous state. Thus, the oil engine differs from the gas 

 engine in that it requires a device (called a carburetor) for con- 

 verting the liquid oil fuel into a gas before it can be used. Since 



