FARM POWER AXD MACHINERY. 



241 



The Gasoline Engine. 



The greatest advantage of the 

 gasoline engine on the farm is the 

 fact that it does not require an ex- 

 pert or skilled mechanic to handle 

 it, and it requires little attention 



The gasoline engine in 

 common use on the farm 

 is called a four-cycle en- 

 gine. It is called this be- 

 cause the engine makes 

 four strokes (two revolu- 

 tions) for each power 

 stroke. These four 

 strokes are represented in 

 the accompan3rIng cut. 

 They are called, respec- 

 tively, the charging 

 stroke, the compression 

 stroke, the power stroke, 

 and the exhaust stroke 

 Since there is only one 

 power stroke In four 

 strokes, a gasoline engine 

 must be enulnned with 

 one or two fly-wheels. It 

 is the momentum of the 

 wheels that drives the en- 

 gine between power 

 strokes. 



The rharfirtnsr Stroke. — 



In (1> the flv-wheel Is 

 nnllinf? the niston down. 

 This leaves a vacuum In 

 the cylinder, and the nres- 

 sure of the atmo^nhere 

 forces ooen the Intake 

 valve. Air and easollne 

 vanor nass Into the cvlln- 

 der from the mixer fnot 

 shown). This stroke 



charees the ovlinder with 

 a mixture of easollne va- 

 nnr pnd sir. It Is called 

 the charging stroke. 



The Comnression 

 Stroke. — In (2) the fly- 

 wheel Is forcing the pis- 

 ton UD. This compresses 

 the mixture to about one- 

 fifth its volume. This Is called the 

 comnression stroke. 



The Power Stroke. — ^When the pis- 

 ton reaches Its highest point, an elec- 

 tric spark Is produced In the mixture 

 bv a device not shown. This ex- 

 plodes the mixture. The force gen- 

 erated by the exploding mixture 

 drives the piston down (see 3). This 

 is the power stroke. 



The Exhaust Stroke. — In (4) the 



after being started. Few farmers 

 to-day are able to do without this 

 engine, it being considered the most 

 useful piece of machinery on the 

 farm. 



Working Strokes of Engine. 



wheel is forcing the piston up again. 

 While the piston is moving up, the 

 exhaust valve is held open by an 

 automatic device not shown in the 

 figure. The burned gases are forced 

 out through the exhaust valve. This 

 is called the exhaust stroke. There- 

 fore, there is only one power stroke 

 in the four. 



A gasoline engine uses 1 pint of 

 gasoline per horse-power per hour 



