494 



ENGINEERING ON THE FARM 



engine proper. A gas engine consists of a cylinder, generally 

 made of cast iron; a piston of cast iron or aluminum alloy; 

 a connecting rod of drop forged steel; a crank shaft of drop 

 forged steel ; a flywheel of cast iron ; a frame or base of cast 

 iron or aluminum; a fuel system, an ignition system, and 

 provision for cooling (Fig. 382). 



The fuel passes from the supply tank through a carburetor, 

 where it is mixed properly with air, to the cylinder, in which it 

 is fired by an electric spark. The explosion drives back the 

 piston, and this force is transmitted by the connecting rod 

 to the crank shaft. The flywheel serves to stabilize the run- 

 ning of the engine. 



GASOLINE 



Composition. Gasoline is the most commonly used fuel 

 for the internal combustion engine. It is a light product 

 distilled from crude petroleum and composed of hydrogen 

 and carbon in the proportion of approximately 93 per cent 

 hydrogen and 7 per cent carbon. Gasoline is offered for 

 sale on a gravity rating on the basis of the Baume scale. 



Gasoline as sold is known as straight-run and blended. 

 Straight-run gasoline tests at the beginning 75 , at the end 

 6o°, yielding an average of possibly 68°. A blended gasoline 

 is made of naphtha or kerosene at 50 to which is added 

 enough of 8o° or 85 gasoline to make the average 68°. The 



