GAS, OIL AND ALCOHOL ENGINES 4! I 



ameter may range from 28 inches on the small engine to 

 60 inches on the larger size." The above weight is to be 

 divided between the two wheels. 



FIG. 2Q5 FLYWHEELS 



Valves (Fig. 296). It makes no great difference where 

 the valves are located, just so they are close to and con- 

 nected to the clearance space. A good rule to follow for 

 size is : Inlet valve diameter should be five-sixteenths 

 diameter of the cylinder, and the exhaust valve about 

 seven-sixteenths. 



559. Governors. There are two types of gasoline en- 

 gine governors in general use. These are the throttling 

 governor and the hit-or-miss governor. 



Throttling governors vary the amount of gasoline mix- 

 ture admitted to the cylinder. Before the engine has 

 reached its normal speed, or when it is carrying a full 

 load, each charge is a full charge, with as near a perfect 

 mixture as possible. Consequently the normal compres- 

 sion pressure for that engine is attained and the engine 

 does its work with its greatest economy. When the en- 

 gine is doing only a part of its rated capacity of work, 

 the throttle acts. This reduces the volume of mixture 

 which enters the cylinder, but the space within the cylin- 



