412 



FARM MOTORS 



FIG. 296 VALVES 



der to be filled is the same ; 

 consequently the compres- 

 sion pressure is not as great 

 as it should be and the en- 

 gine is not economical with 

 fuel. Often the load in an 

 engine is small enough for 

 the charge to be throttled 

 down until of such small 

 volume as not to ignite, but 

 simply pass off to the ex- 

 haust unburned. Throttling- 



governor gasoline engines are not as economical with a 

 variable load as the hit-or-miss type of governed engines. 

 However, their motion is much more steady, and often 

 the matter of economy is waived in order to secure the 

 greater uniformity of speed. 



Hit-or-miss type of governor. In the hit-or-miss type 

 of governor the amount of mixture drawn in for an ex- 

 plosion remains at all times a constant, and the govern- 

 ing is accomplished by cutting out all admissions while 

 the engine is running faster than normal speed. This 

 method of governing is usually accomplished by holding 

 the exhaust valve open and the inlet valve closed until 

 the engine falls a trifle below speed, when the exhaust 

 valve closes and new charges are taken into the cylinder. 

 Fig. 297 shows the manner in which this style of govern- 

 ing is accomplished. When the speed of the engine is 

 above normal the governor sleeve C, which is in the 

 crank shaft, is drawn out, and, acting on the detent roller 

 D, throws the detent lever E down so it becomes en- 

 gaged in the hook-up stop F. The hook-up stop F, being 

 connected to the exhaust valve rod H, holds the exhaust 

 valve open. By reference to Fig. 298 it will be seen how 



