386 



FARM MOTORS 



very small variation of speed. Governors regulate the 

 speed of an engine in two ways : by varying the steam 

 pressure as it enters the cylinder, and by varying the 

 point of cut-off. 



534. Throttling governors. Governors which act upon 

 the steam in such a manner as to vary the pressure in 

 the cylinder are known as throttling governors (Fig. 

 271). In other words, they throttle the steam before it 

 enters the steam chest so there is not enough admitted 

 to fill the space intended for it. Therefore, boiler pres- 

 sure is not attained, and consequently the steam does 

 not exert as much force upon the piston as when the 

 governor is not acting. As a result, the engine does not 

 do its full capacity of work. 



FIG. 271 THROTTLING GOVERNOR 



FIG. 272 SECTIONAL VIEW OF 

 THROTTLING GOVERNOR 



