388 FARM MOTORS 



also acting on the spring. Hence if the spring K is 

 tightened by screwing down on the hand wheel L the 

 engine will have to be running faster before the governor 

 will act. If the hand wheel is loosened, the balls will 

 act more quickly, and consequently the engine cannot 

 attain so high a speed. 



If the belt of this governor be taken off, the engine 

 will have to be controlled by the throttle, since there is 

 nothing else to prevent the steam from flowing into the 

 cylinder as fast as the cylinder will take it. If there is 

 no one at hand to control the throttle, the engine will 

 run away. This is the reason why so many engines run 

 away when the governor belt breaks. A great many 

 governors are now equipped with an idle pulley running 

 on the governor belt. This pulley is attached to the 

 throttle in such a manner that when the belt breaks the 

 pulley is free to fall, and by so doing closes the throttle 

 and stops the engine. 



535. Racing. An engine is said to be racing when its 

 speed of rotation fluctuates badly with a constant load. 

 Racing in nearly all cases is caused by the governor, 

 Either it is not working satisfactorily, or else it is poorly 

 designed. If the valve stem is packed very tight, the 

 engine will have to attain a very high speed before the 

 balls have sufficient force in them to force the valve down. 

 Then when it is down the engine has to slow down en- 

 tirely too much before, the spring will have the energy to 



force the valve up. An en- 

 gine will also race if the gov- 

 ernor belt is loose and slips, 

 or if the governor is im- 

 properly oiled. 



536 ' Indicator diagrams 



FIG. 273 from a throttling-governed 



