378 FARM MOTORS 



524. Reversing gears. Since the simple engine cannot 

 be reversed without stopping and using time, engines 

 which have to be reversed often and quickly are provided 

 with reversing gears. That is, they are arranged so they 

 can be reversed with a lever. There are two general 

 classes of reversing gears, the double-eccentric and the 

 single-eccentric. 



525. Hooking up an engine. Some engine makers des- 

 ignate their reversing gears as expansion gears. Such 

 gears are simply reversing gears which can be used so 

 that the steam works on expansion. Reversing gears are 

 actuated by means of a lever which works in a quadrant. 

 When the lever is in one half of the quadrant steam is 

 admitted so that the engine runs under, and when in the 

 other half the engine runs over. These gears are gen- 

 erally so constructed that if the engineer wishes his fly- 

 wheel to run in a direction away from him he moves the 

 lever in the direction the wheel turns, and if he wishes 

 the wheel to run toward him, he moves his lever in that 

 direction. Some engines are connected up in the oppo- 

 site manner. When an engine is carrying an overload, 

 the lever is thrown into the last notch in the quadrant 

 and the piston receives steam nearly the full length of 

 the stroke. Although this has to be resorted to in some 

 instances, it is not an economical way to run an engine, 

 as the steam has no chance to expand. When an engine 

 is running on full load, that is, when it is doing only its 

 rated capacity of work, the lever should not be in the 

 end notch of the quadrant, but should be somewhere be- 

 tween the end notch and the middle. By having an en- 

 gine hooked up, steam is cut off in an earlier part of the 

 stroke and consequently works on expansion the remain- 

 ing part. 



526. Double-eccentric reverse or link-motion reverse. 



