136 SCIENCE OF THRESHING. 



lever should be set so as to bring one of the eccentric 

 rods in line with the valve stem, and then proceed as 

 above directed; then; shift the lever and bring the 

 other eccentric stem in line, and again set the valve; 

 in each instance turn the engine for each setting in 

 the way it would normally run when the parts are in 

 the position given ; this turning the engine in the way 

 in which it should go as you set it, accounts for and 

 allows for any lost motion in the parts. 



TRACTION GEARING. 



Power is usually transmitted to the drive wheels 

 from the main engine shaft through a train of gear- 

 ing. This gearing is arranged to suit the form and 

 equipment of the engine. It usually consists of a 

 friction clutch and a main pinion which are secured 

 together and run on the main shaft. This main pinion 

 engages an intermediate gear which in turn engages 

 a compensating gear. The latter imparts motion to 

 a pair of bull gears which are secured to the traction 

 wheels, the two gears being connected to the compen- 

 sating gear through an intermediate gear. By the 

 application of the friction brake the engine is coupled 

 to the drive wheels, its motion being greatly reduced 

 in passing through the gearing, and thus the engine is 

 propelled. The compensating gear allows the two 

 traction wheels independent movement so as to follow 

 the curves and irregularities of the road, whereby 

 there is no slipping of the wheels in turning corners, 

 and a consequent loss of power. 



