SCIENCE OF THRESHING. 



127 



liner and screwing the cap down just hard enough to 

 make the shaft run true without causing a great deal 

 of friction. 



There are means of taking up the wear in the 

 bearing brasses of the crank and wrist pin or crank 

 pin, as it is more correctly called. These comprise 

 wedges held against the outer side of the brasses by 

 encircling straps, and drawn in or out by properly 

 arranged screws. The brasses should not be drawn 

 so tightly as to heat and cling to the shaft, the 

 particles of brass thereby becoming abrading par- 

 ticles. 



It must be remembered that taking up the brasses 

 in this manner changes the length of the connecting 

 rod and makes the clearances at the two ends of 

 the cylinder unequal. This must be remedied by the 

 insertion of shim or liner plates, or by changing the 

 length of the piston rod. 



THE ECCENTRIC. 



Motion is imparted to the slide valve by an eccen- 

 tric on the main shaft. This consists of a disc, 9, se- 

 cured to the shaft so that its center does not coincide 



