CHAPTER III 



THE STRAW-RACK AND CONVEYOR 



THE straw-rack and conveyor are both carried by 

 studs on the rocker or "vibrating" arms, the straw- 

 rack having a longer leverage than the conveyor, 

 so that each counterbalances the other. They are more 

 accurately balanced when the machine is in operation and 

 both are loaded than when the machine is running empty. 

 It is very difficult to separate grain from straw that is badly 

 cut up, therefore care should be taken to use as few rows 

 of concave teeth as will thresh clean from the heads. 



Speed. The most important factor in producing good 

 work by the straw-rack is the speed. To do good work, 

 it must make 230 vibrations per minute. Its speed can 

 best be determined by using a revolution-counter on the 

 crank shaft. Some persons can determine the speed by 

 letting one of the pitmans or a key of one of the crank 

 shaft pulleys strike one hand once every revolution, while 

 holding a watch in the other hand and counting for a half 

 or a full minute. The proper speed is as essential to good 

 work by the conveyor sieve or "chaffer" as by the straw- 

 rack ; if too fast, grain will go over the sieve with the chaff, 

 and if too slow the sieve will be overloaded. 



The present style of straw-rack has riser supports, 



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