CHAPTER IV. 

 THE STRAW-RACK AND CONVEYOR. 



, HE 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 bal- 

 anced when the machine is in operation and 

 both are loaded than when the machine is 

 running empty. It is very difficult to sep- 

 arate 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, although not all, 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, which 



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