l8o SCIENCE OF SUCCESSFUL THRESHING 



// waste be caused by failure to separate the grain from 

 the straw, first see that the speed of the crank is 230. The 

 cause may be poor feeding which produces "slugging 1 " of 

 the cylinder and the resultant variable motion. See that 

 the check -board is properly adjusted. The cylinder and 

 concave teeth must be kept in good order so that the grain 

 will all be threshed from the heads and the straw cut up 

 as little as possible. When heads missed by the cylinder 

 are threshed out by the wind stacker fan the machine is 

 often criticised for poor separation when the trouble is ac- 

 tually caused by a neglected cylinder and concaves. 



Why it is difficult to separate grain from straw. Straw 

 and grain to the full capacity of the cylinder pass through 

 the concave teeth at the rate of about one mile (5280 feet) 

 per minute, and after passing the check-board the straw 

 rack moves the straw about 102 feet per minute. At these 

 speeds the straw passes the length of the machine (about 

 15 feet) in approximately ten seconds. The intermingled 

 straw and grain move in the same direction and at the 

 same rate of speed. The problem of separation is, then, 

 to check and divert the course of the grain, at the same time 

 allowing the straw to continue its passage through the ma- 

 chine. If the grain be not interrupted in its course, it will 

 pass out with the straw, while clogging will result if the 

 movement of the straw be arrested for even a second. 



