THE WASTE IN THRESHING. 221 



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 pos- 

 sible. 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 actually caused by a 

 neglected cylinder and concaves. 



The set of the fish-backs on the straw-rack increase the 

 separating capacity. They are nailed to the risers of the 

 straw-rack, two on the first riser back of the beater, three to 

 the next and four to the last riser. 



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 three 

 different speeds the straw passes the length of the machine, 

 (about 14 feet 8 inches counting risers, or 13 feet 4 inches 

 straight), 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 machine. 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. 



