THRESHING MACHINERY 2OO, 



horses or trestles. Two steel carpenter's squares will 

 answer for straight edges. The heavy side of the cylin- 

 der will be found, because it will come to rest at the 

 lower side. Weights may be added in the shape of nuts 

 and wedges to bring the cylinder into balance. This 

 latter method will not bring the cylinder into perfect 

 balance, as one end may be heavy on one side, while at 

 the opposite end the other side will be the heavier, and 

 the cylinder will appear to be in perfect balance on the 

 straight edges. 



The cylinder must have end adjustment in order that 

 its teeth will travel directly between the concave teeth. 

 If the cylinder teeth travel close to the concave teeth on 

 one side they will crack the kernels and break up the 

 straw, and thus leave a larger opening on the opposite 

 side through w r hich the grain may pass unthreshed. It 

 is advisable that the cylinder shaft be heavy and 

 equipped with self-aligning boxes provided with a re- 

 liable oiling device. Some machines are made with an 

 "outboard" bearing on the pulley end of shaft, i. e., out- 

 side of main drive pulley. This arrangement is strong 

 but somewhat difficult to line up, and the belt cannot be 

 detached readily. 



285. The concave received its name from its shape 

 being hollowed out to conform to the shape of the 

 cylinder. The concave carries teeth which resemble the 

 cylinder teeth very much, and have openings through 

 which some of the threshed grain may fall. It is made 

 in sections, so the number of teeth may be varied 

 by substituting different sections. It may 'be moved 

 or adjusted to or from the cylinder. In some machines 

 the adjustment may be made at the front and at the 

 rear independently of each other, it being claimed that 

 an advantage is gained by having the concave lower 



