HARVESTING MACHINERY 145 



Some of the more important features and individual 

 parts will now be discussed in regard to construction and 

 adjustment. Parts are numbered to correspond with 

 numbers in Figs, no and in. 



190. Canvases (i) should be provided with tighteners by 

 which they may be loosened when not in use. Tighteners 

 also make it more convenient to put canvases on the 

 machine. The elevator rollers should be driven from the 

 top, thus placing the tight side next to the grain. The 

 creeping of canvases is due to one of two things, either 

 the canvases are not tight enough or the elevator frame 

 is not square. If the elevator is not square, the slats will 

 be torn from the canvases. This trouble may be over- 

 come by measuring across the rollers diagonally or 

 placing a carpenter's square in the corner between guide 

 and roller, and adjusting. The method of adjustment 

 varies with different makes, but the lower elevator is 

 usually adjusted with a brace rod to the frame, and the 

 upper elevator with a slot in the casting attaching the 

 guide to the pipe frame. 



191. Elevator chains (2). Two kinds of chains are found 

 in use, the steel chain and the malleable. The steel chain 

 is claimed to be the most durable, but has the disadvan- 

 tage of causing the sprocket teeth to cut away faster. 

 This wear is often the greatest upon the driving sprocket, 

 as it has the most work to do. It is thought that the steel 

 chain is the more desirable chain to have. 



192. The chain tightener (3). The chain tightener may 

 have a spring or slot adjustment. The spring adjustment 

 is very handy and an even tension is maintained on the 

 chain. The elevator chain should not be run with more 

 tension than needed, as it produces wear and adds to the 

 draft. 



. 193. Twine box (4). The location of the twine box is 



