322 



AGRICULTURAL ENGINEERING 



The canvas belt is the most economical in cost and is very- 

 strong. It lengthens and contracts, however, with moisture 

 changes; hence is not suitable for pulleys at fixed distances. 

 Canvas belting is used largely in connection with agricultural 

 machinery, being almost universally used in driving threshers 

 and similar machines. 



Lacing of Belts. The common practice of splicing belts 

 is by means of a rawhide thong, often called a belt lace. 

 Holes are punched at about five-eighths 

 inch from each end of the belt and oppo- 

 site each other. In order to give greater 

 strength, two rows of holes are often 

 punched, the second row being set back 

 farther from the end of the belt. The 

 accompanying illustration shows a 

 good style of lacing. The lace on the 

 side next the pulley should not cross 

 diagonally from one hole to another, but should extend 

 directly across the splice. 



Where the belt is to pass around an idler and thus be com- 

 pelled to bend in both directions, the hinge lace is most satis- 

 factory. There are many forms of patent belt splices and wire 

 lacing on the market, some of which are quite satisfactory. 

 Several forms permit the ends of the belt 

 to be separated by removing a rawhide 

 pin which is held in place by the lace. 



Pulleys. Pulleys on which belts run 

 are made of wood, cast-iron, or steel. 

 Wooden pulleys are made in halves, 

 arranged to be easily clamped to the 

 shaft. Cast-iron and steel pulleys are 

 sometimes made in the same manner. 



Wooden pulleys are the cheapest and are very conven- 



Fig. 201. A good 

 way to lace a belt. 



Fig. 



02. A wooden 

 pulley. 



