3O FARM MACHINERY 



adapted to wet places and where it will be exposed to 

 the action of steam. Rubber belting, which clings well to 

 the pulley, is less apt to slip and may be called upon to 

 do very heavy service. Although not as durable as 

 leather, it is quite strong, but offers a little difficulty in 

 the making of splices. Rubber belting is made from two- 

 ply to eight-ply in thickness. A four-ply belt is consid- 

 ered the equal of a single-ply leather belt in the trans- 

 mission of power. All oil and grease must be kept away 

 from rubber belting. 



44. Canvas belting is used extensively for the trans- 

 mission of power supplied by portable and traction en- 

 gines. It is very strong and durable, and is especially 

 well adapted to withstand hard service. When used in 

 the field it is usually made into endless belts. It has one 

 characteristic which bars its extended use between pul- 

 leys at a fixed distance, and that is its stretching and con- 

 tracting, due to moisture changes. Canvas belting, like 

 rubber belting, is made in various thicknesses from two- 

 ply up. A four-ply belt is usually considered the equal of 

 a single leather belt. 



45. Length of belts. Length of belts is usually deter- 

 mined after the pulleys are in place by wrapping a tape 

 line around the pulleys. When this cannot be done con- 

 veniently, the following approximate rule taken from 

 Kent's Mechanical Engineer's Pocketbook may be 

 used: "Add the diameter of the two pulleys, divide by 

 two, and multiply the quotient by 3^, and add the 

 product to twice the distance between the centers of the 

 shafts." 



46. Lacing of belts. Lacing with a rawhide thong is 

 the common method used in connecting the ends of a belt. 

 A laced belt should run noiselessly over the pulleys and 

 should be. as pliable as any part of the belt. The holes 



