FARM MOTORS 323 



ient to attach, but are not so durable as those made of metal. 

 Metal pulleys are sometimes covered with leather in order to 

 increase the friction of contact with the belt. Pulleys from 

 which belts are not to be shifted should have a crowned 

 face. This will cause the belt to keep in the center of the 

 pulley, owing to the fact that the belt 

 always tends to run to the highest part 

 of the pulley. The pulley which supplies 

 the power is generally spoken of as the 

 driver, and the one receiving the power is 

 designated as the driven pulley. 



Calculating the Speed. It is an easy Fig. 203^ a plain 

 matter to calculate the speed or the diam- cast " iron P ulle r- 

 eter of the pulley, when it is remembered that the diameter 

 of the driving pulley multiplied by its revolutions per min- 

 ute is equal to the diameter of the driven pulley multiplied 

 by the number of its revolutions per minute. If any three 

 of the four quantities involved are known, the fourth may be 

 easily obtained. 



Link Belting. A common method of transmitting power 



in agricultural machinery is by means of 



link belting running on sprockets. Link 



belting is positive in its action, as there 



can not be any slippage. It is very strong, 



but its use is often objectionable on account 



of the noise which it makes and because 



Fig. 204. a spnt it cannot be operated at high speed. 



There are several styles in use; in some 



the links or sections are made of malleable iron, and in 



others of pressed steel. Again, some expensive chains are 



made of steel rollers with short steel links riveted on the side. 



Rope Transmission. Where power is to be transmitted 



some distance and where the shafts are not parallel 



