34 



FARM MACHINERY 



less, less power is lost 

 by slippage, and the di- 

 rection of transmission 

 may be easily changed. 

 Transmission ropes are 

 made of hemp, manila, 

 and cotton. Cotton rope 

 is not as strong as the 

 others, but is much more 

 durable, especially when ' 

 run over small pulleys or sheaves. The 

 groove of the pulley or sheaves should be 

 of such a size and shape as to cause the 

 rope to wedge into it, thus permitting the 

 effective tension of rope to be increased to 

 its working strength. 



Fig. 20 illustrates a rope transmission 

 system. Transmission ropes, to insure the 

 highest efficiency in respect to the amount 

 of power transmitted and the durability of 

 the ropes, should have a velocity of from 

 3,000 to 4,000 feet a minute. To lubricate 

 the surface of the rope and prevent it from 

 fraying, a mixture of beeswax and graphite 

 is good. 



52. Wire rope or cable transmission. 

 For transmission of power to a distance 

 and between buildings, wire rope has many 

 advantages. If the distance of transmis- 

 sion be over 500 feet, relay stations with 

 idler pulleys should be installed to carry 

 the rope. Pulleys or sheaves for wire rope 



should not have grooves into which the FIG. 20 TRANS- 

 MISSION OF 

 rope may wedge, as this is very detrimental POWER BY ROPES 



