CHAPTER II 

 TRANSMISSION OF POWER 



It is the function of all machines to receive energy 

 from some source and distribute it to the various parts 

 where it will be converted into useful work. This chapter 

 will treat of the devices used in the transmission and dis- 

 tribution of power and the loss of power during trans- 

 mission. 



39. Belting. Belting is one of the oldest and most com- 

 mon devices used for the transmission of power from one 

 rotating shaft to another. The transmission depends 

 upon the friction between the belt and the pulley face; 

 that is, the belt clings to the pulley face and causes it to 

 rotate as the belt travels around it. The sides of a belt, 

 when connecting two pulleys and transmitting power, are 

 under unequal tension. The effectual tension or actual 

 force transmitted is the difference between the tensions 

 on each side. The effectual tension multiplied by the 

 velocity of the belt in feet a minute will give the foot- 

 pounds of work transmitted a minute. Thus the power 

 varies directly with effectual tension and the velocity of 

 the belt. 



40. Horse power of a leather belt. It is possible to 

 make up a formula with the above quantities to be 

 used in the calculation of the power of a belt or the 

 size required to transmit a certain power. The fol- 

 lowing is a common rule for single-ply belting, which 

 assumes an effectual tension of 33 pounds an inch of 

 width : 



