il 



The following table, calculated from this formula, gives the limits in wliicli 

 the power transmitted by a shaft would be absorbed by the friction of the bear- 

 ings under the above conditions: 



lliameter of Shaft in 

 Inch s. 



Length in Feet Wbfu 

 Total Power is Ab- 

 sorbed. 



Length When 

 i,-o(* per cent. 



Length When 

 ;,^75 per i-ent. 



In the ordinary transmission of power by shafting we find the shaft loaded 

 witii pulleys and the power taken off by varying amounts throughout its entire 

 length. It is unusual, except in short lengths, to receive the power at one end 

 and transmit it at the other. Moreover, in long shafting the head, or receiving 

 shaft, is usually situated midway between the ends, and the power distributed 

 more or less uniformly from this headshaft to either end ; therefore, in estimating 

 the power absorbed by friction in ordinary mill or factory shafting loaded with 

 pulleys, the previous formuhe do not apply, as these relate only to those cases 

 where power is taken off at the end of the shaft. 



The conditions of practice, as we find them in actual transmissions are so 

 various, that it is difficult to lay down any general rule by which the power ab- 

 sorbed by friction may be determined. The number and weight of pulleys and 

 couplings, the intensity and direction of belt-pull, the condition of bearings and 

 their lubrication ; these all affect the amount of work lost in friction. 



For the ordinary factory shafting, from which power is taken fairly uniformly 

 throughout its length and distributed horizontally to counter or auxiliary shafts 

 situated on one or both sides of the main shaft, there will be three general cases 

 to be considered, and each of these will be modified, depending upon the directioa 

 of the belt to and from the main shaft. 



The friction will evidently be proportional to the weight of the shaft and the 

 unbalanced belt-pull acting on the shaft. 



The weight of pulleys, belts, clutches and couplings carried by the line shaft 

 will vary from about one and one-half to three times the weight of shaft, so that 

 the total weight on the bearings will vary from two and one-half to four times the 

 weight of shaft; for head and jack shafts the total weight will probably vary from 

 three to five times the weight of shaft. 



