20 LEATHER BELTING 



per min., that is c = 1000, would transmit one horsepower; 

 whereas, Mr. Taylor's rules indicate the use of a velocity 

 constant of 950 to uoo for a double belt. Assuming that 

 a double belt is twice as strong or will carry twice the power 

 of a single belt, Taylor's rule calls for a belt almost twice 

 as large as was common practice at the time of the experi- 

 ments. This would result in a first cost for belting double 

 that called for by even the most liberal of the then existing 

 rules. Inasmuch as the Taylor practice was aimed at finding 

 the belt which would transmit a given horsepower at the least 

 cost for maintenance, repair and interruptions to manu- 

 facture rather than the smallest belt which would transmit 

 a given horsepower, the rules are on totally different planes. 

 The question might be raised as to why the Taylor rule using 

 uoo for a velocity factor for a double belt is correct when it 

 has been found possible to obtain such good results from a 

 belt proportioned with a velocity factor of only 550 for a 

 single belt; that is, a belt only one-quarter as heavy as a 

 belt called for by the Taylor rule. The answer is that in 

 many cases belts designed under the old rule are really 

 running under the Taylor rule. For instance: A belt pro- 

 portioned for and estimated to be driving four horsepower 

 is usually driving only one horsepower. A belt is usually, in 

 mechanics' or millwrights' practice, made wide enough to 

 drive a machine at the maximum power guessed to be required 

 at any time. If this amount of power was required to 

 be transmitted continually, the belt would probably need 

 tightening once a month, and would be worn out within two 

 years. Having to transmit the maximum power only occa- 

 sionally for brief intervals and averaging a power only one- 

 quarter of the maximum, it may require retightening only 

 once a year and would last for twenty years. It would, 

 therefore, be used as an eminent example of the merits of the 

 old rule, and give rise to conclusions which would be wholly 

 incorrect. 



