286 APPLIED SCIENCE 



about 70% more power than single ones of the same width. 



There are various formulas 

 given for finding the horse- 

 power that can be transmitted 

 safely, but a common rule 

 used by mechanics is : A single 

 belt one inch in width, running 

 at the rate of 1000ft. per minute, 



FIG. 141. Oak-Tanned Leather will transmit one horse-power 



without making the belt so tight 



that undue strain from journal friction will result. 



327. Fastening Belts. There are several methods of 

 fastening the ends of belts together. It is customary in the 

 case of wide belts (8 in. and over) to fasten the ends by 

 cementing. Narrow belts are fastened by lacing, wiring, 

 hooks, or any one of the numerous forms of belt-fasteners on 

 the market. The smooth or hair side of a belt should run 

 next to the pulley with the flesh side out, as this latter side is 

 softer than the other. While belts must be made tight enough 

 to run the machine, they should never be tight enough to 

 strain the journal bearings, or excessive heat and wear will 

 result. 



328. Sag of Belts. When placing in position shafts that 

 are to be connected by belts, care should be taken to separate 

 them by a proper distance, so that the belt may be allowed 

 to sag a little when running. No arbitrary rule can be given, 

 as the location is the determining condition, but a general 

 rule may be stated as follows: Where narrow belts are to run 

 over small pulleys, a separation of 15 ft. is a good average, as 

 the belt may then have a sag of about 2 in. For larger belts, 



