TAYLOR'S RULES 19 



less. The cost of maintenance and repairs of double belts 

 during a total life of 6.7 years, running night and day, amounts 

 to 1 1 times the first cost of the belt when under a total load 

 of 54 Ib. per inch of width. The cost through a term of 8.8 

 years amounts only to 30.4 per cent of the total cost. 



8. The best distance from center to center of shafts is 

 from 20 to 25 ft. The faces of the pulleys should be about 

 25 per cent wider than their belts. When practicable, belts 

 should be tightened by moving one pulley away from the 

 other. Countershafts should be mounted on frames and 

 raised in order to tighten vertical and diagonal belts. 



9. When it is necessary to run night and day through- 

 out the week and work without stopping, each important 

 belt should be supplied with an idler pulley, which can be 

 tightened upon it while running in case of slipping. Idler 

 pulleys work most satisfactorily when located on the slack 

 side of the belt about one-quarter of the distance from the 

 driving pulley. 



10. Belts should be cleaned and greased every five to six 

 months. 



11. Belts of any width can be successfully shifted back- 

 ward and forward on tight and loose pulleys to throw lines 

 of shafting in and out of use. The best form of belt shifter 

 for wide belts is a pair of rollers twice the width of the belt, 

 either of which can be pressed against the flat surface of the 

 belt on its slack side close to the driving pulley, the axis of 

 the roller making an angle of 75 degrees with the center line 

 of the belt. 



Comments on Taylor's Rules. Commenting on Mr. 

 Taylor's conclusions, William Kent 1 has compared the rules 

 for belting given by Mr. Taylor with some of the common rules 

 of thumb of the form H.P. WV^-c adopted by practical 

 mechanics. The practical mechanic very often figured that 

 a single belt one inch wide, running at a rate of 1000 ft. 



1 Transactions, American Society of Mechanical Engineers, vol. xv, p. 242. 



