74 



LEATHER BELTING 



varies according to different authorities, as follows, F being 

 the width of the pulley and H the height of the crown, both 

 in inches: 



Morin H = o.iF 



Molesworth .H = ^F 



Earth H = 0.03 125-^ 



Scott A. Smith says that the crown should not be over -| in. 

 for a pulley of 24 in. face. The chart, Fig. 20, gives the 



FIG. 20. RELATION OF HEIGHT OF CROWN TO WIDTH OF PULLEY. 



height of crown for pulleys up to 12 in. face according to 

 Earth's formula. 



Arrangement of Pulleys. If possible machinery driven 

 from overhead shafting should be so arranged that the belt 

 will make an angle from the vertical of not less than 45 de- 

 grees. Never, unless it is absolutely impossible to avoid it, 

 should the driving and driven pulleys be in the same vertical 

 line. Care should be taken to arrange the pulleys in line with 

 each other, the tops of the crowns being aligned. Otherwise 

 the belt will tend to stretch unevenly and to run crooked. 

 Machinery should be so placed that the tight strand of the 

 belt will be the bottom strand. If, however, the machines 

 are so placed that the pull of the belts at alternate line shaft 

 pulleys is in opposite directions the wear and strain on bear- 



