MULE PULLEY STANDS 85 



mule pulley drives, and in fact of all drives where the belt 

 joins two pulleys that are not in the same plane, is that the 

 belt must be delivered squarely on the pulleys, but that it 

 can leave them at any angle within reasonable limits, it is 

 evident that the mule pulleys can be placed in any location 

 desired. If local conditions make it advisable, the mule 

 pulleys can be so placed as to require the belt to leave 

 either or both of the main driving pulleys in a horizontal 

 position. The method of laying out the drive is the same in 

 any event. The only variation will be in the relative length 

 of the dimensions L and L' '. The sum of these is taken and 

 the position of the circle A' is then determined as before. 

 The angle of the pulleys will be the same, as will the length 

 of the belts. 



The fact that it is possible to vary the position of the 

 mule pulleys without affecting the working of the drive makes 

 it possible to place both mule pulleys on the same shaft. 

 Referring to Fig. 28, if the belt travels in the direction of the 

 arrows, it is evident that if the lower mule pulley be moved 

 in the direction that the belt travels, the belt will still be 

 delivered squarely to pulley B. It will, of course, leave 

 pulley A at an angle, but this will have no effect on it if the 

 mule pulley is maintained at the same angle as before, since 

 the belt will still be received squarely by the mule pulley. 

 If the distance between the axes of the mule pulley shafts 

 is not excessive, the lower mule pulley may be moved until 

 the two shafts are in line, as regards Fig. 28. They will, 

 however, still be out of line as regards Fig. 29. By the same 

 process of reasoning as before, however, it is evident that the 

 upper mule pulley can be similarly moved in the direction of 

 the belt travel until its axis is in line with that of the lower 

 pulley in Fig. 29. The axes of the two mule pulleys then will 

 coincide, and in their new locations they can be mounted 

 on the same shaft. 



The above considerations apply to drives where the main 



