78 LEATHER BELTING 



holes for the belt must be laid out with some care. A method 

 of laying out these holes is described in Machinery, September, 

 1912, by M. H. Ball, and is reproduced below and in Fig. 22. 

 From the end of the horizontal diameter at which the belt 

 leaves the upper pulley a plumb line is dropped to the floor, 

 and the point where it touches the floor is marked. This 

 is point L in the illustration. Through L are drawn on the 

 floor the lines XX and YY respectively perpendicular to the 

 lines of shafting on which the upper and lower pulleys are 

 carried. The outlines of the pulleys in plan are then traced 

 on the floor, these being ABXDLC and EFGHL respectively 

 for the upper and lower pulleys, each being symmetrical about 

 the center lines XX and YY. These center lines, which are 

 the projections of the horizontal diameters of the pulleys, 

 are next divided into eight equal parts, the divisions being 

 numbered as shown. The numbers should start at the end 

 of the diameters toward which the pulley is rotating, that is 

 at the end of the diameter at which the belt runs on the pulley. 

 Next divide the distance in inches between the center lines 

 of the shafts by the number of divisions laid out on the pulley, 

 and the distance from the center line of the upper shaft to 

 the floor by the quotient so obtained. The latter figure 

 represents the number of spaces on the pulley that the belt 

 at the floor will be away from the end of the diameter at 

 which it runs on to the pulleys, that is, the points / and K 

 in the illustration. From / as a center the arc MN is struck 

 with the line JM, perpendicular to XX, as a radius. The 

 arc is divided into eight equal parts and numbered from M 

 to N. The same number of spaces are taken on the arc 

 as were taken on the lines XX and YY, and the line OP is 

 drawn through the point / and the point on the arc so found, 

 PJ being made equal to JO. This line is the position of the 

 center line of one strand of the belt at the floor, while a line 

 parallel to OP through K, and of the same length is the posi- 

 tion of the center line of the other strand. 



