84 LEATHER BELTING 



tangents TT' and 55', which represent the inclination of the 

 belt with respect to the pulleys at all points along its length. 

 At the point a where these tangents intersect the line ZZ the 

 lines ab are drawn parallel to the line XX. The diameter of 

 the mule pulleys having been decided, the point d is set off 

 on ab at a distance from ZZ equal to half the diameter of the 

 mule pulley. Through d is drawn the line ef parallel to ZZ. 

 This represents the center of the mule stand. The lines 

 gh through the point d, perpendicular to the tangent TT' or 

 SS' will be the axis of the mule pulley. The points c and j 

 are laid off on either side of the point d on the line gh, dc and 

 dj being made equal to half the width of the mule pulley. 

 The bearings of the mule pulley will lie on the line gh out- 

 side of the points c and j, and their position with reference to 

 the center lines of the main pulleys can be ascertained by 

 scaling the drawing or by calculation, as preferred. If 

 the drawing is laid out to a large enough scale, scaling will 

 be accurate enough for all practical purposes. The axes of 

 the mule pulleys will necessarily be inclined from the vertical, 

 not only as regards the plane ZZ through the middle of the 

 face of the pulley A, as shown in the elevation Fig. 28, but 

 also as regards the plane WW through the middle of the face 

 of pulley B as shown in Fig. 29, and this angle will be the 

 same in the two views. Lines through the points c and j 

 parallel to the tangents TT' and SS' will be the major axes 

 of the ellipses representing the upper and lower sides of the 

 mule pulleys in the two views in Figs. 28 and 29. The posi- 

 tion of the center of the mule stand and of the mule pulleys 

 in the end view of the drive, Fig. 29, is determined in exactly 

 the same manner as the similar points in the elevation in 

 Fig. 28, and no further explanation is necessary. The vari- 

 ous points in Fig. 29 are designated by the same letters 

 as the corresponding points in Fig. 28, and the same explana- 

 tion will apply. 



If it be borne in mind that the governing principle of 



