XVI
A BELTING AND PULLEY CHART[12]
Rule 1. Pulley Speed.—When the diameter of both pulleys and the speed of one is given, to find the speed of the other: Place the points of spacing dividers upon the two given diameters in inches upon the scale (Fig. 97); then raise the dividers, keeping the space obtained, and place one point on the given speed and the other above it for speed of S, or below it for speed of L (S and L meaning smaller and larger pulley, respectively). This point will fall upon the required speed.
[12] Contributed to Power by A. G. Holman, M. E.
Example: If the two pulley diameters are 10 and 25 inches and speed of larger pulley is 120 revolutions per minute, what is speed of small pulley?
Place the points of dividers on 10 and 25 on scale A, then lift the dividers and place one point on 120 and the other above it upon the scale; the other point now rests on 300 as the speed of S. If the speed of S had been given, one point would have been placed at 300 and the other below it, falling upon 120, the required speed of L.
Note.—In applying this rule, if the speed comes beyond the range of scale A, the result may be read by carrying the space to the revolution scale on scale B, and proceeding in the same way.
