Sheave Ratio Calculation

To calculate the sheave ratio required, first divide the motor speed by the gear drive output speed to find the total ratio required. Select the nominal gear drive ratio that is closest to the total ratio required.  Then divide the total ratio required by the actual gear drive ratio for the model selected to find the sheave ratio required.

For example, if the motor speed is 1750 rpm and the gear drive output speed is 35 rpm, the total ratio required is 50. The nominal gear drive ratio closest to the total ratio required is 40.  For a 207TR, the actual ratio is 39.124.  Therefore, the sheave ratio required in this case is 1.278.

When selecting the sheave, make sure that it is larger than the minimum diameter given in the Minimum Sheave Diameter section, and place the sheave as close as possible to the gear drive housing.