Mr. Generator

106 North Medina Street
Medina, Ohio 44256
800-232-3208

A division of Thermal Aire Technologies, Inc.

Pulley Diameter Formula

The generator shaft must turn a consistent speed of 3600RPM. The formula for sizing a pulley is:

 

Engine Speed (RPM)

=

Pulley Diameter (Generator)

Generator Speed 3600 RPM

Pulley Diameter (Engine)


Example: You want to operate an engine at 2400 RPM. You have a 7.0" diameter pulley on the engine. The generator always operates at 3600 RPM.

 

Engine Speed 2400 (RPM)

=

Pulley Diameter (Generator) X

Generator Speed 3600 RPM

Pulley Diameter (Engine 7.0")

2400 x 7.0

=

16800

3600

3600

=

4.66"


The diameter of the pulley in this example should be 4.66". If the exact size of the pulley is not available, you must slightly adjust the engine speed to compensate for the pulley diameter.

NOTE: The minimum engine horse power required to carry the full electrical load of the generator requires enough RPM's. Most one and two cylinder engines have rated horse power at 3600 RPM. Slower engine speed results in less horse power.