How Do I Calculate Pulley Sizes to Maintain RPM in Exhaust Fans?

[marksmithlegends]

can you help?

I have a restaurant exhaust fan with a drive pulley of 2" and a shaft pulley on the fan of 7 and 3/4 inches. The belt that fits this is 21/32" width. The belts keep wearing out very quickly. I think that larger pulleys would solve the problem. If I doubled the size of the drive pulley, what size would I need to make the driven (fan) pulley to keep the same RPM (about 700 to 750)

Thanks for the help!

Mark

 

[Bystander]

Double. You knew that --- be sure you can get the appropriate belt length.

 

[Arctic Fox]

The belts keep wearing out very quickly. I think that larger pulleys would solve the problem.
Mark

I think the real problem here is not pulley size, but that the belt is too tight, or the berrings in the fan have gone bad; and the pulleys are no longer aligned with each other.

700-750RPM for an exhaust fan does seem a bit slow - I usually see them running at 1350RPM, but direct drive. Increasing the drive pulley would, of course, increase the RPM of the fan.