On Wednesday, July 17, 2013 2:38:21 PM UTC-4, Bob S wrote:





The pulley change is an interesting idea; I should look into that. I

don't know what the curves look like for these propeller fans, but I

assume that slowing down the fans would reduce the load on the motors

and might cause them to last longer. It would have to make them last a

LOT longer to be really useful.




Bob

The simple calculations shown in the Grainger catalog shows the hp required varies withe Cube of the speed. Their example shows increasing the rpm from 5000 to 6000 requires 1.73 times as much hp. So reducing the speed a little will have a large effect on the hp and life.

Dan