Motor sizing

[JeanMicheling]

I'd like to know what is the best way to size a motor in function of a tool inertia. My tool inertia is 72lbf-ft^2 and referring on motor's chart, a 75 hp would be required. I find that really big for a tool that just need to reach full speed and their will be no external applied to the tool (because it's a bench test). Does someone hava an idea?

 

[aolalde]

Windage load is proportional to the torque (friction forces) developed on the spinning wheel surface due to the air disturbance created when the wheel increases speed, multiplied by the wheel speed.
That should be added to any other friction (bearings) or torque taken from the spinning shaft.

 

[jraef]

Without knowing what the tool is, I don't think one can categorically state that windage is not a serious factor at any speed. I can feel a lot of air flow off of a 3600PM grinding wheel, as well as a 600RMP lawn mower blade, and flow = load!

That said, I agree that it is most likely not the most serious factor here, and reiterate that more information on the load would be helpful for us to help you any more.

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