Measuring Torque without a dyno

[hmic21]

I was wondering, what is the easiest way to measure torque on a 1hp dc motor?
I looked on their web site, and the motor manufacturer didn't have torque vs. speed curves. All they had was something like:

Torque(in-lbs): 0 35 70
Current(Amps): 2.35 35.5 69.4

I came up with some numbers but is it possible to get an accuarate torque rating by simply using this figure?

Thanks,
HMIC

 

[Skogsgurra]

It depends on how accurate you need to be. The motor obviously has 2.35 A armature current when not loaded. At what speed is not told. The torque "constant" is 35/35.5 = 0.99 Nm/A and 70/69.4 = 1.01 Nm/A without compensation for idling current. This fact alone points to a possible accuracy around 1 percent.

By calibrating statically and also compensate for speed dependent friction, eddy current and windage losses, you can probably reach about .5 percent or better. It is possible that temperature compensation may be needed. Or that measurements are taken at a constant motor temperature, which can be tricky.



Gunnar Englund

http://www.gke.org