Re: [CAD_CAM_EDM_DRO] Re: Novice - Stepper Motor questions

Lyle Cox wrote:

>
> How could I test a surplus stepper motor for torque ? (oz inch)
>
> When a stepper motor has a rating of NN oz inches, is that holding or
> turning torque? (or is holding and turning torque the same on stepper
> motors?)

Usually the rating is holding torque. Running torque falls off from that
value rapidly as the motor speed goes up.

To test one build a disk of a fairly large size- maybe 4-8" dia, that
can be mounted on the shft. Wrap a string around the disk a few turns
and hang weight on the string. When you reach a weight that lets it slip
you can calculate the torque by weight* radius. Do this with a disk, not
a simple lever arm so the radius stays constant.

If you want to measure a running torque you can step the motor and wind
up the string, at least for a few feet, with a fixed weight. Make
multiple tests with more weight until it slips. RUns tests both lifitng
the weight and lowering it at various speeds.

All sounds very neat and simple, and I have been planning to do this to
several motors I have, but I just havent quite gotten around to it yet!

ron