is there any easy way to know the torque of a stepper

[Urgundiz]

The steppers I can adquire where I live (spain) are mainly surplus, so the info is with luck, an sticker with V and A/phase, angle and no much more. As are surplus, are old models too (but at least are Hybrid and not of Variable Reluctance ).

I am interested in know any easy way to register the approximate torque of a motour in order to discard or reserve it. In fact, I do not know if exist only one kind of torque or more than one..

Any help? thanks in advance

/U

[cnczane]

I apologize for the sophmore-level of my reply, but wish maybe to provoke others into clarifying.

I think:
-- Torque is a Force times the Radius at which it is applied
-- Stepper motor torques are not constant (exc. at very low speed). (Stepper tutorials speak of the Torque vs. Speed curve which is flat at low speeds until some "knee" on the curve is reached above which speed the torque drops off roughly linearly.)

I can imagine putting a spool on the motor shaft and attaching a, long, lightweight line to both it and a known weight (aka force), and applying voltages (with current protection for the motor).

In this experiment the Torque will be fixed by the weight and the radius of the spool, and you're interested in how fast the motor can raise the weight. (Mark the line at two points and measure the time between the two. That distance divided by the spool's circumference = the revs, and rpm is revs divided by the time you measured converted to minutes.)

That gives you one data point. Change the weight or the spool to get others.

[If you think this is nuts, you should see the machine I designed...]

[abasir]

Urgundiz,
Check out this site for simple physical solution for estimating torque. The info is near the bottom of the page.
http://www.hans-w.com/cnc.htm

[Urgundiz]

Thanks to all folks, the link provided shown me a useful way.

By now I'm looking for copier repairers here in my city in order to scavenge some useful steppers. Looking at the ones I got I think are waaay unuseful. NEMA17 with very low V and high A (about 2V, 4A) and mainly bipolar, so the driverboard will be expensive (sure) and (probably) the torque low.

If any spaniard lurks this forum and know some useful place to locate good steppers, please PM me.

TYA

/U