stepper motor torque

I once spoke to a guy who worked at a stepper motor manufacturer. He
claimed they routinely tested motors by wrapping string around the
output shaft. One end it connected to a known mass, the other connected
to a spring balance. The difference is the torque. Load it up until it
stalls.

Use two spring balances to make a simple Prony brake.

Try Google and/or here:

http://www.tpub.com/content/engine/14037/css/14037_53.htm

Pete Harrison

maybe a $2 spring balance, and a lever arm ?
-jg

wv9557@yahoo.com schrieb:

Alternatives:
1. Estimate the torque generated via an FE analysis, but you would have
to know: cross-sections, material data, etc.  Very, very theoretical
approach.

2. Measure, but time-consuming an expensive.

3. Probably the most practical approach: buy a stepper-motor that comes
along with the complete documentation.

Regards,
Peter.

1) Replace it by a stepper motor you *can* find documents for ;-)

2) Build your own torque-meter.  Since you x-posted this from a
robotics newsgroup, I'll boldly assume you know enough about mechanics
to pull that off.  A lever arm, a counterweight and maybe some gears
should do it.  If you want to measure power instead of torque, you
might want to consider Joule's method of measuring mechanical work in
terms of generated heat --- or drive a dynamo.

3) find a cheaper torque meter.  Torque wrenches for car wheel nuts
are generally a good deal cheaper than 600 bucks.


--
Hans-Bernhard Broeker (broeker@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.

http://www.romanblack.com/stepper.htm

Just as important as torque in some applications, is finding
the upper and lower resonance frequencies. Unless this is
spare-time job, get the documentation for the motor!

Stephen


--
Stephen Pelc, stephenXXX@mpeforth.com
MicroProcessor Engineering Ltd - More Real, Less Time
133 Hill Lane, Southampton SO15 5AF, England
tel: +44 (0)23 8063 1441, fax: +44 (0)23 8033 9691
web: http://www.mpeforth.com  - free VFX Forth downloads

There is more than one torque of interest.  There is the stall torque,
which most of the replies to your query address, and there is running
torque.  The latter depends on the speed, generally the faster the motor
steps, the less the torque, but also on the drive method:  direct, R/L, or
chopper drive.  The drive method makes a big difference in complexity,
cost, and efficiency as well as torque.

John Piccirillo

Having played around with turning a drum to mount on a NEMA 23 and
winching a weight up and down with it, realistcally I'd have to say
it's not worth the trouble.

Just bolt the motor onto whatever you want to use it for and see if
it's up to the task.  If it can do it slowly but not quickly, look into
the driver circuit.  If it can't do it, buy a bigger motor.  Chances
you are will be dealing with either NEMA23 of 34 size mounts so you can
change the motor a lot without changing what it bolts onto (off the top
of my head, I'm going to guess you could make a mounting plate with
bolt holes to support either size)

Also consider using toothed timing belts.  These let you have variable
gear ratio, absorb vibration, and tolerate the kind of shaft
misalignments you are likely to introduce in anything built without
carefull use of precision machine tools.  Of course you can also buy
misalignment couplings...