Can Motor Torque: Lack Of.

I've recently found that some 12 V. DC can motors have *very* little
torque when compared to the older open-framed sort, and it seems that
even the can motors themselves vary quite a bit in torque from one
model of motor to another. In fact, three of my can-motored steam
locos have so little torque that you can easily stop the drivers just
by pressing on them lightly with a cotton swab while you're cleaning
them. (This doesn't harm the motor; just stalls it until you release
the tension.)
Needlessly to say, this lack of torque severely limits the number of
cars these 3 locos can pull, and I'd have already replaced the motors
except that I've not been able to find anyone who sells can motors
that lists their stalling torque! All that seems to be available are
their dimensions and their maximum RPMs at 12 V.
So, that being the case, can anyone think of an easy way to test the
stalling torque of a small electric motor, or do I just have to grab
the driveshafts of the different motors and see if I can feel any
A small meter such as this seems as if it would be a natural for some
company such as Micro-Mark, but I can't recall ever having seen one.
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Looking at a Micro Mark catalog p77 #82884 - flat can motor stall torque @12v 160gm-cm/1.5a
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Thank you, Ray; that's one.
But until all or most suppliers give similar ratings what I really need is a method to test motors against each other in order to find out how they compare.
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Understood. Too bad they don't list manufacturer - I would expect it would be easy to get info from them.
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The simplest torque meter woulg be a beam (stripwood, plastic) you could mount on the motor shaft. (at the center of the strip) You could then hang small weights on the end which would give you gram/mm or inch/ounces of stall torque. You would probably need a separate piece of strip for each shaft diameter and a screw to lock it in place. A rough and ready assembly would probably give you a result within 10% of the correct figure, which would be close enough and far better than the finger squeeze test :-) For 99% accuracy you'd need the top surface of the strip where you hang the weights in line with the center of the shaft.
Regards, Greg.P. NZ
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Greg Procter

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