Prony Brake to test a 3/4 HP sewing machine motor. Video.

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Well-Known Member
HMEM Supporting Member
Mar 8, 2019
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Charlottesville, VA
I was in the CNC forum looking for some recommendations for a fraction horsepower variable speed motor. I got a recommendation from SteveM for something much better than what I had in mind. It is a 110VAC sewing machine servo motor with controller and several handy user-settable parameters. Max speed is 4500 rpm, 550 watt, 3/4 Hp, 4NM of torque. The display shows the rpm in real time. The speed is variable, and you can set the max speed with the parameters. Forward and reverse. Adjustable dynamic breaking. PID speed control factor adjustments. It appears to be well made and nicely finished. It is quiet, too. The torque of a DC motor is supposed to be fairly constant throughout the rpm range (I think) and this motor seems to exhibit that (based on limited testing).

I plan on using it to drive some test set-ups at various known speeds.

All for $92 USD on ebay. I am quite pleased.
All comments, including "cheesy looking set-up" are welcome, LOL.

I originally posted seeking info about a motor here:
but I think the prony brake testing is of more general interest, so I am posting that in this forum.

Last edited:
I was watching the video again and one thing that caught my eye was that when I loaded the motor down with the prony brake, it maintained its rpm. The rpm display is real time. I have loaded the motor heavy enough to make the rpm drop and the display also shows that phenomenon in real time.

Here is a picture of what came in the box.


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