Do we have enough force to safely move our arm?

We have an arm that we have measured the required torque at 90 degrees is 32Nm with an actual torque meter at the axle. We are direct driving a 1/2 inch hex shaft through Max Spline with two Neos backed up by 100:1 MAX Planetary Gearboxes. Based on empirical data from REV we should get ~ 500 Nm static load. That is better than 10x safety factor. We have not driven it under power yet – plan to in the next day or two. What is everyone’s prediction of reliability? My first time with Brushless Motors – a lot of experience with CIMs – I look at it and … I don’t know.

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You should be just fine. I think a lot of teams are going to have similar numbers this year!

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I’ll show you how to use my calculator to answer your question. You said you measured the torque needed to hold the arm as 32 Nm, so we can write that as a force of 32 N at a radius of 1 meter. We’ll set the motor type to two NEOs, and the ratio to 100:1.

So we can see that at free speed (when there’s no load on the arm, at the top of the rotation) it will spin at 0.95 rotations/sec, and loaded speed (at maximum load, when the arm is parallel to the floor) it will spin at 0.88 rev/s. In the loaded case, it will take 8.86 Amps to move the arm at that speed, which is plenty low. And it will take 0.82 Volts to hold the arm horizontal at stall, which according to the motor testing on REV’s website it can hold for longer than an entire match.

So bottom line is, you should be fine with that setup.

https://ambcalc.com/mechanism?load-u=1&lin_f-u=1&lin_l-u=1&st_load-u=1&radius-u=1&radius=1&load=32&motor=NEO&mot_num=2&=&rat-c=^&rat=100

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Awesome information to have and a great resource!! Thank you.

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While you have plenty of torque, you might want to consider gearing down the motor more to make the speed more controllable. 0.88 rev/s (~320 degrees per second) is really fast.

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