Motor Physics Question

[ckb614]

If I need to hold and rotate a 120lb load using a motor (at the pivot point) from horizontal to vertical at a distance 10 inches from the pivot point, I would need a holding torque of 1200in-lbs right? Is it possible to increase the holding torque of a motor using gears? or do you just increase it's torque in motion? Can anyone suggest a motor for this application? Stepper or Servo?

 

[GregLocock]

make sure you've got your units right, but yes you need to multiply the force by the moment arm.

You can use gears to increase the torque of a motor. In this case you might find a worm drive has some advantages.


Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[IRstuff]

You should use a gearmotor or a screw or pinion drive. Otherwise, you'll be burning power like crazy holding the object in the up position.

One option to avoid that is to counter balance the system so that the holding torque is minimized.



TTFN

FAQ731-376
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[MintJulep]

Motors are not intended and generally not designed to "hold" at a fixed position.

Motors are design to spin.

 

[drawoh]

ckb614,

I know a stepper motor will hold its position. Will a DC motor really do this, by some means other than exactly matching the rotating moment? In either case, the motor is consuming power, and converting all of it to heat.

If you select a self locking worm drive, the system can be powered into its position, and left there with the power off. Generally, you need a ratio of something in excess of 40:1. The analysis that will get you the correct answer to this, will be explained in your machine design textbook.

JHG

 

[ckb614]

Thanks for all the responses!