# Thread: Motor torque

1. ## Motor torque

Hi there

I need to calculate motor speed and reduction on a drive wheel.

the wheel is 2" diameter and is pulling a wire that is pinched between it and another roller. I'll need 100lbs of pull on the wire. I'll need to pick a dc motor and reducer to get this and we already got it wrong once...

2. Motor torque minimum = 100lbs x 2" = 200 lbs-in.

With a 3:1 factor of safety you will need 600 lbs-in motor.

3. Thanks. Will speed be a factor? Ill want to run that at 200 rpm.

4. Originally Posted by shiloh
Thanks. Will speed be a factor? Ill want to run that at 200 rpm.
Yes, you need motor that is torque rated at that rpm or gear it to perform optimally.

5. Originally Posted by Kelly Bramble
Motor torque minimum = 100lbs x 2" = 200 lbs-in.

With a 3:1 factor of safety you will need 600 lbs-in motor.
Kelly,
The wheel is 2" diameter. Wouldn't the moment arm be 1"? So the calculation is 100 lbs x 1" = 100 lbs-in?

6. Originally Posted by jboggs
Kelly,
The wheel is 2" diameter. Wouldn't the moment arm be 1"? So the calculation is 100 lbs x 1" = 100 lbs-in?
Yes, you're right.. hope the op caught my mistake

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