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# Compound Belt drive total torque

## Compound Belt drive total torque

(OP)
Hi,

I was just wondering, what would be total toque of compound belt drive - having 3 shafts. As shown in the attached screenshot, middle shaft drives one shaft on either side.

would total torque needed by motor will be the sum of total toque of each shaft? Each shaft rotates at same RPM & same size pullies.

thanks,
pkpavv

3 in-lb

### RE: Compound Belt drive total torque

Your sketch appears to show different size pulleys.

Ted

### RE: Compound Belt drive total torque

Looks like each side is 1:1 ratio. If that is true torque is additive, each shaft exerts its 1 in-lb of torque on the middle driver, resulting in a total of 2 in-lb..

But that is the wrong way to look at the problem.

Conservation of power --> Power in = power out. Rotational speed * torque at input = that at output (minus friction).

-OR/ALSO-

T = F * r

Since tension is same for driver and driven pulley, TArA = TBrB for A/B side.
repeat for B/C side.

### RE: Compound Belt drive total torque

The drive shaft (B) has a stated torque of 1 in-lb from what source? It is driving two shafts (A and C) with 1:1 ratio that each have 1 in-lb torque. So was the OP a poorly worded question or does TheTick "torque science" apply? Obviuosly if the torque label on B-shaft was blank or zero, then the total would be 2 in-lb. Back to school!

Walt

### RE: Compound Belt drive total torque

#### Quote:

So was the OP a poorly worded question or does TheTick "torque science" apply?

Both

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