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adcoleman4

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I'm charged with designing a merry-go-round for a class project. It is to be driven by an electric motor and I chose to power it with a gear train. I need to pick a specific horsepower motor to drive the pinion and subsequent gears after it, finally leading to an inner ring gear that turns the whole structure.

My question is this, if the whole merry-go-round weighs about 21,000 pounds, how do I determine the amount of torque the inner ring gear must be applied to turn it at a speed of 4 RPMs?

I've got a good start but am not confident with my answer. I calculated the inertia of three separate bodies that comprise the merry-go-round and found that to be about 108,000 lbf-ft^2. At 4 RPM, I calculated the angular acceleration of the 36'-diameter merry-go-round to be 0.00833 rad/sec^2. I've found some equations online that say torque is equated by this equation:

τ = (I/g)*α and I got about 27.98 lbf-ft. That seems low for a 21,000 lb merry-go-round.

Can anyone on here tell me if I am correct or where I possibly went wrong?

And also could anyone give me any insight as to configure my gear train between the inner ring gear and the motor to accurately size the motor?

Thanks a lot!