Final drive torque

[Joe Clohessy]

I would like to know if someone would be able to help me. I want to find out the ammount of torque at the output shaft on my transmission. Is there a way of taking the motor torque and doing some math with the gear reduction in the transmission? Given I know the RPM of the transmission output shaft. If someone could make a Excel sheet not just for me but for everyone that would be helpful to most. Thankyou

[NoodleKnight]

I believe this is what you're looking for: JVN's FIRST Mechanical Design Calculator (http://www.chiefdelphi.com/forums/papers.php?s=&action=single&paperid=252)
I made my own version of it, but same concept. Very useful tool.

[sanddrag]

If you know the Output RPM and the motor RPM, you have your overall ratio. Speed is inversly proportional to torque. That means, when your speed goes down, the torque goes up. If the speed is cut in half, the torque is doubled.

Say you have a motor that is 5000 RPM with 2 N-m (newton-meters) of torque. It is put through a 12:1 reduction (or 1:12 depending on how you look at it) which makes the transmission output shaft speed (5000/12) 417 RPM. The torque on the output shaft will be 2*12 which is 24 N-m. Other common units of torque are pound-feet (called foot-pounds by some) represented by lb-ft and ounce-inches represented by oz-in.

I hope this helps.

If you have any more questions, just ask and I'll be back here to answer them. :)

[ConKbot of Doom]

That all works in theory... and you have to know the theory to understand the rest. But in real like efficiency of the gears really messes with things. We had a gearing for our arm that should have worked, but it didn't because efficiency of the gears.

So don't rely on something that *should* be right on at the limit, could very well lose a lot of torque to inefficiencies in the gears, and not work.