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Unread 01-05-2008, 08:44
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Re: How much torque can the Dewalt Trannies take?

This is a good problem to do the math on. When you go with a lower overall ratio and therefore more speed, the back drive torque into the transmission actually goes up. Where this applies to this year's game is that the ratios that people were using to get the really high speeds allow for more backdrive torque into the transmissions. We had a dual CIM Single Dewalt design that we were intending to use. This design had a reduction before the Dewalt as part of the 2to1 interface. We decided against it when we ran the stress calcs on the output shaft of the Dewalt. With the speeds we wanted the stress on that component would require a pretty exotic material (approximately 200ksi). While I am sure they are using an extremely strong alloy for that shaft, the factor of safety was just too low (1.2 top depending on exact alloy). One thing for teams to remember is that sometimes the forces coming back into the driveline (especially when a defender hits you at 10 fps) can be way higher than the forces going out. Again this was for our specific design. We ended up going with the old school AM shifter and with some small modifications. They were bullet proof in this design.

If there is a big request for it I will dig those calculations up and put together a paper otherwise I recommend that people run the exercise for themselves.

All that being said, I think the Dewalts are an excellent choice for typical FIRST games. We used them in 05, 06, 07, and 08 in various applications. We have had problems, but that was due to us thinking that we knew better than the NBD paper. Should you use DeWalt's follow that paper to a T and respect every detail. The biggest problem we had is that when we didn't follow the paper, we didn't get immediate failures, we got the kind that only show up after say 8 or 9 hard matches. This leads to a very stressful Saturday.