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Unread 30-04-2008, 17:01
Mr. Van Mr. Van is offline
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Re: How much torque can the Dewalt Trannies take?

Robodox also used 2 CIMs driving 1 Dewalt in a setup very similar to RUSH.

We used a 3:1 belted reduction from each CIM to the input of the Dewalt. The output of the Dewalt directly (via a coupler) drove the center wheel of a 6WD 1/8" center drop drive train.

(RUSH used a slightly lower geared reduction before the Dewalt.)

Some observations:

The Dewalts are planetary transmissions. As such, they have a considerably lower efficiency than a gearbox using only spur gears. (They also take up less space for the same reduction.)

You've got to make sure you hold the actual transmission really well. The original housing from the Dewalt drill is best for this. We found that our major point of failure was the actual transmission spinning inside the housing (we didn't use the entire drill casing - our mistake!) We found this out in testing and never had a problem in an actual match.

Shifting is not always smooth - especially using a single servo to hit all three gears. It is possible to fail to shift - leaving you in neutral unless you quickly shift back to your original gear. Shifting is easiest when under power with a light load. Shifting the Dewalts was our major problem this year. At one point, we thought we had broken a tooth on one of the gears in the Dewalt, but after taking it apart, we couldn't find our what was wrong. Our best guess was that it wasn't shifting completely for some reason. RUSH quickly figured out that they were better off just keeping them in a single gear for the 2008 game.

We have made an alteration to the setup in the NBD paper. In NBD, the planet gears that mate with the gear on the drill motor are removed along with their supporting pins. Then the sun gear is reamed out to be fit onto a shaft. Instead of making this alteration, it is very possible to use the 4 pins that hold the planet gears to drive the sun gear by making a simple coupler. No machining of the Dewalt! This setup worked well for us the past two years and is especially useful when mating two motors to the Dewalt. (Any problems observed with our robots were from other sources.)

In the end, the difficulty in mounting the completed gearbox and the reduced efficiency as well as the costs required for additional hardware (belts, pulleys, bearings, etc.) have turned us away from the Dewalt for the near future.

Andy, the check will be sent soon.

-Mr. Van
Coach, Robodox
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