[ZZII 527]

I think I'm finally ready to put this one to bed.

We ran a BaneBots 42mm 256:1 gearbox at the Boston Regional on our main arm joint. It is followed by a 72:10 chain and sprocket reduction to the arm, which is fairly light, but not counterweighted and has no gas spring. We ran with Victor braking on and ran a position controller. We also used the arm to deploy our not-so-light ramp through a separate linkage, a movement during which the motor sees a significant load. The mounting looks like this:

http://www.chiefdelphi.com/forums/at...2&d=1171338765

I had made hardened tool-steel carriers (see my many posts above), but we ran on annealed tool steel, which is actually slightly SOFTER than the stock plates, to see how long it would last. It lasted the entire regional. There is some backlash, maybe 15-20 degrees, but I don't think it is near failure. I will probably change it out for another soft carrier in Atlanta to be safe.

The bottom line is you absolutely can use a 256:1 gearbox to drive an arm, provided you send it through significant additional reduction. If you are using a FP motor, 256:1 in series with anything less than 4:1 is almost too fast for an arm to rotate anyway. (Ours rotates at about 30-40 degrees per second with the 72:10 additional reduction.) I am now convinced that the ratio of the gearbox itself does not matter nearly as much as what comes after it. The FP torque isn't what kills the final stage, it is the load from the arm. The only way to reduce this is to use additional reduction between the gearbox and the arm.

I am happy that we stayed with the BaneBots gearbox instead of jumping ship, because it was incredibly easy to mount compared to the plastic gearbox and the large reduction was exactly what we needed to slow down the FP enough for our arm. I would use it again, stock, in the future, and if they harden their carriers from now on, I would definitely use it.