[eugenebrooks]

Once we got to a proper design for the gearbox on our arm, we have had no problem at all with our 64:1 banebots gearboxes driving it. We are running a FP motor into this gearbox because the FP motor has better fans to drive air cooling and internal thermal protection that prevents motor burnout.

We are driving our arm with the 64:1 banebots/FP setup through a 40:1 worm gear from Boston Gear, and are using latex tubing to cancel the torque due to gravity on the arm. The result is a very smoothly functioning arm that can be operated in both a manual mode with switches on the motor power and with an on-off feedback setup (not PID) using pots to control position. The BB gearbox drives the worm through a shaft with a hardened pin and the torque is sufficient to snap the pin if the arm gets tangled up in the rack and the driver team miss-handles the power to the arm. This is the only thing that we need to address for future competitons. The worm gear setup has the advantage that no power is applied to the motor in order to hold the arm in a static position, so the motor stays cool. I am not sure that I would want to be running a 256:1 bane bots gearbox and a 10:1 worm setup...

We had no end of trouble before switched to a setup that provided for cancellation of the torque produced by gravity on the arm. If you design your arm drive with a worm gear to get lockup with the power off, and you cancell gravity with latex tubing, you will have no trouble at all with your gearbox. Run current through the motor at stall, or hammer the gearbox with oscillations in the arm and the gear box will die quickly.

We are using the 56mm gearbox, with a 12:1 ratio, and two CIM motors and the two motor adapter for our main drive. We did make our own plate and shaft out of properly heat treated 4130 (with a square drive), and we did carefully check the gear box for any interference problems before breaking it in in both direcitons on the bench. We then tore it down, cleaned it, checked all parts for abnormal wear problmems, and then greased it before putting them back together. These 56mm gear boxes have been through two regionals now without problems, and we are headed to a third regional and the nationals, so I hope that I am not speaking too soon, but we have not had problems with them.

Eugene