Banebots 36mm gearbox: Recommendations for use

[Joe Johnson]

Another Update:

I am impressed with the 64:1 36mm gearbox included in the kit.

I eventually got the gearbox to fail but it was not easy.

Data:
At 350 HARD impact cycles* The backlash in the motor has opened up to 30.5 degrees (I have a way to measure this now before I was eyeballing it) but the gearbox seems fine other than that.

At 500 HARD impact cycles, the gearbox had 35.5 degrees of backlash. As I was re-assembling the test rig, I rotated the output shaft without power (back and forth a bit -- nothing hard, just positioning things to continue the test), we the gearbox locked up. I was eventually able to get the gearbox freed up by wiggling back and forth more, but when I powered the gearbox would run in either direction with no load, but would lock up in one direction if under medium load conditions.

Taking the gearbox apart, the D had opened up asymetrically (my stops must not have been as hard in one direction as the other). It is hard to tell exactly what the exact cause of the bind is because when the gearbox was apart everything moved freely. I believe that the asymetrical wear in the hole was causing the carrier to bind in one direction.

Conclusions:
The gearbox is considerably more robust than I expected. I believe that the test was pretty aggressive and the gearbox took 500 hard impacts to fail.

I believe that the Banebots 64:1 36mm gearbox is a pretty robust solution for many types of FIRST applications.

Bottom Line:
With some care not to repeatedly run the motor into hard stops at full speed**, I believe that this gearbox will serve teams very well.

Joe J.

*1 cycle = + 12 V to motor, free rotation of output shaft for approx 20 deg, Impact stop, -12 V to motor, free rotation of output shaft for appox -20 deg., impact stop.

**I am still a little concerned about non-obvious repeated impact cases. For example using this gearbox for a feedback loop for a large, heavy robot arm with a very rigid connection between the arm and the gearbox (say, chain). The potential problem is that the arm may act as an impact load every time the feedback loop changes the sign of the correction (which is often).