I have been struggling with a drive gearbox binding issue on and off for about a month. Now that we are doing the skills challenges for IR@Home it has become a problem we cannot ignore. In the 2020 season we ran a flipped two stage Falcon gearbox, zero issues over two competitions. The 2021 modifications required the use of a non-flipped gearbox so I re designed and made this:
It is a single stage 8:84 with a single polycarb plate and two 3D printed standoffs, it uses only two mounting bolts to avoid the chain that is inside our drive tube. This is where the binding first appeared. The binding only happens on specific parts of the 84t gear, I can discern no difference between the teeth that cause a bind and the teeth that don’t. The worse the binding is, the more teeth cause it to bind. This version could usually rotate about 90-180 degrees before binding. moving the wheel back and forth hard and fast will usually break past the bind and allow the wheel to spin another 90-180 degrees. I assumed that this was caused by misaligned mounting holes, so I created the second version:
This version used different mounting hole locations, and increased the mounting bolts from 2-> 4. This seemed to solve the problem, moving the wheel by hand showed no signs of binding. A little less than a month later, after the judging materials submission we started driving the robot around, now these V2 gearboxes bound up in the same manner as the V1s. When the gearbox is bound the 8t pinion rides up on the teeth of the 84t spur like this:
I assumed this was the motor shafts or the motors deflecting away from the gear so I designed the V3 gearbox to support the end of the Falcon shafts.
For the second time, this seemed to fix the issue. This version gave us about 3-5 hours of driving before one side began binding again, in the same manner as before. The other worrying thing we noticed about this was after those 3-5 hours of driving the 84t gear had a lot of wear. The teeth got pointy near the ends, there was a small lip of metal around one side of each tooth, and there were thin slivers of metal left inside the gearbox and on our carpet.
(1/4-20 wing nut for scale)
This wear leads me to believe that supporting the Falcon shafts did not solve the problem, only mask it, and now that they were driven a lot the problem has resurfaced. The c-c distance between the gears is 2.352in.
Does anybody know what is causing the binding or gear wear problem? Any similar issues you have had in the past that you found a solution to? Any help is greatly appreciated, I can supply any other photos, information, or CAD that would help shed some light on the problem.
Edit: lots of questions that can be answered by sharing my CAD so here it is https://grabcad.com/library/2021gearboxv3-1