This is something I’ve been working on for awhile now, but never really got around to finishing. I was curious if it would be possible to fit a planetary gearbox inside a 4 inch wheel, and drive it with a NEO (or other motor.) This is what I came up with. Could use some work, and I don’t expect that it’s very practical as it is complex and would be expensive. But the package is neat.
- Wheel runs on (2) 3.25" OD thin section bearings.
- Two stage planetary gear set, all 20DP
- First Stage: 14 tooth sun, 15 tooth planets, fixed 44 tooth ring
- Second Stage: Driven by first stage carrier, 28 tooth sun, 14 tooth planet, 56 tooth ring connected to wheel
- Total reduction: 8.28:1 (12.16 ft/s free speed)
- 4" OD Wheel, 2.29" Wide
- All gears except the ring gears are off the shelf
- 5" x 5" x 4" Overall dimensions
- Second stage is intentionally 2.00:1 so that if you wanted to drive a separate wheel off of this one, you could just extend the hex shaft and use a 30 tooth to 60 tooth pulley to the other wheel.
What I originally was working on that spurred this was a motor in wheel swerve. If you used a slip ring, you could put this in a swerve too. Pivoting off the center of the wheel, the NEO would trace a 7.7" diameter circle. Still pretty compact for a swerve.