This year 1108 went out on a limb and designed our own drivetrain.
We called it “Panther Drive.” Was good for a Creativity award, but did not perform well and our season is over. But we had a great time and learned alot.
We put a mini-cim inside the wheel, used two Andymark 20-dp ‘planets’ and 3d-printed our own ring gear using CF-20 carbon fiber.
We put this motor on a steerable yoke, put one in each corner and made a fully-strafeing double-crab-drive robot. Our two front wheels steered about 270 degrees, our two backs did too.
It was a bold plan.
I first saw a motor in the wheel in 2011 with PWNAGE, but they did a two-pass gear system. and a much larger wheel. They haven’t done it for years now. I’ve never seen another. Except all the bicycles in China today have hub-motors.
Ours was smaller than PWNAGE, so we could get great acceleration with 4" dia wheels set up for about 20 fps. Originally planned to do it as a wheel in a regular six-wheel drop center tank drive. Other mentors on 1108 encouraged going to steered modules.
No chains, no belts, no transmissions. Clear space in the chassis. Center of gravity is really low. Potential for spring suspension too. Efficiency. All of those things rob power and take up space.
Originally designed to be 3d printed, they worked okay that way, but when the motors got hot, the PLA sagged. Had the parts made in aluminum after bag-day and switched out. In 3d printed, we had a module on each corner of the robot for $94 each. Still a really good value with machined parts, estimated $200/wheel, not counting steering motor.
We didn’t have a failure of a gear-set or wheel, but two times welds broke on our aluminum steering yokes to leave us without a wheel and with a shorted motor controller. We have a plan to do those welds better.
The vast majority of our failures were related to the software and the crab steering. We sat still for far too many matches in two regionals for anyone to consider picking us.