FTC: Designing a Drivetrain

In preparation for the next FTC season that will be revealed next month (which hopefully will be one that involves launching things into the air), my team decided we should begin planning out the most basic parts of our robot. Last year, our drive system was extremely cumbersome and not that easy to fix. Swapping out a burned out motor was difficult because they were wedged between all the compact electronics.

In an attempt to fix these issues, I began designing a modular drive train. This time I would also use CAD first, then begin build afterwards.

I had several designs in mind, each of which involved having the axis of the motor be in the same plane as the wheels. I didn't like having the motors stick into the robot, and having the motors closer to the outside would make swapping in new motors easier, in the event that they burn out (hopefully this system solves that problem too). To get this to work, I needed to either use bevel gears or a worm gear to change the axis of rotation from the motor to the wheel. Worm gears would create too much reduction, and were removed from consideration.

I thought about having the motors oriented vertically, but this would make the design wider again.

Eventually, I saw an image of the FRC RAW Box gearbox with two motors oriented towards each other, and perpendicular to the output shaft:

Dead source: https://www.chiefdelphi.com/media/img/bb2/bb21e809691ce201313d00aed3241f3d_l.jpg

Aha!



Inspired,I got to work CADing up a design and came up with this:

Side plate of drive train.

With everything assembled (and one side off) it would look like this:

All parts inside (except for the chain and actual bevel gear models)

There would be two rings of chain per module, one connecting the middle to the front wheel and one connecting the middle to the back wheel. If it doesn't work well, the system could be reconfigured to have only one chain by drilling another hole for another bearing (which in hindsight I should have added in; I already cut out the side panels).

Example drive base.

Hyped to begin building it, I ordered all the parts that I didn't have and got to work.

Cutting out side panels on CNC.	Bearings installed.
Standoffs.	Axles, cut from stock aluminum.

Like a plinko board.