Off Season West Coast Drive

Our team decided to do a practice west coast drive in the off-season and I’m looking for feedback on our current design. Included are the native solidworks files, step files, and grabcad link. Some feedback would be appreciated on the gearbox mounting, tube spacer use in the gearbox, and anything else. I’ve also noticed varying thicknesses on bellypan, so we used 3/32" thickness on our sponsor’s waterjet, but are there any good reasons for a thinner or thicker bellypan? Also, I have noticed the absence of bumper mounting, which is to come in the future and the shafts will be retained using 1/4-20 bolts and washers. Any feedback would be greatly appreciated.
Off Season West Coast Drive (33.5 MB)
Full Chassis (7.4 MB)

iso gb

Native Grabcad:
Onshape: Onshape

You’ll need a bumper rail over the wheels, or frame stubs to support the bumper between wheels. The rules allow no more than 8" between bumpers supports


If you have access to a cnc machine, you can mount the front and back wheels directly in the chassis(bearings set in the tubing), you can save 120$ ish on mounting blocks.

We don’t have a working cnc machine, so we have one of sponsor’s waterjet bearing blocks for us and they provide the sheet metal.

This looks good. Its a nice simple design. I would take inspiration from 254s 2017 bot for how to do a nice bumper support structure on the wheel sides as @nuclearnerd points out the lovely 8" bumper support rule is a very good thing. You are definitely on the right path for ease of manufacturing by making the side bars the same and then the front and back bars the same, that way you dont have to worry about assembly potentially putting one bar on upside down and backwards.

Note that our 2017 chassis was welded, we welded on the 0.5x0.5” tube that was a bumper rail (continuous backing nice but not required), handle to lift robot by, and mounting point for hinges that held sidewalls of polycarb hopper.

If you want a similar design without welding it’ll be a bit trickier, may need rivets and bolts.


Regarding the bellypan, the main use of that is to hold up electronics and other things. I think I have seen teams that use a Polycarp bellypan, just make sure to support main structures with 1x1 or 2x1

It may be good to add a polycarbonate guard around the exposed gears. If you are testing with the chassis on blocks in the workshop or in the pits, fingers can get caught. You also have motor controllers nearby so you would want to keep the wires away from the spinning gears.

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