Nonadrive Concept

[Cothron Theiss]

I took another look at this design since my last reply was from my phone, so I couldn't really see anything then. I'm gonna be a bit more critical this time around so you can correct these things early on in the design process, but if you have an explanation for something or think I'm completely wrong about something, please let me know. I think you've gone in an interesting direction with this, and it could end up being a slick design. You're trying to pack a lot of stuff into a very short profile.

First, I've taken the liberty of calculating your speeds of the specs you provided in the attached document. Screenshots of the spreadsheets are on imgur. I assumed that the omni wheel configuration would be your primary configuration because if your pneumatics were to fail, you would be stuck in omni configuration, though your traction wheels could very easily drag on the ground if your cylinders were to lose pressure. You can fix this with a spring or surgical tubing of some sort to actually lift the traction wheel out of the way in case of some mishap. (Don't forget to bump up the force your cylinders exert accordingly.)

I would really really really recommend changing the way your cylinders actuate your modules. Anyone can disagree with me on this, but the way the clevis rod is intended to slide along the slot in the angles during actuation SCREAMS like trouble waiting to happen to me. The reason it scares me is, when the cylinder actuates, the force the cylinder exerts on the inside of the slot will be almost perpendicular to the direction you want the clevis rod to travel.
Instead of rigidly mounting the cylinder and expecting the connection to the module to take all the movement, I would find a cylinder with a universal mount and pass a bolt through the side plates of the chassis and through the rear pivot of the cylinder. Then, your connection from the end of the cylinder rod to the module can be rigid and your entire cylinder can pivot. That's just what popped into my head first, but you can fix that issue however you like.

I see 32 hex shaft collars. It'd be cheaper and lighter to drill and tap the ends of your shafts and use a screw and washer to fix that ends, with spacers cut to length to determine spacing. In fact, I'd argue that all of your hex collars could be replaced, but I can see why you'd want the ones constraining the strafing wheel so you can change that wheel's placement.
Similar to that train of thought, why are there six sprockets on your strafing wheel drive and not just three?

You mention your strafing wheel being pressed against the ground with springs or tubing or what have you. Does this mean that you are constantly putting weight onto this wheel? This might be an issue if you get into a pushing match or are going over obstacles. If you're in a pushing match, any force the strafing wheel exerts on the ground is lessening the normal force on each of your traction wheels, which means you'll not get as much traction. Also, your strafing wheel might not like going over uneven terrain perpendicular to its primary axis of rotation. Many h-drives handled the scoring platform just fine, but anything more rough than that might give you issues if you can't retract that strafing wheel. That's just a trade-off, so it's entirely up to you.

I would look for ways to increase the rigidity of your chassis at the exact center plane, the mid-plane between the mini-CIMs. I might be wrong about this, but I imagine if you took a section view of your assembly at this mid-plane, you might see less material than you need.

Is the block between those CIMs your battery? If so, good on you for CADding it early. That's something I've forgotten to do and it cost me. But I'd consider where you're going to route your terminals. The battery's got to connect to something for it to work (no ballast!).

As you reconsider some of the things on your design, don't be afraid to abandon some of the perfect symmetry present in a lot of your design. Symmetry can be an excellent design tool to follow, but understand where it's holding you back or adding extra constraints that you don't even notice.