In addition to the many valuable recommendations already made, I'll add these things to check for (I don't know if you've already done some/all of these, just wanted to double-check):
- Make a 2D sketch (or 3D model, if you feel like it) of the chains/belts to ensure none of them hit your standoffs.
+ It looks like a couple of your standoffs may be in the way, but it's hard to tell, obviously
- Design for chain tensioning and/or use a chain length calculator
+ Could be a floating wheel, tensioned by a screw or turnbuckle
+ Could be a larger sprocket placed in the chain run (like 118)
+ Could be a small sprocket (or piece of delrin) pushed against the chain until tight
- I'm having a hard time judging the scale, but if you're pressing bearings into your sidewalls, ensure your holes are toleranced to get a good press fit (depends a lot on machining method used... I'm unfamiliar with the plasma cutter)
- Standoffs can be a lightweight way to make a more rigid structure between two sheet metal plates... I would recommend at least using some pretty large OD standoffs and potentially putting a couple plates across that have two holes in each sidewall. This should add significant rigidity
- Also, you do want to ensure that your drive modules mount to the rest of your frame rigidly and without creating stress-concentrated areas...
What thickness of aluminum do you have modeled so far? With a better-optimized lightening pattern and good structural design I would say you don't need anything thicker than .125; however, I don't have any experience with flangeless sheet metal drivetrains.
Best of luck in your design!
(The wheels) need to be green anodized, and then assembled with yellow anodized spinners. ... and then, on the spinners, you can etch "JVN is a dweeb". That would be cool. - Andy Baker [more] 
17-12-2012, 16:40
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