6WD, #25 chain-in-tube, AndyMark 8" pneumatic hubs with tires off Amazon due to supply constraints. We goofed and designed it for an odd number of chain links, which meant half links with all their issues (especially the ones with the little wire instead of the ones you can get off of McMaster). Next time, even number and the acquired-for-Orlando Dark Soul tool will fix this issue...but somehow we never got stranded on the field from chain. Clean living.
The
frame was octagonal, so our corner wheels were flipped inboard. Easy to do it either way in the future. We supported the other ends of each axle, which was apparently not necessary (especially with our light weight) but we were being cautious because we knew it was a rough game. This design philosophy will be easy to adapt in future seasons to design needs.
The drive tubes were tied together by a riveted octagonal top pan. This was a mistake, as replacing the chains (which happened a lot early on--remember those half links?) called for faster removal than drilling out and replacing that many rivets. Not having the outboard chassis supports would make it a little easier to service without removing ev-er-y-thing, but a better method is necessary for future years.
We played with softer air pressure in the corner wheels to create more rock and be more compliant on the defenses. Only popped one tube in two regionals, on Friday in Orlando (our second). We drove at least two matches on it before replacing it due to time constraints and never had a problem.
All in all? I give this drivetrain a B. For as many new things as we tried, I'm satisfied.