We went with a kitbot chassis (cut to 37x27), but didn't drop the middle wheels. Our wheelbase is 30 inch, split 16/14 so the middle wheels are offset one inch from the true center, toward the claw. AM aluminum six inch omnis on the corners and AM kit wheels in the middle, driven by two CIMS through 12:1 BB 56mm kit gearboxes (unmodified, with no bowtie failures luckily) and 15/28 sprocket ratio. With the winch and compressor in the front and the battery in the back our weight distribution made for very easy maneuvering. And we had no trouble climbing ramps. See our
chassis here.
Of course we don't push anyone around but that has not been an issue: we have seeded better than in any of our previous years (6th at St. Louis and 11th at Boilermaker) and were drafted fifth at both events. Didn't make it past the semifinals but we had a lots of fun and put up quite a few ringers. Even managed to hang a couple of keepers. If I had it to do over, I'd probably only use omnis on one end, and would definitely go with two CIMs per side; didn't want to risk that this year due to concerns about the BB carrier plates. If the budget allowed I'd buy AM Shifters, and go with higher traction center wheels.
__________________
Richard Wallace
Mentor since 2011 for FRC 3620 Average Joes (St. Joseph, Michigan)
Mentor 2002-10 for FRC 931 Perpetual Chaos (St. Louis, Missouri)
since 2003
I believe in intuition and inspiration. Imagination is more important than knowledge. For knowledge is limited, whereas imagination embraces the entire world, stimulating progress, giving birth to evolution. It is, strictly speaking, a real factor in scientific research.
(Cosmic Religion : With Other Opinions and Aphorisms (1931) by Albert Einstein, p. 97)