[s_forbes]

The cg idea is interesting. It fits our 6wd robots; they were both very maneuverable and had a very low center of gravity.

The frame twisting is also interesting... our 2007 robot had a ton of flexibility, twisting wise, in the frame. If you grabbed the arm mast and move it to either side, you could make the outside wheels (on opposite corners) touch the ground simultaneously. It never happened when we were driving around though. (the arm only weighed 15 lbs after all)

It may be possible that your problem is a combination of relatively high cg and a twisty frame. If you try to take a corner with all of that weight higher up it may twist your frame enough to effectively eliminate your dropped center wheels. Just an idea. (maybe someone clever could figure out how to test it...)


EDIT: hmm, your sandbag test is interesting. How high up were the sandbags, and how were they mounted? Our 2007 chassis was only six inches high, and only the arm extended above that amount. The arm was also mounted in the middle of the back end of the chassis (no braces to the corners), maybe that has something to do with it?