[mathking]

We have have had a drive train with the center wheels lowered by 1/8" in the past and it worked pretty well. This year we had 4 traction wheels, two in the middle and two in the back, and then two unpowered omni-wheels in the front. We were told by several teams at our regional that this was a bad design, and that everyone would push us around by spinning us. But actually, no one did.

We had a 4 CIM drive train, geared more for torque than speed, and we were able to push most of the robots we went up against, except that beastly 48 machine. The key for us this year was the welded frame. Because we didn't flex, we pretty much kept 4 wheels on the ground all the time. So we were not easily spun at all. But since the traction wheel axes were only 13" apart, it was very easy to turn. We also implemented a "reverse" button, so we could change the direction of front and back, because we found that for some ramps (those that didn't flex), it was easier to go up leading with the rear traction wheels while for flexible ramps it was better to lead with the unpowerer omni wheels. With last year's (unintentionally) flexible chassis this design might not have worked so well.