[David]

I agree with most of whats been said, but, my teams is also working on a prototype, we found that it will cost less than $500. We do plan on salvaging some old parts to save money, but it is enough to build a working prototype. Also I've estimated that, at best, it will have about 70% of the pushing power of a 4 wheeled robot, and, at worst, about 50%. Remember, your not trying to win pushing matches.