Here's a YouTube video of our 6 wheel modular drive prototype that we worked on during the offseason.
http://www.youtube.com/watch?v=px-QCB9UeCs The drive is housed in a 2x5 inch piece of rectagular aluminum tubing. The current drive is designed to operate at 6 fps. With this years game we're looking at tweaking the final drive ratio to give us a little more speed. For those interested the prototype weighs 17 lbs with motor.