This is my entry to the Mighty Bot Challenge. It's 6 x 12V motors are driven by two FET servo drivers. These drivers are the same circuitry that drives a RC servo but with heavy duty FET outputs so that they can drive loads in excess of 50A. They allow any DC motor to be driven as a servo.
For instructions on how to make the chassis read this walkthrough.
Since this challenge is about power to weight ratio I haven't added sensors. Because the suspension is not really set up for this challenge you'll see the front and back wheels spinning on the ground a bit with the middle wheels doing a lot of the work as they have more spring tension on them.
This photo demonstrates that the tiles are 200mm square. This made measureing out the area easy.
This is a clear picture of the weights. The weight can be clearly read. Click on the photo for alarger image.
This is the underside of the box to demonstrate that there were no wheels or other aids. The weights have left a clear impression on the bottom where it's dragged across the tiles.
This is the volts reading with the switch off. With no load, the reading is higher than 14.4V but still well under the 18V limit.