[Mark Sheridan]

We used this paper too way back to explain why our 4 wheel robot had trouble turning in 2003. I recommend it too.


On a flat surface with drop center 6 wheel drive. Only 4 wheels can touch the ground, 2 have to be the center wheel. So it turns a robot with over 30 inch wheel base, to one that is about 15 inches in length. By reducing the wheel base length, you are reducing the moment around the axis of rotation resulting from wheel friction. You are essentially making a smaller lever arm lowering the force. That is why its easier for wide robots to turn with 4 wheels the long robots running 4 wheels.

On the carpet, because the robot sinks in, the effect merged with description the vikesrock stated above. Really all 6 wheels are touching the carpet, some wheels carry more weight than others. Its the combination of these two effects that make this system work so well in FIRST.