[EricH]

Originally Posted by Al Skierkiewicz

As has been explained to me (thanks Raul! and I hope I am stating this right) adding wheels does nothing to increase the friction between the robot and the floor. As the surface of the floor and the wheels are both extremely hard and flat, they approach ideal surfaces. Theoretically, if the weight of the robot remains constant, the amount of friction applied between the robot and the floor would be the same with one wheel, four wheels or a flat plate as large as the robot.

Would the above hold true if the coefficient of friction suddenly increased? i.e., locking the wheels so that they are 90* to the direction of motion, then lowering them and raising them as needed?

It wouldn't apply for wheels locking while traveling straight ahead, but maybe for that transverse friction...