The roll axes of a Mecanum wheel establish a set of k equidistant generators belonging to a regulus on a one-sheet
hyperboloid H of revolution with axis a. If the wheel moves on a plane terrain π its axis a remaining parallel to π then at each moment at least one roll touches the ground. Hereby a passive (non-driven) rotation around the roll axis b is induced
to the respective roll by the motion. Of course, it is desired to avoid vibration or jiggling of the vehicle throughout the
motion, which means that the wheel axis a must keep a constant distance to the plane π :