Abstract: A mechanical device includes a block of material having a hollow tunnel formed therein. An elongated rotary shaft is floatingly mounted in the tunnel, generally parallel to but off-set from the longitudinal center thereof. A number of holes are diametrically formed through and more or less evenly distributed along the length of the shaft, perpendicular to the axis thereof. Each hole is angularly offset from the other holes, by a predetermined angular distance. A sliding shaft, which slides freely through each of these diametrical holes, has a wheel on each of its opposite ends. The contour of the tunnel wall is unique and is defined by the paths followed by the wheels on the ends of the sliding shafts, as the shaft rotates and as the sliding shafts slide freely through the holes.