Model, of apparatus for producing intermittent rotary motion in opposite directions and at different velocities in two adjacent discs, by Richard Roberts, Manchester, England, 1857. The gear reduction of outer disc is 1:11 of speed of shaft and that of the inner shaft is the same in the opposite direction. The motion is dependent upon an eccentric lobe lifting a disc, with pins on its periphery, in and out of the teeth roots of an adjacent disc. Because there are eleven teeth and four equally spaced pins the relative positions at any one time of the pins to the teeth varies so that at each revolution of the pin disc., a sideways motion is given by the pins, in turn, to the toothed disc.