The major axis of the cam plate 12 and the flexspline 26 is represented, in FIG. 2, at the 12 o'clock position (35), and likewise, the minor axis in FIG. 2 is at the 3 o'clock position (36). The maximum inclination of the teeth 30 of the flexspline 26 are found at the mid-point between the major and minor axes 35 and 36