Pin wheel 1 rotates about fixed axis A and carries pins a which mesh with lens-shaped teeth b of wheel 2. Wheel 2 rotates about fixed axis B. The profiles of teeth b are along curves which are equidistant from a portion of a prolate epicycloid. When driving pin wheel 1 rotates at uniform velocity, driven wheel 2 also rotates at uniform velocity. The transmission ratio from wheel 1 to wheel 2 is i₁₂=ω₁/ω₂=-z₂/z₁ where ω₁ and ω₂ are the angular velocities of wheels 1 and 2, z₁ is the number of pins a and z₂ is the number of teeth b. Wheels 1 and 2 rotate in opposite directions.
$2577$PG,3L$