Friction disk d is keyed to shaft 1, rotates about fixed axis A and is in contact with wheel 2 which can slide along feather key e on shaft 3. Wheel 2 rotates about fixed axis B-B with shaft 3. The transmission ratio from shaft 1 to shaft 3 is i₁₃=ω₁/ω₃=n₁/n₃=r/a where ω₁, ω₃, n₁ and n₃ are the angular velocities and speeds (in rpm) of shafts 1 and 3, r is the radius of wheel 2 and a is the variable distance from axis A to the point of contact between wheel 2 and disk d (at the central plane of wheel 2). In the design shown, the transmission ratio i₁₃ can be varied within the limits of the possible movement of wheel 2 along key e.
$3460$CF,IV$