Pulleys 7 and 8 are of different diameters. They are keyed to shaft a and rotate about fixed axis A-A. Belts 5 and 6 transmit rotation to pulleys 2 and 4 which rotate freely on shaft b about fixed axis B-B. Rigidly attached to pulleys 2 and 4 are identical bevel gears 9 and 10 which mesh with planet bevel gear 11. Gear 11 rotates about axis C of pulley 3 which is the carrier of the differential gearing and is keyed to shaft b. The speeds n_a and n_b of shafts a and b (in rpm) are related by the equation n_b=n_a*((D₄D₇+D₂D₈)/(2D₂D₄)) where D₂, D₄, D₇ and D₈ are the diameters of pulleys 2, 4, 7 and 8. Pulley 1 rotates freely about shaft b and serves to disengage the drive by shifting belt 5 from pulley 2 to pulley 1.
$3567$CFL,DF$