Input is the green shaft of two green pulleys (Dg dia.) rotating regularly with Vg velocity.
Output is the pink crank of Vp velocity.
The blue block of a blue small pulley (Db dia.) and a gear of Zb teeth idly rotates on the pink crank.
The yellow block of a yellow large pulley (Dy dia.) and a gear of Zy teeth idly rotates on the pink crank.
The orange gear of Zo teeth idly rotates on a pin of the pink crank.
Vp = Vg (Dg/(Dy.Db)).((Db.Zy – Dy.Zb)/(Zy + Zb))
This case:
Dy = 3.Dg + 3.Db
Zo = 20; Zb = 40; Zy = 80
Vp = 9.Vg
Vp can be very small by choosing appropriate pulley diameters and gear tooth numbers in order to decrease value of ((Db.Zy – Dy.Zb).