Rotation transmission between parallel shafts, one can move.
Input is the yellow motor (Vy velocity) and the violet motor (Vv velocity). The violet crank carrying a tool (for example a polishing wheel) rotates with velocity Vc.
Alter Vy for a desired Vc.
This case:
The diameter of large pulleys is double the one of small pulleys,
Vy = 60 rev./min. Vv = 252 rev./min.
Vc = 10 rev./min.