Input: red slider of Vr velocity carrying orange gear. Pink rack is fixed to the red slider.
Output: yellow slider of Vy velocity. Yellow rack is fixed to the yellow slider.
Brown rack is stationary. Green rack is fixed to green slider that carries blue gear.
The gears are of the same tooth number.
The orange gear is in mesh with the brown and green racks.
The blue gear is in mesh with the pink and yellow racks.
Vy = 3*Vr