Input: red slider of Vr velocity. It carries block of two gears.
Tooth numbers: Z2 and Z1. (Z2 is larger than Z1)
Output: green slider of Vg velocity.
Brown rack is stationary. Green rack is fixed to the green slider.
Vg = Vr((Z1+Z2)/Z1)
Here Z2 = 2Z1 so Vg = 3Vr
If Z2 = Z1, Vg = 2Vr