i = nc/n1 = 1/(1+ ((Z2.Z4)/(Z1.Z3)))
nc: velocity of the blue crank.
n1: velocity of the orange gear, its tooth number: Z1 = 20.
Z2 = 30 (yellow gear); Z3 = 20 (pink gear); Z4 = 30 (fixed blue gear)
Z1 + Z2 = Z4 – Z3
i = 4/25
The crank, the orange gear always rotate in the same direction independently of the tooth numbers..