i = nc/n4 = 1/(1+ ((Z1.Z3)/(Z2.Z4)))
nc: velocity of the green crank.
n4: velocity of the blue internal gear, its tooth number: Z4 = 70.
Z2 = 30 (yellow gear); Z3 = 20 (pink gear); Z1 = 20 (fixed orange gear)
Z1 + Z2 = Z4 – Z3
i = 21/25
The crank, the blue internal gear always rotate in the same direction independently of the tooth numbers..