i = n4/nc = 1 + ((Z1.Z3)/(Z2.Z4))
n4: velocity of the yellow gear, its tooth number Z4 = 20
nc: velocity of the blue crank.
Z2 = 20 (orange gear); Z3 = 60 (green internal gear); Z1 = 20 (fixed pink gear). The green gear and the orange one are fixed together.
Z1 + Z2 = Z3 – Z4
i = 4
The crank, the yellow gear always rotate the same direction independently of the tooth numbers.