i = nc/n3 = Z3/(Z1+Z3)
nc: velocity of the blue crank.
n3: velocity of the green internal gear, its tooth number: Z3 = 60.
Z1 = 20, tooth number of the fixed orange gear.
Z2 = 20, tooth number of the yellow gear.
Z1 + 2Z2 = Z3
i = 3/4
The crank, the green and yellow gear always rotate the same direction independently of the tooth numbers.