i = n4/nc = 1 – Z1/Z4
nc: velocity of the blue crank.
n4: velocity of the green gear, its tooth number: Z4 = 100.
Z2 = Z3 = 20 (pink gears); Z1 = 50 (fixed orange gear)
i = 1/2
The blue crank and the green gear always rotate in the same direction independently of the tooth numbers..