i3 = n3/nc = (Z1 + Z3)/Z3
i2 = n2/nc = (Z1 + Z2)/Z2
nc: velocity of the blue crank.
n3: velocity of the green gear, its tooth number: Z3 = 50
n2: velocity of the yellow gear, its tooth number: Z2 = 20
Z1 = 24, tooth number of the fixed orange gear.
The crank, the yellow and green gears always rotate the same direction independently of the tooth numbers..