i3 = n3/nc = (Z1 + Z3)/Z3
i2 = n2/nc = (Z2 - Z1)/Z2
nc: velocity of the blue crank.
n3: velocity of the yellow gear, its tooth number: Z3 = 20
n2: velocity of the orange gear, its tooth number: Z2 = 20
Z1 = 70, tooth number of the fixed green gear.