i = n1/nc = 1 – ((Z2.Z4)/(Z1.Z3))
n1: velocity of the yellow gear, its tooth number Z1 = 44
nc: velocity of the blue crank.
Z2 = 44 (green internal gear); Z3 = 40 (orange internal gear); Z4 = 20 (fixed pink gear). The green gear and the orange one are fixed together.
Z2 – Z1 = Z3 – Z4
i = 1/12
The crank, the yellow gear rotate the same direction for this case.