Mechanism for reversing rotation direction i = n1/nc = 1 – Z4/Z1

nc: velocity of the blue crank.

n1: velocity of the orange gear, its tooth number: Z1 = 50. Z2 = Z3 = 20 (pink gears); Z4 = 100 (fixed green gear)

i = - 1

The blue crank and the orange gear have equal velocity but rotate in opposite directions.