Ellipse mechanism with 90 deg. angle between sliding directions.
The conrod and the green gear are fixed together. Center of the green gear is in the middle of the conrod and the center distance of the external gear drive is a half of the conrod length.
Tooth number of the pink gear Z1 = 20
Tooth number of the green gear Z2 = 20
Tooth number of the internal gear: Z3 = 60
n3/n1 = (Z1.Z2)/(Z3.Z3)
n3: velocity of the internal gear
n1: velocity of the pink gear
1 rev. of the internal gear corresponds 9 rev. of the pink gear in the same direction.
The strange thing is that the gear drive acts as a planetary gear one but without a carrier.