Loci in Epicyclic Gearing

R: pitch diameter of the fixed sun gear
r: pitch diameter of the planetary gear
k = R/r = 4
Distance between the pin axis and the gear axis of the planetary gear is (5/3)r to get a appropriate loop locus for the center of the pin.
This produces a smoother indexing motion of the orange Geneva disk because the driving pin moves on a nearly circular curve, center of which is the rotation center of the Geneva disk.