Referencing a June 2014 Article, “High Gear Ratio Epicyclic Drives Analysis,” by Dr. Alex Kapelevich: I have designed a small compound epicyclic gearbox with common planets. Sun = 10 teeth Planet = 14 teeth Ring Gear stationary = 38 teeth Ring gear output = 41 teeth profile shifted onto a 38 tooth pitch diameter. Carriers are simply cages for the planet alignment and location. According to your article, and according to my calculations and the prototype I have built, my inputto- output ratio is a reduction of 65.6:1. I am using a ~ VG1 viscosity grease and Nylatron materials for the gears and carriers.