Customizable planetary gearbox

If you want this printed, please visit this link and ask for the special Thingiverse discount:
https://www.3dhubs.com/eindhoven/hubs/cncreate/3dprint

This is a customizer to create your very own planetary gearbox. Keep these principles in mind while choosing your parameters. If you don't, your gearbox will be useless.

R = amount of teeth in the ring
P = amount of teeth in the planets
S = amount of teeth in the sun

Equations
1. ratio = incoming speed / outgoing speed = (R + S) / S =>