In the words of Ali Gee, this is where you come in.

I should thank the guys at Otvinta for their gears code, and of course the foundation for producing the Pi. I have now lost count of number of Pi’s in house.

Blender also deserves a mention. I am sure its not the best design tool out there, but firstly its free and secondly its programable. Hope to publish the source code for 3d design shortly.