This project means extra funny work for the more daring of you readers ;-) indeed it's only a 3d model, and it has to be built.
I'm not very familiar with 3D printing, so I'm not sure about tolerance between moving parts. Anyway there is a fast explanation of my design and how to model it in 3DS Max
. It's not a full modeling tutorial, because it would have been too long and complicated, but I'll show you the main phases and I'll attach the 3ds complete model in next step so you can see it in your 3D favorite software.