I'm building robot arms that I plan to make available to everyone through my website. To get enough power to move the arm the way I want, I needed a gearbox, which is a way to trade speed for power. Nobody I can find makes to my spec, so I created my own. I'd love your help to improve this design, so I've released the plans for my first version here. See it in action, then read more about the arm, then buy a robot and support my work. Special thanks to http://www.thingiverse.com/LoialOtter for making my first hypocycloid gearbox about 3 years ago. It's taken this long to actually put it to use! Special thanks to http://www.thingiverse.com/johnbiehler for printing this copy. My machine wasn't up to the task and he really came through for me.Edit: So the post mortem about hypocycloids... the big problem is that the forces inside are uneven. A planetary gear has three planets to balance the forces on the sun, keeping the sun in place. a hypocycloid - one or two stage - does not. the center shaft bends (even a little bit) and the interior gear jams. Long story short, these gears don't work in the real word unless you really really know what you're doing (like how to avoid the bending because you know your material strength properties and your torque forces and more I don't know)Design