I need some non-circular gears for my pick-resistant lock. There are a few tools out there, like Gearotic Motion or Gearify, which can do some of the work, but they mostly only support full-cycle gears with integer ratios.

What I actually want is a pair of arc gears inside a ring with ratios I don’t really care about, but relative centres and radii which I do care about. The ring just couples one gear to the other while avoiding other obstacles, and it doesn’t have to turn continuously – just turn up to a pre-defined limit.

So I figure what I could do when I get around to it is to use whatever software to design the two periodic gears on the inside, and then just “cut” the outside gear by rendering those gears as they rotate around the path I want them to follow, repeatedly overlaid into a bitmap until the only thing that’s left is the material which doesn’t bind. Then I just extrude and fabricate the bitmap.

I don’t care about backlash or noise (60rpm would be very fast) so I can just erode it a little to make sure it fits.