This began with the idea of looking at magnetic gears, but also I saw something called the cycloidal drive that’s used in a lot of robotics today. This has a prominent part that is driven in a funny way, with a 2D pin-and-slot. I thought, “if magnetic gears are efficient because they don’t rub, maybe they can help here.” Inventors like James Bruton put bearings in those slots, but I wanted to see if I could get magnetic gearing to do the work.

In short, it worked. In medium, it didn’t. In long, it probably isn’t a good idea. In the first draft, I printed it in PLA and it does work and the elliptical gear is driven, but the PLA doesn’t work very well because the friction is crazy high and I kept having a nagging feeling something was wrong, so I never took the next step to try to make a better version. Looking back at it, I realized that one of the great benefits of magnetic gears is they can’t be over-torqued because the “tooth” will just slip non-destructively, which is great for normal gears because metal gears have to replaced but magnetic gears don’t. But a cycloidal drive provides massive torque multiplication. It’ll always be over-torqued exactly at this location. So, maybe this isn’t the great idea I thought it might be. But it was fun.