Printable Harmonic Drives

For no particular reason I made some printable harmonic drives. I just wanted to try it out. I don't have an application in mind for them. As expected, they have a lot of friction and are nowhere near back-drivable. But they do have decent stiffness as a result of using a ring flex-spline instead of a cup flex-spline. I made 50:1 and 40:1 designs. They use 608ZZ ball bearings and take 3mm shafts as input.