Slide-glide cyclides - a design discovered by Andrew Kepert when investigating ways to “see” why the area of a sphere is four times the area of a disk of the same radius. I added the gears and the base. Full video: https://youtu.be/KD_hRn_97RI
And the files to print out your own version of the mechanism are here: https://www.printables.com/model/651714-slide-glide-cyclides