Parallel mechanism for wrist in robotics hand
based on video: https://www.youtube.com/watch?v=aLaqMreVj9o LIMS2-AMBIDEX wrist principle - the contact of two rolling spheres
(btw. this is also the basic mechanism behind all Delta printers, but usually with ball-joints instead of 2DOF passive joints, old, printable carriages were using something similar)
M3 stock screws (4.5mm holes for them to turn freely)
no bearings, so very crude, but printable without supports
more info on that later gearModule.scad is not mine, but I honestly don't remember the source, if I find it I'll cite it right away