This is a ground up redesign of povsky's designs, made so I could use the more common magnets that I already had on hand and for FreeCAD modelling practice.

Hardware needed

• 2x 608 bearings
  • Printed 608 bearings can also work
• Some 6x3mm magnets
  • 24 at minimum
  • 48 recommended
  • 64 for maximum torque
• 12x 5x6mm steel grub screws
  • Must be steel, not stainless steel

Printing and Assembly

All parts are fairly lenient on print settings. I used 3 walls and 13% infill with a .4mm nozzle and .2mm layer height. Tested with ABS and PLA.

Print one of the two Outer Ring options, two each of the Knob and Crank Handles, and one of everything else. Everything is designed to be easy to print, no supports needed. There are many small features, so a .4mm nozzle or finer is required.

The magnets are arranged in a simple alternating pattern, with the option to add more in a halbach array and more again stacked up for the outer ring. There are holes so you can push out misplaced magnets with a paperclip.

Assemble the rest of the gearbox like so. Make sure to put the inner ring's shaft in before the bearing, as it's difficult to remove if done out of order.

If you're interesting in learning more about how this mechanism works, povsky made a video discussing it here