This is a remix of Thorin Oakenshield's magneto model: https://www.printables.com/model/277626-magneto

I've re-created it from the scratch for 6x2.7mm magnets and improved a few things.

You will need 2 ball bearings (608 type: outer diameter -- 22mm, inner diameter -- 8mm, width -- 7mm) and 16 magnets (6x2.7mm, 6x3mm or 6x3.5mm).

Calibrate your printer (dimentions should be accurate as printed parts have to accomodate the ball bearings and each other).

Print gears (one of each, they are different), 1 axis, 1 spacer, 2 caps and 17 pins (having a spare pin simplifes assembly).

I recomment to print gears first (silk PLA looks awesome), then print one pin and check if it fits into the gears (it should be tight). If it cannot or it is loose -- scale pin in slicer, check again and then print all of them. Then print spacer and axis. Check if they fit. Finally, print one cap. Check if it fits onto axis (it should be tight). If it cannot or it is loose, scale it in slicer (or use X-Y hole compensation option if you use Orca Slicer).

Assembling:

• Insert ball bearings into gears;
• Insert pins into gears;
• Insert 8 magnets into internal gear. You have to make sure correct magnets orientation: all of them must point in one direction -- all inside out or all outside out. Insert spare magnet into spare pin, then attach a magnet you want to insert to the helper tool (it will orient itself) and then insert the magnet into a pin on the gear. Repeat for other pins on the gear;
• Insert magnets into external gear. Correct magnet orientation is also required, however in this case you should also make sure that magnet will be attracted to a magnet on internal gear. Repeat for other pins on the gear;
• Combine gears, axis and spacer;
• Attach caps.

Demo: https://www.youtube.com/watch?v=nrHXomF9xC0

Printed on Elegoo Neptune 4 (0.4mm nozzle) in Jayo/Geeetech/Lonenessl PLA Silk with the following settings: 

Layer height: 0.2mm (0.12mm for caps)

Line width: 0.55mm

Temperatures: 210/60

Speeds around 80-140mm/s (slower on top/bottom/external walls)

Supports: no

Ironing: all top surfaces (optional)