The One Thing - Magnetic Gearbox Fidget Spinner

During the April magnet contest I saw a couple magnetic gearbox designs and started watching videos that gave me some ideas.

A bunch of variations later, after realizing I had to double the magnets I was using, I have a… thing… that works pretty well and is fun to fidget with. 

I designed the main rings to print without supports as long as they print top-down, and I hope the tolerances aren't too tight for some printers. The gap between each ring is only 1mm at the thinnest, and none of my prints with my Mini and .4mm nozzle have had any rubbing. 

The original thin version of Ring 4 bottom outer dial doesn't need supports, but the new one has to print upside-down due to the teeth, so the new “bottom” needs supports all around the outer ring. The smaller screw holes for a couple of the bottom dials and bases also need supports, and organic is best for all.

The bottom dials and bases do need to screw into rings 2, 3, and 4 to sandwich the bearings in between, and I found that once I inevitably stripped out a couple tiny screw holes by assembling and disassembling it over and over that putting a drop of krazy glue in the holes and putting the screws alone half-way in until it dried returned them to usefulness. 

Here's the list of extra parts needed to make this thing work.

Magnets x 96

• All purchased on amazon.ca, and not all are as thick as advertised.
• The magnets in each ring must alternate between North and South, and I built in tiny holes under each magnet slot so that I could push the magnets out during prototyping, but also because you're almost guaranteed to accidentally put some in backwards and need to remove them to try again. Alternating North/South around the rings is critical!
• Ring 5 - 10x2mm round magnets x 48 (actually 1.6mm thick, so doubling them up will fit in the 3.30mm slots)
  • Mixing round and square magnets will only work if they are 1.6mm and 1.7mm thick respectively like mine are. 24 square, 24 round.
  • Doubling up square magnets won't work as they will be too thick.
• Ring 3 - 10x20x2mm rectangular magnets x 16 (actually 1.55mm thick, so doubling them up will fit in the 3.30mm slots)
• Ring 1 - 4x2mm round magnets x 32 (16 pairs stacked in 8mm deep slot)

Bearings x 4 (or just the 2 largest ones for a 3-ring version instead of 5-ring)

• All purchased on amazon.ca, and I opened them and used varsol to remove the grease so they spin freely.
• uxcell 6815-2RS Deep Groove Ball Bearings 75mm Inner Dia 95mm OD 10mm Bore x 1
• uxcell 6710-2RS Deep Groove Ball Bearings 50mm x 62mm x 6mm x 1
• uxcell 6806-2RS Deep Groove Ball Bearing 30x42x7mm x 1
• Donepart 6900 ZZ Bearings C3 High Speed 10mm x22mm x6mm Ball Bearings x 1

Grub and Mounting Screws

• Ring 4 - 8x12mm grub screws x 16
• Ring 2 - 6x10mm grub screws x 12
• Ring 4 bottom outer dial - m3x8 hex socket cap head screws x 6
• Ring 3 bottom middle dial - m2x8 hex socket cap head screws x 4
• Ring 2 bottom inner dial and base - m2x8 hex socket cap head screws x 4

I can't wait to see other people's prints of this weird thing!

Updates:

I made a small knob for the bottom center post, vaguely crown-like, so that I could more easily hold the whole thing using just the center ring between my thumb and middle finger. That ended up letting me turn the whole thing into a spinning top of sorts, and I discovered that if I spin the 4th ring and 5th outer ring with some force in opposite directions I can send the whole thing spinning across a table where it will stop itself abruptly while sitting at an angle.