These are magic nunchucks. As soon as you print them, you will think you know karate. (You do. Believe in yourself.)

-250 mm tall

-Custom supports

-Custom threads for easy printing.

-Print in place chain.

-Requires two 3X30mm screws (FHCS/countersunk) and 4.5mm airgun BBs (4.4mm actual diameter, got mine at ACE Hardware)

Assembly video:

https://youtu.be/DAQZHRp_P1Y

Utilizes a double bearing system to control the axial load

All the previous versions failed me. They were too delicate, and always at the exact same spot: The stem of that bearing coming out of the cap. So this fixes that by using a 3X30mm screw as a spine to absorb all the axial stress of swinging this thing at trespassers.

The bearing area needs to be printed in the Z axis to spin freely–but the chain itself needs to be printed in the XY to be strong enough to swing around. So by separating them, it’s the best of both worlds, and by attaching those two with a 3X30mm screw, it’s no longer limited by the weakness of the plastic. It’s a lot of leverage pulling on that stem.

The threads are also custom to make for easy printing, and it utilizes printed shims (0.8mm to 1.2mm) to tweak the pressure on the bearings–just to help mitigate differences between printers.

Threads are counterclockwise/left-handed!!!

I did this because the way I naturally spin it would otherwise loosen up the cap. With left-handed threads, when the bearing spins, it’s trying to tighten the cap rather than loosen it. Probably a non-issie IRL, but it doesn’t hurt anything.

I used airgun BBs because they are much cheaper than regular bearings and plenty good enough for this purpose. I believe the accuracy and hardness of a regular bearing would be lost on a 3D printed race anyway.

I bought them at ACE Hardware: Crosman Copperhead 4.5mm Copper-Coated BBS. I believe that's a pretty standard size for airguns.

The staff is 250mm tall and comes with a custom stabilizer support to reduce artifacting (recommended) or not! (If you’re feeling risky, risky)

Print the screw on caps upside down with a brim and without supports. You don’t want support scarring on the race of the bearing

I’d call the assembly intermediate level. Need a bit of mechanical proficiency to add that final row of bearings.

Please don’t swing indoors!! Remember: These magic nunchucks only make you think you know karate. (You do. You have to believe, says the TV salesman.)

BB Bearing Nunchucks

0.12mm layer, 4 walls, 15% infill