Fidget Spinner Gyroscope 12 1/2" inch balls

75 mm dia circular spinner with twelve holes at the rim for 1/2" chrome steel ball bearings (slingshot ammo). Standard 608 skate bearing (8x22x7mm). Scale as necessary for a tight press fit for the balls. Adhesive will throw off the balance. (Just a thought: You might even try 50 caliber lead balls used by muzzleloaders.)

Scale Bearing_Button_v1.stl to 99% so you don't have to press fit it. It's tough to remove the grips from the bearing printed full size.

Try printing with three perimeters, a 20% hex infill, and zero top and bottom layers. This will expose the hex infill (as in the photo), which you use a soda straw to blow against to accelerate the spin. Human power only! DO NOT use an air compressor! Ask your science teacher about centrifugal force.

Using a kerosene-lubed Yellow Jacket ceramic bearing, and with all twelve 1/2" balls installed, I got a five and a half minute spin.

This thing was made with Tinkercad. Edit it online https://www.tinkercad.com/things/kOjbeE1PfJq