Heaviest(?) Fidget spinner - 10oz (283g)

This fidget spinner is engineered to give the greatest moment of inertia possible. Read the "How I Designed This" section for more information.

My own build uses steel weights to weigh in at 10oz (283g) but if you have the money for tungsten it would be around 19oz (539g) and >$90 in weights. Even with the steel weights I have not been able to find another spinner with greater mass.

After hand spinning, I timed a spin at 4m 10s with a hybrid bearing.

Hardware & weight:
35x 1/4oz (3/8"dia x 1/2"h) steel cylinder pinewood derby car weights OR 1/2oz tungsten weights
1x 608 bearing of choice
8x M3x16mm bolt
8x M3 nut

Print Settings

Printer:

Geeetech Prusa i3 Pro C

Rafts:

No

No

Resolution:

0.2mm

100%

Notes:

Printed in MeltInk Red PLA

Post-Printing

The first few inner walls for the bolt/nut holes will not be supported. But it is so close to the bed, that it builds its own support quickly. I was always able to cut those first loops out, leaving a somewhat level surface. It is the edges of the holes that are important. They will be sandwiched against the weights.

How I Designed This

I set out to build a fidget spinner with the greatest moment of inertia possible. For a thin cylindrical shell I = mr^2. Increasing the radius of weight would be the most effective, but it wouldn't be a fidget spinner if you can't hold it in your hands. So r is limited to the typical 3" radius. The next best thing is to locate as much mass (weight) as close to the outer edge as possible.

Going down the list of densest metals, platinum and plutonium were out of the question. Searching for tungsten weights, I found a 'standard' sized weight, 3/8" diameter x 1/2" height, normally used for pinewood derby cars. They are available in both tungsten ($$) and steel.

As i started to design around this weight size I concluded that I could fit 21 weights along the standard 3" radius for fidget spinners. Another 15 could fit one diameter inside that. The cheapest tungsten I could find was ~$2.50 per 1/2oz weight. I'm not ready to buy $90+ in weight so I chose 36 steel weights (~$16). Tungsten weights would have totalled 18oz (510g), and steel is half that at 9oz (255g). My final design dropped 1 weight so that it was a repeatable pattern as 7 groups of 5 weights.