Spinnie

The idea started from a video by 3Blue1Brown:

I thought, what would happen if there was no wall, and the blocks were on a loop. The number of collisions should be infinite!

Sadly, we don't live in a frictionless world, so I wasn't able to achieve an infinite number of collisions.

I began with a few simple sketches:

I prototyped different sizes for the dome, and balls. tried the idea of having a circular track but that was hard to play with.

Manufacturing the dome:

I went to CAD and designed the dome and the gate and runner for casting.

And then for sand casting I 3D printed the pattern and sanded it to 500 grit sand paper before ramming up sand and casting.

The brass pins:

To make the brass pins I started by turning down the diameter, cut a 10-24 thread on the ends of pins, then drilled and reamed a hole to press fit the bronze bushings.

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After pressing in the bushings, it was time to turn the pins into shape. I wanted to add a soft radius to the pins.

I started by grinding my own lathe tools.

Half way there!

Next up was sanding and finishing the dome,

before drilling and reaming a hole to press fit the shaft in place.

For the pins, the crucial step:

Slip rolling them into shape, to perfectly line up!

All parts made!