Split Ring Gearbox Generator

Description
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Split Ring gearboxes are known for being able to get large gear
reduction with very few stages. The details for the design captured
here were originally provided by David Hartkop. See:
https://github.com/IdeaPropulsionSystems/CoolEpicyclicGearing
https://www.youtube.com/watch?v=-VtbSvVxaFA
Since I couldn't find any CAD models that you could configure,
I put together this file using his original computations and
images. I took some liberties to make it a bit more configurable
and added extra clearances/features to make it more 3D printable.

The key to high torque carrying capacity is to make it big.
I printed one with the outer diameter over 200mm with a gear
reduction of 184:1 and I was able to load it with over 50ft-lb
of torque before it started to complain. I haven't pushed it
to failure (yet) but I am very surprised how well this has worked
even though it doesn't have any bearings to support any of the
loads (just slip fits).

Configurablity