Description

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

The OpenSCAD file provided supports the configurator and there are messages that show the computed values and asserts to check that the settings you picked work. Most of these came from David's spreadsheet (thanks for that) but some I added.

The Assembly view shows all the parts together as they would be in the final Assembly but I did cut out a section view so you can see inside a bit. To print your design, you would need to dump the STL of all the individual parts. I was able to print them in 4 setups:

1. All the gears
2. The Base
3. The OutputRing
4. The LockingRing I liked the look of printing the Base/LockingRing in grey PETG with the gears and OutputRing in white PETG.

Printing

The torque of the gearbox is carried by the planet gears and the 2 ring gears. To make these strong, I printed them with lots of wall thicknesses (10 which might be overkill). I used 15% infill for the remaining parts and used Gyroid fill pattern (but I'll admit there wasn't much infill needed with 10 walls for most of the parts).