Inspired by Gear Bearing by Emmett Lalish ([https://www.thingiverse.com/thing:53451](https://www.thingiverse.com/thing:53451))

Integrated threads on the ring gear allow these to be stacked by screwing them into each other. No additional hardware required. Input shaft can be turned by fingers, 5mm hex key or 12mm socket/wrench for more torque. As a result, the speed of the sun gear gets multiplied. The more gears are stacked the faster last sun gear will spin. Maybe the community can create something fun to attach to the sun gear to spin fast?
It is quite enjoyable to play with, and test how many gears is possible to stack before everything locks up due to friction. Low viscosity lubricant greatly reduces friction, allowing more gears before binding.

How many can you stack before they break? :)

For 3D printing

It is a hard model to print well. Printing this requires a well tuned machine. Good first layer is critical. If tolerances are not met the gears may fuse together. Planetary carrier requires significant bridging. 
Initially gears may be stuck and require require pliers or 12mm wrench to release.

No supports.

Nozzle: 0,4mm
Layers: 0,2mm works well, 0,1mm gives better clearances and nicer threads.
Walls: 1 works. 4 gives optimal strength.
Top/Bottom thickness: 1,7mm gives optimal strength

Changelog

2026 01 24 - Removed old model with 10mm shaft.
2026 01 10 - Added a new version 3 model, which changed the shaft from 10mm to 12mm.