Six planet orrery

Six planets in circular orbits with relatively exact orbital periods: an exhaustive search of combinations of up to 100 gear teeth was used to determine the inner and outer planet drive gears. Two M5 threaded rods are used for the center of the shafts since the printed versions did not handle the torque.

Maybe more up to date sources https://github.com/osresearch/orrery

Assembly.stl is not printable, but shows how everything fits together.

Todo list:

* The moon should orbit the earth, although the extra parts are not yet in place.
* The concentric Mars/Jupiter/Saturn shafts are a bit sloppy and need to have their diameters adjusted.
* Motor or crank drive mechanism.
* Planet arm attachment is a bit wonky and should be redesigned with dogs.
* Sides should be 3D printed instead of also threaded rod.
* Base plate and top plate are too bulky.