Solar System Orrery

A hand-cranked orrery: turn the handle and the planets go round the Sun, each at its own speed, driven by a stack of gears. It fits on a small (Prusa Mini) printer.

The planets are not to scale with each other, but the base shows each planet's size compared with the Sun, and it doubles as storage for the parts.

Design by MrRestrained on Printables, shared under CC0 1.0 (public domain). The files and photos are the designer's, unchanged.

1. Print the base, axle, crank, gear arms, gears and planets. Use the newer gear files; they print more easily.
2. Assemble the gear stack following the arm numbers.
3. Turn the crank: which planet takes the longest to go round, and why?
4. Extension: count gear teeth and compare the ratios with real orbital periods.