For the updated version 2b of this thing, follow this link:
This second gear toy has undergone some evolution and careful revision by yours truly to improve it to the point that you will actually want to take the time to print it! Allow about one full workday to print it as the outer ring gear and base take a few hours each. The little gears print quickly by comparison.
I'm sending a physical print of this one in blue (see photo) to my niece Ava - I hope she likes it!
The only duplicate is gear2.stl, print six of those. Everything else (gear1.stl, gear3.stl, and base.stl) print at just one item. Then just drop the gears into place. Makes a good puzzle for little ones - be sure to supervise!