This is an endless gear board I created to teach my 3.5y/o son about gears and timing belts in a fun and interactive way.
The board has puzzle-like connecters on all sides so you can connect as much as you want and in any direction you want.

Each board piece is 150mm width and 150mm height (not including the puzzle connecters which stick out another 1.5mm on two sides) - It's designed to be able to print on a prusa mini (which is what I used).

There are gears in various sizes, and you can print as much as you want. They rotate smoothly in the holes.
There is also a gear designed to hold a gt2 timing belt (like this: [https://images-na.ssl-images-amazon.com/images/I/51KDGvyr7BL._SL1000_.jpg](https://images-na.ssl-images-amazon.com/images/I/51KDGvyr7BL._SL1000_.jpg)) so you can print two of them and connect them with the belt. (I admit I didn't get to try it yet, but will soon, and hopefully update here).

There is also an STL file for a board piece without the puzzle connectors, so you can use this one if you're not intending on printing multiple board pieces.

Print instructions

I printed all pieces with 0.2mm layer height.
On the prusa slicer I used the setting "0.20mm quality mini" and used PLA for all parts.

All the gears I printed with 20% infill and no supports.
The board pieces I printed with 10% infill and used supports (because of the small bridges on the sides for connecting them).
The board took me ~8 hours to print. The time for the gears depends on how many you print at once.

The board piece without the puzzle-like connectors on the sides can be printed without any supports.