A simple and fun rack and pinion fidget, the connectors are made in such a way that it stays in place once connected and also does not make it hard to remove in case of changing the gears, some assembly is required (placing the middle rack and the pinions).  the spacing between the pinions (the gears) are up to you, by placing it closer, the middle rack would hit the wall of the container (as shown in the gif), but by placing it farther away, it wont hit it, but rather the pinions would hit the end of their rack, also making a sound. You could also use this fidget as a model showcasing racks and pinions.

[If you feel that the pinions don't mesh well to the racks or the connectors aren't to your liking, you can always adjust the XY compensation in your slicer]

If you have any feedback, please let me know!