Reciprocating Rack and Pinion

Full tutorial:
https://learn.adafruit.com/rack-and-pinion-bot/

https://youtu.be/96P-q38pBaU

Reciprocating Rack and Pinion
Learn how to create an automated geared mechanism with hypnotic motion. Use the Adafruit CRICKIT and Circuit Playground Express to make it dance! This is a mechanism for converting rotary motion to linear oscillating motion. The gear appears to bounce back and forth as it continuously rotates. As the wheel spins, the gear turns and oscillates between two tracks. It emits clacks and sloshes sound while in motion creating the sense of white noise. The teeth engage the lower track as it rotates. When it has travels the length of the slot, the teeth clears the end of the track and catches the teeth in the upper part of the track.

Adafruit Crickit for Circuit Playground Express
https://www.adafruit.com/product/3093

Adafruit Circuit Playground Express
https://www.adafruit.com/product/3333

TT DC Gearbox Motor
https://www.adafruit.com/product/3777

3xA