Instructables user hunrichs made this clever spirograph rig out of old bike parts and a piece of pegboard. This could be a good way to learn about gear ratios!
Spirograph with bike parts
Becky Stern (sternlab.org is a DIY guru and director of wearable electronics at Adafruit. She publishes a new project video every week and hosts a live show on YouTube. Formerly Becky was Senior Video Producer for MAKE. Becky lives in Brooklyn, NY and belongs to art groups Free Art & Technology (“release early, often, and with rap music”) and Madagascar Institute (“fear is never boring”).
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