Gravity-Powered Record Player
This project used gravity to spin a gear through a low-friction gear train, driving a record designed to rotate at 45 rpm. A needle and improvised horn amplified the sound.
Project Overview
My water bottle was attached to the end of a string, which applied torque to a gear train which spun a gear. The main challenge of this project was transforming the constant acceleration of gravity into constant rotational velocity for the record. My main strategy to do this was to match the friction of the system to negate the acceleration due to gravity.
Gear train
I estimated a 47:1 gear ratio was needed based on the pull radius of the water bottle relative to the final cog's spin. Pictured is the system before the sound components and record were added. This prototype served as a proof of concept for achieving very low-friction movement. The speed shown is much faster than the final result, as the record's inertia and needle friction add significant resistance.
Final Result
I designed a spindle that could rotate in both the Z and X axes, allowing it to be placed on the record and track inward as it played. A paper horn mounted on the needle amplified the vibrations. Listen to the result! It sounds… like something!
If I were to do this again, I would build a more robust mechanism for keeping the record at a constant speed, as that ended up being the biggest challenge.