Basic components (based on Google search)

1. Pull-string energy storage Pulling the cord winds an internal spring, storing elastic energy.

2. Release & gear reduction When released, the spring unwinds and drives the drum; gears slow and smooth the output.

3. rebound mechanism

   A ratchet and pawl prevent the spring from snapping back and let the cord slide freely.

Design improvements

1. Use a one-way bearing (sprag clutch) instead of a ratchet & pawl. That cuts noise, reduces wear, and still prevents spring rebound when you pull.
2. Introduce a viscous or friction damper. Damping the output shaft tames the final motion—no more sudden stops or rattling once the spring unwinds.
3. Use more durable and stable material instead of plastic — plastic is too easy to broken if you pull the string too hard.

Reflection

Be careful about the front and back sides of the gears! When we tried to install it back, we failed a lot of times just because the sides were wrong, and that failed the whole system. Because the gears are so small and similar, it’s hard to tell which one should go where. The order in which you put them is also important because some gear needs to be in a specific sequence.

Moreover, I think we didn't do a good job when we tore it apart. The video is so shaky and loses focus, so when we tried to reinstall it based on the video, it was so hard to tell what was happening. Next time I think we shouldn’t be so rushed (just because we wanna see what’s inside lol), and clearly picture every detail.