The Inspiration
The first Assassin's Creed video game was super trendy, and one of the coolest weapons the main character had was his secret hidden blade - a retractable weapon concealed under the wrist.
I had to make my own.
The Build
I created a retractable blade mechanism using:
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Wood for the wrist mount and guide rails
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Aluminium sheet for the blade itself
The mechanism used a spring-loaded system to extend and retract the blade with a flick of the wrist.
The Lesson
Here's where I learned an important lesson about materials science. I thought that putting aluminium sheets together on the flame of the stove would fuse them together like soldering...
Nope!
Aluminium has an oxide layer that prevents simple heat fusion, and its melting point requires much higher temperatures than a kitchen stove. The blade ended up being several layers held together mechanically instead.
Why This Matters
This failure taught me that understanding materials is as important as understanding mechanisms. You can't just assume materials will behave the way you want - you need to understand their properties.
This lesson would prove invaluable years later when designing prosthetics and robotic systems.