This is a project from 8th grade, in my hometown Ratlam, during a summer vacation. I’m listing it under experiments because it’s part of the arc of how I learned to build things — and because several of the mechanisms I worked through here turned up in other projects later — not because the object itself was important.
The build, at a high level
The frame was a plastic BB-bullet gun I already owned. The electric ignition circuit came out of a mosquito-swatter racket — the step-up transformer and capacitor produced the spark. The combustion chamber was repurposed from a plastic bottle.
The problem that actually made it an engineering project was chamber renewal: after a shot, the chamber was full of exhaust gas and wouldn’t support the next combustion until it was cleared. Petrol needed the chamber evacuated before the next load; hydroxy didn’t, because it carries its own oxidiser. I wanted the gun to support both fuels. So I went to the local aquarium shop, bought an air pump, tore out its AC-driven diaphragm mechanism, built a DC-driven replacement using a small motor and a bottle cap as a cam to drive the diaphragm up and down, and plumbed its output into the chamber. After every shot the motor ran for a brief interval, cleared the chamber, and the gun was ready for the next cycle. Petrol and hydroxy both worked.
Why it’s on the list
Not because the end object was worth building — it’s teenage-me doing something most of my adult friends wince at. But the mechanical problem — how do you re-use a single small chamber in rapid cycles without persistent contamination — is a genuinely interesting question, and the way I solved it (an adapted aquarium pump as a cheap cam-driven diaphragm) is the kind of cross-domain scavenging that showed up again and again in my later work. The broader pattern was: I had no Amazon, no catalogues, no budget, and a problem. The shop down the road had adjacent machines. The solution was to see how they came apart.
Where it belongs
On the “earlier experiments” shelf, labelled honestly as adolescent engineering. Left here because hiding it would misrepresent where the resourcefulness comes from.