Thursday, February 12, 2009

Jam Jar Jet Update


I've found some 3/8 drill bits and HAND-drilled (meaning turning the stupid bit around by hand and with nothing else) a single hole in a tomato sauce glass jar cap. And widened it using a can opener. Funfunfun. I've got the thing to ignite using the same rubbing alcohol and have it run for a couple seconds before it chokes itself out.

Possible reasons for choking out:
-gets too hot too fast; liquid alcohol evaporates quicker, messes up fuel/air ratio. there actually seems to be a certain temperature range that makes the thing go better.
-hole is of a bad size. i don't think so, because i've been slowly carving my way up from 3/8 to near 5/8 holes.
-no diffuser. probably not the main reason, but may contribute to the problem. alcohol gets pretty agitated by the constant barrage of explosions inside the jar.

It's fun to ignite. At first, when igniting a cold jar, the flame propogates from the top of the hole where it was ignited, running down the inside wall of the jar in a ring of fire until it gets to the bottom. Then, it coughs and starts to run like it's supposed to. It actually sounds like a car engine, starting slow then slowly speeding up. Then it chokes itself out. If the jar is warm/hot when it is first ignited, there is a HUGE jet of hot gas that BURSTS forth before it starts up. The problem is, if it is too violent of a starting jet, it doesn't start and just sits there. Dunno why.
The exhaust (especially leftover in the jar from running it) smells funky. The cut edge of the cap and several metal shavings in the bottom of the jar have both turned red from corrosion.

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