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Post questions and info about combustion (flammable vapor) powered launchers here. This includes discussion about fuels, ratios, ignition systems and anything else relevant to launchers powered by igniting things like hairspray or propane.

Postby boilingleadbath » Sun Feb 18, 2007 2:33 pm

My experience is that, even with a (pretty close to) perfect propane-air mixture and center ignition, the existance of a small hole (say, 1.4" in a 1 gallon jug) will severely slow the combustion.

For instance, if one takes a 1 gallon milk-jug, rigs up a center ignition point, but doesn't screw the lid on very tightly... it pops off, and you get a "Pwoosh".
Meanwhile, if the lid is on tightly, it goes "woBong". Loudly.

I'm not entirely certain <i>why</i> this happens.

Anyway, that's my geuss: the lid is popping off pretty early, creating the same conditions as in my milk jugs. No pressure... no projectile movement.
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Postby spuzi14 » Sun Feb 18, 2007 2:41 pm

Pretty cool either way.
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