Interesting 'delayed combustion' in a tin can

Insomniac · Fri Sep 05, 2008 3:58 am

I was fooling around with a tin can and deoderant when I discovered that by making a hole in the top, and another in the side near the bottom of a can, you can make it so that it will gently burn for a little while before going WHOOSH. The more deoderant sprayed in, the longer the delay. A smaller 'flame' hole also makes it go longer. Pretty useless really, but interesting. When I get my hands on an old milo tin I might see if I can make it blow off the lid with a bang instead of just going whooosh.

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Hotwired · Fri Sep 05, 2008 6:34 am

Yeah it's a common science class demonstration. Usually a coffee can filled with gas from a bench tap.

Except then there's enough gas/air to make a loud bang and blow the lid off the can.

I don't think when I last saw it it was a demonstration of anything much but just to amuse the class for a bit

iemand · Fri Sep 05, 2008 8:58 am

Hotwired wrote:Yeah it's a common science class demonstration. Usually a coffee can filled with gas from a bench tap.

Except then there's enough gas/air to make a loud bang and blow the lid off the can.

I don't think when I last saw it it was a demonstration of anything much but just to amuse the class for a bit

A balloon filled with hydrogen and lighted was also funny

(strangely the balloon was only 4 ft away from a window, but the window didn't break)

Hotwired · Fri Sep 05, 2008 9:22 am

Oh yes, I did bring up the idea of a delayed action airsoft mine for this, there'd be enough force to hurl a lid of bb's about if using a coffee or milo can.

More risky what with the flame and not really too useful but hey, it's a use

Insomniac · Fri Sep 05, 2008 6:48 pm

Just had an idea.... what if I put some methylated spirits in the bottom? The can is fairly cool, so the meths shouldn't evaporate too quick... hopefully it will fire, the resulting explosion stirring up the meths a bit, making more fumes until it goes off again... Like a really, REALLY slow pulsejet.

jimmy101 · Sat Sep 06, 2008 2:21 pm

Insomniac wrote:Just had an idea.... what if I put some methylated spirits in the bottom? The can is fairly cool, so the meths shouldn't evaporate too quick... hopefully it will fire, the resulting explosion stirring up the meths a bit, making more fumes until it goes off again... Like a really, REALLY slow pulsejet.

That's basically what the "jam jar" + liquid fuel pulse jet is. And it isn't all that slow, they still pulse at something like a hundred hertz.

Insomniac · Sat Sep 06, 2008 8:19 pm

Yeah I've made a few pulsejets like that (look at my youtube channel). I was thinking more of a WHOOSH.... long delay... WHOOSH...long delay etc. I tried it, and it ALMOST worked. It would go whoosh, and stay lit, but it would also have a small flame inside the can, at the small intake hole. This stopped it getting air back in and going off again. If I used the blowtorch to blow out the flame (ironic huh?) it would do the 'delay... whoosh' cycle again, but it would light the flame in the intake again. If I could find a way to stop that happening, it would make a pretty interesting little device.