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biggest combustion ever?

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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biggest combustion ever?

Unread postAuthor: jackssmirkingrevenge » Thu Jul 16, 2009 9:57 am

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Unread postAuthor: jeepkahn » Thu Jul 16, 2009 10:03 am

Which is exactly why WE, in the repair biz, want to know if you've used fix-flat or other chemical in your tires.... i have had 3 close friends hospitalized due to explosions while changing tires/tyres thanx to the explosive propellents in most such products... even if it's merely rubber cement on an internal patch, if it's not dry when the rubber is remounted, you have a great big hybrid chamber waiting to go off....
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Unread postAuthor: inonickname » Thu Jul 16, 2009 10:06 am

Perhaps, but when I move out I'm going to get a small garden shed and put an exercise ball barrel on it. Add to that a propane meter, two large fans for fuel mixing and a 10" long spark gap..

I'd have to crunch some numbers on it, but the forces on the walls would be huge. Perhaps an old rainwater tank would work better
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Unread postAuthor: jimmy101 » Thu Jul 16, 2009 12:31 pm

The guy probably had a combustable mixture of fumes in the entire room and the electric pump ignited those. Hard to imagine an exploding mattress doing that type of damage, and hard to see how a spark would get into it from the inflator.
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Unread postAuthor: Hotwired » Thu Jul 16, 2009 1:54 pm

Could have been low-lying fumes being compressed by the pump into the mattress but still... all electrical sparking is on the motor which is external to the actual pump.

However a large beachball filled with a 1.5 atm mix would still be quite effective at blowing out wood and construction board walls.

What we need is a garden shed in the middle of nowhere to test this :D
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Unread postAuthor: ramses » Thu Jul 16, 2009 4:44 pm

In the garden shed, put a nice 1x mix. If you were really ambitious, you could load it up with a 5x oxy-mapp or similar.

And don't forget the ear protection!
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Unread postAuthor: Hotwired » Thu Jul 16, 2009 5:50 pm

A garden shed wouldn't hold 5x, be lucky if it held 2x.

The beachball explosion would be better because the shed won't be filled with combustible gas which is guaranteed to prawn it, instead it would just be the blast from the relatively small ball doing the work.
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Unread postAuthor: Moonbogg » Thu Jul 16, 2009 6:24 pm

I've created larger combustions after a decent mexican meal.
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Unread postAuthor: Hotwired » Thu Jul 16, 2009 8:02 pm

I've never really seen the appeal in farting onto a lighter personally.
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Unread postAuthor: jackssmirkingrevenge » Fri Jul 17, 2009 12:39 am

Hotwired wrote:However a large beachball filled with a 1.5 atm mix would still be quite effective at blowing out wood and construction board walls.


Isn't this the effect these tossers were after?
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Unread postAuthor: Hotwired » Sun Jul 19, 2009 1:31 pm

Yeaaaah probably. But I have doubts on what they expected to happen, kab00m á la hollywood sfx and a large crater is what I suspect they were thinking.

If it wasn't for the fact that they have more doctorates than I do I'd say they were utter cretins.

If they'd done something like ummmm.... strip the back of a delivery van, put some kind of large inflatable sheep in there or even several inflatable mattresses and have those filled with mixed fuel-air, THAT would work.

Naturally the van itself would have its walls pancaked the moment it went off and all large surface areas in the immediate vicinity made of wood or ceramics would get a serious hammering. A brick wall close to it could be caved in by such a large blast and certainly say goodbye to all windows in sight.

Fact is, the best they could have achieved with their carload of petrol is a burning car, which however you look at it is a pretty dam pathetic terror attack. It only happens what, hundreds of times a night anyway?
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Unread postAuthor: jackssmirkingrevenge » Sun Jul 19, 2009 1:45 pm

Yep, Al Qaeda certainly seems to be experiencing a drop in standards.

Takethis incident.

The public reaction – particularly in the blogosphere – was amusement as much as fear. The humour mainly derived from the perceived ineptitude of the attackers, and also their choice of Glasgow as a target, a city whose citizens are considered by the rest of the United Kingdom to be amongst the toughest, and the last with whom one would pick a fight.


:roll: :D
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Unread postAuthor: jimmy101 » Sun Jul 19, 2009 3:28 pm

I wonder if a 2'D beach ball filled with stoichiometric propane + air would even do much to a typical sized shed. You would only get a PSI or so of over pressure which might be enough to blow out a door or window but I don't think it would be all that impressive. Much better to fill the whole thing up with the proper fuel + air mix.

Lets see, 2"D beach ball would be about 4 cubic feet. Typical midwest "garden shed" is what 10x10x7? That's 700 cubic feet. The propane combustion sends the 4 ft^3 to about 9 ATM. Ignoring the volume of the beach ball relative to the volume of the shed, heat loss, various other details ...

(9 ATM)(4ft^3/700ft^3) = 0.05 ATM (0.8 PSI) overpressure. Not terribly impressive. Of course, there would be a couple (several?, many?) tons total force on the walls but the walls would only have to move a couple inches to drop the pressure back to 1 ATM.
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