# compressor from garage sale

Typical pressure cooker is about 5 liters. It would take 5000 / 270 = 18.5 grams of black powder to produce 5 l of gas at 1 atm pressure -- so developing a pressure of, say, 25 atmospheres would require 25 times that much: 463 g, or just over a pound.
And that's assuming there's nothing else in the pressure cooker, which we know is not the case. Suppose the interior volume was reduced by half, by the ball bearings and nails these guys added. In that case, we're talking a free volume of only about 2.5 liters, and a kilogram of powder would generate pressure well over 100 atmospheres.
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On Mon, 6 May 2013 17:14:58 +0000 (UTC), Doug Miller

Assuming that it didn't rupture first.
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snipped-for-privacy@attt.bizz wrote in

Well, yes, but the point is that a consumer-grade air compressor can't even come close to developing that kind of pressure.
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On Mon, 6 May 2013 18:20:30 +0000 (UTC), Doug Miller

A pressure cooker can't either.
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snipped-for-privacy@attt.bizz wrote in

the

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to

Did this discussion ruffle your hair at all?
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On Mon, 6 May 2013 22:29:03 +0000 (UTC), Doug Miller

Of course not. My hair comes pre-ruffled. You're not going to change it.
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On 5/6/13 4:20 PM, snipped-for-privacy@attt.bizz wrote:

Gun power can.
--

-MIKE-

"Playing is not something I do at night, it's my function in life"
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wrote:

Only if contained. Gun powder a low explosive (the shock wave is sub-sonic in the powder) and will not explode unless it's contained. A pressure cooker isn't the best pressure vessel for this sort of thing, either.
Although this wasn't gun powder, either. It was flash powder (fireworks), which has a higher burn rate (usually contains metal powder).
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Yep, and also depends upon the sensitivity of the explosive on whether it needs a primary explosion (blasting cap) to activate, otherwise it just burns. Cooked my meals, by boiling water for LRP rations, with explosives (C4) for the better part of 7 months, using a thumb sized chunk, in a C-ration peach can "stove" vented with holes made by a church key.
--
www.ewoodshop.com (Mobile)

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On 5/6/13 6:43 PM, snipped-for-privacy@attt.bizz wrote:

Ok, change everything I wrote to include "flash" powder. The point is, an air tank doesn't "explode" sending shrapnel and... A pressure cooker packed with an explosive plus ball bearings... does... very well.
--

-MIKE-

"Playing is not something I do at night, it's my function in life"
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wrote:

compression to explode, so?

Not that I said...
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On 5/6/2013 12:21 PM, snipped-for-privacy@attt.bizz wrote:

Pressure cookers are designed to release pressure, that hissing you hear, at 15 lbs.
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It's not very hard to remove the safety valve and replace it with a nut and bolt.
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On 5/6/2013 2:47 PM, Doug Miller wrote:

Correct. You would also have to defeat the secondary pressure relief and probably glue the lid on.
I made this comment more to address Lew's comment when comparing pressure in a compressor to a pressure cooker being an explosive container.
The compressor in no way would possibly have a comparable amount of pressure that the pressure cooker with the explosives had nor would it come apart the same should it fail under normal operating conditions.
Relatively speaking I seriously doubt that a pressure cooker would contain the extreme pressure generated in an explosive inside more than say a shoe box. With every thing that was in the pressure cooker to create the damage the weight would have probably been too great for a shoe box to hold up. I wold be willing to bet the the lids gave way first.
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wrote:

Sure, but that's not going to relieve much of the blast pressure. What does mean, I suppose, is that the cooker is only designed for 1ATM, or so (*much* less than a compressor tank).
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On 5/6/2013 4:23 PM, snipped-for-privacy@attt.bizz wrote:

That is what I was getting at. I am sure the lids popped off first. I think pressure cookers were used simply because they are relative strong for carrying weight and are not them selves heavy. It was the exploding contents, not the pressure build up because of the pressure cookers ability to hold pressure that caused the damage. Sure it was part of the shrapnel but a metal ammo box would have done the same thing.
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"Leon" wrote in message

That is what I was getting at. I am sure the lids popped off first. I think pressure cookers were used simply because they are relative strong for carrying weight and are not them selves heavy. It was the exploding contents, not the pressure build up because of the pressure cookers ability to hold pressure that caused the damage. Sure it was part of the shrapnel but a metal ammo box would have done the same thing. =======================================================================Black powder, unrestrained, will not explode. It will burn releasing its energy into the atmosphere without much effect. It has to be compressed. The pressure cooker is what makes it a bomb. On a stove, the pressure build up is relatively slow, giving the top, the weakest part, time to distort and separate. If it is filled with black powder, the pressure build up is so fast that the lid does not have time to distort and detach itself. The entire container will let loose. A weaker container such as an ammo can, would not produce near the blast that a pressure cooker would.
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On 5/6/13 2:37 PM, Leon wrote:

Assuming the thing wasn't plugged in, it's probably just a decent vessel for a bomb and not a functional part of the explosion mechanism.
Of course, one could easily find out exactly what, why, and how it works and how to make your own with a simple google search. But I don't care to start a homeland security file on myself, so I'll pass. :-)
--

-MIKE-

"Playing is not something I do at night, it's my function in life"
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One thing I was wondering, did these Boston bombers make a practice bomb first anywhere? Was there ever any mention of that? After all, if someone intends to go out with their homemade bomb to do some damage, they usually want to know if the damned thing will work before they head out.
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On 5/8/2013 10:05 PM, snipped-for-privacy@none.com wrote:

yes. there was a newspaper article that the fbi was questioning some people in reference to an explosion in the woods somewhere around boston.
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