"Leon" wrote in message
...

On 5/6/2013 4:23 PM, wrote:
On Mon, 06 May 2013 14:37:18 -0500, Leon lcb11211@swbelldotnet
wrote:

On 5/6/2013 12:21 PM, wrote:
On Mon, 6 May 2013 17:14:58 +0000 (UTC), Doug Miller
wrote:

Larry Blanchard wrote in
:

On Mon, 06 May 2013 11:34:44 +0000, Doug Miller wrote:

Do you *really*
think that the pressure developed by an air compressor (9 to 10
atmospheres is typical) is anywhere nearly comparable to the pressure
developed by igniting gunpowder in a small confined volume?

I found this:

"One gram of blackpowder gives you 718 calories of heat, 270 cubic
centimeters of gas,"

So if we knew how much powder the bombers used and the volume of the
pressure cooker we could come up with a pressure.

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.

Assuming that it didn't rupture first.



Pressure cookers are designed to release pressure, that hissing you
hear, at 15 lbs.

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).


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.