Cannons

Steve B wrote:


I heard that all you need to do is adjust your OA torch for a "neutral" flame, snuff it out in a sandbox or maybe against the bench, and capture whatever mix you've got. :-)
Have Fun! Rich
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your correct, you get a nice blue" neutral" flame mix [ thats usually a good indicator of perfect ratio], snuff it on a wet rag, not a sand box!!! you'll clog the tip. fill your bag, then re-light the flame and touch off the bag. I do this with Tim Horton/starbucks cups placed upside down with the edge overhanging a table about an inch. Even a small foam coffee cup sounds like a shotgun.
we just did a large garbage bag last weekend hung from a wire about six feet up and touched it off with a E-match and 100' of wire . sounds like a howitzer!!!!
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Radius of what?
My understanding was that a sealing a rigid container with calcium carbide and water can produce acetylene under enough pressure to explode without a spark. Is that right?
Robert
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Bob wrote:

"Probably" . I do know that acetylene becomes unstable above (IIRC) 15psi unless it's dissolved in a solvent (acetone ?) . I think it would depend on how much cc and what size container .
--
Snag
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Snag wrote:

Radius of detonation.
When a substance detonates, energy from the surface of the detonating part is transferred into the not-yet-detonated part of the substance, and causes that part to detonate, and so on - this is how the detonation progresses. This surface usually has a radius.
As an instance, if you start from a point in an infinitely large block of substance then the detonation wave takes the form of an ever expanding sphere.
Now consider a tiny bit of not-yet-detonated substance which is just about to get hit by a detonation wave.
If the wave is tightly curved then the bit is getting energy from the points on the wave which are closest to it in an efficient manner, but the parts of the wave nearby are further away from the bit than they would be if the wave was flat -- the energy transferred to such an bit from a tightly curved wave is less than (and is transferred slower than) the energy transferred by a flat wave.
If the total energy transferred is not enough, or the energy is not transferred fast enough, the bit won't detonate, and the wave will die out.
This process means that in order to propagate a detonation wave has to have at least a certain minimum radius.
In PETN, used in detcord, the minimum radius is very small, less than a millimeter. In more usual high explosives it's on the order of a couple of millimeters. In gunpowder it's about a foot (yes, gunpowder will detonate if there is enough of it).

Probably. It's not something I'd care to try, and it's probably illegal too.

For acetylene at 15 psia the minimum radius of detonation is about a couple of inches - the exact figure is subject to dispute.
This means that it's reasonably safe to use acetylene at 15 psia if the tubes it's in are less than a couple of inches across - even if a detonation starts (for instance in an acetylene/oxygen mix rather than in pure acetylene) it will die out in acetylene at 15 psia if the container is small.
At higher pressures the minimum detonation radius decreases, and a cylinder of high pressure acetylene would be extremely dangerous, so acetylene cylinders are filled with diatomaceous earth [1] mixed with cement, or similar substances, to fill up the spaces.
The acetylene is also dissolved in acetone, so the pressure in the cylinder is less for a specific amount of acetylene.
[1] as used in dynamite to lessen the sensitivity of nitroglycerin - same principle, lowering the maximum radius of the substance available so it's less than the minimum detonation radius
-- Peter Fairbrother
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Rich Grise wrote:

The guy down the street from me has a WW I vintage Howitzer sitting in his front yard. Its too much trouble to top that, so we've quit trying.
--
Paul Hovnanian mailto: snipped-for-privacy@Hovnanian.com
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Not exactly what you asked for but.................I have made a acetylene and air or oxygen cannon out of 4 inch black plastic dwv pipe. I just used a welding torch to blow into the muzzle and then put some saran wrap over the muzzle and secured with a rubber band. The other end was a standard cap for the pipe. Tapped a hole for a spark plug and used a simple circuit that acted like a capacitive discharge into a regular auto spark coil. So I never was close when it went off. It did not bust the plastic pipe, but I would be extremely careful. The pipe was about four feet long. It was extremely loud. I would not want a louder one. I never loaded any projectile in it.
I had a neighbor that was lighting some firecrackers and throwing then down the hill onto my deck. I got the cannon and pointed it in his direction with no projectile. He immediately stopped after I set it off. It did not break any of his windows, but I should have been more cautious.
Dan
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snipped-for-privacy@krl.org wrote:

I'd think oxyacetylene wouldn't make a very effective propellant - I think it detonates, rather than simply deflagrating like BP or Smokeless; if you stuck some kind of projectile in it, I'd think it would greatly increase the odds that the pipe would blow up in your face.
Good Luck! Rich
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If you are near any drilling, such as oilfield. Find some used drill collars, They are thick and have a large hole in the middle around 2 to 2 1/2 inches in diameter. Could possible shoot beer cans full of cement about a mile. Usually weigh about 100 pounds to the foot.
Scott
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And this after I said about three times, I did not use any projectile and was not close to it when I fired it.
Dan
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Trying to disprove Darwin's are you ?
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snipped-for-privacy@krl.org wrote:

Sorry, no offense intended; guess I was reading through your words or something like that. I'm sure I have a good excuse here somewhere...
;-) Rich
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