Improvised Bomb Tanks

[Arkangel]

We've covered the question of where people might test stuff if they were minded to do so, as well as blast screens for working with energetic materials. This question is really to combine the two.

My mother, despite giggling as much as me, is getting a bit pissed off with me blowing her flowerbeds up when I do small underground tests :D . (I can only test when I'm back "home", since I currently live in a city) For bigger things naturally I have to be away from civilisation, but it's sometimes convenient just to pop out and try out an idea.

I have a fair collection of shell cases, from being in the military. Having spent a while in Armoured units, I have some nice 76mm shell cases from the Scorpion AFV, as well as some starter cartridges from Canberra bomber engines. What I plan to do this weekend is try out a few test charges in them, ranging from cherry boomer (guiness widget size) up to about 150g of Flash (since that's all I have to play with at the moment)

I'll try them at all sizes buried first, with just the mouth of the shell visible. I'll then try them in the open air to see what happens. If poss, I'll try to get some pictures and post them, but has anyone got any ideas/thoughts/comments about these, especially about the sort of power that a brass shell case might contain when not contained in a breech. The Scorpion case is about 13" long and yep, 76mm across the mouth. Thickness at the mouth is about 1mm, but tapering from about 5mm at the base. (It might be possible to get say, a naval shell case from a 4.5" gun, and saw the top part of it off to make it more suitable)

These things are available from car boot sales for next to 'nowt, so might be a useful buy.

(By the way, this weekend I also plan to use a series of boomers and timed fuses to blow up an 18" high singing Santa Claus that some dopey relative gave me. I know that's really k3wl and what have you, but I'm sure it will be most amusing, tell me if you want a vid <img border="0" title="" alt="[Wink]" src="wink.gif" /> )

[BoB-]

Huh? Do you mean to detonate a small test charge in a large shell casing underground? For noise suppresion? So close to ground level, and with an open mouth, the charge will be very loud. Rjche posted something about this awhile back, only it was very deep, and had a closeable lid.

I suggest you find well tap (50' hole in the ground covered in wood) or a deep body of water.

[Arkangel]

It's not so much for noise suppression (although that's a factor). It's more to contain the blast and direct it upwards, and I'm wondering how strong a shell case would for that.

Pyro companies sell bomb tanks for firing certain types of charge. Skylighter sell stuff called binary concussion powder, and to fire that in, they sell something made out of 3" steel rod, with a 1" hole drilled 4" down the centre. It looks strong as hell, and will take one ounce of powder.

My query is really to see if anyone's tried a shell case like this at all. Interesting what you say about making it louder. I'll have to let you know how I get on tomorrow

Edit: btw, I have some remote places, and a body of water that I've fired stuff in before. The water in particular was brilliantly effective in deadening the sound. This is more so I can safely test stuff close to my shed - balls to waking the neighbours up, I just don't want to damage anything nearby.

<small>[ September 20, 2002, 06:26 PM: Message edited by: Arkangel ]</small>

[kingspaz]

to replace the barrel effect put the shell in a bucket and fill the bucket with concrete surrounding the shell. should give it alot more strength.

[spydamonkee]

another thing you could add is either water proof your charges or somehow make a seal over the charge then fill the rest of the shell with water IE:

</font><blockquote><font size="1" face="Verdana, Arial, Helvetica">code:</font><hr /><pre style="font-size:x-small; font-family: monospace;">|wtr|
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-----</pre><hr /></blockquote><font size="2" face="Verdana, Arial, Helvetica">should deaden the sound a lil (cant wake nextdoors up too much :D )
also would add to the effect :p
this would be best done combined with Kingspaz's idea though as dependant on charge size and amount of water used you could end up rupturing the shell and "barrel"

<small>[ September 22, 2002, 03:38 AM: Message edited by: spydamonkee ]</small>

[Arkangel]

Well, tried charges in both cartridges, and couldn't be bothered to bury either, as I have some spares. The Scorpion case was the one I put the biggest charges in, and it held up pretty well. I don't have any HE's so Flash was all I tried, however, the largest was a hefty 100g. With successively larger ones it kept punching the case further into the soil, so for the largest charges I put it on a concrete slab. I fired them electrically, and from my vantage point, the smoke fired almost instantaneously up 50 feet or so. I don't know how much pressure was achieved, but I'm fairly sure after this that the case could contain pretty much any pyro charge I'm inclined to make.

Along the lines of what you were thinking Spyda, I reckon the next trick is going to be having a litre and a half of Kerosene in it, with a flash charge at the bottom :D . If it doesn't split the case it will make a fantastic fireball projector for special effects. For all you guys pressing dets, you could well incorporate one of these into your press as a blast guard.

(P.s. Santa is now in many small pieces - no prezzies for you lot <img border="0" title="" alt="[Wink]" src="wink.gif" /> )

Edit: I'll post pics of the shell case tests as soon as my brother develops his film - no digital camera I'm afraid

<small>[ September 22, 2002, 09:13 PM: Message edited by: Arkangel ]</small>

[EP]

A related question: I'm looking at buying a ball mill and want to run it as safely as possible. I can't exactly locate it out in the middle of a field hundreds of feet from my house (there is no field...) so I'm planning on locating it in a shed and having the mill surrouned in sandbags. The question is should I put anything over the top of this? Is there a good way to quiet the thing down in case it does explode so the whole neighborhood doesn't hear it?

[Al Nobel]

If you buy a pyro ball mill there should be no static electricity .So if you mill pure stuff and no mixtures why should it explode ? Sorry for my english

[EP]

There's nothing wrong with having a backup plan <img border="0" title="" alt="[Wink]" src="wink.gif" />

Besides, there are other things that can go wrong, such as powder getting in the gears...

[Microtek]

I am using a blast chamber at one location. It is a small safe ( about 30 cm cubed ) that I have buried in the ground with the door facing upwards. I have only tested detonators in it yet, so about 0.5 grams PETN or RDX, but these are almost silenced. Standing 20 meters away you might miss the sound if you aren't listening carefully.

[xoo1246]

If you dig down a detonatorn 20 cm into the ground you have the same effect. But, sure it can be good if you wish to recover fragments.

[Arkangel]

Xoo, that was an interesting point actually. The widget fragments were all in there. The larger charges were all in screw lid aluminium canisters. (Very neat looking, watertight etc). The lids had gone, but the main body of the cannisters were contained, so as you say, any fragments should be recoverable from this type of container.

Al, if you work on the basis that something "shouldn't" explode because you've got everything right, then sooner or later you're going to hurt yourself. Accidents are just that - something you didn't forsee, or were careless with. I want to test this containment, and a few other ideas, because I don't want to take chances.

[knowledgehungry]

Apologies to all for not searching(have a lot of stuff on my mind, no excuse but I just forgot to search).

Well now that I am in the right place, here are my thoughts. I'm thinking of a relatively large blasting box, large enough to test primarys and maybe some small SC's. I am thinking of buying a fire safe, and filling it with sand. I was thinking fill safe half way with sand, then put in charge that was wanted to be tested inside of a smaller container, for SC's at leats, then fill it up the rest of the way with sand. Do you have any thoughts?

[Mr Cool]

Sand and little polystyrene balls works well. I used the polystyrene also to allow a bit more of the pressure to be absorbed, while the heavy sand takes the energy of the blast. It was about 50/50 by volume. But I used it in a plastic tub, which burst and it all went everywhere :(.
Certainly don't use water to try and deaden the noise, sooner or later this will break any container.
If using a big shell casing, lining it with carpet (a few layers of thick carpet) will help reduce the noise, and also stop frags from being deformed when they strike the walls at the speed of a bullet, so any examination that you might want to do on them will be more useful since there'd be no secondary deformation.
The best thing to do in order to test simple charges would be to get a plastic rainwater collector (I've seen them as big as 150 gallons) and bury it in the ground. Fill it about a third to a half up with sand, and bury your charge in this. If using a witness plate or something similar, drill a hole in it and attach a cord so you can pull it out afterwards. Make a heavy lid for it by sticking a few layers of carpet to a bit of wood (so that it makes a good seal), and weigh it down from above with bricks, earth etc.

Arkangel's observations with the shell casing remind me of putting a flash charge in an old washing machine. It instantly sent a column of smoke out the (open) door. I wonder what it'd have been like to be standing two dozen metres in front...