Det Cord Construction

[X-Wulf]

I'm noy sure exactly in which section this belongs, but I believe it's combustion velocity allows it's classification as an HE.

I recently saw a documentary on movie special effects, and it seems that the most commonly used device is what they call "det cord". It seems to be a brightly coloured (must be hollow and filled with something) plastic tube which they keep coiled up like rope. This stuff is thin, about 1/4" or less, but is claimed to burn at over 22,000 feet/s. This is the stuff the use to cut straight through wooden beams, to shatter PVC tubing and to vapourise petrol for fireballs.

The pastic tubing is easy enough to obtain, but does anyone know what is inside? Flash perhaps?

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Live Forever!

[CyclonitePyro]

Another OUCH, c'mon you've been here how long and don't know waht det cord is?!
It's filled with PETN, it doesn't burn it detonates, nothing magical about it. Wrong section, should go in low explosives if you are talking about using as a detonator and impro. weapons if you want to talk about how to make it. But the whole topic is retarded. You obviously didn't search, this stuff is as well known and as common as
fuse(except you can't just buy it).
Take some flexable tubing and fill with HE, wow!!! You got detcord.
I'd like to get a piece of it and wear it as a necklace, without the PETN though.

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"Friends don't let friends play with
Nitrogen Triiodide"

[Microtek]

I agree that it should go in improvised weapons or misc., but I think the headline is a valid subject. We all know the principle in det cord, but I have thought for some time about how to actually make useful lengths of it ( 10 meters or so ).
The ideas I've been considering includes:
- Liquid filler such as NG or EGDN possibly desensitized with NM. This would be easy to make, but would be difficult to use as you couldn't just cut it into whatever lengths you need.
- Cutting a plastic hose open, and filling with crystalline HE, then closing it with tape or glue of some sort. Here the seam
would likely be either inflexible or unable to hold water.
- I tried a design similar to the KMnO4/S/silicone fuse that I wrote about earlier, but used acetone peroxide as the active ingredient. Detonation wasn't self-sustaining, and the AP volatilized over time.
A variation over this design is still my prime contender; I'll let you know when my testing is done. Also, watch 'Miscellaneous' for the next couple of weeks, as I have something brewing that some of you may find very usefull.
Anyway, if anyone out there has a good idea about how to fill a 4mm hose with explosive and make it stay uniformly distributed, then I'd certainly like to know.

[DBSP]

Is it only me or have the rest of you allso noticed the large ammount of stupid questions asked the last few days ?http://theforum.virtualave.net/ubb/smilies/confused.gif


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¤monte¤

[Yikes]

I tried it once, filling a thin (2mm?) drinking straw with HMTD. Very hard to get the HMTD inside tightly packed, because I only had a thin wire to use as a ram.

Straws filled this way can be kept for months, and will completely detonate from a fuse only. (I used them to scar aluminium plate...just to see if it worked.

Detonating straws are not very useful, though: they are only 8" long.....

[A-BOMB]

Try linking them this way get the ones that that have the flex shaft and fill a fax/htmd compound a little ways from the shorter end and them do the same on the other end except at the end. Now slit the end that you put the compound it so you can slid the end of the next stray and repeat till you get a good side segment of detcord.

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live by the bomb
die by the bomb
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[Mick]

or to save screwing around with straws, just go buy some nylon fuel hose and fill that up.

I tried this with ap, works quite well.
but it all depends on what you want to do with it if will work for you or not.

Also, a good idea is to leave the ends (round 10cm) empty and pack them with tissue paper or something, that way you have something to hold onto. Atleast it gives you a %1 chance of not blowing your fingers off should it detonate while your wrapping it around something.

[Microtek]

I don't think straws are a viable solution.
They are not nearly flexible or strong enough. And as for the nylon hose, well yes that would be good, but how would you go about filling it? Of course it's easy if you only need 20 cm or so, but what about 3 or even 30 meters? And how about when you cut it into whatever lengths you need? HMTD or AP is too sensitive so you'd have to use something else ( not really a problem ), but how to stop it from gushing out of the end?
You could certainly use tape or wax to seal the cut, but that would be a bit messy in my opinion.

[X-Wulf]

If a plasticising agent of some kind could be added to NG, Astrolite, etc. (perhaps nitrocellulose would work for this). This dough-consistency HE could then be rolled or pressed into long rope-like strands and coated with a spray-on plastic covering (such as those aerosol sealants you can buy).
This would provide long, plastic coated lengths of det cord. It could also be cut into strips (could be good to blow doors off http://theforum.virtualave.net/ubb/smilies/smile.gif).

I've also heard of something called "primer cord", but its description is very similar to that of det cord. Is this the same thing?

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Live Forever!

[PYRO500]

I am keeping this topic open beacuse there hasn't been much overall discussion on improvising detcord and linear explosives,
----transfering to misc--------

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[URL=http://www.geocities.com/pyro2000us/]

[mongo blongo]

I think it would be best to plastisize the PETN or RDX (something good, not AP!) so that you get C1, C4 or use both to get Semtex or what ever. ANNM plastique would work I imagine.
Find some tubing good for the job and push it into the tube using a stick or something.
You could then cut it into any length you want without the explosive falling out.
Well that's how I would do it anawys.

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AAARRRRRHHH! My beautiful eyes! It burns!
The goggles do nothing!AAARRRRRHHH!

[Jhonbus]

Just an idea, would it be possible to granulate an explosive (eg PETN) and mix it with a wetting agent in which it is not soluble (not sure what this would be for any particular explosive) Then pump this slurry through a hose, which has some kind of filter on the end to let out the wetting agent but keep the granules of explosive inside the tube. Then you could blow compressed air through the hose, keeping the screen on the end, to completely remove all the wetness.

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You must create.

PGP Key ID on MIT server: 0x0ADBA985

[X-Wulf]

What is the consistency of plastique when it's about half dried out?
Having never had enough to play around with, I have no idea, but if it is that of rubber (hard or soft), then it would be perfect for the job. Maybe fill the tubes with an extra runny plastique (solvent could be acetone or something) and then prick tiny pin holes in the tube so that it can dry (these holes can easily be covered up later).

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What's the matter? Want to live forever?

[Arkangel]

It's worth remembering that Det Cord is more appropriately used for simultaneous firing of multiple charges, rather than cutting or other dems jobs, even though it is often used for that. Pyro500 mentions linear charges and there are a number of these commercially available to think around. The best ones I have seem resemble those bendy rulers or "artists curves". The difference being their cross section is a shaped charge, so rather than have a simple shock wave, you have a linear jet. They charge is some kind of plastic explosive, with a thin lead "skin".

I would have thought that it would be possible to improvise a linear shaped charge more effectively than det cord, assuming you could get hold of thin lead sheet. That is of course if Dems is what you want, rather than a detonation system

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It's easier to get forgiveness than permission

[Mr Cool]

I think the best/easiest way of making it would be to make up some PETN or RDX, and mix it with a mixture of some sort of synthetic rubber dissolved in acetone. Use roughly 80% HE, 20% rubber/acetone. Roll this mixture out into a flat sheet about 5mm thick, let the acetone evapourate and cut it into strips 5mm wide.
Obviously some experimentation will be needed to find a good rubber/gum to bind it together when it's dry, and to find the right proportions. Silicone sealant (for windows, aquaria etc) might work well, it's designed to be tough and flexible when set.

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"Nothing makes a man fear much, more than to know little." - Francis Bacon.

[PYRO500]

It'd be kind of hard to get the thing rolled up into a perfect length of detcord, I like the tubing idea, get a strand of tubing and blow rdx into it with compressed air. although if you could make a plastic explosive that dries out or something that gets thicker you could cut it with out having it pour out the explosive but still maintain flexability. I do not think acetone peroxide is a good choice for det cord beacuse to be useful you'll need to cut the cord and as I recall someone here made detcord with aquarium tubing and AP and tried to cut it causing it to go off. I have wondered what would happen if you made this stuff in hard plastic tubing just flexable enough for your needs, and you pushed it through a length of copper tubing. you'd have very firm self supporting length of detcord that wouldn't kink.

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[URL=http://www.geocities.com/pyro2000us/]

[Microtek]

I think x-wulf's idea with NG/NC is good, especially with the addition of a surface coating; it would make it much easier to handle, and would keep evaporation of nitric ester down to a minimum (though it's not that big a problem; I've had colloidinized EGDN sitting in the open for about 4 months now and it's fine ). BTW I'd prefer EGDN as NG has a tendency to undergo LVD at rather low VoD if it's too thin a sheet.

[nbk2000]

In the FTP file called "Plastic Bonded Explosives for underwater demolitions - Upload by Dave the Rave.zip", there's mention made of using latex bounded PETN and extruding the liquid into an acetone/alcohol bath, causing the latex to coagulate into thick threads (7mm) that can be collected on a reel.

Spinning det-cord sounds possible now. :)

[cpropellant]

1:It usually comes as a long piece of plastic string with some fibrous thread inside.Clothesline-check your mom's backyard or your local whatever.2:MEKP/AP(50/50).3:Vacuum pump!oops,this might be the only problem for one to obtain,but a worthy investment though.I haven't tried this with a water-jet aspirator yet.First off,insert one end of the clothesline into your MEKP/AP mixture (which must be dried by leaving in sun for a week or so under a plastic baggie.wach out for your occasional thunderstorm while away.Anyways,the explosive liqiud will be clear as water and all the acidity will be gone,well thats if you used HCL in your synth,which is the best.)Then insect the other end into a piece of nitrile rubber tubing or fishtank airhose,doesn't matter if it dissolves this.Tape this with normal insulation tape in a spiral direction so as to seal it nicely between the thin clothesline and thicker rubberhose.Now connect the hose to your vacuum pump and make magic!You will see the liquid explosive seeping through the clothesline towards your vacuum pump.This happens slowly with the line I use(very thin) so no worries there.Seal off the ends when finished,by cleaning with cloth or cheap-ass toilet paper and then using a gluegun to close off the ends.I have tested this with great success and it looks great!Neither the clothesline or gluegun rubber dissolves and the fibre inside the clothesline provides extra confinement and cappillary action to retain the oily liquid better,like wood shavings.I have tested these and they work great,well not as strong as high yeald,but perfect for initiating your primary charge that has to be inside the secondary.You might consider a two stage vacuum pump for very long pieces.*Sorry for not paraphrasing O Mihty Moderator,but my internet is down and I am writing from mobile.Thank you.*

[spat]

I would think that commercially the tube is made at the same time it is filled. An improvised method might be to start with a long strip of plastic sheeting then just roll up the HE of choice inside it like a burrito with some appropriate glue after the first layer of plastic completely covers the HE. You would probably want to roll it up so that there are several layers of plastic to make the tube stronger. I would assume that with the correct choice of explosive and plastic and glue and a little care you could make a pretty effective "product"

You couldn't make arbitrarily long sections, but if you were patient and had a long counter to work on you could probably do a couple meters.

If you needed a significant amount you would probably want to build a proper extrusion machine that would form the cylinder of HE and the tube at the same time.

Hmm, now that I'm thinking of it I wonder if you could spirally wind some plastic tape around a bit of plasticized HE extruded from whatever's handy (playdough anyone).

[Setharier]

One could, if all the necessary equipment are available, make butyl rubber plasticized PETN plastex, roll/press it in sheet form 5mm thick and cut or use serial cutter to separate 5mm thick and depending the sheet's size Xcm long rods. These rods are then to be connected each others heads and around the rods are wrapped ordinary 2-3" wide packing tape. By this method one can make advantageous amounts of detcord that has, if carefully wrapped, somewhat good water-resistance, is very elastic and stands pretty well when pulled and it can be cutted with conventional knife in any size and shape.

Theoretically something similar can be done with ordinary A4 paper rollings and tape where buthyl rubber and binder is not freely available. The explosive is binded using silicon or motor oil, grease or about anything that makes it not to just pour out. The exact size of paper sheet is rolled to form pipe sized of 5mm using any stick or device for easier wrapping. The packing tape is rolled around the paper, not yet up to the end, and then in the pipe are pushed the detmat mixture with funnel and/or straw. The end of the roll is wrapped with tape, but is not plugged as there is to be inserted another paper rod and continued until desired length of detcord is complete. This can be as well cutted with knife if plugged to avoid detmat dropping out, is flexible in means of wrapping around a tree and has at least as much power REF than TNT. In the place of oil binding agent one can actually make putty out of ordinary flour and water which acts surprisingly well as a binder, but tends to dry and broke. Using any oil in place of water may possibly increase substantially the shelf-life.

[Alexires]

Instead of wrapping, if you had it as a plastic you could put it in some heat shrink tubing and just have the tubing conform to the shape of the compound. You even could cut the shrink tube in half, extrude the PETN along the length, reseal the tubing with some glue, then shrink it to size.