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Author: Subject: Bickford fuse style home made detonating cord experiment
Hennig Brand
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[*] posted on 20-9-2014 at 16:47


Looks like a nice working fuse & detcord winding machine. It also looks like you have some experience working with motor control. I always wanted to make a winding machine, but never got around to it yet.

How thick is the covering, winding, glue and all?




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markx
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[*] posted on 21-9-2014 at 11:24


Quote: Originally posted by Hennig Brand  
Looks like a nice working fuse & detcord winding machine. It also looks like you have some experience working with motor control. I always wanted to make a winding machine, but never got around to it yet.

How thick is the covering, winding, glue and all?


The core has a diameter of 2mm and the whole cord is 3mm:

DSCF0672.JPG - 2MB

The glue does not practically increase the diameter as it mostly gets absorbed into the layers.




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[*] posted on 22-9-2014 at 12:15



Going a bit off topic I always had a pet project in my head to make /obtain a few hundred meters of det core and let it rip suspended on poles/trees strung out in a somewhat straight line. This would create a sound like thunder as not all sound reaches a spectator at the same time (just like the rapidly expanding channel created by a lightening bolt).
If one were to use ETN how narrow could you go with the center and thus make the cord as long as possible with as little stuff as possible. A pound should make a hundred meters one would hope.
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[*] posted on 22-9-2014 at 13:41


Quote: Originally posted by jock88  

I always had a pet project in my head to make /obtain a few hundred meters of det core and let it rip suspended on poles/trees strung out in a somewhat straight line. This would create a sound like thunder as not all sound reaches a spectator at the same time (just like the rapidly expanding channel created by a lightening bolt).


I have had the experience of being perhaps 200 meters from such a suspended det cord shot, with no prior warning- At PGI convention, someone with a severe passive aggressive problem used a long suspended run of det cord attached with many short sections of shock tube, to ignite individual waterfall sticks via shockwave:flame transducers- Thus lighting a large tight wire "waterfall" (Fargo? Can't remember the year).

The audience effect was not like hearing rolling thunder. It was like being HIT by lightning. Everyone was just holding their ears and cursing as the poor waterfall burnt placidly away...




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[*] posted on 23-9-2014 at 14:16


At what point should we rename this thread 'det cord experiment'. Really excellent cord though. I wish you would've had more luck than only PETN. Have you tried initiating a charge at the other end of the cord?
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[*] posted on 23-9-2014 at 18:12



Quote:

At what point should we rename this thread 'det cord experiment'.


roXefeller has a point- It could aid anyone searching on this topic.

markx, would you agree to a change of the thread title?

Something like:

Home made PETN det cord via Bickford type spun fuse machine (was "Shock tube experiment")

Or other title of your choice...

PM me if you would like the thread title edited?




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markx
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[*] posted on 5-10-2014 at 14:09


Just tested the uncoated cyclonite core:



DSCF0778.JPG - 2.1MB DSCF0779.JPG - 2.1MB DSCF0780.JPG - 2.1MB DSCF0781.JPG - 2MB


It's a no go at this diameter....


For comparison the PETN core at the very same setup:



DSCF0783.JPG - 1.5MB DSCF0784.JPG - 2MB




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[*] posted on 5-10-2014 at 14:20


oooo I like the multicolor thread, kindof like raising the technology to a higher, artistic level. But I'm thinking you could've just grabbed what was available/on-sale.
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[*] posted on 5-10-2014 at 23:39


Quote: Originally posted by roXefeller  
oooo I like the multicolor thread, kindof like raising the technology to a higher, artistic level. But I'm thinking you could've just grabbed what was available/on-sale.


A colorful coincidence, yes, but not by design :)
Although there are countless ways to weave a specific pattern for marking purposes. Just it is too much of a pain to reconfigure the weaving machine with separate threads for every different formulation.

[Edited on 6-10-2014 by markx]




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[*] posted on 6-10-2014 at 02:33


Quote:
Makes an awesome doorplate :)

Indeed, and the art world is waiting . . .

I'm not joking, BTW!

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[*] posted on 6-10-2014 at 03:44


Quote: Originally posted by hissingnoise  
Quote:
Makes an awesome doorplate :)

Indeed, and the art world is waiting . . .

I'm not joking, BTW!



Writing immortal quotes into metal with det cord is rather boring and simplistic....imprinting different natural objects (leaves, feathers etc.) into metal with a thin layer of plastique detonated over them, now thats way more awesome :)
Google Evelyn Rosenberg, she is the grandmaster of the detonographic method. Really cool and unique art.

I have attempted the method on a simple basis, but fortune has not favored these experiments so far. I've had failed initiations and all sorts of just bad luck every time I rig up a piece. But I'm not giving up...it has to work at some point:



DSCF0731.JPG - 2MB DSCF0732.JPG - 1.9MB DSCF0733.JPG - 2MB DSCF0734.JPG - 1.9MB DSCF0735.JPG - 2.1MB

And after all the preparations the det cord failed to initiate the plastique....left a nice imprint of it's woven structure along the edge of the backplate and disintegrated the artwork and the charge. If I had folded the cord twice or even three times along the edge of the plastique, then it probably would have had enough impulse to kick off the plastique. Hindsight....sigh...the only true precise science.




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Laboratory of Liptakov
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[*] posted on 10-10-2014 at 10:10
plant


And what follows. Yes, I know, it's not so nice. The old pot is terrible. The whole thing is terrible. But try it could.
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old pot.jpg - 206kB
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[*] posted on 10-10-2014 at 11:49


Detonographics are cool.:cool:

initiating such plastick sheet is a hard lesson I know:D

2 mm core is little in combination with soft shock-dampening twine,
Seems to be the issue with the RDX cord too, if initiated right it might be a go

20% binder is a lot.




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[*] posted on 10-10-2014 at 13:32


Digressing from the topic of the thread, but here are the remnants of the same plastique from the failed detonography test (20% inerts are quite ok for PETN based compositions):



DSCF0785.JPG - 2MB DSCF0787.JPG - 2.1MB DSCF0788.JPG - 2.1MB DSCF0789.JPG - 2.1MB


Packed behind an "exotic" coin, placed on top of a 13mm steel plate and disposed of in a responsible manner. Leaves quite a mark, especially on the bottom side...the plate is not cast iron, although one could assume that from the coarse cristalline structure.

[Edited on 10-10-2014 by markx]




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[*] posted on 10-10-2014 at 21:28


Nice;)

Did you try a initiation with the exposed core in direct contact with the plastique?




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[*] posted on 14-10-2014 at 06:22


Seeing your test made me think that it was time to try detonating some plastic explosive with my own detcord. My own test was also unsuccessful. The plastique used was 81% ETN, 19% inerts. There is a dent in the steel where the plastique was sitting, but that extra effect could have just been from the confinement the plastique provided for the detcord, or possibly the plastique between the cord and steel detonated, but not the rest.

This cord is the same 2m piece that was made in 2011 and discussed here:

http://www.sciencemadness.org/talk/viewthread.php?tid=14204&...

Notice how one half of the detcord is more yellowed than the other half. Each half was made from a different batch of ETN and it would seem that residual acidity was better neutralized in the less yellowed half and/or the ETN in that half was better stabilized. I don't know if it is obvious from the picture, but it is fairly obvious when holding the cord.


Components.jpg - 518kB Cut Cord on Wooden Board.jpg - 494kB Outstretched Cord.jpg - 516kB Cord With Cap.jpg - 494kB Charge in Place.jpg - 516kB Post Detonation.jpg - 510kB


[Edited on 15-10-2014 by Hennig Brand]




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[*] posted on 14-10-2014 at 09:54


I think the dent come's from a positive detonation of a small part of the plastique. no plastique tamping effect.
Unless there are other factors to consider like it was inserted into the whole length of the charge, or the cord has no bare cut inserted but was capped or plugged.

probably the major part just snottified before the shockwave ran past the bare cut.


[Edited on 14-10-2014 by magneet]

[Edited on 14-10-2014 by magneet]

[Edited on 14-10-2014 by magneet]




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[*] posted on 15-10-2014 at 02:23


The cord was run most of the way through the charge. The charge was however very small (~12g) and the impulse from a single strand of detcord is not nearly as powerful as from a number 8 blasting cap (or similar equivalent). The detcord used has about 14.6g of ETN per meter of length at a density of about 1g/cc. This corresponds to about 0.37g of ETN per inch of cord length at the low density (relative to a typical blasting cap base charge) of about 1g/cc. The vinyl tubing, explosive core covering, is about 1mm thick, which is reasonably thin, but still considerably thicker than the aluminum blasting cap casings I normally use. From reading some of the old U.S. army field manuals it seems that even the military issue detcord is normally knotted, or doubled up in some way, where it will be used to initiate secondary explosives. I haven't tested it yet, but I imagine a single strand would initiate dynamite reliably.


[Edited on 15-10-2014 by Hennig Brand]




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[*] posted on 15-10-2014 at 10:18
detonography


The first attemp.
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detonography.jpg - 131kB
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[*] posted on 15-10-2014 at 10:33


Nice impression you made there.

Regarding dynamite initiation with the homemade vinyl tubing detcord, a test was just performed and it was positive for initiation. The dynamite used was actually nitroglycerine powder (10% NG), so it was not one of the more sensitive dynamite type explosives. All dynamites are sensitive though, relatively speaking. The explosive used weighed 25g and was 10% NG, 10% corn starch and 80% ammonium nitrate. It was lightly tamped to a density of 1-1.1g/cc in a polypropylene pill bottle. An unsharpened pencil was forced through the explosive to the bottom of the casing, making a void, and then the detcord was inserted and the explosive gently packed around it. The dynamite was successfully initiated, but in comparison to plastique it is very ineffective against steel.

Charge Configuration.jpg - 527kB Charge In Place.jpg - 506kB Post Detonation Dent 1.jpg - 511kB Post Detonation Dent 2.jpg - 481kB


[Edited on 16-10-2014 by Hennig Brand]




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[*] posted on 21-10-2014 at 05:37
detonography


Detonography 2

detonography2.jpg - 365kB
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[*] posted on 21-10-2014 at 06:12


Those look excellent.



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[*] posted on 21-10-2014 at 07:51


Very nice L of L

Looks like a more cost eficient method for amateur detonografy.

Did you tamped the whole thing in sand? or in open air?




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cool.gif posted on 21-10-2014 at 08:08
detonography


The whole assembly was in the sand. Thank you. Further tests will follow.
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[*] posted on 22-10-2014 at 01:44
wet gypsum


As the transmission medium used wet gypsum. Other configurations identical.
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wet gips medium m.jpg - 252kB
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