Sciencemadness Discussion Board

A more durable improvised detonating cord?

Deceitful_Frank - 24-7-2010 at 02:56

Hey guys it has been a while!

Just wondered if anyone can help with this one...

I have experimented at length with ETN and obtained great results. It will initiate another cord with a 3cm overlap, ANNM etc. you can have some SERIOUS fun with a few metres of well made 10g/m!

Making it isn't without difficulty though. Using a 1m long strip of Al foil 4cm wide with an "M" crosssection makes getting an even bead of powdered ETN fairly easy and once folded and rolled up in to a long cigerette a couple layers of PIB self amalgamating tape will give you a really well pressed core and a tidy result... untill you kink the cord and the foil inside snaps! then the PIB constricts the core and you end up with what looks like a string of sausages and reliability is pretty much gone.

What we need is a material to roll up the ETN bead inside that when wrapped in compressive tape and kinked, wont snap inside. Do you guys think that I could stick with the Al foil (but using a narrower strip) method and somehow add something flexable under the compressive rubber wrap that will resist the small radius (<3cm) kinking?

Perhaps the ratio of Al foil to rubber is too high and I would do better to use the minimum amount I could possibly get by with that will contain the delicate ETN bead and keep it in one place for long enough for me to get the first compresive wrap of PIB around it. I am thinking the thinner the foil the better and the more wraps of PIB I give the core the less vulnerable to kinking the final cord will be.

Thoughts, ideas?

Regards, Frank

quicksilver - 24-7-2010 at 06:02

Hello Frank; it's been a few years since you've posted in various places.... welcome back.

I know you've seen a fuse machine where the weave is made below a hopper of BP and the result is a BP core inside a round braid; that's the professional method. Getting a fuse weaving machine is not cheap and setting the thing up is a serious nightmare, even for a factory with people who have worked with a weaving machine before.
Methods of making something simple generally hinge on keeping the length at a meter or two at total - max. The best I have heard of is the same technique for BP (naturally).
A woven tube "shell" is available at high-end electronics stores (this is important because it allows the thing to "breath" while holding the material) and a very sharp ended funnel needs to be found. As some material is placed within, it is compacted with compressed air from any compressor that has standard hose fittings - so again, a sharp ended little jet can fit inside and compact the powder with the compressed air. That's why you use a woven shell; to let the air release but retain the crystalline material effectively.
Air is a very effective way to compact various material & is safe. - Unless it's compacted to a great degree it will always kink too easily.

I imagine the science of this agenda would be in the construction of a real weaving machine or even understanding a method to do so. Many of the machines in use today were actually constructed well over 100 yrs ago. There is no real new technology that I'm aware of for fuse mfg. I would be very surprised if there was. The last time this subject had even arisen, someone found a fuse-weaving machine for bout $2000 but the complexity was really a turn-off as you don't know if you're getting all the correct parts (or if they function properly).

If you were really serious, the idea of understanding a round braid would be an important step in considering doing it on a high quality level.
But the manufactured hollow braid material I have seen in electronics stores would work very well for a short section and look quite professional; it would just need to be compacted with serious air (say about 150lb machine to get a good tamping).
Someone MAY post a link to a machine. They are NOT light-weight & they appear complex as all get-out.

[Edited on 24-7-2010 by quicksilver]

The WiZard is In - 24-7-2010 at 06:07

Quote: Originally posted by Deceitful_Frank  
Hey guys it has been a while!

Just wondered if anyone can help with this one...

I have experimented at length with ETN and obtained great results. It will initiate another cord with a 3cm overlap, ANNM etc. you can have some SERIOUS fun with a few metres of well made 10g/m!

Thoughts, ideas?

Regards, Frank

Heat shrink tubing

gnitseretni - 24-7-2010 at 07:02

I've tried loading PETN into heat shrink tubing once. I remember that it was a pain in the arse!!

Jimbo Jones - 24-7-2010 at 07:44

What about mixture based on ETN, NM and NC. Various NM % will make the consistence pliable enough to be extruded from 50 ml. syringe in the form of long, good shaped string. The NM will also ensure the high order detonation, because it’s very stable to LOD.

Instead of aluminum foil you may use a fat, long strip of paper tape (same as the duct tape, but with paper), which after the folding is covered with thin layer of rubber glue.

franklyn - 24-7-2010 at 08:03

Det Cord Post - Now locked

The Dupont TYVEK Tape links above are now extinct , use these instead


The two methods suited to making sleeves are Maypole braiding and Knitted cord

Toy Knit cord machines are available that can produce modest lengths and one
can assess their worth in a particular application before committing to purchase
an industrial machine which can cost a few thousand dollars new. In operation
both types of machines extrude the cord down so that a nozzle very much like
a large eye dropper style turkey baster inserted in the open end of the warp
feeds the filler into it as it is being made.

Useful toys
Bond Magicord Machine ( knitting type )
Real machines

Maypole braiding machines
In the braiding process spindles of yarn (or monofilaments) are placed on
what's called a carrier. Braiding machines range in size from 8 to 144 carriers.
The carrier orbits along the circular deck of the braiding machine in a "zig-zag"
fashion on a sinusoidal track while the yarn is pulled off the spindle. Half the
carriers move in the clockwise direction, while the other half move in the
counter-clockwise direction. This, combined with the wavering motion of the
carriers weaves the warp of a braided sleeve.

Maypole Braider.gif - 100kB

Verticle deck , single head , maypole braiding machine with inverted takeup ( down )
having either 12 or 16 carriers , is what should be sought.

Both Maypole and Knit types compared

This machine is set to feed the braided sleeve downward through the central opening.
The filler feed nozzle would be situated above it as the sleeve is formed over it and
is drawn tight like draw strings over it.


[Edited on 24-7-2010 by franklyn]

quicksilver - 24-7-2010 at 08:08

Wow! There you have it.
Notice that the actual mechanics (most likely) have not changed for a great length of time. The complexity is such that I deeply doubt that such a thing could be duplicated by even the most ardent home mechanic. One of the things illustrated is the customization of the gearing & the very slim likelihood of preexisting machinery to substitute for a machine built from the ground up. This is not a light-weight project....

One possible alternative is to learn a type of Japanese braiding called Maru-To-Kaku (sp?) which can use a wooden loom to produce to round hollow braid used in classical time-fuse. This is hand-made pyrotechnics of the "family tradition" type & also not too easy to learn but it's not impossible. The time-fuse braiding would wrap around almost any tubing of BP (or what have you) & keep it from kinking. It's not a"lost art" as it's practiced just like hand-rolled hex brick firecrackers & you have to get the hang of it.
It does use an "up-ward" direction to the hollow core braid as I think that just may be a practicality in making this stuff. It would certainly keep the tube from kinking as that's it's function.
I have the 1st part of the technique (the technique of the braid) as the 2nd part is too big to post and simply has the various tubing liners, some BP related material and modern methods.

Attachment: maru-to-kaku1.pdf (538kB)
This file has been downloaded 1182 times

I had a look at the real thing (commercial: Austin Powder Sales, orange in color) and it had a tube of what I would bet is Teflon/PTFE to bind the core. With some form of wrapping (previously discussed) on the surface, it's fairly tough to kink. It's "bend-ability" is about 1cm (where it will NOT kink) & a knot is possible provided you don't pull it taught; a knot with a double half-hitch, does not kink at all not matter how hard you tug. So I think the real issue is the core liner. I have NO idea where to get something like it. It comes in various widths (measured by weight in gr. per foot) but the walls are quite thin (0,25mm or finer) and it really does look & feel like Teflon. The reason I believe it's PTFE is that it has a slick feel that seems to "push" the core keeping it from kinking.

[Edited on 24-7-2010 by quicksilver]

In the beginning....

The WiZard is In - 24-7-2010 at 08:52

[GWS was a director of the Bickford,
Smith and Co., Limited. Tuckingmill,
Cornwall England. /djh/]

THE frequent accidents resulting from the use of explosives in tin and copper
mining, chiefly owing to the uncertain duration of the time between the lighting of
the rush or quill and the exploding of the charge, led Mr. William Bickford, of
Tuckingmill, in or about 1830, to turn his thoughts towards the invention of some
method whereby blasting operations could be conducted with the minimum of
risk to the miner. Mr. Bickford's motives were purely philanthropic; it remained for
his successors to turn his invention into an extensive and legitimate commercial

On the 6th September, 1831, Mr. Bickford took out his first Patent (No. 6159) for
the Miner's Safety-Fuse. His object was to provide a protected core of powder,
thin and continuous, along which the fire might travel slowly at a uniform and
determinate rate of speed. This result he obtained by causing a number of jute
threads, passed through an orifice and stretched by means of a weight attached
to their extremities, to rotate slowly while, at the same time, a small current of
fine powder fell into the tube thus formed, and was retained therein as a slender
core. To use his own words in the specification of his process:

" I embrace in the centre of my fuse, in a continuous line throughout its whole
length, a small portion, or compressed cylinder, or rod of gunpowder, or other
proper combustible matter, prepared, in the usual pyrotechnical manner of
fire-work for the discharging of ordnance; and which fuse, so prepared, I
afterwards more effectually secure and defend by a covering of strong twine
made of similar material, and wound [113] thereon, at nearly right angles to the
former twist, by the operation which I call 'countering,' hereinafter described: and
I then immerse them in a bath of heated varnish, and add to them afterwards a
coat of whiting, bran, or other suitable powdery substance, to prevent them from
sticking together or to the fingers of those who handle them; and I thereby also
defend them from wet or moisture or other deterioration, and I cut off the same
fuse in such lengths as occasion may require for use: each of these lengths
constituting, when so cut off, a fuse for blasting of rocks and mining, and I use
them either under water or on land, in quarries of stone and mines for detaching
portions of rocks, or stone, or mine, as occasion may require, in the manner long
practised by, and well known to, miners and blasters of rocks."

&c., &c.

The Rise and Progress of the British Explosives Industry
Published under the auspices of the:—
VIIth International Congress of Applied Chemistry
E A Brayley Hodgetts editor
Whittaker and Co. London 1909

gnitseretni - 24-7-2010 at 08:52

Here's a homemade machine for making fuse:

Maybe it could be used for making det cord?

franklyn - 24-7-2010 at 09:04

Quote: Originally posted by gnitseretni  
Here's a homemade machine for making fuse:

Maybe it could be used for making det cord?

Definitely ! that's really neat.

The cord shown is made with string or twine , not the best choice.

Lacing cord is flat and forms a tight warp.


The hard way _

Maru_Dai_Diagram.gif - 6kB

[Edited on 24-7-2010 by franklyn]

pjig - 25-7-2010 at 10:03

What about using 3/16 poly tube, and packing it with a core of etn? Seal it with a vacuum, then wax or glue the end closed.

I have seen a great patent using NM and al or NM and micro-balloons to sensitize it. I believe that the were able to carry det with as small as a 1/8"id. over several hundred feet.

gregxy - 25-7-2010 at 20:08

I think the problem with shrink tubing and the like is getting the ETN uniformly
into the tubing.

How about absorbing molten ETN (or a saturated acetone ETN solution) into a
loosely woven cotton cord, letting it cool or dry and then placing that into
shrink tubing and shrinking it. (or you could wrap it with treads). The inner
cotton cord would also help stop gaps from forming when you bent it.

[Edited on 26-7-2010 by gregxy]

Deceitful_Frank - 26-7-2010 at 11:34

Quote: Originally posted by gregxy  
I think the problem with shrink tubing and the like is getting the ETN uniformly
into the tubing.

How about absorbing molten ETN (or a saturated acetone ETN solution) into a
loosely woven cotton cord, letting it cool or dry and then placing that into
shrink tubing and shrinking it. (or you could wrap it with treads). The inner
cotton cord would also help stop gaps from forming when you bent it.

[Edited on 26-7-2010 by gregxy]

I have tried a similar method before. loading a hot saturated solution of ETN in ethanol into a syringe and then evenly ditributing it throughout a 1m length of toilet tissue. Tissue absorbs the solution and as it cools, the ETN quickly precipitates and the crystals are trapped within the fibres. The ethanol will then evaporate within a few minutes and you have something very durable that you can wrap at will with your shrink tubing, thread or PIB tape.

There is one major snag though! In order to get all the Ethanol that would contain those 10 grams of ETN for the metre of cord absorbed you really do need 2-3 grams of tissue paper and this will bring the inert content of the central core of the det cord will up to the 20% mark. this degree of inerts may well shoot in a lump of plastique but in a length of detcord whose core is a mere 5mm across... not a chance!

Perhaps if we found a tissue that was absorbant enough that a gram of it could hold the 10ml or so of solution we might get a cap sensitve product but it seems to me unlikely.

How about if we nitrated the tissue as well?

Then even if it accounted for 20% of the mass of the core at least it wouldn't be totally inert. NC does tend to have a rougher feel than the un-nitrated cellulose. Would it be less absorbant? Plus we need to be sure that the NC would not be dissolved by the saturated solution of ETN in the hot ethanol.

[Edited on 26-7-2010 by Deceitful_Frank]

[Edited on 26-7-2010 by Deceitful_Frank]

franklyn - 26-7-2010 at 18:25

Quote = Deceitful_Frank
" How about if we nitrated the tissue as well ? "

My thought exactly , nitration of cellulose to produce " flash paper "
is as simple as it gets. A legacy of experience with this material exists
since it was among the very first commercial high explosives.
Gun cotton was discovered by Braconnot (France,1833) and patented
by Schonbein (1846) , the year Sobrero synthesized glyceryl trinitrate.
Many compositions are based on the two ingredients of nitrate ester
and nitrocellulose.

The question at hand is the cord produced with long term storage in mind
or for immediate use. If the use is only to transmit a detonation wave to
several charges , it doesn't really need to be fast.
Gun cotton that has been washed , neutralized and spindled into twine
then soaked in a hot saturated solution of ammonium nitrate and vacuum
dried , finally covered by a cloth sleeve , can be sensitized in the field by
drenching with Nitromethane.
Sleeved cord.gif - 10kB
If you want pointers on how this is done make friends with someone
who is good with a sewing machine.

It bears emphasizing that producing cord from tape is the simplest means
available as well as cheapest and much stronger than other improvisations.
Because the tape is impermeable it cannot be soaked as described above.


pjig - 26-7-2010 at 18:38

Huh.. you just might be onto something here... I think guncotton its self could serve as a det cord inner material....
While on that thought, ETN or guncotton could be pressed into 3' sections of say 3'16 flexible pvc clear tube, to make det-cord.
One could use a 3/16 wood dowel and pack the explosive substance into the tube. To join the sections of tube to get one long strand, one could tape them together, or use a larger dia. tube as a sleeve to join the two.

The WiZard is In - 27-7-2010 at 06:17

Quote: Originally posted by Deceitful_Frank  

How about if we nitrated the tissue as well?

I would be remiss if I failed to note that unless NC is
carefully neutralized there is ever the possibility of spontaneous
combustion. In the early days several battleships were destroyed
by fires/explosions caused by unstable NC. Remember the
Cleveland clinic X-ray film fire.,280

Faversham explosion, &c.,&c.

Boiling for a week or so with periodic changes of water works
or you could try urea. (See attached)

Attachment: NC Stability.txt (6kB)
This file has been downloaded 1082 times

Attachment: NC Hall-Schonbein.txt (6kB)
This file has been downloaded 1009 times

Hennig Brand - 27-7-2010 at 06:27

ErTeN would definately work in a plastic tube, I am not sure about the Guncotton though. It could be just my perception but Guncotton would be very difficult to work with this way. Guncotton is also expensive and difficult to manufacture in large quantities, relatively(I think). Guncotton can also not go, or go low order if conditions aren't right either I think(correct me if I am wrong).

Your idea of the flexible plastic tube is a good one I think. The first time I saw this was in a post on Rogue Sci, I think it was Boomer maybe, discussing loading ETN(I think), into plastic(polyethylene?) aquarium tubing. He was using a long, flexible, good quality wooden dowl(of appropriate diameter) to pack it in, in increments. I am not sure how he was feeding the explosive in(or I can't remember), but it seemed workable for sure. This would work for short lengths anyway, long lengths is another story. I am going to have to try this, I have been meaning to for awhile.

edit: The Wizard got one in ahead of me. I have used urea in the final wash water with Guncotton because it is what I have and it seems to do the trick. I just read recently that they don't use urea with smokeless powder because as it does its thing it gives off small gas bubbles, and these small gas bubbles are a big problem in the smokeless power(irregular burn rates, etc). Alittle off topic. On topic, the Guncotton neutralization would also add to the difficulties for the amatuer in dealing with this material in that capacity, I agree.

[Edited on 27-7-2010 by Hennig Brand]

gregxy - 27-7-2010 at 09:37

One big advantage of ETN is that it can be melted.

How about :

1. Fill a syringe with ETN.
2. Firmly attach the syringe to a length of plastic tubing,
The following site has every possible type
a tube with 1/8" id should give 10g/M ETN.
3. Immerse the whole in water hot enough to melt the ETN
but leave the open end of the tube above the water
4. Inject the ETN into the tube, with care it should be
possible to displace all of the air.
5. Remove from the hot water and let it cool

If possible it would be best pressurize the liquid ETN enough
to stretch the tubing during step 4. This would compensate
for shrinkage upon cooling.

pjig - 27-7-2010 at 09:40

This is a good topic :D

On the small dia fish tank tubing idea, here is a thought for charging your det cord.

What about using a dbsp and charging the tube via a hopper. Then on site pumping enough nitromethane into the filled tube to saturate the dbsp. Upon swelling of the dbsp, the desity would rise and your cord should have a fairly high VOD that would sustain det through even a smaller dia tube than most explosives.

franklyn - 27-7-2010 at 09:52

Filling tubes is only practical for short lengths if the explosive is solid.
Joining short lengths together requires that continuity of the explosive
be maintained or else the detonation wave will stop where it is joined.
This is why det cord is extended by overlapping the ends to assure
continuity of explosion. At 75 cents per foot , shrink tubing is quite
expensive and practically without any tensile strength.
Tubing containing a liquid explosive may work , providing there are no
kinks or large voids. Small bubbles have the detraction that it serves
to sensitize the explosive making it susceptible to initiation from impact

Guncotton alone cannot serve the purpose but it can serve as the base ingredient
of the explosive. To produce something approximate to gelatin dynamite as a cord ,
a nitrate ester will need to be soaked up in the cord to process into the desired
product. This can be unnerving to do and is not without some risk. Whether the
resulting colloid can be sufficiently insensitive for safe application is unknown by me ,
this is undocumented proprietary know how of the original manufuacturers.
Winding cotton cordage for composition with another explosive is worth examining.
It's a simple matter to nitrate cotton thread or yarn and then use that to produce
cord. - It is necessary to do this before
it is wound into cord so that remnant acidity can be neutralized.
Lline can be secured at one end and twisted from the other end by using an attached
electric drill or screwdriver. Placing in parallel , three lines twisted the same way ,
say counterclockwise , they twist together naturally into a cord clockwise.
Full instruction in the Boy Scout manual. Attachment: BoyScoutRopemaking.pdf (450kB)
This file has been downloaded 820 times
Video how to =>
A usful site on cordage and ropes
Rope making videos - see the other links
Braiding Machines - see the other links
The real stuff

Light speed detonation velocity
Optic Fiber Laser Detonator


[Edited on 27-7-2010 by franklyn]

quicksilver - 28-7-2010 at 06:12

I have access to some equipment and just for experiment's sake I was fooling around and looked at what it would take to fill a tube of moderate length (9ft) with an inert material. Using an "aquarium bubblier" attached to an end of some vinyl tubing I rigged a thin ended funnel and used a air compressor. The "bubblier" allowed the compression to take place with a element of compression bleed-off and the inert I used with diatomasius earth. Several yards of compressed powder presented no problem. As the length got longer, the bleed off of compressed air presented no difficulty IF the bleed-off existed. There IS a bit of "technique" to filling the tube. One needs to start off gently so as to get several inches filled before a full level of compression is used.

What challenges did exist were the powder consistency itself. Even filter diatoms were still too rough. PETN are typically needles, ETN would be platelets; these shapes don't lend themselves to packing! A great deal of shaving was in order OR a method of maintaining low crystal size / density.
The interior of the tube presents another agenda. If Nonel tubing is examined, there is a smattering of powder through out it's length - some of that material is aluminum! This could be ideal material to dry lubricate the walls of the tube and fine enough to adhere to the walls forming a drag-free surface.
Where this needs further examination is [that by making] the filler material becomes finer, the compacting element shuts down the flow of air and the result is that a few yards may be packed quite tightly until the compact mass allows little to no flow of air. Thee are various physical techniques to deal with such as holding the ends while compacting the powder as the force is enough to shoot off the ends, the funnel, etc unless care is taken. To really get this to be a tightly packed item, it needs some serious pressure.

The kinking problem could be dealt with by picking a tubing that gives some resistance to kinking and sheathing that with some supporting tube like a tight round braid. The kinking issue is the less problematic one. It's important to remember that even relatively small tubing can hold as much as 4+ grams per foot. - From a commercial perspective, that's quite large! For effective use the tubing core could certainly be quite thin. This is a very workable exercise. The various stumbling blocks COULD be over come with careful experimentation.

Shock tube

pjig - 28-7-2010 at 08:50

Just another thought on transferring of detonation waves... using the same idea with the small dia tube( like the clear stuff they use for swamp coolers"evaporative coolers") it is around 3/16 " and fairly sturdy.

Could one take a thin liquid glue and pour it through the tube, drain it completely, then let it tack up. Next using a compressor they could blow a fine dusting of high grade explosive like pent+Aluminium, through the tube. And there you have it "shock tube".. This could be used to transfer Det over a long distance, and being easy to make long pieces at a time.

quicksilver - 28-7-2010 at 10:57

Shock tube needs an initiator that has to fit the end of the tube. Some of them look like bridge-wire set-ups without the energetic material. They are then zapped with a CD device. What's used in Nonel is HMX and Al in a SUPER fine coating and it's really thin: just coats the inside. You can barely see it. You see, if you use more than a super small amount it won't travel: it will pop right there.
Imagine getting about a grain of 2 micron (or finer) explosive w/ Al and blowing it through the tube. What would stick to the inside would be what's's really a tiny amount. I've seen it work and it's pretty clever. It's possible that less than a grain is utilized for a meter or more: it's that fine. The initiation needs to be fairly potent to start the travel of the shock tube. As it moves, it builds: just sightly until at the termination point it's fairly potent. But it can't start off that way. The physics of the thing is pretty impressive.


It's SO fine that if you saw a picture or held a piece up to the light you would have a hard time seeing the actual explosive: it's that minute.

Some time back there was a LONG thread about altering the composition of various explosive's crystal formats. Basically, to reduce them to a finer grain or particulate. There ARE ways it can be done via the re-crystallization or initial synthesis. But it becomes more important as the applications widen in scope.

[Edited on 28-7-2010 by quicksilver]

Deceitful_Frank - 28-7-2010 at 23:39

Quote: Originally posted by quicksilver  

ETN would be platelets; these shapes don't lend themselves to packing! A great deal of shaving was in order OR a method of maintaining low crystal size / density.

Just shooting off at a brief tangent, on the subject of crystal shaving, I would just like to pick your brain a little.

I know you also favour ETN. Do you have much experience in shaving or manipulating crystal shapes to give a higher bulk density and less need for inerts to fill the voids? I would love to one day be able to produce a lump of workable, usable, handlable plastique with no volatiles and one active ingredient... ETN makng up 85%. >=92% is possible with PETN so surely this isn't beyond the realms or possibilty?

Using unaltered recrystalized ETN you really need minimum 25-30% inerts to fill those voids and hold it all together. Then you need a big ass cap, strong confinement and you can forget small critical diameters!

Sure I can add 15g of NM to 85g or ETN and deliver some serious hurt. A suspension of ETN in a NM/ETN syrup! but this is messy and unless sealed airtight remains usable for just minutes.

I know nitro-genes has had much success manipulatiung far from helpful PETN needles. Making plastique that is short of platisizer to give a firm feel and rolling it on a hard surface to round off the crystal edges and provide the extra ultra fine fraction of PETN within the mix. I guess this fraction fills in the gaps between the larger crystals to give what would have been a higher bulk density of the active ingredient.

Also IIRC he was had success grinding wet PETN with a pestle and mortar. breaking up the needles just to the point where they are approximately cubic and then adding a small fraction of VERY finely ground PETN. I think he managed to produce a quantity of workable plastique in the region of 1.6g/cc. To be able to deliver such energy into a small space with a material that is safe to handle with bare hands, no volatiles or mess is most impressive.

I believe that ETN is so powerful and easy to make that the extra effort for PETN albeit with 6-7%? extra density, a little more safety and less headaches from skin contact is hardly worth the ENORMOUS increase in effert and expense.

I obtained a substantial quantity of PE at GREAT difficulty, nitrated a small amount using mixed acids (I've neither time nor motive to seriously consider distillation of HONO2)... Terrible yeild. Of course I was impressed with its power but to be fair I would sooner expend half the effort and get twice the amount of ETN for my trouble!

I would like to try some crystal shaving with ETN. I am aware that it is some 30% more sensitive to initiation... and friction? When I recrystalize from MeOH I get short needles. When I use EtOH I get platelets (well 90% EtOH with approx 5% MeOH and 5% gasoline! we call this methylated spirit in the UK and it is used for cleaning tools and as a burner fuel. Pure 95.5% EtOH is EXTREMELY expensive and difficult to abtain due to taxes and safetly law)

If I was to put 1 gram of ETN in to a mortar with say 3 grams of water and grind with a pestle, which crystal shape do you think would give a better bulk density after grinding plus more likely leave my sight, hearing and fingertips intact?

Everything that I have learned about ETN tells me that even a 1:2 ratio with water is TOTALLY safe to grind and near IMPOSSIBLE to detonate but I guess I just need reassurance!

What do you think?

[Edited on 29-7-2010 by Deceitful_Frank]

quicksilver - 29-7-2010 at 05:12

Well, shaving crystals of ETN wouldn't be accomplished by direct grinding; remember they are flat. And, yes, I think it's too dangerous also. Even if you put an amount in a plastic bag and gently manipulated them for quite awhile, they wouldn't shave to the degree you'd want. They are flat platelets & as such they stack like cards; too difficult to have their edge's contact.

You would need to accomplish this in restructuring the crystal. Using near to anhydrous ethanol or methanol, you would dissolve the ETN in warn (50-60C) alcohol and crash that out into near to frozen water. The crystal shape would not form with any rigidity and you would have very irregular grains that would be quite ridged (similar to table salt but non-cubical). Then - those granular particles would shave fairly fast.

Yea; you wouldn't want to grind them...even in water. It's possible to get hurt. Plus it wouldn't work. - PETN shaves because the needles are thin, small, & very brittle. Nitroguanadine also have needles but they are long, fixable, & thick and buddy; there is no easy way to shave that crap down at all. I actually don't know what they do to put that in triple based's very difficult to work with. Where as I have seen PETN that was near to powder as one could want.

Many people get poor yields with PETN and wonder what they did wrong but they didn't know that in industry, companies do NOT use simple PE: they use very high-end reagent grade material. If a person attempt to nitrate the PE that's used for the paint and vinyl industry, they will end up with a looser yield if they are lucky or virtually nothing if they do not work the synthesis correctly. It's possible you got some tech-grade, commercial PE. The fact that you got a yield show that you did the necessary work, but th likelihood was that someone had tech-grade material. It really DOES have to be high quality for PETN to yield high. That's one of the major reasons why PETN costs more than RDX.

[Edited on 29-7-2010 by quicksilver]

franklyn - 29-7-2010 at 09:01

This video shows the rope braided in slow motion
fast forward to a third of the way into the video
and view the middle third of it.


quicksilver - 29-7-2010 at 09:26

The astounding level of intricacy in both the machinery and the production itself is appropriate since in many instances the rope displayed will be relied upon to save / protect human life.
But in a sense couldn't that also be said about fuse or explosives? I would love to see a video of that quality on the production of det-cord, blasting fuse (the real thing) or related industry-standard production techniques. ISEE's web site once had that from the Institute of the Makers of Explosives. But it's been replaced for some time now.
If you search ARCHIVE.ORG you can still find a film I saw as a grammar-school kid with a title called "Blasting Cap Danger!" We used to have to watch several films of that classic genre'. It's a serious safety issue but it may make some people laugh themselves silly.

gnitseretni - 1-8-2010 at 09:18

Quote: Originally posted by franklyn  
Useful toys
Bond Magicord Machine ( knitting type )

Here's a video of such a toy.

Forward to where you can see the sleeve being formed. You could lower a funnel filled with your HE right in the middle of the sleeve.

Now the only problem I see here is that the HE is not compacted at all. But if you ran this sleeve through the fuse machine I posted a link to earlier, that would compact it somewhat. Or maybe tie the sleeve to a post at one end and then pull on the other end.. the stretching will compact it a little, keep the sleeve under tension (hang it over something and tie a weight to the sleeve or something like that) and wrap the sleeve with tape as tight as you can. Or compress the sleeve between your fingers and guesstimate the diameter.. get a piece of tubing with a smaller inner diameter than what you measured and see if you can pull the sleeve through the tubing.

quicksilver - 2-8-2010 at 05:23

The toy is a good one and the fact that it drops from the bottom, even better. Realistically though, after examining the real thing, I don't know if there is a way to pack powdered material within woven structures alone after certain diameters have been reached. The real thing uses a "core tube" & BP blasting fuse as well as time fuse uses a "core tube". The advantage there is not only one of production but of variation in energetic material weight per meter. You would have much finer control over alterations of weight / volume with the "core tube" concept. The woven hull is very valuable to prevent kinks, protect the tube (which would be thin walled) from abrasion, & aid identification. In times past, the use of tar or similar adhesive would further reduce kinks. But I am convinced that the right selection of tubing material and level of compression will help a great deal. It seems to be a two tiered system.

franklyn - 13-8-2010 at 12:31

Det Cord in action
Slow motion view as two lines detonate from the lower left into the shack.
Slow motion view as the line detonates from the lower left on to the bus.


Microtek - 13-8-2010 at 13:20

I think those two clips actually show shock tube instead of det cord. But then, I would much rather have a good way of making shock tube than det cord....

franklyn - 13-8-2010 at 15:17

@ Microtek

Yes I'm sure you"re right , my fault for not distinguishing the two and using
the term indistinctly. Detcord and Shock tube refer to different materials.
The clue in the video is there is no evident blast effect such as dust in the
immediate vicinity of the traveling wave as you would expect from detcord
which is quite violent. Shock tube can be initiated with a handset as seen here _
Shock Tube
Detonation Cord
Det cord demo from a safe distance.

In case some missed it in my earlier post in this thread
there is a third method being developed

Light speed detonation velocity
Optic Fiber Laser Detonator


-=HeX=- - 7-9-2010 at 09:39

Here is something (Microteks idea originally... That man gives me all my best ideas to be honest!)

You know you can buy, from various magic suppliers, a product called 'Flash String'. Well one US suppler sells 'Flash Cord' that is like a thicker flash string made from several 'Strings' braided together. The one I got, 30 feet, was about 6mm diametre.

MHN and NG form a collidon of sorts, as does NG and NC.

I first tried a ten foot length.

Acetone dissolves them all. MHN is mixed with NG (I did not make any measurements, it was more of a timewasting experiment in boredom) and acetone is added. The cord is soaked in this and the acetone allowed to evaporate by heating at 50* celcuis, leaving the cord impregnated uniformly in explosive, and moreso a collidon than a cord. Its physical characteristics were somewhat altered, and it also propagated detonation.

Next, another ten foot length of cord was cut, and a thread tied to one end. The thread was pulled through ten feet of shrink tubing which had an ID of 8mm. It was 'low temp shrinking' stuff.

The cord was treated, and the acetone mostly evaporated normally prior to drawing it into the shrink tube sleeve where it was heated again for several hours at about 50*. use of a hairdryer shrank the tube, sealing it up. Some composition now came out the end, as an 'extruded' plastic. Interesting, I thought.
The cords ends were simply taped shut. Taping a cap to the side, I found again that it propagated detonation.

I know that NC NG MHN mixes sometimes fail so perhaps addition of a nitramine (RDX) would help a bit, I think it would.

What do you think about this idea? Hardly optimum but I think it makes a nice consistent product.

BTW, Microtek, I recall your idea involving tubing, butane and oxygen in stiochemetric ratios as a shock tube. Anything ever happen with that idea?

The WiZard is In - 7-9-2010 at 09:52

Quote: Originally posted by -=HeX=-  

BTW, Microtek, I recall your idea involving tubing, butane and oxygen in stiochemetric ratios as a shock tube. Anything ever happen with that idea?

Acetylene perhaps?!

A Plumber! A PLUMBER!! My kingdom for a Plumber!!!

"In a time estimated to be about 6 sec, an accidental fire-initiated decomposition
flame in acetylene at ca 200 kPa in an extensive piping system traveled
successively through 1830 m of 76-203-m pipe, 8850 m of 203-mm pipe, and
760-m of 152-mm pipe." [37,180 feet of pipe.]

K&O 3rd

There are two things a real man
likes — danger and play; and he
likes woman because she is the most
dangerous of playthings.

Frederic Nietzche

Microtek - 7-9-2010 at 13:18

Well the idea with a gas filled tube was something I saw in a patent. I tried it out with hydrogen and acetylene as well as the propane/butane mix which is commonly used in camping stoves and lighters. I experimented with fuel/air mixtures within the explosive limits, but found that in small diameter tubing (2-3 mm IIRC) you are likely to get a very sedate propagation, at least when simple ignition is employed.
So, I would think that to come up with a system that actually works as a shock tube substitute you should:

- Use pure oxygen rather than air
- Use larger diameter tubing
- Initiate with a small cap rather than simple flame

Personally, I would prefer not having to increase the size of the tube.

Edit: Of the three systems, hydrogen worked best by far under the given conditions.

[Edited on 7-9-2010 by Microtek]

franklyn - 7-9-2010 at 18:27

Hydrogen and Chlorine is photoactive and explosively reacts upon exposure to light in a 1 to 1 molar ratio
to form HCl. Opaque tubing filled with this mixture would achieve wave propagation at some fraction of the
speed of light since the light emitted by the reaction triggers the unreacted portion ahead in the tubing.
The admitted gas mixture follows 3 or 4 ball bearings introduced inside the tubing snugly fitted at one end
but not tightly , so they move through by just jerking the tube , and are pulled along by applied vacuum at
the other end. This assures complete purging , so the charged gas mixture remains unadulterated.


Microtek - 8-9-2010 at 00:26

Nice idea, Franklyn. The question is whether the emitted light is of sufficiently short wavelength to propagate the decomposition at a higher than usual rate.
I remember seeing a demonstration where a photo flash was used. It involved three vials of H2/Cl2 behind three screens of glass. One screen was clear, one was blue and one was red. When the flash was fired through the clear or blue screens, the gas mix would pop, while the red one would block the short wave lengths so no ignition took place.

Or course, it might be possible to use the gas mix as a sort of primer mixture in an ampule preceeding the blasting cap, with a fiberoptic cable in place of the actual shock tube.

franklyn - 8-9-2010 at 05:01

@ Microtek

There's nothing to say that the H2 / Cl2 mixture cannot also additionally be
seeded with something having a different emission spectra , argon perhaps.
Regarding your application of acetylene :
Enthalpy of elemental Oxygen is zero. Substituting a more energetic oxidizer
such as ( N2O ) Nitrous Oxide should markedly improve wave propagation.
On page 185 of International Critical Tables regarding Explosive mixtures is
described a mixture of 1 to 2 molar ratio Acetylene to Nitrous Oxide , noted
as having ~ 2580 m/s velocity of detonation.


The WiZard is In - 8-9-2010 at 10:20

Quote: Originally posted by -=HeX=-  

BTW, Microtek, I recall your idea involving tubing, butane and oxygen in stiochemetric ratios as a shock tube. Anything ever happen with that idea?

No doubt the collective will —

A. Be astounded to know that there is a book on gaseous detonations
B. Be amazed to know that I own a copy.

That said la book is tres theoretical.

MA Nettleton
Gaseous Detonations Their Nature, Effects and Control
Chapman and Hall

'bout the only useful easily found info dobe —

(2H2 + O2) + 5He Calc. 3613 m/sec Exp. 3160
4H2 + O2 Observed 3344 Theoretical 3425

100% HN3 2.60 km s
100% ClN3 2.3
100% C2H2 1.92
90% H2O2 + 10% O2 1.92

NB - Velocity does not guarantee ignition.

One of the
few remaining
analogue people
in a digital world.

[Edited on 8-9-2010 by The WiZard is In]

DNA - 4-2-2011 at 05:02

Maybe a bit of a bump in this topic but I had this idea for a while.
Get a silicone tube and fill it with plx.
Critical diameter can get low as 4.7mm with 2.5 wt% of ethylenediamine.

What are your ideas about this?

Bert - 4-2-2011 at 06:23

One of the nice things about commercial det cord is you just cut what you need and go- liquid or gas filled tubes can propagate a detonation, but I don't see them as practical for field work. Solid is the way.

The original "cordeau" was made by filling a short heavy walled Lead tube with cast TNT (or a tin tube filled with picric acid) and then drawing it through a series of dies in the same way wire is drawn- Producing a long thin moderately flexible tube filled with crushed HE. Perhaps another look at this technique?

[Edited on 4-2-2011 by Bert]

quicksilver - 4-2-2011 at 09:17

@ Bert:

The "draw" concept could work no doubt. but with TNT. I have seen wire drawing machinery before and the Pressure is substantial. TNT appears safe from friction/impact enough to attempt a small section. but the COST (of the device) is substantial. There is a tubing reduction machine that can be hand cranked (if one could be located) it's used in some jewelry applications and there may even be a way to work with this on a manual basis. But where to get lead tubing?

ANY tubing has criteria that is challenging. It must be thick and tough enough to bend without tearing of permanently kinking, yet thin & flexible enough to receive initiation from adjacent shock (cap blast).

[Edited on 4-2-2011 by quicksilver]

DNA - 4-2-2011 at 10:20

But besides the field practical side of it. If you just consider you want a certain length of detcord then you can make it.
The liquid plx has a constant and uniform density therefore no problems with loading and very quick to manufacture.

I tested a 9mm ID tube, but it didn't detonate (blasting cap inserted in the liquid)
While from the same batch of plx a vial of 25ml did detonate (1 minute later) with an exact same blasting cap... how could you explain that?

DougTheMapper - 4-2-2011 at 15:39

Jeez, what about a liquid energetic soaked into a thick string which is pulled through the tube?

I make MEKP caps with straws and cotton wool...

Put a thread through a tube with compressed air, soak a thick cotton yarn in EGDN, methyl nitrate, or maybe NG, then use the thread to pull the yarn into the tube while the end is submersed in the explosive as so not to introduce air. Seal the ends when done...

Heck, dissolve some more powerful explosive into a liquid explosive to make a syrup. Even better! Is ETN soluble in EGDN?

vulture - 5-2-2011 at 06:25

This could be an ignorant idea, but for people in the US (or other countries with lax gun regulation), couldn't one use double based powder as absorbent for the ETN or explosive of choice?

grndpndr - 5-2-2011 at 07:34

Smokeless powder grains are rather large for a small diameter tubing although DBSP/ETN and combinations would be relatively inexpensive.As far as Lax gun regulation thats a matter of opinion and a political statement not altogether popular
in the USA.

holmes1880 - 5-2-2011 at 08:00

How to do it the easy way....

We suspend the very thin nylon tube from 50f-100ft with a weight on the bottom, so this way it is straight. Then, we start filling in all that hotness from the top by simply using an appropriate diameter metal rod (but that can slide more or less freely through the pretty thin rods that I saw at Home Depot) and just have it tied by a thin fishing line/weaving thread. So we just let it slide down all the way to the bottom, bringing with it all the ETN, then pull back up and repeat until the thing is full.

And you ask me if that's impractical and you don't have doubt but it is easy, cause I have a staircase that's over 80 feet high or so...... If that's not enough, I suspend that hotness from somewhere higher. But if you want practical, than I suggest getting some type of pressure machine, having some kind of light fit plug with a lead line. So you put in the pressure, pushing the plug, which pushes ETN. Once done, pull the plug back out by a thread.

I should so flaming patent that! ;) But det cord makes too much noise, so not my specialty.

P.S. Wizard, WTF? seriously.....replying with essays is ridiculous. Sentences of 100 words or less work too. :(

[Edited on 5-2-2011 by holmes1880]

DNA - 5-2-2011 at 08:20

Would plx soacked in cotton also work, like NG?
And when using pure liquid PLX it didn't detonate with a blasting cap.
While it did while it was in a vial where there was more plx right around the blasting cap...
Still can't figure out why that didn't work...
9mm ID tube, 7mm blasting cap OD, glued inside the tube full of plx...

vulture - 5-2-2011 at 09:45


Smokeless powder grains are rather large for a small diameter tubing although DBSP/ETN and combinations would be relatively inexpensive.As far as Lax gun regulation thats a matter of opinion and a political statement not altogether popular in the USA.

I wasn't implying to use the grains as is, rather dissolving them with the explosive of choice, in the hope that this would form a paste. The added bonus is that the stabilizers in the powder reduce the hazards associated with NC.

As for lax gun regulation, I fail to see how that statement is political. You are trying to make it political. In my book it simply means easy access to guns without regulatory hassle. I fail to see how that is a political statement, as there is no judgement or ideology associated with it.

quicksilver - 5-2-2011 at 09:58

The tubing is actually the most critical component. I have already thought of how to fill it with no problem in lengths of up to 10 meters (perhaps more) but the material is not something that can be some ridiculous item like vinyl tubing or such. It must be thin, strong, yet able to transfer shock energy very easily.

A "fuse-weave" machine could be used obviously but the cost and the final sealant would be a serious mess and lack professionalism. A fuse-type weave machine is also unpredictable in-so-far as it's total length as the spools are not that predictable until it's been used for some time.

It's actually a problem in mechanics. A simple experiment will prove what I mean. Use a 10meter section of .25" clear vinyl tubing so that you can watch the interior. To that afix a funnel so that it's quite tight and re-enforce it with a clamp. Use common table salt and go to any area with an over-hang or roof and start to "twirl" the tubing by holding the funnel so that it makes gentle figure "8"'s. as it continues it's movement gently pour in salt and the tube will fill with remarkable compactness. HOWEVER vinyl will never transmit effective energetic shock and you are really only left with 25-30 feet at best. It's a very ghetto method but the filling- per se' is NOT the problem......the tubing and it's characteristics ARE!

You could also do this with forced air and make it actually continuous but the most I have experimented with was several feet and the method worked well.'s not the method to get it within the tube but the choice of tube itself that is a challenge. If you ever really want to experiment with the mechanics of this cheap table salt is a fair go as it does have similar consistency albeit a bit tougher, than many energetics. For Heaven sake NEVER consider peroxides as a kink will be a disaster....

This whole subject had been a "how-to toy idea" for many, many years. I really believe that the best method is to eventually buy a fuse making machine. If anyone has any experience with leather or braiding they know there is several types of braiding that would work manually but it's simply to much bother by hand and with anything but proper tightly woven cotton or a blend. A device similar to a KUMI Loom may be workable (Kumihimo braiding).

grndpndr - 5-2-2011 at 17:24

@ Vulture,In the USA 'lax' is a euphemism among gun control advocates/other control freaks for NEEDING MORE of.

Lax, syn for negligent, Websters

As far as NC/DBSP in combination with other sensitive energetics that has been suggested in many posts as a plastic etc etc.ETN/MHN IIRC was specifically mentioned.No offense.:D

[Edited on 6-2-2011 by grndpndr]

[Edited on 6-2-2011 by grndpndr]

[Edited on 6-2-2011 by grndpndr]

[Edited on 6-2-2011 by grndpndr]

DNA - 7-2-2011 at 01:51

@ quicksilver,

What kind of tubing would you advice then, and why would there be a problem of shockwave propagation through the tube when it is made of polyvinyl?

Would you also think this would be the case when the tube is filled with NG?

quicksilver - 7-2-2011 at 15:30

Well, here is the challenge (IMO).
It would have to be strong enough to retain the energetic material, yet pliable enough to "shatter" & therefore transmit the energy of the cap (or primary, etc).
We know that over a century ago lead tubing was perhaps the 1st sheathing for the concept of a "det-cord". It had certain physics elements in that it could be readily shattered and complete the "train" of energy, yet it was pliable enough to bend from area to area, thus allowing multiple near simultaneous work to be accomplished.

Fabric would certainly work with something like tar to waterproof the containment. If we examine commercial products they use "layers", yet keep them damn thin. It's not an easy question to answer because we would be re-inventing the wheel.

It would need to be thin, yet very strong. It would need to be waterproof yet not "kink" and open from such abuse.
Quite frankly I can't think of a reasonable substitute than the commercial product. Industry designed most all packaging from cord to sheet to plastiques in a VERY special way to preform under a variety of conditions. A GREAT deal of R&D went into these items.

The liquid format would not be too promising as it would not be able to be cut and violent kinking or impact may lead to a tragedy. As an example: a true commercial plastique is not simply a clay-like blob of energetic. It is waterproof, it can stick to surfaces, it can retain shape and become a shaped charge and it can resist temp changes over a wide range; nor would it crumble or flake. ALL commercial products are not simply "look-a-likes" of what we would expect an item to accomplish: there is ENORMOUS amounts of thinking and experimenting that make them so applicable to a great variety of applications.

Quote: Originally posted by DNA  
@ quicksilver,

What kind of tubing would you advice then, and why would there be a problem of shockwave propagation through the tube when it is made of polyvinyl?

Would you also think this would be the case when the tube is filled with NG?

[Edited on 7-2-2011 by quicksilver]

grndpndr - 9-2-2011 at 13:00

I ran into a link name CannonFuse.Whats of interest is it has a tutorial for making simple blackmatch and then quickmatch using BP/dextrin/cotton string.What caught my attention is the simplicity with which the detrinated BP slurry was incorporated into the cotton string and also its consistency.Also the quickmatch deflagrated @close to 500fps w/BP.
Use the same methods as the blackmatch with a different energetic and that may be something of note.

The blackmatch or fuse string is made of 1/16in COTTON string.A mixture of 10gr dextrin and 50gr BP/ water is made into the consistency of thin ketchup inside a plastic bowel with a lid.
The lid is removed and a 1/8 hole drilled in the lid, exactly 1/8 w/o any burrs to interferre with the string coating.Metal might be superior?
3ft of the cotton string is cut and rolled into a loop submerged in the BP slurry until soaked.The end of the string is then threaded thru the lids hole and the lid reattached.The string is then simply pulled out of the container carefully removing excess BP slurry giving a certain amount of consistency.The string is then hung up to dry.Alone this makes blackmatch when dry.When a tubing is covering the blackmatch the propogation is encouraged to nearly 500FPS due to pressure -heat.

It seems to me using longer lengths of string/larger containers
along with a different energetic/dextrin.Maybe ETN,TNP/detrin or a liquid made w/acetone TNP.Or Ethanol/ETN soaking the string-drying and covered by a slightly larger tubing say 3/16 this might work.Ill leave it to those more knowledgable but would a liquid HE be possible.Isopropyl nitrite/nitrate?
Depending on energetic a det of some type size would be needed im assuming. 1/16-string OD .0625, 1/8-string, .125,
3/16 ID tubing, .1875Adequate room that bothe a copper wire winding and an air assist should easily pull the string into the tubing.Max length would be a matter of trial and error.Although Id be suprised if minimally 30-100ft wasnt a doable deal.

Thoughts, criticism,advice? all welcome!

In any event the string even loaded would be less than.125 OD.
The tubing being 3/16 ID should have an ID of .19 using the thin copper wire from motor windings I would think the wire could be attached to the string and partially pulled thru the tube assisted by air pressure. Just a thought.

[Edited on 9-2-2011 by grndpndr]

Bert - 9-2-2011 at 16:57

Main issue I would see is a dextrin bound composition cracks and breaks off the string with handling. Inside a paper match "pipe" the hot gas expanding down the pipe bridges any bare areas. A bare area might stop a detonation propagating-

Perhaps make your pseudo black match, then after drying pull it through a bath of something like thinned down vinyl tool handle coating compound to produce a waterproof flexible outer skin. Then even if the coating did crack up, it would stay in place.

BTW, 500fps would be an unusually high speed for paper jacketed match in my experience. It can go damn near speed of sound in a metal or heavy plastic tube that doesn't burst or burn through though.

grndpndr - 9-2-2011 at 23:59

Im sure the coating would tend to flake off but the tube should eliminate direct contact with the energetic soaked string .Only the exterior less flexible tubing would be subject to direct handling which should be less flexible than the string.Hopefully!
Maybe this is a round about method using a solid crystaline substance.Maybe if the energetic was completely in solution the entire string fibers could be impregnated with the energetic.I would think the grains would be much more difficult to dislodge
from the interior spaces of the string fibers.Cant forget a string soaked in a liquid HE either.With the excess liquid removed and placed inside a nylon/other approx 3/16 ID tubing It would have a limited life span but could be useful.

In the end however ya cant beat the simplicity of a simple fused or electric initiator.The tech for det cord or a shocktube system might be to much to duplicate in the garage.:o

Ultimately potential problems will be found regardless so i would think the only method that would be recognized is the one thats proved successful consistently, should anyone care to pursue the quest.Im gonna be busy unfortunately.

[Edited on 10-2-2011 by grndpndr]

Northhunt - 30-3-2011 at 12:48

Dont know if this have been mentioned before; If so delete this post ASAP.
I have thought about mixing ETN with for example water, NM, NG etc. Put your slurry in a cup, place your tubing in the cup, attach a syringe at the other end, and suck the slurry through your tubing. If water is used-dry, and use as shocktube.

Bot0nist - 30-3-2011 at 13:07

If using water and allowing it to dry I think the energetic material would be loosely dispersed inside the tubing which could cause propagation issues. If using a liquid explosive then you still have the difficulty of a tube filled with liquid. Unless maybe one could draw a thick, non volatile gel into the tube without a lot of air pockets forming. Maybe that could be tried.

holmes1880 - 12-6-2011 at 08:37


Pumping a slurry into a tube would require serious suction/pressure because the resistance would be exponentially increasing with column length.

I like Northhunt's proposal and actually tried mixing ETN/NM at 1:2.5 ratio. The NM dissolved ETN, turning slightly yellow, with only a small particles freefloating inside. I was able to use a syringe to quite easily inject it into a small section of the test tube. It is very convenient.

I calculated that 1:2.5 ETN/NM ratio requires 6.5 grams/1 meter @ 4mm tube ID. That may be a little steep in terms of ETN demands. Thus, perhaps increasing that ratio to 1:5 may be desirable, as long as it is still sensitive to a standard cap and can be initiated via cord overlap. 1:5 ratio, would only require about 3g/meter, which is very attractive and safer.

How does that sound?

holmes1880 - 12-6-2011 at 18:22

Scratch that. It won't work, not in a 4mm vinyl tube as shown per my test. I actually have a hard time penetrating the vinyl tube with a liquid in it. It looks like it just flexes from the impact, with some minor shredding.

Hennig Brand - 10-7-2011 at 11:15

I have a simple idea for making homemade detcord which I don't think has been proposed here before (or at least not in this thread).

The tubing must be carefully taped to a piece of dowel so that it is kept reasonably straight. If it is not straight the plunger dowel/loading dowel will be very hard or impossible to push into the tube reducing loading efficiency. Obviously the dowel diameter needs to be a little smaller than the inside diameter of the tube as well. A notch is cut out of the tube near the end. A small hopper (the bottom open end being slightly larger than the notch) can be fashioned out of cardboard and attached over the notch hole. It is glued in place with hot melt glue.

So, the process is very simple. A little blob of hot melt glue is used to plug the bottom end of tube. Tap the hopper a little, then push the charge into place with the loading dowel. Remove the loading dowel and repeat. The hopper needs a spoonful of ETN (or whatever your HE of choice is) added every now and then. I could load a meter of this stuff in 15 minutes if everything was working properly.

It is sort of like a semi-auto firearm. I tried it without the hopper and it took forever. The hopper is disposable, it is simply cut off after the cord is full. A more permanent setup could most likely be made based on the same idea.

A vibrator motor on the hopper would probably be a very good addition, greatly increasing loading efficiency further. With a vibrator in place it would be non stop stroking;)

Hopper.JPG - 224kB Hopper again.JPG - 229kB Hopper Yet Again.JPG - 229kB Det Cord.JPG - 239kB

[Edited on 11-7-2011 by Hennig Brand]

Hennig Brand - 1-8-2011 at 17:17

Here are a few pictures of my detcord. The first shows about 3 meters in a coil, two of the three are in meter long lengths and two are in half meter lengths. The explosive filler is ETN. The cord used on the tree was about 0.4 meters long. The detonator was 1g PETN, 0.3g lead azide, with a little lead picrate on top. The alder tree was approx. 6cm in diameter, green and healthy. Some tape was used just to keep everything tight and in place, it also provided a bit of confinement I guess.

After some measurements and figuring, I found that my det cord was only 9grams per meter instead of the desired 10g/m. I noticed my density is a little low. The main reason I am persuing this is for setting multiple charges off simultaneously. It sure is a lot of fun just to play with though.

The meter long pieces took me longer than 15 minutes to load (more like 30 minutes), but I can see how it could easily be done in 15 minutes or less with the right setup. Crystal structure of the explosive, as well as having a nice straight smooth loading dowel, plays a huge role in determining how easy the cord is to load. A vibrator motor on the hopper would also be nice, as a lot of time is wasted tapping the hopper.

Pictures are mostly just for entertainment purposes.

detcord.JPG - 464kB detcord plus cap.JPG - 477kB detcord primed.JPG - 470kB detcord on large alder.JPG - 531kB severed alder.JPG - 518kB

[Edited on 2-8-2011 by Hennig Brand]

holmes1880 - 1-8-2011 at 21:53

Activated ammonal 95/5 can detonate in 6mm vinyl tubing. However, it is best to use 10mm, because with 6mm there can be not enough contact between ammonal powder in areas where powdered AN is a little bit coarse.
If you have a good blender, this shouldn't be too much of an issue.

[Edited on 8-2-2011 by Polverone]

Hennig Brand - 2-8-2011 at 16:03

I guess the title of this thread is called, "A more durable improvised detonating cord". Here is something that relates to the title. I saw a show on The Discovery Channel a while back, and it talked about detcord (the show was called "The Detonators" I think). The outside of the commercial 50 grain(~10.6g/m) detonating cord they showed was truly like a synthetic cord of some kind, they even went as far as to say that they could hang a horse by it.

The improvised detcord from vinyl tubing is nowhere near as durable as the commercial counterpart (in particular no tensile strength at all), however aside from that I believe it does have most of the same useful properties. The tough outer coating on the commercial variety must have a lot more to do with safety. I mean, do we really need detcord that doubles as a tow rope for normal use?

I think the stuff from vinyl tubing will work great for setting charges off simultaneously. I need to find a mean stump with several big roots to experiment on.

It seems that the boys on the Discovery channel probably exaggerated a bit. In the wiki page on detcord is a link to an information page from Dyno Nobel. Their 10.8g/m variety (primacord) has a tensile strength of 200 lbs or 90kg (a very small horse!). They must have meant to use the cord doubled up several times to hang the horse? Maybe the stuff they were using was different, but probably not that much. I feel it was a bad description on their part since even dental floss could hang a horse if one used enough.

I attached a link to the dynonobel pdf, it has some interesting specs in it.

[Edited on 3-8-2011 by Hennig Brand]

holmes1880 - 2-8-2011 at 18:37

We have still to learn how they commercially stuff PETN inside that tubing. Same goes for shock tube- oh, how much time I wasted on trying to replicate the shocktube. It looks like it is a well kept secret. Vinyl tubing is OK for the amateur use, but ideally the walls need to be a less flexible tension-wise and thinner. As far as I looked, nothing is available right now on the consumer hardware market.

I also brought up ammonal as an alternative to ETN because in order to make large amounts of the cord, you'd need to open up an ETN factory. 20ft=60grams of ETN. If I recall correctly, it took me 30 minutes to fill up 10ft of 6mm ID ammonal cord. With 1cm ID, it will take probably 10 minutes/20ft and you won't have to make ETN by pound. It is just a more practical solution. With 6mm ID, I had a packing density of 700mg/inch or roughly 30g/meter. With 10mm ID vinyl, that should be close to 50g/meter. It will be capable to initiate charges tied to it without the need to double-loop.

P.S. Don't waste trees. They are good for air and covering up the noise.

Hennig Brand - 3-8-2011 at 13:49

I am pretty sure the explosive filler is inserted and the tubing/cord is put together in a continuous and simultaneous process, it is very much the same way some fuse is made, I think (different materials of course).

One of the main advantages of detcord is that it packs so much power into such a small convenient package. It is amazing the things you can do with tiny charges of this powerful stuff. Of course it is not a substitute for full sized charges and cheap bulk explosives for the other applications that call for less precision and more blunt force.

Ammonal would be cheaper, but TNT is not going to be easier to make for most people, it is also more of a bulk explosive with rather poor performance incomparison to ETN especially in small diameter charges (detcord). I suppose really large detcord could have its uses, but I don't know if ammonal would be my first choice.

I sort of like making ETN, I find it very straight forward, cheap and with fairly good storage stability and performance. I like my small powerful detcord. Detcord is a very expensive product even when made commercially, but it is invaluable for certain applications. The 10g/m variety is supposed to be quite adequate for detonating most normal explosives, but not the insensitive ones like anfo of course. In the case of insensitive secondaries, the end of the 5g/m or 10g/m detcord is connected to a compound cap or booster.

I may have jumped the gun a little by saying that vinyl tubing has not much tensile strength. Many links when googled state that clear soft vinyl tubing has a tensile strength of about 2000psi. So take the total cross sectional area of the tube, minus the cross sectional area of the bore hole in the tube, multiplied by 2000 psi, gives I think ~52.8 pounds for my 1/4" tubing. Unless there is something I missed vinyl tubing is no slouch in the tensile strength department. It would stretch like crazy though. The vinyl tubing being packed full of pressed explosive must help it resist deformation as well, I would think, adding to its strength.

Don't kill trees, yeah a lot of the time I would agree. Those alders are like weeds in the location they are in though. Apparently alders are good at fixing nitrogen for the soil, they have special nodules in their root system with special nitrogen fixing bacteria that allow them to do this, a few other plants that I know of do this too. I should put them to work making nitrates for my hobby.

BTW, the ETN in the detcord, in my post above is close to 2 years old. Recrystallized with a little urea, etc.

edit: If using the same density as your 6mm tube, the 10mm tube would be loaded closer to 80g/m I think.

[Edited on 3-8-2011 by Hennig Brand]

Rosco Bodine - 3-8-2011 at 14:11

Whatever is mysterious was probably done by elves ;) Eternity Road

[Edited on 3-8-2011 by Rosco Bodine]

Hennig Brand - 3-8-2011 at 14:22

Very funny:)
You know it is sort of that mysterious and illusive nature in all of this chemistry stuff that keeps me intrigued though.

I bet Rosco has a few good ideas for detcord;)

Rosco Bodine - 7-8-2011 at 22:04

Seeing those scissors in the picture .....a solemn warning is in order here......
never, do not not ever use scissors or shears to cut det cord, use a razor knife.

hiperion42 - 8-8-2011 at 10:40

Quote: Originally posted by Hennig Brand  

Ammonal would be cheaper, but TNT is not going to be easier to make for most people...

I may be wrong but i think holmes1880 means AN-AL powder aka French ammonal.

[Edited on 8-8-2011 by hiperion42]

Bot0nist - 8-8-2011 at 10:57

Quote: Originally posted by Rosco Bodine  
Seeing those scissors in the picture .....a solemn warning is in order here......
never, do not not ever use scissors or shears to cut det cord, use a razor knife.

I would like to reiterate this. I know that this isn't a straw filled with HMTD, so the convenience of using scissors may seem appealing. Know that the physics involved at the place where the scissor blades meet is not the same as what is experienced when using a straight razor. They are not the forces that one want's to expose a sensitive secondary explosive like ETN to.

Yes, I know many will attest to ETNs safety and practicality, and god knows that if holmes1880 was still here he would rant and rant about it, but scissors should be a no no, IMHO.

I like your project BTW. Good idea with the hopper. Works good for small scale, and speeds up a tedious process.

User - 8-8-2011 at 11:27

When it comes to filling a tube my guess is that a softer material would be easier, something slightly moldable.
Something sprung to mind: see attachment.

This speaks for itself I guess.
I can image this would form some kind of wax/paste that allows possibly easier filling, and it might be easier to achieve higher density.

Cracking my head over a good filling method today.
Might sound very crazy but what about freezing a tube so one can work with a solid object(for the time being).
Or maybe a mantle for it.
The annoying thing about a hose is the flexible part I think.
Just a random throw, dont kill me lol.

pt2.JPG - 86kB

[Edited on 8-8-2011 by User]

Scissors, bad choice for prop

Hennig Brand - 9-8-2011 at 10:27

For the record I didn't use scissors to cut the finished cord. I stuck the scissors in the picture for scale mostly, kind of like a geologists hammer. The scissors were handy because I was using them for many other things, like cutting fuse. I never thought about it much, yeah it wasn't such a good idea putting them in the picture. Actually I haven' t cut any of my finished cords yet, I used them in the size they were made in. To tell the truth, I didn't like the idea of cutting it at all.

I watched a television show on blasting a couple years ago. In the program they demonstrated what they believed to be the safest method of cutting detcord and dynamite. They used a wooden cutting board and a sharp knife, I believe it was an exacto type knife or box-cutter.

I think the loading process is fairly safe, but not entirely without risk. How much risk I am not exactly sure, so be careful. Someone who knows more than me mentioned that ETN' s friction sensitivity could be enough to make the loading process quite risky. I think I may try and quantify this risk a little more in the near future with some tests. The tube and the wooden rod are fairly soft, but I guess the danger could be more than I realize.

BTW, I cut down an aspen tree a couple days ago which was a fair bit larger in diameter than the alder in the previous picture, a piece of detcord a little less than a meter long was used. This stuff is quite a bit of fun.

[Edited on 9-8-2011 by Hennig Brand]

AndersHoveland - 9-8-2011 at 11:33

The methyl ester of picric acid melts at only 68.4 °C.

Would 2,4,6-trinitrophenoxy-ethanol nitrate (TNPEN) be potentially useful in det- cord? The compound has a melting point of 104.5°C, so it should be possible to safely melt it using a magnesium sulfate (epsom salt) boiling hot water bath. The compound is somewhat less sensitive than PETN.

Basically, phenol and ethylene glycol are mixed in the proper ratio, then the ester is formed by slowly adding concentrated sulfuric acid. The reaction is allowed to cool,
then a cold mixture of nitric and sulfuric acids are added (using an ice bath to prevent run-away reaction) to perform the nitration.


[Edited on 9-8-2011 by AndersHoveland]

Hennig Brand - 9-8-2011 at 16:02

I assume you mean to melt it then put it into a tube somehow. Sounds interesting, but there are some other problems this brings up. The obvious one is, what is the tube going to be made of? It can't melt. Vinyl tubing goes into a sloppy mess at way less than boiling water temperature, but there are quite a few other materials to choose from. I don' t know how much of a problem shrinkage and cracking would be, but it could be an issue. How in the heck to keep the molten explosive from setting up solid before getting it into position in the tube? I guess they did use TNT in detcord so it can be done, but it was a bit different thing than PETN detcord though, I think. The idea of using a low melting point solid explosive is neat.

You mentioned a mantle for the tubing. I assume that is like a jig of some sort (not familiar with that use of the word mantle). I like the idea. I have been thinking along those lines too. It would beat taping the tubing to a piece of dowel to hold it straight every time. A permanent hopper could be fitted to the jig/mantle also.

This could be made out of wood very easily. A router and router table could be used to cut half cylinder channels, the same diameter as your detcord, out of 2 identical pieces of wood. To get 2 identical pieces just carefully rip a suitable piece of wood with the right dimentions in half first. I would also suggest a good piece of hardwood if you can get it. Once you have the half cylinder cut out of both sides, put a rod or something the same size as your detcord tube in the channel and clamp the two pieces together with screw clamps. Drill through from side to side (below the channel, not through it, or above it) so short pieces of ready rod can be put through. Wing nuts and washers can go on the ready rod ends, for convenient tightening and loosening. Plane down what will be the top side of the wooden detcord jig until you have enough of the channel showing to make a viewing window through to the tubing/ through to the loading progress. Don' t plane off too much, or you could lose the function of the jig. I would plane down just until the top of the channel becomes visible, then use a chisel to widen it out a little.

A more permanent hopper to go with the jig could be made as well. I like it!

Here is a strange idea. Have a sealed powder funnel capable of being pressurized. Get a tube that is elastic enough that it can be put under pressure and stretch well without deforming it permanently. Seal one end of the tube well, somehow. Pressurize the sealed funnel and tubing so the tubing swells. Turn on the vibrating funnel (did I mention it vibrates?), so the ETN or PETN fills the tube (there could be some technical difficulties with filling, but I think it could be made to work). Once full, release the pressure and the tube shrinks compressing the explosive powder, to what you hope is a decent density. How' s that for a strange solution?

[Edited on 10-8-2011 by Hennig Brand]

User - 9-8-2011 at 22:44

That is indeed what I meant (english is not my native language).
The practical issue with this would be that one can not see what is actually going on, oke slightly inconvenient.
Could you try to sketch your idea for me?

Letting the tube shrink after being filled wouldnt be such a bad idea I guess.
Only it would be diffucult to get an even width , or maybe not with a jig around it...
Pressure could be applied while filling, and released afterwards..
(just trying to think out of the box here)

[Edited on 10-8-2011 by User]

Hennig Brand - 10-8-2011 at 13:26

In the last two or three lines of the paragraph decribing jig construction, there is a basic description of a simple way to make a viewing slit/window for the jig.

Here are a couple of simple diagrams done with Google Sketchup for the detcord Jig I had in mind. You will notice the jig is split down the middle so that it can be taken apart to add tubing and remove finished cord. The three through holes are for threaded rod (ready rod) to go through. The ends of the rods need wing nuts and washers, for easy tightening and loosening.

This should make what I was describing more clear.

note: The dimentions may need to be different, this is only to illustrate the concept.

Detcord Jig Diagram view 1.jpg - 67kB Detcord Jig Diagram view 2.jpg - 30kB

The channel for the tube probably shouldn' t have gone all the way through, or a butplate of some sort could be added on the far end. Also a plate on the front end with a hole just big enough for the bore of the tube and perfectly aligned with it would lock in the tube from that end nicely as well.

[Edited on 10-8-2011 by Hennig Brand]

User - 11-8-2011 at 05:50

I already thought you meant something like that :)
Maybe a top plate made out of transparent plastic would provide a way to see whats going on inside...

I think this should work, plus it allows more pressure to be applied.
Filling proves to be time consuming and I am trying to come up with something that makes it easier, or at least quicker.
Things like using a jack came to mind, but i soon realized that this will also synthesize new problems along the road.

At least some substance that isnt completely solid(moldable) will make it much easier to fill, working with powder in this case seems impractical imo.
Or one could use a powder and add something like PGDN afterwards(also causing new problems on the way.)
Once again just spitting out some thoughts.
There has to be a better way... :P

[Edited on 11-8-2011 by User]

AndersHoveland - 11-8-2011 at 11:25

Could thick, loosely woven cotton rope be nitrated to cellulose nitrate rope? Cellulose nitrate can actually be detonated, although its rapid deflagration is more typical.

Vinylon rope, which is a form of polyvinyl alcohol, could also potentially be nitrated to polyvinyl nitrate, although this might not be as feasible since vinylon is less porous than cotton.

Polyvinyl nitrate takes the form of tough white strands if the starting polymer had a high molecular weight. The detonation velocity is variable, depending on density, but can be up to 6560 m/s. The substance was once used as a component in propellants.

synthesis from RS:
Over a period of 1 hour, very slowly add 5 g of finely pulverized polyvinyl alcohol (containing 10% moisture) to 100 mL of 99-100 nitric acid in a 250-mL beaker. The beaker should be in a salt-ice bath to provide cooling during the addition. Maintain constant stirring and a temperature of -8 °C throughout the addition, and for an additional 2 hours after the addition. The resulting slurry is slowly drowned in an equal volume of ice water while vigorously stirring. Filter this to collect the white powder that should have formed, wash the powder with water until neutral to litmus, then put it in clean water for 12 hours. Repeat the washing and standing process using 95% ethyl alcohol, and again repeat the process with 12% sodium bicarbonate solution. Finally, the powder is washed with water until neutral to litmus, dried in the open air, then in a vacuum desiccator. The yield is about 96%. You will need a graduated cylinder for measuring liquids, a stirring rod or magnetic stirrer for mixing, and a thermometer to monitor the temperature.

Supposedly, higher yields may be obtained by starting with polyvinyl acetate instead, and using more nitric acid.

If it works, nitrated polyvinyl rope may make for an ideal improvised det-cord, being both safer than most of the other alternatives, and very durable/ convenient to work with.

[Edited on 11-8-2011 by AndersHoveland]

Hennig Brand - 11-8-2011 at 17:57

I just wanted to point out one thing about the drawing above. If the "tubing channel" in the jig is made to fit the tube perfectly or nearly perfectly, the force due to static friction could be tremendous. Translation, if the thing is made well and is clamped down onto a meter of vinyl tubing, the tubing isn't going anywhere under any normal working conditions.

I guess in that case the jig could be pretty much used the way it appears in the drawings above. It just needs a hopper. I would suggest pins or a strip or something permanently attached to both sides of the jig that the hopper can slide down onto and off of. Actually what would be best is a track (just something simple) so that when the hopper is slid into place it is locked in (can' t move up and down, or side to side).

This is a pretty sorry looking hopper, and the proportions of everything are off, but it shows a hopper sitting on the jig. As described earlier the hopper should be able to be installed on the jig and removed easily. Once the tubing is in place and the jig tightened around it, the hopper is installed. Once the cord is full, the hopper is removed and the jig can be loosened and the cord removed.

Jig with Hopper.jpg - 62kB

I know the diagram has inaccurate dimentions, however imagine a tube in the jig, and the hopper in place. A notch would have been cut out of the tubing for the hopper to feed into, prior to installing the hopper.

I think once the tooling was made, loading the cord would be fairly pain free. If the tooling was made well, it would last a very long time and be usful to load a meter or so of detcord at a time.

[Edited on 12-8-2011 by Hennig Brand]

Hennig Brand - 13-8-2011 at 10:30

I have another idea that should increase safety greatly. A blast shield could be installed between the detcord jig and the operator. A viewing window made of heavy plexiglass might be a good option for a viewing window in the shield. With a vibrating hopper and an explosive of the right crystal structure it should feed itself with no need for the operator being involved with that part of the process at all. The operator just needs to stay behind the blast shield and run the loading dowl. The dowl could still be a dangerous projectile if not kept in mind where it is pointed. A heavy leather glove could be used to protect the operator' s hand, in the event of an accident were the dowl could fly out of his hand at high speed.

Though not shown, the jig and shield could be bolted down (or otherwise attached) to a table or base plate of some kind.

Jig with Blast Shield.jpg - 53kB

[Edited on 13-8-2011 by Hennig Brand]

Hennig Brand - 8-10-2011 at 18:12

I guess I made the last couple of posts, but that was nearly two months ago, so I hope it is all right if I post again.

Here is a picture of my birch, 1/4" circular channel, 1 meter long detcord jig. It still needs a good hopper, and the vibrator out of an old cell phone or something for the hopper, but it works very nicely.

The loading dowel slides in just as smooth as silk now.:D This is not only very beneficial from a loading efficiency and loading ease perspective, but also from a safety perspective. Friction is very low now in comparison to what it was using more improvised techniques. No matter how much time and care I put into taping the tubing onto a dowel, I never got it really straight for loading. This gets it perfectly straight. Nothing is ever really perfect but, you get the idea, close enough for anyone.

I will get back with some detailed loading results.

Birch Detcord Jig.JPG - 307kB

A material other than wood might have been better for the jig, maybe some kind of polymer/plastic. The birch was nice and dry, but with humidity changes the wood could still bend and/or twist a certain amount. I guess I will find out in a while if wood was a good choice.

[Edited on 9-10-2011 by Hennig Brand]

quicksilver - 9-10-2011 at 12:41

I was looking at that for a few minutes and it occurred to me that it would take a very unique polymer not to make a weak link at the seam. However if you would construct TWO jigs; one slightly larger than the "core" unit and have THAT seam on the opposite side - you may work through the mechanics of bending with a solid core [pressing against the seam].
Vinyl has always been a problem from a standpoint of longevity and elasticity, they also have a poor shelf life when under pressure, UV, & retaining a bend. There may be other candidates for the tubing that could solve a lot of these issues.

I looked into the whole issue of a "weave machine" when we had originated this discussion re: fuse, cord, etc. I could only find the same run-of-the mill industry machines until I looked into the development of fuse in history. The Japanese had that is today called a "Kumi Loom" that is perhaps many hundreds of years old. It is designed to make a round hollow cord covering and was used in fuse and could certainly be applied to cover a water-proof tube. The weaving is done by hand and is rather fast when one gets to understand who it's done. It would place a tight weaving which is hollow around most any size flexible tube. This was actually the original method of hand-making time-fuse but any material could be substituted in an inner tubular container. It could also be as long as one wished. And using the "sealed "inner tube" concept you illustrated, it may lend a great degree of professionalism to the fuse as it would withstand any type of extreme bending.

Hennig Brand - 11-10-2011 at 10:01

Yeah, the jig is a little vulnerable at the upper edge where the tubing meets it on both sides. I plan on gluing a strip of something (wood?) on both sides to strengthen those edges. This will make those edges stronger and will not interfere with the assembly or disassembly of the jig, when inserting tubing or removing cord.

The main purpose of the jig is to hold the tubing perfectly straight while incrementally press loading the explosive filler. The density of the explosive filler is normally much less (around 1-1.2 g/cc ?), than what it is for a blasting cap. I found that it was not a problem to get the explosive filler up to the required density even without the jig when using the dowel and tape method.

Vinyl is definitely an inferior material relative to what the professional cord is made from. It is not as easy to tie, it does not have as much tensile strength, it is sensitive to UV radiation and probably some more problems that I haven't thought of. Vinyl is however readily available and the cord made from it is capable of the same main functions as the professional variety, ( I think).


BTW, the jig was left bulky in the hope that a more substantial piece of wood, would be less likely to twist and bend from humidity changes.

[Edited on 11-10-2011 by Hennig Brand]

quicksilver - 12-10-2011 at 05:58

I am interested to see whether it functions (seals). I only wish I knew of a commercial platform for experimentation and further development. I had looked quite a bit once and didn't find any commercial "flexible tubular binding".

[Edited on 12-10-2011 by quicksilver]

Hennig Brand - 13-10-2011 at 05:44

I am not sure I know exactly what you are saying. I do think that you are putting too much significance on the tubing/cord material. I think the explosive core is the most important component, which has the most influence over the function of the detcord.

In my previous post I said that the jig's main function is to hold the tubing straight. I left something out; it also provides a stable platform from which to work and to install a hopper for the explosive feed.

I also don't think that the UV sensitivity thing is a big deal because for most hobbyist detcord applications the exposure would be limited. It is not good practise to expose explosive materials to UV radiation for any significant length of time anyway. If a cord resistant to the effects of UV radiation was desired, I imagine a suitable coating could be found.

As was already mentioned in this thread the tensile strength of vinyl tubing is less than the professional cord material, however it is still high enough for any normal use. Unless of course you require that your detcord double as parachute cord or climbing rope.;)

I think the biggest limitation of the vinyl tubing detcord is that it does not tie as easily as the professional material.

[Edited on 13-10-2011 by Hennig Brand]

quicksilver - 20-10-2011 at 12:06

Hennig Brand: This is the patent from the polymer extruded det cord concept.

There are some concepts that are fairly cutting edge here Du Pont purchased it (or subsidized the research). The element was simple start from a single micron level powder-crystal, polymerize and extrude.
They could go up to ten grains per foot. It's from 1983. It uses concepts from British Pat. No. 815,534 and U.S. Pat. No. 3,311,056
which was a flexible sheath of a thermoplastic polymer (could an existing vinyl be a fast stand in???).

It was a very interesting idea. Extruding nozzle concepts also illustrated.

Attachment: det-cord_4369688_full.pdf (1.2MB)
This file has been downloaded 808 times

Hennig Brand - 22-10-2011 at 11:03

Thanks Quicksilver, that detcord patent is very interesting. I am not up to that level of sophistication when it comes to detcord manufacture. Even making a detonating cord as small as the patent proposes would be next to impossible by most normal means. Also ETN probably wouldn't work nearly as well as PETN in a small diameter low energy detcord.

Vinyl is often called the world’s most versatile plastic. Vinyl in one form or another has been used for so many different things that it boggles the mind. I imagine that a suitable form of vinyl could be found for your low energy detcord, one with the right melting point, stiffness and durability. There would undoubtedly be forms of vinyl much more appropriate for detcord manufacture than the soft vinyl tubing obtained from hardware stores.

quicksilver - 23-10-2011 at 05:59

No problem. When I first looked at polymer chemistry I winced but you'd be surprised how eventually all the "little things" add up. I (generally) still have to keep a book open when reading a lengthy dialog in come patents, etc but they make more and more sense as time goes on. I do think you're on to something with the vinyl concept.

Hennig Brand - 13-11-2011 at 05:57

Well, I have what I think is a reasonably good detcord jig. I am still pondering about what to do for a hopper. In the following pictures is shown a much improvised hopper made from cardboard and tape (very temporary).

When comparing to the picture I posted a few posts ago, it can be seen that a strip of maple has since been glued to the top of each half of the jig and cut at an angle to make a V-groove above the tubing channel.

In the pictures above I only had ~10g of ETN to load, which gave me a little more than 2/3 of a meter of detcord. At 1g/m loading density (which is approximately what I have been loading at) my 0.17" ID vinyl tubing has over 14.6g of ETN per m of cord length.

I can load a meter of detcord in ~20minutes (not counting setting up for loading, removing cord, etc). I am sure I can do it much more quickly once I figure out a few more things.

A few observations in regards to the hopper. I found while loading the detcord that simply putting a spoonful of ETN into the V-groove over the cut-out notch in the tubing and coaxing the ETN into the tubing with a bamboo skewer while operating the loading dowel was probably more efficient than the cardboard hopper thing. The cardboard hopper was improvised and not well thought out.

Here are a few pictures I took yesterday while loading ~2/3 of a meter of cord for fun.

Improvised Hopper.JPG - 382kB Partially Loaded.JPG - 628kB End View 1.JPG - 340kB Cord Released.JPG - 364kB Finshed Cord.JPG - 393kB End View.JPG - 319kB Hopper Notch.JPG - 348kB

[Edited on 13-11-2011 by Hennig Brand]

Jimbo Jones - 13-11-2011 at 08:51

Nice work! Why not a funnel and vertical setup?

Hennig Brand - 13-11-2011 at 14:17


There are many reasons, but for now I will say that this horizontal set-up allows greater control over the loading process and consequently the specifications of the finished cord. By loading the tubing this way it is easy to control the size of each increment pressed into the tube as well as maintain a uniform charge density.

There may be a vertical set-up that also works well, but so far I have not seen one that facilitates the loading process like this does.

Think about the ergonomics of a horizontal system versus a vertical system. I can set this up at waist height, on a sturdy flat surface, and the loading motion is a very easy natural motion for the body.

The support provided by the jig allows me to increase the density beyond what would normally be possible.

The biggest benefit of a jig, as I see it, is that it holds the tubing perfectly straight while loading (I suppose a vertical jig would also do this).

I think it is intuitive to think that a vertical setup would take advantage of gravity, when in fact gravity just causes problems like loss of control (I think).

There are more things to consider, but those are a few things off the top of my head. There may be a good way to do a vertical system that I haven’t thought of.

[Edited on 13-11-2011 by Hennig Brand]

Jimbo Jones - 14-11-2011 at 01:16

I see your points. The idea was that in vertical position the jig will be very efficient for small scale gravity press. The funnel act as dispenser. Put the maximum amount powder explosive, than press with suitable weight to get uniform density.

Hennig Brand - 15-11-2011 at 10:28

In order to get uniform density the charge must be incrementally pressed into the cord, the smaller the increments the better the uniformity. Without incremental loading it would also be impossible to achieve a high enough overall charge density let alone uniformity.

If a screw-conveyor type loading system could be setup that would be perfect I think. One turn of the crank giving the exact quantity of explosive desired, (adjustable of course), then press it home with the loading dowel. With a little ingenuity a screw conveyor could also be automated so that every time the loading dowel was pulled back a sensor would signal the screw conveyor to push out another charge. Of course it would need to be designed in such a way that friction was reduced to an acceptable level.

Anyway, I had to test that bit of cord I made, so I went into the back yard to find a victim. I found an aspen tree, which was about 3.5 inches in diameter (from the picture with the measuring tape it looks a little smaller than it is). The 2/3 meter of detcord had ~9.5g of ETN in it at ~ 1g/cc. It was wrapped tightly on the tree and held in place with some electrical tape (I went a little over board with the tape).

It was getting dark during the 15 minutes I was at this, which is why the last pictures are darker.

I should have picked a bigger tree because the explosion cut the tree off the stump like it was a twig.

Cord and Cap.JPG - 422kB Tree Measurement.JPG - 408kB Cord On Tree.JPG - 389kB Aftermath.JPG - 272kB

[Edited on 15-11-2011 by Hennig Brand]

Hennig Brand - 20-11-2011 at 09:23

I have a small note to add regarding the loading dowel. The inside diameter of the vinyl tubing I am using is 0.17 inches, but all the common dowel sizes are either quite a bit too small or too large. I have been using a 1/8" loading dowel which was the most suitable thing I found on the store shelves, but loading with it was tedious with often as much as half the powder slipping by the tip of the dowel during a loading stroke. I noticed the old cannon ram-rods were often a long rod which was considerably smaller in diameter than the bore of the cannon and only the last bit of the rod was close to (but not quite) the size of the bore. It is hard to get a perfectly straight dowel especially in very small diameters, and even if you found one it wouldn't stay straight for long. Using a smaller diameter dowel for the bulk of the length of the rod makes a perfectly straight rod much less necessary, as well as reducing the overall frictional forces (greater ease of loading and greater safety).

You could get an oversized dowel and turn, or otherwise remove material until you had the diameter you wanted for the rod and the plunger end, but I found a simpler way. BTW, this would probably be obvious for anyone used to working with wood, but not me. I took the 1/8" long dowel that I had been using to load with all along and a short piece of oversized dowel which I drilled a 1/8" socket into, wood glue was applied to both the end of the long rod and the socket of the short piece and then the two were jammed together. After the glue had cured, a drummel type rotary tool with a grind stone bit was used to sand down the short plunger tip until it was just a little smaller than the inside diameter of the vinyl tubing. A picture of the new dowel plunger tip is included below.

BTW, loading a meter of cord in 15-20 minutes is quite possible now. I didn't time the last loading with the new rod tip, but it was quite straight forward.

Loading Rod Plunger Head.JPG - 334kB

[Edited on 21-11-2011 by Hennig Brand]

Hennig Brand - 27-11-2011 at 08:01

This will be the last post for a while in this thread, because I am mostly talking to myself, and my repeat posting is probably aggravating others.

I have a couple more things of interest to report. It was mentioned to me that detcord in 1 m lengths was of limited usefulness. While I disagree in general, I do think that longer lengths could be useful for certain applications.

The first idea is simply to double up or kink 2 m of tubing then load one end in the jig before flipping it around straightening the tubing out again and loading from the other end to give 2 m of detcord. A picture of the jig with 2 m of tubing clamped in the middle with a paper clamp is shown in the picture below. BTW, this idea of doubling up tubing in order to load a double length was mentioned in passing in another detcord thread by the forum member Marsh back in 2007. I think he would have had a hell of a time with a 2 m rod however, in my opinion 1 m is already pushing it.


Of course you could kink a 4m tube in the middle, pack with a 2m rod, unkink and then pack from the other end for a 4m length of detcord.

Double Up.JPG - 335kB

The second idea allows one to make as long a length of cord as they want. I recently discovered that vinyl tubing can be glued with PVC cement/solvent. Couplings for the detcord can be easily made for about $0.02 each from short pieces of vinyl tubing that has an inside diameter the same as the outside diameter as the detcord (1/4” in my case). I have included a couple of pictures which demonstrate the strength of the joint, as well as a picture of a 2 m length of detcord made from two 1 m long pieces coupled together. In the strength test the tubing used was only 3/16” outside diameter, with one side glued with PVC cement and the other glued with PVC to ABS transition cement. The PVC cement joint failed while holding up half of the 50 lb load for ~3 seconds. When destructive testing the PVC to ABS transition glued joint, it was the tubing and not the glued joint that eventually failed.

25 lbs.JPG - 336kB 50 lbs.JPG - 257kB Couple.JPG - 454kB

In a strength test I did on tubing glued with the PVC to ABS transition solvent /glue it was the tubing which eventually failed, not the glue. The PVC to ABS transition glue may be the way to go. Keep in mind that I have only done a couple of simple tests. Anyway, I doubt I will ever be pulling on my detcord with even 25 lbs of force.

For best results the pieces to be glued should probably be sanded a bit so that there is room for the solvent/glue to get between the two pieces. I have found that the inside and outside diameters often match so closely that sliding them together removes most of the glue and produces a weaker joint. This could be one of the biggest reasons for some of my joints having much greater strength than others.

BTW, when shopping for tubing make sure it has as close as possible to a perfectly circular cross section from end to end. I mistakenly bought some tubing recently that was flattened out and twisted a bit (must have gone on the roll hot), and it was a nightmare to load.

[Edited on 27-11-2011 by Hennig Brand]

Jimbo Jones - 27-11-2011 at 10:10

Keep talking.

Nice work as always. The idea for the joints was good move. In mine tests I used strong duct tape, but the vinyl joint make the finished product way more durable. Congratulations!

“In order to get uniform density the charge must be incrementally pressed into the cord, the smaller the increments the better the uniformity. Without incremental loading it would also be impossible to achieve a high enough overall charge density let alone uniformity.”

I just read your previous post. The idea was to load the maxim amount powder explosive, which allowed seamlessly movement of the dowel. Than press with suitable weight to get the desired density. Than repeat the process again and again…..

[Edited on 27-11-2011 by Jimbo Jones]

Hennig Brand - 27-11-2011 at 10:37

Thanks for the approval.

Sounds like you have the right idea regarding loading, I was (initially) just a little unsure of what you meant in your previous post. As you say, a vertical setup with weight would provide for a consistent applied force time after time. This is a feature of the vertical setup that I do appreciate. There are probably at least "a couple different ways to skin the cat".

[Edited on 27-11-2011 by Hennig Brand]