Shock tube detonator

[Child-of-Bodom]

Doing a search around EBW's, I came across a website of a company that sells 'shock-tubes'. It seems like a nice improved detonation system, also for setting of multiple charges in a ms timeline, as detcord. I like the idea of using it as a detonator, as I am always looking for even safer ways of detonating.

A shock tube is a hollow tube with a thin coating of HE on the inside.
For use as detonator, the shock tube is heated on one side, by a simple pyrotechnic of electrical charge, and a flow of heat will propel in the tube. The HE will accelerate this reaction, bringing it finally up to 6500fps.
A typical mixture used is HMX with 8-10% air float aluminium powder, but I think other HE's can be used also. I found a amount of 45mg/cm² used.
For DIY purposes, the coating of the tube will be the most difficult part. The HE intended to use should be fine powder, for an equal distribution over the inside of the tube. As binder Ethylene/acrylic acid is used, as ethylene vinyl acetate. (US patents 4 607 573(1986) and 5 317 974 (1994) respectively)
Another option would be to damp the explosive on the inside of the tube, by making a saturated solution of, for example, PETN is acetone. in a tube, (not plastic one) apply a small amount of acetone, and roll it until all the solvent has evaporated and the PETN is left equally distributed over the inside of the tube. Heating an explosive over it's boiling point and condensing it in a tube won't be my favourite hobby...
I have search extensively, and couldn't found anything related to this as detonator on this forum.

Here is a good article: Part one (http://www.shocktubesystems.com/sys-tmpl/shocktubetechnologyareview/) and Part two (http://www.shocktubesystems.com/sys-tmpl/shocktubetechnologyareviewpart2/)

There is also a bunch of patents as references under the 2nd page, I feel no need to repeat.

Anyone ideas how to make something like this ourselves?

[SweNMFan]

It sounds like the Dyno Nobel NONEL system.. I think a improvised version would be hard to make, as the real stuff doesn't burst the plastic tube it is in.. I've seen people holding the Nonel tube when "lighting" it .. I wouldn't do that with a improvised one..

[Child-of-Bodom]

Indeed, it is the NONEL system.
RISI actually sells a system which you can connect to your EBW box, it is a system you can re-use, it is connected to the end of the shock-tube. The arc will probably ignite the shock tube.
Is their anything known about other types of ignition, is it also possible with a fuse, or is something like a pulse very nessesary?

[hereno]

or is something like a pulse very nessesary?

Yes, it is. Typically a shotshell primer is used to initiate them, this could be made easily, though the tube itself would be very hard. I cant see why anyoune would use an electrical pulse, since the whole point of using NONEL is to get rid of the electrics. NONEL = non-electric!

[Child-of-Bodom]

Because I like electronics, and I just could hook it up to my EBW system.
Just a single electrolyte cap would do the trick, just shorten a nice NiCr wire, and there is your pulse.

Typically a shotshell primer is used to initiate them, this could be made easily

?? To set of a shotshell you need to make a complete setup with a weight which set of the shotshell primer :confused: That is not very easy in my eyes...

Since it seems to be that no one has made a home improved shock-tube here before, I would like to give it a try. I will start from MHN, and a drinking straw. For HMX + 10% alu 45mg/cm² is given, so I will try to get around the same amount in the tube.
The straw has a ID of 4mm, and a length of 5 cm means an effective surface of 6.3cm², means ~280mg. This amount needs to be dissolved in a as small as possible volume of hot EtOH, whereof the proper amount will be applied to the straw, which is turning around.

The main question is although, is evaporated HE good enough, of do you need to damp it on the inside, under reduced pressure???

[FrankRizzo]

Nah, it's not very involved at all. No caps to charge, no batteries to worry about, just simple mechanical force. You put the shock tube into the hole in the bottom of the little metal gizmo, load a primer into the pocket, and then turn the handle to release a spring-loaded hammer. Simple. It could be improvised using the guts from a retractable BIC pen if necessary.

[amagroup]

Insted of HMX - AL, a technology using PETN - AL is more easy but the drawback is, the coating of mixture has to be inspected visually.
Does anybody have idea,how to ensure the coating by instrumental methods

Don't quote whole posts, or you'll be banned

[FullMetalJacket]

Somebody... I forget who, on TotseBB a while ago had some success with this. I'll ask around.

[Crazy Swede]

The secret of the Shock Tube system is that the plastic tube has a special inner layer that attracts the HMX/Al-mixture statically so it sticks to the inner surface.

If using a tube without this property there is a great risk of getting too thin layers at some parts while forming bigger amounts of explosive dust at bends and ends of the tube, which could lead to improper and even dangerous behaviour when ignited.

It is actually not necessary to use explosives at all. I know people who experimented with finely ground cinnamon and achieved reproducable dust explosions and shock waves through the tube!

[Diabolique]

Something relate that may be useful is a slapper detonator. The EBW is used to accellerate an aluminum foil to hypervelocity through a short tube ( <1 mm) into a PETN base charge. It is used where reliability and high temperature resistance is needed.

For the aluminum in the shock tube, try pyroaluminum or aluminum black. A lot finer than flake. It is also sometimes refered to as sub-micron aluminum.

If you are good working with glass, you may try making a high voltage discharge shock tube. You will have to fuse the glass to a copper sleave that acts as the ground, and a thorium oxide coated wire emitter at the sealed end of the tube about 1 cm away.With enough energy, this should generate a shock wave down the tube that can initiate PETN. I know it was experimented with, but they found the slapper detonators to be better.