Sciencemadness Discussion Board - Detonation systems

Detonation systems

Bfitzy - 17-7-2017 at 13:07

I've been searching for a prospective thread regarding Detonators/ blasting caps. People seem to have a variety of different methods, the most common being pressing some amount of primary (50-500g ) and up to 2.5g of a secondary (HMTD/ETN/PETN) into a metal tube of some diameter >4mm with some kind of metal plugs and I guess everybody has bulk E-match hookups. I am currently trying out of laziness to make my own system using 3D-printed parts. going well so far using 6mm ID 8MM OD 25mm long PLA tubes. Will not be able to test them for a while however.

PHILOU Zrealone - 18-7-2017 at 12:57

Quote: Originally posted by Bfitzy

I've been searching for a prospective thread regarding Detonators/ blasting caps. People seem to have a variety of different methods, the most common being pressing some amount of primary (50-500g ) and up to 2.5g of a secondary (HMTD/ETN/PETN) into a metal tube of some diameter >4mm with some kind of metal plugs and I guess everybody has bulk E-match hookups. I am currently trying out of laziness to make my own system using 3D-printed parts. going well so far using 6mm ID 8MM OD 25mm long PLA tubes. Will not be able to test them for a while however.

I suppose your 3D printer is not working with laser and metallic powder....
PLA? Poly-Lactic acid? (Better write full name aside the accronyms at least once into the tread).

Detonators needs hard casing to ensure confinement...plastic will not be strong enough to confine the deflagration/detonation or transition D2D...what means you will need overkilling quantities to acheive same effect.

At equal densities, the detonation speed (VOD) of PETN is proportionnal to the hardness of the casing...
Paper < rubber < hard plastic < glass < mild copper < hard copper < soft iron < iron steel

For excessive good detonating stuffs (primaries) even 5-10 mg can be enough .... for some less potent initiators sometimes one needs 50 to 100 mg...but 500mg is way too much...so with your "50-500g" you are way over the break-even by a factor 1000 to 10000...

[Edited on 19-7-2017 by PHILOU Zrealone]

Laboratory of Liptakov - 18-7-2017 at 23:13

I mean, that Bfitzy has error in describe. He needed write (50 - 500mg).

XeonTheMGPony - 21-7-2017 at 07:54

and to note HMTD is NOT a secondary!!

D2D the tube

Laboratory of Liptakov - 22-7-2017 at 01:53

The tubes that provide D2D capability may look like this:

........Dr................. :cool:

Chisholm - 25-7-2017 at 03:35

Quote: Originally posted by Laboratory of Liptakov

The tubes that provide D2D capability may look like this:

........Dr................. :cool:

How could someone possibly crimp the aluminium foil in place without wrinkling or tearing it?

XeonTheMGPony - 25-7-2017 at 03:59

I use a medium wall brass tube from the hobby stores for a good while was using the aluminium both work quite well

Tsjerk - 25-7-2017 at 06:39

Most primaries do D2D easily in a drinking straw confinement. I always used lead azide or the complex with picnic acid, about 10 mg, with a centimeter of PETN in a straw and never had a misfire.

D2D

Laboratory of Liptakov - 25-7-2017 at 06:40

Brass is good. But aluminium at some mixtures show failed. Respectively D2D effect failed. For LA is steel cavity luxus, not needed, of course. Solid cavity is for safely non-primary mixtures. Dr.

[Edited on 25-7-2017 by Laboratory of Liptakov]

PHILOU Zrealone - 26-7-2017 at 01:52

Just as explained previously....detonation speed and pressure is dependant onto the density of packing of the compound itself...but that being equal also onto the hardness/resistance of the outer casing...

So a plastic straw will be less good and require more material than aluminium straw/pipe itself a little less good than brass/copper and finally than iron steel.
Of course for amateur work we don't really care about using 50mg or 30mg ;-)...but for professional/military/spying use where miniaturization and weight is important...

In theory thus the best detonator casings would be made of:
1°) diamond or tungsten carbide (WC)...
2°) an active faster explosive casing...ensuring confinement by the compressing wave...it is what happens into a shaped charge...the outer layer initiates and confine the inner material that has not yet detonated...and the later forms an isotropic jet hence reaching faster VOD and pressure into the shaped charge axis...
3°) a material that is very hard inside and outer layers of other materials with decreasing hardness but increased elasticity --> iron steel pipe treated on the Inside with phosphor/carbon and coated on the inside with WC and on the outside with nanofiber glue

[Edited on 26-7-2017 by PHILOU Zrealone]

XeonTheMGPony - 26-7-2017 at 04:10

or in the real world a standard aluminium pipe of 5mm and charges pressed to a min of 100psi loading density

Brass for Mercury Fulminate, Aluminium for Azide. Paper jacket for HMTD in either casing or nitro lacquer coated.

I usually put in a paper jacket and nitro lacquer it as of late since I still use HMTD as it is the best out of the worst far as pressing goes.

The jacket all so serves to make a re-enforcing cap as well, as My goal is to make near mill spec caps. reason being one day I plan to get into hobby mining

won't make millions but will be fun.

[Edited on 26-7-2017 by XeonTheMGPony]

Laboratory of Liptakov - 27-7-2017 at 06:37

Paper jacket liner in cavity is very good idea, simply generally. Decreases it friction effect during filling for anything will inside. And reactivity with metal. From this seen a rich practical experiences. In real world here on Earth.
And on near planets, of course...... :cool:

...Dr