I've been thinking a lot lately about ways to detonate charges without using unstable and unsafe primaries. My goal was to come up with an idea for a detonating device that would not go off with heat or shock. I have been thinking about a mechanical detonater. Instead of having a primary create the initial shock to detonate the secondary charge perhaps using air pressure or another means of propulsion a piece of metal could be sent into the charge with the necessary force to detonate it(think of how bullets detonate explosives). Obviously we will need a relatively shock sensitive explosive for this to work.

If you have any questions on this feel free to ask, I'm sorry that I didn't explain this as well as I possibly could. I'm rushing to get to school.

I don't think there are many way to deliver the necessary energy to detonate safe secondaries. The only one I can think of is EBW.

I think they used falling hammers/weights to detonate pure NG many years ago.

Does a safe primary fufill your requirement to avoid unsafe primaries? :)

Most secondary explosives can take a rifle round and thrown in a fire with little chance of detonation. As Anthony said the best way is with a safer primary and good sense of course. There are some secondary explosives that might go off with a high enough electric current

PETN can be detonated when hit by a 7.62mm Nato round , tried it when I did my service. We made exploding targets wraping detcord around pieces of wood then "plinked" away with a scoped HK G3..

While in the army, I saw in our book about explosives, that the plasticized PETN we used could detonate if it were hit by a projectile with more that 840 m/s. So our C7A1's weren't able to detonate them, but a .50 SLAP would probably do the trick!

In part 3 (IIRC) of The Encyclopedia of Explosives and Related Items is a large table (or 2 tables) with impact sensitivity of bullets on a lot HE's, including the velocity to reach a partial detonation, and a full detonation. Very interesting.

I don't think there are many way to deliver the necessary energy to detonate safe secondaries. The only one I can think of is EBW.

EBW is indeed dafe, but the electronics behind it MUST also be safe. I have made myself an electronic blast box, which can be connected with my EBW box. It use a delay relay in my blast box, so I switch it on, switch it on to 'danger' and turn the switch for the delay-relay. After 30sec. the relay becomes active, and only then it can switch. Switching is performed by a mobile phone, quick and dirty, but it works.

Another 'safe' option would be a shock tube, see the other topic. (If the MODS think it is usefull, merge them) Íf something like that could be made at home of course....

There is of course no safe primary, but I have to say that I like double salts. They are very shock insensitive, and detonate vigoriously in small amounts, you need a very small amount for PETN. The procedure to make it is also piss easy.

I 'prefer' heat-instable primary's above shock instable primary's, as a shock is easier applied then heat. I think DDNP and lead azide are 2 very good primary's, but lead azide is very toxic, and DDNP is rather hard to make.

Just go with the azo-clathrates. You can tailor the exact properties by changing the amount of sodium azide you add. If you prepare it according to Rosco's 4/12 variation you'll get something quite similar to lead azide, in terms of both sensitivity and initiating ability, but using somewhat less sodium azide ( I couldn't tell you exactly how much ) you can get a primary that is flame sensitive but doesn't do DDT unless confined, is about as shock sensitive as RDX and has a much greater chemical stability than DDNP ( or lead azide; the azo-chlathrates don't react with CO2 the way lead azide does ).

Overall, this gives you a primary that is safer than your detonator base charge.

Why not use mechanical dets? I've thought about such a few times but never tried so far. A strong spring can provide as much enery as a EBW wire. Confinement of the primary will be important in my opinion.

Come on, knowledgehungry, tell us more about your idea!
What about a mouse trap + a straw of AP as first try ;)

The mouse trap sounds viable but, I wouldn't want to be the one to set it up.
a centerpunch might be a better choice of "hammer"s

Mechanical systems can malfunction just as chemical ones can; how much do you have to jostle a mousetrap compared to lead azide before they go off ?
You would presumably get around this problem by not cranking back the spring until just before firing, but how is this different from not inserting your blasting cap until just before firing ?

Mechanical systems are most widespread and almost everyone considers them safe: firearms.

While a chemical system already contains the ignition energy, you have to put the enery into a mechanical system before it can fire. You do so by tensioning a spring. If you don't tension it, it can't go off, really. But lead azide can. By spark, by dropping it, by static, by....

Same for electric systems. I do trust in a mechanical switch, but I wouldn't feel good if only a transistor was between the battery and a det in my hand :eek:

The firearm system is more or less what I was thinking of when I brought this idea up. I was thinking that with a strong enough impact from the firing pin some of the more shock sensitive secondaries could be detonated. If there is no way of using a secondary a relatively shock insensitive primary would be my next choice for this system. Since I have a nice Christmas Break I will try to develop this idea a little more I might even get to some testing. I'll keep you posted.

A spring may contain the same amount of energy as an EBW, but over what time scale is it delivered to the explosive? Also, an EBW is simply a little thing on the end of a wire, a mechanical thing will be harder to integrate into a blasting cap.

How would you bury a charge primed with a centre-punch initated cap?

The AP and mousetrap idea suffers from still using the exact sensitive primaries we are trying to get rid of...

Gun ammo is safe true, but then it is meant to go off in your hands (in the gun in your hands), whereas you want to be a long way away from a typical explosive charge.

Prodigychild, the only time when a transistor (or switch!) would be the only thing between battery and det would be the few seconds before you pressed the firing button. Of course you would never connect the battery (and keep the cap wires shunted) until the charge is primed, in place, and you have retired to a safe distance!

I'm not trying to piss on your fire Knowledgehungry, I just think this problem is a difficult one. Fused and electric caps have been developed over 100+ years, and are very safe and reliable when used properly.

No, Anthony, as soon as one uses a remote trigger (no cable) trust in the triggering device is REQUIRED.
Give me a solution to work around this: as soon as one plugs in the det cable (or switches on the receiver) one needs to trust. Maybe it's 1m away from the main charge, but by far not safe distance.
Trust start even earlier. Everytime I connect a electric det with the long wire, I touch the cable with my hands to discharge a possible static, but still feel a bit uncomfortable. Plugging on the other side of the cable is much more relaxed ;)

I'd have a switch between the reciever's battery and circuitry, with approx 10yards of wire on it. So you could at least be that far away when you arm the charge. Even 10yds from a 50lb charge should mean you escape serious injury - perhaps burst eardrums and a little bleeding from bodily cavities :)

One could do as the Madrid bombers.. Use a mobile phone, Just make sure the cash card doesn't have a number that used to belong to a 17 year old girl :)

I'm not trying to piss on your fire Knowledgehungry, I just think this problem is a difficult one. Fused and electric caps have been developed over 100+ years, and are very safe and reliable when used properly.

I understand that this will be difficult to do, but I also understand that this is the place with probably the largest collection of explosive enthusiasts and many of us are quite bright. I'm not even saying that this sort of blasting cap would be an improvement over normal caps, rather I'm interested in coming up with new ideas.

Where my thinking has been lately in terms of this idea is using CO2 powerlets to propel a firing pin with the appropriate force to detonate the cap. Obviously this will not be an everyday blasting cap as I am sure it will be very difficult to make, and as Anthony said when used correctly fused and electrical caps are very safe and reliable.

Another idea might be to have the firing pin propelled by an explosion for a primary, but the way that it could be made safer than your average blasting cap is that there would be a safety mechanism that would stop the pin from hitting the booster even if the primary did go off accidentally.

AFAIK some type of detonator is was developed in US. It consist from pyrotechnical charge (KClO4 + Zr or Zr hydride), metal element and HE.
Pyrotechnic mixture disperse a metal element to high speed on a few cm (or mm - i dont remember) base. HE initiated by shock of this element.

But... There is much more interesting and simple construction for safe detonation. NPED detonator is based on special pyrotechnic charge and HE like PETN or RDX. Detonation is come from DDT. Check patents for NPED detonators: us4727808, us5385098, us6227116.
I tried to make some sort of it with pyrotechnical fuse. But I used a paper tube and its all failed. My first thing was a successive pressing of black powder (a very little - only for next mix ignition), CuO/Al mix 70:30 and pressed RDX dust. There was a little bang with flash and calm rdx burning.
Other 3 stuff I made with more clever: ignition was on surface pyrotechnic mix/rdx. Pyrotechnic mixture was KMnO4/S/Mg 50:6:40. Its one of the most powerful mixture for petardes. There was also flash and bang (with much more sound). But RDX did not detonate.
Next time I plan to use crystall RDX and more thick paper tube (2.5-3mm instead of 1.5mm). I think it needs a metal tube but I dont like to work with metal because I have a metal fragment in my arm.

It will be very hard to get RDX to detonate in this way. A much better choice would be PETN or well neutralized MHN.

PETN is sure preferable than RDX as more detonable HE. But I could not obtain quality pentaerytrite to make it.
From the other side RDX is much more ignitable than PETN and its important. Patent us4727808 discloses using RDX in examples not only PETN.
I am going to add a zink or aluminium dust to increase a burning speed of rdx initiation charge. I have read that I need very fine RDX for this detonator type.
I think the key to success is a strong shell and very small hole for fuse.

Near the end of the "Easily made powerful blasting box" thread I tossed out some speculative ideas about using a large array of capacitors that could discharge enough Volts X Amps to get an impulse in the low megawatt range through enough cheddite-as-booster to achieve detonation in some sort of ANFO main charge. The capacitors could be controlled (charged and discharged) from a safe distance yet located quite close to the HE.

Switching is obviously presents a bit of challenge when were talking hundreds of amps at thousands of volts!

The basic theme here is to find ways to maximise safety and convenience not only with the means of detonation but with the compounding and use of all the energetic materials involved as well.

If anyone in the forum is interested in this approach to safe detonation please read the two posts mentioned above and give some feedback.

Personally, If I were going to detonate something big enough to require remote detonation, I would have the receiver connected to the blasting cap by a LONG wire.

Also, maybe have a mechanism to drop the blasting cap into the main charge, so that in the off chance it does prematurely ejaculate.....I mean detonate, it wouldn't set the main charge off.

Apologies for bringing up an older thread, but I thought it might be justified here. Please correct me if I'm wrong.

A search of the forum has not turned up any mention of the paper titled "Nonprimary-explosive, hot-wire detonator," which I happened upon in the Los Alamos archives. I thought it would be a good idea to post it here:

http://www.sciencemadness.org/lanl2_a/lib-www/la-pubs/00318545.pdf

Briefly, a mere ~1 W (1 Amp, 1 Ohm) of power applied to nichrome wire is used to cause PETN to undergo a DDT within the detonator. Diagrams and test results are provided.

I found this paper very interesting and relevant to this thread, and hopefully members who haven't seen it will find it useful.

On another note, I apologize to knowledgehungry for inadvertently "stealing" his idea regarding mechanical detonation with my post here:

http://www.roguesci.org/theforum/showpost.php?p=93277&postcount=19

I wasn't aware that he had proposed the idea first. :o

I remember somewhere on another thread that CuO+Al is electrostatically sensitive, If I manage to get a paycheck larger than $150 I will try to make a detonator using that as a charge. I'm sure I could make one with 2 camera caps 300v at I think 500mF.

Hope this is not mentioned before and therefore render this unnecessary, but I came with idea of causing detonation by extreme heat. What I mean, is thermite. Could, for ex. ANFO or even AN only get detonated by the extreme heat of thermite? Has anyone ever tried or heard about this? It is just since many explosives will just simply blow up if exposured to extreme impact, friction or heat.

There were some guys that were into Tesla Coils & High Energy (non-chemical on chemical) materials that came VERY close to getting EBW setups to det outside of a closed container. You REALLY need to know your physics for that sort of experimenting. Or at least have a solid grounding (pun intended) in electrical or chemical engineering.

If you have ever worked with popping wire via CD or just heavy amperage you'd see that it VERY possible to get the energy needed. But you have to have the Joules upstairs to make it workable outside the lab.

After looking at that file LibertyOrDeath linked, EBW dets look within reach. For someone with a lathe this would be very easy. For us mortals with less than multi thousand dollar tools it would require a bit more ingenuity, but seems doable.

The header could be made from a 10mm diameter bolt or rod, cut off to about 25mm length and drilled out through the center, first with a 2mm drill all the way through to make the transition barrel, then with a 5mm in one end down 10mm or so to make the beginnings of the donor explosive housing, then drilled with an 8mm bit down 5mm on the other end to make booster housing. The leads would then be attached by casting them into place with epoxy resin after attaching the bridge wire. Then the remaining open chamber could be pressed with PETN or ETN, or even possibly filled with cast ETN. Fortunately the explosive works better at lower densities for DDT so pressing shouldn't be too hard.

While plain nichrome is easy to get, the paper calls for Nichrome V, a higher temperature alloy. It may not be critical but I figure it would be worth the extra money to have more reliability. It is not easy to find but I did find a source.

http://www.coleparmer.com/catalog/product_view.asp?sku=1420320

Inoculating loops, pack of 12, 24 gauge (0.051 mm) wire, ~75mm of it per unit. For $65 thats enough to make about 300 detonators...

A bridge wire with a gap of about 2mm and a resistance of 1 ohm would require 3 volts to get the specified current for reliable detonation. This is fortunately a perfect application for a lithium polymer battery, an extremely small one could release this amount of power. And at the just the right voltage too.

I think ETN would be ideal for this, sensitive, easy, cheap, safe. MHN comes to mind too. I'm sure there are some others.

In comparison, the diffrences between standard nichrome, and nichrome V seem pretty minor:
From wikipedia -

Material Resistance
(ohm-cmil/ft) (ohm-cm)
Nichrome 675 112.2 e-6
Nichrome V 650 108.1 e-6


From metal suppliers online -

Nichrome - Nichrome V
Density (lb / cu. in.) 0.304 - 0.304
Specific Gravity 8.2 - 8.2
Specific Heat (Btu/lb/Deg F - [32-212 Deg F]) 0.107 - 0.107
Electrical Resistivity (microhm-cm (at 68 Deg F)) 675 - 650
Melting Point (Deg F) 2550 - 2550
Mean Coeff Thermal Expansion 0.13 - 0.12

(sorry it didn't seem to like my table too much)

Are the differences that great to warrant the trouble of finding nichrome V at a decent price? McMaster Carr sells standard nichrome wire by the spool at fairly competitive prices.

Yeah.. there doesn't seem to be much of a difference according to that information. From what I read (can't remember where) Nichrome V has a higher working temperature. Not that much different though. I'm sure the plain stuff would work fine too.