hardliner
New Member
Posts: 9
From: Australia
Registered: MAY 2001
posted 05-13-2001 05:26 PM
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Is it reasonably safe to start ripping open boosters and dynamite cartridges as long as you don't use metal?What is the easiest way to plastisize commercial PETN or RDX or a mix of the 2?Can det cord sever telegraph poles?How close must A.N based charges be to each other to set each other off with the one blast?When using large amounts of ANFO is it necessary to use air tight containers or can you just treat the A.N sacks with fuel and pile them up?


Bitter
Frequent Poster
Posts: 290
From: 11 Downing Street, London, England
Registered: SEP 2000
posted 05-13-2001 06:17 PM
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"Is it reasonably safe to start ripping open boosters and dynamite cartridges as long as you don't use metal?"
Erm, what exactly are you going to rip them open with other than metal tools ?

"What is the easiest way to plastisize commercial PETN or RDX or a mix of the 2?"

Mineral oil.

"How close must A.N based charges be to each other to set each other off with the one blast?"

Very close I should think. No more than a few centimetres; it's difficult to detonate.



Anthony
Moderator
Posts: 2306
From: England
Registered: SEP 2000
posted 05-13-2001 06:45 PM
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So many questions...
Yes it should be safe to open dynamite cartridges, but wear gloves or the nitro will fuck you up.

Metal tools *should* be ok since dynamite punches are made of metal and dynamite cartridges are usually slit with a knife.

The maximum distance for propagation firing of "AN based charges" would depend heavily on exactly what the explosive was since ANNM is more sensitive than ANFO. It'd also depend heavily on the medium between the charges such as air/sand/wet soil/water etc. The only way to find out is by testing as each situation is so different.

Yes det cord could sever telegraph poles don't know how much you'd need though. More than for an equal dimater tree though as telegraph poles are tougher than fresh wood.

Fuel oil isn't very volitile at all so it won't evaporate quickly. You could cut open a plastic sack of AN, pour in the FO, tape it up, mix it and throw on a pile ready for detonation.

Not sure what form the base charges you refer to are in.

I have a few questions though, why do you want to open dynamite cartridges? It's a finished product and best used as-is. Also, to have access to this stuff you'd most likely be a bonefide blaster and a real blaster would already know all this stuff, especially about the det cord.

4 wraps of standard military detcord (PETN surrounded by asphalt) should be plenty to take out that telegraph post

Unless you have personally seen otherwise, I seriously doubt that it would. At least not with detcord even remotely similar in size to the stuff you see professional blasters using.

I'm basing this on my own quick experiments with homemade PETN based detcord.

You will need alot more than four wraps....

The standard military det cord contains 6.4 pounds of PETN per 1,000 feet.

Lets assume you telegraph post is 1 foot in circumference. Using four wraps will mean four feet of det cord. This lenght of det cord contains 0.0256 pounds of PETN. Thats only about 56 grams...
Definitely not enough to cut that post.
For an external timber cutting charge you will need a whole lot more det cord.

I would prefer to use the flexible sheet explosive and wrap a 6-12 inch wide band around the average size pole and initiate it with detcord.;)

I don't know what pro blasters use but I know for fact (a friend of mine is on the military demolition squad) that 2 wraps of detcord will bring down a small tree, and according to him, 4 wraps will be enough. I can find out what kind of detcord they used i.e. how much PETN it contains if you want me to.

I can't believe that anything classed as 'det cord' would cut a telegraph pole, as they are pretty strong. IIRC det cord was not designed at all for actual blasting work, but to detonate other explosive charges simultameously, so as to achieve maximum effect for a said amount of explosive. It's for connecting explosives, not for use as an explosive.

If you really do have a friend in a military blasting group, I'm sure you could find a lot of other information that would be very useful to a lot of us here.

Australian army detcord called 'redcord' contains PETN (straight) in a 4.5mm internal diameter plastic tube, which is then encased in yarn and again sealed in plastic.

Discounting the fact that there is a small cotton thread through the centre of the PETN, Does anyone know (assuming average density) what weight of explosive that would be (per metre) ? I don't know exactly, but it surely wouldn't be much. On the printed diagram I have here (Australian army blasting manual) the explosive content is less than half of the actual cross section of the cord. There's more packing than actual explosive !

Another way to use less detcord would be to give it a water backing to focus the explosion towards the pole.

It's known that water absorbs the heat and kinetic energy of the blast, rendering your detcord less powerfull than using on it's own.

I remember a discussion on this a while back, and while I can't remember the outcome, I am sure water as tamping would not be effective.

I base this on a story (I cannot any longer find sorry) that the Autralian Navy was going to using water as a protective barrier around it's munitions on ships, for the reasons stated above: It absorbs all the power of the blast, making it much less dangerous.

Also, while before masive steel magazines were used, which produced large amounts of shrapnel in an explosion, water is converted to steam, or stays as water, so there is little danger from it.

I believe last time this was brought up a few people had a lot of trouble believeing it..... but I'm quite sure. Also, underwater demolitions info states that shockwaves (as from demolition work) travel very well in water, hence you cannot be in water anywhere near underwater blasting work.

It doesn't matter how much tamping you have anyway, 4 rounds of detcord are not going to take out a telegraph pole. (From what I know anyway :rolleyes: )

GibboNet, if you could find out the weight of the detcord per metre and what sort of plastic is coating it (then you can find the plastics density) then you could calculate how much PETN is in the detcord per metre and also, more significantly to us the density at which the PETN is loaded. i think it would be interesting to see just how densely packed the PETN is.

Redcord = 10g/m
volume = 15.9cm3/m

Therefore unless I fucked up some conversions a 4.5mm column will have a density of 0.62g/cm3, not very much.

Ok, I talked to my man who used to clear up fields from trees w/detcord ALONE. Point #1 detcord CAN be used effectively by itself. Point #2, get this, they use only 1 wrap for a tree the size of a telegraph post, point 3 - there is PETN fuse that has pensil-led diameter of PETN and a several different layers of various material around it, and there is detcord which is nothing but PETN (pinkey width, i.e. smaller of five fingers - I am not sure how to spell that) coated with some thin plastic-type material, i forget what he said the name of that coating was. So if that's the type of detcord you have then screw 4 wraps I said originally and use 2 if you are absolutely 100% wanna be sure that that baby comes down.
I suppose there is a difference in what military uses and what is used by civilians...

It may be more likely than some would think of a circular charge of det cord bringing down a utility pole. The shockwave(s) would be concentrated at the center producing a much higher pressure than would a semi-circular charge or many other types of charges. Don't know if that was worth posting though, you fellas seem to me pretty smart.

Yeah I think that might have something to do with it Cricket, colliding shockwaves can really "fuck things up," for want of a better term. I'm sure a few wraps of detcord will do more damage than the same amount of explosive arranged in seperate little bits, and being set off a ms or so after each other.
So the force of the explosion itself would easily eat quite a bit into the pole around the detcord, and the colliding shockwaves will severely weaken the wood in the middle...
I think it could be done, or at least it could weaken it enough for it to fall over, even if it isn't "cut" by the explosion.