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Author: Subject: Det Cap Strategies
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[*] posted on 19-4-2024 at 17:37


Getting closer. This was half a gram of NAP in a sealed PT100 thermometer body. Hand packed densities. Slowly scaling up the amounts as I am testing my det chamber’s ability to cope with these things as well. So far it’s done well to contain small amounts of shrapnel and deaden the sound to the point that the dogs don’t even react. Next test is 1 gram of NAP.

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[*] posted on 20-4-2024 at 04:43


Surely it was a detonator ? It looks like woodpecker pecking.....:cool:



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[*] posted on 20-4-2024 at 05:14


I’m not sure what happened there. It’s very interesting.
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[*] posted on 15-6-2024 at 11:00


After many months, I decided to schedule another trip. It's going to be in a month's time, but I am going to prepare my detonators today.

So I was advised to use ground-up melt-cast ETN to mix with the NHN in a 1:1 ratio as the initiator and around 1g of hard pressed ETN, if I can fit that much. I will make 6 caps in total, 3 using ground-up melt-cast ETN and 3 using solid-cast ETN to see if it will work. Do you think a little loose ETN will still be necessary or will the NHN/ETN mixture (only LIGHTLY tamped) will suffice? I wish to use 0.3g of said mixture. I think I will be able to fit a full gram in the cap body, but I don't want to overload it and make sealing it a problem.

I did think about sanding off part of the cap body, but I think that might not be necessary. I think the actual thickness of the steel is 0.5mm. But that is only the 8x50mm. The longer 100mm body is definitely thicker and has a slightly smaller inner diameter, so for those, I will probably need to do some polishing and sanding.
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[*] posted on 15-6-2024 at 21:46


1) My recommend, create 2 pieces 49 mm from 100 mm cavity and without bottom. 2) High density ETN not must be super high density. Hand pressed on 20 Kg is easy achieve without vise or else tools. 3) Mixture grain ETN + powder NHN 1:1 pressed on 1 Kg is enough for initiation described pressed ETN.......:cool:



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[*] posted on 16-6-2024 at 06:03


I barely did any pressing on the primary. But I think when I inserted the e-match, it might have given the 1 kg as it inserted or, or even less. I wanted that stuff to be as loosely packed as possible. Some of them were overfilled since I put in 0.4g of NHN/ETN mixture, I realize that this might be excessive, and only 0.3g would be sufficient and also give enough room for the fuse/e-match.

Adding the fuse (homemade black powder fuse) and the e-match would have pressed it somewhat, but I am not sure if it is 1kg or not. I really did not want to press the stuff beyond mild tamping, and even then, VERY gently.
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[*] posted on 16-6-2024 at 08:33


If most of the ETN agglomerates are 1x1 to 2x2 mm, a pressure of between 0.5 - 2 Kg can be applied to this primary component (0.15 +0.15 g). There will still be enough air (gaps) left for a quick burn. At using inner diameter of 6 - 8 mm.......:cool:



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[*] posted on 16-6-2024 at 14:19


Quote: Originally posted by Laboratory of Liptakov  
If most of the ETN agglomerates are 1x1 to 2x2 mm, a pressure of between 0.5 - 2 Kg can be applied to this primary component (0.15 +0.15 g). There will still be enough air (gaps) left for a quick burn. At using inner diameter of 6 - 8 mm.......:cool:


I applied perhaps a little less pressure than that. But I am very confident that the mixture is quite homogenous. I pressed them into each other and folded them a few times. I could not see any whiteness of the ETN in the mixture, so I am confident that it is properly mixed and did not unmix when I tapped the side of the cap to get them to gently settle. For several caps, that is all I did, little to no pressure applied.
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[*] posted on 3-7-2024 at 14:52


(ugh! My post didn't make it for some reason. I think it is the attachments. This is my third attempt. I am writing it on word in order to not have it lost again!)

OK, so I went out to test out my blasting caps. I made 9 total caps for testing, 6 steel caps, 2 plastic caps, and 1 7mm remington magnum shell with the neck removed (should have kept it in retrospect). All but the 7mm shell had 1g of ETN + 0.3g of ETN/NHN mix (melt-cast and ground ETN). The ETN/NHN was only very lightly tamped and not pressed. The 7mm shell had 4g of ETN + 0.6g of ETN/NHN mix.

3 of the steel caps and 1 of the plastic caps had solid cast ETN in them, this was done via pressing the powder ETN and then placing the cap inside hotwater to melt the ETN before it was carefully removed and allowed to cool down for 30 minutes at least. These caps had inconsistent performace that convince me that making solid-cast ETN to explode is a lot more difficult than I thought. The plastic cap did no damage to the witness plate but it did fully explode. It was the loudest plastic cap I ever detonated.

Another 3 steel caps and 1 plastic cap had melt-cast and ground ETN pressed in them and they performed much, much better. I am convinced that this is the best material to use for blasting caps. The plastic one, however loud it was, didn't even fully detonate all the ETN! I actually had to tip out the ETN from the cap, which I found very strange.

The 7mm remington magnum shell... holy hell. That was intense. I didn't even all the pieces of my witness plate, it was blown to bits. I wonder if this cap would be sufficient to detonate ammonium picrate?

I think I am mostly done testing out caps. I know that LL will tell me that I need to remove the bottoms of the caps and... I agree. I should be doing that and using a little aluminum foil to stop the stuff from coming out and to hold it in place. Real detonators do have a very thin bottom (sometimes as thin as 0.03mm). I think that without much need for testing them they will be superior what I have now.

Plastic-caps - Copy.jpg - 2.4MB7mmbigcap - Copy.jpg - 2.5MB
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[*] posted on 3-7-2024 at 15:02


The rest of the pics

Melt-cast-steel - Copy.jpg - 2.1MBSoild-cast steel - Copy.jpg - 1.9MBSolid-cast-steel2 - Copy.jpg - 2MB
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[*] posted on 3-7-2024 at 22:17


Your research confirms my long-held suspicions. That ETNs can be "overprinted". In my experiments, if the ETN was pressed in the vise to the highest possible density (estimated at 50 Kg) there was occasional incomplete detonation or even failure. ETN at high densities creates an insensitive block of matter. For this reason, it is better to press only at 10 Kg. For the output segment.

You described 9 attempt, but on photos are 12 damaged plates. It seem weird.....:cool:




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[*] posted on 4-7-2024 at 02:43


Quote: Originally posted by Laboratory of Liptakov  
Your research confirms my long-held suspicions. That ETNs can be "overprinted". In my experiments, if the ETN was pressed in the vise to the highest possible density (estimated at 50 Kg) there was occasional incomplete detonation or even failure. ETN at high densities creates an insensitive block of matter. For this reason, it is better to press only at 10 Kg. For the output segment.

You described 9 attempt, but on photos are 12 damaged plates. It seem weird.....:cool:


The technical term is 'dead pressed', and perhaps you are right. Perhaps the solid-casting is what is causing that dead pressing issue without actually pressing it since it is at the highest possible density.

I don't use a vise, I always hand press, I tried to use a vise but it was always not good. So what I will do going forward is to give a solid press, but not too hard.

Also I showed some of the plates on the reverse. The solid-cast ones. That's why it looks like there are twelve. :)
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[*] posted on 4-7-2024 at 03:37


I've been telling you for at least a year: Forget casting......:D



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[*] posted on 4-7-2024 at 13:46


Quote: Originally posted by Laboratory of Liptakov  
I've been telling you for at least a year: Forget casting......:D


OK! I promise, I will never solid-cast any ETN in the container. :) The ones that were melt-cast and ground back up into powder, however, were excellent.

Now I think most experimentation is done. You believe that I pressed too hard on the ETN on the melt-cast and ground up ETN? If that is the case, then I can simply press much softer the next time. I will need to find a better way to file the bottom of the caps. I know steel will work because you use steel caps. The brass cartridges might be better since the metal is much softer already.
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[*] posted on 12-8-2024 at 16:23


First set of photos.

20240811_213716 - Copy.jpg - 861kB20240811_213723 - Copy.jpg - 937kB20240811_214054 - Copy.jpg - 946kB20240811_214101 - Copy.jpg - 784kB20240811_214315 - Copy.jpg - 950kB20240811_214327 - Copy.jpg - 907kB20240811_214706 - Copy.jpg - 986kB20240811_214715 - Copy.jpg - 811kB
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[*] posted on 12-8-2024 at 16:54


OK, so I wrote a much longer summary previously, but I will try to keep this one short.

I made a total of 13 caps. 4 steel and 9 brass shells. The 'pressed' is decently, but more lightly, pressed melt-cast ETN into the cases, while the 'toppers' were similar but had a little bit of lightly tamped ETN on the top. I think ultimately they were identical. I will let you, LL, if you read this, to decide if these steel cased one in this instance that blew a much nicer hole than last time (which blew more of the steel plate apart, which you said was not good).

I learned a valuable lesson with brass casings. The Improvised Munitions Handbook advised to remove the primer and drill a bigger flash hole in the bottom to allow the fuse to fit through (and in my case an e-match as well). I didn't know why this was the case, but I was told that the bottoms of brass shell casings are very thick and very hard... and I had no idea just how true that was! The results show. There are no holes, because the bottom simply did not allow the explosion to go downwards enough.

So going forward I will make some more detonators made from 5.56x45mm/.223 shell casings but I will have the explosive train start from the bottom to the top.

Now this is the big one: You mentioned bottomless casings, or cavities as you like to cal them. You did put some aluminum foil pressed into the bottom of yours (and I still can't figure how you got them not to slip out... despite mildly crimping and pressing). But would simply applying tape to the other end of the case be sufficient? Will it explode all the way through and make very nice hole in the steel or will it be a problem? I suppose I could crimp it, but that would reduce the case's overall capacity and I wouldn't like that.

What about making a very small dab of baking soda/cotton with super glue? Too hard (they can be really tough), or just adding some aluminum foil to the tape. I am very curious as I think I will finally end my journey to making a super powerful detonator! :D

20240811_214926 - Copy.jpg - 952kB 20240811_214931 - Copy.jpg - 860kB 20240811_215037 - Copy.jpg - 1.2MB

[Edited on 13-8-2024 by ManyInterests]
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[*] posted on 12-8-2024 at 21:10


LL’s method is really simple. Small rolled up ball of foil maybe pea size at most, steal plate and a steel rod . Using a hammer , put the ball in the tube , use hammer to smash it flat in the tube a few good hits. Almost makes a commercial appearance of a cap. Holds very well . Can use super glue to waterproof the exterior if you feel inclined
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[*] posted on 12-8-2024 at 21:58


Exactly......pjig...... explained all about aluminium cap. Interesting results. But I never seen no one tube before test or entire assemble before test. Is diffult introduce it, how to looks entire assemle.....:cool:



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[*] posted on 12-8-2024 at 22:32


You can clearly see the imprint of the back of the casing on those images.
As you have learned you need the output portion of your detonator to be encased in the weakest part of the casing, or at least no stronger than the rest of the casing.
For the end of your detonator you really only want just enough material that the contents are protected sufficiently dependant on your use.
If you are using steel tube as your casing and you want to make an aluminium end cap try to first rough up the inside of the end of the tube with a file or sand paper, then crimp the end a little if possible. Then add a small amount of aluminium foil and press it hard with a rod just small enough to fit down the tube and it will stay in place no trouble at all.
If the detonator does not need to be waterproof and will be protected from damage then you can just use some tape to close the end.
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[*] posted on 13-8-2024 at 00:21


Quote:

You can clearly see the imprint of the back of the casing on those images.


Yep, that gave me the hint that the primer end of the brass case is HARD. I used a small vise to hold them in place for drilling and primer removal and I feared I would deform my case if I held it too tight... but no, I tightened that vise as hard as I could and it made no discernible mark.

I did also cut the end off one of the 100mm steel tubes that I have and I did rough it up with a file and yes! I finally got the pea sized aluminum foil to hold up, with even a solid smack not pushing it out. I put some electrical tape on the end anyway for waterproofing. I will do the same to my 50mm tubes. I hope that I will still be able to load the shorter caps with the same load I normally do after cutting them (1g ETN and 0.3g primary mixture).

In all honesty, after all this I feel a little foolish. I felt like the whole solution was right under my nose the whole time. But i am sure now that I have finally figured it all out when I could have done it a little earlier. Maybe I was just subconsciously enjoying the journey. :p

[Edited on 13-8-2024 by ManyInterests]
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[*] posted on 13-8-2024 at 02:27


https://www.youtube.com/watch?v=1tL42YGfLcE
In 1:04 you can see reduction procedure hole from 6.35 on 5.8 for insert aluminium ball and finally creating output alu bottom....:cool:




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[*] posted on 13-8-2024 at 03:41


I remembered your video and did it. I will need to learn to cut off only the absolute tip of the tube since the hole will be tapering anyway. Plus I want more room for the energetic. 5 or 7mm less on a 50mm tube is significant.

Also I assume that less is more with aluminum? Because I think I might have added a chunk too big and reduced the amount even more.

I will make tests with steel and brass as last time but both minimal aluminum bottoms and taped bottoms. The tape is for keeping the energetic material in, that's why I really want it.
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[*] posted on 13-8-2024 at 04:17


Better than cutting maybe will using coarse emery cloth or a grinding wheel for clamping in a drill. And for a finer adjustment, a scythe sharpener will be suitable....:cool:



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[*] posted on 13-8-2024 at 06:27


I tried to drill my caps against emery cloth and files, that didn't do much. I did order a nice grinding attachment for my drill that I haven't used yet. But maybe it'll work? I just don't know when the end will be filed sufficiently.

Also one other thing is I ordered from aliexpress a 500mm aluminum tube with an OD of 8mm and ID of 7mm, meaning it should be perfect for cutting detonators of the length I would like (60 to 70mm) and I can close off the ends with small bits of foil or just tape the ends as you suggest.

Edit: might as well tape a few layers of foil at the absolute bottom instead of hammering it in. That could work.

[Edited on 13-8-2024 by ManyInterests]
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[*] posted on 13-8-2024 at 14:41


Quote: Originally posted by ManyInterests  
I tried to drill my caps against emery cloth and files, that didn't do much. I did order a nice grinding attachment for my drill that I haven't used yet. But maybe it'll work? I just don't know when the end will be filed sufficiently.

Also one other thing is I ordered from aliexpress a 500mm aluminum tube with an OD of 8mm and ID of 7mm, meaning it should be perfect for cutting detonators of the length I would like (60 to 70mm) and I can close off the ends with small bits of foil or just tape the ends as you suggest.

Edit: might as well tape a few layers of foil at the absolute bottom instead of hammering it in. That could work.

[Edited on 13-8-2024 by ManyInterests]


If you haven't already, get yourself something like this. They are generally pretty reasonably priced. If you keep them tight as you cut they also crimp then end a little, just enough to be able to get the foil cap to stay in place. With your end cap try for less than 0.5 mm of thickness, but with enough strength to do what it needs to. Once you have the right amount push it back out and weight the foil, that way you know exactly how much to use each time. If you are going to be using those aluminium tubes going forward get yourself a 6.5 mm diameter piece of tool steel rod to use with a hammer to get the end cap set and with a press to compact your EM. Once you have a system in place where you can make consistent housings then you can do some really nice comparisons of different types or combinations of EM at a variety of densities. Well done on the tests so far, what was the mass of EM in each of your test caps?

Edit - Typo and after thought

[Edited on 13-8-2024 by B(a)P]
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