Unconventional Shaped Charges

Iäm planning on testing 2 charges of 7g capacity each on a 60mm thick solid steel block with 20mm standoff built into the device.

Charge I : with just the cone stud liner and 7g propellant pressed behind it.

Charge II: with the cone waveshaper placed in an inverted position behind the liner (forming a X geometry if viewed from side) and 7g propellant pressed all around the configuration.

Loading the cases:




I actually planned on 3 charges with 5g capacity (control, x configuration and shallow cone configuration), but 5g of propellant would not cover the x configuration. Hence I had to increace the loads to 7g and drop one of the configurations (the shallow cone one). The woes of rationed propellant amounts....

[Edited on 20-3-2015 by markx]

Markx, I though you would probably try penetrating a 1" plate or so, but it looks like you are really going for it.

Looks like you have a good technique for getting the cone well centered and aligned with the casing. I think improper centering and alignment has been by far my biggest problem in the past. The last test I did the cone was brought right out flush with the bottom edge of the casing so it was very easy to center (visually) and align by simply pressing the casing against a flat surface (assuming the casing end is cut perpendicular to the casing sidewall). Your method makes a more secure charge however. I bet I could just add a threaded, or other form of attachment (adhesive?), end ring to the charge casing with lip which could be installed after the liner was properly centered and aligned with the casing; the end ring would ensure that the cone stayed in position even if the charge was roughly handled.

Well....that was not really what can be called a success, although comparative effects are quite obvious...

"Charge II" with the waveshaper at 2,4CD standoff (30mm):



The crater closer to the edge is the one with the waveshaper, the one further from the block edge is the control without any waveshaper in the design. Both were 7g capacity and at the same 2,4CD standoff. Both performed very unsatisfactory in terms of penetration depth.



Cut open the "charge II" channel and measured the depth...only a meager 17mm:



I did not grind open the "charge I" crater but mesured the depth with a thin wire and it was more or less the same 15-17mm....

I've had 15mm with exactly half the charge capacity under similar conditions and clean entry channels at 40mm standoff.
Bad cones? they were from the same batch that I've used for all of my experiments so far. Unfortunate misalignment of both cones? Very possible scenario. Tougher steel target? Perhaps, although it seemed pretty mild when touched with a file. Lower detonation speed due to using castor oil insted of methyl riccinoleate as plasticiser? Possible, but not very likely...
The charges portrayed here were pressed under arbor style press, all the others before I've compacted by hand.
I'm at a bit of a loss here to be honest...

Ok...all that aside, when we look at the entry points it is pretty much clear that the waveshaper design has much better focus in terms of jet formation. It shows a lot of promise if the kinks are worked out The control charge on the other hand is utterly out of focus and the whole crater is a total mess...this is THE most unsuccesful shot of my entire SC career

Quote: Originally posted by Gargamel

markx, what kind of liner do use with these forms and how does the forming process work?

By forming process do you mean the forming of the liners? They are prefabricated "UK77 cone studs" off the ebay (for the "punk metal" crowd I presume )
They are composed of a soft ferric alloy that is magnetic and surface treated to give a brass like look...

Quote: Originally posted by Fulmen

Shaped charges are quite delicate, and logic suggests that small devices should be most sensitive. It's part of the reason I've stopped experimenting, every study ends with the question of what accuracy one should strive for and how to accomplish this. This combined with the greed of wanting the best performance I can possibly prevents me from getting anything real done. There is also the question of statistics, without a model based on quantifiable data one test can only tell you so much. I know I'm overly fuzzy about this, but that's the way it is. But I also feel the engineering part of me looking for a fun challenge, and revisiting the drawing experiments does have it's appeal. I now have a heat treating furnace, and I have always loved making permanent tooling.

True that...SC-s are a finnicky business, but they fascinate me, nevermind the complications. I guess everyone sometimes picks a topic that may engulf our mind in intricate and seeminlgy hopeless complications, but if our facination drives us to act then we do ever so often succeed...at least partly

About the size vs effect of imperfections on a device....i do not know if it is completely accurate to assume that smaller devices (within reasonable scope) are more prone to failures due to imperfections. I tend to think about it this way:
a) smaller devices are way harder to build precicely and without imperfections
b) but the timeframe of a small device from acutation to completion is also shorter. Hence the forces at play have less time to pronounciate the effects of these imperfections.

From that reasoning I would assume that the most troublesome combination would be a device of mediocre scale that meets the worst of both worlds....it is still hard to eliminate the imperfections, yet the timeframe is long enough to pronounciate the effects of these errors. Perhaps my reasoning is not correct...but the devices that I have constructed have been way less than precise. Hand cut and assembled , sometimes visually crooked, yet have performed very reasonably and ever so often even exceeded all my expectations. The first SC that I slapped together was an abomination in terms of precision and I thought to myself "F*** me if that thing is going to work in any way!" but after seeing the jet crater gaping through an 8mm steel plate I was in awe..."what the heck happened and can this be replicated???"

Quote: Originally posted by Fulmen

Ideally time shouldn't factor in at all. The principal problem as I see it is the limitations in accuracy both during manufacture and assembly. And not only dimensionally (as in shape, thickness or angle of liner) but also variations in density in the explosive or liner, grain structure and even accumulated stresses within the liner. At some level everything factors in. But understanding exactly how these factors scale in respect to each others isn't something learned over the weekend.

And there are at least 25 more factors besides all of the ones that we can conceive and identify in our minds
And it just drives me to explore them, despite having embraced my inability to ever fully understand the "Great design". I mean even the modest "tree body problem" has eluded the scopes of our mighty art for decribing the physical reality with anlytical precicion...the one called mathematics

Quote: Originally posted by markx

Well....that was not really what can be called a success, although comparative effects are quite obvious...

Hi

At first, nice post and all

But...making a 7g HE-SC with a waveshaper doesnt seem to be a good idea for me cause of the critical diametre...even with easy to ignite material it is very hard to make it perfectly work as far as i know/guess

I wouldnt go for waveshapers at a CD under 4cm...

Quote: Originally posted by VladimirLem

Quote: Originally posted by markx   Well....that was not really what can be called a success, although comparative effects are quite obvious... Hi At first, nice post and all But...making a 7g HE-SC with a waveshaper doesnt seem to be a good idea for me cause of the critical diametre...even with easy to ignite material it is very hard to make it perfectly work as far as i know/guess I wouldnt go for waveshapers at a CD under 4cm...

Most of the enterprises that we undertake on this section of the board are several subway stops away from being a "good idea"
But they are just too much fun to make us stop....and I guess being able to find joy in the things we do is the most important aspect

Holy explosive

I feel very spiritual right now, and have even more love for these beautiful explosives.


[Edited on 21-3-2015 by Hennig Brand]

Quote: Originally posted by Laboratory of Liptakov

Beauty is in explosives. Just as in the equation E = m.c2. As in the Sun. This is our most powerful explosive. He works for billions of years. Gives energy, gives life. The blast created life. Our bodies come from supernova. From the most powerful explosions in the Universe. Whole Earth comes from the supernova. The whole universe comes from the Big Bang. Even time and space comes from the explosion. Absolutely everything comes from the explosion. Examination of explosives is the way to God's creation. God is greatest pyrotechnics expert of all time. He could detonate time and space. And we are his disciples. Says the holy Isaiah to his disciples, and everyone watching the stars. [Edited on 21-3-2015 by Laboratory of Liptakov]

Every now and then, a real gem of a statement comes along, well said

5g of ETN Putty Explosive and 1/2" Steel Liner Pierce 28.6mm of Steel Plate

Just performed a very successful test with one of these little 1/2" steel cones. The picture below shows 4g of plastique but with additional casing room left another gram was added for a total of 5g. The plastic explosive used was from the same batch as was used in the last test (80% ETN). The target was one 3/4" plate and one 3/8" plate, one stacked on top of the other. Standoff used was 2.5CD. The liner was not secured but simply held in place once again by the adhesive forces between it and the plastic explosive.

The jet did completely penetrate both pieces of steel, but just barely. A little flap of steel was still left attached on the bottom piece of steel though a hole was blown clean through on one side of it. The hole was so small by the bottom of the last piece that the diameter was even smaller than a pin. The carrot was once again driven into the top plate plugging the entry hole. The tops of the plates are shown in the first picture and the bottoms in the second. Another picture shows the bottom of the bottom plate where it can be seen that the jet escaped but left a little flap of steel still attached.

Explosive: 5g of 80% ETN Plastique
Penetration: 1.125 inches or ca. 2.86cm (28.6mm)




[Edited on 21-3-2015 by Hennig Brand]

Well, liner diameter 12,5 mm trough 3 cm steel and 5g brisant only, this is good result. A good disciple of God, I think.......Isaiah says of the mountain Liptakov

Thanks, I think this is the first time I have been called a disciple before. Makes me feel important.
I think that thick carrot slamming into the top of the target may be at least partly because the cone wasn't anchored, but I have only done two tests with an unanchored cone so I am not completely sure. It is interesting that even at a 2.5CD standoff the result was about the same as with 1.5CD standoff with regards to the large carrot being fused to the top of the steel target and plugging the entry hole.

The scene with the carrot is really interesting...I've had similar, but not quite that epic appearances. And these happened with really small charges below 3g capacity with the carrot mostly splattered into the target like an efp, yet the jet itself passed on strong. Over 5g charges have always managed to disintegrate the liner or fuse it to such a degree that it is no longer distinguishable from the target. I did manage to catch one tough, on the 15mm target test. It was a really well formed specimen that I preserved with great care...a literal carrot and it stuck by a thread on the exiting verge of the crater. I could remove it from the target with just my bare fingers


For entertainment...a peculiar failure from one of my very fist attempts on SC with a ETN based plastique:





Incomplete initiation....but it left a really cool mark on the steel

[Edited on 22-3-2015 by markx]

High explosive stamping? No ink required.
That is interesting to look at. Gave the steel plate a good slap anyway.

Do you have an idea why it didn't shoot properly? What percentage ETN was it?


[Edited on 23-3-2015 by Hennig Brand]

Quote: Originally posted by Hennig Brand

High explosive stamping? No ink required. That is interesting to look at. Gave the steel plate a good slap anyway. Do you have an idea why it didn't shoot properly? What percentage ETN was it? [Edited on 23-3-2015 by Hennig Brand]

I really overdid it with the inerts that time. I was trying to get a very good plasticity of the explosive (30-35% inerts if I remember correctly). It was excellently pliable, just like modelling clay or placticine....didn't shoot too good though

hole

Well, finally! Nice hole. When he wants, so it goes. This second attempt is much better. Through the hole is. And that's the main thing......LL

You know, I remember having a similar experience several years ago. I wasn't doing anything sophisticated like building a shaped charge, I was just going out to "communicate" with the people on the other side of the river setting of commercial fireworks (aerial shells). I remember taking 15-20g of ETN plastique with Pib not polybutene, IIRC, and adding aluminum powder for a more vicious air blast and flash. Now, if you are into a good explosion aluminized explosives are awesome. It is really impressive how even 5% of fine flake aluminum powder can often greatly increase the perceived violence of a detonation. A dynamite with 40% NG, 10-15% fine flake aluminum and the balance inorganic nitrate makes a scary air blast. Anyway, to make a long story short, the charge ended up being only about 65-70 percent ETN and with all the extra material added it failed to detonate using a detonator that would have easily ensured detonation with 20% inerts & 80% ETN.

LL, I hope this isn't how you have been making the holes in your steel targets all along.


[Edited on 25-3-2015 by Hennig Brand]

But of course. I never make a gram of explosives. It's all photomontage. Manufacture explosives is prohibited. Produce virtual reality is permitted without restriction. Whenever I can prove it........LL

Maybe too digression from the topic. However, loud noise, bumps, that's the main problem. Therefore, all tests are under a pile of sand. It is best to charge 5 -100 g.
Directional, SC, EFP. However, I found a great problem of use sand pile. I do not feel the detonation wave on the body. I no hear a sharp bang. I say, I believe it is only half the experience. If it is "on air", for example 50-100 g, VoD 6500 and more, it's a different story. At a distance of 15 meters, it is an amazing experience. Echo lasts 10 seconds. It's like a bolt of lightning. Finally, no worries, God started it first, so what. The last attempt "on air" NM mix 70 g gel. Distance 10m, cover. As if opening 5 dimensions. In short, amazing, beauty. Exactly, in detonation must be beauty......LL

Why so much binder?

But of course, I use for SC and EFP only 4% plasticiser. And pressing hydraulic. 96% TACP + 2% PIB + 2% 5W40 oil.
This is a sufficient quantity of plasticiser for the enclosure. Power explosives determines explosive content. If is the plasticizer passive (PIB + oil) is a good idea to add a little. For active plasticizer (NG + NC, and more) is different, depending on many variables. I charge for stamping adding as little as possible......LL

I found a picture of the mini commercial EBW initiated SC and EFP that diagrams were posted of here:

http://www.sciencemadness.org/talk/viewthread.php?tid=10575&...





And another picture of them with other assorted commercial items from RISI:




[Edited on 20-4-2015 by Hennig Brand]

Very cool....the aluminium (supposedly) confinement seems pretty heavy. I guess it helps the jet formation quite considerably. Still not a setup that I would be comfortable testing in open field...tempting though

Just finished my "milling machine" to be able to make dove tail ways for a mini lathe that I'm building:




Once the lathe is functional it really becomes tempting to try such a SC configuration. Damned mechanical inclination.....

Quote: Originally posted by Hennig Brand

I think the heavy confinement improves performance a lot, at least with tiny charges such as those. Nice looking equipment you have there.

Yeah, trying to hand lap the box ways of the cross slide is a pain, but it turned out quite good. Even the axis orientation happened to be rather exactly at 90 degrees.

With a little bit of patience one can mill intricate contraptions of quite good precicion:

Just wanted to report a final success with small size EFP after a couple of failures.
Instead of a coin, a piece of copper pipe was cut, annealed and flattened out to a small sheet. It was then annealed again and shaped with a ball hammer into a almost perfect 30mm diameter hemisphere of 1mm thickness.
The liner was placed on the end of a cardboard tube, taped in place, and the tube hand packed with 30 grams PETN.
It was placed at a standoff of 120cm and sighted with a laser pointer and the target was a 1/4 inch thick steel/iron beam.
It penetrated fairly well but as can be seen in the photo on the right of the hole, there is a piece of liner embedded right there from another attempt which the liner broke up a little before hitting the plate and some ended up there as I have been using the same target. It looks like a small part of today's liner didn't make it all the way through, I wonder if that is the cause.
The resulting hole is 1.1cm wide by 2cm tall and the slug was caught in the tree behind the target.
Initial liner weight was 5.70 grams.
Final slug weight is 5.01 grams.

Pictures are rotated 90 degrees left and I don't know how to reset them straight.

[Edited on 28-5-2015 by greenlight]



[Edited on 28-5-2015 by greenlight]

[Edited on 28-5-2015 by greenlight]

Nice test! The laser pointer is a good idea. I rotated and resized the images for you. I am not sure that they are exactly the size you wanted though. A picture of the target thickness, with scale, and maybe one of the liner would have been nice too. Too late for the liner shot I guess now though.
I also had a test that splattered the target with copper blotches from a fairly crude liner made from copper pipe. Not saying your liner was crude, but mine definitely was. It was not very symmetrical and had some pretty heavy corrosion roughness on one side.





[Edited on 28-5-2015 by Hennig Brand]

Thankyou for resizing the images I have no idea how to do it
I have uploaded a picture of target thickness with measurement, it is 7mm so turns out a little thicker than 1/4 inch.

I use the laser pointer now because I used to line them up by eye and as you can see in the picture there is a chunk taken out of the top of the plate from another test where it hit the very edge because I wasn't quite accurate in sighting it.

You are probably right about the liner breaking up more because of it not being 100% symmetrical. I think another cause could be that too much explosive is used and over drives the liner so it breaks up, because the splatter was observed when trying 37 grams as the charge.
I think I used a little under what I could have with the latest one, I think an extra 2 grams or so could have pushed a cleaner hole yesterday without breaking up too much.

[Edited on 29-5-2015 by greenlight]

I have not had any success finding any metal formers on the internet useful for SC liners apart from theses dapping blocks and I don't have the equipment to make my own.
I think it might be worth giving them a try as most go up to about 50mm diameter impressions. The steel or brass blocks are expensive but the wooden formers are pretty cheap. There is even a 6 inch diameter hemisphere former on there which would be interesting.

http://www.ebay.com.au/itm/Wooden-Dapping-Doming-Bending-Blo...

http://www.ebay.com.au/itm/2-BRASS-DAPPING-BLOCK-PUNCH-DOMIN...

I think I will try one and see how they go.

Copper is actually much harder to work than you might think. I would judge you should have steel tools to work with it. Then again, all of the copper I have worked with was never annealed right before working and it was probably work hardened to a fair extent before I got my hands on it.

Bert suggested buying some of these tools earlier in this thread here:
http://www.sciencemadness.org/talk/viewthread.php?tid=10575&...

LL also made a block and punch which he posted about around the same time.

I am getting one of these which should be quite durable if only used for shaping copper:
http://www.amazon.com/SE-JT3403DS-Polished-Stainless-Cavitie...




Dimensions (inch): 2 x 2 x 2
• Cavity sizes (mm): 4, 5, 6, 7, 8, 9, 10 ,11, 12, 13, 14, 16, 18, 20, 25, 30 , 35, 40
• Polished stainless steel


I have access to some steel ball bearings in an assortment of sizes which I can probably use to fashion whatever punches I need. Even if starting with a bolt or round stock the punches are the easy thing to make in my experience.


[Edited on 29-5-2015 by Hennig Brand]

EFP - Copper Blank Annealing followed by Shaping using Dapping Block and Punch

Got the dapping block a few days ago. A friend welded pieces of 10" steel spikes to two steel ball bearings which are the start of my punch collection. It works extremely well and of course now that I have thought about it a little more, and examined the block and punch, the blank does not need to be centered in the block at all nor centered on the punch, since the radius/curvature is always the same anywhere on the punch or in the block. Works beautifully!

Have started annealing the copper blanks too in between working them. Even a propane plumbers torch can easily heat copper up to red hot when the blanks are this small (ca. 1" diameter, 1.2mm thick).

An EFP was made using one of the copper blanks. Depth of the curve was ca. 3mm and the diameter after bending was 24mm. Liner mass was about 4.5g. ETN putty explosive was used (14.5g, 80% ETN). Standoff was about 42" and the target was 3/8" steel plate. The target was not penetrated but a piece was blown out from the back of the plate and there are visible cracks which go through the plate. Complete penetration was very close. As can be seen from the size of the entry hole the slug was very blunt, which is one of the reasons for the mediocre penetration. A higher velocity explosive may have made a big difference too such as a pure nitric ester. Certainly a more deeply curved dish should increase slug elongation as well, though I have had problems with slug breakup when using curvature close to the upper limit and consequently even less penetration than with a shallow dish. A stronger casing should help, how much I don't know yet.


Note: In the images the piece of paper says r = 3mm, it is actually depth = 3mm (liner specifications).




[Edited on 17-6-2015 by Hennig Brand]

Had a first test with the dapping block today using a 1mm thick copper liner with a curve indent of 5mm.
The same 30 gram PETN charge was pressed behind the liner with a wooden dowel in a thick-walled cardboard tube. Standoff was 120 cm from 1/4 inch steel plate and the EFP lined up with a laser pointer again.
After intitiation, it was found that the intended effect on the target had not been achieved. Unlike the last time with charge of same specs, there was not a full penetration. It was so close as can be seen in the picture there is a crack running halfway round the other side of the plate where the slug hit as the chunk of steel has nearly been removed by the impact. I think this failure was due to the fact that it was getting dark which made it harder to set up lining up was rushed a bit so the EFP wasn't 100% straight in line with the plate. The plate was slightly offset from the EFP line of fire and in the picture you can see the slug penetrated more on the side it came into contact with first. If the plate was in line I think it would have been a through and through. I think that hitting on a slight angle would also reduce power of the slug.

[Edited on 26-6-2015 by greenlight]

Another test was conducted with an EFP using a copper liner formed with a dapping block:

The liner was a 1mm thick 30 mm diameter copper disc with a curve indent of 5mm like the last test.
This time casing with a higher pressure rating was chosen which was a 30 mm PVC pipe instead of cardboard tube. The charge was 33 grams of PETN which was loaded with a vice press to achieve a higher density.
Target was the usual slightly over 1/4 inch thick steel plate and the standoff was 120cm sighted with a laser pointer.

This time a full penetration was observed and only a small amount of liner breakup as can be seen on the top right of the entry hole.

The initial liner weight was 5.70 grams and final slug which was recovered from tree behind target weighed 4.85 grams.



[Edited on 1-7-2015 by greenlight]



[Edited on 1-7-2015 by greenlight]

That is an interesting video. One of the things I noticed most was how weak the casing was, it was only fairly thin plastic.

I took a snapshot from the video and took a few measurements on my computer screen, then used known quantities to determine the approximate actual dimensions.

From computer screen:

Liner thickness ~ 1mm
Casing inside diameter ~ 37mm
Casing length (holding charge) ~ 38mm
Given charge mass = 30g
Assume C4 explosive, so density = 1.57g/cc
Given steel target thickness = 10mm

V = pi/4 * D^2 * L

L ~= D so let L = D

V = pi/4 * D^3 also V = 30g / 1.57g/cc = 19.11cc
so actual D ~ 29mm

Liner actual thickness ca. 29mm / 38mm * 1mm = 0.76mm

Liner thickness is 0.76mm / 38mm * 100% = 2% of liner diameter

Penetration = 10mm or 10mm / 29mm = 0.34D


Making accurate measurements from the computer screen was difficult, but even if the inaccuracies resulted in a 50% increase in actual liner thickness relative to actual liner diameter that would still only bring the liner thickness to 3% of liner diameter. Also, I have never handled C4, but from the descriptions I have read the plastic explosive in the video seemed almost too soft and mouldable for C4.

Notice how he states in the video that the charge was effective anywhere up to 60 disc diameters from the target. I would have thought that they would be effective, though maybe not as effective, at much greater distances.

Interesting video, I would like to try a 2 or 3% of diameter liner thickness for my next test using a plastic casing.






[Edited on 3-7-2015 by Hennig Brand]

Quote: Originally posted by greenlight

I have seen that video before and alway wondered what his standoff was because he never says, I don't know how you worked that out but well done. This ideo is what gave me the idea to use 30 gram HE for the charge. Does anyone know if the empty section of plastic tube he has in front of the copper liner does anything to enhance slug formation or accuracy. It looks almost like his EFP had a small barrel.

efp

Packaging has almost no influence on the formation liner. It is important to observe the depth charges. Depth greater than 1x average results in tearing the liner. Less than 0.7 reduces the average power EFP. Very important is the accuracy and the same density EM. With a diameter of 30 mm does not affect either 2 mm steel for packaging. 5 mm yes. Plastic and paper packaging has no effect. Production accuracy. That's the main thing. This examples, liner thick 1mm. Liptakov

I found a length of 25 mm alloy rod I had forgotten in my shed so I copied the risi rp4 ebw ssf casing today used my standard ebw head but I think I might change it to have a initiator like the original so I can use plasticised etn as the main charge, its almost to good to destroy . cheers nuxy.

[Edited on 3-7-2015 by nux vomica]

Its not part of my trade, one of my old jobs the forman there was a toolmaker by trade but he was a lazy Austrian shit and I ended up learning how to use a lathe and mill so I could get my jobs done, I suppose I should thank him now

I ran out of plastic explosive a few days ago and made some more. For the last while I have been using 80/10/10, ETN/ polybutene/mineral oil, but this composition is quite oily, falls apart fairly easily and is 20% inert material. I decided to try with only polybutene and ETN, 87% ETN and 13% polybutene was used. The polybutene was smeared out in a thin layer over a previously warmed glass cutting board and then the fine crystalline ETN was worked in with a glass rolling pin. The composition was repeatedly gathered up with a rubber spatula and rolled out until it was well incorporated and dense (this was easier when oil was used). This composition holds together well, much better than the previous composition, is not oily or excessively sticky and contains only 13% inert material. I compared it to "Play-Doh" brand children's modelling compound and it is much stiffer, but still fairly easy to mould. It could be softened by adding a bit of mineral or silicon oil if desired.

Attached is an image of about 79g of the composition (what I have left after doing a little testing).





[Edited on 3-7-2015 by Hennig Brand]

dimethicone

EFP Powered by 87% ETN Putty Explosive Initiated by EBW, ETN, Detonator - Success

After watching the video where an EFP was tested with only a thin plastic casing and what was estimated to be a liner thickness of only 2-3% of its diameter I decided to try reducing the thickness of my liners. A piece of 3/4" grade L copper plumbing pipe is almost exactly the right thickness (0.03" or 0.76mm) to give a liner thickness of 3% of the diameter used (24mm). The test worked beautifully, even at a standoff of only 16" the slug narrowed and elongated and easily penetrated the 3/8" steel target. I should try a 1/2" target next.

The charge was 12.2g of 87% ETN / 13% PB. The casing was a thin polypropylene disposable pill bottle. The cap holder was made from the pill bottle top liner/seal. The cap used was an exploding bridgewire type, with copper bridgewire, one of three which were made about a month ago. Details of how I have been constructing them are in the thread, "Has anyone made a EBW Setup". The only explosive in the caps is ETN. The 0.5uF capacitor bank was charged to about 3800V before firing. The firing line used was 50ft of RG-6 coaxial cable and another 5ft or so of 18 gauge speaker wire added to the ends as sacrificial cable.

The liner was made from a piece of 3/4", L grade copper plumbing pipe as already mentioned. A short piece of the pipe was cut lengthwise with a hack saw and pried and hammered flat into a sheet. A blank was cut out with a homemade cutter and hydraulic press and then annealed and shaped into a dish with a dapping block and ball bearing punch. The thickness of the liner was about 0.03" or about 0.76mm or about 3% of the liners diameter. The depth of curvature of the dish was about 4mm or about 16.7% of its diameter.

Reducing the thickness of the liner from 5% to 3% of its diameter made all the difference, at least with this setup with a very weak, thin plastic, casing. I am fairly sure 1/2" of steel could have easily been penetrated which would be about 0.5D, as it is 3/8" of penetration is about 0.4D which is still respectable.




Polydimethylsiloxane is the most important member of the silicone oils. I have a couple of small bottles and I sometimes add a bit to PIB or PB bound plastic explosives as a plasticizer/softener, but most of the time I have just been using mineral oil and lately just pure PB without any added softener.


[Edited on 6-7-2015 by Hennig Brand]

Nice result Henning looks like all the pieces of the puzzle are coming together, I dont think that plate would take much more abuse looks a shotgun has blasted it

[Edited on 6-7-2015 by nux vomica]

Quote: Originally posted by markx

As an alternative to extracting PIB from selfvulcanizing tape (very expensive option) one can use rodent glues as a fair source of PIB too (cheap option). E.g: http://www.kollant.it/Rat-poison/Glues.aspx I just tried the Norat version and it works like a charm for plastisizing PETN. The glue is a fairly low polymerisation grade PIB that is a viscous liquid and can be used without the need for an additional plastisizer. With 15-20% content one ends up with a very decent plastique that only has 2 components.

plasticizer

A very interesting way of possibly making spherical ETN (PERFORM REMOTE though!!!) that I thought of:

What would happen if you would add recrystallized ETN to a beaker in water, add a stirrerbar and put it on a waterbath of about 80 deg C (just enough to melt the ETN while in water). After putting it in the waterbath you can leave the stirring go on remotely and slowly the ETN will start to melt. Due to the water surrounding and stirring, the ETN will likely form small spherical globules (stirring RPM and stirrer bar will determine size), that upon slowly cooling down of the waterbath may be retained as such. This operation wouldn't need any supervision and can be performed remotely. Maybe an emulsifier could help also. Anyway, just an idea worth trying...


Nice results btw Henning with the last EFP, clean entrance and good penetration! Regarding the after annealing of the liner: for conical shaped charges it has been shown that spun formed liners introduce spin to the jet due to retaining stresses when unannealed. For a shaped charge this would likely be detrimental, unless the SC is used in barrel fired HEAT rounds, where it can counterbalance barrel rotation. My guess would be that, unlike the delicate jet from an SC, an EFP might not be so sensitive to induced spin, maybe even enhancing long range accuray due to gyroscopic stability. Might be interesting to look at spun formed EFP liners. Other approaches for spin stabilized EFP's are introducing fins. I've seen some simple designs in patents that consist of a thick copper plate forming the main liner, with sort of a "cross" pattern of thin coppersheet soldered onto the plate before forming the liner. These thicker liner parts move more slowly compared to the main liner and will form protruding fins for stability.

Also would be really cool if something like a pile of wood, sawdust, rockwool or ballistic gel could be used to retrieve the EFP without to much deformation.

Regarding crystallization, it is difficult to get PETN to recrystallize into equidimensional crystal shapes easiliy, therefore I used to blender small amounts in water to abrass the crystalls into rounded shapes that can make very high density plastiques. I didn't like this process from a safety standpoint and was only performed with small amounts and remote operation. THIS IS NOT ADVISABLE WITH ETN THOUGH!!!!

Depending on whether you want high density, high critical diameter plastique or a lower density, low critical diameter plastique I would a different approach.

High density: Slow crystallization from ethanol (best solvent for crystallization IMO) by cooling in the freezer, than adding icecold water at one to precipitate the remaining ETN as a very fine crystal fraction to fill the voids in the plastique. Than add a liqour of binder+plasticizer in heptane/hexane and keep rolling and needing until fully dried. After prolonged rolling and kneeding to abrass the crystals, it will probably make a good plastique with about 10-12% inerts.

Low density, low critical diameter: Make a fully saturated solution of ETN in ethanol/methanol and slowly poor this into ice cold water with rapid stirring. This will form a very fine amorphous crystal fraction that needs 15-20% inerts, but can detonate in very thin sheets.

[Edited on 7-7-2015 by nitro-genes]

Quote: Originally posted by greenlight

I have heard that crystals that resemble fine sand are good for plasticizing. I think I will try your method but substitute the methanol for acetone. Do you bring the methanol to near boiling, dissolve as much as possible and cool on its own. Then when cool add enough water to precipitate the rest of product? Does this sound correct?

EFP Powered by 87% ETN Putty Explosive Initiated by EBW, ETN, Detonator - Success Again

Quote: Originally posted by Hennig Brand

The charge was 12.2g of 87% ETN / 13% PB. The casing was a thin polypropylene disposable pill bottle. The cap holder was made from the pill bottle top liner/seal. The cap used was an exploding bridgewire type, with copper bridgewire, one of three which were made about a month ago. Details of how I have been constructing them are in the thread, "Has anyone made a EBW Setup". The only explosive in the caps is ETN. The 0.5uF capacitor bank was charged to about 3800V before firing. The firing line used was 50ft of RG-6 coaxial cable and another 5ft or so of 18 gauge speaker wire added to the ends as sacrificial cable. The 24mm diameter liner was made from a piece of 3/4", L grade copper plumbing pipe. A short piece of the pipe was cut lengthwise with a hack saw and pried and hammered flat into a sheet. A blank was cut out with a homemade cutter and hydraulic press and then annealed and shaped into a dish with a dapping block and ball bearing punch. The thickness of the liner was about 0.03" or about 0.76mm or about 3% of the liners diameter. The depth of curvature of the dish was about 4mm or about 16.7% of its diameter.

The copper projectile made a nice clean hole through the target. The best piece of steel I could find in the scrap pile was tapered, but careful aiming allowed me to hit it right where its thickness was slightly over 1/2". All the nice even pieces of plate I could turn up yesterday in the scrap pile seemed to be 7/16" for some reason. I think I need to try a 5/8" target next, since it looked like the projectile possible could have done more. Of course now that I have the formula right EFP technology no longer seems finicky at all.


BTW, a good targeting laser is nice especially for long range targeting, but a low tech method that works really well at close ranges like these is to simply use a straight piece of wood such as a straight meter stick. The EFP can be easily aimed/lined up with the target by holding the straight edge along the EFP casing side and also top.





[Edited on 11-7-2015 by Hennig Brand]

Quote: Originally posted by Hennig Brand

Thanks. This is the first shot since the one described earlier on this page of this thread, the other shallow holes are the result of a bit of liner breakup again I guess. The bulk of the liner seems to have stayed together and gone through the main hole though. The amount of penetration is much more limited with EFPs than with Munroe effect SCs but they can be used at much greater standoff, the exact standoff used is not nearly as critical and the hole made is normally much larger in diameter. This last test produced over 0.5D of penetration (1/2"). Penetrating 5/8" would be well over 0.6D of penetration. [Edited on 12-7-2015 by Hennig Brand]

Haha you nearly got 3 for the price of one there.
I wonder why the liner broke up like that , it would have been interesting to see what it would do if it stayed together.
Maybe the liner is slightly too thin and is being over formed.



[Edited on 12-7-2015 by nux vomica]