Sciencemadness Discussion Board - Unconventional Shaped Charges

Unconventional Shaped Charges

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Hennig Brand - 11-7-2015 at 19:09

The copper for the liner was from a used piece of copper pipe, which may have even had a thin film of solder on one side. The thickness may not have been perfectly uniform.

I think well over 90% of the mass and energy were in the projectile that went through the steel, through the main hole, judging by the size and depth of the other spots on the target. From the little bit I have seen a bit of splatter is a common sight on a target hit by an EFP.

edit:
There is a lot of stress on the outer edge of the liner especially, which often results in breakup from what I have read. A lot of the liners designed professionally use methods such as tapering (thinner towards outer edge) to prevent breakup and to facilitate more desirable slug formation (less mass less force, F = ma). The detonation zone meets the liner center first and by the time the detonation zone meets the outer edge the center of the liner has been accelerated to a very high velocity. The same forces that elongate and narrow the projectile can also pull it apart especially at the outer edge when and where the forces are greatest.

[Edited on 12-7-2015 by Hennig Brand]

nux vomica - 12-7-2015 at 00:01

Quote: Originally posted by Hennig Brand

I think well over 90% of the mass and energy were in the projectile that went through the steel, through the main hole, judging by the size and depth of the other spots on the target. From the little bit I have seen a bit of splatter is a common sight on a target hit by an EFP.

Oh it just looked like there was more penetration in the other holes.

Hennig Brand - 12-7-2015 at 03:48

It is a bit deeper than I thought, the deepest hole is approaching 1/4", but its diameter is much smaller than the main hole. Not a perfect single projectile, but the charge still worked quite well I would judge.

Have a look at these videos. The targets all look to have been blasted with other small projectiles as well as the main large one.

note: I noticed in the first video in one place where they seem to have used the description of what happens in a Munroe effect shaped charge to describe an EFP which is not exactly correct.

https://www.youtube.com/watch?v=Pbf7WEVzKcQ

<iframe sandbox width="420" height="315" src="https://www.youtube.com/embed/Pbf7WEVzKcQ" frameborder="0" allowfullscreen></iframe>

https://www.youtube.com/watch?v=ir4Sppsi5KM

<iframe sandbox width="560" height="315" src="https://www.youtube.com/embed/ir4Sppsi5KM" frameborder="0" allowfullscreen></iframe>

And the video you linked to earlier:

https://www.youtube.com/watch?v=G0ZOPFiuOL8&feature=play...

<iframe sandbox width="560" height="315" src="https://www.youtube.com/embed/G0ZOPFiuOL8" frameborder="0" allowfullscreen></iframe>

[Edited on 12-7-2015 by Hennig Brand]

greenlight - 12-7-2015 at 08:05

Has anyone noticed that the Krakatoa EFP uses a very large amount of HE for the targets it is shown penetrating. It uses 500 grams PE for a 1 inch and 1.9 inch steel plate in the videos, thats thick target material but isn't 500g overkill.

I just plasticized some PETN that had been recrystallized for the first time for use in EFP's.
I tried 13% Polybutene but it didn't seem enough and Semtex has 20% inert's I'm pretty sure so I bumped it up to 16% Polybutene and 6 drops motor oil to add softness. It was rolled for about 2.5 hours
The result 31.9 grams PE is off white (due to the motor oil) and is slightly stiffer than Play doh.
The density was measured and is between 1.42-1.44.

[Edited on 12-7-2015 by greenlight]

Hennig Brand - 12-7-2015 at 09:06

Your plastic explosive looks good and it sounds like you did a much more thorough job of mixing and kneading than I have been doing. Seems like an extreme amount of kneading though actually, I usually knead for 15-20 minutes maybe and that is with 100g quantities. Of course it really depends on the particular mixture how much kneading is required and how much muscular endurance and intensity one can put forth as well.

I heard it stated that about 2lbs of plastic explosive was used in the first video, it does seem like a lot.

Assuming a hemispherical curved liner to keep this calculation more useful to us, which the Krakatoa liner used in the video is not, it is conical. The Krakatoa comes with several different liners, one of them is in fact a dome shaped EFP liner. Using the following equation taken from the NG thread for the volume of contents of a partially filled sphere to determine the amount of volume taken up by the liner and the volume of explosive beside the liner:

Quote: Originally posted by Hennig Brand

Here are a couple of equations which could be useful to someone trying to perform heat transfer calculations based on a partially filled spherical vessel/flask.

V = 1/3 * pi * H^2 * (3 * R - H)

A = 2 * pi * R * H

where:
V = Volume of contents in partially filled spherical vessel
A = Inside Surface Area of curved surface, next to contents, of partially filled spherical vessel
H = Height of contents in partially filled spherical vessel
R = Inner Radius of spherical vessel

Equations for other shapes can be found too, in texts or online.

If we assume the Krakatoa reliably gets 0.5D of penetration, 1 inch of penetration would require a 2 inch (ca. 5.1cm) charge. Assuming the explosive head height is about the same as its diameter, assuming 0.15D for depth of curvature for the liner and given V = pi/4 * D^2 *L + [ pi/4 * D * H - 1/3 * pi * H^2 * (3 * R - H)], V = pi/4 * (5.1cm)^2 * 5.1cm + [ pi/4 * (5.1cm)^2 *0.77cm - 1/3 * pi * (0.77cm)^2 * (3 * 2.55cm - 0.77cm) ] = 115.6 cc. I noticed in the first video that the explosive wrapper was labelled SEMTEX, so I will use an assumed density of 1.43g/cc, so the mass of explosive used should be about 1.43g/cc * 115.6cc = ca. 165.3g or 0.36 lbs.

For the 1.9 inch steel target (same assumptions):
mass of explosive = pi/4 * (9.7cm)^2 * 9.7 + [ pi/4 * (9.7cm)^2 * 1.45cm - 1/3 * pi * (1.45cm)^2 * (3 * 4.85cm - 1.45cm) ] * 1.43g/cc
mass of explosive = 1137g of explosive or 2.50 lbs.

edit:
Just realized that I didn't account for liner thickness when I did the volume calculations. Oh well, close enough I think to make a reasonable comparison.

Yeah the EFP and explosive charge that they used seems to be excessive overkill for the 1 inch plate, but not for the 1.9 inch plate. Then again there are things to consider other than penetration. Penetration is the minimum usually before the target can be significantly damaged, but with a more shallow and/or thicker liner the hole made could be much larger in diameter. The amount of damage done during and after penetration that is achieved depends on the size of the hole and how much energy is left after penetration has been accomplished. There is more to EFP technology than just how much steel is penetrated.

Edit:
Found the following from the Explosives.net site.

http://explosives.net/product/krakatoa/

"
The Krakatoa™ is a highly versatile and modular user-filled charge container for EOD and demolition both in air and under-water.

The Krakatoa™ replaces the Bigjet (MEPS) which has been in service for more than a decade. The new model has significant design improvements aimed at enhancing both performance and usability, both in terms of modularity and user friendliness.

The charge may be orientated in any position. The charge container body is approximately 100mm in diameter x 100mm in length. There are two positions for the projectile, giving two standard loads: 500g and 1000g of plastic explosive.

It is screw-consolidated and able to accept a range of projectiles for a variety of possible applications. Note the sighting arrangement on the body, which can accept a red dot aiming device for longer-range, stand-off attack. It can also be able to receive sights and accessories equipped to fit the Picatinny Rail which is supplied as part of the kit.

The Krakatoa™ Basic Kit is supplied with three charge bodies, a set of legs, a loading kit and sights. A tripod mount allows charges to be used with any standard photographic tripod. The user selects the projectile for the job and fills the charge with plastic explosive.

The Krakatoa™ may be used underwater to depths of approximately 50m by the application of the Underwater Capsule which gives the charge an air gap for jets and projectiles to form in. This makes the Krakatoa™ a completely non-magnetic charge suitable for use as a man-positioned mine counter-charge for destroying magnetic influence sea mines."

So it is made to take either 500g or 1000g of explosive filler and there are a variety of different liners available for it. I can see how we could easily make an underwater shaped charge or EFP as well, very interesting!

[Edited on 13-7-2015 by Hennig Brand]

Spherical Cap or Spherical Dome not Hemisphere

Hennig Brand - 12-7-2015 at 09:26

I thought that hemisphere was likely not the correct term to use to describe our EFP liners and it looks like it isn't.

https://en.wikipedia.org/wiki/Spherical_cap

https://en.wikipedia.org/wiki/Hemisphere

Calling the liner a domed disc would be correct as well, and maybe best.

[Edited on 13-7-2015 by Hennig Brand]

markx - 12-7-2015 at 10:10

Quote: Originally posted by greenlight

I just plasticized some PETN that had been recrystallized for the first time for use in EFP's.
I tried 13% Polybutene but it didn't seem enough and Semtex has 20% inert's I'm pretty sure so I bumped it up to 16% Polybutene and 6 drops motor oil to add softness. It was rolled for about 2.5 hours
The result 31.9 grams PE is off white (due to the motor oil) and is slightly stiffer than Play doh.
The density was measured and is between 1.42-1.44.

[Edited on 12-7-2015 by greenlight]

For loading of SC and EFP you do not need to have a literal plastique with excellent rheological properties, although it is a really cool thing to achieve

Hence one can make do with much less inerts and physical work to only reach phlegmatisation (5-10% is ok) and ease the loading and compaction of the charge. I've used 10% castor oil with PETN and RDX for SC application...the mix is a crumbly granular matter that loads excellently and achieves good density.

greenlight - 12-7-2015 at 21:22

@Hennig, thanks, and I did roll it for a longer time than needed as it was staying too crumbly with just Polybutene and I was trying to hold out on adding anything else. As soon as the small amount of motor oil was added it formed together much more efficiently as well as becoming softer.

@Markx, I realised when it was still crumbly that I could have used it in an EFP as is but I have always wanted the full plastique and as you say it is a cool thing to acheive

I will try less Polybutene next time and try and bring the inert's % down but add a small amount of motor oil straight away instead of after adding the 16% PB.

nux vomica - 12-7-2015 at 23:39

Has anyone seen this video I would have thought that it would have detonated the bombs https://www.youtube.com/watch?feature=player_detailpage&v=xAmraOEGzqU

Anyway tried out my new ebw fireset the setup was 1.2 grams of etn compressed to 1.3 grams c/c plus 0.1 on top for a total of 1.3 grms of etn the copper dish was 6.25mm rad, 0.6mm thick and 11.5 mm dia ,bridge wire 0.030mm dia x 2mm long, coax 7 meters with 200mm twin core on the end connecting with a jst to the shaped charge 10mm ms plate at 40 mm standoff, and yes I have a voltage measurement of 3500v at detonation.

cheers nuxy

[Edited on 13-7-2015 by nux vomica]

greenlight - 13-7-2015 at 03:42

@Nux, was your liner conical in shape and was the target 10mm thick steel plate?

It appears that in the video they are placing shaped charges in an exact location on the unexploded bomb so that the jet penetrates and destroys a part of the firing train or fuze assembly.
With the sensitive initiation system removed or interrupted, the rest of the unexploded bomb is much less sensitive and my guess would be able to be removed by hand.

I think they are using the Vulcan shaped charge from Alford technologies with a liquid projectile liner which will penetrate the thick casing and destroy/remove the fuze assembly but does not detonate the HE filler.
http://explosives.net/product/vulcan/

[Edited on 13-7-2015 by greenlight]

nux vomica - 13-7-2015 at 04:16

As I understand it it sets off the main charge but only a low order explosion ie not a complete detonation you can see the casing has split open like a gas cylinder that has ruptured in a fire.

greenlight - 13-7-2015 at 04:22

From the Alford Tech website: "The Vulcan™ Liquid Projectile Set comprises a pair of thin-walled plastic cones with water between them. These constitute a composite projectile which penetrates steel-cased munitions with wall thickness of up to 10mm. Used to eject fuses and disperse charge contents with minimal risk of detonation."

I don't think it detonates the main charge at all I think the water jet just punches through and ruptures the container and ejects the fuze assembly.

Was your liner conical in the test you performed above?

nux vomica - 13-7-2015 at 04:31

No it is spherical and the steel was 10 mm thick the same setup as the ones on the ebw thread .

[Edited on 13-7-2015 by nux vomica]

greenlight - 13-7-2015 at 04:40

That is quite a good result for using 1.3 grams of explosive!
Is your casing made of metal?

It would be interesting to try one of these liners containing a water jacket which forms a jet.
There is also a magnesium EFP liner as an option with the Vulcan shaped charge which burns when it forms and can ignite or initiate combustibles or explosives behind the target as well as penetrating steel which sounds pretty interesting.

[Edited on 13-7-2015 by greenlight]

nux vomica - 13-7-2015 at 04:52

The caseing is a s/s m10 rivnut we have a couple of hundred of them at work

Hennig Brand - 13-7-2015 at 06:47

Nice compact looking fireset you have made and another successful shaped charge test as well!
Could you tell me what the diameter of the entrance and exit holes are in the 10mm thick steel plate?

Greenlight, it is a good result for 1.3g of explosive, but even though possibly hard to believe the amount of explosive used is proportionately similar to what I have been using in relation to the diameter of the charge. The amount of explosive required goes up exponentially with the diameter of the charge. Assuming an explosive head height approximately equal to the diameter, V = pi/4 * D^3, so to compare a 24mm charge to a 11.5mm charge, (24mm / 11.5mm)^3 = ca. 9.1 times the volume of explosive. Assuming equal explosive densities, 1.3g * 9.1 = 11.83g for the 24mm charge. I used 12.2g, but then again it was 87% ETN and 13% inert material and also the plastic explosive density was about 1.4g/cc.

[Edited on 13-7-2015 by Hennig Brand]

greenlight - 13-7-2015 at 07:27

Ah, yes, I see what you mean now Hennig and the diameter of the Nux's charge is only 6.25mm compared to your 24 mm.

What do you think of these magnesium liners for EFP, they may be something interesting to experiment with in the future as you can buy magnesium sheet on ebay.

http://explosives.net/product/vulcan-magnesium-efp-set/

Hennig Brand - 13-7-2015 at 08:22

I believe 6.25mm is the radius of curvature, the diameter is 11.5mm.

I saw that EFP product with the magnesium liner being used as part of a demonstration in a program on the Discovery channel years ago. For specialized applications it could be useful.

greenlight - 13-7-2015 at 08:30

Damn, I misunderstood again

I've got it now.

I think I will order some 1mm magnesium sheet to experiment with when i have these copper lined EFP's dialed in correctly.

efp

Laboratory of Liptakov - 13-7-2015 at 13:15

My opinion is this: 1.3 g ETN has no power to pierce 10 mm of steel. In any assembly like the photo. The author makes fun of you. Liptakov.

Hennig Brand - 13-7-2015 at 15:29

I had that thought at first, but when I looked at it more closely and thought about it a bit I now think he is probably being straight. His charge is only 11.5mm in diameter, which requires a volume of explosive to have approximately 1D in explosive head height of about V = pi/4 * D^3 = pi/4 * (1.15cm)^3 = 1.19 cc. His explosive density was stated as 1.3g/cc, which would give a charge mas of m = 1.3g/cc * 1.19cc = 1.55g. Ok, so he used a little less but we are still in the ball park. This doesn't count his 0.1g ETN prime either.

Remember this test I performed with a conical steel liner earlier in this thread?

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

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

So that test used only 4g of ETN and penetrated 28.6mm of steel. Since penetration is proportional to energy (assuming same diameter holes), as a first approximation 4g/1.3g * 10mm = 30.8mm which is only 7.7% higher than what I got and he was using pure ETN and a copper liner while I was using 80% ETN plastique and a steel liner which both give lower shaped charge performance. I believe that much is possible. What is a little strange is exactly how he is getting such a small diameter hole and such deep penetration with such short standoff unless his charge is really functioning as a Munroe effect shaped charge (jetting charge).

The thickness of the liner he used also seems too thick to easily form into a tight projectile, but then again he used very brisant pure ETN and I think we are talking Munroe effect again and also he used a very strong steel casing as well, which I am sure makes a huge difference especially with small charges such as these.

Knowing the volume of the hole would allow a good comparison to be made.

[Edited on 14-7-2015 by Hennig Brand]

nux vomica - 13-7-2015 at 15:45

I can get a 2.5 mm drill almost through from the exit side there's a burr on the entry side stopping it .
the photo is with a piece of 2.4mm welding wire.

Cheers nuxy

[Edited on 14-7-2015 by nux vomica]

Hennig Brand - 13-7-2015 at 16:18

According to "Fundamentals of Shaped Charges", by Walters and Zukas, for a given explosive charge the volume of the penetration should be approximately the same regardless of what type of device it was used in, EFP, SC, fragmentation, etc.

Here is a link to where the section from the text was discussed and the table from the text is attached:

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

My volume from the test above:

Explosive used: 12.2g of 87% ETN plastique
Average diameter of hole: ca. 12mm (1.2cm)
Penetration: 1/2" or 12.7mm (1.27cm)
V = pi/4 * (1.2cm)^2 * 1.27cm
V = 1.44 cc or 1.44 mL

From Nux's test:

Explosive used: 1.3g of ETN
Average diameter of hole: ca. 2.5mm (0.25cm)
Penetration: 10mm (1cm)
V = pi/4 * (0.25cm)^2 * 1cm
V = 0.05 cc or 0.05 mL

Comparison:

factor = 1.44cc / 0.05cc = 28.8
assume equal explosives, just to get a ball park comparison:
28.8 * 1.3g = 37.4g......but I only used 12.2g and it was 87% ETN and 13% inert material.

My test produced a much higher volume penetration in proportion to the mass of the explosive charge used. I think his test was fair, but I still think he is getting a jetting charge not a EFP judging by the penetration depth, how small the diameter of the hole is and the extremely short standoff used.

[Edited on 14-7-2015 by Hennig Brand]

nux vomica - 13-7-2015 at 16:25

I did just penertrate that 16mm target in the ebw thread and that was 50mm standoff.

Hennig Brand - 13-7-2015 at 16:40

Yeah, I remember now that you mention it. That amount of penetration and holes that small in diameter are not characteristic of EFPs, especially at such short standoffs. A well made Munroe effect shaped charge can still work quite well at the standoffs you are using and it looks like you are one of the ones here most able to do accurate and precise work. Very nice tests, interesting! :cool:

Maybe they are some sort of transition type charge, not really an EFP and not really a Munroe effect SC, but somewhere in-between?

[Edited on 14-7-2015 by Hennig Brand]

nux vomica - 13-7-2015 at 18:23

Okay everyone i am up for a bit of fun, I will make another ebw charge and this time try it on a piece of 20mm m/s plate im thinking of 23mm standoff this time (2xdia) anyone have any other suggestions.
I don't think that my charges are efp but are shaped charges dont know why but you can only go on the results. Nuxy

[Edited on 14-7-2015 by nux vomica]

nux vomica - 13-7-2015 at 23:33

Pointless post deleted nuxy

[Edited on 15-7-2015 by nux vomica]

Hennig Brand - 14-7-2015 at 07:06

For 0.6g of copper, density 8.96g/cc :

0.6g / 8.96g/cc = Volume = 4/3 * pi * r^3

r = 0.25 cm
D = 2r = 0.50 cm

edit:
I look forward to your next test. It will be interesting to see how much more penetration you can get out of it.

BTW, math just takes practise, no one is born knowing how to do it, though some do of course have a greater affinity and some have greater ability as well (not saying I am an expert and yes I make mistakes too). Rework and understand the above calculation a couple of times and then a day or two later rework it again. If you actually think and follow the process and understand as you are working through it will sink in and you will really know it. Repetition is a good thing!

A lot of times people are trying to prove a mathematical relation so they tend to latch onto, or force even, anything that looks like a connection whether or not it obeys the mathematical laws or not (I have been guilty myself). The same sort of thing often happens when detectives decide someone is guilty before they investigate and a very high percentage of the time they are able to built a strong case against them even when the accused is innocent (the detectives don't necessarily consciously do it on purpose). The math can be completely wrong and still occasionally end up with the right number.

[Edited on 15-7-2015 by Hennig Brand]

greenlight - 14-7-2015 at 07:46

Just found an interesting pdf document about the effects of physical parameter on EFP design.
It has test results on charge weight and height, confining geometry, type of explosive liner thickness and curvature vs. penetration and velocity of slug.

Just had a quick skim through and noticed: "The charge weight dominant projectile test provides insight as to how changing the charge weight of an EFP, and resulting head height, affects the flyer formation and production of a dominant projectile. As the charge weight increases, the projectiles broke apart. As the charge weight decreases, the EFP designs retain more of the initial flyer weight and dominant projectiles are easily identifiable in the high-speed video."

"As the charge weight increased the projectiles velocity continued to increase. This indicates that there is an optimal charge weight for penetration, for an EFP with the physical parameters explained in Section 3, of 868 grams. This also indicates that larger charge weights do not improve EFP performance."

I think what they are saying is that you can increase the charge weight to get more velocity in the slug and more penetration to a certain extent of peak performance which causes more slug breakup and then it doesn't improve performance from there, the slug just breaks up even more during flight.

Would the height of explosive affect the shape of the slug that is formed making it more or less elongated?

[Edited on 14-7-2015 by greenlight]

Attachment: The effects select physical parameters have on an explosively for.pdf (4.5MB)
This file has been downloaded 736 times

[Edited on 14-7-2015 by greenlight]

Hennig Brand - 14-7-2015 at 14:35

Very interesting thesis, thanks.

Here is another one regarding EFP penetration of concrete:

Attachment: Impact Effects of Explosively Formed Projectiles on Concrete.pdf (3.9MB)
This file has been downloaded 639 times

And a good one on linear shaped charges as well:

Attachment: Precision Linear Shaped Charge Analysis.pdf (3.7MB)
This file has been downloaded 832 times

[Edited on 15-7-2015 by Hennig Brand]

greenlight - 14-7-2015 at 20:52

Quite a well done test on the EFP penetration of concrete. Haven't gotten to the linear shaped charge analysis document yet.

It seems that a much thicker heavier EFP liner is needed for penetrating concrete.
The liner they are using in the tests is 95.3mm in diameter and 6.35mm thick with a curvature of 22.2mm. Diameter of liner is 95.3mm so the liner thickness is slightly over 6% of charge diameter which is 101.6mm and even more than 6% of the liner diameter (6% of 95.3=5.718).

It also seems that the proper word for the liner is the "flyer plate".

[Edited on 15-7-2015 by greenlight]

nux vomica - 15-7-2015 at 00:14

I had a go at penetrating 20mm m/s plate, just couldn't get through though it cracked and bulged the back of the plate.

I had 23mm standoff and I think it was too close as the entry looks smaller than normal and there is hardly any copper spatter on the target 2.5 to 3 times standoff might be a better proposition.

Setup was my standard ebw one ie 1.2 grms etn and firing voltage was 3500v.

Cheers Nuxy.

[Edited on 15-7-2015 by nux vomica]

genie

wodejxc - 15-7-2015 at 01:21

Wow, this is really a great idea, after I read your post, I feel like all of a sudden interest in science

greenlight - 15-7-2015 at 03:59

@Nuxy, thats pretty close to complete penetration by the look of the picture, well done.
I agree about the standoff, I think it would have made it through if you had used 40mm standoff like your last test.

nux vomica - 15-7-2015 at 04:10

Quote: Originally posted by greenlight

@Nuxy, thats pretty close to complete penetration by the look of the picture, well done.
I agree about the standoff, I think it would have made it through if you had used 40mm standoff like your last test.

I think that 4x or 46mm could be the sweet spot Ive done 40 mm and 50 mm with 10mm plate and they both penertrated well. Nuxy

[Edited on 15-7-2015 by nux vomica]

Hennig Brand - 15-7-2015 at 05:16

Less standoff would normally produce a larger entry hole, since there is less distance/time for elongation and narrowing of the jet or projectile.
That is a thick piece of steel for the size of the charge that is for sure!

nux vomica - 15-7-2015 at 05:55

Quote: Originally posted by Hennig Brand

Less standoff would normally produce a larger entry hole, since there is less distance/time for elongation and narrowing of the jet or projectile.
That is a thick piece of steel for the size of the charge that is for sure!

Ive got over a meter of the 20mm steel flat bar leaning against my bench at work hopefully I wont have to use all of it to get a hole through both sides.

I agree about the less standoff bigger hole but im wondering if the jet takes longer to focus, the lack of copper splatter is different to the other shots they had spatter and the hole was nice and round not wonky looking with none ,after all it is a bit of a bastard son, looks like a efp but acts like a shaped charge.
Cheers nuxy.

nux vomica - 15-7-2015 at 18:57

Quote: Originally posted by Hennig Brand

For 0.6g of copper, density 8.96g/cc :

0.6g / 8.96g/cc = Volume = 4/3 * pi * r^3

r = 0.25 cm
D = 2r = 0.50 cm

edit:
I look forward to your next test. It will be interesting to see how much more penetration you can get out of it.

BTW, math just takes practise, no one is born knowing how to do it, though some do of course have a greater affinity and some have greater ability as well (not saying I am an expert and yes I make mistakes too). Rework and understand the above calculation a couple of times and then a day or two later rework it again. If you actually think and follow the process and understand as you are working through it will sink in and you will really know it. Repetition is a good thing!

A lot of times people are trying to prove a mathematical relation so they tend to latch onto, or force even, anything that looks like a connection whether or not it obeys the mathematical laws or not (I have been guilty myself). The same sort of thing often happens when detectives decide someone is guilty before they investigate and a very high percentage of the time they are able to built a strong case against them even when the accused is innocent (the detectives don't necessarily consciously do it on purpose). The math can be completely wrong and still occasionally end up with the right number.

[Edited on 15-7-2015 by Hennig Brand]

Yeh im a bit of a rusher somtimes as they say the devil is in the detail.
Smacked a liner with a hammer till it was reasonably round, you were spot on size with 5mm dia, put it next to the exit hole in the 10mm plate and it's close to size where the hole flares out .
Cheers nuxy

[Edited on 16-7-2015 by nux vomica]

greenlight - 16-7-2015 at 04:03

Just wondering how far you guys insert your detonator into the explosive charge in your EFP's as I found this in one of the pdf's:

"Results of the cap depth test determine that inserting the blasting cap 7.5 cm into an EFP creates a more elongated projectile shape with a higher velocity than the projectiles produced from the EFP with a cap depth of 2 cm."

I knew centred detonator placement was important but it seem the depth of insertion is also a factor contributing to the final slug shape and velocity.

nux vomica - 16-7-2015 at 04:23

Quote: Originally posted by greenlight

Just wondering how far you guys insert your detonator into the explosive charge in your EFP's as I found this in one of the pdf's:

"Results of the cap depth test determine that inserting the blasting cap 7.5 cm into an EFP creates a more elongated projectile shape with a higher velocity than the projectiles produced from the EFP with a cap depth of 2 cm."

I knew centred detonator placement was important but it seem the depth of insertion is also a factor contributing to the final slug shape and velocity.

I don't know about everyone else but with my ebw charges there is no detonator just the 0.1 grm priming charge, so I suppose whole charge is a sort of detonator main charge. Nuxy

Hennig Brand - 16-7-2015 at 07:42

It would depend on the size of the charge. I am not sure if what I am doing is correct, but for a 24mm diameter EFP with 20-24mm of explosive head height I estimate that I have been inserting the blasting cap anywhere from 3-5mm. I try not to insert it too far, with the logic being that I don't want to interfere with the function of the main charge on the liner too much.

nitro-genes - 16-7-2015 at 07:48

With these charge sizes, it might also help to give the detonator a thick bottom of foam or plastic (about 3mm), and insert it 4-5 mm into the charge, acting like a sort of a simple waveshaper, helping to "flatten" the shockwave as it hits the liner.

greenlight - 16-7-2015 at 07:56

Thanks for that guys.
I think that is why my EFP's before weren't as effective because the explosive height was about 1.5 to 2 x charge diameter.
I also inserted the detonator about 20mm into the main charge as well which is too far.
The pieces of the puzzle are coming together.

From what I have read, the factors affecting EFP performance are:

* Type of explosive
* Confinement strength (casing strength)
* Confinement thickness (casing thickness)
* Flyer/liner thickness
* Flyer/liner diameter
* Flyer/liner radius of curvature
* Flyer/liner material
* EFP casing diameter
* Charge length
* Explosive height
* Charge weight
* Cap/detonator depth
* Standoff from target

Nitrogenes, do you mean a wave-shaper attached to the bottom of the detonator or have a space of explosive between the wave-shaper and the bottom of the det?

[Edited on 16-7-2015 by greenlight]

nitro-genes - 16-7-2015 at 08:56

Like this (forgive my terrible drawing skills):

So the red colour representing some 3 mm piece of low density inert material, flattening the shockwave.

nux vomica - 16-7-2015 at 14:04

I am a bit more happy with the results of the 20mm plate test now I have cut the plate in half I got 16mm depth with 2.5mm dia at the bottom of the hole .
I added a picture showing the cut plate after I sprayed crack detection fluid on then developer to show things better.

Dont know whether to go up another 5 mm or try 46 mm now. Nuxy

[Edited on 17-7-2015 by nux vomica]

Ebw shaped charge video

nux vomica - 17-7-2015 at 19:26

I took a video of one of my shaped charges going off since it was a bright day and not raining, l protected my phone with a piece of 2mm stainless steel sheet with a 10mm hole drilled in it to just let the lens be exposed I don't know the mathematical odds of a splinter hitting the lens at 4 meters away but I thought it must be minute .

And no I don't know how I would explain to my wife how my phone got a hole through it .

The video charge is ebw fired at the end of 7 m coax at 3500 v using my standard s/s rivnut with 1.2 + 0.1 etn, copper liner and 35mm standoff, target is 20mm plate.

Plate in photo is the target i will cut at work to check penetration.

Cheers nuxy.

Attachment: 20150718_121734_001.3gp (8.4MB)
This file has been downloaded 901 times

[Edited on 18-7-2015 by nux vomica]

nux vomica - 22-7-2015 at 02:55

I just redid the 35mm standoff again because I wasn't happy with the result [12mm] and bingo I got a full penetration through 20mm of steel , I spent a little more time assembling everything and I got the best looking penetration yet, nice and straight and narrowing to 1.75 mm which is the dia of the pin sticking through the target.
It was standard ebw charge fired at 3500v through 7m coax.

Cheers nuxy.

[Edited on 22-7-2015 by nux vomica]

Hennig Brand - 22-7-2015 at 03:53

Nice result! That is a lot of steel penetrated for such a small charge! I also watched your video above, which was interesting. I noticed from the video that you seem to be doing your explosive testing in a more suitable location than I have been. Probably not something to be emulated, but I have been taking 20 or 30 paces off my back door step before setting up a test. Of course where I am is very rural with no close neighbors.

nux vomica - 22-7-2015 at 05:10

Quote: Originally posted by Hennig Brand

Nice result! That is a lot of steel penetrated for such a small charge! I also watched your video above, which was interesting. I noticed from the video that you seem to be doing your explosive testing in a more suitable location than I have been. Probably not something to be emulated, but I have been taking 20 or 30 paces off my back door step before setting up a test. Of course where I am is very rural with no close neighbors.

Yeah I didn't think I was going to make It through at one stage so maybee 35mm standoff is the sweet spot for these small charges.
I realize how lucky you are because were semi rural till 10 years ago now suburbia is everywhere new estates taking over a lot of the farmland

. its getting harder to find quiet spots all the time.
cheers nuxy.

nux vomica - 23-7-2015 at 22:00

Cut the 20mm steel plate that I got full penertation in half looks even better than I thought 3mm dia to 16mm depth then narrowing to 1.75mm for a small amount of etn it sure does some work.
Rod in pic is 1.6 dia.

Cheers Nuxy

pictures

Laboratory of Liptakov - 24-7-2015 at 00:25

Huuh. This is the art of high energy. In the gallery, Christie's sold a lot worse images. Much worse, but for millions of dollars. Send them this picture. :-) Dr. Liptakov

nux vomica - 24-7-2015 at 03:52

Quote: Originally posted by Laboratory of Liptakov

Huuh. This is the art of high energy. In the gallery, Christie's sold a lot worse images. Much worse, but for millions of dollars. Send them this picture. :-) Dr. Liptakov

Thanks, it is amazing to think how much energy is forced so quickly through the target but it still looks like the jet delicately pulsed through the steel.
I dont think you can claim you are a artist to mr plod when he is examining your artistic folio.

nuxy

[

[Edited on 24-7-2015 by nux vomica]

nux vomica - 27-7-2015 at 05:03

Tried something different today sill useing my standard setup eg rivnut 1.2grm etn I machined a flat .6mm copper disc 11.5 mm dia and fired it at 10mm m/s at 35mm standoff it only penertrated 3mm o/d of hole was 15 mm cheers nuxy

Hennig Brand - 27-7-2015 at 08:06

Yeah, without at least a bit of curvature the projectile doesn't narrow and elongate. With curvature the detonation zone hits the apex of the domed disc (highest point in center) first accelerating it to high velocity long before the detonation zone makes it to the bottom outer edge of the domed liner (is the same for Munroe effect shaped charges as well). The different in relative velocity and mass difference going from the inside to the outer edge of the liner generates forces which stretch the liner into a narrower more elongated shape which is much more capable of penetration. Interesting that the hole diameter, in this flat liner test, is so much larger than the initial liner diameter.

nux vomica - 27-7-2015 at 16:19

Quote: Originally posted by Hennig Brand

Yeah, without at least a bit of curvature the projectile doesn't narrow and elongate. With curvature the detonation zone hits the apex of the domed disc (highest point in center) first accelerating it to high velocity long before the detonation zone makes it to the bottom outer edge of the domed liner (is the same for Munroe effect shaped charges as well). The different in relative velocity and mass difference going from the inside to the outer edge of the liner generates forces which stretch the liner into a narrower more elongated shape which is much more capable of penetration. Interesting that the hole diameter, in this flat liner test, is so much larger than the initial liner diameter.

I'm still not happy with the result hennig I didnt have the liner flush with the outside of the rivnut I think the flared edge on the rivnut interfered with the forces acting on the liner as the flare was in front of it and also there is a impact ring where the S/S flare hit the target so the flare and copper liner must have traveled forward , I am going to ether add more etn or a spacer to get the liner flush with the outside of the rivnut.
Cheers nuxy
Edit tried with liner flush gave a smaller dia impact mark and penertrated 4mm at deepest point of impact might start slowly curving liner to see what happens.

[Edited on 28-7-2015 by nux vomica]

franklyn - 2-8-2015 at 10:37

The topic heading ' Unconventional Shaped Charges ' judging by the very conventional ones thus seen here seems has been taken to mean ' improvised ' or not of commercial manufacture. I"M NOT CRITICIZING IT , experimental results posted add to the base of knowledge. I had this passing thought. A ( H.E.P.) High Explosive Plastic anti armor round consists of a plastic explosive composition that is spread on impact into a pie shape against the armor. Used against homogeneous armor ( composite interferes ) a shock wave travels through to the interior , spalling there a pie sized weight of armor. My thought is how might armor behave if the interface with the explosive is patterned or corrugated with ridges or pockets , etcetera. I'm not talking about the surface of the armor itself , rather discrete repeating depressions which are in the explosive's surface. Think of an ice cube tray filled with explosive and the bottom laid against the armor substrate. The intervals having standoff will by Munroe effect cut a pattern of regular deep channels into the armor. The idea then is that partially perforated in this way , the armor section is effectively made thinner and therefore possibly be completely blown inward , making a very large opening. Does anyone know of any investigation or related study of this notion.

In the picture of the ice cube tray the underside is cris crossed with channels which will act like linear shaped charges. These will cut that same pattern deeply into the armor. The unperforated armor beyond the depth of the cuts is thinner and more yielding to the force of the explosion.

These may have been posted before I don't know , found by googling - explosive wave shaping

Explosive Loading of Metals & Related Topics
www.dtic.mil/dtic/tr/fulltext/u2/b102693.pdf

Imaging detonation waves for wave shaper
www.dtic.mil/dtic/tr/fulltext/u2/a513564.pdf

Detonation wave conference
www.dtic.mil/dtic/tr/fulltext/u2/128529.pdf

Method to Increase Tip Velocity of a Shaped Charge Jet
www.mater.upm.es/isb2007/Proceedings/PDF/Volume_1/Vol.I(14)W...

Stopping Power of Explosive Reactive Armours
http://www.cryptocomb.org/Stopping%20Power%20of%20Explosive%...

Patent resource
http://patents.justia.com/patents-by-us-classification/102/4...

Interesting site for the clarity of explanation of nuclear porn
http://nuclear-knowledge.com/explosivelenses.php

Thermonuclear lenses
http://books.google.com/books?id=B7RV_vASz0EC&lpg=PA311&...

[Edited on 3-8-2015 by franklyn]

nux vomica - 2-8-2015 at 13:56

Quote: Originally posted by franklyn

The topic heading ' Unconventional Shaped Charges ' judging by the very conventional ones thus seen here seems has been taken to mean ' improvised ' or not of commercial manufacture. I"M NOT CRITICIZING IT , experimental results posted add to the base of knowledge.

Franklyn I think we need to start another sticky for conventional style shaped charges so if there was a seperate sticky im sure people would use there judgment to post in the right thread, or maybe rename the sticky to conventional and non conventional shaped charges. nuxy

[Edited on 3-8-2015 by nux vomica]

Hennig Brand - 2-8-2015 at 16:11

Franklyn, sounds like you are talking about "High-explosive squash head" (HESH) rounds. It is not classified as a shaped charge I don't think but it is effective against armor.

https://en.wikipedia.org/wiki/High-explosive_squash_head

Here is a good demonstration, start watching at 22:30.

https://www.youtube.com/watch?v=6Z9o5oPMWss

<iframe sandbox width="560" height="315" src="https://www.youtube.com/embed/6Z9o5oPMWss" frameborder="0" allowfullscreen></iframe>

Edit:
I see that you are talking about something related but different now that I have read your post more carefully.

[Edited on 3-8-2015 by Hennig Brand]

VladimirLem - 3-8-2015 at 13:30

Quote: Originally posted by franklyn

...

you are talking about HESH...
You have to know, these charges doesnt penetrate the armor like a shaped charge or an EFP...the enormous pressure on the surface is that high, that the armor rear side (inside of the "tank") gets "brittle" and is bounced off into the tank (with high speed and having alot of kinetic energy)...the armour plate still is not penetrated.
I highly doubt there would be an advantage if you would make the explosive with a higher surface (shapedcharge-like) to the target...well, the projectiles inside the "tank" would be more, but with less energy and if the armor is too thick, no projectile will be build inside the tank. to this comes that the shock have to directly hit the target...mini-shapedcharges would "destroy" the surface, but wouldnt (i guess) improve the power of the shockwave nessesary for the HESH projectile...

I really like HESH...saw a video once...very impressive...i was like "No way, dis wont penetrate"...was right, but....WELLLL....

HESH is 50th...maybe 60th and really fun to do, i guess, but against DU/ceramic-armor its completely useless today

Efp success

nux vomica - 7-8-2015 at 21:22

I have been trying to find the point where my charges turn into a efp , I changed the angles of the cones by 10 ° starting at 120° still a small jet hole ,130° transition small hole but copper spatter was looking like a efp probably should do this one again, 140° definate efp target is 6mm mild steel at 100 mm standoff charge is standard ebw 1.2 etn at 3500 volts.
I also found the carrot in the wood block below more steel than copper must have had only enough energy to just punch through the 6 mm cheers nuxy.

[Edited on 8-8-2015 by nux vomica]

Hennig Brand - 8-8-2015 at 07:56

Very interesting test. That 140 degree value agrees with what I have seen in the literature a few times as well.

nux vomica - 8-8-2015 at 17:37

Quote: Originally posted by Hennig Brand

Very interesting test. That 140 degree value agrees with what I have seen in the literature a few times as well.

Thanks I didnt have any fixed ideas of angles I started with the angle closest to the cone hight of the cylindrical liners .
I have uploaded the120° and 130° test plates for comparison nuxy.

[Edited on 9-8-2015 by nux vomica]

EFP IMPROVEMENT

greenlight - 10-8-2015 at 03:01

I performed another test with an EFP trying to drop the amount of explosive used and use PE instead of the usual pressed powder.
The explosive was 79% PETN, 5% RDX, 15% polybutene, 1% motor oil.
The flyer plate was a 0.9mm copper disc 30mm in diameter.
Casing was a 35mm long PVC pipe.
Explosive weight was 16 grams, almost half the amount I was using with powder.
The target was a 10mm or 3/8 inch steel plate.
Result is a complete penetration leaving a very clean hole with little spalling around it.
Very happy with the plastic as a main charge, makes loading and det insertion much easier too

[Edited on 10-8-2015 by greenlight]

nux vomica - 10-8-2015 at 03:10

Quote: Originally posted by greenlight

I performed another test with an EFP trying to drop the amount of explosive used and use PE instead of the usual pressed powder.
The explosive was 79% PETN, 5% RDX, 15% polybutene, 1% motor oil.
The flyer plate was a 0.9mm copper disc 30mm in diameter.
Casing was a 35mm long PVC pipe.
Explosive weight was 16 grams, almost half the amount I was using with powder.
The target was a 10mm or 3/8 inch steel plate.
Result is a complete penetration leaving a very clean hole with little spalling around it.
Very happy with the plastic as a main charge, makes loading and det insertion much easier too

Sweeeet you would have to be happy with that looks like the efp held together nicely,went through like a hot knife through butter. nuxy

[Edited on 10-8-2015 by nux vomica]

greenlight - 10-8-2015 at 04:26

Yes, much better effect than before.
I think I will see if it can penetrate 3/4 inch steel next.

nux vomica - 10-8-2015 at 04:52

Quote: Originally posted by greenlight

Yes, much better effect than before.
I think I will see if it can penetrate 3/4 inch steel next.

How far away was mr smiley face from the ten mm plate greenlight 16 grams must have kicked him in the arse pretty hard.

greenlight - 10-8-2015 at 04:55

Yes it did haha..
Standoff was 60 cm exactly.

[Edited on 10-8-2015 by greenlight]

nux vomica - 10-8-2015 at 05:27

You didnt catch him after he went through the plate ?
Intresting to see how far 16grams will punch through now you have got it all worked out.. nuxy

greenlight - 10-8-2015 at 05:36

I had the plate against a tree but it penetrated just to the left of it it so I couldn't retrieve it.
I'm going to try and catch one that hasn't been deformed soon. I just have to think of an effective way to stop it without damaging it.

nux vomica - 10-8-2015 at 05:42

Quote: Originally posted by greenlight

I had the plate against a tree but it penetrated just to the left of it it so I couldn't retrieve it.
I'm going to try and catch one that hasn't been deformed soon. I just have to think of an effective way to stop it without damaging it.

Do mythbusters use a stack of phone books didnt they stop a 50 cal bullet with them.

[Edited on 10-8-2015 by nux vomica]

greenlight - 10-8-2015 at 06:09

I think that the speed the slug is travelling will cause it to deform still.
There is a test I found on the internet trying to develop EFPs to take out underwater mines where they were firing them into water and that was causing them to break up a lot.
I also read somewhere about using a pipe filled with sawdust and one following behind filled with water. The sawdust should slow it down enough that it doesn't deform when it hits the water.

catch slug

Laboratory of Liptakov - 11-8-2015 at 01:01

Well, nice piece work. Clear hole, thats very good. Catching slug? I trying one more time. But I catch only 40% from flyer plate. Sawdust and water is good idea. I estimate 2 meter sawdust. I estimate using 2x plast bag with sawdust 1m long, and 3x plast container ( thick 25 cm) 5l water. Liptakov.

greenlight - 11-8-2015 at 04:53

Thankyou..
I was thinking of using a 2 metre long pipe filled with sawdust and another 1 metre long pipe filled with water attached behind it.
This should be enough to stop an EFP of the same size as the last test without damaging the slug or losing any of it.

depth

Laboratory of Liptakov - 11-8-2015 at 06:26

Well, I look forward to the results. The question: I no seen deflection depth of the liner 30mm diameter/ Cu 0,9mm. Important thing. Dr. Liptakov, all what flying.

greenlight - 11-8-2015 at 07:44

If you mean the depth of curvature of the liner it was 5 mm (16.6% of liner diameter).

contruct

Laboratory of Liptakov - 11-8-2015 at 10:43

OK, thanks. This contructions ?

greenlight - 11-8-2015 at 18:31

Yes that's pretty much exact design except there was no powder charge in there. The entire charge was 16 grams plastic and explosive height was about 20mm so 2/3 of liner diameter.

Plastic etn efp

nux vomica - 12-8-2015 at 02:25

I tried the bug board pib to make some plastic etn I used enamel thinners to dissolve the pib then mixed the etn in, the pib ratio was 13%, this pib will work but its crumbly not a mouldable mix like play doh, so I bought some castor oil and will make some Methyl Ricinoleate and see if that makes a better mix.
I had a copy of Risi rp4 sff so I packed 5 grams of the plastic etn in it and used a 0.6mm thick copper disc 19mm in dia with 6mm offset standoff was 410mm and steel angle 10mm thick, setoff with my standard ebw head at the end of 7 meters of rg6 cable at 3500v.

The bang didn't have that sharp crack that I am used to but I got full penetration through the 10mm steel and the flyer penetrated through 150mm of dense clay behind it then shot off at a angle so I didn't find the flyer

p
Pretty happy with result from first try of plastic etn will be making another batch soon for more testing.

cheers nuxy

[Edited on 12-8-2015 by nux vomica]

greenlight - 12-8-2015 at 02:49

Thats a nice result for 5 grams of PE and a 10 mm target.

My PE is the same when I mix the binder in it just stays crumbly, try adding some % motor oil as well and working that in. It holds together much better then.

nux vomica - 12-8-2015 at 02:54

Quote: Originally posted by greenlight

Thats a nice result for 5 grams of PE and a 10 mm target.

My PE is the same when I mix the binder in it just stays crumbly, try adding some % motor oil as well and working that in. It holds together much better then.

Thanks I will try that if my castor oil methyl ricinoleate experiment don't work out. Nuxy

[Edited on 12-8-2015 by nux vomica]

liner

Laboratory of Liptakov - 12-8-2015 at 11:28

Hmm, good work, Nuxy. 5g and 10 steel troughout, its nice results. But I see no precise surface on the Copper liner. Pic 2. It is maybe reason, why is on the target so large dispersal. Bridgewire point is precise center? Thanks, Liptakov

nux vomica - 12-8-2015 at 15:12

Quote: Originally posted by Laboratory of Liptakov

Hmm, good work, Nuxy. 5g and 10 steel troughout, its nice results. But I see no precise surface on the Copper liner. Pic 2. It is maybe reason, why is on the target so large dispersal. Bridgewire point is precise center? Thanks, Liptakov

Yeah thanks, you have sharp eyes the liner was slightly buckled but I decided to use it anyway, plus the liner curvature was the same as the smaller ones that were jetting so I think the liner may have been trying to form a jet the hence the 6.27 dia hole I am going to try a 140° cone next and see if there is a difference.
The bridgewire is jig driled so I dont think that is affecting the results of the charge. cheers Nuxy

[Edited on 13-8-2015 by nux vomica]

greenlight - 12-8-2015 at 22:20

How many mm deep is your depth of curvature (the lowest point in the curve of the liner) nux?

nux vomica - 12-8-2015 at 22:45

Quote: Originally posted by greenlight

How many mm deep is your depth of curvature (the lowest point in the curve of the liner) nux?

6mm greenlight it has the same dia to depth ratio that my rivnut cylindrical liners has, I made it a while ago but useing plastic with lower velocities thought it might work ok as a efp .

Edit if you use 30 plastic pipe the steel ball to form the liner would be 30 x 1.0869= 32 rounded so use a 30 mm hole in hardwood block and drive the 32 mm ball into the copper sheet and trim evenly to 30 mm . Cheers nuxy

[Edited on 13-8-2015 by nux vomica]

greenlight - 13-8-2015 at 01:33

I drew a quick sketch of your liner and my liner to scale with a mm ruler.
I think it would work better as an EFP and produce a more slug-like projectile if you took the depth of curve down to 3 or 4 mm on your liner.
Yours has much more of a curve height and I think this is causing it to form smaller diameter holes because its is almost acting like a CSC/Munroe effect as the sides of the liner collapse around itself.
If you treat the arrows as a shockwave, they are much closer together as they intersect with the liner on your flyer plate which would definately form a more elongated projectile if I am correct.

[Edited on 13-8-2015 by greenlight]

nux vomica - 13-8-2015 at 04:30

Quote: Originally posted by greenlight

I drew a quick sketch of your liner and my liner to scale with a mm ruler.
I think it would work better as an EFP and produce a more slug-like projectile if you took the depth of curve down to 3 or 4 mm on your liner.
Yours has much more of a curve height and I think this is causing it to form smaller diameter holes because its is almost acting like a CSC/Munroe effect as the sides of the liner collapse around itself.
If you treat the arrows as a shockwave, they are much closer together as they intersect with the liner on your flyer plate which would definately form a more elongated projectile if I am correct.

[Edited on 13-8-2015 by greenlight]

You are right about the liners having a effect like a Monroe s/c henning thought the same thing the rivnut ones did the same I was hoping plastic etn would cancel out some of the hybrid affect .
Oh well I wil try a 140° cone next cheers nuxy

Soft recovery system

greenlight - 13-8-2015 at 07:20

Projectile recovery system ready to test.
There is a 1 meter pipe filled with packing styrofoam, a 2 meter pipe following filled with sawdust/wood shavings and a 1 meter pipe behind this filled with 9 liters of water and a clear plastic window so the slug can pass through.
All pipes are 110mm ID.
Hopefully this should catch it without causing extensive damage.

[Edited on 13-8-2015 by greenlight]

[Edited on 13-8-2015 by greenlight]

Laboratory of Liptakov - 13-8-2015 at 09:32

Huuh.. Super digital aparatus catching system. :cool:

But 110 mm diameter is not very. You need very precise aiming on target. I am afraid that slug flips out of tube offside. I look forward to the results.

Liptakov

greenlight - 13-8-2015 at 09:59

I will do my best to get the pipes straight using a level and will aim EFP using a laser pointer.
If it fails to contain the projectile effectively I can always use bigger diameter pipe or cardboard boxes filled up with foam/sawdust/water jugs.

Hennig Brand - 13-8-2015 at 16:12

The projectile may sail off course enough to leave the tubes, even if aiming is done perfectly. Interesting experiment, hope it works out.

greenlight - 13-8-2015 at 18:19

I am hoping nothing causes it to stray, but thanks I will post results as soon as I can

First recovery no-go

greenlight - 14-8-2015 at 01:20

Okay, so the first recovery system went not so well.
Even though a hand level and laser pointer was used to ensure everything lined up correctly, the EFP slug seems to have just touched the side of the first pipe evident by the large piece that has been removed in the picture. This caused it to slide along for a bit before punching through further down and exiting the pipe in the other picture. Theres is a penetration hole in the sawdust pipe right in the middle but after inspecting the contents, it was a small piece of copper shrapnel probably breakup when it exited the tube.

I think for the next test I will use styrofoam boxes with the same setup and contents. Then I will not have to worry about the projectile straying because there will be plenty of room.

[Edited on 14-8-2015 by greenlight]

nitro-genes - 14-8-2015 at 02:00

Really cool to see people are trying to catch the EFP projectile. The idea of holding something in your hand that has travelled around 4000 m/s is pretty awesome.

A thought I had was maybe go to a farmer and ask for a large bale of straw. (It would literally be searching for a needle in a haystack afterwards though...unless you have a metal detector

) Not sure it would be soft enough to catch the EFP reasonably undamaged though.

[Edited on 14-8-2015 by nitro-genes]

greenlight - 14-8-2015 at 03:15

Yes the idea that you can actually catch something that penetrates steel with relatively soft materials is very interesting.

Yes straw could work, maybe pack it into boxes and place them end to end.
In a pdf that Hennig linked a few pages ago about EFP penetration into concrete, they caught a few projectiles without much damage by firing them into about 2 meters of styrofoam, 3 meters of vermiculite which I haven't heard of (I think it would be similar to swadust), and a couple of cardboard boxes all wrapped together in bails like you see out the back of shops with a water container behind as a last effort.
Considering that the EFP's had diameters of 110mm and charge weights of 800+ grams this setup did quite well as the slugs never made it into the water, they were all caught in the cardboard.
Very little damage too so the straw would work well.

nux vomica - 14-8-2015 at 03:20

Its looks a bit like threading a needle greenlight, still nice try pity it didn't work, how big was the efp charge.

greenlight - 14-8-2015 at 03:31

Yes it was kind of like that haha, took about 15 minutes to just sight the charge.
I used the exact same EFP dimensions as the last test on steel.
16g plastic/30mm diameter liner/0.9mm Cu/ 60cm standoff.

nitro-genes - 14-8-2015 at 03:32

One pack of straw might be enough to get most of the kinetic energy absorbed for these charge sizes indeed. Maybe a bucket of water placed directly after the straw pack could provide some insurance that it hasn't penetrated the entire pack (else a lot of searching could be done, while the projectile is 1 km further down range

)

It might even be possible to make a standarized setup in which the fired projectile travels throught the straw and ends up at the bottom of the bucket of water and can be simply fished out. Blocks of gassed concrete (the low density stuff)directly after the pack of straw might also do well indeed, good idea!

[Edited on 14-8-2015 by nitro-genes]

nux vomica - 14-8-2015 at 03:34

Had a bit of a failure myself too, running low of etn and going to make new batch on the weekend but wanting to try a bigger efp, I tried a annmal charge its 70% ammonium nitrate 23%nitro methane and 7% aluminium powder, used a cardboard tube with a 140 degree cone and 20 grms annmal setoff with a ebw detonator standoff 500mm and the other side of the 10mm angle as a target.

It didn't penetrate the ten mm angle got almost 9mm through in half of the 13mm dia hole and bulged the back of the plate I am drying the ammonium nitrate as I think its slightly damp being stored for several years and will have another go in the next couple of days nuxy.

[Edited on 14-8-2015 by nux vomica]

greenlight - 14-8-2015 at 03:49

@ Nitrogenes...Yes I think the water is essential as a last ditch effort to ensure that you collect the EFP slug.
I think another problem is to make sure that it does not ricochet off anything as mine just skimmed the inside of the pipe which sent it straight out the side.
I think I will try: box of foam. box of foam. box of wood dust. box of wood dust. box of water.
Hopefully that should do it with minimal damage.

@Nux...What is the VOD of ANNM? 6000-6500m/s?
I have seen CSC's with ANNM explosive that worked but never EFP. I wonder if it is as suitable as (P)ETN which have higher VOD'S.
Sounds like it worked okay though for a non-plastic explosive. I had the same problems when I was using powder HE's as main charge. Used 30 grams once and still didn't get through the damn 7.5mm plate.

Maybe get rid of the aluminium powder, I read somewhere I think that it doesn't work as well in shaped charges. I may be wrong though so don't quote it.

What diameter was your EFP?

nux vomica - 14-8-2015 at 04:05

28 m dia .6 thick 140 degree cone

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