Sciencemadness Discussion Board

Unconventional Shaped Charges

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Microtek - 6-1-2016 at 05:14

Actually, if it follows either a quadratic or an exponential expression, the larger the charge the MORE is gained by increasing the charge weight (the curve gets steeper). This may well be counter-intuitive (and rather nonsensical, physically speaking), but there it is.

Fulmen - 6-1-2016 at 05:22

Not for a shaped charge.

nitro-genes - 6-1-2016 at 08:35

IIRC, shaped charge performance correlates very strongly and linearly with VoD indeed, there should be a graph in PATR somewhere. The non-linerarity in the LBT model is likely an effect of several phenomena earlier mentioned. One thing is that relatively small charge weights are used, if the non-linearity is caused by critical diameter, above a certain threshold (like fulmen suggests) there should be no further increase. From the observed delta observed/expected (linearity from larger test) you might be able to calculate the "missing energy" and calculate back to how much TNT this would correspond and determine critical diameter. :P

The data seems to support a contribution of this effect, since the non-linearity is not observed for MEDINA. Likely, more effects play a role here though, the cavity volume, explosive volume/weight and density used are probably inseparable factors determining the efficiency by which the expansion is realized.

[Edited on 6-1-2016 by nitro-genes]

Microtek - 7-1-2016 at 05:30

Quote: Originally posted by Fulmen  
Not for a shaped charge.


You misunderstand. My point is that if you say that the curve follows an (increasing) exponential curve then it follows that at higher values of x, the relative increase in y increases. It doesn't matter what you are trying to model. The same holds true for a quadratic curve (depending on sign).

greenlight - 8-1-2016 at 03:38

New 30 mm EFP attempt with a 16mm steel plate as the target.
Copper liner was used 0.91mm in thickness.
Charge was 18.5 grams of a new batch of PETN plastic explosive.
Standoff was 60cm.
What's unusual is the damage to the plate with not a full circle of copper splashed around the hole like normal. The plate looks like it has been literally punched through with great force. This time the PE was so dense that the head height was only a little over half the diameter of the charge so this could be the cause as it would make a wider less pointy projectile. Hole diameter is 17 x 18mm in diameter.

[Edited on 8-1-2016 by greenlight]

20160108_181051.jpg - 5.2MB 20160108_191844.jpg - 3.1MB 20160108_185743.jpg - 3.5MB 20160108_185850.jpg - 4MB

[Edited on 8-1-2016 by greenlight]

nux vomica - 8-1-2016 at 04:23

Nice one as usual greenlight but the fracture and the look of the metal in the hole seems almost like cast iron to me.
In the picture of the calipers showing the thickness is the edge of the plate oxy cut ?

greenlight - 8-1-2016 at 04:28

Thanks Nux, I am beginning to think it may be cast iron as well..
All of the targets come from a scrap yard so I just grab whatever steel I can find. This stuff looked exactly like steel.
I don't know if it is oxy cut, how do you tell?


[Edited on 8-1-2016 by greenlight]

O

nux vomica - 8-1-2016 at 05:02

I was wondering as you cant oxy cut cast iron this is a m/s oxy cut.

OxyCutonPlate.jpg - 8kB

greenlight - 8-1-2016 at 06:10

Yeah it does have those similar ripples on the outside surface.
I will have a closer look tomorrow in the daytime.

PHILOU Zrealone - 8-1-2016 at 11:37

Quote: Originally posted by ecos  

I am also interested about this effect of adding metal oxides to accelerate the detonation wave inside EM. Do you know any analytical way to calculate it ? I don't think the patent is mistaken.

This effect may be measured accurately with methods to determine VOD:
-with an oscilloscope device, thus electronically;
-or physically with the Dautriche Test Method (a simple geometric system)
See this document.
And this link p72 Explosives 6th edition by Rudolph Meyer, Josef Köhler, Axel Homburg

PHILOU Zrealone - 8-1-2016 at 11:56

Quote: Originally posted by Fulmen  
Philou: While that is true it's not relevant to shaped charges. Beyond a certain level more explosives has little impact on the performance, so trying to calculate the charge from it's performance alone is impossible.


OK Fulmen, it seems strange to me that it doesn't apply to shaped charges, but I'm open minded :D ;) so do you have a reference, graph or document for me?

Quote: Originally posted by Fulmen  
Quote: Originally posted by PHILOU Zrealone  
I expressed that the dependance is not linear but quadratic.

And you'd be wrong. It's closer to an exponential curve, above a certain value you gain nothing from increasing the charge.

Honnestly, I'm lost, how can it be exponential (or quadratic) and then suddently no more extra energy while increasing the charge? Even for shaped charge, I can understand that hydrodynamic may give weird effect while scaling up, but this may be "arranged" by changing the angle or the charge shape.

Quote: Originally posted by Microtek  
Actually, if it follows either a quadratic or an exponential expression, the larger the charge the MORE is gained by increasing the charge weight (the curve gets steeper). This may well be counter-intuitive (and rather nonsensical, physically speaking), but there it is.

Yes that's what I tried to express...maybe that when large charges are used the quadratic or exponential curve looks like linear...

Quote: Originally posted by Microtek  
Quote: Originally posted by Fulmen  
Not for a shaped charge.


You misunderstand. My point is that if you say that the curve follows an (increasing) exponential curve then it follows that at higher values of x, the relative increase in y increases. It doesn't matter what you are trying to model. The same holds true for a quadratic curve (depending on sign).

I'm also confused by Fulmen sentence...

[Edited on 8-1-2016 by PHILOU Zrealone]

Microtek - 8-1-2016 at 15:14

I think we are simply dealing with a case of the mathematical model only being a good fit in a certain region. A simple expression such as a quadratic or exponential one never model a real-world phenomenon perfectly for all values of the independent variable (since both it and the dependent variable goes to infinity). Maybe a better model would be something resembling logistical growth, with behavior approaching some limit asymptotically. More datapoints are required. At any rate, extrapolating beyond the last datapoint is always shaky ground.

Hennig Brand - 14-1-2016 at 10:17

Yeah, definitely an inverse curve of some kind if performance is on the y axis.

Edit: I am not a math expert but I guess saying inverse curve is kind of ambiguous if a curve isn't specified first. I am thinking of something like the upper half of a parabola opening to the right centered on the positive x axis, increasing quickly at first and then tapering off. Yeah, some sort of exponential curve would seem to be right.

Microtek, I agree and in school I saw that often with the "messier" subjects where complex models with sometimes several (or more) different equations each one corresponding to a separate range of values were used. The course on heat transfer I took comes to mind and some others.

I am having a little fun with this, feel free to correct me if I am wrong. Fairly easy to see that an explosives ability to do work on a liner eventually becomes less and less after a certain point with increased explosive mass for a number of reasons. As the liner is accelerated the relative speed (maybe should say energy level) of the explosive and liner becomes less resulting in less potential for further energy transfer and progressively less efficiency in energy transfer. Once there is enough explosive to satisfy the optimum/efficient head height requirement (for a particular diameter) increases in explosive head height/weight result in smaller and smaller increases in explosive pressure and velocity applied to the liner. Defining what is optimum may be somewhat subjective, but IIRC the point of diminishing return is reached quite quickly for most purposes. For the ultra high performance shaped charges, I think the sometimes massive charges used have as much to do with ensuring a very even, stable and guaranteed maximum velocity detonation zone than anything else (not exactly practical devices).


[Edited on 15-1-2016 by Hennig Brand]

greenlight - 19-1-2016 at 03:24

@ Nux, finally got a closeup of the last target plate.
Do you think it is cast iron or oxycut steel?

[Edited on 19-1-2016 by greenlight]

16mm.jpg - 3.2MB

Fulmen - 19-1-2016 at 04:56

I've kinda lost track of this discussion, but I'm pretty sure I was wrong. Let's start over.
This started with ecos assuming that the explosive charge is proportional to the penetration: http://www.sciencemadness.org/talk/viewthread.php?tid=10575&...
Then PHILOU Zrealone claimed that " the increase of explosion power is quadratic as a function of weight":http://www.sciencemadness.org/talk/viewthread.php?tid=10575&...

There are two ways of looking at this:
1. How charge weight affects penetration for a given liner. Figure 6, page 21 in this document shows the relationship between penetration and explosive height which seems to be logarithmic. But when we look at the explosive with to diameter ratio (figure 8, p.25) we see a fairly linear relationship. So assuming a fixed explosive height the penetration should follow the square root of the explosive charge, at least within a limited range. I think it's reasonable to assume that this will also taper off as the ratio increases.

2. How SC's scale assuming a fixed design. This is much simpler as penetration is proportional to it's diameter while the volume increases with the cube of the diameter. In other words, to double the penetration you would need to double the diameter but the explosive charge would be 8 times greater.

[Edited on 19-1-16 by Fulmen]

Microtek - 19-1-2016 at 08:09

I'm quite sure that we all more or less agree with this; increasing the explosive height improves performance up to a point, but asymptotically so (diminishing returns). I was simply nit-picking. Nice find with the attached report by the way.

Fulmen - 19-1-2016 at 16:04

Nit-picking is fine (I do it all the time), but sometimes it obscures the real issue. In those cases it's usually better to start anew than to figure out just who said what and why they were wrong.

The data on diameter ratio is interesting, but the range is fairly limited. Nevertheless it would be useful to calculate "explosive efficiency" within this range, I'll see if I can get around to it tomorrow. I'm pretty swamped with building a new machine shop and moving the equipment, but it would be a nice distraction from hard labor in freezing conditions.

nitro-genes - 19-1-2016 at 17:14

Regarding the scaling of a fixed geometry shaped charge: What relation would be found when plotting explosive weight against displaced penetration volume instead of penetration depth? My guess would be that newtons law would still apply, and this would again be fairly linear, in other words... a CSC twice the size (needing 8 times more explosive, penetrating twice as deep) displace 8 times more volume upon penetration.

[Editted to make question more clear]

[Edited on 20-1-2016 by nitro-genes]

Fulmen - 20-1-2016 at 01:57

Sorry, I don't understand the question.

Hennig Brand - 20-1-2016 at 04:31

Nitro-genes, assuming equal efficiency, from what I have read I believe you are correct that the relationship between volume of penetration and explosive weight used is directly proportional (for the same explosive). IIRC in "Fundamentals of Shaped Charges", it is stated that for a given explosive charge the volume of penetration is the same for the various shaped charges as well as fragmentation type charges. I have always questioned this, however, because of the different mechanism of penetration between a fragmentation (projectile) and a jetting SC or even a EFP and a jetting SC. A lot of energy can be put into pushing something at slow speed without causing any penetration, or a very little bit of energy at high speed can be used to perform a great deal of penetration. I am assuming the differences between the different types of shaped charges and fragmentation charges are small enough that assuming equal penetration volumes for a given explosive charge is a close enough approximation for most purposes.

Fulmen - 20-1-2016 at 06:39

Nitro-genes: That sounds like a reasonable assumption but I don't have any data on that. At least I can't remember seeing much on hole diameters for SC's as penetration is usually the main goal.

As for explosive width, it appears that an large-diameter (>1CD) charge increases performance. If you look at the data (http://prod.sandia.gov/techlib/access-control.cgi/1988/88179..., Figure 8 & Table VI)
the 1.42CD charge performed as well as as a conventional SC of the same diameter (explosive width =1CD) but with only 80% of the explosive charge.

This makes sense, with the explosive width equal to the liner diameter the end of the liner will have no explosive charge surrounding it.

nitro-genes - 23-1-2016 at 14:01

Henning, you remember what page that was about the volume displacements in FoSC by any chance? Considering the differences in mass/velocity relation between an EFP and CSC would seem counter intuitive to have the same volume displacement indeed.

Also target effects are likely different, the jet of a CSC moves so fast, the collision behaves nearly completely fluid, similar to a stream of water hitting a mudbank as I understand it. Forces are exerted to all sides from the colliding jet tip, like a fluid would, pushing the target material out of the way and even creates a "backward" stream of liner/target material that is expelled from the formed canal. So not all energy is transferred to the target and seems different from an EFP impact indeed. Wondered if you would weigh the target before and after firing, how much of the target material would be gone, though, the liner will also deposit material of course, making this hard to determine.

[Edited on 23-1-2016 by nitro-genes]

greenlight - 24-1-2016 at 03:31

@Nitro-genes, I think you have the jet behaviour spot on. I was just looking through Intro to technology of Explosives by Paul Cooper and found this:
"The erosion of a target by a penetrating jet is very similar to what one sees when a stream of water from a hose is directed into a bank of dirt. Material dislodged at the deepest part of the hole turns to mud and flows back along the walls of the hole.
Metal targets under shaped-charge jet attack behave like fluids because the impact velocities of the jet are at several megabar's pressure, well into the plastic region for almost all materials. This erosion process continues until the entire jet has been used up or the target has been perforated."

I think that this effect would happen to a certain degree with an explosively formed slug contacting and penetrating a steel plate. I have two picture of an EFP right as it has contacted the steel target. The first shows the initial position of the charge and the first contact with the plate and the second is right after this moment. The material being thrown back from the impact point must be from the slug and target plate and is a somewhat similar effect to what is described above.








[Edited on 24-1-2016 by greenlight]

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[Edited on 24-1-2016 by greenlight]



[Edited on 24-1-2016 by greenlight]

Screenshot_2016-01-24-19-12-37.png - 2.2MB

magicchemist - 24-1-2016 at 07:36

Hi everyone,

I made last week 10gr of plastic (PETN/RDX) with this ratio: 85% HE/10% PIB (from self amalgamating)/5% motor oil (5w40). My plastic is modelable but it's not like Play doh. It's little bit hard. Someone would have an advise to ameliorate the quality, please ? Thank you very much.

1453649759-dscf3027.png - 82kB

[Edited on 24-1-2016 by magicchemist]

[Edited on 24-1-2016 by magicchemist]

greenlight - 24-1-2016 at 08:28

Don't know if your question is in the right section but how long did you roll it for?
I have a similar formula myself and roll for 3 to 4 hours to get the density up. It doesn't really matter if its not super soft and moldable. Commercial semtex is about 20% binder and plasticizer so the softness comes from the extra inerts I suppose.
I used 20% binder/plasticizer once and got it much more moldable but the explosive lost power and didn't perform as effectively in SC.

[Edited on 24-1-2016 by greenlight]

magicchemist - 24-1-2016 at 08:52


I roll until all gasoline is evaporated (3-4 hours).

nitro-genes - 24-1-2016 at 15:37

@greenlight, nice still shot there, btw... you wouldn't happen to have an e-version of the book by any chance? :)

greenlight - 24-1-2016 at 21:16

Unfortunately, I only have the book as an actual hardcover for the bookshelf:(

Hennig Brand - 26-1-2016 at 09:18

Quote: Originally posted by nitro-genes  
Henning, you remember what page that was about the volume displacements in FoSC by any chance? Considering the differences in mass/velocity relation between an EFP and CSC would seem counter intuitive to have the same volume displacement indeed.

Also target effects are likely different, the jet of a CSC moves so fast, the collision behaves nearly completely fluid, similar to a stream of water hitting a mudbank as I understand it. Forces are exerted to all sides from the colliding jet tip, like a fluid would, pushing the target material out of the way and even creates a "backward" stream of liner/target material that is expelled from the formed canal. So not all energy is transferred to the target and seems different from an EFP impact indeed. Wondered if you would weigh the target before and after firing, how much of the target material would be gone, though, the liner will also deposit material of course, making this hard to determine.

[Edited on 23-1-2016 by nitro-genes]


Had to do a little back tracking in this thread. Found it!
http://www.sciencemadness.org/talk/viewthread.php?tid=10575&...

cast iron

Laboratory of Liptakov - 27-1-2016 at 11:24

Greenlight, congratulations. But:
Cast iron is much less firm. Especially on impact is low. If the tanks were made of cast iron, a big steel mallet would be enough to break apart. It are not same conditions for attempts. At drilling cast iron, arises grain. At drilling steel, arises long metal chips. Cast iron has high content carbon. About 4%. Steel only about 1%. From cast iron grain, you will be dirty the fingers from carbon. As from pencil. You can try and see. Therefore is hole crushed as ice. So as so, nice a piece of work. And beauty photos.
Dr. Liptakov

nux vomica - 27-1-2016 at 21:36

Quote: Originally posted by Laboratory of Liptakov  
Greenlight, congratulations. But:
Cast iron is much less firm. Especially on impact is low. If the tanks were made of cast iron, a big steel mallet would be enough to break apart. It are not same conditions for attempts. At drilling cast iron, arises grain. At drilling steel, arises long metal chips. Cast iron has high content carbon. About 4%. Steel only about 1%. From cast iron grain, you will be dirty the fingers from carbon. As from pencil. You can try and see. Therefore is hole crushed as ice. So as so, nice a piece of work. And beauty photos.
Dr. Liptakov


Your right there liptakov here is a photo of the differance
Between steel and cast iron when its drilled

20160128_162335.jpg - 1.3MB

Cheers nux.

cast iron

Laboratory of Liptakov - 27-1-2016 at 23:50

Well, we everybody thanks for this photo. Clearly different material. Doc....:-)

greenlight - 28-1-2016 at 08:48

Thanks guys, celebrated too early:)

New target next time i think, I have a 19mm plate that has been hit 3 times with a 30mm EFP and I haven't been able to get a penetration yet (nothing worth posting).
I think a 40mm EFP might be in order...

nitro-genes - 2-2-2016 at 05:29

Thanks for looking up that chart of volume displacements for different charge types Henning. Curious how they measured 300 individual hole volumes for the fragmenting charge. Considering the difference in surface area between the flat cone SC and the fragmenting charge, it would seem the fragmenting charge would transfer considerably more energy to the witness plate, would seem that above a certain headheight the energy transfer to the liner in the flat bottom CSC is not transfered miraculously all to the liner, so my guess would also be that this has to be taken with a grain of salt indeed. :)

[Edited on 2-2-2016 by nitro-genes]

liner

Laboratory of Liptakov - 2-2-2016 at 07:21

40mm diameter of liner? Huuh...:o heavy caliber. How will be thick copper concave? Thanks, Im curious. LL ...:cool:

greenlight - 2-2-2016 at 17:58

Yeah, I think I need to step it up after hitting this 19mm plate with three 30mm EFP's of varying charge weights and only getting half to 2/3 through the target and in the case of the larger charge, the start of liner breakup.

I will be using 1mm thick copper and using the dapping tool I have and the 40mm side, I think the concave (dish) will be around 6 mm deep. I am curious to see result as well, will be uploaded soon as a new batch of PE is made.

ratio EFP

Laboratory of Liptakov - 3-2-2016 at 03:02

Thanks green, 1 mm copper? Hmm... It is maybe thin plate. Of course, working will be it always. But transfer energy on target can be weakly. Maybe using soldering 1+1 mm Cu. I somewhere spend data for counting EFP assemble. Therefore I only estimated. So as so, I am curious. Height of cylinder explosive is same as diameter, it is usually basic. Thus 0,8 - 1,2 from diameter. But counting of ratio for thick of liner and his depth no and no find. LL...:cool:

greenlight - 3-2-2016 at 03:50

1mm is the only copper plate I have at the moment. If it is not sufficient, I will use thicker.
Are u suggesting to use 2mm as the copper liner thickness?
I do try and keep the head height of the explosive the same as the diameter of the liner but with the last two batches of plastic explosive, they have only been 1/2 to 2/3 the diameter of the liner due to the higher densities from extended rolling to improve performance.

Hennig Brand - 3-2-2016 at 07:38

Quote: Originally posted by nitro-genes  
Thanks for looking up that chart of volume displacements for different charge types Henning. Curious how they measured 300 individual hole volumes for the fragmenting charge. Considering the difference in surface area between the flat cone SC and the fragmenting charge, it would seem the fragmenting charge would transfer considerably more energy to the witness plate, would seem that above a certain headheight the energy transfer to the liner in the flat bottom CSC is not transfered miraculously all to the liner, so my guess would also be that this has to be taken with a grain of salt indeed. :)

[Edited on 2-2-2016 by nitro-genes]


No problem, I find it interesting too. Those values in the chart are estimates, just how much I don't know. I have made quite a few small shaped charges, but I still find my understanding pretty basic and probably inaccurate in many ways.

This is just the first reference I found in minutes.
From, "Shaped Charges Pierce Toughest Targets":

"A shaped charge, by design, focuses all of its energy on a single line, making it very accurate and controllable. When size is added to that accuracy, the effect can be dramatic"

This says two things which we already know:

1. Shaped charges focus the explosive energy into the liner, not omnidirectionally like in most fragmentation type charges.

2. Given a certain accuracy large shaped charges will perform much better (it is much harder to make efficient the tiny shaped charges that we make!). Being off by 1 mm in a shaped charge with a 25mm dimension is much worse than being off by 1 mm in a shaped charge with 500 mm for the same dimension. It may say things about other improvements in efficiency/effect as well with larger charges.

In a simple energy conversion situation (ex. such as when electrical energy is made from some sort of mechanical energy, then transferred, then stored, then transferred, then converted to mechanical energy again, etc, etc) all of these processes have a certain efficiency. The overall efficiency for the process is the product of all those efficiencies. It is easy to see with even small inaccuracies that the overall efficiency could get very low. Lets say we have 5 variables/processes and they are all 90% efficient, 0.90 * 0.90 * 0.90 * 0.90 * 0.90 = 0.59 or only 59% efficiency overall. I assume it would be the same type of situation with shaped charges.


Attachment: Shaped Charges Pierce Toughest Targets.pdf (334kB)
This file has been downloaded 553 times



Thought I might make one or two more comments here.

Quote: Originally posted by nitro-genes  
Henning, you remember what page that was about the volume displacements in FoSC by any chance? Considering the differences in mass/velocity relation between an EFP and CSC would seem counter intuitive to have the same volume displacement indeed.

Also target effects are likely different, the jet of a CSC moves so fast, the collision behaves nearly completely fluid, similar to a stream of water hitting a mudbank as I understand it. Forces are exerted to all sides from the colliding jet tip, like a fluid would, pushing the target material out of the way and even creates a "backward" stream of liner/target material that is expelled from the formed canal. So not all energy is transferred to the target and seems different from an EFP impact indeed. Wondered if you would weigh the target before and after firing, how much of the target material would be gone, though, the liner will also deposit material of course, making this hard to determine.

[Edited on 23-1-2016 by nitro-genes]


I believe most of those losses, especially in full sized devices, would be fairly minor in comparison to what is transferred to the target. The author did use the term approximation, or approximate, at least once or twice I believe also. I also think that once above the pressure needed to cause plastic deformation in the target that the amount of energy needed to remove material, or most often push material out of the way, is likely fairly consistent even as pressure increases well beyond this lower limit.


[Edited on 3-2-2016 by Hennig Brand]

recounting EFP

Laboratory of Liptakov - 3-2-2016 at 08:40

Well, understand. 1/2 from dia is low height of cylinder. Here is original assemble the scheme from factory. Original scheme is black, my write is red. Thus: we have 19,05 mm diameter, for Copper thickness 0,505 mm. But We need counting thick liner from flat. No from line. Thus, Pí r2. = 19,05 is flat 2,85 cm2. But Dia 4 cm is flat 12,56 cm2. Next: 0,505 mm is good for 2,85 cm2. And for 12,56 cm2 is good thick 2,22 mm copper plate. ( 0,505: 2,85 = 0,177 x 12,56 = 2,223) Thus index is thick 0,177 mm on one and every cm2 of flat large. 4cm diameter = flat (radius x radius x3,14) = 12,56 x index 0,177 = 2,23 thick of copper. And next important is of course height of cylinder. In scheme 86% from diameter. However is there still PETN, which creates 15 % from all amount of charge. But also height of cylinder, partially. After recounting it is almost precise height = diameter. From this reasons, I recommended thick of liner minimal 2 mm, for dia. 4cm. Because professional engineers (from factory on EFP) know what they do it.

recounting.jpg - 195kB
Dr. Liptakov

greenlight - 3-2-2016 at 21:51

Thanks LL...
The head height of explosive is usually closer to 2/3 diameter of liner. It is hard because density of my PE is about 1.4-1.44 g/cm3 and the optimum charge weight I have found for 0.91mm liner is about 17-18 grams. This amount only comes up about 2/3 high when pressed into the charge casing. If more explosive is used like last time with the 19mm plate 20 grams was used and resulted in more breakup of the liner and not a good hit on the target.

I think you are right about the thicker liner and I will increase the thickness for the 40mm EFP.
Maybe even 30mm calibre EFP could benefit with a better effect on the 19mm plate if liner is thicker and charge weight increased slightly.

[Edited on 4-2-2016 by greenlight]

Microtek - 4-2-2016 at 02:18

If the liner breaks up with more explosive, then I think that is an indication that a thicker liner should be used (at least if you have ruled other factors, such as imprecisions in the symmetry, out).

greenlight - 4-2-2016 at 03:08

The liners are made with a dapping block and rounded by being rotated on a bench grinder until the exact diameter is reached so they are quite symmetrical.
I have hit the 19 mm plate with 3 EFP's so far of 30mm diameter and liner thickness 0.91mm and the maximum penetration I have achieved is 12.5mm.
Thicker liner it is then, I will try a 1.2mm and 1.5mm thick liner before moving on to the 40mm size charge.

Hennig Brand - 4-2-2016 at 07:48

Getting the right liner thickness was definitely my biggest stumbling block. In my case though I was using liners that were too thick for the diameter, and other aspects of the configuration, so they weren't narrowing and elongating the way they needed to in order to produce good penetration. A fraction of a mm difference in liner thickness is a much larger proportion than the same fraction of a mm in liner diameter. Making these small charges work right can be tricky business. On the plus side, they don't use a lot of expensive resources and tend to be less dangerous than the larger charges.

Hybrid efp shaped charge

nux vomica - 22-3-2016 at 01:20

I had 8 grams of plastic etn that was getting old so i tried a 19mm dia hybrid efp i used 80mm standoff and my standard ebw setup .
I got a nice shaped entry hole and 28mm penetration with a 3mm dia hole, not great but there is .chance of more penetration wit more tests ;).

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[Edited on 22-3-2016 by nux vomica]

greenlight - 22-3-2016 at 10:35

Nice to see another test from you, over an inch of penetration is very good.
The entry hole looks like an EFP hit but the penetration is like the effect from an actual jet.
Is it possible that your device functioned as both at once with a combined effect of a large entry with deep penetration.
Very interesting.

nux vomica - 22-3-2016 at 13:46

Quote: Originally posted by greenlight  
Nice to see another test from you, over an inch of penetration is very good.
The entry hole looks like an EFP hit but the penetration is like the effect from an actual jet.
Is it possible that your device functioned as both at once with a combined effect of a large entry with deep penetration.
Very interesting.


Thanks greenlight , it looks like it is forming a jet but the edges of the disc collapse in and form a small efp at the same time.
I cut the plate stack to show penetration each plate is 10mm thick.
Nux

20160323_074830.jpg - 573kB

NeonPulse - 22-3-2016 at 15:43

Very nice! I was wondering when this thread would revive. How was it a hybrid?

nux vomica - 22-3-2016 at 16:16

Quote: Originally posted by NeonPulse  
Very nice! I was wondering when this thread would revive. How was it a hybrid?

Thanks neon , its has been a bit quiet lately , i called it a hybrid as it should be forming a efp projectile only, but it forms a jetting affect like a cone shaped liner instead .
So it seems to be in a transition point between a efp and a liner that forms a jetting affect.

This is my other use for hybrid cones.

images.jpg - 16kB

[Edited on 23-3-2016 by nux vomica]

NeonPulse - 16-4-2016 at 20:29

So it's been a while since this thread has had a post so here goes: Recently I did a test of a cyclotol/pentolite composition in a shaped charge. An electroformed liner I had made some time ago was jb welded into a piece of stainless steel tubing with a wall thickness of 1.5 mm. A snug fitting plastic cap used on steel tube furniture was the cap and it was filled with steel epoxy putty and drilled dead centre for the cap. The cone thickness was 1.5mm thick.Also the angle was steeper than I usually go as an experiment. I didn't actually measure it though but I didn't think of that until after it was in place.oops. I also had annealed the copper first which I also don't usually do either. A bit of 40 mm PVC was standoff and a couple of wraps of tape around the charge and it fit snugly inside.
I chose a X1.75 CD as the standoff distance this time.

For the filler I decided to use a 75g casting consisting of 40g TNT, 20g RDX and 15g PETN. The fine powder TNT was mixed with the other two components and this was melted together in a small beaker in a hot water bath with the casing submerged also. The molten mixture was then poured into the hot casing which was then tapped gently on the floor to release any trapped air bubbles and a small glass test tube was put in the centre held there with a couple of skewer to make a cap well and then it was allowed to cool slowly in the hot water bath over the next hour and a half.
The heating was gradually bought up over a period of around 20 mins and This was done at no hotter than 84c. There appeared to be little shrinking and no visible cracking was seen in the cast. An aluminium cap was constructed filled with 1g RDX,300 mg Azo-Clathrate and a further 150 mg lead styphnate as the igniter to be set off electronically.

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NeonPulse - 16-4-2016 at 21:07

Continued: some loose packed PETN was used to fill the cap well and to Fill the spaces in the top of the cast and to fill the gap between the cap and cast. At the site a hole was dug and the charge was duct taped to the sledge hammer head and place into the hole and earth was packed around it,the cap was placed in the cap well and the whole thing buried. Firing line was connected and from a safe distance behind a large tree I heard the dull thud and dirt showering the ground. Great. The anticipation of digging through the crater for the target was great.

This charge had Successfully penetrated the target to a brilliant 110mm of solid steel plus the air gap. 65mm through the first section and the jet and carrot continued through to the second section for another 45mm exiting out the side on an angle.
I think if the jet was straight it wi old have gone clean through both ends no problem. I was thrilled! All the effort of ensuring everything was done as carefully as possible payed off.
On looking at the hole there was very little splatter and no raised edges at the entry, it was pretty clean. The carrot was plugged in tight and I had to poke it out through the exit it was like a little copper spear.

All in all it was a great attempt and I would say a complete success with just over 3CD penetration. The Cyclotol/pentolite combo worked very well along with the dirt tamping. This is by far the most penetration I've gotten out of all the tests I've ever done, I thought it would be hard to beat the last effort.

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nux vomica - 16-4-2016 at 23:33

Nice job neon , looks like there was some more penertration if the jet hadnt come through the side of the target .

Microtek - 17-4-2016 at 07:48

Perhaps you could try it with a higher RDX/PETN content. Cyclotol is usually around 75 % RDX. Of course, not all the RDX will dissolve in the TNT.

NeonPulse - 17-4-2016 at 17:08

Quote: Originally posted by Microtek  
Perhaps you could try it with a higher RDX/PETN content. Cyclotol is usually around 75 % RDX. Of course, not all the RDX will dissolve in the TNT.


I plan to now I know that casting it is not as difficult as I thought. I had tried a 50/50 pentolite before and it was a co-precipitation of TNT and PETN which took a while to melt properly. Not only that but I only had 40g of RDX left and did not want to use it all in that charge. It would be a while before I can test it again since I'd have to distill more nitric for an RDX batch and to make another cone like the one I used. Maybe I'll try a waveshaper to cut the amount of HE needed. Maybe even a smaller charge. I do have a couple of other cones I could use too.

gnitseretni - 19-4-2016 at 18:16

Nice one Neonpulse!

Those electroformed liners work pretty good huh?! And they're easy to make!

electroplanting

Laboratory of Liptakov - 20-4-2016 at 01:41

Electroplating of copper cone? Very interesting question. Maybe same interesting, as result, thus the long hole. Some electro device we will see? WE are curious...:cool:...LL

NeonPulse - 20-4-2016 at 04:50

Quote: Originally posted by Laboratory of Liptakov  
Electroplating of copper cone? Very interesting question. Maybe same interesting, as result, thus the long hole. Some electro device we will see? WE are curious...:cool:...LL


They work very well but require a little effort to produce. The guy who posted above you here Gnitseretni came up with the idea and even wrote up a PDF about it. It is very simple and reproducible. No special equipment needed but a cell phone charger or other power supply. There's a whole thread about it in technochemistry thread. I think it was called "electroforming copper liners" or something like that.

Laboratory of Liptakov - 20-4-2016 at 11:14

Thanks Neon, will be study....:cool:...LL

Hennig Brand - 21-4-2016 at 16:37

Very interesting test. You took the time to do good work and it definitely paid off. Shaped charge experiments involving cast explosives, especially TNT or mixtures with it, are very interesting I find. Yeah, electroforming is a decent option for making copper liners for the hobbyist in my opinion as well.

greenlight - 8-8-2016 at 23:05

That is a very nice result NP!
I like how you could recover the copper jet/carrot.

I am in the process of designing a EFP with a diameter of 39mm to penetrate 20mm steel. The pipe casing inside diameter was supposed to be 40 mm but upon measuring it, it is slightly smaller.
I have 1.1mm thick Copper sheet and 1.85mm thick copper sheet. Before I cut and shape the liner, I was wondering if anyone had any suggestions on which thickness would be better?

[Edited on 9-8-2016 by greenlight]

[Edited on 9-8-2016 by greenlight]

NeonPulse - 11-8-2016 at 17:20

Why don't you try both? I would probably go the thicker of the two. Just anneal it nicely and it should be fine. 40 mm is nice and wide and no doubt you will be using a highly brisant explosive. 40 mm is wide enough to consider trying a waveshaper to ensure a nice evenly formed slug and slam through the test plate.

greenlight - 11-8-2016 at 21:13

Thanks, I will try the thicker copper plate for the first test and yes explosive will be PETN plastic explosive with minimal inerts.
I will attempt using a waveshaper after the I see how the first test goes.

Zyxel - 23-9-2016 at 13:20

Hi, Im new here.Today I lathe small shaped charge.Tomorrow will be tested.

Cone diameter is 24 mm, height 30mm thickness 1mm, cone angle is 42° .

Cone material is brass.

I use genuine military grade plasticized PETN, 40 gram.

Detonator is military grade, I aded electric match.

Casing tube is from LED flashlight, material aluminium, thickness 1mm.

Standoff is 85mm.

Target is 145mm mild steel plates.







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nitro-genes - 23-9-2016 at 13:25

Your plastique looks like a potato...stealth plastique? Nice looking cone! Was it spunformed or machined, why brass btw?

[Edited on 23-9-2016 by nitro-genes]

Zyxel - 23-9-2016 at 13:34

My plastiqe and detonator is from Yougoslav M75 hand granade.Cone is machined in lathe.I dont have copper so I use brass.
Velocity of detonation is 7800m/s.

https://www.marstar.ca/html/reflibrary/YugoOrdnance/handgren...

MineMan - 23-9-2016 at 15:10

nice, please post pics of the result!

NeonPulse - 23-9-2016 at 16:43

I think I remember brass doesn't work very well for liners. Still a nice looking charge though. Is that an old torch?

greenlight - 23-9-2016 at 21:35

Hmmm, brass, will be interesting to see the results.
I would say the same as NP that brass liners wouldn't afford much penetration compared to copper.
I had a quick look for documents with tests and found this pdf were the penetration of different shaped charge liners was tested in granite. On page 56 in the conclusions section, it says that "copper and brass liners gave equal penetration for 42 degree apex angles".
I am sure copper is still superior to brass so maybe this was just an effect seen when penetrating rock and copper take the lead in metal targets.


BTW: I finally put together a 40mm EFP, took it out and fired it but the detonator was inferior and didn't give enough shock for the PE to go high order.
It sounded like a loud firecracker instead of a HE and scattered bits of PVC pipe from the casing around proving it was indeed low order. I still don't know what caused it , I did use some very old PETN for the base charge in the det so that may be it. :(



[Edited on 24-9-2016 by greenlight]

[Edited on 24-9-2016 by greenlight]

Fulmen - 23-9-2016 at 23:39

I've been wondering about brass as well, but so far I haven't found much data on it.
Copper works, but it machines like crap and can be hard to find. Brass has roughly the same density and melting point, and while not as ductile as copper it's not bad either.

greenlight - 24-9-2016 at 00:12

I just use the copper pipes sold at hardware stores, cut through one side, anneal and flatten them, cut out a rough circle and shape it on a bench grinder.

One thing that is different is that copper has a high speed of sound than brass by about 1000 m/s I think which may make the copper behave better than brass under the extreme pressures of an SC.

Zyxel - 24-9-2016 at 14:43

Here are results penetration is 15,5mm.I think cone is not good centered or explosive is not equally pressed.
But explosion make big holes in concrete blocks.

I found this chinese company that manufactures tungsten copper alloy liners.I asked they to manufacure one for me with same dimension as previous brass cone but they cant manufacture so thin (1mm) liner.I cant test bigger liners.If someone will try these tungsten copper allyo liner can ask they to make bigger liner.

This is company: http://www.tungsten-alloy.com/shaped-charge-liners.htm




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[Edited on 24-9-2016 by Zyxel]

nux vomica - 24-9-2016 at 23:13

Nice maybe useing a 60° cone would be a less difficult to set up , i didnt have much luck with 42° cones , i had better forming jets useing the 60° ones .


[Edited on 25-9-2016 by nux vomica]

Microtek - 26-9-2016 at 00:29

With non-zero manufacturing error, brass could prove to be better than copper. Since copper is difficult to machine on a lathe (apart from spinning which introduces torsion in the jet), and brass is not, using brass for the liner could produce cones with micrometer precision.
Since this is not possible with handmade cones of copper, maybe it would be advantageous to go with brass.

nux vomica - 26-9-2016 at 02:32

Quote: Originally posted by Zyxel  
Hi, Im new here.Today I lathe small shaped charge.Tomorrow will be tested.

Cone diameter is 24 mm, height 30mm thickness 1mm, cone angle is 42° .

Cone material is brass.

I use genuine military grade plasticized PETN, 40 gram.

Detonator is military grade, I aded electric match.

Casing tube is from LED flashlight, material aluminium, thickness 1mm.

Standoff is 85mm.

Target is 145mm mild steel plates.







Just looking at the photos again and i notice the detonator is in the charge a long way i wonder if you should of only let it enter the charge 2 or 3 mm so as to give you more head hight and give the detonation wave more time form correctly .
Nux





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[Edited on 26-9-2016 by nux vomica]

Zyxel - 2-10-2016 at 11:27

Hi, new test cone.

Cone diameter is 34 mm, height 26mm thickness 1,5mm, cone angle is 60° .
Cone material copper.
Explosive 34 grams.

Does is better to put detonator depper or shallower in explosive.


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greenlight - 2-10-2016 at 21:35

I agree with what Nux said, place detonator as shallow as you can so as to allow maximum head height for a nice detonation wave to form before it interacts with the cone tip.
Also make sure the detonator is well centered.


Zyxel - 3-10-2016 at 17:10

Detonator protrudes only 4mm in explosive.What is best standoff.I use 3,5 CD.

Would beryllium copper made better results?






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nux vomica - 3-10-2016 at 17:53

Quote: Originally posted by Zyxel  
Detonator protrudes only 4mm in explosive.What is best standoff.I use 3,5 CD.

Would beryllium copper made better results?







Looking good Zyxel 4mm is plenty of depth.
Pure copper is fine.
3.5 is a good starting point you could try 4 x if you have machined the cone with precision and your build alignment is accurate at least the charge and det are military so that is going to work ok and not skew the results.

[Edited on 4-10-2016 by nux vomica]

Zyxel - 3-10-2016 at 18:54

Problem is that cone is not precision manufactured because man that made it for me dont have skill to made precise cone.
Which is best distance for non precise cone.

nux vomica - 3-10-2016 at 22:01

Quote: Originally posted by Zyxel  
Problem is that cone is not precision manufactured because man that made it for me dont have skill to made precise cone.
Which is best distance for non precise cone.


3.5 to 4 cone dia is a safe bet .

NeonPulse - 4-10-2016 at 16:59

Nice looking cone but I would shorten the ring of unused material at the base of the cone to get more explosive in the tube if you fit it flush like your picture. The excess copper will hinder the collapse of the cone lowering its performance.

You only need the detonator just into the plastique enough to ensure it will fire otherwise it looks like you will get a pretty good result. It will be good to see the results.
You are lucky to have the right machinery or knowing someone who does ;)

Zyxel - 5-10-2016 at 08:16

I use ring of unused material at the base of the cone for easier centering the cone against wall of tube.Without it is more difficult to center cone.

Here are my baies form which I use explosive and detonator.






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Bert - 5-10-2016 at 20:03

I am somewhat surprised at your source of raw materials.

And the open display of them in a public forum. I assume you were not just freely given those frags by your local army. Did they just "fall off a truck"?


Zyxel - 6-10-2016 at 13:11

Bro I live in shit hole state called Bosnia and Herzegovina, there was war 20 years ago.And here rules anarchy.You can buy any weapons(explosvie,ak-47,rocket launcher,ATGM, MANPAD Strela 2M missile etc.) like you buy a patato in store.
I dont use weapons to harm peope I use it for experiments,its better that this handgranade is used in shaped charge project or to kill somebody.

Fulmen - 6-10-2016 at 13:15

I call that controlled destruction of military ordnance. He should be payed for his work.

Bert - 6-10-2016 at 17:54

After identifying those grenades as leftovers of or reproductions of the Yugo M-75, I understand that these DO fall off the truck, have been falling off trucks for several decades, and are found throughout EU (and the rest of the world) wherever sketchy, violent and mercenary people are.-


Bert - 7-10-2016 at 05:18

Quote: Originally posted by Zyxel  
Bro I live in shit hole state called Bosnia and Herzegovina


Република Српскa?

Zyxel - 7-10-2016 at 11:06

No, Im in entity Federation.

Zyxel - 8-10-2016 at 12:46

Here are results. 39mm of penetration.Two scews that hold that together borke and bent, some holes also bent.Aluminium ring that hold detonator is 10mm thick but I find only 4 fragments from him.
Interesting is that on first plate is seen impact of cone copper ring that I use for easier centering of cone.His impact only leave light mark.But it is not round it is deformed.The same problem as the previous cone, not consistent explosive desinty or not good centered/machined cone.But Im happy.







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NeonPulse - 8-10-2016 at 18:15

Did another test yesterday again with pleasing results.
I had a tiny cone I had around and decided to set it into a copper pipe reducer fitting of 25 mm
The cone was epoxied in place about a week ago so it was well set.
The filling was a cast 2-5 PETN/ETN mixture developed Mr anonymous... this was achieved by melting 4g ETN in a small plastic medicine cup and gradually introducing 10g PETN into it with stirring.
The charge casing was also warmed in the water bath and the liquid explosive was poured in.
The weight of cast filling was 12.7g. Standoff was 50mm 2x CD.
the target was a cylinder of 420 stainless steel and the charge penetrated nicely going into it 61mm deep with a 13mm entry hole.
Given the small amount of explosive and the small diameter of the cone I would call this a pretty good success.

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[Edited on 9-10-2016 by NeonPulse]

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greenlight - 9-10-2016 at 12:07

@NP, nice test!!
That is a decent result for the amount of explosive used and the size of the charge.
You should make a much larger version next time and go for a forum penetration record haha.

@zyxel, I still find it funny how most people on make their own explosive and dets but this guy takes apart frags to get his materials.
I can't figure out the huge entry holes on the first three plates. They are jagged and very big compared to the usual small mostly circular hole's seen from conicals SC'S.
It is decent improvement over the first one though.
Maybe the cone deformed faster on one side than the other or something when forming the fluid-like jet or it could have something to do with the extra copper on the base of the cone which you use to centre it in the casing?

NeonPulse - 9-10-2016 at 16:55

It looks like the jet was skewed off and entering at an angle giving the odd shaped entry. The excess ring at the base of the cone probably caused this. Off central initiation will cause it too.


And the record belongs to NUKE but his cone was so perfect it was suspected to have come from an anti tank round or similar. He used a whopping 1.5kg of PETN and NG in combination so it is no wonder he holds the record. I have 110mm which is second or third place and I will be trying to beat that since I still have these guys to use. I just need to go to the scrap yard and find a decent target and synth a bunch more PETN and EGDN to fill it with.:D

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greenlight - 10-10-2016 at 01:36

I think I saw his results on here before I joined and there was a dispute about whether it was wood or steel target material.
That is a huge charge weight though!!

Can't wait to see the results of the cones in the pictures you uploaded. What is the diameter of them? Its hard to judge with the tape in the photo


[Edited on 10-10-2016 by greenlight]

Casting copper for cones.

nux vomica - 13-10-2016 at 17:27

Thought i would share a idea i had recently after seeing zyxel machined copper cones and not wanting to buy round stock to fabricate cones from because of the cost of the material.

I decided that casting a rough form and machining that back would work ok as long as the copper was not full of porosity holes.

The copper is from old coins and i used the sand casting method and melted the copper in a graphite crucible in a pocket i cut in a soft fire brick and a oxy torch to heat it up.


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The copper casting machined ok and i have made 3 cones so far , i need to redesign the mold to cut down on the amount of copper per pour as well as i need 56 grams to make a 6 gram 20mm diameter cone.



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Now to test one out.





[Edited on 14-10-2016 by nux vomica]

greenlight - 13-10-2016 at 19:05

Nux, that looks fkin sweet, I've never thought of actually melt-casting liners at home haha. The final product came out beautiful especially for a first design.

Whats the wall thickness on those cones?

nux vomica - 13-10-2016 at 20:24

Quote: Originally posted by greenlight  
Nux, that looks fkin sweet, I've never thought of actually melt-casting liners at home haha. The final product came out beautiful especially for a first design.

Whats the wall thickness on those cones?


The one i am going to shoot is 1mm and the one in the pictures is around 0.8 mm.

greenlight - 13-10-2016 at 21:20

Interesting, I look forward to the results.
I am well overdue for testing as well. Last time I went out after spending a couple days crafting the 40mm EFP, the det failed and the explosive went low order barely fragmenting the PVC casing.

Good luck

nux vomica - 13-10-2016 at 23:09

Thnx Greenlight

I am also trying a new etn mix i noticed that the wax off miny babybell cheese whent quite soft from kneeding it in your hands so i made a 8% wax 92% etn mix by melting the wax in a hot water bath and mixing in the etn it mankes a crumbly mix that compacts well.


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I mistakenly deleted some of the assembly photos but this is the cone i am useing for the first test the inside has some marking on it from it spinning on the arbor during machining ,the casting i used for this cone looked rough but it cut ok and has a good finish.
The i/d of the cone is 19mm and its 1mm thick.



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I am trying a detonator that the petn is made from homemade pentaerythrol, ive had some tests and it seems to be as good as petn made from ebay pentaaerythritol so this is the big test which is 110mm of steel.

greenlight - 13-10-2016 at 23:46

The wax from the outer coating of cheese, thats new.
The 8% inert shouldn't matter much at all, C4 has 9% and semtex has something like nearly 20% from memory.

Very interested to see how that cone goes, make sure to upload results.

nux vomica - 14-10-2016 at 05:19

Haha even though the first steel block blew off when the welds holding it broke and dissipated the jet before the jet was finished doing its work, i got 78mm penertration into the target (4.10 × cone diameter ) the entry hole is almost perfectly round so the cone collapsed equally and the bottom 30mm of the hole was plugged with copper.

The detonator had 1.2 grams of petn set off by lead azide, The main charge was 17.4 grams of etn wax , cone angle of 60° and dia of 19mm , wall thickness of 1mm and standoff of 50mm ( 2.63 cone dia ). Cheers nux


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[Edited on 14-10-2016 by nux vomica]

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