Unconventional Shaped Charges

Quote: Originally posted by watson.fawkes

On the other hand, it might be more, because a small block might act like a thinner block, more flexible and getting out of the way.

Did another shaped charge. But it was a failure. Wasn't nearly as loud as it shoulda been. I think I know what happened. The detonator was too short, too little stuck out underneath the 3/4" thick cap that I turned from MDF to center the detonator. I thought about turning a concave cavity on the inside of the cap, but no.. numbnuts (me) was too impatient!!
I'm quite pissed off at myself as I had high hopes for that beautiful shiny liner that I turned on my lathe to a uniform wall thickness of 0.95mm. And now it's gone

http://youtu.be/KXVbMwotE9g

Well here are a few pictures from a shaped charge experiment. Performance was nothing to brag about, but I learned a few things.
The liner was a 1.5" ID, 60 degree angle copper cone with ~2% CD wall thickness. Standoff was 1.5 times CD. Charge head height was only about 1 CD. If I had more explosive prepared, 1.5 times CD or more for charge head height would have been better.

Charge was 114g of 16% inerts ETN platique, with a density of ~1.43g/cc. Initiation was accomplished with 1g PETN base charge, 0.3g lead azide and basic lead picrate flash igniter in aluminum tube & ignited by fuse.

That small hole in the last steel piece actually goes more than half way through. Total penetration was ~1.88 inches or ~1.25 times CD. It is obvious from inspection of the plates that the jet trifurcated, or split into three parts. Performance wasn't great, but several things were less than optimal. The aluminum form, used to electroform the cone, was turned on an older lathe and the resultant cone was not symmetrical by quite a bit (I am starting to realize just how important perfect symmetry is). The charge head height should have been larger for best results. The SC might have performed better if the liner thickness was 3% CD instead of 2%.

I am going to find someone with a precise lathe to clean up my aluminum form.

BTW, each steel piece is 3/4" thick.






[Edited on 7-6-2012 by Hennig Brand]

Some improvements would be like you already said, thicker liner, more head height, perhaps increase standoff to 2 CD.
Also, that blue thingy.. It looks like it was made of plastic and I assume that was what held the liner in place? If so, no good. You want your liner to sit on a strong edge that ain't going nowhere. Next time, cut a thin slice of the same diameter pipe you use for confinement and cut a little piece out of the ring. Squeeze it together and place it inside the pipe and tack it in place. Make sure it's level otherwise your liner sits at an angle.. unless you're going to face it in the lathe then it won't matter.
Also, one reason I like to use liquid HE is because it has a perfect uniform density every single time. Making plastic HE at home, your density will vary with each batch.
Just my 2cents.

Oops, yeah I thought it was steel. Was kinda wondering why you'd use a steel pipe and then hold the liner in place with something made of plastic

I don't advise against plastic. I'd say use whatever material is easiest for you to work with. Perhaps not the best advise from a safety standpoint.

Quote: Originally posted by CaliusOptimus

Check out this shaped charge I found on the tube: http://www.youtube.com/watch?v=QlTFBvsSijU

Another failed SC. Like the third one in a row or something. Pretty frustrating!

2.3mm thick walled, 1.5" diameter, 60 degree electroformed copper cone. Yeah, pretty thick liner.
Aluminum container, 2" ID, 2-1/4" OD.. so 1/8" thick walls. Height of container about 6".
Standoff was 6" (4CD). This charge had subcalibration. Walls off container were 1/4" from base of liner.
HE used was methyl nitrate/nitromethane (25/75 % by volume).
Target: 4 mild steel plates stacked together, bottom 3 plates were 2" thick and top plate was 1-1/2" thick, so total of 7-1/2".

Not sure why this SC failed. I wonder if I didn't get full detonation. It could be that I didn't mix the MN with the NM well because shaking it was a little nerve wrecking so maybe I shook it a little too careful Or maybe they separated in two layers (MN is heavier after all). Time between mixing and detonation was probably about 5 mins.
The explosion sounded a little different than usual as well. It wasn't a sharp crack, it was more like ANNM, a gutsy boom.

Looking at the top plate you can see the charge included subcalibration. There's a nice round pattern around the hole left by the jet, not the other much wider hole. And it's odd there are two holes. One was clearly produced by the jet because the copper slug is still in it and there's shiny pink copper all over, but the walls of the other hole, which is much wider and just as deep if not deeper, is not lined by shiny pink copper.. it's lined with a color that looks a hell of a lot like brass. I once melted some aluminum and mixed in a little bit of copper. When cooled it looked like brass, just like this. So I'm guessing it was mostly aluminum with a tiny bit of copper from the liner mixed in that made the wide hole.

I went through quite a bit of trouble trying to make sure everything was as symmetrical as possible because I've been trying to improve on the 6-1/4" penetration I got a while ago. I thought the thick liner would perform great with the added subcalibration.

I won't go through this trouble again. The SC that penetrated 6-1/4" was everything BUT symmetrical. The container was thin walled stainless steel off round tubing. The liner was electroformed on an off round fence cap. The container however was fairly tall (a lot of head height), I wonder if that was why it performed so well. Actually penetration was only like 3 and a 1/4 CD or something which really isn't that impressive, but considering how far from perfect everything else about the charge was, I'd say it did pretty well.

That was my last electroformed copper. These liners do work but they take so long to make. I'll give the rubber pad forming process a try in the future.

Video: http://youtu.be/DbTA-MNA-kc



[Edited on 12-28-2012 by gnitseretni]

Wine bottle bottoms as liners.

i was wondering if anyone else has tried the bottoms of wine bottles as a liner? I thought that they may be too thick but after testing one to see for myself, the results were OK. so i used 225g ANNM but in fairly weak confinement- a high pressure plastic gas pipe. The liner was epoxied in place.the target was 4 6mm structural steel plates stacked up, and i gave it minimal standoff of 1.5 cone diameter and was very surprised at how well this liner performed. A nice round 25mm hole and 30mm deep. The first two plates had full penetration and the others dented fairly hard. There was also a rather large plug of highly compressed powdered glass that was slightly fused by pressure and heat i suspect. These plugs were very hard. A lot harder than the actual glass it was made from and almost like stone. Took a while to clear them out to see the damage.. All up i would say the cone did well and i will be testing another one or two very soon but this time using stronger confinement and greater standoff distance.

Quote: Originally posted by SherlockHolmes

I also tried to do a shaped charge but did not work. Any idea why? http://www.youtube.com/watch?v=jU3TIpoMQN4

Quote: Originally posted by NeonPulse

i was wondering if anyone else has tried the bottoms of wine bottles as a liner? I thought that they may be too thick but after testing one to see for myself, the results were OK. so i used 225g ANNM but in fairly weak confinement- a high pressure plastic gas pipe. The liner was epoxied in place.the target was 4 6mm structural steel plates stacked up, and i gave it minimal standoff of 1.5 cone diameter and was very surprised at how well this liner performed. A nice round 25mm hole and 30mm deep. The first two plates had full penetration and the others dented fairly hard. There was also a rather large plug of highly compressed powdered glass that was slightly fused by pressure and heat i suspect. These plugs were very hard. A lot harder than the actual glass it was made from and almost like stone. Took a while to clear them out to see the damage.. All up i would say the cone did well and i will be testing another one or two very soon but this time using stronger confinement and greater standoff distance.

Quote: Originally posted by Pard

Quote: Originally posted by NeonPulse   i was wondering if anyone else has tried the bottoms of wine bottles as a liner? I thought that they may be too thick but after testing one to see for myself, the results were OK. so i used 225g ANNM but in fairly weak confinement- a high pressure plastic gas pipe. The liner was epoxied in place.the target was 4 6mm structural steel plates stacked up, and i gave it minimal standoff of 1.5 cone diameter and was very surprised at how well this liner performed. A nice round 25mm hole and 30mm deep. The first two plates had full penetration and the others dented fairly hard. There was also a rather large plug of highly compressed powdered glass that was slightly fused by pressure and heat i suspect. These plugs were very hard. A lot harder than the actual glass it was made from and almost like stone. Took a while to clear them out to see the damage.. All up i would say the cone did well and i will be testing another one or two very soon but this time using stronger confinement and greater standoff distance. Why to use just the bottoms? I've seen before to use the whole bottle without the neck. Like wine bottles. Is it better using just conical bottom? By the way, how do you guys design your copper cones? I thought about maybe going to metal work place to ask to do it. It is a strange request but I'm sure they would. It's not like they'd realise what it is for.

Anyone ever tried these as liners? :

http://www.ebay.com/itm/500-UK-77-Cone-Studs-Spike-Charged-G...

Works pretty sweet....


12mm aluplex tubing as the casing with the stud attached...the witness plate underneath is 8mm mild galvanised steel:




Loaded with 2,88g phlegmatized PETN (10% PIB+methyl riccinoleate):



Standoff attached...20mm :



Primed and ready to go:



From the top after firing under sand:



From the bottom after firing...clean through 8mm mild steel:



Judging from the entry point I would say that the standoff was a bit too small...an additional 5-10mm would have probably been beneficial.

[Edited on 11-2-2014 by markx]

Quote: Originally posted by markx

Works pretty sweet....

well done....thats a really sweet project

and i thought my 1" cone was pretty little

Quote: Originally posted by Hennig Brand

Impressive that it works so well even though it's so small. Nice test.

Quote: Originally posted by markx

Anyone ever tried these as liners? : http://www.ebay.com/itm/500-UK-77-Cone-Studs-Spike-Charged-G... Works pretty sweet.... 12mm aluplex tubing as the casing with the stud attached...the witness plate underneath is 8mm mild galvanised steel: Loaded with 2,88g phlegmatized PETN (10% PIB+methyl riccinoleate): Standoff attached...20mm : Primed and ready to go: From the top after firing under sand: From the bottom after firing...clean through 8mm mild steel: Judging from the entry point I would say that the standoff was a bit too small...an additional 5-10mm would have probably been beneficial. [Edited on 11-2-2014 by markx]

Electroforming is a versatile tool....I earned my bachelor degree on the subject of pulse plating thick layers of metal/alloy on geometrically complicated substrates (concave horrors with near zero electrical field in them). Initially electroforming moulds for production of plastic details out of copper and nickel. Then electroforming Ni/Mo/Cu alloy details for hi temp fuel cell construction. The idea was to plate an alloy with adjustable thermal expansion coefficient (ceramic electrodes of the fuel cell did not like the excessive expansion of the support frame ). The main problem with plating thick layers (beyond decorative or corrosion resistant effect) is the formation of dendrites. To counter it, one can use basically three approaches:
a) very low current density
b) additives (mostly surface active detergent type compounds)
c) pulse plating

The most effective being pulse plating....it allows the cathion concentration near the electrode surface layer to replenish between current pulses, therefore minimizing the formation of dendrites. And one can reverse the polarity of applied voltage to turn the cathode into anode for a certain percentage of duty cycle. As dendrites are predominantely formed during the cathodic cycle, they also are predominantly dissolved during the anodic portion of cycle.

Utter success!!

The same type of setup as seen in my previous pictures. But this time the target was 15mm steel sheet.

With 3,5g 10% phlegmatized PETN charge at 20mm and 40mm standoffs:



The 40mm standoff did not penetrate the target...it was 2mm shy of the objective after measuring channel depth.

But the 20mm standoff:









Like a hot needle through butter

Btw. I really do need a decent camera and some practice in the field of photography...these blurry pictures are frankly embarrassing.

[Edited on 14-2-2014 by markx]

A bit clearer pictures of the last test are in order....

Comparison of targets:




The construct for creating the jet:




Entry points on the 15mm target at 40mm and 20mm standoff:








Exit point of the 20mm standoff:




Entry and exit points on the 8mm target from the first test (20mm standoff)

so finally i got around to testing an electroformed liner produced using a method found in this thread. i suspected that it would have performed quite well and i was not disapointed! the liner thickness measured 1mm evenly after cleaning it up some.i forgot to measure the angle but i guess around 60deg. the portion of the cone used was 20mm wide at the bottom to fit in the tube used and with the end cap gave excellent confinement for the charge, which was a mix of 75%MHN and 25%ETN and weighed 16g. initiation was electric, using 400mg lead azide (more than enough...)
Standoff was 2 cone diameters at 40mm. Penetration was pretty good: 38mm into a very hard steel sledgehammer head with a perfectly formed jet that went straight down. No carrot but a nice copper colour lining the hole. looking forward to testing some more perhaps with a liquid ester or cast ETN. i think with some tweaking the penetrating distance could be more. i have always wanted to try a lens.

also a linear SC was tested on a 10mm thick bit of hardened steel. This charge was 24g MHN with a 400mg lead azide cap fired electronically also. Results were a poor 5mm penetration which i think was due to a poor design and next to zero standoff distance. The casing was a 70mm long Al channel that had 2.5mm thick walls with 2mm thick liner at 90 degree angle the ends were also Al and it was all held together with JB cold weld epoxy. that stuff is brilliant! the liner was mangled in the groove and most of it eventually was pried out in order to see the cut. results could certainly be improved here. seems a jet was formed but im guessing that lack of stronger confinement and no standoff played a big part in its reduced cutting ability.

Quote: Originally posted by NeonPulse

also a linear SC was tested on a 10mm thick bit of hardened steel. This charge was 24g MHN with a 400mg lead azide cap fired electronically also. Results were a poor 5mm penetration which i think was due to a poor design and next to zero standoff distance. The casing was a 70mm long Al channel that had 2.5mm thick walls with 2mm thick liner at 90 degree angle the ends were also Al and it was all held together with JB cold weld epoxy. that stuff is brilliant! the liner was mangled in the groove and most of it eventually was pried out in order to see the cut. results could certainly be improved here. seems a jet was formed but im guessing that lack of stronger confinement and no standoff played a big part in its reduced cutting ability.

nice projects

I think that the 2mm thick liner at the linear shaped charge should be replaced to a 0.5-1mm to get optimal results

how did you get the coppercone off the kathode?

I made some 1" diametre 42dagree cone and fucked it up...i couldnt get it off the kathode

Quote: Originally posted by NeonPulse

it was hard, going around it with a knife several times and tapping it with a hammer,the Al not the copper, and the viabrations caused it to just fall off, alot of it i did not need to use so i could bend and tear also. before placing it in the plating bath i sanded it to a glass like finish too, i think that helped it pop off easier.

Quote: Originally posted by markx

Try conductive silver paint as the intermediate layer between cathode and the plating. It makes separation much easier and one can use a nonconducting object as the mould for the plating.....paint will act as cathode on the surface. The only downside is the cost of the paint, but a failure to separate the liner is probably even more frustrating. You could also try a graphite coating as the intermediate layer, although I don't have any personal experience to claim or deny it's effectiveness.

cool idea

i had the idea of plating a extreme thin layer of tin- or lead on the cathode and then plating the copper cone...after the cone is ready, then heating to the melting point of tin/lead....but im too lazy to try that, so i think im going to buy silver paint

Another attempt was made using another electroformed liner. instead of plating for 24 hours it was left to plate for 32 hours. the thickness was increased to around 1mm.
the performance of this liner was also excellent. the filling this time was 11mls of good old NG and to increase the density, 8g ETN and 1g NC were added. fired with a 600mg MHN/200mg Lead azide. A nice even jet was formed and no carrot left in the hole.
the penetration was a rather nice 42mm which is just over 2 cone diameters.
I am pretty impressed with these little liners perfomance especially considering how hard this particular steel is.
My aim is to go all the way through it and with a little tweaking i think that it is realistic as there are only another 30mm to get through. As for the conductive paint i have ordered some- no shit it is expensive, but worth it since i dont have access to a lathe to make my own forms. A form is to be made at the optimal angle of 42 degrees and plated- well see how it goes if it works as well as the others then it will be formidable.

Quote: Originally posted by NeonPulse

Another attempt was made using another electroformed liner. instead of plating for 24 hours it was left to plate for 32 hours. the thickness was increased to around 1mm. the performance of this liner was also excellent. the filling this time was 11mls of good old NG and to increase the density, 8g ETN and 1g NC were added. fired with a 600mg MHN/200mg Lead azide. A nice even jet was formed and no carrot left in the hole. the penetration was a rather nice 42mm which is just over 2 cone diameters. I am pretty impressed with these little liners perfomance especially considering how hard this particular steel is. My aim is to go all the way through it and with a little tweaking i think that it is realistic as there are only another 30mm to get through. As for the conductive paint i have ordered some- no shit it is expensive, but worth it since i dont have access to a lathe to make my own forms. A form is to be made at the optimal angle of 42 degrees and plated- well see how it goes if it works as well as the others then it will be formidable.

Quote: Originally posted by Dornier 335A

Correct me if I'm wrong, but isn't gel one of the worst things to put in a shaped charge? Air bubbles will easily form and get trapped inside it, and that will create hot spots that affect the shock wave. Just using a liquid explosive would be better.

Quote: Originally posted by ecos

Did anybody try to do shaped charges with NG Gel ? I mean to pour the NG Gel in the container and let it cool down and use it afterwords.

Use of conductive coatings for unconventional liners

So i recently decided to try making another electroplated liner. For this process i filled a plastic funnel with car body filler and after it hardened i shaped a tip on the end as it was flat. The angle of the funnel is around 55-57 degrees. The resin form was sanded with some 800 grit sandpaper after this it was then coated with 3 nice even coats with a conductive silver paint. copper wire was threaded through 4 pre drilled holes on the base of the form and it was plated as usual. the coating of copper onto the form was nice and even all around and there was no thin or bare spots. In a previous experiment only one coat of the silver was applied but this produced poor results and a rather slow plating which was uneven in places. I also think the plating bath attacked the coating before a layer of copper was plated to protect it so 3 coats is needed for a faster plating and better coverage all round.The coating goes on very easily and any brush strokes with an artist's brush level out on drying leaving a nice even surface to plate onto. Using this process opens up an avenue to create liners of many sizes and shapes. fluted, trumpet and bi-angled or stepped liners are possible as long as you can form them out of the resin. i guess most materials that can be shaped conically or otherwise can be used (sealing porous surfaces first) and there also is no real limit to the size that can be formed like with cutting metal forms on a lathe. The cone was very easy to remove from the form and the paint stuck to the inside of the liner which is very easily removed with some acetone if it is a problem. The drawbacks are the general cost of a liner as a whole unit, the silver paint is pretty expensive at $10 for a mere 3mls vial but it really does go a long way if used sparingly. throw in the costs of the body filler, copper sulfate, Cu metal, acid and electricity to plate and you have a pretty expensive liner to produce. I haven't any access to a lathe so spinning liners is out for me else i would certainly attempt it.

Quote: Originally posted by Manifest

Aluminium is easy enough to melt, there are many videos on youtube with people melting it using make-shift furnaces. I'm thinking it would be easy enough to make a aluminium cone. I am not sure how you could make the mold of it.

Quote: Originally posted by Oscilllator

Having said that though, Aluminium is not a very good material to make a liner because of its low density.

Quote: Originally posted by careysub

Quote: Originally posted by Oscilllator   Having said that though, Aluminium is not a very good material to make a liner because of its low density. That's not the only reason - aluminum has a tendency to react energetically with the explosive gases and burn up (that's why so many explosive compositions have "aluminized" versions).

Quote: Originally posted by Energetic Einstein

Quote: Originally posted by careysub   Quote: Originally posted by Oscilllator   Having said that though, Aluminium is not a very good material to make a liner because of its low density. That's not the only reason - aluminum has a tendency to react energetically with the explosive gases and burn up (that's why so many explosive compositions have "aluminized" versions). Are you assuming all of the aluminum liner is going to react upon detonation, or just that a thin layer of the aluminum will?

Quote: Originally posted by Energetic Einstein

Interesting. So "Newtons Penetration Approximation" would be be useful when it comes to designing a liner?

Kumula

Needless to invent an aluminum insert. Needless to test copper plating. Needless to produce glass exploding shrapnel. Producing a steel mandrel with an angle of 84 degrees. A 0.55 mm Cu sheet strength. Or 1 mm. Hammer. Wooden chopping block. Steel rectangle. Propane-butane torch. The annealing. Production takes 10 minutes. No lathe. The pictorial compilation hopefully everyone will understand. Loaded: Cyklonan III. 25 grams. Density 1.2 g / cc. Bar diameter 26 mm. Distanc 39 mm. Steel 20 mm.
LL

I tried some of the nice Bachmann cyclonite as a shaped charge:






Substrate is 30mm construction steel (we got greedy and added 2 plates under the charge). That was an obvious mistake, as the second plate effectively relaxed the impulse and stopped the jet. So instead of a nice penetration of 15mm steel we got a carrot stuck in the crater.

work

Perfect work. Cyclonit is much stronger than Cyklonane. Course. Beautiful photos. Detonation seqence. Better of fireworks...... I appreciate handmade. Good handwork? Good documentation? That is always a little. Many speech? Without documentation? That is always very much.
LL


[Edited on 25-9-2014 by Laboratory of Liptakov]

Quote: Originally posted by Laboratory of Liptakov

Perfect work. Cyclonit is much stronger than Cyklonane. Course. Beautiful photos. Detonation seqence. Better of fireworks...... I appreciate handmade. Good handwork? Good documentation? That is always a little. Many speech? Without documentation? That is always very much. LL [Edited on 25-9-2014 by Laboratory of Liptakov]

Only a test with stacked plates will show the real results, but from what I saw in my endeavour, the second plate stopped the jet dead still at the verge of the interface. The second plate was dented just like a blob of plastique had been detonated on top of it , but there was not the slightest of jet transition into it. The carrot was stuck in the crater also at the interface layer....one could basically see it from the other side of the plate, so thin was the metal left around the possible penetration area.

For comparison, here is a snapshot of 30mm uniform steel plate suffering from a 8,3g PETN shaped charge set off on top:




Unfortunately no scale reference again....oh well

The construction, placement and initiation of the charge were identical to the one portrayed in cyclonite test above. In this case there was no sign of the carrot anywhere to be found...I guess it disintegrated or was joined completely with the crater surface.

Sometimes there are very interesting and peculiar branching phenomenons of the jet that curve into the target off the main flow or move basically perpendicular to the main jet direction. Also in this shot one can see such effects on the top of the crater and also in the bottom part. Truly facinating subject...



[Edited on 29-9-2014 by markx]

EFP

It is the exact shape of the copper pads? If yes, does the hole inaccurate and causes material. It's like magic. Liquid copper drills (evaporate) steel. Again, a perfect piece of work. Markx: I see you have a lot of experience and you can make anything. Have you tried EFP? The basic proposal here. Diameter 68 mm = 2 mm copper..........
LL






[Edited on 29-9-2014 by Laboratory of Liptakov]

Quote: Originally posted by Laboratory of Liptakov

It is the exact shape of the copper pads? If yes, does the hole inaccurate and causes material. It's like magic. Liquid copper drills (evaporate) steel. Again, a perfect piece of work. Markx: I see you have a lot of experience and you can make anything. Have you tried EFP? The basic proposal here. Diameter 68 mm = 2 mm copper.......... LL [Edited on 29-9-2014 by Laboratory of Liptakov]

EFP 2 inch

You have the same thoughts as me. A similar reasons. Therefore, even in LL EFP was not tested. It is technically very challenging project. The maximum diameter plates for tests I see is 50mm. This is the weight load from 60 to 100 grams. About 0.73 mm thick Cu. On your test track as possible. I know this is an expensive test. But: 50mm = penetration (up to) 25 mm steel. Large hole! It has all to see! .................

copper cone

Sergeant James

I got a message from Sergeant James. It's a really tough guy......LL

Explosively Formed Penetrator (EFP); Misznay–Schardin Effect

I started experimenting with explosively formed penetrators a little bit. Below are a few pictures of my first, and only, test so far. Thanks go to Markx for the idea of using coins to make the platters. In this test a Canadian dime was used. The coin was pressed into the curved shape (dish) using a ball peen hammer, a nut the appropriate size and a vise to apply force. The charge casing was made from a section of cardboard tube from a spent consumer fireworks aerial shell mortar tube, which happened to be the right size for the curved dime. The charge used was 8.5g of a putty explosive composed of, 81% ETN and 19% inerts, which was initiated with a 5mm id aluminum cap containing 0.5g of PETN and 0.15g LA. The target was 3/8" steel. The stand-off was arbitrarily set at 10cm.

Charge Casing:
D = ~1.8 cm id, ~2.4 cm od
L = ~3 cm

I think I was a little over enthusiastic when I chose to use 3/8" steel over 1/4" steel as the target. It didn't penetrate the 3/8" target, but it looked like it would have if the plate had been only 1/4". There was a large welt on the back of the plate. The width of the hole in the witness plate indicates low slug velocity and a short wide slug with low penetration. Higher velocities would cause the slug to elongate more and produce more penetration. According to Wiki, (referring to improvised devices I believe) "As a rule of thumb, an EFP can perforate a thickness of armour steel equal to half the diameter of its charge for a copper or iron liner, and armour steel equal to the diameter of its charge for a tantalum liner, whereas a typical shaped charge will go through six or more diameters."

The target was a bit more than half the thickness of the charge used and I am sure many things were not optimized. I will try it again possibly with a higher velocity explosive or with a 1/4" steel target.







[Edited on 26-12-2014 by Hennig Brand]

Pretty cool test you did, Hennig

I think the standoff is very important at EFPs too (like SCs)...
Maybe you give it a try with 50cm< standoff at the same CD?

perfect

Again a very good job Hennig. The best I've ever seen. Vladimir writes important thing. 10 cm distance is too small. I studied patents. Projektyl is not enough to shape. It must be at least 40 cm. Top 50cm. (for this diameter). I see significant deformation of steel 10 mm. This is the beginning of a very good result. In such a small scale are materials (steel) strength. A lower efficiency in explosives. It is due to finite size of an atom. I'll try to explain it differently: 1) For airplanes (1 km height) throw ant (5mm). He lands on the grass. Nothing will happen. 2) For airplanes (1km) throw a giant ant chitin (1500 mm). It certainly will be broken up into pieces. It is due to finite size of an atom. It is due to the number of atomic bonds at the object. I hope you understand me ......LL

Cu tube

Interesting idea, option. But: the shock wave has tremendous power. At a distance of 30 cm fractured (broken) 20 mm thick oak plank. When 10 g ETN. It is my experience. Produce suitable partitions will be challenging. At a distance of 10 cm from the epicenter almost impossible. I think in amateur conditions. In expensive (equipped) laboratory is easier to use a high speed camera. I recommend using a 1 mm thick copper plate. From the Cu tube. This material is very suitable for directional charges. Annealed copper. Much better than 0.55 mm Cu. Tested. Excellent results for diameter 20-30 mm ......LL

Thanks everyone. I found a few things this morning which are informative I think.

From, "Standoff sensor antennae for munitions having explosively formed penetrators
US 5070786 A" the following can be read. I have also attached the patent.

"Those skilled in the art recognize that certain anti armor munitions employing EFP warheads, such as a Miznay-Shardin type of warhead, generally require five to six charge diameters of standoff distance from armor surfaces at the time of detonation to properly form the penetrating, molten metal jet used to defeat the armored target."

Except for the fact that EFPs don't form a jet the way conical shaped charge penetrators do, from what I understand, this seems reasonable.

Attachment: US5070786 Standoff Sensor Antennae For Munitions Having EFPs.pdf (454kB)
This file has been downloaded 519 times



I also found a nice graph in, "Chemistry of High-Energy Materials" By Thomas M. Klapötke, which shows how, unlike conical shaped charges, EFPs can be used effectively at very long standoffs (even over 100m in many cases for practical devices).





The following is a copy/paste from one of the Wiki pages on shaped charges,

"Misznay-Schardin effect

As opposed to the cylinder/cone of the Munroe effect, which produces a narrow jet, the critical aspects of this weapon are a relatively large sheet of explosive, with a sturdy metal backing plate. The basic principle is that the main force of the explosion is directed away from the backing plate. The explosive wave, in general, is broader than a Munroe effect, producing a more-or-less flat wave rather than a jet.

If objects of considerable mass, but still less dense that the backing plate, are in front of the "open" side of the explosive, they will be propelled forward by the expanding shock wave. This is the principle in the U.S. M18A1 Claymore mine, which is a book-sized device, with a mildly concave backing plate, a sheet of explosive over it, and metal fragments on the surface of the explosive. Detonating the charge sends a fan-shaped blast and fragmentation pattern in the direction of the target.

Since the wave is straight or diverging, there is no critical standoff requirement as with the converging Munroe effect."

Well, I definitely didn't have a "sturdy metal backing plate", hell that wooden disc/bushing I was using to plug the end of the charge and align the blasting cap wasn't even glued in place. Also notice that there is not nearly the same need for precise control of standoff distance with an EFP, at least once a bare minimum is obtained.


Here is something interesting regarding the effects of casing thickness of cylindrical EFP charges on performance, taken from, "Explosive Effects and Applications", edited by Jonas A. Zukas, William Walters, William P. Walters.




[Edited on 26-12-2014 by Hennig Brand]

counterweight

It occurred to me to use less plasticizer. Around 5-10% only. For ETN (PETN) can be pressed. In the solid pipe. Copper or steel pipe. I estimate the pressure of 300 kg (20 mm dia). With hardwood logs. Further: Other explosives could make a counterweight. (green in the pic.) It may be less efficient. Around 3-4000mps. It's just a suggestion.

Yeah, that was one of my next moves. I was going to try only 5% inerts, which should be fine since the explosive doesn't have to be a mouldable plastic explosive like Semtex. I noticed that Markx uses a very small amount of inerts for his shaped charge tests also. I may try casting some ETN:TNT tetrolite into one as well.

Examining the standoff issue a little more. The following jpg image is of a page from, "Explosive Effects and Applications", edited by Jonas A. Zukas, William Walters, William P. Walters. It looks as though full slug formation happens in about 100 microseconds. If we assume a slug velocity of 1500m/s that would mean that the slug is fully formed in 15cm (if I did that right). Yeah, a little more standoff than the 10cm I used probably wouldn't hurt.





[Edited on 26-12-2014 by Hennig Brand]

Ah, yes....good to see the thread awaken again. And also delighted to see someone trying out the things I've been lacking time for lately
I see from the EFP test pictures of Hennig that the standoff is likely too small...seems that the coin hit the witness plate flat on without having time to form into a more ergonomic projectile. I guess there is ample room for experimentation with the standoff. I would be very surprised if the optimum lies in the the range of 10 CD with such small designs. It may hold true to bigger charges, but since the forces at play do not scale well I'm more inclined to thinking that the optimum may lie well beyond the 10 CD limit here....
Waiting with great anticipation

Quote: Originally posted by Hennig Brand

I think you and VladimirLem, LL, and Fulmen are most likely right. Your point about things not scaling well could be more true than I originally thought. I don't imagine that 50cm would be needed, but I might try doubling it and going with 20cm for the next test. Also, according to the "Explosive Effects and Applications" and others, slug formation would be faster and more complete, and slug velocity would be higher, with a strong dense casing. A steel back plate and casing is really the way to go, but I would prefer not to go that route for safety reasons. A test could be performed though, if steps were taken to ensure safety.

plate

This is it, what I wrote. When the diameter 1.8 cm, will cause strong nuclear forces and constraints. The test must be done in a polystyrene box. Buried in the sand. Especially, if will be use supporting plate. Maybe 2cm thick the lead plate?.....LL

Interesting idea you have there, LL.

Found another picture which would indicate that more standoff is definitely needed for proper slug formation. This one comes from the "USAF Research Laboratory". It may be hard to get a definitive answer it seems.

So for 400 microseconds and an assumed 1500m/s:

Distance required for proper slug formation = 0.0004s * 1500m/s * 100cm/m = 60cm

Well hell, I might as well try 50cm or more standoff; except for a little more difficulty in aiming the device this is still very close range for this type of shaped charge.

pit

My opinion, I prefer a bit more. Maybe 80 cm. Still, it must be in the sand. Or in the snow. Snow is nonsense. It must be a pit 90x30cm. Depth 40-50 cm....LL

Found something very interesting in, "Fundamentals of Shaped Charges", by Walters and Zukas.

"In general, the hole volume remains approximately constant for various shaped charges of the same diameter and at a given standoff. For example, for shaped charges of various liner materials and various wall thicknesses, the penetration depth varies, but the hole diameter also varies such that the hole volume is practically unchanged (Klamer 1964). This is because the hole volume varies directly with specific explosive energy. Thus, for a fixed explosive energy, the hole volume is fixed, and the hole depth times the hole area remains approximately constant.

Further, Held (1976) observed that the hole volume remains approximately constant for a variety of explosive devices. In figure 10, several conventional high explosive charges are compared with respect to standoffs, penetration depths, and crater diameters, all expressed in calibers."

It is a trade-off between hole depth and hole width, since hole volume remains fairly constant, so it really just depends on what one is trying to achieve.

Attached below is the associated table taken from the text. The 0.19D^3 value for volume, in the table, is particular to those sets of experiments and is not a universal constant.





[Edited on 28-12-2014 by Hennig Brand]

I had my first attempt at an EFP charge today using Hennig brands coin method of forming a liner from a coin in a vice with a ball hammer. I used an Australian 20 cent piece which are 2.85cm in diameter and 2.5mm thick and are 75% Copper which is a good liner material the remaining 25% being Nickel.
The charge casing was a 4 cm long tough cardboard tube with 2.85cm internal diameter and 3.2mm outside diameter.
The actual charge was 25 grams of hand pressed PETN and the target was a 1/4 inch steel girder/plate offcut from a building site.
The standoff used was 50cm which I realize now is probably much too short.
The plate was only badly dented/dimpled where it was hit. The dimple is 3.5mm deep and 2 cm in diameter which leads me to believe that the standoff wasn't far enough as it seems the coin has inverted but only partially formed a slug as the dent diameter is only .85cm smaller than the original coin size (second picture).
I think I will double the standoff distance next time and use the same plate to see how much of a difference I get and whether it will penetrate the whole plate thickness.
Would Pentolite be better suited for a charge like this or should I stick with the straight PETN?


[Edited on 28-12-2014 by greenlight]



[Edited on 28-12-2014 by greenlight]

[Edited on 28-12-2014 by greenlight]



[Edited on 28-12-2014 by greenlight]

EFP

Liner 2.5 fat? 28mm diameter? This is wrong. Thickness should be 28,5x 0.0146 = 0.41 mm thick Cu liner. Maybe one millimeter. Maximum. The slug will not shape. 2.5 mm is too much. It is a waste of PETN. That there could be a steel matrix. Or stone. This is not EFP. In one book is described liner for diameter 68 mm. Copper is 1.8 to 2.2 mm thick. Here is a modified scheme......LL For dia. 28,5x0,57 is target thick 16mm. 75%= 12mm steel through. For dia. 18mm x 75% = 8mm tuti durch in durch.



[Edited on 28-12-2014 by Laboratory of Liptakov]

US 3 217 647

Patent from Thomanek US 3 217 647
It is very interesting. He says something else. Liner thick 5% from diameter. The bow depth 10 to 30% from diameter. Therefore 20%. For diameter 28 mm is depth = 5.6 mm. And thick liner = 1.4 mm. I enclose a picture of a patent.

lens liner

pressing

To be a good result, it is necessary to use a steel tools production liner and the same steel tools for stamping. The pipe may be thick plastic. Pressing connect liner, pipe and EM. For D = 20 mm estimate the pressing pressure of 3 tons. D x 0,6 for cilinder is minimal. I thing......LL







[Edited on 29-12-2014 by Laboratory of Liptakov]

liner EFP

This post is designed especially for today's youth. Only by using hand drills can produce tools for making the liner. Without a lathe. The image is a 1000 words. The diameter is 22 mm liner from 1 mm Cu. Or 1 mm mild steel. It's all work for one afternoon. Any questions?......LL