| Pages:
1
..
17
18
19
20
21
..
68 |
nitro-genes
International Hazard
Posts: 1048
Registered: 5-4-2005
Member Is Offline
|
|
Hehe, for a moment there I thought startrek had become oldfashioned! 
The counter projectiles are likely to be fired by the "metal storm" principle, which can produce a beam or cloud of projectiles. Since the metal storm
system contains no moving parts it is probably the only thing fast enough to react in the small timeframe given during an RPG attack. The response
time of the radar and targetting systems must be incredibly fast. it is hard to believe it is fast enough to counter high velocity recoilless weapon
projectiles from close range...
http://www.youtube.com/watch?v=Ih2vPGMQzlo
|
|
|
Axt
National Hazard
Posts: 778
Registered: 28-1-2003
Member Is Offline
Mood: No Mood
|
|
| Quote: | Originally posted by Axt
Though there is the book, "Evaluation of Improvised Shaped Charges" search amazon for it, still available on special order. Essentially the book is a
reprint of a study on cylindrical lined charges. Its just a heap of tables with charge dimensions, materials and penetrations. I cant remember much
from it, only that a short standoff was desirable ~1/4" or something. I had it opened it once, then lost it  It was for Al/steel/Cu tubes but unsure what explosive was used, C4 or equivalent plastic explosive I think.
|
Found it and scanned it. Beng a "desert publications" book, the source of its information isn't given but in the text it is mentioned that its the
original study of improvised cylindrical liners to determine the best dimensions to be used in the army training manual "TM 31-210 Improvised
Munitions Handbook" and indeed it is in there on pg 87. See attachment.
Attachment: Evaluation of Improvised Shaped Charges.pdf (1MB)
This file has been downloaded 1994 times
|
|
|
pyrotekniker
Harmless
Posts: 8
Registered: 3-12-2006
Member Is Offline
Mood: No Mood
|
|
Hello
I've been reading about shaped charges, and decided to try it. I've done some tests using NM/HNO3 and found that this is the explosive I want to use.
As a linear I found this:
Copper Linear
I know the quality sucks, but you can at least see the shape. It's about 5cm across at the bottom,
and has a hole in the middle at the top which has a diametere of about 1cm.
Could it be used?
I think I have to build the charge the way that Axt's glass linear charge is built.
|
|
|
Boomer
Hazard to Others
Posts: 190
Registered: 11-11-2005
Member Is Offline
Mood: No Mood
|
|
Adobe tells me the book-pdf is damaged.
The cone could be used, but why start so big? You'll need at least half a pound HE.
How thick are the walls? How will you protect it from the nitric? Not funny having it start boilling before you're finished.
|
|
|
pyrotekniker
Harmless
Posts: 8
Registered: 3-12-2006
Member Is Offline
Mood: No Mood
|
|
Have no plans of beginning with that one  Going to try smaller ones with
cartridges and hollow bullets.
I just found it, and saw that it had the right shape and thought; why not? Probably going to cover the walls with some plastics. The walls are
probably 2mm or something.
|
|
|
nitro-genes
International Hazard
Posts: 1048
Registered: 5-4-2005
Member Is Offline
|
|
Waveshapers can save a lot of explosive, as well as give better performance. Alligning it into the charge container however is very difficult to do
precise enough to function well. Military charges use the planewave generator a lot, which is an upside down coneshaped waveshaper that creates a
plain detonation wave even with small headheight...
So I thought of a simple way (admittedly, pure genious  ) to make this and
allign it easily inside the charge.
First you press in the PBX after which you press hard onto it with a dowel having a cone shaped end. This will leave a cone shaped cavity. Then you
make sure the charge is level, and pour in some epoxy resin, leaving at least 2 times critical diameter at the sides. Then press some PBX on top...
By varying the slope of the cone you can alter the effect, large angles produce converging detonation waves, while smaller angles produce a plain
detonation wave...
I tested a 32 mm charge this way, with 20-25 grams of 85/15 PETN/Pib at 1.5 g/cc, 210 kbar, critical diameter of 0.7-1 mm. (Thanks to HMTD! ) It penetrated the entire side of the steel block, which was 12 cm, and another 3 cm
into the ground...
[Edited on by nitro-genes]
|
|
|
gnitseretni
Hazard to Others
Posts: 280
Registered: 5-1-2007
Location: Medellin
Member Is Offline
Mood: No Mood
|
|
An idea just popped up. Make (or have them made) a cast iron male and female mold of a cone with a metal bolt inside and sticking out a little and
weld them to a vice. Then place a sheet of copper in between the molds and "press" as many liners as you need. What do you think?
|
|
|
nitro-genes
International Hazard
Posts: 1048
Registered: 5-4-2005
Member Is Offline
|
|
Pressing is not as easy as it may look. When you want to press a cone shape out of soft copper sheet in one press you will tear through the metal for
sure. In order to do so you would need to make a series of pressing molds, going from a very blunt apex in the beginning and more cone shaped for the
last pressings. There is a los alamos report on how to do this with the punch and die technique, though making al the different pressing molds would
be a quite a job. Hemispherical liners would be the best option for pressing, though still it is difficult to get a liner with a constant
wallthickness this way. The coppersheet can have problems sliding in the mold smoothly, resulting in one side beeing more streched and thus thinner
than the other. You would need to polish and lubricate the mold well in order to prevent this...
I've uploaded the movieclip of the charge with the waveshaper, I hope this extra MB of space isn't a problem, else let me know...
The charge was recorded from a larger distance this time to capture the jet spray consisting of copper beeing thrown out of the formed jethole better.
It is in essence very anologous to the effect when you spray a stream of water into a mudbank, in which the excess water traveles along the sides of
the formed channel in the opposite direction of the stream itself. It goes at least 4 meters in the air judging from the movieclip. 
[Edited on 3-2-2007 by nitro-genes]
Attachment: 32 mm charge 85% EF PETN-15% Pib at 1.50-1.53 density + plastic waveshaper compressed.avi (959kB)
This file has been downloaded 1952 times
|
|
|
gnitseretni
Hazard to Others
Posts: 280
Registered: 5-1-2007
Location: Medellin
Member Is Offline
Mood: No Mood
|
|
as long as it doesn't tear and the little wallthickness variation that may occur here and there doesn't affect the performance of the shaped charge
too much, than I could live with it
|
|
|
nitro-genes
International Hazard
Posts: 1048
Registered: 5-4-2005
Member Is Offline
|
|
An equidimensional wallthickness is the most important feature of the liner that determines the performance, especially for cone shaped liners that
are much more sensitive for variations in symmetry than hemispherical ones. So both for pressing as for performance I would recommend using
hemispherical liners first. There is a slight performance decrease for hemispherical liners, but this is mainly because of the pole region disrupting
the formation of the jet. Hemispherical liners with a hole 25% of the liner diameter in the pole region are said to have much higher jettip velocities
and can perform as well as cone shaped liners...
|
|
|
gnitseretni
Hazard to Others
Posts: 280
Registered: 5-1-2007
Location: Medellin
Member Is Offline
Mood: No Mood
|
|
Thanks for the info Nitro. I still have much to learn. I actually thought I had a good idea there though
|
|
|
mfilip62
pierced by a crossbow under a bridge while eating Billy goats
Posts: 140
Registered: 25-8-2006
Member Is Offline
Mood: I like turtles!
|
|
Nitro,are you saying that hemispheric liner with hole in it would be better?!?!
How thick (for exp. Cu liner) shuld bee!? Why?
Is ti true,that (conical) liner should bee;"As thin as posible!"
[Edited on 15-2-2007 by mfilip62]
|
|
|
nitro-genes
International Hazard
Posts: 1048
Registered: 5-4-2005
Member Is Offline
|
|
Yes, though use of explosive lenses (an inert rod from center of liner up to the detonator for example) could give the same performance. Supposedly
they give higher jettip velocities...
Thickness depends on the liner diameter, apex angle, and detonation pressure of your explosive, usually 2-3% of the liner diameter for copper though
in combination with a brisant explosive like plasticized PETN, RDX, cast TNT etc...
|
|
|
nitro-genes
International Hazard
Posts: 1048
Registered: 5-4-2005
Member Is Offline
|
|
I selected some nice video demonstrations of the shaped charge, the squashead principle and the EFP. The shaped charge demonstration is accompanied by
Manfred Held, inventor of the explosive reactive armour and an authority in this research field.
Shaped charge and squashead:
http://rapidshare.com/files/18536608/New_WinZip_File.zip.htm...
EFP:
http://rapidshare.com/files/18549805/New_WinZip_File_2.zip.h...
PS: Don't know how long the links will be available since their probably a copyright violation.
|
|
|
quicksilver
International Hazard
Posts: 1820
Registered: 7-9-2005
Location: Inches from the keyboard....
Member Is Offline
Mood: ~-=SWINGS=-~
|
|
This whole thread is great. It would be very nice to extract this whole thread and make a pdf from the material. The information disseminated is quite
vast and the thing actually could be expanded to encompass the embedded stuff as well.
- =-= I hate having to wait a day w/ rapidshare. The first avi was good & wanting to see the next one makes it so I have to keep a reminder to
snag it or else rapidshare will zonk it soon =-=--
|
|
|
nitro-genes
International Hazard
Posts: 1048
Registered: 5-4-2005
Member Is Offline
|
|
The PDF idea is a good one, it would be a lot of work though to extract all the usefull information from this huge thread. I've made a start in making
a detailed description of how to produce spunformed liners, the charge itself, waveshapers and the synth of several highperformance plastiques and
castable mixtures to be used with these liners. I am willing to make a start with writing such an exerpt from this whole thread and other resources,
if noone objects against I'm doing so because a lot of the information was provided by others like Axt, NBK, Boomer and HMTD by U2U...
Sorry for the double download btw, somehow I got an error when I attempted to upload them all together in one zip...
[Edited on 27-2-2007 by nitro-genes]
|
|
|
MRUD
Harmless
Posts: 10
Registered: 28-2-2007
Member Is Offline
Mood: No Mood
|
|
This is my first post, and sorry, english isn't my native language.
I've seen the video nitro-genes posted, and now im wondering.
The man in the shaped charge part said, the con diameter was about 65mm and the standoff at 120 mm, thats nearly 4 times of con diameter.
But everywere i read something about chaped charges, it's written that the standoff schould be equals the con diameter.
Are there some other things i didn't now about that problem, or i'm totally wrong?
I would be pleased, if you can help me finding out.
MRUD
|
|
|
Microtek
National Hazard
Posts: 828
Registered: 23-9-2002
Member Is Offline
Mood: No Mood
|
|
Hmm, 120 mm is actually only about two times the cone diameter of 65 mm. Anyway, you can use a variety of standoff distances; what's optimal depends
on cone angle and charge geometry.
|
|
|
nitro-genes
International Hazard
Posts: 1048
Registered: 5-4-2005
Member Is Offline
|
|
They used 250 mm standoff, so little under 4 times cone diameters indeed. This is because the penetration is mainly determined by the lenght of the
jet at the time it hits the target. Longer standoffs give the jet more time to stretch longer and thinner than for shorter standoffs. As a result the
penetration is deeper, but also less wide. The problem is that the longer and thinner the jet stretches, the more sensitive it will become to flaws in
the liner symmetry, allignment of the charge and liner etc. Professional shaped charges, like used in warheads, actually have an optimum penetration
depth at about 6-8 charge diameters. An improvised shaped charge isn't constructed precise enough to able to stretch to such lengths before the jet
dissintegrates, so in this case more than 2 cone diameters is about the limit. The standoff also dependends on the shape of the liner, like the apex
angle of the cone. EFP liners of 140 deg need as much as 10-20 cone diameter standoff, while cylindrical liners (0 deg) are optimal at 0 CD standoff.
Hemispherical liners also need a somewhat larger standoff. The purpose of the charge is also a factor, some demolition charges don't need long and
thin penetrations in steel, so they are deliberately used at smaller standoffs to produce less deep, but wider penetration holes since their momentum
will be about the same...
The charge used in the video should have been used at smaller standoff as well, since the jet clearly seperates into two independant parts as the
penetration progresses, and the entrance hole is surrounded by dimples. Shows how sensitive the formation of the jet is for imperfections in the
charge. I've had the same phenomena on several occasions as well, I wonder what determines this odd behaviour.
The last charge with the waveshaper, from which I posted the video, used 3.5 times standoff which is about the limit with these spunformed liners,
since I tried several smaller charges before with 4 CD standoff that showed a very messy entrance and reduced penetration. Then again, maybe it was
just a lucky shot, since the penetration was really perfect, with a smooth and straight penetration channel...
[Edited on 28-2-2007 by nitro-genes]
|
|
|
nitro-genes
International Hazard
Posts: 1048
Registered: 5-4-2005
Member Is Offline
|
|
Ok, just to show what a real shaped charge should look like (and some people wanted to see the pictures) I've made effort to take some pictures of the
results of the charge with waveshaper.
The first thing that is striking is the opening width of the entrance, that is only about 10 mm. This is clearly the result of the increased standoff,
since the other charges, fired at 2 CD standoff had a much wider entrance diameter of 22 and 17 mm respectively. Proof to the increased stretching of
the jet at longer standoffs.
The other thing that is obvious is the "cleaness" of the penetration, no dimples are visible surrounding the entrance and the entrance hole itself
would have been perfectly round if it were not for the off-center carrot that hit the side of the entrance hole. (left of the entrance in the first
picture) It was better visible right after the charge was fired, since there was some coppersmear at that spot. Rusting of the block has made that it
is not very clearly visible anymore. Just an observation, but I noticed that the areas on the steel that have been subjected to high pressures somehow
rust much faster on storage, maybe due to microfracturing...
The remnants of the 30 mm grey PVC standoff tubing can be seen as grey circles on the block as well...
Due to the fact that I had little space left on the steel block for another penetration () I had to put it pretty near one of the holes on the corner of the block. The sideway displacement of the steel ruptered the steel into an
opening about 5 cm after the entrance, which gave a perfect opportunity to lighten and thus photograph the inside of the penetration channel. This
rupture can be seen on the photo on the right, at the top of the picture on the right...
Unfortunately, you can't look entirely through the channel since about 3 cm before the end there is some piece of the liner/carrot obstructing. Maybe
because I used a more trumpet shaped liner, I noticed these trumpets produce much narrower carrots than straight liners, and this could possibly be
another reason why it is used in HEAT rounds, the carrots are narrow enough to enter the tank through the jet channel and cause secondary effects
inside the tank...
[Edited on 1-3-2007 by nitro-genes]
|
|
|
12AX7
Post Harlot
Posts: 4803
Registered: 8-3-2005
Location: oscillating
Member Is Offline
Mood: informative
|
|
Possibly electrolytic reaction with the copper "carrot" / spray?
Tim
|
|
|
nitro-genes
International Hazard
Posts: 1048
Registered: 5-4-2005
Member Is Offline
|
|
Think so, Fe3+ can displace copper easily, a friend of mine used strong FeCl3 solutions to develop his own circuitboards. The plugsmear is gone on all
the other charges as well. Could just be the volume of the rust though, someone told me that 1 mm of steel forms about 1 cm of rust!
|
|
|
MRUD
Harmless
Posts: 10
Registered: 28-2-2007
Member Is Offline
Mood: No Mood
|
|
Ohh, sorry for that mistake "what the hell was i thinking, while typing 120mm" shure, i meant 250mm.
And by the way, tanks for your good explanation and graph nitro-genes.
MRUD
|
|
|
MRUD
Harmless
Posts: 10
Registered: 28-2-2007
Member Is Offline
Mood: No Mood
|
|
Thanks to all posters in this thread.
Whith your help and the many good explainations i managed to set off my first shaped charge, wo was able to penetrate 1cm of steal.
Thanks
1
2
3
|
|
|
kiknet
Harmless
Posts: 7
Registered: 2-5-2006
Member Is Offline
Mood: chargin
|
|
I think thats a good effort for a first Shaped Charge, what were the specifications of it?
|
|
|
| Pages:
1
..
17
18
19
20
21
..
68 |
![[*]](images/xpblue/default_icon.gif){kind=icon}
