plan-x
New Member
Posts: 5
From:
Registered: MAR 2001
posted 06-10-2001 11:43 AM
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After numerous searches and lurking on this board for ages, i've been unable to find relevant info on te forming of copper cones for shaped charges. Everyone seems to agree that Copper is the ultimate liner, if so, how does one form it to the neccessary shape? pressing it over a die? An interesting idea that i have had would be explosively forming it into a plaster-of-paris female die, assuming that the copper was stretched successfully just above it's elastic limit but below its Ultimate tensile strength (which would result in tearing).
Any ideas guys?


wantsomfet
Frequent Poster
Posts: 236
From: EU
Registered: JAN 2001
posted 06-10-2001 01:00 PM
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I mad a cone a few weeks ago. I used 0,5mm thick copper sheet (from conrad-electronics, europeans might know them). It's also available in 0,3mm 0,8mm 1,0mm 1,5mm thickness. You can cut it with a strong scissor or take a dremel.
60� is the optimum angel for the cone.
To form a 60� cone you have to cut an exact half circle from the copper.
Then bent a little in the middle & fold in shape. Then soldering the cone would be optimal.
OK, i'm in a hurry. Formula One starts in a few minutes... I'd love to see some nice accidents!

I can make a pic of the cone tomorrow.
http://nettrash.com/users/altreal/grfx/sccone.gif


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for best catfood visit:
kangaroooo.cjb.net

[This message has been edited by wantsomfet (edited June 10, 2001).]



a_bab
Frequent Poster
Posts: 44
From: doesn't matter
Registered: MAY 2001
posted 06-10-2001 04:42 PM
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So, Shumacher brother was the winner... (F1)
I don't think that soldering the copper cone will be a good option, but I never tried a shapped charge (but i'll do). The best is to deforme the cone somehow. What do you think ?Did you tried a shapped charge with your soldered cone ?





SMAG 12B/E5
Frequent Poster
Posts: 61
From:
Registered: FEB 2001
posted 06-10-2001 07:12 PM
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If you need a large number of liners, the die-pressing method is probably the most suitable. You will need to fabricate a slightly complex die.
If you want only a small number of liners, spinning would be your best choice. You will need to turn a male form, fabricate a live blunt center and a few turning tools. Copper responds well to this technique.


plan-x
New Member
Posts: 5
From:
Registered: MAR 2001
posted 06-11-2001 07:15 AM
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ok, i tested explosively forming a liner with 0.8mm thick copper sheet, it worked well with a liner diameter of 8cm. I turned up a male blank from soft iron on a lathe, and used this to make a female impression in plaster.I then placed the sheet over the female blank, and used a charge of AP Putty approx 20 grams to form the liner to the shape of the die. All went well, the die shattered as expected, but the liner turned out almost perfectly, except for a minor irregularity where i had drilled a small hole through the cast die, which i attached to a vacuum pump from a refrigerator to prevent the copper compressing the air underneath it in the die as it was stretched to shape. The thickness after the test was approximately 0.4mm near the apex of the cone. I shall test the liner in a few days. I wish to coat it in wax and try a Sprengel type explosive, with 99% nitric Acid and PolyStyrene. I will also coat the inside of the pipe i use to form the rest of the shaped charge.

1. Liner

A uniform copper liner can be the biggest problem in the manufacture of a shaped charge. I took a plastic funnel with a 60 degree opening and filled it with epoxy. Putting a 10mm screw in the middle gave a way to clamp it in a vice after hardening. I cut a complete circle from 0.3mm copper sheet and made a cut towards the centre. If the cut edge is taped vertically to the cone, the sheet can be rolled around twice to form a perfect cone. After wrapping it once, the touching surface was wetted with superglue and it was wrapped the second time.

The advantage is that the thinner material is easier to roll up, and there is no solder joint of higher mass. The resulting cone is of perfectly equal thickness, and the non-symmetry is less than a millimetre for a two-inch cone. The sandwich walls are not too common, but are sometimes also used in the Oil Industry (or they sinter metal powders, but the jet does not travel so far). I made several one-inch and two-inch cones to conduct some testing.


2A. APAN

The obvious choice is AP, but the VoD is too low. I had 1/2 pound of old APAN to get rid of and tried it anyway, if only to compare it to better HEs. The charge was 2" dia in a 4" long PE tube with a 2g AP cap and 3" standoff (1.5 times dia is my standard for these tests). It went through 16mm of steel, leaving a 3mm hole. I did not expect this penetration, so used no more plates. It would probably have gone even deeper. Nobody tell me APAN gives no jet!

2B. HDN

With a VoD of 6000 m/s HDN is a little better than APAN. I added 20% MHN to increase sensitivity and VoD. Using 20g mix in a 1" dia x 2" PE tube, it penetrated two 3mm plates of steel and went 2mm into a third. But the jet had not fully formed, the holes were clogged with copper particles.

2C. Nitrostarch dynamite

I also had to get rid of a pound of 10-year old dynamite made of 65% AN and 32% nitro starch. Though containing 3% stabiliser it just slowly started to decompose, but 10 years storage stability is OK IMO. Copying the test in 2A it went through 3" of brick (forgot the steel plates at home).

2D. MHN/HDN/NG plastique

Repeating the test in 2B with 12g of HDN, plasticised with 6g MHN in 1.5ml NG, penetration was only 6mm. Maybe the cap was too weak, or the jet did not form properly this time.

2E. MHN/NG/RDX plastique

To have an ultimate comparison, I'll use pure RDX instead of HDN for the last test. With 20% NG so it just fills the gaps, VoD should be very near the maximum value for MHN of 8250 m/s at density 1.6 (Naoum/Kast/Stettbacher etc), or even near that of RDX of 8500 m/s. Repeating the test in 2B with xxg of this stuff, penetration was x mm, hole dia was y mm (not done yet).

A standoff of 3x charge diameter is about optimum.

That's really not the case, iv used very small SC with a 6" standoff and large SC with a 1.5" standoff. It depends on shape and angle more that anything.

How about using electroforming to create a SC cone? Make a mold (hard bit I suppose), fill with wax, remove when hard, then paint (but leave the bottom) with something like the conductive silver paint available at electronics suppliers. Set it up for the electroplating of copper, when it's at the required thickness heat to melt the wax from the inside. With a mold, you could crank them out pretty quickly. Just a thought...

Yes Cyclonite, you will know from your job! The wider the liner angle, the longer (= further away from the charge) it takes for the jet to form. An EFP could be called the extreme, with an only slightly curved ?liner? like a saucer. Of course it is no longer a jet in that case.

I?ll try to attach images of my liners and the tool to make them. For the scale, the small cone is 1? and the big one 2? diameter. The PE pipe adapters are ideal casings, you need less HE as they are smaller at the top

Aren?t they nice? :D

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Please reduce the size of the attached images by applying stronger compression.

Rhadon

Sorry, this was the first time I ever worked with pics on a computer.
Better now?

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Fine!

As I cannot edit the last post, I am putting the results here. The most surprising thing is that the above liners worked well even with APANFO (1:1 of ANFO-94/6 + APAN-70/30)! Everybody insists that AP is too slow for SCs. Well, APAN is slower and ANFO even more so. Why did it work?

The target was 18mm stell, 12mm-plate below + 2x 3mm-plates on top. The top one got lost, the photos show the lower two. It would have penetrated deeper, but I did not expect this so used too little steel.
The names are self-explaining:

Nightstalker was correct about the 3x standoff being about optimum, but he was assuming that most people would be using the typical cone of 40°~60° angle, which is what most people here would likely be using.

Using 160° (EFP) gives 20x+ standoff, while 0° liners (tubes) requires zero standoff.