Sciencemadness Discussion Board

Unconventional Shaped Charges

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Hennig Brand - 30-12-2014 at 17:02

Good work, LL. Nice pictures. There are a lot of things that can be done reasonably well with a drill that would normally be done with a lathe. I have used a drill in the past to turn a piece of small round stock down, for instance, and other small tasks as well.

EFP

Laboratory of Liptakov - 31-12-2014 at 03:47

Thank you, here's left: Liner diameter Cu 28/30,5 mm and plast container for pressing 30,5x45 hi 42. Plast is a connector for water pipes. Furthermore, the assembly for EFP caliber 22 mm. Plastic (24,2/35 hi 40) becomes integral part of EFP. This happens pressing pressure ...:cool:...LL

EFP22ab.jpg - 96kB

EFP 22

Laboratory of Liptakov - 2-1-2015 at 08:55

Ladies and gentlemen, here it is. The first attempt failed, but the second attempt, yes. It really works. Construction steel is destroyed by other experiments, but I finally hit that target. For 22 mm diameter x 0.56 can shoot through steel 12.3 mm. Here was using 8mm. Yes, it's small, but it's just research...:cool:...LL

EFP22.jpg - 305kB

Hennig Brand - 2-1-2015 at 09:19

Nice results you have there. What was the explosive you used? Also, the thickness of your liner was only 0.56mm right? Seems very thin, at only about 2.5% of the diameter, compared to some of the patent and explosive literature suggestions, but you can't argue with results.

EFP

Laboratory of Liptakov - 2-1-2015 at 09:42

This is a misunderstanding. Liner is 1 mm thick soft copper. It is on the picture. EM is an ecological high explosive. VoD about 7450 m / s. EM is the official meeting as a patent application. The composition will not be published. I'm sorry. But that's okay, mainly that it works...:cool:...LL

[Edited on 2-1-2015 by Laboratory of Liptakov]

EFP

Laboratory of Liptakov - 3-1-2015 at 06:07

Here is a successful attempt. Overcome 10 mm mild steel...:cool:...LL

EFP22.jpg - 169kB

22.3mm Diameter Liner EFP Experiment

Hennig Brand - 3-1-2015 at 13:34

A Canadian quarter was used this time. A ball peen hammer, vise and an appropriately sized nut were used again to form the curved dish.

EFP Liner Specifics:
Diameter: 22.3mm
Depth: ~4mm
Thickness: 1.58mm
Mass: 4.4g

Composition of coin/liner (according to Wikipedia):
94% steel
3.8% Cu
2.2% Ni plating

Stand-off:
30cm

Explosive Used:
14.2g of 80% ETN Plastic Explosive
80% ETN / 10% Polybutene / 10% Paraffinic mineral oil

Initiation:
7.6mm aluminum casing
0.8g PETN
0.3g lead azide
bit of basic lead picrate flash igniter
Core burning safety fuse

Casing:
~0.5mm thick side wall polypropylene pill bottle

Backing Plate:
~15mm thick disc/slice of softwood broom handle

Target:
3/8 inch (~9.5mm) mild steel plate

Penetration:
>8mm

The slug did not go completely through, but it came very close. If the explosive had been 90-95% ETN instead of 80%, or if there had been stronger confinement and a stronger/denser backing plate, the slug would likely have easily penetrated the 3/8" target. More standoff might have resulted in complete penetration, but then the hole would have been smaller in diameter as well. Using a copper liner would have resulted in a certain increase in performance as well.

The 80% ETN plastic explosive was used because it has very desirable handling properties, and although not an optimized explosive for shaped charge applications it is a good general purpose explosive.

The curve of the liner was not perfectly symmetrical (because the press wasn't lined up right during pressing), the liner was not perfectly centered in the casing and the blasting cap was not centered properly, all because of being in a rush. The charge performed reasonably well, but it is obvious that for best results things should be as symmetrical and well centered as possible.

Here are a few pictures and also a few stills from a video taken of the blast:


Pre-blast set-up

Set-up 1.jpg - 243kB Set-up 2.jpg - 241kB Set-up 3.jpg - 211kB


Stills

BLAST 1.jpg - 337kB BLAST 2.jpg - 359kB
BLAST 3.jpg - 348kB BLAST 4.jpg - 347kB


Results: (the slug was easily remove with fingers from the target)

Slug.jpg - 275kB Hole.jpg - 216kB Lump.jpg - 151kB


[Edited on 4-1-2015 by Hennig Brand]

Fulmen - 3-1-2015 at 16:58

Interesting work, but somewhat unfulfilling by your own admissions of substandard workmanship (no offense intended). A more detailed pic of the slug would be quite interesting as the great Dr. Liptakov did not recover his slug. I would suggest a soft backstop to collect the slug in future experiments, all details matter.

Another interesting idea would be to use something like a plated liner, if done correctly you could maybe get some data about the forming process by cutting it in half.

Bert - 3-1-2015 at 17:52

If those free to experiment with such technologies could fire the EFP into a sufficiently deep container of water (swimming pool? Series of garbage bags filled with water???) and then recover the projectile. To see somewhat more clearly what the projectile shape was after explosive forming?

Metacelsus - 3-1-2015 at 18:42

Would the projectile survive impact with water? I guess the experimenter will have to find out.

Hennig Brand - 3-1-2015 at 18:53

Quote: Originally posted by Fulmen  
Interesting work, but somewhat unfulfilling by your own admissions of substandard workmanship (no offense intended). A more detailed pic of the slug would be quite interesting as the great Dr. Liptakov did not recover his slug. I would suggest a soft backstop to collect the slug in future experiments, all details matter.

Another interesting idea would be to use something like a plated liner, if done correctly you could maybe get some data about the forming process by cutting it in half.


Ha, you must think this is a contest of the type where the guy with the most inches wins. I actually thought it was a fairly successful test. I simply pointed out a few things that I thought were significant and might be useful to others trying to make their own charges. Penetration depth is not necessarily the be all and end all of EFPs. Yes, it is normally how Monroe effect conical shaped charges are judged, but there are other aspects which are important with EFPs. The BEST EFP might be different from situation to situation. Yes, using a bent quarter in a plastic pill bottle casing is not cutting edge technology.


Quote: Originally posted by Cheddite Cheese  
Would the projectile survive impact with water? I guess the experimenter will have to find out.


I imagine most would break up or at least be damaged since they are traveling at the speed of a very high powered rifle bullet. I remember seeing the episode of Mythbusters years ago where they were trying to determine if hiding under water would save you from a bullet. I found the following summary of that episode here:

http://mythbustersresults.com/episode34

"Hiding underwater can stop bullets from hitting you.

partly confirmed

All supersonic bullets (up to .50-caliber) disintegrated in less than 3 feet (90 cm) of water, but slower velocity bullets, like pistol rounds, need up to 8 feet (2.4 metres) of water to slow to non-lethal speeds. Shotgun slugs require even more depth (the exact depth couldn’t be determined because their one test broke the rig). However, as most water-bound shots are fired from an angle, less actual depth is needed to create the necessary separation."


[Edited on 4-1-2015 by Hennig Brand]

Bert - 3-1-2015 at 19:34

I have run plenty of Copper & Lead projectiles into water, at speeds up to 1,100 m/sec. Yes, they deform. A projectile with a round nosed shape such as these would deform less, compared to one with an open, cup shaped nose (expanding copper jacketed bullet). Much less than on impacting an 8mm thick piece of mild steel...

http://youtu.be/QfDoQwIAaXg

This high speed video is instructive, unfortunately the maker did not list velocities and target materials.

[Edited on 4-1-2015 by Bert]

Hennig Brand - 3-1-2015 at 22:20

You could be right, pretty much the only exposure I have had to this is that Mythbusters episode. There is a lot of discussion on the net in various places about the MB's episode and what actually happens when a bullet hits water. A common assertion, which makes sense I think, is that when the bullet hits water at an angle (like on the MB show), that the side hitting the water first undergoes extreme deceleration causing huge shear forces which can tear the bullet apart. Hitting the water straight on should reduce the shear forces a lot. Also, more blunt nosed projectiles are apparently more immune to being torn apart when entering water at high velocity, as Bert said.

Fulmen - 4-1-2015 at 06:00

Quote: Originally posted by Hennig Brand  

the guy with the most inches wins.

That's life, son :D

I honestly wasn't trying to belittle your work, recovery of the slug was a huge plus (more pics?). But with all such charges the performance should be closely tied to the accuracy it is made to, although EFPs might be less sensitive than SC. In that sense this WAS a huge success as you got quite decent performance with a fairly crude setup.
A repeat with a more (or even less) accurate setup would provide interesting data on this.

Hennig Brand - 4-1-2015 at 07:54

Fair enough, some people do seem to feel the need to bring out their rulers a lot more than others though. :D
Oftentimes things that were measured shouldn't have been, and things that should have been were not. :D
Sometimes I may be too quick to react to people's comments.

Anyway, I took a depth gauge and more carefully measured the penetration depth this morning and when excluding the bulged up steel around the periphery of the hole penetration is about 7.2mm not 8mm. The diameter is however ca. 16mm. Assuming a perfectly cylindrical hole, the volume can be calculated as follows:

V = pi/4 * D^2 * depth
V = 3.14159/4 * (1.6cm)^2 * 0.72cm
V = 1.45cm^3

The volume is quite high and if desired a lot more penetration could be obtained by creating a slug that was smaller in diameter and had more length. At the small scales of our tests, the ease of slug formation and performance increase that comes from using a copper liner over a steel liner could very well be even more significant than it is with larger EFPs.

Attached below are a few pictures of the slug. The slug has an uneven distribution of mass which is characteristic of when there is asymmetry in the liner and/or charge or uneven confinement, etc.

Mass of unaltered quarter: 4.50g (Wiki gave 4.4g, which is the value quoted above)
Mass of recovered slug: 3.85g (0.65g of material is missing)

1.jpg - 277kB 2.jpg - 123kB 3.jpg - 121kB 4.jpg - 120kB 5.jpg - 118kB


[Edited on 4-1-2015 by Hennig Brand]

EFP 22

Laboratory of Liptakov - 4-1-2015 at 10:03

On the overall, final performance thus affects everything. My assembly was buried in the sand. Therefore, performance is noticeably larger. Also Cu liner is important. Henning work I can really appreciate. It's evolution, it is challenging. It's dangerous. It's a heroic job. It's like working for Moss.. Flying slug must be made exactly. Established exactly in the package. On the tenth of a millimeter. You need to use special forms, steel (or duraluminum) products, tools. For the energetic material to be pressing. No need 20% inerts. ETN can be clean. Because itself is like wax. PETN about maybe 5% plasticizer, I do not know, I've never seen PETN. Great Dr. Liptakov...:D not use the nitro or nitroesters. But it is not so much important. What is important is precision production, I think. Precise positioning and centering of the detonator. Tolerance estimated at a maximum 0.5 mm from the exact center.
The overlap any material package must be zero. Max 1 mm...:cool:...Dr. Liptakov, Tel Aviv

efp lis.jpg - 31kB

Hennig Brand - 4-1-2015 at 12:48

Thanks for the kind words LL, but performance is only larger if you measure it in terms of penetration. The volume of the hole you produced in your last test was about 0.95cm^3, while mine was about 1.45cm^3. So actually my charge did far more damage to the target. We don't know exactly how much more than 0.95cm^3 your charge was capable of, however, since it penetrated right through.

Ok, I think I feel my ego kicking in. ;)
I think my next charge will have a steel casing, thick steel backing plate and a copper liner. Parts will be made to high precision and possibly also an upgrade to an explosive with a higher Gurney velocity value. If it is inches you want, it is inches you will get. :D
Really though, shouldn't we just go back to making really deep pin holes with conical shaped charges if depth is the only important thing?


I personally have found that PETN is easier to press to a dense cohesive mass than ETN is. I also noticed that a plastic explosive is much easier to load into a shaped charge at high density and with good uniformity than a crystalline or granular explosive is.


[Edited on 4-1-2015 by Hennig Brand]

Bert - 4-1-2015 at 13:01

A mile wide and inch deep, or an inch wide and a mile deep?

How about trying for a symmetrical dispersion of multiple, precisely formed fragments derived from a single liner, once you've optimized performance of a single projectile?

Wire grid over the liner, precision shaping of liner & forming/propelling charge, multiple initiation points... So many possibilities.

Fulmen - 4-1-2015 at 13:05

That's the spirit, Hennig. You are of course right in that there are more to this than penetration, if it's diameter you're looking for then by all means go for that.

Hennig Brand - 4-1-2015 at 13:22

Thanks, I feel a little more spirited lately. :D
Well, both are important, of course it really does depend on application. Even though the volume of the hole produced in my test was high, I would like more penetration and there are several ways of getting it. One of the easiest ways is to simply increase the size of the charge, which would increase penetration depth as well as hole diameter. If there is a specific target that needs to be completely penetrated to do any real damage, and it is X inches thick, then of course the charge must be able to penetrate at least that thickness.

Bert, there are indeed a lot of possibilities. I find these explosively formed penetrators very interesting and fun to work with.


[Edited on 4-1-2015 by Hennig Brand]

12mm

Laboratory of Liptakov - 4-1-2015 at 14:17

Blade diameter 22.3 (x0,56) = 12.48 mm, steel Through the target. This means at least 10 mm passed through. Also: In 1990, EM was Oktol, liner from Tantalum was reached aperture diameter of 1.2 x D. (EFP course) ...I slowly am going to target steel 12 mm thick...:cool: And I have not even PETN. I do not even ETN. Maybe that detonate only flash No.9. And to light a cigar. Also shooting at a greater distance ...:cool:...LL

[Edited on 4-1-2015 by Laboratory of Liptakov]

Hennig Brand - 4-1-2015 at 14:59

That 0.56D factor you are using is a rule of thumb and actual results will depend on many things. Heavy/dense confinement and backing plate, such as a steel backing plate and steel casing, could greatly improve performance, especially with a small scale device. Heavy steel confinement is often not used in practise, from what I understand, because the weight increase would not be worth the performance increase and the danger to those using the device would be much greater also. I expect a significant improvement in performance by simply upgrading the casing and backing plate, when working at scales as small as I am currently.

You haven't stated what explosive was used in your tests so I don't know what was used. I assume the detonation velocity is at least 4500m/s because much below that the EFP effect gets very poor from what I have read. Everything I have is homemade with the exception of the fuse I guess, but I can make that as well if I had to.

edit:
Ok, I see where you said detonation velocity is 7450m/s.


[Edited on 5-1-2015 by Hennig Brand]

markx - 5-1-2015 at 00:47

Hennig, perhaps you could try the test with much larger standoff before the metallic confinement upgrade....say in the order of 70cm to even 1m. Judging from the impact crater it still seems to me that the slug formation is incomplete and partial. Since you have the means to test without burying the setup it might be quite easy to rig up that experiment and compare the craters. Maybe it's just the formation stage that is limited by unscalable effects in small settings. Just my 2 cents :)

capturing

Laboratory of Liptakov - 5-1-2015 at 02:25

If I had the opportunity to shoot freely, open space, I will shoot at 70 cm. For dia. 20-25 mm. Bert: plastic garbage bag, it is a very good idea. (ingeniously simple) Ordered bags behind. The first bag may be no water, I think. I suggest wood shavings. Not sawdust. The first bag may be polystyrene beads. It is sold in building. The second bag (width, depth 50 cm for alls), I suggest mineral wool (building). 3. sack of wool as well. Fourth bag of water. A total of 2 meters. 1. bag distance 100cm. As ballistic chamber. Capturing EFP projectile is a very interesting idea ...:cool:...LL

Hennig Brand - 5-1-2015 at 06:35

I actually planned on using 50cm+ as the standoff, but when I got to the site and was setting up I got worried that I would miss the target so I went with only 30cm. Not as easy and cheap to reload this gun as it is to reload a .22 cal for instance. ;)

More standoff should give more penetration you are right (smaller diameter, longer, slug). There was also very little confinement in my last test. More confinement does give better slug formation and higher slug velocities according to, "Explosive Effects and Applications". I posted a diagram from the text a page back in this thread showing slug formation with different amounts of confinement.


edit:
Made a few copper liners today. A 3lb piece of scrap copper pipe, 3 inch diameter, 1-1.2mm wall thickness was used as the source of copper. A hydraulic press and homemade cutter/punch were used to cut out copper discs and then they were formed by pressing between a ball peen hammer and steel nut the same way the coins were shaped. Some dies for pressing should be made, something like LL did, to ensure consistent symmetrical liners (I may make a set soon). I am going to do a test the same as the last test except that a copper liner will be used. The thickness of the copper liners is also a bit less which is likely a good thing.


Pressing out Copper Discs.jpg - 258kB Copper EFP Liners.jpg - 195kB


[Edited on 5-1-2015 by Hennig Brand]

packaging

Laboratory of Liptakov - 5-1-2015 at 11:45

Well! It looks good. I see that a lot of copper is annealed. That is good. I made a few more unsuccessful attempts. Attention. The packaging is very important. It must be hard, preferably steel wall at least 2 mm thick. It is minimum. If the packaging is soft (plastic only) or weak (only Cu clutch 1mm), EFP does not work good. Use soft or weak packaging waste EM...:cool:...LL

Hennig Brand - 5-1-2015 at 14:47

Thanks, good to know about the casing requirements. I might try one more test before I go for stronger confinement anyway though.

What you are looking at in my last post is an old piece of copper plumbing pipe that was cut down the middle, lengthwise, and folded out. The black is black copper oxide. Annealing probably would be a good idea though.

Hennig Brand - 8-1-2015 at 05:31

LL, are you anchoring the steel target? I have been just standing the target up and using a small spring clamp to steady it. Trying to decide if anchoring the steel plate/target better would make much difference.

The following snip-it was taken from, "History of the Shaped Charge Effect - The First 100 Years", by Donald R. Kennedy. I thought it was kind of interesting.

History of Explosively Formed Projectile.jpg - 440kB

gold sands

Laboratory of Liptakov - 8-1-2015 at 07:55

Henning, I know how attached the target. It is in the figures, the photo. If the target is large and heavy, so it's unimportant. The target may be in the air or sand. This does not affect the result. If so, I guess only difference is 5%. Maximum 10% of the whole assembly sand versus air. The sand will always be a little better results. And most importantly, it's safer. In particular, if the device is made of steel...:cool:...LL

Hennig Brand - 8-1-2015 at 08:24

I didn't try to work it out, at least not yet, but that is what I figured too. The diameter of the projectile is small and moving at very high velocity and the target is relatively heavy (a lot of inertia).


Success with Conical (Munroe Effect) Shaped Charge

I bought some of the steel cones that Markx discussed earlier in this thread here:
http://www.sciencemadness.org/talk/viewthread.php?tid=10575&...

I got a half order of the 1"W X 1"H (~53 degree apex angle) UK cones that Markx was using and the other half in 1"W X 1/2"H (~90 degree apex angle) US style cone studs. I used one of the 1" X 1/2" cones for my first test. An aluminum tube was bored out on the lathe so that it had an inside diameter slightly larger than the cone with a lip left for the cone to sit on. A section of hardwood dowel was turned down, so that it would fit the aluminum casing snugly. The wooden dowel section was also bored so that one end could accept safety fuse and the other end could have 0.15g LA, and 0.5g of PETN pressed in. Plastic explosive was used (3g of 80% ETN/10% polybutene/10% mineral oil). The PETN was in direct contact with the plastic explosive when the wooden bushing was put in place. Standoff used was 1.5 CD (charge diameter). Cone/liner diameter was ca. 1/2" (12.7mm). Charge diameter was ca. 15mm.

The charge easily penetrated the 3/8" (ca. 9.5mm) steel plate. Hole diameter was ca. 4mm at entry and ca. 3.4mm at exit. I know Markx has already been here with a similar type of charge, but it really is impressive how well these work. I feel I should have tried a thicker steel target, especially since I see looking back that Markx penetrated 15mm of steel with the more acute angled cones of the same type.

I don't have a lot of pictures because I forgot my phone when leaving for the test site. I did take one before assembling the charge and a couple of the target once I returned home.



Components.jpg - 125kB

Witness Plate Top View.jpg - 432kB Witness Plate Bottom View.jpg - 373kB


[Edited on 9-1-2015 by Hennig Brand]

dangerous amateur - 8-1-2015 at 12:34

Do you have an opinion on EFPs based on rather slow explosives? Like AN or even Chlorate binaries?

When I tested such charges on metal witnes plates I found that often holes with charge diameter where punched, and the loose material hit the ground with a lot of penetration power.

But the standoff was only 30mm or so. I wonder what would happen with the right standoff?


2500 or maybe 3000m per second is not hypervelocity, but maybe there will still be some kind of flowing or maybe forging of the metal into a "penetrating something"?

Hennig Brand - 8-1-2015 at 12:40

I don't have a lot of experience with it, but the literature indicates that those low velocity type explosives don't perform well in shaped charge applications.

cone 84

Laboratory of Liptakov - 8-1-2015 at 14:38

For deep penetration cumulative effect better is VoD + 6000 m/s. For EFP + 7000 m/s. (for quality efects). Use of plastic / copper / for the SC device. Construction steel 30mm / 1.18 inch. Inclined cone a few degrees. This is the error impact on the TOP...:cool:...LL

kumula 22.jpg - 170kB

Hennig Brand - 8-1-2015 at 14:55

That was a nice result you got there. I am anxious to try again with one of those little steel cones on a thicker piece of steel. I am looking at a piece of 3/4" (~19mm) steel plate right now which might just be the next victim. :D

armor

Laboratory of Liptakov - 8-1-2015 at 15:11

Amateur human mind is difficult to understand how this is possible. A piece of soft copper pierces thick armor. Unbelievable. But it works ...:cool:...LL

Hennig Brand - 8-1-2015 at 16:22

It is very amazing that it works, yes. Steel, and other materials also, behaves very differently when subjected to very high velocities and pressures.

markx - 8-1-2015 at 23:25

Quote: Originally posted by Hennig Brand  
I am anxious to try again with one of those little steel cones on a thicker piece of steel. I am looking at a piece of 3/4" (~19mm) steel plate right now which might just be the next victim. :D


These little buggers really leave a mark, don't they :D For 19mm steel plate I would suggest charge masses upwards of 5g (more likely 7-9g of nitroester/nitramine base for a clean penetration with mediocre confinement and presicion).
Really excellent work on the steel plate btw! Very clean uniform penetration, no deflection or divided jet patterns. Looking forward to the test results with 19mm plate :)

Bert - 9-1-2015 at 09:26

A long time back, in high school, I combined some of my metal working shop and art class projects- I tried making my own Copper blanks and then enameling these, besides other metal jewelry work. Never considered back then, I could have added some of my organic chemistry extra curricular activities to those projects? Probably not with instructor approval though.

I always wanted some of the nicer specialty tools for small metal working jobs...

Like these precision punches



image.jpg - 53kB

Or this set which also makes concave/convex discs...

Even if the profile wasn't exactly correct, a little free hand work with a diamond home on a punch mounted in drill press chuck could be done to alter such punches.



image.jpg - 55kB

I am a tool slut.

[Edited on 9-1-2015 by Bert]

markx - 9-1-2015 at 11:59

Here's the results of a 7g phlegmatized (10% PIB+methyl riccinoleate) PETN charge on 15mm steel plate:

20140328_194223.jpg - 1.3MB 20140328_201517.jpg - 1.2MB

20140328_202227.jpg - 1.6MB 20140328_202338.jpg - 1.6MB 20140328_203353.jpg - 950kB 20140328_202815.jpg - 1.2MB

I managed to recover the carrot...what a blessed find....the bastard was stuck at the outer exiting verge of the crater :D
I guess just 100mg more energetic would have sufficed and it would have left the target to never be found again.


20140328_202631.jpg - 1.1MB

[Edited on 9-1-2015 by markx]

Bert - 9-1-2015 at 12:06

Such a cute little hole punch.

It would be really nice to include a scale with such pictures, or use a piece of graph paper of a specified size for the background?

markx - 9-1-2015 at 12:37

Quote: Originally posted by Bert  
Such a cute little hole punch.

It would be really nice to include a scale with such pictures, or use a piece of graph paper of a specified size for the background?


I know, I know....I stand ashamed, facing multiple accusations of chronical incapabablity to include a proper scale reference in the graphical evidence of experimental results. But I was having just too much fun and the excitement of success can do weird things to ones' judgement for executing the correct scientifical method:D
In light of this the reported thickness of the plate can be viewed as anecdotal reference and I have no intention to file an appeal on the matter.
I promise to correct my wicked ways in future reports :D

Fulmen - 9-1-2015 at 15:09

But it's hard, isn't it? Doing the experiment is fun, even measuring the result is fun. But to document things properly, that's actually hard work. At least it is for me, and I suspect I'm not the only one. I think we owe our self to push each other, not only to do good note-keeping but also to share our work with enough detail so that others can replicate it. That's what science is all about really.

Other than that little derailment, I just wanted to say: Keep up the good work! I love reading about them, all the cool experiments you do.

I'm seriously considering revisiting my experiments with drawing liners, especially now that I have my furnace working. Sadly I have so much on my plate I can barely focus on the things I <i>have</i> to do even though it's my own projects that keep me going. I don't have time to do a write-up, but if others are looking into this route I'm sure I could offer up some advice.

This of course requires access to a lathe and quite a bit of theory, I have a PDF of "Handbook of Die Design", second edition from McGraw-Hill that was quite useful there. Don't know where I got it from but I'm sure you will find it if you search.

Hennig Brand - 9-1-2015 at 15:13

Nice work Markx. I like those cutters and dies Bert, but I think I am going to make one on the lathe to start. I think most of my problems have been because of asymmetrical liners, which may be what you were picking up on.

Yes Fulmen, the research, the experimentation and the documentation all take work. Most things done of any significance take work. People who do the work generally don't like to be belittled. We have been getting a look at LL's greatest hits, which is nice and I appreciate it, but there is maybe as much or even more to learn from some of the things others did (like myself) where things didn't go perfectly.


[Edited on 9-1-2015 by Hennig Brand]

Fulmen - 9-1-2015 at 15:24

Access to a lathe greatly improves your chances. Accuracy, not only in the manufacture of the liner but equally in the assembly greatly affects performance. If you can, make tools for the assembly as well. As always, the more effort you put into something the more you can expect in return. I suspect EFPs are somewhat more forgiving in this aspect.

NeonPulse - 9-1-2015 at 19:45

I agree hennig, for all our successes how many failures have we had? I know I tested at least 10 charges before I got any significant penetration nd these failures are what presses us to try again. If we got it perfect first go then where is the incentive to keep researching? Keep it up guys this is a great thread and its great to see it revived. In the near future I plan to attempt some EFP devices for myself. Its been a while since my last SC test and have found some nice old AUS pennies to try. They are copper only and 1.8mm thick. getting other factors right they should work well. Also hennig did you aim the efp somehow? Like a laser dot from the center of the charge and a mark on the target to match, just to see how far off supposed center the projectile strikes? If it hits close to the prediction then increased standoff should not be a worry with missing the target. NP

Hennig Brand - 10-1-2015 at 03:31

Glad to hear you are enjoying the thread. Regarding aiming an EFP, I was on rough ground, but the target and charge were both placed on a piece of plywood, which was relatively flat, which lined them up. A carpenters square can be used to make sure the charge is parallel to the wood rest and perpendicular to the target. The target and charge can be placed close together to ensure that they are lined up at the right height and then pulled apart to the desired standoff. Once at the right standoff I literally lied down on the ground behind the charge and sighted the EFP in by looking down the top of the charge casing. It is amazing how well the EFP can be aimed by sighting down the casing. A laser level would likely be a great way to line up an EFP with a target.

smart container

Laboratory of Liptakov - 10-1-2015 at 15:29

Using polystyrene container is very easy. Production takes 20 minutes. The entire device buries itself in the sand. EFP warhead can be very precisely adjusted. At the right angle 90x90 deg. Easy, cheap, fast. Safe. For the brave hero (for video) Needless to bury...:cool:...LL

EFP device.jpg - 177kB

Bert - 10-1-2015 at 21:42

You are using the plasticized perchlorate explosive described elsewhere as a an "active" backing plate/counter charge on the side of propelling charge opposite the EFP?

Thanks for the graph paper background! What size are the squares?


image.jpg - 61kB

[Edited on 11-1-2015 by Bert]

steel 12

Laboratory of Liptakov - 11-1-2015 at 02:50

Yes, slow plastic explosive is described in the thread cheddite, pag. 7, title AP plastic. Squares on the paper are 5x5mm. The mass used around 4g. Slow AP plastic as an active supporting plate. The detonation propagates in two directions. Thus it is meant. Here are the results of this report. Unfortunately, the device was not accurate. I do not know where the error is. Everything was made very accurately. EFP-quality effect is difficult to create. Despite this, 12 mm steel shot through. Although little, but still...:cool:..LL

verze.jpg - 296kB

markx - 11-1-2015 at 05:36

Congratulations! Excellent results LL! Now this impact looks more like the projectile had time and space to form into a rather decent slug. It also looks like the projectile parted or perhaps it is the impact of the separation plate that you had between the main charge and the backcharge. I guess the root cause of the partitions lies in the overcomplicated design of the separated charges. The separation plate, the copper tube through it coupled with the initiator....all this creates quite a mess at the back end of the main "brizant" charge when fired and can possibly do more harm than good to the overall performance of the device (by disrupting the uniform propagation of detonation wave in the main charge)
If one could embed a centrally placed initator between the main and backing charge in direct contact with both of them and with no penetrating channels through the backing charge then I think this concept might work magnificent. Technically very demanding task though...

floating liner

Laboratory of Liptakov - 11-1-2015 at 13:13

Here I want to do one more thought. Only one liner functioned flawlessly, perfect. And when it shot through the steel of 10mm. It was the only liner, which had a floating liner. Thus, as in the diagram. Other liners have been associated with the edge too hard, tight, firmly. After some consideration I come to the conclusion that the imposition of free disk space is a key structure, point. If the packaging paper, the detail is not important. But if the packaging is very hard (metal and more), it is important floating liner. It's just my opinion for discussion, it's not 100% confirmed. This opinion is based only 4 attempts...:cool:...LL



efp ring.jpg - 72kB

[Edited on 12-1-2015 by Laboratory of Liptakov]

Fulmen - 11-1-2015 at 14:06

Idunno... To me the hole looks more like something you'd expect from a SC with less than ideal focus, the dent more like you'd expect from a blunt projectile. And while it's hard to tell from the pics, the hole seems to be copper coated while the dent isn't. This leads me to believe that you actually made a SC/EFP combination, the SC being the Cu-tube.

On the other hand, getting that kind of performance from an accidental SC with low VOD explosives seems incredible, and how could this happen without the jet and penetrator affecting each other? Maybe I'm over-thinking this?

pressing

Laboratory of Liptakov - 12-1-2015 at 05:34

This is a misunderstanding. The scheme is modified, changed. After the molding process should liner little swim, do not touch the pipe...:cool:...LL

Hennig Brand - 12-1-2015 at 09:30

Quote: Originally posted by Laboratory of Liptakov  
Using polystyrene container is very easy. Production takes 20 minutes. The entire device buries itself in the sand. EFP warhead can be very precisely adjusted. At the right angle 90x90 deg. Easy, cheap, fast. Safe. For the brave hero (for video) Needless to bury...:cool:...LL


Nice results again LL. You know, I wouldn't say that I was a hero even though I am a little braver than many. I am not a kid anymore, but I still really do get a lot of pleasure out of a good detonation. As long as the risks aren't ridiculous I don't think there is anything wrong with that.

You're making good progress with your tests, keep it up! :)

I have also been trying to decide how well the EFP liner should be anchored, or if anchoring is needed at all really.


Here are a couple mini commercially produced shaped charges that are kind of interesting I think.

Attachment: Mini EBW Inititated Shaped Charge.pdf (29kB)
This file has been downloaded 518 times

Attachment: Mini EBW Inititated EFP.pdf (29kB)
This file has been downloaded 475 times


[Edited on 12-1-2015 by Hennig Brand]

edge

Laboratory of Liptakov - 12-1-2015 at 12:24

Well, Henning, In the scheme of these PDF attachments can be seen clearly saving liner. The liner is completely on edge. A wrap around is thick. This confirms the importance of this detail. Especially for EFP...:cool:...LL

efp edge.jpg - 75kB

Hennig Brand - 12-1-2015 at 13:11

I had the same thoughts myself, but at the same time I wasn't 100% sure if these diagrams could be taken as exact representations of the actual devices. At any rate they do provide a lot of useful information. I think you are right.

confirmed

Laboratory of Liptakov - 13-1-2015 at 01:04

The assumption idea marginal edge was confirmed. The backing plate is not important. Mechanical or active. That is unimportant. It is important to: 1) accurate initiation axis. 2) A uniform density of energetic material. 3) The exact and precise liner on the edge. Constructions used for overcoming the steel is 12 mm on the diagram. Dispersion of the slug is minimal. A force is huge. Attention: on the other side of the steel plate was damaged in the previous shot. Therefore, it is not a relevant result. But even so, Mythbusters are satisfied...:cool:..LL

clutch.jpg - 277kB

markx - 13-1-2015 at 04:37

Impressive performance LL! As we see, simplified designs tend to deliver reliable results and it is easier to pinpoint relevant details and causes for effects...either in a positive or negative direction. I always encourage myself not to overengineer things, even though it is tempting to try a complicated solution sometimes :D

Fulmen - 13-1-2015 at 05:36

Impressive indeed. And I agree with you that accurate assembly can make or break the performance. As for the backing I suspect this becomes more critical as the charge gets smaller. A charge height of 1 caliber seems to provide excellent performance without it, question is what happens if it's reduced to say 1/3?
When it comes to choice of material for backing I would assume that mass is more important than strength. The hoop stress for a thin walled cylinder is equal to p*r/t, and with detonation pressures in the 30GPa-range hoop stresses could conceivably be up to 1000 times the yield strength of mild steel.

Catching...

Laboratory of Liptakov - 13-1-2015 at 06:28

Thank you all for your support. Another attempt will be caught slug projectile. We all know that Slug is a very fast and powerful. As a Kalashnikov, maybe even stronger. Any suggestions? Definitely will be used 4-5 x bag filled 70x70cm. (50x50) Question: What do fill those bags? Condition 1: Slug must remain whole. Condition 2: Must be caught...:cool:...LL

slug.jpg - 17kB

Hennig Brand - 13-1-2015 at 11:09

I have searched around a bit on the net. This author seemed to have it figured out pretty well.


Attachment: High Speed Bullet Recovery for Analysis.pdf (421kB)
This file has been downloaded 547 times


Dornier 335A - 13-1-2015 at 12:36

Phone books or a tall stack of newspapers could probably be used as a first soft filler. Mythbusters used something like 10 phone books to catch a .30 bullet I believe, but I can't remember what shape the bullet was in afterwards. Maybe wood could be used as a last stop for the slug.
I remember reading about how aerogel was used to catch the hypersonic projectiles from light gas guns without damaging them. Considering how most materials say splat at 7-8 km/s, this is a pretty impressive achievement. But I doubt aerogel would be useful at this scale unless you have several cubic metres.

slug

Laboratory of Liptakov - 14-1-2015 at 08:04

Slug caught. But only half. Exactly 55%. Liner weight of 3.40g and slug 1.87g. Tried, but it is challenging attempt. Will not be repeated...:cool:...LL

break device.jpg - 160kB

Bert - 14-1-2015 at 09:14

I still like water-

Or snow. Soft, fluffy snow is a cheap stand in for the "aerojell" used in the gas gun projectile captures.

When I was a kid, I took a rifle to a very wide frozen lake with fresh snow about a foot deep. Set up a paper target, fired 50 rounds or so on a nearly horizontal trajectory about a meter above snow level- The projectiles intersected snow surface perhaps 200 m past target as they dropped.

When I walked out on the lake, the bullet path in snow made it easy to get a handful of nearly perfectly preserved fired bullets with nice, clear rifling marks. These were soft Lead .22 LR bullets, Copper carrots at 10X rimfire cartridge velocity will behave differently, I'm sure!

snow

Laboratory of Liptakov - 14-1-2015 at 11:13

Snow is a good idea. The density of snow can be controlled, modified. First meter light, the second meter medium density, mouthing shovel. 3rd meter pedaling shoes. Another obstacle water bag. Or very wet snow + water. But there is one problem. Nowhere is snow. If so, very little. OK, I wait for the snow ...:cool:...LL

Hennig Brand - 14-1-2015 at 12:57

I have tons of snow and you can have as much as you like. You have to transport it yourself though.
:D;):D

Laboratory of Liptakov - 14-1-2015 at 13:15

Henning, you have a lot of snow? Nothing you wait! Hurry up and catch fire! ...:D...LL

Hennig Brand - 14-1-2015 at 17:50

I hope that means you want me to do a test and not that you are fed up with me and would like for me to spontaneously combust. :D

I just remembered something from 25-30 years ago. My next door neighbor used to reload and shoot a lot. I remember a couple of times in the spring, when the large snow banks were melting, finding handgun bullets in the snow in his yard that looked like they had never been fired from a gun. These were not high velocity rifle bullets, but they were various large caliber handgun bullets cast from wheel weight lead. I remember as a kid marveling at the perfect condition of the bullets. I remember discussing it with him and he had in fact shot many rounds into the snow banks.

Fulmen - 15-1-2015 at 00:51

I agree, snow would be the perfect medium. But water should work as well, even though the velocity is quite extreme a solid copper projectile is pretty sturdy compared to a regular jacketed rifle bullet.

Also, good job catching the slug Liptakov. I assume it wasn't fired at any solid target? I find the low mass a bit odd, one should think that even a modestly well shaped liner should produce a single solid projectile.


2 top EFP

Laboratory of Liptakov - 16-1-2015 at 13:22

Snow still not. Here are other (2top) laboratory results. Liner has other outdoor establishment. This change of mind. On the contrary, it is easier to manufacture. Important dimensions are indicated. Freedom edges of the liner is maintained. This is important ... LL ... university of תל אביב

EFP 2.jpg - 394kB

Fulmen - 17-1-2015 at 02:42

Damn impressive work, Liptakov. Seems like you have cracked the code on EFPs, I'd love to see you do it again with a 2m standoff.

EFP m16

Laboratory of Liptakov - 17-1-2015 at 07:39

Effective range for liner 22mm is 22 meters. For professional device. I suggest shooting at 16 meters, about 75% of maximum distance. Target doors. Metal or wood. Laser pointer sight. Target will not be thick iron. It is necessary to determine the variance (divergence) to 16 meters. This will be a challenge. (Oh my God, this task will be) ...:cool:...LL

Fulmen - 17-1-2015 at 08:14

I don't think there is any absolute limits to the range, once formed the projectile should behave like any other ballistic object. Even with the poor aerodynamic shape it could probably still do serious damage at 100m, but I doubt you could hit the broad side of a barn at that range.

For a DIY device such as this I would be more than impressed with good performance at 100-200 x diameter (2-4m for your 22mm). 16m would blow my mind, but I have a feeling you just might pull that off.

[Edited on 17-1-15 by Fulmen]

Hennig Brand - 17-1-2015 at 10:33

From what I have read they are normally reasonably aerodynamic. Some of the fancy military grade EFPs are designed to form in such a way so as to improve accuracy (such as forming fins). Also, the liners are often tapered (thinner closer to the outer edge) which produces a slug that is less likely to break up and has better aerodynamic qualities. For a homemade device, as long as the slug is reasonably symmetrical and doesn't break up, the accuracy is likely very similar to an old smooth bore cannon. Since the projectile does not have the stability provided by rotation, as is provided to a rifle bullet by the rifled barrel, the projectile can sail and drift and even become unstable and flip depending on the symmetry and length to diameter ratio of the slug. It really depends on the size of the target, but even a reasonably well made homemade EFP should normally be very effective at 16m (I think). This is just the impression I got from the things I have read in the last few weeks.

Bert - 17-1-2015 at 13:17

If center of drag is 1 caliber behind center of mass, it's likely going to fly stable (like a rocket coasting, or a badminton bird). As far as accuracy... Who knows, without a lot of testing.


Hennig Brand - 17-1-2015 at 13:38

These devices have been extensively tested by different groups, guaranteed, but probably not much at the scale we are working at. Finding reporting of these test results in the literature might be a challenge though.

lead

Laboratory of Liptakov - 18-1-2015 at 01:38

In one patent, unfortunately I do not know the source, is center of the liner filled with lead. This method can readily be formed thick and heavy center. For better stability...LL

lead.jpg - 14kB

Fulmen - 18-1-2015 at 03:06

Interesting idea, however it will increase the complexity of the liner. I'd suggest making a smaller dimple that can be filled with lead and sanded flat before inverting the liner.

Bert - 18-1-2015 at 15:11

Keeping the Lead bonded to the Copper layer under the forces applied might be an issue?

Two layers of Copper @ 1/2 the desired thickness, very slightly different in curvature near center, such that they could be clamped into proper relationship, heated and a flux cored solder fed into the central void- Capilary action should take solder right to the outside edges, forming a solid unit

Fulmen - 18-1-2015 at 19:08

Quote: Originally posted by Bert  
Keeping the Lead bonded to the Copper layer under the forces applied might be an issue?

Shouldn't be a problem, lead solders well to copper and is extremely ductile. Use a good flux or pre-tin the copper and you should be safe.
But building a more complex geometry by soldering/brazing sheats of Cu would also be an option, I agree.

center lead

Laboratory of Liptakov - 19-1-2015 at 09:02

Produce lead center is very laborious. Nevertheless, the result is not good. Liner is uneven, not regular. Precision production (with lead) requires more precise instruments. Fulmen method is a good way to go. For further experiments (yet) will be used classic concave copper...:cool:...LL

lead center.jpg - 219kB

Laboratory of Liptakov - 9-2-2015 at 07:24

There is a way for 20 minutes to produce a relatively precise cone for use SC...LL...:cool:
https://www.youtube.com/watch?v=s0vgSBIc2UY

Bert - 9-2-2015 at 07:52

That's a nice low tech metal forming process- The results look good.

Did you measure thickness of finished cone? Thickness tapers from near apex of cone to outer edge?

cone

Laboratory of Liptakov - 9-2-2015 at 10:28

The outer edges are thicker, thus no change, 1 mm thick. The top of the cone is copper certainly weaker, thinner. But the measurement is difficult. Estimating peak cone is about 0.5mm thick...:cool:...LL

Gargamel - 9-2-2015 at 13:19

Thank you for the good video LL.

One question:
How important is it to solder the cone in place?
Does it improve performance or does it just help to keep the come in position while pressing the charge in there?

SC

Laboratory of Liptakov - 10-2-2015 at 00:16

First question: Performance is about the same. The second question, yes. Solder holds exactly the shape of the edge of the cone. This is important for accurate beam Cu. Fill the charge is much easier. Energetic materials can be easily molded. This pressing operation is required short cone. It is better to use plastic hard cover. As for EFP devices...:cool:...LL

SC press.jpg - 306kB

SC 22

Laboratory of Liptakov - 10-2-2015 at 03:02

For the following experiment is used edge with the solder, from video. For home exam I think it's good. Of course, it's not professional equipment. TeACP 15g @1,75..:cool:...LL

SC 39.jpg - 223kB

Dual liner shaped charge

Bert - 25-2-2015 at 08:57

A patent for same:

https://docs.google.com/viewer?url=patentimages.storage.goog...

I came across a set of these liners in "trumpet" configuration, outer Aluminum and inner Copper. Has anyone experimented with this configuration?



image.jpg - 134kB

Found something interesting today

NeonPulse - 17-3-2015 at 01:12

While at work today i came across this little guy. since i work in the construction sector i have seen a few of these things laying around but never took any notice. until today when i picked on up to look at it, and it looks like it would make a great little liner. it is copper, symmetrical and is 0.5mm thick all the way. it took me a little to figure out what it may be from and i think i found out. since i was near to an aircon unit being installed where i picked it up i searched a bit about it and came up with this. its some sort of dust plug for the copper piping i think. i reckon a test is in order to see if it work as i think it may. it fits nicely into some 20mm Cu tube but i may bend out the flange to get a little more area in the dish and punch a point into the dead center.if so it may be possible to obtain more if you were to find airconditioner installation place and ask if you could have a few. if i see them again i will be collecting them. NP

iaircon tubeages.jpg - 7kB 1.JPG - 143kB 2.JPG - 146kB

1/2" Steel Cone and 4g of ETN Plastique Penetrates 3/4" (ca. 19mm) of Plate Steel

Hennig Brand - 17-3-2015 at 06:50

A test was just performed with one of the 1/2"W X 7/16""H (~53 degree apex angle) UK steel cones that Markx introduced earlier in this thread. The steel plate was successfully penetrated, though a large carrot was left plugging the hole.

BTW, what I said back on page 38 of this thread, "I got a half order of the 1"W X 1"H (~53 degree apex angle) UK cones that Markx was using and the other half in 1"W X 1/2"H (~90 degree apex angle) US style cone studs", was wrong, the steel cones are actually, ca. 1/2"W by 7/16"H and 1/2"W by 1/4"H.

Energetic Material Specifics

Charge:
4g of plastique; 80% ETN/10% polybutene/10% mineral oil

Initiation:
0.4g of PETN, 0.1g LA, pinch of basic lead picrate, cannon fuse

The steel cone was only held in place by the adhesive forces between it and the plastic explosive it was pressed into. A bit of scrap wood, with a hole the diameter of the casing drilled into it, was used to provide the standoff (1.5CD).

Eighty grams of the recently made ETN (discussed in the NG thread) was used to make 100g of plastic explosive. The picture below shows 6.4g separated from the 100g, but because it would not fit into the casing only 4g of it was actually used. A carrot was formed and was left jammed into the top 1/3 to 1/2 of the hole height. On examining the bottom of the 3/4" steel plate and the piece of firewood below, it was clear the jet passed completely through however. A hole roughly 1/2" deep was blown into the piece of firewood below the steel target.



ETN Plastic Explosive 100g.jpg - 206kB Charge Bottom View.jpg - 162kB Charge in Place.jpg - 241kB
Top.jpg - 264kB Bottom.jpg - 240kB Plate Thickness.jpg - 180kB
Hole Underneith (1).jpg - 250kB Hole Underneith (2).jpg - 251kB



NeonPulse, those do look like they might make decent liners for EFPs.


[Edited on 17-3-2015 by Hennig Brand]

Bert - 17-3-2015 at 07:44

Could you estimate the density of plastic?

We are looking at which of the smaller holes? There are several tests on this target, apparently.

[Edited on 17-3-2015 by Bert]

Hennig Brand - 17-3-2015 at 08:03

The density of this type of plastique was around 1.43g/cc the couple of time I measured it in the past, but it can vary a bit. I could maybe measure some in a while and get back to you.

Ok, I just measured the density. The water displacement method was used to measure volume. A piece of the plastic explosive was carefully weighed, then the sample was placed into a graduated cylinder which contained enough water that when the plastic explosive was added it was not too far from full (graduated cylinders are more accurate the more close to being full they are in general).

Mass of Plastique: 11.35g
Volume before addition: 212.0mL
Volume after addition: 219.6mL
Volume of Plastique: 219.6mL - 212.0mL = 7.6mL

Density of plastique = 11.35g / 7.6mL = ca. 1.49 g/mL


Top Highlighted Hole.jpg - 178kB Bottom Highlighted Hole.jpg - 190kB



Found an interesting Doctoral thesis on shaped charge theory. In the near future I think I will have a closer look at it.


Attachment: Penetration of the Shaped Charge.pdf (4.3MB)
This file has been downloaded 889 times


Plastic Explosive Stability
I wonder if mineral oil helps stabilize the ETN the way that Vaseline stabilizes Cordite propellants.


[Edited on 17-3-2015 by Hennig Brand]

Bert - 17-3-2015 at 11:01

Do you mean stabilize ETN against chemical degradation/deterioration, or stabilize as in render less susceptible to accidental detonation?

If you previously gave the composition of the plastic, perhaps you could provide a link to that- Certainly seems to have VOD & power suitable for the use.

Hennig Brand - 17-3-2015 at 11:10

To act as a chemical stabilizer, making the explosive more storage stable. It does also desensitize the explosive to initiation a lot as well, but that was not what I was commenting on. The following was taken from the Naval Propellants page which has a pdf made of it in the propellants thread, "Mark I cordite consisted of 37% nitrocellulose (13.1% Nitrogen), 58% nitroglycerine and 5% petroleum jelly. This last ingredient had originally been used as a lubricant during the manufacturing process, but it was found that it also acted as a stabilizer as its unsaturated hydrocarbons counteracted the byproducts of the decomposition process."

I wonder if the Vaseline we buy at the drug store is the same as what they were using to make Cordite. Has it been purified and the unsaturated hydrocarbons been removed for the most part?

I just recently added the plastic explosive composition in the above description.


[Edited on 17-3-2015 by Hennig Brand]

Jimbo Jones - 18-3-2015 at 01:55

Can you give some details about your plastic explosive manufacturing process?

Do you make different fractions, or just use the recrystallized ETN? Rolling or kneading?

I’m just curios, because the PE above have very good properties for such a primitive binder.

Hennig Brand - 18-3-2015 at 04:12

Hot water from the tap (ca. 50C) was used to make a warm water bath. The polybutene and mineral oil were added to a glass bowl and heated on the warm water bath and mixed until warm, soft and of much lower viscosity than when cold. The fine crystalline ETN was then added to the softened polybutene and mineral oil mixture and then mixed with a plastic spoon. The partially incorporated plastic explosive "dough" was then placed on a previously warmed (ca. 30-40C) glass cutting board and repeatedly rolled out with a smooth glass bottle or glass or non-stick rolling pin of some kind. A rubber spatula can be used to scrap the "dough" off of the glass cutting board and off of the rolling pin when repeatedly rolling out the "dough". The material may also be placed in some waxed paper and kneaded by hand through the waxed paper, which I often do at the end of the kneading process.

markx - 18-3-2015 at 09:50

Nicely done! Although you might want to try a bigger standoff with these small cones....I found that 3-3,5CD gives the best result in terms of clean penetration. With smaller standoffs I had a very similar picture with the carrot getting stuck in the target, but the jet passing cleanly through. I guess with small charges and a 1,5CD standoff the cone has not enough time to fully form into a "spearhead", the edges hit the target on a wide area and seem to break the impulse.

Hennig Brand - 18-3-2015 at 13:54

Thanks, yeah, I was thinking that too the more I looked at the images above. However, I only used 1.5CD for the last test, with a 3/8" steel target, and there was a nice clean hole, but in that case the cone was anchored (sitting on a lip of aluminum left in the casing when it was bored out on the lathe) and this time the cone was not anchored at all. I will increase the standoff, for the next test, which should help.

markx - 19-3-2015 at 11:25

Time for waveshapers :D



WP_20150319_002.jpg - 1.4MB WP_20150319_001.jpg - 1.3MB WP_20150319_003.jpg - 1.4MB WP_20150319_008.jpg - 1.2MB WP_20150319_009.jpg - 1.3MB WP_20150319_010.jpg - 1.1MB WP_20150319_011.jpg - 1.1MB WP_20150319_012.jpg - 1.2MB


I think NitroGenes already tested some configuration of waveshapers with quite a success on this thread....I'll try to meet the challenge tomorrow ;)

The power source ( PETN with 10% by mass 5/2 mix of polybutene and castor oil:

WP_20150319_013.jpg - 1.2MB

[Edited on 19-3-2015 by markx]

Hennig Brand - 19-3-2015 at 16:24

Looking forward to your test and to learn a little bit about wave shaping. Nice neat assembly.
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