Jump to content
Sturgeon's House

Iron Drapes

  • Content count

  • Joined

  • Last visited

About Iron Drapes

  • Rank
    Advanced Member
  1. General AFV Thread

    What's the story here? Did it freeze up as they were halfway through or something? Or maybe the tank got stuck and they couldn't get it out before the water froze?
  2. Tanks guns and ammunition.

    I hope you appreciated my attempt at humor.
  3. Tanks guns and ammunition.

    Now I'm wondering if you are just trying to spite me because you won't let go of your preconceived notions or if you really have something to say. Held said that the main effect comes from vaporising and sputtering of the passing shaped charge jet, as it touches iteratively the edge of the flying plates. If there is a nearly 50/50 split between the contributions of dynamic plate thickness and jet disruption, he would not attribute greater importance to one mechanism over the other. I am going to sleep. If you want to know something, ask Held.
  4. Russians know Russian. Thanks for the correction.
  5. Tanks guns and ammunition.

    For a range of ERA plate thicknesses, jet velocities, angles and so on, disrupting the SCJ is by far the biggest mechanism. Feeding material into it is one of the reasons, sure, but it does not contribute to the effect nearly as much as the disruption effect. I predict that for some ERA like the Ukrainian Nozh with something like 2 kg of RDX, the disruption of the tip of the jet might already approach the same significance as the "feeding material effect". 2 kg really is a lot compared to many of the ERAs used in experiments, which have something like 0.2 kg of RDX or PETN or something, and let's not even mention the ERA block that got hit chain-detonating the ERA block beside it. We also have to take into account the fact that SCJs are not always continuous jets. Disturbance can cause it to break up and particulate. For example, in the armour array of an M1 Abrams, there NERA plates are located behind a simple spaced steel front wall. Impacting the front wall and emerging into the air gap behind it will cause an SCJ to partially particulate, and the behaviour of the jet will not be the same as a continuous jet when it impacts the NERA plates. Particulated jets will be easy to deflect by the moving plate of the NERA because the jet will tend to "splash" on the surface of the plate itself instead of going through, so sometimes there is very little penetration into the plate itself, and therefore almost no material being "fed". I suspect that you may see this at the end of a stack of NERA plates, when the jet is more or less expended. Older shaped charge warheads like the type you find on the old PG-7V (1961) are not so precise, and antiquated shaped charges like the Panzerfaust and RPG-2 are even more imprecise, so the jet is already a little particulated when it forms and hits the ERA, and less and less material is being "fed", so to speak. So for all intents and purposes, the value of ERA comes from disruption of the SCJ. BTW I think we all should use "dynamic plate thickness" instead of "feeding material". The former is an established scientific term and it is more specific than the latter.
  6. Tanks guns and ammunition.

    As a ratio to the experimental result. Ptot will equal something like 0.983 Ptot' or 1.0143 Ptot', so one over the other will get you a ratio. Sure you could get a fixed answer, and that answer will be the new Ptot but adjusted for the new variable. You can't actually get Ptot from the equation. To do that, you'll need this: PR is useful for finding out the residual penetration, which is what we actually want to know, and Ptot finds out how much the jet penetrates, including the ERA itself, which is not actually a useful value for us anyway because Ptot is basically the penetration of the shaped charge warhead. He also said: "This means a reduction of about 10% to 15%. But in reality it is again 70% and more. These numerical examples show that the ™dynamic thickness of the flying plates explains only partially the reduction effects of ERA sandwiches." But you choose to ignore it. So if the total effect of ERA can be expressed as a 70% reduction in the penetration of ERA, and various methods of identifying the factors in the reduction tell us that the dynamic plate thickness has an effect of between only 30% and 10-15%.... Yes, I consider that as a minor factor compared to the disruption and interference of the jet. It is not the primary mechanism of defeat. I never said that ERA can have an effect on a cumulative jet without any of the moving plates touching it, as if the plate simply disappears into thin air when it is touched by the jet. That is simply your imagination of what I am saying. I have said many, many times that the effect comes from the destabilization, disruption, interference, etc, etc of the jet as the moving plate impacts and cuts through it. Some of the effect comes from the thickness of the plate itself, yes, I never disputed that, because it would be stupid to do so, because no, I am not stupid enough to not realize that the plate itself has some thickness, and that moving it laterally across a jet or some other penetrator increases that thickness. Ask and ye sh- blah blah blah. And I wasn't even talking to you when I posted that. So in the context of this discussion, it has absolutely 0 relevance. Besides, the picture was from you, and you did not give the sources for any of the three pictures you posted. Don't make it harder for yourself.
  7. A Ukrainian friend told me that "Zaryazhaniya" was grammatically wrong, but yes, the manual does indeed call it "Avtomat Zaryazhaniya". Product code of the autoloader is probably not AZ, but it is called AZ in the manual.
  8. Fun fact: the T-72 uses the "AZ" autoloader, and "AZ" stands for "Avtomat Zaryazhaniya", literally meaning automatic loader. They were not very creative with names. The failure rate of the AZ autoloader as of 1971 was 1 per 448 loading cycles, which was equivalent to the barrel life of 600 EFC of the 2A26M2 cannon when a couple of high pressure APFSDS rounds were mixed into its usual diet of HE-Frag and HEAT. As a rule, the autoloader would be inspected and refurbished whenever the cannon had worn out its barrel. This was convenient, because the 2A26M2 did not have a quick-change barrel. You had to lift up the turret to pull the entire cannon out, and once the turret was off, you might as well do some work on the autoloader anyway.
  9. Absolutely. I am sure that window lickers like me will fit right in.
  10. Tanks guns and ammunition.

    Thank you for being objective. My "resume" can be found here: https://thesovietarmourblog.blogspot.com/
  11. Noted. I will be sure to follow this guideline to make high quality posts such as this:
  12. Tanks guns and ammunition.

    I respect that you are the admin of this entire forum, so I will cease and desist. The truth is up to the audience to decide. I simply express my hope that the criteria for "density of sources, citations and facts" also includes the fact that I actually shared links to the papers I cited so that everyone can benefit by reading them, whereas Bronezhilet did not share a single link or give a page number, or even share the names of the papers he cited.
  13. Tanks guns and ammunition.

    BTW, Manfred Held has actually done research that deals exactly with the phenomenon that you describe in a paper called "Dynamic Plate Thickness of ERA Sandwiches against Shaped Charge Jets": http://onlinelibrary.wiley.com/doi/10.1002/prep.200400051/epdf Held acknowledges that the relative thickness of the moving plate as it moves laterally across the SCJ is a factor in the reduction in penetration, but it is a minor factor compared to the disruption and interference of the jet itself. This is what he says: The equation for the dynamic plate thickness is derived as a function of standoff distance Z0, jet tip velocity vj0, cutoff velocity vjc, plate velocities vPI and NATO angle of the ERA sandwich. The dynamic thickness is presented as functions of the different parameters for the front plate – flying against the shaped charge jet – and the rear plate – flying with the shaped charge jet. But the dynamic thickness is only one of the reduction factors of ERA sandwiches. In the introduction he says this; The remarkable reduction of the shaped charge jet penetration can be explained by three different phenomenological effects [5]: increased dynamic plate thickness jet deflection by the interference of the flying plates wit hthe passing shaped charge jet [6] introduced detonative shock waves into the stretching jetand the interaction of the reaction products with passingjet sections [7] These are all his words verbatim: "As mentioned in the introduction, the reason for the disturbances of shaped charge jets and KE rounds by ERA sandwiches are split, into the dynamic thickness, described in detail here, the jet deflection and the interaction with the reaction products of the detonating high explosive charge.Besides smaller interacting effects, like not at all or less disturbed jet tip regions [12], the main effect comes from vaporising and sputtering of the passing shaped charge jet, as it touches iteratively the edge of the flying plates. This is summarised under the term deflection effect. Partially the jet and especially KE rounds are also lifted up by the transferred momentum [13]. This explains the experimental findings that thicker slower flying plates with less achieved dynamic thickness have at least the same or more effect against shaped charge jets and KE rounds. The dynamic plate thickness is definitely also one part of the effects, which disturb shaped charge jets and KE rounds,but does not give the full story for the defeat mechanisms of ERA sandwiches." "In a numerical example these diagrams should be explained. Using 270 mm as one typical Z0 value for the virtual origin of a shaped charge to an ERA sandwich, a jet tip velocity of 9 mm/ms and a cutoff velocity of vjc of 3 mm/ms under a typical NATO angle of 608, the dynamic thickness Ds of the plate flying with the jet ± rear plate ± is 206 mm and against the jet 63 mm, therefore in total around 270 mm. The used values correspond typically to an add-on reactive armour sandwich of equal layer thicknesses with 3/3/3 mm. Independent of the standoff against a 100 mm shaped charge such a sandwich gives a penetration reduction of 560 mm compared to the standard penetration of 800 mm. The perforation through a reactive armour plate means a reduction of 70%. But the dynamic thickness would give only a value of about 30%. Assuming a heavy reactive armour which is typically using thicker plates with slower velocities in the range of 0.4 mm/ms, the dynamic plate thickness is much less. According to Fig. 3 the sum of the dynamic thickness of the front and rear plates gives around 100 mm. This means a reduction of about 10% to 15%. But in reality it is again 70% and more. These numerical examples show that the dynamic thickness of the flying plates explains only partially the reduction effects of ERA sandwiches." So the major reason why SCJs have a reduced penetration when interacting with ERA is because it is actually damaged and destroyed. A minor reason is that it has to penetrate the plate itself and deplete itself that way. Compare you, genius of Sturgeonshouse forum, expert in terminal ballistics, who said this: "Anyway, yes, the main reason why ERA/NERA works is due to feeding material into the jet. Since a penetrator can only penetrate a finite amount of armour, you can lower the thickness of main armour it can penetrate by feeding material (armour) into its path." To Manfred Held, father of ERA: "These numerical examples show that the dynamic thickness of the flying plates explains only partially the reduction effects of ERA sandwiches." "the main effect comes from vaporising and sputtering of the passing shaped charge jet, as it touches iteratively the edge of the flying plates. This is summarised under the term deflection effect." But I guess Dr. Held is just a senile window licking old man. What does he know? Curb your egotism and stop insulting people just because they disagree with you.
  14. Tanks guns and ammunition.

    It's almost funny to see you pretending to be of the same caliber as the researchers that you cite, because clearly, you only pick out what you want to read and discard the rest, and it's also funny how you berate me for citing papers that I apparently do not have, because you are just referring to free open source papers like everyone else. I know this because I am reading the same paper that you are reading: "A Model for Explosive Reactive Armor Interaction with Shaped Charge Jet": http://onlinelibrary.wiley.com/doi/10.1002/prep.201500163/epdf At least have the courtesy to share what you are reading instead of trying to be all high and mighty about how great and smart you are. Yes, I see where you took that equation from (p. 60), and you are assuming that I know nothing about it. You are trying to fool me and everyone reading by bullshitting me and outright lying to everyone. That equation has nothing to do with finding out penetration of SCJ after interaction with ERA, and you are trying to conceal that fact by omitting information. Read the sentence below that equation: In other words, the equation is designed to find out the difference in results when the distance from the target, Z0, is compared to Z0' in the NERA code, NERA code being a computer code for simulating ERA. A single glance at the equation already tells you that it will give you a ratio, not a figure of armour penetration. That's because this paper is dealing with verifying NERA computer code with experimental results, not to find out why ERA works the way it does. And no, ERA still doesn't work the way you think it works just because you are throwing a temper tantrum. For example, this is something Held stated: One effective protection method used at present is disturbance of the SCJ stabilities by additional armour to reduce the SCJ's penetration ability prior to attacking the main armour. Explosive reactive armours are widely used in tanks because of their excellent interference ability The keywords are "disturbance of the SCJ stabilities" and "interference ability". Yes, feeding material into the jet is how the disturbance and interference is achieved. How else do you get the jet and the plate to interact? However, that is simply not the reason why ERA works, and it is one of the main reasons why ERA cannot be modeled as a fixed figure of extra steel armour on top of the base armour, which is what you are suggesting. You are deliberately ignoring what happens to the jet itself when it passes through the ERA: the stable flow of the jet material (copper) from the tail to the tip (accelerating along the way) is cut by the moving plates of the ERA. The cutting action produces shockwaves in the jet, causing it to disintegrate. The tip, which moves at hypervelocity, usually escapes the interaction with the moving plate and will continue to penetrate some small amount of armour. Maybe you are having some sort of crisis because you have been believing that ERA works like some magical extra armour your whole life. But please, don't post blatant lies. It makes you look bad.