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  1. The test of Soviet show that the 88mm not so power as we know when shot T-34 upper hull front. As my analysis, the impact angle is 52°50′, if the T-34 is real on a 20 degrees downgrade as the data, the impact angle is 43°57′. That's mean, if 800m is a 30 deg in maximum kill distances, the percent of penetration rate is very very low. I also show that, in the Soviet test conditions, if the percent of penetration rate is high, like 90%, and the 50% may be at 1800m or more, the estimated reasult will fit the data which 800m impact angle 60° 50% penetrated. Of course, there are so less datas like this test, it is not easy to get a accurate reasult.
  2. Hi, developers, this is an article about T-34/76 and T-34-85 protection and 85mm gun firepower. I think it could help you for the "Tank Crews". Another article about the principle of armor piercing is at here: Chapter 1 The T-34 armor quality 1-1 The dry cargo (original data) of T-34 armor test In 20th and 21st July 1943, a T-34/76 (1941 or 1942 model) was used for firing trials of the Tiger I Kwk36 88mm gun. The tests are at a distance of 1500 meters, the results are shown in follow pictures: Fig 1-01 The photos about 88mm shot T-34/76 Fig 1-02 The details about 88mm shot T-34/76 In table of Fig 1-02: (1) The first column is the hit place in tank. (2) The second column is the shells type. (3) The third column is the armor thickness. (4) The fourth column is the “Structural angle”, we can call it as “armor plate set angle”, which means the angle between the armor plate and the normal of the flat ground. (5) The fifth column directly translation is "meeting angle", the real name is “complementary angle of the path angle”, which means the complementary angle between the gun direction and the hull front direction in horizontal flat, 70 degrees means gun shots from side with 20 degrees angle. (6) The sixth column is the results. Many peoples mistake the fifth column as the "normal angle" or "impact angle", it was a wrong view. One reason is, we could find the fifth column datas are almost 70 degrees, and the different armor plate had different “set angle”, so if the fifth column was the "impact angle", it means after every shot, the testers should move the tank accurately to let the " impact angle" was 70 degrees. Obviously, it was impossible; the other reason is, in the fourth column, the upper hull front “structural angle” is 40 degrees, and on the plain, the T-34 upper hull front is 60 degrees “structural angle”, that’s mean T-34 is on a 20 degrees downgrade in test. Then if testers want to take 70 degrees “impact angle”, they will shoot it from a very large angle from side, it was a meaningless way, because this test purpose was simulating the performance in actual combat. The results are: 1. Turret ring, APCBC, 16 mm thickness, 0 degrees armor plate set angle, 20 degrees "side angle" with shell. Total penetration, turret is ripped off the tank, 130 mm long crack in turret skirt. 2. Glacis (Upper hull front), APCBC, 45 mm thickness, 40 degrees armor plate set angle, 20 degrees side angle, breach in armor, driver's hatch torn off, cracks in armor in length of 160-170 mm, shell ricocheted. 3. Nose part, APCBC, 45mm, 10 degrees armor plate set angle, 20 degrees side angle, penetration through, 160x90mm opening. Cracks in armor, 30-130-160mm length. Crack in weld seam, 300mm. 4. Nose "beam" (where UFP and LFP meets), APCBC, 140mm thickness, 0 degrees armor plate set angle, 15 degrees side angle, opening is 90x90mm, exit hole is 200x100mm. 5. Glacis, HE hit, 45mm thickness, 40 degrees armor plate set angle, 20 degrees side angle, insignificant dent, holding of frontal plate meeting with side armor skirt on the left side is destroyed. Base on these results, Soviets thought that T-34/76 can be penetrated by kwk36 88mm gun at 1500m. It looks like that the T-34/76 armor is weak to against 88mm gun. But if we look at the results again, we will find many interesting things. Let we see the three penetrated places at T-34/76, one is at turret ring, two are at “nose” area, all of them are the weak places at T-34/76. The HE also caused weld joint damaged. That’s why the T-34/85 had such changes: (1) Turret ring up to 90mm. (2) The meeting area of upper hull and lower hull had redesigned. (3) The lower hull plate slope angle from 53 degrees to 60 degrees. (4) Use the automatic submerged arc welding machine to deal the weld joint. The hit which can prove the resistance of T-34/76 armor, is only the 2# shoot at the upper hull. Soviet put T-34 in adverse conditions, they are strict with T-34. So how did this hit? A piece of armor had cracked, but the shell ricocheted!!! The driver's hatch torn off by the ricocheted shell. Well, maybe only one shoot result can’t prove a certain resistance, but it can prove that the Kwk36 gun can’t 100% penetrate T-34/76 upper hull front armor at these conditions. The penetrate percent at these conditions, may be was 10%, or 90%. For ease of calculation, we suppose this shoot 100% penetrated the hull. So how the “impact angle” is? The 40 degrees armor plate set angle, 20 degrees side angle, if you know how to calculate it, you can get the “impact angle” is about 43°57′. Someone may think this angle is too overstate, OK, let’s suppose the writer who record these datas drink too much vodka, he recorded the fourth column as the angle between armor plate set and the flat ground. Then the T-34 is on a 10 degrees downgrade not 20 degrees, the “impact angle” is about 52°50′, now we will use the DeMarre formula to calculate the Kwk36 88mm gun penetration distance when the T-34 is at a flat ground. DeMarre formula: Vc=K*b^0.7*d^0.75/(m^0.5*cosα^n) In the formula, “b” is armor thickness, “d” is the caliber of gun, b and d are commonly used for “cm (=10mm)”, Vc is the impact speed, calculated by “m/s”, and m is the mass of the projectile, calculated by “g”. “α” is the “impact angle”. K is the armor anti-ballistic coefficient, it is a comprehensive coefficient representing the physical properties of the armor material, which should be determined by the firing test, it cannot be calculated according to a certain stress. For vertical armor, n=0.7. For slope armor, the experimental results show that n>0.7, it is related to the relative thickness of Cb=b/d, armor type and the shape of projectile. The recommended K values from datas are as follows: Low carbon steel plate: 1530 Nickel steel plate: 1900 Generally homogeneous armor: 2000-2400 (the lower value is suitable for low carbon or medium hardness armor, while the higher value is suitable for high hardness thin armor) Surface treated (face hardened) armor 2400-2600 For T-34 and Kwk36 gun: “b” = 4.5cm “d” = 8.8cm “m” = 10200g We don’t know the Vc at 1500m, but we know the vertical penetration of kwk36, and the shell velocity decrease is linear with distance, so we can calculate the velocity decrease rate every 100m. Fig 1-03 The vertical penetration of kwk36 (from Wiki) Base on this table, we can calculate the velocity decrease rate is Vd≈9.1716m/s, so Vc at 1500m is 773-15*Vd=635.426m/s. We know, more “K” value, less the “n” value, the 1/((cos60)^n) will less, the Vc value of penetrating 60 degrees armor velocity will less, the distance of Kwk36 penetrate T-34 will more far. We calculate the Vc by using unfavorable conditions for T-34. We set the “K” value as high as possible. The T-34 armor was high hardness armor, so we set the K=2400 in this equation. Now let’s substitute the data in DeMarre formula: When T-34 in Soviet test conditions: 635.426=2400*4.5 ^0.7*8.8 ^0.75/(10200 ^0.5*(cos52°50′) ^n) We calculate the n≈1.1950 Now let’s substitute the data in DeMarre formula: When T-34 at flat ground: “α” = 60° The formula changes to such equation: Vc=2400*4.5^0.7*8.8^0.75/(10200^0.5*(cos60)^1.1950)≈796.62m/s The PzGr. 39 (APCBC) Muzzle velocity is only 773m/s, that’s mean Kwk36 can’t penetrate the hull front armor when T-34 at flat ground. Well, something was wrong. Where was the wrong? It is the Vc and the K value. The conditions which we supposed are based on 100% penetration, but the penetrate percent on penetration table always 50%, that’s mean the distance will more far than 100% penetration, the Vc will also less than 100%. And the K value of T-34 maybe higher than 2400. If the 50% penetration distance in Soviet Kwk36 test was at 1800m, the equation is: 635.426=2400*4.5 ^0.7*8.8 ^0.75/(10200 ^0.5*(cos52°50′) ^n) We calculate the n≈1.107 Then the Vc of 60° impact is: Vc=2400*4.5^0.7*8.8^0.75/(10200^0.5*(cos60)^1.1071)≈749.48m/s That’s mean Kwk36 can penetrate it at 256m. If the K=2800, the n≈0.801, the Vc≈707.28m/s, Kwk36 can penetrate it at 716m. Of course, K=2800 is looks like too high, but remember that, the K is “a comprehensive coefficient representing the physical properties of the armor material, which should be determined by the firing test, it cannot be calculated according to a certain stress.” These two reasons let us has calculated an exaggerated result. But please noticed that, although the Vc=796.62m/s was exaggerated, but it also proved T-34 armor had a high resistance to Kwk36 gun. And when the K=2800 or higher, the n=0.801, the Vc will more reasonable, and is very close the datas in Tiger crew manual. There are other original datas about T-34 armor, which came from German tank manuals: Fig 1-04a The Tiger crew manual about T-34 penetrated distance 1 Fig 1-04b The Tiger crew manual about T-34 penetrated distance 2 Fig 1-05 The Panther crew manual about T-34 penetrated distance Fig 1-06 The Pak40 manual about T-34 penetrated distance Fig 1-04, 1-05, 1-06 were some manuals of German tanks and gun, T-34A is normal type T-34/76, T-34B is the type with additional armor. Many people think German “animals” could easily penetrate T-34 upper hull front far than 2000m, but obviously fact was, German didn’t think their guns so power. In Tiger, Panther, Pak40 manual, the distances of penetrating T-34 upper hull front were 800m, 1000m, 100m. I think German had no reason to overstate the resistance of T-34 armor, and they also had no reason to use uncertain penetrate distance in tank and gun manuals. These distance datas were reliably, and the T-34 probably at flat ground, which mean the impact angle was 60 degrees. There was also an original data about Soviet test Pak40 vs T-34 upper hull front: (http://tankarchives.blogspot.com/2014/04/spare-track-links.html) Fig 1-07 T-34 spare track test It shows that Pak40 can penetrate at 1000m, but can’t penetrate at 1100m. This data has no detailed angles and hits data, but refer to the test of Kwk36 vs T-34, Soviet also put T-34 in adverse conditions, and the “can’t penetrate” means 0% penetrate, so the “can penetrate at 1000m”, may means there was a low percent penetrate rate. Compare with the original datas above, the inference of <WWII Ballistics- Armor and Gunnery> was so unreasonable and prejudiced. The author of <WWII Ballistics- Armor and Gunnery>, had no detailed shot datas, even no hit place details, and he used these uncertain “reports”, refer to American armor tests to inference T-34 upper hull front resistance of 75mm APCBC was 93mm. How unreasonable and prejudiced was. The T-34 and M4 upper hull front resistance on German tank and gun manuals, may could explain why Soviet and American didn’t extensive increase T-34 and M4 hull armor. Different with German Panzer IV, the T-34 and M4 hull front armor resistance were enough to against most German guns. Don’t forget, the most German tank and anti-tank guns are Pak40 and Kwk40, for penetrating a T-34 at flat ground, if Pak 40 need 100m distance, the Kwk40 even can’t penetrate it, Panzer IV need to attack the turret ring or other “weak points” from front. And in Tiger crew manual, to penetrate T-34 and M4 hull front, both needed 800m distance. So Soviet and American only need to improve and increase T-34/ M4 turret armor, German had to design a new tank—Panther, because Panzer IV had so weak hull armor. 1-2 The improvement of T-34/76 and T-34/85 armor The test of Kwk36 vs T-34/76 let Soviet knew what’s the problems in T-34 design and build, they improve them, let’s see the improvement on T-34/85 again: (1) Turret ring up to 90mm. (2) The meeting area of upper hull and lower hull had redesigned. (3) The lower hull plate slope angle from 53 degrees to 60 degrees. (4) Use the automatic submerged arc welding machine to deal the weld joint. The automatic submerged arc welding machine was used not only in T-34/85 building, but also some late T-34/76 model 1943. Some pictures show that: Fig 1-08 Build T-34-76 Fig 1-09 Build T-34-85 A Fig 1-10 Build T-34-85 B Fig 1-11 Build T-34-85 C Except welding improvement, the heat treatment of armor also improved. Fig 1-12 T-34-76 armor property The fig 1-12 is came from “AD011426 < Review of Soviet ordnance metallurgy>”, the T-34 armor datas are based on the T-34 model 1943 which sent to Aberdeen Proving Grounds. The “Impact Energy V-Notch Charpy Ft. Lbs. at -40°F” was a data which could directly reflect the resistance of armor. We could see in T-34/76 model 1943, hull lower side, sponson floor, turret roof, bow casting had low “Impact Energy V-Notch Charpy”, the data of bow casting even was 2.2, that’s why it was so 140mm but could be penetrated by Kwk36 at 1500m. These parts of armor had a bad heat treatment because of decreasing man-hours. Then let’s see how was the T-34/85 armor. In 1951, a captured T-34/85 was sent to American for testing, the results formed a report called “CIA-RDP81-01044R000100070001-4 <Engineering analysis of the Russian T34/85 tank>”. Unfortunately, because the hull had no big change, Americans didn’t test the “Impact Energy V-Notch Charpy” of T-34/85 hull armor, but they test the turret: Fig 1-13 T-34-85 turret armor property Compare T-34/76 turret roof, T-34/85 turret top plate “Impact Energy V-Notch Charpy” from 5.5 up to 10, which show the improvement in armor heat treatment. And don’t forget, in most cases, the lower side armor, sponson floor armor are more important than turret top armor, so this improvement also proved that the heat treatment of T-34/85 lower side and sponson floor armor had improved. 1-3 The change of Americans views about Soviet high hardness armor resistance American views about Soviet high hardness armor also changed when they test T-34/85. In AD011426, Americans think: “The very high hardness encountered in most Soviet tank armor has caused much unnecessary concern regarding the relative ballistic performance of the hard Soviet armor and the softer American armor.” “Competitive ballistic triale which have been condacted at ordnance proving grounds on both very hard beyond question of doubt that in many cases, representative of actual battlefield attack conditions, very hard armor is distinctly inferior in resistacne to penetration as compared to armor of more convertional hardness.” Fig 1-14 AD011426 Soviet armor views But in < Engineering analysis of the Russian T34/85 tank >, Americans think: “The flat sloping armor in the front could be expected to provide desirable shell deflection properties.” “Alloying materials had been effectively used to obtain toughness along with the desired hardness. The armor, for example, was much harder than our specifications call form yet at the same time tougher.” Fig 1-15 <Engineering analysis of the Russian T34-85 tank> armor views 1 Fig 1-16 <Engineering analysis of the Russian T34-85 tank> armor views 2 Obviously, in 1951, Americans realized that their high hardness armor had a low performance, and can’t treat as same as Soviet high hardness armor. Soviets also negated American views about their high hardness armor, in the report “"Minutes of the meeting on the question of the evaluation of T-34 and KV tanks by Americans", CAMD RF 38-11355-360”, a transport link is: http://tankarchives.blogspot.com/2013/04/aberdeen-t-34-and-kv-1-test.html In this data, Soviets said: “The Americans insist that the T-34 and KV tanks' plates are hardened shallowly, and most of the armour is soft steel. They suggest that we change the hardening technology, which will increase the armour's resistance to impacts. This opinion has no basis in reality, and was likely caused by poor analysis of the armour.” Clearly, the resistance of T-34 armor was not a “93mm” joking level, it is higher than most people think. The only problem was, for example, although the Pak40 could only penetrate the upper hull front at 100m, but when T-34 at a downgrade conditions, the resistance will decrease many. The weak places on turret also can be penetrated by Pak40 from far than 100m, although these weak places not so easy to hit. Most people often ignore that, the T-34/85 had the best side armor in WWII medium tanks (except “Jumbo” “Assault tank”, which more like a heavy tank), the designer make T-34/85 as a “Offensive tank”, they need considering the front 60 degrees and side resistance, the 75mm thickness turret side had a well resistance even more than Tiger I, and the turret and hull had a well bulletproof shape, you could hardly find weak points on each side. Compared T-34/85, Panther turret side looks like a paper, in combat, 45mm anti-tank gun could easy penetrate it at a not so near distance. T-34/85 turret rotate speed is 25°/s, was the fastest speed in WWII tanks, could make sure that its gun quickly directing the targets in large front area range, this is very important in “offensive”. In < Finnish Impressions of the T-34-85>, had evaluations about T-34/85 in armor, guns, engine and others. (the link is: http://tankarchives.blogspot.com/search?q=Finnish+Impressions+of+the+T-34-85) How did it said T-34/85 armor? "Armour: the armour is mostly the same design and same thickness. The hull in general has no advantages over the precursor. The turret is roomier. The armour is improved in the front. It resists 47-75 mm guns well at medium and long range. The sharper shape of the front increases the chance that armour piercing shells will ricochet. The quality of armour is higher than on the model 1943 tank.” 1-4 The quality of German tanks armor Many people think that most of German tanks in WWII had a high quality armor. But is that true? Let’s see some original datas about Panther armor: Fig 1-17 Panther armor property 1 In fig 1-17, we can see that the Panther upper hull side armor (52mm) “V-Notch Charpy Impact Energy at -40°F” was 2.2-3.2 Ft. Lbs., this is so bad as T-34/76 bow casting. Americans heat treatment this armor again, the data is: Fig 1-18 Panther armor property 2 Well, the V-Notch Charpy Impact Energy had a little increase, but it still less than T-34/76 lower hull side, which had not good heat treatment in building. In fact, in WWII, Germans still walking on a wrong way of heat treatment and armor elements using. Only Tiger I armor had the nickel (Ni) element, other type tank armor had none of this important element. And many people also think the Soviet tests on German tanks armor are unfair, they claim that the trials should not count because of two things: one is that certain parts of the tank (such as guns, optical devices, etc) are removed from the tank prior to testing and the other is that the tanks' plates are hit several times over the duration of the test. A title can explain these things: http://tankarchives.blogspot.com/2015/04/common-questions-unfair-testing.html First: multiple hits per plate. This test simply represents the harsh realities of war. Rarely, if ever, are tank battles one on one encounters where only one shot is fired. Usually you are facing a battery of guns or a platoon of tanks that will all fire at the same time, and they will do without being gentlemen and letting the other party reload. Of course, you will get some instances where a section that was compromised by previous hits is penetrated, but, at least in the case of Soviet tests, this is plainly noted in the document. Fig 1-19 Panther destoried Fig 1-20 KV1 hits Fig 1-21 Panther test Fig 1-22 Tiger destoried Fig 1-23 T-34-76 test 1 Fig 1-24 T-34-76 test 2 Fig 1-25 M4 test Now for the next part: removing components before testing. You can see that some components are missing from the vehicles above: guns, vision blocks, etc. This is also caused by harsh reality. When you capture an enemy vehicle, everyone wants a piece: the artillerymen, the optics scientists, the electricians, the mechanics. By the time the tank reaches the range, odds are it will be stripped of any components other than the hull, since nothing inside will survive the rigorous testing displayed above. Sometimes you don't even get an entire tank. Nevertheless, this is another reality of life and simply how everyone tested. Fig 1-26 T-34-85M test. The tank is simply an empty hull with just enough wheels attached to get it to the range. Fig 1-27 Sherman ballistic test Fig 1-28 Object 701 test A trial about Panzer III armor test could show how the German armor was: http://tankarchives.blogspot.com/2014/02/pziii-armour.html Obviously, not only German tanks got multiple hits in Soviet test, not only German tanks removing components before testing. Soviet also test their tanks at same ways. But only German tanks armor had a poor performance at same conditions, which also prove the poor quality of German tanks armor. Chapter 2 The T-34/85 firepower 2-1 The dry cargo (original data) of 85mm gun test One famous test of Tiger I in Kubinka was the 85mm gun shooting, the 1000m penetrate distance became a well-known result of 85mm series gun. Someone think it was 90 degrees “impact angle”, so considering the “side angle”, they said 85mm gun could penetrate Tiger I upper hull front at only 500-800m in actual combat. Now let’s see what’s the details of the 85mm gun test: Fig 2-01a 85mm 800m penetrate Tiger lower hull side twice Fig 2-01b 85mm 1450m penetrate Tiger lower hull side Fig 2-01c 85mm 1000m penetrate Tiger upper hull front Fig 2-01d 85mm 1500m penetrate Tiger lower hull front Fig 2-01e Details of 85mm gun shoot Tiger In Fig 2-01e, the armor plate set angle of upper and lower hull front were 27 degrees and 5 degrees, we also know that the angle of them on flat ground were 8 degrees and 27 degrees, considering a certain amount of error in measure, the Tiger I was at a certainly about 19-20 degrees upgrade status. OK, we could see that Soviet are strict with their weapons, in the test of Kwk36 shot T-34, they let T-34 in adverse conditions, and in the test of 85mm gun shot Tiger I, they let their 85mm gun in adverse conditions. Then how the “impact angle” in this shot? The 27 degrees armor plate set angle, 30 degrees side angle, means the “impact angle” was about 39°30′. Well, the 85mm gun could penetrate Tiger I upper hull front far than 1000m from 60 degrees front range. The penetration at Tiger I lower hull side also proved 85mm gun firepower, this shot penetrated in one side, and penetrated out from other side, and in Soviet official data, the 85mm APBC penetration at 500m was 110mm, and the two Tiger I lower side hull plates were 124mm thickness. These results proved two things: one was, in actual combat, the penetration performance of 85mm gun APBC shell was more better than the “penetration tables”, and it had well performance on penetrating large angle sloped armor; the other one was, compared the Soviet armor and penetration standards, the Tiger I armor quality performed not as well as Soviet. It’s not means that the Tiger I was easy penetrated in actual combat. Because the upper hull area was not a very large place at Tiger I front, the lower hull front often had spare track link at later version Tiger I, the most area of turret front superimposed thickness was more than 120mm. And the most important thing was, Germans used Tiger I as a “sniper” in most time, if they use it as a “attacker” as T-34, Tiger I would very easy lost in 1944-1945 battles. 2-2 The accuracy of 85mm gun In 1944, a captured King Tiger was trailed in Kubinka, one result was the KwK43 88mm L71 gun had same accuracy with D-25T 122mm gun, which showed the well accuracy of Soviet guns. Then how about 85mm guns on T-34/85? There are some original datas: Fig 2-02 Details of 122mm BR-471B accuracy Fig 2-03 Details of 85mm BR-365(A) accuracy In fig 2-02 and 2-03, the last but two and last but one columns are the vertical dispersion and horizontal dispersion, we can see that the 85mm APBC had 0.2m×0.3m dispersion at 1000m, better than 122mm APBC 0.3m×0.3m performance. Someone will say Germans had better quality and large magnification aiming telescope. But we should know one thing, Soviet use Zeiss optics technologies to build their telescopes, these technologies are import at the time of “Soviet-German honeymoon period” before WWII. Americans and UK also gave well evaluations about the telescope on T-34/76 which had been sent for testing. The quality of Soviet telescopes was good. Then let’s see the magnification: Fig 2-04 German telescopes magnification Fig 2-05 Soviet telescopes magnification Fig 2-06 US and UK telescopes magnification We can see that the advantage of German “animals” telescopes not the magnification, is the visual field, and the capacity of changing between 2.5X and 5X. The only exception was the telescope of T-34/85, Soviet designer select a balance point between magnification and visual field, compared the 5X magnification, the 4X magnification had very small gap but wider visual field. The German telescopes often need a wide visual field, the reason was not the German had well technologies in building telescopes, just because German tanks had not a well visual field in late wars. OK, maybe someone still think the numbers can’t prove anything, there is a test of Zis-s-53 on T-44: Fig 2-07 Details of 85mm gun accuracy in T-44 In this table, the T-44 use the Tsh-15 telescope, the different between Tsh-15 and Tsh-16 was the Tsh-16 had electrical heating for demisting. The target on the front sector area, crews don’t know where and how far the targets were. The results were clearly, the accuracy was 100% at 1000m, even rough aiming by using the electric turn motor. In < Finnish Impressions of the T-34-85> said: “Observation devices: the refractive telescopic sight is greatly superior to the sight of the model 1942-1943 T-34 tank. The clarity of the sight is on the level of the German 75 mm model 1940 gun. The field of view was increased by 15%. The markings are more convenient when firing on tanks up to 1000 meters. Injury during motion is nearly impossible due to comfortable pads. The periscopic observation device is simple, has a clear glass block, and is convenient to use. The commander's cupola allows the commander to observe the battlefield, and the turret traverse mechanism is a positive influence on the gunner's target acquisition.” 2-3 The visual field of T-34/85 The T-34/76 and KV-1 had no commander tower, so many peoples think all of Soviet WWII tanks had a bad visual field, that’s was wrong. If you compare T-34/85, JS-2, Sherman with German tanks, you will find that German tanks had bad visual field than Allies later war tanks. Don’t know why? Let’s analyze it. On T-34/85 turret, commander, gunner, loader everyone had a periscope, this periscope could turn 360 degrees, and could put up and down in a range for looking up and down. On turret each side, there was a watch split for gunner and loader. Commander had a tower, except the periscope on top, the tower had 5 watch splits. The tower had two types hatch, the early type was two semi-circle parts, the later type was one big part. Both of two types hatch could turn 360 degrees, the periscope on hatch also could be turned follow the hatch turning. The visual equipment on T-34/85 turret could give crews very convenient conditions for watching outside, searching and locking the target. But how “animals” were? For example, Tiger I, commander had a tower, 7 watch splits, in mid version, for keeping commander’s safety, 7 periscopes instead the watch splits, but it was only a substitute for watch splits. 360 degrees turn periscope? No. Gunner and loader periscope? No. Only in late version, Tiger I loader had a periscope, but can’t turn. The gunner, still no any periscope for watching, the only visual equipment was the watch splits on turret left side. In fact, in most WWII German tanks, only commander had visual equipment, gunner and loader even had no watch split. That’s why German telescopes had wide visual field, because gunners need to use it for watching, searching, locking targets. But we know, the visual field of telescope was still small, and gunners also can’t turn turret left and right quick just for taking a watch, so the efficiency of German tanks watching was still low in later wars. Some Sherman crews recalls that, the Sherman could cost little time from search to lock target, but Panther may cost over 25s. This saying maybe not very exactly, but it could prove the low efficiency of German tanks watching. In < Finnish Impressions of the T-34-85> said: “Armament: the 85 mm gun is a compact tank gun, identical to the German 88 mm tank gun in main parameters, losing out slightly in range and trajectory due to superior quality of German gunpowder. Compared to the 75 mm tank gun, the new Soviet gun has superior armour piercing and high explosive capability. The design of the gun is very good. It is smaller than the German 75 and 88 mm guns. The design is simple. It surpasses the 76 mm gun in flat shot range by 1.5-2 times.” “Conclusions: the new T-34 tank is significantly different from the previous model, not only in armament, but in terms of general combat characteristics. Drawbacks of this tank include the control system, suspension, and transmission. Currently, this type of tank is one of the best medium tanks, on par with new German tanks.” T-34/85 was not a simple 85mm gun upgrade of T-34/76, Soviets learn from the war and use the experience in improving their tanks, when German walking on the ways of too thick armor and powerful guns, Soviets were improving their tanks more reliable, better quality, and better combat efficiency of the crews. Chapter 3 Some prejudices and rumours about T-34 1. The prejudices of “Western views” People thinks American and “Western” tests and reports were puritanical and fair. In some cases, it was. As long as it is a human being, there will be subjective consciousness. Of course, many “Western” tests and reports were puritanical and fair than others, but no one could keep absolute puritanical and fair. Except the prejudices of Soviet high hardness armor, there are other two examples in <Engineering Analysis of the Russian T34/85 tank>, the first one was the air filter of engine, the other one was gearbox. Americans thought that the engine air cleaner of T-34/85 was low efficiency and may case problems, but the reason was very interest, they looked at structure of air filter, found it was outdated and less dust in it, so they had the conclusion, without any test. Well, even if the air filter of T-34/85 had low efficiency, but is it not enough for use? Not to mention that the air cleaner maybe had a well efficiency. The same thing happened on gearbox, Americans found the structure of T-34/85 gearbox was outdated and some gears heat treatment not well, so they evaluate it not well. In < Finnish Impressions of the T-34-85 > said: “Power plant: the diesel engine is the same type, but more carefully produced, is 20-30 hp more powerful, and has a longer lifespan under medium loads. The oil system is of the same type, but oil consumption is reduced by 30-40%. The exhaust is less smoky. The air filter does its job. In the summer, the diesel engine overheats less, in the winter, it starts more easily. The electrical equipment has isolated copper wiring.” And there is an initial data which the 6th Guards Tank Army discovered the following lifespans of their tank engine and power system: Fig 3-01 T-34 reliability In this data: “T-34: 2000-2500 km, 250-300 hours IS/ISU-122: 1200-1800 km, 230-280 hours M4A2: 2000-2500 km, 250-300 hours SU-76: 1200-1800 km, 180-200 hours Individual tanks made it as far as 3000 km, and their motors functioned for 300-350 hours.” The other famous thing was the air filter in T-34/76 which be sent to Aberdeen. We should notice one thing first, the air filter in T-34/85 was a new model with well efficiency, it was different with T-34/76. And in Aberdeen, after traveling 343 km, T-34/76 1943 model was disabled by the breakdown of the V-2 diesel engine. The Americans are of the opinion that this was caused by a poor air filter on the diesel engine. The T-34 sent to America had an air filter of the “Pomon” type. This filter was installed on T-34 and BT tanks. If properly cleaned and supplied with oil (in exceptionally dusty environments, this must be done once every 2-3 hours), the “Pomon” filter guarantees normal engine operation with 79.6% air purity at air dustiness of 1 gram per cubic meter. The filter at Aberdeen was not cleaned [Note: the filter was also not oiled. The Americans wonder why the filter is called "oily" by the Soviets in their impressions], which led to uncharacteristic engine wear. Obviously, the reason of this T-34/76 broke down was not cleaned and oiled, but a lot of people said the reason was the poor efficiency and T-34s (include T-34/85) were unreliable. A typical “Western prejudices views”. 2. The lost numbers and “rush by numbers” When we see the lost of Soviet AFVs (Armored Fighting Vehicles), we will amazing that so much the number was, and think Soviet had forever lost so much AFVs and mans. But this is a wrong view. What is the truth? How Soviet counted the AFV lost? The vehicles broken in marching, it was lost, the vehicle was shut down by enemies but can be repaired, it was lost, even the vehicles out of fuel in marching, it was also lost. The vehicles can't work in action, it was the lost, this was the standard of Soviet “lost”. So, the number of Soviet “lost” not the “true lost” or “forever lost”, many of them are not cause by enemies, or broken in battle but can be repaired, most of them are "lost" more than twice even three times. A book could show this: <РОССИЯ И СССР В ВОЙНАХ XX ВЕКА ПОТЕРИ ВООРУЖЕННЫХ СИЛ Статистическое исследование>, Под общей редакцией кандидата военных наук, профессора АВН генерал-полковника Г. Ф. Кривошеева, МОСКВА “ОЛМА-ПРЕСС”, 2001. In this book said, in 1944, only 24.6% Soviet AFVs lost are "true lost", and in 1945, it was 14.7%. And as many peoples thinks, Soviet won by numbers, it is true in some cases, but please remember, only the numbers and rushing can’t win, it just sent the experience and records to enemy. In fact, from 1943, Soviet had shortage of mans, if you see the data about Eastern campaigns, you will find in most campaigns, Soviet “numbers” of tanks were 1.2-1.5 rate to German, in sometimes, Soviet had less tanks than German. The shortage of mans, and the resources cost limited Soviet numbers of AFVs, there are a group interesting date about it: In 1943.01.01, Soviet has about 20600 AFVs, about 8100 service in front line. In 1944.01.01, Soviet has about 24400 AFVs, about 5800 service in front line. In 1945.01.01, Soviet has about 35400 AFVs, about 8300 service in front line. In 1945.05.09, Soviet has about 35200 AFVs, about 8100 service in front line. These data mean, for Soviet army, one crew group, had four tanks ready for them, if I’m a Soviet general, I will cherish my crews and soldiers more than tanks and other equipment. 3. The ergonomic of T-34 A mainstream of view about T-34 is its ergonomic was bad. This view is not all right. The most comfortless maybe the driver of T-34, but if you had got in T-34, JS-2 and T-54, you will know that the driver in T-34 is more comfortable than other two tanks. The reason of bad ergonomic about driver in Soviet tanks, is the pursuit of low hull height. The low hull height let driver keep a comfortless posture in tank. But that’s not mean the crews in turret are same. In fact, if put cutaway drawings of T-34/85, Sherman, Panther in same scale, you will find the space of T-34/85 crews even more than most medium tanks. The most tanks in WWII had a transmission axis in floor, this design occupied the space of fighting compartment, and let the height of hull become high, but Soviet tanks no. Maybe only Tiger I and II had larger turret space than T-34/85. Some tanks, like Panzer IV, its turret space even less than T-34/76, the crews in it also had a bad ergonomic than T-34/76. The Panther’s loader, had a crowded space for loading, it influence the efficiency of loading. The designer of T-34/85 still try to improve the ergonomic in T-34. In T-34/85, for driver, an overcenter spring for main clutch reduced the foot pedal pressure required to disengage it; and in turret, there is a mechanism to help loader in loading ammos, loader could easy load the ammos from the turret back ammunition rack into bore, just sit in his seat and need not to move. In < Engineering Analysis of the Russian T34/85 tank >, Americans also praised the improvements in convenience of crews. 4. The lost rate of crews and bad performance in Korea The report of American in Korea let people think the T-34/85 crews had a high lost rate after penetrated, this is a one-sided view. There are two reasons for that: the one is the lost reason not only the penetration, if crews escape from tank but killed by infantries or tank machineguns, it was also “lost”; the other reason is American crews will shoot the target many times after it had been destroyed in Korea, the multiple shooting let crews had a less chance to escape after penetrated. Another view is the Sherman had water jacket, and Soviet no. We should know that, the water jacket will decrease the influence of the fire after penetrating, not mean the shell hit the ammunition rack won’t explode, if the shell hit the water jacket, the steam may cause more problem. And for T-34/85, most ammos are in the floor below the turret, a place which is the hardest to hit after penetrating. The diesel oil tank in hull side also ensure that the fire won’t burn to sky like the petrol. And the most American and German tanks, the oil tank is in floor, the ammos at the hull side or near the basket of the turret, were more dangers than T-34. Many pictures show that the tanks had terrible destroyed by fire or explode, but we need to know that, most of these tanks, won’t burning serious or explode at once after penetrated, crews often had some time to escape, a terrible destroyed tank not means the crews all lost. Even in sometimes, the tank in pictures were deliberate destroyed to a terrible status, just for “the effects of publicity”. A table contains total losses in the 5th Tank Corps during the Rezhitsa-Dvinsk Offensive Operation (July 18-28th, 1944) could prove something, the detailed data could be found in: http://tankarchives.blogspot.com/2016/03/tank-crew-losses.html The table had both of T-34/76 and T-34/85, figures gathered from American medium tanks (presumably Shermans of various makes) let us compare the safety of the T-34 series to that of the Sherman. The radio operator is in a lot more danger (27.3% vs 10%), but the loader is in a lot less (39% vs 21.4%). The rest of the figures are comparable. Overall, 24.6% of the Shermans' crews died when their tank was destroyed, compared to about 28% of T-34 crewmen of both types (the nature of the Soviet chart makes it difficult to calculate the exact percentage), because T-34/76 is 4 crews, T-34/85 is 5 crews, the rate of T-34/76 is up 28%, T-34/85 is below 28%. Well, I think this comparison can explain many things. The exchange rate of T-34/85 in Korea was also bad, but it means T-34/85 is a bad tank? No. Compared Americans, North Korea had a bad war system, they had control of the air, bad cooperation between tanks and infantries, and the important thing is, although many North Korea crews were return from Soviet, but they fighting formalist, they don’t know how to flexible application of the knowledge and tactics. Look at their parade step, then compare the using and results of M1A1 between US and Iraqi Government Army, you will know why North Korea were defeated by US, but Chinese put the front line to “The 38th Parallel”. 5. Using hammer to shift gears This was the most absurd view, if you had got into a tank, you will find it is very hard to shake a hammer in driver seat. This rumours was came from a story of KV1, in early type, KV1 the rod of shift often jammed, so the driver using a hammer to take a knock, then it will work well. But it was impossible of using hammer to shift gears. 6. The “advanced” technologies will have a well performance Most of us think the “advanced” technologies will help weapons have a well performance, even roll the weapons which using the “outdate” technologies. In some cases, it is right. But most of us also forgot that, how “advanced” is suitable, and does “advanced” must case a well performance? Take the gearbox as example. At first, we should know the three forms of tank turn: (1) Gradual turns Two tracks run at different speed, then tank will turn to the side which has a low speed. The turn axis is out the tank, and the turn radius is large than other forms. (2) Sharp turns One side track moves forward or back, the other side track braked and don’t run, the tank will turn the braked side. The turn axis is in the middle of braked track. The turn radius is very small. (3) Pivot turns One side track moves forward, the other side track move back. The turn axis is in the middle of tank. The turn radius is minimum. Then, let’s see the gearbox of T-34 series first, which was deemed to outdated structure by Americans. The T-34 has two levers at driver’s left and right, for control left and right track. When control the tank make a turn, driver need to pull the lever at the side which he wants to turn. At the first half range, the lever controls the clutch in that side; at the second half range, the lever controls the brake in that side. This structure is simple and reliable, tank drivers could use it to do “sharp turns” and “gradual turns”. Because it could directly control each side clutch and brake, it could do many complex operations, which could help the tank has a well maneuverability in combat. But in “gradual turns”, the power will has some lost, because there is only one side track link to engine, the other side track will had resistance from ground. This type gearbox is easy for training the drivers who came from the tractor driver. But it still a different gearbox with the tractor. If a driver wants to become a “good” driver, he needs many experience and hard training, compare to Sherman or Panther drivers, that’s not an easy way. Then let’s see the Sherman. Dmitriy Loza, who was the Hero of the Soviet Union, a Sherman tank commander in Soviet, in his book < Commanding the Red Army's Sherman Tanks>, he said that: “It is easy to say, "Offload the tanks!" But how was this to be accomplished without any loading platform? Our first obstacle. And after this, another obstacle, no less troubling. The Sherman turned by using both differentials. This tank could not easily turn "on a dime," to rotate 90 or 180 degrees, not a problem for the Soviet T-34. The American tank required a significant area to turn around. How could this be accomplished on a flatcar? The front staff representative was in a hurry to get us offloaded. Apparently, the situation at the front demanded the immediate introduction of fresh reserves.” Well, the Sherman which Americans aided was M4A2, I don’t know how many types Sherman can’t do a “Sharp turns”, but the M4A2 can’t. Of course, M4A2 can’t do a “Sharp turns” not means its turn radius is very large, but obviously, its maneuverability in a cabined place will be poor, like narrow streets. That’s the “advanced” structure of American gearbox, although it may be easy handled, but not a right equipment for tanks. Then let’s see Panther. Panther and most of “Animals” used a “Double flow drive” (maybe called this name) gearbox, which let the tank could do “Gradual turns”, “Sharp turns”, “Pivot turns”, and it lost less power in turns. This type gearbox was very advanced in structure and technology, but it was too “advanced” in WWII, it was only saw at WWII German tanks, and after that, no tank used it, until in the third generation main battle tanks. Although Panther gearbox looks like had a well performance in maneuverability, but in combat, it was very unreliable. The Panther final driver also had bad quality, its life span was only 150km. Then if driver want tank work well, he should not do a “Pivot turns”, even can’t turn in fall back. Finally, the “advanced” technology didn’t give Panther “advanced” performance in battle.
  3. Hi, developers, this is an article about the principle of armor piercing. I think it could help you for the "Tank Crews". Another article about the T-34/76 and T-34-85 protection and 85mm gun firepower is here: As a main theme, the armor vs gun is an important thing for every tank, so expound the armor piercing principle is important for us. Of course, this is not necessary to read other chapters, you can skip this chapter and go straight to the next chapter. But as a basic knowledge about “armor vs gun”, I highly recommend you read this chapter. When talking about the armor piercing, we often thing it is a simple process and easy to calculate by some formulas, but it is a whole wrong view, the process of armor piercing is very complex. Chapter 1 The summary of armor-piercing principle 1. Development of armor-piercing projectile types and armor types (1) Rolled Homogeneous Armor (RHA) and Armor-Piercing projectile (AP) Rifling emerged in the 1840s, high-speed spin shells were sharping steadily, and armor-piercing shells became possible. Sharped armor piercing projectiles appeared in the 1960s, the process of piercing mainly by extrusion, can effectively deal with low hardness homogeneous steel armor, used to attack the rising armor warship. (2) Face Hardened Armor (FHA) and Armor-Piercing Capped (APC) In the 1880s, Countries began to use hardened armor on warships A sharped armor-piercing projectile is prone to fragmentation and failure when it strikes a surface hardened armor, so its armor-piercing ability is greatly reduced. In the 1890s, Rear Admiral Makarov of Saudi Arabia put a low-hardness steel cap in front of the sharped bullet and designed a cap-pierced bullet. But after Makarov died in the Japanese-Russian War, the APC was paid attention to by the Russian authorities and was distributed in 1907. The Royal Navy had issued APCs in 1904. APC projectile can effectively deal with surface hardened armor, but the penetration force is greatly reduced when the angle is large, so it is not easy to break through warship armor during long-range curved firing. (3) Slope armor, clearance armor and armor-piercing carbide ballistic cap (APCBC) After World War I, blunt cap by the surface hardened appeared. The blunt cap behaves better when the angle is larger than the cuspidal cap. In order to improve the aerodynamic shape, a thin hood was added to the cap, this is APCBC. The hood is thin and has no effect on armor- piercing. The warship began to use a double-layer surface hardened armor to fight APCBC shell. The thinner outer armor causes the cap to work ahead of time, and the thicker inner armor breaks the projectile. (4) High hardness armor and armor piercing blunt cap (APBC) In the 1930s, for many countries, tank armor became generally high in hardness, and the Soviets developed blunt-headed armor-piercing projectiles. The armor-piercing process of APBC is dominated by shear and punch, it can effectively deal with high hardness armor, surface hardening armor effect is also good, but for low hardness armor effect is general. Because of the aerodynamic shape, APBC need to have wind caps. In addition, APBC have good effects on large angle sloped armor and multi-layer armor. However, APBC are sensitive to T/D value than AP, so when used in small caliber guns, it doesn't work well. That’s also a reason why Soviet aspire large caliber guns for their tanks, the APBC shells are basic ammo type for their tanks. Fig 1-01 Force condition of bullet impact on armor plate (5) Armor-piercing discarding sabot (APDS) There was a way to “large caliber gun shot small caliber shell” in the 1930s, this will increase the initial velocity and range of the shell. Since the diameter of the projectile is relatively small, APDS projectiles are required to fit the caliber of the gun by sabot. The sabot does not participate in armor piercing, in order to reduce the dead weight, the quality of the sabot is relatively small, and has a negative impact on the storage speed, so after the loading, the sabot will be separated from the cartridge core. In 1940, the Frenchman developed a cemented carbide core (usually tungsten carbide) for shell removal. Because the diameter of the projectile is small and the core hardness is high, the perforation is very small, which can reduce the kinetic energy loss and effectively deal with the vertical armor with low hardness. But France was soon defeated. In World War II, only the British were equipped with a hard-metal core of the APDS ammunition. However, the problem of incomplete de-hulling led to poor firing accuracy of the shell-piercing projectile, which was not resolved until the end of the war. (6) Armor-piercing-composite rigid/ Hyper-Velocity Armor Piercing (APCR/HVAP) In order to reduce the kinetic energy loss during armor piercing, the Germans developed cemented carbide subcaliber armor piercing projectiles before 1940. The body of this armor-piercing projectile is made of high-hardness alloy (usually tungsten carbide) with a smaller diameter and a very small perforation, which can reduce kinetic energy loss and effectively deal with low-hardness vertical armor. In order to prevent fragmentation, the front end of the projectile needs to be covered with a cap. Since the diameter of the projectile is far smaller than the caliber of the gun, it is necessary to add the sabot. For conical cannon, the receptacle is retractable. In addition, there are non-cemented carbide subcaliber armor piercers (APNCR), but very rare. 2. The value of Thickness/Diameter Thickness/ Diameter value, also known as "T/D" or "B/D", is the ratio of armor thickness to the diameter of armor-piercing projectiles. The diameter here is actually another expression of the mass of the projectile. In theory, the greater the density and the ratio of length to diameter of the rigid projectile, the better, because the kinetic energy can be concentrated on the smallest possible area and the loss of kinetic energy can be reduced. However, spin projectiles need to maintain a sufficiently large axial moment of inertia, so that the ratio of length to diameter cannot be too large (according to the formula for calculating the moment of inertia, when the mass is far from the axis of rotation, the moment of inertia is greater). So, this ratio is only for steel spin-stabilized projectiles. 3. Process of armor piercing The current armor piercing process is similar and is a combination of multiple destruction processes. But different T/D values, projectile types and armor types will change the proportion of each process. (1) Impact During a high-speed impact armor (especially a surface hardened armor), the projectile may break down due to stress concentration. High-hardness projectile are easy to break down. If left uncontrolled, the crack extends throughout the projectile and invalidatas the projectile. The tip stress of normal AP is very concentrated, so the it should not be made too sharp, the shoulder is usually caused by circular arc, the smaller the radius of the arc busbar, the more dispersed the stress. Adding a cap to the tip can disperse the stress to the shoulder and prevent the body from breaking. The cap is usually made of low-hardness material so that it does not cause too much resistance to the body. APBC do not have a tip and do not cause stress concentration, so blunt-headed bullets do not need to be capped. In addition, in order to enhance the effect of adiabatic shear, APBC should not be added the cap. (2) Adiabatic shear failure As the projectile began to penetrate the armor, the temperature at the point of contact rose sharply. The armor at the point of contact was melted because the time was very short and the heat was too late to spread. As the projectile advances intermittently, the armor surface is cut off and the adiabatic shear process ends. The contact point area of the sharped projectile (normal AP) is very small and round; if the angle is larger, the contact area will be larger and triangular. The contact point of blunt head projectile (APBC) is circular and the kinetic energy loss is larger. For high hardness armor, adiabatic shear time is shorter and kinetic energy loss is smaller. As a result, the kinetic energy loss of APBC projectiles is relatively large when shearing low hardness armor. (3) Layer crack damage The projectile also produces shock waves when it hits the armor. Because the sound speed in the steel is fast and the attenuation of the unit distance is very small, the shock wave usually reaches the back of the armor more quickly and reflects than the projectile. The reflected wave peak interferes with the subsequent wave peak, resulting in local stress concentration. When the armor has poor toughness (usually too high hardness or improper heat treatment). This stress separates the back armor from the armor body, and in severe cases causes the back armor to collapse in the form of a diskette. The form of destruction is the same as that of the armor buster. Spallation damage can turn a single armor into a double armor, which makes it more vulnerable to flushing damage. If a fall occurs, dished debris has a lot of damage, and the armor thickness will be smaller. (4) Extrusion failure When the heat generated by friction is not enough to melt the projectile, the projectile begins to squeeze the armor, and the armor is squeezed sideways. The extrusion resistance increases with the increase of armor hardness. For ductile armor, the extruded armor produces a circle of bulge around the perforated perimeter. When the hardness of the projectile is higher, the deformation of the extrusion process is smaller, the diameter of the bullet hole is smaller, and the kinetic energy loss is smaller. The DeMarre formula is suitable for simulating the extrusion process of rigid projectile to ductile armor. The extrusion process of the sharped projectile (AP and APCBC) accounts for a large proportion, which is also the main process of kinetic energy loss. When the radius of busbar is large, the extrusion resistance is smaller. The proportion of extrusion process of blunt head projectile (APBC) is small, and the kinetic energy loss is very small. The proportion of extrusion process also decreases with the decrease of T/D value. (5) Positive rotation and negative rotation When the thickness of armor on one side of the armor path is small, the radial pressure of the projectile is unbalanced and a deflecting moment is produced, which makes the projectile deflect towards the small thickness side. This effect is evident when the impact angle is large. Because the outer pressure is small, the projectile deflects to the outside of the armor, that is, negative rotation. The larger the radius of the bus, the greater the torque. When the negative positive moment action time is longer, the projectile will jump. However, when the mass of projectile is large, the deflection to jump requires greater angular momentum, larger radius of deflection path, and thicker armor to provide deflection torque. In other words, the higher the T/D value, the more obvious the negative deflection. The deflecting moment of blunt-headed projectile is much smaller than that of sharped-headed projectile, so the negative rotation is not obvious. When the angle of impact is not large, it can even make the projectile deflect in the direction of vertical armor and positive rotation. The AP is easy to jump, so there is a blunt cap hardened through the surface (APCBC). The deflection moment produced by the blunt cap can also make the projectile turn positive when the angle is small, but when the angle is large, the torque of the cap to the projectile makes the projectile turn negative. Therefore, in the case of large impact angle, the armor-piercing path of APBC projectiles is smaller than that of AP projectiles. (6) Self-blunt and self-sharpening The steel body of projectile may be torn during penetration. Especially the charge body, the strength is relatively low, the chamber damage may cause the aftereffect to be affected. The fracture groove can control the position of the bullet body fracture and protect the medicine chamber. The fracture groove of different shapes can control the shape of the projectile after fracture, which can be sharped or blunt. The velocity of long-rod armor-piercing projectile is still very high in the process of penetration. The friction heat between projectile and armor causes heat, the projectile is melted, the length becomes shorter, and the shape of projectile changes. This process occurs only when the projectile has a high speed, usually a long-rod armor-piercing projectile with a speed greater than 1200m/s. Because the metal between the projectile and the armor is molten, the projectile can be regarded as liquid, the same principle as the HEAT. For tungsten projectiles, because the melting point is relatively high, the length change is small, the front end of the bullet is self-blunted, becomes mushroom-shaped, the perforation is increased, and the kinetic energy loss is increased. For uranium projectiles, the melting point is relatively low, the length varies greatly, and the front end of the projectile is self-sharpened and needle-shaped because of falling off. The self-sharpening effect can also be achieved by adjusting the molecular structure of some tungsten projectiles. With the increase of armor hardness, the resistance of self-blunt and self-sharpening process increases. Multi-material composite armor can cause a complex process, which is not detailed here (7) Plugging damage When the residual thickness of the armor is small, the T/D value decreases and the armor is cut off to form a plug. The process of getting the plug out of the armor by the projectile is the plugging. The kinetic energy loss of projectile is very small in the process of plugging. Krupp formula is suitable for simulating the plugging process. The percentage of the plugging process of a sharped bullet (AP and APCBC) is relatively small. The smaller the T/D value, or the higher the armor hardness, the greater the percentage of the plugging. The plugging process of blunt head projectile accounts for a large proportion, which is the main process of armor piercing. The proportion of the flush process also increases with the decrease of T/D value. So the armor-piercing power of blunt-headed bullets is sensitive to the T/D value. (8) Second rotation When the piercing path is not perpendicular to the armor on the back of the armor, the radial pressure imbalance and deflection will occur when the projectile passes through the armor. The projectile deflects perpendicular to the armor so that the length of the path is smaller than the thickness of the armor, but the residual thickness of the armor is small at this time, so this rotation is not of much help to the armor-piercing. For the shaped projectile, two deflections in the slope armor result in a S-shaped path longer than the horizontal thickness of the armor. Each deflection also loses kinetic energy, so the sharp-headed projectile is not conducive to dealing with large angle sloped armor. For the blunt projectile, the first deflection is very small, the length of the piercing path is small, the kinetic energy of deflection loss is also small, and the second deflection makes the armor-piercing path smaller than the horizontal thickness, so it is advantageous to deal with the large angle sloped armor. All kinds of projectile which used kinetic energy to piercing armor in WWII, will lost its kinetic energy in above 8 steps. That is mean, for slope armor, no matter what kind of kinetic energy projectiles in WWII, the resistance will large than its horizontal thickness. That’s why so many tanks use slope armor after T-34. Chapter 2 The characterization of armor-piercing phenomenon and bulletproof ability In WWII, the most widely used bullets are kinetic energy bullets, like AP, APC, APBC, APCBC and APCR, all of them are using the kinetic energy to penetrate the armor plate, so in this chapter, I will focus on the principle of kinetic energy, some other types bullets like HEAT will be also included. The kinetic energy bullets penetrate the armor plate by directly impact, the process of impact is very complex. The kinetic energy of a projectile (W) before impacting armor is: W=1/2*m*Vc^2 In this formula, “m” is projectile mass, “Vc” is velocity of projectile impact armor. The kinetic energy of the projectile is consumed in many aspects during the armor piercing process, including damage to the armor, deformation of the projectile itself, elastic vibration of the armor plate, collision and friction heating, etc. Among them, damage to armor is the main work. From a mechanical point of view, there are several possible stresses for armor damage: (1) Ductile extrusion: σx=F/π*d^2 (2) Annular shear: τ=F/π*d*b (3) Tensile stress rupture: Radial direction: σn Circumference: σm In above formulas, “F” is the force of a projectile on armor, “d” is projectile diameter(caliber), “b” is armor thickness. When the projectile collides with the armor, these kinds of stresses occur at the same time. Any stress reaching the limit will cause damage to the armor. Which kind of stress damage will vary depending on the material properties and size of the projectile and armor. The form of movement after the armor-piercing projectile impact the target, there will be three possibilities, namely penetration, embedding and ricochet. There are also three possible forms of armor-piercing projectile after impact with the target: integrity, deformation, and rupture. The actual forms of armor damage are as follows: Fig 2-01 The forms of armor damage (a) Ductile reaming (Ductile damage) Mainly due to the effect of extrusion stress σx, the metal is extruded plastic flow by projectile, some of them are stacked at the entrance, others are extruded from the outlet, and the pore diameter of the metal is about equal to the diameter of the projectile. This usually happens when the armor is thick and tough, the projectile is sharp and hard, and the armor thickness b is slightly greater than caliber d. (b) Plugging perforation (Punch damage) Mainly due to the destruction caused by the failure of shear stress τ, the armor is punched out of a large cylindrical plug by the projectile, and its outlet is slightly larger than the projectile diameter d. This usually happens when the medium-thickness armor has considerable hardness, the warhead is blunt, and the armor plate thickness is slightly less than the projectile diameter. (c) Petal shaped hole (Petal shaped damage) Mainly due to the effect of the circumferential tensile stress σm, radial cracks appear, and the armor plate rolls to the rear of the hole. The hole diameter is approximately equal to the diameter of the projectile d. This generally occurs when the armor is thin and tough, and when the projectile speed is low. (d) Block caving (Broken block damage) When the armor is not too thick and the toughness is poor, the radial stress σn is the main cause of circular cracks, and the armor is pierced into a large hole several times the diameter of the projectile. (e) Fragment in armor back (Layer crack/ Slabbing damage) When the strength of the thicker armor is sufficient and the toughness is insufficient, the shock stress wave caused by the projectile hitting can cause the back of the armor to collapse and break up and fly out to kill. At this time, the hole in front of the board is not large, and it may not penetrate. The actual phenomenon of armor piercing may also be a different combination of the above. Generally, Under the condition of the thickness and hardness of the armor, armor-piercing bullets are mainly composed of the first two conditions. That is, the first ductile reaming, when the armor projectile remaining thickness is a little smaller than the diameter of the projectile, then punching into the hole. For thin armor, perforation is generally petal or punching, depending on the relative ratio of projectile diameter to armor thickness. The reason why the block caving is unusual is that the over-hard and brittle thin armor is difficult to be machined and prone to crack, so it is not suitable for cutting and welding the hull body. The HESH destroys the armor mainly with the slabbing damage, which is a special form of damage that does not penetrate the armor. In the general armor-piercing projectile armor, except for the metal defects in the armor's back, it rarely appears. In order to calculate and test the anti-penetration ability of projectile, it is necessary to have a kind of metrology standard to show the resistance to projectile. The practical representation is expressed separately for each particular plate, that is, the resistance of a armor to be "Vc to a certain projectile" for a certain gun. The Vc was confirmed in a large number of firing experiments in the grounding tests. In the test, use a certain gun and projectile to fire at a certain target plate, and gradually increase the quantity of the projectile to increase the velocity of the projectile until it has just penetrated the plate (or the drop point is near the back of the plate, for example, within 5m). The Vc of the projectile is used to indicate the resistance of the armor plate. Of course, the thicker the plate and the better the material, the higher the Vc is required to penetrate. To indicate the ability of a certain armor to resist projectiles of different calibres. This method of representation can ensure that it conforms to the reality and is accurate and reliable, so it has been used all the time. As long as a few accurate values are obtained in the shooting tests, the different plate thickness, projectile diameter and velocity can be calculated according to the law. The method of calculation is shown in the following section. For thinner plates, such as the deck below 30mm, a gun is generally used to test fire (if the caliber is too large, it must penetrate the armor and no critical velocity can be tested). But the projectile cannot change the propellant, that is, the initial velocity of the projectile from the tube opening is fixed, and it cannot be changed. Therefore, it is necessary to use the air resistance in the projectile flight to cause a large velocity drop, that is, to change the distance S to get different hit speeds. As a result, the resistance at this time, becomes resistance to "a bullet (penetration) minimum distance" to denote. In the experiment, it is sometimes inconvenient to change the distance, or fixed distance to change the hit angle of the target. The larger the hit angle α is, the more difficult it is to penetrate the target plate. Therefore, the bullet resistance can be expressed by the α angle of a certain projectile at a certain distance (penetration). In either of these ways, there is also a question that what is the standard of penetration. There are usually two standards: (1) Back strength limit When the armor is impacted by projectile, in order to damage the continuity of the metal on the back of armor, that is, the maximum velocity when there is no crack, no protuberance, etc., is expressed in terms of m/s or the corresponding distance (m) or angle. (2) Penetration strength limit The armor won’t be penetrated when impacted by a projectile, that is, the maximum speed at which the shell consumes up energy and the armor does not appear to have holes. Denoted by m/s or corresponding distance m or angle. The first is more about the toughness/ tenacity of the armor, and the second is more about the strength of the armor. The velocity value of the second standard is generally greater than the veloocity value of the first, and it is also the standard for starting to have a killing aftereffect. The penetration strength limit is mainly used at now. Chapter 3 The basic formula for calculating the resistance 1. The basic formula for vertical armor resistance (1) Krupp formula In Krupp formula, the armor is considered according to the larger projectile, the thinner armor, that is, the lower b/d value, and the armor is destroyed by the projectile in the form of a slug. According to this assumption, the work dW of the force R per stroke dx distance in the thrust process is a variable. In the formula, the resistance R is proportional to the remaining thickness of the deck during the flush process, that is: R=π*d*(b-x)*τ From 0 to b integral, get the total work that completely washed the plug off: W=π*d*τ∫b→0 xdx=τ*π*d*(b^2/2) But the dynamic source of work is the kinetic energy of the projectile. W=m*Vc^2 Get the so-called Krupp formula: Vc=sqrt(τ*π)*d^0.5*b*m^(-0.5)=K*d^0.5*b*m^(-0.5) (Formula 3-1) K=sqrt(τ*π) known as the armor anti-ballistic coefficient, depending on armor material Krupp formula is a more primitive formula for armor-piercing. It is only suitable for low-speed projectiles to judge armor-piercing when a value is small, it is not used now, but it is the basis for understanding armor-piercing calculation. (2) DeMarre formula For the case where the thickness of the armor that usually needs to be calculated is larger than the diameter of the projectile, the armor is not punched at the beginning, but is mainly ductile(extrusion). During the piercing process, the speed of the bullet decreases, the shape of the projectile gradually becomes dull, and the remaining armor is slightly smaller than the projectile diameter. Only then, the plug was rushed out. The entire armor-piercing process is close to the compliance of the extrusion and the punching. If the extrusion damage is considered completely, the total work of the damage armor should be: W=R*b=π*d^2/(4*σx*b)=m*Vc^2/2 Get the: Vc=sqrt(π*σx/2)*d*b^0.5*m^(-0.5)=K**d*b^0.5*m^(-0.5) Comparing Krupp's formula, except K is different, (d^0.5)*b change to (d*b^0.5). Therefore, the DeMarre formula can be understood as considering the combination of punch and extrusion. That is, the damage resistance is proportional to the geometric average, which the circumference (shear stress) of the ram and the value of the circular area (compressive stress). Based on experience, modify to: DeMarre formula: Vc=K*b^0.7*d^0.75*m^(-0.5) (Formula 3-2) or: b=Vc^1.43*m^0.715/(K^1.43*d^1.07) (Formula 3-3) In the formula, b and d are commonly used for “dm (=100 mm)”, Vc is calculated by “m/s”, and m is calculated by “Kg”. At this time, the armor anti-ballistic coefficient K becomes a comprehensive coefficient representing the physical properties of the armor material, which should be determined by the firing test, it cannot be calculated according to a certain stress. The recommended K values from datas are as follows: Low carbon steel plate: 1530 Nickel steel plate: 1900 Generally homogeneous armor: 2000-2400 (the lower value is suitable for low carbon or medium hardness armor, while the higher value is suitable for high hardness thin armor) Surface treated (face hard) armor 2400-2600 DeMarre formula has been widely used up to now, and it is the main basic formula for calculating the anti-ballistic ability. There are also many other formulas for calculating the anti-ballistic ability, but most of them are based on Krupp formula and DeMarre formula, so I won’t list them at here. 2. The basic formula for slope armor resistance Due to the high initial velocity and low trajectory extension of anti-tank projectiles, it can be considered as a horizontal target. When the armor is slope to a β angle with the horizontal plane, the α angle between the projectile centerline and the normal of the armor plate is also called "normal angle" or "impact angle", which is the common angle used in the calculation of the ballistic ability. α and β angles are complementary angles to each other. When the armor is sloped, the range through which the projectile passes through the armor increases as the thickness of the armor increases to b/cosα, will increase the resistance. The formula for slope armor is: Vc=K*b^0.7*d^0.75/(m^0.5*cosα^n) (Formula 3-4) The experimental results show that n>0.7, it is related to the relative thickness of Cb=b/d, armor type and the shape of projectile. Why is n > 0.7 and changed? Mainly because of the impact of the "ricochet" factor, when the projectile contacts and begins to destroy the slope armor, the armor has a reaction to the projectile, slow down the projectile, and the projectile has the inertia force forward. Force of reaction and inertia force of projectile make up force couple. When α is not large, especially for blunt-headed armor-piercing projectiles (APBC), this force couple will make the projectile rotate in the direction of decreasing α angle, which is called the positive effect, which is beneficial to armor-piercing. When the α angle is large, the direction of the couple will make the projectile rotate in the direction of the α angle, and the penetration distance will be increased. Even when the force couple is large enough to make the projectile reflect and jump off the surface of the armor, the so-called "ricochet" is formed. When the hardness of the armor is low, the projectile is prone to hit into a pit on the armor, that is, the direction of the reaction force is less likely to form a ricochet. Or when the armor is thinner, the less strong the reaction to the projectile, the less likely it is to form a ricochet. That is why the larger the Cb, or the harder the armor is, the higher the n value is. When designing projectiles, in order to avoid forming a blunt-topped head shape, it can also avoid sharp-headed projectiles so easily broken that they can't be penetrated. The diameter of the blunt head is even up to 0.8d, often with a sharped head of thin windbreak cap to reduce the flight resistance. The windbreak cap is destroyed at the first touch, and it does not work on armor-piercing. Some projectiles are capped with cemented carbide on the head (APC or APCBC). The purpose is also to improve the performance of armor piercing. As the against armor piercing side, the armor material and its manufacturing process have also been improving. Under the conditions of price and processing permit, it is necessary to have a large n-value to cause the projectile to ricochet. In addition, while increasing the thickness of armor to increase the Cb, a smaller and smaller β angle has been used, that is, increasing the α angle when hit to cause the projectile to ricochet. No matter how the angle β of the armor changes, the horizontal thickness of the armor is the same, and the cross-section area and mass are the same. But the larger the α, the more likely to cause a ricochet, which is why sloping armor is better than vertical armor against armor-piercing projectiles. The speed of the modern long-rod overspeed armor-piercing projectile (APFSDS) has doubled. When hitting armor at high speed, it is often the ever-forming fragments to ricochet, while the rest of the rod-shaped projectile will continue to penetrate forward, and the positive effect is stronger than that of the ordinary armor-piercing projectile. When the velocity of projectile is not too high, the calculation result of DeMarre formula is not different from the actual situation. Its accuracy often depends on the selection of K value. The source of K value is based on experiments, and many complicated practical factors have been included, which can guarantee the accuracy of calculation. However, such tests are destructive, and K values may not necessarily be obtained for each batch or armor calculated. Therefore, some improvement attempts to reflect the general mechanical properties of armor and projectile materials in the formula. One is K.A. Belkin formula: Vc=215*sqrt(K1*σs*(1+φ))*b^0.7*d^0.75/(m^0.5*cosα) σs : Armor yield limit, kg/mm^2. φ: coefficient reflecting relative mass of projectile and relative thickness of armor, the value is 6.16*Cm/Cb=6.16*m/(b*d^2). K1: considering the structural characteristics of projectile and the force coefficient of armor, when the value of b/d is not too different, the K1 value of ordinary armor-piercing projectile shooting homogeneous armor can be used the recommended value of the following table: AP (head bus radius=1.5-2.0d): 0.95~1.05 APBC (passivation diameter=0.6 × 0.7d, head bus radius=1.5/2.0d): 1.20~1.30 APCBC: 0.9~0.95 K1 values can also be calculated using the following formula: AP: K1=0.9427*Cb^0.5(2.6*i/(1+φ)+0.333) APBC: K1=0.9427*Cb^0.5(2.2*i/(1+φ)+0.333) The “i” is a projectile shape coefficient: For AP: i=8/n1*sqrt(2*n1-1) For APBC: i=8-5n1/(15*n1)*sqrt((1-n1)*(2*n1-n2-1)+n2^2) For APCBC: i=(0.9~0.95)*8/(n1*sqrt(2*n1-1)) “n1”: curvature radius of projectile head/diameter of projectile, r/d “n2”: passivation diameter of projectile head/diameter of projectile, d*/d Belkin's formula can be applied to one of the deformations of DeMarre formula. Its application is not as extensive as that of DeMarre formula or the above-mentioned formulas for calculating slope armor. 3. The standard of penetration determination For a gun, its penetration is needed to test by massive shootings, but because the many influential factor, the tests results are floating, so a standard to determine the penetration are necessary. Most Countries are used this standard: For numbers of a type projectile, at a certain distance, shot a certain thickness of a certain type armor plate, it will have different percent can penetration: IP: Initial the armor penetration thickness, for example: 20% CP: Confirm the armor penetration thickness, for example: 80% Different Countries standards are different, and for different thickness, the armor type maybe different, and IP and CP also different for Countries. Usually, the test armors are not the standard requested type, so it need to convert the actual datas as the standards, it means the penetration in battle of a certain gun maybe higher than the data sheets, because its test standards are strict. Some Countries standards: USSR: The definition of the penetration: the whole projectile pass through the armor plate CP: 80% Armor type: RHA Hardness (BHN): 250-380. USA: The definition of the penetration: a meaningful designated part of the projectile must pass through the plate CP: 50% Armor type: RHA Hardness (BHN): 6-13mm: 330-370 38, 51, 63mm: 240 76-127mm: 220-240 Above 127mm: 220 German: The definition of the penetration: the whole projectile pass through the armor plate CP: 50% Armor type: RHA Hardness (BHN): 5-15mm: 435-465 16-30mm: 338-382 31-50mm: 323-368 51-80mm: 309-338 81-120mm: 279-309 121-150mm: 235-265 151-275mm: 206-235 We can see the USSR used the strictest standards for penetration determination, that’s a reason why USSR guns’ penetration look like “lower” than other Countries. Chapter 4 American misunderstanding of USSR APBC In American reports (like AD011426) from their tests about Soviet tanks in 1950s had many misunderstandings. One of them is about USSR APBC. 1. The purpose of the USSR using APBC The US believes that the Soviet APBC is mainly used to deal with the large angle sloped armor. This is obviously a mistake, when the Soviets popularized APBC projectiles in the 1930s, large sloped armor had not yet become popular. Of course, Americans also found that blunt-headed bullets have a better effect on high-hardness armor. However, they believe that the blunt head "ensures the integrity of the warhead is not damaged," and, like the principle of the cap. They had not found the most important principle of blunt-headed projectiles: the instantaneous high-temperature shear and extrusion. 2. The purpose of circular groove on APBC Americans believe that the role of "circular grooves" on APBC is to "create more debris." In fact, the role of the circular grooves is to control the position of the warhead fracture and protect the charge of HE. Obviously, the circular grooves are not helpful for armor piercing. In AD011426, it’s mentioned that the targets can be solved by most of the AP projectiles, will also can be solved well by APBC bullets, this may because one of the properties of a blunt-headed bullet. When the blunt head projectile hits the surface of the armor, it will change the metallic phase of the armor to martensite, the hardness will be higher, the toughness will become worse, and the armor will be more easily to extrusion. Of course, if the armor is inherently low in hardness, it will not be hard to go there after being converted to martensite. 3. The puzzle about the low hardness of Soviet armor-piercing projectiles Americans say they don't understand the low hardness of Soviet-made armor-piercing projectiles. First of all, why should the US-made armor-piercing projectiles add more "carbon"? Because the American armor has very low hardness and good toughness, it is not easy to produce impingement damage, but the penetration resistance is small, so it can not effectively resist the sharped projectile. On the other hand, when the sharped projectile hits the armor surface, it will have some deformation, make the caliber larger, and increase the penetration resistance. To control deformation, Americans add more "carbon" to armor-piercing bullets, increasing hardness. At the same time, "carbon" also makes the warhead toughness worse, when it impact armor at the high-speed, it is easy to break, so the US normal AP projectiles usually do not charge. When faced with high-hardness or slope armor, the performance of this high-carbon, cap-less armor-piercing projectile is very poor. In March 1942, British forces carried out shooting tests on captured tanks in North Africa. It was found that the M72 armor piercing projectile launched by M2 could only penetrate the surface hardened armor of the 50mm at 500m distance. Then, it is obvious that the low hardness of the Soviet armor piercing projectile is to prevent the body from breaking, especially to resist the tangential shear stress during the impact on the slope armor. It is also mentioned that blunt-headed bullets are "almost broken" during armor piercing, which should be the normal work of the broken ring (circular groove). 4. The wrong views about the performance of AP and APBC against slope armor In AD011426, it mentioned that, when dealing with large angle sloping armor, regardless of the alloy composition and physical properties, the whole piece of sharped projectile will lead to the sharp head rupture at the moment of impact, and this (sharp head bumped into blunt head) state, it will be very effective against the slope surface. Considering that the sharp head will be ruptured in impact, the blunt-head bullets used by the Russians may not be necessary. Of course, when using the APHE bullets, the blunt-head bullet is very effective in ensuring the penetration of the explosion and the debris killing through the armor. Americans stumbled to find that their high-carbon AP had a special effect on sloping armor. This is because "the moment of impact will cause a sharp head to break" and become a blunt head. As a result, they thought it was "less necessary" for the Soviets to use blunt-headed bullets with relatively poor vertical penetration in order to deal with sloping armor. Aside from the Soviet motive to use blunt-headed bullets, the problem of deal with sloping armor was not in all cases capable of breaking the sharped-headed bullets in the right position, speed, incidence, armor hardness all have an impact, and there's no special fracture slot, so this fracture position is uncontrollable. The way of sharp head impact to blunt head, its scope of application is quite limited. It can be seen that until the 1950s, Americans still had a lot of misunderstandings about Soviet blunt-headed armor-piercing bullets of the 1930s. With regard to the generality of blunt-headed projectiles, AD011426 only gives good results for large-angle sloping armor and high-hardness armor, especially for large-angle sloping armor. But, in principle, the versatility of blunt-headed bullets goes far beyond that: Normal AP with no cap-- advantages: low hardness armor; disadvantage: high hardness armor, surface hardened armor, large angle sloping armor. APC or APCBC-- advantages: low hardness armor, surface hardened armor; disadvantage: high hardness armor, double-layer high hardness armor (or double-layer surface hardened armor), large angle sloping armor. APBC-- Advantages: high hardness armor, surface hardened armor, double-layer armor, large angle sloping armor; disadvantage: low hardness armor. So obviously, APBC bullets are the most versatile. German using low-hardness armor in the later war was also targeted. In response, the Soviets distributing K-suffixed no cap AP from 1944. APBC bullets with AP bullets, there's no need to use APC or APCBC. As for the post-war, the armors all over the world large using of nickel, they had good toughness, not easy to extrusion. And blunt-headed bullets are also sensitive to a value of T/D, so they are naturally be replaced by APCBC. However, due to the good effect for dealing with large-angle sloping armor, the US and the Soviet Union still used a long period of APBC bullets after the war. Chapter 5 The transitory APBC in history In the 1930s, anti-tank guns all over the world were small caliber high initial speed, AP shells were without cap. In the process of armor piercing, extrusion is the main. When the hardness of the armor is low, the compressive ability of armor is poor, and the resistance to the bullet is low, so the armor is easy to be pressed around by the bullet, thus forming a bulging perforation inside and outside the armor. When the caliber of the bullet is relatively small, it will even break because the stress is too concentrated. Although large caliber shells can produce punch effect instead of extrusion, but large caliber gun is heavy, difficult to produce, difficult to maneuvering, and difficult to be competent for anti-tank work. So, the Soviet have developed a series of high-hardness armor represented by 8S. After heat treatment, the hardness of 8S had high hardness at 375~477HB, and also had well toughness, which can effectively resist the AP bullets at that time. The high-hardness armor gave Soviet tanks well resistance performance in battle, but Soviet also worried that: if enemy also used high-hardness armor, how to deal it? The Soviets quickly found a solution by cutting off the tip of the shell and forming a 0.6~0.7 rate of the caliber at the front of the bullet. The blunt head AP for tank gun was born. The appearance of T-34 has set off a craze of slope armor. When the projectile hit the slope armor, the projectiles were subjected to upward by elastic force, thus deflecting upward. When the deflection radius of the projectile is relatively small, the projectile slips out of a small crater and flies on the surface of the armor, which is called ricochet. When the deflection radius of the projectile is large, the back of the lower armor may lose its elasticity due to fracture, and the projectile will deflect down and break through the armor because of the lateral elastic force, which is called rotation effect. That is, when the projectile breaks through the slope armor, the path is S-shaped, and the path length is larger than the horizontal thickness of the armor. Moreover, the projectile also consumes a certain amount of kinetic energy in the process of two deflections. Soviet found when the APBC projectiles squeeze the slope armor, the direction of the elastic force is closer to the center of gravity of the projectiles, resulting in the upward deflection angle of the projectiles becomes smaller, the energy loss is relatively small, and the passage path is also relatively short. If the slope angle is small, the APBC can even rotate straight on the surface of the armor. So the APBC become the standard ammo for most Soviet guns, like 45mm, 57mm, 76.2mm, 85mm guns. From 1940s, most German tanks armor hardness were 280~360HB, at the beginning of 1941, the front armor of Panzer III H start using the FHA (Face hardened armor), which had 600HB surface hardness. For the face hardened armor, the thin surface hardening layer can’t break the APBC, but even more easily be cut off. And the thickness of the non-hardened layer is much lower than the caliber of the bullet, which aggravates the plugging. The same thing also happened in Panzer IV. But in Tiger I, it was different. The side armor of Tiger I was 255~265HB. When the 76mm APBC (BR-350A) begins to shear cut the low hardness armor, the deformation of the armor is larger and the shear force becomes smaller, so it is difficult for the bullet to cut out the complete fragments. When the armor deformation reaches a certain extent, the armor piercing process becomes mainly extrusion. Another important reason, the ahead working of the fracture ring also affects the integrity of the bullet, which makes it difficult for the bullet to move forward. To solve that, Soviet designed BR-350B APBC, the weight up to 6.5kg, fracture ring was change very small and move to the nose, it was hard to fragment. The BR-350B quickly instead of the BR-350A, which could help T-34/76 penetrate Tiger I from side. After WWII, former allies stood on both sides of the Iron Curtain. Because the immature heat treatment process in high hardness armor, Americans still use a low hardness armor, which was only about 210HB. The main target of APBC was gone, although the APBC still had a good performance in against low hardness armor, but the APCBC will perform better. Soviet came back on the way of APCBC, the APBC became a transitory ammo type in history.
  4. I would love to see a pakage of those "final" props, like La-11, F8F, P51H, becasue many reasons, these porps have little chance to perfomance better. Although Soviet pilots join the war, but Soviet/China have too less planes and airfields, their war systems also not so holonomic as USSR, and because the jets well performance, many US props not so famous as their should be. So, if there are a chance to put them in game without the maps and campaigns, just play in quick mission and online service will also be a interesting and exciting thing.
  5. For China/Soviet, the La-11 maybe the most prop aircraft used, although most of us think that La-11 has low performance than La-9. I think there are something wrong views about La-11, just like many "web dates" said that La-11 has 562km/h in sea level, and La-7 is only 570+km/h, if you think about it by your brains, you will find that it is obviously wrong. And if La-11 has so much low performace than La-9, Soviet/China won't use it replace La-9, most La-11 in Korea are used as a night fighter and other mission rather than escort. As I know, there is no sim game realease La-9/11 serious, although the WarThunder do it, but they even can't make a right shape of La-9/11's nose, the cockpit of La-11 is just La-9's, and the flap angle indicator won't move as it in La-9 cockpit, they only want use La-9/11 to earn money. So if IL2 Great Battles can realease La-9/11, it will be very interesting. For players, La-11 has advanced instruments, automatic radiator and supercharger contorl, and gyro gunsight, it will be a good experience. And for those airplanes in Korea, devs needn't to realease as a campaign, may be a extended package DLC which has 6-8 after WWII prop planes, give these planes a chance to fight in online sevice or quick mission, just like IL2 1946.
  6. Want the Mig-15bis, want the F-86, want the La-11, and want the F8F, any plan about the battle of Korea?
  7. If we look the picture about La-5FN, La-7, La-9/11, we will find that La-7/9/11 has a exhaust port after the engine cool air outlet each side, but La-5FN has not, I try to see the engine cool air outlet in IL2 BOS, and found that La-5FN engine's cylinder exhaust direct in air respective. So the exhaust port in La-7/9-11 may be your mentioned "muffler exhaust"? The date I had ever see were said that ASh-82FN has a single stage superchargers with two speed drive, but I think "the late version ASh-82FN has two TK-3 turbo" is not without cause, although it may has lost a fair amount in translation. The article I read mention that La-7 late models has increase its performance in hight altitude, I don't know there is other way to "increase its performance in hight altitude" expect let the engine has better power output in hight altitude. And as a long range fighter ot protect Tu-4, the La-11 also need better power in hight altitude. The engine in USSR often keep a model in many years, but it was improve many in these years. Like T-34's engine V-2-34, from T-34-76 to T-34-85, it still called V-2-34, but it has changed a lot, even some core parts has been improved much, just for better performance and life. So may be ASh-82FN has turbo model in Lavochkin series used. And it also may be only a single stage superchargers with two speed drive in ASh-82FN until it discontinued.
  8. Hi, everybody. In wiki Shvetsov ASh-82, the "Supercharger" said that:"Single-stage, One TK-2 two-speed centrifugal type supercharger on early production. Two TK-3 two-speed exhaust gas-driven forced-induction compressor on FN and FNV models". Many years ago, I had read a article about Lavochkin series in WWII, it said that in 1945, La-7 late models has increase ite performance in hight altitude, so it is ture that ASh-82FN has "gas-driven forced-induction compressor" model in used? Is that mean La-5FN and La-7 used TK-2 two-speed centrifugal type supercharger ASh-82FN, and La-9 and La-11 used Two TK-3 two-speed exhaust gas-driven forced-induction compressor ASh-82FN?
  9. Want to play "final stage" propeller aircraft like La-11/9, Ta-152, F8F, Spitfire IXV as soon as possible! Don't want to wait them one by one campaign many years later! Don't want to play "final stage" propeller to be jet aircrafts' foil in 1950! Need a actual or fictitious battle/campaign and multiplayer map for "final stage" propeller aircraft battle each other, just like IL2 1946. Even if they are playable only in quick mission, I'll like to buy them!!!
  10. Yugoslav tests had been quote in some articles, but I didn't found the provenance of Yugoslav tests, and this tests show T-34 armor has 350 BHN, also inconsistent with other tests, so I don't think "Yugoslav tests" is a reliable date. If you have the provenance of Yugoslav tests, I'd like to see it. And don't wuzzle the standards and test results, the penetration can be different because the different standards, but the test results always is yes or not. The date of Soviet test T-34 in March of 1944, said that Pak40 can penetrate T-34 UFP without track links attached at 1000m, but can't penetrate at 1100m is just mean yes or not penetrate.
  11. Your views and date are based on American tests, but remember, Soviet high hardness armor not is American high hardness armor.The link in my post show that Pak40 can only penetrate T-34 UFP at 1000m, and Pak40 has 118mm penetration at 1000m according <WWII Ballistics- Armor and Gunnery>.
  12. I just want flyable La-9/La-11, just can be used in Quick Mission will be OK And I also want to know how devleopers get and collect history dates about Tanks to keep them real, as I know, most dates that we can find in English were full of political prejudice to USSR, for example, the hull front of T-34 armor has about 118mm resistance to German 75mm APCBC(http://tankarchives.blogspot.com/2014/04/spare-track-links.html), but many "Western books" think it has only 90+mm, and the same example to USSR losts in WWII, Russia report their losts mean lost times, but most "Western books" understand it as lost numbers, and in fact, only 24.6% Soviet AFVs losts are "true losts" (irreversible losts) in 1944, and in 1945, it was 14.7%.
  13. Every time I play the campaign, for example, I used the IL2. in plane setup, I need to set the guns, the bombs, the rockets, the rear turret, and paint scheme, then when I get in mission and go to fly it, I need to reset pitch trim from -60% to 0%, oil mixture from 50% to 100%, rockets launch mode from single to pair, bombs drop mode from single to pair..........Oh, please! This is to complicated! Can't devs set a key to save these modifications, just like the key " save current corrections in head snap position"? Or creat a panel in main menu to set every planes starting status and modifications?!!
  14. We can soon pre-order Yak-1b and Ju-52 now, but when the senior piston-engined aircrafts? Like Ta-152, Bf109K4. La-9, IL-10, IL-2 type3, maybe early and mid time of WWII piston-engined aircrafts are good idea, but I think there are more people love senior piston-engined aircrafts, that's why DCS world released Bf109K4, Fw190D9 and P51, not Bf109F4, Fw190A9 and P40. Almost my friends want to fly a senior piston-engined aircrafts in IL2 BOS, so why not make a plan for that? Campaign? We don't need it, just give us a fictitious map or campaign, which can play senior piston-engined aircrafts and other pre-order planes on it will be OK. Too less aircrafts( especially senior piston-engined aircrafts) is a very serious deficiencies of IL2 BOS series, why not try to fix it?
  15. You plan the right planes of USA and UK, but why give Soviet only two antiquated planes in your plan? At least, the Soviet should have La-7, Yak-9 and IL-10 in Battle of Berlin! And as premium planes, Yak-3 and La-9 & La-11 will be better, although La-9 & La-11 not service in 1945, but they are also famous fights and will very interesting if they are added in game.
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