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Showing content with the highest reputation since 08/24/2018 in all areas

  1. 9 points
    Supremacy of glorious T-72 over filthy Kharkovite tractor
  2. 7 points

    Israeli AFVs

    Couple more of the Mk.3-based Ofek
  3. 6 points
    German concept proposed during the Kampfpanzer 3 / FMBT project to the UK via https://andrei-bt.livejournal.com/928203.html Twin-gun casemat tank from Maschinenbau Kiel: Low-profile turret tank with driver in turret by Krauss-Maffei (similar to MBT-70, but with 120 mm smoothbore gun and manual loader - maybe derived from the Eber concept): Data: Armor is spaced steel plates, sometimes with fuel inbetween them. The MaK design has 727 mm thick armor, but the actual steel thickness is just 259 mm... Note that according to Krapke a third concept (AFAIK either turretless or with unmanned turret?) was proposed.
  4. 6 points
    Let's say you're developing a tank with a unique (AKA non-historical) gun for one of our competitions here on SH. It would be nice to have an idea of the size of the gun, its shells, and what their performance both in terms of shell weight and velocity but also penetration, wouldn't it? Well, fortunately there is a way to do this with reasonably accurate results using your solid modeling software and some free to use browser tools. First, you want to have a general idea of the size and performance of your gun. For this example, I decided I wanted an optimized, high velocity 85mm caliber gun with a case about as big as the 7.5cm KwK 42 (as it happened, I ended up with a case that had significantly greater volume, but that fact is unimportant for this example). The cartridge I decided on has a 130mm wide rim and a 640mm long case, of course in 85mm caliber. My first step was to model this case in SolidWorks: You will also need to model your projectile, in this case a tungsten-carbide cored APCR round: Next, we need a bit of freeware: A Powley computer. Originally developed by DuPont engineers for small arms ammunition, the Powley computer is an accurate enough tool to use for much larger tank rounds as well! When you click the link, you'll be greeted with this screen: You'll note the dimensions are in inches and this thing called "grains" (abbreviated "gn"). The grain is an archaic Imperial mass unit equal to 1/7000th of a pound which is still used in the small arms field, today. Another quirk of small arms has the case capacity - a volume measurement - listed in grains as well. This is in fact grains of water (gn H2O), or the weight of water that will fill the case to the top. To find this, simply multiply the volume in cubic centimeters by 15.43 - which is also the exchange rate between the metric gram and grains mass. Finding the volume of the case is easy with a solid modeling program; simply model the interior as a solid and find the volume of that solid: Filling in my Powley inputs gives me this: Note that I typically use the diameter of the projectile across the driving bands for "Bullet Diameter", but it really makes very little difference. So far, though, we haven't actually produced any results. That's because our gun is well outside the bounds of DuPont production IMR powders, hence the output "Much slower than (IMR) 4831" in the lower left. So, we need to override the computer by checking the box next to the blue "Pressure" function, and typing in a pressure value in CUP that is reflective of tank guns of whatever era we are trying to represent. My tank gun is trying to represent something from about the late 1940s/early 1950s, so I'm going to use 45500 CUP EDIT: USE 41000 CUP for APCBC and 42800 CUP FOR APCR (or better yet, do your own calibration!): This gives me an estimated muzzle velocity of 3,964 ft/s for my L/50 barrel. Not bad! Note the outputs on the left, which tell you a bunch of fun facts about your round but aren't terribly relevant to what we're doing here today. Next, we need to put this gun's performance in terms of penetration. The way I like to do this is through comparative analysis. The first thing we need is to know to find penetration the ballistic performance of our round. We can estimate this using JBM's ballistic calculator and a few rules of thumb. When opening the calculator, the first thing you'll see is this: We care about basically none of these settings except BC, velocity, and maximum range. Caliber, projectile weight, chronograph distance, etc are all pretty irrelevant to us. Keep the environmental settings (temperature, pressure, etc.) set to their defaults. First, change the ballistic coefficient type from G1 to G7 using the dropdown menu. Then, change the muzzle velocity from 3000 to whatever the muzzle velocity was that was calculated by the Powley computer. Finally, set the maximum range to your desired distance - in my case 2,000 yards. For my round, I now have inputs that look like this: We also need to get some idea of how fast our projectile loses velocity, something we can't know for certain without actually building a real gun and test firing it - or at least without some really sophisticated simulations. However, projectiles with the same shape tend to fly the same way, and that's something we can exploit here. To figure this out, we need a graph showing us the performance of a real-life gun. Fortunately, there is a handy one for an IRL gun similar to what I'm designing, the 90mm M3 from World War II, and its M304 HVAP-T, which is broadly similar in construction and shape to my 85mm APCR projectile: Based on this chart, we see that the M304 should drop from its 3,350 ft/s muzzle velocity to about 2,500 ft/s at 2,000 yards. Doing a little trial and error with JBM tells me that this means the M304 has a G7 ballistic coefficient of about 1.13. Now, our projectile will not have the same ballistic coefficient, due to it being a different size and mass. But, we can figure out what its ballistic coefficient would be by finding its sectional density and comparing that to the sectional density of M304. To find sectional density, take the projectile's weight in grains and divide it by the square of the projectile's diameter in inches, times 7000. So for M304, we get: And for my 85mm, we get: This means that the ballistic coefficient for an identical-shape projectile with our size and weight will be about 1.019/1.330 - or 76.6% as much - as that of the 90mm M304. That means a BC of 0.866 G7 should be approximately correct for my 85mm APCR round. Let's plug that in: And then scroll down to the bottom to click "calculate", which gives us a big ol' chart that goes out to 2,000 yards: O-Kay! Now we have some data. It looks like at 2,000 yards, my projectile holds about 2,800 ft/s striking velocity. It's important to note here that what we really care about isn't the striking velocity of the projectile per se, but the velocity and energy of the projectile's core. The core is what's actually doing a lot of work to the armor, so for now let's stop thinking in terms of the whole projectile, and take a look at these two cores, that of the M304 90mm HVAP, and that of my 85mm APCR round. The core of the 90mm M304 is an approximately 8 pound lump of tungsten-carbide that is about 45mm in width. My penetrator is also 8 pounds, but it's longer and thinner in proportion - just 40mm wide, rather than 45mm. This means my penetrator will penetrate more armor at a given striking velocity, and we can estimate how much more by taking the specific energy of the rounds and comparing them. That is, the energy in Joules of the penetrator alone, divided by the penetrator's diameter squared: So the specific energy at 2,000 yards is about 826J/mm^2. Now, we need to find out at what impact velocity the M304 penetrator produces this same specific energy. Do do that, we go backwards, using the figures for M304: Therefore, the equivalent impact velocity for my 85mm APCR round at 2,000 yards is 3,150 ft/s for the M304. That means, in theory, that the M304 would have to impact a target at 3,150 ft/s to produce equivalent penetration of RHA to my 85mm APCR striking at just 2,800 ft/s. Now, we head back to that chart: On the left side of the graph, we put our cursor on the line that corresponds to approximately 3,150 ft/s velocity, and follow it over until it hits the curved line that corresponds with the angle of plate we care about - arbitrarily, let's pick 20 degrees. Then, we follow that point straight down until it hits the x-axis: Therefore, we estimate that at 2,000 yards, my 85mm has just over 10 inches of RHA penetration - not bad at all for a lowly APCR round!
  5. 5 points
    There is more direct evidence linking McCain to Russian meddling than Trump. There is more direct evidence linking the Clintons to Russian meddling than the President. But Trump hosted the Miss Universe pageant one year in Moscow and made a funny one-liner about the Russkies finding Hillary’s e-mails so clearly he is a Putin stooge.
  6. 5 points
    Also that story is purely indicative of what everyone in the RtBA community has been seeing and saying for years. Just before we had instant communication with millions of people 24/7 via an affordable pocket device, we were called names. Crazy, paranoid, psychotic, you name it. It was just a few years ago that yet another mental health bill was knocked down that was really just a backdoor gun control measure. We've been called mentally deranged for YEARS by the left, all for pointing out the very obvious narrative that they've been trying to push for the past three to four decades. And the craziest part is that the argument has literally never changed. It's the exact same tired talking points that they started with in the 70s and 80s. They got the GCA68 passed and smelled blood in the water. Since then it's been a constant fight, with "debates" barely measuring up to what I've seen in high school debate clubs. It's always clueless people trying to fool or scare an ignorant majority into giving rights away. And anytime an argument is made, it gets batted around with ad hominems and strawmen are set on fire. The left had one hell of a chance with Obama. But amazingly, he was too lazy or spineless to go after guns. He made damning speeches that really portrayed how little the left thinks of the average American in fly over states ("it's easier for a student to buy a Glock than a book!"). But he never actually did anything. Pathetic. So yes, everyone is tired. All the facts and data and logic are on the side of rights activists. Emotionally pleas are the only thing the left has, so it trots out crocodile tears and children every chance they get to sway public opinion. They are creating talk shows and news programs that deliberately attempt to erode conservative ideals that are shared by a majority of people in this country ("you don't really believe in X, do you? Only dummies believe in X. It's just common sense that Y is right. Now here's a thinly veiled insult disguised as a joke and a word from our sponsors, pharmaceutical industry C and coke product D"). I am grateful that independent sources are so easily obtainable these days. That is, until the internet is 100 percent owned by the left. Looking at their contributions to Google, they are trying to buy their way into that now.
  7. 5 points

    United States Gun Control Megathread

    Lott is a controversial figure primarily because his analyses are difficult for anti-gun groups to defend against. I've read a lot of his research and he generally is extremely fair and even-handed with his data - the data just does not support the agenda those people want it to. So, just like the leftist constitutional scholars who debunked the "collective right" of the Second Amendment, Lott has been unpersoned for heresy, essentially. Naturally, once labeled as shills for the NRA, the opinions of Lott, Tribe, and anyone else who points out uncomfortable or inconvenient facts can be safely dismissed. All this sounds terribly melodramatic, but it's something gun owners have been dealing with for years. Opinionated turds from the coastal megalopoleis and from foreign countries with no gun rights tell us all sorts of nasty things about us and our guns, despite not having the first clue. We're all quite sick of it.
  8. 5 points
  9. 5 points

    Competition: Tank Design 2239

    Alright, at long last I think I have finally finished. Or, at least I am going to post up some basic data from my worksheets, writeups to follow later. XM12 Donward Main Battle Tank Crew: 4 Curb weight: 43.1 t Gross weight: 45.3 t Armament: 100x685R L/52 rifled gun firing APCBC, HE, and APCR 53 rounds capacity, +25/-10 elevation 20x140mm coaxial autocannon firing APHE, HEI, and APDS 7.62mm M240 coaxial machine gun .50 caliber M2 machine gun 7.62mm coaxial machine gun Hull armor: Upper glacis - 4.4" at 28 degrees - 239mm LOS (slightly elliptical) Lower glacis - 3" at 44.6 degrees - 108mm LOS Side - 2" at 15 degrees, plus 1"side skirts - 78.4mm LOS (spaced) Turret armor: 0 degree: 512mm at forehead, 240mm at nose, 186mm above ring 15 degrees: 502mm at forehead, 220mm at nose, 167mm above ring, 339mm sides 30 degrees: 358mm at forehead, 200mm at nose, 147mm above ring, 175mm sides 45 degrees: 262mm at forehead, 154mm at nose, 136mm above ring, 124mm sides Powerplant: 750 hp air-cooled turbocharged V12 diesel, 29.4 L displacement, cross-drive transmission 16.6 hp/t XM13E4 Sandy Airdroppable Reconnaissance Vehicle Crew: 3 Curb weight: 12.9 t Gross weight: 13.9 t Armament: 85x640mmR rifled gun firing APCBC, HE, and APCR 34 rounds capacity, +25/-5 elevation .50 caliber M2 machine gun 7.62mm coaxial machine gun Hull armor: Upper glacis - 20mm at 5 degrees, 35mm at 35 degrees (aluminum) Lower glacis - 35mm at 33.5 degrees (aluminum Side - 10mm all around (aluminum) Turret armor 1" thick cupola walls (steel) Powerplant: 305 hp turbocharged water-cooled V6 diesel, 7 L displacement, cross-drive hydrokinetic transmission 22.0 hp/t XM13E6 Sandy Light Reconnaissance Vehicle Crew: 4 Curb weight: 17.7 t Gross weight: 18.6 t Armament: 85x640mmR rifled gun firing APCBC, HE, and APCR 34 rounds capacity, +25/-10 elevation (-5 over tracks) 20x140mm coaxial autocannon firing APHE, HEI, and APDS 7.62mm M240 coaxial machine gun .50 caliber M2 machine gun 7.62mm coaxial machine gun Hull armor: Upper glacis - 20mm at 5 degrees, 35mm at 35 degrees (aluminum) Lower glacis - 35mm at 33.5 degrees (aluminum Side - 10mm all around (aluminum) Turret armor: 0 degree: 211mm at base to 248mm at top of gun shield, 244mm at roof 15 degrees: 209mm at base to 245mm at top of gun shield, 241mm at roof 30 degrees: 201mm at base to 238mm at top of gun shield, 234mm at roof 45 degrees: 190mm at base to 226mm at top of gun shield, 221mm at roof 60 degrees: 174mm at base to 210mm at top of gun shield, 205mm at roof Powerplant: 475 hp turbocharged water-cooled V6 diesel, 9 L displacement, cross-drive hydrokinetic transmission 25.5 hp/t XM15 Roach Medium Tank Crew: 4 Curb weight: 36.0 t Gross weight: 37.8 t Armament: 100x685R L/52 rifled gun firing APCBC, HE, and APCR 45 rounds capacity, +25/-9 elevation 20x140mm coaxial autocannon firing APHE, HEI, and APDS 7.62mm M240 coaxial machine gun .50 caliber M2 machine gun 7.62mm coaxial machine gun Hull armor: Upper glacis - 55mm at 5 degrees - 631mm LOS Lower glacis - 125mm at 45 degrees - 177mm LOS Side - 80mm at 0 degrees Turret armor: 0 degree: 225mm at base, 225mm at top of gun shield, 225mm at roof 15 degrees: 227mm at base, 212mm at top of gun shield, 217mm at roof 30 degrees: 234mm at base, 197mm at top of gun shield, 211mm at roof 45 degrees: 235mm at base, 191mm at top of gun shield, 198mm at roof 60 degrees: 223mm at base, 187mm at top of gun shield, 191mm at roof Powerplant: 620 hp liquid-cooled V12 diesel, 38 L displacement, cross-drive transmission 16.4 hp/t
  10. 5 points
  11. 5 points
    Proper, god-fearing Soviet tanks use four-stroke diesel engines. When the tank is cruising, the engine should be happy and produce very little smoke. But when the engine is suddenly changing RPM, the fuel/air mix usually isn't quite right, and there will be some un-burned fuel that creates the clouds of black smoke. If you watch videos of Soviet tanks they usually smoke a bit whenever they turn, because Soviet tank steering mechanisms don't maintain the same average track velocity when the tank turns, which means that the engine changes RPM. It's the same thing as the puff of smoke you usually see big rig semis produce when they accelerate. The Kharkov design bureau favored two-stroke diesel engines for their tanks. The advantage of a two-stroke diesel is that it produces a lot more power for a given size and weight of engine than a four-stroke diesel. In theory they are also more fuel-efficient, although I am not sure they are in practice. The disadvantage is... well, there are lots of disadvantages. One other quirk of two-stroke diesels is that they aren't lubricated the same way as four-stroke diesel engines. A normal four-stroke engine has separate oil and fuel. You fill up your car with gas, and every once in a while you check the oil and replace the oil. Two-stroke motors aren't like that. They don't have separate fuel and lubrication systems. Think of a chainsaw; the fuel and lubrication oil are mixed together, and the moving parts of the engine are lubricated using this fuel/oil mixture. This further reduces the size of the engine, but it means that there's a bunch of oil mixed in with the fuel, which tends to produce a blue or white smoke as the motor runs. If you look at pictures of Chieftains on parade, they're usually surrounded with a blue/white smoke for the same reason.
  12. 4 points

    The Leopard 2 Thread

    PERI R17 of an Austrian Leopard 2A4 without armored cover during maintenance: Mainframe of the Leopard 2A4's digital ballistic computer: Spanish Leopard 2A6E with slat armor:
  13. 4 points
    Since we've got an arms race, my tank has been showly shifting more and more towards Not An M41. Going to improve the suspension. Gave it a meaner gun and a better shaped turret, but made sure to keep all the comfort. Turret's gotten pretty fat, may be able to trim some off the back half still. On second thought, it's entirely possible that I've also just got the turret itself at too large of a scale
  14. 4 points
    from 2ch.hk/wm/ - photos of pages from some brochure from Army-2018 about RCWS and Derivatsiya-PVO's SPAAG turret
  15. 4 points


    Armata IFV with 57mm canon, top view.
  16. 3 points
    I fear that this is another "no justice no peace", where justice equates Trump being found guilty no matter what the truth is.
  17. 3 points
    And the birth certificate thing could have been put to rest in 24 hours, or 3 business days tops. But Obama WANTED the Republicans to chase that red herring for six years.
  18. 3 points

    United States Gun Control Megathread

    No, because Lott is counting shooters, not casualties: Sorry you've been lied to. :|
  19. 3 points

    Land 400 Phase 3: Australian IFV

    More on the (indicative) turret:
  20. 3 points

    Polish Armoured Vehicles

    Some pics of Borsuk/Badger IFV. This time with Soucy tracks instead of DST(iDST 364D). . Rest of the photos. Prototype of Leopard 2PL.
  21. 3 points
  22. 3 points

    General news thread

    The Pentagon has cut aid to Pakistan over militant ties
  23. 3 points

    General AFV Thread

  24. 3 points
    Andrei_BT made post in his blog, where he also posted another picture of this mockup: ...along with some words about this vehicle been example of cool and too-complicated-for-brasshats-to-understand way of designing tanks - they decided to use fresh new layout to keep tank lightweight, instead of using a traditional one (with more than 2 man inside) and simply adding more armor - which eventually leads to Maus-alike weight. It reminds me of another, 15-20 years earlier, soviet attempt to make the same "great leap forward" using the same design of 2-man-crew-in-turret - Chelyabinsk's object 775.
  25. 3 points
    Our hosting costs would go down, but we would also loose our funding from Putin.