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Collimatrix

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Collimatrix last won the day on June 29

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  1.    Collimatrix reacted to a post in a topic: Models and pictures of Soviet MBT designs from 80s. Object 477A, Object 490 Buntar and Object 299.
  2.    Collimatrix reacted to a post in a topic: Kimchi armoured vehicles: K1, K2, K21 and other AFVs from Worse Korea
  3.    SuperComrade reacted to a post in a topic: Imperial Japanese Army Tank Nomenclature
  4.    Collimatrix reacted to a post in a topic: The Leopard 2 Thread
  5. Collimatrix
    A quick search didn't turn anything up, so I apologize if this has already been asked before. Most sources credit the Leo 2's hull ammo rack with 27 rounds, in a hexagonally packed arrangement of two rows of six rounds and three rows of five rounds for five rows total. This is illustrated schematically: but actual photos show only 22 rounds, with four rows alternating six and five like so: What gives?
  6.    Dragonstriker reacted to a post in a topic: Bash the Pak-Fa thread
  7.    Dragonstriker reacted to a post in a topic: Bash the Pak-Fa thread
  8.    Dragonstriker reacted to a post in a topic: General AFV Thread
  9.    Collimatrix reacted to a post in a topic: Kimchi armoured vehicles: K1, K2, K21 and other AFVs from Worse Korea
  10.    Dragonstriker reacted to a post in a topic: Trade-offs in WWII Fighter Design
  11.    Dragonstriker reacted to a post in a topic: Trade-offs in WWII Fighter Design
  12.    Collimatrix reacted to a post in a topic: Land 400 Phase 3: Australian IFV
  13.    Collimatrix reacted to a post in a topic: Active Protection System (APS) for tanks
  14. Collimatrix
    What the fuck is this horrifying abomination?
  15.    watch_your_fire reacted to a post in a topic: J2M Raiden
  16.    Beer reacted to a post in a topic: J2M Raiden
  17. Collimatrix
    True!
  18.    Zyklon reacted to a post in a topic: J2M Raiden
  19.    Domus Acipenseris reacted to a post in a topic: Ballistics FEA on Youtube
  20.    Collimatrix reacted to a post in a topic: ATGMs and RPGs for infantry - a thread for rebels around the world to choose their ATGM supplier.
  21. Collimatrix
    Does anyone have pictures of the MILAN's motor nozzle? @Alzoc?
  22.    Collimatrix reacted to a post in a topic: The Soviet Tank Thread: Transversely Mounted 1000hp Engines
  23. Collimatrix
  24. Collimatrix
    Were there ever problems with logistics because the tank MGs and infantry MGs didn't use the same belts?
  25.    Collimatrix reacted to a post in a topic: The Soviet Tank Thread: Transversely Mounted 1000hp Engines
  26. Collimatrix
    The numbers he's getting for that test though; ~50% reduction with a large and variable amount of fragments, are in line with other estimates I'd seen published of APS vs APFSDS.
  27. Collimatrix
    @Beer I have a question for the beardiest of Eastern Bloc tank grognards. What coaxial MG did Czech-made T-55s and T-72s use in Czech service? PKT or UK Vz. 59T?
  28. Collimatrix
    I'm somewhat sanguine on radar stealth for ground vehicles. Aircraft stealth is a formidable engineering problem, of course. But consider that aircraft are very often being illuminated by radars against the backdrop of the sky, which might as well be pitch black as far as a radar is concerned. The contrast is nearly perfect. Aircraft have to worry about being lit up with many different frequencies of radar waves too, which makes the problem harder because not all RAM works well against all frequencies, and different frequencies respond differently to different sized features on the aircraft. A ground vehicle is, well, on the ground. It's hiding out amongst a bunch of ground clutter, so its RCS reduction will have to be somewhat less extreme for it to blend in vs. against a cold, featureless sky. Furthermore, the range of frequencies used for fire control and detection radars against ground targets is much smaller; typically millimetric-wave. So I suspect that useful reduction in detection and targeting range against the sorts of radars seen on attack helicopters is possible for tanks without anything like the extreme shaping seen on stealth aircraft.
  29. Collimatrix
  30. Collimatrix
    I've noticed a lot of ballistics FEA simulations popping up on Youtube lately. A result of the ever-dropping price of number-crunching power? Who knows. I cannot, of course, vouch for the accuracy of these simulations. They sure are pretty to look at though.
  31. Collimatrix
    Hello, and welcome to the forums. The standard J2M definitely had a mechanically driven supercharger; basically all WWII piston engines do. I believe that little accessory case strapped to the back of the engine has the supercharger in it somewhere: The heat dissipation finning on WWII radial engines is truly a magnificent form of art. AIUI, the engine cowling cooling fan reduces power at low airspeeds, since it's strapped to the engine crankshaft and is therefore taking some power to generate cooling airflow, but that this power loss basically goes away at high airspeeds as the ram air pressure of the incoming airstream forces the fan around and offloads and power loss it would otherwise cause. I don't think it does much, if anything, for manifold pressure. The FW-190 and the Raiden both have exceptionally tightly wrapped radial engine cowlings. In order to ensure adequate airflow for cooling at low speeds, that fan needs to be there to actively shove more air over the cylinder fins. As for why high altitude favors the Jack over the Hellcat, according to this site, the Jack has 1,800 horsepower at takeoff and 1,410 horsepower at 15,700 feet. Per this very good book, the F6F3 has 2000 horsepower at takeoff, 1800 at 13,500 feet and 1650 at 22,500 feet. In other words, the Hellcat has a slightly higher percentage of its takeoff power rating (82.5% vs 80%) 6,800 feet higher than the Jack. So, that big P&W mill is clearly capable of maintaining a better percentage of its power at altitude, on top of being a more powerful (and larger) engine to begin with. However, the Raiden was a land-based fighter, you know, despite being operated by the Imperial Japanese Navy. The F6F has gigantic barn door wings to ensure good handling during carrier approaches. The Raiden has teeny tiny little wings, since as a land-based fighter it can afford much higher landing speeds.
  32. Collimatrix
    Part of my brain still refuses to accept that "solutionize" is an actual piece of metallurgical terminology and not something that George W. Bush came up with. He's not a problemifier, he's a solutionizer.
  33. Collimatrix
    Paul Hazell has a patent on ERA that uses a ceramic flyer plate which fragments shortly after interacting with the jet or penetrator, with the idea being that it reduces collateral damage. Other than that, I am not sure.
  34. Collimatrix
    That's a good question, and I'm not sure. Per the spec sheet N-L-M posted, it is a solution hardening (which is the same thing as "age hardening;" metallurgical terminology is nonsense sometimes) alloy. I bet that small titanium addition is what's doing the trick. So the precipitation hardened part could be reset. However, it also has a bit of carbon in it, unlike a lot of other maraging steels. If you tried to "reset" the heat treatment, that carbon could cause some problems. Some carbides form at higher temperatures than the intermetallic precipitates, and if the metal is hot enough that the carbon is mobile and can diffuse (basically, the hotter the alloy gets, the more random kinetic energy the carbon atoms have, and the more they can drift around), then the carbon may start to form larger and larger carbide inclusions through a process called Ostwald Ripening. There's an ideal size of carbide or intermetallic inclusion particle size. If they're too small, they don't do much of anything. If they're too big, they tend to embrittle the steel because the carbides themselves are very hard but brittle. If they're just right they tend to pin dislocations and prevent plastic deformation thereby.
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