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Collimatrix last won the day on January 6

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About Collimatrix

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    The Atomic Prince of Punk

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  1. Collimatrix

    AFV Engines

    This slide explains that opposed piston diesels have a small inherent efficiency advantage due to lower surface area/volume ratio.
  2. Collimatrix

    Bash the Pak-Fa thread

    You can see that the SU-57 with the UCAV flash on the vertical stabilizer also has replaced the upper and lower DIRCM turrets with antenna fairings. The obvious guess is that those antenna fairings are for controlling UCAVs.
  3. Collimatrix

    T-80 Megathread: Astronomical speed and price!

    If there was, I haven't been able to find it. @Monochromelody mentions what sound like one-off T-80 variants with neutral steer capability in this thread. Mysteriously vanished SH user @Levi posted this excellent guide to Soviet MBT transmission design here. Sadly, most of the important material has fallen prey to the dreaded link rot. But I remember the basics well enough. In short, the T-64, T-72 and T-80 have basically the same transmission. The parts aren't compatible between the three (that would just be silly!), but they all work basically the same way. In a typical Western MBT the power flowing from the engine is split into a steering drive and the transmission. The transmission varies the drive ratio, and the steering drive alters the balance between the left and right tracks as needed. The power is then re-combined and sent to the final drives. In the Soviet tanks the power is split into left and right half transmissions. Essentially, each track has its own transmission, and these transmissions also double as steering drives and final drives. It's very simple and compact, and making a Western-style system that could fit in the same footprint would be quite a trick. Not necessarily impossible, but quite a trick.
  4. The beautiful new Trump thread is filled with Frank Zappa hating troglodytes.
  5. Collimatrix

    General news thread

    Haven't these people seen Zoolander?
  6. Collimatrix

    T-80 Megathread: Astronomical speed and price!

    I don't think so. A poster here a long time ago mentioned that the Kharkov factory was working on an upgraded transmission for the T-80UD/T-84/Oplot family that would have a continuously variable drive ratio as well as neutral steering, but that this was never actually mass-produced.
  7. I wonder if Trump will start ratcheting up the amount he wants for the wall, or other high-pressure sales tactics.
  8. Collimatrix

    Dealing with declassified/classified/secret data

    Don't post anything on this forum that will get it shut down by goons in suits. Don't post anything on this forum that might get your countrymen killed. If you screw up and accidentally post something that is uncomfortably close to any of the two categories I just listed, PM a moderator and they will disappear it like Stalin. Other than that, go nuts. If the super-secret specifications of some exotic armor array get leaked or accidentally photographed elsewhere and flood the 'net? It doesn't make sense to pretend that shit is secret.
  9. Collimatrix


    Perforated armor does not work particularly well against APFSDS in general. Doesn't matter what country the factory is located in. Perforated armor works by having an array of holes (thus the name) that are sized such that it is statistically likely that an incoming KE threat will catch one of the holes on the very edge. This tends to mangle the KE threat and also yaw the penetrator so it hit slightly side-on. APFSDS darts have a very high aspect ratio and a relatively small diameter, so they should be fairly easy to mangle and they should be enormously degraded if they rotate even slightly, right? So far so good. But APFSDS has a number of properties that also make it less vulnerable to perforated armor. The biggest problem is that APFSDS is really, really fast. If you impart a given amount of torque on an incoming projectile with a perforated stand-off plate, it will yaw less by the time it reaches the main plate if it's going faster. A given amount of torque will impart a given angular velocity on a given penetrator, and with APFSDS the penetrators are moving so fast that they don't have much time to yaw before they strike the main plate. On top of that, APFSDS has an extremely high moment of inertia about the yaw axes because it is so long. A given torque applied to the rod will rotate it less. Finally, APFSDS operates within a semi hydrodynamic regime, and the penetrators erode by design. They're not like traditional, full-caliber AP rounds that live and die by penetrator integrity, and this makes it a lot harder to apply torques to them in the first place. So, APFSDS is moving too fast to get turnt in time, it's resistant to getting turnt, and it's not easy to turnt it in the first place. All my sources on the matter (e.g. Hazell 2016) say that armor arrays that try to yaw APFSDS don't work particularly well. That said, a perforated array would work much better if the perforated array has more inertia. So, a perforated array made out of, say, depleted uranium might work against APFSDS where steel would fail. I have suspected in the past that this might be what the "DU mesh" in the Abrams' turret is, but @SH_MM has stated that he thinks a DU-based NERA array is more likely. In any case, the design of the DU arrays in the armor have changed from model to model. The T-14 almost certainly has ERA built in, and there is no reason to expect that future Russian ERA will look like 1980s vintage K1 "postage stamps". The grain size will only go down so much from a single rolling operation. To get ideal grain sizes, the process needs to be rinsed and repeated a few times. That costs.
  10. Collimatrix


    Everything I've read suggests that perforated armor does not work terribly well against APFSDS. I buy the rest of what you say, more or less. There have been substantial improvements to armor steel metallurgy over the past several decades. But they are costly improvements.
  11. You could have a conventional cartridge case that has perforations it bursts along.
  12. Complete speculation on my part. However, a hi-lo gun does not necessarily need the expansion chamber to be located in each casing, that's just how 40mm does it. It's entirely possible to have an oversize firing chamber.
  13. This is surprising. What could the Israelis possibly get from Ukrainian radar technology that they can't already make better on their own?