Collimatrix

I don't get it. What was the big political uproar about the US withdrawing ground troops from the Kurdish areas in Syria? They're clearly still there.

This is the breakaway/sacrificial tip that isolates the damage to the rod to the first third or so, right?

I suspect that it's gotten better over the years. The numbers I've seen in older sources are lower, and the number I've seen in more recent sources are considerably higher. A while back there was a link to a monolithic high hardness steel that was 2x effectiveness over RHA. I suspect that anything that hard can't be made in particularly thick sections, and is likely impossible to weld, but it does seem that there has been significant improvement in steel armor technology.

Depending on exactly what grade of steel it is, it may be weldable, or at the very least it could be riveted and used to carry loads. Even extremely high hardness steel is a much better structural material than any ceramic, which is purely dead weight from a structural standpoint.

Rolled metal laminates are less limited in thickness than explosively bonded ones. On the other hand, explosive bonding (at least if you do it right) has a stronger bond between the layers, and allows the bonding of highly dissimilar metals (like steel and aluminum). One thing that the designer must be very careful with when making double or triple hardness steel laminates is that the different sorts of steel laminated together have the same martensite start temperature even if they do not have the same final hardness. The martensitic phase transformation has a small, but extremely rapid volume change (and actually this is why katanas are curved back like that; when the edge transforms into martensite it actually gets slightly more voluminous and bends the entire blade backwards). If the two plates don't transform simultaneously they can shear apart.

All the early jet engines were kinda bad. The Jumo 004 had its merits, notably low cost, as it was cheaper than the fighter piston engines to produce. There are many, many, many things wrong with the Jumo 004, and people who try to oversimplify them to shoddy worksmanship or poor metallurgy are, well, oversimplifying. If you watch footage of Jumo 004s running, for instance, you'll frequently see big gouts of flame transiently come out the nozzle. This is due to big, poorly atomized blobs of fuel making it through the turbine stage and exiting the back. I think it was basically par for the course for a first-generation technology made under duress, but it's difficult to exaggerate just how janky they were.

If you're going to be pedantic, you should at least try to be correct. This is the real fucking world we're talking about here. There isn't some infinitesimal dribble of rebound in all cases because there are plenty of sources of damping, like friction from locking, or any of the several deliberate ways to damp carrier motion as it comes into battery that I detailed in the OP.

Was the entire engine in the Ikv. 91 cooled that way or just the steering system?

As I understand it, this is part of why a lot of proposed nuclear space reactors have used exotic working fluids like mercury vapors to spin the turbines. Mercury can be used with a very high heat rejection temperature, which helps keep the radiators smaller.

Yeah, I think I see a problem. The return spring for the bolt carrier has to be stronger than the bolt spring, or the bolt carrier cannot force the bolt into battery. The return spring is exerting the least force when the bolt carrier is near battery, because that's how springs work (Hooke's Law, yo). So there's a very fine balance between having the bolt spring be strong enough to do anything but having the bolt carrier return spring still be able to perform its job. Needless to say, this is not a good way to do things.

Nanostructured bainite's day in the sun as armor may have come to an end: This is the same guy who worked on the nanostructured bainite. Apparently Tata steel has come out with the next big advance. The claims made in this video are remarkable. This steel is 550 Vickers hardness, which is about 500 Brinell. That's definitely high hardness armor by most definitions. However, the toughness is just as good as a rolled homogeneous armor like Armox 370, and it's weldable! On top of that, the steel is supposed to be reasonably inexpensive, and readily mass-producible using mostly existing tooling.

M1 Garands and M14s both have the gas system on the bottom of the barrel, and both have to go to some pains to wrap around and up the sides to avoid the magazine well. What possible advantage is there to putting the gas system under the barrel?

I found a very good lecture on this subject:

Are there any pictures of the coolant lines that take the engine heat from the front mounted engine to the rear-mounted radiator?

And the K21 that the Redback is based on is also advertised as resisting "30mm APDS" from the front, despite that arguably not being a particularly common threat in world arsenals these days. But who knows, maybe that's what the North Koreans are still using.

I haven't done the extensive modelling Sturgeon has, but, to a reasonable first approximation: -Most new rifles these days are multi-lug, rotary bolt types -There's a practical limit on how many lugs the bolt's locking area can be divided into -There's a practical limit on how steep the cam track can be before the action of locking the bolt makes too much friction -Therefore there is a practical limit on how much the length needed for the bolt carrier to lock and unlock the bolt can be minimized

I've been having a good time with the Knife Steel Nerds blog. It's a good balance of accessible and technical for me. The author just wrote a book, which I have purchased but not read. Obviously, it's aimed at knifemakers, but it goes enough into the basic theory of steel that it works for general metallurgy.

2020 Update: 2019 and 2020 have proven to be turbulent years for computer hardware development. Since I last posted in this thread, there have been several significant developments. 1) AMD's Navi 2, Ryzen 3000 series 7nm CPUs came out in Summer of 2019, and matched Intel CPUs in all but a few, extremely single-threaded benchmarks: The 3000 series sold more than anticipated, with significant price scalping occurring. The AMD 5000 series GPUs, based on the new RDNA architecture came out as well. They were... OK, I guess. Several of the mid and low end models were good value, but the large, high-performing models simply failed to materialize (and were likely cancelled late in development). Driver support was also rocky at first, and unlike the competing RTX-2000 series, the RX-5000 series has no hardware-level support for ray tracing. Intel, meanwhile, hasn't been having such a great time. Several additional security vulnerabilities have been disclosed, and their own 7nm node was postponed by at least six months. This threw their shareholders into a rage, and they are now facing a class-action lawsuit. Global supply chains for electronics have been disrupted not only by COVID-19, but also by the trade war between South Korea and Japan. Taiwan's TSMC is the undisputed industry leader in lithography, and the Trump Administration would like them to build a plant in the USA. As the global leader in lithography, TSMC has their pick of suitors and has no difficulty selling off fab capacity. Currently, Qualcomm, Apple, AMD, Nvidia and others jockey for their limited supply of silicon. In Q3 or Q4 the new video game consoles are expected out, presumably just in time for the holidays. Both will feature AMD-designed APUs based off their Zen 2 CPU architecture and RDNA2 GPU architecture, with some degree of hardware-level raytracing support. Innocenceii's youtube channel does an excellent job going into the technical specifics of the designs. Alas, he is constantly under siege by an army of unwashed console fanboys who keep accusing him of shilling for one side or the other. Nvidia's next-generation GPUs, all but confirmed to be called the 3000-series, are expected out somewhat sooner, possibly as early as September 2020. Interestingly, the persistent rumor is that they will be made at Samsung, and not at TSMC. Samsung has invested heavily in ASML Extreme Ultra Violent (EUV) technology, and while TSMC currently has the highest density, best yielding lithography technology, Samsung may contest that in the coming years. It is likely that the future of lithography for microelectronic manufacture will be a contest between TSMC in Taiwan and Samsung in South Korea, with Intel trailing far, far behind.

Hopefully this has not been posted already:

If you would like to learn more about steel microstructures and phase changes, you should find an an actual textbook that wasn't written by someone who was strung out on heroin, unlike this one.

I have learned enough about ferrous metallurgy to contribute to this discussion. Sooooo... Bainite itself isn't brittle. Bainite itself is fairly tough, but less hard than the more typical tempered martensitic steels used for armor. However, a funny thing can happen during the formation of bainite. Bainite doesn't just form; it grows within and eventually replaces crystals of a phase called austenite, like so: This is done during a special heat treating process called austempering. Compared to other heat treatment processes, austempering is fairly slow, but it also produces low amounts of warpage and cracking in the steel, works well with simple and cheap low-alloy steels, and does not require any secondary processes like additional tempering after it is done. What can happen during bainite formation is that the growth of those little lathe crystals segregates out impurities like sulfur and phosphorus, piling them up into dense bands that promote crack propagation. There are ways to counteract this, but if the bainite/pearlite formation was an unintended side effect of an imperfect heat treatment in the first place, then they probably didn't do anything to counteract it. Also, steel mills today are probably a bit better at removing the sulfur and phosphorus in the first place. Small grain size is desirable regardless of the microstructure of the steel. The Hall-Petch strengthening mechanism is of considerable interest because it is one of the few mechanisms that simultaneously improves the hardness and toughness of steel.

I haven't logged into your account and posted as you a long account of being sexually attracted to little boys and then banned you for it. This would suggest that some of my anger issues have been mitigated by the regimen of powerful schedule III drugs I have been taking off-label for several months. Congratulations on the successful outcome of this test. The reason we're treating what you're saying as laughable and obvious nonsense is because it is. It doesn't help that, when I very gently (by my standards) point out what's wrong with it, you just make shit up. If the receiver on the H is wider, then how does this exist? If the receiver on the H is wider then how come its bolt carrier isn't visibly wider? That especially doesn't make sense when you consider that the SCAR bolt carrier rides on rails that are an integral part of the receiver extrusion: The SCAR-L and SCAR-H have exactly the same receiver cross section. Originally, they were going to have a common receiver. The program later relaxed the requirement for a unified receiver, which means that the uppers aren't identical. They are, however, very close. But you don't need to know details of the SCAR's program history to work out that the receivers probably have the same cross section. You just need to use your goddamned head and think about it. What. Why would you think this. Do you even think? For one thing, caliber conversions for the SCAR-L for 7.62x39 do exist. For another thing, this entire tangent of nonsense is internally inconsistent with the other nonsense you posted already. If the HK 433 can accept larger calibers simply by having a magazine well that's a few pixels longer, then why does the FN SCAR require a receiver that's both wider and longer? Like, think about this for just a fraction of a second. Your entire train(wreck) of thought is just plain stupid. This is what I was trying to hint at with the picture comparing the SCAR-L and SCAR-H, but this point went whistling harmlessly far, far above your head. 1) The distance between the trunnion and the rear of the magazine well isn't what determines the maximum cartridge overall length a rifle can handle for several reasons. The rifle needs enough distance from the inside of the rear of the magazine to the breech of the barrel plus distance to cam the locking mechanism into engagement and/or ramp the round up into alignment with the bore. The breech of the barrel doesn't necessarily coincide with the trunnion. Indeed, it could be argued that the FN SCAR doesn't really have a trunnion at all: See? There's no big internal buttress that the barrel attaches to. It's held in from the side by screws. 2) The thing you think is a trunnion isn't. If you actually look at the patent, you can see that the thing you marked is the crosspin attachment for the lower portion of the handguard and the lower receiver. It is not what holds the barrel on. It happens to be near the barrel mounting hardware, but it does not hold the barrel on nor does it mark the breech of the barrel, which is several millimetres further back. 3) The lower receiver is clearly intended to take 5.56x45mm COAL rounds and magazines. If they were intending to fire 7.62x51mm from that rifle... they would put a new lower receiver on it that can take the appropriate magazines. 4) Again, I was gently hinting at this, but you missed it, the SCAR-H has a larger ejection port to accommodate the larger cases and a longer charging handle slot to accommodate the larger stroke of the bolt carrier. If the 433 were designed with the option of longer calibers in mind, we would also see those features, but we don't so it isn't. Actually think next time in order to prevent yourself from posting long and tiresome nonsense.