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Showing content with the highest reputation on 04/16/2018 in all areas

  1. 3 points
    Alzoc

    Tank Layout

    There was a shitload of concept for the Leclerc (same for any 3rd gen MBT I guess). Take your pick:
  2. 2 points
    Collimatrix

    Tanks guns and ammunition.

    It might be that the bottleneck in the CTA is designed to be disposable. The portion of the bore closest to the burning propellant usually takes the most damage, so if the cartridge case takes some of the damage instead of the bore throat, it could allow higher propellant burn temperatures without sacrificing barrel life. But it's hard to say for sure from the information that I have if that's what they're trying to do. I would need to see more of the exact design of the firing chamber to say for sure. The design does have the advantage that it has no exposed case material, while the rimless ammunition used in small arms has a fair amount of exposed area. The rimmed ammo used in tank guns has close to no exposure though, so the so-called "cased telescoped" ammunition only enjoys an advantage vs. small arms ammunition in that respect. The CT ammunition has the disadvantage that the cartridge case is completely cylindrical with, so far as I can tell, no taper to aid in extraction. That could make getting the rounds out of the chamber at higher pressures harder. On the other hand though, they are being pushed out of the chamber rather than pulled, and that may be a more positive way to get the spent case out. From what I've read about the development of the British 110mm gun, the extremely high pressures required by tank guns necessitate a caseless or semi-caseless ammunition design. The peak pressure is simply so high (120mm APFSDS peak pressure is about double that of rifle ammunition) that a conventional metal case will try to weld itself inside the chamber, and extraction becomes too unreliable.
  3. 2 points
    Collimatrix

    Tanks guns and ammunition.

    The autocannon breech and ammunition feed are both considerably less intrusive into the turret: The cannon feeds through the trunnion, so the feed mechanism doesn't need to rotate with the cannon and can be pushed all the way to the front of the turret wall. I'm not sure how well this design would scale up. Certainly an MBT main cannon would present some serious problems, like the fact that the trunnions are buried in the frontal armor package. The ammunition is somewhat more space efficient than 40mm L70 Bofors. The outside diameter of the 40mm CTA is the same as the rim diameter of the L70 ammo, but the case only about 70% as long. Ballistic performance somewhat favors the CTA.
  4. 1 point
    I'm guessing everyone has heard about the SpaceX party balloon by now; A lot of people (at least in parts of the internet that I frequent) did think he was crazy; Thing is, it's not actually that stupid of an idea. NASA has looked at the idea; https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20030106138.pdf And their analysis shows that a ballute can save a lot of mass when used for aerocapture from interplanetary trajectories. The second stage will be reentering from LEO, at a significantly lower velocity. The second stage already has a pretty low ballistic coefficient, so I'd guess it sheds a bunch of energy in the upper atmosphere. Adding the ballute/party balloon will let it dump even more energy high up. Also, by massively increasing the surface area, the heat flux per unit area goes down, which gets to the real reason why Musk is probably doing this; to avoid sticking a heat shield on the second stage. (There isn't really a great place to put one anyway.) Presumably, at a low speed / altitude, the second stage will ditch the party balloon and deploy regular parachutes. A re-entry capable balloon won't be cheap, but it should be a lot less expensive than a whole second stage. Bonus scene from 2010
  5. 1 point
    Xoon

    Tank Layout

    Image uploading site, like imagur. Oh well, I guess the French needs their quirks.
  6. 1 point
    Serge

    Tank Layout

    Yes. The Leclerc MBT barrel is very rearward compared the manualy loaded turret. This way, artillery is naturally balanced. Yes. Leclerc MBT was the first tank designed to achieve fire on the move at hight speed. Firing off road at 40km/h to a mobile target is basic. Maybe Type-10 and K2 are better today. Maybe. Yes. Aluminium tracks can’t last as long as classical steel ones. They were found too much expensive to support for peace time. You have such a mechanical link. I don’t know the exact purpose. I was AMX-10RC tank commander. I never served with Leclerc MBT. So, I can’t help for very detailed data. In France, you have Leclerc, Darklabor, Totochez, Rescator. They are not bullshiting.
  7. 1 point
    Alzoc

    Tank Layout

    On the mass balance topic, here's a citation of a book I (and probably other French speaking members) own. Even if you don't speak French it's quite a nice book to have with plenty of pictures (all those pictures of the various early EPC concept comes from here), though you have the impression that nobody ever proofread it (screw grammar and the orthograph^^). P58: Comme pour la fonction mobilité, une mécanique de haute technologie est requise pour la fonction feu. Celle-ci est entièrement conçue pour faire du tir en roulant le mode normal d'engagement des cibles. La précision de la stabilisation est donc au cœur des performances du système. Stabiliser un objet dans l'espace (en l’occurrence la tourelle et son canon) est un défi technique qui requiert de la part de l'ingénieur en mécanique le respect des trois règles d'or: -La recherche des équilibres ; -Le contrôle des élasticités et des déformations dynamiques ; -La chasse au jeu entre les pièces. Ces équilibres sont obtenus par conception du canon de 120mm et de la tourelle dont les centres de gravité sont respectivement situés sur les axes de rotation site et gisement. Canon et tourelle sont mis en mouvement à l'aide de moteurs électriques transmettant leur puissance à des boîtes mécaniques de pointage dont les élasticité sont contrôlées en permanence grâce à un montage utilisant des barres de torsion. Enfin des roulements à billes sans jeu assistent le mouvement du canon dans l'axe vertical. Sans ces technologies mécaniques particulières, la meilleure électronique du monde ne saurait conserver le canon en direction de la cible sans une débauche de puissance peu compatible avec les contraintes d'emport dans une tourelle. Google trad doesn't make too bad of a job translating it but the main points are: -The gun center of gravity lay on the level of the trunnion -The turret center of gravity is on the axis of rotation of said turret -The elasticity of the mechanical parts driving the gun and the turret are monitered in real time using torsion bars (don't know exactly how) -Ball bearings with minimal backlash (and same apply for most moving parts) are used. -No hydraulics, everything is electrically driven.
  8. 1 point
    Collimatrix

    Tanks guns and ammunition.

    Cased in this instance means not caseless. There's a... I think it's polymer and metal, mixed contruction case keeping everything together. The old G11 ammo was just a blob of propellant with the bullet, primer and booster inside. The 25mm ammo for the GAU-7 was, if I'm remembering this correctly, of an absolutely bizarre configuration where each round was coated in a waterproof/fire resistant coating that was shucked off like a corn husk before each round went into the firing chamber. The "telescoped" is nearly meaningless, but it's basically the same configuration as the Textron small arms rounds that are also called "telescoped" even though they don't have any propellant ahead of the projectile either.
  9. 1 point
    LoooSeR

    Syrian conflict.

    This is well fucking made subway system in Eastern Ghouta.
  10. 1 point
    LoooSeR

    Syrian conflict.

    http://tass.ru/armiya-i-opk/5131781 Fresh: So, according to MoD S-200 have 0% effectivness against cruise missiles. And appears that Isreali jet was shot down by it.
  11. 1 point
    LoooSeR

    Syrian conflict.

    Another look at sat photos from object, that US claimed to be hit by 22 cruise missiles Number 5 and 6 hit open fields, maybe those 2 are missiles that were claimed to be jammed by EW or maybe were hit by short range AA, which changed their trajectory. Number 4 hit kind of nothing, if it was cruise missile hit.
  12. 1 point
    Alzoc

    Tank Layout

    I remember reading that they payed a particular attention on mass balance around the trunnion for the Leclerc's gun, so that the strain on the electric drive of the gun would be as limited as possible. Don't know the final performance level they reached, but Nexter/GIAT commonly marketed the Leclerc as the only tank with a true fire on the move capability (describing the M1, Leo 2 and Challenger 2 as tanks that have merely acquired this capacity at limited speed and only in the frontal arc). When reading on the history of it's development one have the really distinct feeling that they went full retarted on having the best stabilization possible. The initial aluminum tracks that had awful service life were chosen for their light weight but mostly because they generated less vibrations, for example. Dunno if the M1, Challenger 2 and Leo 2 still use an hydraulic drive for their guns or if their most recent versions switched to electric. A sort of mechanical arm that would measure the angular difference? Well that's a question for a crewman for once. Does the gunner lose the target when the gun is reloading? @Serge Aren't you the one who knows an ex Leclerc TC? Or was it @Laviduce?
  13. 1 point
    Alzoc

    Tank Layout

    It is, and AFAIK it was done to eliminate any alignment issue with the gun. The designers went to great length to have an extremely stable gun so why not link the gunner sight to it? (Should be stable as well right?) The problem it cause is obviously the infamous gunner sight weakspot. Nowadays electronics and informatics have come a long way (Remember that when the Leclerc came out, having a tank fully digitalized and not relying on analogical devices at all was kinda rare) so I doubt they would bother with all those mechanical parts if they had to remake it.
  14. 1 point
    Collimatrix

    Tanks guns and ammunition.

    I see now that the old link is gone, victim of the dreaded link rot. So I will have to explain this all again. Telescoped ammunition, like the way the G11's ammunition was constructed with the projectile buried in solid-cast propellant: Barely works for small arms and works less and less well as it is scaled up. For any gun to work well the bullet has to seal with the bore and prevent gas from flowing past the projectile. Gas that flows past the projectile and up the bore causes greatly accelerated bore erosion, and reduces performance because not only is that gas no longer behind the bullet to push it, but the gas is contributing the pressure in front of the bullet, which partially counteracts the pressure behind the bullet. For normal, boring, conventional, functional ammunition, this is not a problem. All the propellant is behind the projectile, and the surface of the projectile that seals the inside of the bore is jammed into the bore or very close to it. No muss, no fuss. But look at that G11 ammunition again. The bullet is buried in the propellant. More importantly, the full caliber part of the bullet that seals the bore is sitting behind the propellant, and a long, long way from the bore. In order to seal the bore, the entire bullet is going to have to jump about half of its entire length before any of the propellant gas can get around it. The telescoped ammunition is usually designed with a booster charge that breaks up the propellant and helps start the bullet down the bore, but in practice some of the propellant gas will make it around the bullet before it can seal. As the design is scaled up, this problem gets worse and worse. The inertia of the bullet scales with the cube of caliber and the distance it needs to travel before sealing is achieved scales linearly. The amount of force at the base of the bullet only scales at the square of caliber, so it will take longer and longer for the bullet to jump a greater and greater distance, which means more time where the propellant is burning and simply going around the bullet and out the muzzle instead of pushing the bullet. Large-caliber telescoped ammunition, such as the 25mm GAU-7 intended for the F-15, is complete garbage and burns the barrel out in a few hundred rounds, as well as burning much more propellant for the same ballistic performance as conventional ammo. And like I said, if you look at a cross section of the new 40mm CT, they get around this problem by not actually being telescoped. There is no propellant in front of the sealing ring of the projectile. This sidesteps all the technical problems of telescoped ammunition, but it also means that the round enjoys no greater volumetric efficiency than conventional ammunition.
  15. 1 point
    Oedipus Wreckx-n-Effect

    Let's Talk Dark Souls

    This is a good tutorial of what I was talking about in chat. Also, I love killing Havels.
  16. 1 point
    BMPT that is offered by UVZ isn't even most optimised designs of BMPT-like vehicles (some of Soviet prototypes made more sense that UVZ creation for claimed job). 1) BMPT inflate manpower of the unit. For 2 BMPTs you need 10 people to train and support in the field. Russian tanks and current/future IFVs allow you to have 3 vehicles per 9 people. Army is saving money on every fucking bolt (T-72B3 pic should be here for no apperent reason), inflating number of people needed to crew a unit of vehicles isn't best decision from economical POV (salaries, social benefits and so on in peacetime, especially during local conflicts). Moreover, vehicle carry 5 people into battle, and simple logic speaks that this will increase chances of higher casualties per vehicle, especially because they are intended for urban warfare. One critical mistake done by single vehicle - more people would be at risk that in a 3-man tank. Best decision would be decrease number of humans in unit that you send on a frontline to risk their lifes, to decrease overall casualties. I wouldn't mind higher number of soldiers (per vehicle) send to place where they have high chance of being killed if that vehicle provided serious increase in chances to win fight. 2) BMPT from UVZ isn't usefull in open fields. Everything what BMPT can do in field tanks can do better. BMPT's autocannons have inferior range and firepower than 125 mm gun, 125mm cannons also can be used to suppress enemies from max 12 km range using HEs with indirect fire. In open fields using ATGMs such as Ataka (which cost more than your usual Fagot or Konkurs that you got from free from Soviet Union) against infantry isn't best idea either. Instead of bying BMPTs designers could upgrade existing T-72B3s by installing programmable HEs and probem more or less solved. 3) In urban-ish conditions tank gun is still more usefull than 2 30 mm autocannons - for example in Syria militants in Eastern Ghouta created serious defensive lines with hardened MG nest, observation points and so on. 30 mm would have hard time to punch through it, thats why tanks or even 152 mm SPG like Akatsiya in direct fire are used to break through. Only useful role that BMPT can occupy is suppression, that is currently occupied by Shilka. But you don't need 5 guys to do this job. 4) In big cities with tall buildings ("true" urban warfare) tanks could be supported by infantry moving through buildings around it. Soviets in late part of WW2 developed and used rather effective tactics to do that. I don't think that problem of not being able to aim at enemies is frequent, but problem of spotting their movement and positions first - is. Moreover, enemies are usually trying to not engage targets from tall structures and keep themselfs closer to the ground so they will have higher maneuverability, ability to move through multiply buildings is easier to achive on ground/underground levels. The more they stay in same place, the higher is a chance to get smacked by something more serious than autocannons or tank cannon. So AFAIK main problem with enemy infantry in urban fights is ability to detect enemies first, before RPG gunner or other AT weapon team will engage you. After they fire it is either too late, or they are already running away, as fire from RPGs and ATGMs are not particularly noiseless and unnoticeable events, they will draw fire from every other vehicle/infatryman that saw that anyway. BMPT doesn't have anything more in that aspect than modern tank have. Thermal imagers and panoramic sights are not locked to BMPTs only. And problem of firing at targets beyond main gun elevation can be solved by RCWS with AGL in it, like Turkish upgrade of M60T apprently have, or Chinese RCWS. In fact our tanks already were tested with 30 mm autocannon in RCWS, they could just put AGS instead and problem with high recoil of 30 mm AC will be solved. So instead of buying BMPTs engineers could put RCWS with AGS and add more sophisticated 360 degrees observation system with cameras/thermal imagers with software to detect movement, probably intergrate it into digital battlefield management system on top of that. UVZ's BMPT simply doesn't have any aspect that can't be intergrated on existing systems, without bloating human count per army unit. If they want BMPT/BMOP anyway, they should change design. What would i like to see instead of current vehicle is 2-3 man AFV with tank level of armor (including sides and rear, higher level protection of roof), armed with 40-60 mm autocannon with medium-high velocity shells and programmable HE-frags in unmanned turret. Vehicle will be able to engage infantry in trenches/cover with fragmentation (OICW on tracks, basically), can detect and destroy drones, and even ATGMs (like Pantsir claimed to be able to do), so it will have a place on open field combat of frontline SPAAG/APS with ability to suppress and kill lower priority targets like infantry (non AT teams), light AFVs, technicals and so on at same distances as tanks in direct contact to leave more important targets for tanks. Moreover, lower number of people inside of this vehicle will allow to decrease internal volume and this "BMPT" could be made smaller, and weight savings could be used to put more armor on this thing. That AFV needs serious protection from tandem HEAT from sides, rear and roof also should be able to hold direct hits from mortar rounds and light AT at considerable angles. Unmanned turret also should be able to hold well against 23 - 40 mm autocannons and RPG/ATGMs. Some sort of short range APS will be usefull. Vehicle should have serious package of passive sensors that are able to detect small drones at distance (including suicide drones) and ATGMs (incl. top attack) and destroy them with high probability. Same package of sensors will be usefull to detect and destroy infantry in fields/forested areas/villages/towns. Combination of weapon and sensors will make this "BMPT" capable to do things that no other AFV can do - tanks can't engage drones and ATGMs, Pantsir (or other SPAAGs) can't be deployed to frontline to cover them either without high risk to a crews. In urban warfare high caliber autocannon can deal with VBIEDs, technicals, an destroy infantry in protected areas (thanks to higher penetration of AP rounds than 30 mm and programmable HE-frags) and not just suppress them.
  17. 1 point
    First 10 South Korean K9 build in India
  18. 0 points
  19. 0 points
    LoooSeR

    Syrian conflict.

    lol, Syrian cafes
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