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Kal

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Everything posted by Kal

  1. The issue for the obus G, is not the rotation force in flight, its that the acceleration within the barrel is too much for the bearings to handle. The ports may also assist in flight rotation, but seem primarily there for launch. And reducing thrust accross the bearings.
  2. Lord James Just angle/stack the fuel tanks so that NERA can be co-located. That should give a close enough approximation as the nera has both a reactive and a slicing element. Which is comparable to how cellular fuel tanks work anyway. So instead of a giant cube of fuel. It becomes a stack of rhombus of fuel.
  3. I'm considering obus g style ammunition for premium situations. While not in obus g, i would consider a small amount of mercury would be beneficial to the obus g concept. In particular, it could transfer thrust to the shaped charge, while minimising torque transfer. Such a round would be too expensive for use against the Mormonhideen, but could be very useful against the Cascadians
  4. Can i use a small amount of mercury in the anti tank ammo? Just a teaspoon worth.
  5. Im trying to solve the issue, the techology base is early 1960s, how can i get first look, first kill with that. I use 2 gunners, 2 guns, same traverse, linked elevation, but the slower gun gets additional elevation also. These are technology's that should work with mechanical computers, and optical distance measurements.
  6. Original firepower idea was basically BMP 3 but with 57mm like the s-60 or even T-15. First intuition was 57mm for targetting and then use a rpg 29/32 equivalent warhead at whatever velocity i could get. So i try to understand bmp 3, i do the calcs and reverse calculate that both the 30mm and 100mm apply the same force to the structure. So despite the 100mm having a lot more reaction, the actual MPa or force on the bmp is equivalent. So that became the guiding principle for the design But my borosilicate and spaced armour package suggested that rpg 29/32 was not sufficient for future threats, So i analysed 2 more large calibre rounds. , necked out 57mm which by pixel counting became 91mm HEAT And a 125mm HEAT. The necked out 91mm is real tempting, its basically same exit velocity as 57mm round and same stored number of rounds and mostly same autocannon, just different barrel. Then i went Nera/Era and it could handle 60/160 warhead. So that pretty much forced the decision, its either 60/160 HEAT or go kinetic and drop the 57mm autocannon. Yes it will be a slower round (but still 50%-100% faster than bmp's 100mm round), but landing a half dozen 57mm rounds on a target first wiill help get the 160mm to be more accurate. And the 57mm might even knock out some optics etcs. If there is a lot of LIC, the utility of 57mm will be profound, especially against Mormonhideen with Toyotas. Shooting at a fleeting, moving Toyotas 4-5kms away wont be easy or cheap with a 1960s tank with a big gun. The turret can carry a lot of stored kills. A lot. Anyway, the tank will be a very logistically useful vehicle. A nice balance between HiC and LIC duties. 1960s technology was difficult to shoot precise. Spamming with 57mm round helps solve that problem.
  7. Re Mg vs Al for welding. The Mg is easier for fine welding like bikes and lightweight structures, but is unsuitable for thick welds. Mg welding uses only about 40% of the heat for the same thickness as. Al welding but is unsuitable for deep penetrating welds because the Mg boiling point is a lot lower than Al boiling point. (Even though the melting points are almost the same.) Al obviously conducts heat away from the weld a lot faster than Mg.
  8. So if proposed tank uses russian 57mm autocannon, ke is 1,425,000j, exit velocity 1000m/a To balance force on vehicle allows HEAT 91mm At 940m/s 105 mm at 760m/s 125 mm at 660m/s 160 mm at 500m/s Seeing how easy it is to defeat smaller HEAT warheads, the complementary cannon is either the 160 mm at 500m/s. (Is is similar ratio to BMP 3 guns) or just go with the 90mm and make that an auto cannon also.
  9. BMP 3 30mm 2a72 has ke about 180,000j, exit velocity about 960-1120m/s 100mm 2a70 has ke about. 480,000 to 840,000j, exit velocity 250-350m/s Resolve for different durations, turns out that the 30mm and 100mm have same force on vehicle structure, but the 100mm has a longer duration. Hmmmm
  10. Magnesium alloy is generally better for welding than aluminium. But Aluminium makes better sheet and plate than Magnesium. But Magnesium makes better castings than Aluminum. So while Magnesium is better for welding than Aluminum, much less welding is used with Magnesium because its generally a casting anyway. Magnesium is sweet for castings, but its just not worth it for sheet or plate work. The alloy i would suggest is ZE41, popular from late 1940s to late 1960s. https://www.slideshare.net/mobile/GkhanBier/mg-alloys-in-industry
  11. Mg Hull casting including glass inserts and 25mm textolite liner. 12.7 tonne Armour packages 11 tonne Frontal arc 60/160 resistant Side 50/150 resistant. Limited 60/160 area Turret incomplete Roof nera/era still to optimise
  12. Target is can i reduce weight down to low enough that 2 rolls K60 motors will suffice.
  13. Reduced front armour weight to 2.9 tonne per m2 with fuel. And 2.5 tonne per m2 without fuel. Defeats 360/960 CE, but only defeats about 800mm KE (depending on fuel). Glacis top protection is still crazy high, but thats inevitable with ricochet angle plate sheathed with reactive armour.
  14. There were lessons why Merkava have front engines. Merkava front engine layout works because High Intensity Combat included having infiltrated, tens of thousands Egyptian soldiers with ATGM shooting the sides of the tanks. On Israeli territory. Merkava front engine layout works because High Intensity Combat included having a last stand all out battle against hordes of Syrian tanks until ammo gets rationed down to 1 round per tank. Re stocking tanks in action, at the front, under fire is needed. Rear entry is safest for manual reloading. This is neither Nato nor warsaw pact expection of high intensity combat. Classic cold war armour is very face first. Rear engine pushes the parts of the tank that needs protection forward, thus reducing the length of side hull armour to defeat. Less armour to sides allow more amour to front. More armour to front was expected to be superior tank.
  15. Wow, a deltic. And i thought going with twin 5TD, L60 , K60 design was adventurous. Do tell, how big are your fuel tanks gonna be?
  16. I just want to confirm. If i model the fuel cells as a stack of jerry cans between 2 bulkheads. That when full, it is only 'Mass efficiency vs RHA of 1.3 vs CE, 1 vs KE. Thickness efficiency vs RHA of 0.14 vs CE, 0.1 vs KE. Density-0.82g/cm^3.' ie no space multipler effects. and when empty, the space effects can be in full force. 'Reduces penetration by a factor of 1.1 vs CE or 1.05 vs KE for every 10 cm air gap.'
  17. Im also treating polycarbonate as selfsupporting diesel. Is that ok or can you give values for that. The polycarbonate is mostly just a placeholder for replacement with interface defeat voodoo prior to combat Scrap that, I'll treat all that polycarbonate etc as ' Assorted stowage/systems Mass efficiency vs RHA- 1 vs CE, 0.8 vs KE.'
  18. thats fine. Interface defeat is not that simple to model. Also My ulterior motive for all the magnesium is that it would be most suitable for a 1970s tank to use for incorporating alumina LIBA (1990s concept) into the stucture of the tank itself. Fused quartz would also be compatible with that manufacture method. Which couldv'e been used in 1950s or 1960s if anyone had tried. Can I do that under the rules or is it no go? Of the 4 bulkheads, 3 are suitable and 1 is not, for cast in situ quartz LIBA. I would also use it for sides and rear but not the roof or floor.
  19. hull armour Nose 189mm CE, 125mm KE includes bulkhead 1 Fuel tank 120mm CE, 103mm KE includes bulkhead 2 NERA ERA array Horizontal Nera at 82 Vertical lefthand Era at 60 Vertical righthand ERA at 60 Horizontal NERA at 82 contines Includes bulkhead 3 Final armour, ceramic dwell package 193mm CE, 132mm KE Includes bulkhead 4 Each bulkhead is 100mm Structual Cast Magnesium followed by 25mm textolite (as spall liner/fire resistence). Bulkheads take up 30% of volume but maybe 10% of protection, 20% of weight I have used interface defeat / dwell structures (shock wave attenuator, confinement, buffer/shear support, weak layer, ceramic, base ) twice but left the KE and CE as given for borosilicate. Against steel, borosilicate glass can provide some dwell protection but doubtful against tungsten etc. Is mullite an acceptable choice for 1961? its roughly halfway between quartz and alumina and is basically just high quality porcelain. Total array is about 4.5 tonne per m2. And fits within the 1.75m depth allotted to it (1.68m). No way is turret anywhere as well armoured as hull. But design is commander and driver in hull, gunner 1 and gunner 2 in turret.
  20. Oops, my light NERA ERA array kinda defeated 360/960 shaped charge. It starts with light NERA at same slant as upper glacis at 8 degrees. Then 2 small rhomboid light ERA at 30 degree. Then a trailing second shot through light NERA at 8 degrees again. Starting was just projecting roof line down. Nb this is after some frontal protection against autocannon
  21. On an equal weight, bending basis, Mg is about 205% the stiffness of steel vs Al which is about 166% the stiffness of steel. But the Mg fragments burn, whereas the Al fragments dont. Its probable that 1% pb would be added for nuclear radiation scenario, this would actually improve damping propertics and thus the ballistic backing ability of the Mg. With appropiate design a Mg hull floor would have great blast resistance. Being that a little curvature would add massive blast resistance. Given that is 100mm thick anyway. But the main reason, Mg is easy for casting. 1 piece cast hulls are quick and easy, gravity sand casting will do.
  22. Proposed tank design has dual Kharkov engines at back, so a hit to one will not necessarily disable the other. But wow, 1500mm of space does wonders to CE. I would wager that its a lot quicker to replace a motor (kept as a field spare) than to rewire/rehose a fighting compartment. And probably cheaper too. In the automotive world a car's wiring harness is a higher cost item than the engine, its probably the same in tanks also. This is a 1960s tank, not a 1940s tank.
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