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A. T. Mahan

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Posts posted by A. T. Mahan

  2. COMPETITION Steel Chariot of The Prairie: The Lone Free State's First Battle Tank (2247)

    in Sturgeon's Contests

    Posted

    3 hours ago, N-L-M said:

    As I recall that armor array left much to be desired in terms of coverage, as the cassettes weren't properly overlapped.

     

    There were coverage gaps due to the NERA cassette being poorly angled from an error in the optimization script. I was going to fix that for this competition, but I don't think it will cut the protection offered by all that much. Additionally, the weight with ERA was about 55 tons, which I think is pretty reasonable compared to its contemporaries. I also would like to point out that for this competition, I dramatically reduced the size of the underlying turret structure to reduce protected volume and thereby save weight, since the previous turret was almost comically over-large as a result of my relative lack of experience designing armored vehicles. I think the reduced mass efficiency of the fixed armor package design will likely soak up some of those weight savings, but I would need to actually go model it to check my weight budget, and as I previously stated, I no longer have an NX seat as of when I initially posted. I therefore am unable to actually submit an entry to this competition, so I'm rambling about what my plans were.

  3. COMPETITION Steel Chariot of The Prairie: The Lone Free State's First Battle Tank (2247)

    in Sturgeon's Contests

    Posted

    5 hours ago, Sturgeon said:

     

    I'm a little confused by this. Could you show your math? You're describing a tank that is 12t lighter than Comanche with almost triple the armor protection.

     

    This is based on the math for the previous competition, and those numbers were directly taken from that report and should be viewed in that context. I have not recalculated it with the current coefficients yet because I've been busy, although I suspect it will not lose a huge amount of protection. I will try to recalculate it tonight. The various members of the California team and I spent a lot of time and effort working up the previous armor package concept, and it seems to work extremely well. The vehicle also has a relatively small protected volume. The weight analysis comes from the volume of modeled components in NX, so I believe it to be quite robust. 

  4. COMPETITION Steel Chariot of The Prairie: The Lone Free State's First Battle Tank (2247)

    in Sturgeon's Contests

    Posted

    I lost my NX license and ran into some other technical issues, so I doubt I'll be able to finish the modelling for my submission. I'll explain what the submission was below, though, for your consideration. If some "fluff" or in-universe explanation is desired as to how this was feasible, one can be provided. I also have as a prototype the "B" hull with the newer NERA-optimized frontal geometry with the legacy "A" turret. Please feel free to ask any questions you may have.

     

    Believing that the fundamentals of the "T-52" design from the Californian heavy tank competition were sound, I sought to rework it to incorporate the feedback that was given. The idea was to continue maturing the design through successive iterations until it would either A) win something or B) some crucial flaw be found that required restarting. To that end, there were two major areas of work. First, the hull shared the 68-degree glacis of a T-72 family tank. While we had previously made it work as a NERA array, it was kind of dodgy against the threats presented by the Californian RFP without heavy use of our Kontakt-1 knockoff. As the screenshots I posted showed, I had reprofiled the front of the vehicle to be more Abrams-ey, because the M1 family is a perfectly good NATO Box Tank and I like the looks. This provided a very large NERA array space, which would have been able to exceed the protection requirements handily. 

     

    Next, I undertook to revise the turret design. My goal was to produce something much more in line with the Object 187/welded T-90 turret, although the turret had a more pronounced bustle, as in the "T-52". In broad terms, the layout of the turret was to be similar to the previous "T-52" turret design -- commander to the right of the gun, gunner to the left. The armor packages were substantially pushed inwards, removing the front overhang that caused the driver issues when attempting to enter and exit the vehicle while retaining the quite substantial level of protection and protection arc of that previous turret. The armor package composition was to be moderately revised, as there were gaps in it that required fixing, but that would have been relatively quick to resolve had not I lost access to the script that had been written to optimize the armor packages. I would like to reiterate that the previous turret frontal armor package design was capable of withstanding 43/59" RHAe tandem charges and 31" RHAe kinetic penetrators before the inclusion of the ERA package. It also had quite satisfactory turret side armor. The reduced turret overall size would also have shaved several tons off of the overall weight, as the protected volume would have been reduced from the previous great excess. A new gunner's doghouse sight would have been designed, with proper two-axis stabilization and provision for the laser rangefinder, as well as a stadiametric auxiliary rangefinder. Ammunition was to have been a derivative of the 125mm combustible-case APFSDS, HEAT-FS, and HE-FS projectiles in a fixed steel case cartridge. Performance would have been satisfactory based on preliminary results, and I may finish working that out because I don't need NX for it. 

     

    Mobility was to be moderately reduced from the original 1,562 hp VDS-2240 design due to the lack of FADEC engine controls and thereby reduced specific power output, but the available 1,200hp turbosupercharged diesel V12 in an approximately 50-ton tank is quite solid, and the powerpack offered substantial room for growth in automotive performance. Studies were underway to determine the feasibility of a gas turbine, but I doubt such a power unit would be truly viable in this timeline until perhaps 2270.  The track system was to be the same T158 derivative. 

     

    As a note, much of the advanced computer equipment was to be removed, or replaced with much more basic electrical or electromechanical systems, as possible. 

  13. COMPETITION Steel Chariot of The Prairie: The Lone Free State's First Battle Tank (2247)

    in Sturgeon's Contests

    Posted

    4 minutes ago, Toxn said:

    Textolite is phenolic resin rather than epoxy, although still an exothermic reaction.

     

    I knew a guy who used to be the plant manager for a plant that used phenolic to make grinding disks. Apparently he had one of the cooling loops on a large tank go out in the dead of night as it was setting up and it blew the top off the thing. He also had a tank that failed less spectacularly but ran to completion in the tank. Apparently some poor bastards had to spend a week jackhammering the hardened resin out from the inside of the tank.

     

    One advantage to phenolics though: they don't melt, and they don't really burn. Instead they keep structural integrity more or less up until the point that they char, then crumble. Hence the use in grinding disks.

     

    Fair, I've never done work with phenolic resins, just epoxy and polyester/vinylester. 

     

    Fun fact, if you accidentally drop a pint or a quart or so of hardener into a 55-gallon drum of epoxy, it eventually will throw flames about 30' in the air. There were scorch marks on the ceiling of the building hall from that.

  14. COMPETITION Steel Chariot of The Prairie: The Lone Free State's First Battle Tank (2247)

    in Sturgeon's Contests

    Posted

    2 hours ago, Lord_James said:


    From what I’ve seen, many large boats have fiberglass hull plating, with metal supporting frames. I haven’t seen a multi ton, all fiberglass boat, just canoes and small personal craft... but then again, I don’t go looking. 
     


    Sounds good. I know in high performance race cars, they have similar issues. 

     

    There's plenty of quite large vessels made of glass, including racing sailboats -- the VOR 70s are designed for round-the-world racing and are about 14 tons (metric) all up. The first fiberglass 12-meter yachts are also in the 12-25 ton (metric) range, but they were built in the 70s if I remember correctly. I would suggest that composite structures of this type were very poorly understood at the time, and would be extremely difficult to lay up properly -- while boats with 2-3" thick solid fiberglass hulls were being built in the '60s and '70s because they didn't know how strong fiberglass was, there were also severe quality control issues that needed resolving.

     

    Laying up the structure itself would prove difficult, as you need to ensure appropriate resin fill during the layup process and you don't really have vacuum bagging or pre-impregnated heat-activated resins at this time.  Most epoxy or polyester/vinylester resins set in an exothermic reaction, and are also extremely flammable. In very thick layups, like a >12" thick turret front, this could result in the layup heating up sufficiently to spontaneously combust. 

     

    Plus, laying up composites is time consuming and miserable work that kills the necessarily quite skilled workers with silicosis from thickening agents and VOC poisoning from the epoxy unless they wear respirators, and if the vehicle gets hot enough it melts. 

  15. COMPETITION Steel Chariot of The Prairie: The Lone Free State's First Battle Tank (2247)

    in Sturgeon's Contests

    Posted

    41 minutes ago, Sturgeon said:

     

    At the same time, as you point out, guns bigger than 5-inch are a hard sell. They virtually demand an autoloader (and in the back of their heads people expect Texas to field these guns with caveman HE, it's just their style), and the compromises get out of control fast on a tank that already demands quite a bit of internal volume.

     

    Actually, on that, do we have statistical information on how big the average Texan tanker is and what the SDs and max allowable height is? I'm sure I can accommodate a corn-fed good ol' boy but it would be easier to not have to

  16. COMPETITION Steel Chariot of The Prairie: The Lone Free State's First Battle Tank (2247)

    in Sturgeon's Contests

    Posted

    42 minutes ago, Sturgeon said:

     

    I'd honestly be surprised to see any guns under 120mm.

     

    Fair enough. I don't see a huge advantage to going much bigger than 120/125/5" unless it's for a pure HEAT-chucker -- even with armor protection where it stands in 2021, it's still possible to make suitable gun and dart in 120mm caliber that provides sufficient performance. Further, the armor penetration requirements are more than suitably met with a ~125mm caliber HEAT charge, even a high velocity one, with substantial growth margin as improvements in warhead design come to fruition, and it's a pain in the ass to manhandle anything bigger than about 5" into the tank. Even 105mm dummy rounds are kind of a pain in the ass, from personal experience. 

  21. COMPETITION Steel Chariot of The Prairie: The Lone Free State's First Battle Tank (2247)

    in Sturgeon's Contests

    Posted

    I mean, I've just always set NX to inches. I will say, I'm looking forward to getting the hull finished enough tonight so that I can post a screenshot, then start on the turret. Sizing the turret properly is being a pain in the ass, especially in the weight regime I'm working in, as well as getting the under-armor structural shape done right to balance the gun nicely.

  24. COMPETITION Steel Chariot of The Prairie: The Lone Free State's First Battle Tank (2247)

    in Sturgeon's Contests

    Posted

    I mean, I did all the CAD work for the Cali competition in inches anyway -- I haven't had a chance to look at the appendices to the RFP yet, but I'm quite confident that once I finish up the turret and frontal hull, and then work up the armor arrays, that my vehicle will meet the appropriate requirements. The lots-of-independent-machine-guns thing is going to certainly be interesting on a relatively light three man tank, but I'm sure I'll manage. 

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