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4 minutes ago, Toxn said:

probably give trouble to anything that isn't the roach's stupid-thick turret front.

I take it you haven't heard of the Norman's frontal arc.

200mm steel base+~180mm air gap +60mm hard steel LOS.

+- 30 degrees for the turret, +- 20 degrees for the hull.

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To the best of my knowledge the NERA's usual effect does nothing of any importance, as the projectile is so much larger and more rigid, so it's just like firing AP into a series of thin plates. You get decapping and possible yawing, but I doubt the NERA plates are rigid enough to shatter the AP. So it's probably less weight-efficient than plain homogenous steel.

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1 minute ago, Zadlo said:

Isn't the APFSDS round the late 50s technology?

More, I think it's not possible to load 200 mm round to 120 mm gun or to create 50:1 L/D steel rod :)

APFSDS is a future technology, yes, so we're partly discussing prospective upgrades.

 

My one proposed gun is a smooth-bore based on the late-war German 8cm PAW 600 and 10cm PAW 1000, however. This kind of bends the rules by firing finned mortar-type shells out of smoothbore barrel. So I was also dicking around with what filling the shells in to make a sort of weirdo finned AP round could do.

 

You are absolutely right that a 20mm, 1m long rod is a bit much ITO L/D ratio. I was just using the existing bomb designs I have and making the tail rod run through the whole thing.

I will check out more realistic/optimised versions of the concept later, perhaps.

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1 minute ago, N-L-M said:

To the best of my knowledge the NERA does nothing of any importance, as the projectile is so much larger and more rigid, so it's just like firing AP into a series of thin plates. You get decapping and possible yawing, but I doubt the NERA plates are rigid enough to shatter the AP. So it's probably less weight-efficient than plain homogenous steel.

That sounds plausible, but I'd love some actual tests or numbers.

 

I've said it before, but there might come a day when some desperate (and lucky) T-55 tanker fires a BR-412 into the turret front of a modern MBT and goes through.

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Okay, I quickly mocked up the case and ran a bit of optimisation. The more realistic APFS round is 70cm long and 2.5cm wide at the core. The case needs to be about 1.2m long (a tad longer than I originally designed it) if a base plate is used, and the powder load needs to be a full 1.5MJ higher than the ML-30 round used as a reference.

 

If the driving band is located on the aluminium sabot itself, then the case only needs to be about 80cm long.

 

All in all: less good than I was hoping for, but still doable.

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Been a little while; busy with all kinds of stuff, but here's an update: 

 

Added suspension components, as well as front idler and drive sprocket. 

Revised gun mount and C3 cannon 

Turret needs another revision, as I removed the loader and am going to use a version of the T22E1 autoloader ( I also don't need the long bustle for a ready rack). 

 

Spoiler

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Weight thus far is 23.3 tons.  

700mm roadwheels (drive sprocket is also 700mm) 

Ground clearance is ~600mm 

 

Gun depression is (ATM): 

Front - 19.5 

Side: -29 (when it hits the ground :P

Rear: -8 

Elevation: +36 

 

Breach is now a semi-automatic, vertical sliding wedge, similar to the 5" Mark 12 naval gun. 

 

The front idler needs to be raised and enlarged slightly, and maybe I need to shorten the suspension arms slightly (as well as increase the angle of the arms, from the vertical), but I'm pretty pleased with my first suspension attempt. Might put some holes in all the wheels to reduce their weight. 

 

 

Turret revision: 

I realized that the gunner wouldn't be able to see what they're shooting at when at maximum depression, so I have to rework some parts of the turret face, as well as remove the rear bustle since there's no need for it anymore. Though, I could use something like the TZF 9 sights on the Tigers (both 1 and 2) to avoid the roof sight messing up my turret shape. 

 

I am also considering offsetting the gun to one side and placing both commander and gunner in line, as well as modifying the autoloader (one rack will be smaller than the other); this will allow me to increase the size of the gun mount to place a coaxial MG comfortably, rather than having to cut into the front armor... or I could go full Ferdinand and not have any coax :rolleyes: 

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So I think I'm getting to the point where I should stop fiddling and finalise my designs.

 

My thinking right now is as follows:

 

XM-8 "universal" tank

- Retains a single hull, suspension, engine, transmission and most fittings (vision devices, radios, rangefinder, 1-axis stabilizer etc.)

- Now has a properly unified hull: armour blocks are welded into the air gaps to uparmour.

- The turret will get reworked a bit, might become universal as well.

- New 80/105mm guns (an average between the 17/20-pounder and a 105mm L7 made with 1940's-era metallurgy)

- Represents a general-issue vehicle

 

XM-16 "modular" tank

- Retains the existing hull, suspension, engine and transmission.

- Might have a reworked turret (Present one is functional but ugly).

- Gets a new 135mm smoothbore (essentially an A19 bored out) capable of slinging low-velocity finned HEAT rounds and gonky finned AP initially, but easily upgradeably to proper HEAT-FS and APFSDS when that comes online

-  Retains dedicated rangefinder

- Represents expensive, exquisite vehicle designed with upgradeability in mind.

 

I'm struggling to type so I'm afraid that my descriptions will be a lot sparser where they aren't copy-pasted directly.

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On 8/20/2018 at 10:14 PM, Lord_James said:

I present to you, the 94/74mm C2 squeezebore anti-tank gun: 

 

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currently, the sliding breach and mount are not made. 

 

Recoil stroke: 300mm 

Barrel length: 3.76m (L/40 if using the 94mm as reference, it's an L/50.8 using the 74mm reference) 

Mass: 833.5kg (using steel alloy 7.73 g/cm3

 

Only the first 10 calibers are rifled (940mm), the rest is smoothbore (I hope this is acceptable, it is very similar to the 7,5cm PaK 41 I'm basing this off) 

 

Can I borrow your gun?

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2 hours ago, Zadlo said:

 

Can I borrow your gun?

 

Which one? I’ve updated it twice, and now I have the C3. 

 

... also, I don’t know how to send components to someone, or even if my autodesk inventor files will translate well into whatever software you’re using. 

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32 minutes ago, Lord_James said:

 

Which one? I’ve updated it twice, and now I have the C3. 

 

... also, I don’t know how to send components to someone, or even if my autodesk inventor files will translate well into whatever software you’re using. 

 

C1. You can send me measurements of the gun via PM.

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Finalised gun designs:

 

80mm L/55

AP: 8.4kg @ 955m/s, ~180mm @ 500m

APCR: 4.7kg @ 1280m/s, ~240mm @ 500m

HE: 7.5kg @ 700m/s

Max ME: 3.85MJ

Notes: Gun is a 17-pounder/20-pounder hybrid.

 

105mm L/52

AP: 17kg @ 900m/s, ~200mm @ 500m

APCR: 10kg @ 1230m/s, ~290mm @ 500m

HE: 15.1kg @ 700m/s

Max ME: 7.6MJ

Notes: Gun is a L7 with the serial numbers filed off.

 

135mm L/40

HEAT-FS: 29.0kg @ 600m/s, ~270mm @ all ranges

HE-FS: @ 27.5kg @ 600m/s

AP-FS: 17.5kg @ 950 m/s, ~180mm @ 500m

APCR-FS: 8.8kg @ 1350m/s, ~250mm @ 500m

Max ME: 8MJ

Note: gun is a bored-out 122mm D25. "Finned Sabot" refers here to a more primitive design compared to the post-war stuff.

 

General note: AP and APCR penetration values for the 80mm and 105mm were calculated using a number of DeMarre values with similar real-world guns as references. These were then averaged and rounded to the nearesr 10mm to get the final value. The 135mm AP-FS value was obtained by mocking up and calculating values using BR-471D as a reference. The APCR-FS value was obtained by mocking up the round, running the core through longrods and then sanity-checking against known APCR/APDS rounds with similar characteristics. The core is modelled as a 30x220mm tungsten rod (~2.7kg). 

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6 hours ago, N-L-M said:

Really looking familiar...

It's like there's an optimum design we're all converging towards.

Who'da thunk?

I know, right?

 

There will be even more convergence to come - I had a bright idea that may obviate the need for all the cool-looking-but-fiddly armour spaces on the XM8.

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