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8 hours ago, Whatismoo said:

But... why?

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.

 

 

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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.

 

 

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On 4/27/2019 at 2:39 PM, Xoon said:

 

Do you use the supercharger as a blower or for better torque and low end RPM? 

 

For the compound turbo, is it something like this:
800px-NomadSchematic_185kBpng360kB.png

 

I suppose that you could have a compound turbo sized so that it spools up at a large way of the rev range. 

For example. Lets say the tank spends most of its time between 800-1400 RPM, then it would be able to produce enough exhaust gas to power the turbine at roughly 8-900 RPM, and for the higher rev range rarely used, a turbocharger would be employed? 

 

So, if I understand the engine correctly, at low RPM, the supercharger would be used to provide power and compression instead of using the crank to compression.  At medium RPM the recovery turbine would have been spooled up to max, and at higher RPM the supercharger would be decoupled by a magnetic clutch or similar and the turbocharger would kick in. 

 

Am I correct? or am I completely off?  

 

Also, are gas turbine turbochargers allowed, @N-L-M

 

Now that it doesn’t feel like I have an ice pick slowly being pushed into my head, I can elaborate. 

 

My engine is closer to the Nomad 2, except the axial compressor is literally the super and turbo chargers. After the compressor, it splits into the ignition air ducts and cooling air ducts. After the cooling air ducts make their way through the engine, they reconnect to the exhaust, then go through the power recovery turbines. 

 

The supercharger is used at all speeds, and instead of disconnecting at high speeds, it “shifts down a gear” and acts as a second compressor stage to the turbo. 

 

On 4/27/2019 at 2:39 PM, Xoon said:

 

Well, the thing is, a CVT, is a continuously variable transmission, meaning infinite gears in theory. 

Which means you can have a gearbox with a ratio of 1 to 20, with anything in between. Like 15, 12, 7, 2, 10,12312321 etc. 

 

This means that the engine will always have the appropriate gear ratio for the RPM. No gear selection, just the engine humming happily at its optimal RPM. 

You can, however have a selector for economy and power. 

 

Lets say the engine produces its max power at 3000RPM, but runs the most efficient at 2000RPM, then the transmission would aim to always have the engine at 2000RPM for economy, or 3000 RPm for max power. 

You should have a "first gear" and reverse gear though, as a conventional CVT provides poor torque initially,  and is incapable of switching direction. 

 

It would have 3 gears, first gear, continuous gear and reverse. 

 

I might have mixed up dual clutch and CVTs, but yes I want a CVT. 

 

I think I’m going to have 5 gears: 

continuous forward, high torque forwards, neutral, high torque backwards, continuous backwards. 

 

On 4/27/2019 at 2:39 PM, Xoon said:

 

Love your engine so far btw, certainly a neglected design in the automotive world. 

 

:) 

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1 hour ago, Lord_James said:

Now that it doesn’t feel like I have an ice pick slowly being pushed into my head, I can elaborate. 

 

My engine is closer to the Nomad 2, except the axial compressor is literally the super and turbo chargers. After the compressor, it splits into the ignition air ducts and cooling air ducts. After the cooling air ducts make their way through the engine, they reconnect to the exhaust, then go through the power recovery turbines. 

 

The supercharger is used at all speeds, and instead of disconnecting at high speeds, it “shifts down a gear” and acts as a second compressor stage to the turbo. 

Ah, I see.

 

By ignition air, do you mean the air that goes into the cylinder for combustion? 

And why use air as cooling instead of watercooling? 

 

Considering the recovery turbine, I think it could be possible to use a gas turbine for even better power and acceleration, which also doubles as a APU. 

Water injection is also a alternative. 

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1 hour ago, Kal said:

Can i use a small amount of mercury in the anti tank ammo?  Just a teaspoon worth.

Yes, assuming there is a sufficiently good reason for it.

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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

Edited by Kal

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I started drafting up the IFV and APC versions: 

 

APC (SH-1A) 

Crew: 4 + 10 

Armament: either 23mm + 7.62mm machine guns in a low profile turret, or a 107mm recoilless rifle and 7.62mm coax (and 12.7mm spotting gun), with below armor reload. 

 

The SH-1A is a modified version of the SH-1T MBT, trading the large turret and ammo racks for a small, 2 person turret and 10 dismount seats. It still incorporates the same armor cavities, but with a lighter array utilizing more spaced components and no special materials (non steel). The crew consists of the Driver, the Gunner and Commander in the turret, and a thespian assistant who removes spent MG and autocannon shells, or loads the RR if that turret is equipped. A third turret is in the works, similar to the RR turret, equipping an ATGM with under armor reload potential. 

 

IFV (SH-1V)

Crew: 5 

Armament: 2x 45mm autocannons (SM-7 or NS-45 derivatives / maybe 4 if I think I can fit them) + 4x 107mm RRs + 107mm mortar (same as SH-1T) + 2x 7.62mm MGs (coax and commander’s MG). 

 

Also based off the SH-1T, the SH-1V is a heavily armed supplement vehicle to armored forces in the DPRC. Fulfilling a role similar to the ancient BMPT, it is designed to assist infantry and act as heavy armor in urban or mountainous environments, and to provide rapid and heavy suppressing fire for armor groups moving through hostile terrain. The crew consists of a Driver, Gunner and Commander in the turret, and 2 thespian assistants to clear the vehicle floor of spent casings, and to reload the externally mounted RRs. As ATGMs mature, the RRs can easily be replaced with missile systems on a volumetric basis (probably 2 RRs to 1 ATGM). 

 

Also in the drafting phase are an AA variant, an artillery variant, a heavy mortar variant, and CiC, medevac, CBRN, radio relay, EW, and others. 

 

 

PS. SH-1(x) is the company designation for the vehicle; military designations will be given when/if these vehicles are accepted for service. 

 

PSS. I’ve been either too busy, or unable to access the internet for the past couple of days, which has lead to delays. But I should be getting back on track later today or tomorrow, now that all of the shit is out of the way. 

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So, for the record, this is how Obus-G works:

2XRdbFs.png

 

See those little ports at the back end of the shell?  Those let in propellant gas to the inside of the shell, which then vents out the ports in the front and through the gap between the nose fuze and the shell body.  The inner HEAT warhead is "floating" on the high-propellant gas that gets vented inside the shell.

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I cannot, for the life of me, find the document about fluid filled armor on this forum, DTIC, or the internet at large. I remember it describes storing fluids (could be fuel, like a gas tank, or something else) in long, thin containers and when struck, the shockwaves from the projectile are transferred through the fluid, reflected off the container walls, and erodes the penetrator via hydrodynamic ram effects by the fluid. 

 

The only thing I found on DTIC was a study: 

https://apps.dtic.mil/dtic/tr/fulltext/u2/848937.pdf

Which does remark, in the conclusions, that smaller cavities of fluid (as well as using non-Newtonian fluids) could produce better results. 

 

If anyone knows where that study is, I would appreciate it. 

 

My my idea is for the side armor around the engine: it would be composed of hexagonal tubes, 50mm between opposing faces, and vertically arranged, so when looking down, it looks like honeycombs. After 2-3 layers, there is a back plate, then a real fuel tank, then the engine. 

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On 5/2/2019 at 9:58 AM, Collimatrix said:

So, for the record, this is how Obus-G works:

2XRdbFs.png

 

See those little ports at the back end of the shell?  Those let in propellant gas to the inside of the shell, which then vents out the ports in the front and through the gap between the nose fuze and the shell body.  The inner HEAT warhead is "floating" on the high-propellant gas that gets vented inside the shell.

So it levitates on a cushion of gas? 

 

I read something about it on the War Thunder forum that it used bearings. 

Is the gas used for counteracting the rotation? 

 

 

 

19 minutes ago, Lord_James said:

I cannot, for the life of me, find the document about fluid filled armor on this forum, DTIC, or the internet at large. I remember it describes storing fluids (could be fuel, like a gas tank, or something else) in long, thin containers and when struck, the shockwaves from the projectile are transferred through the fluid, reflected off the container walls, and erodes the penetrator via hydrodynamic ram effects by the fluid. 

 

The only thing I found on DTIC was a study: 

https://apps.dtic.mil/dtic/tr/fulltext/u2/848937.pdf

Which does remark, in the conclusions, that smaller cavities of fluid (as well as using non-Newtonian fluids) could produce better results. 

 

If anyone knows where that study is, I would appreciate it. 

 

My my idea is for the side armor around the engine: it would be composed of hexagonal tubes, 50mm between opposing faces, and vertically arranged, so when looking down, it looks like honeycombs. After 2-3 layers, there is a back plate, then a real fuel tank, then the engine. 

 

Page 7 SH_MM talks about liquids in armor. The only time I know the forum talked about it. 

 

Bronez also links a document:
http://onlinelibrary.wiley.com/doi/10.1002/prep.201500137/full

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1 hour ago, Xoon said:

So it levitates on a cushion of gas? 

 

I read something about it on the War Thunder forum that it used bearings. 

Is the gas used for counteracting the rotation? 

 

You can see the bearings and their tracks near the front and rear of the main body. 

 

1 hour ago, Xoon said:

 

Bah, requires dosh to read. 

 

Though, I did find a free one, that covers pretty much the same topic :) 

https://www.researchgate.net/publication/327940101_Mechanism_of_hermetic_single-cell_structure_interfering_with_shaped_charge_jet 

 

@N-L-M, is this technology accepted for use? 

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2 hours ago, Xoon said:

So it levitates on a cushion of gas? 

 

I read something about it on the War Thunder forum that it used bearings. 

Is the gas used for counteracting the rotation? 

 

 

 

 

You can see that there are ball bearing races in there also, at the front and back.  But a shell in a rifled gun rotates at approximately a billionty RPM, and a ball bearing isn't actually perfectly frictionless.  It just has extremely low friction.  But even an extremely low fraction of the enormous G-force in a gun tube multiplied by a billionty RPM is enough to disturb proper jet formation:

O7ReZkK.png

 

By floating the inner body of the shell on a cushion of gas, the acceleration on the inner and outer shell bodies is made approximately equal, and the axial force on the ball bearings is reduced to a low enough value that negligible torque acts on the inner shell.

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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. 

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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.

Edited by Kal

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10 hours ago, Kal said:

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.

 

That's my read as well.

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On 5/5/2019 at 7:10 PM, Kal said:

What would be the rifling for the obus G? CN-105 F-1. 

 

I'm not sure what you're asking exactly.

 

The AMX-30's gun, as I understand it, used exactly the same firing chamber dimensions as the L7, but it had a different rifling twist rate that was selected specifically for the Obus G.  The rifling twist rate needed is a function of the moments of inertia of the shell, distance between the center of pressure and center of gravity, and shell velocity.  With a shell with rotating and non-rotating components, I imagine this gets... interesting to calculate.

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So here's some other food for thought:

 

If you run a 120mm L/70 gun at maximum barrel pressure for 2A46 (510 MPa) and use a shell design similar to 130mm BR-482B, then you get something like a souped-up M58. This nets you an extra 65m/s at the muzzle and results in a penetration of ~300mm of RHA at 2000m using AP. This is also around the largest warhead that our Californian conscripts can lift, assuming that you use a two-part shell.

 

If, on the other hand, you decide to blow past all the most powerful tank guns in existence and opt for a 140mm L/70, then you end up with a monster that slings ~40kg AP at over 1100m/s and punches through a hair under 320mm of RHA at 2000m.

 

The issue with both, of course, is that the guns are LOLhueg and have obscene recoil. But, you know, if you want to stomp main battle tanks flat with 1940's-era shell technology, that's just what you're going to have to do.

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