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12 hours ago, Xoon said:

What is the advantage of this hull cross section, say over the IS-7s hull cross section?

 

The US egg-hulled tanks (M48, M103, M60) were, IIRC designed with ellpitical curved hulls that provided decent ballistics shaped plus a high volume to surface area ratio, to keep them light relative to the volume they protected.

 

The problem with this is that the hulls end up being rather tall.

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12 minutes ago, Collimatrix said:

 

The US egg-hulled tanks (M48, M103, M60) were, IIRC designed with ellpitical curved hulls that provided decent ballistics shaped plus a high volume to surface area ratio, to keep them light relative to the volume they protected.

 

The problem with this is that the hulls end up being rather tall.

I'm assuming that the designers all had a really rough night at the bar when APFSDS came in and curving stuff was rendered largely pointless.

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3 hours ago, Collimatrix said:

 

The US egg-hulled tanks (M48, M103, M60) were, IIRC designed with ellpitical curved hulls that provided decent ballistics shaped plus a high volume to surface area ratio, to keep them light relative to the volume they protected.

 

The problem with this is that the hulls end up being rather tall.

I see the the reasons why, but did it really work out that well in practice? 

 

Does it provide any more protection than the T-54s hull shape, for the same weight?

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5 hours ago, Toxn said:

I'm assuming that the designers all had a really rough night at the bar when APFSDS came in and curving stuff was rendered largely pointless.

Its pretty clear they gave up on the idea by the late 1950s.  The did away with the curved glacis with the M60 and then got rid of the rounded turret with M60A1.  

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The project of the Yugoslav main battle tank M-91 Vihor. Yugoslav empire will be in our hearts!

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   The decision to create a domestic tank came to the Yugoslav leadership in 1982-1984. This was favored by the results demonstrated by the Yugoslav defense industry in the early 1980s in general and in the production of armored vehicles in particular. So, by the mid-80's the Yugoslav defense industry successfully mastered the production of T-72 licensed tanks and an domestic M-80A BMP.

   Based on this, in 1984 the Military Technical Institute was given the task to create the main battle tank, and the work on the creation of the machine was entrusted to Professor Milorad Dragoevich

 

Spoiler

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   the specialists, who were entrusted with the creation of a new machine, took the M-84/T-72 tanks as a basis, which were modified in a design, and according to the designers should significantly enhance the combat capabilities of the prospective tank in comparison with the base tanks. So, in the design of the M-91, it was planned to use a new fire control system, a new engine (up to 1,200 hp), a new radio station, and the design of the turret and hull of the tank was also planned be changed in comparison with the basic design. The gun on the tank was a standart 125-mm, but it was planned to create new types of ammunition, and work was done to improve the gun.

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   According to preliminary plans, the prototype was to be presented in 1991. Until 1993, it was planned to complete the stage of factory testing, and until 1994 - state tests. In 1995, it was planned to produce a "zero" series of 15 machines, and in the future to switch to mass production of a tank with a rate of 100 vehicles per year, which would allow the tank fleet of YPA to be completely renewed by 2012. In reality, the creation of the tank was stopped before the creation of the prototype - a civil war broke out in Yugoslavia.
   At the time, only two sets of armored parts and a number of other units were manufactured. However, work, put into development of this tank did not went nowhere - it was used by Croatian specialists in developing a deep upgrade of the M-84 - M-95 Degman

 

 

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On 5/30/2017 at 8:25 AM, LoooSeR said:

"Deceives death"

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On 5/31/2017 at 2:47 PM, Renegade334 said:

 

In French, un trompe-la-mort (yeah, hyphens) means someone who either doesn't fear death or had a close brush with it. Can also mean a stuntman or daredevil.

 

---- The more you know!(tm)

That's also an historic name for a French tank: After convincing Estienne of the necessity of leading his groupement from the front, Chef d'Escadron Louis Bossut rode into battle in a Schneider CA with the same name on 16 April 1917 in an attack on Berry-au-Bac during the Nivelle Offensive. During the fight, his tank was hit by a shell and caught fire. Bossut and his mechanic were the only ones who managed to exit the vehicle, but both shortly succumbed to the flames.

 

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On 7. 6. 2017 at 6:09 PM, MrMartin said:

Philippines, Marawi city. LAV-300 with "carton-5" protection.

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After carton here comes the wood. (Cadillac Gage Commando V-150)

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On 11. 6. 2017 at 10:22 PM, MrMartin said:

After all of these, here comes the "mad max"

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So, "carton-5" got improved, now its waterproof. Plastic bags cover added.

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"So far so good" & "Rock n roll to the world"

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On 6/13/2017 at 6:35 AM, Xoon said:

I see the the reasons why, but did it really work out that well in practice? 

 

Does it provide any more protection than the T-54s hull shape, for the same weight?

 

Did it work in practice?  Yes and no.

 

The egg-shaped hull definitely provides more armor relative to the internal volume, and this is geometrically provable.  A circle has more area relative to its perimeter than a square does, and the egg-shaped tanks will have more internal volume relative to their surface area for the same reason.

 

But the T-54's hull does a better job of utilizing volume close to the ground, which means it has a lower profile even if it pays a little extra weight for it.  Given that there weren't effective countermeasures to HEAT warheads at that time, making a slightly less efficient shape that was easier to hide and just got hit less was probably a better idea than making a more efficient shape with a higher profile.

 

Also, not all internal volume is created equal.  A tank's turret looks to have all sorts of internal volume, but it's hard to utilize that volume in practice because the turret is divided down the center by the gun breech.  The egg-shaped hulls forced rather shorter turret baskets than one would expect for a hull of that height because they were forced to fit into the funky-shaped envelope.

 

On 6/13/2017 at 8:52 AM, Walter_Sobchak said:

Its pretty clear they gave up on the idea by the late 1950s.  The did away with the curved glacis with the M60 and then got rid of the rounded turret with M60A1.  

 

M60's straight glacis was as a provision for the silica-cored armor that was never fitted AIUI, the rest of the hull was still egg-shaped, which is part of why the M1 Abrams is so much squatter than the M60.

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19 minutes ago, Collimatrix said:

 

Did it work in practice?  Yes and no.

 

The egg-shaped hull definitely provides more armor relative to the internal volume, and this is geometrically provable.  A circle has more area relative to its perimeter than a square does, and the egg-shaped tanks will have more internal volume relative to their surface area for the same reason.

 

But the T-54's hull does a better job of utilizing volume close to the ground, which means it has a lower profile even if it pays a little extra weight for it.  Given that there weren't effective countermeasures to HEAT warheads at that time, making a slightly less efficient shape that was easier to hide and just got hit less was probably a better idea than making a more efficient shape with a higher profile.

 

Also, not all internal volume is created equal.  A tank's turret looks to have all sorts of internal volume, but it's hard to utilize that volume in practice because the turret is divided down the center by the gun breech.  The egg-shaped hulls forced rather shorter turret baskets than one would expect for a hull of that height because they were forced to fit into the funky-shaped envelope.

 

I see what you are saying. But I feel the egg shape falls flat because of this:
WhAyRlX.png

Yes, a circle provides the most volume alone, followed by the hexagon when grouped together. 

 

But the thing is, most equipment is usually square, some with rounded edges. Radios, engines, ammo racks, seats, the turret basket/floor in the horizontal plane.  This makes it really hard to use the extra volume created by a circle, as visualized above.  All this volume becomes wasted and may add more weight to the vehicle. You could, of course, use fuel tanks, hydraulic lines, cabling or specially made equipment to better utilize the volume. Though this is not very optimal. The egg shape also removes some useful volume where it angles inwards, before it angles out again.

 

Considering the wasted volume, the need for casting for because of the complex shapes and the added height of the vehicle, it is really hard to say if this shape really pays off. The angled side can be thinner, but it also has to be thicker than a similar RHA plate, since it is cast. And with the lost volume, you might end up finding the flat RHA plate lighter. 

 

It is a little unfair to compare the bottom of the hulls, since the egg shape could still be flat, at the cost of less blast mine protection. But it still shows off the amount of wasted volume.  

 

I feel the Russians really nailed with their shape, combing the best of both worlds, (The green is optional to show protection against blast mines):
3NUvqIt.png

 

 

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Not all perimeter weights the same. Against the threats M48 et al were designed to stop, angled plate is more weight efficient than vertical plate so the wasp waist probably does come out more weight efficient than flat sides. Having to use cast components isn't really a huge issue, with the massive man power savings evident on the cast shermans it's hard to see america wanting to abandon it all for the slight improvement in the strength of flat plate (casting the entire M103 hull in one shot really shows how smitten they were with castings).

 

Other than the turret basket, most things in the hull aren't very square. Engines are not square, radios are in the turret, and the crew don't have many right angles on them. Ammo racks are a bunch of cones, why would they be square?

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On 6/18/2017 at 7:28 AM, Xlucine said:

Not all perimeter weights the same. Against the threats M48 et al were designed to stop, angled plate is more weight efficient than vertical plate so the wasp waist probably does come out more weight efficient than flat sides. Having to use cast components isn't really a huge issue, with the massive man power savings evident on the cast shermans it's hard to see america wanting to abandon it all for the slight improvement in the strength of flat plate (casting the entire M103 hull in one shot really shows how smitten they were with castings).

 

Other than the turret basket, most things in the hull aren't very square. Engines are not square, radios are in the turret, and the crew don't have many right angles on them. Ammo racks are a bunch of cones, why would they be square?

One of the nice things about engine compartments is that you can design a fuel tank to conform to just about any oddball shaped space that is available.  

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