Sloped Armour - isnt it obvious ?

[Fly Pusher]

One thing that struck me whist playing both CMBB and CMBO is the sudden, and visually striking, change from essentially vertical armour (such as the Churchill, PII and many others) to the graceful slopes of later tanks such as the T34 and Panther.

With the benefit of hindsight it seems blindingly obvious that a given thickness of armour held at a slope would be more difficult to defeat than flat plate (not to mention the increased chance of ricochet).

Was this effect really unknown in the 1930's when many of the early war tanks were being designed ? If so this is quite an amazing lack of insight. Alternatively, was there some other reason I dont know about responsible for the early box style tanks ?

A Groggish insight would be much appreciated....

Edit: coz I cant spell...

[ September 18, 2003, 06:39 AM: Message edited by: Fly Pusher ]

[Lt Bull]

Sloped armour sure is good vs AP rounds but as far as creating adequate space within the vehicle goes, it actually works against you. It can lead to very cramped spaces within the tank leaving less space for things like a big gun, engines, radios, ammo, crew space etc.

The challenge was to get a good balance once you were aware of the benefits of sloped armour.

Lt Bull

[Bastables]

For the Germans, it seems to have been construction technique bottlenecks, Spielberger states 'achieved by the use of manufacturing equipment for rotating the vehicle and for component welding. In doing so the nearly vertical glacis.... was finally dispensed with.

The Churchill was a mid war design as were the boxy Cromwell?s and Comets, the British tank designers throughout the war preferred vertical armour. Also Vertical armour allows for comparably greater internal volume allied with less armour weight. For instance one needs less 8cm armour on the Panzer IV in covering the front than the sloped glacis of the Panther.

You'll also note that the Pz I was designed to be proof versus APCR MG bullets with 13mm vertical armour and thinner sloped armour. The Pz II design is also similar.

Soviet "Christies" designs (Christies tank it self sported sloped armour) as a rule ran around with continuous sloped armour even during the 30s with the BT series.

Sloped armour and it?s effects on increasing protection was noted even during the design of the Pz I, yet was consciously not applied over the whole tank as construction techniques had not advanced far enough or as Spielberger implies not applied due to cost/bureaucratic inaction. The British on the other hand seemed to have preferred the ?vertical configuration? even late in the war. They did not miss the significance, they just went down the vertical armour route for verious other reasons.

[Blackbear]

Hein Guderian, in his superb previous war studies about tank warfare, said that there is an ancient and endless competition of shield (armor) vs proyectile penetration. And so, it had no sense to try to produce indestructible tanks. The key of armor vehicles success in the first campaings of WWII was over all, the massive and coordinate attack of big armor units. He thought that good optics and wireless equipment fitted in a equilibrated machine, and good training of five men crews was much more important.

Of course they knew about the advantages of slope armor, but apparently they had other priorities.

To fit five men in tanks hull with slope armor was a dificult task to 1930´s german engeniers. And also existed some tecnical troubles in the factories.

As the war evolutioned to a more static form, the advantages of better armor design arose.

In XXI century H.Guderian statements are still alive.

[Fly Pusher]

Originally posted by Bastables:

Also Vertical armour allows for comparably greater internal volume allied with less armour weight. For instance one needs less 8cm armour on the Panzer IV in covering the front than the sloped glacis of the Panther.

I must take acception to at least part of this statement. I just did a quick back of an envelope calculation ..

A 100cmx100cm vertical armour plate that is 10cm thick contains 100,000cm3 of metal.

To cover the same frontal area with an armour plate sloped at 45o the plate now needs to be 141.4cm long , its still 100cm wide , but now need be only 7.07cm thick to present an effective (horizontal) thickness of 10cm.

141.4x100x7.07 = 100,000cm3 (more or less)

So assuming a constant density the weight is the same in both cases and the chance of ricochet significantly increased.

I would certainly agree that a slab sided tank would give more internal room though....

[Yaba]

I am no grog here but my understanding of why the Britsh stayed away from the sloped armour was due to falling so far behind in the technology of tanks that they never had a chance to really explore "radical" new tank design. The higher uppers were not convinced that sloped armour helped in all cases and in some cases would actually make the situation worse. My guess is that they were so far behind in good armour production that they tried to stick with simple designs that addressed problems as they arose as opposed to trying to be inovative and lead the way forcing others to adapt to their tanks. Reading tank books about British armour one classic line keeps coming up regarding how, "by the time the armour was in the field the main gun was hopelessly out classed and needed to be upgraded". It seems that the British solution was to jam a bigger gun into the existing tank and add more armour on the outside to deal with the new threats as they came (eg. 2 lber - 6 lber - 17 lber) A simple but not necessarily effective way of dealing with things.

[JasonC]

In WW I tanks had to stop MG bullets but weren't expected to withstand anything else. 75mm HE was sufficient to KO them. Flat plates were used because they were simplest to produce and fit together. The armor of WW I era tanks was not much more than that of halftracks in WW II.

In the inter war period designs improved considerably, but armor protection against gunfire was not a primary design goal. It was just assumed serious guns would succeed in KOing tanks if they managed to hit them. Protection against small arms was the main point. Other design goals were small size and weight (especially to use roads and bridges, also to make more of them), improved speed and reliability, while keeping enough room for men and weapons.

The idea of infantry tanks or breakthrough tanks is what initially led to thicker armor. The opponent envisioned was the guns supporting an infantry defense, bunker positions, and the like. Matildas, Char-Bs, and KVs were initially designed thick not to duel other tanks but to approach gun-equipped bunkers safely. (The first Matildas had thick armor but MG main armament, clearly showing that dueling tanks was not the idea).

So part of the answer is that a need for thick armor in the first place was not obvious, and when it first appeared they weren't thinking of the AP threat, let alone the AP threat from other tanks. The idea that a tank should resist AP well, and be thick enough for that without sacrificing the mobility characteristics of "cavalry tanks", came quite late. The Germans uparmored their IIIs and IVs after France, but they had been originally designed thinking an inch or so of armor was all a tank would ever need.

There was also a technical issue on the production side. It is awkward to get good slope effects with entirely flat plates. (You get a "trapezoidal" tank). The easiest way to get shaped or rounded armor is to cast it into shape. But casting tended to make weak armor, with existing metallurgy.

Notice how sparing the Germans are of round shapes in their tanks, even after they start using slope. (The Tiger turret sides and Panther mantlet are about it, at midwar. Compare the rounded look of the T-34 or Sherman). That isn't because round is a bad shape for armor - it is an excellent one in slope terms. It is because it is hard to get round steel shapes without using processes that weaken the steel.

For what it is worth.

[ September 18, 2003, 03:00 PM: Message edited by: JasonC ]

[Hensworth]

Never mind, carry on .

[ September 18, 2003, 03:14 PM: Message edited by: Sgt_Kelly ]

[Bastables]

Originally posted by Fly Pusher:

[

[/qb]

I must take acception to at least part of this statement. I just did a quick back of an envelope calculation ..

A 100cmx100cm vertical armour plate that is 10cm thick contains 100,000cm3 of metal.

To cover the same frontal area with an armour plate sloped at 45o the plate now needs to be 141.4cm long , its still 100cm wide , but now need be only 7.07cm thick to present an effective (horizontal) thickness of 10cm.

141.4x100x7.07 = 100,000cm3 (more or less)

So assuming a constant density the weight is the same in both cases and the chance of ricochet significantly increased.

[/QB]

[Michael Emrys]

Originally posted by Bastables:

Disagree; "Vertical" armoured tanks do not sport single piece armour hull plates, they are stepped. The mid/late war PIV for instance has only the vertical sections at 8cm, these are connected by almost horizontal strips of 10-16mm armour. The Tigers armour configuration mirrors this.

Hmm, so then—correct me if I'm wrong—you're actually saying that tanks using vertical armor were heavier than equivalent sized tanks using sloped armor offering the same degree of protection?

Michael

[Halberdier]

Actually the T34 was produced much earlier (late 40's). The Soviets seem to be aware of the benefits of sloped armor very early. The Russian Battlefield site has a lot of interesting information BTW.

Also, the early to mid-war US M3 Lee tank had curved and sloped armor. (Another BTW: The AFV Database has some good info on US and German tanks (and other systems) plus a bibliography.)

Although the Tiger I is my favorite tank, I am amazed that the Germans used completely vertical armor on it. Moot comment warning: If they made the turret sides shaped like an open-horseshoe (instead of the straight rectangle) they could have made a well sloped (but less spacious assuming base was the same) turret. The Panther had a well-sloped front hull, but I wouldn't call the turret very well sloped. It wasn't until the IS-3 until someone had a well-sloped turret.

cheers,

-gabe-

[Bastables]

Originally posted by Yaba:

I am no grog here but my understanding of why the Britsh stayed away from the sloped armour was due to falling so far behind in the technology of tanks that they never had a chance to really explore "radical" new tank design. The higher uppers were not convinced that sloped armour helped in all cases and in some cases would actually make the situation worse. My guess is that they were so far behind in good armour production that they tried to stick with simple designs that addressed problems as they arose as opposed to trying to be inovative and lead the way forcing others to adapt to their tanks. Reading tank books about British armour one classic line keeps coming up regarding how, "by the time the armour was in the field the main gun was hopelessly out classed and needed to be upgraded". It seems that the British solution was to jam a bigger gun into the existing tank and add more armour on the outside to deal with the new threats as they came (eg. 2 lber - 6 lber - 17 lber) A simple but not necessarily effective way of dealing with things.

This idea of British falling behind technologically does not square with the fact that the Churchill was the first to employ Single/multiple radius clutch steering. This is the transmission that made the heavy Panther and Tiger series feasible as a "reliable" combat veh and insured that the British late war mediums, heavies and German heavies actually more manoeuvrable than the Sherman?s and T-34s. The 17pdr was a much better AP weapon than the Soviet 8,5cm and the USA 7,62cm.

At the time that the PIIIs had hand cranked turrets the British cruisers had hydraulic powered turrets. The British were also the first to deploy what we know of today as sabot rounds, everyone else used APCR with the higher drop off of velocity at range.

It?s a bit like arguing that the USAAF was falling behind technologically by sticking with the 50cal, when everyone else was mounting or developing 2cm cannon even pre-war for fighter combat. USAAF just held a different philosophy of aircraft armament. This does not mean development stagnated in other aircraft design areas.

[ September 18, 2003, 05:28 PM: Message edited by: Bastables ]

[Bastables]

Originally posted by Michael Emrys:

</font><blockquote>quote:</font><hr />Originally posted by Bastables:

Disagree; "Vertical" armoured tanks do not sport single piece armour hull plates, they are stepped. The mid/late war PIV for instance has only the vertical sections at 8cm, these are connected by almost horizontal strips of 10-16mm armour. The Tigers armour configuration mirrors this.

Hmm, so then?correct me if I'm wrong?you're actually saying that tanks using vertical armor were heavier than equivalent sized tanks using sloped armor offering the same degree of protection?

Michael </font>

[Yaba]

Originally posted by Bastables:

_________________________________________

This idea of British falling behind technologically does not square with the fact that the Churchill was the first to employ Single/multiple radius clutch steering. This is the transmission that made the heavy Panther and Tiger series feasible as a "reliable" combat veh and insured that the British late war mediums, heavies and German heavies actually more manoeuvrable than the Sherman?s and T-34s. The 17pdr was a much better AP weapon than the Soviet 8,5cm and the USA 7,62cm.

At the time that the PIIIs had hand cranked turrets the British cruisers had hydraulic powered turrets. The British were also the first to deploy what we know of today as sabot rounds, everyone else used APCR with the higher drop off of velocity at range.

It?s a bit like arguing that the USAAF was falling behind technologically by sticking with the 50cal, when everyone else was mounting or developing 2cm cannon even pre-war for fighter combat. USAAF just held a different philosophy of aircraft armament. This does not mean development stagnated in other aircraft design areas.

_____________________________________________

Those are good points. I was unaware of that the transmission system that the tigers and panthers would employ was a British design. I was also unaware of the sabot was a British invention.

I agree that the 17lb was the best AT weapon that the allies had. However, I still must say that the British tanks were far behind both thier American and Soviet friends. I suggest this based on the lack of longevity for the British tanks after the war. If the British had got it right with the Churhill or Comet then you would think that there would have been a market for the tank such as the Hetzer for Sweeden (?), the Panther for the French, the Sherman for Israel, and the T-34/85 for Eastern European countries and China.

Now I am not saying that the Sherman was such a great tank - in fact, the British conversion with the 17 lber was a far superior AT tank. However, the Sherman and it's million variations saw service in many contries for decades after the second world war - no doubt in part to its mass production. The T-34/85 saw service with some armies right up into the 80s. Again - huge numbers but it seems to me it still points towards a good tank.

Out on a limb but I would suggest that it was the Soviets who had the best idea of where tank warfare was going first with the IS-2 and eventually with the IS-3 with its poached egg-like turret. The Soviets stuck with that design for many years and it would be the turn of the western armies to catch up for a decade or so after the war.

Just my two bits...

[Andreas]

The Centurion was a wartime design, used for a long time after the war, although, like the IS-3, it did not see service in WW2.

[Bastables]

Originally posted by JasonC:

So part of the answer is that a need for thick armor in the first place was not obvious, and when it first appeared they weren't thinking of the AP threat, let alone the AP threat from other tanks. The idea that a tank should resist AP well, and be thick enough for that without sacrificing the mobility characteristics of "cavalry tanks", came quite late. The Germans uparmored their IIIs and IVs after France, but they had been originally designed thinking an inch or so of armor was all a tank would ever need.

Disagree Pz II, III and IV all sported upgraded armour due permeability to Polish anti-tank Guns and rifles. The PIII had initially been designed with 3cm armour to defeat 2cm and 3,7cm anti-tank weapons; the Polish experience proved that 3cm was insufficient.

The Design brief of the T-34 was to provide all round protection versus the German 3,7cm PaK that had proved so devastating in Spain versus BT and T-26s.

British thinly armoured British cruiser tanks were adopted over the thicker armoured mediums because of cost cutting of the inter war governments. The British had the conception of AP gun proof Mediums but they did not have the money to green light adoption and production.

[ September 18, 2003, 09:15 PM: Message edited by: Bastables ]

[Bastables]

Originally posted by Yaba:

Originally posted by Bastables:

_________________________________________

Out on a limb but I would suggest that it was the Soviets who had the best idea of where tank warfare was going first with the IS-2 and eventually with the IS-3 with its poached egg-like turret. The Soviets stuck with that design for many years and it would be the turn of the western armies to catch up for a decade or so after the war.

Just my two bits...

Disagree the highly effective British composite armour due to it's properties tends to preclude slope armour (As did the PIII spaced armour), which is why we see slab/boxy armoured Leopard II, M1s and Challengers. The Soviet mania for sloping has meant less effective armour than the three NATO designs with internal space at a premium.

Also Schmalturm (SP) for the Panther F dropped curved armour, increasing internal space, increasing armour thickness, providing a smaller target and actually kept the same weight as the more inefficient curved mantel design of earlier Panthers.

[ September 18, 2003, 09:15 PM: Message edited by: Bastables ]

[Wisbech_lad]

The Churchill AVRE remained in service until 1962 AFAIK. The Comet likewise was in use for a long time after the war.

Arguably the Centurion (WW2 design) was the blueprint of the universal tank, and more successful than IS3 and its ilk, which were badly compromised by the small/ cramped fighting compartment. Having a comfortable crew, who can quickly see and react to new threats, seems to be an important factor in tank warfare that is rarely given prominence. Centurions don't seem to have had much problem defeating T55's and M48's

Actually, can't think of a single Western tank design that went the Soviet route. All seem to have preferred a higher shilouette rather than relying on 5' 3" tank crews... The Swedesh S tank maybe?

[Wisbech_lad]

Editted due double post...

[ September 19, 2003, 05:18 AM: Message edited by: Wisbech_lad ]

[IntelWeenie]

Originally posted by Fly Pusher:

Was this effect really unknown in the 1930's when many of the early war tanks were being designed ?

Sloped armor was used as early as the 1860s on several ironclads in the American Civil War....

Even then it was thought by some to be more effective than vertical armor (though due more to the tendency of low velocity round cannon shot to ricochet than any benefits of greater armor thickness.)

[flamingknives]

It seems that the British solution was to jam a bigger gun into the existing tank and add more armour on the outside to deal with the new threats as they came (eg. 2 lber - 6 lber - 17 lber) A simple but not necessarily effective way of dealing with things

This solution is more line with what the Germans did with MkIIIs and MkIVs and Soviets did with T34s than British Doctrine.

In fact, most British tanks couldn't be upgunned, due to small turret rings. No tank was ever up-gunned to 17pdr from 6pdr without extensive re-design. This problem mean that the British needed to produce a whole new tank each time they wanted to increase combat power.

Another factor was, when threatened by invasion, the British produced as much as possible from existing lines rather than develop new products. This led to the delay of the 6pdr and production of 6000 Covenanters - which were essentially worthless as gun tanks. None were ever used outside of training in the UK.

In addition, resources were taken up designing and building prototypes of a vast array of armour that was never used - The TOG series is an exceptional example of this waste.

The Centurion was a wartime design, used for a long time after the war, although, like the IS-3, it did not see service in WW2

Exactly what I would have said, had I not been beaten to it.

Also consider that the Centurion is in the same class as the T34, and is still in service in some areas as an MBT (the Swedish have an up-armoured version, or at least, did until recently)

Disagree the highly effective British composite armour due to it's properties tends to preclude slope armour (As did the PIII spaced armour), which is why we see slab/boxy armoured Leopard II, M1s and Challengers. The Soviet mania for sloping has meant less effective armour than the three NATO designs with internal space at a premium.

I strongly suspect that you mean curved and not sloped

[manchildstein (ii)]

--At the time that the PIIIs had hand cranked turrets the British cruisers had hydraulic powered turrets. --

is that right?... if so, when exactly was that?... 1940?...

[Bastables]

Originally posted by manchildstein II:

--At the time that the PIIIs had hand cranked turrets the British cruisers had hydraulic powered turrets. --

is that right?... if so, when exactly was that?... 1940?...

The PIII had a hand "powered" turret during it's entire lifetime.

[rexford]

One of the advantages of sloped armor is the slope effect, where the effective resistance is much greater than the horizontal distance that must be pierced.

When an 80mm plate is angled at 55 degrees from vertical, the horizontal distance across the angled plate equals 80mm/cosine(55 degrees), or 139.5mm.

However, when 17 pdr APCBC strikes the 80mm plate at 55 degrees from vertical the effective resistance is the same as a 202mm vertical plate.

Say the 80mm plate at 55 degrees must cover a vertical distance of 0.915m and a lateral distance of 3m.

The total volume of sloped plate to provide 202mm vertical resistance would equal:

0.080m x 0.915m/cosine(55 degrees) x 3m = 0.383 cubic meters.

If a 202mm vertical plate were used the volume of that plate would equal:

0.202m x 3m x 0.915m = 0.554 cubic meters.

But with a vertical plate a hull top plate must then be added to cover a 1.60 meter distance, which adds:

1.60m x 3m x 0.020m (hull top thickness) = 0.096m

So, to get 202mm vertical equivalent resistance, 80mm at 55 degrees from vertical uses 0.383 cubic meters of armor plate while a 202mm vertical plate requires 0.650 cubic meters (70% more than the 55 degree case).

Sloped plate allows high resistance to penetration with a decrease in weight, which is why it was used on Panther, Pershing, King Tiger, etc.

IMPORTANT NOTE

Projectiles do NOT penetrate sloped armor by moving through it horizontally. The first reaction during penetration is a tendency of the round to rotate nose up and start to ricochet. While the rotation is going on a plug is formed which starts to be driven out. The projectile then changes direction suddenly and pierces the plate going DOWNWARD, with the nose bouncing against the hole and it moves thru.

There is alot going on and that is why 80mm/55 degrees resists like 202mm vertical instead fo 139.5mm vertical.

[Captain Wacky]

I think the wheel was pretty obvious, and look how long that took!