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I think my earlyer post should be the final word, and has possibly bee over looked my some?

The very, very first tank to have armour intentionally sloped to deflect shot was Walter Christie's M1931.  The US army wasnt that interested and only purchased three.  Poland orderd two but didnt pay for them. It was Russia who took two, and by developing the renowned suspension and implementing the sloped armour into their designs that the BT series and then T34 were born.  

http://www.wwiivehic...istie-m1931.asp

Quite independantly and around the same time.  The French FCM36 small infantry tank was the first battle tank to implement 45 degree all round sloped armour for shot defelection.  Other highlights was the use of a diesel engine, quite ahead of its time.  However it was not purschased in large numbers due to cost.  The R35 and H35 were cheaper to produce.  Germnay captured a number and used the hulls for some of the Marder tank destroyers.

http://ww2armor.jexi...M-36/FCM-36.htm

The fench realised the benifits of sloped armour, as you can see in the game looking at the AMX38.  Whose turret is a direct dererative of the FCM36 one.  They tried to introduce sloped armour into the Char B1, with the B1ter

http://mailer.fsu.ed...a-CharB1ter.jpg

Question answered, end of...

Sorry mate those links dont work

but

Tank mk 1 and all rhomboids
Medium Tank Mk A (Whippet)
Char D'Assault Schneider (Schneider CA)
Char D'Assault St. Chamond
Medium Mark C (Hornet)
Sturmpanzerwagen A7V

all of the above made some use of sloped armor

You forgot the FT17 from the list... anyway, more as a fortunate side effect of other design concerns than an intentional protection-improvement scheme AFAIK. Bit curious as such, as the idea had been used in warships for a while already by that point and was already familiar (if only in "black box" fashion) to Medieval armourers.

Grat discussion. Thanks to all.

However, I would like to point out a factor to take in count when deciding for or against sloped armour: A 64mm plate @ 45º weighs the same as a flat 90mm plate, that we all agree to. But the thinner plate is easier to manufacture as rolled steel. In fact no one knew how to make rolled armour that thick at the start of WW2, so I regard sloping as a way to increase the protection with available technology. The impossibility to effectively roll thicker plates is behind the use of apliqué plates, which I suspect is not as effective as a single plate just as thick (someone might want to weigh in on this).

I read about this in a little book on russian heavies I got to through this forum can't bother to look for it again.

It's hard to determine which tank actually used sloped armor for protection then design. It wasn't definitly T-34 but more likely one of the French tank most likely.

And heres intresting thing you should know: They used sloped armor on T-34 sides because the christie suspension. Christie suspension took a LOT space from tank so it was natural to use armor shaping that creates space. So it's possible that T-34 designers didn't think about protection so much but rather the mobility and the role it was meaned for.


Oh, I did find the grandpa of the T-34: Type 89B I-Go Otsu

The Japanese Type 89 is a vastly improved version of the Vickers Mark.C. medium tank purchased by Japan in the 1920's.

It was also the first tank powered by a Diesel engine.

The Mark.C. front is identical to that of the Type 89 though the latter has superior performance, considerably more armour than the Mark.C.'s 6.5mm. but weaker armament.

On a parallel subject....

Up until Britain joined NATO, the British War Office quoted armour thicknesses AFTER the Cosine equation had been applied (shot line) in order to match and be comparable with range test results of anti-tank weapons. (Armour thickness quoted as through the horizontal line through the vehicle which is what the penetrating projectile would take).

A couple of typical examples are that the rear sloped armour of the Valentine is quoted as being 61mm. by the British and 30mm. by the Russians and Germans (and WoT). Also that the British quote the M-3 Lee / Grant as having a maximum of 3.5 Inches (88mm.) of hull frontal armour on the glacis and 57mm. on the driver's plate. However the Americans, Germans and Russians quote the by the actual plate thickness of 51mm. with the relavent angles included for Cosine equation calculation.The original M-4 A-1 cast hull Sherman was quoted by the British as sporting 81mm. of glacis armour and not the 51mm. actual plate thickness. (Obviously of some propoganda and morale value to the British army at the time).

One theory was this was in order to recognise possible obstellence and to "dumb things down" enough for polliticians and generals to understand why the army might need new weapons to deal with a newer enemy tank. Another possiblity is deliberate deception of the enemy by assuming that they will take the with Cosine value as being plate thickness, though once the enemy had secured said tank the ruse would be discovered.

It still causes confusion today much in the same way as the confusion between engine power quoted in metric PS (Power Starken) has some people (and motormagazines, advertisers, some millitary books, etc.) thinking it is another name for horsepower, which it isn't. (Actually 1 PS = 0.86 HP so 100 PS = 86 HP).

However the old British War Office System does create problems for tank enthusiasts when dealing with quoted sloped and angled armour thicknesses on British produced tanks as to what system was used to measure the thickness.

After joining NATO Britain started to quote armour thicknesses by plate thickness and angle in keeping with everyone else. However British produced tanks before NATO will have their sloped and angled armour quoted as "shot line" or "presented thickness" as opposed to plate thickness with angle if measured by the British.

It even catches out the DEVs in WoT hence the correction of the Centurion Mark.I. glacis plate thickness to 76mm. after it was realised that the quoted British "shot line" measured thickness had been mistaken as plate thickness, which in effect meant that the Cosine equation was applied twice in WoT.

One metric horsepower, in German Pferdestärke (PS), is approximately equal to 735,5 Watts. One mechanical horsepower is approximately equal to 745,7 Watts. That is a difference of about 1,4 percent, making the two terms equal for all practical purposes.
Edited by TrackAttackerDK, 18 February 2013 - 11:12 PM.

Pruden, on 04 February 2013 - 01:44 PM, said:

Your assumption is true.

In a test performed 1945-01-04 on the Aberdeen Proving Grounds, penetration tests with a 90 mm APC M82 shot were conducted against:

• a single three inch armour plate,
  
• two 1½ inch armour plates placed together, and
  
• two 1½ inch armour plates placed six inches apart,

all at angles of 45 degrees. The result was that the three inch plate could resist the shot at up to 2350 feet per second, the two plates placed together could resist the shot at up to 1980 feet per second, and the two plates six inches apart could resist the shot at up to 1640 feet per second. Observing the terminal velocity table of the 90 mm M3 firing the 90 mm APC M82, this is the equivilant of ranges of 1900, 3600, and 5200 yards, respectively.

The reason given in the analysis is that the middle part of an armour plate offers the most resistance, because plate material has to be pushed sideways, whereas the edges can be pushed outward. In addition, when the spaced plates are seperated, the striking angle on the second plate will, to some extent, be normalised by the first plate, reducing relative thickness of the second plate.
Edited by TrackAttackerDK, 19 February 2013 - 12:00 AM.

sloped armor.. well i guess it goes a waaaay back ;)



http://en.wikipedia....onardo_tank.JPG


interesting topic and discussion , really enoyed it so far

Razorvine, on 22 February 2013 - 03:09 PM, said:

It does indeed: "Gothic armour, especially suits made under Maximilian I, Holy Roman Emperor, were modelled with curves, flutings and ridges in order to enhance the strength of the armour and deflect arrows.[citation needed] Such armour was made during the 15th century and reached its peak in the 1480s, when it was considered the best in Europe. Its structure featured points and ridges influenced by Gothic architecture and Gothic art. In addition to steel plates it included mail to protect under the bevor, joints and crotch." (wikipedia)

TrackAttackerDK, on 18 February 2013 - 11:56 PM, said:

Very interesting.
I believe the german did use separated plates on purpose on some tanks as it reduced spalling by imprisonating the spall between 2 plates of armor.
Can anyone confirm this?

I've seen a lot of different designs ideas, including one with a thin inner plate, which would catch any spalling from the real plate.

To supplement my post above, spaced armor can in fact increase shot resistance. If a thin armor plate is placed in front of the main armor plate, the thin plate can strip the cap from APC and APCBC ammunition, and cause the shot to yaw or fracture. This is only possible beyond a certain distance between the two plates, which I seem to recall is relative to the shot. This can significantly increase the ballistic limit, but the effect is largely irrelevant of the skirting armor's thickness, beyond a certain range. This is why Schürzen were effective in defeating Russian anti-tank rifle rounds.