T-54/55 turret armour layout

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Peasant
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T-54/55 turret armour layout

Post by Peasant » 08 Jan 2019 15:55

Recently I've found this schematic of the T-54/55 tank's turret armour layout:

Image

I've tracked the source of this picture to the book «Боевые машины Уралвагонзавода — Танки Т-54/Т-55» by С.Устьянцев, Д. Колмаков (2006)

This is very fascinating piece of data. Every source I've seen so far has been very concise on this matter, "200mm effective" and that's it. Finally we can examine in detail the level of protection given to this tank by its designers.
Here I've began an analysis of calculating simple LOS thickness from various directions in frontal 90° arc.

Image
Image
Image
Image
Image

I will next calculate the effective thicknesses against various weapons that could've been used against it.
I've uploaded the Excel sheet made here: https://docs.google.com/spreadsheets/d/ ... sp=sharing
Edit: Updated the sheet link to a cleaner version. Edit2: Again.
Last edited by Peasant on 08 Jan 2019 19:21, edited 4 times in total.

critical mass
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Re: T-54/55 turret armour layout

Post by critical mass » 08 Jan 2019 16:28

That´s the "classic" turret. I think it´s either the 3rd or 5th incarnation of turret design of the T54 series (depending on whether or not You might want to count the protoypes).

initial Prototype turret
(3rd) Prototype turret mod. 1946 (reinforced)
Turret 1947 series (shot traps all around)
Turret 1949(?) series (shot traps at the rear of the turret, only)
Turret 1953 series (classic turret)

Do You happen to know whether or not the other turrets are discussed in the volume, too?

best,
cm

Peasant
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Re: T-54/55 turret armour layout

Post by Peasant » 08 Jan 2019 17:14

They are mentioned in the part talking about the development of the tank but doesnt go into details. It only provides several photos and approximate armour values and explains the reasons why they were eventually supplanted by the "classic" turret design. I have made it only up to the first half of the book, but it seems to focus more on the production variants of the T-54/55 and how it compares to the Western counterparts.
I have uploaded the PDF online, if you wanna check it out yourself (its pretty heavy, 242MB): https://mega.nz/#!mTAg1Aya!BPFG7U7N2lrw ... peNsPCzRiU

Edit: I should mention that although it doesnt give much information about the early turret designs, it has a large portion of its contents dedicated to exploring in great detail the evolution of other parts of the vehicle, like hull, tracks, suspension, engine, commanders cupola, ect.

Peasant
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Re: T-54/55 turret armour layout

Post by Peasant » 09 Jan 2019 15:59

Calculated the average LOS thickness weighted against the vertical area presented:

0° azimuth: 278,39 mm

To the right:
10°: 262,06 mm
20°: 244,31 mm
30°: 224,67 mm
To the left:
-10°: 261,90 mm
-20°: 245,14 mm
-30°: 225,60 mm

I feel like these values are more telling than just min/max LOS thicknesses.

Some considerations in applying these numbers: I have limited the values used for calculating these to under 72° of compound obliquity. Otherwise at some azimuth angles the LOS values exceeded >1000 mm which is clearly impossible in but some fringe scenarios. This way the maximum at exactly 72° of obliquity is "only" around 500mm LOS. The limit imposed is largely arbitrary so feel free to help with constructive criticism.

critical mass
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Re: T-54/55 turret armour layout

Post by critical mass » 10 Jan 2019 17:06

Peasant,

do You mind to directly specify both, the original angles and the resultant compound angle, instead of loS thicknesses? I have problems to understand and/ or recreate the numbers (vector calculated properly?).

A-B-V-G (in original: A-Б-B-г)

f.e.
A-2 right hand
10° target angle deviation
-23.5° constructive angle
resultant netto obliquity: 25.43°
actual thickness: 159mm

B-3 left hand
10° target angle deviation
-39.5° constructive angle
resultant netto obliquity: 41.81°
actual thickness: 140mm

V-5 right hand
20° target angle deviation
-54° constructive angle
resultant netto obliquity: 56.47°
actual thickness: 103mm

G-3 left hand
10° target angle deviation
-61° constructive angle
resultant netto obliquity: 61.48°
actual thickness: 84mm


line of sight may not be an ideal construct if a proxy of ballistic resistence is to be attempted. Armor base curves may be more precise, but are specific for certain projectiles (plus, there is the problem of cast armor here). F.e. all four examples above are within penetration envelope of the KWK43 but arguably not within the penetration envelope of the KWK42, PAK40 or other.

Peasant
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Re: T-54/55 turret armour layout

Post by Peasant » 10 Jan 2019 18:47

Image

I've made this to better understand the complex 3D slope of the T-54 turret and troubleshoot any anomalies in calculations. (WIP, this is not the actual geometric layout of the turret face)

So, the point A2 has 23,5° slope, relative to the turret ring's plane. But since its also set at 30° to the front (the line 8 is set at 90° and they are spaced 10° between each, I assume), the compound slope from the front would be acos(cos(30°)*cos(23,5°)) = 37,42° for 159/cos(37,42°) = 200,20 mm of LOS.

The compound angles calculated from 0° azimuth are listed here:

Image
Last edited by Peasant on 11 Jan 2019 02:13, edited 4 times in total.

Peasant
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Re: T-54/55 turret armour layout

Post by Peasant » 10 Jan 2019 19:06

critical mass wrote:
10 Jan 2019 17:06
Snip
Yes, I was planning on eventually calculating the effective thickness against various projectiles. So far I have applied the slope multipliers from "BIOS Report N.1343" for late German APCBC designs. I've then added a variable cast armour multiplier from 0,9 at 0° to 0,95° at 60°(just some easy to work with arbitrary values, but the idea is that the cast armour looses some of its weaknesses at high obliquities).

Edit: Something to keep in mind: here we are implicitly assuming that every square unit of area of the projected in equally likely be hit and therefore contributes equally to the protection, and at sufficiently long ranges this is pretty close to being true, things would change drastically for close range engagements.
Also the data we have is a discreet set of points and we have no choice but assume that the thickness/slope values are the same as the average for the +-5° sectors of vertical/horizontal areas around each point, which might actually be slightly/greatly different(unlikely though since the cast contours are designed to vary gradually along their surfaces).

Image
Last edited by Peasant on 11 Jan 2019 00:47, edited 1 time in total.

Peasant
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Re: T-54/55 turret armour layout

Post by Peasant » 10 Jan 2019 23:06

Image

I have superimposed the schematic on top of one of the drawings to better understand how the points are mapped on top of real turret.
One thing I've noticed is although the lines A;B;C; run perfectly vertical and continuous throughout, the "D" breaks off between 6-12 and when resumes its course, its located about twice as high as before.

Edit: The schematic and the real turret do not fit together because every single drawing of T-54/55 in the book is made from the Left side. Annoying to say the least. This image is flipped.

critical mass
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Re: T-54/55 turret armour layout

Post by critical mass » 11 Jan 2019 13:54

maybe this helps?
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Peasant
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Re: T-54/55 turret armour layout

Post by Peasant » 12 Jan 2019 23:24

Some progress. Observe the relative position of the lines relative to the bolts on the gunmask. It's fits pretty well.
Now onto the other projections.

Image

critical mass
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Re: T-54/55 turret armour layout

Post by critical mass » 14 Jan 2019 14:06

Peasant,

the measurements appear to me as too vague. According to the initial drawing, I´d expect a curvature angle at the sides of the turret approx. at the extreme beam of:

A-8: 21°
B-8: 31°
V-8: 42°

Yet, Your front side drawing measurements of these sections shows consistely only roughly half these values:
A-line: 10°
B-line: 15°
V-line: 20°

Peasant
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Re: T-54/55 turret armour layout

Post by Peasant » 14 Jan 2019 17:48

Ahh, I see, Yes the slope of the surface in those spots is the one indicated in the table that comes with the schematic, no doubt about it.
I was talking about the drawing lines projected onto the surface of a virtual sphere, originating from the center of the turret ring, used to map the points A2, B4, C7, ect. on the surface of the turret itself.

critical mass
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Re: T-54/55 turret armour layout

Post by critical mass » 23 Jan 2019 18:24

Thanks for clarification. Much appreciated. Do You happen to know the thickness of the gun collar (not exactly a mantlet here)?
From the drawings I have seen, it seems rather thinner than the turret casting.
Edge effects have to be accounted for along the rectangular cutout of the gun opening
The turret layout seems to represent an example for proof as well as vulnerable under all conditions. A hit at the centre of the turret will engage least resistence but even the sides are proof under oblique impact. It´s an excellent design when viewed with full bore AP protection in mind.

Peasant
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Re: T-54/55 turret armour layout

Post by Peasant » 25 Jan 2019 04:06

critical mass wrote:
23 Jan 2019 18:24
Thanks for clarification. Much appreciated. Do You happen to know the thickness of the gun collar (not exactly a mantlet here)?
From the drawings I have seen, it seems rather thinner than the turret casting.
Edge effects have to be accounted for along the rectangular cutout of the gun opening
The turret layout seems to represent an example for proof as well as vulnerable under all conditions. A hit at the centre of the turret will engage least resistence but even the sides are proof under oblique impact. It´s an excellent design when viewed with full bore AP protection in mind.
No, I dont have it.

critical mass
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Re: T-54/55 turret armour layout

Post by critical mass » 26 Jan 2019 16:29

From Your source, FWIW

T54A turret front (casting from 90-L grade steel, 270BHN) represents the same target as Yugo tests:

88mm KWK43 front turret: vulnerable out to 600m to Pzgr39
90mm M36 front turret: vulnerable out to 350m to T33 APBC
100mm D10 front turret: vulnerable out to 300m to BR-412B APBC

88mm KWK43 side fwd turret half: vulnerable out to 1750m to Pzgr39
90mm M36 side fwd turret half: vulnerable out to 850m to T33 APBC
100mm D10 side fwd turret half: vulnerable out to 1000m to BR-412B APBC

88mm KWK43 side rear turret half: vulnerable out to >2km to Pzgr39
90mm M36 side rear turret half: vulnerable out to >2km to T33 APBC
100mm D10 side rear turret half: vulnerable out to >2km to BR-412B APBC
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