KV-85 armor values generated from German photos.

[Mobius]

The KV-85 is made from the hull of the KV-1S and a heavy JS type turret.
The armor values of the KV-85 are at odds with photographic evidence.
http://www.armchairgeneral.com/rkkaww2/ ... _85_bp.htm

Here is what Russian and other sites claim to be the armor scheme of the KV-85.

Example of data:
https://ru.wikipedia.org/wiki/КВ-85
http://www.armchairgeneral.com/rkkaww2/ ... /KV_85.htm
http://www.armchairgeneral.com/rkkaww2/ ... _85_bp.htm

However German photo of a captured KV-85 shows a different story.
An upper hull of 75mm@30°; lower hull of 60mm @ 25°.
Turret front and side of 110mm.

The SU-152 hull is from the KV-1S too and would have the same glacis as the KV-85.

SU-152 values.jpg (100.71 KiB) Viewed 3627 times

A glacis of 50mm@70°.

So using the information from the photos I get a KV-85 armor scheme like this:

The rear turret could be 100mm or 110mm. The rear turret of the JS-2 was 110mm but that could have been changed later to balance the weight of the 122mm gun.
More of the story here:
http://panzer-war.com/page66.html

[Yoozername]

In the case of cast components, there is a bigger variation in accepted items. That is, if they are designed so that a wider specification does not interfere with functioning/etc.. RHA tolerances are usually tighter. Germans would have specs like minus 0/plus 5%. The way it actually works in the real world is that a manufacturer of plates does not want rejects that he eats...so they lean towards the side of practicality. And therefore, you see components like the glacis on a Panther leaning more towards 84-85mm rather than being just a passing 'nominal' 8 cm.

But it is a something I am not sure of as far as the evolution/transition of those series tanks. The acceptance tests for the IS-2 (122mm) were November/December 43. It was being manufactured in that time frame. But many sources claim May 44 as the initial combat debut?

[Mobius]

(Luckily I had time to correct a math error in the last KV-85 drawing.)
From the production records the JS-2 production started in January 1944. There where several test vehicles running around before this.
I also have a German photo of a captured JS-2 that differs from the armor scheme drawings.

[Peasant]

As far as I know, that first picture of KV-85 armour scheme originates from this book:



So you think that number on the SU-152 glacis is "50mm"? Looks like 60mm to me, look, the upper left corner of the digit is curved like a "6" not angled like a "5".
It would make sense to limit the number of different thicknesses used in assembly, and there should be no reason to prefer one over the other since both thicknesses would be more than sufficient, when sloped at 70°, against any german weapon at the time.
Also, I'm pretty sure that the engine deck is 30mm not 50mm.

[Mobius]

The reason I believe the glacis is 50mm and the engine deck is because that is what the KV-1S has.
It looks more like a '5' than '6' because the '6's in 60 on the front superstructure looks more like '8's as the hook comes back down.

kv1s_armor_scheme.gif (8.16 KiB) Viewed 3281 times

[Peasant]

The reason I believe the glacis is 50mm and the engine deck is because that is what the KV-1S has.
It looks more like a '5' than '6' because the '6's in 60 on the front superstructure looks more like '8's as the hook comes back down.
kv1s_armor_scheme.gif

I was talking about the german photos.

I've found a much better quality scan of the schematic here: http://www.armchairgeneral.com/rkkaww2/ ... _85_bp.htm
Also here is a SU-152 armour profile schematic from another book dedicated to soviet heavy SPGs, by the same author: https://i.imgur.com/mv3pYmA.jpg The text part describing the armour protection explicitly states that the hull was made from plates of 20,30,60 and 75mm, so although you see what looks like "50" in some spots, I guess it must be issue with the scan quality.

Looking at them, I've noticed that in SU-152, unlike in KV-1S and KV-85 there are no plates of 40mm gauge used anywhere in the structure, so my theory explaining everything we found so far is: because they didnt want to bother producing the 40mm plate just for this small part of the hull they've eliminated it, replacing with the next thicker gauge that was already in production (60mm), while the plants assembling KV-1s didnt have this issue. The weight increase would've been minimal because of the small size of this part, compared to the weight of the vehicle, and they probably felt that it was worth it to streamline the production.
What do you think?

[Mobius]

Somebody should get one of those ultrasonic thickness measuring devices and head out to see some old tanks.
But that SU-drawing is wrong compared to this:
The artists can't even get the lower hull angle correct.

Su-152-armor.jpg (50.73 KiB) Viewed 3149 times

SU-152armor2.jpg (23.06 KiB) Viewed 3149 times

[Yoozername]

Looking at them, I've noticed that in SU-152, unlike in KV-1S and KV-85 there are no plates of 40mm gauge used anywhere in the structure, so my theory explaining everything we found so far is: because they didnt want to bother producing the 40mm plate just for this small part of the hull they've eliminated it, replacing with the next thicker gauge that was already in production (60mm), while the plants assembling KV-1s didnt have this issue. The weight increase would've been minimal because of the small size of this part, compared to the weight of the vehicle, and they probably felt that it was worth it to streamline the production.
What do you think?

It would certainly make sense not to introduce RHA plate of new sizes in a production stream. I suppose they had 45 mm plate in great quantities considering the T34 use of it.

Just so we are on the same page, the KV-85 was the interim model they only made less than ~200 or so? Basically till teh short lived JS-1 came out?

[Mobius]

It would certainly make sense not to introduce RHA plate of new sizes in a production stream. I suppose they had 45 mm plate in great quantities considering the T34 use of it.
Just so we are on the same page, the KV-85 was the interim model they only made less than ~200 or so? Basically till teh short lived JS-1 came out?

That what I think. The Soviets were developing heavy tanks at a rapid pace and they had the JS-1 in pre-production and the JS-2 in development.
From here:
http://tankarchives.blogspot.com/2018/0 ... -tank.html

The second KV-14 variant was chosen as the winner. It retained the chassis and gun unchanged.

The article shows that the KV-85 and SU-152 were being developed at the same factory that was making the KV-1S so they didn't have to go far to get a chassis.

[Yoozername]

Some interesting pics....

http://the.shadock.free.fr/Surviving_KV_series.pdf


KV-1S? has a bow MG so I guess it might be?

https://www.facebook.com/pg/Militarne-P ... 8160998220

[Yoozername]

(Luckily I had time to correct a math error in the last KV-85 drawing.)
From the production records the JS-2 production started in January 1944. There where several test vehicles running around before this.
I also have a German photo of a captured JS-2 that differs from the armor scheme drawings.

I am not sure that is correct. There is another source saying that the JS-1 and JS-2 were built alongside each other along with T34 and assault guns also. I will dig it up. It seemed like it was hectic at that one plant. In any case, it seems JS-2 were built in December. I just wonder what it's real first combat dates were?

I believe there were only about 140 KV-85, and just 107 JS-1?

[Mobius]

This what I have one the KVs

You might be right and I shifted the date by one month in the wrong direction.
From the old Russian Battlefield site.

Here is one guy who actually went out to measure the thickness of JS-2 with an ultrasonic device.
https://forum.warthunder.com/index.php? ... -measured/
In one spot the numbers he found differ from German photographic evidence. And what it could mean.

[Yoozername]

Maybe worth a read....

On October 31, 1943, an experimental heavy tank Object 240 was adopted by the Red Army. So the evolution of the KV-1 heavy tank, which appeared back in 1939, reached the final point. The finishing touch to the portrait of the new car was the 122-mm D-25T gun, which was able to fight any Wehrmacht tank. Soviet heavy tank designers not only caught up with the Germans with their Tiger, but were also able to get ahead of them. Today's story is about the production of the IS-2 and the development of its design from the end of 1943 to mid-1944.

https://warspot.ru/11457-borba-za-mesto-na-konveyere

[Peasant]

During the first half of 1943 figures have been obtained on required thickness and obliquity of high hardness cast armour required for complete protection (PTP limit) against german 88mm AP shells at point blanc (probably actually 100m). 100mm/45° and 120mm/40°

I dont know if they used Tiger I gun or the Flak canon and either old or new 8.8cm ammunition.

[critical mass]

In the first half of 1943, there was a lot of 8.8cm Pzgr Gg around and few Pzgr39....

Tiger could and did fire Flak ammo during 1943.