Monday 16 May 2016

Heavy Tank Production, Spring-Summer 1945

"State Committee of Defense Decree #7950ss
Moscow, Kremlin
March 29th, 1945

On the modernization of the heavy IS-2 tank, the State Committee of Defense decrees that:
  1. The proposal of the People's Commissar of Tank Production (comrade Malyshev) and Deputy Commander of Armoured and Motorized Forces (comrade Korobkov) to accept the IS-3 (modernized IS-2 heavy tank) tank with the following characteristics, designed by the Kirov factory in Chelyabinsk, into service.
    1. Overall data, mass, and size:
      1. Combat mass, tons: 46-46.5
      2. Hull length: 6850 mm
      3. Height to periscope top: 2450 mm
      4. Full width: 3170 mm
      5. Clearance: 465 mm
      6. Bore axis height: 1800 mm
      7. Range with main tanks: 120-150 km
    2. Armour:
      1. Hull: welded
      2. Thickness and angle of armour plates:
        1. Upper front plates: 120 mm at 55 deg
        2. Lower front plate: 110 mm at 55 deg
        3. Lower side: 90 mm at 0 deg
        4. Upper side: 90 mm at 60 deg
        5. Upper rear: 60 mm at 49 deg
        6. Lower rear: 60 mm at 41 deg
        7. Floor: 16-20 mm
        8. Roof: 20-30 mm
        9. Turret: cast with variable thickness from 75 to 250 mm, with slopes from 30 to 70 deg
    3. Turret ring diameter: 1840 mm
    4. Armament:
      1. 122 mm D-25 gun
      2. DShK AA machinegun
      3. DT machinegun
      4. Gun elevation: +20 degrees +/- 2 degrees
      5. Gun depression: -3 degrees +/- 0.5 degrees
      6. Ammunition:
        1. 28 gun shells
        2. 5 DShK belts
        3. 12 DT magazines
        4. 25 F-1 grenades
    5. Observation and aiming devices:
      1. Telescopic T-Sh-14 sight
      2. Collimating KV-T sight
      3. Prismatic MK-IV periscopes:
        1. Commander (1)
        2. Driver (1)
        3. Loader (1)
        4. Gunner (1)
    6. Other characteristics are same as on the IS-2 tank.
  2. The People's Commissariat of Tank Production (comrade Malyshev) and Kirov factory (comrade Zaltsmann) must correct the defects discovered in the trials of the IS-3 tank before organization of its mass production.
  3. The People's Commissariat of Tank Production (comrade Malyshev) and Kirov factory (comrade Zaltsmann) must provide for production of heavy tanks and SPGs in the following amounts:

    April
    May
    June
    IS-3
    25
    100
    250
    IS-2
    225
    150
    -
    ISU-152
    100
    100
    100
    ISU-122
    150
    150
    150
    Total
    500
    500
    500
  4. The People's Commissariat of Tank Production (comrade Malyshev) and factory #200 (comrade Sherbakov) must provide for production of hulls and turrets for them in the following amounts:

    Uralmash factory
    Factory #200
    Total
    April
    May
    June
    April
    May
    June
    April
    May
    June
    IS-3
    30
    75
    100
    25
    90
    175
    55
    165
    275
    IS-2
    60
    15
    -
    150
    90
    -
    210
    105
    -
    ISU
    225
    225
    250
    -
    -
    -
    225
    225
    250
    Total
    315
    315
    350
    175
    180
    175
    490
    495
    525
  5. The GOKO operations bureau must review the measures taken by the NKTP for production of the IS-3 tank in 5 days.
  6. The secretaries of the Chelyabinsk and Sverdlovsk VKP(b) regional committees must aid the Kirov factory, factory #200, Uralmash, and factory #255 in their execution of this decree on production of IS-3 heavy tanks.
Chair of the State Committee of Defense, I. Stalin."

10 comments:

  1. There is an error about the total amount of heavy tanks and SPG in the third point on May. It should be 600 instead of 500.
    Regards.

    ReplyDelete
  2. Very interesting, note how IS-3 is referred as a "modernised IS-2".

    Is there a final answer on why production of IS-3 was terminated? Svirin states that there was a ballistic test where a 100mm round hit the weld at the front chassis, destroying it completely. After this confidence in the vehicle was broken and never restored.

    I have never seen any evidence of this test. Other people have added that the weld was faulty in this vehicle, or that the welding was improved to fix the problem.

    Other sources point out at issues that prevented proper "exploitation" of the type. The chassis was prone to cracks due to it's new features.

    Thanks.

    ReplyDelete
    Replies
    1. The introduction of the successor IS-8/T-10 might of been related... though I remember reading that the IS-3 hull proved to be a bit too extreme in its design and, due to lacking sufficient structural rigidity and suchlike, prone to problematic levels of deformation in the long run.

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    2. Yeah, the IS-3 was built for wartime service, when the requirement is to last for thousands of kilometers. Peacetime service needed tens of thousands. Looks like the IS-2 could meet that requirement and the IS-3 could not.

      As for a 100 mm test, I too have never seen any evidence of such an event. The ballistics requirements for heavy tanks were to resist the D-25 and KwK 43, not the D-10. Perhaps later, a scrapped IS-3 used as a range target suffered such a hit?

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    3. Speaking of welding though, I remember once running across a discussion on the topic of joining armour plate of tanks by that method. IIRC someone who claimed to have professional experience with welding pointed out that very thick plates get increasingly difficult to properly weld together by hand, what with humans lacking the precise thermal sensors and split-second timing industrial robots boast. (We may recall here the persistent problems the Germans had with the seams of their heavier tanks.) I also recall seeing it mentioned in various separate instances that the complex "pike nose" was tricky to construct and as a result exact angles and dimensions could vary a fair bit between individual tanks.

      Probably one of the many reasons castings were popular.

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    4. Yes, cast armour was easier to make complex shapes with than welded, both the Soviets and Americans realized this early on. Unfortunately you can't get away from problems with thickness here either: the thicker the cast armour the higher the chance that there will be defects.

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    5. Welding armor seams does not work without flaws with the technology of the time. Thick armor plates require the presence of chromium and nickel to be tough. Yet those alloying agents increase the sensitivity to temper britellness. Any welding, secondary heat treatment will have a portion of the two joined plates being in the ideal temperature zone for temper britellness.
      Due to the characteristics of the austenitic weld seams it became necessary to design the structures in such a way that forces, particularly those resulting from combat action or operation, would not be absorbed exclusively through the weld seams. Rather, the structures were designed so that the sheet metals or components to be connected were mutually supported in such a manner that the forces did not flow only through the weld seams (e.g. by keyed plates). It was further necessary to design the structure of the weld seams in such a manner that direct firing on the weld seams was impossible. This was accomplished in that the weld seams were protected, if possible, by a cover of armor steel. Butt joints or similar connections of sheet metals made of armor steel must be avoided by any means since the region of the weld seam has a lower resistance to enemy fire than the unwelded sheet metal so that these points would constitute a particularly weak point of the structure.

      The IS3 pike nose is suffering because the welds are unprotected by armor plate and thus constitute a weak zone and the nose is the principal structural strength member and subject to many forces going through.

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  3. This comment has been removed by the author.

    ReplyDelete
  4. Regarding IS-3 reliability, when prototype Kirovets-1 was tested, the reliability was judged to be comparable to IS-2. Svirin states that IS-2 and other WW2 vehicles were also subjected to UKN programs to make them adequate during peace use. Priority was given to T-44, T-54 and IS-3 because they were going to form the backbone of the Soviet Army Tank Armies.

    Regarding the misterious ballistic test, Svirin quotes an Army officer named Gorlitskiy (*). He is quoted several times in his book (Steel fist of Stalin. History of Soviet tank 1943-1955), but he is not in the references.

    In any case, IS-3 was removed from production and IS-4 rushed to it.

    (*) He is also quoted when explaining UKN program.

    P.S I read your blog daily, I hope you carry on with this excellent work.

    ReplyDelete
    Replies
    1. Pretty sure the only thing the IS-4 was rushed into was de facto exile in the Far Eastern military districts where its excessive weight caused fewer bridge-related problems...
      And given the comparatively minuscule production numbers and cancellation already around '49 it certainly wasn't much of a replacement for anything. :/

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