Wednesday, 15 January 2014

Birth of the KV

"History of the development of the KV tank

The KV tank began development according to the decisions of the Main Military Council on December 9th, 1938. Tactical-technical requirements were set by RKKA ABTU and confirmed by the People's Commissar of Defense on February 19th, 1939. The final revision of the requirements and permission to build the tank was given on February 27th, 1939, by the decision of the Commissar of Defense in the Council of People's Commissars #45ss and #118ss from May 15th, 1939.

The factory began working on the design on February 1st, 1939. The chief engineer of the project was Nikolai Leonidovich Dukhov. The technical project and a model were provided for inspection on April 7th, 1939. The model commission, chaired by deputy ABTU chief, military engineer 1st grade comrade Korobkov, with the following suggestions:
  1. Hull and turret:
    1. Increase the thickness of the rear plates to 75 mm and the front sloped plate to 60 mm.
    2. Test the hull, turret, and hatches by firing at them.
    3. Install a guard against hand grenades outside the turret and under the turret bay.
    4. Move the turning mechanism of the turret forward to make it more convenient. 
  2. Armament:
    1. Place machinegun ammunition in the turret first, and then use the remaining space for shells.
    2. Simplify the gun mantlet.
    3. Follow the Commissar of Defense's order and install a removable AA machinegun in addition to the forward facing machinegun. 
    4. Provide a means for every crew member to open fire from personal weapons.
  3. Engine:
    1. Lower the engine by 50 mm.
  4. Transmission:
    1. Robustness calculations should use a 660 hp M-17F engine with M=330 kg-m. Dynamic calculations should use the 580 hp V-2F engine with [missing handwritten figures make the rest of the paragraph meaningless]
    2. From the gearboxes provided, #3 (planetary gearbox with a reductor) should be the main variant. In parallel, develop a simple gearbox. The gearboxes should be able to replace each other. Lower the engine axis by 50 mm. The side friction clutch should be the same type as on the SMK, with a diameter of 500 mm.
    3. The final drive should be of the same type as on the SMK. Change the design of attaching the inner gears to make it easier to produce. 
  5. Suspension:
    1. Increase the length of the foundation to 4600 mm, with the width of 700 mm and ground pressure of 0.6 kg/cm^2.
    2. Use an SMK-style track (stamped). The space between the wing and track must be no less than 20 mm.The track spur should be at least 70 mm away from the hull.
    3. Develop two kinds of idlers and drive wheels: one with rolling bearing, one with a sliding bearing.
    4. Use SMK-style road wheels and idlers, with armoured bearings, according to the technical requirements. Place the torsion bars in armoured covers.
  6. Observation devices and equipment:
    1. Give the driver mirrored devices for looking left and right, as well as a periscope in a hatch as a backup.
      The radio operator should have a mirrored observation device for looking left.
      The turret needs devices to look forward, back, left, and right, as well as a backup periscope.
    2. Place the radio left of the driver, as stated in the technical requirements.
    3. Provide a spare parts and instruments container for the tank.
    4. Add small hatches for throwing hand grenades from the tank.
    5. Develop a project for servo-controls, and present it to ABTU for approval.
Working blueprints were delivered to the Izhor factory on May 20th, 1939. The approximate processing time was one week. On May 28th, 1939, the following list of changes was provided to ABTU.
  1. The tank hull is 50 mm lower.
  2. The turret is 60 mm lower.
  3. The rear plate was thickened to 75 mm.
  4. A planetary gearbox is being developed.
  5. The foundation length was increased to 4.4 m.
  6. The diameter of the brake drum was decreased to 500 mm.
  7. A 700 mm wide track was developed.
  8. Mirrored observation devices are being developed.
May 25th: factory #75 receives an order for two V-2 tank engines. The first is due by June 10th, the second by July 1st. 

June 4th: the 75 mm armour plates are tested at the Izhor factory against the 76 mm 40-caliber gun with the muzzle velocity of 650 m/s. The homogeneous armour with hardness of 3.5-3.6 successfully resists these shells at 200 meters. At 50 meters, the armour forms bumps 25-30 mm deep, and occasionally forms cracks.

June 5th: ABTU instructs the factory to:
  1.  Use the V-2 engine only, and not use the M-17 engine anymore.
  2. Change the air intake and exhaust. Install a coaxial 45 mm gun.
June 10th: the factory begins production of a simple gearbox, final drive, suspension, tracks.

September 1st: the first tank was assembled. After travelling 7 km, due to poor assembly, the clutch between the gearbox and final drive disconnected. This defect was temporarily solved by sleeve welding. A variant with a cam-bearing sleeve is in development.

September 2nd: the tank travelled 45 km at factory trials. The following was discovered.
  1. The 4 small oil reservoirs in the tank aid foaming of the oil, as a result of which it escapes the reservoirs. A decision was made to throw these reservoirs away and use the rear left 120 L gas tank as an oil reservoir.
  2. Due to the 45 mm and 76 mm L-11 guns installed in the tank, the position of the crew was not finalized.
  3. The mechanism for tightening tracks is inconvenient.
  4. The mirrored observation devices are not installed.
September 5th: the tank was sent to Moscow to show to the Government."

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