Monday, 3 April 2017

T-34 Tank Destroyer

"Approved by Deputy People's Commissar of Defense, Marshal of the Soviet Union, G. Kulik
May 27th, 1941

Tactical-Technical Requirements for an 85 mm SPG

1. Purpose of the SPG
  1. The 85 mm SPG is designed to accompany moto-mechanized units and for combat with enemy tanks and armoured cars.
  2. The 85 mm SPG must be able to combat strongholds and personnel positioned in the open, or behind light field fortifications, support direct and indirect fire, and be able to penetrate 85-90 mm of armour with a coefficient of K=2400 at 30 degrees at a range of 1000 meters.
2. Tactical Requirements for the Gun

The 85 mm SPG must satisfy the following requirements:
  1. Rate of fire: 15 RPM
  2. Gun elevation: no less than 25 degrees
  3. Gun depression: no less than 5 degrees
  4. Horizontal range for fire up to 3000 meters: 360 degrees. Fire at a range of over 3000 meters can be limited to a range of +/- 25 degrees.
  5. The rate of horizontal and vertical aiming must be the same as on the 85 mm mod. 1939 AA gun, namely:
    1. Horizontal aiming:
      1. In first gear: 3 degrees per turn of the flywheel, with efforts no greater than 6 kg.
      2. In second gear: 7 degrees per turn of the flywheel, with efforts no greater than 12 kg.
    2. Vertical aiming:
      1. In first gear: 1.2 degrees per turn of the flywheel, with efforts no greater than 10 kg.
      2. In second gear: 3.65 degrees per turn of the flywheel, with effort no greater than 20 kg.
3. Technical Requirements for the SPG

The 85 mm SPG must satisfy the following requirements:
  1. Muzzle velocity: 800-850 m/s
  2. Ammunition: armour piercing and fragmentation grenades from the 85 mm mod. 1939 AA gun.
    Note: if the muzzle velocity is greater than 800 m/s, it is permissible to alter the propellant load, in other ways the ammunition must be identical to that of the 85 mm mod. 1939 AA gun.
  3. The recoil mechanisms must allow for 50 nonstop shots before a pause to cool the system. The recoil mechanism must not leak fluid.
  4. The design of the recoil mechanisms must allow for firing at all angles between -20 degrees and +40 degrees at a 15 degree tilt.
  5. The gun must be comfortable to load at all angles of elevation and depression.
  6. The position of the sight equipment must ensure that the gunner's work is comfortable.
  7. The gun must be balanced. A balancing mechanism is permitted.
  8. The gun must have a travel lock.
  9. The gun and crew must be covered from the front, sides, and top by 8-10 mm of armour.
  10. The gun crew consists of five men.
  11. The SPG uses the A-42 tractor as the chassis, which is produced on the improved T-34 chassis.
    The SPG must satisfy the tactical-technical characteristics applied to the A-42 by the GABTU and GAU, including the addendum for SPGs included in these requirements.
    The travel mass of the SPG must not be greater than 25 tons.
    The SPG must be able to tow wheeled artillery systems weighing up to 25 tons.
    It is not necessary to equip the SPG with a winch, compressor, or demultiplexer.
  12. The armour must protect the crew (driver and machinegunner), engine compartment, fuel, and oil tanks.
    The armour covering the driver and engine compartment must be 30 mm thick from the front and the sides. The roof and floor must be 15 mm thick.
  13. The armour of the tractor must allow easy access to its components for service in the field.
  14. The armoured cabin must fit two men, and provide for:
    1. Comfortable positions of the crew during driving and firing of the machinegun. The seats must be adjustable based on the height of the driver and machinegunner.
    2. Quick and easy exit and entry into the cabin.
    3. Communication between the cabin and the gun crew during movement.
  15. The front wall of the cabin must contain a DT machinegun mount. The range of fire must be +/- 15 degrees horizontally and +15 to -7 degrees vertically. No fewer than 20 disks of ammunition must be carried.
  16. The design and position of the observation devices must allow for good visibility of the road and surroundings. The deadzone in front of the SPG may be no more than 4-5 meters.
  17. The cabin must be isolates from exhaust fumes or precipitation. The floor and walls separating the cabin from the engine must be isolated from heat. The cabin must be well ventilated.
  18. The gun platform can fit an artillery system weighing 4700 kg with recoil resistance of 10 tons.
  19. The platform must have armoured sides 1 meter tall and 10-12 mm thick. The rear panel must flip out.
    Semi-soft foldable seats for 5 men must be attached to the walls.
  20. The platform floor must have transmission maintenance hatches.
  21. The overall height of the SPG must be no greater than 2800 mm. The height of the platform must be no more than 1100 mm above the ground.
  22. The onboard ammunition capacity must be no fewer than 50 shells.
  23. A one-axle trailer can be used to transport ammunition. The capacity of the trailer must be 100 shells in the stock packaging for 85 mm AA gun shells. The weight limit of the trailer must be no less than 2000 kg. The mass of the trailer can be no more than 1500 kg. The sides of the trailer must be armoured. The thickness of the armour must be 10 mm.
  24. During the development of working blueprints, develop blueprints for necessary instruments, equipment, spare parts, and toolboxes.
  25. Technical requirements #1 and #22 will be reviewed during development and examination of the design during a meeting between GAU and GABTU."

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