Wednesday, 6 February 2019

L-11 Installation

"To: AU, ABTU, 520, AU Military Representative at factory #183

The installation of the L-11 system in the A-34 tank can be done without changes to the following parts only:
  • Gun barrel
  • Recoil mechanism
As for the remaining parts, all of them must be changed to some degree, largely covered by the following:
  1. Group 02: breech
    1. The semiautomatic cutoff mechanism is removed and the roller cutoff mechanism from the L-10 is installed.
    2. The breech handle is shortened by 20 mm.
  2. Group 03: trigger mechanism
    1. The hand trigger is different, and the attachment point is different.
    2. The hand trigger (pedal) is used from the 45 mm gun.
  3. Group 05: gun shield
    1. The gun shield is completely different, including a coaxial machinegun. The telescope mount from the old gun shield is used, but with changes. The elevation mechanism sector is different.
  4. Brass catcher: a new one with smaller dimensions (on the left side) will be used, with a trimmed stopper and a new carrier.
  5. Frame: the L-11 frame is removed completely. The gun is mounted on two vertical posts welded from the inside to the front of the turret, replacing the frame.
  6. Mantlet: a new one based on the changes to the gun shield and carrier.
  7. Elevation mechanism is used from the L-11, but with small changes.
  8. The periscope link is from the 45 mm gun.
As you can see, in order to install the L-11 gun in the A-34 tank, the factory will need to receive the system in the following configuration:
  • Barrel
  • Breech with semiautomatic mechanism
  • Trigger mechanisms
  • Recoil mechanisms
  • Telescope mount (assembled)
  • Elevation mechanism
  • Brass catcher with carriers
It is necessary to demand that factory #183 register all of their alterations in blueprints, first of all. Second of all, it is necessary for the factory itself to perform these changes, as Kirov factory will not ship the L-11 system with parts not used at the Kirov factory.

There are no fundamental protests on my part regarding the proposed changes, given that the two conditions are met. The blueprints must be presented for approval.

As for the evaluation of the installation, I deem that the L-11 installation in the A-34 turret is unsatisfactory, largely from the point of view of servicing. I cannot recommend the adoption of this gun mount in any case.

I consider that the width of the turret must be enlarged at least by 200 mm without widening the turret ring. It is also necessary to raise the turret roof.

In addition, it is necessary to:
  • Change the backs of the seats, as they impede work.
  • Move the elevation mechanism far to the right as was on the L-11.
  • Move the PT-1 to the left, as far as the turret allows, and allow access to the TOD sight (in the future, it is desirable to replace the TOD with the TMFD).
After these and other changes recommended by the commission are made, I consider that the L-11 mount can be recommended as a limited measure for short term use.

When mobility trials are done, it is necessary to:
  • Assemble and disassemble the system to check the installation.
  • Perform robustness trials with 200-300 overcharged shells.
  • Mandate that the factory develop technical requirements for the welding of the vertical plates that serve as a frame as to either prohibit defects or make them easily detectable.
Military Engineer 2nd Class, Sorokin
March 3rd, 1940"

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