January 5th, 1944
The preliminary tactical-technical requirements for a light tank that you sent were examined by a small circle of design and technology managers. Having studied your requirements in detail, we came to the following conclusions:
- In general, the requirements are realistic and such a tank can be designed and built at our factory.
- A number of issues you presented require special investigation and only then can they be implemented in a production vehicle.
Based on the above, we ask you to consider the following wishes of the factory when composing the revised tactical-technical requirements.
- Set the thickness of turret armour at 60 mm for a cast armour variant and 45 mm for rolled armour.
- Do not specify the position of the transmission and drive sprocket. Let the designer select the best possible position of the transmission and drive sprocket.
- Reduce the maximum speed from 50 kph to 42 kph in order to retain more torque at top speed and all intermediate speeds.
- Allow a torsion bar suspension with bogeys instead of only an independent torsion bar suspension, as this will allow for reduced weight and still allow for sufficient flexibility.
- Set the maximum ground pressure at 0.65 kg/cm² instead of 0.6 kg/cm², as it will still allow for satisfactory off-road mobility and lower the weight of the tank in otherwise equal conditions.
- Don't specify the mounting of the gun, leaving it up to the designer. Installation of the gun from the outside makes the turret larger and increases the weight. Installation of the gun from the inside decreases weight and allows for a better shape, but makes assembly more difficult. The final decision should be up to the designer, who will weigh all the advantages and disadvantages.
In connection with that, we consider the following:
- A long and careful investigation must be conducted due to the fact that the MK-4 observation device will make using an AA machinegun on the commander's cupola difficult and the optimal positions of the machinegun, observation device, and sight during firing of the machinegun must be found.
- Planetary transmissions. This is a completely new topic for domestic tank building. It will require a long design period and a long production refinement period, which will cause delays in production of a new type of tank or growing pains during initial stages of production. Work on a planetary transmission must be done in parallel, and the tank's design must allow for painless installation of the transmission after it has been refined.
- Two-stage turning mechanism. In our opinion, there is no reason to complicate the turning mechanism for this class of tank and a one-stage turning mechanism that's a part of the planetary transmission is acceptable.
- We consider it necessary to build a new 8 cylinder engine for a new light tank. A diesel based on the V-2 engine with a 60 degree angle between cylinders will reduce the length of the engine, increase power, and allow the use of major V-2 components.
I ask that you immediately reply with your decisions regarding the issues we raised. We consider that the topic of a new light tank is timely and the decision to start working on such a tank must be made immediately.
Chief engineer of the factory, Demyanovich
Chief designer, Gudkov"