KV-1 vs KV-1S

"Proposal on improvement of the design of the KV tank

1. It is necessary to improve the reliability of the V-2K diesel to 500 service hours. The components and assemblies of the running gear and transmission last for this time, but the tank goes out of service after 150-200 hours exclusively due to the engine. The latest engines break even earlier, 80-100 hours. The weakest parts are:
1. Valve foundation (it unseats itself, tearing the valve and piston)
2. The hold-down studs work themselves out and penetrate the cylinder bank head (there were cases where this happened after 30-40 hours).
3. The piston rings are worn out quickly, and while the crank and connecting-rod assembly can keep working for 150-200 hours the engine consumes 1 kg of oil per 1 km.
2. Gearbox. The 8-speed gearbox with elastic gear switching is desirable, but the existing gearbox is fine for the KV tank.
3. Final drive. May-June 1941 production tanks had cases where the driving drum stem twists up (5 cases) and bearing #3518 breaks often (5 cases).
4. Running gear. The weakest part of the running gear is the bearing in the new type of idler with shortened rollers that breaks after 75-100 hours. Replace it with the older type.
5. Armament. The ZIS-5 gun requires complete disassembly to replace the barrel.
6. Hull. In the old type of tanks, the armour could resist cannon hits even from short range. Lately this is unsatisfactory. The armour is always penetrated, the tank burns, the crew is killed. There are more cases on recent tanks, as the armour is weaker.
   While old type tanks could resist enemy shells at 500 meters, new tanks can be penetrated from 700-800 meters.
   The location of observation devices on the old KV tank was not fully adequate for battle, but the new tank turret is completely unsatisfactory. It is necessary to return the old turret with a large 300x300 mm triplex near the commander's station with a triple armour shutter.
   The attachment of the turrets to turret rings and the protection of the turret ring is unsatisfactory. The splash protection is weak and turrets jam often. The bearing separator is low in quality, it breaks often and the turrets jam.
   It is necessary to protect the turret rings with armour and build the separator from high quality metal.
7. Methods to protect the tank from fires:
1. Improve ventilation in the fighting and engine compartments (there were cases where there was a fire even though the shell burst outside the tank).
2. Install a powerful sprinkler style fire extinguisher.
3. Create pressure in fuel tanks with an inert gas using a portion of exhaust fumes so that there are no explosions in the part of the fuel tank that is not filled with fuel.

Commander of the 3rd Guards Heavy Tank Brigade, Guards Colonel Vovchenko

Military Commissar of the 3rd Guards Heavy Tank Brigade, Guards Regimental Commissar Sidyakin

Technical Assistant to the Commander of the 3rd Guards Heavy Tank Brigade, Guards Major Rotmistrov

October 8th, 1942."

Via iam-krasnoyarsk.