The low build quality of the planetary transmission was apparent during the first few kilometers of the tests. All of the bronze rings were replaced with steel rings and the control ball bearings with forged needle bearings.
Furthermore, an oil leak needed to be corrected and the Ferodo brakes replaced with cast-iron brake shoes. After the defects were corrected, the transmission was again installed in the KV-7, after which it traveled a distance of 545 km on March 4 without a problem. In a memorandum to People’s Commissar Zaltsman on June 5, 1943, the chief of the GABTU’s Armor Directorate stated the following:
The tank with a planetary transmission is becoming more maneuverable and responsive. Changing gears is accomplished easily and quickly without losing speed.
The design defects identified during testing—oil leaks through seals, increased effort on the pedals and control levers, no automatic adjustment of brake bands—can be corrected when the transmission is refined for mass production.
In order to completely determine the performance of the planetary transmission, testing on the tank with this transmission is extended until the full guaranteed distance of 2000 km is achieved.{9}
Meanwhile, the testing dragged on. A final reduction gear failed in April after a 160 km run (excluding the 545 km traveled during February-March). Testing of the planetary transmission continued after repairs were made. The tank was driven a total of 843 km between February and April 1943, and then strange things began happening. Factory No. 100 delayed completion of testing for various reasons, and the KV-7 did not move for the entire month of May. The situation was the same in June. Factory No. 100’s management cited a simple lack of manpower as the reason, although the true reason was unwillingness to work with a transmission developed elsewhere. According to reports by Eng. Maj. Dolitsky, deputy to the senior military representative of GABTU’s Tank Directorate, only two people would be needed to correct the defects and continue testing. It is difficult to believe that the factory did not have them. The situation continued unchanged in July and August 1943, even though the GABTU management sent a letter “up the chain” demanding that testing be continued. In September, tests on the planetary transmission designed by Zaychik simply vanished from Factory No. 100’s plans, and it reported on November 30 that assembly of a planetary transmission designed by Factory No. 100’s special design bureau was complete. Development was delayed, and in the spring of 1944 the transmission was installed in the first prototype of heavy tank Object 701. The conflict continued: the second prototype of the new tank had the transmission developed by Zaychik’s team.
Judging from the correspondence, the second phase of testing on the planetary transmission did not take place. The KV-7 traveled another 1089 km, after which the transmission was removed. This marked the end of this vehicle’s career. According to a decision by Factory No. 100’s management, in late December 1943 the KV-7, KV-9, and KV-12 were decommissioned and scrapped.
Despite the unfortunate fate and lack of soundness of the concept of an assault tank equipped with a salvo fire system, the KV-7 was a major milestone in the history of the Soviet tank industry. It was actually the first wartime Soviet heavy SP assault gun, and its design was the point of departure for the development of SP guns of that class. Development along those lines actually began simultaneously with work on the KV-7 that was equipped with the U-14. In addition, the scheme featuring installation of weapons in a frame was subsequently used in a number of wartime Soviet SP guns.
CHAPTER 5.
The Sverdlovsk Era
In early January, ideas of arming the KV-7 with weapons more powerful than the twin 76 mm guns or the 122 mm howitzer began making the rounds of GABTU management and were mentioned in a report about tests of the assault tank. An example of this kind of proposal can be found in a January 8, 1942, finding about the KV-7 signed by Maj. Gorokhov, chief of the 4th Branch of the 3rd Department of the Red Army’s Armor Directorate:
After reviewing the system and the firing conducted with it, I believe that this type of weapon is unacceptable to the armored forces for the following reasons:
1. The system is useless against tanks because it has little flexibility of fire; it can traverse only 15° to each side.
2. Nor can it be used against reinforced concrete bunkers or earth-andtimber emplacements because it is ballistically inefficient and its shells are insufficiently destructive.
I believe it would be better if the gun on this type of system were larger in caliber, approximately 152 mm, and mounted on a KV-2 tank—the M10.{1}
Meanwhile, the situation with the KV-7 was becoming rather delicate. As the first assault tank prototype was undergoing firing trials, preparations were underway at Factory No. 200 to begin mass production of the hull. On December 30, 1941, Factory No. 200’s chief engineer, L. I. Eyranov, signed off on the specifications for manufacturing a preproduction batch consisting of 20 hulls. We do not know for sure how many hulls the factory manufactured, but judging by subsequent events, the technical specifications in Chelyabinsk did not place a limit on the number. The GABTU faced an unpleasant fact: the assault tank had gone from being a high-priority task to an experimental program, and something needed to be done with the hulls that had been built. In all fairness, this rarely happened in the Soviet tank industry, in contrast to the situation with the Germans, where Krupp regularly turned out turrets for canceled tanks.
The situation with the KV-7, however, was not that hopeless. The triple gun system was a failure, but that did not mean the effort was wasted. The superstructure for the KV-7 that had been developed for three relatively small tank guns was entirely suitable for mounting howitzers. The idea of mounting a 122 mm howitzer was dropped because there was a plan to place a similar weapon in a normal turret on a KV-9 tank. That left two larger guns: the 152 mm howitzer model 1938 (M-10) and the 152 mm gun-howitzer model 1937 (ML-20). Also, the idea of mounting the BR-2 152 mm gun on a vehicle was not going away.
It should be noted that two enterprises were designing heavy SP guns at the same time in early 1942. The Bauman Institute of Mechanical Engineering in Moscow (now named the Bauman State Technical University (MGTU)) was tasked by the People’s Commissariat of Arms to work on conceptual designs for self-propelled guns, including bunker busters, armed either with the BR-2 (SA-BR-2) 152 mm gun or the B-4 (SU-B-4) 203 mm howitzer. The second enterprise was Factory No. 221 of the People’s Commissariat of Arms, the manufacturer of the BR-2 gun and B-4 howitzer. In March 1942, the factory’s design bureau offered designs for the BR-33P and BR-33G SP guns. Both designs were based on assemblies from the T-34 medium tank. According to the documentation, the BR-33P would be equipped with the BR-2 gun, and the BR-33G with the B-4 203 mm howitzer. Upon review of the designs, it was decided not to manufacture them because they did not meet the requirements for bunker busters. That seems a little strange, because the initial task was to mechanize corps-level artillery, not develop systems for destroying enemy fortifications by direct fire.