Cases where vehicles that never reached mass production become milestones are common in tank building history. The Soviet KV-13 tank is one of those cases. This tank is often referred to as a "heavily armoured medium tank", which is incorrect. The KV-13 was designed as a heavy tank from the very beginning. The revolutionary vehicle satisfied the requirements of the Soviet military completely. This was the first maneuverable heavy tank that combined impressive armour with small mass, and, most importantly, high mobility.
The KV-13 appeared at a difficult time, which is a part of the reason why it did not enter production. Nevertheless, further Soviet tank development was influenced by the last design of the talented Nikolai Valentinovich Tseits.
Backup plan
The precise date that this completely new project began at the Chelyabinsk Kirov Factory is shrouded in mystery. There is an opinion that work began in 1941, but that is not the case. There was also a claim that the KV-13 was present among the list of experimental works that continued on in 1942, sent for approval to Zh.Ya. Kotin on December 22nd, 1941. However, that vehicle is not the KV-13, but the KV-3, which was still assigned to ChKZ.
Additionally, problems with the KV-1's overloaded chassis had not yet surfaced completely. The heavy tank's armament and armour were still being increased. If the tank was not plagued with decreased mobility and transmission issues, the Red Army could have had its own Tiger by the spring or summer of 1942.
Alas, it was not meant to be. For starters, the U-12 85 mm gun died before it was born. Later, in January of 1942, Stalin raised the issue of insufficient mobility of the KV-1. There was nothing surprising about this, since the tank's weight increased to 50 tons. Two solutions were considered: increasing the engine power to 650-700 hp and decreasing the mass.
Draft of the KV-13 heavy tank, May 1942.
Work on boosting the output of the V-2K engine began in February of 1942. It was quickly discovered that this was insufficient, since the cooling system could not handle such an engine and overheated. A new cooling system was needed. On February 23rd, 1942, GKO decree #1331 was issued, which ordered that the weight of the KV tank to be decreased by 1.3 tons. By this time, far more serious gearbox issues surfaced. Gearboxes on the overloaded tanks broke often. It was clear that the KV-1 was in need of a redesign.
In March of 1942, gearbox issues became a full scale disaster. ChKZ's SKB-2 began working on a thorough modernization of the KV-1. It included lightening the vehicle and changing a number of components, but the tank's concept remained the same. The result of this work was the creation of the KV-1S.
Work on a completely new tank went on in parallel. N.V. Tseits was appointed as the chief engineer of the project, indexed KV-13. Nikolai Valentinovich was a member of the first generation of Soviet tank designers. He was there from the start, taking part in the famous MS-1. On October 2nd, 1930, he was arrested on suspicion of counter-revolutionary activity. That is how he ended up in the design bureau of the technical department of the Economic Directorate of the United State Political Directorate (EKU OGPU), where he worked on PT-1 and PT-1A amphibious tanks alongside N.A. Astrov. He continued to work there after his early release on April 22nd, 1932.
In 1934, Tseits left Moscow and moved to Leningrad, where he took up a key role at Kirov factory #185, which was the USSR's leading developer of tanks and SPGs at the time. Here, Nikolai Valentinovich continued the work that he started at EKU OGPU on the convertible drive T-29 tank.
The T-29's unfortunate fate was directly connected with Tseits'. First, he was taken off the SMK-1, project, then arrested. He might have shared the fate of Firsov, Shukalov, Ivanov, Syachintov, or others, but he got lucky. It's not known who vouched for Tseits, but he returned to his job in the winter of 1941.
His new workplace was SKB-2 of the Kirov factory, where Tseits worked on his own variant of the KV-4 tank. The 90 ton design, exceptional for its originality, won a bonus of 2000 rubles. In many ways, this project served as the starting point for the KV-5 tank.
Nikolai Valentinovich also worked on the KV-1 tank. In July of 1941, he proposed an original way of cooling the engine. In the fall of 1941, Tseits and other workers of the Kirov factory were evacuated to Chelyabinsk. According to N.F. Shashmurin's memoirs, Tseits was sent to the Northern Urals, where he worked in the gold mining industry. The People's Commissar of Tank Building, V.A. Malyshev, pulled him back into tank building after being prompted by the Deputy Chief of the Technical Department of the NKTP, S.A. Ginsburg, a former coworkers of Tseits from factory #185.
A cutaway of the KV-13. The blueprint footer shows that this is the name of the vehicle. N.V. Tseits is marked as the chief engineer of this project.
With Tseits, the design group received a manager who was capable of dealing with difficult tasks. The task ahead of them was indeed difficult. The first year of the Great Patriotic War showed that the heavy tank as envisioned before the war was no longer satisfactory. Now, the heavy tank needed to provide not only a high degree of protection, but tactical mobility. The KV-1 was no longer satisfactory even with its reliability issues. The T-34 was selected as the reference point, which was 1.5 times lighter than the KV-1. In other words, the military required a tank with the mobility of the T-34 and with similar weight, but with the protection of a KV-1.
GABTU's requirements for 30-ton class heavy tanks. The KV-13 and a medium tank called T-44 were built to these specifications.
Some sources (such as Shashmurin) call the KV-13 an attempt to create a competitor to the T-34, demonizing Kotin. In reality, the "heavily armoured medium tank", as it is sometimes called, was requested by the GABTU. The order for a heavy tank with the mass of a medium was given not only to Chelyabinsk, but to Nizhniy Tagil as well. On June 1st, 1942, the GABTU prepared a document to instruct factory #183 to built an experimental 30 ton tank. It is not known if this is the same T-44 (A-44) that was designed at factory #183 in 1941, or a new tank altogether. In parallel, ChKZ was tasked with making a 30 ton heavy tank. This was the KV-13.
As such, it is incorrect to call the tank a medium tank, or to classify it as a direct competitor to the T-34.
Footer of an IS-1 heavy tank blueprint, factory #100 SKB, May 1942.
The index of Tseits' prospective tank deserves a separate discussion. Nikolai Valentinovich was a superstitious man. He turned out to be quite unhappy to have been assigned the "devil's dozen" for an index. Tseits tried to get rid of it with every available method, and partially succeeded. In March of 1942, experimental factory #100 was organized at ChKZ. N.N. Voroshilov became its director, N.M. Sinev its chief engineer, and A.S. Yermolayev its chief designer. Partially, work on the KV-13 transitioned to this factory, and became one of its first projects. This is when the tank received a second index. Since correspondence was mainly written to ChKZ, the index KV-13 was used. However, factory #100's design documentation used a different index: IS-1.
The name "Object 233", frequently used in reference to this tank, has no connection to it. Like other vehicles of the Kirov factory, KV-13/IS-1 received a blueprint code: 233. This was the next sequential number after the KV-13 (232). The word "Object" was only applied to vehicles developed at ChKZ and factory #100 in the summer of 1943, after the KV-13 project was cancelled. The name "Object 233" is the creation of some unscrupulous researchers.
GKO decree text on the production of KV-13 prototypes. As you can see, the turret was changed to fit three crewmen by July 1st.
The overall design of the KV-13 was finalized in May of 1942. The requirements led to the tank's size and mass to be within the range of a medium tank. The creators were inspired by the T-34 during development. Several running gear components were taken from the T-34, specifically (in part) the track links and somewhat altered drive sprocket. The turret was also based on the T-34. Initially, it was supposed to hold two crewmen, but a decision was made to make it fit three in early summer of 1942. At the same time, a commander's cupola and a rear machinegun were added. Even though the three-man turret remained on paper, the effort was not wasted. Although in a slightly altered form, this turret appeared on the KV-1S.
KV-1S with a three man turret.
Despite the presence of the letters "KV" in the KV-13's name, it had little to do with the KV-1. The forefather of the KV family only contributed its engine, torsion bars, and other components. However, the KV-13 was far from being entirely composed of new solutions. ChKZ and factory #100 engineers used their existing experience. The driver's compartment with a central seat was already used on the Kirov factory's T-50 tank. The hull machinegun was also partially borrowed from there, as was the cooling system with its characteristic placement of radiators. A distinctive "hump" had to be added to the engine deck to fit it. The air intakes on the engine deck were also reminiscent of those used on some KV-4 designs.
There were plenty of new solutions. For instance, a 9-speed gearbox with a triple range gear developed by engineer F.A. Marishkin was proposed. The hull and turret were also largely composed of cast components. This allowed production to be simplified and internal volume to be reduced. The tank's armour was 90 mm thick in the first variant, increased to 100 mm by July of 1942, and reached 120 mm in the final variant. The estimated mass of an empty hull was 13,250 kg, and the turret 4,150 kg.
Between the T-34 and KV-1S
On June 5th, 1942, a meeting was held with Stalin and V.A. Malyshev, then the People's Commissar of Tank Production. During this meeting, the KV-1S was finally approved. Prospective factory #183 and ChKZ tanks were also shown. Malyshev recalls in his memoirs:
"We showed comrade Stalin models of two new tanks that completely satisfied the requirements. Stalin replied: "Let's not build new tanks for now. Don't distract designers from the task of improving and modernizing existing tanks. Of course, every designer wants to make a new tank, every designer seeks fame. We need to wait. Let's return to new tanks after a month and a half or two, when designers finish improving existing tanks."
Experimental KV-13, late September 1942.
Stalin's decision was reflected in GKO decree #1878 "On improvement of KV tanks", signed on June 5th, 1942. Sections 9 and 10 had to do with the KV-13 tank. According to them, two prototypes were due on August 10th, 1942, but Stalin himself crossed them out.
The same tank from the front. Track links taken from the T-34 are visible.
Despite this decision, work on the KV-13 continued, but at a slower pace. Most of the work was done at factory #100, while ChKZ expedited the KV-1S. Experience with the KV-13 came in handy during the modernization of the heavy tank. On the other hand, some of the solutions developed for the KV-13 migrated to the prospective tank.
The decision to freeze the development of the KV-13 did not prohibit work on individual components. KV-1 with serial number 25810 was used for this purpose. Starting with July of 1942, it was used to test elements of the KV-13 running gear, especially road wheels and return rollers.
KV-13 from the rear. The layout with two transmission access hatches in the upper rear plate will later become a trademark of IS series tanks.
The KV-13 took another hit on July 3rd, 1942. A GKO decree titled "On T-34 and T-70 tanks" was published, ordering ChKZ to begin production of T-34 tanks. All efforts went to producing the tank, and production of the KV-1 slowed down. The organization of T-34 production also affected the KV-1S tank. As for the KV-13, everything went silent for a while. The entire project was under threat of cancellation.
Tseits' death from a heart attack on July 19th, 1942, may have been the cause of this situation. There were different theories as to why this happened. For instance, Shashmurin blames Kotin in his memoirs. Most likely, Tseits was stressed over the fate of another one of his tanks, which could have turned out to be unnecessary once more.
The KV-13 looked similar to the T-34 from the side. Nevertheless, this was indeed a heavy tank.
N.F. Shashmurin was appointed as the chief engineer of the orphaned tank. According to Shashmurin's memoirs, he never liked the project. Nevertheless, it was up to him to finish Tseits' work. Due to the factory being occupied with KV-1S and T-34 tanks, development of the KV-13 only restarted in September of 1942. Factory #100 was tasked with the design and assembly.
The characteristic shape of the radiators that migrated from the T-50 can be seen here.
On September 14th, the factory received a message from I.M. Zaltsmann, who ordered that all experimental work at the factory stop. Factory #100 had to support the launch of T-34 production at ChKZ. However, work on the KV-13 never stopped. By September 13th, the hull and turret were ready. On the same day, markings were made for installation of components and assemblies. Weighing showed that the mass of the turret and hull was less than estimated: 3,600 kg and 12,900 kg respectively.
The design of the drive sprockets was reminiscent of the T-34, but the configuration was slightly different.
Assembly began on September 13th. As it often happened with experimental vehicles, some dimensions were off. The control lever mounts had to be welded to the evacuation hatch, and there was no space on the floor for the control rods. The final drives didn't fit into the hull openings, and issues arose with installation of fuel tanks. These issues pursued the assembly team throughout the process. It took another two weeks to receive all required components and finish assembling the tank.
Closeup of the KV-13's road wheel.
Overall, the KV-13 was true to Tseits' design. Of course, there were certain changes, especially in the running gear. Instead of road wheels with internal shock absorbers, similar to the LKZ T-50 road wheels, the KV-13 had fully metallic wheels. They turned out to be simpler and lighter. The idlers were designed to be similar. Despite the overall design of the turret being the same, some improvements were made here as well. Some of them, like the handrails, migrated from the KV-1S.
Not a day without trouble
The KV-13 went out on its first test run on September 26th, 1942. All transmission and suspension elements functioned normally, but there was already a defect. At high engine RPM, the oil pressure fell to two atmospheres. The cause was found quickly discovered: a malfunction of the oil pressure regulator. The next day of trials brought many more problems. The tank's top speed was measured by a GAZ M1 car that was driving behind the tank. The result of 55 kph was satisfactory, but was followed by a whole load of issues. After 30 km, the gearbox controls began working poorly, the engine started overheating, and the engine power in 9th gear was low. Finally, the hubcaps from three road wheels fell off. It also became difficult to steer the tank.
KV-13 during trials, October 1942.
The trials of September 26th-27th are mentioned in Shashmurin's memoirs, "50 years of struggle". In his memoirs, the designer holds nothing back about his feelings towards the idea of making a heavy tank with the mass and size of a medium. His actions during the trials led to breakdowns, which Nikolai Fedorovich describes with a certain sense of satisfaction, although he mixes up the first and second KV-13 prototypes.
"In factory conditions and during delivery trials, the drivers learned to avoid dangerous stresses. The character of the trial routes was known, and the volume of trials was limited. There were cases of uncontrolled replacement of parts, etc. I composed a 50 km trial run, but performed it in a special way. The route was Chelyabinsk, Kopeysk, and back. The driving surface was unsettled cobblestones. The crew was: Shashmurin, deputy chief designer, Kovsh, driver, and Rozov, the military representative.
Kovsh drove in one direction. Everything went well, just small cracks developed in a few wheels. I drove the tank back myself, at top speed. I arrived at the factory with smashed up road wheels. There was a scandal, and later I received major consequences for my "initiative". However, the fate of the KV-13 was sealed, and this phenomenon was over."
Shashmurin took a risk, since he could have been accused of sabotage. However, Nikolai Fedorovich was right. The tank was very unpolished, and its suitability for production was in question. The road wheel issue was just one of a long list of problems. For instance, the note about "difficult steering" meant that the levers took up to 60 kg of force to operate, and the friction clutch pedal took 90 kg. There was a number of issues with the comfort of the driver. Servicing the tank was also difficult. For instance, the air filter could not be removed without taking off the oil radiators. There was trouble with the track tension mechanism that could not be attributed to rough driving. There were also design flaws in the turret. The travel lock disengaged during motion, and the locks of the pistol ports were deemed unsuitable.
Climbing a grade. At high RPM, the engine overheated.
The degree of the defects discovered during the first run of the KV-13 can be seen from the fact that it took a week to correct the.m. After the changes, the efforts on the levers dropped to 24 kg. Much more interestingly, the T-34 style running gear was deemed a poor choice. After the defects were corrected, the trials continued. Factory #100 began working on a second set of transmission and suspension mechanisms. A decision was made to use KV tracks and KV style drive sprockets.
KV-13 in the forest.
On October 5th, the improved KV-13 began its third trip, covering a distance of 35 km. It turned out that the track tension mechanism stopped unscrewed itself during travel, the track loosened, and beat up the fenders. The right fender was torn off completely, the left lost its attachment bolts. The missing fenders impacted the performance of the engine, since mud was thrown onto the air intakes. The transmission worked reliably, but the engine had a tendency to overheat at high RPM. Upon returning to the factory, the KV-13 was subjected to a week of repairs. The tank resumed trials on October 13th. The pelting of air intakes and engine overheating continued. The track tension issues were not solved. Old issues were followed by gearbox problems, which cropped up against during the following two outings on October 16th and 19th.
Nearly every trial run was accompanied by malfunctions.
The KV-13 travelled for a total of 715 km in September-November of 1942, which revealed about 50 various defects. After 565 km, the T-34 tracks and drive sprocker were replaced with KV tracks and sprocket. It's hard to say that this radically improved the situation. The track slipped three times during the trial run on November 3rd. Different issues were discovered, such as a large number of openings in the floor of the tank, through which water seeped in.
The final configuration of the KV-13, summer of 1943. It was already a museum exhibit at this point. The second KV-13 variant is seen behind it, which shared its predecessor's fate.
Despite the fact that the tank continued participating in trials until the end of 1942, it was clear that the design was unsuccessful. ChKZ understood it as well. It's not surprising that work on an improved KV-13 began in November of 1942. This tank was noticeably different from its predecessor. As for the first KV-13, it was a step towards the IS-2, the best Soviet heavy tank of the war, and perhaps the best heavy tank of the war in general.