KV-4 Bykov. Illustration by Pavel ‘Carpaticus’ Alexe.
Soviet Union (1941)
Super Heavy Tank – Blueprints Only
The KV-4 heavy tank program was an ambitious development over previous heavy tank projects developed at the LKZ plant in Leningrad. Catalyzed by the rumors of German heavy tank developments, the KV-4 was to have thick 120 mm or more of armor and a powerful 107 mm gun. Almost two dozen different proposals were designed by the factory’s engineers, with various features and layouts. One of these was designed by Bykov, which featured two rotating turrets and a long, well-armored hull. Neither this nor any of the other KV-4 proposals left the drawing board, as the focus shifted towards developing the KV-5, and after the start of the invasion of the Soviet Union, these projects were scrapped.
Development
–Dear reader: A more detailed development analysis of the KV-4 program can be found in the KV-4 Dukhov article–-
The KV-4 program had its origins in a pivotal letter dispatched by the Soviet Intelligence Services to the Soviet military on 11 March, 1941. This letter contained critical information concerning a formidable German heavy tank, boasting an impressive 90-tonne weight and armed with a formidable 105 mm gun. The revelation raised alarms within the Main Directorate of Armed Forces (GABTU), given that the heaviest tank in Soviet service at that time was the KV-1, weighing in at 45 tonnes and plagued by mechanical unreliability, rendering it entirely unsuitable for mass production. While the LKZ (Leningrad Kirov Factory), home to the SKB-2 design bureau responsible for the KV-1, had previously conceived heavier tanks, like the KV-220 and KV-3, these designs were still deemed inadequate to counter the suspected German heavy tank threat.
Consequently, on 21 March, the GABTU issued the original specifications for the KV-4 project. The tank was to weigh approximately 70 tonnes, armed with a 107 mm ZiS-6 gun in a turret and a 45 mm 20-K in a secondary turret. The powerplant designated was a potent 1,200 hp enhanced aviation diesel V-12 M-40. Armor requirements were set at 120 to 130 mm for the front, sides, and rear. The deadline for the complete blueprints was established as 17 July.
However, by 7 April, the requirements underwent another revision. The KV-3 was slated for resurrection with substantial improvements to its specifications. Consequently, the KV-4’s weight increased to 75 tonnes, with its armor bolstered to 135 mm. The deadline was also moved forward to 15 June. Notably, LKZ was also tasked with developing the KV-5, a massive 90-tonne tank sporting 150 to 170 mm of armor, while still being armed with the 107 mm ZiS-6 gun. It was expected to compete against the KV-4, with trials anticipated to commence in early 1942. In the interim, until one of these designs entered mass production, the KV-3 was to serve as a temporary solution.
The program’s Chief Designer was J.Y. Kotin, who, in light of the generous program requirements, adopted an unconventional approach to the design process. He initiated a competition among the engineers at SKB-2 and even offered financial incentives for the top seven best designs. One of these KV-4 designs was created by a certain Bykov, which was awarded 500 rubles for receiving 7th place.
The Designer – Bykov
Unfortunately, at the time of writing, there is no information about the designer of this KV-4 proposal, known so far only by the name Bykov, with unverified sources claiming “V. Bykov”. While there were several soldiers and tankers in the Soviet Army with this name, there is no way to tell if they match this designer. It was possible that an engineer would be sent to the front, especially if they had military training. One such example was SKB-2 engineer L.N. Pereverzev, who at the start of the war was transferred to a tank mobile repair battalion.
Another possibility is that “Bykov” was actually N.V. Barykov, an experienced SKB-2 engineer, and the text was incorrectly rewritten or damaged.
Design
The general layout of the tank was conventional, with the main turret in the center of the hull and powerplant in the rear. At the front, a secondary turret was added, on the right side of the hull. The main turret was mounted higher up than the secondary turret to allow for more internal space, as well as better clearance for the main gun. The running gear consisted of seven steel roadwheels per side, sprung by torsion bars. The idler was at the front.
The main turret had a rounded heptagonal shape, with the sides angled inwards. Although the blueprints do not provide much detail, a machine gun cupola with a rotating periscope was present. However, the blurriness of this cupola might suggest that it was removed in later design stages.
Directly underneath the main turret ring was the fighting compartment, 107 mm gun ammunition stowage racks, fuel tanks (on the floor), and part of the engine bay, which was separated by a firewall. The final drive and sprocket were in the very rear end of the hull, with the air cooling system above. To save space, the fuel tanks were modeled around the torsion bars running across the hull’s width.
Side cutout view of Bykov’s KV-4, showing the different components, such as engine compartment, ammunition stowage, and armament. Source: ASKM via Stalin’s Supertanks IS-7Transverse view of the hull, showing the fuel tanks and ammunition stowage for the 107 mm gun. Source: ASKM via Stalin’s Supertanks IS-7Top view of Bykov’s tank. Next to the secondary turret, the flamethrower and 45 mm gun ammunition stowage can be seen.
Crew
The crew of Bykov’s KV-4 consisted of 8 crewmembers: commander, main gunner, 2x main loaders, secondary gunner, secondary loader, driver, and bow machine gunner/radio operator.
The gunner was seated to the left side of the gun, with the commander likely behind him. The commander had a rotating cupola armed with a DS-39 machine gun. Unfortunately, the blueprints do not show enough detail, but it is likely that it was intended to mount several periscopes or vision slits, like on other KV-4 tanks. The main gun loaders would load the main gun, one operating the breech and the other lifting the shells from the hull stowage racks.
In the hull, the driver was positioned in the center, with a slight offset towards the left, to allow for additional space for the secondary turret to his right. The driver, aside from driving the tank, would also operate the flamethrower to his left. The bow machine gunner sat on the right side of the hull, in front of the secondary turret fighting compartment. He likely would have been in charge of operating the 10-R radio system. The secondary gunner and secondary loader sat inside the smaller turret to the left and right of the gun respectively, though oddly, the secondary ammunition was stowed on the right side of the hull, underneath the flamethrower.
Armor
The armor on Bykov’s KV-4 design maintained the typical required thicknesses. Frontal plates were 125 to 130 mm thick, while side and rear plates were 125 mm thick. Much of the design maintained the same angles and features as most other KV designs, such as the stepped frontal hull design and split rear hull plates for engine air cooling intake. The turrets were made out of pressed armor plates with a thickness of 125 mm. Hull and belly armor varied between 30 and 50 mm thick plates.
Armament
All KV-4 proposals were to be armed with the new 107 mm ZiS-6 gun developed at Plant No.92 as well as a variety of other weapons, including a 45 mm 20-K gun, several 7.62 machine guns and in some cases, even a flamethrower.
In Bykov’s design, the 107 mm gun was mounted in the main turret in the center of the chassis. This gun had excellent ballistic values, having a muzzle velocity of 800 m/s and penetrating 115 mm of armor from 1,000 m. The large, single piece shell weighed 18.8 kg and was 120 cm long.
The 45 mm 20-K gun was still the most prevalent gun within the Soviet armored forces and was still capable of dealing with a variety of lightly armored targets. It was placed in a secondary turret at the front of the hull. This gun had a muzzle velocity of 750 m/s.
For protection against infantry, Bykov’s KV-4 had a DS-39 7.62 mm machine gun in a ball mount in the front of the hull and one in a small rotating cupola, on top of the main turret. The tank also featured a flamethrower mounted in the left side of the frontal armor plate.
Fate and Conclusion
By 9 May, the competition concluded, and the winners were announced. In total, between 24 and 27 proposals were submitted, resulting in 11 prizes awarded to 13 designers, as some designs earned the same ranking, and a few designers collaborated.
The leading design was that created by N.L. Dukhov, which maintained a standard layout, largely influenced from the KV-220. Second place was initially awarded to a group of three engineers working together, resulting in a vehicle with the main gun enclosed in a casemate with the secondary turret on top. However, this design was later disqualified due to the fact that the original requirements meant that the KV-4 was to have the main gun in a fully rotating turret. Instead, what was originally third place was moved up to second and so forth. This design was by experienced engineer N.V. Tseits, who focused on making a very low-profile hull by enlarging the turret. Bykov’s design was one of the three engineers to be awarded third place, alongside Pereverzev and Kalivod.
After the competition, work on the KV-4 disappeared from the records. Instead attention was shifted to the KV-3 and KV-5, the latter which was based largely on design features of the KV-4 projects. Work on these two tanks would continue until 22 June 1941 when the Axis powers invaded the Soviet Union, work on the projects stagnated. Shortly after, between July and August, the staff of the SKB-2 design bureau were evacuated to the Chelyabinsk Tractor Plant (ChTZ), while the LKZ plant fully transferred towards the production and maintenance of KV-1 tanks. With the move, the super heavy tank KV-4 and KV-5 projects were abandoned, and never picked up again.
KV-4 Bykov. Illustration by Pavel ‘Carpaticus’ Alexe.
KV-4 Bykov Specifications
Dimensions (L-W-H)
9.5 x 4.03 x 3.65 m
Total weight, battle-ready
98.6 tonnes
Crew
8 (commander, main gunner, 2x main loaders, secondary gunner, secondary loader, driver and bow machine gunner/radio operator.
Propulsion
1,200 hp diesel V-12 M-40 with 4 TK-88 turbochargers
Speed
36 km/h (hypothetical)
Armament
107 mm ZiS-6 (F-42)
45 mm 20-K
1 or 2 DS-39 machine guns
1 flamethrower
Armor
Front: 130 mm
Sides & rear: 125 mm
Top: 40 mm
Belly: 50 mm
KV-4 Grigoriev & Pavlov). Illustration by Pavel ‘Carpaticus’ Alexe
Soviet Union (1941)
Super Heavy Tank – Blueprints Only
Development
–Dear reader: A more detailed development analysis of the KV-4 program can be found in the KV-4 Dukhov article–-
At the start of 1941, the Soviet Union’s heavy tank fleet consisted of the KV-1, which had its share of problems, including poor mobility and mechanical unreliability, and the hopelessly obsolete T-35A. To address these shortcomings, work had already begun in 1940 on creating a heavier and better-armored KV-1, leading to designs like the T-150, KV-220, and Object 222.
However, in March 1941, two reports would drastically change the course of Soviet heavy tank development. Firstly, the testing of German anti-aircraft guns of calibers 88 mm and 105 mm concluded that future Soviet heavy tanks would need at least 130 mm of armor to withstand incoming fire from these guns. Secondly, and likely more importantly, reports on German heavy tank developments were presented to the Soviet officials. The most unnerving of these tanks was the Pz.Kpfw.VIII, which was to weigh 90 tonnes and be armed with a 105 mm gun.
On March 21, 1941, the Main Directorate of Armed Forces (GABTU) issued requirements for the development of the KV-4 (Object 224), specifying a 70 to 72-tonne heavy tank armed with a 107 mm ZiS-6 gun in the turret, a secondary 45 mm 20-K gun, and at least three DT machine guns. The armor was to be 130 mm thick at the front and 120 mm on the sides and rear, with a powerful 1,200 hp M-40 engine to provide propulsion, and a six-man crew. The deadline for the tank design was set for July 17, with prototype building and armament testing scheduled for October.
However, on April 7, 1941, the GABTU revised its requirements for the KV-4. The weight was increased to 75 tonnes, and the armor thickness was raised to 135 mm at the front and 125 mm on the sides and rear. The deadline for blueprints was tightened to June 15. At the same time, the GABTU requested an even heavier tank, the KV-5, weighing at least 90 tonnes with 170 mm frontal armor and 150 mm on the sides, to be developed alongside the KV-4, as well as the KV-3 (Object 223), also armed with the same gun, but with only 120 mm of frontal armor and weighing 68 tonnes.
The Leningrad Kirov Plant (LKZ), with its SKB-2 design bureau, began work on the KV-4 on April 10, 1941, under the leadership of J. Y. Kotin. In an unusual approach, Kotin organized a competition among the SKB-2 engineers to encourage innovation in the tank’s design. Over 20 engineers submitted more than 20 individual designs. The winning design, created by N. L. Dukhov, resembled an enlarged KV-220. Second place went to a design by K. I. Kuzmin, P. S. Tarotko, and V. I. Tarapatin, featuring the main gun in the hull and a secondary gun in a small turret. Third place was awarded to N. V. Tseits, who proposed a tank with a low hull and a large turret to compensate for limited hull space. One of the designs was submitted by a duo of designers, Grigoriev and Pavlov, however, their project was not rewarded in the competition.
Designers Grigoriev & Pavlov
Unfortunately, not much is available about the two designers of this tank. Based on the little information available, both were likely young, recent graduates from the Leningrad Technical Institute. D.E. Grigoriev’s first work at LKZ was on a mine plower, designing and building it using various methods of mine deactivation. For his work, Grigoriev would be amongst three SKB-2 engineers to receive the medal ‘For Labor Valor’. It is uncertain who D. G. Pavlov was, since his name is only mentioned by author Maxim Kolomiets in this context. Additionally, it most likely was not Soviet Army General D.G. Pavlov. Another possibility is that Kolomiets made a mistake, and that the person was actually B.P. Pavlov, a recent graduate student from the Military Academy of Mechanization and Motorization of the Red Army, who had worked on the layout and design of the KV-1, and was deputy designer of the KV-220 (later chief designer) as well as senior engineer of the KV-3 at the ChTZ.
Despite there being over 20 KV-4 designs, the one presented by the Pavlov and Grigoriev duo was one of the more unorthodox. The main turret was placed at the rear of the hull, while the powerplant was moved towards the front. At the bow of the hull, the final drive and engine air intake were placed. The driver’s position was in the center of the hull, in front of the fighting compartment but behind the engine, which was separated by a firewall. To his right was the secondary turret, which had limited traverse due to the protrusion in the upper hull for the driver’s position. The upper frontal plate of the hull was heavily angled, while the lower plate was curved, as opposed to flat on most KV tanks. The main turret had a large, hexagonal shape, with no particular details drawn in the blueprints. The fuel tanks were in the rear of the hull. Ammunition was stored horizontally, stacked underneath the turret ring.
One of the blueprints of the Grigoriev and Pavlov KV-4 design. Source: ASKM via Stalin’s Supertanks IS-7Second blueprint presented by the duo. Note the placement of the secondary turret, on the extreme right side of the hull, with an overhang over the tracks. Source: ASKM via Stalin’s Supertanks IS-7
Crew
The crew consisted of 6 men, commander, main gunner, main loader, secondary gunner, secondary loader, and driver. The gunner was seated to the left side of the gun, while the commander was seated behind him. Unfortunately, there are no additional details available, such as what equipment they had, aside that the commander likely operated the 10-R radio. The right side of the gun housed the main loader, which had the task of lifting the shells from the hull into the gun breech.
In the secondary turret were the secondary gunner and loader. They shared a single service hatch in the roof of the secondary turret. They were separated from the rest of the crew.
Lastly, the driver’s position was on the left side of the hull, in front of the fighting compartment. Directly to his left was a flamethrower, which he likely had to operate.
Armament
The 107 mm ZiS-6 was the main armament of all KV-4 tanks. It was developed at Plant No.92 by V.G. Grabin in a very short time. Due to its excellent penetration capabilities, it would equip all of the new Soviet super heavy tanks. In the summer of 1941, the gun was tested on a KV-2, using a KV-3 gun mantlet. There, the excellent power was proven, being able to penetrate 120 mm of armor angled at 30° from 1,600 meters. A total of 120 rounds were stowed in the hull for this gun.
The secondary gun was the 45 mm 20-K gun, which was the most numerous gun on Soviet tanks at the time. Although it was obsolete on a 1941 design, it was still a capable gun for soft-skin targets. The 170 ammunition shells were stowed behind the turret, on the hull floor.
As the Soviets mounted coaxial guns to the right of the main weapon, the KV-4 designed by Grigoriev and Pavlov was equipped with two machine guns (either DT or DS-39 models) with 4,000 spare ammunition. Additionally, a flamethrower was present as well, a weapon which a few other KV-4 designs featured. However, it was mounted to the left of the driver, meaning only he could operate it, and because his position was so far back, with the engine right in front, this could have been a serious fire hazard, as well as reducing the flamethrower’s effective range. The flamethrower had 150 liters of fuel.
The KV-2 used during the ZiS-6 gun trials, mounted with a KV-3 mantlet, June 1941. Source: Warspot
Powerplant
All KV-4 tanks were to use the aviation diesel M-40 engine with four TK-88 turbochargers, outputting 1,200 hp. This engine had also been developed at LKZ a few months prior. The top speed was to be 40 km/h, though that was slightly optimistic.
The M-40 aviation engine. Note the two TK-88 turbochargers. Source: Yuri Pasholok
Fate
After the winners of the competition were announced, work on the KV-4 program halted, focus shifting to the KV-3 and KV-5. However, with the start of the war on 22 June 1941, and the bleak situation on the front, these heavy tanks were further pushed back and delayed. The KV-4 and KV-5 were ultimately canceled in mid-July, when a large portion of the SKB-2 design bureau was evacuated from Leningrad to Chelyabinsk, at the ChTZ, due to the approaching German forces.
Conclusion
The ever-changing specifications, tight deadlines, and sheer complexity of the design process, including in a competition among engineers, made the KV-4 a short-lived but interesting project. Kotin’s idea of starting a design competition led to a range of innovative designs. This dynamic period in tank development reflects the urgency and adaptability of Soviet efforts to counter the threat of the perceived German super-heavy tanks, but also the wrong direction which Soviet tank design was taking. With the start of the war and cancellation of most heavy tank projects, focus went to improving existing tanks, as well as using trialed designs. This is how the KV-1S was born, and while far from perfect, it was arguably the best Soviet heavy tank at the time, especially considering the often-ignored fact that it worked.
KV-4 Grigoriev & Pavlov). Illustration by Pavel ‘Carpaticus’ Alexe
KV-4 Grigoriev & Pavlov Specifications
Dimensions (L-W-H) (approx.)
8.5 x 4 x 3.6 m
Total weight, battle-ready
91 tonnes
Crew
6 (commander, main gunner, 2x main loaders, driver, secondary loader)
Propulsion
1,200 hp diesel V-12 M-40 with 4 TK-88 turbochargers
Speed
40 km/h (hypothetical)
Armament
107 mm ZiS-6 (F-42)
45 mm 20-K
2x DT machine guns
1 flamethrower
Armor
Front: 125 mm
Front UFP: 100 mm
Sides & rear: 125 mm
Top: 40 mm
Belly: 50 mm
KV-4 (Object 224) Turchaninov. Illustration by Pavel Alexe.
Soviet Union (1941)
Super Heavy Tank – Blueprints Only
The KV-4 was conceived in spring 1941 to deal with the rumors of new, powerful German heavy tanks. Its development process consisted of a design competition between several SKB-2 workers. One of these designs was made by the young engineer G.A. Turchaninov, heavily resembling an enlarged KV-3, which was being developed simultaneously. However, his design was not taken into consideration, and has been largely forgotten since.
Development
–Dear reader: A more detailed development analysis of the KV-4 program can be found in the KV-4 Dukhov article–
The KV-4 (Object 244) Soviet heavy tank program was initiated by the Soviet Union in response to the German expansion over Europe, despite the Molotov-Ribbentrop Pact. The program aimed to develop a new heavy tank to match the alleged German heavy tanks which were rumored to be in development. The KV-1 heavy tank, which was rushed into service due to Stalin’s requests, had significant quality, weight, and reliability problems. The most advanced heavy tanks in development at the time were the KV-150 and the KV-220, which had even more serious reliability issues and were still in the prototype testing phase. Thus, the GABTU set out to develop a new heavier tank to match the suspected German tanks.
The requirements for the new heavy tank were laid out on 21 March 1941, which included a 107 mm ZiS-6 gun, armor of 120 mm to 130 mm all-round, a weight between 70 to 72 tonnes, a M-40 diesel aviation engine with 4 TK-88 turbochargers for propulsion, a secondary 45 mm gun, at least three 7.62 mm machine guns, and a flamethrower. The development of the KV-4 took place at the LKZ (Kirov Leningrad Factory) SKB-2 design bureau, the same office responsible for all the previous KV tanks. The first prototype production was assigned to the Izhora plant based on LKZ drawings. Blueprint deadline was set for 17 July 1941.
The GABTU edited their request on 7 April, demanding a heavy upgrade of the KV-220, named KV-3 (Object 223), that would act as a stopgap until the heavier tanks were ready, and an even heavier tank named KV-5 (Object 225). To better fit the KV-4 between the two new vehicles, its weight threshold was lifted to at least 75 tonnes, and 125 mm of armor at the sides. The deadline was tightened to 15 June. Work on all 3 tanks commenced at SKB-2 design bureau, which was headed by J.Y. Kotin.
Kotin challenged his engineers to a design competition, and 24 designers entered the competition with equally as many different designs presented. The winners were announced on 9 May, with 13 designers having received monetary prizes. However, work on the KV-4 stagnated severely after the competition was ready. Most of the efforts shifted to the KV-5, which was developed based on knowledge from the KV-4. However, the KV-5 was in a very early stage when the German Reich began their invasion of the Soviet Union, and their quick advance into Soviet territory put great strain on the LKZ tank factory, which had to switch focus on optimization and repair of KV-1 and KV-2 tanks.
By September 1941, the German forces were advancing towards Leningrad, and the SKB-2 design bureau was ordered to evacuate to the ChTZ in Chelyabinsk. The KV-4 project was canceled due to the evacuation, and no prototypes were produced.
One of the designs submitted was by the young Military-Engineer G.A. Turchaninov, though he was not rewarded for his tank design.
G.A. Turchaninov
During his studies at the Military Academy of Motorization and Mechanization, Turchaninov worked on his undergraduate practice at the SKB-2 design bureau. He worked on the general design of the SMK tank, as well as a mine-clearing roller. Later, he was part of the design team of the KV tank, both in terms of general layout, but also the transmission. By 1940, he had finished his studies and began working at SKB-2 as a Military Engineer. With the outbreak of the war, he began work on crew training on KV-1 tanks and the fortifications of Leningrad.
Group photo of engineers at the first KV trials, 1940. G.V. Turchaninov can be seen in the last row, pointed with the arrow. Photograph source: Constructors of combat vehicles
Design
Unlike many of the other KV-4 tanks designs, Turchaninov’s design was very sensible in layout, without any extravagant features. It was very similar to the final KV-3 layout, with a rounded turret and standard hull layout, a stepped front portion, much like on the earlier KV tanks, central turret and fighting compartment, and powerplant and final drive in the rear.
The most bizarre feature, and likely a flaw in the design, was the mounting of the 45 mm 20-K secondary gun in the center of the front hull plate. While this option offered the maximum firing angle, its range was still inferior to that of competing KV-4 designs, which usually placed the secondary gun in a separate turret or coaxial to the main gun. However, the main problem with this layout was that there was no room in the hull for a designated gunner. Thus, the driver was forced to be its gunner.
The engine, as requested by the GABTU, was the experimental 1,200 hp M-40 aviation engine, capable of running on kerosene and diesel. It was boosted with four TK-88 turbochargers. The fuel tank was over the 5th roadwheel, underneath the ammunition stowage racks.
Side cutout view of Turchaninov’s KV-4 proposal. Source: Stalin Supertanks IS-7Top view of the tank, showing the rounded turret edges and traverse of the hull-mounted secondary gun. Source: Stalin Supertanks IS-7
Crew
The tank’s crew was of 6, consisting of commander, main gunner, 2x main loaders, driver/secondary gunner, and secondary loader/flamethrower operator.
The gunner and commander were seated in the main turret, on the left side of the main gun, with the commander behind the gunner. The two loaders were on the other side of the gun, with one loading the shells in the gun and the other lifting them up from the hull stowage racks.
The driver was seated to the left side of the hull, but due to the central mounting of the secondary gun in the hull, the driver was also forced to aim and fire the gun. The loader was seated on the right side of the hull, loading the secondary gun but also firing the flamethrower, placed on the extreme right side of the hull.
Armament
The main armament used on all KV-4 proposals was the 107 mm ZiS-6 gun. It was developed by V.G. Grabin at Plant No.92, starting in December 1940 and finishing first prototype in May 1941.
The gun was an excellent anti-tank weapon, with a muzzle velocity of 800 m/s, and during trials, was able to penetrate 120 mm of armor angled at 30° from 1,600 m.
Secondary armament consisted of the older 45 mm 20-K, which was still the most widely used gun on armored vehicles at the time. Although it was completely dated for anti-tank use, it was still a cheap and readily available gun for soft-skin targets and infantry. The main problem in Turchaninov’s design was its position. While most designers placed it in an independent turret or coaxially to the main gun, Turchaninov placed it in the front hull plate, limiting its traverse to 30° in both directions.
For close-range infantry defense, the tank was equipped with three to four 7.62 mm DT machine guns. An unspecified type of flamethrower was mounted on the extreme right side of the front plate, with 30 shots.
Armor
Like most KV tanks, Turchaninov’s KV-4 had the same armor thickness all around, 125 mm. Only the turret’s roof and engine/hull’s deck plates were just 40 mm thick, while the hull’s belly was 50 mm thick.
The shape of the turret, clearly inspired by the KV-3’s (Object 223), is noteworthy. It is important to note, however, that this rounded shape would have been achieved via stamping the RHA plates, rather than casting. Soviet industrial technology severely lacked the ability to reliably cast such thick armor plates before the war, and this would be a continuous issue throughout the war.
Fate of the Project
By the end of May, the competition was over, the winning designs were announced, and their respective designers awarded accordingly. Unfortunately, Turchaninov was not amongst these. There are no documents regarding why certain designs won and others did not. We may only speculate based on the design looks and the engineers’ relation with factory director I.M. Zaltsman and head of SKB-2 J.Y. Kotin, the ‘judges’. Winner of the competition was N.L. Dukhov, who proposed an enlarged KV-220 design. After the competition ended, work on the KV-4 completely stalled, with focus shifting to the KV-3 and KV-5. Work progressed through summer 1941 and as with the start of the war, but was halted in September, when the SKB-2 design bureau was transferred from Leningrad to Chelyabinsk due to German forces advancing towards the city. Work on the heavy KVs never restarted.
Photo collage showing the front and side of the KV-3 mock-up. Source: Yuri PasholokPhoto collage showing the side of the KV-3 mock-up. Note the complex turret shape, including the bulge for the commander’s cupola. Source: Yuri Pasholok
Conclusion
The design path chosen by Turchaninov seemed like a fail-proof formula, heavily inspired by the KV-3, using the complex turret shape and standard hull layout. Despite this, the poor placement of the secondary armaments and lack of innovation likely put this design at a disadvantage and was not considered. As a whole, in spite of the efforts of Turchaninov and the other designers, the KV-4 program proved to be a failure, born from the impulsive acts of a disorganised military leadership, and killed by the realities of war.
KV-4 (Object 224) Turchaninov. Illustration by Pavel Alexe.
KV-4 Turchaninov Specifications
Dimensions (L-W-H) (approx.)
9.8 x 4 x 3.82 m
Total weight, battle-ready
89.5 tonnes
Crew
6 (commander, main gunner, 2x main loaders, driver,, secondary loader)
Propulsion
1,200 hp diesel V-12 M-40 with 4 TK-88 turbochargers
Speed
38 km/h (hypothetical)
Armament
107 mm ZiS-6 (F-42)
45 mm 20-K
3-4x DT 7.62 mm machine guns
Flamethrower (30 shots)
Soviet Union (1941)
Super Heavy Tank – Blueprints Only
The KV-4 heavy tank program was born from the perceived need for a much more powerful heavy tank than its predecessors. It was designed at the SKB-2 design bureau via a thorough competition. Thus, several different versions were proposed, including the one by G.N. Moskvin. Although the tank had a very traditional design, his design was not rewarded in the competition and forgotten. Nowadays, it is playable in Wargaming’s ‘World of Tanks’ video game.
KV-4 by Moskvin, as represented in World of Tanks. Though several details are missing or inaccurately modeled, it offers a good overall perspective on its design. Source; in-game screenshot
Development
–Dear reader: A more detailed development analysis of the KV-4 program can be found in the KV-4 Dukhov article–
The development of the Soviet KV-4 heavy tank, designated as Object 224, began in March 1941. The development of a 90-tonne German tank was reported in a letter from the Soviet Intelligence Services on 11 March 1941, which alarmed the Soviet military officials, leading to the GABTU requesting the development of a new super-heavy tank. The KV-4 was to weigh 70-72 tonnes, be armed with the 107 mm ZiS-6 in the turret, and have 130 mm thick armor at the front and 120 mm towards the sides and rear. The deadline for the tank design was set to 17 July 1941, with the prototype building and armament testing set for October of the same year.
However, on 7 April 1941, the GABTU revised their requests, raising the weight to 75 tonnes and the armor thickness to 135 mm at the front and 125 mm towards the sides and rear. The blueprints’ deadline was also narrowed to 15 June 1941. At the same time, the KV-5 was requested, a tank that would weigh at least 90 tonnes, have 170 mm of armor at the front, and 150 mm at the sides. Additionally, the KV-3 was ‘revived’ and improved to fulfill a stopgap role until the KV-4 and KV-5 tanks were ready for production.
At LKZ (Kirov Leningrad Factory), the SKB-2 design bureau began work on the KV-4 on 10 April 1941. The head of the project was J. Y. Kotin, who created a competition between the SKB-2 engineers, with the top few designs receiving financial rewards. Over 20 engineers competed, submitting over 20 individual designs. The winning design was that of N. L. Dukhov, which was essentially an enlarged KV-220. Second place went to the K. I. Kuzmin, V. I. Tarotko, and P. S. Tarapatin trio, who submitted a tank with the main gun in the hull and secondary gun in a small turret. Third place went to N. V. Tseits, who submitted a tank with a very low hull but large turret to offset the lack of hull space.
Despite the efforts put into the development of the KV-4, it never saw production. The outbreak of World War II on 22 June 1941 disrupted the Soviet tank development program, and the resources were redirected to immediate production of already existing designs. Additionally, the heavy losses suffered by the Soviet army during the initial stages of the war showed that the development of heavy tanks was not a priority. The KV-4 project was eventually canceled, and the KV-3 was abandoned as well, with the resources redirected to the development of the IS series of tanks.
G.N. Moskvin
Born in November 1909 in Nizhny Novgorod, Grigory Nikolaevich Moskvin began working at a waterway administration and later at the Svetlana Plant. In 1931, he was drafted into military service, and shortly thereafter was assigned to the design bureau of the Artillery Institute (SKB-4) at the Leningrad Kirov Plant. There, he would work on various self-propelled gun systems, such as the SU-14, SU-5 series of SPGs, SU-6 and armament system of the T-111 tank. He also worked on the design of tanks at Plant No.185, but was fired due to his brother’s arrest. In 1940, Moskvin was hired by the SKB-2 heavy tank design bureau. Here he worked on the T-50 light tank, KV-220, KV-4, and, after SKB-2s transfer to ChTZ and the start of the Second World War, he worked on the KV-7, KV-13, SU-152, and ISU-152. He also participated in the design of the well-known ‘pike nose’ of the IS-3 heavy tank. After the war, he worked on heavy tank armor, as well as other projects, such as the Object 740/750 and PST-54. Prior to his retirement in 1972, he worked on the development of the Lunokhod lunar rover project. He later passed away in 1986, aged 77.
Moskvin had been awarded the Order of Lenin, The Stalin Prize, Order of the Patriotic War and Order of the Badge of Honor.
G.N. Moskvin in 1943. Source: TiV No.11 2013
Design
Unlike most other KV-4 designs, Moskvin provided detailed drawings of his design, from all relevant angles. The tank was to weigh 101 tonnes on paper, being 9.573 meters long, 4.03 m wide and 3.74 m tall.
The tank had a standard layout, with the turret in the center and the powerpack in the middle. The hull was akin to most previous KV tanks, with a stepped front plate, flat sides, and a large engine deck, with its unique engine cooling system vent at the rear.
The main turret was very large, to be able to accommodate both the large main gun and the secondary turret, mounted at the rear of the turret. Ammunition was stowed underneath the main turret ring, for both the main and secondary guns.
The mantlet was mounted over the frontal curved turret plate and protected by two ‘fins’ on either side, protecting the internal mechanism from outside elements. The side walls were curved, offering great effective protection frontally, with small arm firing ports in the center. The secondary turret had a cupola with an unspecified amount of periscopes, for clear battlefield vision.
The engine was a 1,200 hp M-40 aviation engine, boosted with the help of four TK-88 turbochargers. It was connected directly to the final drives and sprockets, at the rear.
Blueprints of Moskvin’s KV-4 design, with a cutout view of the interior from the side, and top view of the hull interior Source: Stalin Supertanks IS-7Front view of the tank, as well as a cutout of the front and top of the turret. Source: Stalin Supertanks IS-7
Crew
The crew likely consisted of 8 men, commander, main gunner, 2x main loaders, secondary gunner, secondary loader, driver, and bow machine gun/radio operator.
The gunner sat in the front of the turret, to the left side of the gun, and the commander sat right behind him. The two main loaders were seated on stools slightly facing the gun, on its right side. From here, the loader in the front could pass on shells from the front side wall or hull, while the rear loader could operate the breech and load the shells. Behind the gun breech, the two crewmen for the secondary turret were seated, gunner and loader. They were seated on either side of the 45 mm gun with enough clearance from the main gun breech.
In the front of the hull, the driver and radio operator had their positions. The latter would operate the flamethrower, while the driver operated the ball-mount machine gun.
Armament
The main armament was the 107 mm ZiS-6 gun developed at Plant No.92 by V.G. Grabin in early 1941. It was specifically developed to be fitted on the KV series of heavy tanks. It offered excellent anti-tank capabilities, with an alleged penetration of 120 mm angled at 30° from 1,600 meters. The shells were 120 cm long and weighed 18.8 kg.
Secondary armament was the 20-K 45 mm gun mounted in the secondary turret, as well as 2 or 3 DS-39 7.62 mm machine guns which were mounted in ball mounts and coaxially. A flamethrower was also mounted in the front of the hull. These secondary weapons offered, on paper, adequate offensive power against both soft-skin vehicles and infantry.
Armor
The massive 101 tonne tank was very well protected for its time. The front hull and turret plates were 130 mm thick, while the side and rear plates were 125 mm thick. The secondary turret was also 125 mm thick all around, offering great protection at the cost of a very cramped interior.
Fate of the project
After the announcement of the competition winners, work on the KV-4 did not progress any further. Engineers from SKB-2 shifted their attention to the design of the KV-3, with a full-scale mockup of it built. In June, work on the KV-5 also began, based on the winning designs of the KV-4, hence why its appearance was similar to that of the KV-4 by N.V. Tseits.
However, with the start of the war, the LKZ plant had to focus on the realities of war. More KV-1 tanks had to be built, and large numbers had to be repaired. As such, work on these super heavy tanks slowed down. The situation turned sour in August and September, when German forces were advancing towards Leningrad and the SKB-2 design bureau was transferred to ChTZ in Chelyabinsk. The heavy KV designs were left behind and never brought up again. Only the KV-3 was still being discussed, but it eventually faded away as well.
Conclusion
The KV-4 heavy tank program was born as a counter to the elusive German heavy tank developments (specifically the Löwe) which themselves hardly materialized. While the nature of development via competition brought up innovative features, the realities of the situation and the start of the war required the Soviet tank industry to focus on realistic targets. The Soviet tank arsenal was heavily outclassed across most elements, and while propagandistic stories of the T-35 and KV-1 shined, their unreliability and lack of combat effectiveness led to the need for better heavy tanks. The even heavier KV-4 was certainly not the answer.
KV-4 by G.N. Moskvin, ilustration by Pavel Alexe.
KV-4 Moskvin Specifications
Dimensions (L-W-H) (approx.)
9.573 x 4.03 x 3.74 m
Total weight, battle-ready
101 tonnes
Crew
8 (commander, main gunner, 2x main loaders, driver, secondary gunner, secondary loader)
Propulsion
1,200 hp diesel V-12 M-40 with 4 TK-88 turbochargers
Speed
40 km/h (hypothetical)
Armament
107 mm ZiS-6 (F-42)
45 mm 20-K
3x DS-39 7.62 mm machine guns
Flamethrower
Armor
Front: 130 mm
Sides: 125 mm
Rear: 125 mm
Roof & belly; 50 mm
KV-4 (Object 224) Buganov. Illustration by Pavel Alexe.
Soviet Union (1941)
Super Heavy Tank – Blueprints Only
In spring of 1941, the Soviets were working on KV-1 replacements of various sizes and weights, from the moderate upgrade T-150, to the much larger KV-220. But rumors of German super heavy tank projects catalyzed the development of a variety of even larger heavy tank projects, one of them being the KV-4. Its development consisted of a tank design competition, in which engineer K.I. Buganov participated. His unusual proposal was appreciated and was awarded sixth place in the competition.
Development
–Dear reader: A more detailed development analysis of the KV-4 program can be found in the KV-4 Dukhov article–
The Soviet Union was caught off guard in 1941 when intelligence reports revealed that Germany was developing a 90-tonne heavy tank armed with a 105 mm gun. The Soviets realized that their existing heavy tanks, the T-35 and the KV-1, were not enough to match the German threat. Work on developing heavier tanks commenced, and on 21 March 1941, the GABTU sent requirements to LKZ for the development of the KV-4, designated Object 224.
The KV-4 was required to be a 70-72 tonne heavy tank armed with a 107 mm ZiS-6 gun, a secondary 45 mm 20-K gun, and at least three DT machine guns. Armor was to be 130 mm at the front and 120 mm towards the sides and rear. Propulsion was to be provided by a 1,200 hp M-40 engine, also developed at LKZ, and the crew was to consist of six. The deadline for the blueprints was set for July 17, 1941.
On 7 April, the GABTU completely redesigned their request, introducing two new heavy tanks, the KV-3 (Object 223) and KV-5 (Object 225). The KV-3 was based on the previous KV-220, but with thicker 120 mm armor and the larger 107 mm ZiS-6 gun. It was intended as a stopgap vehicle, until the KV-4 and KV-5 were ready for production. The KV-5 was an even larger heavy tank, weighing at least 100 tonnes, and with armor of 170 mm at the front and 150 mm at the sides and rear. The KV-4, to better fit in between these two tanks, was also edited, with side and rear armor increased to 125 mm and weight threshold increased to at least 75 tonnes.
Work on the KV-4 began on April 10, 1941, with J. Y. Kotin as the head of the project. Kotin set up a competition for the tank’s design, encouraging engineers to come up with original and innovative features. Over 24 engineers submitted more than 20 individual designs, and the winning design was that of N. L. Dukhov. Second place went to K. I. Kuzmin, V. I. Tarotko, and P. S. Tarapatin, who designed a tank with the gun mounted in a central rotating sponson, with a smaller turret on top. Third place went to N.V. Tseits, with a more conventional design, featuring a very large turret and low-profile hull.
Work on the KV-4 stagnated after the end of the competition and was further delayed by the German invasion of the Soviet Union in June 1941. Despite this setback, the project was still active, but most of the focus had shifted to the KV-5, which was being developed by the winners of the KV-4 competition.
One of the designs submitted was by SKB-2 engineer K.I. Buganov. His tank’s unique and unorthodox features allowed his proposal to receive the sixth place prize of 1,000 rubles.
K.I. Buganov
K.I. Buganov began his military engineering career at the Experimental Design Machine-Building Department (OKMO), working on earlier Soviet tank designs, such as the T-28 and T-35, and in the late 1930s was transferred to the SKB-2 design bureau. After 1951, Buganov worked under Kotin at the Special Design Bureau of Heavy Tanks, as head of the hull and armor testing section, and in 1952, as part of VNII-100, he was chief-designer of the Object 907 medium tank.
Unfortunately, no further information on K.I. Buganov could be found publicly.
Design
The design presented by Buganov for the KV-4 was all but conventional. The engine and final drive were moved to the front, as opposed to the other KV tanks, and the main turret was moved to the rear, with the secondary turret on top. Furthest back were the fuel tanks.
To allow for a narrower hull but still a large turret, the turret had ‘lips’ protruding from either side of the hull, allowing for full 360° rotation. The main turret shape was peculiar as well, resembling a disk segment, with heavily sloped turret cheeks on either side.
The secondary turret was mounted on the right side of the main turret, and was of an usual design, akin to that of the T-50 light tank. It was capable of full 360° rotation, independent of the main turret.
Due to the narrowness and shortness of the hull, the engine bay area was exceptionally small. Thus, the entire air cooling and intake systems were moved into sponsons on the sides of the hull.
The ammunition was stowed both horizontally and vertically at the bottom of the fighting compartment, starting from the engine bay firewall, all the way through to the fuel tank.
Side and top cross-view of Buganov’s KV-4 design. Note the bizarre shape of the turret. Source: Yuri PasholokFront view of Buganov’s KV-4 and a cross-section of the engine bay, showing the cooling system sponsons. Source: Stalin Supertanks IS-7
Crew
The only information provided regarding the crew is the number, six n. However, due to the peculiarities of the design, it is challenging to accurately assign what roles these six crew members had, and where their exact positions were.
One hypothesis is that the crew consisted of a commander, main gunner, main loader, secondary gunner, secondary loader, and driver. The main gunner and commander would have been to the left of the gun, while the secondary gunner and loader would have been high in the secondary turret. The main loader would have been underneath the secondary turret, with ample access to the ammunition stowage below. The driver would have sat alone in the hull’s front and driven the tank, as well as fired the ball-mounted DS-39 machine gun.
Another theory is that the commander was also the gunner of the secondary turret. This would have given him an excellent view of the battlefield, but burdened him with the task of also aiming and firing the secondary gun. The sixth crew member in this case would be the radio-operator/bow machine gun, seated on the right side of the hull, opposite to the driver.
Armament
Much like the other KV-4 designs, the tank was armed with the new 107 mm ZiS-6 (F-42) gun, developed at Plant No.92 by V.G. Grabin in late 1940, early 1941. It was first tested on a tank platform on a specially modified KV-2 in June 1940, where it proved to be a formidable anti-tank weapon. It fired a 120 cm, 18.8 kg shell at 800 to 840 m/s, penetrating 115 mm of armor at 1,000 m.
The secondary armament consisted of a single 20-K 45 mm gun and 3x DS-39 7.62 mm medium machine guns, one in the hull (ball-mounted) and one mounted coaxially to each cannon.
The 20-K, though older in design, was still one of the most common guns used on Soviet armor, in tanks such as the BT-series fast tanks, T-26 and T-50 light tanks, or T-35 heavy tanks. Though comparatively obsolete by 1941 as an anti-tank weapon, as proven by the aforementioned tanks in the first stages of Operation Barbarossa, it was still a viable weapon against infantry and soft skin vehicles.
Armor
The hull was built out of 125 mm thick armored plates, stamped into shape, like on the rounded portion of the front, covering the transmission and final drive. The sides and rear were equally thick. The front of the main turret was 140 mm thick, with the cheeks angled outwards, angled at 45°. Less critical areas such as the hull belly and hull/turret decks were 50 mm thick.
Fate of the Project
After the competition had ended in May, nothing new was documented regarding the KV-4. Instead, most work shifted towards developing the KV-5. Things took a turn for the worse with the Axi’ invasion of the Soviet Union. As a result, LKZ had to shift focus from prototypes to KV-1 tank production and repairs. Nonetheless, work on the KV-5 still continued until August, when German forces began approaching Leningrad, home of LKZ. Consequently, the SKB-2 design bureau was disbanded and members were moved to ChTZ in Chelyabinsk. Aside from a few select projects, most tank programs were left behind, including the KV-4 and KV-5.
Conclusion
Born around the fear of German tank rumors, the KV-4 tank program was very short-lived and arguably a large waste of efforts and resources. Yet its circumstances, oversize proportions and capabilities, and, most importantly, the original tank design competition make it one of the more fascinating Soviet tank programs of the period. Buganov’s entry for the competition was in no way less peculiar, with a very bizarre approach in overall layout and using a variety of quirky features. For these ‘accomplishments’, he was awarded sixth place.
KV-4 (Object 224) Buganov. Illustration by Pavel Alexe.
KV-4 Buganov Specifications
Dimensions (L-W-H) (approx.)
7.7 x 3.8 x 3.32 m
Total weight, battle-ready
83 tonnes
Crew
6 (commander, main gunner, 2x main loaders, driver, secondary gunner, secondary loader)
Propulsion
1,200 hp diesel V-12 M-40 with 4 TK-88 turbochargers
Speed
50 km/h (hypothetical)
Suspension
Torsion bar, 8 wheels per side
Armament
107 mm ZiS-6 (F-42)
45 mm 20-K
3x DS-39 7.62 mm machine guns
Armor
Hull: 125 mm
Turret front: 140 mm
Turret rear: 110 mm
Top & belly: 50 mm
KV-4 Pereverzev variant with a shorter turret. Illustration by Pavel Alexe.
Soviet Union (1941)
Super Heavy Tank – Blueprints Only
Based on rumors of German heavy tank developments, the Soviets expanded their heavy tank programs in the spring of 1941. One of these projects was that of the KV-4, which entailed a competition among several designers from the SKB-2 design bureau. One of these proposed designs came from military engineer L.N. Pereverzev, who proposed a massive 100-tonne tank, with several unique features, such as tracks returning over the entirety of the hull. For his efforts, he was awarded 7th place in the competition.
Development
–Dear reader: A more detailed development analysis of the KV-4 program can be found in the KV-4 Dukhov article–
In early 1941, the Soviets were experimenting with KV-1 based tanks with increased armor and firepower, ranging from the T-150, which was essentially a KV-1 with 90 mm armor, to the KV-220, with 100 mm of armor, the 85 mm F-30 gun, and a longer hull. Other projects included the Object 221 and Object 222. The latter was set to enter mass production in July 1941, under the name KV-3. These tanks were designed and built at the LKZ (Leningrad Kirov Plant), by the SKB-2 design bureau.
Yet in a quick turn of events, on 11 March 1941, the Soviet Intelligence Services passed forward a report on the development of German heavy tanks. The heavy tanks Mark V, Mark VI and Mark VII were mentioned, weighing at 36, 45 and 90 tonnes respectively. The Mark VII, which can be assumed to have been an early proposal of the Pz.Kpfw.VII Löwe, greatly worried the Soviet officials. Aside from its heavy weight and supposedly thick armor, it allegedly was to be armed with a 105 mm gun.
If these German tanks were to become a reality, combined with the increasing threat of German invasion, the Soviets would have no realistic answer. The only true heavy tank in service at the time was the KV-1, and while it was adequately armed and very well protected, its weight, rushed development, and unreliable mechanics would make the KV-1 tank a problematic vehicle during wartime use. The heavier tanks, such as the T-150 and KV-220, relied on many of the KV-1’s components, with thicker armor and larger guns, while still failing to match the theoretical power of the new German heavy tank.
It was clear that a new heavy tank was needed, thus on 21 March, a new heavy tank was ordered to be developed at LKZ. Named KV-4, it was to be armed with the recently developed 107 mm ZiS-6 gun as well as a secondary 45 mm gun, several machine guns and a flamethrower. Armor was to be 130 mm at the front and 120 mm at the sides. Due to these measures, the weight of the tank was expected to be between 70 and 72 tonnes. To power this new heavy tank, a 1,200 hp M-40 aviation diesel engine with four TK-88 turbochargers was used. The SKB-2 design bureau at LKZ was tasked to develop the tank, which received index 224 (Object 224). The project deadline was 17 July.
Shortly thereafter, on 7 April, the heavy tank programs were reconsidered. Firstly, the KV-3 was to become a larger tank, based on the uparmored hull (to 120 mm) of the KV-220, with a new turret and the same 107 mm ZiS-6. The KV-4 was also changed, its side armor was increased to 125 mm, the weight estimate was increased to at least 75 tonnes and other small changes were made. Lastly, the KV-5 (Object 225) was to be designed, with the same 107 mm gun, but with 170 mm of frontal armor on a 100 tonne platform. Furthermore, the deadline for the KV-4 was brought forward to 15 June.
The head of the KV-4 project was head of SKB-2, J.Y. Kotin, but instead of appointing a design team, he would launch a design competition for the SKB-2 engineers. The goal was to incorporate as many original and innovative features as possible, and the best designs would be rewarded financially. With the funding and project approval from LKZ director I.M. Zaltsman, the competition began.
After evaluation, the results of the submitted designs were given on 9 May. Over a dozen different drawings and engineers partook. First place went to N.L. Dukhov, second to the trio of K.I. Kuzmin, V.I. Tarotko and P.S. Taraptatin. Third place went to N.V. Tseits. In total, 11 designs were awarded placements, with 13 designers receiving monetary prizes.
One of these awarded designs was by L.N. Pereverzev, whose design was ranked 7th, alongside the designs of Kalivod and Bykov. As an award for receiving 7th place, Pereverzev received 500 rubles.
L.N. Pereverzev
After graduating from the Military Academy of Mechanization and Motorization of the Red Army in 1939, Leonid Nikolevich Pereverzev started working as a military engineer at the LKZ SKB-2 design bureau. There, he would be involved in most of their projects, with the development of the KV-1, being chief engineer of the KV-150 and the gearbox designer for the KV-220, as well as partaking in the design of the KV-3 and KV-4. However, these would be his last tank design projects. In August of 1941, shortly after the German invasion, Pereverzev would be transferred to the newly formed 22nd PRB (Mobile Repair Battalion) at LKZ. Both he and his unit quickly received recognition for their skill in the repair and maintenance of KV-1 tanks.
By the end of the war, Pereverzev had received the Medal For Military Merit, Medal For Defense of Moscow, Medal For the Capture of Köningsberg, Medal For Victory against Germany in the Great Patriotic War of 1941-1945, Order of the Patriotic War (both I and II Degrees), and Order of the Red Star.
Leonid Nikolevich Pereverzev after the war. Source: Yuri Pasholok
Design
Of the two dozen KV-4 designs submitted, Pereverzev’s was one of the strangest. The turrets were arranged in a battleship-style layout, consisting of a smaller turret armed with a 45 mm gun in front of the main turret, armed with a 107 mm gun, allowing for good horizontal firing angles for both turrets. The engine, gearbox and final drive were located at the rear. The sprockets were extended far beyond the armored hull, in lightly armored housings, allowing for trench crossing capabilities, a design concept found as early as the British ‘tadpole tail’ found on the First World War Mark IV tank. This design choice allowed for a wider hull with more internal space, but greatly sacrificed the protection of the tracks, which had no cover over them and were susceptible to any kind of enemy fire.
The frontal hull section consisted of two main armor plates that were pressed into shape and welded together. The sides were more peculiar, as no drawings give a clear picture. Only the top cutout view drawing shows that the fighting compartment and fuel tanks were pushed underneath the track returns, protected by thick 125 mm armor. The rear consisted of the standard KV-style armor plates with room for air circulation for the cooling system.
Side cutout view of Pereverzev’s proposal, showing the track return riding over the hull, on small rollers. Note that the top machine gun turret had faded out. Source: ASKMTop cutout view of Pereverzev’s KV-4. On the top track, the sponson and subsequent sideskirts can be seen. Fuel and ammunition was stored here. Source: TsAMO
The tank was to be powered by a 1,200 hp M-40 aviation engine, which could run on both diesel and kerosene, and was boosted with four TK-88 turbochargers. The fuel tanks were mounted in the sides of the hull, and provided the tank with an estimated range of 15 hours of operation or 300 km. Its estimated top speed was 38 km/h.
Turrets
Like most KV-4 designs, Pereverzev opted for two turrets in a battleship-style configuration, with the smaller turret at the front, and the larger one on an elevated platform, allowing both to fire forwards without interfering with each other. Additionally, the main turret was mounted back far enough to provide a greater field of fire for the front turret.
One of the drawings also showcases two different turret designs, one with and the other without a turret bustle. A few other differences were made as well, like the removal of the rear-facing DT machine gun for more ammunition space in the turret bustle, and a new turret front armor plate construction.
The two different turret designs, the one on top showing a larger turret bustle and one-piece frontal section. The lower turret is shorter, and features a DT machine gun. Source: Stalin Supertanks IS-7
Crew
The crew was to be 7 men, consisting of the commander, 2 gunners, 3 loaders (1 for the secondary gun and 2 for the main gun) and driver.
The gunner sat to the left of the gun, and would fire the 107 mm gun. His vision was only provided by the main gun’s sight, as no other periscopes are drawn. The commander was seated behind him, and would operate the small rotating cupola, armed with a DT machine gun. Similarly, no periscopes are drawn in the blueprints, so his vision likely consisted of slits within the cupola. One of the main gun loaders sat to the right of the gun. In the turret variant without the turret bustle, he would also fire the rear-facing machine gun. The other loader likely sat in the hull, underneath the turret, and lifted the 107 mm shells to the other loader.
The driver sat in the front of the hull, in a station akin to the one on the KV-1. Behind him were the gunner and loader for the secondary turret.
Armor
Protection consisted of armor ranging from 105 mm to 125 mm on the hull, with the exception of the hull belly and decks, which were 40 mm and 50 mm respectively. The main turret had a 125 mm frontal plate, with the 125 mm thick mantlet taking up large amounts of space for extra armor. Sides and rear were 140 to 150 mm thick. The secondary turret had just 60 mm of armor at the front, due to the space constraints, but the sides and rear were 125 mm thick. The large size combined with the thick armor of the tank would have pushed its total weight to 100 tonnes.
Estimated armored thickness on Pereverzev’s KV-4, short variant turret. Source: Zinoviy Alexeev
Armament
The main armament consisted of the powerful 107 mm ZiS-6 (F-42) cannon, developed by V.G. Grabin at Plant No.92 for such heavy tanks, and was the main armament on all KV-4 designs. It had a muzzle velocity of 800 to 840 m/s and used an 18.8 kg shell, penetrating 115 mm of armor at 1,000 meters (calculated ballistics). In total, 108 rounds of 107 mm ammunition were provided.
Secondary armament consisted of the classic 45 mm 20-K mod.1937 gun, fitted on most Soviet light tanks at the time, and was a great complementary weapon, and still potent by 1941 against soft-skin targets. For the secondary gun, 195 rounds were provided.
Additionally, three (two for the turret-bustle variant) DT 7.62 machine guns were mounted, one coaxially with the 45 mm gun, one in the commander’s cupola and one at the rear of the main turret. In total, 3,000 rounds were given, in drum magazines.
The blueprints also mention a flamethrower with 100 liters of fuel, but where it was positioned is unclear.
Start of the war
After the competition results were announced in May 1941, progress on the KV-4 stagnated, focus shifting to the KV-5. The Axis’ invasion of the Soviet Union on 22 June 1941 further slowed down the development, as LKZ’s focus shifted to increasing production of the KV-1. The final nail in the coffin for the KV-4 and KV-5 came when the German troops were approaching the city of Leningrad, home of the LKZ plant. The SKB-2 design bureau had to be evacuated to ChTZ in Chelyabinsk, and the KV-4 and KV-5 projects were never continued, considering that the alleged German super heavy tank never appeared and the resources were better spent on more rational tasks.
Conclusion
Pereverzev’s expertise in tank design and as a military engineer was shown in his proposal for the KV-4 tank program, with several unusual features, such as the track running over the entire hull for more internal space and the extended sprocket for better trench crossing capabilities, as well as seeing the advantages of a turret bustle. For these attributes, his design was awarded 7th place in the design competition, but would not lead to any further work.
KV-4 Pereverzev variant with a shorter turret. Illustration by Pavel Alexe.KV-4 Pereverzev variant with a bustle turret. Illustration by Pavel Alexe.
KV-4 Pereverzev Specifications
Dimensions (L-W-H) (approx.)
9.5 x 3.8 x 3.82 m
Total weight, battle-ready
100 tonnes
Crew
7 (commander, main gunner, 2x main loaders, driver, secondary gunner, secondary loader)
Propulsion
1,200 hp diesel V-12 M-40 with 4 TK-88 turbochargers
Speed
38 km/h (hypothetical)
Suspension
Torsion bar, 8 wheels per side
Armament
107 mm ZiS-6 (F-42)
45 mm 20-K
2-3x DT 7.62 mm machine guns
Flamethrower (100 liters)
Armor
Turret: 140 mm
Hull: 100-125 mm UFP
105 mm LFP
105-125 mm sides and rear
Top: 50 mm
Belly; 40 mm
KV-4 Ermolaev variant with 2 turret. Illustration by Pavel Alexe.
Soviet Union (1941)
Super Heavy Tank – Blueprints Only
During the spring of 1941, the Soviet SKB-2 heavy tank bureau was working on various types of heavy tanks, ranging from the uparmored KV-1, the T-150, to the super heavy KV-4 and KV-5 tanks. The development of the KV-4 entailed a new philosophy in which engineers would propose independent designs, in an attempt to bring out as many innovative features as possible. One of these designers was A.S. Ermolaev, who designed two KV-4 variants, one “standard” layout, weighing 90 tonnes, and one with a secondary turret, weighing 95 tonnes.
Development
–Dear reader: A more detailed development analysis of the KV-4 program can be found in the KV-4 Dukhov article–
The Soviet heavy tank project named KV-4, also known as Object 224, was developed during the early months of 1941. The development of the tank was triggered by a letter sent by the Soviet Intelligence services to the Soviet Main Directorate of Armed Forces (GABTU) in March 1941. The letter discussed the development of German tanks, including a 90-tonne heavy tank armed with a 105 mm gun. Realizing how far behind their heavy tank development was, the Soviets urgently began the development of a new heavy tank.
The Kirov Leningrad Plant (LKZ) and its SKB-2 design bureau were responsible for the development of the KV-4. LKZ had previously designed the KV-1, which was the only somewhat capable heavy tank in service at the time. However, the KV-1 proved to be unreliable, slow, and heavy during the war. LKZ had also designed several heavy tanks parallel to the KV-1 or as direct developments of it, such as the T-150, KV-220, and KV-3. The KV-220, in particular, was a capable design, comparable to the later German Tiger I heavy tank. It weighed 62.7 tonnes and was armed with an 85 mm F-30 gun, but it was cumbersome and unreliable during trials.
The KV-4 was requested to be a 70-tonne tank armed with the 107 mm ZiS-6 gun, a 45 mm Model 1937 or 1938 as a secondary gun, 3 DT 7.62 machine guns, and a flamethrower. The tank’s armor was to be 130 mm at the front and 120 mm at the sides. The tank was to be powered by a massive 12-cylinder M-40 engine with 4 TK-88 turbochargers that outputted 1,200 hp and had a displacement of 61 liters. The tank’s crew should have consisted of 6 members. The GABTU released the specifications for the tank just 10 days after receiving the letter, and the project deadline was set to 17 July. Plant No.92 was to build the guns by 1 September, and the Izhora plant was to finish the turret and hull by 1 October.
On 7 April, just 17 days later, the GABTU requested that the KV-4’s specifications be increased to 75 tonnes in weight and have armor improvements to 125 mm at the sides and rear. The deadline was also tightened to 15 June. In the same letter, the GABTU requested an even heavier vehicle, the KV-5, with 170 mm at the front and 150 mm at the rear, and a weight of 90 tonnes. Stalin’s personal involvement in the heavy tank projects and the sudden changes in design and increased time pressure would speed up the design process. The previously designed KV-3 was also given improved parameters, up to 68 tonnes, and armed with the same ZiS-6 107 mm gun as on the heavier tanks, with the purpose of acting as a stopgap tank.
To speed up the development of the KV-4, the SKB-2 design bureau head, J.Y. Kotin, set up a design competition. The competition was to gather as many diverse and revolutionary design elements as possible, and the top places were awarded financial rewards. Over 27 designs were presented by the SKB-2 bureau, and the first place was awarded to N.L. Dukhov, who presented an enlarged KV-220. Second place originally went to K.I. Kuzmin, V.I. Tarotko and P.S. Tarapatin, but were later disqualified because of the turretless design, and N.V. Tseits’ design (who was initially awarded third place) came second.
Ermolaev’s expertise in tank design and influence at SKB-2 landed his proposal in fourth place alongside Sychev’s design. For this achievement, he received 2,000 rubles.
A.S. Ermolaev
Born in the village of Kliny, Kaluga Oblast, in 1904, Afanasy Semyonovich Ermolaev would begin studying at the Military Academy of Mechanization and Motorization of the Red Army in 1932 and graduate two years later. He would then begin work at the SKB-2 design bureau at LKZ, working on the development of the T-28, SMK and KV-1. During the war, he would continue designing under Kotin’s leadership, working on the KV-1S, KV-85, IS, IS-2, SU-152, ISU-152 and ISU-122S. Post war, he would continue his activities at ChKZ in Chelyabinsk, working on several tanks, most notably the T-10, but also agricultural tractors K-700 and S-80.
He would receive 2x Order of Lenin, 2x Order of Kutuzov (1st and 2nd deg.), 2x Stalin Prize (1st and 2nd deg.), Order of the Red Banner of Labour, Order of the October Revolution, Medal “For the Victory over Germany in the Great Patriotic War 1941.1945” and the Medal “For the Defense of Leningrad”.
Afanasy Semyonovich Ermolaev after the war. Source: Famhist.ru
Design
Unlike most other designers, Ermolaev presented two variants for his entry, a traditional layout tank with one large central turret, and a longer tank with two smaller turrets.
Between the two variants, the hull was mostly identical. Following the general shape and layout of previous KV designs, the front featured a stepped plate which was pressed into shape, while the sides were completely flat. One difference was that the rear air cooling hole was protected by a flat armor plate instead of a curved one.
The main difference between the hulls of the two variants was the length, one was 8.22 meters long, while the other reached 8.52 meters, in order to fit the secondary turret. Both hulls had the same amount of roadwheels, but they were closer spaced on the shorter variant. Due to the various differences between the two, weight would also become a variable factor, with the single turret version weighing 90 tonnes, while the other weighed 95 tonnes.The main turret on both variants was remarkably similar, the only difference being the lack of a turret bustle on the two-turret variant. Otherwise, the turret was a hexagonal shape, made out of four different plates, where the side walls were stamped in shape. A large non-rotating cupola with six periscopes was located at the back of the turret and was used by the commander. No other details are shown regarding the turret.
Both variants were equipped with the 107 mm ZiS-6 and 45 mm 20-K mod.1937 guns, however they each were in their own individual turrets on the two-turret variant (the secondary turret had 270° rotation while the main full 360°), and mounted coaxially in the single-turret variant.
The variant with a single turret, which featured the 107 mm ZiS-6 and 45 mm 20-K mounted coaxially. Source: ASKMThe variant with 2 turrets, where the smaller turret was mounted in front of the main turret. Source: ASKM
The tank was powered by the M-40 1,200 hp aviation engine, capable of running on both diesel and kerosene. It was boosted by four TK-88 turbochargers. Fuel tanks were placed on the side walls. It was estimated that the tank could (optimistically) reach 40 to 45 km/h.
Crew
The single turret variant had a crew of 6 men; commander, gunner, 2x loaders, driver, and radio operator. The gunner sat to the left of the main gun, and operated both the 107 mm gun and 45 mm gun, which was mounted coaxially. The commander sat behind him, in an elevated position, with his head in the cupola, from where he could acquire targets and easily inform the gunner. The two loaders both sat on the right side of the gun, one tasked with loading the 107 mm gun and the other the 45 mm gun. The driver sat in the hull, in the center, with an emergency escape hatch in the floor, to his right. The position of the radio operator is unclear.
For the two-turret variant, the main gunner and commander had the same positions, while the two designated loaders for the main 107 mm gun sat on the right side of the gun, one loading the shells in the gun and the other lifting them from the hull stowage boxes.
The driver was also in the front of the hull, but seated to the extreme left side, to make space for the secondary turret, where the secondary gunner and loader worked. Also in the front of the hull, underneath the secondary turret. was a flamethrower of unspecified type. The position of the radio operator is, once again, unclear.
Armor
The hull consisted of 130 mm of frontal armor plates, while the sides and rear were 125 mm thick. The belly and roof were 50 mm thick. The front of the turret consisted of a 130 mm plate angled at 60° from horizontal, for a relative thickness of 150 mm. The sides and rear of the turret were also 125 mm thick.
Armament
Like on most other KV-4 designs, the main gun was the 107 mm ZiS-6 (F-42) developed by V.G. Grabin at Plant No.92 from autumn 1940 to spring 1941, and was later tested on a KV-2 in June 1941. It was a potent anti-tank cannon, with a muzzle velocity of 800 to 840 m/s and a shell weight of 18.8 kg, with a calculated penetration of 115 mm of armor at 1,000 meters. The main gun had +20° elevation and -5° depression (same applies for the 45 mm coaxial). The 45 mm in the secondary turret variant had +25° elevation and -5° depression.
The 45 mm 20-K mod.1937 was still widely used on Soviet tanks at the time, but by 1941, its anti-tank capabilities were lackluster. However, it still provided good performance against soft-skin targets.
For defense against infantry, a 7.62 mm DT machine gun was placed in a ball mount in the rear of the turret, but the two-turret variant had an additional coaxial DT machine gun. The two-turret variant also featured an unspecified type of flamethrower in the front of the hull, to be operated by the driver or secondary gunner.
Discontinuation of the project
After the announcement of the competition results, the KV-4 project stagnated, with SKB-2 focusing on the KV-3 and KV-5. Progress on these heavy tank projects was further halted by the start of the war on 22 June, as the LKZ factory shifted focus to the production and repair of KV-1 tanks.
The situation would turn grave when German forces were approaching the city of Leningrad, home of the LKZ plant. In September, the SKB-2 design bureau was moved to ChTZ to continue work. However, with this move, the KV-4 and KV-5 projects were not reconsidered and canceled. Only the KV-3 project remained active, but with focus on improving the KV-1 tank, no progress was made on the KV-3 either and it was canceled by 1942.
Conclusion
The rational and conventional KV-4 design presented by A.S. Ermolaev offered a realistic alternative to the more unorthodox designs, landing him the fourth spot in the competition. Still, the high crew number and excessive weight, especially for the two-turret variant, could have proven problematic. The entire project was deemed expensive and irrelevant to the military needs of the Soviet military, even by its own designers. Once abandoned following the SKB-2’s move to ChTZ, the project was forgotten.
KV-4 Ermolaev variant with 2 turrets. Illustration by Pavel Alexe.
KV-4 Ermolaev variant with a single turret. Illustration by Pavel Alexe.
KV-4 Ermolaev Specifications
Variant
1 Turret
2 Turrets
Dimensions (L-W-H)
8.22 x 4 x 3.25 m
8.52 x 4.00 x 3.25 m
Total weight, battle-ready
90 tonnes
95 tonnes
Crew
6 men (commander, gunner, 2x loaders, driver, radio operator)
8 men (commander, main gunner, 2x main gun loaders, driver, secondary gunner, secondary loader, radio operator)
Propulsion
1,200 hp diesel V-12 M-40 with 4 TK-88 turbochargers
Speed
40-45 km/h (hypothetical)
Armament
107 mm ZiS-6 (F-42)
45 mm 20-K (?)
7.62 DT machine gun
107 mm ZiS-6 (F-42)
45 mm 20-K
2x 7.62 DT machine gun
Flamethrower
Armor
Turret: 125-130 mm
Hull: 125-130 mm
Top: 50 mm
Belly: 50 mm
Marishkin's KV-4 design. Illustration by Pavel Alexe.
Soviet Union (1941)
Super Heavy Tank – Blueprints Only
The KV-4 program was started in March 1941 to deal with alleged new heavy tank advances by the German Reich. Development took place at the Leningrad Kirov Factory design bureau SKB-2 headed by J.Y. Kotin. A design competition was held, with over 27 different design proposals. While many designs were appreciated for their innovative features, even more were disregarded. One of these was proposed by engineer F.A. Marishkin, who’s design featured a large complex turret and an unremarkable hull.
Development
–Dear reader: A more detailed development analysis of the KV-4 program can be found in the KV-4 Dukhov article–
With the expansion of German aggression over Europe in 1940, Soviet leadership followed events with unease, despite their non-aggression pact with the German Reich, signed in August 1939. Their successful use of tanks was unprecedented and other nations rushed to expand their tank development and armament programs. During this time, the Soviets would start fielding the KV-1 heavy tank, based on experiences from the Winter War. However, it would quickly become apparent that it was rushed due to Stalin’s requests and still needed plenty of fine tuning. By the start of Operation Barbarossa, the KV-1 would still prove a lethal weapon, with excellent protection and adequate firepower, but was let down by significant quality, logistical and training problems.
On 11 March 1941, the Soviet Intelligence services submitted a report to the GABTU (Main Directorate of Armored Forces) regarding the development of German tanks. Most noticeable was the section on heavy tanks, where, amongst others developments akin to the VK.30.01(H) and VK.36.01(H), was the mention of a 90 tonne Mark VII tank, armed with a 105 mm gun, which is know now was some early variant of the later Pz.Kpfw.VII Löwe. This came as an unpleasant surprise to Soviet officials, who only had the aforementioned KV-1 and the hopelessly obsolete T-35 tank. The most advanced heavy tanks in development were the KV-150 (T-150), an improvement based on the KV-1 with 90 mm of frontal turret armor and total weight of 50 tonnes, and the KV-220, armed with an 85 mm F-30 gun, 100 mm of armor all-round, and total weight of over 60 tonnes. While both were very respectable on paper and superior to all German tanks of the time, they had reliability issues, with the KV-220 breaking two engines while testing, though the engine was equally unreliable and only two were built.
Thus, the GABTU set out to develop a new heavy tank to match the German tanks. On 21 March, they laid out all the requirements for the new heavy tank. It was to be armed with the new 107 mm ZiS-6 developed at Factory No.92 by V.G. Grabin. The armor was to be 130 mm to 120 mm all-round and a weight between 70 to 72 tonnes. Propulsion was set to be the M-40 diesel aviation engine with 4 TK-88 turbochargers. The tank was to be equipped with a vast array of secondary weapons as well, namely a 45 mm gun and at least three 7.62 mm machine guns, as well as a flamethrower.
Development of the KV-4 would take place at the LKZ (Kirov Leningrad Factory) SKB-2 design bureau, the same office responsible for all the previous KV tanks. Production of the first prototype was assigned to the Izhora plant, based on LKZ drawings. Thus, the tank was named KV-4 and received index Object 224. The project deadline was set to 17 July for the drawings and October for first prototype production.
Shortly after the initial release of the requirements, the GABTU edited their request, specifically on 7 April. Firstly, they would request a heavy upgrade of the KV-220, named KV-3, that would act as a stopgap until the heavier tanks were ready, armed with a 107 mm gun and 120 mm of frontal armor. Likewise, an even heavier tank was requested, named KV-5, with frontal armor thickness of 170 mm and side of 150 mm, and weight of at least 90 tonnes, also armed with the 107 mm ZiS-6. To better fit the KV-4 between the two new vehicles, its weight threshold was lifted to at least 75 tonnes, and 125 mm of armor at the sides. To increase the urgency of the matter, the deadline was tightened to 15 June.
Over at SKB-2 design bureau, which was headed by J.Y. Kotin, work would set on developing all 3 tanks. Interestingly, as a result of the loose requirements set by the military, Kotin would challenge his engineers to a design competition, in an attempt to bring out the most innovative ideas. With the approval of the factory director, I.M. Saltzman, Kotin was given the necessary funds to award the top designers with significant financial awards. Over 24 designers entered the competition, with just as many different concepts submitted. On the 9 May, the winners were announced, in first place being N.L. Dukhov, a trio of designers, K.I. Kuzmin, P.S. Tarapatin and V. I. Tarotko in second place and N.V. Tseits on third. In total, 11 designs and 13 engineers were awarded.
However after the competition was over, work on the KV-4 severely stagnated, to the point where Marshal of the Soviet Union G.I. Kulik had to personally come over and attempt to speed up the process, to no avail. Truth is, most of the efforts went to the KV-5, based on knowledge from the KV-4. Even so, the KV-5 was in a very early stage when the German Reich began their invasion of the Soviet Union, on 22 June 1941, and their quick advance into Soviet territory would put great strain on tank factories.
By September, the German forces were advancing towards Leningrad, and the SKB-2 design bureau was evacuated to ChTZ (Chelyabinsk Tractor Plant), which was renamed ChKZ (Chelyabinsk Kirov Plant), or as more commonly known, Tankograd. Unfortunately for the heavy KV designs, they were seen as a massive resource drain and work on them did not recommence.
F.A. Marishkin
Alongside 5 other engineers, F.A. Marishkin was head of the design of the transmission of the KV-1 while also being part of the design team of the SMK and T-150. After the war, he would continue working at the Kirov plant as one of the designers of the KT-12 forestry tractor, but also on the development stages of the T-10.
F.A. Marishkin after the war Source: Constructor of Combat Vehicles
Design
Compared to the majority of the KV-4 designs presented, Marishkin’s can be seen as one of the more conservative ones in regards to general layout and design. What was essentially an enlarged KV-220 hull was mated to a very large main turret, with a secondary turret on top. The front of the hull was a ‘stepped’ design, consisting of a large lower plate, a steeply angled ‘hood’ followed by a flatter but thickened section in the armor connecting to the hull roof. The side armor was simply flat all along. The rear was very similar to the KV-1, consisting of two plates with a gap in between for engine cooling airflow. The main turret was mounted between the second and sixth roadwheels. Frontally, it consisted of a single plate stamped into a curved shape. The sides of the turret are not specifically drawn out on the blueprints, but they curved inwards at the rear, as well as being angled upwards for improved protection.
Perhaps the only unusual aspect of Marishkin’s design was the secondary turret, specifically its placement. It was towards the rear of the turret and offset to the right. As the main turret was curved and angled inwards, the secondary turret hung over the main turret walls, requiring a form of extension of the turret walls to support the turret ring. This certainly complicated the construction process.
Side cutout view of the KV-4 proposed by Marishkin. Source: ASKM
The recoil distance of the ZiS-6 107 mm gun was not specified, but it is clear that, if the secondary turret was placed centrally, the gun recoil would slice the secondary turret gunner’s legs off (see KV-4 Kruchenykh). The only other option would have been extending the turret’s bustle size, but that might have not been possible considering balance and the limited turret ring size.
Top view of the hull, showing the different fuel tanks on the sidewalls and floor, engine, and final drive. Of significant interest are the two circles in the center, the big one representing the main turret ring, and the smaller one, the secondary turret. Source: ASKM
The engine used was a M-40 1,200 hp engine, originating from an aviation engine and capable of running on both diesel and kerosene. It had a V12 configuration, 61.07 liters displacement, and featured 4 TK-88 turbochargers. Fuel tanks were fitted alongside the hull sides and floor, underneath the turret.
Side cutout view of the hull layout, with a cross section of the M-40 engine and fuel tanks. The armor is not shown. Source: ASKM
The suspension was a standard KV series layout, with 8 steel-rimmed roadwheels sprung by torsion bars and with travel stops. The drive sprocket was at the back, connected to the brakes and final drive ensemble.
Crew
The crew on Marishkin’s proposal was 7, one more than the GABTU-specified 6. The exact layout and positions are unknown, but based on the tank layout and similar designs, the following can be concluded. The crew consisted of the driver, radio operator, main gunner, 2 main gun loaders, commander (which was also the secondary armament gunner), and secondary loader.
The driver would be seated (as seen in the drawing above) in the front of the hull. Next to him would be the operator of the 10-R tank radio.
The remaining 5 crewmembers would be seated in the turret. The main gunner was seated to the left of the gun, with a loader behind him. The other main loader was likely on the opposite side, to the right of the gun breech. The commander was seated to the left of the 45 mm secondary gun and the loader to the right.
This layout is purely speculation by the author, largely based on space, practicality, and other KV-4 designs with known crew positions. It could be argued that certain positions did not exist or should be rearranged, for example, the second main loader replaced with the tank commander and the secondary gun to receive its own designated gunner.
Armor
Like most of the pre-war Soviet heavy tanks, the armored plates were simply welded together without interlocking. A likely form of connection for the heavier plates was via pins, like on the German Maus tank. These would physically improve the connection between plates but could prove to further complicate the manufacturing process and cause weakening of the armor in those areas to be more susceptible to cracking and shattering.
The lower frontal plate was 130 mm thick, pressed into shape. The upper part of the armor consisted of a single plate, with the bottom being 80 mm thick and the top part 130 mm, pressed to form a steep hood and driver’s front plate. The side was a single flat 120 mm thick plate. The turret consisted of a single frontal plate, 130 mm thick, pressed into shape. The side armor is more speculative due to the lack of drawings, but would also have followed a similar process, albeit with a 125 mm thick plate.
Armament
The main weapon used on all KV-4 designs was the 107 mm ZiS-6 developed a few months earlier by Factory No.92 by V.G. Grabin by own initiative. With 800 to 840 m/s muzzle velocity and a 18.8 kg shell, it was a very potent anti-tank weapon, capable of penetrating 115 mm of armor at 1,000 m. The gun was tested in June and July on a KV-2 testbed and would enter production a few months later. However due to the KV-4 and subsequently KV-3 and KV-5 tanks never being built, the half-built guns had to be melted and recycled.
Secondary armament consisted of the 45 mm 20-K gun, used on the majority of Soviet light tanks at the time, as well as at least two 7.62 DT machine guns.
The KV-2 testbed with the 107 mm ZiS-6 gun, June 1941. Source: Warspot
Death of LKZ’s Heavy Tanks
The Axis forces made quick progress into Soviet territory and by August were already approaching the city of Leningrad. To avoid capture and disruption of developments, many of the engineers of the SKB-2 design bureau were relocated to the Chelyabinsk Tractor Plant (ChTZ), which was renamed to Chelyabinsk Kirov Plant (ChKZ) upon their arrival. However, it was clear that the heavy tank developments in the form of the KV-3, KV-4, and KV-5 were more resource and financial pits for the Soviet defense than any actual help. The projects were all abandoned and development switched to improving the KV-1, which resulted in new successful vehicles, such as the KV-1S.
Conclusion
While, with hindsight, the entire KV-4 program ended up being a massive waste of resources, it is clear that some designs were fundamentally better than others, like the winning design by N.L. Dukhov. In contrast, the design by Marishkin was not particularly original and was not deemed as effective considering the liberal requirements and effective armament. Even today, his design is one of the lesser known and least appreciated designs from the program.
Marishkin’s KV-4 design. Illustration by Pavel Alexe.
KV-4 (Object 223) Marishkin specifications
Dimensions (L-W-H)
8.7 – 3.8 – 3.5 m
Total Weight, Battle Ready
86.4 tonnes
Crew
7
Propulsion
1,200 hp diesel V-12 M-40 with 4 turbochargers
Speed
40 km/h (hypothetical)
Armament
107 mm ZiS-6
45 mm 20-K
>2 DT 7.62 machine guns
Armor
Turret: 130 mm
Frontal upper hull: 80 mm
Frontal lower hull: 130 mm
Side hull: 125 mm
Rear hull: 125 mm
Top: 40-50 mm
Belly:40-50 mm
Total Production
0; blueprints only
Sources:
Breakthrough tank KV – Maxim Kolomiets
Stalin’s Supertanks IS-7 – Maxim Kolomiets
KV 163 1939-1941 – Maxim Kolomiets
Confrontation – Ibragimov Danyial Sabirovich
Constructor of Combat Vehicles – N.Popov
Bronevoy Schit Stalina. Istoriya Sovetskogo Tanka (1937-1943) M. Svirin
About the forgotten creators of Soviet armored power. (historyntagil.ru) – S.I. Pudovkin
German Lion | Warspot.ru – Yuri Pasholok
Крупный калибр для крупных КВ | Юрий Пашолок | Дзен (dzen.ru) – Yuri Pasholok
Tank building on the verge of common sense | Warspot.ru – Yuri Pasholok
Large caliber for large HF | Yuriy Pasholok | Yandex Zen – Yuri Pasholok
Tank Archives: Soviet 107 mm Guns – Peter Samsonov
Tank Archives: KV-3 Mulligan – Peter Samsonov
Tank Archives: Heavy Tank Costs – Peter Samsonov
Tank Archives: ZIS-6 Characteristics – Peter Samsonov
Marishkin F.A. (famhist.ru)
KV-4 as designed by Sychev. illustration by Pavel Alexe, funded through our Patreon campaign.
Soviet Union (1941)
Super Heavy Tank – Blueprints Only
A few months before the German invasion of the USSR, the Soviets were working on developing massive heavy tanks. One of these programs was the KV-4 projects, which included 27 different proposals. One of these was from LKZ engineer L.E. Sychev. Instead of focusing on revolutionary and unique features, he built upon and perfected the concept already tested on the SMK heavy tank. These efforts placed his design in 4th place in the KV-4 design competition.
Development
–Dear reader: A more detailed development analysis of the KV-4 program can be found in the KV-4 Dukhov article–
In March 1941, the Soviet Intelligence services sent a letter to the Soviet Main Directorate of Armed Forces (GABTU) discussing the development of German tanks. Here, a 90 tonne heavy tank was described, armed with a 105 mm gun. Yet, only by November 1941, the first mentions of a tank fitting this description appeared, the Pz.Kpfw. VII, or Löwe. Understanding how far behind their heavy tank development was, the Soviets set about the urgent development of a new heavy tank.
Development of the new beast became the responsibility of the Kirov Leningrad Plant (LKZ) and its SKB-2 design bureau. The bureau had already designed the only somewhat capable heavy tank in service, the KV-1, however, it proved to be unreliable, slow, and heavy once war commenced. Up until that point, LKZ had also designed several heavy tanks in parallel with the KV-1 or as a direct development from it, such as the T-150, KV-220, and KV-3. With hindsight, the KV-220 was a genuinely capable design, comparable to the later German Tiger I heavy tank. It weighed 62.7 tonnes and was armed with an 85 mm F-30 gun. On the other hand, during trials, it was cumbersome and unreliable, breaking 2 engines.
The new heavy tank to be designed by LKZ was given the designation KV-4 or Object 224. Just 10 days after the original letter was sent, on 21 March, the GABTU had released the specifications for the technical capabilities of the tank. It was to be a 70-tonne tank, armed with the 107 mm ZiS-6 gun in, a 45 mm Model 1937 or 1938 as a secondary gun, 3 DT 7.62 machine guns, and a flamethrower. Armor was to be 130 mm at the front and 120 mm at the sides. Propulsion was provided by a massive 12 cylinder M-40 engine with 4 TK-88 turbochargers, outputting 1,200 hp with a displacement of 61 liters. The crew was to be of 6. Just 6 days later, the project deadline was set to 17 July. Subsequently, based on the LKZ blueprints, Plant No.92 was to build the guns by 1 September and the Izhora plant was to finish the turret and hull by 1 October.
Just 17 days later, on 7 April, the GABTU requested the KV-4 specifications be increased to 75 tonnes weight and armor improvements to 125 mm at the sides and rear. The deadline was also tightened to 15 June. In the same letter, the GABTU requested an even heavier vehicle, the KV-5, with 170 mm at the front and 150 mm at the rear, and weight of 90 tonnes. The sudden changes in design, and the increased time pressure, combined with Stalin’s personal involvement in the heavy tank projects would hurry up the design process. Lastly, the previously designed KV-3 would receive improved parameters, up to 68 tonnes and arming it with the same ZiS-6 107 mm gun as on the heavier tanks, with the purpose of acting as a stopgap tank.
Due to the urgent nature of the project, LKZ began work on the heavy tanks on 10 April. The SKB-2 design bureau headed by J.Y. Kotin was put in charge of their development. Yet instead of pursuing a traditional development path, Kotin, with the approval and funds allocation from factory director I.M. Zaltsman, would set up a design competition for the KV-4. The idea behind this was to gather as diverse and revolutionary design elements as possible. To further encourage this, the competition results would be ranked and the top places awarded financial rewards. By 9 May, the competition was over and over 27 designs were presented by the SKB-2 bureau. First place was awarded to N.L. Dukhov, who designed an enlarged KV-220 with an automated loader aiding system. He received 3,000 rubles. To put this in context, a frontline soldier received 500 rubles for destroying an enemy tank. Second place went to a trio of engineers, K.I. Kuzmin, P.S. Tarapatin and V.I. Tarotko, who together designed a variant with a sponson mounted main gun and secondary gun mounted in a small turret on top. They were awarded 3,000 rubles to split, however their design would be disqualified later because the main gun had limited traverse. Third place went to senior engineer N.V. Tseits, who designed a tank with a very low hull at the expense of a very large turret. He received 2,800 rubles. Due to the disqualification of the second place contender, Tseits’ design would later be selected as the basis for the KV-5. In total, 11 designs were awarded funds. The design by L.E. Sychev was appreciated due to the well-thought-out layout and origins from a trialed tank, the SMK. Thus he was given 4th place in the competition and awarded with 2,000 rubles.
The SMK multi-turreted tank, likely a source for Sychev’s KV-4. Source: Drikus club
L.E. Sychev
Born in 1913 in, what was at the time St. Petersburg, Leonid Efimovich Sychev undertook his bachelors project at the SKB-2 design bureau at LKZ while studying at the Leningrad Polytechnic Institute in 1932. Just 2 years later, he graduated, and in 1935, started work at SKB-2. He worked on the T-28 and later SMK. As for the KV-1, he first refined the torsion bar suspension alongside N.V. Tseits and G.A. Seregin. Later, he was appointed chief designer for the KV-1 and became the SKB-2’s chief designer of armament in 1940. He was chief designer of the KV-220 and initially, he was also to be chief designer for the KV-3, but was replaced by B. P. Pavlov. After the outbreak of the war, he also worked on improving the T-34, alongside A.A. Morozov. He was awarded the Order of the Red Star, among many others.
Leonid Efimovich Sychev likely after the war. Source: Museum of SPbPU
Design
As with a handful of other KV-4 designs, Sychev heavily inspired his tank layout upon that of the SMK heavy tank, designed by the same bureau just a few years prior. It featured a long hull, with a steeply angled frontal armor plate. Likewise, the engine was mounted in an upwards rising deck plate. Like on the previous SMK and T-100, a smaller turret armed with the 20-K 45 mm gun was mounted towards the front of the hull and slightly offset to the right, while a larger turret, armed with the 107 ZiS-6 gun was mounted centrally. On top of the main turret was an additional fully rotating commander cupola, armed with a 7.62 DT machine gun. An additional DT machine gun was mounted coaxially in the secondary turret.
As required by the state, the KV-4 featured a 1,200 hp V-2SN diesel engine with 4 turbochargers. According to Sychev, it was enough to allow the 95 to 100 tonne tank to reach top speeds between 40 and 45 km/h, though that is extremely optimistic. The entire powerpack ensemble was situated in the rear and featured an ingenious air intake and cooling system, using overlapping armor plates to prevent entry of shrapnel and debris. The fuel tanks were positioned in the sides of the hull.
Side cutout view of Sychev’s KV-4 proposal. Note the steeply angled frontal hull. Source: ASKMPartial top view of Sychev’s KV-4. While the drawing provides excellent view and understanding of the hull, the turrets only have their outlines drawn in. Source: ASKM
Crew
Similarly to the SMK, Sychev’s KV-4 had a crew of 8: commander, main gunner, main loader, turret mechanic/loader assistant, driver, radio operator, secondary gunner, and secondary loader. To further complicate the topic, the exact positions and roles of the crew were never specified or detailed. This leaves a lot of room for interpretation and guesswork based on other KV-4 designs and previous similar tanks, such as the SMK and T-100.
The main turret housed 4 crew members. The main gunner sat to the left of the main gun, and used his main gun sight for vision, though it is likely he would have received his own periscope. The exact position of the tank commander is unknown, though he would have sat on either side of the gun. His head would be inside the main rotating cupola, giving him a commanding view of the battlefield (at 4 m), as well as the ability to independently engage infantry and suppressive fire. The main gun loader would have stood on one side of the gun. He only had 4 rounds in the turret bustle before he would require assistance from the additional loader, standing underneath the turret ring, feeding him shells stowed in the hull.
Towards the bow of the hull sat the driver, to the left side of the hull. Stored to his right was the 20-K 45 mm secondary gun ammunition. Right behind him was the 10-R radio and the radio operator, whose round seat can be seen in the blueprint. The secondary gunner and loader sat in the additional turret, though they were able to have direct communication with both the driver and radio operator.
Armor
All KV-4 designs had more or less the same armor thicknesses all around, i.e. 130 mm at the front and 125 mm at the side and rear. Nonetheless, the layout and angling of these plates varied widely. Unlike previous LKZ heavy tank designs, Sychev used a single sloped plate for the upper hull and the hull extension on which the main turret was placed. This would present a very well armored silhouette from the front. Only the frontal sections of the 2 turrets could be considered weak points. To decrease the effect of this, the front of the turret was rounded, while the entire turret resembled a horseshoe from the top, which made the weaker frontal plate as small as possible, similar to the later German Tiger I heavy tank.
While certainly ingenious, such use of thick armored plates would require intensive steel rolling and bending methods, which the Soviet industry lacked. This was a concern for almost all KV-4 designs, which featured various complex shapes. This issue would be fixed later in the war, with complex casting methods, though a new series of problems would be introduced, such as brittleness and porous steel.
The small commander’s cupola was not necessarily a weak spot in the overall tank’s armor, as it had around 100 mm of armor all around. When in use, only the head of the operator would be inside of it. The machine gun and turret were operated via mechanical controls that were lowered down to chest level.
Armament
Regarding the armament, the main gun used on all KV-4 designs was the 107 mm ZiS-6, developed earlier that year at Factory No.92 under the name F-42. Its designer was the famous Soviet gun designer, V.G.Grabin. It was to be mounted on the KV-3, KV-4, and KV-5 heavy tanks. During summer 1941, the gun was tested on a modified KV-2, with the KV-3 gun mantlet. It had a muzzle velocity of 800 to 880 m/s, shell weight of 18.8 kg, and could penetrate 115 mm of armor at 1,000 m.
The secondary armament on Sychev’s KV-4 consisted of a 45 mm 20-K gun, which was the main gun in service on Soviet tanks at the time. It was mounted in an independent turret, allowing it to engage infantry or lighter armored AFVs independently of the main turret. Moreover, two 7.62 mm DT machine guns were mounted, one coaxially with the 45 mm gun and one in the small cupola on top of the main turret.
KV-2 armed with a 107 mm ZiS-6 during firing trials, June 1941. The man in white uniform was V.G. Grabin himself. Source: State Archives
Conclusion
Sychev’s KV-4 design had impressed Kotin and Zaltsman, was given 4th place in the competition, and he was awarded 2,000 Rubles. The tank featured 2 roomy turrets, well spaced from each other, offering great firing angles and fire coverage. The solutions regarding the engine cooling system and layout were inspired from the SMK and were deemed as effective. Lastly, the flat and steeply armored upper frontal plate ensured excellent protection, especially compared to the designs that opted for a “stepped” layout, like on the KV-1. Despite the large sums of money poured into the project, as well as almost an entire design bureau focusing on it, the KV-4s development stagnated after the competition results were announced. Instead, based on these results, the KV-5 began being developed. The final nail in the coffin for all the LKZ’s heavy tanks was the German invasion of the USSR, and, subsequently, their fast approach towards the city of Leningrad. Consequently, the entire SKB-2 design bureau was evacuated to the ChTZ factory in Chelyabinsk. Here, the wild dreams of heavy tanks were left behind and focus shifted on more down-to-earth solutions.
KV-4 as designed by Sychev. illustration by Pavel Alexe, funded through our Patreon campaign.
KV-4 Sychev specifications
Dimensions (L-W-H)
9.23 – 3.40 – 4 m
Total Weight, Battle Ready
95 – 100 tonnes
Crew
8 (commander, main gunner, main loader, turret mechanic/loader assistant, driver, radio operator, secondary gunner, secondary loader)
Propulsion
1,200 hp diesel V-12 M-40 with 4 TK-88 turbochargers
Speed
40 – 45 km/h (hypothetical)
Armament
107 mm ZiS-6 (F-42)
45 mm 20-K
2x DT 7.62 mm machine guns
Armor
Turret: 135-125 mm
Hull: 130 mm front, 125 mm sides and rear
Top and belly: 40 mm
KV-4 as designed by G. Kruchyonyh, which was the heaviest design of them all, at 107 tonnes.
Soviet Union (1941)
Super Heavy Tank – Blueprints Only
A few months prior to the German invasion of the USSR in 1941, the Soviets started a heavy tank program based on rumors of German heavy tank developments. One of the outcomes was the KV-4 competition, which involved 27 different tank proposals. The heaviest of them all, designed by G.V. Kruchyonyh, would have weighed 107 tonnes, but the design was not successful.
Development
–Dear reader: A more detailed development analysis of the KV-4 program can be found in the KV-4 Dukhov article–-
By 1941, the Soviet Union had experimented with several types of heavy tanks, from some very extravagant super heavy tanks, such as the Grotte proposals and T-42, to more “sensible” designs, such as the KV-1 and its later development, the KV-220. Yet, when the Soviet intelligence services sent a report about the development of German tanks in March 1941, the GABTU (Main Directorate of Armed Forces) was caught off-guard. The report mentioned, among others, the development of a 90-tonne heavy tank armed with a 105 mm gun.
At the time, the USSR’s main heavy tank force consisted of the hopelessly obsolete T-35 and the mechanically unreliable KV-1, which was pressed into service prematurely. Their most capable vehicle was the aforementioned KV-220, which weighed 67 tonnes, had 100 mm of armor and an 85 mm F-30 gun. While this was by no means an inadequate tank on paper, in practice, the testing of the vehicle was going slowly due to a wide variety of issues, such as the unreliability of the engine and various mechanical breakdowns. By the end of the program, only 2 prototypes were built.
Thus, the GABTU began the urgent development of a new heavy tank, and on 21 March 1941, they requested that a new 70-tonne tank be designed and developed to face this new German threat. It was to be armed with the new 107 mm ZiS-6 as well as a 45 mm gun and 3 machine guns. The engine was to be the M-40 1,200 hp V-12, with 4 TK-88 turbochargers. Armor was 130 mm at the front and 120 mm at the sides. The SKB-2 design bureau at the Kirov Leningrad Plant (LKZ) was tasked with its development and thus was named KV-4, with the GABTU index Object 224. This design bureau had plenty of experience in designing heavy tanks, having already designed tanks such as the SMK, KV-1, T-150, KV-220, and KV-3. As part of this, SKB-2 was ordered to have blueprints ready by 17 July 1942.
However, on 7 April, the requirements were once again changed. The KV-3 was to be revived, and its specifications vastly improved. In turn, the KV-4’s weight would be increased to 75 tonnes, and have its armor increased to 125 mm at the sides and rear. The deadline was also brought forward to 15 June. Most interestingly, LKZ was also assigned the development of the KV-5, a 90 tonne tank, with 150 to 170 mm of armor but also armed with the 107 mm ZiS-6. It would compete against the KV-4, with trials expected to be held in the beginning of 1942. In the meantime, until either entered mass production, the KV-3 would act as a stopgap.
The head of the project was J.Y. Kotin, who was also the head of the design bureaus at LKZ. However, instead of giving direct design orders, he took advantage of the loose requirements and set off to test his engineers. Thus, with the approval and budget from factory director I.M. Saltzman, he forged a competition for the KV-4’s development. The idea was that the engineers from the SKB-2 design bureau would compete against each other, with the top 7 places receiving financial rewards.
The results of the competition were announced on 9 May, with 13 designers receiving awards (7 total places, with some designs receiving the same spot). First place went to N.L. Dukhov’s design, which was considered the most sensible alternative, essentially just an enlarged KV-220. He received 5,000 rubles. Second place went to the Kuzmin, Tarotko, and Tarapantin, a trio of designers who worked together. They received 3,000 rubles to split. Their design had the main gun mounted in the hull, with a small turret over the fighting compartment. Third place went to N.V. Tseits, who designed a tank with a very low hull but massive cylindrical turret. He received 2,800 rubles. Fourth place was given to 2 designs. The first was by L.E. Sychev, who designed an enlarged SMK/style vehicle with a steeply angled frontal place, receiving 2000 rubles. Second 4th place was given to A.S. Yermolaev (also awarded 2000 rubles) who designed two standard layout tanks, with the only difference being the addition of a secondary turret on one of them. N.F. Shasmurin received 5th place with one of the more unique designs, mounting the main gun inside a casemate and a KV-1 turret on top. On 6th place, two more designers were awarded the same place. One of the was by K.I. Buganov, with a compact hull and rear mounted stacked turrets. The other was by N.G. Moskvin, which also proposed a standard layout tank with stacked turrets. Both designers were awarded 1000 rubles. Lastly, 6th place was given to 3 designs, with one by L.N. Pereverzev, which featured exposed tracks, similar to early Churchill tank designs. Another 6th place was awarded to Bykov, which was inspired from the SMK layout. Another designer, Kalivod, was also given 6th place but we do not yet know how his design looked like. The remaining designs did not receive any awards. Amongst them was that by G.V. Kruchyonyh, who designed the heaviest competitor, a 107 tonne tank.
As a peculiar side note, allegedly the blueprints of Kruchyonyh’s designed had been misslabeled by N.F. Shashmurin as the KV-5, to show the poor design of the KV-5. This claim was made by historian Yuri Pasholok.
G.V. Kruchyonyh
Georgy Vasilyevich Kruchyonyh was one of the oldest and most experienced tank designers at the SKB-2 design bureau in Leningrad, having worked on Soviet tanks since the 1920s at the Leningrad No.100 experimental tank building factory. During the 1930s, he worked on the T-28, SMK, and KV-1 at the renamed LKZ, and, after the factory’s transfer to ChTZ (later ChKZ), he would work on the KV-13, IS, and various tank vision devices. Yet, one of his most influential works was his marvelous design for the turret for the Kirovets-1, later IS-3. He retired from ChKZ in 1957, having received throughout his career the Stalin Prize, Order of the Great Patriotic War, and the Badge of Honor.
Georgy Vasilyevich Kruchyonyh with his awards. He was a photography enthusiast. Source: Constructor of Combat Vehicles
Design
During the 1930s and 1940s, when multi-turreted tanks were a common theme, two main solutions were used when 2 turrets of different sizes were involved. One was to mount the turrets in a “battleship style” configuration, where the smaller turret would be mounted at the front, while the larger one was pushed behind it. This was by far the most common solution, and had the main advantage of a lower silhouette and presented a smaller frontal target. This would automatically require a much longer hull, as well as decreasing the firing arc of the frontal turret. To fix this, the secondary turret could be mounted on top of the main turret, allowing for a 360° firing angle for both turrets, independent of one another, at the cost of a much taller tank profile and larger main turret.
Side cutout view of Kruchyonyh’s KV-4 proposal. The complex turret layout can be seen. Source: ASKM
Kruchyonyh went with the second option. He would have the secondary turret, which was a simple cylindrical shape on top of the main turret. He would take this concept to the extreme, giving the commander, seated in the secondary turret, his own fully rotating cupola, armed with a DT machine gun, effectively having 3 turrets stacked on top of each other. Another such armed cupola was also placed on the frontal engine deck, for the bow gunner, as opposed to a ball-mounted machine gun in the hull. Despite this, the total height of the tank was 3.78 m, which was still lower than other KV-4 designs, namely the designs by Pereverzev and Shashmurin.
A problem created by placing the secondary turret centrally over the main turret is main gun recoil. From the drawings, it is clear that the gunner of the secondary 45 mm gun would have to be very careful with the position of his right leg. If the seats were attached to the secondary turret and offered independent rotation from the main turret, he and the other crewmen operating the secondary turret would be in the direct path of the main gun recoil, essentially rendering only 1 of the guns operational at the time. The more sensible option is to have the seats fixed into the main turret, however this would mean that the crewmen had to individually rotate themselves to keep in-line with the secondary turret.
The front of the hull was made from a single, curved plate, 130 mm thick. This offered maximal protection without several interlocking plates. The engine was right between the driver and main fighting compartment, with firewalls on either side. The ammunition for the main gun was stowed horizontally in the hull. Behind it was the fuel tanks, engine cooling, and air intake systems.
Top view of the tank, with cutouts for the 3 turrets. Note the rounded rear section of the main turret. Source: ASKM
Crew
Though the GABTU specifications would request a crew of around 6 men, Kruchyonyh would design a tank with a crew of 9, which was likely the reason for why his design was not awarded anything in the competition.
The exact crew positions are not specified, but analysis of the blueprints suggests the following crew setup: tank commander, main gunner, 2 main loaders, secondary gunner, secondary loader, radio operator, driver, and bow machine gunner.
The driver sat at the front of the hull, on the left side. The bow machine gunner operated the small machine gun cupola on the engine deck. Only his head would fit in it, so the cupola and machine gun were operated via mechanical controls lower down.
The gunner, who had to be seated further away from the normal position due to the limitations of the turret ring and the need to push the gun forwards for space for the extra turret, was placed in the main turret. As a result, the gunner’s controls, including sight, had to be moved and angled. One of the main loaders was seated to the left of the main gun, with the other loader was likely in the hull, lifting shells from within it.
The 45 mm gun’s gunner and loader were positioned on the left and right side of the secondary turret respectively. The commander was seated behind the secondary gunner, in an elevated position and used the rotating cupola for a towering overview of the battlefield.
Armor
At 107 tonnes, one would expect that the armor would exceed its peer KV-4 designs. But that was not the case. It had 130 mm at the frontal plates and 125 mm at the sides and rear, just like most other designs. The dimensions were not drastically larger than other designs, with several KV-4s being both taller and longer. This could be attributed to many designers underestimating the final mass of their tanks, while Kruchyonyh was more accurate or was too pessimistic. In contrast, the lightest design was the winning one by Dukhov, weighing 82.5 tonnes, resulting in a 24.5 tonne weight span between the designs.
Armament
As required by the GABTU, the tank was armed with the 107 mm ZiS-6 gun, designed by legendary gun designer V.G. Grabin at Factory No.92, under the name F-42. It was tested on a modified KV-2 in summer 1941 and meant for the KV-3, KV-4, and KV-5 tanks. Production began shortly after, but only when it became clear that LKZ and subsequently Izhora factory could not deliver the tanks in time, the guns were melted, as there was nothing to mount them to. This deeply saddened and angered Grabin, who found it appalling that such powerful and functional guns were being destroyed at a time when any weapon was needed to fight the Germans.
The secondary armament was a 45 mm model 1937 or 1938 anti-tank gun, the same which was mounted on most Soviet light tanks of the time. While certainly obsolete in tank warfare by mid-1941 standards, it would have proven useful against infantry and soft-skin vehicles and in decreasing the wear and ammunition use of the main gun.
The tank was also equipped with 4 DT machine guns (tank variant of the DP-27). One was in each of the small rotating cupolas. The other 2 were mounted coaxially to the left of the main gun and secondary gun, giving the crew great flexibility in engaging several types of threats at different angles simultaneously.
KV-2 testing 107 mm ZiS-6 gun, summer 1941. Source: State Archives
Tower of Babel
Kruchyonyh’s KV-4 was not seen as advantageous or having any original features and thus not rewarded. Its main drawbacks were the very high weight compared to other designs and the huge crew count of 9, while the GABTU had specified just 6 men. His convoluted 3 turrets stacked on top of another was likely seen as complicated, not revolutionary. In these regards, his design can be compared more to the KV-5, which would enter the design phase in May 1941. Despite weighing over 100 tonnes, the KV-5 had 170 mm of frontal armor and 150 mm of side armor, essentially making Kruchyonyh’s design pointless.
KV-4 as designed by G. Kruchyonyh, which was the heaviest design of them all, at 107 tonnes. Illustration by Pavel Alexe.
KV-4 Kruchyonyh specifications
Dimensions (L-W-H)
9.13 – 4.03 – 3.78 m
Total Weight, Battle Ready
107 tonnes
Crew
9
Propulsion
1,200 hp diesel/kerosene V-12 M-40 with 4 turbochargers
Speed
30 km/h (hypothetical)/h
Armament
107 mm ZiS-6
45 mm 20-K
4x DT machine guns
Armor
Turret: 130 mm
Front hull: 130 mm
Side hull:125 mm
Top: 50 mm
Belly:40 mm
KV-4 by the Kuzmin, Tarotko and Tarapatin. Illustrated by Pavel Alexe.
Soviet Union (1941)
Super Heavy Tank – Blueprints Only
The KV-4 program started in March of 1941 at LKZ (Leningrad Kirov Factory), after rumors of the development of German heavy tanks. Instead of undergoing a conventional design path, J. Y. Kotin, head of the project, suggested a competition between engineers and the best entries to receive rewards. Second place was originally given to a trio of engineers, but the entry was later disqualified as it lacked a turret.
As the designs never received individual designations, aside from the general KV-4 and 224 (Object 224), most KV-4 designs are differentiated by adding the designers’ name(s). In this case, Kuzmin, Tarotko, and Tarapatin (KTT). A common name to refer to this design is K.T.T.S., which adds the Russian word “самоходка” (samokhodka) meaning self-propelled gun. This is misleading, however, as this was a heavy tank, not a self-propelled gun.
Development
–Dear reader: A more detailed development analysis of the KV-4 program can be found in the KV-4 Dukhov article–
Soviet intelligence services sent a report to the Main Directorate of Armored Forces (GABTU) on 11 March 1941, concerning the development of German tanks. Most noteworthy, or perhaps alarming, was the development of a 90 tonne heavy tank, armed with a 105 mm gun. With hindsight, we can say that these were some early plans of the Pz.Kpfw.VII or Löwe.
Soviet military officials immediately realized their lack of preparation in this regard. The only genuine heavy tank in service during the spring of 1941 was the KV-1. While it was good on paper, it had been rushed into service for propaganda purposes, more than as a direct combat weapon. Just a few months later, these critical shortcomings would come to haunt not just its LKZ designers, but the Soviet Army altogether, showing how unreliable, slow, and heavy the tank was. The KV-1, even on its best day, would not be enough in an all-out war. Thus, as early as 1940, work on heavier tanks commenced at LKZ, in the form of the T-150, the T-220, and later the KV-3. These were fine vehicles on paper, with guns and armor far superior to even the much later Tiger I, but they were very unreliable, i.e. the KV-220 broke 2 engines during its trials and weighed 62.7 tonnes.
A T-150 towing the KV-220 during trials. Source: ofis-7andotherthings
Just 10 days after the initial report, on 21 March 1941, the GABTU sent the requirements for the development of the KV-4, designated Object 224 to LKZ, tasked with designing the vehicle, where it would be simply called “224”. The military required it to be a 70 to 72 tonne heavy tank, armed with the 107 mm ZiS-6 in the turret, as well as a secondary 45 mm 20-K and at least 3 DT machine guns. Armor was to be of 130 mm at the front and 120 mm towards the sides and rear. Propulsion was provided by a 1,200 hp M-40 engine, also developed at LKZ. Crew was to be of 6 men. The deadline for the blueprints was 17 July, after which they were to be sent to various factories responsible for component production, namely Plant No.92 for construction of armaments in September and to Izhora plant in October, in charge of hull and turret production.
At LKZ, specifically the SKB-2 design bureau, work had not even started when the GABTU changed their minds and altered the KV-4 requirements on 7 April, as well as those of the KV-3, which was now to be improved and act as a stopgap until the heavier KVs were made. Most surprisingly was the introduction of a new tank, even larger and heavier than the KV-4, the KV-5, with a mass of at least 90 tonnes and 170 mm of frontal armor. The KV-4 itself was also improved, its weight increased to 75 tonnes, frontal armor to 135 mm and side/rear to 125 mm.
Work on the KV-4 began on 10 April, with J. Y. Kotint as the head of the project. Due to the very loose requirements and ability to start from scratch, he decided to test his engineer’s creativity. Thus, with the approval of the factory director I.M. Zaltsman, he set up a competition for the KV-4’s designs. Engineers would brainstorm what the KV-4 would look like, encouraging original and innovative features.The top few designs would get a financial reward. Over 20 engineers competed, submitting over 20 individual designs. The winning design was that of N. L. Dukhov, which was essentially an enlarged KV-220, but with a peculiar semi-automatic loading system. Second place went to the trio of K. I. Kuzmin, V. I Tarotko, and P. S. Tarapatin, who designed a very unorthodox tank, resembling nothing seen before, with the gun mounted in a central rotating sponson, with a smaller turret on top, in a more ‘symmetric’ fashion compared to the American M3 Lee tank. Third place went to N.V. Tseits, with a more conventional design, but which sought to have as low a hull as possible, with a large cylindrical turret. Several other designers also received monetary compensation for their designs.
The Designers
This design was created by 3 different engineers working together, K. I. Kuzmin, V. I. Tarotko, and P. S. Tarapatin.
K.I. Kuzmin began his work at the Krasny Putilovets tractor plant, and would begin work at SKB-2 on the T-28. He would go on to work on most of SKB-2s tank projects, including the T-29, SMK, KV-1 also worked alongside L.E. Sychev on the PPG (Object 217). Furthermore, he worked on the KV-3, KV-4 and was design group leader on the KV-5 and was the hull designer of the KV-13.
V.I. Tarotko’s first project at SKB-2 was on the SMK, and later worked the KV-1 as part of a trainee team of young design engineers. After the start of the war, he began work on SPGs, including the SU-122 and SU-152. In late 1944, alongside G.N. Moskvin, V.I. Tarotko would develop the “pike-nose” armor layout for the Object 252U and IS-2U, becoming an iconic design feature on Soviet post-war heavy tanks. Afterwards he would work on the development of the IS-3 and IS-4. Worthy to note is that some documents mention S.V. Mickiewicz instead of V.I. Tarotko, though likely a mistake.
V.I. Tarotko Source: Constructors of combat vehicles
Similarly to Tarotko, P.S. Tarapatin was also a young engineers, having just finished his studies. His career began working on developing the KV-1, but after the start of the war, he would work alongside his colleague Tarotko on the SU-122 and SU-152.
Design
The general layout of the KV-4 as proposed by the K.T.T. trio is one of the most unorthodox and unique amongst all other proposals. The driver and bow machine gunner sat in the hull, as on most other KV tanks. Yet right behind them was the engine and gearbox compartment, without any firewall or separation. Behind the powerpack was the fighting compartment, separated by a firewall. The main 107 mm ZiS-6 gun was mounted in a large, rotating sponson which could traverse 60° to both the left and right. Behind it, on the roof of the fighting compartment was a fully rotating turret, armed with a 45 mm 20-K gun. Right behind the fighting compartiment, separated by a partially curved firewall, was the air cooling system, which would both evacuate and intake air for the engine. While not ideal, there was simply no room to locate it closer to the engine. Thanks to the well integrated gun and low roof, the vehicle could have been relatively easy to transport (setting aside its weight) and presented a low profile, was it not for the small turret which placed it amongst the taller KV-4 designs, at 3.78 m. The engine was a M-40 V-12 aircraft engine, equipped with 4x TK-88 turbochargers, despite being a diesel engine. It had an output of 1,200 hp, and was connected to the gearbox which ran through the hull, in between the driver and bow machine gunner. Thus, the tank had frontal drive sprockets. It was estimated to reach a top speed of 36 km/h.
Due to its “turretless” layout, the tank is sometimes mistaken for a self-propelled gun, most notably, by Wargaming’s videogame World of Tanks. This is simply not the case. Similarly, N.F. Shashmurin had also opted to mount the main gun of his tank inside the hull, and after being forced (otherwise it would have been disqualified), he added a KV-1 turret on top. Truth is that there were plans on 18 April to design a KV-4 based SPG, but with just 60 mm of casemate armor and an improved 107 mm gun. The design by the K.T.T. trio is simply a heavy tank with the main gun mounted in the hull, albeit with a significant gun arc.
Side profile of the trio’s KV-4 proposal. The engine is situated between the driver and the fighting compartiment. Source: ASKM
Crew
The crew was to be of 6 men, commander, gunner, 2 loaders, bow machine gunner, and driver. The gunner and one of the loaders sat within the fighting compartiment in the hull and manned the 107 mm ZiS-6 gun. The main gun shells were stowed on the floor of the tank and in racks to the rear of the compartiment. The tank’s commander and a second loader were in the turret. Here, the commander could scan the battlefield with the rotating turret, offering an excellent view, while also being able to independently engage targets. The second loader was also in the turret, but had to bend down from his seat to lift the light, 1.43 kg, 45 mm shells into the breech. Down into the hull, at the front, was the driver (left) and bow machine gunner (right), likely also tasked with operating the radio. Both had ball-mounted DS-39 7.62 mm machine guns at their disposal, for suppressive fire more than anything. Though lack of any other machine guns, especially one with an extended firing arc, in a “mostly” turretless vehicle is a major downside, especially as many other KV-4 designs had several turrets capable of rotating independently of each other.
Top down view of the KV-4 proposal where the 2 7.62 mm DS-39 bow machine guns can be seen. Source: ASKM
Armor
Compared to other KV-4 designs, the tank in question’s armor was on the thinner side, with “just” 125 mm thick plates at the front, sides and rear. Top and belly plates were 40 mm thick. Curiously, despite being very similar to the T-50 or T-50-2 turret, the top turret was just as well armored, with what appears to be 125 mm thick plates all around, aside for the area around the gun mantlet and roof, which were 40 mm thick.
Armament
The main gun was the 107 mm ZiS-6, designed by V. G. Grabin in 45 days, at the request of Stalin himself for the new heavy tanks, although experiments and testing of similar guns started long before, in 1940. The shells weighed 18.8 kg and had a muzzle velocity of 800 to 840 m/s. Some sources claim it could penetrate 115 m of armor from 1,000 m.
The gun was mounted in a semi-rotating sponson. In other words, it was fixed on a rotating armored housing, where it could traverse 60° in both directions. Additionally, the gun had vertical movement of -5°. However, the elevation is unknown, as the document is damaged where the value is written. The crew would be required to move along with the gun, unless the gunner was attached to it, like in a conventional turret.
Regarding secondary armament, the tank had a single 45 mm 20-K Mod. 1938 gun, mounted in a smaller turret. It had 360° horizontal traverse and vertical elevation of +20°/-5°. This gun fired 1.43 kg shells with a velocity of 760 m/s. While this gun might seem underwhelming, in tandem with the 107 mm ZiS-6, it was more than useful. It was still the main gun in use on several Soviet tanks in service, from the BT-5, BT-7 and T-26, to the new T-50 and massive T-35. With hindsight, it is clear that this gun would quickly become obsolete, especially as a main weapon.
The KV-2 with the ZiS-6 107 mm gun and KV-3 mantlet during testing, June 1941. Source: Thinky via WT forums
The tank only featured 2 DS-39 7.62 mm machine guns, both in fixed ball mounts in the hull, for the driver and bow gunner/radio operator. This opened large fire blindspots for the semi-turretless tank, increasing the dependence on the 45 mm gun, and in turn, strain on the commander, who acted as its gunner. Even so, the lack of any other machine gun meant that suppressive fire was impossible and the tank was vulnerable to rear infantry attacks.
Misinterpretation
The 3 engineers sought to create an eccentric vehicle, with several unique features, such as the sponson-mounted main gun or engine cooling layout. For these, Kotin and the judges initially awarded the design second place, landing the 3 men 3000 Rubles to share. However their joy was short-lived, as their design was later disqualified after concerns that it did not fit the GABTU’s requirements, which originally specified that the main gun was to be mounted in a fully-rotating turret. This detail was (likely) omitted in the second request. The result of their disqualification meant that the design by N.V. Tseits would be lifted to second place, which had a direct impact on the development of the KV-5, which used many aspects of Tseits’ KV-4 proposal. Oddly, Shashmurin’s design, which also mounted the main gun in a casemate, was not disqualified. Furthermore, he used the “wrong” gun, placing a KV-1 turret and gun on the roof of the casemate.
The KV-4 proposal as it is represented in the game World of Tanks, called KTTS. Note that it does not have the original 107 mm ZiS-6, but rather it has the 107 mm M-75, a gun which the KV-4 heavy tank was never intended to equip. Source: Wargaming
The entire KV-4 project was rather hopeless. After the announcement in May of the competition’s winner, N.L. Dukhov, work on the KV-4 virtually stopped. Instead, the team shifted focus towards preparing blueprints for the KV-5. Work on these heavy tanks was slowed down by the German invasion of the USSR on 22 June, and eventually, completely halted in September, when German troops were approaching Leningrad and the SKB-2’s design bureau was evacuated to ChTZ, later renamed ChKZ, in Chelyabinsk.
The KV-4 as designed by Kuzmin, Tarotko, and Tarapatin (KTT). Illustration by Pavel Alexe.
Interpretation of Kreslavsky's KV-4 design by Pavel Alexe. Illustration funded through our Patreon campaign.
Soviet Union (1941)
Super Heavy Tank – Blueprints Only
The KV-4 program can be regarded as one of the most unsuccessful and short-lived tank design ideas of the Soviet Union during the WW2 period. This is especially true considering its expectations, the caliber of the engineers behind it, J. Y. Kotin and N. L. Dukhov, to name a few, and those who ordered it to begin with, including Stalin himself. Many designs were proposed in what was essentially a drawing competition, some quite sensible, while some were less so. One rather forgettable design was that by young engineer M. I. Kresavsky, who did not receive any awards for his design. Big, heavy, and with no advantages over other designs, it remained, and still is largely, forgotten, with just minor recognition in Wargaming’s World of Tanks.
Development
–Dear reader: A more detailed development analysis of the KV-4 program can be found in the KV-4 Dukhov article–
Despite the Molotov-Ribbentrop Pact, and previous German-Soviet tank collaborations, in 1941, the situation in Europe was ugly, and German expansion was worrying for the Soviets. Things took a turn for the worse when, on 11 March, a report submitted by the Soviet Intelligence agencies regarding German armament development included a chapter on German heavy tanks. Here, amongst other tanks, a 90-tonne heavy tank armed with a 105 mm gun was mentioned. The Soviet military, recognising its unpreparedness against such a threat, ordered work on a Soviet tank that could match such an enemy tank.
Just 10 days after the initial report was sent, on 21 March, the GABTU (Main Directorate of Armed Forces) sent out the request for a new heavy tank, designated Object 224 or KV-4, as it was to be designed at the Leningrad Kirov plant (LKZ). The design of the tank was to be done by the SKB-2 design bureau, headed by the famous tank designer J. Y. Kotin. The Soviet state requested the tank to be a 70-72 tonne tank and armed with the 107 mm ZiS-6 main gun, a secondary 20-K 45 mm gun, 3 machine guns, and 1 flamethrower. Armor was to be of 130 mm at the front and 120 mm towards the sides and rear. Propulsion was to be provided by an M-40 aviation diesel engine, with 4 TK-88 turbochargers, outputting 1,200 hp. The crew was to be of 6. Deadline for the tank plans was 17 July.
It was not long until the GABTU changed their minds and, on 7 April, reordered the entire program. Firstly, the KV-3, which was previously under development, was reinstated and upgraded to act as a stopgap tank until the KV-4 and KV-5 were ready for production. The KV-5 itself was created, a 90-tonne tank which would have had 170 mm of armor at the front and 150 mm at the sides, though same armament and powerpack as the KV-4. The 2 would compete against each other, and the winning vehicle would be produced. The specifications of the KV-4 were also tampered with, increasing the weight to at least 75 tonnes, 135 mm of frontal armor and 125 mm on the sides and rear. The deadline for the tank’s drawings was narrowed to 15 June.
Work began on 10 April at LKZ, and Kotin, after seeking approval and funding from factory director I. M. Zaltsman, decided to let the engineers compete against each other. The best designs would be financially rewarded. The SKB-2 design bureau already had experience with heavy tank development. It was the same group of people behind the SMK, T-100, KV-1, T-150, KV-220, and KV-3. Over 20 engineers from SKB-2 competed against each other, some even teaming up, presenting well over 20 different tank designs. The winner was N. L. Dukhov, with a KV-4 that was essentially just an enlarged KV-220. Second place went to the trio of K. I. Kuzmin, V. I Tarotko and P. S. Tarapatin, which had the main gun inside the turret (and later got disqualified), and third place to N. V. Tseits, whose design featured a very low profile hull, but a massive turret. Though not all designs were as well received. Over 10 designs did not receive any rewards. One of these was the one by engineer M. I. Kresavsky.
M.I. Kresavsky
A young engineer from the Leningrad Politechnic institute, M.I. Kresavsky (also sometimes spelled Kreslavsky) was drafted by Kotin and worked for him for 30 years. Apart from his work on the KV-4, Kresavsky worked on the SMK and the transmission of the KV-1, alongside V. A. Kozlovsky. He also participated in the design of the KV-2 IS and IS-3 tanks.
A young M.I. Kresavsky at SKB-2. Source: Constructor of Combat vehicles- N.Popov
Design
At first glance, the KV-4, as designed by Kresavsky, was nothing special, other than its sheer size. At exactly 9 m in length, and over 4 m in width, it landed on the larger side of the KV-4 spectrum. Mass-wise, the 92.6 tonne design was around average, with the lightest design being 82.5 tonnes and the heaviest 107.7 tonnes. Yet, a couple of details make it into a rather strange design from a mechanical aspect. Primarily, the engine was mounted over the 3rd and 4th roadwheels, right behind the driver, separated by a firewall. The transmission protruded through the firewall towards the final drive, located at the driver’s feet. This, in turn, worked the front drive sprockets. In terms of propulsion, the tank was, as requested by the GABTU, equipped with an 1,200 hp M-40 engine, with 4 TK-88 turbochargers. For vision, the driver had a complex, rounded armored bulge, extending from the hull, made from several cast and welded components. The bow machine gunner had his own such “bulge” on the opposite side of the hull.
The turret and fighting compartment were behind the engine room, separated by another firewall. Inside the hull, ammunition was stowed. Above was the hexagonal turret, made from 125 to 130 mm plates pressed into shape and welded together. On top, a conical turret with several vision slits was attached. The main 107 mm ZiS-6 gun was mounted to the left of the center, while the 45 mm 20-K to the right. Back inside the hull, a 4th compartment was added, which housed the fuel tanks and engine cooling system, which was pulled through the fighting compartment. While seemingly complex, this entire layout offered several advantages. Firstly, it protected the crew, ammunition, and fuel tanks from frontal impacts. Secondly, the turret was offset far enough to the rear that the gun barely hung over the hull, easing transport and reducing potential barrel damage during maneuvers in areas such as cities or forests.
Cutout side view of Kreslavsky’s design. Source: ASKM
Crew
The vehicle had a crew of 6: commander, gunner, 2 loaders, driver, and bow machine gunner/radio operator. The commander, seated in the back of the turret, operated the cupola, equipped with 6 vision slits and one 7.62 mm DT machine gun. The gunner sat to the right of the 107 mm main gun and was very likely able to remotely operate the 45 mm gun too. The 2 guns had individual loaders sat behind them. Another ball-mounted DT machine gun was mounted on the rear plate of the turret, likely to be used by one of the loaders. There are no visible entry/exit hatches, but a reasonable assumption would conclude that there would be 2 hatches, one on the cupola and another on the left side of the turret roof.
The driver and bow gunner were seated in the hull, each on either side of the gearbox. Both had their own armored, rounded protrusions, which allowed for more headroom and better visibility, equipped with at least 4 vision slits each.
Top view drawing of Kreslavsky’s KV-4. The tracks are missing from this scheme. Note the gun mantlet and the way the guns are placed. Source: AKSM
Armor
In relation to other KV-4 designs, the armor on Kreslavsky’s KV-4 was nothing special. Frontal plates on both the hull and turret were 130 mm thick and rounded, increasing the effectiveness from certain angles. Only the frontal upper plate was thinner, at just 80 mm, though it was angled at 10° from horizontal, bringing it to an LoS thickness of 461 mm. Armor on the driver’s cupola varied from 125 mm at the front to 60 mm on the roof. Side and rear armor was 125 mm thick, while roof armor was 50 mm and belly armor was 40 mm thick.
Armament
The main gun on all KV-4 designs was the ZiS-6, with a 107 mm caliber, designed by the famous V. A. Grabin. By March 1941, the Soviets had already worked for several months on 107 mm caliber guns, and were proving to be very powerful, especially in regards to armor penetration. Thus, when the news of German heavy tanks came, Stalin himself rang Grabin, requesting the design of a new, powerful gun. Thus the F-42 was born, completed in just 45 days. In March, it was renamed to ZiS-6. Factory trials proved promising after delayed tests were conducted on a KV-2 armed with the gun and a KV-3 gun mantlet. Production started shortly after. However, according to Grabin’s memoirs, after the cancellation of the LKZ heavy tanks, over 800 such gun barrels had to be melted. The gun itself had an 18.8 kg one-piece shell, with a muzzle velocity between 800 to 840 m/s.
One of the first ZiS-6 107 mm guns produced. Source: Yuri Pasholok via Warspot
The secondary armament, a 20-K 45 mm, was mounted coaxially, to the right of the center of the mantlet. There was no space in between the 2 guns for another gunner, so it is assumed that the main and single gunner sat to the left of the main gun, and could remotely operate the 45 mm gun too, using some form of mechanical system. The gun itself fired BR-240SP AP rounds, which weighed 1.43 kg, had a muzzle velocity of 757 m/s and a (artificially calculated) penetration of 73 mm at 0 m.
A total of 3 DT 7.62 mm machine guns were mounted on ball mounts in the tank, one by the bow machine gunner, in the hull, one in the commander’s cupola and one on the rear turret plate, likely operated by one of the loaders, when necessary.
Drawings og the 45 mm K-20 gun with its turret gun mount. Source: Armored Wiki via VK.com
Dinosaur Extinction
The KV-4 program did not go far at all. The LKZ staff failed to present final blueprints in time, and the program was delayed. Without them, the Izhora plant, tasked with production of the tank prototype, could not begin work either. The truth is that the program slowly died after the competition, and work shifted towards the more exciting KV-5. With the German invasion of the Soviet Union on 22 June 1941, work still continued. Only in August, when the German forces were approaching Leningrad, did work on these tanks pause. The SKB-2 design bureau was evacuated to the ChTZ, later renamed ChKZ in Chelyabinsk, and work on the KV-4 never resumed.
Conclusion
Though one might see the KV-4 program as unlucky and doomed, Kresavsky’s own proposal was even more so. It failed to spark any interest from the ‘judges’ and brought nothing revolutionary enough, in what was actually quite a large tank, even compared to other KV-4 designs. Only in the recent decade has Kreslavsky’s proposal received some ‘love’, being introduced in the massively multiplayer online game, World of Tanks.
KV-4 Kresavsky as interpreted by Wargaming. Note that it does not have the original 107 mm ZiS-6, but rather it has the 107 mm M-75, a gun that the KV-4 heavy tank was never intended to mount. Source: TheDailyBounce.netInterpretation of Kresavsky’s KV-4 design by Pavel Alexe. Illustration funded through our Patreon campaign.
KV-4 Kresavsky Specifications
Dimensions (L-W-H)
9.0 – 4.0 – 3.225 m
Total weight, battle-ready
92.6 tonnes
Crew
6 (commander, main gunner, driver, secondary gunner, radio operator, & loader )
Propulsion
1,200 hp diesel V-12 M-40 with 4 turbochargers
Speed
45 km/h
Suspension
Torsion bar, 7 wheels per side
Armament
107 mm ZiS-6 (F-42) (103 rounds)
45 mm Mod.1937 20-K coaxial (140 rounds)
3x 7.62 mm DT machine guns (4,000 rounds)
Armor
Turret: 130 mm
Front hull plate: 130 mm
Front upper plate: 80 mm
Side plate: 125 mm
Rear plate: 130 mm
Top: 50 mm
Bottom: 40 mm
Interpretation of Tseits' KV-4 design by Pavel Alexe. Illustration funded through our Patreon campaign.
Soviet Union (1941)
Super Heavy Tank – Blueprints Only
The KV-4 heavy tank program was started in April of 1941, based on an illusion of Soviet Intelligence services, which claimed that the Germans were working on a 90-tonne heavy tank. Design was undertaken at the LKZ factory via a competition of engineers. Amongst them was senior engineer N. V. Tseits, who designed one of the most successful KV-4 designs, being awarded third, and later, second place.
Development
–Dear reader: A more detailed development analysis of the KV-4 program can be found in the KV-4 Dukhov article–
On 11 March 1941, the Soviet intelligence services sent a report to the Main Directorate of Armed Forces (GABTU) regarding German tank development. Amongst several other topics, heavy tanks had been discussed, of which a 90 tonne heavy tank armed with a 105 mm gun which was apparently under development.
This came as a large surprise to the Soviet military officials, which immediately realized their lack of preparation in this regard. At the time, the KV-1 was the main heavy tank of the Soviet armored forces, but it was completely unprepared for service, let alone combat. Its problems would become apparent at the start of the German invasion of the USSR, highlighting its poor mobility and mechanical unreliability. Work began as early as 1940 on creating a heavier and better armored KV-1, most notably the T-150, KV-220, and later the KV-3. Here, it is relevant to remember that even the KV-220, armored with a 85 mm gun, could have stood up to even the Tiger I, which entered service over a year later, had its crucial mechanical problems been fixed.
Shortly after, on 21 March 1941, the GABTU sent out the requirements for the development of the KV-4, designated Object 224, or just 224. It was to be a 70 to 72 tonne heavy tank, armed with the 107 mm ZiS-6 in the turret, as well as a secondary 45 mm 20-K and at least 3 DT machine guns. Armor was to be of 130 mm at the front and 120 mm towards the sides and rear. Propulsion was provided by a 1,200 hp M-40 engine, also developed at LKZ. Crew was to be of 6 men. On 27 March 1941, the deadline for the tank design was set to 17 July, not including the prototype building and armament testing, which were set as late as October of the same year.
Yet, in an unanticipated turn of events, on 7 April 1941, the GABTU rethought the requests on the KV-4. The weight was raised to 75 tonnes, and armor as thick as 135 mm. Side and rear armor was to be 125 mm thick. The blueprints’ deadline was also narrowed, to 15 June. It was at this time that the KV-5 was requested, a tank that was to weigh at least 90-tonnes, have 170 mm of armor at the front and 150 mm at the sides. Additionally, the KV-3 was ‘revived’ and improved to fulfill a stopgap role until the KV-4 and KV-5 tanks were ready for production.
At LKZ, the SKB-2 design bureau began work on 10 April. Head of the project was the famous J. Y. Kotin, who, after seeking approval and funding from factory director I. M. Zaltsman, decided approach the design of the tank in an unusual way, by creating a competition between the SKB-2 engineers. The top few designs would get a financial rewards. Over 20 engineers competed, submitting over 20 individual designs. The winning design was that of N. L. Dukhov, which was essentially an enlarged KV-220. Second place went to the K. I. Kuzmin, V. I Tarotko and P. S. Tarapatin trio, who submitted a tank with the main gun in the hull and secondary gun in a small turret. Third place went to N. V. Tseits, who submitted a tank with a very low hull, but large turret, to offset the lack of hull space.
N.V. Tseits
Nikolai Valentinovich Tseits* was born in Moscow in 1884 and studied engineering at the Bauman Moscow State Technical University, graduating in 1922. In 1925, he started working at the Ordnance-Arsenal Trust and from 1928 onwards worked in the Kazan German-Soviet tank facility. In 1930, he was arrested on counter-revolutionary charges and sentenced to 10 years in labor camps, but the charges were dropped in 1932, after working at a automobile and tractor design bureau. From 1934, he worked at the experimental plant No.185 and, from 1937, at the SKB-2 design bureau of LKZ, where he was the oldest, most knowledgeable and, in turn, most respected engineer. Through his tank design career, he worked on the T-28, T-29, T-35, SMK, KV-3, KV-5, and, lastly, the KV-13. In 1942, after working non-stop for months on the KV-13, he was granted 1 week leave by head engineer J. Y. Kotin, which he used for hunting. Upon his return to ChKZ in Chelyabinsk, he felt unwell and died shortly after at the factory medical office from an unidentified cause. According to the memoirs of N. F. Shashmurin, who was in the room before his death, Tseits had gifted him a slide ruler to remember him by. Tseits was 68 years old at the time. He was awarded the Order of Lenin and Order of the Badge of Honor.
*the spelling Tseits is an anglicized version of the Cyrillic name Цейц.
Nikolai Valentinovich Tseits. Source: Wikimedia commons
Design
In terms of general layout, Tseits kept his design traditional, with the engine towards the rear and turret in the center of the hull. What was not traditional, at least for a Soviet tank, was the final drive, which had been moved to the front, as opposed to having it combined with the engine. Another unusual feature was the very low hull roof. In order to offset the low hull, the turret was large in all directions, so much so that it had to be ‘lowered’ into the hull, with the turret ring being below the level of the driver’s head. The height of the turret allowed for the main gun ammunition to be stowed vertically, in great numbers, with 100 to 120 rounds stowed on the turret side walls and underneath the turret ring. A secondary turret was placed on top, armed with a DT 7.62 machine gun.
The 1,200 hp M-40 engine, with 4 TK-88 turbochargers, was housed at the rear of the hull, resembling modern MBTs, as opposed to a design from 1941. The air cooling was directed via a protruding chamber, at the rear, as opposed to a curved plate, as on most KV tanks. The driveshaft ran from the engine over the torsion bars and underneath the fuel tanks that were in the center of the hull, underneath the turret ring. The final drive, brakes and gearbox were placed at the tip of the hull, at the feet of the driver and bow machine gunner.
Side view of Tseits’ KV-4 design. Note just how short the hull is in comparison to the turret height. Source: ASKMTop view of Tseit’s design. The circular turret can be seen, as well as part of the ammunition layout. Source: ASKM
Crew
As designed, the tank was to have a crew of 7 men: commander, main gunner, main loader, loader assistant, driver, bow machine gunner and radio operator/secondary turret operator.
Unfortunately, exact positions for all the crewmen are not given, so some speculation is required. The driver and bow machine gunner were both seated inside the hull. Here, the hull roof was lifted to allow for placement of the 7.62 mm bow machine gun in a ball mount and to give room for the 2 crewmen’s heads. The driver had 3 periscopes for vision, in addition to the vision slit in the hull. The rest of the crewmembers were likely placed in the roomy turret. The gunner was to the left of the gun and the commander to the opposite side, on the right. Behind them were the 2 main loaders, each tasked with loading the gun from the opposing sides of the turret walls. The ammunition stowage did not have any rotation system, similar to later autoloaders, thus requiring several loaders to reach all sides.
Armor
The turret was made from curved armor plates into a semicircle 125 mm thick. The only exception was the front of the turret, which consisted of a single, angled, flat plate, 130 mm thick. On it was the gun mantlet. The roof of the turret was partly angled at the front and 50 mm thick. The lower frontal plate was 130 mm, as was the front of the driver’s cubicle. The upper frontal plate, angled very steeply, sas just 50 mm thick. Hull sides and rear were 125 mm thick. Other areas were 50 to 40 mm thick.
Armament
The main armament was the ZiS-6 107 mm gun, previously named F-42. It was designed by the famous V. G. Grabin in record time at Stalin’s personal request for the new heavy tanks. The gun was tested, after many delays, in June 1941 on a KV-2 with a KV-3 mantlet, and after good performances, entered production. According to Grabin’s memoirs, around 800 barrels had been built, and subsequently melted down after the failure of the KV-3, KV-4. and KV-5 programs. The gun could fire an 18.8 kg one-piece shell at 800 to 840 m/s.
KV-5
Tseits’ design was greatly appreciated and placed 3rd in the competition, losing only to Dukhov’s design and the design by the K. I. Kuzmin, V. I. Tarotko, and P. S. Tarapatin trio. However, shortly after, the latter design, which placed second, was ‘disqualified’, likely due to the design not respecting original technical specifications and requirements. This, in turn, moved Tseits’ design up to second place.
On 7 April, in addition to changing the specifications of the KV-3 and KV-4, the GABTU requested an entirely new tank, larger and heavier than the already 80 to 90 tonne KV-4. It was to weigh at least 90 tonnes, have armor as thick as 170 mm at the front and 150 mm at the sides. J. Y. Kotin initially intended to start its development in the same way as on the KV-4, via a competition between engineers. But, as the requirements were similar (and equally vague) to the KV-4, it was decided to save time and use the results from the KV-4 competition. As a result, Tseits’ design, now being on second place, was chosen as the basis for the KV-5, and N.V. Tseits was chosen as senior machine designer of the project. Other engineers that placed high in the competition were given different roles in designing different segments, such as K.I. Kuzmin (head of design group), L. E. Sychev, A. S. Ermolayev, L. N. Pereverzev, and V. Bykov among others.
The design was kept very similar to Tseits’ KV-4 design, such as the large turret and low hull, but major changes were made, including moving the final drive to the rear, making the turret a pentagonal shape (much easier to weld straight plates compared to stamping them into a curve), as well as the driver and bow machine gunner being seated into individual ‘pods’.
Original blueprints of the KV-5 showing the hull. Source: ASKM
Conclusion
The KV-4 design created by N.V. Tseits was, arguably, the most successful KV-4 design. While N.L. Dukhov’s design did win the competition and was to become the final variant of the KV-4, Tseits’ design was the basis of an even more powerful tank, in the form of the KV-5. However, considering the KV-5s nearly pointless birth, short life and unmourned death, it is not much of a gratification to a series of projects considered by the designers themselves as madness.
Interpretation of Tseits’ KV-4 design by Pavel Alexe. Illustration funded through our Patreon campaign.
P. P. Mikhailov's KV-4 proposal. Note the cylindrical turret and sideskirts. Illustration by Pavel Alexe, funded through our Patreon campaign.
Soviet Union (1941)
Super Heavy Tank – Blueprints Only
The KV-4 program started in spring 1941 as the response to rumors of German heavy tank development. A design competition between engineers at LKZ in Leningrad was held, with several designs awarded, though most others were ignored. One of these was the design proposed by P.P. Mikhailov, which brought several innovative features to the table, such as tracks within the hull, conical turret, and sideskirts. Who P.P. Mikhailov was, and his role at LKZ, is yet to be uncovered.
Development
–Dear reader: A more detailed development analysis of the KV-4 program can be found in the KV-4 Dukhov article–
The KV-4 program was born from a letter sent by the Soviet Intelligence Services to the Soviet military. This letter, sent on 11 March 1941, had information regarding a German heavy tank, weighing 90 tonnes, and armed with a 105 mm gun. The Main Directorate of Armed Forces (GABTU) was alarmed, as the heaviest tank in Soviet service was the 45 tonnes KV-1, which at the time was mechanically unreliable, and entirely unfit for production. Over at LKZ (Leningrad Kirov Factory) in Leningrad, at the SKB-2 design bureau, where the KV-1 was created, several heavier tanks had been designed, such as the KV-220 and KV-3, but these were still no match for the suspected German heavy tank.
Thus, on 21 March, the GABTU sent LKZ the original requirements for the KV-4. It was to weigh around 70 tonnes and armed with the 107 mm ZiS-6 in a turret and a 45 mm 20-K in a secondary turret. The engine was to be a 1,200 hp enhanced aviation diesel V-12 M-40. Armor was set between 130 and 120 mm at the front, sides, and rear. On 27 March, the deadline for the complete blueprints was set to 17 July.
However, by 7 April, the requirements were changed again. The KV-3 was to be revived, and its specifications vastly improved. In turn, the KV-4 would also weigh 75 tonnes, and have its armor increased to 135 mm. The deadline was also brought forward to 15 June. Most interestingly, LKZ was also assigned the development of the KV-5, a 90 tonne tank, with 150 to 170 mm of armor but also armed with the 107 mm ZiS-6. It would compete against the KV-4, with trials expected to be held in the beginning of 1942. In the meantime, until either entered mass production, the KV-3 would act as a stopgap.
Chief Designer of the program was J.Y. Kotin, who, considering the liberal requirements for the program, decided to approach the design in a unique fashion. He set up a competition between the engineers at SKB-2. For encouragement, he offered financial rewards for the top 7 best designs. By 9 May, the competition was over and the winners were announced. In total, between 24 and 27 proposals were submitted, and 11 prizes were awarded to 13 designers, as several designs were given the same spot and some designers teamed up.
First place went to N.L. Dukhov, second to Kuzmin, Tarotko and Tarapantin, and third to Tseits. Mikhailov’s design was less fortunate, and was one of the many who did not receive any awards for his creation, despite a handful of creative features.
Unfortunately, unlike some of the other competitors, so far, there is no information on who P.P. Mikhailov was, his position at LKZ, what he worked on later on, or his life in general.
Design
In terms of general layout, Mikhailov had a standard approach, with the driver in the hull front, centrally mounted turret, and powerplant package in the rear. Yet the design of these components was very bizarre. The turret was inspired from that of the KV-3, having a large conical shape. Inside, the main 107 mm gun was mounted.
Cutout side view of the design. Note the pattern of the track being forced down by the two return rollers at the base of the hull, right above the roadwheels. Source: ASKM
The hull is where the design gets more bizarre. The tracks were pushed into the hull, a unique feature, as most Soviet (and modern Russian tanks) have them mounted outside the hull, including the KV-1. Consequently, as moving the tracks inside the hull removed significant usable space the hull, the tracks were forced down onto the roadwheels, instead of laying straight in the center of the hull. This allowed for more space, increasing the hull width in those areas where ammunition and fuel tanks would be placed. Yet the hull was still shorter than many other KV-4 designs. The front of the hull was standard for a KV tank, but the driver and radio operator compartiment were raised in relation to the rest of the hull. The rear was a single plate, stamped into shape.
The KV-4 was powered by a M-40 V12 diesel engine outputting 1,200 hp, also developed at LKZ from 1938 (after the original designer was arrested and killed). It was mounted in the rear of the hull, separated from the crew compartment by a designated firewall. The V12 power plant was coupled to the transmission and final drive, which in turn drove the sprockets. To compensate for the bizarre angling of the tracks and their incorporation within the hull, the air cooling vents had to be angled at the same plane as the tracks, from where the air housing would protrude from the hull. As for air intakes, these were mounted on the engine deck, behind the turret.
Top view drawing of Mikhailov’s KV-4. Notice how the tracks are underneath the hull, and not outside of it. Source: AKSM
The sprocket and idler were mounted at a “normal” level in relation to the hull. This allowed for adequate angles of attack, and in turn, the off-road capabilities were unharmed by the deviation of the track path. To lower the tracks down, two guide wheels were mounted on the external side of the track. These would also allow for smoother track travel, lowering the chance of the track hitting the hull and potentially hopping out of its travel path. Furthermore, the track’s guide pins would enter the roadwheels, which in turn acted as return rollers. There were 7 roadwheels per side, sprung by torsion bars. These were far larger in diameter compared to the standard KV wheel, while the idler was the same size.
Cutout rear view of Mikhailov’s design. Note the side skirts, which act as the side armor in itself. Source: ASKM
Crew
The crew was to be of 6, consisting of the tank commander, main gunner, main loader, driver, secondary gun operator, and radio operator. They would communicate with a 10-R intercom.
The commander, main gunner, and loader were placed in the turret, with the gunner to the left of the gun, commander to the right, and loader behind the commander. The loader had to stand up and load the shells mounted in the hull, underneath the turret and to the sides. The drawings only show a single entry/exit hatch, right above the breech of the main gun. If the commander and gunner would not have their own hatches, this would have posed a great issue, not only in emergency exit situations, but in standard service and operation of the tank, with the 3 crewmembers having to wait for the others to enter and exit. The amount of periscopes and/or vision slits is unspecified, but if it were to follow a typical KV design, the commander and gunner would receive their own rotating periscope, in addition to various fixed periscopes around the turret. In contrast to other KV designs, the commander was also the operator of the radio, allowing for direct communication with other tanks.
The driver’s position was to the left of the side of the hull, while the secondary gun operator was to the right. He was quite overburdened, having to aim, fire and load the hull-mounted 45 mm 20-K gun. The two had their own individual entry/exit hatches, situated right above their seats, in the roof of the hull. Notable is that the roof was elevated in their positions, offering more room. The driver also had a ball-mounted DT machine gun. The radio operator was likely situated further in the hull or inside the turret.
Armor
At 86.5 tonnes, it would have been the third lightest design submitted. Yet despite its lower mass and smaller dimensions, it had the thickest plate out of all designs, regarding sheer thickness. The entirety of the turret was 130 mm thick. Measurements of the drawings reveal that the frontal turret plate was 130 mm (the mantlet had the same thickness, resulting in a cumulative of 260 mm). The turret did not have the shape of a homogenous cone, as it was angled at 75º at the front and rear, resulting in 135 mm of effective thickness, and 60º at the sides, resulting in 150 mm. The hull protection was standard, with 130 mm at the front and sides. Here, it is important to highlight that the side armor was on the external side, acting as a side skirt, a feature common on heavy tanks of the 1930s. Belly armor was 50 mm and roof and deck armor was 40 mm. The design of the turret resembles that of the KV-3, but rounder.
Wooden mock-up of the KV-3 tank in its later stages. Source: Tank Archives
Armament
The main gun, just like on all the other KV-4s, was the 107 mm ZiS-6 gun. It was first designed by V.G. Grabin for the KV-3, after Stalin himself reached out, concerned about the armaments of the KV series of tanks. It was designed in just 38 days, based on the already existing F-42, but renamed ZiS-6. In March of 1941, the Izhora plant was tasked with building a test turret fitting the ZiS-6 in a KV-2. After tests in that summer, the gun was ready to enter production, but the tanks themselves were not ready. It has a muzzle velocity of 88 to 840 m/s and a shell weight of 18.8 kg. Ammunition appears to have been stored exclusively in the hull, underneath the turret. The gun could elevate to +20 and depress to -5. The B-420 rounds had a muzzle velocity of 830 m/s and could penetrate a 120 mm plate angled at 30° from vertical, from 1,600 m. These rounds weighed 18.8 kg.
One of the first ZiS-6 107 mm guns produced. Source: Yuri Pasholok via Warspot
The secondary armament, a 20-K 45 mm, was mounted in the hull, with limited traverse. Its ammunition was stowed to the right of the gun, in between the track and fuel tank. It used BR-240SP AP rounds, which weighed 1.43 kg, had a muzzle velocity of 757 m/s and a (artificially calculated) penetration of 73 mm at 0 m. An unspecified flamethrower was also mounted in the hull, on the left side over the track.
Drawings of the 45 mm K-20 gun with its turret gun mount. Source: Armored Wiki via VK.com
Scattered around the tank were three ball-mounted DT 7.62 mm machine guns, one in the hull, operated by the driver, and two in the turret, facing the rear. These would have been operated by the loader and commander, and offered some protection against approaching infantry.
Failed Program
After the competition was completed, progress on the KV-4 virtually halted. The situation worsened when Germany started their invasion of the USSR in June 1941. Work instead shifted to the KV-5, which had complete detailed blueprints by August. However, the German forces were getting closer and closer to Leningrad and the factory workers and engineers were evacuated to ChKZ in Chelyabinsk. The KV-4 and KV-5 programs were canceled, as they would not be of any immediate military use, and divert necessary funds for the war effort.
Conclusion
The entire KV-4 program ended up as a failure, but Mikhailov’s design was not considered as having any beneficial features, and was not taken in consideration or awarded in the competition. Mikhailov did add a series of interesting features, such as bringing the returning track links down, for a wider hull. But one of the most sensible decisions, and unique features of the program, was moving the tracks within the hull altogether, as opposed to having them on the outside. This allowed for a more compact tank and less overall mass.
Special thanks to Zinoviy Alexeev
P. P. Mikhailov’s KV-4 proposal. Note the cylindrical turret and sideskirts. Illustration by Pavel Alexe, funded through our Patreon campaign.Side view of Mikhailov’s KV-4 with the sideskirts removed, showing the interior of the hull and running gear.
KV-4 Mikhailov Specifications
Dimensions (L-W-H)
9 – 3.6 – 3 m
Total Weight, Battle Ready
86.5 tonnes
Crew
6 (commander, main gunner, driver, secondary gunner, radio operator, & loader )
Propulsion
1,200 hp diesel V-12 M-40 with 4 turbochargers
Speed
50 km/h (hypothetical), 35 km/h (realistic)/td>
Suspension
Torsion bar, 7 wheels per side
Armament
107 mm ZiS-6 (F-42)
45 mm Mod.1937 20-K (hull-mounted)
3x 7.62 mm DT machine guns
Unspecied flamethrower
Armor
Turret: 130 mm
Front hull plates: 130 mm
Side plate: 130 mm
Belly: 50 mm
Top: 40 mm
The KV-4 design as drawn by S.V. Fedorenko. Illustration by Pavel Alexe, funded through our Patreon campaign.
Soviet Union (1941)
Super Heavy Tank – Blueprints Only
In the spring of 1941, with the alleged new of a new German super-heavy tank under development, the Soviets triggered the development of several heavy tank programs. One of them was the KV-4, or Object 224. The LKZ factory in Leningrad was tasked with developing these via a competition amongst factory engineers. One of them was S.V. Fedorenko, the SKB-2 design bureau armament specialist. Yet despite his knowledge and vast array of tanks worked on, his KV-4 design was not taken into consideration.
Development
–Dear reader: A more detailed development analysis of the KV-4 program can be found in the KV-4 Dukhov article–-
A letter sent to the Soviet authorities by the Soviet Intelligence Services regarding German tank development on 11th March 1941 included a section on the development of German heavy tanks. Here, 3 different models were described, a 30-tonne Pz.Kpfw.V, a 45-tonne Pz.Kpfw.VI, and lastly, a 90-tonne Pz.Kpfw.VII. Which exact tanks these were is unclear, as the real Pz.Kpfw.VII, nicknamed Löwe, did not appear in official documents until November of the same year. Previous tank designs fitting (loosely) descriptions would be the VK30.01 series, VK36.01 and VK65.01.
The idea of a 90-tonne German tank was alarming and the GABTU (Main Directorate of Armed Forces) would quickly request the development of a new super-heavy tank. It was designated Object 224 or, more commonly, KV-4, as called by the factory that would develop it- the Leningrad Kirov plant (LKZ) at its SKB-2 design bureau. The factory had not only designed the KV-1 and SMK heavy tanks, but also heavier variants, such as the T-150, KV-220, and KV-3.
It is important to note that the heaviest tank in service with the Soviet army at the time was the KV-1 itself, which, once the war broke out, would prove a great disappointment. This came as a result of the political rush to push it into military service, even when it was not completely ready. Thus, KV tanks suffered from constant breakdowns from the poorly designed gearbox. They were slow and crews generally preferred the T-34. The situation reached a point where Stalin himself wanted to remove it from production if the issues would not be fixed. To compound the problems with the KV-1, at the time, it was only equipped with the F-32 76 mm gun, a gun inferior to the F-34 on the lighter and more reliable T-34.
On 21st March 1941, the GABTU requested that the KV-4 would be a 70-tonne heavy tank, armed with the ZiS-6 (previously called F-42) 107 mm gun, a 45 mm 20-K secondary gun, 3 DT 7.62 mm machine guns, and even a flamethrower. Armor was to be as thick as 130 mm at the front and 120 mm at the sides and rear. The engine would be a M-40 1,200 hp V-12 engine, with 4 turbochargers. The crew was to be around 6 men. Only 6 days later, the LKZ plant was ordered to complete the blueprints by 17th July, the Izhora plant to complete the prototype turret and hull by 1st October and Plant No. 92 to deliver the necessary armament by 1st September.
However, by 7th April, the GABTU changed their minds. They would request heavier parameters for the KV-3, up to 68 tonnes and the same ZiS-6, while the KV-4 would be increased to 75 tonnes weight, armor improved to 135 mm at the front and 125 mm at the sides and rear. The deadline was also tightened to 15 June. In the same request, the GABTU requested an even heavier vehicle, the KV-5, with 170 mm at the front and 150 mm at the rear, and weight of 90 tonnes. The sudden changes in design, and the increased time pressure, as well as the pressure of Stalin’s interest in the project served to make the design process more problematic and have knock-on effects.
LKZ began work on the KV-4 on 10th April. The head engineer was J.Y. Kotin. Here, the requirements would be changed once again, placing the mass between 80 and 100 tonnes. Considering the loose specifications, Kotin approached the design in a unique manner. With approval from the factory director I.M. Zaltsman, Kotin would make the design of the KV-4 a competition between the best engineers of the SKB-2 design bureau. To encourage seriousness, the top places would even receive monetary compensation. By 9th May, the competition was over, and up to 27 different designs were submitted by over 23 different engineers. The first place went to N.L. Dukhov, who received the first prize of 3,000 Roubles. Second prize went to a design by 3 engineers working together, K.I. Kuzmin, P.S. Tarapanin and V. I. Tarotko, who split the 3,000 Roubles award. Third place went to senior engineer N.V. Tseits who received 2,800 Roubles. Another 8 designs would receive awards. However, S.V. Fedorenko’s design would not receive any awards for his bizarre but innovative design.
S.V. Fedorenko
Born in Chernihiv in 1907, Sergey Vasilyevich Fedorenko graduated from the Leningrad Polytechnic Institute in 1930. At just 23, he began working at the Krasniy Putilovets tractor plant, later renamed to Kirov Leningrad plant (LKZ). By 1937, he was head of SKB-2 artillery and armament section at LKZ. After the transfer to ChKZ in 1941, he was deputy chief designer, on which he worked on tanks like the IS-4. Post-war, he had various jobs, but would settle down for the last two decades of his life as a teacher on tanks at the KGM institute at the South Ural State University. He would pass away a few hours after holding lectures, in 1986, aged 79.
Working mostly with tank armaments and their implementation, S.V. Fedorenko was the man behind various aiming systems, tank optics, turret turning mechanisms, (he was the designer of the entire gun mount, aiming system and overall integration of the armaments on the first KV-1 U-0 prototype, which had a 76 mm gun and a 45 mm one) as well as the flamethrowers for the KV-8 and KV-8S. He would also work under leadership of N.L. Dukhov on the IS-4. During his career, he was awarded 2 Orders of the Badge of Honour, the Order of the Red Star, the Medal for Labour Valour, the Medal for Defence of Leningrad, and the Medal for Valiant Labour during the Great Patriotic War of 1941-1945.
S.V. Fedorenko while working as a professor on tanks and armament at the South Ural State University. Source: Sergey Fedorenko – SUSU Encyclopedia
The KV-4 (Object 224) Fedorenko’s Design
In terms of the hull, Fedorenko’s KV-4 design approach was revolutionary, barely resembling that of its forebears. Firstly, the entire front consisted of a large single upper frontal plate, akin to that on the later variants of the IS-2. As for the lower plate, it too was a single plate, stamped to form a curve connecting the upper plate to the hull belly, similar to the style used on the American Sherman tanks. The rear was also unique, with the air intake hole being narrower and composed of two welded plates, as opposed to a single, curved steel sheet, as on other KV tanks. The sides were flat and vertical, forming a simple and efficient internal volume in which to install components as well as to mount the 8 road wheels per side, sprung by torsion bars. The sprocket was in the rear and the idler in the front. Armor on the lower frontal plate was 125 mm thick, while the upper was thinner, at just 100 mm, but being angled at 45°, it had a line-of-sight thickness of circa 141 mm. The side and rear plates were 125 mm thick, but were mostly flat. The driver and radio operator sat next to each other in the hull, with the driver in the centre and the radio operator to his left. To his right, he had the fuel tanks. Direct vision slits were cut through the hull armor. The radio operator had his communication equipment on the side walls, and a ball-mounted DT machine gun in the front.
The engine was the M-40 V-12 diesel engine, with 4 turbochargers, delivering 1,200 hp. A hypothetical top speed was to be circa 35 km/h. Fuel tanks were on the right side wall, next to the driver and ammunition. The engine and fighting compartment were separated by a firewall. It was mounted rather high in the hull, which required a protrusion in the engine deck and belts for the final drive.
Multi-view plans of Fedorenko’s KV-4. The front view shows the unorthodox profile of the vehicle. Source: ASKMCutout view of the hull. Note the ammunition storage racks and fuel tanks. Source: ASKM
Turret
As an armaments implementation engineer, Fedorenko let his creativity loose when it came to the turret and armaments. The turret had a distinctive and unusual rhomboid shape, allowing for a unique weapons layout and turret positions. It was centrally mounted in relation to the hull, but it had more overhang on the right side of the hull than on the left. The main armament was mounted centrally (with regards to the turret face) and had a coaxial DT machine gun. Behind the gunner’s seat, on the rear turret face, a ball-mounted DT machine gun was added. Additionally, a flamethrower was placed in a ball mount at the ‘corner’ of the turret cheek. Next to it, the tank for ignition fuel was placed, On the opposite side, the turret slanted towards the rear, creating a curved edge. Here, a spherical secondary turret was mounted, armed with a 45 mm gun. This turret would be able to move 360° on the horizontal axis, while the gun itself could elevate to 75°, presumably with an eye to engaging airborne or highly elevated targets, such as on the top floors of buildings. The secondary turret had no gun depression due to the recoil mechanism being mounted as low into the turret as possible. This turret can be seen as similar to a ball turret found in bombers.
Frontal view of the design. Note how the hull has been made as narrow as the engine allows. This causes a significant overhang of the turret. Source. ASKM
Crew
The tank was intended with a crew of 6, tank commander, main gunner, 2x loaders, driver and radio operator. How exactly the crew operated this turret and how they were seated is unspecified and complex. Estimation and study of the drawings can reveal some possibilities. The gunner was seated to the left of the main gun, but would also be tasked with manning the flamethrower. The first loader would load the gun and probably operate the rear-facing DT machine gun. The commander would likely sit in the secondary turret, where he would not only have better vision but also rotation independent of the main turret. He would operate the 45 mm gun by himself, as the turret is too small to allow for a second crewmember. There are no periscopes drawn in on the secondary turret, so likely eye-level vision slits were intended. The second loader was likely in a position ‘between’ the turret and hull, and would be tasked with passing the ammunition for the various armaments, which was stowed in the hull. The driver and radio operator sat in the hull, with the driver in the center and the radio operator to his left, having a ball-mounted DT machine gun at his disposal.
The bizarre shape of the turret proposed by Fedorenko. Note that the rear-facing machine gun has had the armor pushed outwards to allow for additional room in the turret. Source. ASKM
Armaments
As required by the state, the main armament was the 107 mm ZiS-6 (previously named F-42) gun, designed by V.G. Grabin a few months prior. It was mounted centrally (with regards to the hull) in the turret, and had a DT 7.62 mm coaxial machine gun. Circa 100 rounds for the main armament were stored in a horizontal ammunition rack placed against the left wall, with 8 more being stored between the torsion bars, running across the floor. The gun had a muzzle velocity between 800 and 840 m/s. Ammunition weighed 18.8 kg and was of the one-piece (unitary) type.
Secondary armament, as required, was a 45 mm 20-K gun model 1938 placed in an independently rotating turret. This iconic weapon was used on the vast majority of Soviet light tanks, such as the BT-7 and T-26, but was obsolete for fighting tanks in 1941. Even so, it would still have had considerable fighting value against lightly armored vehicles and other soft targets, where the ZiS-6 would have been ‘overkill’. Also, with HE rounds, it could have been very effective against infantry. The gun featured an electrical trigger and vertical plane gyroscopic stabiliser. It had a muzzle velocity of circa 760 m/s, and an elevation of 75°. A total of 150 rounds were carried for this gun.
Other weapons scattered around the tank were a coaxial 7.62 mm DT machine gun, a rear-facing DT machine gun in the turret, a ball-mounted DT machine gun in the front hull and a flamethrower of unspecified type in the turret cheek, facing the front. Its implementation was interesting, as it was vaguely required by the GABTU and, as a result, many designers left it out completely.
War!
After the end of the competition, the KV-4 progress was slow and focus shifted more to the drawings of the KV-5. The situation got so bad that on 12th June, Marshall of the Soviet Union G.I. Kulik requested LKZ to speed up work. Yet, just 10 days later, the German invasion of the USSR began. Work continued at LKZ, but the heavy tanks were no longer any priority. Nonetheless, the drawings of the KV-5 were complete by the time the Germans reached Leningrad in August. Then the SKB-2 design bureau would be evacuated to the ChKZ plant in Chelyabinsk. Work on these heavy tanks would not resume.
Conclusion
Fedorenko’s design was one of the many ‘unsuccessful’ KV-4 designs, as he did not receive any placement and monetary awards, though this may seem unjustified. His turret design had one of the most interesting and unusual turret layouts, being a rhomboid. He exploited this unusual shape to mount a variety of weapons in different positions. The hemispherical secondary turret is another interesting addition that did not feature a machine gun, as commonly seen on later tanks, but a full-fledged 45 mm gun. Even the hull had its own merits, employing a flat, slanted upper frontal plate, and elevating the engine deck for a shorter overall hull length. It is safe to say that Fedorenko presented a ‘delicate’ KV-4, as opposed to many other designs which were rawer, though this seemingly did not impress Kotin or Saltzman.
The KV-4 design as drawn by S.V. Fedorenko. Illustration by Pavel Alexe, funded through our Patreon campaign.
107 mm ZiS-6 (F-42) (110 rounds)
45 mm M.1938 20-K
3x 7.62 mm DT machine guns
Unspecified flamethrower
Armor
Front upper plate: 140 mm
Front lower plate: 125 mm
Side plate: 125 mm
Turret: 125 mm
Top and belly: 50 to 40 mm
Total Production
0, blueprints only
Sources
Breakthrough tank KV – Maxim Kolomiets
Supertanki Stalina IS-7 – Maxim Kolomiets
KV 163 1939-1941 – Maxim Kolomiets
Confrontation – Ibragimov Danyial Sabirovic
Bronevoy Schit Stalina. Istoriya Sovetskogo Tanka (1937-1943) M. Svirin
Gunsmith S.V. Fedorenko (famhist.ru)
About the forgotten creators of Soviet armored power. (historyntagil.ru) – S.I. Pudovkin
German Lion | Warspot.ru – Yuri Pasholok
Tank building on the verge of common sense | Warspot.ru – Yuri Pasholok
Large caliber for large HF | Yuriy Pasholok | Yandex Zen – Yuri Pasholok
Tank Archives: Soviet 107 mm Guns – Peter Samsonov
Tank Archives: KV-3 Mulligan – Peter Samsonov
Tank Archives: Heavy Tank Costs – Peter Samsonov
Tank Archives: ZIS-6 Characteristics – Peter Samsonov
Final variant of Shashmurin's KV-4. Illustration by Pavel Alexe.
Soviet Union (1941)
Super Heavy Tank – Blueprints Only
The KV-4 program was launched in the spring of 1941 as a response to the rumor of a German super heavy tank. Thus the LKZ factory in Leningrad was set to design a heavy tank capable of challenging the alleged German tank. A design competition was started, with over 20 different tanks presented by engineers at LKZ. One of them was N.F. Shashmurin, who presented a vehicle with a KV-1 trurret over a casemate which housed the 107 mm ZiS-6 gun. For this design, he was awarded 5th place in the competition. However due to his personal disputes with the chief engineer, J.Y. Kotin, he did not participate in the development of the KV-5.
Development
–Dear reader: A more detailed development analysis of the KV-4 program can be found in the KV-4 Dukhov article—
On 11th March, 1941, the Soviet Intelligence Services provided a letter to the state discussing the development of German tanks. One of the subsections focused on development of heavy tanks, and showcased 3 main types; a Mark V weighing 36 tonnes and armed with a 75 mm gun, a Mark VI weighing 45 tonnes and armed with a 75 mm gun and 20 mm, and finally, a Mark VII, weighing 90 tonnes and armed with a 105 mm gun and dual 20 mm guns.
This was slightly bizarre, as, during the spring of 1941, the Pz.Kpfw.VII, commonly known as the Löwe, did not exist. It would only appear in documentation in November. Other German heavy tanks however existed, such as the VK30.01, VK36.01 and VK65.01. What exactly was ‘discovered’ by Soviet agents remains a mystery and may have been little more than speculation.
The Soviets only had the KV-1 in service as anything even remotely close to the above mentioned German tanks. Yet the KV-1 was armed with rather lacklustre guns, the 76 mm F-11 and later F-32, and its gearbox would prove very unreliable. The original gearbox was designed by N.F. Shashmurin, but Kotin favored N.L. Dukhov’s gearbox, which proved to be a disaster. Other Soviet heavy tanks, the T-150 and KV-220, were still under development when the news of new German heavy tanks came in. Even so, their development would not continue, as the improvements in armament and armor they would have brought were not seen as significant enough. With hindsight, the KV-220, with its 85 mm L-30 gun and 100 mm of armor, would have been on par with the German Tiger tank entering production in August 1942, well over a year later.
Naturally, the prospect of even more heavily armored and armed German tanks potentially coming out raised an alarm at the GABTU (Main Directorate of Armed Forces), which did not have a heavy tank on par with these parameters. As a result, on 21st March, the GABTU released a set of requirements for a new tank which was to receive the index Object 224 and general name KV-4. This would have a weight of around 70 tonnes, armed with an 107 mm ZiS-6 gun in a fully rotating turret, and a coaxial 45 mm gun. Additionally, at least 3 DT 7.62 mm machine guns and potentially a flamethrower had to be added. Armor was to be 130 mm at the front and 120 mm at the sides and rear. The engine for this new tank was to be one capable of producing 1,200 hp. Unfortunately, there were no engines powerful enough at that moment, so temporarily, a 850 hp V-2SN would be used. The crew was supposed to be of 6 men; commander, gunner, driver, radio operator, and 2 loaders. On 27th March, GABTU requested that the blueprints be finished by 17th July.
However, by 7th April, the requirements were changed. The armor was increased to 135 mm and 125 mm to the front and sides, respectively. With increased armor, the prospective weight of the vehicle was increased to 75 tonnes. Submission date for the blueprints was also brought closer, to 15th June, nearly a month earlier than had been asked for previously and indicating the urgency of the work at hand. It was also on this day that the KV-3 requirements were improved, and the KV-5 was born. Both the KV-4 and KV-5 were expected to enter testing in 1942.
It was the LKZ, Leningrad Kirov Plant, headed by I.M. Zaltsman, that was tasked with designing the new heavy tank. LKZ had previously worked on the SMK, KV-1, T-150 and KV-220 heavy tanks, but none came to the sheer mass and size that the KV-4 had to reach. The lead engineer of the project was J.Y. Kotin. The Izhora plant had to construct a turret and hull prototype, while plant No.92 was tasked with supplying the main gun
Work at LKZ started 3 days later, on 10th April. Since it was an entirely new project with relatively loose requirements, J.Y. Kotin decided to make the general design of the tank a competition between the engineers at the SKB-2 design bureau. The result was that over 24 designs were submitted by 9th May. First place was awarded to N.L. Dukhov, receiving 5,000 Roubles. Shashmurin received the 5th place, with an award of 1,500 Roubles.
Unfortunately, much confusion surrounded the actual winner of the KV-4 competition. This was caused by a segment in N.F. Shashmurin’s memoirs, from which readers interpreted that he had won. This is incorrect, as his design had received 5th place, for which the 1,500 Rubles award was given. Below is the relevant translation. It must be noted that, throughout his memoirs, titled ‘50 years of Confrontation’, Shashmurin makes a series of mistakes and inaccuracies, but this is to be expected, as he wrote it in 1987, 50 years later.
Having received, along with other leading employees at the design bureau (SKB-2), the task of developing a project for such a cyclops*, obviously multi-turreted, I, without sharing the same optimism considering the previous circumstances (multi-turreted, how long ago have we given up on the ‘Muir & Mirrielees’**, crumbled by the SMK) made a ‘knight’s move’. Basically, the turret was removed, and the process as when installing the M-10 152 mm on the KV-1 was repeated, that is, a casemate superstructure on the hull. And since a new, practically super-heavy KV-3 had already been created,*** I decided to not be smart about the ‘supernova’ tank. Having dropped the turret, the process was repeated from previous high-power self-propelled guns, but this time with a 107 mm Grabin gun. Notiyfing in an explanatory note that, under specific conditions, the gun can be removed and instead a rifle squad of infantrymen can be placed in the fighting compartiment. This option was not accepted, as the requirements were not met – (it required) higher protection, weight between 80 – 100 tonnes, turreted (multi-turreted) gun placement. To avoid an unnecessary confrontation, I complied. Considering that a superheavy tank cannot be a (true) tank, to fulfil the specified protection parameters, (I) had to invest into about 90 tonnes, kept the casemate mounted main gun, and installed a serially produced KV-1 turret on the now shortened (casemate) roof. It ended up that I.M. Saltzman really liked the variant, (given its ‘sensibleness’, or as he put it, ‘versatility’) and I received the second prize with the amount of 1000 Roubles.**** That was great. I bought my wife a fur coat with this money.
– Nikolai Fedorovich Shashmurin, extract from ‘50 years of Confrontations’.
*Referring to ancient Greek mythology where Odysseus blinds the giant cyclops Polyphemus.
**Scottish-owned Trading company in then St. Petersburg, started by Muir and Mirrielees, famous for its two devastating fires.
***Probably referring to designs by his fellow engineers.
****Documents from the time prove him wrong. He had in fact received 5th place and 1,500 Roubles.
Interestingly, Shashmurin disliked the KV-4, not only his own creation, but the entire program. According to historian Dr. Gennadiy Petrov, who knew Shashmurin personally, he had written on the back of his drawings the letters Б.С. (B.S.) acronym for Бред сумасшедшего, translating to “delirium of a madman”. This unconfirmed, but plausible detail gives insight to Shashmurin’s long-lived jealousy and dislike for J.Y. Kotin, Chief Engineer at LKZ. His strong feelings were made public again in a magazine interview taken by Sergey Ptichkin in the 1990s, which was mostly aimed at answering questions regarding the shortcomings of the KV-1, though the KV-4 was once again mentioned. A translated extract:
“Instead of eliminating the identified defects (of the KV-1) at the Kirov plant, they (in regards to the GABTU, I.M. Zaltsman and J.Y. Kotin) began to design a series of armored mastodons: KV-3 weighing 65 tonnes, KV-4 – 80 tonnes, KV-5 – 100 tonnes! Regrettably, we showed clear signs of technical madness much earlier than in Germany, where only at the end of the Second World War they tried to create weapons of retaliation like the ‘mouse’ tank, weighing 180 tonnes.* The first days of the Great Patriotic War only confirmed that the KV-1 in the form in which it was produced, was not fit for fighting, since it did not have a reliable powerplant. So there was this tragic paradox; the armor was strong, but it was not a fast tank. It would seem that faith itself pushed for an urgent modernization of the KV, for the replacement of the inoperable gearbox**, but, alas, in the most difficult time for the country, from the end of the summer of 1941 to the spring of 1942, we continued to spend huge material resources and human forces for further scientific and technical research. In the autumn of 1941, an attempt was even made to remove the KV-1 from production and replace it with the KV-3, a powerful, but completely “raw” and unnecessarily heavy machine.”
– N.F. Shashmurin, extract from ‘Soviet Warrior’, interview by Sergey Ptichkin, 1990s.
*With hindsight this is wrong, German superheavy tank development started long before WWII, more or less simultaneously with Soviet superheavy tank projects. However, in pre-internet, post-Soviet Russia, this was not common knowledge.
**The iconically unreliable gearbox and transmission of the KV-1 was a sensible spot for Shashmurin, as he had designed the original gearbox, but the production gearbox was designed by N.L. Dukhov.
In a way, Shashmurin was conservative in regards to tank design. From his post-war works, he made it clear that he preferred a more controlled testing and development of the KV-1, which was more or less rushed into production. He had wished for modernising and improving its faults. He liked the KV-1S but greatly despised the KV-13, which he considered redundant, despite the fact that he was its Chief Designer, after the death of N.V. Tseits, which Shashmurin once again blamed Kotin for. He was also Chief Designer of the IS-2, which he believed was a very worthy tank and should have been upgraded and improved upon, instead of rushing new tanks into production like the IS-3 and IS-4, which he called “impressive but unreliable”.
In hindsight, Shashmurin was correct in this regard. Oddly though, he was very proud of the IS-7, of which he was Chief Designer, and claimed Western tanks would not match its capabilities for decades, and blamed its cancellation on Khrushchev’s* obsession with rockets and missiles.
(*Nikita Khrushchev, First Secretary of the Communist Party of the Soviet Union 1953 – 1964)
Prototype of the SMK, the tank for which N.F. Shashmurin designed the torsion bar suspension. Source: TsAMO via Maxim Kolomiets
N.F. Shashmurin
Born in 1910 in what was called at the time St. Petersburg, Nikolai Fedorovich Shashmurin started his engineering studies at the Leningrad Polytechnic Institute in 1930, and graduated in 1936. By 1937, he had started to work at LKZ as an engineer for both the SKB-2 design bureau and the VNII-100 research institute. He designed important elements of mechanical components, such as torsion bars and transmissions. Likewise, he worked on the development of the majority of LKZ wartime developed tanks, such as the SMK, KV-1, KV-1S, KV-13, KV-85, IS, and IS-2. Postwar, he worked on tanks like the IS-7 and PT-76, as well as various tractors (LKZ partly resumed civilian tractor production).
By the 1970s, he was a PhD in technical sciences and worked as a professor at the Leningrad Polytechnic Institute. He died in 1996, aged 86. During his career, he received 2 Stalin Prizes, the Order of Lenin, the Order of the Red Star, and the Medal for Victory over Germany during the Great Patriotic War of 1941-1945 (II Degree).
N.F. Shashmurin in the 1930s. He was an important part of many tanks developed at LKZ. Source: Bronetechnikamira.ru
Shashmurin’s design
Original layout
If his memoirs are to be believed, Shashmurin originally intended to have an enclosed casemate for the main armament, without the additional turret. The casemate would have also been taller, resulting in something akin, a parallel he drew himself, to the KV-1 with M-10 152 mm howitzer. This suggests a much taller casemate to what was used on the final design. The driver and radio operator were likely placed within the fighting compartment, instead of being ‘pushed out’. He had also intended that the gun could be removed and a rifle squad of infantrymen be carried instead. However, this variant was not approved as it was ‘too light’, did not have at least one turret-mounted armament and the armor was too thin.
Final design
When designing his final KV-4 proposal, Shashmurin had a different approach. As per the original state requirements, the main gun had to be mounted in a fully rotating turret, but after the additional requirements (some of which were contradicting with each other) set by the GABTU, several designers decided to install the 107 mm ZiS-6 main gun in a limited traverse mount.
Shashmurin, however, would decide to add what appears to be a KV-1 mod.1939 turret on top, armed with an L-11 76.2 mm gun. The fighting compartment was moved towards the centre of the hull and morphed with the engine compartment, which was kept more or less identical to the previous KV series of tanks. His design would have been a colossal vehicle. Weighing in at 92 tonnes, it would have also been the longest KV-4 designs, at 10 meters long including the barrel.
The blueprints of the KV-4 drawn by N.F. Shashmurin. They provide extensive detail to technical specifications of the vehicle, including internal and external views. Source. ASKM
The type of armament layout Shashmurin decided upon had a series of advantages and disadvantages over methods employed by other engineers. Firstly, the KV-1 style turret allowed for engaging armored vehicles completely independently of the 107 mm main gun. In addition, the usage of a readily available turret in combination with a simple casemate construction meant the production cost would have been significantly lower compared to that of many large KV-4 proposals. The silhouette of the tank was also lower.
Having a limited main gun traverse significantly decreased the battle value of the 107 mm gun, although horizontal traverse was kept at an acceptable range of 15° to both sides. Nonetheless, other issues were created by this weapon arrangement, such as an extra crewman and a cramped interior complicated coordination and communications. Also, the lack of the coaxial 45 mm gun meant that there was no way to range in the main gun, leading to longer target engagement times and more ‘wasted’ 107 mm shells.
Other than the superstructure and upper hull, Shashmurin kept his design simplistic in terms of the lower hull. Most components were identical and reused from the previous KV series of tanks. The idler was in the front, sprocket in the rear, and 9 road wheels on each side, sprung by torsion bars. The engine used would have been the aviation diesel 4x turbocharged M-40 V-12 1,200 hp engine, partially developed at LKZ after the original designer was arrested in 1938.
Armor was, for the most part, straightforward. The frontal facing elements were 125 mm thick, with side and rear plates also at 125 mm thick. The lower plate was bent into a rounded shape. Top and roof plates were all 40 mm, while belly plates were 50 mm up to the first 3 wheels, from after which they decreased to 40 mm. The rear was stamped in the classic KV style, with a curved cover of the cooling intake.
KV-1 turret mystery
As aforementioned, there was, seemingly, a KV-1 turret added on top of the main superstructure. Yet what model this was is a mystery. From the side, it appears to be an original turret from 1939 and 1940, with rounded edges. However, the top view brings additional details of the turret. Instead of being mostly flat, aside from the rounded edges and rear bustle, the turret bustle angled inwards sharply, resembling the turret of the T-28 and T-35A. The implementation of a L-11 gun is equally strange. As early as 1940, this gun was replaced with more powerful 76 mm guns. The pig nose gun mantlet was also kept. To the right of the gun, on the same axis, a 7.62 mm DT machine gun was mounted. Likewise, a DT machine gun was mounted at the back of the turret, in a ball mount.
In terms of armor, it is unclear if Shashmurin kept the original KV-1 turret armor values of 75 mm all around the turret. If this was the case, it would have made it more vulnerable compared to the rest of the vehicle.
Side view of the KV-1 turret. Note the clear L-11 gun with its iconic gun mount. Source. ASKMTop view of the KV-1 turret. The sides are not flat, but rather curve towards the rear, like on a T-28 turret. Note the coaxial DT machine gun. Source. ASKM
Crew
The crew consisted of 7 men. The driver and radio operator were seated in two protrusions from the main casemate, with the main gun barrel between them. Study of the blueprints shows that the two would have had plenty of space all around. Further inside the casemate were the main armament’s gunner and loader. In many KV-4 designs, two loaders were dedicated to manning the ZiS-6, however, as the ammunition was placed close by and there was no coaxial armament, it required only one loader. In the KV-1 turret, another gunner and loader were seated, manning the L-11 gun. Inside the turret was the commander as well, a position which would have offered great vision. Nonetheless, commanding the tank would have been a true challenge. The commander had to prioritise and coordinate target acquisition and engagement of both guns. He was completely isolated from the driver and radio operator, who relied upon the commander for orders. Additionally, as is the case with many turretless AFV, the main gunner and driver had to have good communication and synchronisation for engaging targets. This communication was provided by a 10-R intercom.
Armaments
The main armament used was a ZiS-6 (F-42) 107 mm gun, designed by V.G. Grabin between December 1940 and early months of 1941. It had a muzzle velocity of 800 to 840 m/s. Ammunition was one-piece and weighed 18.8 kg. The breech lock was mounted vertically and was semiautomatic. It could allegedly penetrate 115 mm of armor at 1,000 m. Gun elevation was of +13° and depression of -4°, while horizontal traverse was 15° to both sides. Ammunition was stowed vertically, with circa 112 or 102 (according to Shashmurin’s blueprints) rounds stowed inside. Armament in the turret was the L-11 76 mm gun, used on the first production variants of the T-34 and KV-1. It had a muzzle velocity of 610 m/s and a shell weight of 6.5 kg. Its gun elevation was +26° and depression was -7°. Around 120 76 mm rounds were stowed horizontally in the hull. Additionally, there was a coaxial DT 7.62 machine gun and one ball-mounted in the back of the turret, with +25° and -15°. A flamethrower was also mounted in the radio operator’s location, in a ball mount, with ’20 shots”.
Unlucky Cyclops
The KV-4 program as a whole was unsuccessful. After Dukhov’s design was named as winner, work should have started on detailed blueprints, allowing for the other factories involved to start prototype production. However, by the deadline (15th June), the blueprints were not submitted. Just a week later, on 22nd June, 1941, Nazi Germany attacked the Soviet Union. Work continued at the SKB-2 design bureau, especially on the KV-5, but the KV-4 seems to have been forgotten. By August, German forces were approaching Leningrad, and SKB-2 was evacuated to ChKZ. Work on these heavy tanks would not resume.
With the KV-1 engaging in full-fledged battles, its weaknesses were immediately apparent. It suffered countless gearbox failures, was slow and bulky and crews preferred the T-34. The situation was so bad that it was threatened to be put out of production. Hearing about the gearbox disaster, which he expected, Shashmurin was furious. Kotin would adopt his design, not after a fair share of arguments, for the gearbox of the KV-1S, a very well liked development of the KV-1. Shashmurin would later head the development of the KV-13 and IS as well.
Shashmurin’s KV-4 design was even less successful. While he did receive the 5th place in the competition, none of his design features would be reapplied in the KV-5. It was indeed one of the more distinctive and unusual designs, though its combat value would have been questionable.
Final variant of Shashmurin’s KV-4. Illustration by Pavel Alexe.
KV-4 Shashmurin specifications
Dimensions (L-W-H)
10.00 (9.50 without barrel) – 4.00 – 3.85 m
Total Weight, Battle Ready
92 tonnes
Crew
7 (Commander, main Gunner, turret Gunner, Driver, Radio operator, main loader & turret loader) )
Propulsion
1,200 hp diesel V-12 M-40 with 4 turbochargers
Speed
35 km/h
Armament
107 mm ZiS-6 (F-42) main cannon (112 or 102 rounds)
76 mm F-11 secondary cannon (120 rounds)
2x 7.62 mm DT machine guns (400 rounds)
Unspecified flamethrower (hull)
Armor
Front top plate: 125 mm
Side plate: 125 mm
Top and belly: 50 to 40 mm
The KV-4 as designed by N. L. Dukhov. Illustration by Pavel Alexe.
Soviet Union (1941)
Super Heavy Tank – Blueprints Only
Tank design in the 1930s Soviet Union was a period of great experimentation and versatility, with designs ranging from jumping and flying tanks to super heavy multi-turreted ones. Yet as the Soviet tank industry matured, tank designs became more sensible and, by the late 1930s, some very promising vehicles were in development, such as the T-34 and KV-1. Nevertheless, with tensions rising in Europe after the German invasion of Czechoslovakia, Poland, and then France through the Benelux, Soviet engineers had to fall back to some older drastic ideas. One of these was the KV-4, one of the most curious heavy tank programs in Soviet tank history, as it involved a competition between dozens of designers.
On 11th March, 1941, the GABTU (Main Directorate of Armoured Forces) was informed by the Soviet Intelligence services of the existence of new German heavy tank projects. The report, naturally, was a mixed bag of real information and rumours. It is important to note that, while the Soviet Union and Nazi Germany were more or less allies during this period, tensions were high and any sort of technological advancement of the opposition had to be met with a proportional (or, in this case, disproportional) response.
The document received was titled “The direction of development of the German armed forces and changes in their state” and discussed several tank projects. When it came to heavy tanks, a chart presenting 3 tank models was shown:
Mark V (36 tonnes, 75 mm gun, 2x machine guns, ≤ 60 mm of armor)
Mark VI (45 tonnes, 75 mm gun, 20 mm gun, 3x machine guns, ≤ 70 mm of armor)
Mark VII (90 tonnes, 105 mm gun, 2x 20 mm gun, 4x machine guns, unknown armor)
The report also mentioned, based on unconfirmed information, 72 tonne French tanks (possibly the Char 2C, which weighed 69 tonnes) present at the occupied Renault factory, in addition to 60 and 80 tonne tanks being built at Škoda and Krupp.
On the one hand, the Germans had indeed begun development of several heavy tanks, such as the 30-and 36-tonne projects (VK30.01(H) and VK36.01(H)). A month after the original Soviet report, in May, the Germans decided that, for 1942, the armor of future heavy tanks had to be improved. This would consist of 100 mm of frontal armor and 60 mm at the side. In terms of heavier vehicles, the VK65.01 appeared in January 1939.
Interestingly, the Pz. Kpfw. VII, commonly known as the Löwe, with its many variants and stages, would not appear until November of 1941, with development starting in December. Mentions of a tank armed with a 15 cm L/40 existed earlier on. This begs the question on what the Soviet report was based on. It was very likely a combination of several tank designs and proposals, alongside rumours and speculations, likely cherry picked to sound as alarming as possible.
To put things into perspective, during this period, the best heavy tank in Soviet service was the KV-1, armed with the 76 mm L-11, meant as a stopgap until the introduction of the F-32 gun, which was not a significant improvement anyway. These guns were seen as problematic, especially by armament designer V.G. Grabin, but the political rush to push the KV-1 into production and military service left it with considerable faults and problems, including the armament and the infamous gearbox, which, it must be noted, was designed by N.L. Dukhov himself. The most important aspect of the KV-1 was its armor, with 90 mm at the front of the turret and 75 mm at the front of the hull. By 1941, the Soviets had several improvements of the KV-1 in the works, including the T-150 and KV-220, which brought more armor and better armament. With hindsight, the KV-220, with its 85 mm F-30 gun and 100 mm of armor all around, would have been (on paper) on par with the German Tiger I, which entered production only in August of 1942, 1.5 years later. It seems it would have been rather reliable, running 967 km with the V-5 700 hp engine (only needing 2 idlers, a torsion bar, 6 idler axles replaced and shearing 2 teeth in the transmission and destroying the eyelet of the clutch) after the 2 V-2N supercharged experimental engines broke.
Nonetheless, the Soviet authorities did not take the report lightly and immediately ordered work on an even heavier tank. It was expected that the gun used would be the 105 mm Flak 39. The Soviets had previously purchased this gun in 1940 for testing and, after firing trials, it was noted that a tank required 130 mm of armor or more to withstand fire from it. The Kirov Leningrad plant’s SKB-2 design bureau was tasked with the design of the new tank. At the same time, they were working on the KV-3, at the time a 50-tonne heavy tank, already superior to any German tank at the time. The Kirov plant had also worked on the T-150 and KV-220 tanks, which were further developments of the KV-1.
Technical requirements
Design and technical requirements were given only 10 days after the initial report, on 21st March, 1941. The new super heavy tank was named KV-4 (the acronym KV stands for Kliment Voroshilov, People’s Commissar for Defense of the Soviet Union until 1940) and received the GABTU designation Object 224. It was to weigh around 70 to 72 tonnes, with a frontal armor of 130 mm, side armor of 120 mm, and 40 mm on the belly and top. The main armament was to consist of the ZiS-6 F-42 107 mm gun. It was meant to have a full traverse range of 360° (though a handful of designs would mount the gun in a casemate with limited traverse). Elevation was to be between 15° to 17° and depression between -2° and -3°. Secondary armament would consist of a 45 mm gun (model 1937 or 1938) and 3 DT machine guns; one coaxial, one in the turret bustle and one at the front of the hull. Mounting of a 76 mm ZiS-5 gun was also desired as an alternative to the ZiS-6, though this was eventually dropped. A flamethrower was also mentioned for protection against approaching infantry.
The powerplant was meant to be a 1,200 hp engine, with the tank reaching an estimated top speed of 35 km/h. However, since there were no such powerful engines available at the moment, the 850 hp V-2SN was to be used as a temporary fix. For the KV-5 (and potentially the KV-4 as well), mounting 2 V-2SN was also considered until the M-40s were ready. Eventually, LKZ managed to produce 58 M-40 engines by August. Another variant was considered, the M-50, giving out 1,000 hp, which was meant for torpedo boats. The fuel was meant to last for 10 hours of continuous driving, in conditions between -40° and 40° Celsius. The gearbox had to be an automatic planetary type and the brakes had to hold up the tank’s weight on a 45° slope angle. The crew was to be composed of 6 men: Commander, gunner, loader, turret mechanic (loader assistant), driver, and radio operator, with the last two in the hull.
On 27th March, the Council of Ministers of the USSR released the plans for the development of the heavy tanks, presenting the deadlines of the development process. The LKZ plant was to provide drawings by 17th July, Plant No. 92 to deliver a 107 mm ZiS-6 and 76 mm ZiS-5 by 1st September and Izhora plant in Leningrad to build the hull and turret by 1st October. In terms of powerplants, the V-2SN and M-40 engines were considered. From a letter dated 30th May, the development (from blueprints to prototype testing and improvement) of the KV-4 was expected to cost 3,100,000 Roubles, while the KV-5 was estimated at 3,600,000 Roubles. Just the construction and factory trials of the KV-4 were estimated at around 1,800,000 Roubles. To put this into perspective, the production of a single KV-1 was around 295,000 Roubles (May 1942).
In an interesting turn of events, by 7th April the plans were changed entirely. The KV-3 program was revitalized, with the weight increased to 68 tonnes, armor increased to 120 mm and mounting a 107 mm gun. Consequently, in a letter to LKZ factory director I.M. Zaltsman, the KV-4 requirements were increased to a weight of 75 tonnes, 135 mm (some sources claim as much as 140 to 150 mm) of armor on frontal areas, and 125 mm on the sides and rear. The deadline for the blueprints was brought forward to 15th June. The hull and turret were expected on 15th August. Simultaneously, the KV-5 was brought to life. It was to be a response to the so-called ‘Pz.Kpfw.VII’, with a mass of 90 tonnes, frontal armor 170 mm thick, and 150 mm thick on the sides. It was to be built by 10th November.
The turrets had to be of welded and stamped construction, as castings at these thicknesses were not technologically possible at the time. Another issue with the armor was the connection. The Soviet armor industry could barely handle welding 75 mm armor plates, let alone anything above 125 mm. This issue was partially solved on the KV-5 (which got further into its developmental stage), where steel rods would be pushed and welded in holes drilled through the two armored plates, which in turn would be laid onto one another.
The main gun required between 70 and 80 rounds of ammunition. To top it all off, in a letter from the chief or the Main Auto and Armour Directorate of the Armoured Forces to the LKZ and Izhor factories, the prototypes of KV-4 (and KV-5) were expected to be completed and enter the testing phase by 1942.
Connecting pins for the large steel plates. This system was used on the KV-5, and likely on the KV-4 as well. The German Maus used them as well. Note, however, that the Soviet counterparts did not use interlocking plates, but rather L-shaped connections. Source: Andrew Hills
Drawing competition
Work began on the KV-4 at Kirov on 10th April. The head designer was J. Y. Kotin. Considering that the tanks were to be designed from scratch, Kotin decided upon doing a competition. After getting Zaltsman onboard, they decided to even give prizes for the best designs. Most of the engineers at the Kirov SKB-2 design bureau would participate in the competition. No details were given about the layout, prompting a variety of unique and creative designs. However, a bit of confusion seems to have risen regarding specific details, as the specifications set up at LKZ did not entirely match the ones requested by the GABTU. The mass was set between 80 and 100 tonnes, armament consisting of the ZiS-6 107 mm and a 45 mm gun mod.1937, with the second gun meant for zeroing in the main gun and for dealing with softer targets. The Soviet military allegedly requested a flamethrower as well, but some designs lack it.
By 9th May, the competition was over and the winners were announced by I.M. Saltzman. In total, 27 different designs were submitted (excluding different variations of the same design). In first place came N.L. Dukhov, who received 5,000 Roubles. Second place was given to a design made by 3 engineers, K.I. Kuzmin, P.S. Tarapatin, and V. I. Tarotko, who received 3,000 Roubles to be split between them. On third place came N.V. Zeits, who received 2,800 Roubles. The list continues to the 7th spot, with many places having several designs. Unfortunately, some designs have been lost to time, and some designs have unknown authors, or some lost drawings. From the 11 ‘winning’ designs, only Kalivoda’s project is missing blueprints. Kotin himself received 3,100 Rubles for leading the engineering team. To put these sums in perspective, a soldier would be awarded 500 rubles for destroying an enemy tank on the front.
Designer name
Place
Prize received (Rubles)
N.L. Dukhov
1
5,000
K.I. Kuzmin, P.S. Tarapanin and V. I. Tarotko
2
3,000
N.V. Tseits
3
2,800 (2,000 according to another archive document)
Other engineers who presented designs but did not receive any awards were F.A. Marishkin, S.V. Federenko, M.I. Kreslavsky, V. Pavlov and D. Grigorev, P. Mikhailov, G. Turchaninov, N. Strukov, and 2 other unnamed designers.
Despite the exciting competition, the progress was slow. By 12th June, 3 days prior to the deadline, Marshal of the Soviet Union G.I. Kulik sent a letter to LKZ demanding the speed-up of the design process. Yet the drawings were never submitted. Just 10 days later, on 22nd June 1941, German forces began their invasion of the Soviet Union.
The GABTU decided that the KV-3, which was in an advanced stage, would continue development and be implemented as a stopgap measure until the KV-4 and KV-5 were ready. These two would be tested against each other and the winner would be produced. Development of the KV-5 continued until August, albeit at a much slower rate, when the Germans had already reached Leningrad. The workers and engineers at LKZ, including SKB-2, were moved to ChKZ in Chelyabinsk.
N. L. Dukhov
The winner of the KV-4 competition, Nikolai Leonidovich Dukhov, was born in 1904 in Veprik, in modern day Ukraine. He was behind several Soviet tank projects. In his first years as an engineer, he worked at the Putilovets tractor factory, on the Universal tractor. In 1936, he worked on his first tank project, a modernization of the T-28. A few years later, his team at the LKZ (Kirov) SKB-2 design bureau was responsible for designing the KV-1 heavy tank. After the Siege of Leningrad, SKB-2 was moved to ChKZ, from where he continued designing tanks. Other noteworthy tanks designed under his leadership were the KV-1S, KV-2, KV-85, KV-13, IS, IS-2, IS-3, and IS-4.
After 1948, he was involved in the Soviet nuclear program, being deputy chief designer at KB-11 (since 1992 known as the ‘Russian Federal Nuclear Center’) and participated in the development and testing of the RDS-6s thermonuclear hydrogen bomb, with a yield between 400 to 500 kt. In 1954, he became chief director and supervisor at branch No.1 of KB-11, which still bears his name to this day. He led it until his death in 1964, at just 59 years. He received 3 Hero of Socialist Labour medals, 4 Lenin Orders, 5 Stalin Prizes, the Lenin Prize, the Order of Suvorov, the Order of the Red Banner of Labour, the Order of the Red Star, the medal for Labour Valour, the Medal For the Victory over Germany in the Great Patriotic War 1941–1945, the Medal for Valiant Labour in the Great Patriotic War 1941–1945, the Jubilee Medal 30 Years of the Soviet Army and Navy, and the Jubilee Medal 40 Years of the Armed Forces of the USSR.
Nikolai Leonidovich Dukhov, one of the most important Soviet tank designers of the Second World War, in charge of designing some of the most iconic Soviet tanks, like the KV-1. Source: Wikipedia.ru
Dukhov’s design
Dukhov presented at least 4 drawings of his proposal, one side view of the entire tank, one cutout top view of the turret, one partial cutout of the hull and one showing the automated round lifting system. The design was very similar to the KV-220, a tank designed with L.E. Sychev and B.P. Pavlov (both of whom submitted KV-4 designs), but much larger. The hull was essentially an up-armored and lengthened KV-1 hull, with 8 wheels per side, sprung by torsion bars. Other details and components remained mostly identical to those of previous prototypes and of the KV-1 mod.1941. The exact number of return rollers is unknown, but comparing to previous designs, 4 appears most likely. Curiously, the rear engine deck plate was angled downwards, similar to the KV-1S. His design was the lightest of all KV-4 designs, estimated at ‘just’ 82.5 tonnes.
The single KV-220 prototype, armed with an 85 mm F-30 gun. It served as a basis for the KV-3 tank, and as a great inspiration for Dukhov and his KV-4 drawings. Source: Tank Archives, colorized by Smargd123
The main engine considered was the M-40 aviation engine, developed at LKZ (after the original designer, A.D. Charomsky, was arrested in 1938, during the Purges). It had an output of 1,000 horsepower (later improved to 1,200) with 12 cylinders arranged in a V-shape, and 4 TK-88 turbochargers. Displacement was of 91.07 liters. Since it was based on an aviation engine, it could run on both diesel and kerosene, allegedly even gasoline. With such a powerplant, Dukhov expected his design to reach an optimistic 40 km/ top speed. There was also an upgraded version, the M-40F, delivering up to 1,500 hp. The other engine considered was the V-2SN, which was an upgraded variant of the classic V-2 12 cylinder engine. It was boosted with a turbocharger to 850 hp.
Side cutout view of Dukhov’s KV-4. The similarities to the KV-220 are very clear. Source: ASKM
The turret designed by Dukhov was also similar to the KV-220, with the main difference being that the frontal plate (mostly covered by the mantlet) was angled, as opposed to flat like on previous KV tanks. A total of 4 plates were used for the turret, with the frontal plate angled at circa 20° and 130 mm thick. The side armor plate would have been circa 125 mm thick and stamped into shape. The rear plate was flat and 125 mm thick. On top of the main turret, a smaller turret was added armed with a DT machine gun. This turret had circa 3 vision periscopes for the commander. Another 4 periscopes were scattered around the turret to give vision to the rest of the crew members.
Top view of the turret, with view of the two guns and turret floor. Source. ASKM
In terms of placement of the 6 crewmen, the driver and radioman were placed in the hull, in identical positions to other KV series tanks. The gunner was seated to the right of the 107 mm gun, while the commander was standing behind him, operating the cupola. As for the loaders, one was seated to the right of the 45 mm gun and was tasked with loading it and lifting ammunition for the 107 mm. The other loader was standing behind the main gun and had the task of loading the main gun. They used a 10-R intercom for communication between each other.
Top view of Dukhov’s hull, the front of the hull has been cut out. The ammunition loading system can be seen, using special components holding the shells by the ends. Source: ASKM
Armament
The KV-4 used the F-42 ZiS-6 107 mm as the main gun. It was designed by the iconic V.G. Grabin at factory No.92. First appearing in documentation in December 1940 as the F-42, but renamed to ZiS-6 in March 1941. The gun was ready by 14th May, taking only 38 days to design according to Grabin himself, after both Marshal of the Soviet Union Kulik and Stalin spoke to Grabin about the issue, though a phonecall between Grabin and Stalin revealed that the gun had to be designed in 45 days. Plant No-92 was forced to work ahead of schedule, and on 27th May, sent a gun to LKZ for mounting on the KV-2 for testing. Yet the Izhora plant, tasked with making the turret for the test ring, using a KV-3 gun mount, was progressing very slowly. On 18 June, Marshal Kulik had to intervene (again), for the Izhora plant to finish the turret. Testing finally began on 25th June and ended on 5th July. After the initial test, faults were fixed, and the gun was deemed ready for production. Serial production began at the New Sormovo plant in July. But, according to Grabin’s memoirs, the lack of cooperation and work from the tank factories was a large dissapointment.
The production of the ZiS-6 increased daily. But there was still no sign of the tank for which the gun was intended. Even after the beginning of the war, the Kirov plant did not deliver a single tank. The lack of the new tank forced us to limit production and eventually, cancel it. It is difficult and embarrassing to write about this, in those days when everything that could shoot, even museum pieces, were sent to the front, around 800 gun barrels had to be sent back to the melting furnace
– V.A. Grabin, extract from his memoirs.
In September, the ZiS-6A was discussed for the KV-4, which involved the mounting of a 45 mm gun coaxially, but it remained just an idea, mostly because of the abandonment of the KV-4.
The KV-2 fitted with an 107 mm ZiS-6 and the KV-3 gun mantlet in June 1941. Source: Thinky via WT forums
In terms of technical data, the ZiS-6 had an muzzle velocity of 800 to 840 m/s. Ammunition was one-piece and weighed 18.8 kg. The breech lock was mounted vertically and was semiautomatic. It could allegedly penetrate 115 mm of armor at 1,000 m.
Regarding secondary armament, Dukhov fitted his design with a coaxial 45 mm mod.1937. With a muzzle velocity of 750 m/s, it would be used for ranging in the main gun, while also engaging targets that would not require the main 107 mm gun. Loading would be done by any of the two loaders. There was no firing mechanism designed for it, but it was likely fired independently from the main gun by the gunner. The tank also had at least two DT machine guns, one mounted in a ball mount in the hull, and the other in the secondary turret on the top of the main turret. Ammunition for it was stowed in the hull, on both sides of the turret ring.
Dukhov had envisioned 2 ways to load the main gun. The first was the classic way, by simply lifting the ammunition stored in the floor of the tank’s hull. There must have been a form of turret floor, as the entire hull floor was peppered with ammunition. This was in no way a simple endeavour, but with two loaders, it was a realistic task. The second option was a semiautomatic loader system, which had a system that would lift up the shells from the hull to the same level to the gun breech, from where the loader could load them in. The shells would be lifted by a chain-like system, in-line with the gun breech. These would be stored across the hull, and would have been required to be placed manually in the lifting system.
View of the loading layout and system proposed by N.L. Dukhov for his KV-4. Source: ASKM
German invasion
Even after the German attack on the Soviet Union, work on tanks continued at LKZ. For the KV-5, the engineers who had received the top places in the KV-4 competition (except the 3 in second place) would work together on the KV-5. This gained traction and blueprints were being drawn, including the turret, hull and running gear components. As for the KV-4, there was barely any progress. Dukhov’s design was awarded as the best, but what this truly meant for the KV-4 is all speculation. Whether Dukhov’s would have been the main layout of the final KV-4 prototype is unknown. Work continued on the KV-5 and KV-3 until August, by which time the Germans were quickly approaching Leningrad. To deal with this, the SKB-2 design bureau was evacuated to ChKZ in Chelyabinsk. There, work on the KV-4 and KV-5 would not resume, as they were seen as a large waste of time and money when the Soviet Union needed tanks yesterday.
With the KV-1 seeing combat against the Germans, it was truly confirmed how unprepared for service it truly was. Dozens of reports came in about transmission and gearbox failures, the vehicle being too heavy and slow, and crews preferring the T-34. The situation got so serious that Stalin himself said that, if the issues would not be fixed, the KV production would be discontinued. This obviously came as a serious blow to LKZ engineers, which immediately began improving the KV.
Additionally, the conspired German heavy tanks never came. Thus, all unnecessary heavy KV projects were left behind and work was focused on improving the KV-1. The work eventually resulted in the heavily praised KV-1S, experimental KV-13 and, finally, the iconic IS.
The KV-4 designed by Dukhov, as represented in the MMO World of Tanks by Wargaming.net. Source: Wargaming.ne
Conclusion
Arguably one of the most interesting Soviet heavy tanks of the Second World War, the KV-4 was not just a massive vehicle, but also involved the interesting competition tactic which would not be applied again by Soviet designers. This brought a variety of interesting and unique ideas. However, no matter how advanced or revolutionary the KV-4 designs were, the entire program was simply too expensive and worthless, especially once the Soviets had entered war against the Axis. The program was not without its merits.
Dukhov’s KV-4 incorporated an efficient and trialed design into what was seen as the most successful KV-4 variant. It was the lightest, simplest, and almost a natural evolution from the KV-220. Equally interesting, he envisioned a partially automated loading system, with shells being lifted to the level of the gun breech. This gave him the victory against all the other engineers, but it was to no avail.
The KV-4 as designed by N. L. Dukhov. Illustration by Pavel Alexe.
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Soviet Union (1941)
