Category: WW2 Soviet Prototypes

Soviet Union (1931)
Experimental Self-Propelled Gun – At Least 2 Prototypes Built, Possibly A Small Production Series

During the 1920s, the Soviet Army was rather poorly armed and equipped. As it was slowly built, the need for armored vehicles, such as tanks, arose. The initial attempt to develop domestic tank design failed, as the Soviets lacked experience in designing such vehicles. For this, a military delegation was dispatched to countries, including the United States and Great Britain, in hope of acquiring a foreign design that was to be built under licenses. From Britain, the license for the Carden Loyd tankette was acquired. The Soviets further improved this design, which led to the creation of the T-27 tankette. As it was only armed with a machine gun, the Soviets wanted to increase its firepower by adding a 37 mm gun, creating a small series of experimental vehicles.

The T-27’s Brief History

During the 1920s, the Soviet armored forces were in a process of reorganization and rearmament. Initial Soviet attempts to develop armored vehicles were rather unuseful, and only smaller series were built. The first domestically built tank, the T-18 (MS-1), was adopted in small numbers to service in July 1927. Soviet industry was experiencing constant delays in delivery and poor quality of production. In November 1929, Управление по механизации и моторизации – YMM (English: Department of Mechanization and Motorization – UMM) instructed that the current development situation was unfeasible in the near future. To remedy this situation, YMM was instructed to seek technological help abroad.

On 30th December 1929, a commission led by the head of the UMM, Innokentii Khalepskii, went abroad. The plan was to visit Czechoslovakia, France, Germany, Great Britain, and US in order to purchase technologies and armaments. The negotiation with Great Britain proved most promising, as the Soviets managed to purchase a few different tank designs, including the Vickers Carden Loyd tankettes, the Vickers-Armstrong 6-ton, and the Mk.II medium tanks.

Some of the newly acquired Carden Loyd Mk.VI tankettes were sent to Zavod No.37, a factory in Moscow. There, an engineering team led by N. Kozyrev examined this vehicle in great detail, in order to be put into production as quickly as possible. The Soviet engineers were generally satisfied with this vehicle, but noted a number of shortcomings. Consequently, they implemented a series of improvements (such as modifications to the suspension, adding a stronger engine, etcetera) before the vehicle under the name T-27 was finally accepted for service.
The T-27 was basically a two-man tankette armed with one DT 7.62 mm machine gun. Its production began in 1931, and by the time the production stopped in 1933, slightly fewer than 3,300 had been built (the precise number differs greatly between sources). Given their obsolescence, the T-27 did not stay long in active service, as it was replaced by much more modern tank designs. The T-27s were allocated for crew training, but during the Axis invasion of the Soviet Union in 1941, many would be put into service. They performed poorly due to their weak armament and armor.

Improving Firepower

While the T-27 filled the gap of a lack of armored vehicles, its potential combat effectiveness was limited due to its weak armament and its general configuration which lacked a turret. As they were available in great numbers, discarding them was not a proper solution. On the other hand, increasing their overall combat performance by adding new armament was something that the Soviet Army considered doing.

For this reason, in October 1930, an official order was issued that such modification be implemented. The following year, a design team led by K.K. Sirken from the Leningrad Bolshevik, began the first steps to do exactly that. The overall T-27 design was to remain the same, with the exception of the vehicle’s right superstructure, where some modification would be required in order to fit the larger gun. This would lead to the creation of two prototypes. These received slightly different armament rearrangements. In addition, the first prototype used a four-wheel suspension, while the latter used the more common six-wheel suspension. Due to the rather short development time, this project appears to have received no official designation.

Design

Hull

The hull of this vehicle could be divided into three compartments or sections. The front-mounted transmission with the drive unit, the central engine compartment, and the two fully enclosed crew positions (opposite of the engine).

Engine

The engine from this T-27 modification was unchanged. It was powered by a Ford four-cylinder petrol, water-cooled engine delivering 40 hp @ 2,200 rpm. The T-27’s maximum speed with this engine was around 35 km/h, while the operational range was 110 km and 60 km cross-country. The weight of this vehicle was 2.7 tonnes. The modified versions with the extra added weight likely had slightly worse overall driver performance.

Suspension

The T-27 was used in two similar suspension configurations. One used the original 4 road wheels placed on a suspension cradle. In addition, there was a front drive sprocket and rear idler. The road wheels were placed in par on bogies which were suspended using simple flat leaf springs. The Soviets were not satisfied with this design, so they improved it by adding another pair of wheels.

The first prototype armed with the 37 mm gun used a four-wheel suspension. While there is very little information on these vehicles’ overall construction, thanks to surviving photographs, it is possible to identify that some structural changes were made. Given the recoil force of the gun, the integral structure of the suspension had to be strong. The part of the suspension cradle that held the rear idler was reinforced. Lastly, the upper track guiding rod was replaced with two simple return rollers.

This arrangement appears to have been insufficient for this modified vehicle. So, on the second prototype, a six-wheel suspension was used. It also received extensive structural improvement to better cope with the gun’s recoil. Its suspension cradle appears to have been slightly larger than on a standard T-27 vehicle. While the two upper return rollers remained, they appear to have received some kind of leaf spring addition.

Superstructure

The superstructure is another part of the vehicle that was heavily modified. Originally, the T-27 had a simple box shape superstructure that covered most parts of the vehicle. The crew’s head (and the engine’s top) were protected by a pyramidal-shaped hatch. In front of the crew compartment, there was a hatch placed on the upper glacis that provided access to their transmission unit. The T-27 was built using simple plates connected using bolts.

The right part of the superstructure, where the machine gun port was originally located, was redesigned in order to fit the larger gun inside of it. This part was greatly extended forward to provide room for the gun mount. Not much is detailed in the sources about this new superstructure’s design. We can assume though, that due to the T-27’s small size, it would be quite cramped and difficult for the gunner to operate this gun.

Armament

The initial armament of the T-27 consisted of only one 7.62 mm DT machine gun. This proved to be completely inadequate and was the main reason why this project was initiated. Instead, the Soviet designers wanted to install a 37 mm gun. Two guns were initially considered: the PS-2 and the B-3. Due to delays in production, neither of them was available for use.

As a replacement, a 37 mm Hotchkiss which was in service by the Soviet Army was chosen instead. In the first prototype, this gun was placed in the enlarged gunner position. The overall construction and the general characteristic of this gun mounted on the modified T-27 are not specified in the sources. What is known is that the performance of this vehicle was poor. The chassis became overburdened with the added weight of the gun, ammunition, and extra armor. It was noted that the ammunition for the main gun took up too much space inside the vehicle. As a temporary solution, a trailer was to be used to transport additional ammunition.

The second prototype received more modifications in order to provide more working room for the gun. The Soviet engineers were a bit overambitious, as they added a machine gun to this vehicle. For this reason, the main gun was placed in a lower position. Above it, a Degtyaryov 7.62 mm DT machine gun was placed on a ball mount. The machine gun could be operated independently of the main gun. In theory, this would provide armament to deal with the enemy armor and infantry. Realistically, this arrangement proved too much for the small vehicle and cumbersome to use.

Crew

The crew consisted of only two: the commander/gunner and the driver. The driver’s position was on the left and the gunner was on the other side. This arrangement was not changed on the modified T-27. Interestingly, on the second prototype, the Soviets tested the use of dual controls, meaning that both crew members could drive should the need arise.

Armor

Given its slight weight and small size, the T-27 was only lightly protected. The armor thickness of the front armor was 9 mm, the side and rear were 8 mm thick, the bottom was 4 mm, and the top was 6 mm thick. There is no mention in the sources that the armor of the modified T-27 was changed. This level of protection ensured that the vehicle was protected against small arms fire and shell splinters, but little else.

Ultimate Fate

After a series of examinations, it quickly became obvious that this concept was flawed. The gun was simply too heavy for the chassis. The use of machine gun placed above the gun was difficult to operate. The added weight led to engine overheating problems. As a result, the project was rather quickly terminated. It is not clear if any additional vehicles were built beside the two already mentioned prototypes. Some sources, such as D. Nešić (Naoružanje Drugog Svetsko Rata-SSSR) mention that a small production run was made.

Despite the cancellation of this project, the experimenting with stronger armament on the T-27 continued. An installation of a recoilless gun on the right side of the vehicle was tested. In addition, a modified version with a 76.2 cm gun installed to the vehicle’s rear was also built. None of these entered productions and any further work on improving the armament of the T-27 was discontinued.

Conclusion

While the whole concept of rearming the older design with a stronger gun was sound, in reality, this was impossible to achieve. The T-27’s chassis was simply too small and weak. The 37 mm armed T-27 project was essentially doomed from the start. The gun weight and its recoil were probably too much for the small chassis. In addition, the working space inside it was quite limited to effectively operate this gun. This ultimately led to the cancellation of this project, but at least, it offered some experience to the Soviet tank engineers.

T-27 with the 37 mm gun Technical specification
Crew	Commander/Gunner, and Driver
Weight	over 2.7 tonnes
Dimensions	Length 2.65 m, Width 1.83 m, Height 1.47 m
Engine	44 hp Ford petrol engine
Speed	45 km/h
Primary Armament	37 mm gun
Secondary Armament	One 7.62 mm DT machine gun (second prototype)
Armor	6 to 9 mm

Source

S. J. Zaloga and J. Grandsen (1984) Soviet Tanks and Combat Vehicle of World War Two, Lionel Leventhal
T. Bean and W. Fowler (2002) Russian Tanks Of World War II MBI Publishing Company
Svirin M. N. (2008) Самоходки Сталина. История советской САУ 1919-1945, Эксмо
A.G. Solyankin (2002) Отечественные бронированные машины. XX век Том 1, Цейхгауз
D. Nešić, (2008), Naoružanje Drugog Svetsko Rata-SSSR, Beograd
http://battlefield.ru/content/view/72/50/lang,en/
https://www.armedconflicts.com/T-27-t6527

Soviet Union (1940-1943)
Heavy Tank – 1 Prototype Built

The KV-150, or more commonly named T-150, was an attempt to improve the armor of the KV-1 even before the KV-1 entered mass production. With 90 mm of armor all around and a 700 hp engine, it could have been a better option had it not been for some critical events during its development phase. It was, however, groundbreaking in what would become a series of KV heavy tanks, and the single prototype saw combat service until the end of 1943.

The KV-1

As one of the most iconic and recognizable tanks of the Second World War, the KV-1 (or simply KV, acronym for the People’s Commissar of Defense for the Soviet Union, Kliment Voroshilov), proved to have unmatched armor and a very potent gun at the start of the German invasion of the Soviet Union, on 22 June, 1941. It had been developed in the late 1930s and tested in combat alongside its 2 much larger competitors, the SMK and T-100, during the Winter War. As the latter 2 followed a much more complex and archaic breakthrough tank philosophy, namely multi-turreted “landships”, the KV-1 (at the time U-0) would be selected for further development. It was created at the Kirov Leningrad Plant (LKZ), where the previous T-28 and its own competitor, the SMK, were designed and built.

By 19 December, 1939, production of 50 KVs was ordered, with mass production to begin in 1941. But, during this time, the ugly side of the vehicle started to come to light. Truth is that, by that time, the KV was far from ready for production, and dozens of mechanical problems, mostly caused by the heavy weight, had to be sorted out. However, due to Stalin’s personal involvement and pressure on the project, the KV entered preseries production in February 1940, which were indexed with a “U” prefix. These differed from vehicle to vehicle and were tested thoroughly to diagnose any issues.

Naturally, Stalin’s patience would not last, and in June 1940, in what would be called “The Stalin Task”, a decree from the Council of People’s Commissars of the Soviet Union would increase the yearly production quota of the KV to 230 units of both variants (130 standard KV-1 and 100 KV-2s with 152 mm howitzers). This immediate increase in production strained the LKZ plant into mass producing what was effectively an unfinished tank. Naturally, corners and compromises had to be cut over all fields in order to streamline production and cut costs. As some KVs were built, others were still vigorously tested, and results showed that the reliability of the gearbox and transmission were poor. Although changes were made, this aspect would become the bane of the KV-1’s existence. From February to July, 32 KV tanks had been built, and production would increase to 20 during the month of August and 32 during September.

More Armor

As early as May 1940, before the KV-1 even entered its shy mass production, the topic of improving the armor of the KV was discussed both by the GABTU (Main Directorate of Armored Forces) and by the People’s Commissariat of Heavy Engineering, where the LKZ plant was represented at. First mentions of thickening the KV tank’s armor came on 11 June, which claimed the need to up-armor the tank to armor between 90 and 100 mm. Furthermore, on 17 July, 1940, the Council of People’s Commissars of the Soviet Union adopted decree No. 1288-495cc, which stated:

• By November 1, 1940, the Kirov Plant will produce two KV tanks with 90 mm of armor: one with a 76 mm F-32 gun, the other with an 85 mm gun. The Izhora Plant will deliver one hull at the end of October, the production of the tank is scheduled to be completed by November 5. The second hull will be made by November 5th.
• By December 1, 1940, the Kirov Plant will produce two KV tanks with 100 mm of armor: one with a 76 mm F-32 gun, the other with a 85 mm gun. One hull will be delivered by the end of October and by the end in November.

In comparison to its predecessor, the KV-1, as being built in summer-autumn 1940, had 90 mm around the gun mantlet and 75 mm all around. These were exquisite levels of armor not just for Soviet tank standards, but also internationally, being able to withstand most anti-tank guns. It also put the weight of the KV at 44 tonnes, already a tonne increase from the U-0. The weight of the KV would keep on increasing, peaking at 47.5 tonnes by 1941.

Regarding the armament mentioned in the decree, the KV-1 was equipped, as a stopgap measure, with the L-11 76 mm gun until mass production of the more potent 76 mm F-32 could begin. As for the 85 mm gun, it was likely to be the F-30 gun developed by V.G. Grabin at plant No. 92 in Gorky, based on the 85 mm M1939 52-K. However, it is noteworthy that only one such gun had been built, and its testing had yet to conclude.

The first obstacle that the up-armored KV faced was the KV itself. By July, the design bureau tasked with its development, SKB-2 and the entire LKZ factory were busy producing and improving the KV, with little room to spare for a new development. The situation was worsened by the delayed delivery of the tank requirements from the military to SKB-2.

In August, head of the SKB-2’s design bureau, J.Y. Kotin, made two teams for the development of the two tanks. The 90 mm-armor KV was to be designed by a team led by Military Engineer L.N. Pereverzev and indexed as T-150 or Object 150 / KV-150. All 3 names were used in documents. For the sake of simplicity and consistency, it will be called T-150 in the article, with the exception of direct document translations. At this point, Pereverzev was still rather new to SKB-2, having just graduated from the Military Academy of Mechanization and Motorisation of the Red Army in 1939, and had only worked on the KV-1.

For designing the 100 mm-armored KV, the more experienced L.E. Sychev was appointed as chief designer. This variant would be indexed T-220 or Object 220 / KV-220. Sychev was a tank design veteran. He had worked on his bachelors at SKB-2 and then began his career in the same place, working on the T-28, SMK, and KV-1.

Once SKB-2 had sent over the documents (likely in September 1940) to the Izhora plant, the T-150 faced another issue. The Izhora plant was working at a very high capacity trying to increase its KV tank output. The 4 prototype KVs were to be built at Hall No.2, where 4 KV tanks were already being built at the same time. This meant that the October 1 deadline for the T-150 was missed, but not by much.

The Izhora plant delivered the hull of the T-150 and a turret on November 1 and LKZ completed the prototype by December. The T-220 was completed shortly after.

In November, during the latter stages of the development of the T-150, a new turret was proposed. It moved the commander to the rear of the turret and gave him a low cupola with a PTC rotating periscope. Other aspects remained the same as on the original T-150 turret. Only a simple sketch of it was done, with a slightly more detailed drawing of the new commander’s position. It was not considered, but it was used as the basis of the Object 222’s turret, which was essentially the T-150 with a completely new turret .

Object 221 – The T-150’s Bigger Brother

As per the request from 17 July, 1940, two tanks were supposed to be built with 90 mm armor, one with a 76 mm gun and one with an 85 mm gun. The first became the T-150, however, the latter had a more troubled development. When researching about the mounting of a 85 mm gun on the chassis of the KV-1, it was realized that it would not fit in the standard KV turret and a larger turret combined with additional armor would require a longer hull. This meant that both the 90 mm and 100 mm variants armed with an 85 mm gun would receive a longer hull, by one roadwheel (a total of seven). The 100 mm armored variant armed with the 85 mm gun became the T-220.

The 90 mm variant was named Object 221 or T-221. It was intended to mount the same turret and 85 mm F-30 gun as the T-220. However, there were serious delays, and the Izhora plant only managed to deliver hull components for the T-221 by 10 February 1941, and the F-30 gun and turret were not ready. On 19 February, Marshall of the Soviet Union G.I. Kulik proposed that the 76 mm F-27 gun be mounted inside a KV-1 turret instead, but nothing was done. The Object 221 remained abandoned until April, when it was used as the basis for the KV-3 (Object 223), though 30 mm of extra frontal armor were required for it to reach the specified armor thickness.

Design

For the most part, the T-150 was identical to the KV-1. As the additional 15 mm of armor were added on the outside of the hull, the internal layout for the crew was unchanged. The main armament was, as requested, a 76.2 mm F-32 gun, coaxially paired with a 7.62 mm DT machine gun to the right of the main gun, with another DT machine gun at the rear of the turret and one in the hull, next to the driver. Both machine guns were mounted in ball mounts.

The weight of the T-150 reached 50.16 tonnes, around 6 tonnes heavier than a KV, and went past the weight threshold by over 2 tonnes. Due to the increased weight, the suspension was reinforced. Otherwise, the hull remained identical to that of the KV-1, with front idler, large rear sprocket and 6 steel-rimmed roadwheels.

The front of the tank had the same features as the KV-1, with 2 tow hooks on the lower plate, a single driver viewport in the center of the upper plate, with a driving light to its right and ball mounted machine gun to its left.

The turret was essentially a KV-1 turret with thicker armor, but certain changes were made to accommodate the commander’s cupola. It was fixed in place and of cast construction. At the front, a fully rotating PTC periscope was mounted, with 6 other triplex periscopes around the cupola. The commander’s cupola likely lacked a service hatch, meaning that the commander and loader would likely have to share a hatch. The turret also featured the standard KV-1 vision devices, a PTC rotating periscope for the gunner and another periscope to the side and 2 facing the rear. Direct vision slits were provided over the machine gun ports. This meant that, on paper, the T-150 offered better vision for the crew than the KV-1. The driver’s vision systems were not changed.

The main novelty of the T-150 was its 90 mm armor all around the turret and hull. The turret deck, hull deck and hull belly were 30-40 mm thick. The commander’s cupola was rather large, but was also 90 mm all around and, thus, was not a weak spot. Frontally, this was a 20% increase in raw thickness over the KV-1 in most areas.

Crew

The crew of the T-150 was the same as that on the KV-1, with 5 men: driver, radio operator/bow machine gunner, commander, gunner, and loader.

The commander was seated to the right of the gun, where he would be able to observe the battlefield from his cupola. He was also tasked with loading the coaxial DT machine gun on his side. The gunner sat on the other side of the gun, to the left of the turret. He would aim and fire the gun via a TOD sight. He had a rotating PTC and fixed periscope for external vision. He was able to rotate the turret via an electric system but also with a hand crank. Behind the commander sat the loader, on a removable seat (for easier maintenance/loading). He would load the main gun with shells stored on the side turret walls and in cases on the hull floor. He would also operate the rare turret machine gun, should the situation require.

In the center of the hull sat the driver, and to his left the radio operator, who also manned the bow DT machine gun. The radio was mounted underneath the frontal plate.

Engine and Propulsion

The engine installed on the T-150 (and T-220) was the four-stroke V-5 diesel, 12-cylinder in V-config with an output of 700 hp. It was essentially a boosted V-2K (600 hp), which itself was a boosted variant of the V-2. The main problem was that the V-2K was unreliable and barely guaranteed to work for up to 100 hours. Consequently, the V-5 was even less reliable. So much so that, during trials, the chief designer from Plant No.75 could not guarantee the function of the engines on the T-150 and T-220. Combined with the poor design of the engine’s cooling system done by SKB-2 engineers, the engine would have several major issues during the trials and only worked for 199 km, or 24 hours.

The fuel tank capacity remained the same as on the KV-1, at 615 liters, which reduced the range to 220 km (on roads).

Armament

The main armament on the T-150 was the 76.2 mm F-32 gun. It was developed by Plant No.92 in Gorky in the late 1930s and was tested on the BT-7. It could fire BR-350A and BR-350B (APHE), BR-350SP (AP), and OF-350M (HE). The shell weight varied between 6.2 kg and 6.78 kg, depending on the type. The muzzle velocity was between 613 and 621 m/s (figures vary depending on the source consulted). In January 1941, the KV-1 would enter production with the F-32 gun. It was ballistically very similar to the L-11 it was replacing on the KV-1, while the T-34 would receive the far more potent F-34 76 mm gun the same year.

For proximity and anti-infantry defense, three 7.62 mm DT machine guns were mounted, one coaxially, to the right of the gun, which could be used for ranging closer targets (muzzle velocity around 840 m/s). The front facing machine gun in the bow was for suppression of infantry and the machine gun in the rear of the turret was for defense against flanking infantry.

Trials

On 14 January 1941, the People’s Commissariats of Defence and People’s Commissariats of Heavy Engineering requested that the T-150 and T-220 be tested at the LKZ proving grounds. A commission, headed by the Military Engineer 1st Rank Glukhov and with representatives from the GABTU, would monitor the testing of the tanks. According to the commission for field testing, the following goals were intended.

• Determining the tactical and technical characteristics of the tank.
• Identifying the shortcomings in the designs and their elimination prior to mass production.
• Judging whether it is possible to conduct military tests.
• Accumulating data for operating and repairing the tanks.

The tests would begin the following day on both tanks. During this time, several issues were quickly identified. On 25 January, the two prototype tanks were weighed, with the T-150 weighing 50,160 kg and the T-220, 62,700 kg. The problem here was that the GABTU specifically requested the T-150 to weigh a maximum of 48 tonnes and the T-220 56 tonnes. A report written by Military Engineer 1st Rank Glukhov on 28 January to the Head of Armored Department of the GABTU, Military Engineer 1st Rank Korobov, in the midst of the trials, showed that the commander’s cupola was poorly made (the observation devices were located too high, vision was inconvenient) and was placed in the loader’s position, who is not in command of the tank. Comically, the Chief Designer of Plant No.75, T. Chuptakhin, who was present at the trials, was not able to guarantee the operation of the engines installed on the T-150 and T-220 tanks. One of Glukhov’s reports included the following passage:

“The T-150 tank, after replacing the engine that failed during the factory run on 21 January, has not yet been brought back to the accepted state required by the Quality Control Department and military representatives.”

The gunshield was crudely made and provides only 3º of gun depression, instead of the 6.5º, as specified by the drawings.”

Due to the breakdown of the experimental V-5 engine provided by Factory No.75, the T-150 traveled only 199 km, or 24 work hours. Several issues were found and once again reported by Glukhov:

“The engine’s oil cooling system prevents the tank from driving at high speeds in the 3rd and 4th gear (at an outside temperature of 9° to 12°, the temperature of the injected engine oil increased rapidly after 5 minutes of motion in 3rd and 4th gears). Normal operation of the engine (inlet oil temp. 70°-80°). Due to the poor design of the cooling system, driving trials on the T-150 would cease.”

Instead, focus shifted towards firing trials, especially relevant as the F-32 gun had just replaced the L-11 gun on the KV-1’s production lines. Firing while stationary and firing during short stops went as expected (considering the 4-5 second aiming time), but firing on the move was unsatisfactory, though many of these results were entirely based on circumstances such as terrain and gunner skill, and the gunner conducting the trials, although experienced, was still not entirely familiar with the gun and tank.

Simultaneously, loading times were measured, depending on where the rounds were stowed. When loading shells from the right turret side (9 rounds), 5-7 rounds per minute were sustained. When loading shells from the left side of the turret (9 rounds), the rate of fire dropped to 3 rounds per minute, as the loader had to lean to the other side of the turret. The situation got worse when loading via casings that held 3 rounds. These would have to be lifted up and opened before the shells could be loaded in. This process slowed the rate of fire to 1-2 rounds per minute. In contrast, although not practical, when the shells were simply laid on the floor, 11 rounds per minute could be sustained. Furthermore, the ammunition cases, stowed on the hull floor, would often catch on one another when attempting to lift them, and on 6 separate instances, rounds were jammed inside. The sharp edges of the cases also injured the loader’s hands. Consequently, the commission noted that the ammunition stowage system had to be reworked.

Several issues had been noted with the crew’s positions as well. Firstly, the commander’s seat (combined with the cupola) were criticized for being fixed in place, preventing the commander from viewing out of the periscopes while seated. Likewise, he could not stand, as there was no room, but rather the commander had to stand with his knees slightly bent, in a semi-squatting position (naturally very tiring) to see out of the cupola. Other complaints included that he had to turn very frequently to communicate to the rest of the crew and he was also charged with loading the coaxial DT machine gun.

The gunner’s position also required improvements. The sight was deemed too far forward and slightly to the left, and the seat required more adjustment. The footrests and pedals required work as well. The knee would be bent too much. Additionally, the heel rest was too far down, requiring the gunner to keep his heel in the air in order to maintain his toes on the pedal, or overextend his ankle, both very tedious tasks.

The loader, aside from the aforementioned loading problems, would have his workspace cramped up by the commander’s seat, only 6-8 ammunition cases were easily accessible, and the machine gun drums were in the way when lifting rounds from the left turret wall.

Testing of the T-150 was concluded on 14 February. The trial results were reported back to the GABTU and People’s Commissariat of Heavy Engineering. Although the aforementioned issues were noted (and such problems were understandable for a prototype vehicle), it was decided to move forwards with the T-150 project, but in an altered form. Based on reports during this time, both the T-150 and T-220 were sometimes called KV-3. The more common use of this name came with the Object 222 and later with the Object 223, the KV-3 commonly known today.

On 21 February, a commission was made for analyzing the reason for the failure of Plant No.75’s engines on both the T-150 and T-220, and estimating a time of arrival of the fixed engines. The deadline was set for 10 April.

During the same period, between 18 and 24 February, Plant No.75 tested the V-5 engine on KV tank U-21, and it broke down once again, after 40 hours of operation.

On 1 March, the T-150 was officially canceled. The V-5 engine was still unrefined, and the tank was deemed to have several issues necessary to fix, but there was no point in doing so. Instead focus was shifted to the Object 222, which was based on the T-150.

Object 222

Many of the issues of the T-150 that were discovered during the factory trials were identified far earlier on. As a result, the SKB-2’s design bureau started work on a new tank in January-February, 1941 to fix these issues. The new tank, which used the same hull as the T-150, would be indexed Object 222. Originally, the differences between it and its predecessor consisted of a new cooling system and a new turret. This new turret was slightly larger, had flat sides (as opposed to 15° angled inwards on the KV-1 and T-150), and a slightly sloped frontal plate. The commander and his cupola were moved to the back of the turret as well.

By the end of February, the People’s Commissariat of Defence and the Central Committee of the Communist Party proposed accepting the KV-3 (Object 222) into service. Additionally, the topic of improving the main armament to the 76.2 mm F-34 was also raised. This gun had improved ballistics over the previous F-32 on the T-150. As for the propulsion, the tank was to use the same V-5 engine.

On 3 March 1941, a commission was formed, consisting of Military Engineers 2nd Rank I.A. Burtsev and I.A. Shpitanov, Military Engineer 3rd Rank Kaulin, LKZ Director I.M. Zaltsman, SKB-2 Director J.Y. Kotin, Director of LKZ 1st Dept. A.Y. Lantsberg, and NII-48 research institute engineers V. Dalle and A.P. Goryachev. Together, they reviewed the drawings and a full-scale wooden mock-up turret of the Object 222 turret mounted on a KV-1 (for simplicity’s sake). Turret armor would have been 90 mm all around and 40 mm on top. Several issues were identified, such as the flat turret walls, which were deemed to decrease protection, the less than ideal commander position, and the lack of hatch on the cupola for the commander. Despite these issues, the commission concluded that the turret should be built anyways, since there was little time to redesign it.

On March 15, the Council of People’s Commissars of the Soviet Union and the Central Committee of the Communist Party gave decree No. 548-232§, which imposed that LKZ had to switch mass production to the KV-3 (Object 222) in June.

The officials were confident that, by then, the new turret could be tested and refined. As for the T-150’s hull, with the new cooling system and properly tuned V-5 engine, it would run smoothly, as it was essentially just an up-armored KV-1 hull.

German Heavy Tanks

However, 4 days earlier, on 11 March, the Soviet Intelligence services had just released a report regarding the German Reich’s tank developments. Notes of several heavy tanks were highlighted, notably three new tanks that were under development. One of them was labeled Mark V, was to weigh 36 tonnes, and be armed with a 75 mm gun. The Mark VI was to weigh 45 tonnes and be armed with a 75 mm gun, and, finally, the Mark VII was to weigh 90 tonnes and be armed with a 105 mm. The first 2 tanks can be confidently identified now as the VK.30.01(H) and VK.36.01(H) and early Tiger mentions. But the latter can only be described as some early proposal to what would become the Pz.Kpfw.VII Löwe, which was first mentioned officially in German documents in November 1941.

This new German heavy tank was nearly double in weight of the KV-3 and considerably above the T-220. The 105 mm gun was far more alarming than the 76.2 mm F-34 that the KV-3 (Object 222) was to be equipped with and the 85 mm F-30 on the T-220.

On 21 March, the GABTU requested the urgent development of a new heavy tank from SKB-2 at LKZ, capable of matching the supposed German heavy tanks. It was to weigh up to 72 tonnes, have 130 mm of frontal armor, and be armed with the 107 mm ZiS-6 gun. It was indexed Object 224 / KV-4. On April 7, the GABTU would rework their approach, requesting that the KV-3 be based on the T-220 (Object 220) and armed with a 107 mm ZiS-6 and weigh 68 tonnes. The new KV-3 was indexed Object 223. An even heavier tank was also conceived, the KV-5 (Object 225), with 170 mm of frontal armor and 150 mm of side and rear armor, weighing over 100 tonnes.

After the invasion of the Soviet Union and the Siege of Leningrad in September, much of the SKB-2’s design bureau and its prototype tanks were evacuated to the ChTZ plant in Chelyabinsk, which was now renamed ChKZ, or Tankograd.

Most of the work on the heavy tanks was stopped in order to focus on more sensible topics at ChKZ. The only exception was the Object 222 (which had now been renamed to KV-6) and the Object 223 (KV-3). The GABTU was against the KV-6 and insisted on improving the armor of the T-150 to 120 mm and adding a new ZiS-5 gun. These were the last efforts on these tanks. The Object 223 (KV-3) progressed until December 1941.

These experimental tanks were incredibly expensive. A letter sent on 30 May 1941 to Military Engineer 1st Rank Korobov by A.Y. Lantsberg described the development costs of the major KV series of heavy tanks (Object 150, Object 220, Object 221, Object 212, Object 218, Object 223, Object 224, and Object 225). These had a total development sum of 5,350,000 rubles. The T-150 project would cost in total 1,500,000 rubles. In perspective, a KV-1 in 1941 would cost between 523,000 to 635,000 rubles.

Stage of T-150 Development	Price (thousands of rubles)
Draft drawings	50
Technical drawings	50
Prototype construction and factory trials	900
Proving ground trials	100
Drawing correction after trials	25
Repair of prototypes and improvements	375
Total cost	1500

Source: CAMO RF 38-11355-101

One of the more sensible alternatives was the KV-1E (the E is a post-war addition and derives from the Russian word meaning shield or screens), a regular production KV-1 with 30 mm to 25 mm additional armor plates, making the protection of the KV-1E superior to that of the T-150. The idea of the KV-1 with appliqué armor appeared on 19 June, 1941 and would be given to troops by July.

Second trials

The work on Object 222, Object 223, Object 224, and Object 225 tanks did not mark the end of the T-150 prototype’s career. During the month of June 1941, the T-150 was retested with a worked-out V-5 engine and improved cooling system. This time, it traveled 2,237 km by 19 June. In total, 5 different V-5 engines had been installed on the tank during its trials. Amongst the issues noted were:

Oil leaks from the gearbox’s primary oil retainer.
Teeth from the 3rd and 4th gear as well as conical gear were sheared off.
Collar bracket of the 2nd and 4th gears were worn out by 4 mm.
2 rubber shock absorbers had been destroyed.
Paper fuel filters failed

Several new production methods had also worked well, such as hot-pressing the torsion bar with the torsion arm together, and the gearbox casing, made out of recycled aluminium, did not show sign of damage or failures after 1671 km.

T-150 in Combat

As the Soviet Union was suffering rapid defeats against the Axis powers, prototype tanks were pressed into service. The T-150 would be no exception. It entered service with the 123rd Tank Brigade on 11 October 1941. A week later, on 18 October, the brigade, part of the 8th Army, fought around Neva Dubrovka and later crossed the Neva river. On 18 May 1943, the T-150, by then part of the 31st Guards Heavy Tank Regiment, was listed as knocked out beyond repair. But the need for tanks was there and it was sent to Plant No.371 for repairs and entered service with the same regiment in July. The commander was Guards Junior Lieutenant I.A. Kuksin and driver-mechanic was Technician-Lieutenant M.I. Shinalsky and the tank received the number 220 and callsign “Som” (Catfish).

Shortly after, Kuksin’s tank would partake in the Mga Offensive or Third Battle of Lake Ladova, and on 22 July 1943, the 31st Guards Heavy Tank Regiment, alongside 63rd Guards Rifle Division, engaged enemy forces south-east of Leningrad. During the fighting between July 22 and August 6, the 31st Guards Heavy Tank Regiment recorded kills of 10 enemy tanks (allegedly 5 Tiger tanks, 3 Panzer IVs, and 2 Panzer IIIs), 10 pillboxes, 34 foxholes, and 750 enemy personnel. Kuksin’s T-150 and his crew also performed well. During this period, they recorded the destruction of 5 foxholes, 2 light machine gun posts destroyed, and 36 soldiers. Their tank was also hit in the track and immobilized, yet the crew managed to get the track together and continue fighting. The tank held its position for 4 days, for which Kuksin and his crew received the Order of the Red Star.

On 12 August, the Regiment was assigned, with the 73rd Marine Rifle brigade, to capture the village of Anenskoye. The 1st and 4th companies attacked on 18 August at 04:55. The companies suffered heavy losses and, by 06:00, 9 out of the 10 tanks were taken out of battle, with only tank 206 being in working order. Amongst these casulties suffered on that day, the T-150 was one of them. Junior Lieutenant I.A. Kuksin, gunner Senior Sergeant A.S. Yurdin, driver Technician-Lieutenant M.I. Shinalsky, and loader Guards Seargant I.M. Brezhak were killed in action on 18 August and the T-150 was sent back to Plant No.371 for repairs.

Alternatively, a document dated 18 November 1943 shows that a new driver was assigned to the T-150 (noted as KV No.T-150, raising the question as to if the T-150 was ever given number “220”), and was still commanded by Kuksin.

It is worth highlighting that the T-220 also saw combat service, but its new turret and 85 mm F-30 gun were replaced with a regular KV-1 turret. The tank was knocked out during the defense of Leningrad.

Conclusion

The T-150 (KV-150 / Object 150) was, on paper, a minor upgrade to the KV-1, with just 15 mm of additional frontal armor, a more powerful 700 hp engine, and a new commander’s cupola. While the implementation of these changes proved problematic at first, the T-150 proved to be a very important step towards the design of even larger and heavier KV tanks. These ultimately proved to be a waste of money, time, and resources, assets which the Soviet tank industry did not have, especially with the Axis invasion. Like many Soviet pre-war prototypes and its larger brother, the T-220, the T-150 prototype saw combat service well into 1943, but what happened after is unknown.

T-150 / KV-150 / Object 150 Specifications
Dimensions (L-W-H) (approx.)	6.76 x 3.33 x 3.01 m
Total weight, battle-ready	50.16 tonnes
Crew	5 (Commander, gunner, loader, driver, radio operator)
Propulsion	V-5 12-cylinder diesel, outputting 700 hp.
Speed	35 km/h
Suspension	Torsion bar, 6
Armament	76.2 mm F-32 3x 7.62 mm DT machine guns
Armor	Front/sides/rear of hull and turret: 90 mm Top/Belly: 30 to 40 mm
No. Built	1 prototype built and saw service

Sources

Breakthrough tank KV – Maxim Kolomiets
Supertanki Stalina IS-7 – Maxim Kolomiets
KV 1939-1941 – Maxim Kolomiets
Victory Tank KV Vol.1 & 2 – Maxim Kolomiets
Tanks in the Winter War 1939-1940 – Maxim Kolomiets
Constructors of Combat Vehicles – N.S. Popov
Domestic Armored Vehicles 1941-1945 – A.G. Solyakin
Bronevoy Schit Stalina. Istoriya Sovetskogo Tanka (1937-1943) – M. Svirin
About the forgotten creators of Soviet armored power. (historyntagil.ru) – S.I. Pudovkin
Yuriy Pasholok. HF Small Upgrade – Alternate History (alternathistory.com) – Yuri Pasholok
Малая модернизация КВ | Warspot.ru – Yuri Pasholok
КВ-3: набор танковой массы | Warspot.ru – Yuri Pasholok
Опытный танк с боевой биографией | Warspot.ru – Yuri Pasholok
Tank Archives: KV’s Replacements – Peter Samsonov
Tank Archives: Heavy Trials – Peter Samsonov
Tank Archives: Heavy Tank Costs – Peter Samsonov
Tank Archives: T-150 Revival – Peter Samsonov
Tank Archives: Tank Plans for 1941 – Peter Samsonov
Tank Archives: Mass Breakdown – Peter Samsonov
Tank Archives: F-32 Technical Passport – Peter Samsonov
Tank Archives: Kirov Experiments, June 1941 – Peter Samsonov
How much cheaper than German tanks actually cost – Russian Seven (russian7.ru) – Kirill Shishkin
Heavyweight tanks KV-3, KV-4, KV-5 (famhist.ru)
https://sovetarmy.forum2x2.ru/t745-topic

Soviet Union (1944)
Heavy Tank – Drawings Only

Just months after the IS-2 began production, work began on developing a new heavy tank to replace it down the line. Engineer N. F. Shashmurin and his team envisioned an unusual tank, meant as a direct IS-2 upgrade, the IS-M. The most notable aspects of Shashmurin’s design were the large-diameter road wheels and the rear mounted turret. However, his project was not taken into consideration and was short-lived, although it did pave the way to the IS-6, which used some of its features.

Shashmurin and the IS

Tank designers are usually overlooked in the popular imagination, and those few acknowledged are usually limited to the likes of Ferdinand Porsche or Alexander A. Morozov. Even when limited to Soviet heavy tanks, the names of Nikolai L. Dukhov and Joseph Y. Kotin overshadow the others. Yet Nikolai Fedorovich Shashmurin was the man behind the creation of one of the USSR’s greatest war-winning tanks, the IS-2.

Born in 1910 in what at the time was called St. Petersburg (to be renamed Leningrad in 1924), 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 (Leningrad Kirov Plant) as an engineer for the SKB-2 design bureau. Before the war, he would work on the T-28 medium tank and create the torsion bar suspension system (T-28 No.1552) fitted on the SMK and U-0 (first KV-1 prototype), a system which would be implemented further on all future Soviet heavy tanks and self-propelled guns. Additionally, he developed gearboxes for the KV-1 (his gearbox would be dropped in favor of Dukhov’s infamous gearbox which would haunt the KV-1 for its entire service life), KV-220, KV-3, and even his own design for the KV-4 program.

With the beginning of the German siege of Leningrad in 1941, the LKZ (Leningrad Kirov Factory), specifically SKB-2 engineers, were evacuated to ChTZ (Chelyabinsk Tractor Plant) in Chelyabinsk (near the Ural Mountains), renamed ChKZ (Chelyabinsk Kirov Plant) a few weeks later. At Chelyabinsk, Shashmurin would develop the gearbox of the KV-1S and, after N. V. Tseits’ death in summer 1942, he became the head engineer for the KV-13 (at the time called IS-1), a vehicle which he did not like. Nonetheless, he would build upon it, and by May 1943, he had designed a new variant, equipped with an 85 mm D-5T gun specifically for the task of penetrating the German Tiger I, mated to a new hull. This was the Object 237 (at the time named IS-3), which would be adopted in service in September 1943 as the IS.

In parallel, Shashmurin designed the Object 238, meant to fit the new 85 mm S-31 gun in the KV-1S, but it was unsuccessful due to the cramped conditions within the turret. Production of the IS-1 started in November of that year, but it would not last long, as, by May 1943, work began on fitting the IS with the 122 mm D-25T gun, and by December 1943, the Object 240 would enter service as the IS-2. The mounting of such a powerful high-caliber gun was unprecedented in Soviet heavy tanks, which normally had similar, if not the same, guns as medium tanks.

Improving the IS-2

Extensive testing of the IS-2 was done at the NIBT (38th Research Test Institute of Armored Vehicle) proving grounds at Kubinka in January and February 1944, where it was concluded that the armor of the tank was not sufficient. Most notably, the “stepped” frontal hull was considered a weak spot, and it was proposed that the frontal hull should be made out of one angled plate.

Even after the first IS combat engagements, it became clear that, with the introduction of the German Panther tank, armed with a 75 mm KwK 42 L/70 (which could pierce the frontal armor of the IS heavy tanks) that the IS was insufficient. As early as September 1943, General Fedorenko (Head of the Armored Vehicle Directorate of the Red Army) would send a letter to Stalin, requesting the thickening of the IS armor and increasing its weight to 55-60 tonnes.

Additionally, in November 1943, the technical requirements for a new heavy tank were set by the GABTU (Main Directorate of Armored Forces). It was to have a mass of 55 tonnes, crew of 5, 160-200 mm of armor(frontal turret and hull), 800-1,000 hp engine, and a 122 or 152 mm gun. Speed was to be at least 35 km/h. These requirements would be laid down at the ChKZ plant on 3 December (10 December according to other sources) by factory director I.M. Saltzman.

The ChKZ SKB-2 design bureau, headed by N.L. Dukhov, had already worked on a new heavy tank since July, with its own funds. It was the 56-tonne K tank, which had 2 variants. The project was named Object 701. Only 2 K tank models were built.

However, on 21 March 1944, the GABTU changed the technical requirements. The weight was lowered to 55-56 tonnes, armament was a 122 mm gun with a muzzle velocity of 1,000 m/s, and 30 to 40 rounds had to be carried. The engine was to have a 1,000 hp output and allow for 40 km/h top speed. Armor thickness was not specified, instead, it was to be immune frontally to the Panther’s 75 mm KwK 42 L/70 and the 88 mm PaK 43/2 L/71 of the Ferdinand/Elefant.

These changes forced the reworking of the existing Object 701, but a green light was given the same month to produce 2 prototypes, leading to the IS-4 tank’s long development, with the first prototype, the Object 701-0, being built in May 1944.

At the same time as the developments at SKB-2, the other design institution at ChKZ, Factory No.100, also worked on their own tanks based on the same requirements. Headed by J.Y. Kotin, their approach was different to that of SKB-2. Instead of designing a new tank, they focused on a deep modernization based on the IS-2. By 18 April 1944, Factory No.100 would present its initial designs. Again, 2 models were built, one with a frontal plate separated into 3 parts (as on the first K tank) and one with a UFO-shaped hull, akin to the Object 279, designed and built decades later. Despite the increased protection, both variants had the same weight as the IS-2, 46 tonnes.

A document dated 8 April 1944, ordered J.Y. Kotin and his team to develop an upgraded variant of the IS-2 and subsequent SPGs over a 3-month period. The improvements should have included, but not been limited to, strengthened the armor protection, transmission, and chassis.

This would likely trigger the development of a new IS-2 modernisation, based on the requirements from 21 March. The design was to be less ‘radical’ and closer to the IS-2, but some very big changes were made. The tank would be called the breakthrough tank IS-M, the M standing for модернизация, meaning ‘modernisation’.

Sources do not agree exactly when development started, some arguing March, whereas others early April 1944. Nonetheless, N.F. Shashmurin was head of the project. While some design elements were taken from the previous upgraded designs, the main change was moving the turret to the rear of the hull, creating a very unique tank. A drawing of the tank would be made by Dobrovolsky. Who he was is so far unknown.

Design

The design of the IS-M was peculiar and unorthodox. The entire upper hull was made from several stamped steel plates, slightly angled inwards, with both the front and rear angled heavily. These were welded to the lower hull, which, while still mostly flat, had angled corners for extra weight saving. In addition to the main variant, a second variant was drawn out, with standard IS running gear. An SPG version was drawn as well, although only with very superficial details.

The IS-style turret was mounted at the rear of the hull, which allowed for very little gun overhang, decreasing the chance of the gun getting damaged in tight places such as forests and cities, or steep maneuvers, such as trenchcrossing. Despite its general shape being similar to the turret of the IS, several key components had been done away with, such as the big commander cupola or air vent.

Powerplant

The engine was to be an M-40 aviation engine, equipped with 4 TK-88 turbochargers. The displacement was of 61.07 l and had an output of 1,200 hp. Other sources claim it was a modified variant of the standard V-2-IS, such as the V-11 or V-16, yet these would only output between 500 and 700 hp, far less than the 800 to 1,000 hp specified. The M-40 engine was based on an aviation engine, thus could run on both diesel and kerosene. Whatever the engine was, it had a 10 h running time. The powerplant was kept inside an own compartment in the center of the hull, protecting the fighting compartiment and ammunition, consequently isolating the driver. Fuel tank was in the front, to the right of the driver. As the sprocket remained to the rear of the hull, the entire braking and final drive ensemble was kept at the rear, as on the original IS. However, this meant that the gearbox and driveshaft ran through the floor of the crew compartment. The transmission was likely offered in 2 variations, electromechanical, very similar to that on the Ferdinand/Elefant, or a conventional mechanical one. The gearbox was of planetary type.

For access to these components, the rear engine plate could be opened and rested on the hinges, for access to the final drive and brakes. The roof of the engine compartment was also removable, and had one engine access hatch, 4 air vents and 4 air purification filters.

Suspension

Two different running gear options were presented, one with 6 large-diameter road wheels, which allowed the returning track to rest on them, or 6 IS road wheels with 3 return rollers. The large road wheels would offer improved mobility over very muddy terrain, where smaller road wheels would clog up with mud. Additionally, they removed the need for return rollers. In turn, the standard IS wheel layout was already in use on various IS and KV series of tanks, resulting in a cheaper and smarter logistic choice. In both variations, the wheels were sprung by torsion bars.

Crew

The crew was larger than on the IS-2, with 5 men; a commander, gunner, loader, driver, and radio operator. The commander sat in the left corner of the turret. He had a low profile cupola equipped with 2 opposite facing periscopes for vision. Sat in front of him was the gunner, who operated the main gun. He had the main gun sight for vision and an extra, fully rotating periscope for a better field of view. Opposite him, to the right of the gun, sat the loader. He had to load the 2-part ammunition gun, as well as assist the commander in various tasks. For entry and exit, he had his own hatch with a periscope. The driver sat in the front of the hull, from where he would control the tank with 2 tillers. One direct vision slit in the armor was provided, as well as a fully rotating periscope. For ease of driving during the night and visibility during maneuvers, the tank had a single headlamp on the right side of the upper hull. The radio operator was likely seated to the driver’s right, also in the hull. He also had a rotating periscope for vision.

Armament

The exact armament of the IS-M was never specified, other than its caliber, 122 mm. However, considering the German-style muzzle brake, it was a D-25T, as on the standard IS-2. The tank was equipped with 40 shells for the main gun.

122 mm D-25T ammunition specifications
Shell type	APHE (BR-471)	APHE (BR-471B)	HE (OF-471)
Mass (kg)	25	25	25
Muzzle velocity (m/s)	795	795	800
Explosive	160 g	160 g	3.6 kg TNT
Penetration	200 mm	207 mm	42 mm (calculated)

Around the tank, 3 GVG 7.62 mm machine guns were mounted, one coaxial to the main gun, one in a ball-mount at the rear of the turret, and one in the frontal hull, which is not visible in the drawings. A ‘large caliber’ machine gun was to be added to the commander’s cupola for anti-aircraft purposes, likely a DhSK 12.7 mm machine gun, but it is not shown in the drawings either.

The SPG variant of the IS-M was likely armed with an 152.4 mm BL-8 gun, developed at the beginning of 1944 and tested during July of the same year on the ISU-152-1 (Object 246).

152 mm BL-8 ammunition specifications
Shell type	APHE (BR-540)	APHE (BR-540B)	HE (OF-540)
Mass (kg)	48.8	48.96	43.56
Muzzle velocity (m/s)	850	850	850
Explosive	0.66 g	480 g	5.86 kg TNT
Penetration	247 mm	276 mm

Armor

The frontal plate was a continuous flat plate of 200 mm angled at around 45°. Side armor was 160 mm thick and angled at 60° on the upper hull and flat on the lower hull. The rear was also heavily angled and 120 mm thick. The turret was 160 mm all around, but being awkwardly rounded, it increased its effectiveness significantly frontally. This gave the IS-M superior protection to any heavy tank of the time, while still maintaining a modest 55 tonnes weight.

Variants

In the background of the original drawing, 2 additional vehicles can be seen. The first is also an IS-M, but with a different set of running gear, namely 6 IS-style road wheels and 3 smaller return rollers. This was likely added as an alternative to the large roadwheel design.

Further back, a completely different vehicle is shown, a form of SPG based on the IS-M. The turret was replaced with a fixed casemate with a large 152 mm BL-8 gun. Interestingly, the running gear is the same as on the previously described IS-M.

Return to Leningrad and Further Developments

The IS-M was short-lived. Alongside its 2 earlier counterparts, all were abandoned in April 1944. Instead, Factory No.100 began work on a vehicle meant to rival the SKB-2’s Object 701 and thus become the new generation heavy tank. It would incorporate several features from both the IS-M and the 2 wooden mock-ups presented on 18 April 1944. This was the IS-6, designed at first in secrecy. Like on the IS-M, 2 variants were designed, one with large diameter road wheels and a steeply armored hull (Object 252). The second would use an electromechanical transmission on an IS-2 lower hull (Object 253).

In May, with the Soviets having lifted the Siege of Leningrad, the SKB-2 design bureau and Factory No.100 were moved back, and thus the LKZ was revamped. Many engineers moved back, including Shashmurin. Back in Leningrad, they would continue work on the IS-6. In August 1944, the Object 244 was used as a testbed for the Object 252’s wheels, first designed on the IS-M, and later the 122 mm D-30 gun. The Object 244 itself was a prototype dating back to February 1944, meant to test the new 85 mm D-5T-85BM on an unmodified IS-1 (Object 237). The project was named IS-3, although this has nothing to do with the later IS-3 heavy tank (Object 703). After a military representative from Factory No.100 reported the IS-6 secret development to the GABTU, it was ordered that further development and prototype production should take place at Uralmashzavod in Yekaterinburg, but without the end game of entering production.

Back at ChKZ, which had been working full-time on the Object 701, it was realized that it needed to present its own modernization of the IS-2. Thus, in August 1944, they presented the blueprints of an upgrade to the IS-2. At first glance, it looked like an unchanged IS-2, but it featured various improvements, such as refined frontal armor layout, thicker turret armor, improved turret design, and many mechanical changes, such as improved cooling system and engine room. Allegedly, one prototype was built. Yet, by October 1944, the project was abandoned in favor of a new tank, which incorporated many IS-2 features, but was still radically new. It was called the Kirovets-1 and given the Object 703 index. After several alterations, most notably the addition of its most famous feature, the legendary pike-nose, the IS-3 was born.

The pike-nose on the IS-3 was ‘borrowed’ from the IS-2U and Object 252U, an upgrade of the IS-2 and Object 252 meant to equip them with pike-noses. As a matter of fact, the IS-2U, designed in November 1944, was the last genuine attempt to fundamentally upgrade the IS-2 heavy tank. The IS-2 U’s turret was itself heavily inspired by earlier designs, such as the IS-M.

The IS-6 would end up unsatisfactory. The GABTU never intended to adopt it into service regardless. The Object 253 with the electromechanical transmission caught fire during testing. Both IS-6s were deemed insufficiently armored in comparison to the IS-4, and once the IS-3 was nearing production, the fate of the IS-6 was sealed.

Shashmurin himself, who had worked throughout the entire development of the IS-6, was never fond of the idea. Just like on the KV-13, he was a true believer in what he called “tank of maximum parameters” a tank which pushed the capabilities of the industry and designers to their limit, in an attempt to reach an unstoppable heavy tank. His first such vehicle was the IS-1 and later IS-2. For him, the IS-6 was a waste of time, especially considering the end of the war. As for the rivaling ChKZ heavy tanks, he had the following to say:

“We had finally created an almost perfect tank, capable of breaking through any enemy defenses. Ideal in its potential, all the qualities of the IS-2 could manifest themselves only in the development of the solutions found and tested in it. Alas, the improvement of the IS-2 was left to chance, and instead of developing already tested solutions, they began to invent new “bicycles”. An unjustified race began in the creation of independent models of heavy tanks, in many respects similar to the race that took place when creating the KV. The sad experience of the very recent past had taught us nothing…
The impressive, but unreliable IS-4 and IS-3 were being designed and created, another “monster” with two engines was being designed, a kind of electric locomotive was being built on tracks – a tank with an electromechanical transmission IS-6, which burned down after driving through the factory yard only 50 meters. In general, the design idea was in full swing, and in the meantime, the fighting was done by the “rude” workers of the IS-2, and not by the “handsome” IS-3, the production of which began in the early ‘45 and which immediately began to break down with the regularity of the sad memory of the KV-1.”

After the war, Shashmurin would finally fulfill his dream of designing a true “tank of maximum parameters”, the IS-7, which indeed, pushed the technology of the time to its limits, being the heaviest Soviet tank ever built, as well as several work on ATGM-based heavy tanks, PT-76 and more.

Conclusion

The IS-M itself was a short-lived design meant to offer an arguably unnecessary upgrade to the IS-2. It would incorporate some very interesting features and solutions, such as a rear mounted turret, large diameter road wheels, and a curved hull. It alo took in consideration several running gear designs and an SPG layout. Nonetheless, despite its short life, it was a crucial factor in the developmental progress of Soviet heavy tanks during the Second World War, by leading directly into the development of the IS-6, which lost in turn to the more refined, though still crude, IS-3 and IS-4 designed at ChKZ. For Shashmurin, the IS-M was certainly not his most prideful creation, but through its odd nature, it complements well the career of one of the USSR’s most important heavy tank designers of the Second World War.

IS-M specifications
Dimensions (L-W-H)	7 x 3.2 x 2.7 (m)/td>
Total Weight, Battle Ready	55 tonness
Crew	5
Propulsion	1,200 hp diesel (V12) M-40 with 4 turbochargers or 500-700 V series engines
Speed	40 km/h
Armament	122 mm D-25T 3x GVG machine guns 1 (?) DhSK machine gun
Armor	Turret: 160 mm (hull) front: 200 mm Sides: 160 mm Rear: 120 mm Roof and belly: 30 mm
Total Production	0, drawings only

Sources:

IS Tanks – Igor Zheltov, Alexander Sergeev, Ivan Pavlov, Mikhail Pavlov
Supertanki Stalina IS-7 – Maxim Kolomiets
Heavy Tank IS-4 – Maxim Kolomiets
Tank Power of the USSR – M. N. Svirin
Modest genius: who created the IS-2 tank, which became a symbol of Victory – Rossiyskaya Gazeta (rg.ru) – Sergey Ptichkin
Holes in the armor -Sergey Ptichkin, Sergey Zykov
Tank Archives: Modernization on Paper – Yuri Pasholok, Igor Zheltov, Kirill Kokhsarov
Tank Archives: Wrong Place, Wrong Time – Yuri Pasholok
IS-2: Struggle for the Assembly Line | Warspot.net – Yuri Pasholok
Not in the amplitude of the | Warspot.ru -Yuri Pasholok
Muzzle wedge for heavy tank | Yuriy Pasholok | Zen (dzen.ru) – Yuri Pasholok
Tank Archives: Improving the IS-2 – Peter Samsonov
“>Russian Heavy Tank Object 244 – The Original IS-3 (thedailybounce.net) -Harkonnen
IS-2Sh – unusual “Stalin” (voentex.ru)

Soviet Union (1944-1945)
Heavy Tank – None Built

The Panzerkampfwagen VI “Tiger” Ausführung E is one of the most outstanding and iconic vehicles in the history of tank building. The Tiger caused significant problems for the Allies when it first appeared at the front. Fortunately for the Allies, shortly after, several vehicles were captured by the Red Army and tested. In the Soviet Union, designers even worked on the option of re-equipping this German heavy tank with ‘domestic’ Soviet guns. However, this project appeared too late, and the imminent end of the war did not give this proposal any chance to materialize.

The Heavy Cat of the Wehrmacht

The Tiger I, or ‘Panzerkampfwagen Tiger Ausführung E’ (Pz.Kpfw.Tiger Ausf.E), was born in May 1942, but its conception and development can be traced directly back to 1936 and 1937, with work on a 30-33 tonne tank by the firm of Henschel und Sohn in Kassel. Just like other German tank projects, the development was very complex, overlapping with dozens of other projects, and has been the subject of a large number of books and movies. The name ‘Tiger’ itself has a no less complex history. It was first used in February 1942, when the project “Pz.Kpfw.VI (VK45.01/H) Ausf.H1 (Tiger)” was approved. The design was clearly identified as the Pz.Kpfw.VI or Tiger, with “Tiger I” first used on 15th October 1942, followed by “Pz.Kpfw.VI H Ausf.H1 (Tiger H1)” on 1st December 1942 and then “Panzerkampfwagen Tiger Ausf.E” in March 1943.

The Tiger I had a crew of five: commander (back left), gunner (front left), and loader (right) in the turret, and the driver and radio operator in the front left and right of the hull, respectively.
The main armament consisted of the 8.8 cm Kw.K. 36 L/56 gun in the turret. This gun was derived from the 8.8 cm Flak 18 and Flak 36 AA guns and delivered similar ballistic performance. It was combined with the excellent T.Z.F.9b 2.5 x magnification binocular telescope for the gunner. This T.Z.F.9b binocular sight was later replaced by the cheaper but no less effective T.Z.F.9c monocular sight, a change identifiable by the switch to a single hole in the left side of the mantlet. The Tiger carried 92 rounds of Armor-Piercing (AP) and High Explosive (HE) ammunition. Where available, the Pz.Gr.40 (high velocity, sub-caliber, tungsten core, with no explosive filler) round was also carried for use against heavy enemy armor.

Secondary armament consisted of a 7.92 mm MG.34 machine gun mounted coaxially with the main gun. This weapon had a maximum elevation of -8º to +15º. A second machine gun, a ball-mounted MG.34, was located in the right-hand side of the driver’s plate. This second machine gun was capable of 15º traverse to either side (total arc of 30º) and an elevation of -7º to +20º. It was fitted with a K.Z.F.2 episcopic sighting telescope with a magnification of x1.75. For these machine guns, 4,500 rounds of ammunition were carried. Another M.G.34 anti-aircraft machine gun (Flieger-M.G.) could also be carried on the turret (also fitted to the Befehlswagen-Tiger).

After June 1942, six 95 mm diameter smoke grenade launchers (in two sets of three) were approved for mounting on the turret, a process which started in August 1942. The launchers could fire the Nb.K.39 90 mm smoke generator grenades but, following combat reports of gunfire setting them off and blinding the crews, these were dropped in June 1943.

The Tiger was powered in the early production runs by the HL 210 TRM P45 21-liter V-12 Maybach petrol engine producing 650 hp at 3,000 rpm. Due to problems with the reliability of this engine, the maximum performance could not be achieved, restricting mobility for this heavy tank. As a result of the poor performance, the more powerful HL 230 TRM P45 23 liter V-12 Maybach engine producing 700 hp was introduced in its place from May 1943 onwards.

The Tiger’s suspension consisted of 55 mm diameter torsion bars (Stabfedern), which ran the complete width of the tank’s hull, with splined heads, although the two front and rearmost two bars were wider than the rest, at 58 mm diameter. The bars were connected to the road wheel arms (Laufrad-Kurbel), each of which had three road wheels. Their arrangement overlapped wheels from adjacent road wheel-arms, creating an interleaved pattern to spread the load of the tank onto the track. Hydraulic shock absorbers were fitted to the inside of the front and rear road-wheel arms which, combined with the damping effect of the torsion bar, created a very smooth ride.

Unsuccessful Debut

On 29th August 1942, the first batch of Tigers from the 502nd Heavy Tank Battalion, consisting of four Pz.Kpfw. VI, advanced to combat positions from the railway station Mga, near Leningrad. Three vehicles suffered serious breakdowns leaving the station, and, in general, were not so successful. Later, during the battles to break the blockade of Leningrad, on 16th January 1943, Soviet troops captured a Tiger which was previously hit by artillery. This was followed by a practically intact one on 17th January. The crew left it without destroying even a brand-new technical passport, different tools, and weapons. Both tanks were evacuated from the combat area and sent to the Kubinka Proving Ground for studies.

Studying the «Wild Beast»

Initially, the captured tanks appeared in the correspondence as “captured tanks of the HENSHEL type”, later called T-VI. The tanks that arrived aroused great interest among the Soviet military command. By that time, the “Tigers” were actively used by the Germans both on the Soviet-German front and in North Africa. These vehicles were used for the first time on a truly massive scale during the battle for Kharkov, making a significant contribution to the defeat of the Red Army on this sector of the war front. Around the same time, the Tigers fought in Tunisia against American, British and Commonwealth troops, inflicting serious losses on them.

By April 1943, the two tanks, with turret numbers 100 and 121, were already at the proving ground. It was decided to test ‘121’ for armor durability and use ‘100’ for testing the gun against the armor of Soviet tanks.

The armor on the side of the Tiger’s hull managed to withstand the Soviet 45 mm guns. However, 57 mm guns of the ZiS-2 type overcame the 80 mm side armor with ease even from a long distance (up to 1 km). The frontal armor of the tank could not be penetrated by the 76 mm F-34 gun, the main Soviet tank gun at that time. The 85 mm “anti-aircraft gun” 52-K performed much better in this regard, penetrating the “Tiger” in the front from a distance of 1 km. The 122 mm A-19 gun performed the best at this. Until that moment, it had not yet been considered as a possible tank cannon. After two hits fired from it, the once formidable German heavy tank turned into a pile of scrap metal.

The tests of the German 88 mm tank gun were much more impressive. It was used to fire at Soviet T-34 and KV tanks. The main Soviet heavy tank of that time was easily penetrated from a distance of 1.5 km. Even the uparmored version with additional protection was also penetrated. For the T-34, the very first shot, from a distance of 1.5 km, “decapitated” the tank. Its turret was “knocked off” the hull, while significant damage to the frontal part of the hull was caused by further shelling. It is worth noting that the aforementioned Soviet anti-aircraft gun 52-K showed similar results in tests.

Tests of the new German heavy tanks showed the Soviet military command the need to gradually abandon 76 mm tank guns in favor of larger calibers, such as 85 mm and 122 mm. At around the same time, accelerated work began on self-propelled guns, such as the SU-85 and SU-152, as well as on the KV-85 and IS-1 heavy tanks.

A Stranger Amongst Us

The sporadic capture of workable versions of the Tiger tank by the Red Army was the main reason for the episodic nature of its combat use on the side of the USSR. In addition, Soviet tankers, in an effort to get a high reward, almost always destroyed the rare Pz.Kpfw. VI.

The first reliable case of the use of a captured “Tiger” in battle was recorded only at the very end of 1943, with the crew under the command of Lieutenant N.I. Revyakin from the 28th Guards Tank Brigade. On 27th December 1943, one of the “Tigers” of the 501st Tank Battalion got stuck in a crater, its crew ran away, and the tank itself was captured. On the next day, the tank was assigned to the 28th Brigade. Revyakin was appointed commander of the captured heavy tank because he already had extensive combat experience and military awards, two Orders of the Patriotic War of the 1st degree and the Order of the Red Star. On January 5th, the captured tank, with red stars painted on the sides of the turret and with the writing “Tiger” added as well, went into battle.

The operational service of this vehicle with Soviet units looked quite typical for German heavy tanks. It almost always required repairs. The matter was greatly complicated by the lack of spare parts. But this was on the battlefield. In the bowels of the Soviet design bureaus, there had been several projects developed to re-equip captured German vehicles with Soviet guns since 1942. Similar proposals were made for the Tiger, but they started much later, at the end of 1944 and the beginning of 1945.

T-VI-100: Unrealized “Frankenstank”

On 28th November 1944, the Artillery Committee at the Main Artillery Directorate of the Ministry of Defense of the USSR (AK GAU) issued tactical and technical requirements No. 2820 “For the installation of domestic weapons in the turrets of captured German tanks T-IV, T-V, T-VI and the Royal Tiger” (due to the lack of a full-scale model of the Pz.Kpfw. VIB Tiger II turret, the study of the change of armament of this tank with a domestic gun was not carried out), including the adaptation of these turrets as stationary firing structures. Simply put, OKB-43 needed to take the turrets from captured tanks, replace the German guns with Soviet ones, along with sights, and further adapt them for installation on armored vehicles.

In January 1945, GSOKB (рус. Государственное Союзное Особое Конструкторское бюро – State Union Special Design Bureau) No. 43 at the NKV (рус. Народный Комиссариат Вооружения СССР – Ministry of Armaments of the USSR) presented a project for installing the latest 100 mm D-10T tank gun, which in the future would become the main armament of the T-54 medium tank, with the Soviet TSh-17 sight, in the turret of the T-VI tank (how trophy “Tigers” were designated in the USSR) while retaining its gun mantlet. This conversion process was estimated at 90 hours of work. The conversion provided for the installation of a shell casing removal system, which simplified the work of the turret crew.

№	Works	T-IV-76 with F-34	T-V-85	T-VI-100	T-IV-76 with ZiS-5
I	Lathing	18.0	40.0	15.0	9.0
II	Gouging and milling	4.0	7.0	4.0	5.0
III	Drilling	10.0	10.0	9.0	9.0
IV	Welding	16.0	22.0	12.0	12.0
V	Gas cutting	8.0	8.0	7.0	8.0
VI	Forging, pressing and bending works	4.0	6.0	6.0	4.0
Summary		60.0	93.0	53.0	47.0
Fitter and assemblyman hours, 5 people per team		80.0	120.0	90.0	80.0
Head of Special Design Bureau (OKB-43) – Salin; Senior technologist – Petrov;				January 3, 1945

New gun: D-10T

At the end of 1943, on an initiative basis and in the shortest possible time, the team of designers of Design Bureau of Plant No. 9, headed by F.F. Petrov, developed a 100 mm gun system designed for installation in the SU-100 tank destroyer. The cannon, the lead designer of which was M.E. Bezusov, received the designation D-10. The barrel length was 56 calibers (5,610 mm), and the initial velocity of the projectile was 900 m/s. The rollback length of the D-10S turned out to be longer than that of its competitors and was about 510-560 mm. Structurally, the gun system was a logical successor of the Design Bureau of Plant No. 9’s earlier projects, and when it was created, maximum unification with them was achieved. For example, cradle, lifting and turning mechanisms were taken from the D-25T 122 mm gun.

The history of the 100 mm D-10 gun did not end with the SU-100 tank destroyer. It would also appear on such Soviet late-war prototypes as the T-34-100 and SU-101 (a.k.a. Uralmash-1). After the war, it would be modified many times (hence versions like D-10T, D-10T2, M-63, D-33, 2A48, etc.) and become the main gun of the Soviet medium tanks of that period, the T-54 and T-55. It would also be proposed for some Cold War Soviet tank destroyers, such as the SU-100P and the Obj. 416, for Chinese medium tank Type 59 (WZ-120), and for light amphibious tanks prototypes, such as the Obj. 685 and the Obj. 934.

Project Description. Comparison with Tiger I Ausf. E

The Soviet military command liked the proposal of the installation of the Soviet D-10 gun, which had proven itself on SU-100 self-propelled guns, in the turret of the German Tiger tank. Indeed, the 88 mm KwK 36 tank gun, so formidable in the early stages of the war, was no longer that impressive by 1945. This was understood by the Germans themselves, who managed to design a lot of self-propelled guns armed with a 128 mm KwK 44 gun, and one of them, the JagdTiger, was even built and used in battle.

8,8 cm KwK 36	APHEBC		APCR	HEAT	HE
	PzGr	PzGr 39	PzGr 40	HIGr 39	SprGr
	9.5 kg	10.2 kg	7.3 kg
	810 m/s	773 m/s	930 m/s	600 m/s	820 m/s
	168 g charge (285.6 g TNT eq.)	64 g charge (108.8 g TNT eq.)	–	0.646 kg charge (1.1 kg TNT eq.)	689 g TNT
	146 mm pen	165 mm pen	210 mm pen	110 mm pen	–
	7-8 rpm	Parameters of penetration are given for 0 m and 0°.

Original T-VI gun… (source — ZA DB, Pablo Escobar’s gun table)

100 mm D-10T	APHE		HE
	BR-412	BR-412B	OF-412
	16 kg		15.2 kg
	895 m/s		880 m/s
	65 g charge (100.1 g TNT eq.)		1.46 kg TNT
	210 mm pen	215 mm pen	–
	7-8 rpm	Parameters of penetration are given for 0 m and 0°.

… and a Soviet “replacement” for the T-VI-100 proposal (source — ZA DB, Pablo Escobar’s gun table)

The Soviet gun significantly surpassed the KwK 36 in terms of firepower. With comparable accuracy, it had higher penetration, muzzle velocity, and much more powerful HE shells. With all the ‘pluses’, it was only slightly inferior to the German gun in terms of rate of fire.

The larger caliber affected two technical characteristics of the vehicle, the elevation arc and the amount of ammunition. According to the author’s estimates, instead of 92 shells of 88 mm caliber in the German original, the T-VI-100 could carry only about 50 shells of 100 mm caliber. The dimensions of the breech and the shape of the barrel influenced the downward elevation arc of the gun: instead of -8° in the frontal part and -3° in the rear in the Tiger I Ausf. E, the maximum depression became -4° all around. The upward elevation arc of the gun remained the same at +15°.

Inside the turret, space became much tighter. The breech of the new gun would now occupy ~75% of the turret length instead of 50% previously.

The cannon was not the only German component replaced with a domestic one in the proposal, with the coaxial machine gun as well as the sight being changed. The German 7.92 mm MG-34 was substituted with the Soviet 7.62 mm DT with a disk magazine, while the German TFZ-9 sight was replaced by the Soviet TSh-17. In the future, the same sight would be used on IS-2 and IS-3 Soviet tanks. It can be assumed that the machine gun in the hull would also have been replaced by a DT. Although there is no documentary substantiation of this hypothesis, such a decision would have been logical.

However, many other problems remained unresolved. There was no talk of replacing the transmission, engine, and other hull components with Soviet ones, which means that repairing them would have been problematic. Obviously, if the T-VI-100 was built in metal, in field use, all the ‘charms’ of exploiting captured German vehicles by the Red Army would have been preserved to the great displeasure of the crews and mechanics.

The Fate and Prospects of the Project

In general, the project was judged positively and was approved by the High Command, but things did not move beyond the project documentation. By spring 1945, the need for such projects had disappeared due to the proximity of the end of the war in Europe.

The Tiger I itself was outdated by 1945. Its armor could no longer ‘surprise’ anyone. All this indicates that the T-VI-100, if built, could not fulfill the previous role of “heavy tank for breakthroughs”, which was performed by the Tiger I in the first years after its appearance at the front.

It seems, however, that there was another possible option for using the developments on the project, selling a “modified” version to third countries. However, the logic behind this seems flawed, as most of these, especially those that never operated such a heavy tank before, the “Tiger”, even with a 100 mm gun, would probably not have been needed (and Germany itself was already not allowed to have its own army). For the emerging Soviet-bloc countries, such as Czechoslovakia, Hungary or Poland, especially ones bordering what would in the future become NATO, the T-VI-100 might have been a good temporary stopgap for their weakened armies until Soviet supplies of T-34-85s, IS-2s, T-54s, etc. would have become the norm. It is important to keep in mind that plans including Operation Unthinkable, a British invasion of East Germany, were actively developed, and tremendously dangerous for the weakened and war-torn USSR and its satellites at that time. Moreover, the first frontier of the possible Third World War would surely have been in Eastern Europe. On the other hand, it is doubtful that rearming a quite rare and outdated captured tank type was easier and more useful for the aforementioned countries rather than waiting for the mass-produced T-34 or IS-2.

Conclusion

The project of the T-VI-100 tank, like many of its analogs, belongs to the category of “the war ended too soon”. On the one hand, although this was a fairly reasonable alternative to the simple disposal of captured vehicles, serious improvements were still required for its full-fledged and practical implementation, especially to the hull. On the other hand, for one of the tasks of the project (the aforementioned possibility of using turrets with a new gun system as stationary firing points), the existing level of development was more than enough. But such defensive systems would have also hardly been needed by the Soviet Union after 1945.

Instead of an Afterword: T-VIB-100

As mentioned above, captured King Tigers were also considered for rearming with domestic (Soviet) weapons, but these proposals were not worked on due to the lack of turrets and data on them.

Still, it can be speculated what exactly may have been included in the hypothetical ‘domestication’ of the “Tiger-B” (or “T-VIB”), as it was called in the USSR. TZF-9 sights, just like on T-VI-100, would likely have been replaced by the TSh-17. The 7.62 mm DT machine gun would have likely taken the place of the MG 34.

A more difficult question is which Soviet weapon could have replaced the German 8.8 cm KwK 43. The choice would probably have been between the 100 mm D-10 and the 122 mm D-25 tank guns (there is no sense in replacing KwK 43 with less powerful guns of smaller caliber). Since the second variant, due to its large caliber, would require a large amount of space (for the breech, counter-recoil mechanism, and ammunition), the D-10 seems to have been the most optimal alternative to the German gun.

The vehicle itself would probably have been named similarly to the T-VI-100: T-VIB-100, but “Tiger-B 100” variant is also possible. However, all this is just a hypothetical conception and speculative thought of “what-could-have-been”, and was never actually developed.

Special thanks from the author to his colleagues Andrej Sinyukovich, Pavel “Carpaticus” Alexe and Pablo Escobar.

T-VI-100 specifications table
Dimensions (L-W-H)	8.45 x 3.547 x 3 m
Total weight, battle ready	~57 tonnes
Crew	5 (commander, gunner, loader, driver, and radio operator)
Propulsion	Maybach HL 210 P.30 petrol engine (650 hp) or Maybach HL 230 P.45 petrol engine (700 hp)
Performance	45 km/h (road max.), 30 km/h (road sustained) or 40 km/h, 20-25 km/h (firm ground sustained)
Fuel	348 liters, sufficient for a range of up to 120 km road, 85 km firm ground. Two spare 200-liter fuel drums could be carried on the back deck for long road marches.
Primary Armament	100 mm D-10T
Secondary Armament	2x 7.62 mm DT
Gunner’s sight	TSh-17
Ammunition	~50 rounds 100 mm, ~4,500 7.62 mm ammunition
Hull Armor	Driver’s plate – 100 mm @ 9º Nose – 100 mm @ 25º Glacis 60 mm glacis @ 80º Hull Sides Upper – 80 mm @ 0º Hull Sides Lower – 60 mm @ 0º Rear – 80 mm @ 9º Roof and Belly – 25 mm
Turret armor	Mantlet – 120 mm @ 0º Front – 100 mm @ 5º Sides and Rear – 80 mm @ 0º
№ built	0, blueprints only;

Sources

Central Archives of the Russian Ministry of Defense 81-12038-775;
Russian State Archive of Film and Photo Documents;
https://tanks-encyclopedia.com/ww2/germany/panzer-vi_tiger.php
https://waralbum.ru/41232/;
https://warspot.net/38-heavy-trophy;
https://pastvu.com/p/105441;
http://www.tankarchives.ca/2013/05/re-arming-german-tanks.html;
http://www.dogswar.ru/artilleriia/pyshki-gaybicy/7576-100-mm-nareznaia-tan.html;
Pablo Escobar’s guns’ parameters table;
https://vk.com/@zinoviy_alexeev-t-vi-100;

Soviet Union (1935)
Self-Propelled Gun – 1 Prototype Built

Prior to the Second World War, the Soviets were experimenting and developing a series of projects intended to improve the performance of already existing armored vehicles. One of these projects was an attempt to resolve the issues with the weak armament of Soviet amphibious tanks. This would lead to the creation of the experimental SU-45. While one prototype would be built, its poor performance would eventually lead to the cancelation of this project.

The SU-37 project

The Soviet Scientific and Technical Department Agency of Automobiles and Tanks (which was part of the Ministry of Defense of Red Army) issued a request to the director of plant №37 to begin designing and building a new self-propelled vehicle based on the T-37A amphibious light tank. The timeline was quite short. The order was given on 22nd March and the first prototype was to be completed by 11th April the same year. In reality, this task could not be achieved effectively in such a short period of time.

The T-37A was an amphibious light tank developed during the early 1930s in the Soviet Union. It was lightly protected and armed with only a single machine gun. The crew consisted of the driver and the commander/machine gunner. The T-37A was primarily intended to perform reconnaissance operations. Over 2,000 vehicles would be built, with most being lost during Operation Barbarossa in 1941.

When the tactical and technical requirements arrived, they included an option to use either an unchanged T-37A chassis or to build a completely new chassis with some elements taken from this vehicle. Other requirements included a maximum weight of the vehicle of 3 tonnes. The armament would include one 45 mm gun with a traverse of 30° (in both directions) and elevation of -8° to +25° and a DP machine gun. The ammunition load for the gun was to be 50 rounds, with an additional 1,000 for the machine gun. The overall armor protection had to be at least 5 mm thick (except the roof, which would be open-top) including an armored shield for the gun.

The new vehicle, which would receive the SU-37 (Samokhodnaya ustanovka – self-propelled) designation, was to have the same amphibious properties as the T-37A. It should have supplemented the weak firepower of the T-37A formations with its stronger armament. In addition, it was to fulfill a mobile anti-tank role on a regimental level.

The improved SU-45 replacement project 

Despite the short-term development goal, the actual design work on the new self-propelled vehicle dragged on. Almost from the start, a number of problems arose. One issue was the weight of the new vehicle was much larger than expected. This prevented it from being able to cross water obstacles. Another even greater problem was that many components for the T-37A were no longer being produced. A team of engineers under the leadership of I. Arharov was tasked with resolving the problems with the SU-37 and trying to find a better solution.

In November 1935, a mock-up version of the new modified self-propelled vehicle was presented to the Agency of Automobiles and Tanks of the Ministry of Defense. The basis for this new vehicle was the T-38 amphibious light tank. The T-38 was an improved version of the T-37A. It had a slightly modified suspension, overall simpler construction, better buoyancy properties, and the turret position was changed to the left side of the hull. The armament, crew configuration, and armor were the same. Over 1,200 of his vehicles would be built from 1936 to 1939.

This vehicle incorporated the chassis, transmission, and engine from the T-38. The main gun was still the same 45 mm anti-tank gun. The driver/gunner was initially positioned on the right side. The commission requested that the driver’s position be changed to the left side and that he no longer have to operate the gun. The first prototype was to be built by the start of 1936.

Name 

In the documents of the Agency of Automobiles and Tanks of the Ministry of Defense, the project received the “SU-45” designation. It is somewhat confusing that the Soviet Military Authorities decided to name the previous prototype based on the chassis on which it was based (SU-37 from T-37A) and the second prototype by the main gun caliber. This designation practice would continue on, many later developed self-propelled vehicles receiving names based on their gun caliber.

Author D. Nešić, (Naoružanje Drugog Svetsko Rata-SSSR) notes that the designation for this vehicle was T-45. This should not be confused with a Soviet attempt to improve the T-60 tank during the Second World War. If this is a mistake or misunderstanding on behalf of the author is difficult to know.

Specifications

Note that, due to the generally obscure history of this vehicle, sources greatly disagree about nearly all of the SU-45 components.

Chassis

For the construction of the SU-45, a modified chassis of a T-38 light amphibious tank was used. The front part of the chassis housed the crew and the main gun. To the rear, the engine and the transmission were placed.

Engine and transmission 

The SU-45 was powered by a four-cylinder liquid cooling 40-45 hp GAZ-A engine. The maximum speed of the SU-45 with this engine, on a good road, was 45 km/h. The off-road speed and operational range are unknown. The GAZ-A engine was started by using a MAF-4001 electrical starter. The position of the transmission was changed to the rear.

Suspension

With the increased number of crewmen, added ammunition, and other changes, the weight of the vehicle reached 4.5 tonnes (or 4.3 tonnes, depending on the source). The T-38 running gear had to be redesigned. This included adding an additional roadwheel (on both sides), making it five in total (from the original four on the T-38). While the added wheel was suspended individually, the remaining four were placed in pairs on a bogie suspension unit. All five wheels were rubber-tired. The idler and drive sprocket on the SU-45, in comparison to the T-38, had switched positions. The driver sprocket was now at the rear, while the idler was at the front. The two return rollers remained unchanged.

Superstructure

Not much is detailed in the sources about the superstructure’s design. The SU-45 was actually an open-topped vehicle. To shield the crew from the weather and elements, a canvas cover could be placed on top of the vehicle. Its overall construction, based on the few existing photographs, appears to have been simple in design. The SU-45’s side armor plates were flat, while the front plate was at an angle. The front, where the crew compartment was located, was slightly raised in comparison to the rear engine compartment. This was meant to provide the crew with protection but also to reduce the vehicle’s overall weight.

On the right front plate, a large square-shaped driver’s visor was placed. In its center, a smaller vision port was located. On the opposite side of it, a ball mount for the machine gun was located. Close to it, a pyramid-shaped cover can be seen. Its purpose is not clear, but it is likely to have been a protective cover for the gun’s sights.

Armament

The 45 mm M1932 anti-tank gun was chosen as the main armament of this vehicle. It was the standard Soviet infantry anti-tank gun prior to and during the first years of the war. While it would be replaced with larger caliber weapons, due to the large production numbers, it remained in use during the war. The 45 mm M1932’s armor penetration at 500 m (at 0 degrees) was 38 mm. The rate of fire was some 12 rounds per minute.

The main gun on the SU-45 was positioned in the front center of the vehicle. It was protected by a round shield placed in front of the gun. The elevation of the gun was -3° to +10°, while the traverse was 10° in both directions. The ammunition load consisted of (depending on the sources) between 50 to 100 rounds. The latter number seems to be unlikely, given the small size of the vehicle. The secondary armament consisted of one 7.62 mm DT machine gun. It was placed in a ball mount and positioned to the left side of the vehicle. It was operated by the vehicle’s commander. The ammunition load for this machine gun was around 1,100 rounds. The machine gun was also provided with a pivoting mount to be used as an anti-aircraft weapon.

The Crew

Depending on the source, this vehicle is listed to have either two or three crew members. In case it had three crew members, these included a commander/gunner, loader, and the driver. Despite initial plans to change the position of the driver to the left, on the prototype, he was seated on the right side. The remaining crew members were positioned opposite the driver. The commander was overburdened, as he had to operate the gun and the machine gun and command the vehicle, greatly reducing his effectiveness.

Armor protection 

The SU-45 was lightly protected, with armor plate thicknesses ranging from 6 mm on the sides to 9 mm on the front. These armor plates were connected using screws and rivets. This armor thickness was sufficient, at best, against small-caliber bullets.

Ultimate fate

Despite the plans to complete the first prototype by January 1st, 1936, due to many delays, it was only completed in the spring of that year. Once ready, a series of trails with the SU-45 were carried out. During these, a number of flaws in the design were noted. The T-38 chassis was overloaded and often led to mechanical breakdowns. The engine was underpowered, with an ineffective cooling system which often led to overheating. The transmission was also problematic and unreliable.

Seeing the results of these trials, the Agency of Automobiles and Tanks of the Ministry of Defense insisted that all these flaws and problems be resolved. The experiment would be carried on to the experimental T-38M chassis, but ultimately lead nowhere, and the whole SU-45 project was scrapped.

Conclusion

The SU-45 was intended as a lightweight self-propelled vehicle which was to provide additional support fire for the amphibious light tanks in cooperation with other units. The SU-45 design ultimately proved to be a failure. Having too great weight prevented it from being used as an amphibious vehicle. The engine had overheating problems. While it had much-improved firepower in comparison to the vehicle it was based on, it retained weak armor protection. This vehicle would never enter production and the Soviet units had to rely on their obsolete T-37 and T-38 vehicles. During the Second World War, these also proved to be unsatisfactory designs in many regards.

 

SU-45 specifications
Dimensions (L-w-h)	4.2 x 2.36 x 1.62 m
Weight	4.3 to 4.5  tonnes
Crew	3 (Commander/Gunner, Loader, and Drive)
Propulsion	40-45 HP GAZ-A engine
Speed (road)	45 km/h
Primary Armament	45 mm M1932
Secondary Armament	7.62 mm DT machine gun
Armor	6 to 9 mm
Total production	1

 

Source

• L. Ness (2012) World War II tanks,  Harper Collins Publisher
• D. Nešić, (2008), Naoružanje Drugog Svetsko Rata-SSSR, Beograd
• Svirin M. N. (2008) Самоходки Сталина. История советской САУ 1919-1945, Эксмо
• A.G. Solyankin (2002) Отечественные бронированные машины. XX век Том 1, Цейхгауз
• http://aviarmor.net/tww2/tanks/ussr/su-45.htm