Author: Zinoviy Alexeev

Categories
WW2 Czechoslovak Prototypes WW2 German Prototypes

Škoda SK 13

Left side view 3D model of Skoda SK 13 by Phantom_25_Sniper.
Left side view 3D model of Skoda SK 13 by Phantom_25_Sniper.

German Reich/Protectorate of Bohemia and Moravia (1944-1945)
Light Tractor – 1-2 Prototypes Built

At the beginning of the Second World War, Germany faced a total resource crisis, especially in terms of fuel. In a panic, the country’s leadership sought for a cheap and plentiful equivalent. Along with synthetic fuel, steam engines were one of many potential substitutes considered. The Škoda SK 13 was amongst the late-war survivors of this technology, combining both archaic and modern elements.

Not From a Good Life

Many European politicians’ hopes for victory at the early stage of World War Two were based on the fact that a lion’s share of global resources was controlled by the Allies or, at least, were beyond Hitler’s reach. The Allies outnumbered the Axis ~3 times in population and ~8 times in territory. Moreover, the British Navy managed to practically cut off the aggressor from the rest of the world.

The only strategic resource that the Germans had in abundance was coal. On the other hand, oil production covered less than 9% of the state’s demand. Only 11% of imported oil came to the Third Reich from Romania, which was accessible by land, another 1.7% from the USSR, and the rest came from overseas. In its article of September 7th, 1939, the American magazine ‘The Oil and Gas journal’ emphasized:

“At this time, the South American countries are the principal suppliers of nations now at war, as well as many of the neutral countries of Europe, with the exception of the U.S.S.R. and Romania, which have crude oil in excess of their requirements. It is apparent that it is to these South American countries and the United States that these European countries must look for any large increase in their requirements as a result of war activities.”

World map showing crude-oil production by countries based on daily average output in barrels during the first six months of 1938. Map includes representative tanker routes. Source: The Oil and Gas journal, Vol. 38, Iss. 17, ‘Few Nations Supply War Oil Needs’ article

A week later, an article by H. Stanley Norman titled ‘The Nazi War Machine in the Face of Oil Shortages’ appeared in the same magazine, predicting that the German shortage of liquid fuels would begin by the middle of 1940. Alongside that, the presence of large reserves of oil and oil products in the German Reich, a significant production of synthetic gasoline and diesel fuel from coal, as well as ethyl alcohol from potatoes, were mentioned.

Actually, this is what made Blitzkrieg essential for the Wehrmacht: Germany simply could not afford a long-lasting war. In September 1939, the resources of the western half of Poland went under German control. In April 1940, the resources of Norway (with the path to the Swedish Kiruna ore) went the same way. In June, 1940, the French State signed the ‘reconciliation’, so the Lorraine iron ore, along with many resources from the French colonies, became accessible to the Reich.

By the beginning of 1941, oil and petroleum products came to Germany, in certain volumes, from Stalin’s Soviet Union, as well as from Romania and Hungary, which had completely fallen under German influence. Of course, it was no longer possible to legally bring anything from across the oceans, but some bits were still smuggled – even from Britain (via Spain).

In addition, allied Italy turned out to be resource dependent on Berlin. The Germans lacked oil and some metals, while the Italians lacked almost everything. Even though military production (both aviation and military shipbuilding) was well developed, the basic industries – metallurgy, chemistry, machine tool construction – lagged far behind or depended on the import of raw materials. With the entry of Italy into World War II, Hitler had to practically take Italy on the balance sheet and to supply petroleum products, as well as iron ore with coal for metallurgical plants.

Expenses on Italy were comparable to the Reich’s own consumption. In 1942, the last year before Italy surrendered, the consumption of motor fuel in Germany (without the Wehrmacht) was equal to 357,000 tons, and exports to Italy – 285,000 tons. Fuel supplies for the Italian Navy were 280,000 tons, while the German Kriegsmarine got only 140,000 tons.

According to the experience of the previous world war, everyone knew in advance that the need for oil products in wartime increases by about 3 times compared to peacetime. Already in 1937, the famous German economist F. Freudenberg calculated the German need for oil imports in the event of war at 20 million tons, and it was one of the most optimistic forecasts. This level was not achieved, even though the Reich’s own oil production (including annexed Austria, Czechoslovakia, and French Alsace) increased in the period from 1940 to 1944 (according to the 1st quarter in terms of the year) from about 1.5 million tons to 2 million tons. The country could not fully provide itself with essential resources.

By the end of the war, Germany’s fuel supply had seriously deteriorated. This was due both to the destruction of synthetic fuel production plants and to the crisis of coal mining enterprises that supplied raw materials to these plants. The fuel supply to the army and economy of the German Reich in the first quarter of 1945 was kept at the level of 23,163 barrels per day, i.e. 10 times less than in the first quarter of 1944.

Hence, various “ersatz methods” had become widespread, amongst which were:

Mercedes-Benz 170V (W136) mit Holzvergaser (with wood carburetor). About 500 thousand cars were equipped with gas generators by 1944. In other words, almost all non-military German cars were refueled not with gasoline, but with firewood and brown coal. Moreover, gas generators were also installed on training tanks. Source: drewnozamiastbenzyny.pl

Another ‘living fossil’ resurrected by the fuel crisis was the steam engine. It seemed to be a great substitute for gasoline engines, so in December 1944, works began on creating a steam-powered tractor named SK 13. The vehicle used Czechoslovak groundworks: a Škoda Sentinel steam truck engine and a Jagdpanzer 38(t) tank destroyer, based on the chassis of the Pz.Kpfw.38(t) light tank, developed by Alexei Surin. The mass production of the vehicle was launched in spring of 1944 at BMM (Böhmisch-Mährische Maschinenfabrik AG, the name of the Českomoravská Kolben-Danek (ČKD) company during the German occupation of Czechoslovakia). The excellent characteristics and the cheapness of the chassis made it possible to build various new vehicles on its basis, including tank destroyers, artillery and, of course, tractors.

Design

Hull

Early version of the SK 13. Note the missing roof and water/fuel containers. Source: armedconflicts.com

For the construction of the SK 13, the base of 38(t) was significantly altered. One of the most important changes was the increase in length. The hull was lengthened and two roadwheels were added on each side, resulting in six roadwheels on each side. They were interlocked on three bogies with spring suspension. The location of the sprockets at the rear of the vehicle was not changed. The idlers, in turn, remained in the front. Despite the relatively large diameter of the roadwheels, a set of two return rollers was retained as part of the chassis.

Later version of the SK 13, in its final configuration. Note the roof and large fuel and water containers in the rear part of the hull. Source: armedconflicts.com

To solve the main layout problems, it was proposed to seriously redesign the hull. The existing hull was extended by about a quarter, which allowed it to maintain an acceptable ground pressure and internal volume. The inclined frontal plate of a small height was kept, and boxes were added above the tracks. The design of the rear part was also revised several times due to multiple changes to the technical task.

There is no information about the armor layout of the tractor. It can be assumed that the use of an existing chassis led to the preservation of the armor of the base Jagdpanzer 38(t). In favor of this version, in particular, are the weight indicators of the prototype. The steam tractor could have had armor from 8 to 60 mm thick, capable of protecting the crew and components from small arms and some artillery systems. This made it possible to use the vehicle in some combat formations with other armored vehicles without fear for its safety.

Engine

Škoda Sentinel boiler scheme. Source: topwar.ru

The chassis was not the only part that was proposed to be borrowed from existing vehicles. Steam boilers with reciprocating machines for use as a power plant were supposed to be taken from the Škoda Sentinel steam truck.

These trucks were equipped with 70 hp steam engines and could carry up to 5 tonnes of cargo. The standing, tubular boiler, with a heating surface of 5.06 square meters, was located in the front part of the truck. It could burn coke, coal, charcoal, wood, and briquettes in it, but coke was the most suitable. The boiler was also equipped with a pressure gauge, a water level mark with a safety valve, and the steam output was controlled by a slide valve. Preparation for driving took about 30 minutes.

Škoda Sentinel’s boiler. Source: sentinel.cz

With a bore diameter of 170 mm and a stroke of 230 mm, a steam pressure of 19 atp and at 250 rpm, it delivered 70 hp. The crank mechanism was then equipped with a patented differential acting on the chain pinions. The transmission of power to the fixed rear axle was by massive Gallo chains, which drove the double wheels, freely rotating on the axis. The average speed of the truck was about 25 km/h. Lubrication of the steam engine and chains was by an oilcan, separate for each side.

The furnace of the boiler of the later version: water pipes are located in the spiral recesses. Source: topwar.ru

The Škoda SK 13’s steam engine was developed based on the units of the Škoda Sentinel truck, some of which were used in the basic configuration, without any changes. The basis of such an engine was a cylindrical steam boiler. A cylindrical furnace for burning solid fuel was placed inside the outer casing, through which a large number of tubes passed. Water was poured between the furnace and the outer body of the boiler. During the combustion of fuel, water entered the tubes of the furnace and came into contact with its walls. At the same time, the water boiled, after which steam passed through the superheater and entered the cylinder of the piston machine.

To supply air to the fuel, the lower lid of the furnace was made in the form of a movable plate with water, which performed the functions of an ash pan (a container for solid fuel combustion products). Air access was carried out through a gap between the furnace body and the lower lid, the dimensions of which could be changed using a special lever mechanism.

The SK 13 in its final configuration on trials. Source: armedconflicts.com

The SK 13 tractor received two steam boilers, both of which were mounted in the center of the hull, one next to another. The piston engines of the two engines were mechanically connected to the rear part of the hull, into the existing transmission. Containers for water and fuel were placed in the free space of the hull. In the later version of the SK 13, fuel and water were placed in two large rectangular containers installed in the rear part of the hull. It is noteworthy that, due to the larger hull and hence larger volumes for fuel, it was possible to achieve a significant increase in the range compared to the Sentinel truck. On the other hand, the increase in the amount of fuel and water led to an additional mass of the tractor.

Boiler Donor: Škoda Sentinel

In the beginning of the 1920s, a new automobile department in the Škoda factories in Pilsen was established. In 1923, the management of the company purchased licenses for the production of the French Hispano-Suiza passenger car and steam trucks from The Sentinel Waggon Works Ltd., Shrewsbury, England (United Kingdom). Part of the British license was also the technology of the steam-powered cars. This was not a new thing in Czechoslovakia, as they were preceded by several vehicles ordered by the Ministry of National Defense in Prague. For example, Kopřivnická vozovka (later known as Tatra) was engaged in the production of steam cars and buses many years earlier. The machine shop in Adamov also tried to produce a model of steam truck under the license of a British company, Richard Garrett & Sons Ltd., Leiston, Suffolk.

Plans of the Škoda Sentinel truck, model 1925. Source: sentinel.cz

At that time, the steam engine had a number of indisputable advantages over the gasoline one, such as its flexibility and that it accelerated quickly. Steam-powered vehicles comfortably climbed steep hills and were easily controlled by a single shut-off valve. It was also possible to stop the trucks immediately by simply closing the valve, as the engine worked as a compressor and braked. Another advantage was lower oil consumption, as, at the time, it was topped up daily in cars. Its low rotations per minute (~300) played another important economic role, by reducing the wear-out of particular parts of the vehicle. However, the far slower start of the steam car proved to be disadvantageous, as the boiler had to be heated first.

The Škoda Sentinel truck. Source: sentinel.cz

The Škoda-Sentinel was, according to the standards of the time, a truck of classic design. It was capable of operating in the most difficult conditions. More than that, thanks to the possibility of flexible operation of the steam engine, the truck also proved itself well in steep terrain. This was demonstrated during Czechoslovak Army tests in 1923 of several imported vehicles, in which the Ministry of Railways also participated. The tests then took place on the Prague – Brandýs nad Labem-Stará Boleslav – Mochov – Prague line. The results were satisfactory and Škoda’s factories, which were looking for production possibilities for their new vehicle department in Pilsen, saw new profitable opportunities and therefore bought a license from the United Kingdom. The vehicle was introduced in many versions: as a flatbed, one-sided or three-sided dump truck, sprinkler or garbage truck, and also as a city omnibus or rail vehicle. Some continued to serve long after the Second World War and were gradually taken out of service only due to the lack of spare parts.

Crew

The crew of the experimental armored vehicle consisted of three: driver, commander, and engineer, who operated the steam boilers and reciprocating machines. In addition to controlling the parameters, the engineer had to throw coal into the furnaces, as well as regulate the water supply to the boilers. Direct control of the car, such as the choice of speed and direction of movement, was carried out by the driver using a set of levers and pedals.

Trials

In 1944, Škoda completed the development of the SK 13 project and built the first prototype. During the assembly and preliminary tests, it underwent some changes, primarily related to the exterior design. In particular, a light roof and containers for coal and water were added, as well as steps being installed on the upper frontal part of the hull to make the process of getting inside easier.

The SK 13 in its final configuration on trials. Source: armedconflicts.com

During the tests, it was found that the steam engine was able to accelerate the SK 13 tractor only up to 12-15 km/h. The transported fuel and water supply was only enough for a range of 150 km. Apparently, these figures only concerned driving on roads, whereas, when driving over rough terrain, performance dropped significantly. It is not difficult to notice that in terms of its mobility performance, the steam tractor was significantly inferior to the existing gasoline technology and could not compete with it in any way. Even efficiency in terms of fuel cost was not enough for the SK 13.

Tests of the SK 13 prototype led to two main conclusions about the future of steam technology. The first concerned the fundamental possibility of creating tractors or other military vehicles, including armored ones, with steam engines. The second conclusion imposed new requirements on steam engines for such equipment. The tests clearly showed that two boilers from the outdated Škoda Sentinel truck, with a capacity of 70 hp each, could not provide the required mobility for a relatively heavy and large tracked vehicle.

Due to a number of factors, the steam tracked vehicles of Czechoslovak design were not adopted by the German Army. For this reason, until the end of the war, the problem of fuel shortage was solved by other methods, including the widespread use of gas generators using firewood or coal chips. In addition, the operation of a certain number of steam engines continued. However, this did not last, as in spring 1945, Germany capitulated, eliminating the need of creating military vehicles with alternative power plants.

Škoda SK 23 and BMM SK 33 Projects

Soon after the construction of the updated SK 13, a second participant joined the work. Škoda continued to develop the existing project of a steam tractor for troops, resulting in a vehicle under the designation SK 23. As in the case of the SK 13, a ready-made chassis was proposed in a modified form. At the same time, it was planned to use steam engines of a new type supplied by Krupp. Due to the use of modern steam engines, it was supposed to provide a significant increase in performance compared to the previous SK 13. There were supposed to be certain advantages in speed and power reserve. The efficiency of operating the new steam engine, in turn, had to be ensured through the use of cheap fuel. Due to various production and administrative reasons, Škoda was unable to build a SK 23 prototype for testing. This project never left the drawing board. Various factors contributed to this, mainly problems at the front and the need to focus on the construction of other equipment.

Model of the SK 23 tractor. Source: valka.cz

Based on the test results of the SK 13 machine, the company BMM proposed its own concept, which resulted in the appearance of the SK 33 ‘Dampfschlepper’ project, created in two versions (differing only by the steam engine used). In order to increase the mobility of the tractor, it was proposed to reduce the weight of the structure and increase the power of the steam engine. Due to the removal and lightening of certain components, the curb weight of the tractor was reduced to 18 tonnes. The power of each of the two engines was to be increased to 80 hp. Thus, the specific power could grow to 8.7-9 hp per tonne with some positive implications on mobility.

The BMM SK 33 project suffered the same fate as the rival company’s SK 23. By the end of 1944, the situation on the Eastern Front had seriously deteriorated. In addition, Allied troops were developing an offensive in Western Europe. In such conditions, the industry of Germany and the occupied states no longer had the opportunity to engage in prospective projects, as they could threaten the fulfillment of other more pressing orders. As a result, the Czechoslovak industry focused on the production of other vehicles and a lot of new developments were canceled, including the BMM SK 33 steam tractor.

SK 33 ‘Dampfschlepper I’ tractor. Source: valka.cz
SK 33 ‘Dampfschlepper II’ tractor. Source: valka.cz

Side Note – Possible Inspiration Source for Wargaming

In 2022, Wargaming introduced a branch of Czechoslovak heavy tanks in their World of Tanks (WoT) game. All of the vehicles presented might be, at best, undiscovered and poorly-developed concepts. It is more likely that in reality they are just fakes without any documentary evidence, created by the developers of the game inspired by some real prototypes (like they earlier did with the Polish medium tank line or Czechoslovak premium medium tank Škoda T 27, which is just an elongated and heavily armed version of real Škoda T 17 light tank).

Czechoslovak ‘tech tree’ as presented in WoT. Source: Wargaming Wiki

The tier VIII of the branch is named TNH-105/1000. This designation resembles real ones. Some Czechoslovak vehicle blueprints of that time have the name of the developing company, gun caliber, and muzzle velocity (e.g. TNH-57/900 light tank) on them.

TNH-105/1000 as presented in WoT. Source: World of Tanks Official Youtube Channel

Description from World of Tanks:

In the latter half of the 1940s, ČKD and Škoda engineers developed a joint project for a heavy tank for the Czechoslovakian Army and for possible export purposes. The TNH 105/1000 design was based on available concepts of German and Soviet tank-building and original ideas from Czechoslovakian engineers. In November 1949, the Communist Party of Czechoslovakia decided to discontinue the development of its own vehicles and switched to producing a licensed copy of the Soviet T-34-85 tank. All activity on the TNH 105/1000 was canceled and no prototypes were ever built.

The hull of the vehicle resembles th SK 13 steam tractor in many important aspects:

  • Both hulls have almost identical proportions;
  • Both hulls have a Surin-type suspension with three bogies;
  • The drivers of both vehicles are located in the right part of hull’s front;
  • The chassis of both vehicles have a sprocket in rear and an idler in front;

The main difference, apart from the external appearance and rear shape, is propulsion. Unlike the SK 13, Wargaming’s TNH 105/1000 is not powered by a steam engine. In-game, it has two variable engines: Škoda AHK (in-game designation ‘Škoda V16 AHK-2’) and ČKD AXK (in-game designation ‘ČKD AXK proto’) 1000 hp engines, developed for the Tank všeobecného použití (TVP) project at the beginning of 1950s.

WoT’s ‘historical description’ places the TNH-105/1000 ‘development period’ to the late 1940s (probably 1947/48), when preliminary TVP designs by Škoda and ČKD were not even finished. The possibility of their engines being used for a separate project is quite low. It is the same story in regards to the chassis. A 50-tonne heavy tank with 100 mm frontal armor is unlikely to be based on an unmodified and not reinforced (as presented in-game) SK 13 hull (and, probably, any hull with Surin suspension in general). At 2.5 times heavier than the tractor’s hull, the question of technical reliability emerges.

Conclusion

The Czechoslovak program of developing a steam tractor in the interests of Germany ended in late 1944 or early 1945. By this time, two machine-building enterprises had managed to create three projects (SK 13, SK 23, and SK 33), of which only one had reached the prototype stage. Studying the SK 13 machine provided necessary experience and knowledge for further development of the concept of steam powered tractors. Nevertheless, the drastically deteriorating situation in the war for Germany contributed to the termination of the project.

Left side view 3D model of Skoda SK 13 by Phantom_25_Sniper.
Right side view 3D model of Skoda SK 13 by Phantom_25_Sniper.
Front view 3D model of Skoda SK 13 by Phantom_25_Sniper.
Rear view 3D model of Skoda SK 13 by Phantom_25_Sniper.
Top view 3D model of Skoda SK 13 by Phantom_25_Sniper.
Škoda SK 13 specifications table
Total weight, battle ready 20 tonnes
Crew 3 (commander, driver, motorman)
Propulsion 2x Škoda Sentinel steam engines (70 hp at 250 rpm)
Suspension Surin-type, leaf springs
Performance 12-15 km/h (7-9 mph)
Hull Armor 8 – 60 mm

Sources

https://www.valka.cz/topic/view/79671
https://www.valka.cz/topic/view/253870
https://www.valka.cz/topic/view/253871
Ivo Pejčoch.’Československé Pásové Dělostřelecké Tahače, 1918-1950’;
‘The Oil and Gas Journal’, Vol. 38, Iss. 17 (September 7th, 1939);
‘The Oil and Gas Journal’, Vol. 38, Iss. 18 (September 14th, 1939);
https://shusharmor.livejournal.com/656677.html
https://topwar.ru/92719-proekt-parovogo-gusenichnogo-tyagacha-dampfschlepper-chehoslovakiya.html;
http://www.sentinel.cz/;
http://www.drewnozamiastbenzyny.pl/gaz-drzewny-definicja/
https://tanks-encyclopedia.com/ww2/nazi_germany/gas-powered-fahrschulwanne-tanks.php;
http://samlib.ru/p/polo_m/6letvehrmacht.shtml;
https://history.ric.mil.ru/Stati/item/408834/;
https://wiki.wargaming.net/en/Tank:Czechoslovakia;

Categories
Cold War Bulgarian Armor

Light Amphibious Tank Project – Lek Plavasht Tank ‘Oktopod’

LPT ‘Oktopod’. Illustration by Pavel ‘Carpaticus’ Alexe
LPT ‘Oktopod’. Illustration by Pavel ‘Carpaticus’ Alexe

People’s Republic of Bulgaria (1988-1990)
Light Amphibious Tank – Small Scale Mock-up Only

While thinking of tank-building countries, Bulgaria is unlikely to be amongst the first dozen to come into one’s head. Just like other Warsaw Treaty Organization (WTO) countries (composed of the Soviet Union, Bulgaria, Czechoslovakia, East Germany, Hungary, Poland, and Romania), which usually used imported Soviet vehicles and, at best, proposed modifications for those, Bulgaria is not rich in unique projects. However, one such project, born at the dawn of the existence of Socialist Bulgaria, is known. This was a project for a light amphibious tank based on the Bulgarian BMP-23 IFV.

History of the Project

Soviet ‘Great Grandpa’ and ‘Grandpa’

Pansarbandvagn 401, the Swedish MT-LB APC. Source: researchgate.net

The history of the Oktopod goes back to the beginning of the 1960s, when the Soviet ‘MT-LB’ APC, or, during development, ‘Object 6’, was adopted by the Red Army. One of the most recognisable and mass-produced lightly armored vehicles of the Cold War period, along with the American M113, it was also used as a base for dozens of not only Soviet, but also Belorussian, Kazakhstani, Polish, Russian, Ukrainian, and even Swedish concepts, prototypes and serial modifications. Bulgaria was another country that has been using this vehicle for more than half of a century.

2S1 ‘Gvozdika’. Source: vitalykuzmin.net

A Soviet project of self-propelled howitzer named 2S1 was being developed after 1967. The main point was to create a modern 122 mm SPG which would be on par with its analogues from NATO. In 1970, it was adopted by the Red Army and named 2S1 ‘Gvozdika’ (Russian for Carnation). This was the first Soviet flower-named artillery piece, followed later by 2S2 ‘Fialka’ (Russian for Violet), 2S3 ‘Akatsiya’ (Russian for Acacia), 2S4 ‘Tulpan’ (Russian for Tulip), 2S5 ‘Giatsint’ (Russian for Hyacinth), 2S7 ‘Pion’ (Russian for Peony), 2S8 ‘Astra’ (Russian for Aster), and 2B9 ‘Vasilek’ (Russian for Cornflower). Gvozdika became another iconic vehicle of the Soviet army, with more than 10,000 examples produced. It was exported to literally half of the world, and was used as a base for many projects. Amongst those projects was the Bulgarian BMP-23 IFV.

Son of an Immigrant

Bulgarian BMP-23 IFV. Source: topwar.ru

The BMP-23 was developed in the 1980s. It was a vehicle tailored to the needs of the Bulgarian Army, then under the Soviet sphere of influence as part of the Warsaw Pact. The overall goal was to have an improved IFV compared to the BMP-1 already in service. The vehicles were first shown on a military parade in 1984. Given the goals of the military, it had to be given sturdier armor than that of the BMP-1. The better engine and reinforced suspension of the 2S1 helped in this way. The hull was also comprehensively modified to integrate a roomy troop compartment at the rear for six fully-equipped infantrymen seated back-to-back. The rear was modified to accept two doors for dismounting, in addition to the two large roof hatches. Three pistol ports were also placed in the sides of the hull, all of which were fitted with bulletproof vision devices.

Development of the ‘Oktopod’

At the end of the 1980s, Bulgarian engineers were working on a concept of light amphibious tank based on the BMB-23 Infantry Fighting Vehicle. The vehicle was meant to be used in the Balkan mountains. The main potential opponents were Greece and Turkey, both members of NATO. At the time, the Bulgarians thought these countries were going to buy Leopard 2 main battle tanks. The assessments of the new tank’s firepower were based on the T-72 tanks Bulgaria had and also on the Yugoslavian M-84. The new light tank was suggested not only for the Bulgarian army, but also for exporting. By the end of 1988, the preliminary project was ready and was being reviewed at the highest state level.

Bulgarian BMP-23 IFV. Source: offroad-bulgaria.com

Amongst the specialist team there were both Bulgarian and Soviet experts, which judged the project very highly. Despite this, the Soviets offered to supply PT-76 light tanks at a very low price, as well as assistance in their modernization. The offer was rejected, as these Soviet tanks did not meet Bulgarian requirements. The armor was too poor, and the 76 mm D-56 gun was too outdated and could not be used to fight against modern vehicles. The Soviets had to give in, and the development of the tank was continued. Work on producing a mock-up of the vehicle began, and soon it was planned to produce its first prototypes. Trials were planned.

Bulgarian Light Amphibious Tank mock-up. Source: topwar.ru

Meanwhile, after 10th November 1989, a process of fundamental political reformation had begun in Bulgaria. The end result, beside the dissolution of the Eastern Bloc and the fall of Bulgarian communism, was that the amount of funding for the project declined rapidly. At this time, development was still in full swing, with negotiations being held with Sweden and Israel regarding the supply of modern turbo-diesel engines and observation devices for the tank.
Everything changed in the beginning of the 1990s, when funding was stopped, and the development team was dismissed. The project was abandoned, and most of the documents about the light tank vanished. Some sources claim they were deliberately destroyed. However, there is a chance they are still yet to be discovered. The only thing that has somehow survived through all this was the mock-up of the vehicle.

Name of the Project

The exact name of the vehicle is unknown. Hence, descriptive terms are usually used to distinguish it, such as ‘Light Amphibious Tank’ in English or ‘Лек Плаващ Танк’ in Bulgarian.

The Russian Sprut SD light self-propelled tank destroyer during a Victory Parade in Moscow (May 9th, 2008). Source: vitalykuzmin.net

Some sources also relate the name ‘Oktopod’ (Bulgarian for ‘octopus’) to this vehicle. However, this is highly likely a contemporary term based on project’s similarity with Russian 2S25 ‘Sprut SD’ light self-propelled tank destroyer, although some sources claim this was the original name of the vehicle.
For convenience and better recognition, from now on, the vehicle will be referred to as ‘LPT Oktopod’ or simply ‘Oktopod’ in this article.

Description of the Vehicle

Hull and Turret

The hull of the ‘Oktopod’ was based on BMP-23 (which, in its turn, was based on the Soviet 2S1 Gvozdika self-propelled howitzer). It was shortened, with one row of road wheels removed and two rows of return rollers added. Clearance was increased.
Like the BMP-23, the vehicle was also supposed to be amphibious; hence, some aspects of its design were improved for better buoyancy – for example, the height of sides was increased. Swimming was supposed to be carried out by moving the tracks.
The turret of the vehicle was made in the form of a truncated cone, with two crew hatches on the roof. The estimated ring diameter was ~2.3 m. Installation of smoke grenade launchers was also planned.

Armament

100 mm MT-12 ‘Rapira’ gun. Source: vitalykuzmin.net

The new light tank was supposed to be armed with the Soviet MT-12 ‘Rapira’ (Russian for Rapier) 100 mm anti-tank gun as its main armament, with a coaxial 7.62 mm PKT machine gun. According to some sources, a 14.5 mm KPVT was also planned (probably as an anti-infantry machine gun installed near the commander’s hatch).

100 mm
MT-12
‘Rapira’ 		APDSFS HEATFS
3BM1 3BM2 3BM24 ‘Kalach’ 3BK3 3BK8
3.38 kg 3.63 kg 10.072 kg 9.5 kg
1,575 m/s 1,548 m/s 975 m/s 1,075 m/s
– – – 0.84 kg charge
(1.29 kg TNT equiv.) 		1 kg charge
(1.54 kg TNT equiv.)
300 mm pen 235 mm pen 352 mm pen 350 mm pen 400 mm pen
8-10 rpm Parameters of penetration are given for 0 m and 0°.

100 mm MT-12 ‘Rapira’ gun parameters. Source: ZA DB, Pablo Escobar’s gun table

The MT-12 (2A29) Rapira was a smoothbore anti-tank gun developed in the Soviet Union, based on the T-12 (2A19) cannon. It was adopted by the Soviet army and entered mass production in 1970. The gun was designed primarily for direct fire, but it could also be used as an ordinary field gun for firing high-explosive ammunition from closed positions. The MT-12 took part in many conflicts, such as the Soviet–Afghan War (1979–1989), Transnistrian conflict (1989-1992), and Chechen Campaigns (1994-1996). Recently, the gun has been used in the Syrian Civil War and the 2022 conflict in Ukraine.

7.62 mm
PKT 		AP
LPS
3.38 kg
855 m/s
12 mm pen
750 rpm
(250 shots clip)

7.62 mm PKT machine gun parameters. Source: ZA DB, Pablo Escobar’s gun table

The 7.62 mm PKT machine gun was a tank version of Kalashnikov’s machine gun (Russian: ‘Пулемёт Калашникова‘). It was equipped with an electric trigger. The barrel was made longer and with thicker sides. This allowed more sustained fire and also required replacing the barrel less often. The PKT was installed on many Soviet and Russian tanks, APCs and IFVs, like the BMP-1, MT-LB, BTR-60, BRDM-2, and others. It was exported, produced and used by several dozens of countries, including China, Cuba, Czechoslovakia, DPRK, Finland, Poland, Romania, Serbia, Ukraine, Yugoslavia, and many others.

14.5 mm
KPVT 		AP
B31 BS41
0.06344 kg 0.06441 kg
976 m/s
37 mm pen 45 mm pen
600 rpm

14.5 mm KPVT machine gun specifications. Source: ZA DB, Pablo Escobar’s gun table

The 14.5 mm KPVT (Russian: Крупнокалиберный Пулемёт Владимирова, English: Vladimirov’s heavy machine gun) was developed in 1944 and adopted in 1949. It combined the rate of fire of a heavy machine gun with the armor-piercing capabilities of anti-tank rifles. It was designed to combat lightly armored targets and manpower of the enemy located behind light cover, as well as to be an anti-aircraft machine gun. It was one of the most powerful machine guns ever used by the Soviet and later Russian armed forces. The KPVT used a 50-round belt.

Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

It was planned to equip the 100 mm gun with an autoloader. The estimated elevation arc of the main armament was -6/+24o. It is worth mentioning that there is no data about any plans on equipping the vehicle with night-vision devices or thermal imagers. If there were no such plans, it would have been a serious drawback of the vehicle at that time.

Armor

Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

The mass of the new vehicle was had to be less than 18 tonnes. Still, the vehicle had to be quite well-protected in comparison with its analogues. An innovative aspect of Oktopod’s armor was its multilayer structure.
The plates of rolled homogeneous steel armor were combined with plates of zeolite and stealth-armor.

Zeolite mineral. Source: chemistryworld.com

Zeolite is a mineral used as an anticumulative filler. It is refractory and difficult to compress, which makes it a good protection feature for armored vehicles. According to some sources, the Bulgarians tested this technology on turrets of T-54/55 medium tanks. The external armor layer was to have radio-absorbing functions, provided by special materials and the absence of a gap between the sheets.

Swedish Scania DS14 V8 turbo diesel engine (550 hp), a probable candidate for the Oktopod.
Source: gruzovikpress.ru

For sufficient mobility, it was planned to use a 500-700 horsepower diesel engine. At first, the designers wanted to use the engine of the T-55 or T-72. However, an opportunity of buying cheap and compact-sized Swedish turbo-diesel engines appeared. The engineers decided to seize it, so negotiations began. It was planned to organize the production of their licensed copies in the ‘Vasil Kolarov’ plant in Varna.
Although there is no data about the particular engine, it was highly likely to be Scania DS14 V8 turbo diesel engine, which could produce about 500-550 hp.

Scania DS14 V8 turbo diesel engine. In the background, a Scania LB140 truck can be seen – one of the first to be equipped with DS14 engine.
Source: gruzovikpress.ru

The DS14 was released in 1969 and was presented by Scania Trucks company as one of the most powerful truck engines of its time. It could raise power up to 350 hp – while average truck engine power of that time was almost 1.5 times less. Its construction (8 cylinders set in V-shape and divided into two equal groups, with piston groups forming a 90º angle) was beneficial in another aspect: its compact size, which made it possible to put the engine under the truck’s cabin. Since its release, DS14 was constantly being improved, and by the end of the 1980s, it already could outpet more than 500 hp in the version for the Scania R143 Streamline truck series.

Crew

Inner layout scheme.
Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

The crew of the vehicle would have consisted of three men: commander, driver and gunner. The driver’s place was in the front-right part of the hull, next to the engine. The other two tankmen were to sit in the turret, to the left and to the right of the gun.

Israeli Observation Devices

Lights of the Merkava Mk.I MBT. The dark colored lens belongs to the infrared light.
Source: primeportal.net

It was planned to equip the vehicle with Israeli observation devices (periscopes), and negotiations for this took place. The exact model Bulgarians wanted to buy is not specified and currently unknown.

AN/VVS-2 night vision device. Source: army-guide.com

The Israeli main battle tank, the Merkava, developed at the end of 1970s, was equipped with an ‘Oranit’ ballistic computer. The driver’s periscope was equipped with a ‘Vilon’ night-vision device, the operation of which required the presence of infrared (IR) lights in the front of the vehicle. The commander and gunner could not see outside at night unless using a Star Light Scope (SLS) binocular or external illumination by spotlights. Later, the ‘Vilonʼ was replaced with the ‘Radian’, an Israeli copy of the American AN/VSS-2 periscope, working on SLS technology. It did not require IR lights to function any more.

The ‘Radian’, an Israeli copy of the American AN/VVS-2 night vision device.
Source: yadlashiryon.com

The AN/VSS-2, or more precisely, its Israeli ‘Radian’ variant, is the most probable candidate to have been bought for Oktopod.

Possible Modernization

The concept of a light armored vehicle based on the MT-LB/2S1/BMP-23 has reappeared during a recent Bulgarian exhibition organized by Terem-Khan-Krum LLC (bulg. ‘Терем-Хан Крум ЕО­ОД’) – a Bulgarian company, specializing in the production, overhaul and upgrade of armored military vehicles. The exhibition was a part of the European Night of Museums event by UNESCO.
During the exhibition, a model was shown, which is similar to the known LPT ‘Oktopod’ mock-up in many aspects. First, the suspension and chassis are based on BMP-23’s. Second, the layout, as the model has a rear-mounted turret and a front-mounted engine compartment. Finally, the gun has aspect and proportions similar to those of MT-12 ‘Rapira’ ones.
On the other hand, there are some differences. The turret of the mock-up has significantly sloped armor plates, which probably indicates that it is cast (unlike the turret of the original mock-up, which is definitely welded). Sides of the rear part of the hull are made of two armor plates (one sloped plus one vertical). In addition, the general appearance of the described mock-up has significantly more details – as compared to the original one.
Nevertheless, it is important to remember that mock-ups often do not represent all details, as their main aim is usually to show general layout and the most important elements of the vehicles. Plus, the represented mock-up may be not the better detailed or modernized version of the LPT ‘Oktopod’, but a completely different unrelated project.

Model of an armored vehicle, displayed at the temporary exhibition organized by Terem-Khan-Krum LLC – Bulgarian military plant – in their showroom in Targovishte.
Source: ‘Отзвук от една изложба’ article (via znametrg.com, 12.06.2018)

Conclusion

External appearance reconstruction of the vehicle.
Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

The project of Bulgarian Light Amphibious Tank was one of the most interesting vehicles designed in one of the Warsaw Treaty countries at the far edge of its existence. If built, it could have become the first serious AFV project developed in Bulgaria. Moreover, a mixture of different technologies (from the USSR, Israel, and Sweden) meant to be used to construct it would have significantly distinguished it from its analogues.
It is possible that in future, with further exploration of East European (mainly former WP) countries’ archives and private collections, which are tremendously lacking research now, more precious information (pictures, documents, blueprints, mock-ups, etc.) may be found. Thus, data about known vehicles (including LPT ‘Oktopod’) will be refined and clarified, and even new proposals may be unveiled.

Soviet 2S1 Gvozdika ‘410’ in the late 1970s
Bulgarian BMP-23 in a regular green livery, 1980s
Russian 2S25 Sprut-SD tank destroyer
LPT ‘Oktopod’. Illustration by Pavel ‘Carpaticus’ Alexe
Vehicle, represented at Terem-Khan Krum LLC exhibition in Targovishte, Bulgaria. Illustration by Pavel ‘Carpaticus’ Alexe
LPT ‘Oktopod’(*) specifications table
Dimensions (L-W-H) 7.3 (8.8 with the gun) x 3.43 x 2.8 m
Ground clearance 0.43 m
Weight 18 tonnes
Engine Scania DS-14 (~550 hp)
Suspension torsion bar
Power-to-weight ratio (in hp/ton) 30.5 hp/ton
Maximum speed (ground/water) 60/4.5 km/h
Crew 3 (Commander, Driver, Gunner)
Driver vision’s devices SLS-Vision ‘Radian’ or AN/VVS-2
Main Armament 100 mm MT-12 ‘Rapira’ with autoloader
Secondary Armament 7.62 mm PKT and 14.5 mm KPVT
Production numbers 0 built, mock-up only
(*) – vehicle’s original name is unknown; LPT ‘Oktopod’ is a speculative one.

Sources

https://www.vitalykuzmin.net/;
https://www.armedconflicts.com/The-nameless-project-of-a-Bulgarian-mountain-tank-t239318;
https://offroad-bulgaria.com/forum/основни-форуми/оръжие-бойни-действия-тактика-и-стратегия/оръдия-тежко-въоръжение/112321-бмп-23-1300-прашясаха-ли-вече/page2;
https://en.topwar.ru/143744-bolgarskiy-sprut-legkiy-plavayuschiy-tank-kotoryy-ubila-demokratiya.html;
http://www.gruzovikpress.ru/article/24532-yubiley-dvigatelya-scania-v8-ds-14-neveroyatno-realniy-motor/;
https://epicenter.bg/article/Shtyahme-da-proizvezhdame-balgarski-tankove/76768/2/0;
https://it.dir.bg/tehnologii/kak-balgariya-be-na-krachka-ot-sazdavaneto-na-sobstven-tank;
https://www.primeportal.net/tanks/david_lueck/merkava_mk1/index.php;
http://znametrg.com/2018/06/12/отзвук-от-една-изложба/;

Categories
Has Own Video WW2 Soviet Medium Tank Prototypes

T-V-85

T-V-85. Illustration by Godzilla
T-V-85. Illustration by Godzilla

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

One of the most recognizable tanks of the Third Reich was the Panzerkampfwagen V “Panther”. Created as a replacement for the medium Panzer III and Panzer IV tanks and as a “response” to the Soviet KV and T-34, the Panther was a formidable opponent on the battlefield. A powerful and rapid-firing gun, good aiming devices for the crew, and strong frontal armor made the vehicle excellent in both defensive and offensive operations. Panthers captured by the Red Army were highly valued. During the war, Soviet troops captured a significant number of serviceable or damaged, but recoverable Pz.Kpfw.Vs, and even combat units of the Red Army were created on their basis. The option of rearming them with “domestic” guns was also considered, however, the T-V-85 appeared too late, and the end of the war left it no chance of appearing in reality.

The Medium Cat of the Wehrmacht

The first considerations for a new medium tank which could replace the Panzer III and Panzer IV appeared in 1938, with the VK20 project series, a fully tracked vehicle weighing ~20 tonnes. Design proposals by Daimler Benz, Krupp, and MAN ensued, but soon, these designs were abandoned and Krupp dropped out of the competition entirely. The requirements increased to a vehicle weighing 30 tonnes as a reaction to the encounters with the Soviet T-34 and KV-1 tanks.
At the insistence of General Heinz Guderian, a special tank commission was created to assess the T-34. Among the features of the Soviet tank considered most significant were the sloping armor, which gave much improved shot deflection and also increased the effective armor thickness against penetration that could be achieved with thinner plates, the wide tracks, which improved mobility over soft ground; and the 76 mm gun, which had good armor penetration and also fired an effective high-explosive round. All this outclassed the existing models of the German Panzer III and IV. Daimler-Benz (DB), which had designed the successful Panzer III and StuG III, and Maschinenfabrik Augsburg-Nürnberg AG (MAN) were given the task of designing a new 30- to 35-tonne tank, designated VK 30, by April 1942.
MAN’s design won the competition, despite DB’s one having several advantages and having the admiration of the Reich’s Ministers for Armaments and Munitions, Fritz Todd and his successor, Albert Speer. One of the principal reasons given for this decision was that the MAN design used an existing turret designed by Rheinmetall-Borsig, while the DB design would have required a brand new turret and engine to be designed and produced, delaying the mass production of the vehicle.

Pz.Kpfw.V Panther Ausf. G external appearance.
Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

The initial production target was 250 tanks per month at the MAN plant at Nuremberg. The first production Panther tanks were designated Panther Ausf.D, not Ausf.A. Later production targets were increased to 600 per month in January 1943. Despite determined efforts, this figure was never reached due to disruption by Allied bombing, and manufacturing and resource bottlenecks. Production in 1943 averaged 148 tanks per month. In 1944, it averaged 315 a month, with 3,777 built throughout the year. Monthly production peaked at 380 in July 1944. Production ended around the end of March 1945, with at least 6,000 built in total. A Panther tank cost 117,100 Reichsmark (~US$60 mln in 2022) to produce.

Panther in Soviet Use

Soviet soldiers inspecting a destroyed Panther with hull number 834. Kursk, 1943. Source: War Photo Archive via Yandex.Zen

By the middle of 1943, the Red Army already had experience in operating the PzKpfw.38 (t), PzKpfw.II, PzKpfw.III, and PzKpfw.IV, as well as self-propelled guns based on them. However, the use of Pz.Kpfw.V was a very difficult task, requiring appropriate training of crews and the availability of a repair base. Soviet tankers, lacking necessary experience in operating such complex and foreign equipment, often disabled Panthers after driving 15–20 km, and then could not repair them due to the lack of necessary spare parts, tools, and the experience in repairing such vehicles.

Line of Pz.Kpfw.V Panthers (T-V ‘Pantera’), from the 3rd Ukrainian Front, in Sofia, 1945, after being passed to the First Armored Brigade of Bulgaria. Source: War Photo Archive via Yandex.Zen

The headquarters of the 4th Guards Tank Army reported to the GBTU of the Red Army:

“These tanks (Pz.Kpfw.V) are difficult to operate and repair. There are no spare parts for them, which leaves no chance for their maintenance.
To fuel the tanks, it is necessary to provide for an uninterrupted supply of high-quality aviation gasoline. In addition, there are big problems with ammunition for the German 75 mm tank gun mod. 1942 (Kw.K. 42), since the ammunition from the gun mod. 1940 (Kw.K.40) is unsuitable for the Panther tank.
We believe that a German tank of the Pz.Kpfw. IV type is more suitable for carrying out offensive operations, as it has a simpler layout, is easy to operate and repair, and is also widely used in the German army.”

The captured Panthers from the 366th Gds. Heavy SP Arty Regt, 47th Army, vic. Lake Balaton. Hungary, March 1945. German numbers and emblemas are overpainted by red stars with white edges. Source: armchairgeneral.com

However, since the Pz.Kpfw.V was armed with a gun with excellent ballistic characteristics, it had the ability to fight enemy armored vehicles at distances exceeding the effective firing range of Soviet 76 and 85 mm tank guns, which partially compensated for the complexity of its combat operation. In addition, the excellent, by the standards of that time, radio and aiming devices made the Panther a good command vehicle.
In the first half of 1944, the GBTU KA considered the use of serviceable captured Panthers as tank destroyers. In March 1944, a “Short Guide of Using the Captured T-V (‘Pantera’) Tank” was released.

Pz.Kpfw.V Panther (T-V ‘Pantera’) tanks, captured from the 5th SS Panzer Division “Viking”, as part of the 8th Guards Tank Corps of the Red Army, 1944. Source: wio.ru

In January 1944, by order of the Deputy Commander of the 3rd Guards Tank Army, Major General Solovyov, one platoon of the most experienced repair engineers was created in the 41st and 148th Separate Repair and Restoration Battalions, which were later involved in the repair and maintenance of the captured Panthers. The 991st Self-Propelled Artillery Regiment (46th Army of the 3rd Ukrainian Front) had 16 SU-76Ms and 3 Panthers, which were used as command vehicles. In spring 1945, in addition to heavy ISU-152 self-propelled guns and several captured Hummels and Nashorns, there were 5 Pz.Kpfw.V and one Pz.Kpfw.IV in use in the unit.

Captured Pz.Kpfw.V Panther tank with Soviet identification signs — red stars, number 197. Source: wio.ru

It is worth noting that the drivers of the Pz.Kpfw.V had to choose their route very carefully. In places where the light SU-76M passed freely, the heavy Panther could get stuck. Overcoming water barriers was also a major issue. Not all bridges could sustain a tank weighing 45 tonnes, and after fording a river, there were almost always difficulties in getting the Pz.Kpfw.V onto a steep bank.

T-V-85

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.VI Tiger II turret, the study of the change of armament on 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.
Another conversion that had to take place at that time was replacing the German 7.5 cm KwK 42 gun on the Pz.Kpfw.V Panther tank with the 85 mm Soviet one. Not many details are known about this project. The whole process of gun replacement was estimated at 120 hours of work. More than that, it is highly likely that the vehicle could also gain new Soviet sights and 7.62 mm machine guns instead of German Maschinengewehr 34 (MG 34).

Approximate number of machine-hours required to perform work on re-equipping captured German armored vehicles with Soviet guns in small-scale production. Source: CAMD RF 81-12038-775
№ 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: ZiS-S-53

The exact model of the 85 mm gun is not mentioned in any of the known documents. Fortunately, it can easily be deduced. Firstly, a new gun was not an option, as in this case, rearming the Panthers would not fulfill the tasks set of a cheap and easily-made conversion. Secondly, the new gun should not have differed significantly from the 7.5 cm KwK 42 and allow the Panther to continue to perform as usual, without any impact on its mobility and other specifications. Hence, two main candidates appear: the 85 mm D-5T and the 85 mm ZiS-S-53.

The 85 mm D-5. Source: M.A. Svirin, “Artillerijskoe vooruzhenie sovetskih tankov 1940-1945”
85 mm D-5T APHE APCR HE
BR-365A BR-365K BR-365P OF-365K
9.2 kg 4.99 kg 9.54 kg
792 m/s 1050 m/s 793 m/s
0.164 kg TNT 0.048 kg charge
(0.07392 kg TNT eq.)		 – 0.66 kg TNT
142 mm pen 145 mm pen 194 mm pen –
6-7 rpm Parameters of penetration are given for 0 m and 0°.

85 mm D-5T parameters. (source — ZA DB, Pablo Escobar’s gun table)

The history of the 85 mm D-5T gun dates back to May 1943, when the Design Bureau of Plant No. 9 reworked the design of the U-12 gun and offered its own version of the 85 mm tank gun. The new product received the D-5T (or D-5T-85) index and differed from the U-12 by a semi-automatic breech mechanism borrowed from the ZIS-5 gun, as well as some recoil brake and recoil system assemblies. The tight layout of the gun and the short length of its rollback allowed it to be installed in the turret of any existing heavy tank without altering the turret. The gun compared favorably to the S-18 and S-31, with a small recoil length and breech mass, but had a large number of small details and parts, which required precise processing.
Four tanks were tested together (two IS and two KV-1S tanks), armed with S-31 and D-5T guns. Trials demonstrated the great operational advantages of the D-5T gun, which was adopted by the Soviet Army. At the same time, Plant No. 9 was preparing for the mass production of new guns. The peculiarities of the D-5T resulted in difficulties in production for the plant. The plan for the production of 85 mm tank guns for the KV-85 and IS-85 was hardly fulfilled by Plant No. 9, but its capacity was clearly not enough for another gun order for the T-34-85. Factories No. 8 and No. 13 involved in the production could not build this new gun, as they were unprepared for such a complex device. From 1st March 1944, the production of the 85 mm tank gun D-5T ceased.

The 85 mm ZiS-S-53 on trestles. Source: M.A. Svirin, “Artillerijskoe vooruzhenie sovetskih tankov 1940-1945”
85 mm ZiS-S-53 APHE APCR HE
BR-365A BR-365K BR-365P OF-365K
9.2 kg 4.99 kg 9.54 kg
792 m/s 1050 m/s 793 m/s
0.164 kg TNT 0.048 kg charge
(0.07392 kg TNT eq.)		 – 0.66 kg TNT
142 mm pen 145 mm pen 194 mm pen –
7-8 rpm Parameters of penetration are given for 0 m and 0°.

85 mm ZiS-S-53 ammunition parameters. Note they were almost identical to D-5T’s. (source — ZA DB, Pablo Escobar’s gun table)

Fulfilling the order of the NKVD (rus. for ‘People’s Commissariat for Internal Affairs’) to create an 85 mm cannon for the T-34, TsAKB, alongside plant No. 92, quickly carried out complex design work and, by 10th December 1943, two 85 mm artillery systems, the S-50 and the S-53, were tested at the TSLKB firing range.
The S-50 gun (developed by V. Meshchaninov, L. Boglevsky, and V. Tyurin), which had improved ballistics (the initial velocity of the BB projectile was 920 m/s), was not so successful.
The S-53 differed from other similar guns in its simple design and reliability. It was created by the group consisting of I. Ivanov, G. Shabirov, and G. Sergeev. The recoil brake and the recoil system were moved under the base of the breechlock, which made it possible to reduce the height of the firing line and increase the distance between the breech section and the rear wall of the turret. The metal usage coefficient (the ratio of the mass of a part to the standard metal consumption for that part) in the S-53 was very high, and its cost was lower than those of the F-34 and the D-5T. Within 2 months, all the necessary design and technological documentation was prepared for the production of the gun, and on 5th February 1944, the gun went into mass production.

Comparison of the 7.5 cm KwK 42, 85 mm ZiS-S-53, and 85 mm D-5T’s virtual appearance. (Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich; based on original blueprints.)

Considering all the factors, the ZiS-S-53 seems to have been the most optimal choice for rearming captured German Panthers. It had a simple design, compact size, and was rather reliable. Moreover, in spring 1945, a version with stabilizer was developed, the ZiS-S-54, which could possibly have been installed later.

Project Description – Comparison with the Panther Ausf.G

The Soviet military command liked the proposal to instal the Soviet ZiS-S-53 gun, which had proven itself on T-34-85 medium tanks, in the turret of the German Panther tank. Its breech took the same amount of space as the German KwK 42, despite the larger caliber.

75 mm KwK 42 L/70 APHEBC APCR HE
PzGr 39/42 PzGr 40/42 SprGr 42
6.8 kg 4.75 kg 5.74 kg
935 m/s 1120 m/s 700 m/s
17 g charge
(28.9 TNT eq.)		 – 725 g TNT
187 mm pen 226 mm pen –
6-8 rpm Parameters of penetration are given for 0 m and 0°.

The 75 mm KwK 42’s ammunition parameters (source — ZA DB, Pablo Escobar’s gun table)

  • APHEBC – Armor-Piercing High Explosive with Ballistic Cap;
  • APCR – Armour-Piercing Composite Rigid
  • HE – High Explosive

All in all, the new Soviet gun was significantly worse than the German original in penetration and shell flight speed. On the other hand, the ZiS-S-53 was adopted by the Soviet Army in 1944, almost a year before T-V-85 was developed, hence its mass production was well organized by then, and soldiers were used to it.

Comparison of the T-V-85 and the Pz.Kpfw.V Panther’s turret inner layout.
Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

Like the T-VI-100 project, the T-V-85 would most likely have had similar changes. The German 7.92 mm MG 34 would have been replaced by the Soviet 7.62 mm DT and the TSh-17 sights (later used on the IS-2 and IS-3 Soviet tanks) would replace the original TFZ-12A sights. 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.

T-V-85 and Pz.Kpfw.V Panther elevation arc comparison.
Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

Unlike in the T-VI-100, the space inside the T-V-85’s turret would have remained almost the same as on the Panther. As a result, elevation arcs would have been nearly identical (-8°/+18° in the frontal part and -4°/+18° in the rear).
However, just like for the T-VI-100 proposal, many other problems would remain unresolved on the T-V-85. There were no considerations on replacing the transmission, engine, and other hull components with Soviet ones, which means that repairing the tanks would have been problematic. Obviously, had the T-V-85 been converted from Panthers, in field use, all the challenges associated in using captured German vehicles by the Red Army would have been preserved, to the great displeasure of 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.

T-V-85 inner layout scheme.
Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

The Panther itself was outdated by 1945 when compared to the newest medium tanks of that time, the Soviet T-44/T-54, the British Cromwell, Comet, and Centurion, or the American M26 Pershing. Its armor could no longer “surprise” anyone, but almost 50 tonnes of mass was a serious drawback. All this indicates that had the T-V-85 been conceived, it would have hardly been able to perform well, even as a tank destroyer.

The T-V-85’s armor scheme.
Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

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 for most of these, especially those that never operated such a medium tank before, the “Panther”, even with a 85 mm gun (even with stabilizer and newest post-war ammunition), would probably not have been needed. Germany itself was not allowed to have its own army for some years. For the emerging Soviet Bloc countries, such as Czechoslovakia, Hungary, or Poland, especially those bordering what would become NATO, the T-V-85 might have been a good temporary stopgap for their weakened armies until Soviet supplies of T-34-85s, 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. The first frontlines of a hypothetical Third World War would surely have been in Eastern Europe. On the other hand, it is doubtful that rearming an outdated, and difficult to maintain captured tank type was easier and more useful for the aforementioned countries than waiting for the mass-produced T-34 or T-54.

Conclusion

T-V-85 external appearance reconstruction.
Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

The T-V-85 tank project, like many of its counterparts, belongs to the category of “the war ended too soon”. 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.

T-V-85. Illustration by Godzilla
Pz.Kpfw. V Panther (T-V) tanks, captured from the 5th SS Panzer Division “Viking”, as part of the 8th Guards Tank Corps of the Red Army, 1944. Illustration by Godzilla
The captured Panthers from the 366th Gds. Heavy SP Arty Regt, 47th Army, vic. Lake Balaton. Illustration by Godzilla
Pz.Kpfw.V Panther (T-V ‘Pantera’) from the 3rd Ukrainian Front, in Sofia, 1945, after being passed to the First Armored Brigade of Bulgaria. Illustration by Godzilla
T-V-85 specifications table
Dimensions (L-W-H) Length: 8.86 m
Length (without gun): 6.866 m
Width: 3.42 m
Height: 2.917 m
Total weight, battle ready 45.5 tonnes
Crew 5 men (commander, gunner, loader, radio operator, and driver)
Propulsion Water-cooled, gasoline Maybach HL 230 P30 V12 motor producing 600 hp at 2500 rpm
coupled to a ZF A.K.7/200 transmission
Max speed 46 km/h (28.6 mph)
Range (road) On road: 200 km
Cross-country: 100 km
Primary Armament 85 mm ZiS-S-53
Elevation Arc -8°/+18° (frontal part), -4°/+18° (rear part)
Secondary Armament 2 x 7.62 mm DT
Hull Armor 85 mm (55°) upper frontal
65 mm (55°) lower frontal
50 mm (29°) upper side
40 (vertically flat) lower side
40 mm (30°) rear
40-15 mm (horizontally flat) roof
17 mm (horizontally flat) engine deck
30 mm (horizontally flat) frontward belly
17 mm (horizontally flat) rearward belly
17 mm (horizontally flat) pannier
Turret armor 110 mm (10°) frontal
45 mm (25°) side and rear
30 mm roof
№ built 0, blueprints only;

Special author’s thanks to his colleagues: Andrej Sinyukovich and Pablo Escobar.

Sources

Central Archive of the Ministry of Defense of the Russian Federation, 81-12038-775;
Russian State Archive of Film and Photo Documents;
M.A. Svirin, “Artillerijskoe vooruzhenie sovetskih tankov 1940-1945”;
http://wio.ru/tank/capt/capt-ru.htm;
http://armchairgeneral.com/rkkaww2//galleries/axiscaptured/axiscaptured_tanks_img.htm;
https://vpk-news.ru/articles/57834;
https://pikabu.ru/story/krasnaya_pantera_kak_sovetskie_tankistyi_otzhali_u_nemtsev_tank_7473239;
https://shrott.ru/news/88/;
https://topwar.ru/179167-ispolzovanie-trofejnyh-panter-i-tigrov-na-zavershajuschem-jetape-velikoj-otechestvennoj-vojny.html;
https://zen.yandex.ru/media/id/5cd1d04c9daa6300b389ab55/soviet-army-soldiers-inspect-the-destroyed-german-panther-tank-834-5fdea3a23713a37b86ba235b;
https://tanks-encyclopedia.com/ww2/germany/panzer-v_panther.php;
Pablo Escobar’s gun parameters table;

Categories
WW2 Soviet Heavy Tank Prototypes

T-VI-100

T-VI-100 in Soviet colors, with star emblem and writing “Tiger” – illustration by Pavel Alexe
T-VI-100 in Soviet colors, with star emblem and writing “Tiger” – illustration by Pavel Alexe

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.

Tiger I external appearance.
Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

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.

Tiger I №211 near Belgorod, USSR. Source: waralbum.ru

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

Red Army soldiers study a captured German heavy tank. January 18, 1943. Source: warspot.ru

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»

Soviet 57 mm guns easily penetrated the sides of “Tiger”. Source: warspot.ru

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.

“Tiger” after being shelled by a Soviet 122 mm A-19 gun. Source: warspot.ru

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.

KV-1 heavy tank after being shelled by the German 88 mm KwK 36 L/56 gun. Источник: warspot.ru

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.

Remains of T-34 after it was shelled by a German 88 mm KwK 36 L/56 gun. Источник: warspot.ru

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.

G.K. Zhukov, N.N. Voronov, and K.E. Voroshilov inspect the first captured “Tiger”. Source: pastvu.com

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”

T-VI-100 plan description. The writing in Russian says: “Installation of a 100 mm D-10T gun into the turret of a T-VI tank, longitudinal section”. Source CAMD RF 81-12038-775.

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.

Aforementioned blueprint of T-VI-100 turret (source — CAMD RF 81-12038-775) and its restored version. Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

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.

Approximate number of machine hours required to perform work on re-equipping captured German armored vehicles with Soviet guns in small-scale production. Source: CAMD RF 81-12038-775
№ 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
  1. Head of Special Design Bureau (OKB-43) – Salin;
  2. 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.

D-10T gun (source — dogswar.ru)

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.

T-VI-100 and Pz. Kpfw. VI Ausf. E elevation arc comparison
Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

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.

T-VI-100 and Pz. Kpfw. VI Ausf. E turret inner layout comparison
Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

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.

T-VI-100 armor scheme.
Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

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.

T-VI-100 inner layout.
Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

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

T-VI-100 external appearance reconstruction.
Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

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.

Captured Tiger II №502, side view. Writing in the frontal part of the hull says “Glory to our people!” (rus. “Слава нашим”), and writing on the barrel of the gun says “Glory to Korobov!” (rus. “Слава Коробову!”). Source: Report of the Research Proving Ground on brief tests of the German Tiger-B tank.

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 in Soviet colors, with star emblem and writing “Tiger” – illustration by Pavel Alexe
Captured Tiger №121 with washed-off camo, used for durability tests in the USSR. Note the first road wheel is missing. – illustration by Pavel Alexe.
Captured Tiger №100 with washed-off camo, used for 8.8 cm KwK 36 tests in the USSR. – illustration by Pavel Alexe.
Tiger II №502, captured by Soviets. – illustration by Pavel Alexe.
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;