In the thirties, Soviet tank builders were actively involved in the development of wheeled-tracked tanks. In view of certain problems with the resource of the tracked propeller, it was necessary to look for an alternative solution, which ultimately became the use of a combined chassis. In the future, the problems with the tracks were resolved, which led to the abandonment of wheeled-tracked tanks. After that, all domestic armored vehicles of this class were equipped only with a tracked mover. However, in the mid-thirties, the necessary technologies and materials were lacking, which forced the designers to study and develop several projects at the same time.
Even before the end of the war in Spain, the Soviet military and designers began to discuss the appearance of a promising tank. The rapid development of anti-tank artillery led to the emergence of a requirement to equip vehicles with anti-cannon armor, a rack for 37 and 45 mm guns. There were general views on the armament of promising tanks. The chassis was the cause for much controversy. Experts divided into two camps that advocated the need to use a tracked or combined propulsion system.
Experienced A-20
The main prerequisite for the creation of wheeled-tracked tanks was the low resource of the tracks that existed at that time. The military wanted a tracked propulsion unit with a resource of at least 3000 km. In this case, it was possible to abandon the idea of driving equipment over long distances using wheels. The lack of required tracks was an argument in favor of a combined propulsion system. At the same time, the wheeled-tracked scheme complicated the design of the tank, and also negatively affected production and operation. In addition, foreign countries by this time began the transition to full-fledged tracked vehicles.
October 13, 1937 Kharkov Locomotive Plant named after I. The Comintern (KhPZ) received a technical assignment for the development of a new wheeled-tracked tank. This machine was supposed to have six pairs of driving wheels, a combat weight of 13-14 tons, anti-cannon armor with an inclined arrangement of sheets, as well as a 45-mm cannon in a rotating turret and several machine guns. The project received the designation BT-20.
In March 1938, the People's Commissar of Defense K. E. Voroshilov made a proposal regarding the future of armored units. In a memo addressed to the chairman of the Council of People's Commissars, he noted that tank units only need one tank. To determine the most profitable version of such a machine, the People's Commissar proposed to develop two similar projects of tanks with different propellers. Having the same protection and armament, the new tanks were to be equipped with wheeled-tracked and tracked propellers.
By September 1938, Kharkov engineers completed the development of the BT-20 project and presented it to the specialists of the People's Commissariat of Defense. The staff of the Armored Directorate reviewed the project and approved it, making some suggestions. In particular, it was proposed to develop a variant of a tank with a 76-mm cannon, to provide for the possibility of circular observation from the tower without the use of viewing devices, etc.
Further work was carried out taking into account the proposals of ABTU. Already in October, the 38th KhPZ presented a set of drawings and mock-ups of two promising medium tanks, differing in the type of chassis. The main military council examined the documentation and layouts in early December of the same year. Soon the preparation of working drawings of a wheeled-tracked tank began, which by this time had received a new designation A-20. In addition, the design of a tracked vehicle called A-20G was started. In the future, this project will receive its own name A-32. The lead engineer of both projects was A. A. Morozov.
At this stage of the implementation of the two projects, serious disagreements arose. Back in the fall of the 38th, the military agreed on the need to build and test two experimental tanks. However, at a meeting of the Defense Committee on February 27, 1939, representatives of the People's Commissariat of Defense subjected the A-32 tracked tank to serious criticism. The wheeled-tracked A-20, as it was then believed, had great operational mobility. In addition, the current state of the A-32 project left much to be desired. As a result, doubts arose about the need to build and test a tracked vehicle.
Nevertheless, the chief designer of the KhPZ M. I. Koshkin insisted on the need to build two prototypes. According to various sources, the military offered to close the A-32 project due to the impossibility of quickly completing its development and building a prototype vehicle within an acceptable time frame. Nevertheless, M. I. Koshkin managed to convince them of the need to continue the work and, as it turned out later, was right. In the future, the A-32, after a lot of modifications, was put into service under the T-34 designation. The T-34 medium tank became one of the most successful combat vehicles of the Great Patriotic War.
The A-20 tank was inferior to its tracked counterpart in a number of characteristics, but it is of great interest from a technical and historical point of view. So, it became the last wheeled-tracked tank of the Soviet Union. In the future, the problem of unacceptably high wear of the tracks was solved and the combined chassis was abandoned.
The A-20 medium tank was built according to the classic layout. In front of the armored hull there was a driver (at the left side) and a gunner. Behind them there was a fighting compartment with a turret. The hull feed was given for the engine and transmission units. The tower provided jobs for the commander and gunner. The vehicle commander also served as a loader.
The armored hull of the vehicle had a welded structure. It was proposed to assemble it from several armor plates 16-20 mm thick. To increase the level of protection, the hull sheets were located at an angle to the vertical: the frontal sheet - at 56 °, the sides - 35 °, the stern - 45 °. The welded tower was made from sheets up to 25 mm thick.
Reservations up to 25 mm thick, located at rational angles, made it possible to provide protection against bullets of large-caliber small arms and small-caliber artillery, as well as to keep the combat weight of the vehicle at the level of 18 tons.
In the rear of the hull there was a V-2 diesel engine with a capacity of 500 hp. The transmission consisted of a four-speed three-way gearbox, two side clutches and two single row final drives. The use of a wheel-tracked propeller affected the design of the transmission. To move on tracks, the machine had to use the drive wheels with ridge engagement located in the stern. In a wheel configuration, the three rear pairs of road wheels became the driving wheels. An interesting fact is that as part of the transmission of the A-20 tank, the units of the BT-7M armored vehicle were widely used.
The undercarriage of the A-20 medium tank had four road wheels per side. In the front of the hull, guide wheels were attached, in the stern - leading. The road wheels were equipped with an individual spring suspension. Three rear pairs of rollers were connected to the transmission and were leading. The two front ones had a turning mechanism to control the machine when driving "on wheels".
A 45 mm 20-K tank gun was installed in the turret of the tank. 152 cannon shells were placed inside the fighting compartment. In one installation with a cannon, a coaxial 7.62 mm DT machine gun was mounted. Another machine gun of the same type was located in the ball mount of the frontal hull sheet. The total ammunition load of the two machine guns is 2709 rounds.
The gunner of the A-20 tank had telescopic and periscopic sights. Mechanisms with electric and manual drives were used to guide the gun. The vehicle commander could monitor the situation on the battlefield using his own panorama.
Communication with other tanks and units was provided using the 71-TK radio station. The crew of the car was supposed to use the TPU-2 tank intercom.
At the beginning of the summer of 1939, plant No. 183 (the new name of KhPZ) completed the construction of two experimental tanks of the A-20 and A-32 models. The wheeled-tracked vehicle was transferred to the military representation of ABTU on June 15, 39th. Two days later, the second experimental tank was handed over to the military. After some preliminary checks, on July 18, comparative field tests of the new tank started, which lasted until August 23.
The A-20 medium tank showed fairly high performance. On a wheel drive, he developed a speed of up to 75 km / h. The maximum speed on tracks on a dirt road reached 55-57 km / h. When driving on the highway, the cruising range was 400 km. The car could climb a 39-degree slope and wade water obstacles up to 1.5 m deep. During the tests, the prototype A-20 passed 4500 km along different routes.
Experienced A-32
The test report stated that the presented A-20 and A-32 tanks were superior to all existing serial equipment in a number of characteristics. In particular, there was a significant increase in the level of protection in comparison with the old technology. It was argued that rational angles of inclination of armor and other design features provide greater resistance to shells, grenades and flammable liquids. In terms of cross-country ability, the A-20 and A-32 were superior to the existing BT series tanks.
The commission that conducted the tests concluded that both tanks meet the requirements of the People's Commissariat of Defense, so they can be adopted. In addition, the commission made a proposal regarding the design of the A-32 tank. This vehicle, which had a certain margin of weight gain, could be equipped with more powerful armor after minor modifications. Finally, the report indicated some of the shortcomings of the new armored vehicles that needed to be addressed.
New tanks were compared not only with serial ones, but also with each other. During the tests, some of the advantages of the A-20 in terms of mobility were revealed. This vehicle has proven its ability to perform long marches with any chassis configuration. In addition, the A-20 retained the required mobility with the loss of tracks or damage to two road wheels. However, there were also disadvantages. The A-20 was inferior to the tracked A-32 in terms of firepower and protection. In addition, the wheeled-tracked tank had no reserves for modernization. Its undercarriage was heavily loaded, which would require redesigning it for any noticeable modifications to the car.
On September 19, 1939, the People's Commissariat for Defense came up with a proposal to adopt two new medium tanks for the Red Army. Before starting the assembly of the first production vehicles, the designers of factory # 183 were advised to correct the identified shortcomings, as well as slightly change the design of the hull. The frontal sheet of the hull was now supposed to have a thickness of 25 mm, the front of the bottom - 15 mm.
By December 1, 1939, it was required to build an experimental batch of A-32 tanks. It was planned to make some adjustments to the design of the first ten vehicles (project A-34). A month later, Kharkov specialists were supposed to transfer the first 10 A-20 tanks to the military, also in a modified version. Full-scale serial production of the A-20 was supposed to begin on March 1, 1940. The annual production plan was set at 2,500 tanks. The assembly of new tanks was to be carried out by the Kharkov plant number 183. The production of armor parts was going to be entrusted to the Mariupol Metallurgical Plant.
Experienced tanks at the Kubinka training ground. From left to right: BT-7M, A-20, T-34 mod. 1940, T-34 mod. 1941 g.
The development of the updated project A-20 was delayed. The Kharkov plant was loaded with orders, which is why the creation of the modernized project was associated with certain difficulties. New design work began in November 1939. It was planned to test the modernized A-20 with reinforced armor and a chassis at the very beginning of the 40th year. Soberly assessing its capabilities, plant No. 183 turned to the industry management with a request to transfer the serial production of A-20 to another enterprise. The Kharkov plant could not cope with the full-scale production of two tanks at the same time.
According to some reports, work on the A-20 project continued until the spring of 1940. Plant No. 183 had certain plans for this project, and also wanted to transfer the construction of serial tanks to another enterprise. Apparently, no one willing to start production of new medium tanks was found. In June 1940, a decree was issued by the Politburo of the All-Union Communist Party of Bolsheviks, according to which it was required to start mass production of medium tanks T-34 (formerly A-32/34) and heavy KV. Tank A-20 did not go into production.
There is some information about the further fate of the only built experimental tank A-20. At the beginning of World War II, this machine was included in the tank company of Semyonov, which, according to some reports, was formed from the equipment available at the 22nd Scientific Testing Auto-Armored Range (now the 38th Research Institute of the Ministry of Defense, Kubinka). In mid-November 1941, the A-20 prototype was added to the 22nd Tank Brigade. On December 1, the car received minor damage and returned to service in a few days. For several weeks, the 22nd brigade carried out combat missions together with the cavalry of Major General L. M. Dovator. In mid-December, the A-20 tank was damaged again, after which it was withdrawn to the rear for repairs. On this, the traces of the prototype are lost. Her further fate is unknown.
The A-20 medium tank did not go into production. Nevertheless, its development, construction and testing were of great importance for the domestic tank building. Despite the not entirely successful completion, this project helped establish the real prospects for tracked and wheeled-tracked vehicles. Tests of the A-20 and A-32 tanks showed that, with existing technologies, armored vehicles with a combined chassis are rapidly losing their advantages over tracked vehicles, but they cannot get rid of their congenital defects. In addition, the A-32 had a certain stock of characteristics for modernization. As a result, the updated A-32 tank went into production, and the A-20 vehicle never left the stage of testing and refinement, becoming the last Soviet wheeled-tracked tank.
