The index "SP" stands for "Maintenance of the infantry." It was assumed that the deeply upgraded light tank T-26 will retain its basic functions, but will receive higher performance compared with the base version. Interestingly, in the T-26-5 project it was intended to use components and assemblies already mastered in serial production, as well as new components and developed for the T-26М tank. Using this approach, a number of technical and technological problems could be solved.
According to the requirements of the Armored Armor Directorate (ABTU), the designers of the plant №185 should have taken the T-26М tank with its suspension, borrowed from foreign armored vehicles, as a basis. The forehead and armor of the hull of the T-26-5 tank were to be made of cemented armor and have a thickness of 20 millimeters, and it was planned to compensate for the increased weight using a forced engine with a power of about 130 hp. It was necessary to take into account the possibility of further replacing the engine with a more powerful one. Within the framework of the T-26-5 project, it was proposed to once again apply a “Czechoslovak” suspension with characteristic carts, as well as test the new spring suspension of the Pereverzev design. The latter with similar characteristics could significantly simplify the manufacture of the chassis.
The development of the “SP” project in the T-26-5 variant continued until the end of the spring of 1940. In May, 40 Plant No. 185 was merged with Leningrad State Plant No. XXUMX. K.E. Voroshilov. Shortly thereafter, the Armored Directorate corrected the terms of reference on the topic of "SP". In accordance with the updated requirements, the T-174-26 tank had to have cemented armor with a thickness of up to 5 mm or homogeneous to 30 mm. In the first case, the maximum combat weight was set at 40 tons, in the second - 12,5 tons. When using heavier and thicker homogeneous armor, the tank needed to be equipped with an 14 hp engine, and the old 160-strong engine could keep the tank. .
Employees of the former plant No. 185 completed the development of the T-26-5 project in accordance with the updated requirements and prepared documentation for the construction of a prototype of a new combat vehicle. In the spring of 1940, the representatives of the Armored Directorate were able to familiarize themselves with the project and draw up a list of necessary improvements. After the elimination of the identified deficiencies, preparations began for the construction of an experienced T-26-5 tank.
At the beginning of 1940 of the year, before the end of the war with Finland, Glavspetsmash of the People's Commissariat of Medium Machine Building issued to plant No. XXUMX the task of creating another project of the tank "SP". On a number of points, these requirements coincided with those set forth for the development of Plant No. XXUMX, but had several significant differences. Tank factory them. Voroshilov needed to equip the six-cylinder version of the diesel engine B-174 (a simplified version of the B-185), torsion suspension and machine guns DS-3.
Work on the topic of “joint venture” at plant No. 174 was carried out as part of the project with the symbol “126”. After the merger of the two enterprises, the project T-26-5 of the former plant them. Kirov received a new designation - "126-1". The own project of the 174 plant, in turn, was designated as “126-2”.
Developing the “126-2” project in accordance with the requirements was quite challenging. Compliance with all requirements was associated with a number of problems, primarily of a layout nature. For example, when placing a B-3 diesel engine and a transmission in the rear part of the hull, the combat weight of the entire machine reached 20 tons, the length reached the 5,5 meter, and the feed was unacceptably high. The use of the layout used in the T-26 tank gave almost no gain in size or weight: when transferring transmission units and driving wheels to the front of the hull, the gain in length and weight did not exceed the 0,3 meter and 0,5-1,5 tons, respectively. Installing the engine across the hull made it possible to slightly reduce the size and weight, but did not allow to unify the transmissions of the 126-2 and A-32 tanks.
Following the comparison of different layouts, it was decided to sacrifice the width of the machine, having received a gain in length and weight. The drive wheels and part of the transmission units were moved to the front of the case. This and the lateral placement of the engine led to a slight increase in the width of the tank (no more than 75-80 mm), however, the length remained at the level of the dimensions of the T-26 - about 4,6 meter. The estimated combat weight of the tank "126-2" did not exceed 15 tons. In addition to meeting the requirements for size and weight, such a layout allowed equipping the new tank with onboard clutches or even a gearbox borrowed from the А-32 project.
In March, 1940, the ABTU analyzed two projects: "126-1" and "126-2". The original layout, applied in the project of the plant No. XXUMX, caused a lot of complaints. First of all, the placement of the engine literally in the fighting compartment was criticized. However, its transfer to a separate volume threatened with an unacceptable increase in the length of the body. Other shortcomings of the project could be relatively quickly and easily fixed.
In January, the Leningrad Kirov Plant developed its own version of the Light Tank Support Vehicle, the 1940. Unlike the combat vehicles described above, the Leningrad light tank was supposed to be made with minimal use of the designs of the T-26 project. Probably, this particular feature of the project allowed to use the experience gained in the development of the T-50 light tank, which was mass-produced and took part in combat operations.
As part of the 211 project, two versions of a light tank were developed. The first was to get a cast hull and a tower with armor up to 45 mm thick, and the second meant the use of a welded hull of sheets up to 25 mm thick. Both tanks were to be equipped with a B-3 diesel engine and fuel tanks with a total capacity of the order of 350 liters. A light tank with a cast hull was supposed to carry an 45-mm cannon and two DT machine guns - twin and anti-aircraft. The armament of a tank with a welded hull was to consist of a pair of DT machine guns and one anti-aircraft machine gun. The combat weight of the "cast" and "welded" tanks was 14 and 12 tons, respectively.
The weight and size restrictions imposed by the terms of reference on the “SP” theme made Leningrad designers study the possible configurations of the tank’s internal units. As a result, employees of the design office of LKZ came to the same conclusions as their colleagues from the plant number XXUMX. A relatively large diesel engine B-174 was not placed in a separate engine-transmission compartment, but installed in the rear part of the hull, with a shift to the board. This should have a negative impact on the convenience of the crew, but allowed to reduce the size of the combat vehicle and, as a result, its weight.
It was proposed to equip both versions of the 211 tank with an individual torsion bar suspension with six support rollers on board. In addition to the road wheels, the chassis should have four supporting rollers, a drive and guide wheel on each side.
In March, the 1940 of the Year, the Armored Directorate, along with other projects, studied the development with the “211” index. As in the case of the project "126-2" the main claims of the military were related to the placement of the engine. Other shortcomings of the project could be solved without serious interference with the layout and design of the tank.
Completion of projects
The meetings at ABTU lasted three days, after which the responsible persons of the administration and tank factories agreed on the prospects of the three projects. It was decided to continue work on the project “126-1”, and later to take it as a basis for the modernization of the fleet of existing and newly produced serial T-26-1. Until the end of June, 1940 was required to prepare documentation on the finalization of the T-26-1 to the level of “126-1” as part of the overhaul of the equipment. The production tanks of the old model were to receive new diesel engines D-744, as well as additional reservations, increasing the total thickness of protection to 40-45 mm.
The design work on the 126-1 and 211 tanks was required to continue. The main goal of the designers of the plant number XXUMX and the Kirov Plant was to change the layout of their tanks. The military did not accept the contact of the engine with the fighting compartment. It was necessary to make all the units of the power plant beyond the habitable volume. Updated projects were required to submit in early July.
At the end of April 1940, the military, after analyzing the projects submitted earlier, clarified the terms of reference on the topic "SP". A prospective light tank with a tracked propulsor and one turret should have a combat mass of no more than 13 tons. The maximum dimensions were set in accordance with the restrictions imposed by rail transport and road and road structures. The maximum travel speed was determined in 35 km / h. Perspective light tank "SP" had to rise and descend with a slope of the surface to 45 ° and move with a roll to 40 °. It was necessary to ensure the overcoming of a wall up to 0,7 meters in height and the crossing of water barriers to a depth of up to 1,2 ford without preparation. The capacity of the fuel tanks should be enough for 10 hours of movement.
The armor of the tank "SP" was supposed to protect the crew and units from projectiles caliber 45 mm when firing from any distance. For this, the forehead, sides and stern of the hull were to be made of 45-mm armor plates. The thickness of the roof and the bottom, according to the task, should have been 20 and 15 mm, respectively. The layout of the internal volume was supposed to provide not only comfortable accommodation for a crew of four, but also allow them to replace each other without leaving the car. A new tank was required to be equipped with an intercom system for the commander, driver and gunner, as well as the 71-TK-3 radio station with a whip antenna suitable for replacement from the fighting compartment.
The armament of the SP tank was to consist of one 45 mm caliber cannon with an ammunition of at least 150 shells and DT machine guns with 4000 ammunition of ammunition. For self-defense, the crew needed to equip Degtyarev machine pistols with a common 750 ammunition ammunition, as well as 24 F-1 grenades.
Also, the updated technical task stipulated a number of requirements for various components and assemblies of a promising tank and for the convenience of the crew. In accordance with these requirements, it was necessary to continue the development of all three projects.
5 June 1940 of the Year The Defense Committee allowed Plant No.174 to begin construction of a prototype tank of the SP in the T-126-2 variant. However, before that it was necessary to bring the engine into a separate volume and move the drive wheels to the rear of the hull. Shortly thereafter, updated requirements for the armored corps appeared. A few months before, the proposed use of the armor of the Mariupol plant was tested. During the test shelling of 45-mm anti-tank guns using the latest projectiles, it turned out that the protection against such weapons provide only sheets with a thickness of more than 50 mm, however, after such a bombardment, the rear strength of the armor is broken. In this regard, the T-126-2 tank was to receive frontal and airborne armor with a thickness of 55 mm. The roof and bottom to protect against enemy planes and mines now needed to be made from 30-mm and 20-mm sheets, respectively. In view of the increase in the weight of the hull, it was allowed to bring the combat mass of the promising tank to 17 tons.
In August, 40-th completed the construction of two experimental tanks T-126. One of them, equipped with armor no thicker than 45 mm, weighed about 17 tons, and the machine with thicker armor had a mass of about 18,3 tons. Despite the relatively large weight, both tanks were cramped and not very comfortable for crews. The restrictions imposed by various customer requirements have led to a severe economy of internal volumes.
The tests of the first prototype of the T-126 tank began on August 31. Before September 9, an armored vehicle with a crew of testers passed 312 kilometers: 195 km along the highway, 95 km over rough terrain and 22 km along various obstacles. September 10 began finishing the tank with the elimination of the detected deficiencies. 19 September launched the second stage of testing, during which an experienced tank overcame 973 kilometers.
Despite constant improvements, the tanks of the 126 project retained a lot of flaws, the main of which was a large combat mass. In accordance with the first versions of the technical specification, the tank “SP” should not weigh more than 13-15 tons, but 17- and 18-ton machines were put to the test. Customer reaction was expected. After some not very successful improvements, both 126 projects, and with them 211, were closed.
In May, the 1940 of the year, when the constant increase in the 126 tank mass became visible, works on the 174 project began at plant No. 127. As part of this preliminary design, it was intended to work out the possibility of maximally facilitating a promising tank with the fulfillment of existing requirements. A group of engineers led by young specialists Goltvyansky and Makarova got down to business and soon presented her version of the light tank “SP”.
The 127-126 project was taken as the basis for the 1, from which the hull was borrowed with serious modifications, as well as the gearbox, final drives and a number of other units. The tank was supposed to get a diesel engine D-744 power 250 hp With armor thickness from 30 to 45 mm, the new armored vehicle had to weigh no more than 12,6 tons and have smaller dimensions in comparison with the “126-1”. In the undercarriage it was proposed to use three torsions aboard, on each of which it was proposed to place a balancer with a two-wheel carriage.
The sketch project “127” looked promising. A relatively light armored vehicle had a fairly high level of protection, and its mobility, according to calculations, was noticeably higher than that of other tanks created under the theme "SP". The only problem with the 127 project was the lack of an engine. Diesel D-744 was not ready for mass production and even on the stands could not give the required power. Moreover, only one of the three prototypes of the engine was able to develop the power of the 200 hp for a short time, after which they failed. Two other engines with great difficulty took the bar in the 150 hp Nevertheless, the authors of the project believed that without significant modifications this motor could “give out” 250 hp. and thus provide a new tank with high performance.
By the time the tests of the T-126 tank began, engineers Goltvyansky and Makarov offered to start full-scale work on the 127 project. The management of the plant No. XXUMX saw its inherent flaws and therefore did not share the optimism of the authors of the project. The absence of the engine, as well as the ambiguous characteristics of the undercarriage became the cause of the corresponding attitude to the project. Nevertheless, the authors of the project continued the struggle and even sent a complaint to the Defense Committee, the Main Armored Directorate (GABTU) and the People's Commissariat for Medium Machine Building.
Shortly after sending such a letter to the plant number 174 arrived commission GABTU. Management Specialists familiarized themselves with the documentation on the project of the tank "127" and rendered their verdict. The Commission noted the closeness of the fighting compartment, which did not provide sufficient crew comfort; the absence of the necessary engine, as well as the impossibility of raising its power to the required 250 hp; low reliability of the torsion bar suspension with carts; the complexity of manufacturing the body with a large number of bent parts. Finally, the tank "127" had no prospects for booking. With an increase in the thickness of the hull sheets, the proposed diesel engine could no longer provide sufficient mobility. The use of a different power plant would entail significant changes to the hull with corresponding consequences for the size and weight of the tank.
Shortly after the commission report appeared, all work on the 127 project ceased.
As part of the “SP” theme, the Soviet defense industry created four different light tank projects. All these projects had both advantages and disadvantages. A common feature of the developed tanks "126-1", "126-2", "211" and "127" was a constant increase in combat mass. The reason for this can be considered ambiguous technical task. The infantry escort tank was supposed to be light enough, but at the same time to have relatively thick armor. As shown by the projects of plants No. XXUMX, No. XXUMX and the Leningrad Kirovsky Plant, the creation of a promising armored vehicle with similar characteristics is a very difficult task. Moreover, at the level of development of materials science and motor engineering of the late thirties, the creation of a tank with specified characteristics turned out to be almost impossible. Because of this, the most successful of the projects on the subject of the “joint venture” - “185-174” - remained at the prototype testing stage.
Svirin M. Stalin's armor shield. History of the Soviet tank 1937-43 - M .: Yauza, Eksmo, 2006