BT-5-IS Ioseph Stalin
Trying to further improve the combat properties of the BT tanks in early 1936, N.F.Tsyganov proceeded to create an experimental model of the BT-5-IS tank. The work on the creation of the BT-5-IS tank was aimed primarily at increasing the maneuverability of the BT-5 serial tank, increasing its power reserve and ensuring that the tank could move on one track.
The main structural difference of the BT-5-IS tank from the base machine was the presence of three pairs of road wheels, which were leading when driving on a wheeled course, which made it possible to use more than 75% of the tank's mass as the coupling weight. The transition to the wheel propulsion was carried out in 13-15 minutes and did not require a “disastrous” tank stop during the battle and leaving the crew car under enemy fire. The equalization of speeds on wheels and tracks was carried out by a special mechanism - a synchronizer. The tank could move on all gears on tracks with the wheel course engaged. Turning the machine on the spot when acting on the control lever was the same both on the wheels and on the tracks, but overloading appeared in the rubber bands of the road wheels caused by lateral shear.
Additional transmission for power supply to the leading support rollers was located in the inter-air space under removable outer side plates. The power was taken from the side gearbox to the synchronizer, then through a semi-rigid gear coupling to the shaft of the corner box and through the coupling to the intermediate roller and the second coupling to the shaft of the first upper junction box. From the first upper distribution box, the torque was transmitted successively to the second and third upper boxes. From the upper boxes through the telescopic drive shafts, the torque was transmitted to the wheel gears of the road wheels.
As a result of the installation of an additional transmission in the cross-border space, new struts, as well as an additional fuel tank in the stern of the tank, the body of the car has undergone some changes. The aft part of the hull was made like a BT-7 tank. In addition, the reservation was introduced for the housings of the onboard gearboxes of the auxiliary drive. In addition to the additional transmission in the cross-space, additional tanks were installed (one on each side). In the undercarriage of the machine, the balancers of the rollers, suspension elements and crawler drive wheels were changed.
Armament machine remained unchanged, with the exception of ammunition to the 7.62-mm machine gun DT, which was reduced to 2016 rounds. The radio station and the tank intercom on an experienced machine was not installed. Due to the increase in the capacity of fuel tanks up to 650 l, the power reserve increased to 250–300 km while driving on tracks and up to 450–500 km on a wheeled course. The speed of the car on wheels was 80 km / h.
In 1936, after successful testing of the first prototype under the direction of N. F.Tsyganov, at repair plant No. 48, located in Kharkov, drawings were developed for the manufacture of an experimental series of machines. Originally it was planned to make three samples of the machine at KhPZ and three machines at the Kirov plant in Leningrad. In reality, an experimental series of BT-5-IS tanks in the amount of ten vehicles in the second half of 1936 was manufactured at plant No. 48. In particular, three tanks from this experimental series took part in the Kharkov-Moscow route. According to the results of this run, the design of three BT-5-IS tanks: Nos. 05, 06 and 010 were modified and in May-June 1937 these modified machines were subjected to troop tests in the HVO.
The troop tests of the BT-5-IS tanks were carried out on the basis of the order of the Chief of the UMM RKKA No. 015 dated January 31, 1937. He headed the commission for troop testing of the head of the 1st branch of the Military Military District HVO Colonel Schnepp. The commission included the Chief of Staff of the 5th Tank Brigade, Colonel Zelentsov, the representative of the NIBT of the test site, Captain Kulchitsky, the engineer of the 5th Tank Brigade, military engineer of rank 3 Dick, military engineer of the 2nd rank Tsyganov, head of the Design Bureau of the Plant 48 of Spetsmashtrest Revin.
During the tests, the BT-5-IS tanks passed from 1,500 to 2,500 km (mainly on wheels). They showed significantly better throughput and survivability compared with BT-5 tanks., as "well moved with the loss of one track, one or two rollers." Despite a number of identified deficiencies - “weakness of synchronizer gears, overload of rubber of the rear wheels, breakdown of the thread of the vertical spark plug rods and poor access to the additional transmission,” the commission members concluded that the “BT-IS should be adopted” tank. The head of the ABTU RKKA division commander G.G. Bokis immediately ordered: “to produce an installation batch of 5 BT-IS machines in 1937”, conduct troop tests and eliminate the identified shortcomings with the expectation that in 1938 to release 300 BT tanks -5-IC at plant number 48. But these plans did not come true.
This time both the KhPZ management and the management of Plant No. 48 reacted coolly to the next "alien" improvement in the undercarriage of the BT-5 tank . This fact is confirmed by both the repeated demands of the UMM RKKA leadership "about sending designers to the test for gaining experience" and the angry letter of rank 2 military technician N.F.Tsyganov, sent to the Politburo of the Central Committee of the CPSU (b) tov.Stalin and comrade Voroshilov. In this letter "On pests in the manufacture of BT-IS", sent on October 26, 1937, in particular, he wrote that "manufacturing was delayed due to: the pest Firsov, the former head of the design bureau at the KhPZ plant, where it was transferred by the pest Neiman, the former head of Spetsmashrestrest; at the plant No. 48 (Kharkov), where the technical director was the fascist Simsky who dragged the plant Number 48 of the fascist Gakkel and put him at the head of the production of BT-IS. ... Farmanyants - Deputy Head of the 8th Main Administration. NCOP tried to disrupt the release of BT-IS. ... Your intervention is necessary. "
This letter, or rather, Tsyganov's "cry of the soul" for some time moved the work on the BT-IS tanks off the ground. Thus, at the KhPZ, the timing of manufacturing and testing of an experienced BT-7-IS tank was corrected, and at plant No. 48 they accelerated the production of a modernized version of an experienced BT-5-IS tank. Back in July 1937, Tsyganov, in order to improve the security of the BT-5 tank, suggested placing the hull side plates not vertically, but at an angle.
By the autumn of 1938, Plant No. 48 was able to produce a single improved prototype of the BT-5-IS tank. In the period from November 1938 to January 1939, the BT-5-IS tank with inclined armor plates was tested. The car was created on the basis of the BT-5 tank and differed from the BT-5-IS tank. 1936. The capacity of fuel tanks reduced to 570 liters and the installation of a four-stroke, twelve-cylinder Y-shaped carburetor engine M-17T with a capacity of 400 hp. (294 kW). Armament and tank ammunition remained unchanged.
Modernization of the hull was partly to increase the thickness of the armor and the introduction of inclined sheets. In the bow of the body were installed additional sheets 13 mm thick with a slope in two planes. Additional sheets were riveted and welded to the main sheets of the bow. The total thickness of the armor in the upper part of the nose, which is located at an angle of 61 °, reached 26 mm, and a sheet 13 mm thick, placed at an angle of 24 ° to the vertical, was inserted into the side of the hull. The thickness of the sheets of armor of the lower part of the hull sides, located vertically, was 15 mm. The stern sheets of the tank hull were made of armor 13 mm thick and located at an angle of 33 °.
In addition, the armor space was increased on the body of the BT-5-IS, new struts were installed, the exhaust pipes were made according to the type of exhaust pipes of the BT-7 , the front tube of the guide wheels was enhanced by installing a more reliable console. Additionally, places were reserved in front of the cutouts in the side armor, as well as the crankcase of the onboard gearboxes and the aft tube at the location of the radial bearings. Strengthening the frontal armor allowed to protect the crew and the internal equipment of the tank from the bullets of a 12.7-mm large-caliber DK machine gun when firing from all distances. The side and stern sheets were protected by the crew from 7.62-mm armor-piercing bullets at any distances, and from 12.7-mm armor-piercing bullets - at a distance of over 1000 m. The combat weight of the tank increased to 13.8 tons.
The car developed a maximum speed on tracks up to 53.3 km / h and on wheels - up to 84.1 km / h. Cruising on the highway by wheel was 550 km. With the loss of the tracks of one of the sides, the car could continue to move to another - at a speed of up to 17 km / h and at a distance of up to 190 km.
Tests of the machine by fire and undermining on a mine showed that the tank BT-5-IS retains mobility in case of partial destruction of the undercarriage, to protect the undercarriage components and the additional transmission from being hit by DT and DK machine guns, as well as from small-caliber projectile damage by projectiles on the hubs of all wheels enter armor caps, and on the outer disks of the steered and driving wheels - armor plates. However, the booking of the undercarriage was considered inexpedient, since the main danger was not the defeat of the undercarriage, but the defeat of the crew and the internal equipment of the tank.
In the winter of 1937, it was decided to launch the BT-7-IS machine into mass production, and KhPZ received tactical and technical requirements (TTT) for the tank from ABTU. Large volumes of new design were not foreseen, it was about upgrading the serial BT-7 to the level of BT-IS. It was planned in 1937 to release 100 BT-7-IS tanks at KhPZ. But because of the scandal that flared up at the plant, modernization work was not carried out.
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