HEAVY TANK is-7 (“object 260”)

In the postwar period the plans for the organization of our armored forces military experts associated primarily with the latest heavy tank is-3. Commercially the tank was produced at the Chelyabinsk Kirov plant in 1945-1946 very fast pace. So, in the summer 1945 issue was, for example, 250 items per month. There were manufactured 2305 machines.

However, in the beginning of the service in the army revealed a number of fundamental flaws. The fact that many of the mechanisms and units, the is-3 proved to be unsuitable for prolonged use in peacetime because of the very low reliability. Apparently, affected the calculation of the short military life of machinery, which lasted in combat just a few weeks. Therefore, after 1948, they were subjected to alteration and modernization program of eliminating design flaws at the same Kirov factory in Chelyabinsk.

Almost simultaneously since the beginning of 1945 in the branch of experimental plant No. 100 in Leningrad Kirov plant under the supervision of chief designer J. Kotin started designing a new heavy tank “model 260”, which was supposed to embody the latest achievements of the domestic tank, linking them with the experience in combat.

Preliminary design was completed in a short time, 9 September of the same year J. Kotin signed drawings for the first sample. Vehicle weight was assumed to equal 65 tons length with gun – 11,17 m, a width of 3.44 m, height – 2.6 m; armament-a 122 mm gun with a muzzle velocity of about 1000 m/s, three 7.62-mm machine gun DT (Degtyarev tank) and two 14.5 mm KPVT (Vladimirov heavy machine gun tank). It was planned to install two diesel engines-16 with a total capacity of 1200 HP with electrical transmission. The building was designed with large angles of inclination of the armor plates, the front part is triangular, “pike nose” like the is-3, tower – cast flattened. Fuel tanks were located in the sub base. A wooden mock-up tank, built life-size, looked very compact. However, to realization in the metal case then it did not come.

After elimination of remarks the mock-up Committee in 1946, undertook the design of the second version. Almost immediately the decision was made to build two prototypes, and in September passed the sea trials, which one of them has successfully overcome the route length of 1000 km, showing high for a machine speed of about 60 km/h on the highway and 32 km/h on cobbles, after completing the basic requirements of technical specifications.

The tank was installed 130-mm gun S-26. The fact that previously announced a 122-mm gun on a deadline to develop failed. Therefore, in the suburban Central artillery design Bureau of V. Grabin for a new machine gun developed on the basis of already existing marine 130 mm B-13.

The exposition of the Military historical Museum of armored vehicles and armament in Kubinka. The prototype tank is-7 — the first in a series

Gun S-26 had a dual core loading. The weight of the projectile was equal to 33 kg for easy action loader was specially designed loading mechanism with pneumatic actuator, which allowed to increase the rate to 6 – 7 RDS./min Gun had slotted muzzle brake.

With the rest of the weapons ordered in the following way. The car has placed six 7.62 mm machine guns of RP-46 (company machine gun of 1946 arr.):

two – paired with a gun, two – side, installed on the sides of the tower only on the shelves, two on a tower aft turrets with servo drive. In addition to the exchange rate of 14.6-mm machine gun KPVT the same mounted on the turret for anti-air purposes.

The crew with so many weapons to five. The driver was in the corps in the Department machine control and the other four located in the tower. The gunner on the left of the gun, the commander on the right side, the two loaders in the rear of the turret; they also, when necessary, was to fire machine guns.

Because creating a spark engine V-16 was not possible for an experienced machine set diesel TD-30 – revised aircraft engine AH-300 production plant No. 500 of the Ministry of aviation industry. It was the first time tanks used for cooling ejection system.

Tank is-7:

1 – 130-mm gun S-70; 2 – exchange rate of 14.6-mm machine gun KPVT; 3 – gun mask; 4 – anti-aircraft 14,6 mm machine gun KPVT; 5 – timer remote -motor machine gun; 6 – 7.62 mm machine gun on the fender; 7 – driving wheel; 8 – double support roller; 9 – front suspended wheel; 10 – gun muzzle brake; 11 – the forehead of the body – triangular (“pike nose”); 12 – hatch commander; 13 – Luke gunner; 14-fuel barrels; 15 – tow-rope; 16-driver’s hatch; 17-feed turret 7.62-mm machine gun; 18 – the radio antenna; 19 – the caterpillar tracks with rubber-metallicheskimi joints; 20 – the bottom feed plate; 21 is a coaxially mounted 7.62-mm machine gun; 22 – a surveillance device of the driver; 23 – headlight; 24 – lower front plate

In addition, instead of the electric drivetrain had to settle for a conventional manual; the steering mechanism – two-stage planetary. Management had hydraulic servos. Suspension consisted of seven large diameter rollers on Board without support rollers, drive sprocket located on the rear.

In 1947, continued intense development of improved version of the draft “model 260”. Increased booking machine body: increased to 150 mm the thickness of the frontal sheet and the upper side, and put these sheets at angles of inclination 50°, and fodder – up to 70 mm at 55° tilt. Changed the profile of the tower, bringing the thickness of the frontal parts up to 240 – 350 mm at angles of 0 – 45°, it’s side -to 185 – 240 mm at 30° – 45° tilt. It was thought that such a tower will not be able to penetrate even the 130-mm caliber armor-piercing shells – the largest of which was at the time on arms of foreign armies.

The tank installed a new 130-mm gun S-70 with a barrel length of 54 caliber. Its a projectile with a mass of 33.4 kg had an initial speed of 900 m/s and could penetrate 160 mm of armour plate set at an angle of 30° at a distance of 1000 m, and 140 mm sheet – 2000 m. the Ammunition consisted of 30 rounds.

Gunner got stabilized sight, with the possibility of guidance regardless of the position of the cannon: the shot at the same time could produced only when the combination of the axis of the bore with the line of sight.

Bulky pneumatic loading mechanism was replaced with a small chain drive.

The number of guns brought to eight: two RP-46, is placed in armoured boxes at the rear of only the niches were intended for firing forward, two machine guns mounted on the sides of the niche tower, shot ago, another two remained paired with a gun; to this is added a second 14.5 mm machine gun KPVT. It was mounted on the special high post and provided synchronous servo remote actuator, with which it was possible to fire both air and ground targets directly from the tower.

Ammunition rounds for the KPVT -400 and for RP – 2500.

The designers of weapons developed for the is-7 even-rare variant of the anti-aircraft guns, consisting of two machine guns of RP-46 and one KPVT.

The engine was replaced by 12-cylinder V-shaped four-stroke M-50T with a capacity of 1050 HP at 1850 Rev/min with an ejector-cooling, which was a tank version of the marine diesel, which has been used on high-speed offshore boats.

M-50 had, however, in contrast to the TD-30 some large size, which required the adoption of a number of constructive solutions to install it on the tank without increasing the height of the housing. For example, was designed independent suspension with a short “beam” torsion rod, allowing free space for the placement of the crankcase. Each “beam” torsion consisted of 19 rods with hex heads.

Form front part of the hull “pike nose” of the is-7 is similar to is-3

Suspension tank is-7 has no support rollers. The upper part of the tracks lies directly on the supporting rollers

Comparison of tanks is-7 and E100 German heavy, alternatives to the failed

The comparison of tanks is-7 and E100 German heavy, the alternatives failed the “mouse”

The hull of is-7 and the German “Tiger”

Heavy tank is-7 (“object 260”), By the summer of 1948 at the Leningrad Kirov factory had produced four prototypes of the tank

Is-7 with gun S-70 at the experimental site during the trials, 1948

Transmission gidrotruboprovod and a rotation mechanism mounted in one unit, and it had eight forward gears and two reverse.

Rollers undercarriage executed double, with the internal cushioning. Used hydraulic shock absorbers, double-acting, which is very positive impact on smoothness. Caterpillar width 710 mm consisted of cast trucks box section with rubber mount.

The fuel is placed in the rubber 14 tanks with a total capacity of 800 l; six of them were outside on the sides in metal boxes.

The machine had an automatic fire extinguishing system three inclusions, consisting of sensors and fire extinguishers installed in motorradreisen office.

In 1948, the plant manufactured four prototypes of the new machine. After passing factory tests, they were sent to the state.

Armor tanks withstood the fire not only of the most powerful 128-mm gun, which was mounted on German super-heavy tank “Maus”, but of the 130-mm gun S-70, which were armed with the is-7.

Prototypes of the is-7 has withstood the test. However, while none of the heavy tanks at that time had similar technical and combat performance, the acceptance, the state Commission issued a negative decision. Apparently, it was due to too much weight – 68 tons, but perhaps the argument that at the Chelyabinsk Kirov plant is already commercially available from 1947 tank is-4.

Anyway, tank is-7 (“object 260”) is the most powerful tank of its time on the arms was not adopted…

Tactical and technical characteristics of the prototype tank is-7

Combat weight, t…….. ……………………………68

Crew………… ……………………………..5

Length of body, mm ………………………..7380

Length with gun forward, mm………….11 170

Width, mm……………………….3440

Height, mm…………. …………………………2600

Ground clearance, mm……….. …………………………..410

Booking, mm:

the forehead of the body……… …………………………..150

the Board body……. ………………….100-150

feed corps….. ……………………60- 100

the bottom……………… …………………………….20

forehead tower……….. …………………………..210

mask tools……. …………………………..350

the side of the tower………. …………………………..150

the tower feed……. …………………………….94

the roof of the tower…… …………………………….50

Arms: 130 mm cannon, 2 x 14,6 mm machine guns 6 x 7.62 mm machine guns

Ammunition:

shells………….. ……………………………32,

cartridges:

14.5 mm………………………….400.

7.62 mm…………………………2500

Engine: diesel M-50T, 12-cylinder, four-stroke

liquid-cooled,

power 1050 HP

at 1850 rpm

Specific power, HP/t………………..15,4

Speed on highway, km/h…………………….60

Speed on country road, km/h…………………32

Cruising on the highway, km……………………300

Specific ground pressure, kg/cm2…..0,96

A. MISHAKOV

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