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IS-7 Object 260

The IS-7 was the last tank named after Josef Stalin. The IS-7 (Object 260) was a heavy Soviet tank of the IS series, which was designed shortly after the War as a successor to the IS-3. It was one of the heaviest tanks ever built in the Soviet Union. The first sample of the IS-7 was assembled in September 1946. In 4 months, the vehicle managed to cover 1000 km, demonstrating full compliance with the technical requirements put forward. The car was virtually invulnerable. Even a German 128mm cannon could not penetrate the IS-7's armor. Unfortunately, the order for the first 50 units, issued to the Kirov plant, was not fulfilled due to lack of money. In addition, practitioners who encountered problems during the transportation of the 68-ton vehicle began to demand that its weight be reduced, since the railway platforms could only accept 55 tons. As a result, work on the IS-7 was stopped.

The Great Patriotic War was a confrontation of armor and shell. Tanks evolved from low-powered, bulletproof armored vehicles to real “dinosaurs” with 150 mm frontal armor, weighing up to 70 tons and a 88 - 120 mm caliber cannon. These include the heaviest production tank of World War II - the Nazi Pzkpfg VI Ausf.B, better known as the “Royal Tiger”. The preliminary design of the new heavy tank, actually the same age as the Tiger II, began in late 1944. The godfather of the tank was L. Beria, who, despite the resistance of the People's Commissar of the tank industry V. Malyshev, assisted the director and chief designer of Chelyabinsk Plant No. 100 J. Kotin.

In January 1945, the first design developments of facilities 257, 258 and 259 appeared. which differed only in the type of power plant and transmission (mechanical or electrical). In the summer, a new project 260 received the IS-7 index. For a detailed study of the design, several highly specialized groups were created under the guidance of specialists who had enormous experience gained over the years of World War II. Already on September 9, 1945, the working drawings of the IS-7 tank were signed by the chief designer Zh.Ya. Kotin. In a new, hitherto unseen vehicle, the experience of designing, operating and combat use of heavy tanks of the past war was embodied. working drawings of the IS-7 tank was signed by the chief designer Zh.Ya. Kotin. In a new, hitherto unseen vehicle, the experience of designing, operating and combat use of heavy tanks of the past war was embodied. working drawings of the IS-7 tank was signed by the chief designer Zh.Ya. Kotin. In a new, hitherto unprecedented vehicle, the experience of designing, operating and combat use of heavy tanks of the past war was embodied.

The model was developed in the Leningrad Kirov factory under the direction of Nikolai Fyodorovich Shashmurin. Director and chief designer of the design office was Sh. Yes. Kotin. The first two prototypes were completed on 8 and 25 December 1946. Overall, only six prototypes were produced from 1946 to 1949. The mass of the IS-7 corresponded approximately to that of the German King Tiger from the Second World War; with significantly stronger armor and a much larger caliber of the main weapon.

The IS-7 hull was designed with large angles of inclination. The frontal part (trihedral “pike nose”) repeated the similar construction of the IS-3. The side armor at the top had a reverse slope, the sheets were not welded, but bent under the press. The thickness of the armor plates was distributed as follows: the forehead of the hull - 150 mm, the side - 150-100 mm, the turret - 210-94 mm. The electric transmission was borrowed from the heavy IS-6, on which this innovation was applied for the first time in Soviet tank construction.

A powerful 130-mm S-26 sea gun equipped with a new slotted muzzle brake was installed on the IS-7. In the mask of the gun mounted a 14.5-mm machine gun KPVT and two SGMT-43. Two more SGMT-43s were installed on the sides of the rear of the turret, and a couple of others on the sides of the hull.

Object 261 carried a 152mm cannon, Object 263 was armed with the 130mm S-70 cannon. It should be noted that the armament of the IS-7 model 1946 was the 130mm S-26 (besides minor differences the same gun as the S-70) or the 122mm BL-13-1 (high velocity 122mm with the same ballistics as the BL-9).

Like the other IS series IS-2 tanks, the IS-7 had a muzzle brake, which was unusual in Soviet tanks. The S-70 cannon was developed from the 130mm B-13 naval gun from 1935 and already had a stabilizer and semi-automatic loading device. The combat set was 25-28 rounds, the ammunition was like the IS-2 in two parts. This cannon was used outside the Navy only in the IS-7 and in the only prototype of the self-propelled gun Object 263. The maximum firing range was 27 km, the muzzle velocity 900 m/s and the mass of the projectiles 33.4 kg.

The IS-7 had a strong secondary armament with a total of eight machine guns. Two MGs were mounted laterally in the tub and turret. The SGMT were all remotely operated. To conduct anti-aircraft fire on an armored cupboard in the aft of the turret roof, a KPVT machine gun was installed (according to other sources, an upgraded version of the DT, RP-46 machine gun of 7.62 mm caliber was installed on the IS-7). It is noteworthy that the turret anti-aircraft machine gun was equipped with a synchronously-tracking remote electric drive guidance, which allowed to fire at ground targets without leaving the crew from the tank. In the design bureau of the Kirov plant, as an initiative, they developed a version of the built anti-aircraft installation: one 14.5 mm machine gun and two 7.62 mm caliber.

Gun guidance was facilitated by power electric drives, and shells were fed by conveyor. For the first version of the IS-7, even a pneumatic drive for the loading mechanism (25 atmospheres) was developed at the Scientific Research Institute of Armament. The combat load of the KPWT consisted of 1000 14.5 × 114 mm cartridges, for the SGMT 6000 7.62 × 54 mm R cartridges were carried.

While the King Tiger was clearly underpowered with 10 PS / t, the IS-7 had a power-to-weight ratio of over 15 PS / t, which gave it sufficient maneuverability. Due to the high total mass of the tank could pass only a few of the former bridges. Since the trend after the Second World War to lighter tanks went, the IS -7 was not produced in series and instead the T-10 developed, which also ended in the Soviet Union, the era of heavy tanks. All subsequent models were lighter, faster and more agile.

The engine was derived from a marine diesel V12 four-stroke diesel engine. To power a 6-speed planetary gear was used (8 forward and two reverse gears). As the first heavy Soviet tank, the IS-7 had a caster with large rollers instead of a support roller drive. Its specific bottom pressure was 0.90 kg / cm². The gradeability was 30 °, the wading ability 1.50 m and the ground clearance 45 cm.

The electromechanical transmission of the supercharged V-12u diesel engine mounted coaxially with a generator fed reversible electric motors connected through planetary gears to drive wheels. In a block with them was a three-phase generator for charging batteries and cooling system drive (power transmission was also installed on the American TIEI tank in 1941, on the T-23, jointly built by General Electric and the Detroit Arsenal. Traction electric motors with clutches also stood on the German tank destroyer "Elephant"). Due to the large weight of the electric transmission (the main generator weighed 1.7 tons.)

In another version of the IS-7, developed in 1946, they decided to abandon it. In the second half of 1946, two experimental Objekt 260 were manufactured in the shops of the Kirov Plant and the branch of Plant No. 100. Due to the lack of a tank engine of the required power (1200 hp), the designers proposed to install two twin V-16 diesel engines on the IS-7 , but tests of this "spark" revealed its complete unsuitability. For the first version of the IS-7, the Kirov Plant together with the Minaviaprom Plant No. 500 developed the TD-30 diesel engine based on the aviation ACh-300. A number of technical innovations were introduced at IS-7: soft rubber fuel tanks with a total capacity of 800 liters; fire-fighting equipment with automatic thermal closers that worked at a temperature of 100–110°?; ejection engine cooling system; remote synchronizer machine gun installation.

For the first time in Soviet tank building, tracks with a rubber-metal joint and double-acting hydraulic shock absorbers were used. In the large-diameter track rollers, internal depreciation was introduced, similar in structure to the similar system on the German “Royal Tiger” and “Elephant”. The beam torsion bars working on twisting and bending had seven rods with hexagonal heads.

A new version of the IS-7 received a serial marine 12-cylinder diesel engine M-50T with a capacity of 1050 hp. at 1850 rpm Engine cooling was carried out according to the latest ejection scheme. The air stream flowing through the radiators was created by exhaust gases passing through a special-shaped duct. There was an ejection effect, which significantly increased the power of the power plant: it was not spent on a fan drive. Five ejector models passed preliminary bench tests. An automatic fire extinguishing system designed by M. Shelemin was installed in the engine and transmission compartment and was designed for three times switching on. The large dimensions of the M-50T diesel engine, the volume of its auxiliary systems, forced the designers to move their ammunition load (30 rounds) into the developed turret niche. The latter had to be slightly lengthened due to the cumbersomeness of the gun shutter and recoil devices. The solid weight of the shells required another loader, the crew increased to five people, and only the driver was outside the turret.

Representatives of GABTU and the Kirov factory inspected the prototype in 1946. Chief test pilot of the USSR Ministry of Transport Engineering EA Kulchytskyy wrote "I was given the best part, I got an offer to drive this wonderful tank. Hard to express feelings. At speeds over 60 km / h this heavy machine easily responds to the slightest forces applied to the levers and pedals. Gears are shifted by a small lever, the machine is completely submissive to the driver.

In the summer of 1948, the Kirov Plant manufactured four pre-production IS-7s, which, after carrying out factory tests, were submitted to the State tests. However, despite the outstanding characteristics of the IS-7 (none of the modern heavy tanks to it had such a set of basic combat properties), the machine did not receive the approval of the State Commission.

The tanks successfully passed factory tests and were transferred to state ones. IS-7 stunned members of the state commission with its unprecedented power. Wonder tank with a mass of 68 tons with amazing ease accelerated to 59.6 km / h, had excellent cross-country ability. Armor protection withstood shelling of the German 128-mm gun, shells of its own hundred-thirty jumped from its "pike nose".

In general, despite a number of comments, the test results were found to be quite satisfactory. Among the advantages in terms of weapons, according to the IS-7, it was noted, first of all, the convenience of the crew of the vehicle: this was ensured both by the use of a rotating polic in the turret and by the use of a mechanism for purging the barrel bore after a shot, which significantly reduced the gas content of the fighting compartment of the tank. The 130-mm S-70 gun showed satisfactory accuracy of the battle and the reliability of the units and mechanisms. A high rate of fire was also noted - up to six rounds per minute) due to the use of a loading mechanism. The latter, designed by the engineers of the Leningrad Kirov Plant, turned out to be simple in design, reliable in operation and provided convenient loading of loading shells and charges into it.

Unfortunately, the trials immediately started trouble. Huge IS-7 froze at an artillery range in front of an anti-tank gun. A shot, one more. Suddenly another heavy projectile slid along the bent board and hit the suspension block with a ringing sound, which was thrown away with the ice rink. Experts established a marriage of welding ... Another IS-7 during the run suddenly caught fire. The fire extinguishing system produced two flashes, but fire engulfed the engine compartment. Tankers managed to leave the car before it turned into a pile of metal. The cause of the fire was the engine that was still under the warranty period.

In addition to failures during the tests, this result was caused by the fundamental flaws of this “supertank”, first of all its too large mass. The installation on the IS-7 of super-powerful artillery armament, which needed to be serviced by a crew of five (which resulted in a significant reserved tank volume), and the attempt to provide such a large machine with the highest level of protection that its mass reached a record 68 tons for Soviet tank building (instead of the planned 65.5 tons).

The running and combat characteristics of the "Object 260" were, at least, not lower than those of foreign armored vehicles of the same class. The latest prototypes of the IS-7 weighed 68 tons, which the military did not like much. Not every bridge in the Soviet Union could withstand such a load. As a result, the mobility of units armed with heavy tanks deteriorated greatly. The same problem arose with transportation by rail. The weight restrictions of the transport infrastructure will subsequently affect the development of all domestic armored vehicles, primarily on heavy tanks.

It should be admitted that foreign tank builders also faced this problem. In the 70s, British and German designers developed a promising MBT-80 tank and found a rather interesting solution to the problems: As in the design of the Chieftain. one of the most critical was the problem of the mass. The specification of the General Staff limited the mass of the promising tank to 54.8 tons (the mass of the Chieftain Mk.5 tank), however, even during the development of the MVT-80 project, British experts came to the conclusion that it was impossible to strengthen the armor provided that the mass of the new tank remained at the level the masses of the Chieftain Mk.5. The mass had to be increased to 60-62 tons, in this case it became possible to strengthen the armor of the frontal part of the hull and turret, as well as the sides.

MVEE engineers, as a justification for the possibility of increasing the mass, put forward the thesis about the insignificant difference between 50- and 60-ton tanks. So, with equal power density and ground pressure, mobility, average speed, throttle response and passability will be approximately the same. One of the criteria limiting the mass of a tank is the carrying capacity of road bridges. The British carried out an analysis of the distribution in the European theater of operations of engineering structures limiting the mobility of tanks; it turned out that most of the bridges are designed for a load of 20 tons, that is, they will fail with equal success under a 50-ton tank, and under a tank weighing 60 tons, and bridges with a carrying capacity of 50 and 60 tons are "smeared" across Europe approximately evenly.

Despite the setbacks, the impression of the selection committee turned out to be so great that in 1949 the IS-7 was recommended for serial production and the Kirov Plant received an order for a batch of 50 tanks. However, some dark story begins. Mutual accusations of factory workers and the Main Armored Directorate followed. The first reproached the customer for the intentional rejection of the new tank, the requirement to reduce its weight to 50 tons. The GBTU accused the plant of sabotaging production, delaying the production of equipment and auxiliary mechanisms. Amazingly, the fact is that not one of the 50 IS-7 tanks entered the troops.

In 1949, the LKZ issued an order for 50 IS-7 tanks. However, in the same year, a resolution was adopted to cease work on all tanks weighing over 50 tons and to create a new tank, the weight of which did not fit into these restrictions. The consequence of this decision was the removal from serial production of the IS-4 and the cessation of all work on the IS-7.

A number of historians of tank building note that the military from the very beginning treated the IS-7 with a certain degree of suspicion, and over time, skepticism only intensified. Perhaps the reason for this was the failure of the IS-4 heavy tank, which had excellent booking, but too much combat weight and, as a result, poor maneuverability. Another interesting explanation for the refusal to adopt the "Object 260" concerns a change in views on future war. In the late forties and early fifties, the point of view was formed, according to which in the major wars of the near future, the rapid and massive deployment of a large number of tank units will be required. In addition, nuclear strikes in the first hours of the war could easily disable up to a third of all armored vehicles. Obviously, a heavy, unsuitable for transportation and expensive tank, Finally, the production of a new heavy tank could seriously affect the pace of construction of the mastered types. The Leningrad and Chelyabinsk plants could not cope with this task without sacrificing anything. Therefore, the Object 260 project was closed.

Although the IS-7 series was never launched, however, while working on this project, the designers had gained a wealth of experience on later models of Soviet heavy tanks, including the T-10 tank. Another Soviet heavy tank, the 60-tonne IS-4 (developed and put into production in 1947 at ChKZ after the discontinuation of the IS-3 here), turned out to be overloaded with limited operational mobility and transportability. The mass of both the IS-4 and the IS-7 exceeded the carrying capacity of most of the vehicles (railway platforms) and bridges that existed at the time (the automobile bridges simply could not stand such a heavy tank).

One of the prototypes of the IS-7 can be admired in Kubinka.

The vaunted “Royal Tiger”, with a mass comparable to the IS-7, accelerated along the highway only to 41 km / h and helplessly mated on ordinary ground. The armament of these peers (Tiger-II - December 1943, IS-7 - September 1945) is completely incomparable: the 88-mm gun versus the 130-mm gun. The aarmor form for the “heavyweights” is nothing to compare. Even his IS-7 brothers who appeared much later in weight category (American M 103 (1953, 62t.), British FV 214 “Conqueror” (1956, 66 tons) look like a timid attempt to imitate the ideal.

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Page last modified: 13-09-2021 17:23:59 ZULU