IS-2 Heavy Tank

 IS-2 Heavy Tank

IS-2 tanks in Vyborg 1944

 

Striving to create a new heavy tank that would retain the best features of the KV tanks, but would be lighter in weight and easier to manufacture, the Special Design Bureau No. 2 (SKB-2) at the Chelyabinsk Kirov Plant started intensive design and construction work from March 1942 . The result was over a dozen designs for tanks and other vehicles, the most important being the KV-1s, KV-8, KW-85 and KW-13.

Experimental tank IS-85 later re-designated as IS-1 Plant 100 Chelyabinsk, July 1943

 

 In the fall of 1942, the head of SKB-2 Ż. Kotin started designing a new heavy tank. From the KV-13 tank, a fairly carefully profiled hull made of cast elements, a new efficient and rarely failing drivetrain, an effective engine cooling system and a modernized chassis were taken over. The tank was named Josif Stalin (abbreviated as IS) and from the beginning it was designed in two versions with different armament. A vehicle armed with a 76.2 mm cannon received the factory designation "IS-1 model 1 tank, Object 2331S", and with a 122 mm howitzer - "IS-2 model 2 tank, Object 2341S".

IS-2 in Poznan February 1945

 

At the same time, in April 1943, further prototypes of IS tanks were prepared, but armed with 85 mm guns. Shortly after the tests at the training ground in Gorokhovets on August 7, 1943, the State Defense Committee adopted a heavy IS tank armed with an 85 mm D-5T cannon. It received the designation IS-1. From October 1943 to January 1944, 107 tanks of this type were produced. Test firing of 85 mm cannons at a captured PzKpfw tank. VI "Tiger" and the conclusions of the Battle of Kursk showed the limited effectiveness of guns of this caliber. Therefore, on September 4, 1943, the State Defense Committee ordered the installation of more powerful cannons in IS heavy tanks, but there was no suitable gun at that time. After a series of theoretical calculations, Z. Kotin and F. Petrov came to the conclusion that the IS tank should be armed with a 122 mm gun. 

IS-2 and Germany 1945

 

Before such a gun existed in the form of a prototype, on October 31, 1943, Stalin and the State Defense Committee decided to adopt the IS tank with a 122 mm cannon. F. Petrov's team built the first experimental copy of the 122 mm D-25T gun only two weeks later (November 12, 1943). The prototype of the tank with the new cannon, called IS-122 (Object 240), was completed at the end of November 1943. The results of the test firings were satisfactory, although it should be noted right away that the gun was not a miracle of technology. In terms of armor penetration, it was comparable to the German 88 mm Pak 43 gun, with much better ballistics and firing more modern ammunition. From December 1943 to December 1945, 4,392 IS-2 heavy tanks were produced (in April 1944, IS tanks with a 122 mm gun were designated as such).

Destroyed IS-2 of the 6th Independent Guards Heavy Tank Regiment, Romania May 1944

The hull of the IS-1 tank was welded from cast and rolled armor plates. The armor thickness of the front part of the hull was: bottom plate 100 mm, top plate 60 mm, turret base 120 mm, sides 90 mm, rear 60 mm, top plate and bottom 20-30 mm. In the front part of the hull, on the right side, there was a stationary 7.62 mm DT machine gun, operated by a loader, in the longitudinal axis of the tank. The combat weight of the tank was 44 tons

The tower was cast. It had a streamlined shape and all edges were rounded. The thickness of the turret armor was variable. In the front part it was 100 mm, sides 90 mm, rear 60 mm, ceiling 30 mm.

In the front part of the hull, in the driver's compartment, in the center was the driver-mechanic. It observed the terrain through a large observation slit in the small forward hatch and two observation periscopes. To its left and right were the two main fuel tanks. Access to the control compartment was possible only through hatches in the turret.

A column of IS2 tanks 1945

The IS-1 tank was powered by a 12-cylinder water-cooled W-2-IS (W-2-10) 520 hp (382.2 kW) diesel engine at 2,000 rpm. The total capacity of the fuel tanks was 520 dm³. Four additional tanks, carried on special handles on the sides of the rear part of the hull, contained 300 dm³ of fuel.
The landing gear consisted of 10 double steel road wheels, a pair of idler wheels at the front and a pair of drive wheels at the rear. The road wheels were independently suspended on torsion bars. The upper part of the track was supported by three double rollers. The track width was 650 mm. The IS-2 tank retains all the basic structural elements and equipment of the IS-1 tank, with the exception of the turret with armament and the chassis (12 road wheels). Of course, some changes were made in the course of production, modernizing the hull structure and replacing some instruments with newer ones. The IS-2 tank had a slightly modernized turret in comparison to the IS-1, in which the 122 mm D-25T gun was placed. Some of the tanks were mounted on a special base, mounted on the commander's turret, wkm DSZK wz. 1938 cal. 12.7mm. It was to be used mainly for combating air targets. The ammunition supply for the gun was only 28 rounds, for the DT-2331 machine gun, and for the DSZK-250 machine gun. The gunner had a 10T-17 telescopic sight and a PT4-17 periscope sight. The latter was replaced in the spring of 1944 by the MKIV rotary periscope. In turn, the commander received the TPK-1 observation device. Subsequently, the 10T-17 sight was replaced sight TSZ-17. 

The IS-2 tank turned out to be exceptionally long-lived. In the years 1944-1947, projects of a dozen or so heavy tanks were created in the USSR, which were to replace the IS-2. However, these tanks were too complicated, expensive to produce and expensive to operate, so the war veteran was never replaced. The IS-2 tank was constantly modernized. The IS-2M tank, with significantly improved combat and technical characteristics, remained in service with the Soviet Army until the 1980s. It was officially withdrawn from service by order of the Minister of Defense of the Russian Federation only in 1995.

On the chassis of the IS heavy tank, huge numbers were produced (in the period 1944 - September 1945, a total of as many as 4,635 copies, and until the end of production in 1947 - 6,102 copies.

AC1 Sentinel Fast Tank

 Australia

AC1 Sentinel fast tank

After the outbreak of war in Europe on September 1, 1939, the Australian government asked Britain to supply various types of armaments, including tanks. It was assessed that the threat could be Japan, which does not hide its aggressive plans towards Australia and the entire region of Southeast Asia.

Preserved AC I on display at the RAAC museum – Credits: Wikimedia Commons

 

 In the autumn of 1939, Britain had no surplus armaments, especially modern ones, and could not help its dominions. In addition, in June 1940, after the fall of France and the defeat of the British Expeditionary Force, all its armor and heavy weapons, then the best in the British army, remained on the beaches of Dunkirk. For Australia, the only real possibility to quickly increase its defense potential was to place orders for weapons in the USA. In 1940, only the now obsolete M2 light tank was available. It wasn't until 1941 that the production of the new M3 General Stuart light tank began and it was shipped to Australia. 

The AC I under construction at the Chullora tank annex. (Source:- Australian War Memorial)

 

 

At the same time, a group of engineers was working on a tank project that was supposed to meet the requirements of tactical-techn. specified by the General Staff of the Australian Army in November 1940. In order to speed up the design work, it was planned to use components of the M3 medium tank, which was introduced into production in the USA in 1941. Plans to start its license production in Australia fell through, so the design of the tank was resumed based on own forces and local industrial potential. The new tank was designated AC1 (Australia Cruiser 1), meaning it was supposed to be a fast tank. The hull of the prototype was ready in October 1941, and the entire vehicle in January 1942. The tests, research and improvement of the structure lasted over a year. The tank was named Sentinel and its serial production began in August 1942 at Chullon Tank Assembly in New South Wales. It was a unique achievement because from the time the order was placed only 22 months had passed and Australia had no experience in tank design or production.

RAAC tank crew on their new Australian Cruiser Tank AC1 Sentinel

By July 1943, 66 AC1 Sentinel tanks had been produced, but then the better armed and armored M3 and M4 tanks, purchased in the USA, were already entering the armament of the Australian army. The 40 mm gun was ineffective against most Japanese tanks and was not suitable for fighting against infantry and fortifications (no high-explosive shells). At that time, the AC3 version was developed, armed with an 87.6 mm (25-pounder) field gun, manufactured in Australia. Unfortunately, it was not very suitable for fighting tanks. In this situation, in mid-1943, Australian designers equipped the AC tank with an anti-tank gun. 76.2 mm (17-pounder). However, the production of the tank - designated AC4 - was not undertaken because deliveries of equally good, mass-produced American tanks continued.

Source: https://www.reddit.com/r/interestingasfuck/comments/s8a1c8/the_aci_sentinel_an_australian_tank_design_meant/

 

The AC1 Sentinel fast tank had a hull made of joined cast parts. In the left side wall of the hull, between the carriages of the road wheels and the upper part of the track, there was an escape hatch. The thickness of the hull armor ranged from 25 to 65 mm. Combat weight - 28.45 t. The turret of a characteristic, slightly flattened, oval shape was cast. The thickness of the frontal part of the armor and armament yokes was 65 mm. In the front part of the hull, on the left, sat the driver, and next to him, on the right - the gunner who operated the front, hull-mounted 7.7 mm Vickers machine gun. They had rotating observation periscopes. The driver could also observe the terrain through a rectangular hatch in the frontal armor or through the observation slit. Two headlights were placed on the fenders. Two towing hooks were attached to the front and rear hull plates.

Sentinel AC1

The three-person turret could be rotated by an electric motor, powered by a generator driven by the tank engine, or it could be manually rotated in emergency mode. In the right part of the turret there was a loader's station, which also operated a radio station mounted at the rear of the turret. In the left part of the turret there was a gunner's station, and behind him - the tank commander. The commander had a small observation turret with periscopes. There was only one two-piece hatch in the turret (in the commander's turret).

Source: www.tankarchives.ca

The main armament of the tank was placed in the turret - the 40 mm OQF Mk IX cannon and the 7.7 mm Vickers machine gun coupled with it. The cannon yoke was very characteristic, clearly protruding in relation to the turret. 140 cannon rounds were carried in the tank. The AC1 Sentinel fast tank was powered by three 8-cylinder, carbureted, liquid-cooled Cadillac engines mod. 75 with 117 hp (86 kW) each. The gearbox had four forward ratios and one reverse ratio. The maximum speed on the roads was high - 48 km/h.

Source: www.tankarchives.ca

The undercarriage (similar to the Hotchkiss H-35 tank) consisted of 12 twin road wheels, a pair of idler wheels at the rear and a pair of driving wheels at the front. The road wheels were grouped in pairs in 6 bogies amortized with spring springs. The road wheels and tension wheels had rubber bandages. The upper part of the track rested on three supporting rollers. The track width was 419 mm.

• Crew: 5
• Weight: 28.45 tons 
• Dimensions: length 6.325 m, width 2.77 m, height 2.565 m 
• Engine: three 8-cylinder, carburettor, water-cooled, Cadillac mod. 75 with 117 hp (86 kW) 
• Performance: max. road speed 48 km/h, max. range 320 km
• Overcome obstacles: fords 1.2 m, vertical walls 0.6 m, ditches 2.8 m 
• Armament: 1x 40mm Mk IX gun, 2x 7.7mm Vickers