Oscillating turret
Encyclopedia
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Armoured fighting vehicle
An armoured fighting vehicle is a combat vehicle, protected by strong armour and armed with weapons. AFVs can be wheeled or tracked....
s, both tank
Tank
A tank is a tracked, armoured fighting vehicle designed for front-line combat which combines operational mobility, tactical offensive, and defensive capabilities...
s and armoured cars. The turret is unusual in being made of two hinged parts. Both elevation
Elevation (ballistics)
In ballistics, the elevation is the angle between the horizontal plane and the direction of the barrel of a gun, mortar or heavy artillery. Originally, elevation was a linear measure of how high the gunners had to physically lift the muzzle of a gun up from the gun carriage to hit targets at a...
and recoil
Recoil
Recoil is the backward momentum of a gun when it is discharged. In technical terms, the recoil caused by the gun exactly balances the forward momentum of the projectile and exhaust gasses, according to Newton's third law...
rely on the upper part of the turret moving relative to the lower part.
Oscillating turrets have only rarely been used. Their only widespread use was on two French designs, the AMX-13
AMX-13
The AMX-13 is a French light tank produced from 1953 to 1985. It served with the French Army and was exported to over twenty-five other nations...
light tank and the Panhard EBR
Panhard EBR
The Panhard EBR is a light armoured car designed by Panhard for the French Army and later used across the globe, notably by the French Army during the Algerian War and the Portuguese Army during the Portuguese Colonial War in Angola, Mozambique and Guinea-Bissau.The EBR is an 8x8 wheeled...
armoured car. Both of these used the advantages of the oscillating turret to mount a relatively heavy gun
Tank gun
A tank gun is the main armament of a tank. Modern tank guns are large-caliber high-velocity guns, capable of firing kinetic energy penetrators, high explosive anti-tank rounds, and in some cases guided missiles. Anti-aircraft guns can also be mounted to tanks.-Overview:Tank guns are a specific...
on a lightweight chassis.
Design
The turret is formed from upper and lower parts, joined by a swinging hinge. In appearance, the gap between these two parts is covered by a distinctively visible rubber or canvas bellows.The gun itself is fixed rigidly to the upper part of the turret. Elevation
Elevation (ballistics)
In ballistics, the elevation is the angle between the horizontal plane and the direction of the barrel of a gun, mortar or heavy artillery. Originally, elevation was a linear measure of how high the gunners had to physically lift the muzzle of a gun up from the gun carriage to hit targets at a...
of the gun, i.e. aiming for range, is achieved by tilting the entire upper part of the turret. Traverse is achieved conventionally, by rotating the turret.
Since the gun barrel is attached rigidly to the turret, the entire upper part of the turret recoil
Recoil
Recoil is the backward momentum of a gun when it is discharged. In technical terms, the recoil caused by the gun exactly balances the forward momentum of the projectile and exhaust gasses, according to Newton's third law...
s when fired. There is no mantlet
Gun mantlet
A gun mantlet is an armour plate or shield attached to an armoured fighting vehicle's gun, protecting the opening through which the weapon's barrel projects from the hull or turret armour and, in many cases, ensuring the vulnerable warhead of a loaded shell does not protrude past the vehicle's...
as such and the barrel and breech retain their position in the upper turret. Recoil energy is absorbed by the usual oleo-pneumatic dampers, but these are mounted between the turret halves, rather than linearly alongside the gun.
Advantages
There are two major advantages, smaller turret size and simpler fitment of an autoloaderAutoloader
An autoloader or auto-loader is a mechanical aid or replacement for the personnel that load ordnance into crew-served weapons, such as tanks and artillery...
, although these benefits were outweighed in practice by the disadvantages, which included auto-loaders not living up to their promised performance.
Heavy tanks and the AMX-50
Main battle tank
A main battle tank , also known as a battle tank or universal tank, is a tank that fills the heavy direct fire role of many modern armies. They were originally conceived to replace the light, medium, heavy and super-heavy tanks. Development was spurred onwards in the Cold War with the development...
gun. In the 1950s, tanks were rapidly growing more heavily armed, larger and heavier. Western armed forces were trying to catch up with the increasingly formidable Soviet tanks, such as the T-55
T-55
The T-54 and T-55 tanks were a series of main battle tanks designed in the Soviet Union. The first T-54 prototype appeared in March 1945, just before the end of the Second World War. The T-54 entered full production in 1947 and became the main tank for armored units of the Soviet Army, armies of...
. Weight was the main problem, particularly where this then required extra engine power or a stronger transmission. As the thickest armour is generally on the turret, reducing turret size appeared to be a worthwhile goal.
Size may be reduced because the non-elevating gun breech does not need to move up and down inside the upper turret. Working space thus does not need to be allowed for it above or below the breech, space that is normally wasted in conventional turret designs. In particular, the oscillating turret design is particularly shallow above the breech, allowing for a low turret silhouette, a considerable advantage.
This was the justification for the first oscillating turret, that of the French AMX-50 medium or heavy tank in the 50 tonnes class. This used first a 90 mm, then 100 mm, gun in an oscilllating turret, primarily to save weight. The final 120 mm version first reverted to a conventional turret, but then used another oscillating design, the Tourelle D. However the need to elevate the gun still requires room for the breech to be lowered into the lower turret. This has tended to produce oscillating turret designs with a high gun axis relative to a conventional turret, even where the turret height is otherwise shallow.
One problem was that the armour of a turret is primarily in the front face of the turret and this was not made any smaller in the AMX-50 design, the turret of the 120 mm version being so tall as to be reminiscent of the WW2 Challenger
Cruiser Mk VIII Challenger
The Tank, Cruiser, Challenger was a British tank of World War II. It mounted the 17 Pounder gun on the Cromwell chassis to add heavier anti-tank firepower to the cruiser tank units....
, the turret being a whole foot taller than the contemporary and comparably armoured Conqueror
Conqueror tank
The FV 214 Conqueror, also known as "Tank, Heavy No. 1, 120 mm Gun, Conqueror" was a British heavy tank of the post-war era. It was developed as a response to the Soviet Joseph Stalin IS-3 heavy tanks and carried a larger 120 mm gun compared to the 20-pounder gun carried by its peer the...
. The AMX-50 grew progressively heavier and although it might have proved a capable heavy tank by 1950s standards, this whole class of slow-moving AFV was becoming outdated by the development of lightweight anti-tank guided missile
Anti-tank guided missile
An anti-tank missile , anti-tank guided missile , anti-tank guided weapon or anti-armor guided weapon is a guided missile primarily designed to hit and destroy heavily-armored military vehicles....
s in the 1960s and so the project was abandoned.
Light tanks
Whilst the oscillating turret was unsuccessful for the heavy tank, it proved more successful in allowing light tankLight tank
A light tank is a tank variant initially designed for rapid movement, and now primarily employed in low-intensity conflict. Early light tanks were generally armed and armored similar to an armored car, but used tracks in order to provide better cross-country mobility.The light tank was a major...
s and armoured cars to carry an unusually heavy main gun of 90 mm. In French doctrine, light reconnaissance vehicle
Reconnaissance vehicle
A reconnaissance vehicle, also known as a scout vehicle, is a military vehicle used for forward reconnaissance.- Design :Smaller caliber weapons help reduce the vehicle's profile and noise signatures...
s were heavily armed and expected to also fulfil a role in defending the flank
Flank
Flank may refer to:* Flank, the side of either a horse or a military unit*Flanking maneuver in military tactics* Flank , the waveform edge formed when a signal goes high or low...
s of a main force. They were not expected to act as tank destroyer
Tank destroyer
A tank destroyer is a type of armored fighting vehicle armed with a gun or missile launcher, and is designed specifically to engage enemy armored vehicles...
s though, and so a heavy-calibre but relatively low velocity gun with high-explosive shells was effective in their role.
To give an additional anti-tank capability to the AMX-13, it was later fitted with four SS.11
SS.11
SS.11 is the designation of the Nord Aviation MCLOS wire-guided anti-tank missile. In American service the missile was designated the AGM-22. The missile entered service with the French Army in 1956. Production of the SS.11 ceased some time in the 1980s but in 1978 168,450 missiles had been produced...
missiles on a turret-front rack.
Auto-loading
As the gun remains fixed relative to the upper turret, even during recoil, it is easier to install an ammunition autoloaderAutoloader
An autoloader or auto-loader is a mechanical aid or replacement for the personnel that load ordnance into crew-served weapons, such as tanks and artillery...
than for a conventional turret, where the gun must return to a fixed elevation for reloading. The French design used two six-round rotating magazines, allowing a high rate of fire and also a selection of two ammunition types. The disadvantage was that once the magazine ready capacity was used, reloading of the magazines was a slow process that could not be carried out under fire. For the AMX-13
AMX-13
The AMX-13 is a French light tank produced from 1953 to 1985. It served with the French Army and was exported to over twenty-five other nations...
, this reloading had to be carried out from outside the vehicle.
As was so often the case with autoloaders though, their complexity was their downfall. The 120mm for the AMX-50 was simply unreliable, due to the weight of the ammunition round.
AFVs fitted with oscillating turrets
French- AMX-13AMX-13The AMX-13 is a French light tank produced from 1953 to 1985. It served with the French Army and was exported to over twenty-five other nations...
– Widely used light tankLight tankA light tank is a tank variant initially designed for rapid movement, and now primarily employed in low-intensity conflict. Early light tanks were generally armed and armored similar to an armored car, but used tracks in order to provide better cross-country mobility.The light tank was a major... - AMX-50 – Heavy tank, prototypes only
- Panhard EBRPanhard EBRThe Panhard EBR is a light armoured car designed by Panhard for the French Army and later used across the globe, notably by the French Army during the Algerian War and the Portuguese Army during the Portuguese Colonial War in Angola, Mozambique and Guinea-Bissau.The EBR is an 8x8 wheeled...
– Armoured car
Austrian
- SK-105 KürassierSK-105 KurassierThe SK-105 Kürassier is an Austrian light tank armed with a rifled 105 mm gun in an oscillating turret. It is estimated that over 700 have been produced.-History:...
– Used the 105 mm FL-12 turret of the AMX-13AMX-13The AMX-13 is a French light tank produced from 1953 to 1985. It served with the French Army and was exported to over twenty-five other nations...
Jane's Weapon Systems, 1977, p. 295
United States
- T54E1 Tank, Heavy, 105mm Gun – Two prototype vehicles with 105mm guns and autoloaders were constructed on the M48 tankM48 PattonThe M48 Patton is a medium tank that was designed in the United States. It was the third and final tank to be officially named after General George S. Patton, commander of the U.S. Third Army during World War II and one of the earliest American advocates for the use of tanks in battle It was a...
chassis. They were constructed around 1952 by United Shoe Manufacturing. One T54 had a conventional turret, the other T54E1 an oscillating turret.- T57 Tank, Heavy, 120mm Gun – A single prototype was constructed in the 1950s on a T32 heavy tank chassis, with a 120mm gun in an oscillating turret.Haugh, 1999, p. 67