Gun turret
From Wikipedia, the free encyclopedia
A gun turret is a device that protects the crew or mechanism of a projectile firing weapon and at the same time lets the weapon be aimed and fired in many directions.
A turret is usually a rotating weapon platform. This can be mounted on a fortified building or structure such as an anti-naval land battery, or on an armoured fighting vehicle, a naval ship, or a military aircraft.
Turrets may be armed with one or more machine guns, automatic cannon, large-calibre guns, or missile launchers. It may be manned or remotely controlled, and is often armoured. A small turret, or sub-turret on a larger one is called a cupola. Cupola is also used for rotating turrets that carry no weapons but instead sighting devices as in the case of tank commanders.
The protection provided by the turret may be against battle damage or against the weather, conditions and environment in which the weapon or its crew operate.
The term comes from turret - a protective position on a fortification situated on top of a building or wall, as opposed to rising directly from the ground which is a tower.
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[edit] Warships
[edit] History
Before the development of large calibre, long range guns in the middle 1800s, the classic battleship design used rows of port mounted guns on each side of the ship. Firepower was provided by a large number of guns which could only be aimed in a limited arc from one side of the ship. Due to instability, fewer larger and heavier guns can be carried on a ship. Turrets allowed the smaller number of guns to be aimed and fired on both sides of the ship and at the same time provide armoured protection to the gun crew.
One of the earliest turret gun ships was the USS Monitor, which mounted two cannons in a fully rotating armoured drum. An alternative at the time used a static drum, the barbette, inside which the gun mount rotated - the gun barrel projecting over the edge of the drum. In latter designs this was developed to have an armoured portion that sat over the gun and the edge of the barbette leading to the term "hooded barbette".
The largest warship turrets were in World War II battleship where a heavily armoured enclosure protected the large gun crew during battle. The calibre of the main armament on large battleships was typically 12" / 30 cm to 18" / 45cm. The secondary armament of battleships was typically 6" / 15cm. Smaller ships typically mounted guns from 3" / 75mm upwards.
[edit] Design
The rotating part of a battleship turret is the "gunhouse" where the guns are loaded. Below the gunhouse are the loading hoists that bring ammunition up from the magazines to the gunhouse. The handling equipment and hoists can be complex arrangements of machinery and labour intensive. They have to take the shells and propelling charges from the magazine into the base of the turret. There they have to be lined up with the hoists, which are fixed in orientation to the guns. The hoists then lift the ammunition up to the gunhouse where the shells and the appropriate charge is mechanically loaded into each gun breech. It was not until the last of the rotating drum designs was phased out that the hooded barbette arrangement - which is the style associated with modern warships - took the name "turret". The barbette is armoured down to where it reaches the main armoured deck of the warship. The gunhouse is not attached to the ship in any way, but rides on rollers; if the ship were to capsize, the gunhouses would fall out.
[edit] Modern turrets
Many modern surface warships have turrets with large calibre guns, although the greatest calibres are now less than 6" / 15cm and the guns are less important to ships with modern missile systems and fewer in number. These turrets are often just covers for the gun mounting equipment, and are made of light un-armoured materials such as fibreglass. Modern turrets are often fully automatic with no humans working inside them.
[edit] Naming
On board warships, each turret is given an identification. In British use, these would be letters: "A," "B," "C," etc. for the turrets from the front of the ship backwards, and letters near the end of the alphabet (i.e., "X," "Y," etc.) for turrets in the rear of the ship. Mounts in the middle of the ship would be "Q," "R," etc. In one instance (HMS Agincourt), the battleship's turrets were named "Monday," "Tuesday," etc. up to "Sunday." In German use, turrets were generally "A," "B," "C," "D," "E" going backwards from stem to stern. Usually the phonetic alphabet was used on naming the turrets, e.g. "Anton", "Bruno", "Caesar," "Dora" as on the German battleship Bismarck.
[edit] Land fortifications
Image:Maginot2ix.jpg Gun turrets have been placed in static, land fortifications such as the Maginot Line forts in France and particularly in coastal artillery defences such as Fort Drum, the "concrete battleship", near Corregidor Philippines.
[edit] Aircraft
At first, guns on aircraft were either fixed in orientation or mounted on simple swivel mounts. The latter evolved into the Scarff ring, a rotating ring mount which allowed the gun to be turned to any direction with the gunner remaining directly behind it. As aircraft flew higher and faster, the need for protection from the elements led to the enclosure or shielding of the gun positions. The first bomber in the Royal Air Force to carry a power operated turret was the Boulton Paul Overstrand which first flew in 1933. The Overstrand had a single turret, which was at the front of the bomber fitted with one machine gun. In time the number of turrets carried and the number of guns mounted increased. RAF heavy bombers of the Second World War typically had 3 powered turrets, with the rear one - the "Tail End Charlie" position - mounting four 0.303 inch machine guns.
The UK tried the concept of the "turret fighter" in planes such as the Boulton Paul Defiant where the sole armament was in a turret mounted behind the pilot rather than in fixed positions in the wings. Though the idea had some merits in attacking bombers, it was found to be impractical when dealing with other fighters as the weight and drag slowed the aeroplane. The defensive turret on bombers fell from favour with the advent of the jet age, though the Boeing B-52 jet bomber and many of its contemporaries featured a tail mounted barbette - a form of turret but with more limited field of fire. However like other turrets these were soon phased out to reduce manpower needs as well as to increase payload and speed.
Aircraft carry their turrets in various locations:
- "dorsal" - on top of the fuselage
- "ventral" - underneath the fuselage
- "rear" or “tail” - at the very end of the fuselage
- "nose" - at the front of the fuselage
- "chin" - below the nose of the aircraft
[edit] Armoured fighting vehicles
In modern tanks the turret is armoured for crew protection and rotates a full 360 degrees carrying a single large-calibre tank gun, typically in the range of 105 mm to 125 mm calibre. Aiming machine guns may be mounted inside the turret. The turret houses two or more crewmen, typically a tank commander, gunner, and often a gun loader.
For other armoured fighting vehicles, the turrets are equipped with other weapons dependent on role. An infantry fighting vehicle may carry a smaller calibre gun or an autocannon, or a anti-tank missile launcher, or a combination of weapons. A modern self-propelled gun mounts a large artillery gun but less armour. Lighter vehicles may carry a one-man turret with a single machine gun.
