Australian Military Vehicles Research

Centurions Turret development
 

With the recent release of the AFV Centurion, a high level of interest has focused on Centurions, particularly on the turrets. People are using the terms Mk 3 and Mk 5 turret to define certain groupings of features. This is incorrect! The British Army never differentiated Centurion turrets by name. There AFV nomenclature system only covered matters related to vehicle performance, armament systems, protection and engines.

The following is my attempt to develop a framework in which to analyse Centurion turrets. It is not official, but is based on the production period of the vehicle in which we know certain groupings of features and fittings were used.

According to Simon Dunstan, production of the Centurion Mk. 3/5 medium tank ran from 1946 to 1958, during which 2,833 Mk. 3 tanks (1946-56) and 221 Mk. 5 tanks (1955-58) were manufactured. Three facilities were responsible for Centurion final assembly: Vickers Armstrong and the Royal Ordnance Factories at Leeds and Dalmuir. The fact that three facilities and a number of sub contractors were responsible for production increases the number of minor permutations. This is particulary applicable to what i refer to as the 'Transition' period vehicles.

The turret comprised three externally visible components, the body, the top plate and the fittings. The turret body design of the Centurion Mk 3 was identical to its predecessor, the 17 pounder armed Mk 2. A single casting, it was produced by a number of sub contractors, then delivered to the main production line for final assembly and fitting to the hull. Due to this the finishes of the castings varied considerably from relatively smooth to quite pebbly.

Welded on top of the turret body was a top plate. This provided the roof of the turret, onto which a number of turret fittings were placed. These include the crew commanders vision cupola, the gunners periscopic sight, loaders access hatch, 2-inch bomb thrower, loaders periscope and over pressure valve.

Early production tanks
Early production vehicles cover Centurion Mk. 3 manufactured during 1947-50. Approximately 500 tanks were manufactured during this period.

On manufacture, hulls of this period were distinguishable by the top loading hull stowage bins. Most were retrospectively replaced with side loading stowage bins later in the vehicles service life.

Turret bodies of early production vehicles were cast to the 39887T design. This refers to the drawing number and was frequently cast into the turret body sides. 39887T turret bodies are identifiable by the large, circular maintenance access hatch at the turret rear. This was inherited from the earlier Centurion Mk. 2 where it had been necessary to fully withdraw the 17 pr main armament to replace the barrel. The hatch was unnecessary on the Centurion Mk. 3 as the 20 pr barrel was designed to unscrew from the breech and could be replaced without withdrawing the whole weapon. The hatch was generally welded shut to improve the ballistic integrity of the turret as it was unnecessary to the operation and servicing of the tank.

The top plate was welded flush to the sides of the turret body. Other turret features of this period were the:
• Combined loader’s periscope and 2-inch bomb thrower
• Inwards-facing loader’s hatch

The Tamiya 1/35 and 1/25 scale kits are early production vehicles.

Transition production tanks
The term transition period refers an approximately 12-month period of manufacture covering 1950 / early 1951, during which a number of design changes were progressively introduced on the various Centurion production lines. These changes were driven by user feedback, technological advances and manufacturing improvements.

Many of these design changes effected turret fittings and occurred under UK (probably FVRDE) Authority 8125. This stated:
‘Loader’s escape hatch repositioned. New periscope housing, also repositioned. New bomb thrower housing , also repositioned.’

Thus, the inwards facing loaders hatch was rotated 180 to be parallel with the edge of the turret top plate. The loaders periscope was repositioned within an armoured housing on the top face of the turret body. The previous combined bomb thrower and loaders periscope housing was replaced with a single housing holding the 2-inch bomb thrower.

During the transition period the 40796T turret body design was introduced onto the production line. This turret body design deleted the rear turret maintenance access hatch and saw the turret top plate welded on top of the turret body, rather than flush with it as on its predecessor. It also featured an aperture for the relocated loaders periscope.

The design and production changes were not introduced systematically on either Centurion production line. This resulted in vehicles produced during this period displaying a range of new and old turret features.

Mid production tanks

The mid-production period covers Centurions manufactured circa-1951 to 1954. This saw the culmination of the design changes undertaken during the transition period resulting in the standardisation of turret production features between the two manufacturers.

Tanks of this period are characterised by turrets featuring the 40796T turret body with a raised top plate. On the top plate the loaders hatch was repositioned parallel with the side of the top plate. The earlier combined loaders periscope and the 2-inch bomb thrower were deleted and in its place a redesigned 2-inch bomb thrower was fitted. The loaders periscope, removed from the top plate was relocated to a redesigned housing on the forward face of the turret body.

Identified features are:
• No rear escape hatch.
• Relocated loaders hatch to be parallel with the side of the top plate.
• Relocated loaders periscope to the upper forward face of the turret body
• Replacement of the earlier loaders periscope with a 2 inch bomb thrower.
• Turret air pressure valve and armoured ring.
• Top plate welded in a raised position above the turret body.

Late production tanks
Late production Centurions cover those vehicles manufactured between 1954 and 1956. This includes the end of Centurion Mk. 3 production and all Centurion Mk. 5 production.

Inheriting the turret design and fittings of the mid production vehicles, late production tanks are identifiable by production line changes to the over pressure valve and 2-inch bomb thrower. The over pressure valve and its armoured ring were removed and the remaining aperture covered by a blanking plate. An amended top plate deleted the 2-inch bomb thrower and its housing.
Identified features are:

1. No rear escape hatch.
2. Relocated loaders hatch to be parallel with the side of the top plate.
3. Relocated loaders periscope to the upper forward face of the turret body
4. Removal of the earlier loaders periscope aperture.
5. Replacement of the air pressure valve and armoured ring with a blanking plate.
6. Top plate welded in a raised position on top of the turret body.

The AFV Club Centurion displays these features.