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Colossus had two turrets, each carrying two 12 inch rifled breech loading guns of 45 tons. This section shows how the guns were arranged within the turret, and gives an overview of the loading process (or "drill").

Each turret rested on a ring of rollers. The turret base rode on these rollers, which were tapered to ensure the turret remained central.



The beams that carried the guns were connected in a frame with the recoil cylinder in between. The frame was pivoted at the front, so that the guns could be elevated and depressed with the smallest cutout in the turret frontal armour. Hydraulic elevation rams were fitted to the centre of the turret base and these elevated the frames.

The hydraulic systems in Colossus used plain water as the hydraulic medium.



The guns were 12 inch Mk IV of 45 tons, with a length of 25 calibres (25 feet). The gun barrels were connected to a slide by two straps, thus dispensing with several hundred years of gun manufacturing tradition – no trunnions. This arrangement allowed the guns to be mounted closer together.[2]

The slides were connected to pistons that moved within the recoil cylinder. In this way, the recoil cylinder could be used to dampen and slow the recoiling guns as the slide leapt backward.



The loading equipment is now shown (right). External to the turret you can see the two rams that can be raised into line with the guns when elevated to the reload position of 13 degrees. The internal reloading frame and saddles are visible, mounted at the rear of the turret.

The guns, therefore, could only be reloaded when they were trained to line up with the loading rams: 90 degrees on the beam for the starboard turret, and 85 degrees for the port turret.



The image above shows the port guns in their reloading position, trained to Red 85 degrees. The guns are fully run in (retracted) and are elevated to 13 degrees.

The external loading rams are raised. In the sister ship to Colossus, HMS Edinburgh, loading rams were fixed in the raised position.

The armour plating base of the turret is also depicted in this image. Two access holes cut in the armour at the rear of the turret allow the loading rams access. Although not shown, there may also have been hatches to close the holes when not actually loading.

The armoured turret base also carried gearing that connected to gear wheels driven by two hydraulic turning engines situated in the bunker space below. It is probable that the turret could be trained through 360 degrees in about one minute.

(double-click the image to right to see the engine in action)

(c) 2008 Rob Brassington, all rights reserved