| Notes:
1) The Mark XXIII designation was apparently
given to both the quadruple (four-gun) turrets originally planned for the
Edinburgh class and to the triple (three-gun) turrets actually used on
the Edinburgh and Fiji classes. See Note 4.
2) The Mark XXII and Mark XXIII Triple
Mounts had the center gun set back 30" (76.2 cm) in order to reduce the
interference between shells in flight and to give the loading crews more
"elbow room." Triple mounts had two right-handed guns and one left-handed
gun.
3) The weight differences for the triple
mounts is primarily due to armor thickness. For the Mark XXII, Southampton
had 1 inch (2.54 cm) armor all around. Gloucester had 3.9 inch (10
cm) glacis plate armor with the rest 2 in (5.1 cm). For the Mark
XXIII, Edinburgh had 3.9 inch (10 cm) glacis plate and the rest 2 in (5.1
cm). Fiji had 2 inch (5.1 cm) glacis plate and roof, the rest was
1 inch (2.54 cm).
4) The Edinburgh class were originally
planned to carry four quadruple mountings. Testing at Shoeburyness
in early 1936 with a mockup where all four guns were equally spaced at
42" (106.7 cm) apart showed considerable shell interference and collision
problems, with the resultant large dispersal patterns. A later design
had the guns mounted as two pairs, somewhat similar in concept to the French
quad mounts. This design had each pair of guns only 27.5 inches (69.9
cm) apart and the innermost pair 46.5 in (118.1 cm) apart. This design
did not produce acceptable results and the quad project was cancelled in
favor of improved triple mountings. Delay coils were under consideration
at the time of the cancellation.
5) Many cruisers had "X" turret removed
as weight compensation for added electronic equipment. Its place
was usually taken by additional AA guns. HMS Belfast, of the larger
"Modified Town" class, was unique in keeping all four of her mountings
throughout the war and beyond.
6) The gunlayers usually followed the pointer
using hand control, changing to power elevation only for larger movements.
7) Guns were hand loaded and rammed.
8) The twin Mark XXI was a "short trunk"
design powered by a 65 HP electric motor and hydraulic pump using light
mineral oil, located on the revolving structure. The guns were individually
sleeved and runout was via compressed air. Elevation was by a swashplate
engine driving a worm gear. There were two training engines which
were usually operated together as control was better, although training
speed was faster when only one was used. Provisions were made to
allow manual training. The fore and aft turret groups had a single
magazine, with each turret having its own handling room, which was part
of the fixed structure. Charges were delivered by a single endless
chain hoist to each handling room at the rate of 16 per minute. Shells
were delivered to the handling room by another endless chain hoist at the
rate of 16 shells per minute. What this arrangement meant is that
once the ready supply of rounds from the handling rooms were used up, the
ammunition supply would have limited each three-gun turret to no more than
16 rounds per minute. From the handling room, another endless chain
for each gun carried the powder charge to the rear of the gun. Shells
were delivered vertically to the gunhouse, where a tilting bucket transferred
them to a fixed tray. From here they went to an intermediate tray
and then to the loading tray which pivoted on an arm from the cradle.
Shells were hand rammed and then charges were placed on the loading tray
and hand loaded.
9) The triple Mark XXII was a short trunk
design with similar features as the Mark XXI. The electric motor
was increased to 103 HP. These ships had a magazine for each turret
with a shell room on the same level. A handling room just below the
turret was part of the fixed structure. Dual electric powered endless
chains delivered 32 charges per minute from the magazine to the handling
room. Charges were carried by hand to crewmen in "cordite pockets"
attached to the revolving structure where they were passed by hand via
hand-ups into the gunhouse. Shells were delivered by dual hoists
to the handling room at the rate of 32 rounds per minute. Each gun
had its own shell hoist attached to the revolving structure that delivered
shells vertically to the gunhouse. Arrangements were similar to those
for the twin mounts, with the exception that the center gun had a longer
intermediate tray as it was further from the hoist than the other two guns.
10) The triple Mark XXIII was powered by
a 114 HP motor and had a completely different ammunition supply systems
as compared to the earlier Marks. These were "long trunk" with each
turret having a magazine and a handling room with a shell room located
one deck above. Charges were passed via scuttles from the magazines
to a handling room where they were loaded onto endless chain hoists.
There was one charge hoist per gun and these ran directly from the handling
room up to the gunhouse, with the charges being delivered vertically.
Each hoist could each deliver 12 charges per minute. In the shell
room, shells were passed to an electrically powered and independently-revolving
shell ring that could hold up to 56 projectiles inclined with noses upwards
and outwards. From here they were passed by hand to a loading trays
of the shell hoists. Each gun was provided with its own shell hoist
which could supply 12 shells per minute, delivering the shells vertically
to the gunhouse. Arrangements from moving projectiles to the breeches
were similar to those for the Mark XXII.
11) Gun axes were 84 in (213 cm) apart
on the Mark XXI mounting and 78 in (198 cm) apart on the Mark XXII and
Mark XXIII mountings.
12) As these guns were hand-rammed, firing
at high elevations meant that the guns would need considerable time just
to depress to the loading elevation and then elevate back into firing position.
13) The Mark XXIV was a war-time development
based upon the Mark XXII. This was to have achieved a dual-purpose
capability by increasing the maximum elevation to +60 degrees and possibly
using a new, fully-automatic 6" (15.2 cm) gun. However, the barbette
and roller path diameters were no larger than the previous triple mountings,
which would have entailed a rather cramped design. This project was
superseded by the Mark XXV which was in
turned cancelled by the end of the war. |
