| Notes:
1) These guns were first tried on HMS Mackay
in a clumsy CPXIII mounting which allowed +60 degrees elevation.
This particular mounting was removed and then fitted to HMS Bulldog.
This mounting was not adopted for British service, but it appears to have
been used on ships built for Argentina, Chile and China. This mounting
had a 68 inch (173 cm) trunnion height making it difficult to load at low
angles. 55 inches (140 cm) is considered the maximum desirable trunnion
height for a 50 - 55 lbs. (22.7 - 24.9 kg) projectile.
2) The CPXVII mount achieved +40 degree
elevation by having a 14" (35.6 cm) gun well with a removable cover which
allowed the breech end to go below the deck level. With the cover
in place, the mounting could only elevate to 29.5 degrees. "An obviously
makeshift design, one wonders how it managed to make it into a service
weapon let alone off the drafting table" - John Campbell in "Naval Weapons
of World War Two."
3) The CPXVIII mounting had the balance
weight repositioned above the loading tray which allowed +40 degree elevation
without the necessity of the gun wells. These mountings used a circular
base plate that was directly bolted to the weather deck and were supported
underneath by a ring-shaped bulkhead called the "gun support." A
lower roller path was machined on the base ring with a similar upper roller
path machined into the underside of the mounting turntable platform.
A ring of horizontal roller bearings in these paths held the weight of
the mounting. At the center of rotation a light cage held vertical
thrust roller bearings and the electrical cabling for fire control and
lighting ran up through this cage.
4) The CPXIX twin mounting was the first
British power mounting specifically designed for destroyers. These
guns had a trunnion height 13" (33 cm) higher than the single mountings.
This required raising the wheelhouse to enable to helmsman to see over
the gun shields. It also made loading the weapons at low elevations
more difficult. The gun axes were 38 in (96.5 cm) apart.
5) The Tribal class had their four CPXIX
mountings split in two groups, each powered by a 140 HP steam turbine and
oil hydraulic pump. The J, K and N classes had a 70 HP electric motor
and pump on each individual mounting. Elevation was by a hydraulic
motor driving pinions on a common shaft which in turn drove arcs fixed
to the gun cradles while training was by a hydraulic motor with a similar
worm gear. For unknown reasons, "X" mounting on the "J" class was
originally set up such that the mid-training position was dead ahead.
This meant that this stern mounting on these ships could not bear directly
astern and that having to train from the port quarter to the starboard
quarter meant that the gun had to slew "the long way round." Early
in the war, the mountings were modified to move the mid-train position
to the more normal dead astern position. The other destroyers with
these mountings were all completed with the stern mountings mid-train position
at dead astern.
6) In order to improve their AA capabilities,
four of the "O" class destroyers received
4"
(10.2 cm) guns in lieu of 4.7" (12 cm) guns. The "S" class destroyer
HMS Savage did not receive these 4.7" (12 cm) guns as did her sisters,
as she was used as a test bed for 4.5" (11.4
cm) guns on destroyers.
7) The mountings used in LCG (L) 3 class,
Barracuda and Rochester Castle are unknown.
8) The CPXXII single mounting had a spring-operated
rammer, a single-shell fuze setting machine and a shorter recoil stroke.
These improvements also allowed a higher elevation than in previous mountings,
but it was still inadequate for AA purposes. The spring-operated
rammer was interesting. The rammer spring was cocked by the recoil
of the weapon. When the loading tray was pushed across into line
with the chamber, the spring tripped automatically and operated the ramming
head. This moved the shell and cartridge into the breech while at
the same time cocking a smaller "rammer return spring." When the
loading tray was moved outwards, ready for reloading, the return spring
moved the rammer head to the rear. The automatic tray operation was
a large improvement over the earlier hand worked versions, but it needed
careful adjustment to ensure that the rammer head tripped at the proper
time. These mountings may be easily distinguished from earlier ones
by the "raked-back" nature of their front shields, a modification necessitated
by their higher maximum elevations. The "X" position for ships with
this mounting had modified stops which allowed a total training arc of
about 580 degrees. This is why many photographs of these ships show
this mounting stowed pointing dead ahead.
9) Many of the Tribal class had "X" mounting
removed and a twin 4"/45 (10.2 cm) HA/LA mounting
installed in its place in order to increase their anti-aircraft capabilities.
For similar reasons, the Abdiel class had their three 4.7" (12 cm) twin
mountings replaced with three twin 4"/45 (10.2
cm) HA/LA mountings. Destroyers of the A-I classes reconfigured
as ASW escorts had "A" and "Y" guns removed in order to ship more depth
charges and to add a Hedgehog launcher.
10) Submarine CPXVI mounts were all replaced
during the 1930s with standard 4"/40 (10.2
cm) submarine guns. Four CPXVI were converted for use on destroyers
and one of these was carried by HMS Acasta.
11) One of the more noticeable features
of these destroyers was the large "sprayshields" forward of "B" gun platform
and aft of "X" gun platform. Although these structures did reduce
spray on the upper decks, their true purpose was to reduce the problem
of blast from the upper guns disrupting the crews of the guns on the lower
levels. Similar "sprayshields" can be seen on those USN destroyers
armed with open 5" (12.7 cm) pedestal mounts.
This may be taken as a rather unobvious example of how weapon design influences
the design of the rest of the ship. By choosing "lightweight" open
mountings for these destroyers, the designers paid a weight penalty in
having to add these shield structures. Likewise, the L-M destroyer
classes with their "heavyweight" enclosed 4.7"
(12 cm) mounts saved some compensating weight by being able to eliminate
the blast shields.
12) Gun shields on the Vickers "E" guns
were pedestal types with abbreviated shields very similar to those used
for the British 4.7"/45 (12 cm) BL Mark I
mountings. |
