Difference between revisions of "Iron Duke Class Battleship (1912)"

Revision as of 15:32, 31 July 2011

Armament

Main Battery

This section is sourced from The Sight Manual, 1916.^[1]

The 13.5-in Mark V(H) guns were in Mark II mountings able to elevate 20 degrees and depress 5 degrees. The sighting arrangements were similar to those in Tiger and the King George V class.

The sights were cam-worked and limited to 15 degrees elevation, but the central sights had "20 degree super-elevation strips". Additionally, 6 degree super-elevation prisms would have been provided by 1916. The deflection gearing constant was 61.3, with 1 knot equalling 2.51 arc minutes, calculated as 2500 fps at 5000 yards.

Range drums were provided for full charge at 2450 fps, three-quarter charge at 2000 fps, as well as 6-pdr sub-calibre gun and .303-in aiming rifle. Muzzle velocity was corrected by adjustable scale plate between 2560 and 2260 fps. The adjustable temperature scale plate could vary between 40 to 100 degrees Fahrenheit, and a "C" corrector could alter the ballistic coefficient by +/- 20%.

The periscope holder was inclined 1 degree 37 minutes (which may have effectively been 2.5 degrees for mechanical reasons; it equalled .195 degrees correction at 10,000 yards).

The side sighting scopes were 43.25 inches above and 39 inches abreast the bore. The central scopes were offset 56.25 inches above and 42 inches abreast.

OOQ open director sights capable of 20 degrees elevation were to be fitted sometime following 1916.

Torpedoes

Four 21-in broadside tubes, the forward ones bearing 80 degrees and the aft tubes bearing 100 degrees.^[2]

Fire Control

Phones

Main Battery

Secondary Battery

Navyphones for 6-in Fire Control
As shown in Annual Report of the Torpedo School, 1913.

Each of the six 2-gun groups was on its own navyphone circuit, feeding a Pattern 2464 Navyphone for the group officer as well as a pair of Telaupads for each gun. These led to six 2-way C.O.S.es in the 6-in TS which would dictate whether the given 6-in group's phones were tied to either

1. the Pattern 2463 Navyphone and its associated Pattern 2465 transmitter
2. the single 2464 in the G.C.T. for its broadside.

Additionally, when the C.O.S. was in position one, each group's panel in the TS had a grouping switch so that any transmitter could address either or both of the other groups on its broadside. See the notes on the gunnery groups to see how this loosely mimics the fire control instruments.^[3]

Rangefinders

The T.C.T. rangefinder, initially a 9-foot instrument of unknown model, sat on an M.Q. 8 mounting.^[4]

Sometime, likely not before 1918, these were to be upgraded to 15-foot instruments, with new armoured hoods and racers and training driving the hood directly rather than through the rangefinder mounting. These rangefinders lacked hand-following gear to facilitate in transmission of range cuts, and when it was considered as an addition around 1917, space concerns were causing issues.^[5]

By 1918, two additional 9-foot instruments were also to be provided for torpedo control, abreast the captain's sea cabin, except on Iron Duke, where they were placed on either side of the lower charthouse platform, displacing a pair of 23-in signalling searchlights to the compass platform.^[6]

Evershed Bearing Indicators

All 4 units were likely fitted with this equipment before late 1914.^{[Inference][7]}

However, it is clear that all 6-in guns had a bearing indicator fitted.^[8] This strongly implies that a rich installation supported the main battery at least.

Otherwise, one might reasonably assume the particulars resembled those of the King George V class.^[Inference]

Mechanical Aid-to-Spotter

At some point, all ships in this class were equipped with four Mark II Mechanical Aid-to-Spotters:

• one on each side of the foretop, driven by flexible shafting from the Evershed rack on the director
• one on each side of the Gun Control Tower employing an electrical F.T.P. system.

As the need for such gear was apparently first identified in early 1916, it seems likely that these installations were effected well after Jutland.^[9]

Gunnery Control

The control arrangements were as follows.^[10]

Control Positions

Main battery:

• Gun control tower
• 'B' turret
• 'X' turret

Each 6-in broadside:^[11]

• G.C.T. (abreast conning tower)
• Alternative positions aft (Groups 1 & 2 from one, group 3 from a second one)

Some ships had COSes within the control positions so they could be connected to either TS.^[12]

Control Groups

The five 13.5-in turrets were each a separate group with a local C.O.S. so that it could be connected to

• Transmitting Station
• Local control from officer's position within turret

The 6-in guns were formed into three 2 gun groups on each side^[13], and the circuits for each side are led through one of two 3-way C.O.S.es offering the following modes:^[14]

1. each group on that broadside worked by its own transmitters in the TS
2. the broadside as a whole is connected to the adapted Vickers range clock situated in its 6-in GCT
3. each group on that broadside is connected to the alternative control position, where (1? 3?) portable range-and-deflection transmitters with tell-tales are used.

See the section below for a diagram.

Directors

Main Battery

Training and Elevation Circuits
As shown in Annual Report of the Torpedo School, 1913.

The ships were fitted with a cam-type tripod-type director in a light aloft tower on the foremast along with a directing gun in 'X' turret.^[15][16]

The main battery could be divided into forward ('A', 'B' & 'Q') and aft ('X' & 'Y') groups for split director control.^[17]

A C.O.S. in the TS afforded these options:^[18]

1. All turrets on aloft tower
2. All turrets on directing gun
3. Forward group on aloft tower, aft group on directing gun

Secondary Battery

The ships had a pair of directors fitted to port and starboard on the forward superstructure to direct the 6-in broadside guns. Marlborough's were pedestal-mounted, and the others tripod-mounted.^[19]

Transmitting Stations

Like Tiger and possibly later ships,^[Inference] these had a TS for the main battery and another for the 6-in secondary battery.^[20] It is not clear to me whether the secondary battery's TS had a Dreyer table.

Dreyer Table

In June 1918, Marlborough had a Mark I Dreyer Table while the other three units had Mark IV Dreyer Tables^[21] and all had been provided Dreyer Turret Control Tables.^[22] The disparity in Dreyer Marks creates a loose impression that all ships were initially given Mark I tables and for some reason Marlborough missed her chance for an upgrade, perhaps due to her damage at the Battle of Jutland.

At some point, the ships each received Dreyer Turret Control Tables, but it is unclear when and whether each turret received one or simply the two control position turrets.^[23]

Fire Control Instruments

Continuing the pattern established in the Colossus class, all 4 units used Vickers F.T.P. Mark III range and deflection instruments to the gun sights (except Mark III* in the 6-in TS panels) and Barr and Stroud (probably Mark II* or later^[Inference]) instruments for other purposes.^[24]

The Mark III F.T.P. range receivers on the 6-in guns were fitted with Usborne Accelerating Gear. An adapted Vickers Range Clock similar to that used in the Mark I Dreyer Table could be employed to relay ranges to the 6-in guns. An operator on the clock would have to follow-the-pointer to transmit the ranges. Each 6-in broadside had its own independent Captain's cease fire gong circuit. Firing keys were Pattern 872, and each gun had a fire gong.^[25]

The ships also had Gun Ready signals in the TS and control positions, but had no Target Visible signals.^[26]

In 1916, it was approved that the ships should have a range rate transmitter/receiver pair between TS and spotting top for the main armament. Additionally, it was ordered that Lion and King George V classes and` later should receive instruments such that the fore top could be interchangeable as a gun control position with the GCT.^[27]

Secondary Battery

Diagram of 6-in Fire Control
As shown in Annual Report of the Torpedo School, 1913. Pardon the blurry photo.

A description of the fire control system for the 6-in guns is found in the Annual Report of the Torpedo School, 1913.

Torpedo Control

By the end of 1915, all four ships had been equipped with a Torpedo Control Plotting Instrument Mark I in their TCT.^[28]

In 1916, a number of further changes were decided upon:^[29]

• Navyphone communication between CT and aft torpedo flat and TCT and fore torpedo flat
• removal of secondary director hoods
• "transfer of instruments in the secondary positions" to the CT and TCT. I presume that "secondary positions" means the secondary director hoods.
• it was approved that the ships should have a transmitters in the T.S. and receivers in T.C.T. and C.T. so that gunnery data for range, course and speed could be shared with the torpedo control group.
• arrangements were to be made that all capital ships with 21-in torpedoes to receive transmitters and receivers so that the T.C.T. could pass the plotted torpedo deflection to the C.T., which could then use a reciprocal set of equipment to send the T.C.T. a deflection to be placed on the sight and range to open fire.

See Also

• Wikipedia

Footnotes

Bibliography

Template:CatClassUKDreadnought

Template:Iron Duke Class (1912)