Tzoli

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From the navweaps site:
http://navweaps.com/Weapons/index_weapons.htm

Nomenclature notes: The 5.25" (13.4 cm) Mark II, Mark III and Mark V were Army AA guns with a higher muzzle velocity. Only a few of these guns were manufactured. A further naval development, the Mark IV gun in the Mark III twin mounting, was to have vertical-sliding breech blocks, fire fixed ammunition and have a much higher rate of fire. Two experimental guns were ordered in 1944, but the mounting never progressed beyond the sketch stage. A postwar project for a twin Mark III mounting capable of 70 RPM using fixed ammunition did not make it off the drawing board.

My question is:
Does anybody here ever found drawings or photos of this post war naval mount?
 
Funny you should ask as I was looking at this just yesterday at Kew.

First, there is a drawing in existence that purports to be of the Mk.III 5.25" mounting, I don't have it as I didn't photograph it when I found it as I didn't have time but it does exist.

The Mk.III mounting wasn't really a post-war mounting; it was originally intended for the 1944 cruisers prior to the decision that they should have 6" guns. After that the 5.25" Mk.III was kept as a research programme and as an insurance against the prospect of not being able to get the desired 12 twin 4.5" mounts on the redesigned Lion class battleships.

There were actually two Mk.III mountings, one that was hydro-electric and one that was full electric.

Ultimately, around 1947/8 work on the Mk.III mountings (which had been progressing very slowly) stopped and work began on the automatic MCDP concept- this was actually charged to the original Mk.III mounting/Mk.IV gun contracts with Vickers. Calibre at this stage wasn't fixed so studies looked at feed systems/mounting that could be scaled to weapons between 4.5" and 5.5". I suspect this is where the 70rpm 5.25" reference comes from (and the 70 cal 5"). The Mk.III was not a 70 RPM mounting.
 
It would be great to re-find that drawing or photo.

Interesting that DNC proposed 5,25inch triple turrets for and Australian CLAA design of 1944 but those should look like the boxy ones used for the 6inch guns.
Again 5,25inch gun re appeared in the 50's for some of the GW series of missile cruisers.
Not to mention the turrets of the Vanguard looks very similar to the Mark 26 turrets of the 6inch Mark V of the Tiger class!
 
Which GW designs included 5.25"? I know 5" briefly made a reappearance before someone pointed out how long it would take to develop the new gun mount but I don't recall 5.25".

The last reference to 5.25" for new construction I have found is in a study of an "emergency cruiser" (basically just a repeat Dido) which compared 3 x twin 5.25" to 4 x 4.5" twin as armament alternatives and decided the latter was superior.
 
JFC Fuller said:
Which GW designs included 5.25"? I know 5" briefly made a reappearance before someone pointed out how long it would take to develop the new gun mount but I don't recall 5.25".

The last reference to 5.25" for new construction I have found is in a study of an "emergency cruiser" (basically just a repeat Dido) which compared 3 x twin 5.25" to 4 x 4.5" twin as armament alternatives and decided the latter was superior.

GW 36 and GW 37 from 1955
2x2 5,25, 1x2 Sea Slug, 4x2 40mm
GW 36A have two launchers but no main guns
GW 37 was a bit longer-
GW 36: 10700t
GW 36A: 10600t
GW 37: 11300t
 
In the list of GW series variants Phil Gollin found GW.36 and GW.37 are listed as having 5.5" guns, not 5.25".
 
JFC Fuller said:
Sorry Tzoli, its edited now.

Yes I've checked too, but Friedman stated 5,25inch.
So we have some inconstancy. But I think 5,25 is much more logical as it was a newer gun design then the WW1 5,5inch. The documents was probably more extensive for the 5,25 then for the 5,5 as I do not know any WW2 projects to use new 5,5inch guns. While as you written the 5,25 was developed though slowly even postwar.
 
The archive source says 5.5". 5.25" was dead as a development project in 1947. If I had to guess this 5.5" is either an error and should read 4.5" or its some as yet unknown (to us) short lived study for a new weapon.
 
I would not say the 5,25 was not considered especially if you look at the Vanguard turrets:
SANY0718.JPG

Very similar to the Tiger 6" turrets.



But indeed this is weird, 4.5", 5", 5.25" or 5.5" all possible guns to mount.


Also here is something sort of related:
From the game Navyfield 1, a mount called 5,25 QF Mark II:
2_x2_4_www.kepfeltoltes.hu_.jpg

Did you seen anything similar?
 
How the turret looks externally is irrelevant. All 5.25" development stopped in 1947, the mounts on Vanguard were low RoF weapons with heavy manual involvement. Even the improved Mk.IV gun in the Mk.III mounting that was abandoned in 1947 was considered inferior to larger numbers of 4.5" Mk.VI and 5.25" mounts were being rejected from cruiser designs in 1950.

Aside from the 4.5" Mk.VI every gun I can think of that was being considered for new construction in the 1950s was an automatic weapon which the Vanguard mountings were not.
 
Tzoli said:
My question is:
Does anybody here ever found drawings or photos of this post war naval mount?

There is a drawing in DK Brown's "Rebuilding the RN" of the N2 light cruiser that was to be armed with 8 of the new guns in 4 of the new turrets. The drawing is conjectural based on the written description of the ship and new armaments and shows a conventional looking turret rather than the side cut-out turrets in the previous 5.25 inch mountings.

Attached is lores copy of this N2 picture.
 

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JFC Fuller said:
Even the improved Mk.IV gun in the Mk.III mounting that was abandoned in 1947 was considered inferior to larger numbers of 4.5" Mk.VI and 5.25" mounts were being rejected from cruiser designs in 1950.

8 of the new 5.25" guns firing fixed ammo was considered equal to 12 of the 4.5" in Mk 6 mounts in AA fire. DK Brown's "Nelson to Vanguard" has quite a bit of info about the capability of this then new gun and how it even outperformed the 6" in surface fire (thanks to lots more hits and near equal bursting charge) but just not in armour piercing. Enter a conservative like First Sea Lord "There won't be any aircraft carriers afloat in 20 years" Cunningham* and therefore a massive 12x6" and 12x4.5" gun cruiser was required that would of course never be built.

* As quoted in 1944!!!
 
Tzoli said:
Interesting that DNC proposed 5,25inch triple turrets for and Australian CLAA design of 1944 but those should look like the boxy ones used for the 6inch guns.

Are you sure they were triples? All the reporting about the plan for a new build Australian light cruiser in 1944 that I have seen mention it as an improved and Australianised Dido class. You couldn't fit a triple on the hull of these ships.
 
Abraham Gubler said:
Tzoli said:
Interesting that DNC proposed 5,25inch triple turrets for and Australian CLAA design of 1944 but those should look like the boxy ones used for the 6inch guns.

Are you sure they were triples? All the reporting about the plan for a new build Australian light cruiser in 1944 that I have seen mention it as an improved and Australianised Dido class. You couldn't fit a triple on the hull of these ships.

To my knowledge they would be based on the Crown Colony class rather the small and top heavy Dido:

From the archives.

The 1944 proposals for the RAN home building program gets some mention in the popular histories, but I had the opportunity to flesh this out somewhat by getting a copy of “MP1049/5 2026/3/516 Cruiser and Destroyer Building Program”.

The file begins in mid 1943, discussing the advisability of building cruisers and destroyers in Australia to replace war losses and the aging remaining ships, and the file ends with the dispatch of the RA Eng and Director ordinance from the Naval Boards Melbourne office being ordered to London from June-Aug 1944 to consider current vessels under construction in Britain.

Prior to this mission, the ACNB set out what it thought were the war lessons.

A Air Power – neither side seeks surface action in daylight without air support, consequently there are more night actions than day, and all ships require maximum AA fire power and ability to stand up to bomb and aerial torpedo damage.
B The destructive power of the modern torpedo. C The ever increasing efficiency of radar.

The devastating effect of high volume of fire at night ranges from medium calibre guns.

They then set out what the ACNB thought would be the desirable features of an RAN future cruiser given the war lessons.

A Main armament dual purpose guns. The 5.25in gun appears to be the most satisfactory calibre for HA/LA (with “at present” added in pencil)
B Secondary armament guns more numerous than in present design 40mm guns are required in addition to 20mm.C Side armour and deck armour.
D Improved under water protection. Large compartments should be partitioned by water tight bulkheads.
E Maximum speed 30-32 knots. Higher speeds are not considered necessary.
F Large endurance.

The paper then considers a number of British designs, improved Southampton, Fiji, Dido.

It selects the Dido as the most suitable based on its HA/LA armament, but the offers this appreciation of their weaknesses.

A Endurance much too small. (stated at 7500miles econ, 1,700 miles full speed)
B Too vulnerable to under water attack.
C Insufficient HA firepower abaft the beam.
D Insufficient medium and short range AA armament.
E Inability to engage more than two AA targets in primary control with main armament.

They then go on to outline a cruiser the authors think would be perfect for the RAN post war.

Speed – 30 knots
Endurance – 10-12,000 miles at economical speed.
Gun armament – 12-15 5.25 HA/LA, 12 or more 40mm bofors, 12 or more 20mm.
Protection – Side and deck armour, improved watertight subdivision.
Displacement – 8-9000 tons
Length 550-570ft
Beam 60-65ft



No aircraft. The author proposes no torpedoes, but the paper is edited by someone who finds them essential, and points out that doctrine is to “fix by gunfire, and sink by torpedo”.



They propose the main slipway at Cockatoo Island by built up from its present 450ft to 600ft, all designs, plans, skilled technical personnel etc to be sourced from GB.



Imports would include



80% of all steel (the right grades were not made in Australia – this was cited by the minister in the 1930’s as a reason not to order an Australian Leander).
All armour plate.
All armament,
All fire control.
80% of aux machinery.
Forgings for main turbines.
60% of electrical cable.
80% of electrical equipment.
Anchor cables.


To be laid down in 1944 for completion in 1948, and to be followed by another 5 similar ships from 1944-1953, replacing entirely the wartime losses and pre war ships.
 
Abraham Gubler said:
8 of the new 5.25" guns firing fixed ammo was considered equal to 12 of the 4.5" in Mk 6 mounts in AA fire. DK Brown's "Nelson to Vanguard" has quite a bit of info about the capability of this then new gun and how it even outperformed the 6" in surface fire (thanks to lots more hits and near equal bursting charge) but just not in armour piercing. Enter a conservative like First Sea Lord "There won't be any aircraft carriers afloat in 20 years" Cunningham* and therefore a massive 12x6" and 12x4.5" gun cruiser was required that would of course never be built.

There was obviously a change of heart then. The study undertaken into providing secondary armament for the Lion redesign in 44/45 decided that 24*4.5" MkVI was superior in AA fire to 16*5.25" MkIV. It was specifically mentioned as justification for continuing the 5.25" MkIV that it might be needed if it was found impossible to get six twin 4.5" Mk.VI on each side of the new battleship design.
 
Tzoli said:
To my knowledge they would be based on the Crown Colony class rather the small and top heavy Dido:


The RN was looking at triple 5.25" turrets for some of the 1942-43 proposals for the 1944 program light cruiser. These were all new designs. The "L" design had three triple 5.25" of the new type (fixed ammo) on a 575' long hull, displacing 10,500 tons at standard. The "g" and "J" designs had four triple 5.25" turrets and a larger hull (610' or 615' long). Design L was drawn up in November 1942. But by the end of 1943 they had settled on the four twin 5.25" N2 design with half the usual horsepower (48,000 hp) so as to save cost and improve torpedo protection, but at the cost of not being able to keep up with a fleet carrier at flank speed (which seems a bit daft). Anyway it was Lord Cunningham who squashed the possibility of a war design light carrier being built in the UK or Australia when he insisted on 6" guns.
 
JFC Fuller said:
There was obviously a change of heart then. The study undertaken into providing secondary armament for the Lion redesign in 44/45 decided that 24*4.5" MkVI was superior in AA fire to 16*5.25" MkIV. It was specifically mentioned as justification for continuing the 5.25" MkIV that it might be needed if it was found impossible to get six twin 4.5" Mk.VI on each side of the new battleship design.


It is mentioned as such (8 x 5.25" Mk 4 = 12 x 4.5" Mk 6) in "Nelson to Vanguard" as reported in ADM 116/5151 "Comparison of 5.25in and Improved Belfast Cruiser" of 26 Jan 1944. There might be differences in the measure based on a cruiser fitout vs a battleship fitout. In the cruiser all eight 5.25" are centreline so all can bear on abeam targets and half on those right forward and right aft. However in a battleship and an Improved Belfast (with four triple 6" turrets) usually only half of the high angle guns carried will be able to bear on each of the beams and even less right forward and right aft. So in a battleship the firing arcs of all guns is likely to be roughly the same between the calibres but in a 1944 cruiser the 5.25" guns will have better firing arcs than the 4.5" guns allowing for more guns to bear.
 
Abraham,

I might be missing it because I am looking for it but I just checked both Nelson to Vanguard and Friedman's British cruisers book and neither of the mention fixed rounds for for 5.25" weapons. Do you recall where you got the reference from?

The reason I ask is that the notes I took whilst looking at the files suggest very strongly the 5.25" MkIV and the associated Mk.III turrets used a separate cartridge and shell. I know navweaps suggests a fixed round but i have another reason for thinking it might have been separate too. Rather like the eventual 4.5" Mk.VI, this mount was apparently to have the shell and cartridge manually transferred to the loading tray in order to achieve the desired RoF.

I might be wrong and I need to get back to the archives to check but the evidence immediately at hand suggests separate ammunition.
 
JFC Fuller said:
Yup, that's the issue, it's 6 x 4.5" versus 8 x 5.25".

I looked a bit closer at Friedman's "British Cruisers" and it has quite a bit of info on the Improved Belfast design aka Design "Q" and "R". The Improved Belfast concept was approved by the Future Shipbuilding Committee in Feb 44 over the "N2" 5.25" cruiser and "R", armed with 12x6" in Mk 24 (5-6 rpm, low angle guns) was approved later that year for the 1944 Program with the proviso that fast loading, high angle guns be researched which lead to the better known Design "Y" (aka Neptune) and Design "Z" (Minotaur) ships and the end of any hope of laying down these ships in the mid 1940s.

Anyway there is a bit of information about the configuration and design of the "Q/R" ships (basically identical) including an indirect statement that they have a 'Star of David' type arrangement for the secondary 4.5" HA/LA guns. That is two on each beam at the waist and two on the centreline, one forward, one aft, superfiring over the B and X turrets respectively. The text mentions specifically that there are two waist guns on each beam as they were each giving short range directors to contribute to the short range barrage (usually 20mm and 40mm). These directors replacing four twin 20mm. It also mentions that the six 4.5" mounts were "explicitly mirroring the US Cleveland class".

This would mean in the case of the 5.25" vs 6"/4.5" Improved Belfast cruiser the equivalent anti aircraft accounting would be the same number of high angle guns bearing on possible targets. Eight of each to the beams and four of each forward and aft (assuming that the waist guns can't train across the ship's azimuth, which is likely).
 
JFC Fuller said:
I might be missing it because I am looking for it but I just checked both Nelson to Vanguard and Friedman's British cruisers book and neither of the mention fixed rounds for for 5.25" weapons. Do you recall where you got the reference from?

From NavWeps:

http://www.navweaps.com/Weapons/WNBR_525-50_mk1.htm

A further naval development, the Mark IV gun in the Mark III twin mounting, was to have vertical-sliding breech blocks, fire fixed ammunition and have a much higher rate of fire. Two experimental guns were ordered in 1944, but the mounting never progressed beyond the sketch stage.
 
Tzoli said:
To my knowledge they would be based on the Crown Colony class rather the small and top heavy Dido:

BTW thanks for this specification, I hadn't seen it before.

They then go on to outline a cruiser the authors think would be perfect for the RAN post war.

Speed – 30 knots
Endurance – 10-12,000 miles at economical speed.
Gun armament – 12-15 5.25 HA/LA, 12 or more 40mm bofors, 12 or more 20mm.
Protection – Side and deck armour, improved watertight subdivision.
Displacement – 8-9000 tons
Length 550-570ft
Beam 60-65ft

They were never going to get such a ship using British technology. 12x5.25" (in triples), 10-12,000 NM range and armour would have required a a hull 600' long, 70' wide with 90,000 HP and displacing up to 15,000 tons (full) of which around 4,000 tons would be fuel. You could probably get such a ship in under 10,000 tons using American steam turbine technology because they had moved on to far more efficient civilian power industry technology over legacy British naval technology (Westinghouse and GE vs Parsons) during the 1930s. But you couldn't mix and match back in those days, politics alone wouldn't allow it.
 
Abraham Gubler said:
Tzoli said:
To my knowledge they would be based on the Crown Colony class rather the small and top heavy Dido:

BTW thanks for this specification, I hadn't seen it before.

They then go on to outline a cruiser the authors think would be perfect for the RAN post war.

Speed – 30 knots
Endurance – 10-12,000 miles at economical speed.
Gun armament – 12-15 5.25 HA/LA, 12 or more 40mm bofors, 12 or more 20mm.
Protection – Side and deck armour, improved watertight subdivision.
Displacement – 8-9000 tons
Length 550-570ft
Beam 60-65ft

They were never going to get such a ship using British technology. 12x5.25" (in triples), 10-12,000 NM range and armour would have required a a hull 600' long, 70' wide with 90,000 HP and displacing up to 15,000 tons (full) of which around 4,000 tons would be fuel. You could probably get such a ship in under 10,000 tons using American steam turbine technology because they had moved on to far more efficient civilian power industry technology over legacy British naval technology (Westinghouse and GE vs Parsons) during the 1930s. But you couldn't mix and match back in those days, politics alone wouldn't allow it.

It's more of a requirement proposal then a fully fledged design, it shows what the Australians wanted, but work was not progressed beyond this level.
 
Given that a Fiji could make 10,000nm at 12 knots on 1,700 tons of fuel I am rather puzzled as to why you think a vessel designed in 1944 would suddenly need to be so large and carry so much fuel to achieve a similar range.

Not to mention that by 1944 the RN was already pursuing much more efficient steam plants, which eventually ended up with the plant in the Darings. Exactly the same technology could have been used on any cruiser conceived at the same time.
 
JFC Fuller said:
Given that a Fiji could make 10,000nm at 12 knots on 1,700 tons of fuel I am rather puzzled as to why you think a vessel designed in 1944 would suddenly need to be so large and carry so much fuel to achieve a similar range.

Not to mention that by 1944 the RN was already pursuing much more efficient steam plants, which eventually ended up with the plant in the Darings. Exactly the same technology could have been used on any cruiser conceived at the same time.

No need to extrapolate from unrelated classes. Friedman's "British Cruisers" has quite extensive legend information on the various letter designs of the 1944 Program Cruiser in the footnotes. I don't know why these books have such data in the notes, anyone reading them is more than happy to have it presented in the main body. But I'm not their editor and the editor in this case quite humorously put tons beside a few too many measure in one table. So some of these cruisers have a complement massing around 1,000 tons according to the tabulation.

To the question at hand the widebody 1944 cruisers (those with the triple 5.25" or 6" turrets) had a beam between 68' and 74' and a 100,000 hp propulsion unit (massing 1,900 tons). On the smallest hull (Design "L" with 9x5.25", 575'x68'x18'3" and 10,500 tons standard) this needed 2,500 tons of oil to reach 6,000 NM at 20 knots. The biggest hull (Design "Q/R" with 9x6", 12x4.5", 630'x74'x21'6" and 14,500 tons standard) this same propulsion unit needed 2,650 tons for 6,500 NM at 20 knots (fineness helps). Both endurance figures were clean in temperate waters.

So its pretty easy to extrapolate from this information that a 12x5.25" ship for the RAN would need more fuel and a bigger hull to carry it. My original estimate was far to generous. Using the 1944 Program Cruiser technology such a ship would need around 5,000 tons for 12,000 NM at 20 knots. If they wanted 12,000 NM at 20 knots while dirty in tropical waters they would need 7,500 tons of fuel! Even if they were to accept a lower economical speed (as in earlier in the war) of 16 knots they would require around 3,500 tons of fuel for it with the propulsion plants planned for this program. A version of Design "J" which had the armament and armour the RAN wanted but with a range of 12,000 NM at 16 knots would still displace around 11,500 tons standard and 15,000 tons deep (ie with full fuel onboard).

Building a ship with the same technology proposed for the later RN cruisers or USN propulsion would have enabled much better fuel efficiency and lighter propulsion units. But it would not be a ship that could be laid down in this required time frame.
 
Extrapolation is entirely appropriate. Those designs only need more fuel for 10,000nm because the listed speed for 6,000nm was a high 20 knots. Cut the speed and the range goes up rapidly.

Even a Worcester only made 8,000nm at 15 knots.
 
JFC Fuller said:
Those designs only need more fuel for 10,000nm because the listed speed for 6,000nm was a high 20 knots.

Which was what the RN wanted as their economical speed at the time (1943-44): 20 knots, not 15, 16 or 12 knots. Since the RAN specification was written in the context of wanting something better than the Dido class the economical speed may be the same as this ship. That is 16 knots and it required 1,100 tons of oil to make 4,500 NM at this speed. In which case the RAN's requirement for 12,000 NM at 16 knots would require at least 3,500 tons for a ship with 12x5.25" guns. So we're back to me still being right the first time.
 
Abraham Gubler said:
Which was what the RN wanted as their economical speed at the time (1943-44): 20 knots, not 15, 16 or 12 knots.
Do you have a source for the 20 knots economical speed? Is it Friedman?

Added to wish list: a copy of copies of both British Cruisers books.
 
Mid/Late RN cruiser designs specified desired endurance at 20 knots (not necessarily economical), I have never seen anything suggesting a formal policy for an economical speed of 20 knots. And anyway, such a speed for 10,000nm would be highly impractical at the time. Even the USN wasn't getting close to that.

Also, the document Tzoli provided compares a Dido against the desired characteristics of an Australian cruiser stating an endurance of 7,500nm (not the 4,500nm given by Abraham) at economical speed for the Dido. It does not give that speed in knots but I understand it to be 12 knots (based on previous research), not 16 knots as stated by Abraham. The document does not criticise the economical speed- just the endurance. That makes the stated displacement much more reasonable, indeed the lower end of the desired endurance range was achieved by the Fiji class on approximately the displacement desired at 12 knots. I also note that the proposed hull dimensions are also near identical to those of a Fiji or Swiftsure.
 
Economical speed is going to be less than 20 knots.


The BPF had a general cruising speed of between 17 and 21 knots, much time being spent at either 17 or 20 knots - but different formations used different speeds considering the ships involved.


Different ships had different endurances. The KGVs, for example, worked their endurance out at so many miles at most economic, PLUS so many hours at various (at least three, including top speed) higher speeds. This mixing up of miles for the basic and hours for higher is an oddity.


In addition, war service showed that having to have all boilers available in possible war zones also affected endurance greatly.
 
Questions about the 5,25inch turrets:ű
First:
it was known that KGV's Mark I and Dido's Mark II was cramped and difficult to train while the last, the RP10 Mark I* of the Vanguard was an excellent mount but what about the RP10 Mark II used on the Bellona class?
Second:
Who produced these guns?
Vickers?
 
From the navweaps site:
http://navweaps.com/Weapons/index_weapons.htm



My question is:
Does anybody here ever found drawings or photos of this post war naval mount?
Good news, for I bring answers.

As far as I am aware there are a few mount developments of this type.
There is the 5.25" Mk III (also known as HA/LA, RP40, 80° electric-hydraulic) mount. I do not have a lot of info on these yet, but I suspect the design started in 1938 as a 6" mount and from 1942 as 5.25". These would be developed by Vickers-Armstrong Limited.
Another project is the 5.25" Mk III star (aka RP50, 80° all-electric) mount. This project started around 1944. I just finished writing an article about this on my blog here.

From what I have found the Mk III mount is a Vickers Armstrong development that works on the same principles as the 4.5" Mk VI. The Mk III* mount is a Vickers Armstrong and Messr Metropolitan Vickers-Electrical Co. development (and as far as I remember similar to the 4.5" Mk VII). There was also development of the 6" Mk XXV RP40 and RP50 mounts.

Unfortunately I can not share photos of the drawings. However I do have a sketch of the Mk III * mount prepared and attached.

The 5.25" hand-loading HA/LA mount (dated 1946) is visually similar from the top, and has the same 16 rpmpg ROF. However, from the side and front it's rectangular with chipped corners and no fixed potrusions in the roof. The guns are also positioned closer to each other (2x 2'4" as opposed to 2x 3'9") with operation happening from the outer sides and an additional lookout post with extendable roof would be positioned on either side.

There is also an experimental 5.25" Mk III design with telescopic hoists from 1948. These had 90° elevation and weighed 120 tons. Uniquely they had 3 hoists which loaded complete rounds instead of seperate rounds. 2 hoists were dedicated to HA fire and 1 to LA fire. Giving each gun a 24 RPM (LA) and 48 RPM (HA) ROF. I suspect this is where some authors got the 72rpm idea from. Furthermore, this design also included tables for 4.5", 5" and 5.5" mounting sizes and weights, both accounting for 50 calibres and 70 calibres long barrels.

I'm still working on collecting and processing more information, but for now I hope this helps.

Yours truly,
Sanglune
 

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I managed to get around to do the rest, including a part of the tables. I couldn't fit the full size images in my blog posts [Handloading 1] [Telescopic 2] so here they are.
 

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In case it's of interest a fully automatic 5.25" was developed for the Army and installed at five sites around Glasgow in the Clyde GDA post war. The shells and cartridges were placed on a conical magazine under the mount holding 48 rounds and the guns could be controlled remotely from the command post with a rate of fire of around 18 rds/min.

There is a photo of the gun at the Eskmeals range here:

 
Different ships had different endurances. The KGVs, for example, worked their endurance out at so many miles at most economic, PLUS so many hours at various (at least three, including top speed) higher speeds. This mixing up of miles for the basic and hours for higher is an oddity.
That actually makes sense, from the point of a Naval officer or navigation enlisted. "We can cruise X many miles, and during that time we can spend Y many hours at higher speeds if needed."
 
That actually makes sense, from the point of a Naval officer or navigation enlisted. "We can cruise X many miles, and during that time we can spend Y many hours at higher speeds if needed."
The original staff requirement was for oil fuel to achieve the more demanding of the following:
  1. A 35% margin over that required to achieve the following mission profile, 6 months out of dock:
    1. 200 hours at 16 knots with steam for 18 knots
    2. 8 hours at full speed
    3. 16 hours at 18 knots with steam for full speed
    4. 12 hours at 16 knots with steam for full speed
  2. 14,000 [nautical] miles at 10 knots under trial conditions
The former is very clearly a nominal operating profile developed by an operator. It's probably no coincidence that the 'cruising' portion - 16 knots with steam for 18 knots - equates to a radius of action from Singapore to about a day's sailing north of Hong Kong.

That extended period with steam for full speed - i.e. with all boilers fired up - will have burnt a lot of fuel. One of the fun things you don't have to worry about with gas turbines.
 
The former is very clearly a nominal operating profile developed by an operator. It's probably no coincidence that the 'cruising' portion - 16 knots with steam for 18 knots - equates to a radius of action from Singapore to about a day's sailing north of Hong Kong.
Exactly. It's an operational range with some "oops, we need to do more speed for a bit" written into it.



That extended period with steam for full speed - i.e. with all boilers fired up - will have burnt a lot of fuel. One of the fun things you don't have to worry about with gas turbines.
True enough. GTs have their advantages, especially with controllable-pitch props on the end so you can keep the turbines at closer to their design RPM all the time.
 

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