British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

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dunmunro
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Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by dunmunro »

Byron Angel wrote: Mon May 10, 2021 12:05 am
Steve Crandell wrote: Sun May 09, 2021 6:07 pm Didn't british cruisers with the 5"/38 and Mark 37 combo like it a lot? Did they get infected with US enthusiasm for the system?
Yes indeed, Iville Porteous (father of "Flyplane") and Hugh Clausen (then Chief Technical Advisor to DNO) went aboard HMS Delhi to inspect its 5in/38 Mk37GFCS in February 1942. Porteous later wrote - "I went aboard her and was most impressed. For the first time in my experience I was able to examine in detail a completely integrated gunnery system such as I had always hoped would be possible." .....and..... "I wrote a hurried and scrappy report which is of little significance except that it stung Clausen awake (so he says) and brought him back into the arena with a bang in fighting mood."

See also "Progress in Naval Gunnery - 1942" (page 40).

Note also, when the US finally did deliver a limited number of Mk37 GFCS late in the war, what new British ships received them.

B
This is just an editorial comment. HMS Delhi's war record was less than stellar.
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Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by dunmunro »

Byron Angel wrote: Sun May 09, 2021 11:00 pm
dunmunro wrote: Sun May 09, 2021 6:46 am There was nothing ground breaking about Mk37, as the Mk33 had all the same features and Mk37 was not fitted with 'autotracking radar'. The MK4 FD radar was manually tracked.
I'm sorry to say, dunmunro, that you have some things rather wrong here.

Design of the Mk37 was undertaken only two years after the introduction of the Mk33 in 1934, due to the Navy's dissatisfaction with the performance of the Mk33. The Mk37 was a completely new approach in configuration. Unlike the Mk33, the Mk37 featured a lightweight director aloft designed ab initio to accommodate a FC radar, while the plotting/FC system was situated in a protected position below decks. The Range Keeper Mk10 of the Mk33 Gun Director was discarded and an entirely new and more capable Computer Mk1 substituted. The technological difference was considered so considerable that the term "Gun Director" was replaced by "Gun Fire Control System" and the term "Range Keeper" replaced by "Computer". The Mk 37 GFCS (Gun Fire Control System) was the first such devices to employ servos in its data transmission system, which enabled computation time required to produce a targeting solution to be materially reduced. In addition, courtesy of the more sophisticated Computer Mk1, the Mk37 was the first such AA fire control system with the ability to compute target movement in all three-dimensions. Neither Mk33 (see Crenshaw and OD1347) nor the British HACS (see Pout, Pugh, Marland and Porteous) could compute/predict target movement in the vertical dimension; both systems employed after the fact "kludges" to account for vertical movement vectors.

The Mk37GFCS weighed 40,000 pounds in comparison to 14,000 lbs for the Mk33 and took up valuable below deck space which the Mk33 did not. Are you are prepared to argue that the USN consciously chose to spend precious time and funding to design and build a 40,000 lb fire control system which took up precious below deck space in order to replace a 14,000 lb gun director that "had all the same features"? I don't think so.

You are correct that the FD4 had no auto-tracking capability. It was the Mk22 late in the war. My apologies to the readership.


B
In 2009 I went to Washington DC and spent a week doing research at the USN NHC Library, and it's you have things wrong and you don't seem to understand some of the key concepts involved.

In no particular order:

MK33's Mk10 rangekeeper featured automatic gun drives, just like Mk37.
MK 33 featured automatic rate control, including change of altitude "" ""
Mk37 had no technological advances over Mk33 nor did the USN claim any. Mk37/Mk1 was certainly not the first AA FC computer to be able to predict target change of altitude.
MK37 director was heavier than the Mk33 director despite the fact that Mk33 had the Mk10 Rangekeeper incorporated into the director!

From the official BuOrd history:
In operation, the Mark 33 was almost completely automatic
once it was sighted on the target by telescopes. Present range
was determined by its own rangefinder, and advanced range was
computed by the rangekeeper, which received the course and speed
of own ship and computed those of the target. This information
permitted the director to supply the guns with orders for train,
elevation, and fuze settings. Early in the war the Mark 33 was
further improved by the addition of radar, which supplied smooth,
accurate data and made blind firing possible. But for all its virtues,
the Mark 33 suffered a notable defect: each equipment
weighed almost 20,000 pounds. This was considered too much
weight at best, and the problem was compounded by the fact that
all the director components were designed for topside, even lofty,
installation—a fact that gave the director the descriptive appellation,
"apple on a stick." The unusual mounting made the equipment
especially susceptible to vibration, and the concentration of
several instruments into a single unit meant that the operating
personnel were crowded and vulnerable.
While the defects were not prohibitive and the Mark 33 remained
in production until fairly late in World War II, the Bureau started
the development of an improved director in 1936, only 2 years after
the first installation of a Mark 33. The objective of weight reduction
was not met, since the resulting director system actually
weighed about 8000 pounds more than the equipment it was slated
to replace
, but the Gun Director Mark 37 that emerged from the
program possessed virtues that more than compensated for its extra
weight. Though the gun orders it provided were the same as those
of the Mark 33
, it supplied them with greater reliability and gave
generally improved performance with 5-inch gun batteries, whether
they were used for surface or antiaircraft use. Moreover, the stable
element and computer, instead of being contained in the director
housing were installed below deck where they were less vulnerable
to attack and less of a jeopardy to a ship's stability.
(my emphasis)

Minimum weight for a Mk37 director was about 5000lb more than the Mk33 director which was a serious flaw.

Mk37 followed the pattern set by HACS 1 in 1930 of an above decks director feeding data to a below decks FC computer. It only took the USN 10 years to abandon the unworkable scheme set by their Mk19-33 GFCS, but even then Mk37 was so heavy that it seriously impaired destroyer stability and forced a reduction in armament to ensure stability.

Why is it that none of the drawbacks of USN AA FC are never mentioned?
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Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by Steve Crandell »

dunmunro wrote: Mon May 10, 2021 2:39 am Why is it that none of the drawbacks of USN AA FC are never mentioned?
I was under the impression that is what you have been doing. In fact, your latest claim is that Mk 37 was worse than Mk 33.

Why is it that none of the drawbacks of RN AA FC are never mentioned?

What armament was removed from the Fletcher class DDs to permit the use of the Mk 37?
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Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by dunmunro »

Steve Crandell wrote: Mon May 10, 2021 3:24 am
dunmunro wrote: Mon May 10, 2021 2:39 am Why is it that none of the drawbacks of USN AA FC are never mentioned?
I was under the impression that is what you have been doing. In fact, your latest claim is that Mk 37 was worse than Mk 33.

Why is it that none of the drawbacks of RN AA FC are never mentioned?

What armament was removed from the Fletcher class DDs to permit the use of the Mk 37?
The drawbacks of RN AA FC are all that's ever mentioned.

You can read the BuOrd official history as well as I, so I don't understand your 2nd sentence.

The Fletcher class were very large destroyers, and were designed outside the treaty limits, unlike the Sims, and subsequent classes, that had to surrender a 5in mount and restrict their CIWS to maintain stability.
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Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by Steve Crandell »

The Fletcher class was the largest class of destroyers built during WWII. Subsequent classes also used the Mark 37. If it was too heavy for previous classes I think that's actually kind of irrelevant.
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Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by dunmunro »

Steve Crandell wrote: Mon May 10, 2021 4:26 pm The Fletcher class was the largest class of destroyers built during WWII. Subsequent classes also used the Mark 37. If it was too heavy for previous classes I think that's actually kind of irrelevant.
The weight of Mk37 was very relevant to the classes prior to the Fletcher class, considering that it effected 108 USN destroyers (12 Sims and 96 Benson-Gleaves class). The extreme weight of the Mk37 also meant that USN DEs had no AA FC until 1944, when BuOrd was finally able to design a lighter AA FCS suitable for a DE (The RN had am operational DE suitable AA FCS from 1938).
Byron Angel
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Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by Byron Angel »

dunmunro wrote: Sun May 09, 2021 6:46 am There was nothing ground breaking about Mk37, as the Mk33 had all the same features .....

OD3147 – DEFENSE AGAINST DIVE BOMBERS USING GUN DIRECTORS Mk. XIX, Mk. XXVIII, Mk. XXXIII and MK. XXXVII

14 September 1939

OBJECT
1. The object of this pamphlet is to p[resent the various methods of defense against dive-bomber attack and to illustrate the adaptability thereto of the A.A. director systems now in service.
METHODS OF DEFENSE
1. In defending against the attack of a dive-bomber, the following methods are considered:

(a) A ladder barrage or fixed barrage using pointer fire from individual guns with pre-set fuzes.
(b) A fixed barrage, MPI stationary in the path of the dive-bomber, using director fire.
(c) A creeping barrage, MPI moving in slower than dive-bomber approaches, using director fire.
(d) Director fire attempting to keep the MPI on the dive-bomber continuously.

In the case of (d) above -

“GUN DIRECTOR Mk. XXXVII with COMPUTER Mk. 1
Within the limiting speeds given in the table on the following page, this director system will operate against a dive attack exactly the same as against any normal air target. In this condition, the problem should be rate controlled, then will automatically be compensated for all movements of the target away from the direct line of sight.”

Neither the Mk19, Mk28 nor Mk33 was capable of performing in this manner. Even the Mk33, best of the other three other systems, was required to enter a guessed dive speed and artificially set horizontal target speed and angle of climb to zero on the gun director.

See below as well -

- - -

Russell Sydnor Crenshaw, Jr.
Captain, U.S. Navy. Retired

http://www.destroyerhisto.../goldplater/crest01.html


Crenshaw began service on USS Maury on "23rd of March, 1941." USS Maury had an AA armament of 4 x 5"/38 with Mk 33 DCT and "four .50 Cal. Machineguns".

Description of the MK 33 FC system:

"My "Battle Station" was in the Mk-33 Director as Assistant Rangekeeper Operator to Chief Firecontrolman Wilson while I learned my duties. A "Director" is like a "master" gun, without a barrel, to which the firing guns are "slaved". It's telescopic optics follow the target, its rangekeeper calculates the corrections and off-sets for the guns, and its gyroscopic "Stable Element" compensates for the roll and pitch of the ship. The heart of the Mk-33 was the Mk-10 Rangekeeper, a 5 ft. cube jammed with shafts, gears, cams and switches, which continuously solves the three-dimensional, ever-changing problem presented by a moving target. The director transmits the resulting firing "Orders" to the guns electrically through a system of "Synchros". The guns could be shifted to "Automatic" and could follow the director's orders without further action by the Pointer, Trainer, or Sightsetter. An essential key to accurate firing is Range-to-the-Target, which was measured by a stabilized "Stereo" Rangefinder mounted in the front of the director. The inputs and outputs of the rangekeeper were presented symbolically on the face of the rangekeeper where the operator could make adjustments and corrections as required. A good rangekeeper operator could produce a "Solution" on a moving target, air or surface, in about 30 seconds.

The Mk-33 was really a small "house" which pivotted on a pedestal on top of the Pilothouse. Its top sloped gently forward and the Rangefinder, looking like a 12 ft section of large pipe, was mounted horizontally across the front. The house was about 10 feet cube and at General Quarters almost a dozen operators were crammed inside around the central Rangekeeper and complex optical system. The Pointer and Trainer kept the Director pointed at the Target through telescopic sights. The Leveller and Cross-Leveler were "standing by" to stabilize the system +using horizon telescopes should the Stable Element fail. The Rangekeeper Operator and his Assistant were on the right side of the central box and two other operators, handling "Follow-ups" and "Illumination Control", were on the left side. The "Prima Donna" of the Director Crew was the Rangefinder Operator, sitting front-center, who had to be able to "see" stereo-optically to measure ranges, and who, through his powerfully magnified "Eyes", ten feet apart, had the best view of the target. The Control Officer stood in the right, after corner of the director, with his head out a small hatch in the top, from where he commanded the director and all of the 5"/38 guns."


Limitations of the Mk 33, or straight and level as she goes:

From the "Sham battles" we had with our own carrier planes it became clear that in war we would be subjected to attacks which broke very quickly, seldom with any warning. When an incoming plane was sighted we would struggle to get our director's sights on target, measure the rapidly closing range, adjust the Mk-10 to a solution, and simulate opening fire before the attacker could complete his attack. Frequently we'd still be "slewing" the director to get on target when he roared overhead, attack completed. We held tracking drills at every opportunity to improve our ability to acquire targets quickly, but we had no mechanism to point out the target to the men on the director's telescopes- the control officer had to coax them on by voice. I became seriously concerned that we couldn't handle incoming dive or strafing attacks.
There was knob on the front of the Mk-10 labeled "Dive Attack", which was to be pulled out in case of such an attack and by which "Dive Speed" could be set into the rangekeeper. When I dug into the schematic to see what this did, I discovered that it only decreased 'Target Range" at the rate set in, but did nothing about the "Lead Angles" in either elevation or bearing. Our fancy Mk-10 Rangekeeper couldn't calculate a solution for a dive attack! It could calculate correctly only for horizontal, or nearly horizontal flight! With the help of the firecontrolmen, I worked out a system to eliminate any errors from previous settings and provide an estimated lead angle which should be effective for an attacker coming straight in at us. I showed this to Ed Miller, the "Gun Boss", to get his permission to use it, but got "chewed out" for getting into things that weren't the province of a junior gunnery officer!


B
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Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by Byron Angel »

dunmunro wrote: Mon May 10, 2021 2:08 am
Byron Angel wrote: Mon May 10, 2021 1:46 am
dunmunro wrote: Sun May 09, 2021 6:40 am The USN claimed 127 AA kills at Santa Cruz, this is in addition to USN CAP, Escort and strike aircraft claims, and the AA numbers. alone, are far in excess of the total number of IJN strike sorties at Santa Cruz, not all of which were shot down. Similar USN overclaims were made in almost all naval surface to air battles in 1942.
Please advise where this figure of 127 AA kills has come from in connection with the Battle of Santa Cruz.
I am at a bit of a loss to understand why you made this statement:
In the first eight months of the war (Dec 1942 through Jul 1942) 1,033 IJNAF aircraft were listed as combat losses, of which 128 (12.4 percent) were claimed by the USN as shot down by naval AA gunfire. In the following five months (Aug 1942 through Dec 1942) 1,006 IJNAF aircraft were listed as combat losses, of which 276 (27.4 percent) were claimed by the USN as shot down by naval AA gunfire. A total of 388 (19 percent) were claimed by USN naval AA gunfire of all calibers over the entire 13 month period. The other 1,651 IJNAF aircraft losses (81 percent) presumably fell to the fighter defense.
when the figure of 127 AA kill claims comes from BuOrd's Bulletin 22 (which covers July-Dec 1942) which you also referenced earlier. Have you actually read it? It seems to me that you are trying to obfuscate rather than clarify things here.

The figure of 127 kills by antiaircraft fire at the Battle of Santa Cruz does indeed appear in Bulletin 22. That number is the sum of raw unvetted kill claims mentioned in the action reports of the ships that took part in the battle; none of these claims were subjected to any scrutiny or critical operational analysis. The official report covering the Battle of Santa Cruz (also included in Bulletin No. 22), submitted under the name of Admiral Chester Nimitz - Commander in Chief of the US Pacific Fleet, gave a substantially different assessment of estimated enemy a/c losses, presumably after a review of the above-mentioned raw claims. The relevant passage is herewith quoted verbatim for the sake of good order -

"In addition, Commander Task Force reports that air and antiaircraft together destroyed 123 enemy carrier planes."

In "Comments and Conclusions", it is further stated that -

"Antiaircraft fire continues to grow in effectiveness. In this action for the first time AA fire from carrier forces shot down more planes than did our fighters. This gratifying advance results from increased experience and training, from improved guns (40-mm and 20-mm) and fire control equipment, and from the greater number of automatic weapons installed. The 40-mm was highly effective in its first baptism of fire. It is to date, the best answer to the need for a gun to cover the middle ranges between the 5"/38 and 20-mm."

Given that Japanese sources (see Dull and USSBS "Interrogation of Japanese Officials") indicate a/c losses of 100 or more a/c at Santa Cruz, accusations of rabid USN over-claiming in the arena of AA kills may well depend upon which particular kill claim figures are being referenced.

B
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Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by dunmunro »

Byron Angel wrote: Mon May 10, 2021 11:07 pm
dunmunro wrote: Mon May 10, 2021 2:08 am
Byron Angel wrote: Mon May 10, 2021 1:46 am

Please advise where this figure of 127 AA kills has come from in connection with the Battle of Santa Cruz.
I am at a bit of a loss to understand why you made this statement:
In the first eight months of the war (Dec 1942 through Jul 1942) 1,033 IJNAF aircraft were listed as combat losses, of which 128 (12.4 percent) were claimed by the USN as shot down by naval AA gunfire. In the following five months (Aug 1942 through Dec 1942) 1,006 IJNAF aircraft were listed as combat losses, of which 276 (27.4 percent) were claimed by the USN as shot down by naval AA gunfire. A total of 388 (19 percent) were claimed by USN naval AA gunfire of all calibers over the entire 13 month period. The other 1,651 IJNAF aircraft losses (81 percent) presumably fell to the fighter defense.
when the figure of 127 AA kill claims comes from BuOrd's Bulletin 22 (which covers July-Dec 1942) which you also referenced earlier. Have you actually read it? It seems to me that you are trying to obfuscate rather than clarify things here.

The figure of 127 kills by antiaircraft fire at the Battle of Santa Cruz does indeed appear in Bulletin 22. That number is the sum of raw unvetted kill claims mentioned in the action reports of the ships that took part in the battle; none of these claims were subjected to any scrutiny or critical operational analysis. The official report covering the Battle of Santa Cruz (also included in Bulletin No. 22), submitted under the name of Admiral Chester Nimitz - Commander in Chief of the US Pacific Fleet, gave a substantially different assessment of estimated enemy a/c losses, presumably after a review of the above-mentioned raw claims. The relevant passage is herewith quoted verbatim for the sake of good order -

"In addition, Commander Task Force reports that air and antiaircraft together destroyed 123 enemy carrier planes."

In "Comments and Conclusions", it is further stated that -

"Antiaircraft fire continues to grow in effectiveness. In this action for the first time AA fire from carrier forces shot down more planes than did our fighters. This gratifying advance results from increased experience and training, from improved guns (40-mm and 20-mm) and fire control equipment, and from the greater number of automatic weapons installed. The 40-mm was highly effective in its first baptism of fire. It is to date, the best answer to the need for a gun to cover the middle ranges between the 5"/38 and 20-mm."

Given that Japanese sources (see Dull and USSBS "Interrogation of Japanese Officials") indicate a/c losses of 100 or more a/c at Santa Cruz, accusations of rabid USN over-claiming in the arena of AA kills may well depend upon which particular kill claim figures are being referenced.

B
Again, this is a wartime analysis based solely on US claims. For a variety of reasons 5in AA was ineffective at Santa Cruz with South Dakota's captain estimating that only 5% of her AA kills were via 5in AA. Lundstrom, who analysed the battle with reference to both IJN and USN records, in the 2nd volume of his First Team books states:
Interestingly, the potency of AA at the battle became a bone of contention between veterans of the Enterprise and the South Dakota. Some sources (but significantly not the South Dakota’s action report) ascribed twenty-six kills to the battlewagon alone. Without going into detail it is possible, based on all available sources, including Japanese, to offer a reasoned estimate of relative effectiveness of AA versus the CAP in destroying Japanese planes. Counting only aircraft believed destroyed in the vicinity of the two U.S. task forces, the ratio between CAP and AA kills counting all the raids was twenty-nine by aircraft to twenty-five by AA (see table 22.1).That the fierce AA did not actually finish nearly as many Japanese aircraft as estimated in no way diminished its role in ruining the attacker’s accuracy.
Lundstrom states that 4 IJN aircraft were destroyed on bombed carriers and 28 ditched or crash landed in the vicinity of IJN carriers for a total loss of 99 aircraft. The rest of IJNAF losses were due to USN escort fighters and bomber defensive fire; 25 via AA, 29 via CAP, 32 ditched/crash landed, and 12 from other causes, mainly the aforementioned USN fighters and bomber defensive fire.

The idea that the 5in AA was effective at Santa Cruz, or elsewhere in the Pacific, in 1942 is a myth.
Last edited by dunmunro on Tue May 11, 2021 4:39 am, edited 2 times in total.
dunmunro
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Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by dunmunro »

Byron Angel wrote: Mon May 10, 2021 10:29 pm
dunmunro wrote: Sun May 09, 2021 6:46 am There was nothing ground breaking about Mk37, as the Mk33 had all the same features .....

OD3147 – DEFENSE AGAINST DIVE BOMBERS USING GUN DIRECTORS Mk. XIX, Mk. XXVIII, Mk. XXXIII and MK. XXXVII

14 September 1939

OBJECT
1. The object of this pamphlet is to p[resent the various methods of defense against dive-bomber attack and to illustrate the adaptability thereto of the A.A. director systems now in service.
METHODS OF DEFENSE
1. In defending against the attack of a dive-bomber, the following methods are considered:

(a) A ladder barrage or fixed barrage using pointer fire from individual guns with pre-set fuzes.
(b) A fixed barrage, MPI stationary in the path of the dive-bomber, using director fire.
(c) A creeping barrage, MPI moving in slower than dive-bomber approaches, using director fire.
(d) Director fire attempting to keep the MPI on the dive-bomber continuously.

In the case of (d) above -

“GUN DIRECTOR Mk. XXXVII with COMPUTER Mk. 1
Within the limiting speeds given in the table on the following page, this director system will operate against a dive attack exactly the same as against any normal air target. In this condition, the problem should be rate controlled, then will automatically be compensated for all movements of the target away from the direct line of sight.”

Neither the Mk19, Mk28 nor Mk33 was capable of performing in this manner. Even the Mk33, best of the other three other systems, was required to enter a guessed dive speed and artificially set horizontal target speed and angle of climb to zero on the gun director.

See below as well -

- - -

Russell Sydnor Crenshaw, Jr.
Captain, U.S. Navy. Retired

http://www.destroyerhisto.../goldplater/crest01.html


Crenshaw began service on USS Maury on "23rd of March, 1941." USS Maury had an AA armament of 4 x 5"/38 with Mk 33 DCT and "four .50 Cal. Machineguns".

Description of the MK 33 FC system:

"My "Battle Station" was in the Mk-33 Director as Assistant Rangekeeper Operator to Chief Firecontrolman Wilson while I learned my duties. A "Director" is like a "master" gun, without a barrel, to which the firing guns are "slaved". It's telescopic optics follow the target, its rangekeeper calculates the corrections and off-sets for the guns, and its gyroscopic "Stable Element" compensates for the roll and pitch of the ship. The heart of the Mk-33 was the Mk-10 Rangekeeper, a 5 ft. cube jammed with shafts, gears, cams and switches, which continuously solves the three-dimensional, ever-changing problem presented by a moving target. The director transmits the resulting firing "Orders" to the guns electrically through a system of "Synchros". The guns could be shifted to "Automatic" and could follow the director's orders without further action by the Pointer, Trainer, or Sightsetter. An essential key to accurate firing is Range-to-the-Target, which was measured by a stabilized "Stereo" Rangefinder mounted in the front of the director. The inputs and outputs of the rangekeeper were presented symbolically on the face of the rangekeeper where the operator could make adjustments and corrections as required. A good rangekeeper operator could produce a "Solution" on a moving target, air or surface, in about 30 seconds.

The Mk-33 was really a small "house" which pivotted on a pedestal on top of the Pilothouse. Its top sloped gently forward and the Rangefinder, looking like a 12 ft section of large pipe, was mounted horizontally across the front. The house was about 10 feet cube and at General Quarters almost a dozen operators were crammed inside around the central Rangekeeper and complex optical system. The Pointer and Trainer kept the Director pointed at the Target through telescopic sights. The Leveller and Cross-Leveler were "standing by" to stabilize the system +using horizon telescopes should the Stable Element fail. The Rangekeeper Operator and his Assistant were on the right side of the central box and two other operators, handling "Follow-ups" and "Illumination Control", were on the left side. The "Prima Donna" of the Director Crew was the Rangefinder Operator, sitting front-center, who had to be able to "see" stereo-optically to measure ranges, and who, through his powerfully magnified "Eyes", ten feet apart, had the best view of the target. The Control Officer stood in the right, after corner of the director, with his head out a small hatch in the top, from where he commanded the director and all of the 5"/38 guns."


Limitations of the Mk 33, or straight and level as she goes:

From the "Sham battles" we had with our own carrier planes it became clear that in war we would be subjected to attacks which broke very quickly, seldom with any warning. When an incoming plane was sighted we would struggle to get our director's sights on target, measure the rapidly closing range, adjust the Mk-10 to a solution, and simulate opening fire before the attacker could complete his attack. Frequently we'd still be "slewing" the director to get on target when he roared overhead, attack completed. We held tracking drills at every opportunity to improve our ability to acquire targets quickly, but we had no mechanism to point out the target to the men on the director's telescopes- the control officer had to coax them on by voice. I became seriously concerned that we couldn't handle incoming dive or strafing attacks.
There was knob on the front of the Mk-10 labeled "Dive Attack", which was to be pulled out in case of such an attack and by which "Dive Speed" could be set into the rangekeeper. When I dug into the schematic to see what this did, I discovered that it only decreased 'Target Range" at the rate set in, but did nothing about the "Lead Angles" in either elevation or bearing. Our fancy Mk-10 Rangekeeper couldn't calculate a solution for a dive attack! It could calculate correctly only for horizontal, or nearly horizontal flight! With the help of the firecontrolmen, I worked out a system to eliminate any errors from previous settings and provide an estimated lead angle which should be effective for an attacker coming straight in at us. I showed this to Ed Miller, the "Gun Boss", to get his permission to use it, but got "chewed out" for getting into things that weren't the province of a junior gunnery officer!


B
I'm afraid that you're misinterpreting this. I'll reply in detail later. Regardless, a divebomber attack against the firing ship is not the same as being able to predict against aircraft changing altitude.
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Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by Byron Angel »

Steve Crandell wrote: Mon May 10, 2021 4:26 pm The Fletcher class was the largest class of destroyers built during WWII. Subsequent classes also used the Mark 37. If it was too heavy for previous classes I think that's actually kind of irrelevant.

Hi Steve,
The Farragut Class (followed by the pre-war Mahans, Gridleys, Dunlaps, Bagleys, Benhams - all generally 1500t "boutique" designs built in relatively small numbers) were the first USN DDs to mount the Mk33 Gun Director, which included everything including its Ford Rangekeeper MK10 in an all-in-one aloft-mounted director. It weighed about 14,000-15,000 pounds, depending upon degree of weather shielding/splinter protection. 85 Mk33s were in service by December 1941, with a total of 124 built by the end of the war

The Sims were the first USN DD class to mount the MK37 GFCS, followed by the war-built DD classes (Bensons, Gleaves, Fletchers, Sumners and Gearings). The rotating aloft director (with 0.5in splinter protection on DDs) weighed approx 30,000 pounds, while the below deck Mk1 computer set-up accounted for approximately another 10,000 lbs. This assumes 0.5-in splinter protection on DD systems. Mk37s mounted on battleships carried as much as 1.5-in splinter protection and would weigh commensurately (and considerably) more. IIRC, 841 Mk37s were built during the war.

I do not know whether these weight figures reflected the associated radars mounted upon the directors.

Some of the Mk33s were fitted to pre-war heavy ships (pre-war CVs, treaty cruisers for example - too lazy to check on the old BBs) to control secondary batteries. Numerous Mk37s were carried aboard the new CVs, fast BBs, war-built CAs and CLs to control 5-in/38 secondary batteries.

The greater weight of the Mk37 was not the reason for removal of main battery guns and torpedo tubes in US DDs. The pre-war DD classes were very tight designs, with heavy main gun and torpedo armaments (but next to no close/medium range AA armament) for their limited displacement. As designed and built, the pre-war DD classes from Farragut to Gleaves featured a light AA armament of only 4 to 6 x 50cal MGs - that was it; not even a 1.1-inch quad until the early Fletchers! They were forced to shed at least one 5-inch mount and often a bank of torpedoes in order to add any sort of effective close range light/medium AA armament. The Sims (and most war-built follow-ons) had been designed with the new Mk37 in mind; but they came out tight as well for the same reasons and were similarly forced to sacrifice some of their heavy surface weapons in exchange for improved AA armament. Another factor to consider is that limited deck space was also an issue on these small ships.

FWIW - Hope this helps.

B
dunmunro
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Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by dunmunro »

Byron Angel wrote: Wed May 12, 2021 3:51 am
Steve Crandell wrote: Mon May 10, 2021 4:26 pm The Fletcher class was the largest class of destroyers built during WWII. Subsequent classes also used the Mark 37. If it was too heavy for previous classes I think that's actually kind of irrelevant.

Hi Steve,
The Farragut Class (followed by the pre-war Mahans, Gridleys, Dunlaps, Bagleys, Benhams - all generally 1500t "boutique" designs built in relatively small numbers) were the first USN DDs to mount the Mk33 Gun Director, which included everything including its Ford Rangekeeper MK10 in an all-in-one aloft-mounted director. It weighed about 14,000-15,000 pounds, depending upon degree of weather shielding/splinter protection. 85 Mk33s were in service by December 1941, with a total of 124 built by the end of the war

The Sims were the first USN DD class to mount the MK37 GFCS, followed by the war-built DD classes (Bensons, Gleaves, Fletchers, Sumners and Gearings). The rotating aloft director (with 0.5in splinter protection on DDs) weighed approx 30,000 pounds, while the below deck Mk1 computer set-up accounted for approximately another 10,000 lbs. This assumes 0.5-in splinter protection on DD systems. Mk37s mounted on battleships carried as much as 1.5-in splinter protection and would weigh commensurately (and considerably) more. IIRC, 841 Mk37s were built during the war.

I do not know whether these weight figures reflected the associated radars mounted upon the directors.

Some of the Mk33s were fitted to pre-war heavy ships (pre-war CVs, treaty cruisers for example - too lazy to check on the old BBs) to control secondary batteries. Numerous Mk37s were carried aboard the new CVs, fast BBs, war-built CAs and CLs to control 5-in/38 secondary batteries.

The greater weight of the Mk37 was not the reason for removal of main battery guns and torpedo tubes in US DDs. The pre-war DD classes were very tight designs, with heavy main gun and torpedo armaments (but next to no close/medium range AA armament) for their limited displacement. As designed and built, the pre-war DD classes from Farragut to Gleaves featured a light AA armament of only 4 to 6 x 50cal MGs - that was it; not even a 1.1-inch quad until the early Fletchers! They were forced to shed at least one 5-inch mount and often a bank of torpedoes in order to add any sort of effective close range light/medium AA armament. The Sims (and most war-built follow-ons) had been designed with the new Mk37 in mind; but they came out tight as well for the same reasons and were similarly forced to sacrifice some of their heavy surface weapons in exchange for improved AA armament. Another factor to consider is that limited deck space was also an issue on these small ships.

FWIW - Hope this helps.

B
It not possible to add ~4 tons at the director level (~55ft AWL) and not have it cause serious issues for ship stability. As the BuOrd history makes clear, one of the design goals of Mk37 was to reduce topweight, and this goal was not met.
Byron Angel
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Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by Byron Angel »

dunmunro wrote: Wed May 12, 2021 9:07 am It not possible to add ~4 tons at the director level (~55ft AWL) and not have it cause serious issues for ship stability. As the BuOrd history makes clear, one of the design goals of Mk37 was to reduce topweight, and this goal was not met.

Hi dunmunro,
Apparently, Bureau of Ships did not share your concerns.

B
dunmunro
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Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by dunmunro »

Byron Angel wrote: Wed May 12, 2021 6:09 pm
dunmunro wrote: Wed May 12, 2021 9:07 am It not possible to add ~4 tons at the director level (~55ft AWL) and not have it cause serious issues for ship stability. As the BuOrd history makes clear, one of the design goals of Mk37 was to reduce topweight, and this goal was not met.

Hi dunmunro,
Apparently, Bureau of Ships did not share your concerns.

B
Really, so the fact that the pre-Fletcher Mk37 equipped destroyers all came out seriously top heavy and overweight, forcing a reduction in armament, was not true?
dunmunro
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Re: British 4.5"/45 (11.4 cm) vs American 5"/38 (12.7 cm) Mark 12

Post by dunmunro »

dunmunro wrote: Tue May 11, 2021 4:16 am
Byron Angel wrote: Mon May 10, 2021 10:29 pm
dunmunro wrote: Sun May 09, 2021 6:46 am There was nothing ground breaking about Mk37, as the Mk33 had all the same features .....

OD3147 – DEFENSE AGAINST DIVE BOMBERS USING GUN DIRECTORS Mk. XIX, Mk. XXVIII, Mk. XXXIII and MK. XXXVII

14 September 1939

OBJECT
1. The object of this pamphlet is to p[resent the various methods of defense against dive-bomber attack and to illustrate the adaptability thereto of the A.A. director systems now in service.
METHODS OF DEFENSE
1. In defending against the attack of a dive-bomber, the following methods are considered:

(a) A ladder barrage or fixed barrage using pointer fire from individual guns with pre-set fuzes.
(b) A fixed barrage, MPI stationary in the path of the dive-bomber, using director fire.
(c) A creeping barrage, MPI moving in slower than dive-bomber approaches, using director fire.
(d) Director fire attempting to keep the MPI on the dive-bomber continuously.

In the case of (d) above -

“GUN DIRECTOR Mk. XXXVII with COMPUTER Mk. 1
Within the limiting speeds given in the table on the following page, this director system will operate against a dive attack exactly the same as against any normal air target. In this condition, the problem should be rate controlled, then will automatically be compensated for all movements of the target away from the direct line of sight.”

Neither the Mk19, Mk28 nor Mk33 was capable of performing in this manner. Even the Mk33, best of the other three other systems, was required to enter a guessed dive speed and artificially set horizontal target speed and angle of climb to zero on the gun director.

See below as well -

- - -

Russell Sydnor Crenshaw, Jr.
Captain, U.S. Navy. Retired

http://www.destroyerhisto.../goldplater/crest01.html


Crenshaw began service on USS Maury on "23rd of March, 1941." USS Maury had an AA armament of 4 x 5"/38 with Mk 33 DCT and "four .50 Cal. Machineguns".

Description of the MK 33 FC system:

"My "Battle Station" was in the Mk-33 Director as Assistant Rangekeeper Operator to Chief Firecontrolman Wilson while I learned my duties. A "Director" is like a "master" gun, without a barrel, to which the firing guns are "slaved". It's telescopic optics follow the target, its rangekeeper calculates the corrections and off-sets for the guns, and its gyroscopic "Stable Element" compensates for the roll and pitch of the ship. The heart of the Mk-33 was the Mk-10 Rangekeeper, a 5 ft. cube jammed with shafts, gears, cams and switches, which continuously solves the three-dimensional, ever-changing problem presented by a moving target. The director transmits the resulting firing "Orders" to the guns electrically through a system of "Synchros". The guns could be shifted to "Automatic" and could follow the director's orders without further action by the Pointer, Trainer, or Sightsetter. An essential key to accurate firing is Range-to-the-Target, which was measured by a stabilized "Stereo" Rangefinder mounted in the front of the director. The inputs and outputs of the rangekeeper were presented symbolically on the face of the rangekeeper where the operator could make adjustments and corrections as required. A good rangekeeper operator could produce a "Solution" on a moving target, air or surface, in about 30 seconds.

The Mk-33 was really a small "house" which pivotted on a pedestal on top of the Pilothouse. Its top sloped gently forward and the Rangefinder, looking like a 12 ft section of large pipe, was mounted horizontally across the front. The house was about 10 feet cube and at General Quarters almost a dozen operators were crammed inside around the central Rangekeeper and complex optical system. The Pointer and Trainer kept the Director pointed at the Target through telescopic sights. The Leveller and Cross-Leveler were "standing by" to stabilize the system +using horizon telescopes should the Stable Element fail. The Rangekeeper Operator and his Assistant were on the right side of the central box and two other operators, handling "Follow-ups" and "Illumination Control", were on the left side. The "Prima Donna" of the Director Crew was the Rangefinder Operator, sitting front-center, who had to be able to "see" stereo-optically to measure ranges, and who, through his powerfully magnified "Eyes", ten feet apart, had the best view of the target. The Control Officer stood in the right, after corner of the director, with his head out a small hatch in the top, from where he commanded the director and all of the 5"/38 guns."


Limitations of the Mk 33, or straight and level as she goes:

From the "Sham battles" we had with our own carrier planes it became clear that in war we would be subjected to attacks which broke very quickly, seldom with any warning. When an incoming plane was sighted we would struggle to get our director's sights on target, measure the rapidly closing range, adjust the Mk-10 to a solution, and simulate opening fire before the attacker could complete his attack. Frequently we'd still be "slewing" the director to get on target when he roared overhead, attack completed. We held tracking drills at every opportunity to improve our ability to acquire targets quickly, but we had no mechanism to point out the target to the men on the director's telescopes- the control officer had to coax them on by voice. I became seriously concerned that we couldn't handle incoming dive or strafing attacks.
There was knob on the front of the Mk-10 labeled "Dive Attack", which was to be pulled out in case of such an attack and by which "Dive Speed" could be set into the rangekeeper. When I dug into the schematic to see what this did, I discovered that it only decreased 'Target Range" at the rate set in, but did nothing about the "Lead Angles" in either elevation or bearing. Our fancy Mk-10 Rangekeeper couldn't calculate a solution for a dive attack! It could calculate correctly only for horizontal, or nearly horizontal flight! With the help of the firecontrolmen, I worked out a system to eliminate any errors from previous settings and provide an estimated lead angle which should be effective for an attacker coming straight in at us. I showed this to Ed Miller, the "Gun Boss", to get his permission to use it, but got "chewed out" for getting into things that weren't the province of a junior gunnery officer!


B
Note that Crenshaw was able to work out a system to provide essentially the same solution as per Mk37, which is not surprising because the Mk10 Rangekeeper was nearly identica; to the Mk1 computer in the Mk37 GFCS.

I'm afraid that you're misinterpreting this. I'll reply in detail later. Regardless, a divebomber attack against the firing ship is not the same as being able to predict against aircraft changing altitude.
The Mk28/33/37 all allowed for prediction against targets changing altitude (as per glide bombing) , and while the Mk37 Dive Attack mode sounds impressive, it was really quite useless when firing TM fuzed shells. Prior to radar, optical RFs simply couldn't provide ranges accurately enough or fast enough to provide an accurate rate, and DBs are typically in a state of constant acceleration anyways (the computer always assumed constant speed and direction during the prediction cycle) and the average DB was in it's dive for only 20-30 secs which was barely enough time to setup the the FC problem in the computer, much less determine an accurate rate and dive angle. Finally the Mk1 computer could not calculate accurate solutions when total elevations reached 70deg:

http://archive.hnsa.org/doc/computermk1/pg379.htm

and

http://archive.hnsa.org/doc/computermk1/pg380.htm

and during a dive bomber attack the target ship will probably be maneuvering radically, and the director will have a nearly impossible time staying on target, which was a problem that hampered AA FC in all the 1942 carrier battles, especially at Santa Cruz.
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