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Old 03-04-2020, 06:43 AM   #1
LoneWolf_gabo
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Default WW2 1940's tech questions

Hello everybody,

As part of the development of my sim i need to get some info regarding the functionality of some tech of 1940's. While most topics can be researched on the web there are some stuff that remains unknown to me.
And i think this forum is the best resource for the matter.

One key topic i have been trying to get right is how big deck guns of for example a destroyer or a cruiser work for the aiming. I understand there's a "turret" called the fire director where inside it there's crew tracking and providing data for the firing solution. Not sure wich data other than range finding and target tracking maybe?
Also, does guns automatically track where the director is aiming? or was this done manually inside each gun turret? if so, did the fire director transmit via radio the range and direction to shoot?

The main reason for needing to know this is that crew will have to be trained to speed up and improve the function they do. So i need to know what rely on crew on what rely on automatization.

Hope it's not too much to ask
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Old 03-04-2020, 09:41 AM   #2
Kptlt. Neuerburg
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This might help some https://en.wikipedia.org/wiki/Fire-c...d_fire_control
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Old 03-04-2020, 12:06 PM   #3
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THIS MAY SHED SOME LIGHT:
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GENERAL COMMENTS: The bottom line is that, after 1943 or so, having the world's best optical fire-control systems was largely irrelevant. The night battle between Washington and Kirishima near Savo pretty much settled the point; good radar usually beats good optics in a stand-up fight. And the radar used by Washington off of Guadalcanal was not as good as the sets fitted aboard Iowa.

Then there's the fact that all radar fire-control is not created equal. Radar operating at meter or decimeter wavelengths is useful for ranging, but lacks the angular accuracy necessary for training. In practical terms, this means that a decimetric set can develop a range solution via radar, but must rely on an optical director to supply training information for the battery. This hybrid fire-control solution is, of course, limited by the quality of the optics available, and also by the visual horizon (which is closer than the radar horizon), and weather conditions. Only with the advent of 10cm and (later) 3cm wavelength sets was true 'blindfire' radar fire-control achievable, wherein the firing ship need never come into visual range of the opposing vessel. The Germans, Japanese, and Italians never developed sets of this capability (both the Japanese (despite its 10cm wavelength) and German sets were usable for fire control against a battleship-sized target only out to a range of about 27,000 yards.) The bottom line is, then, that the Allied vessels, and particularly Iowa and South Dakota, would enjoy an enormous advantage in gunfire control over their adversaries. She would have the ability to lob shells over the visual horizon, and would also perform better in complete darkness or adverse weather conditions. The final adjusted rating also reflects the fact that American FC systems employed by far the most advanced stable vertical elements in the world. In practical terms, this meant that American vessels could keep a solution on a target even when performing radical maneuvers. In 1945 test, an American battleship (the North Carolina) was able to maintain a constant solution even when performing back to back high-speed 450-degree turns, followed by back-to-back 100-degree turns. This was a much better performance than other contemporary systems, and gave U.S. battleships a major tactical advantage, in that they could both shoot and maneuver, whereas their opponents could only do one or the other. http://www.combinedfleet.com/b_fire.htm
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The above is a good capsule summary of the FCS of the major battleships of each nation and I'm going to refer to it in this post. For purposes of simplicity, I am only going to discuss the British, German, Japanese and US ships. Since you are only interested in optical FC, I'm also not going to discuss radar FC except to state, once again, that radar FC beats optical in almost any situation and so there's little point in comparing the two.
Now, three points to note:
  1. The British battleships lacked RPC almost entirely until late in the war. The Japanese never implemented it in any meaningful way. The Germans had it only for elevation (more on that later) while the USN had it for both elevation and bearing. To me, RPC is one of the single most important advancements in the development of accurate gunnery. No longer did the director operator shout down a voice tube "target bearing 230 degrees at 20,500 yards" to which another sailor dialed into the rangekeeper (analog computer) which was then transmitted to a set of dials in the gun mounts which then the gun captain had his trainers and elevators match by slewing/elevating the guns to match the dials, with at every point a potential for operator errors. Instead, the director operator now controlled the laying of the guns almost directly. Plus, in the US system, there was a feedback system where the rangekeeper moved the director sights to where it thought the ship should be shooting. If it wasn't correct, the director operator adjusted the sights back on target, thus setting up a closed-loop system (for a living, I design process control computers that do this digitally. So, please trust me on this, I'm amazed at what was achieved in closed-loop systems using 1930s analog computers). The German system had RPC only for the elevation, but this is not as bad as it may seem. Since, in the German system of "bracket salvos," the first half salvo is really to determine bearing, they did not feel that the extra complication was necessary. Judging from the results at River Plate and Denmark Strait, it's hard to argue, but, my personal opinion is that it would have been worth the investment. The Japanese, as in much of their naval technology, used the same methodology as their British mentors and used a "follow the pointer" system for both elevation and training.
  2. The main director baselength on the Japanese, German and US ships was roughly about as long as on the main turrets and was relatively large. By contrast, the British had a relatively short baselength both as compared to the turret rangefinders and as compared to those of other nation's ships. In fact, the main director on British ships was almost an afterthought, intended to be used more for fire direction than for fire control. The real FC rangefinders in the British ships were the ones on the main turrets. Again, I was surprised when I discovered this a couple of years ago, as the British pioneered centralized FC and the Nelson class with their high-mounted directors greatly influenced subsequent designs. The British reliance on turret RF's is really a holdover from pre- and early-dreadnought days, where each individual turret layed the guns for themselves.
    This reliance on turret RF was shown flawed at the Denmark Strait: Since Adm. Holland chose to push his ships directly towards the Germans and thus into the wind; sea spray coated the optics on all four forward turrets and forced the British to use the less accurate main directors. I think that the results speak for themselves: The British fired long-spaced ladder salvos and didn't land a hit until after the POW turned broadside to the Germans (i.e., the turrets no longer faced into the sea spray) at a relatively short range of about 16,000 yards. As a result of this engagement, the British belatedly realized their design/concept flaw and installed a larger (but still relatively short) baselength director on the last three KGV ships. However, only the forward director was modified, the aft director was unchanged.
  3. The use of stable vertical elements in the US systems. I call your attention to the paragraph at the bottom of the above "Baddest" link, describing the performance of the USS North Carolina (the oldest of the new battleships) during a series of maneuvers where she still maintained target lock. Since you own "British Battleships," I won't repeat the problems and successes that the British had with their systems. I have only limited information on what other nation's ships were capable of, but it appears that the German's systems were at least equivalent to those of the British (I assume this from descriptions in Whitley's and Campbell's books plus Baron Mullenheim-Rechburg's comments in "Survivor").
Bottom line: The Japanese and the Germans had better optical RF's than any other nation. In a fight where only optical systems are used, they had a clear advantage as shown at Denmark Strait, the River Platte and First Savo (I assume that you've seen my previous posts regarding the POW's radar and won't revisit the subject). However, the US had the best FC as a system (FCS). What this meant is that, when 10cm fire-control radar became available, the US was able to easily integrate it into their FCS, thus creating the best overall FCS as compared to the FCS used by any other nation. My (strictly amateur) conclusion is that the US FCS with radar was the most advanced of any nation in the 1942-1945 timeframe.
One other item, per your last post: I do not take the Bismarck's performance at her last battle as being truly indicative of her performance. The crew was exhausted by their night-long skirmishing with Capt. Vian's destroyers and the Bismarck's motion was subject to random direction changes. By contrast, the British battleships had rested crews firing from stable platforms. As always, I dislike to speculate upon "what-ifs," especially this one, as, in my opinion, an undamaged Bismarck with Adm. Lutjens in command wouldn't have fought against the KGV and Rodney, she would have beat feet in the opposite direction as fast as possible. So, I'll leave any thought as to what the outcome of an engagement between healthy ships to others.
BOTTOM LINE: REGARDLESS OF ANY 'BEST' SPOTTING FIRE CONTROL SYSTEM, ALL BATTLESHIPS CAN HAVE A BAD DAY....1989 #2 TURRET OF USS IOWA KILLS 47 GUNNERS AND AN IDEA OF THE FULL BROADSIDE'S POWER:
 
Sandia investigators asked if two similar explosions on the battleship USS Mississippi could be related to the Iowa explosion. In 1924 and 1943, open breech explosions had occurred in the Turret Two center gun aboard Mississippi, each time killing most of the crewmen in the turret. Miceli's team responded that the explosions were not related, because the Mississippi incidents were not actual explosions, but "intense burnings" of the powder which resulted from different causes than the Iowa incident. A staff officer from Naval Sea Systems Command, Rear Admiral Robert H. Ailes, told Sandia that the Mississippi explosions "would not be discussed".The team determined that the "tare" or "trim" layer (a small amount of powder placed at the end of each bag to equalize the bag's weight, inserted in the mid-1980s when the powder was mixed and rebagged under Miceli's direction) would often ignite when compressed at high speed. Cooper found that the burning fragments did not ignite adjacent powder in the same bag, but instead would burn through the bag material and ignite the adjacent bag's black powder patch and thereby ignite the rest of the bags. The week of 7 May, Schwoebel asked Miceli to conduct drop tests at Dahlgren using five actual bags of powder compressed into a steel cylinder of the same diameter as a 16-inch gun. Miceli responded that Cooper's finding "has no relation to actual 16-inch gun conditions" and refused repeated requests from Sandia to conduct the tests. Concerned that Miceli's refusal to conduct full-scale drop tests was placing Navy gun crews at risk, on 11 May Schwoebel contacted Rick DeBobes, Nunn's counsel for the SASC. On 14 May 1990, a letter from Nunn was sent to Trost requesting that the Navy conduct the tests as requested by Sandia and that Sandia be allowed to observe the tests. That same day, Miceli's supervisor, Vice Admiral Peter Hekman, commander of Sea Systems Command, called Sandia's president, Al Narath, and told him that the Navy would conduct the full-scale drop tests as requested and Sandia was invited to participate.
The drops tests were conducted at Dahlgren under Miceli's and Tom Doran's direction. The tests consisted of vertically stacking five D-846 powder bags under an 860-pound (390 kg) weight and dropping them three feet onto a steel plate to simulate a high-speed overram in a 16-inch gun barrel. On 24 May 1990 on the 18th drop test, witnessed by Cooper and Schuler, the powder bags exploded, destroying the entire testing apparatus. Miceli immediately told Hekman, who notified the Navy's leadership to halt any further use of 16-inch guns and to reopen the Navy's investigation.
USS IOWA'S FCS 1943: WITH MARK 38 DIRECTOR (RADAR AND OPTICS) ATOP.
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Mark 41 Stable Vertical, Mk13 FC Radar controls and displays, Parallax Correctors, Fire Control Switchboard, battle telephone switchboard, battery status indicators, assistant Gunnery Officers, and Fire Control Technicians (FTs) <Mark 8 Rangekeeper



The Mk 8 Rangekeeper was an electromechanical analog computer[16] whose function was to continuously calculate the gun's bearing and elevation, Line-Of-Fire (LOF), to hit a future position of the target. It did this by automatically receiving information from the director (LOS), the FC Radar (range), the ship's gyrocompass (true ship's course), the ship's Pitometer log (ship's speed), the Stable Vertical (ship's roll and pitch), and the ship's anemometer (relative wind speed and direction). Also, before the surface action started, the FTs made manual inputs for the average initial velocity of the projectiles fired out of the battery's gun barrels, and air density. With all this information, the Rangekeeper calculated the relative motion between "OWN SHIP" and "TARGET". It then could calculate an offset angle and change of range between the target's present position (LOS) and future position at the end of the projectile's time of flight. To this bearing and range offset, it added corrections for gravity, wind, Magnus effect of the spinning projectile, earth's curvature, and coriolis effect. The result was the turret's bearing and elevation orders (LOF) During the surface action, range and deflection Spots and target altitude (not zero during Gun Fire Support) were manually entered.
<Mark 41 Stable Vertical



The Mk 41 Stable Vertical (also called Gun Director) was a vertical seeking gyroscope. Its function was to establish and maintain a stable earth vertical with its associated horizontal plane. With the horizontal plane established, the Mk 41 continuously measured the angles between the deck and the horizontal plane. These deck angles were continuously transmitted to the Rangekeeper so that it could keep the guns correctly elevated as the ship rolled and pitched. Mounted waist high on its side were the battery's firing keys. (see picture). The left key was the Salvo Signal Key, and it sounded the Salvo Buzzer in each of the turrets to warn the gun crews that the guns were about to fire.. The center key (with bumps on its handle for tactile identification) was the Automatic Firing Key. When this key was held closed, the Mk 41 was enabled to automatically fire the guns whenever the ship's deck was parallel the horizontal plane. Also, if the sea state was such that the turrets' elevation power drives could not keep up with the ship's motion, the guns could be held at a fixed elevation, and the MK 41 could again automatically fire the guns as described. The right key was the Hand Firing Key. It bypassed the Mk 41, and fired the guns directly.
The Mk 13 FC Radar supplied present target range, and it showed the fall of shot around the target so the Gunnery Officer could correct the system's aim with range and deflection spots put into the Rangekeeper. It could also automatically track the target by controlling the director's bearing power drive.. Because of radar, Fire Control systems are able to track and fire at targets at a greater range and with increased accuracy during the day, night, or inclement weather. This was demonstrated in November 1942 when the battleship USS Washington engaged the Imperial Japanese NavybattlecruiserKirishima
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at a range of 8,500 yards (7,800 m) at night. The engagement left Kirishima in flames, and she was ultimately scuttled by her crew. This capability gave the United States Navy a major advantage in World War II, as the Japanese did not develop radar or automated fire control to the level of the US Navy and were at a significant disadvantage.
The Parallax Correctors were needed because the turrets were located hundreds of feet from the director. There was one for each turret, and each had the turret/director distance manually set in. They automatically received Relative Target Bearing (bearing from own ship's bow), and Target Range. They corrected the bearing order for each turret so that all rounds fired in a salvo converged on the same point.
The Fire Control Switchboard configured the battery. With it, the Gunnery Officer could mix and match the three turrets to the two GFCSs. He could have the turrets all controlled by the forward system, all controlled by the aft system, or split the battery to shoot at two targets.
The assistant Gunnery Officers and Fire Control Technicians operated the equipment, talked to the turrets and ship's command by sound-powered telephone, and watched the Rangekeeper's dials and system status indicators for problems. If a problem arose, they could correct the problem, or reconfigure the system to mitigate its effect.
....ENOUGH HIGH-TECH 1940'S TO SINK A BATTLESHIP... ALL GOES A KABLOOEY WHEN A LITTLE EXTRA BLACK POWDER GOES IN THE CHARGE BAG!
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Last edited by Aktungbby; 03-04-2020 at 12:47 PM.
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Old 03-04-2020, 12:23 PM   #4
bracer
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Usually there was a command room inside the ship which had one or more fire control computers (FCC).
These computers had inputs with range and bearing information from rangefinders and fire directors and in some cases radarstations.

The speed of the target ship, heading and sometimes other factors like windspeed had to be entered manually.
The computer usually also took in information about the ships own speed, heading and maybe list.
All this information got processed by the computer and outputted aiming data for the guns.
The computer also calculated and corrected the parralax of the guns.


It was probably different from country to country and over the years,

but as far as I know during wwii there was trainers in the guns who aimed and elevated the guns based on the info from the computers.
Some german battleships had electric drive for the elevation.


Hope it helps!


edit: I see Aktungbby updated with excellent info above!


edit2:
Quote:
Originally Posted by LoneWolf_gabo View Post
...did the fire director transmit via radio the range and direction to shoot?
This was done with dials.
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Last edited by bracer; 03-04-2020 at 12:56 PM.
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Old 03-05-2020, 05:27 AM   #5
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Thanks a lot to all for the information! It is very helpfull.
I was asuming that guns movement was automatic with some kind of hidraulic system. But knowing the fact that 1940's british ships had crew do manually the aiming is a key point for the sim's crew stats and timings. Wich also means that even with damage to the fire director or plotting room, guns can continue to be operational.
So if player would like to direct the firing he would go into the fire director position. In wich case, i see in other sims that the player would visually aim or offset the aim realative to the target tracking (as in War Thunder). But now i have a doubt. What would a human operator do as fire director? just aim the ragefinder and optics directly at the target and let the computer calculate? wich is pretty much what the AI is doing allready.
I ask this because if we talk about realism, then the player task could probably resume to select a target to shot at and nothing else.
Any thoughts on this?

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Old 03-11-2020, 03:57 PM   #6
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Quote:
Originally Posted by LoneWolf_gabo View Post
What would a human operator do as fire director? just aim the ragefinder and optics directly at the target and let the computer calculate? wich is pretty much what the AI is doing allready.
I ask this because if we talk about realism, then the player task could probably resume to select a target to shot at and nothing else.
Any thoughts on this?


I imagine that the firedirector simply aims directly at a target and designates it as a target.
The rangefinder would be a different crew member.
To lead the target, as you mention from War Thunder, would be done by the computer.


I imagine you have to make choices here yourself for gameplay. "Realisticly" you would not steer the ship either if you were at the firedirector station.
Do you want the player to work for the accuracy or point the aimdot and let randomness control the accuracy?
Letting you lead the target is a simple way of adding rangefinding to the players tasks and making gunnery more interesting.
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Old 03-16-2020, 06:02 AM   #7
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Yes, that's what i was thinking. I like the way War Thunder handles it. When you designate a target your aiming get's relative to the tracking of the target. Basically manipulating offset values. Even if AI would calculate and make the firing the player could adjust the offset values for the correction.
AI commanded ships would do the same.
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