Bismarck firing procedures at DS

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alecsandros
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Bismarck firing procedures at DS

Postby alecsandros » Mon Jan 28, 2013 9:42 am

Hi,

I read from survivor testimonies that Bismarck made course alterations during the initial stages of the battle of DS (5:53 - 6:00) in order to complicate Prince of Wales firing solution.

Are there any indications regarding the amount of course alterations done ? 10* ? 20* ?

And, following this, is there any info regarding the type of firing procedure used during the first time interval ? (5:55 - 6:00)

The reason I'm asking this is to see if there are any hints onto using the RPC system during the early part of the battle (more precisely, to see if turret train and elevation were automatically kept by the onboard systems while the ship was manouvreing)

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Re: Bismarck firing procedures at DS

Postby tommy303 » Mon Jan 28, 2013 7:31 pm

I believe RPC for the main guns was elevation only.

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Re: Bismarck firing procedures at DS

Postby Thorsten Wahl » Tue Jan 29, 2013 10:51 am

tommy303 wrote:I believe RPC for the main guns was elevation only.


from myself
main firing procedure "Höhenfernstuerung mit Seitenvorzündwerk"

that means remote control for elevation - Seitenvorzündwerk. unfortunately I dont know a useful translation for Seitenvorzündwerk as it appears to me that there is no technical correspondence in foreign equipment, even the quality of this solution appears as technically equivalent to the US stable vertical in connection with RPC.

In the main firing procedure the guns were fired during rotation of the turret.
the correct train angle was continously held by the firecontrol computer
On the firing command the turrets with its guns were moved through this train angle and the shooting was automatically triggered by the Vorzündwerk
-as there is some delay between closure of the electric firing contacts until the time the projectile leaves the muzzle it is required to close the electrical contacts some hundredths of a seconds before the correct train angle was reached so knowing the correct times of projectilemovement within the barrel was extremely important to reduce scatter.
the german system avoids continous oscillations of the turret as in the case of complete automated stabilization for side as the ship was contiously moving around all three axes

The guns were fired by the so called "Vorzündwerk" during rotation of the barrel/turret
-at the beginning the gun house is on hold(red line) wich is not the aiming direction
-the fire control continously calculates a dynamic firing solution (green line)
at the "march through" command the turret/barrel was driven through the fire solution


attached is also a photo of Gneisenau, here you can see the different alignments of both turrets, one turret has fired shortly before this photography.


Details on the used firing procedure you can findn only in the book of B.Freiherr v. Müllenheim-Rechberg.
but even this informations wernt that meaningful to derive clearly on the selected firing procedure
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Meine Herren, es kann ein siebenjähriger, es kann ein dreißigjähriger Krieg werden – und wehe dem, der zuerst die Lunte in das Pulverfaß schleudert!

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Re: Bismarck firing procedures at DS

Postby Thorsten Wahl » Tue Jan 29, 2013 10:53 am

dobble post
Meine Herren, es kann ein siebenjähriger, es kann ein dreißigjähriger Krieg werden – und wehe dem, der zuerst die Lunte in das Pulverfaß schleudert!

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Re: Bismarck firing procedures at DS

Postby alecsandros » Tue Jan 29, 2013 12:29 pm

Thorsten Wahl wrote:dobble post

Thorsten,

I remember talking about this,

My question isn't IF such a system existed on board the Bismarck, but IF the system was operational and actualy used during the battle (instead of the more common fire the pointer procedure)

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Re: Bismarck firing procedures at DS

Postby Dreadnought » Fri Mar 01, 2013 4:07 am

Gentlemen,
Having been equated with US fc sytems and a sense of sound fc pratices and theory I would not agree with all of the above. Certain points made above defly fc theory. I cannot say I would be intimately familar with Bismarks fc system but I have read minor briefs about it in books.

My point, is some of those points refelect someone not at all familiar with fc and turret operation with large naval guns.

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Re: Bismarck firing procedures at DS

Postby Thorsten Wahl » Sat Mar 02, 2013 9:26 pm

You did not say anthing in contribution to your assessment " i would not agree with all of the above.."
What seem wrong or unclear to you.

After World War II, the development of german anti-ship and anti-aircraft artillery was pushed forward under the following assumptions:

"Fastest achieving of the first hit on the enemy, as far as possible with the first salvo, fast and safe tracking of the enemy
Independence of roll and pitch effects in the Atlantic even in bad weather
Independence of the own ship maneuvers"

According to own assessment of the Kriegsmarine these general goals were fullfilled with "the excellent gunnery performance of Bismarck and Tirpitz"
Meine Herren, es kann ein siebenjähriger, es kann ein dreißigjähriger Krieg werden – und wehe dem, der zuerst die Lunte in das Pulverfaß schleudert!

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Re: Bismarck firing procedures at DS

Postby tommy303 » Sat Mar 02, 2013 10:03 pm

The German fire control systems as used on the Hipper, Scharnhorst, and Bismarck classes were very flexible with several different proceedures being possible. Firing could be done at the director, in similar fashion to the British DFC system, or it could be done from the central fire control station by computer and automated firing mechanism in the transmitting station. If the ship were holding a set course and the sea state was not too extreme, it was possible to fire the guns directly from the director where by the director layer judged when the guns were properly aimed and fired by blowing into the mouth piece of a pneumatic tube, thereby closing the firing circuit. However, in Bismarck at least, though the ship had a small amount of roll in a sea way, the roll time was very quick (stiff); this made direct firing from the director difficult as RPC might not be able to keep up with the swift roll moment and it was too hard for the layer to judge the correct point in the roll to fire. Consequently, it was usual for the computer to measure the velocity of roll and calculate the correct point at which to fire the guns, taking into account the vertical velocity of the gun muzzles and the length of time it would take the shells to exit the muzzles. The layer would initiate firing by pressing a firing key, but the circuit would only close when the optimum point in the roll as calculated by the FC computer and set into the firing gyro was reached.

Similarly, if the ship was manoeuvring, turning, or swinging due to the seaway, or if the target was moving particularly quickly, the lateral movement might be too great for the turret trainers to keep up with. In this instance, as Thorsten points out, it was usual for the turrets to be held at an arbitrary angle of train until the firing signal came, then rotate and let the transmitting station fire the guns based on the output of the computer's calculation of the lateral velocity of the gun muzzles. The guns would then fire as the turret train reached the optimum lateral point of aim.

Their shoulders held the sky suspended;
They stood and Earth's foundations stay;
What God abandoned these defended;
And saved the sum of things for pay.

Dreadnought

Re: Bismarck firing procedures at DS

Postby Dreadnought » Tue Mar 05, 2013 12:11 am

Im not so sure I can agree with the above. Bismark used two charges for her main battery. One case fixed brass (to seal the breech end) and one bag charge like British and USN units up front at the projectile base. When a fire control circuit is "closed" that sends somewhere close to 12-25 volts of electricty through the fire control circuits to whatever caliber primer was used in the firing lock of the gun. It takes a few seconds for that voltage to reach the turrets. If they waited for the fire control circuits to close before training the turret (even a few degrees) and then ignite the charge the accuracy would be very questionable. For some reason I also seem to question a "breathable" pnematic control to close the FC loop.

Can I see some reference to this breathable nematic FC closure?

Thank You.

Dreadnought

Re: Bismarck firing procedures at DS

Postby Dreadnought » Tue Mar 05, 2013 4:49 am

tommy303 wrote:The German fire control systems as used on the Hipper, Scharnhorst, and Bismarck classes were very flexible with several different proceedures being possible. Firing could be done at the director, in similar fashion to the British DFC system, or it could be done from the central fire control station by computer and automated firing mechanism in the transmitting station. If the ship were holding a set course and the sea state was not too extreme, it was possible to fire the guns directly from the director where by the director layer judged when the guns were properly aimed and fired by blowing into the mouth piece of a pneumatic tube, thereby closing the firing circuit. However, in Bismarck at least, though the ship had a small amount of roll in a sea way, the roll time was very quick (stiff); this made direct firing from the director difficult as RPC might not be able to keep up with the swift roll moment and it was too hard for the layer to judge the correct point in the roll to fire. Consequently, it was usual for the computer to measure the velocity of roll and calculate the correct point at which to fire the guns, taking into account the vertical velocity of the gun muzzles and the length of time it would take the shells to exit the muzzles. The layer would initiate firing by pressing a firing key, but the circuit would only close when the optimum point in the roll as calculated by the FC computer and set into the firing gyro was reached.

Similarly, if the ship was manoeuvring, turning, or swinging due to the seaway, or if the target was moving particularly quickly, the lateral movement might be too great for the turret trainers to keep up with. In this instance, as Thorsten points out, it was usual for the turrets to be held at an arbitrary angle of train until the firing signal came, then rotate and let the transmitting station fire the guns based on the output of the computer's calculation of the lateral velocity of the gun muzzles. The guns would then fire as the turret train reached the optimum lateral point of aim.



This I would somewhat agree with. On USN battleships the stable vertical measures the roll of the ship for the FC computer (range finder) which delays the actual FC circuit voltage once the loop is closed (all safetys closed at turret in semi auto mode, salvo warning closed, and then trigger closed) and they are firing from main plot (fore or aft) which also served as the location (stable vertical) the triggers are pulled from if not the director or turret itself. Whichever location is serving at the time for the main battery. Otherwise they can fire from the directors or the turrets themselves (7 locations total). I just dont see how breathing down a pneumatic tube is going to close the fire control loop for the main battery from the director. It seems to "sloppy" and circumstancial and very much unlike German precision design. I can believe that sets of triggers mounted on handwheels were in the director on the telescopes as they were in many naval designs including the USN design not just to fire the main battery but also to send FC input to down to gun plot for FC computer input.This saying that the vertical measuring gyros of the German design would adjust the FC solution in the vertical axis as disperssion in the horizontal axis plane would have to be manually adjusted to radar bearings being supplied for horizontal training of the turret. Otherwise in a rough sea state your shots would be either well over or well under.

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Re: Bismarck firing procedures at DS

Postby tommy303 » Tue Mar 05, 2013 5:24 am

The pneumatic firing tube is described in Paul Schmalenbach's Die Geschichte der deutschen Schiffsartillerie and is illustrated in a photo at:

http://www.navweaps.com/Weapons/WNGER_8 ... 4_pics.htm

While the photo shows a gun captain, a similar arrangement was provided for the director layer.

When a fire control circuit is "closed" that sends somewhere close to 12-25 volts of electricty through the fire control circuits to whatever caliber primer was used in the firing lock of the gun. It takes a few seconds for that voltage to reach the turrets.


The electrical primer was carried in the base of the cased main charge, not in the firing lock as in US and British guns. The whole point of using electricity to fire the guns was it was nearly instantaneous, the time taken from the closing of the firing circuit to the ignition of the primer being a matter of nano seconds not seconds, thus making it possible to precisely time the instant of firing so that the shells left the gun muzzles at the optimum point. Electromagnetic wave travels through copper wire at between 66 and 95% c, where c is the speed of light, the actual figure being dependent on the nature of the wire and its insulation.

Their shoulders held the sky suspended;
They stood and Earth's foundations stay;
What God abandoned these defended;
And saved the sum of things for pay.

Dreadnought

Re: Bismarck firing procedures at DS

Postby Dreadnought » Wed Mar 06, 2013 1:00 am

Tommy, I am well aware that Bismarks main case charge carries the primer charge in very much the same way case fixed ammunition carries its primer internal. However, when the firing circuits are closed there is still a delay that is calculated by whatever the stable element may be. Until that gyro rights the calculation for the roll seconds tick away. Ships do not right themselves in nano seconds and in some cases pending sea state it will take more then a few seconds. I believe what you described earlier in this column is a German version of the "follow the pointer mode" to which the gun will be constantly adjusted in the vertical sense (Bismarks elevation gear showed wear in certain points during her last inspection the reports are both translated and available) and as you mentioned before, when the turret crosses the horizontal plane the contacts for that part of the fc circuit match. If the fire control circuit hit the primer charge instantaniously from the time the loop was closed the gun would fire instatanious. It has alot to do with the fire control solution particularly when the ship is in heavy sea state which we know she was during her final days. It takes numerous inputs to the fire control computer (some are immediate say from the radars, the director, even the pitometer) Other inputs are human hands on inputs to generate the fc solution such as speed, course, targets course and speed, which projectile is being used, windspeed etc to name a few. Bismarks fire control like all navies fc of the time were configured to predict where that target will be when the gun fires and this is why it takes so many inputs to the rangekeeper to make gunnery accurate. As I mentioned prior, if the gun fired instantanious when the loop is closed you would have wasted several rounds, perhaps exausted your gun crews and perhaps your chance at survival in a gunnery duel.

Dreadnought

Re: Bismarck firing procedures at DS

Postby Dreadnought » Wed Mar 06, 2013 1:21 am

I knew there had to be a trigger mechanism in the the fc system inside the turret. I would bet that the breathing tube shown is a way of closing one of the safety switches on the system. But not the only safety on the system. That tube IMO, more then likely acts as the gunnery officers safety switch since he has "eyes on". As noted in that same picture, the wheel he is holding has the actual trigger for firing the gun. But, as you can also tell from that picture they are in "local" mode. In other words firing from the turret itself which would negate the stable vertical (auto and semi auto mode in other wordes the director or gun plot shooting) and therefore the delay in the fire control circuits. The charge to fire the primer is more then likely coming from battery back-ups inside the turret which act as a fail safe to be able to trigger the electric charge to the primer in case the main fc circuits are severed in battle. You will also note, that is not a gun captain, that man is either a gunnery officer or the turret captain and therfore he has final closure of the fc circuits for safety reasons including gunnery crew safety.

Dreadnought

Re: Bismarck firing procedures at DS

Postby Dreadnought » Wed Mar 06, 2013 2:02 am

After a closer look at that picture I would be more inclined to believe that the tube the gunnery officer is blowing into is an audio annunciator and not a fc system safety, warning the gunners mates on the opposite side of that bulkhead to clear the back of the guns for recoil. It was also explain the "second trigger" in that photo. All battleship turrets of that era had the audio warning in the turret for when they were in "local" mode as a safety precaution for recoil and runout of the gun. I would also be inclined that the safety's were in fact mechanical switching and not "blow powered". The Iowa class built in that same timeframe were no different as they had the "pigtail" audio buzzer for the very same reason mounted to the forward bulkhead in the turret officercers compartment. :wink:

I think someone needs to rewrite the caption on that photo.

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Re: Bismarck firing procedures at DS

Postby tommy303 » Wed Mar 06, 2013 4:57 am

That tube IMO, more then likely acts as the gunnery officers safety switch since he has "eyes on". As noted in that same picture, the wheel he is holding has the actual trigger for firing the gun.


The safety, as it were, was the S-F-S Anzieger, one of which is shown below:

Image

These instruments were the equivalent of the British gun-ready board and were used to not only indicate the status of each gun during the loading cycle, but also to interrupt the firing circuits (safety) and select which gun or groups of guns were to fire.

The tube held in the mouth of the petty officer is a pneumatic firing device, although he does have a trigger on the hand wheel as a stand by and for firing the guns when operating with the Krag (the local gyro firing device which required the trigger to remain depressed until the gyro closed the firing circuit). The pneumatic device was preferred for rapid fire and in situations where continuous aim was possible. The bulb in the tube held a pressure sensitive firing switch. This arrangement was duplicated at the director as well. In the following photo, the director--the column-like object, has a coiled firing tube on the right at the director layer's position. He also had a trigger on his hand wheel. The periscope device in the foreground is an observation periscope.

Image

I think you are also making the mistake of assuming the German FC system was the same as that used in the USN. Although its purpose was the same, it was by no means identical the the US system any more than the US system was like the Admiralty Fire Control Table used by the British. There were different operating procedures--the German system having more automation in inputs than most others.

Their shoulders held the sky suspended;
They stood and Earth's foundations stay;
What God abandoned these defended;
And saved the sum of things for pay.


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