How to maintain effective fire

[Terje Langoy]

I was searching through the net for all sorts of information upon the Gneisenau when I came across a sketch, showing the principles of the optical rangefinder, which I most certainly was fascinated by. The principles are simple and elegant shown, but some questions still arise from my little survey. Maybe some of you can help me out?

The rangefinder, along with the turrets and guns, was operated independent of the ship, right? How was the relation between the bridge and the fire control, regarding the need for evasive maneuvring and at the same time directing fire effectively? Who has the supreme command between these stations? When the fire director has achieved the target, how can he keep a "lock-on-target" if the captain keeps steering the target out of his scope all the time? Wouldn't this reduce their fire efficiency severely if the fire director has to compensate for ship maneuvers frequently? Can the artillery officer ever exceed the captains command in order to minimize the maneuvres and so forth lock on his target? I assume the ideal conditions would be to equal the speed and bearing between base of fire and target to a minimum of changes, right? I don't know if this is just silly questions but hopefully they're not. I simply know very little about this.

Very best regards

[Karl Heidenreich]

Your answers are here, Terje:

http://www.eugeneleeslover.com/FIRE-CONTROL-PAGE.html


Best regards.

[Bgile]

I was searching through the net for all sorts of information upon the Gneisenau when I came across a sketch, showing the principles of the optical rangefinder, which I most certainly was fascinated by. The principles are simple and elegant shown, but some questions still arise from my little survey. Maybe some of you can help me out?

The rangefinder, along with the turrets and guns, was operated independent of the ship, right? How was the relation between the bridge and the fire control, regarding the need for evasive maneuvring and at the same time directing fire effectively? Who has the supreme command between these stations? When the fire director has achieved the target, how can he keep a "lock-on-target" if the captain keeps steering the target out of his scope all the time? Wouldn't this reduce their fire efficiency severely if the fire director has to compensate for ship maneuvers frequently? Can the artillery officer ever exceed the captains command in order to minimize the maneuvres and so forth lock on his target? I assume the ideal conditions would be to equal the speed and bearing between base of fire and target to a minimum of changes, right? I don't know if this is just silly questions but hopefully they're not. I simply know very little about this.

Very best regards

Maneuvering did interfere with gunnery. Things got a little better toward the end of the war, but the effect was still there. The decision was the captain's and he was expected to understand the effect on gunnery, but he still had to make decisions regarding the tactical situation.

[Terje Langoy]

Lots of thanks for providing me a link, Karl. I suddenly gained a lot of reading, but it's worth every minute. Really fascinating, don't you think?

I came to think of it right after I posted this topic, Bgile. I guess that safety exceeds all offensive measures. What good will it do to aquire the target and then get blown sky-high the next minute? If they had good communication between the different stations, I guess most maneuvres could be announced early to compensate for the change of bearings between FC and target. Maybe it's just a matter of proper coordination?

Best regards

[Karl Heidenreich]

Terje:

the mechanical target adqiusition computer on board of the BBs (the Dreyer Table or Admiralty Table for example) use every known variable to predict the position of the target and get a firing solution. What I don´t know was if the manouvers ordered by the Captn. at the bridge were another "input" or they were translated as readings from the enemy´s position, bearing and speed from rangefinders. If that have to be quick then I believe they must come from the rangefinding stations.

Best regards.

[tommy303]

In German fire control of WW2, course and speed were provided to the fire control system automatically by master gyro compass and pitot log. As long as the course changes by own ship did not exceed run time of the analog computers and training speeds of the directors, rangefinders, and mounts, continuous tracking of the target was possible

[Terje Langoy]

OK, folks. Let me see if I got this right... The range to target was determined optically by some form of "mirror triangulation" on a horizontal split target, right? A matter of alignment to set the range. All info concerning their own ship was provided automatically by master gyro compass and Pilot log. Where were these located? I understand from your post, Tommy, that the training speed of the turrets and FC's set the limit, but what do you mean by run time of the analog computer?

Maybe you've already explained this, but how did the FC get data such as target speed and bearing? The optical method can, as I've understood, provide range, but does it also provide the other datas? I haven't found the time yet, Karl, to look further into that exciting link you provided so my sincerest apologies if some if these questions may be answered by looking into the other site.

By the way, where can I find any info upon the Dreyer Table or Admiralty Table?

Best Regards

[Karl Heidenreich]

Hi Terje:

About the Dreyer Table and such there is this thread on this very forum:

http://kbismarck.org/forum/viewtopic.php?t=808&start=0

In the book "Battlecruiser HMS Hood: An ilustrated biography" by Bruce Taylor there are some references about the system.

But here is some thought: if you´re sailing in a ship which is firing against some target then you are in the origin of x,y,z coordinates and everything around you is relative to your position as good as if you are standing still and everything is moving relative to you. Then the rangefinder readings give all the info you need: enemy relative position, course and speed. Of course, if you need to be more exact the gyro and the pilot log are of great help in order to predict the position of the target when your shells are supossed to hit.

Best regards

[Tiornu]

If you want an achingly detailed look at the development of helm-free fire control in the RN, get a copy of Dreadnought Gunnery and the Battle of Jutland by John Brooks. The author's thesis is that Sumida's version of the competition between the Dreyer and Pollen systems is inaccurate. The engineering issues are described with a literally nuts-and-bolts focus, so detailed that much of it went over my head.

[tommy303]

Hi Terje,

The analog gunnery computers of WW2, such as the Admiralty FCT, the USN's Rangekeeper, and the German Schusswertrechner were large analog calculators--ie they were motor driven and produced their data through a series of gears and cams. Like a clock, they ran at a certain speed and produced solutions at a constant rate. The speed at which they ran imposed a limitation since it could not be speeded up to deal with a rapidly changing circumstance, such as a major alteration of course or rapid and violent evasive manouvers. Thus there was a (usually) small lag time between input of corrections and fire control orders at the gun mounts.

[tommy303]

but how did the FC get data such as target speed and bearing

This was the function of the gun director: it measured the target angle in both the horizontal and vertical planes relative to own ship, as well as tracking the target. Enemy course and speed was estimated by observers and fine tuned by the fire control computers as corrections for bearing and range rate came in.

[Terje Langoy]

Thanks a lot for your enlightening replies...

Best regards