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Naval Fire control equipment
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RobB



Joined: 22 Aug 2005
Posts: 11
Location: Woking, United Kingdom

PostPosted: Mon Aug 22, 2005 5:28 pm    Post subject: Naval Fire control equipment Reply with quote

Tone
My congratulations on your project. I too am interested in the technicalities of fire control at the turn of the last century, and I was so inspired by your movies that I resolved to have a go myself. So far I have modelled an Evershed bearing transmitter, and an Argo clock Mk IV. I attach a view of this device, derived from the "Handbook for the Argo range and Bearing Clock, Mark IV", dated 10 Jan 1912. I have high hopes for animating this clock - if only I can get to grips with the java machine!! Still early days.
Regards
Rob
I have two other views you may be interested in.
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RobB



Joined: 22 Aug 2005
Posts: 11
Location: Woking, United Kingdom

PostPosted: Mon Aug 22, 2005 5:40 pm    Post subject: Reply with quote

Tone
OK, so I'm just learning to use a forum!
Here are two other views of the clock.
Front view


view of the working area


Regards
Rob
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tone
Site Admin


Joined: 29 Oct 2004
Posts: 478
Location: Boston

PostPosted: Mon Aug 22, 2005 6:08 pm    Post subject: Reply with quote

Rob -- that is fantastic work. What did you model in?
I certainly want you helping out, but sadly I am rebuilding my entire app from the ground up and so it may be awhile before I can bring it to life, though it is tempting to go back to the old engine where this could come up fairly quickly (must... resist... old engine!).

Where did you obtain the manual?

Please update your email address in the profile, however -- it appears to be incorrect.

tone
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RobB



Joined: 22 Aug 2005
Posts: 11
Location: Woking, United Kingdom

PostPosted: Tue Aug 23, 2005 1:53 pm    Post subject: Reply with quote

Tone
I am modelling in Rhino, and trying to render with Flamingo, but I have only had these tools a few months, so presentation is rather crude.

Fixed my e-mail - I missed out a full stop (period to you no doubt!).

The handbook is in the Naval Library, Portsmouth (England).

Regards
Rob
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RobB



Joined: 22 Aug 2005
Posts: 11
Location: Woking, United Kingdom

PostPosted: Sat Sep 03, 2005 7:39 pm    Post subject: Reply with quote

You said you were interested in fire control equipmemt. These are modeled from the Manual of Fire Vontrol Instruments, 1914









Rob
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RobB



Joined: 22 Aug 2005
Posts: 11
Location: Woking, United Kingdom

PostPosted: Mon Nov 14, 2005 6:22 pm    Post subject: Reply with quote

Continuing with the Argo theme, I offer some models of the other components of the Aim Corrector (AC) system. These are derived from the drawings in the 'Technical Comparison with Cdr F. C. Dreyer's Fire Control System' .


Firstly, the Argo 10 foot gyro stabilised range and bearing finder.

This model (circa 1912) shows the range finder mounting on its pedestal stabilised in azimuth by a pair(?) of torpedo air-blast gyroscopes. This was a poor arrangement, but better than other arrangements, until the Anchultz gyro was introduced.




The operator used the controls on the left to slew the rangefinder onto the target bearing (handwheel) and then used a lever by the handwheel to match the target bearing rate. With his right hand, he had to set the split image rangefinder (note the arm rest). When a range was measured, the operator would push a button on right hand footplate, to transmit both range and stabilised bearing to the Transmitting station (TS).




Another view of the Rangefinder. Not shown are a number of cables that must have festooned the rangefinder - which did not have slip rings as far as I can see.



The production rangefinder was modified to have two operators, one for bearing, the other for range, and photos of this variant are very different from this model, so this model may simply be of a paper design. Oh well....

The ranges and bearings would be transmitted electrically to an Argo plotter in the TS, possibly the weakest element of the AC system.



A large sheet of paper was gripped by a pair of carriages representing own ship, the range being the distance between the fixed target pencil at the end of the target arm, and own ship. The paper was rotated under the own ship carriages to show the bearing



Next figure shows the lower carriage. The wheels would be rotated to align the paper to the target bearing cut, and also would be driven in real time to move the paper to plot own ship's course.




The Argo plotter was not a success, and was never purchased by the Royal Navy.

Ranges and bearings would then have been fed (manually) into an Argo clock (see above) which would in turn generate the gun ranges for the guns.

The Argo Rangefinder was the only element purchased in any number (45). Assuming that these were to be mounted in the Spotting platform (and I have no evidence yet that they were), the next diagrams show how they may have looked. The Director turret was mounted above the spotting platform - not a good place of work if you suffer from vertigo.





Finally, a couple of images of the Director mounting (derived from photos in the Director Firing Handbook). The accuracy and completeness of this model is not as high as I would have preferred. The sight setter (front right seat) sets the range transmitted from TS. The Director Layer (rear left seat) adjusts his telescope to the target in elevation, while the director Trainer sets the azimiuth. All the guns follow the elevation and bearing of the director. When on target, the layer fires all guns. The operator at front left is the communication number.



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tone
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Joined: 29 Oct 2004
Posts: 478
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PostPosted: Tue Nov 15, 2005 12:12 pm    Post subject: Reply with quote

Splendid models! The gearing on the Argo plotter is spectacular.

FYI, the Argo RFs were often mounted in armored hoods, as in Queen Mary's which was situated not aloft but on the conning tower. Installations might have varied elsewhere to arbitrary degree.

I regret that you modeled the tripod-type director without asking me first for my model of it -- though mine is optimzed for low-poly work for use in simulations, it would have helped speed your effort.

tone
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RobB



Joined: 22 Aug 2005
Posts: 11
Location: Woking, United Kingdom

PostPosted: Tue Nov 15, 2005 6:26 pm    Post subject: Reply with quote

Tone
Thanks for the information. The gearing is a bitmapped decal rather than a large set of surfaces (as in earlier Argo clock model). Technique I used is to model the shapes in Rhino (as a series of surfaces), then use Flamingo to render them, with a white background. Save the rendition as a bitmap, and then use the Decals facility (Flamingo) to apply the bitmap as a surface to the gearwheel, or bearing dial. It is a bit fiddly getting the decal to align with the gearwheel / bearing ring.

Next stage will be to experiment with these models in Unity, and see whether the bitmapped decals are reproduced, and how much of a processing load this imposes. Hopefully, I can then animate the clock, rangefinder and plotter.

The Director model was done for fun, and in a bit of a rush but was very helpful in understanding how the director worked. If I get round to re-working the model I would appreciate access to your model, but my immediate plans (after animating the argo clock) are to look at Dreyer Tables.
Regards
Rob
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sonofdavros



Joined: 29 Nov 2005
Posts: 6
Location: Dorset, UK.

PostPosted: Tue Nov 29, 2005 9:10 am    Post subject: Reply with quote

Wow, I've just found this site and watched Tone's 2 videos of WWI gunnery - amazing stuff.

I can offer no skills at all, just enthusiasm for this period of history. :)
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sonofdavros



Joined: 29 Nov 2005
Posts: 6
Location: Dorset, UK.

PostPosted: Tue Nov 29, 2005 9:11 am    Post subject: Reply with quote

D'oh! Double post. :oops: Good start.
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Horsa



Joined: 09 Dec 2005
Posts: 32
Location: England

PostPosted: Fri Dec 09, 2005 6:05 pm    Post subject: Reply with quote

These models are sublime :D
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maxyang



Joined: 31 Oct 2004
Posts: 100
Location: Shanghai, China

PostPosted: Sat Dec 17, 2005 11:55 am    Post subject: Reply with quote

Claps, I like super detailed model. Just wonder how it will look with the full scale ship. :)
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RobB



Joined: 22 Aug 2005
Posts: 11
Location: Woking, United Kingdom

PostPosted: Fri Jul 14, 2006 5:09 pm    Post subject: Reply with quote

The fire control problem can be simply stated as 'how do you manage to hit a moving target from a moving platform when the target may be many miles away?' To illustrate the problem, consider two WW1 battle cruisers charging headlong towards each other at about 30 knots each. If the ships are 10 miles apart when you fire, the target could have moved a mile before the shell lands. Consequently you have to predict where the target will be when the shell can arrive. In mathematical terms this requires the solution of three simultaneous equations, since the solution changes second by second.

Put simply, if you know your own course and speed, and the enemy's course, speed and relative bearing from you, and you can calculate the time of flight for a shell to travel the predicted point, you should be able to hit the target. Lots of 'ifs'.

I am not going to pretend that I am an expert in this field; there are many more qualified than I. However, I shall sketch out the problems and issues in order to explain some of the features of the Dreyer Table models that are included in this posting.

Ok, so in order to predict you must first measure. The equipment available are optical rangefinders and bearing indicators. Unfortunately, the Royal Navy entered the first world war with range finders with a baseline of 9 or 10 ft, which were not really accurate enough for longer ranges (10 miles or 20,000 yards).

But knowing the range of a target is not enough - you also need to know the bearing. The ship builders and engineers in the early years of 1900 were fully capable of building mechanical devices to measure bearings to fractions of a degree, but only relative to the ships keel line. A ship at sea, however, continuously yaws about its course, possibly only a degree either side, but sometimes more. Thus a relative bearing of a target is of little use if the ship yaws a different amount when the guns fire; a 1 degree error for a target at 10 miles is 350 yards, more than enough for a complete miss.

Gyro-stabilised bearings are the answer. The first commercially available maritime gyro compass was the German Anschutz compass, but this was soon replaced in the Royal Navy by the American Sperry gyro compass, introduced in 1911.

So now we have moderately accurate rangefinders (at long ranges) and moderately accurate bearing indicators. Accuracy can be improved if you plot a number of range finder cuts over a period of time, and are able to note the rate of change of range. Likewise if you plot a series of bearing cuts against time, you can measure the rate of change of bearing.

The next item in our fire control tool set is a form of 'circular sliderule' (for those old enough to remember what a sliderule was, before the age of digital calculators). The device used was the Dumaresq ( named after the inventor but pronounced Doomerick). On a Dumeresq, you can set own course and speed, and if you know them, the target course, speed and bearing, which will give you the target's bearing rate and rate of change of range. Or if you can measure the rate of change of range and/or rate of change of bearing, you can find out the targets course and speed. Once you know these factors, it is possible, to predict the range and true bearing from your ship where the target will be in the time it takes for the shells to travel the distance.

However, this prediction is only true at a given instance of time. As the target closes the range, the range rate and bearing rate will alter, necessitating a continuous update to the range and firing bearings set on the main armament. As an example, consider a train passing through a station. The bearing of the train changes slowly as it approaches the platform, but then rapidly changes as it passes you and then steadies down as it recedes. Consequently, in a Dreyer Table fire control system, the target parameters, range, bearing and angle on the bow are continuously updated through a motor driven 'clock'. Again, I am simplifying quite a complex electro-mechanical system, and anyone interested should read up on the Dumaresq and Dreyer Table. For now I want to show you some images of a Dreyer Table.

Lets not forget the purpose of all this ingenuity and hard work. We need to know the range, bearing, rate of change of range and rate of change of bearing relative to our on ship in order to predict the range and bearing of the target in the future when we can get a shell to him. The fire control team therefore provide the Director (see earlier posts) with a range and bearing offset. Our director then applies these offsets and commands all the main armament to follow the directed bearing and ranges. When the director's telescope crosswires (which have been set up with the required offset) lie on the target, he pulls the trigger, and boom. We hope we get a hit.

This first image shows a Mark 3 Dreyer table as it had evolved by 1918. In the four years of the War, there had been a number of technical improvements, and also a number of different marks of Dreyer table. This is the Mark 3 table.



On the right of this image is the Time-Range plot, where bearings called down from all the rangefinders in the ship could be plotted on a paper sheet that scrolled at a fixed rate. Given enough range cuts, it is possible to estimate the rate of change of range, and predict a future range by extrapolating through the scatter of range cuts.

In the centre is a Mark VI Dumaresq. This is the 'sliderule' that is used to refine the estimate of the target's course, speed and range, and therefore the bearing and range rates passed up to the Director. The settings on this sliderule can be updated both by visual observation by the Director, but also by measurements from the range and bearing plots.

On the left are two devices. At the front is a 'totaliser' which takes the raw predicted bearing, and applies further corrections for time of flight of the shell, wind, and other corrections.

Behind the totaliser is the time-bearing plot. This device will plot gyro-stabilised bearing cuts from the various bearing indicators, and from this can be derived the target's bearing rate, which can then be set on the Dumaresq to refine the target solution.

The next image shows the rear of the Dreyer table, and in particular the electric motor that drives the Dumaresq' s 'clock' and the scrolls the paper at fixed rate over the time-range and time-bearing plots. drives. On the right of this image will be see a small Dumaresq which is used to calculate the true wind speed, given own ships speed and course, and measuring the apparent wind speed. This is a simple 'triangle of velocities' problem ideally suited to the sliderule-type Dumaresq.




The next images show the Mark VI Dumaresq


and two views of the Wind Dumaresq.





Ok, this is a complicated subject, and many books have been written on it. May I invite authors of these learned tomes to post references and links to more complete descriptions. Likewise, anyone with a question of detail is invited to post a query. Apologies in advance if the images are too large for your display, I am still a bit of a 'luddite' with all this new-fangled electronic stuff... when I first went to sea, we still used electro-mechnical analogue calculators for fire control!

Rob.b1904
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tone
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Joined: 29 Oct 2004
Posts: 478
Location: Boston

PostPosted: Tue Jul 18, 2006 6:37 pm    Post subject: Reply with quote

Rob, as ever these are stupendous images.

We clearly need to create a fire control section of the site proper.

tone
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Horsa



Joined: 09 Dec 2005
Posts: 32
Location: England

PostPosted: Wed Jul 19, 2006 1:51 pm    Post subject: Reply with quote

Breathtaking !! :shock:
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