Turret Control Table
A proposal for what became the Turret Control Table was drafted around October, 1913. This range-only table was meant to be fixed to the bulkhead of the turret and plot data from the turret's rangefinder and to take over if the connection to the TS were to break down for any reason.
The device as first proposed included a Mark IV (or "turret") dumaresq which tracked the training angle of the turret, a range clock to drive a clock range pencil on the range plot, an automatic plotter to display cuts triggered from the RF, and a spotting corrector to convert clock range to gun range.
Just as the large Dreyer tables, the Turret Control Table was powered by an electric motor with a hand-crank governed by a stopwatch being available should power fail.
An adapted Mark IV dumaresq was connected by flexible shafting to the turret training ring, and thereby kept the fore-and-aft bar aligned with own ship's keel. In this way, and line of bearing was always that of the turret's present training angle. Except for deflection, this was the correct setting for the dumaresq.
The range clock's familiar variable speed drive (frictional disc spinning at 15 RPM) was housed within the table (not under the separate dumaresq). Its rate was indicated both by a pipper in the dial plate of the dumaresq (where it could be moved to track the enemy marker in line of bearing) as well as on a scale on the table where it read against a scale of +/- 2000 yards per minute.
The tables had no bearing clock, but did not require one. The dumaresq was set up to portray the line of bearing relative to own ship's keel, and this was driven mechanically by a flexible shaft geared to the turret training ring. Therefore, as the turret trained about, the dumaresq's bearing was updated to the relative training angle. This entirely obviated the need for a bearing clock, but relied (of course), on the turret being trained on the enemy.
The spotting corrector in the 1918 handbook is significantly different from those on the larger Dreyer tables. It is smaller, incorporates a 5 digit Gun Range Counter (all being single digits, unlike the commonplace 00, 25, 50, 75 standard used elsewhere). A spotting handle on the side works in corrections, and 3 hands seem to indicate that it was also able to receive a Straddle Correction.
It lacks any means of conveying the resultant gun range to sights. Apparently, this would be manually copied over on the turret's local transmitters or simply shouted across on telaupads or voicepipes.
The range plot was very compact and similar to the Original Dreyer Table's in that the range cuts were plotted "automatically" by a pricker. The range on the turret's rangefinder was conveyed to the table by an [F.T.P.] link instrument at the rangefinder which appears to be a minor adaptation of the Range Master Transmitter. A two-position lever on the table caused this link to drive the marker across the range plot when it was in the "Auto" position. When thrown into the "Hand" position, a handle on the table could position the marker, and a knob was pressed in to cause it to prick the paper. A 5-digit cyclometric display on the table indicated the position of the marker in yards of range.
The paper was 38.5 inches wide (plottable over 37.5 inches) and supplied in rolls 30 feet long.
|Early tables||Later tables||Hood's tables|
|Plotting Ranges (yards):||2,000 - 17,000||4,000 - 19,00||4,000-26,500|
|Paper speed (inches/minute):||2||2||4/3|
It seems likely to me that the move to increase the minimum range to 4,000 yards probably become ubiquitous by retrofit, and the change in scale and paper speed also a possibility after the war.[Inference] At any rate, the Handbook advises that greatly increased ranges should be supported by tuning down the clock range pencil by 10,000 yards and plotting ranges by hand rather than by the automated transmission from the RF.
Rate Grid The rate grid's wires did not automatically slant to the angle corresponding to the rate on the clock as did the grids on later grids for the larger tables.
Plotting Range Cuts
Range Pencil The tables had a single red pencil to plot clock range. It could be tuned by a hand-wheel.
The tables featured no bearing plot. A simple "deflection batten" resembling a slide rule was provided instead. Presumably, this simply allowed a current deflection correction to be tracked as a form of simple tally board.
The Dreyer Handbook of 1918 lists the ships supplied with these tables.
- Capital Ships with Tables in Turrets
It would be interesting to compare these lists against those light cruisers that received the larger and more comprehensive Mark III* Dreyer Tables in their TS. Was it a matter of TS size? Number of rangefinders? Simple availability of tables?
- Brooks. Dreadnought Gunnery and the Battle of Jutland. p. ???.
- Captain F. C. Dreyer's Fire Control System for Local Control, 1913, Fig. 1.
- Captain F. C. Dreyer's Fire Control System for Local Control, 1913, p. 4.
- Dreyer Handbook, 1918. p. 82.
- Dreyer Handbook, 1918. Plate 38.
- Dreyer Handbook, 1918. Plate 36.
- Dreyer Handbook, 1918. pp. 81-2.
- Dreyer Handbook, 1918. p. 81.
- Dreyer Handbook, 1918. p. 82.
- Handbook of Captain F.C. Dreyer's Fire Control Tables, 1918. p. 3.
- order NS14083/14, 27 March 1914, ADM 182/5, thanks to Mark Harris