Dreyer Fire Control Table

The Dreyer Fire Control Table was the Royal Navy's highest-level Fire Control instrument during World War I.

Mark III Dreyer Fire Control Table as it appeared by 1918, front
Bearing plot, deflection drums and deflection totaliser on left (Wind Dumaresq obscured behind this equipment), Mark VI* dumaresq with integral range and bearing clocks beneath gyrocompass repeater and Forbes log in centre, and range plot, gun range counter and spotting corrector on right.

Mark III Dreyer Fire Control Table as it appeared by 1918, back
Spotting Corrector, Range plot and range plot grid on left, emergency manual drive hand-crank and stop-watch governor housing in centre (dumaresq, etc in rear), axle and chain drive to actuate bearing plot is prominent, and the wind dumaresq is visible here with the bearing plot, bearing grid, and deflection drums beyond. Though the Mark III table was introduced in 1912, this image depicts it after it had ripened through the addition of several accessories, most notably by the addition of deflection drums, deflection totaliser, wind dumaresq, and an improved range plot typewriter. These improvements typified the continual refinement process the Dreyer tables' open-faced nature seemed to welcome.

The tables existed in various Marks, vexingly not developed in the order of their Roman numeral Mark numbers (Mark III was first). The Dreyer tables were based on semi-automated plotting of range cuts and bearings versus time on separate sheets of paper and employing a dumaresq and other appliances to relate these data, guess their derivatives, and compute a continuous range and deflection for use at the guns and/or the director.

For many decades, Dreyer tables have been a scapegoat for poor shooting by the Royal Navy. This criticism is misdirected.

Overview

Dreyer Fire Control Tables were early mechanical computers ("calculating workbenches" might be a better term) meant to process data to permit a ship to engage a distant target with heavy artillery. They were fairly involved pieces of equipment, and grew more intricate between the invention of the first prototype table in 1911, their first deployment on dreadnoughts in 1912 (?) and the creation of the Mark V table in 1918. The dreadnoughts of the Grand Fleet relied on Dreyer equipment at Jutland to convert sporadic and imprecise estimates of range and bearing into workable firing parameters. Sadly, the level of success was spotty, as visibility conditions made such systematic data collection too occasional for performing the sort of graphical analysis on which the Dreyer relied.

The Dreyer FCTs were literally sturdy iron tables fitted with a number of fire control devices tied together by rotating shafts, bicycle chains and other linkages, worked by 7 or more men simultaneously as a corporate endeavour. They were housed deep within the ship in the Transmitting Station located beneath the armoured deck. By the time the Mark V table was fitted in H.M.S. Hood, as many as 30 people might occupy the T.S., working the table and its many ancillary devices or serving as liaisons to the fighting positions of the ship. It is fair to suggest that the Dreyer and its environment and attendants resembled a premonition of the Mission Control centres of the Apollo program 50 years later: a human/machine system on a broad scale to factor down a torrent of real time sensory data to create a manageable environment for exerting command at a rate tolerable to humans.

Dreyer Table as CPU in a Ship/Computer

It is not possible to study the Dreyer tables without developing a familiarity with the ship-wide art of fire control, the process of calculation and articulation by which the shells can be made to rapidly and continually fall in a pattern around a distant maneuvering enemy. The Dreyer's role was akin to that of a CPU within a modern computer system, and its "socket" was the T.S.

Examining a dreadnought as a computer system is the best way to develop this understanding. Just as a CPU processes input received via keyboard, mouse, and network adapter, the Dreyer table was given data on what the enemy appeared to be doing. And, just as a CPU might generate output on a screen or printer, the Dreyer's output peripherals were powerful naval guns. Without paying too much attention to the input and output devices, let's examine the T.S.'s role in the system by drawing a circle around it and observing which inputs and outputs crossed this membrane.

Inputs to a Mark III Dreyer Table, c1918
Input Received	Source of Data	Nature of Data
Observations of Target Range	Optical rangefinders	sporadic, imprecise
Observations of Target Relative Bearing	Optical device	sporadic, granular
Reports where shells are falling	Verbal reports	fairly often, fairly precise
Own ship's heading	Gyrocompass	continuous, fairly precise
Own ship's speed	Forbes Log (a speedometer)	continuous, fairly precise
Apparent wind speed	Anemometer	continuous, fairly precise
Apparent wind direction	Wind vane	continuous, fairly precise
Temperature	Thermometer	one reading suffices for the action

The outputs a Dreyer table delivered were simple and did not have far to go — nothing left the T.S., directly. Remember, the Dreyer is just the CPU... the T.S. is the motherboard, and the ship is the computer.

Outputs from a Mark III Dreyer Table
Output Generated	Source of Data	Nature of Data
Gun range	Range clock + accrued spotting corrections	continuous, 25 yard granularity
Gun Deflection	Computed totals + accrued spotting corrections	continuous, "1 knot" granularity

Distribution of Dreyer Fire Control Tables

As of June, 1918 Dreyer Fire Control Tables were allocated as shown:

Table	Fitted In
Mark I	Dreadnought, Colossus, Hercules, Neptune, Collingwood, St. Vincent, Agincourt, Erin, Bellerophon, Marlborough, Superb, Temeraire, Australia, New Zealand, Inflexible
Mark I*	Cavendish, Effingham, Frobisher, Hawkins, Raleigh, Glatton, Gorgon
Mark II	Ajax, Centurion, Conqueror, Orion
Mark III	King George V, Monarch, Thunderer, Excellent, Chatham Gunnery Training School
Mark III*	Cairo, Calcutta, Cape Town, Carlisle, Colombo, Dehli, Dunedin, Durban
[[Mark IV	Queen Elizabeth, Benbow, Emperor of India, Iron Duke, Tiger
Mark IV*	Resolution, Revenge, Royal Oak, Barham, Malaya, Valiant, Warspite, Canada, Renown, Repulse, Lion, Princess Royal, Courageous, Glorious
Mark V	Ramillies, Anson, Hood, Howe, Rodney
Turret Tables (in turrets)	Ramillies, Resolution, Revenge, Royal Oak, Royal Sovereign, Barham, Malaya, Queen Elizabeth, Valiant, Warspite, Benbow, Emperor of India, Iron Duke, Marlborough, Renown, Repulse, Tiger, Courageous, Glorious
Turret Tables (in T.S. of Light Cruisers)	Ceres, Chester, Carysfort, Comus, Melbourne, Royalist

See Also

• Argo Clock
• Ford Rangekeeper
• Admiralty Fire Control Table

Bibliography

• Template:BibDreyerTableHandbook1918