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Handbook of Captain F. C. Dreyer's Fire Control Tables 1918

Handbook of Captain F. C. Dreyer's Fire Control Tables

1918

Repository
Document ID
Pages
Dimensions
Plates
Admiralty Library
C.B. 1456

92

including plates

28cm x 16cm

46

 

A distribution notice inside the cover indicates a date of June 25th, 1918 and expresses in stronger than usual terms the need to keep its contents confidential.  My copy of this handbook is a black and white photocopy of an original Copy No. 10, generously provided me by Bill Schleihauf.

This manual is totally indispensible for those wishing to learn of Dreyer equipment.

My copy lacks a table of contents, but I have reconstructed one from the text.  It also appears to be missing several plates. The original plates are in color, and quite glorious, so you might inquire after color processes if ordering a copy.

 

  Page
List of ships carrying Dreyer Fire Control Tables (see Notes section) 3
 
CHAPTER I.
Definitions  
Overview of the Components 4
Definitions 8
Notes on Manufacture 9
  Ball Bearings, Bicycle Chain, Flexible Shafting , Tapered Pins, Lubrication and Upkeep, Stripping  
 
CHAPTER II.
Description, with Photographs and Diagrams  
Table Mark I. 13
  Rangekeeping Unit, Range Plot, Bearing Plot  
Table Mark I.*, Table Mark II. 15
Table Mark III. 17
  Rangekeeping Unit, Range Plot, Bearing Plot  
Table Mark III.* 19
  Rangekeeping Unit, Range Plot, Bearing Plot  
Table Mark IV., IV.* 21
  Rangekeeping Unit, Range Plot, Bearing Plot  
Table Mark V. 23
  Rangekeeping Unit, Range Plot, Change of Bearing Gear, Bearing Plot, Bearing Tell-Tale  
Stripping the Mark IV.* Table 25
  Main Drive Motor, Backboard, Range Plot, Dumaresq, Bearing Plot  
 
CHAPTER III.
Components of the Table  
The Range Plot 29
  Range Scale, Typewriter, Range-rate Grid, Plot, Typical Range Plot, Clock Range Screw, Tuning Handle, Pedalling Clutch, Spotting Corrector, Gun Range Counter, Gun Range Pencil, Minute Marker  
The Bearing Plot -- Standard Pattern 35
The Bearing Plot on Mark V. Tables 36
The Deflection Totaliser 37
The Deflection Corrector Link Gear 40
    The Corrector Link as Fitted in "Ramillies" (Plate 19)  
    The Corrector Link as Fitted to Mark V. Tables other than in "Ramillies" (Plate 20)  
    The Corrector Link as Fitted to Mark III.* Tables (Plate 20)  
  The Dumaresq in the Mark I., I.*, and III.* Tables 46
  The Dumaresq in the Mark III. Table 49
  The Electrical Dumaresq in the Mark IV., IV.*, and V. Tables 51
       
  Other Dumaresqs 60
    Mark IV., Mark VII.*, Wind Dumaresq  
  The Clock (Plates 26 & 27) 61
  The Change of Bearing gear, Tables Mark IV., IV.*, and V. 61
  The Compass Control Gear 64
  The Main Drive Control and Governor 67
  The Watch Box 68
  The Rate Transmitter 70
  The Range Master Transmitter 72
  The Deflection Master Transmitter 75
  The Repeater 76
  The Standard Pattern Transmitting Commutator 78
  The Motor-- Standard (2-Pole_ Pattern as used in the Bearing Plot 78
  Signal Lamps on the Table 78
 
CHAPTER IV.
Description, Photographs and Diagrams of the Turret Table  
The Rangefinder Plot 81
The Clock Range Disc 82
The Electric Motor Drive 83
Lining up the Turret Table 83
 
CHAPTER V.
The Positions which are recommended for the operators of the various marks of Table  
Lining Up 87
Instructions in Closing Up at the Table 87
Testing the Clock 87
    On Tables Mark IV., IV.*, and V. 87
    On Tables Mark I., I.*, III., and III.* 88
Table Giving the Relation Between Range, Dumaresq Deflection, and Rate of Change of Bearing 89
Dimensions of the Tables 90
    The Rangefinder Plot  
    70

PLATES

No.
 
1. ?
Untitled -- a plan view of a generic Dreyer table
2.
Missing
3.
Mark I Table - diagram
4.
Mark I* Table - diagram
5.
Missing
6.
Missing
7.
Missing
8.
Missing
9.
Missing
10.
Missing
11.
Missing
12.
Missing
13.
The Range-rate Grid
14.
The Spotting Corrector and Tuning Gear-boxes
15.
The Gun Range Commutator and a typical Counter
16.
The Bearing Plot -- standard pattern
17.
The Bearing Plot - Mark V table
18.
The Deflection Totaliser
19.
The Deflection Corrector Link Gear
20.
The Deflection Corrector Link Gear - Mark V and III* Tables
21.
Mark I Table - front view
22.
The Dumaresq Dials
    Mark I, I*, and III* Tables and Mark IV, IV* and V Tables
23.
The Dumaresq in the Mark III Table
24.
The Electrical Dumaresq
25.
The Electrical Dumaresq  - centrework
26.
The Range Clock Mechanism
27.
The Clock Drive and the Change of Bearing Gear
28.
The Compass Control Gear
29.
The Motor and Governor
30.
The Rate Transmitter
31.
The Range Master Transmitter
32.
The Deflection Master Transmitter
33.
The Repeater
34.
The Standard Commutator
35.
The Staandard Motor
36.
The Turret Table - in use
37.
The Turret Table - diagram
38.
Title missing apparently, a turret table with covers removed
39.
Position of Operators - Mark I and I* tables
40.
Position of Operators - Mark III table
41.
Position of Operators - Mark III* table
42.
Position of Operators - Mark IV and IV* tables
43.
Position of Operators - Mark V table
44.
Testing Diagram
45.
The Original Table
46.
Analysis of the Plot

 

NOTES

On page 3 a table shows which ships are fitted with which Mark of Dreyer table.  Many of the names are crossed out in pencil, owing to their passage from service after the time the document was created or because their equipment has been altered from the original noted, or the equipment noted was never supplied.  The table is reproduced here, but with red being used to denote a ship name that was crossed out in pencil and blue to note a ship name pencilled in in a section other than where it had originally been printed.

Mark I. Tables
Dreadnought
Colossus
Hercules
Neptune
Collingwood
St. Vincent
Agincourt
Erin
Bellerophon
Marlborough
Superb
Temeraire
Austrailia
New Zealand
Inflexible
 
Mark I.* Tables
Cavendish
Effingham
Frobisher
Hawkins
Raleigh
Glatton
Gorgon
 
Mark II. Tables
Ajax
Centurion
Conqueror
Orion
 
Mark III. Tables
King George V.
Monarch
Thunderer
Excellent
Chatham Gunnery School
 
Mark III.* Tables
Cairo
Calcutta
Capetown
Carlisle
Colombo
Delhi
Dunedin
Durban
 
Mark IV. Tables
Queen Elizabeth
Benbow
Emperor of India
Iron Duke
Tiger
 
Mark IV.* Tables
Resolution
Revenge
Royal Oak
Royal Sovereign
Barham
Malaya
Valiant
Warspite
Canada
Renown
Repulse
Lion
Princess Royal
Courageous
Glorious
Tiger
Ramilllies
Queen Elizabeth
 
Mark V. Tables
Ramillies
Anson
Hood
Howe
Rodney
Gunnery School Chatham
Gunnery School Portsmouth
Gunnery School Devonport
 
Turret Control Tables
Ramillies
Resolution
Revenge
Royal Oak
Royal Sovereign
Barham
Malaya
Queen Elizabeth
Valiant
Warspite
Benbow
Emperor of Indeia
Iron Duke
Marlborough
Renown
Repulse
Tiger
Courageous
Glorious
 
Turret Control Tables in Light Cruisers
Ceres
Chester
Carysfort
Comus
Melbourne
Royalist

The Mark numbers of the Dreyer tables do not reflect the order in which the machines were devised and fielded.  The Mark III. was actually the first version and the Mark I. tables were conceived later as a smaller installation able to fit into the comparatively smaller Transmitting Stations of the earlier ships.  The Mark II series and IV series had more features and automatic functionality, but the essence of these devices remained as follows throughout their life span.

A Dreyer table had 3 primary elements: a Range Plot, a Dumaresq fitted with a Range Clock, and a Bearing Plot.  Additionally, several secondary elements on the table or nearby helped tie the table's function together:  Deflection Drums, Deflection Totaliser, Spotting Corrector, and devices to relay its results to the ship's gunnery positions.  Apart from those common elements, different Marks diverged considerably.  Between 5 and 12 people would directly operate the table, with an additional 10 to 30 people assisting.

It is easiest to start by examining the Dreyer's function, which was one of calculation and prettifying noisy data.  Viewed as a computational black box, a Transmitting Station equipped with an early model Mark III Dreyer table had the following inputs and outputs.

Data

 Input From/Output To

Units Notes
Range reports From rangefinders yards discrete, infrequent, noisy, 25 yard granularity, relayed electro-mechanically, manually plotted on Range Plot
Bearing reports From main rangefinder relative degrees discrete, 1/4 or 1/15th degree granularity, relayed electro-mechanically, automatically plotted on Bearing Plot
Own Heading From gyrocompass true degrees continuous, automatically fed to Dumaresq and Bearing Plot
Own Speed From Forbes log knots continuous, manually fed to Dumaresq
Spotting corrections (range) From spotting officer in top yards verbally relayed, usually incremental
Spotting corrections (deflection) From spotting officer in top Left/right knots verbally relayed, usually incremental
Range Rate settings From rate officer topside yards per minute verbally relayed, manually fed to Range Clock
Range Rate suggestions To rate officer topside yards per minute verbally relayed
Gun Range To director & guns yards continuous, relayed electro-mechanically
Gun Deflection To director & guns Left/right knots continuous, relayed electro-mechanically

A Dreyer table generally had 3 main elements arranged left to right as you faced it:   a Bearing Plot, a Dumaresq with an integral range clock, and a Range Plot. The position, degree of interconnectedness and exact character of the elements differed between the Marks, but we'll discuss each in turn.  The explanations that follow pertain most closely to the Mark III. table, but many of the principles are helpful when examining the later versions although one might care to take the details with a grain of salt.

The Range Plot was a moving paper scroll 36 inches wide which advanced at 2 inches per minute and provided a range-vs-time graphing area where pencil lines and typewritten letters could respectively plot a range hypothesis and the discrete range data from which it was derived.  A ruler-like range gauge marked from 2000-16,400 yards (it could be thrown into a long range setting of 10,000-24,400 yards) was positioned across the face of the paper, and a small, specialized typewriter equipped with an index could slide back and forth along this gauge until its index precisely matched a range observation called down from a rangefinder above-decks.  By typing the typewriter key corresponding to the rangefinder making the report, a small letter or symbol would be tacked onto the paper at the proper position.  Over time, as various reports were received and typed onto the paper, the operators would have assembled a noisy set of datapoints which statistically indicated the range as it changed over time.

Another operator could then employ a circular grid of wires positioned over the paper to try to discern the "range rate", or a linear approximation of how rapidly range was changing over time as a result of the relative maneuvering of own ship and target ship.  By working small knobs on this grid, the wires within could be deflected to various angles and the operator would look through these wires to the pointset beyond and try to determine a visual regression of the data.

The Dumaresq was a clever analog computer to relate the motion of one's own ship, the target ship and target bearing to the Range Rate in yards per minute along the line of fire and the "speed across" (in knots) across the line of fire .  On the Dreyer tables, the Dumaresq was additionally fitted with a Vickers Range Clock which could represent a constant derivative of range over time.  Just as the range grid was used to visually estimate a constant range rate, the simple nature of the Vickers implies one of the general characteristics of Dreyer equipment:  it liked to think of range as a variable which changed linearly over time, and any other dynamics to this relationship had to be accommodated either by manual corrections or by the additions of ancillary mechanisms to the basic table design.

The Range Clock's output was not a range per se, but a sequence of changes in range.  It was tied into an odometer-like "gun range counter" which would count upward (or downward) at the range rate set on the clock.  It would also drive a worm screw that lay across the face of the range clock and on which was fitted a plotting pencil.  When the clock was stopped, the pencil would remain in place, drawing a line down the advancing paper at its present position on the range scale.  In this case, the pencil could be said to be plotting a constant range versus time.  But if a closing or opening range rate were applied on the range clock, the worm screw would then act to drag the pencil to the left or right across the paper at constant speed, and the result would be a pencilled curve depicting a linear range versus time hypothesis-- a graphical analog to the data being digitally displayed on the Gun Range Counter.

The Bearing Plot was the last primary component of the Dreyer table.  It resembled a smaller version of the Range Plot but it tracked the target's True Bearing over time.  Relative bearings to the target observed by the main range finder were signalled down electrically, rectified by gyroscope input to True Bearings, and pricked into the paper by a small pin actuated by a solenoid.   A Bearing Grid similar to the Range Grid could be twisted until its wires seemed parallel to the trend of bearing data, and in this way the Bearing Rate in degrees per minute could be estimated.

Situated near the Bearing Plot was a set of Deflection Drums etched with curves.  One of these drums indicated Corrected Deflection (or Sight Deflection) and the other related Dumaresq Deflection (Speed Across) as a function of Bearing Rate (across the drums) to Gun Range (the rotation of the drums).  Conveniently, a flexible drive from the Gun Range Counter rotated the drums to the proper Gun Range and an index across the drums pointed to the proper point as the operator adjusted the Bearing Grid to match the trend indicated on the Bearing Plot.

The last supportive element on the table itself was a simple adding machine called the Deflection Totaliser which could add the Corrected Deflection indicated on the Deflection Drum to any other necessary sources of deflection to yield a total deflection.  It was this total Deflection and the Gun Range which constituted the primary outputs of the Dreyer Table.

Dreyer Table Crewing and Dimension

Dreyer Table

Mark

Crew Required

Width,

Depth

RGrid Height, Dumaresq Height
I.
8

5' 8"

5' 1.5"

3' 4"

3' 9.5"

I.*
8

5' 8"

5' 1.5"

3' 4"

5' 9"

II.
7 (+1)?
N/A
N/A
III.
7 (+1 if motor breaks)

9' 1.5"

4' 2"

3' 5"

5' 9"

III.*
7 (+1)

9' 5.5"

4' 3.5"

3' 7.5"

4' 2"

IV.
7 (+1)

9' 3"

4' 6.5"

3' 5"

5' 9"

IV.*
7 (+1)

9' 10.5"

4' 6.5"

3' 5"

5' 9"

V.
7 (+1)

10' 2"

4' 3.5"

3' 7.5"

5' 9"

  • The Mark II. table is largely glossed over in this handbook.
  • "RGrid Height" is the height to the top of the Range Grid.
  • Width and Depth figures include any protruding handles

Dreyer Table Dumaresq and Change of Bearing Gear Data

Dreyer Table

Mark

Dumaresq
Own Heading via
Enemy Inclination Maintained?
Change of Bearing Gear
I.
VI.*
handwheel input
yes
none
I.*
VI.*
automatic input
yes
none
II.
VI. ?
automatic input ?
no?
manually set to a constant bearing rate?, +/-15 degs/min maximum?
III.
VI.
automatic input
no
manually set to a constant bearing rate, +/-15 degs/min maximum
III.*
VI.*
"
yes
C.B.
IV.
electrical
"
?
C.B.
IV.*
"
"
?
C.B.
V.
"
"
?
C.B. plus bearing tuning handle
  • The C.B. (change of bearing) gear of the III.* and later marks was sensitive to the Gun Range, and would "do the right thing" to update the bearing as range changed.
  • Prior to the Mark V., any corrections to bearing required the bearing clock to be declutched and the dial plate moved to the correct position.  The Mark V. added a tuning handle that would allow correction without declutching.
  • The electrical dumaresq was electrical in the sense that small gears driving commutators would transmit the enemy speed and inclination on the dumaresq, allowing its settings to be remotely indicated on repeaters aloft.  In other dumaresqs, this data would have to be manually recorded and verbally reported.

Dreyer Table

Mark

Range Clock
I.
Vickers, external, clockwork driven
I.*
"
II.
Argo
III.
Vickers, integral to dumaresq, motor driven
III.*
"
IV.
"
IV.*
"
V.
"
  • The clockwork Vickers in the Mark I family did not have sufficient power to drive the plotting pencil worm screw or the gun range counter.  Instead, it merely drove a clock hand around an integral range dial and an operator chased this pointer with another worked by handwheel, and this action drove the counter and pencil.
  • Generally, the range clocks ran from 1200 yards per minute closing to 1200 yards per minute opening

Dreyer Table

Mark

Range Plot Width
Power
Yards per Inch
Lower Range Scale
Upper Range Scale
Paper Speed
I.
45 inches
Hand cranked
400
2,000 to 20,000

10,000 to

28,000

2 inches per minute
I.*
"
"
"
"
"
"
II.
36 inches ?
Electric motor with handcrank back-up
" ?

2,000 to

16,400 ?

10,000 to

24,400 ?

" ?
III.
36 inches
"
400
2,000 to 16,400
10,000 to 24,400
2 inches per minute
III.*
45 inches
"
600

2,000 to

29,000

none
4/3 inches per minute
IV.
37.5 inches
"
400
2,000 to 17,000
10,000 to 25,000
2 inches per minute
IV.*
45 inches
"
400
2,000 to 20,000
10,000 to 28,000
"
V.
45 inches
"
600
2,000 to 29,000
none
4/3 inches per minute
  • The tables with two range scales could shift between them by flipping a small tab that would add 8,000 yards to the gauge markings, pressing a clutch, and then tuning the range pencils up or down by 8,000 yards (20 inches).  The clutch would prevent the gun range counter's reading from changing.  The clutch would be re-engaged and operation could continue.