HNSA Crest with photos of visitors at the ships.
Folks,

B.R. 1534, Handbook on Minor Fire Control Instruments, 1946, describes the Vickers Range Clock, Dumaresq, Coventry Range Clock, Portable Fire Control Tray, Range Transmitter and Spotting Box, Deflection Transmitter and Spotting Box. Some of these had been in use since the turn of the century.

In this online version of the manual we have attempted to keep the flavor of the original layout while taking advantage of the Web's universal accessibility. Different browsers and fonts will cause the text to move, but the text will remain roughly where it is in the original manual. We have not attempted to correct any errors found in the original document. However, this text was captured by optical character recognition and then encoded for the Web which has added new errors we wish to correct.

I apologize for the uneven photographs of the plates and the missing plate plate 7. I hope to get back to Portsmouth some day to take better photos. Please let me know if you live near the Library and might be able to get better photographs. Please report any typos, or particularly annoying layout issues to the Mail Feedback Form for correction.

Our thanks to the Royal Navy, Naval Historical Branch Library in Portsmouth, UK for access to the original document.

Richard Pekelney
Webmaster



RESTRICTED-FOR OFFICIAL USE ONLY
B.R. 1534 (Restricted)
GUARD BOOK AND INDEX
FOR
HANDBOOK ON
MINOR FIRE CONTROL INSTRUMENTS
1946



A.F.O. P.339/49

RESTRICTED
(FOR OFFICIAL USE ONLY)

P.339-B.R.1534 (Restricted)-Guard Book and Index for Handbook on Minor Fire Control Instruments-
Amendment No. 1

(G. 02071/48-2 Sep. 1949.)

Inside cover, under heading PLATES-add in sequence:-

10. Star Shell Deflection Calculator-General Arrangement.
11. Star Shell Deflection Calculator-Deflection Slides.
12. Star Shell Transmitter Unit, Mark 2.
13. Control Officer's Aid-mechanism.

(G. 02071/48-A.F.O. P.339/49.)


(90527) Wt 8014/2179 2,000 9/49 Hw.
 

A.F.O. P.446/49

RESTRICTED
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P.446.-B.R. 1534 Series (Restricted) -Guard Book and Index for Handbook on Minor Fire Control Instruments-
Amendment No. 3

(G. 07383/49.-4 Nov. 1949.)

B.R. 1534(11)- Paragraph 13. Lines 6 and 7. Delete phantom inclination plot and substitute "target ship dial".

(G. 07383/49.-A.F.O. P.446/49.)

(Previous amendment No. 2-A.F.O. P.384/49.)


(91366) Wt. 8014/2179 2,000 11/40 Hw.
 

A.F.O. P.384/49

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P.384.-B.R. 1534-(Restricted)-Guard Book and Index for Handbook on Minor Fire Control Instruments-
Amendment No. 2

(G. 02071/48.-7 Oct. 1949.)

B.R. 1534(9). Remove photograph titled "Star Shell Transmitter Unit, Mark 2 -front cover removed" and insert in B.R. 1534(10).

(G. 02071/48.-A.F.O. P.384/49.)

(Previous amendment No. .1-A.F.O. P.339/49.)


(90975) Wt. 8014/2179 2,000 10/49 Hw.
 

A.F.O. P.519/50

RESTRICTED
(FOR OFFICIAL USE ONLY)

P.519.-B.R. 1534 Series (Restricted)-Guard Book and Index for Handbook on Minor Fire Control Instruments-
Amendment No. 4.

(G. 07995/50.-3 Nov. 1950.)

B.R. 1534 (10)
Page 1.
Paragraph 1. Last sentence. Delete and substitute:
The second photograph in this book shows the Star Shell Transmitter Unit, Mark 2, and Star Shell Deflection Calculator, Mark 5, as used in H.M.S. VANGUARD.

Paragraph 3. Line 1. After "VANGUARD" Insert:-
"and scheduled to be fitted in H.M.S. NEWFOUNDLAND on re-armament."

Under Object:- Line 12. Delete figure "5".
Line 13. Amend "6 or 10," to read "6, 6* or 10,".

Paragraph 7. Last line. Delete full-stop and add "for 5.25-in. guns and at a height of 1,700 feet for 4-in., Mark 16 or 16* guns."

Paragraph 8. Lines 4 and 5. Delete "(see Range Table 607)." and substitute" for 5.25-in. guns and at a height of 1,700 feet for 4-in., Marks 16 and 16* guns."

(G. 07995/50.-A.F.O. P.519/50.)

(Previous amendment No. 3-A.F.O. P.446/49.)


(96114) Wt. 8069/2216 2,000 11/50 Hw.
 

INDEX TO SERIES

B.R. 1534 (G.B. & I) Binder and Index.
B.R. 1534 (1) Dumaresq Mark VIII.
B.R. 1534 (2) Dumaresq Mark XI.
B.R. 1534 (3) Dumaresq Mark XII.
B.R. 1534 (4) Vickers Range Clock.
B.R. 1534 (5) Coventry Range Clock.
B.R. 1534 (6) Portable Fire Control Tray.
B.R. 1534 (7) Range Transmitter and Spotting Box.
B.R. 1534 (8) Deflection Transmitter and Spotting Box.
B.R. 1534 (9) Starshell Deflection Calculator.
B.R. 1534 (10) Starshell Transmitter Unit.
B.R. 1534 (11) Control Officers Aid Box.
B.R. 1534 (12)
B.R. 1534 (13)
B.R. 1534 (14)
B.R. 1534 (15)

PLATES

1. Dumaresq Mark VIII AD. Patt. No. 5969A.
2. Dumaresq Mark XI AD. Patt. No. 10724.
3. Dumaresq Mark XII AD. Patt. No. 10758.
4. Vickers Range Clock, AD. Patt. No. 3778.
5. Coventry Range Clock, AD. Patt. No. 10447.
6. Portable Fire Control Tray (Outside view), AD. Patt. No. 10497.
7. Portable Fire Control Tray (Mechanism).
8. Range Transmitter and Spotting Box, AD. Patt. No. 10725.
9. Deflection Transmitter and Spotting Box, AD. Patt. No. 10726.

(SO 235)

 

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HANDBOOK
ON
MINOR FIRE CONTROL INSTRUMENTS


1946

ADMIRALTY, S.W.1
GUNNERY BRANCH

(SO 235)

 

iii
 

Admiralty, S.W.1.
13th. May, 1946.

G. 7521/45.

B.R. 1534 (Restricted) Handbook for Minor Fire Control Instruments, 1946, having been approved by My Lords Commissioners of the Admiralty, is hereby promulgated for information and guidance.

By Command of Their Lordships,
H.V. Markham

To Flag Officers and
Commanding Officers
of H.M. Ships and
vessels concerned.

 

iv
 
This book has been written for the instruction and guidance of officers and men of the Fleet. If it does not provide the information required or if the description of the plates are not sufficiently clear, then it does not fulfil its purpose. Criticism and suggestions of every kind are invited and are to be forwarded through the Administrative Authority, with a copy to the Captain, H.M.S. Excellent.

INTRODUCTION

Certain Minor Fire Control instruments in general use have not so far been included in Admiralty Handbooks.

These instruments are described in the following pages and include a revised edition of the Vickers Range Clock AD. Patt. 3778 and the Dumaresq Mark VIII, which also appear in B.R. 973, published in 1933. The latter instrument is a modified version of the original Mark VIII, having a blank deflection drum.

Special attention has been paid to the illustrations, which are now in colour, and all named parts have been brought up in heavy type in the text.

The descriptions of further Minor Fire Control Instruments will be issued as written, for inclusion in the Guard Book.

 

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DUMARESQ MARK VIII


1946
 

DUMARESQ MARK VIII. AD. PATT. No. 5909A

Plate 1

1. The Dumaresq is an instrument which, set with own speed and the relative bearing of the enemy, and her inclination and speed, will calculate the relative course and speed and resolve it into two components-one along the line of sight, i.e., rate of change of range, and the other across the line of sight, i.e., Dumaresq deflection.

Description

2. The Dumaresq consists of a circular frame and on its upper edge from 0° to 180°, Red and Green relative to the Fore an Aft Bar which is mounted on the frame. The frame itself is clamped down with this bar parallel to the Fore and Aft line of the ship.

Under this bar is mounted a slider which travels along a feathered shaft and carrying an index cursor which can be moved aft from the centre a scale graduated from 0 to 35 knots for own speed. This feathered shaft is connected by gearing to the base plate carrying the line of sight arrow and keeps the zero line of inclination plate parallel to this line of sight. The inclination plate is graduated from 0° to 180° right and left, to which is set the inclination of the enemy by an index carried on the Enemy Bar. The underside of the inclination plate is serrated and can be engaged with similar serrations on the upper side of another plate by pressing down on the thumb plate on the top of the slider. This lower plate carries the Enemy Bar.

The Enemy Bar is graduated in knots for speed of enemy from 0 to 35 knots towards the stern and carries on the underside a pointer from which is read off the Rate and Deflection on the base plate. The base plate on which is engraved the line of sight arrow is revolved inside the circular frame by means of a milled wheel. It is inscribed with lines parallel to the line of sight, the distance apart representing 4 knots. Lines at right angles to the line of sight are graduated in 200 yard steps from zero to 2,000 yards opening on the upper half and zero to 2,000 yards closing on the lower half of the plate. A slot is cut at right angles to the line of sight through the centre of the base plate; under the slot a deflection drum is mounted capable of being revolved to a scale of range on the left perimeter and having scribed curves graduated from zero on the centre, out to left and right. The graduations are either in units or knots, depending upon the graduations on the deflection dial of the gun sight. These curves and ranges are applicable only to the gun from whose Range Tables the graduations are calculated. This drum is easily detachable for replacing another drum graduated for a different calibre of gun.

Operation

3. Set own speed on Fore and Aft Bar.

Train line of sight on enemy by open sight or set to relative bearing by means of the milled wheel.

Set enemy speed on Enemy Bar.

Set Enemy Bar to inclination ordered.

Set Range on drum.

Read off on base plate, the Rate on the horizontal lines, indicated by the pointer.

Follow the vertical line directly under the pointer to where it cuts the drum and read off the gun deflection.

Note.-A knot of deflection represents the angular movement of the line of sight to a target which is moving at a speed of one knot across the line of sight during time of flight, the target being at the range for which the deflection dial is graduated. A further explanation is given in B.R. 981, page 11.

In the diagram the pointer is indicating Rate 800 Closing, Gun Deflection 4 Right.

When own ship alters course, press down on the thumb to plate to engage Enemy Bar to slider so that the inclination is kept constant, although the bearing alters. Thumb plate must be released as soon as own ship is steady. It must be remembered that inclination will alter equally with bearing, if neither ship alters course, whereas the angle between keels remains constant.

(SO 235) A3

 

2
 
Maintenance

4. The instrument should be protected from weather and dust when not in us, otherwise the centre base plate is liable to seize up with the circular frame.

The following parts should be cleaned and oiled periodically:-

The feathered shaft carrying the slider and its associated pinions.

The base plate where it rests in the circular frame.

The small pinion on the feathered shaft operating the inclination plate.

The deflection drum bearings.

The base plate should be wiped clean with a slightly oiled cleaning rag.

The whole instrument should be stripped down annually and thoroughly cleaned and oiled.

To Strip the Dumaresq

5. Remove six screws underneath the circular frame, securing the brackets and Fore and Aft Bar and remove complete.

Remove three keep plates under the circular frame and lift out the base plate.

The Fore and Aft Bar and attached gear can now be stripped down by first removing the set and check nuts on the thumb plate and removing the lower serrated plate with Enemy Bar attached, complete with spiral spring. Remove four screws in the thumb plate and remove plate and lever.

Take out two screws and keep plate at after end and two screws at forward end of own speed bar and lift the bar out with a V block bearing.

Remove the after end bracket and slide off centre post carrying the inclination plate. This plate can now be removed by taking out four screws under the plate. The pinion driving the inclination plate is carried in a bracket and secured by two screws. Remove this bracket and the inner rack can then be lifted out clear of the centre post.

Reassemble in the reverse order, taking care when connecting up the pinion and inclination plate that the zero of the inclination scale is in line with the point of the line of sight arrow and that the pinion driving the inclination plate is on the after side of the sliding block.

6-9.

 

DUMARESQ MARK VIII-AD. PATT. NO. 5969A. Plate 1
DEFLECTION DRUM NOTE.- THIS DRUM IS SUPPLIED BLANK; GRADUATIONS TO SUIT THE NATURE OF THE GUN ARE PRINTED ON A PAPER STRP WHICH IS THEN PASTED ON THE DRUM

RESTRICTED-FOR OFFICIAL. USE ONLY

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HANDBOOK ON
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DUMARESQ MARK XI
1946
 

DUMARESQ MARK XI, AD. PATT. No. 10724

Plate 2.

1. The instrument is designed to produce an initial approximate deflection only, and has been made as simple as possible. Provision is made to fit the instrument on either side of the bridge ; to be clamped down in the fore and aft line.

Figures for bearing and inclination have been omitted in order to keep the dial clean and to facilitate rapid setting and reading off.

The deflection produced will be reasonably correct for "Enemy Speed Across" and that for "Own Speed Across" is calculated for a standard speed of "Own Ship" of 12 knots which has been used in the design.

Operation

2. (i) Point the Line of Fire arrow running through the centre of the revolving plate, blue, towards the target.

(ii) Set estimated enemy's speed by moving the cursor, yellow, on Enemy Speed Bar, pink.

(iii) Set the bar with the model ship to the approximate inclination of the enemy by aligning it parallel to the course of the enemy by eye.

(iv) Read off deflection from the revolving plate against the pointer of the cursor of the Enemy Speed Bar.

Maintenance

3. The instrument must be kept clean and a light application of oil made to the bearing surfaces as required.

A suitable painted canvas cover should be made by ship's staff and the instrument protected when not in use.

4-5.

 

DUMARESQ MARK XI -AD. PATT. NO. 10724 Plate 2
 

RESTRICTED-FOR OFFICIAL USE ONLY

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DUMARESQ MARK XII

1946

 

DUMARESQ MARK XII, AD. PATT. No. 10758

Plate 3

1. The instrument is designed to produce an initial approximate rate and deflection only, and has been made as simple as possible. Provision is made to fit the instrument on either side of the bridge; to be clamped down in the fore and aft line.

Figures for bearing and inclination have been omitted in order to keep the dial clear and to facilitate rapid setting and reading off.

The deflection produced will be reasonably correct for "Enemy Speed Across" and that for "Own Speed Across" is calculated for a standard speed of " Own Ship " of 12 knots which has been used in the design.

Similarly, the rate shown on the dial will be reasonably correct for "Enemy Speed Along," and for "Own Speed Along," due to an "Own Ship's Speed" of 12 knots.

Operation

2. (i) Point the Line of Fire arrow running through the centre of the revolving plate, blue, towards the target.

(ii) Set estimated enemy's speed by moving the cursor, yellow, on Enemy Speed Bar, pink.

(iii) Set the bar with the model ship to the approximate inclination of the enemy by aligning it parallel to the course of the enemy by eye.

(iv) Read off rate and deflection from the revolving plate against the pointer of the cursor on Enemy Speed Bar.

Maintenance

3. The instrument must be kept clean and a light application of oil made to the bearing surfaces as required.

A suitable painted canvas cover should be made by ship's staff and the instrument protected when not in use.

4-5.

 

DUMARESQ MARK XII-AD. PATT. NO. 10758. Plate 3
 

RESTRICTED-FOR OFFICIAL USE ONLY

B.R. 1534 (4) (Restricted)

HANDBOOK ON
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VICKERS RANGE CLOCK

1946

 

VICKERS RANGE CLOCK, AD. PATT. No. 3778

Plate 4

1. The instrument is designed to apply a rate of range automatically to an initial range, and also to provide a means of easily applying spotting corrections.

Description

2. Clockwork mechanism, controlled by a spring and ball governor, drives two friction discs in opposite directions. A friction roller which can be moved along a splined shaft, is mounted between the two discs.

The friction roller can be placed at any radial distance from the centre of the friction discs and its speed of rotation will be proportional to that distance.

When the rate is set on the Rate dial by turning the Rate handle, the friction roller is moved across the disc and its rotation is transmitted by the splined shaft and suitable gearing to the range pointer on the large Range dial.

The pointer will then indicate the range corrected for Rate. The Rate dial is graduated from 0 to 2,000 yards opening and closing. The figures on the range scale on the clock face are arranged in six series, one series being exposed at a time, by operating the range series change knob. The scale is graduated from 0 to 32,400 yards. The Range scale can be revolved completely by means of the spotting correction handle. An additional pointer painted Red is frictionally attached to the Range pointer and can be used for recording the straddle correction.

There is a starting and stopping milled knob, marked "Stop", and "Go," and a rewind tell tale in the clock face.

A shutter at the back of the clock gives access to the speed regulator. Alongside this shutter is a handle for transporting purposes. The clock's overall dimensions are 13 1/2 ins. x 19 ins. x 7 ins.

Operation

3. Wind up the clock fully by means of the winding handle on the right mid subsequently re-wind each time the tell tale appears to ensure that the clock runs accurately. Care must be taken not to over-wind the clock. This is easily done if any undue force is used.

Start the clock by means of the starting device on the left. Run the rate pointer to zero by means of the Rate handle.

Set the initial range opposite the Range pointer by means of the spotting correction handle, exposing the appropriate series of ranges as necessary by means of the milled knob on the outer circumference of the Range dial. Set Rate ordered on the Rate dial. The range pointer will now indicate the range, which is read off by the Clock operator and passed to the guns verbally or by transmitter.

The range should be forecast by 25 yards or 50 yards according to the Rate, to allow for lag in transmission.

Spotting corrections are applied by means of the spotting handle. One complete revolution of the spotting handle equals 100 yards.

When the range pointer reaches the Red mark on the range scale the operator should change to the next series of ranges, taking care that the movement is made in the appropriate direction.

Note.-(i) The clock should always be left to run down with the Rate set to 2,000 yards opening or closing when no longer required for time being.

(ii) The Rate handle must never be moved with the clock stopped, as the friction roller will be damaged. This is one of the commoner faults of clock operators.

TESTS:

Rate Adjustment Test

4. Wind the clock fully and start it.

Set Rate pointer to zero. The range pointer should now remain stationary.

If the range pointer moves, ease up the set and check nuts below the worm wheel on the Rate pointer spindle, revolve the Rate setting handle until the Range pointer stops.

 

2
 
Remove glass cover of the Rate dial and re-set pointer to zero by hand. Set up the nuts and check by timing high and low Rates.

Replace glass cover.

Speed Test

Start the clock.

Set 2,000 yards opening on the Rate dial.

Time the movement of the Range pointer over 4,000 yards.

Repeat the operation with 2,000 yards Closing Rate.

The sum of the two times should be four minutes.

If the time is more, move the regulator lever towards "F" to increase the speed.

If less, move regulator towards "S" to reduce speed.

Repeat the test and adjust as necessary until the correct speed is obtained.

TO STRIP THE CLOCK AND NOTES ON MAINTENANCE

5. The range clocks have been made reasonably substantial, having regard to ordinary handling, but they should not be subjected to rough usage. They should be carefully protected from the weather.

A rubber pad is provided on the base of the clock to deaden the effect of local vibration or shock, so as not to effect the readings.

The instrument, if in general use, should be overhauled, cleaned and oiled once in 12 months; no cleaning or oiling in the interval should be necessary. The only parts which may require attention in the matter of cleaning and lubrication are the lead screws and spindle for the friction roller. When oiling these, the clock should be suspended by the handle on the casing so that any excess of oil will not fall on the surfaces of the driving discs, but will fall in the lower part of the casing and can be wiped clean afterwards. The screws and spindle should be wiped clean of surplus oil after lubricating, a piece of soft leather being used for the purpose. Only the very best lubricant should be used, and that very sparingly; a copious supply of oil applied indiscriminately will eventually find its way on to the friction discs and completely disarrange the working.

Taking to pieces for examination should be avoided, as skill and care are necessary in reassembling to ensure satisfactory working. It will be found sufficient in ordinary circumstances for examination and cleaning to remove the rear cover plate, the dial rings and the fixed plate of the dial. Parts should be removed in the following sequence:-

Remove the small screws securing the glass frame and lift off.

Remove the screw securing the Range pointer to the centre spindle.

Remove the eight screws under the toothed rack; this will enable the perimeter to be removed bodily.

Remove the screws securing the thin brass cover plate of the dial face and detach the plate.

Remove eight screws securing the rear cover plate. These screws are found just above the rubber band, and the rear cover can then be removed.

The main portion of the interior of the instrument will then be seen and can be examined, cleaned and oiled. No further parts should be disturbed unless absolutely necessary. The gear beneath the Rate dial can be examined, cleaned and oiled by the removal of the cover on the underside bracket.

If it is necessary further to dismantle the instrument, the driving mechanism can be taken out bodily by removing the screws fixing the mechanism cheek plates to the frame of the instrument, care being taken first to remove the winding key and the spindle connecting the Rate setting gear to the lead screws.

The winding key is arranged in such a manner that, if turned in the wrong direction, the key will simply unscrew. To disconnect the spindle of the rate setting gear from the lead screws, remove the screws securing the Rate dial Bracket. The rate dial and its parts can then be removed, including the spindle.

When replacing the rate dial care should be taken that the squared hole in the end of the spindle engages correctly with the square on the lead screw when the friction roller is in its mid position and the rate pointer is at zero. In the event of the setting securing the worm wheel on the lower end of the pointer spindle and resetting the pointer to zero by hand as required. The graduated Range strip requires occasional oiling.

6-10.

 

VICKERS RANGE CLOCK - AD. PATT. NO. 3778. Plate 4
 

RESTRICTED-FOR OFFICIAL USE ONLY

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COVENTRY RANGE CLOCK

1946

 

COVENTRY RANGE CLOCK, AD. PATT. No. 10447

Plate 5

1. The instrument is designed to apply a rate of change of range automatically to an initial range, and also to provide an easy means of applying spotting corrections.

It is supplied for use in L.C.G's.

Description

2. Clockwork mechanism, controlled by a spring and governor, drives the rate disc. A friction roller, capable of being moved by a lead screw along a feathered shaft, can be placed at any radial distance from the centre of the rate disc and its speed of rotation will be proportional to that distance. This distance is governed by setting the Rate by means of the Rate setting knob on the Rate scale, which is graduated from 0 to 2,000 yards opening, and 0 to 2,000 yards closing, and works in 100 yard steps. These steps are controlled by a spring and ball, the ball engaging in a recess every 100 yards. When rate is applied the friction roller is rotated and its movement is transmitted through the feathered shaft and suitable gearing to the range dial, causing it to rotate with reference to a Range Cursor, which then indicates the up-to-date Range.

3. The Range dial is graduated in 100 yard steps from 0 to 10,000 yards and together with the Rate scale can be viewed through windows in the cover. The central portion of the cover immediately above the range dial is free to revolve by means of a Range setting knob, and teeth on the movable perimeter of this portion are engaged by a spring lever which clicks into engagement at each 100 yards. On the outer side of the window are graduations from 0 to Up 800 and 0 to Down 800 yards, and corresponding 100 yard graduations are engraved on the fixed portion of the cover to facilitate the application of spotting corrections.

4. The feathered shaft and gearing to the Range dial are carried in the frame, pale blue, which rocks on its adjustable bearings. The friction roller is kept down in contact with the rate disc by means of a spring, the upper end of which is secured to the rocking frame and the lower end to the fixed portion of the clock.

5. The clock is started and stopped by means of a milled knob on the lower side of the clock, which operates an "on" and "off" brake to the disc on the governor. A shaft fitted with a handle passes through the hand grip to wind the clock mechanism and a spring fitted round the shaft of the handle prevents a reversal of motion of the handle. Adjustable bearings are fitted at each end of the speed governor shaft. A speed regulator is fitted which works in conjunction with the governor, access to which is obtained by removing a small cover plate marked " REGULATOR."

6. An adjustable sling attached to two studs on the clock is provided for the operator. The clock is supplied in a strong waterproofed cover with a sling for transport.

Operation

7. The clock is worked by one operator, who carries the clock by means of the adjustable sling and hand grip.

8. His duties are as follows:-

(i) To keep the motor wound up.

(ii) To set range by rotating the range window until the cursor is over the range ordered.

(iii) To start the motor by means of the Start/Stop knob.

(iv) To set the rate ordered.

(v) To call out the range every 100 yards.

(vi) To apply Spotting Corrections.

In applying spotting corrections the following method is employed. Place the nail of the thumb on the division of the outer scale against the spotting correction ordered as shown on the spotting scale. Turn the range setting and spotting knob to bring the arrow in line with the mark on the outer scale indicated by the thumb nail. Read off the new range under the range cursor. Movement of the range spotting knob operates a clicker mechanism, one click for each 100 yards, so that a correction of down 400 can be applied by moving the cursor by four clicks in the required direction, but this method is not recommended as the clicker gear may get worn and become unreliable.

 

2
 
SPEED TEST:

9. (i) Fully wind the clock, and start it.

(ii) Set 9,000 yards opening on the Rate scale.

(iii) Time the movement of the Range dial against the Range Cursor over 4,000 yards.

(iv) Repeat the operation with 2,000 yards closing Rate.

The total time should be four minutes. If the time is more move the regulator towards the left, i.e., "Fast," to increase speed. If less move the regulator towards the right, i.e., "Slow," to reduce speed. Repeat the test and adjust as necessary until correct speed is obtained.

Maintenance

10. The clock is a very delicate instrument and should be handled with care; the sling should always be placed over the shoulder when the clock is being used.

11. The clock should on no account be stripped, beyond the state indicated below.

12. Access can be obtained to the friction roller, disc and associated gearing by removing four screws securing the cover. The Range dial can be removed by taking out three small screws securing it to the centre spindle. The feathered shaft and lead screw should be lightly oiled, using the best instrument oil, care being taken that no oil is allowed to fall on the friction disc.

13. Defective clocks should be returned to the dockyard. No attempt being made to repair them on board.

14-15.

 

COVENTRY RANGE CLOCK - AD. PATT. NO.10447 Plate 5
 

RESTRICTED-FOR OFFICIAL USE ONLY

B.R. 1534 (6) (Restricted)

HANDBOOK ON
MINOR FIRE CONTROL INSTRUMENTS



PORTABLE FIRE CONTROL TRAY

1946

 

PORTABLE F.C. TRAY MARK II, AD. PATT. No. 10497

Plates 6 and 7

Object

1. This instrument is designed to supersede the Vickers Clock and Dumaresq in;-

(a) Controlling turrets of capital ships and cruisers where no F.C.B. is fitted.
(b) H.A.C.P.s where no other L.A. Fire-Control arrangements are fitted.
(c) T.S.s fitted with A.F.C.T.s, as the emergency system.
(d) After Control in "Tribals."

Description

2. The mechanism is contained in a light metal box which can be the carried, use, by means of webbing slings attached to links at each corner of the box.

The tray itself is supplied in a wooden case for transportation.

Own and Enemy Settings

3. On the left of the tray are own and enemy-ship dials which are set for speed by means of butterfly nuts against scales graduated from 0 to 25 knots and 0 to 40 knots respectively.

Bearing and Inclination are set by means of knobs against a line-of-sight arrow. The bearing is graduated relative to own ship's head from 0° to 180° Red and Green and the inclination is graduated from 0° to 180° Right and Left relative to the Line-of-Sight arrow.

These settings position a "Spot" under a transparent plate by means of a lattice and this "Spot" indicates the Rate and Deflection to be set.

Range

4. On the right are two Range Counters, one marked "SET RANGE" and the other READ RANGE," both reading from 0 to 9,950 yards.

Below these counters is a Range-tuning handle marked "SET RANGE."

The Set-Range counter is provided with a shutter which also acts as a clutch.

When the shutter is swung clear in an anti-clockwise direction to disclose the Set-Range counter, the Rate drive is disconnected and the Range-tuning handle connected up.

In Plate 7 the pivot of the shutter is shown at the right upper corner instead of the left upper corner in order that a clearer idea of the mechanism may be indicated still assuming an anti-clockwise motion will swing the shutter clear. It is correctly drawn in Plate 6, showing the outside view.

This allows the initial range to be set on both counters. When this is set the shutter should be swung back over the Set-Range counter, thus disconnecting the Range-tuning handle and connecting up the Rate drive. Change of Range due to Rate is then driven into both counters. Spotting corrections are applied by either of two Range-Spotting handles, one each side of the box. The actual correction is set by counting the number of turns. 1 turn = 200 yards, away for "UP" and towards for "DOWN" corrections. The result is added to the Read-Range Counter only.

Range Rate

5. Range Rate is applied by turning the Rate-keeping (marked "KEEP RATE TURNING") at a steady speed so as to keep the hand of a stop watch (visible through a perspex window in the centre of the instrument) under the engraved line, the actual rate being determined by the Rate Mechanism. The perspex window with its engraved line can be aligned with the hand of the stop watch in any position.

Rate Mechanism

6. Applying own and enemy movements positions a "Spot" under a transparent window. The Rate cursor is aligned over this spot by means of the Rate-Setting knob, which, through pinion "A", yellow, positions the rocker plate and, through connecting links and rocking web, the ratchet gear of the Rate-adding mechanism.

A2
(SO235)

 

3
 
The mechanism should be kept well oiled and the following parts should receive special attention.

(a) Own and Enemy-speed sliders.
(b) Ratchet mechanisms.
(c) Oscillating drive and tension spring.

Access to the mechanism can be obtained by removing the base of the tray, secured by 20 screws. The mechanism itself is secured to the underneath side of the lid.

Two inspection plates are fitted in the base, each secured by a screw in the centre. One is fitted over the ratchet mechanism, the other over the rocker plate and Own-speed slider.

Two spare springs are supplied for the ratchet mechanism and are housed on the inside of the base plate.

11-15.

 

PORTABLE FIRE CONTROL TRAY (EXTERNAL VIEW) - AD. PATT. NO. 10497. Plate 6
 

RESTRICTED-FOR OFFICIAL USE ONLY
B.R. 1534 (7) (Restricted)

HANDBOOK ON
MINOR FIRE CONTROL INSTRUMENTS



RANGE TRANSMITTER AND
SPOTTING BOX

1946

 

RANGE TRANSMITTER AND SPOTTING BOX

AD. PATT. No. 10725

Plate 8

Object

1. The instrument is designed to enable an up-to-date Radar Range plus or minus spotting corrections to be transmitted to the guns.

Description

2. The instrument measures approximately 10 ins. x 10 ins. x 5 ins. The range counters and spotting dial can be viewed through windows in the cover. Illumination is provided by two bulbs inside the casing. Access to the bulbs is one provided by two small removable covers. The two springs, coloured green in the Plate, one on each of the tuning and spotting shafts, prevent the handles turning when not held by the hand. When not in use the roller of the recentring lever is held clear of the heart-shaped cam by a spring attached to the lever and to a fixed collar. The two range counter drums can be brought into coincidence by running the "gun range" counter to the range shown on the "set range" counter, using the spotting handle and recentring the spotting pointer as necessary.

Operation

3. (i) Set the initial range from Radar on the "SET RANGE" counter, using the tuning handle. This will show on both counter drums, and the range will be transmitted to receivers at the guns.

(ii) Keep the range from Radar continually set on the "SET RANGE" counter by the tuning handle.

(iii) Apply spotting corrections by means of the spotting handle which operates the spotting pointer to show on the spotting dial the amount of correction applied. It also works the gun range counter drum and the step by step transmitter.

Note.-The spotting pointer should be reset to zero after each correction by means of the recentring lever.

Care and Maintenance

4. The casing of the instrument is watertight and the gearing is simple and requires very little attention.

The cover should be removed annually and the gears lubricated with Light Torpoil or G.S. oil.

The transmitter can be removed for attention by removing a screw and securing plate on top of the transmitter casing.

To Strip the Box.

5. (i) Remove ten screws securing the cover and lift off; the cover is positioned by two pins.

(ii) Remove four screws securing the tuning handle and withdraw the handle complete with the shaft carrying the spur and spiral pinions.

(iii) Remove four screws securing the spotting handle and withdraw the handle complete with shaft carrying the worm.

(iv) The spotting pointer can be removed by taking out three small securing screws and lifting off the plate.

(v) Remove taper pin from the top of the centre spindle; this enables the parts to be removed in the following sequence:-

Recentring cam.
Distance Piece which take over two flats on the centre spindle.
Collar.
Spring washer.
Worm Wheel.
Spiral pinion (driven).
Differential.
Base Pinion.

Note.-Before removing the recentring cam, its position relative to the pointer and the direction of the point of the cam should be noted to facilitate reassembly.

(So 235)

 

2
 
(vi) Disconnect transmitter leads, remove four screws at base of transmitter and lift out transmitter complete with driving pinion. The transmitter is secured in the casing by a screw and plate.

(vii) Remove four screws securing each counter drum bracket and lift out the bracket complete with driving pinion. The drums are secured to the bracket by end plates and three screws, the driving pins are secured to the shaft by means of taper pins.

(viii) The box is reassembled in the reverse order.

6-10.

 

RANGE TRANSMITTER AND SPOTTING BOX - AD. PATT. NO. 10725. Plate 8
 

RESTRICTED-FOR OFFICIAL USE ONLY

B.R. 1534 (8) (Restricted)

HANDBOOK ON
MINOR FIRE CONTROL INSTRUMENTS



DEFLECTION TRANSMITTER AND
SPOTTING BOX

1946

 

DEFLECTION TRANSMITTER AND SPOTTING BOX

AD. PATT. No. 10726

Plate 9

Object

1. The instrument is designed to enable initial deflection to be set, LEFT or RIGHT spotting corrections to be applied and the resulting deflection transmitted to the guns.

Description

2. The instrument measures approximately 10 ins. x 10 ins. x 5 ins. The deflection counters and spotting dial can be viewed through windows in the cover. Illumination is provided by two bulbs; access to the bulbs is provided by two removable covers.

Movement of the handles, when not held by the hand, is prevented by friction maintained by two springs, coloured green, one on each of the tuning and spotting shafts. The recentring lever is kept clear when not in use by a spring attached to the lever and to a fixed collar.

Operation

3. The two deflection counter drums can be brought into coincidence by running the "Gun Deflection" counter, pink, to the deflection shown on the "Set Deflection" counter, orange, using the spotting handle and recentring the spotting pointer as necessary.

(i) Set initial deflection, using the tuning handle; this will be shown on both counters and the deflection will be transmitted to the guns.

(ii) Apply spotting corrections by means of the spotting handle, which operates the spotting pointer to show the amount of correction applied and adds this amount to the gun deflection counter; it also operates the step by step transmitter to transmit deflection to the guns.

The spotting pointer should be reset to zero after each correction by means of the recentring lever and heart-shaped cam.

Care and Maintenance

4. The casing of the instrument is watertight and the gearing is simple and requires very little attention.

The cover should be removed annually and the gears lubricated with Light Torpoil or G.S. oil.

The transmitter can be withdrawn for attention by removing a screw and securing plate on the top of the transmitter casing.

To Strip the Box

5. (i) Remove ten screws securing the cover and lift off. The cover is positioned by two pins.

(ii) Remove four screws securing the tuning handle and withdraw handle complete with shaft and pinions.

(iii) Remove four screws securing the spotting handle and withdraw handle complete with shaft carrying the worm.

(iv) The spotting pointer can then be removed by taking out three small securing screws and lifting off the plate.

(v) Remove taper pin from the top of the centre spindle; this enables the parts to be removed in the following sequence:-

Recentring cam.
Distance piece which takes over two flats on the centre spindle.
Collar.
Spring washer.
Worm wheel.
Spiral pinion.
The differential.
Base pinion.

Note.- Before removing the recentring cam, its position relative to the pointer, and the direction of the point of the cam should be noted to facilitate reassembly.
 

2
 
(vi) Disconnect transmitter leads, remove four screws at base of transmitter casing and lift out transmitter complete with driving pinion. The transmitter is secured in the casing by a screw and plate.

(vii) Remove four screws securing each counter drum bracket and lift out the bracket complete with driving pinion.

The drums are secured to the brackets by end plates and three screws.

The driving pinions are secured to the shaft by means of taper pins.

(viii) The box is reassembled in the reverse order.

6-10
(SO 235) Wt.45133-D.8498 1750 6/45 H&S Ltd. Gp. 399

 

DEFLECTION TRANSMITTER AND SPOTTING BOX - AD. PATT. NO. 10726. Plate 9

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