ADMIRALTY, S.W.1.
  Gunnery Branch

ADMIRALTY, S.W.1.
16th September, 1943.

G. 3338/43.

B.R. 901/43. Handbook of the Admiralty Five Control Clock-Marks I and I*, 1943, having been approved by My Lords Commissioners of the Admiralty, is hereby promulgated for information and guidance.

B.R. 901 (formerly C.B. 1886/38). Handbook of the Admiralty Fire Control Clock-Mark I is hereby cancelled and all copies should be disposed of in accordance with the instructions in B.R. 1-Books of Reference and I.D. Catalogue.

By Command of their Lordships,

To Flag Officers and Commanding Officers of all H.M. Ships and Vessels concerned.

(SO 2214) A2

CONTENTS.

LIST OF DIAGRAMS IN THE TEXT.

1. Layout of fire control installation-"Q" and "R" class destroyers.
2. Arrangement of bearings drives.
3. Arrangement of deflection shafting.
4. Arrangement of range shafting.
5. P.I.L. links showing the triangles formed.
6. Special range spotting dials for use with bombardment charges.
7. Reversible motor and relays and time of flight circuits.
8. Deflection factors.
9. Range correction factors.
10. Ballistic correction factors.
11. Time of flight.
12. Fudging of dip curve at low ranges.
13. Upper portion of range to elevation curve.
14. Equivalent full charge range (sub-calibre and reduced charge).
15. Deflection and range correction factors (sub-calibre).
16. Deflection and range correction factors (reduced charge).
17. A.F.C.C. I* Deflection factors (full and reduced charge).
18. A.F.C.C. I* Range correction factors (full and reduced charge).
19. A.F.C.C. I* Time of flight (full and reduced charge).
20. A.F.C.C. I* Fudging of dip curve at low ranges.

PLATES.

1. General diagrammatic arrangement.
2. Top of the clock.
3. Own, enemy and wind elements-speed settings.
4. Own, enemy and wind elements-bearing settings.
5. Speed across slides, deflection link, and gun range shafting.
6. Deflection dial and gun deflection shafting.
7. Drift link and drift relay.
8. Transmitter gearbox.
9. Cross levelling gear.
10. Speed along slides.
11. Range rate clock and clock range shafting.
12. Range correction links and ballistic settings.
13. Range P.I.L. follower and range spotting dials.
14. Range to elevation gear and gun range stop gear.
15. Gun elevation hunter and dip cam.
16. Gun elevation repeat receiver and Radar range matching receiver.
17. Time of flight clock.
18. Timing shafting.
19. P.I.L. gear.
20. Electrical diagram.
21. A.F.C.C. I and A.F.C.C I* wiring diagram arrangement of clock and relay.

(SO 2214) A 3

Admiralty Fire Control Clock Mark I

Frontpiece - To face page 1

PREFACE.

The A.F.C.C. I and I* are identical except that the former is made for the 4.7-inch Marks IX and XII, and is in all of fleet destroyers ("C" class and later except "L" and "M" class) and the latter is made for 4.7-inch Mark XI, and is in "L" and "M" class of destroyers only.

In consequence this Handbook is written for the A.F.C.C. I and the differences in the A.F.C.C. I* noted where they occur. (All gear ratios in the Plates are for A.F.C.C. I only.)

The following points about the contents of this Handbook should be noted:-

Chapter I (General description) is intended to be read by all officers and men who may be required to work the clock.

Chapter II (Reduced charge, sub-calibre and bombardment arrangements) gives the reduced charge and sub-calibre arrangements which vary slightly in different clocks.

Chapters III to VI. These chapters are for the use of officers and maintenance staffs for the initial adjustments and maintenance of the clock.

Chapter VII (Theory). This chapter compares the clock values with the theoretical values, and also gives the mathematics of the P.I.L. mechanism.

The Appendices, Diagrams and Plates are referred to in the text and are listed in the contents.

For all drills and procedures with the clock and associated H.A. and L.A. equipments, see separate Drill Book.

It should be noted that the A.F.C.C. referred to in this Handbook is fitted with cross levelling unit, Radar (including range matching receiver and clock range transmitter) and range correction indicator, and that these were not fitted in the original clocks.

FOOTNOTE.-in conformity with the decision made in 1943 the terms "Line of Sight Training" and "Director Setting" should in future be known as "Director Training" and "Director Elevation." The old terms which were printed on the Plates have been used throughout this book.

(S02214) A4

CHAPTER I.

GENERAL DESCRIPTION.
See also Appendices I and II.

The Fire Control Installation.

1. The installation for which the clock is designed consists of:

(i) The director control tower, containing the control and rate officer, the director sight, and the cross levelling gear. (ii) The transmitting station, containing the A.F.C.C. and F.K.C. (iii) Radar Type 285 and a rangefinder fitted on a rangefinder director or three man rangefinder.

A typical installation is shown in Diagram 1.

The director transmits to the clock the bearing of the target relative to the fore and aft line of own ship-called line-of-sight training (L.S.T.)-and, at the moment of firing, the elevation of the. target relative to the deck plane of the ship-called director setting (D.S.)-corrected for the tilt of the D.C.T. (See Footnote on page 1.)

Uses of the Clock.

2. The clock performs the following operations:-

(i) Calculates the DEFLECTION due to own ship, enemy and wind, and provides a means of adding these and applying deflection spotting correction to give GUN DEFLECTION. (ii) Transmits GUN TRAINING to the guns. Gun training is the sum of line of sight training, gun deflection (deflection plus deflection spotting), drift and cross levelling correction (or for H.A. fire, line of sight training, and total training correction transmitted from the fuze keeping clock). Convergence is corrected for at the training receivers at the guns. (iii) Applies rate of change of range to the range set. (iv) Calculates the range corrections for enemy, wind and ballistics, and provides a means of adding these and applying range spotting correction to give GUN RANGE. (v) Calculates the tangent elevation, plus dip (from the director to the standard level) necessary for this range and adds it to the director setting, giving GUN ELEVATION which is transmitted from the clock to the guns. Dip (from the standard level to the guns), alterations in M.V. due to wear, and tilt are corrected for at the elevation receivers at the guns. (vi) Transmits gun deflection and gun range to the guns for gunlayers and quarters firing. (Gun deflection does not include drift-see (i) above-and this is corrected for at the gunsights.) (vii) Provides means for accurate calculation of P.I.L. correction to datum range and datum bearing. Also for application of range P.I.L. to datum range. (viii) Incorporates a Time-of-Flight unit automatically set for range, and set by hand to the mean M.V. of all guns.

Settings required on the Clock.

3. Of the data required to set the clock, the following are automatically set:-

(i) Ship's head from gyro compass. (ii) L.S.T. from D.C.T. (iii) Director setting from D.C.T. (iv) Cross-levelling from cross-levelling gear in D.C.T.

4. The following are set before opening fire and, unless conditions change abnormally, should not require resetting while firing:-

(i) Barometer. (ii) Therometer. (iii) Type of shell. (iv) Drift constant "A." (v) Wind direction and speed. (vi) Muzzle velocity in as much as it affects time of flight.

5. The following must be kept set:-

(i) Range (by tuning to the Radar range matching receiver or to a range receiver in the T.S.). (ii) Own speed (by setting to the amount shown on the own speed receiver in the T.S.). (iii) Enemy speed. (Passed by telephone by the ratekeeper.) (iv) Inclination. (Passed by telephone by the ratekeeper.)

(i) Datum range (by tuning to datum range signalled and by following on the P.I.L. dials). (ii) Datum deflection (by setting deflection pointer "C" to datum deflection signalled). (iii) Datum distance (passed by telephone by the P.I.L. rangetaker). (iv) Datum angle (by following a pointer controlled from the D.C.T.).

7. The range and deflection spotting handles require constant attention, and the time of firing pushes and fire gong must be operated by hand. The main drive (timing drive) motor and L.S.T. motor are provided with alternative hand drives.

General Arrangements.

8. The shape and general arrangement of the clock are shown in the Photograph facing page 1. Plate 2 shows the top of the clock where most of the dials and counters are situated. Plate 1 is a diagrammatic layout of the clock.

In the following description the "front" of the clock refers to the side on which the range tuning handwheel, the bearing handwheel and the gun training repeat are situated.

The whole of the calculating mechanisms are contained in the upper, or calculating case portion of the clock. The right-hand side of the calculating case portion deals with the own ship, enemy and wind settings and with deflection. The left side deals principally with range and P.I.L. calculations.

Plate 2 shows the arrangement of the dials and handles of the clock, and the following is a general description of the working of the clock without delving into its inside.

The lower or pedestal portion contains, at the left-hand end, the terminal box, while the rest is divided into two storeys, the upper carrying the gun range transmitters, compass control hunter, and the deflection and training gearbox and- transmitters, and the lower storey of the pedestal carrying the main drive motor, gearbox and governor, the training motor and compass control motor with their combined gearbox and, attached to the right-hand end, the cross levelling motor.

Own, Enemy and Wind Settings.

9. All the dials move relative to the line of sight which is represented by a red line running across the clock through the own and enemy dials. (See Diagram 2.)

Own and enemy dials are each surrounded by a gyro compass ring graduated in white. These rings are kept set by the navigational gyro.

10. At the outer edge of own ship's gyro ring is a red training repeat pointer, worked differentially by the normal L.S.T. follow-up motor and by an emergency step-by-step L.S.T. transmitter. (See paragraph 65.)

If the clock is following the D.C.T. correctly this pointer will remain opposite the red line of sight arrow.

On the right of the own ship dial there is a vernier dial. The red pointer corresponds to the red emergency pointer on the own ship dial and should remain central. The outer dial engraved in white and the inner dial engraved in red and green correspond to the gyro and own ship dials respectively.

One revolution of the repeat dial is equivalent to ten degrees on the own ship dial.

11. The enemy dial is set for inclination either by the handle on the front of the clock or the handle at the right-hand end.

On the outer edge of the enemy gyro ring there is a yellow wind pointer which is set to the direction the wind comes from by a handle below the inclination setting handle on the front of the clock.

The pointer is arranged so that once set to the direction of the wind, the own course motor and the L.S.T. motor will keep it set to that direction.

12. Own, enemy and wide speeds are set by means of the butterfly heads on the top of the clock.

13. The effects of applying the six settings, i.e., L.S.T. and own speed, inclination and enemy speed, and wind direction and wind speed are:-

(i) Rate of change of range is set on the range-rate clock, the amount thus set being indicated on the range-rate scale. (ii) The range. corrections for enemy and wind speeds along are set on the range-spotting dial. (iii) The deflections due to enemy and wind are set on the inner of the three pointers (pointer "A") on the deflection dial. (iv) Deflection due to own ship's speed across is supplied in the reverse direction to the outer pointer (pointer "C") of the deflection dial and to the datum deflection transmitter.

14. The following facts should be noted:-

(i) No range correction for own ship's speed along is made. (ii) The deflection applied due to own ship's speed across is the same at all ranges, only changing when own ship's speed across changes. (iii) Pointer "B" on the datum deflection dial, the one which carries the spotting graduations, is normally locked to "A"; if the recentring push is pressed it springs in line with "C." (iv) The deflection and range corrections are worked out for the gun range set on the clock. (v) White graduations are used for -right deflection, right datum angle and right inclination, and yellow-green graduations for starboard relative bearings on own ship dials. These colours are clearer than green for the purposes required.

15. L.S.T. is received in the clock by both synchronous and step-by-step transmission from the D.C.T. The use of the step-by-step is described in paragraph 65. The synchronous besides being used as in paragraph 66, where it passes through the training clutch, has added to its cross levelling correction, gun deflection and drift to become gun training. (See paragraph 86.)

A three-positioned training clutch is fitted on the front of the pedestal near the top. The three positions are:-

(i) Normal.-L.S.T. table and gun training driven by motor controlled from the D.C.T. (ii) Hand.-L.S.T. and table training set by hand. Gun training by motor controlled from the D.C.T. (iii) Auxiliary.-L.S.T. table and gun training driven by hand. Motor switched off. Note.-For further details of the training clutch see paragraph 67.

Gun Deflection.

16. As shown in paragraph 76, enemy and wind settings move pointer "A" (with "B" locked to it) and own settings move pointer "C" in the opposite direction. (See Diagram 3.)

If pointer "C" is now aligned with pointer "B" by means of the deflection handle the total gun deflection will be indicated on the counters on the clock face and will be transmitted to the receivers at the guns. Deflection spotting is further added by moving the deflection handle so that pointer "C" is moved relative to the spotting scale on the battleaxe portion of pointer "B." Subsequently the recentring push is pressed so that "B" is re-aligned with "C's" new position.

Drift.

17. Drift constant "A," which is given in the range tables and also on a small plate on the clock itself, is set on the small dial provided, close to the ballistic correction dials. A correction is then automatically applied to the gun training transmitted to the guns. The amount of drift so applied is shown on a small black dial on the front of the clock, on the right.

The drift relay is worked from the timing drive, and drift will not be applied unless the main drive motor or alternative hand drive is operated.

Cross Levelling.

18. Cross levelling correction is received from the cross levelling sight in the D.C.T. and controls the cross levelling motor in the pedestal. The cross levelling correction applied is shown on the cross levelling dial which is on the right of the pedestal. Cross levelling correction is fed into the L.S.T. drive and appears as part of gun training. The motor is not fitted with alternative hand drive.

19. The cross levelling clutch has three positions:-

(i) Normal.-Cross levelling fed from the D.C.T. is automatically fed into gun training. (ii) Locked.-The cross levelling motor is stopped and no correction passes to the guns. (iii) Hand Setting.-Used for lining-up, or for setting to zero in case of failure.

Gun Training.

20. Gun training is produced as shown in paragraph 86 and is transmitted to the guns by step-by-step transmission. There is a repeat receiver on the front of the clock which shows both gun training as being produced mechanically by the clock and that being transmitted electrically by the clock.

Range.

21. There are three range counters, one clock range counter, on the left in the middle of the top, and two gun range counters on the right at the front and back edges of the top.

The left-hand drum of the clock range counter is coloured red over a portion of its periphery, to facilitate lining-up should the clock range counter have been run beyond the upper or zero graduations. An instruction plate is fitted on the clock as follows:-"IF THE CLOCK RANGE COUNTER SHOWS RED, TUNE UP AND SPOT DOWN TO ALIGN GUN AND CLOCK RANGE COUNTERS."

The rate of change of range clock affects both the clock range and the gun range. Throughout the book this is referred to as a range rate clock.

In front of the left-hand side is the range tuning handle. It is pushed in to engage the clock range drive. The action of pushing it in also disengages the drive from the range-rate clock and shows the tell-tale on the face of the clock to indicate that the rate-of-change of range is not being applied.

The action of tuning affects both clock range and gun range.

22. The clock may be tuned to one of the Radar sets or to the rangefinder, or to an estimated range.

There are counterdrum receivers on a pedestal beside the clock. One of these receivers shows the range from the rangefinder, the other from the Radar warning set.

There is also a range matching receiver Mark V-on which clock range is compared with Radar range from the R.T.U. A frictional pointer enables the clock to be tuned to Radar range from Type 285 corrected for straddle correction.

Each of these receivers is fitted with a cut lamp lit by the Radar operator or the rangetaker when he has a cut.

23. The range spotting handle applies range spotting and range corrections and adds them differentially to clock range to produce gun range. (See Diagram 4.)

24. Range corrections for enemy, wind and ballistics move the dial, and by initially aligning the outside pointer to the zero of the dial by means of the range spotting handle these corrections are applied. There is a small range correction indicator above the range spotting dial which shows which way the outside pointer should be moved if the dial has turned through 180° or more.

Corrections due to enemy and wind are automatically applied by the enemy and wind settings. (There is no range correction for own ship in the A.F.C.C.).

Ballistics are set on two dials at the left end of the clock in front.

One dial is for temperature of the air and is marked in degrees Fahrenheit. The other dial is for the barometer and is marked in either millibars or inches. Both dials have alternative positions for setting the barometer and thermometer readings. These alternative positions are for use when using H.E. or other shell whose percentage B.C. are other than zero. In these cases use the following table:-

Paragraph 24. Delete the table therein and substitute:-

To set a % B.C. for shell of	Set temperature against	Set barometer against
0	Normal	Normal
+1%	Normal	+4%
+2%	Normal	+5%
+3%	+3%	Normal
+4%	+3%	+4%
+5%	+3%	+5%
+6%	+3%	+6%
+7%	+3%	+7%

(G.8291/34.-A.F.O. P.846/45.)
(Previous amendment No. 1, A.F.O. P.236/44.)

is shown on page 1 of the Range Table.

25. The spotting dial has a central pointer and a rim pointer. The rim pointer is moved when corrections are applied by the range spotting handle. The central pointer is frictionally connected to the rim pointer, but if the recentring push is pressed it will fly in line with zero on the dial itself.

If the rim pointer is now brought in line with the zero of the dial and range spotting carried out relative to this zero, then the total of range corrections and range spotting will be added to the clock range set, and the correct gun range will be shown on the gun range counters and will be transmitted to the guns.

Gun Range.

26. Range spotting and range corrections are added differentially to clock range to produce gun range. Gun range is transmitted to the guns for quarters and gunlayers firing and is used in the clock in the calculation of deflection, range correction, dip and time of flight. It is also transmitted to the elevation and training receivers at the guns for dip M.V. and convergence.

Stop gear is fitted in the gun range drive, which operates on the tuning and spotting handles and also throws out the range-rate drive when the range reaches zero or 15,700 yards (19,000 yards in A.F.C.C. I*). This prevents damage to any of the mechanism worked off the gun range.

Director Setting and Tangent Elevation.

27. Director setting is received in the clock by step-by-step transmission from the D.C.T.

Tangent elevation is produced from gun range by a large pin wheel cam in the clock. Tangent elevation is used in calculation of dip, time of flight and drift.

Gun Elevation.

28. Tangent elevation and dip are added to the director setting and the resultant gun elevation is transmitted to a synchronous unit on the bulkhead of the T.S., where it is re-transmitted by step-by-step transmission to the elevation receivers at the guns to the repeat receiver on the bulkhead of the T.S. and to an "M" type motor in the clock to re-centre the hunter. (See paragraph 104.)

The R. to E. unit gives the tangent elevation for an M.V. of 2,542 ft./sec., and the dip cam for a dip height of 16 ft. 4 ins. Full charge range Table No. 255. (See Appendix III.)

29. There is a combined gun elevation, director setting and range repeat receiver fitted on the bulkhead opposite the clock. It consists of a fixed rim graduated in degrees, a double ended pointer and a moving dial graduated with range and the corresponding tangent elevation on a spiral scale.

Director setting and gun elevation are fed in, and from it gun elevation, range and T.E., can be read off.

A small dial below indicates tens of degrees of gun elevation and director setting.

Time of Flight.

30. There are two pairs of time of flight pushes, one pair at the left end of the clock, on top, and the other pair on the back; each pair consists of an "ordinary" and a "selector" push.

NOTE.-It is common practice in most ships to render the "selector" push inoperative and to remove the warning - tripper" from the "ordinary" push. The "ordinary" push is then pressed once, twice or three times for the A, B, or C broadside respectively.

The time of flight clock does not function below 2,000 yards gun range.

The time of flight clock is automatically set for the time of flight corresponding to the gun range set at the moment of firing, and can be adjusted for muzzle velocity if the guns get worn, by setting the mean M.V. of the guns on a small friction dial which is disclosed by removing a cover plate on the front of the clock.

31. Beside the range spotting handle there is a salvo interval watch.

The arrow on the glass dial above this watch is set to the salvo interval (less time-on-aim) desired in rapid salvos. The hand of the watch is returned to zero whenever either of the time of flight pushes is pressed, and starts again at once. The watch is an ordinary service stop watch-Pattern 3.

Main Drive (or Timing Drive).

32. The range rate clock and the time of flight clock and the drift relay are driven by the timing drive from the main drive motor in the pedestal.

The speed governor can be adjusted. The speed of the motor is checked by the usual method of a stop watch rotated counter-clockwise.

A handle for turning the main drive by hand is provided at the right end, close to the watch. The main drive motor works through a free wheel, and does not have to be disconnected before the clock is driven by hand.

The watch-holder is designed to take a stop watch-Pattern 3-but in an emergency, any service stop watch could be fitted in. Care should be taken to see that the ring of the watch is tucked in snugly or it may foul the casing.

A small indicator is provided close to the deflection dial to show whether the timing drive is running.

P.I.L.

33. Datum deflection is set on the "C" pointer of the deflection dial against the datum deflection scale by means of the deflection spotting handle. (See Diagrams 3&5) No.1.

34. Datum range is set on the clock range counter by means of the range tuning handle. Log datum range is applied by following the datum range follower dial. Datum angle is set by keeping the datum angle receiver pointer (from the D.C.T.) in line with the bearing P.I.L. pointer by means of the datum angle follower handle. Log datum distance is set on a scale by the log datum distance handle.

Range P.I.L. correction is shown on the pointer of the range P.I.L. follower dial and is applied to datum range (set on the clock range counter) by aligning the two pointers on the dial, using the range spotting handle. The resultant gun range is shown on the gun range counter and converted to tangent elevation in the R. to E. gear.

A shutter keeps either the range spotting dial or the range P.I.L. follower dial covered, whichever is not in use.

35.- 40.

(SO 2214) B

44. The following "REDUCED CHARGE EQUIVALENT RANGE TABLE" should be engraved by ship's staff on a suitable unattached plate.

TRUE RANGE.	SET CLOCK RANGE.
1,000	1,700
2,000	3,300
3,000	4,750
4,000	6,050
5,000	7,350
6,000	8,500
7,000	9,650
8,000	10,800
9,000	11,900
10,000	12,950
11,000	14,050
12,000	15,150

45. In addition the following are also required:-

All full charge/sub-calibre clutches to be set to full charge.

Rate and Time of Flight.-The clock main drive motor is to be made to run at full speed (about 2,400 r.p.m.) by short circuiting the governor and associated resistances. This is most easily done by connecting together terminals A and F on the main drive motor. By this means the rate generated will be correct. By setting the M.V. dial to 2,500 feet/sec. at the time of flight clock the generated time of flight will be about 10 per cent. early.

Drift.-The relevant drift constant for reduced charge is to be set.

Corrections.-Full charge speed settings are used, and the corrections generated will be about 85 per cent. accurate.

A.F.C.C. I fitted for reduced charge firing sub-calibre.

46. Similar arrangements as described in paragraph 44. A "SUB-CALIBRE EQUIVALENT RANGE TABLE" engraved on a suitable unattached plate is provided with each clock fitted for reduced charge, and reads as follows:-

TRUE RANGE.	SET CLOCK RANGE.
1,000	2,350
1,500	3,650
2,000	4,900
2,500	6,100
3,000	7,200
3,500	8,300
4,000	9,400
4,500	10,500
5,000	11,750
5,500	13,000
6,000	14,500

47. In addition the reduced charge speed settings are to be used giving only approximate range rate, time of flight, deflections and range corrections. Sub-calibre drift constant must be set, and convergence should be set to the mean range of the practice. Also connect together main drive motor terminals A. and F.

A.F.C.C. I fitted for reduced charge firing reduced charge.

48. Similar arrangements as described in paragraph 42. The E.F.C. range approximates to 1.33 times the true range.

TRUE RANGE.	SET CLOCK RANGE.
1,000	1,200
2,000	3,300
3,000	4,750
4,000	6,050
5,000	7,350
6,000	8,500
7,000	9,650
8,000	10,800
9,000	11,900
10,000	12,950
11,000	14,050
12,000	15,150

49. The other adjustments are similar to paragraphs 42 and 43, but a spotting correction of 400 yards will move the fall of shot 300 yards an the words "Reduced charge" must be substituted for "Sub-calibre" throughout. The main drive motor should run at its governed speed.

50. This is exactly similar to paragraph 46, except sub-calibre equivalent range table, which is as follows:-

TRUE RANGE.	SET CLOCK RANGE.
1,000	2,100
1,500	3,450
2,000	4,900
2,500	6,300
3,000	7,750
3,500	9,100
4,000	10,350
4,500	11,550
5,000	12,800
5,500	14,050
6,000	15,350

Connect together main drive motor terminals A and F.

A.F.C.C. I* fitted for reduced charge firing reduced charge.

51. This is exactly similar to paragraph 48, but the E.F.C. range approximates to 1-42 times the true range.

TRUE RANGE.	SET CLOCK RANGE.
1,000	1,700
2,000	3,350
3,000	4,900
4,000	6,400
5,000	7,850
6,000	9,200
7,000	10,500
8,000	11,800
9,000	13,000
10,000	14,200
11,000	15,400
12,000	16,600
13,000	17,900

The main drive motor should run at its governed speed.

Firing special bombardment charges.

52. The bombardment charges in supply at present are as follows:-

(i) 4.7-inch Marks IX, IX*, IX** and XII (A.F.C.C. I): Charge No. 1, MV. 800 f.s., Max. Range 5,200, R.T. 395. Charge No. 2, MV. 960 f.s., Max. Range 6,800, R.T. 394. Charge No. 3, MV. 1,415 f.s., Max. Range 9,900, R.T. 393. (ii) 4.7-inch Mark XI (A.F.C.C. I*): Charge No. 1, MV. 825 f.s., Max. Range 5,400, R.T. 524. Charge No. 2, MV. 1,250 f.s., Max. Range 6,800, R.T. 523.

53. When using bombardment charges, corrections have to be made in the Fire Control System, due to the following being in error:-

(i) Tangent elevation. (ii) Ballistic correction. (iii) Range spotting corrections. (iv) Drift.

No allowance is, however, made for errors in range corrections, target height corrections, deflection, deflection spotting and convergence, as the application of the necessary corrections at the clock would be impracticable under action conditions.

54. In ships with 4.7-inch Marks IX, IX*, IX** and XII guns, (A.F.C.C. I), the following action must be taken:-

With all corrections set for Full Charge.

(i) Tangent Elevation	With the aid of Table 1 the clock is tuned continuously to the equivalent full charge range.
(ii) Ballistic Correction	With the aid of Table 3 apply an initial range correction on the spotting dial. (If the percentage B.C. is plus, the additional correction set must be UP and vice versa.) This correction should be kept up to date for range, if possible.
(iii) Range Spotting Corrections	A special paper dial is positioned over range spotting dial. (See paragraph 57.)
(iv) Drift	With the aid of Table 2 an initial deflection spotting correction is made (always to the right). This correction should be kept up to date for range, if possible.

Note. -All corrections are set on the clock as for full charge.

(SO 2214)B3

(i) Tangent Elevation	With the aid of Table 4 the clock is tuned continuously to the equivalent full charge range.
(ii) Ballistic Correction	With the aid of Table 6 apply an initial range correction on the spotting dial. (If the percentage B.C. is plus, the additional correction set must be UP and vice versa.) This correction should be kept up to date for range, if possible.
(iii) Range Spotting Corrections	A special paper dial is positioned over range spotting dial. (See paragraph 57.)
(iv) Drift	With the aid of Table 5 an initial deflection spotting correction is made (always to the right). This correction should he kept up to date for range, if possible.

Note.-All corrections are set on the clock as for full charge.

56. EXAMPLE:-

4.7-inch Mark IX using bombardment charge No. 2 (R.T. 394). Actual range of target is 5,500 yards. Equivalent full charge range to set on clock is 14,000 yards. If ballistic correction set on the clock is -6 per cent., then range spotting correction for ballistic is DOWN 350 yards. Drift set on clock is 140, and the deflection spotting correction for drift is R.8.

Special Range Spotting Dials for use with Bombardment Charges.

57. These dials are given in Diagram 6 and also at the end of the book and used when firing bombardment charges. This paragraph may be taken as a permissive authority to cut out the dial required from the end of the book but Diagram 6 must not be cut up. They are' to be held in place on top of the range spotting dial and kept so that the zero mark is in line with the zero mark on the proper dial. Spotting is then carried out on the special dial. These dials are only accurate above certain ranges which are shown below. Below these ranges the spotting corrections will be too small, e.g., a correction of DOWN 400 yards will only he applied to the table or clock as one of DOWN 300 yards.

	ACTUAL RANGE
4.7-inch IX, IX*, IX**, XII, B.C. No. 1	Accurate above 2,000 yards.
4.7-inch IX, IX*, IX**, XII, B.C. No. 2	Accurate above 2,600 yards.
4.7-inch IX, IX*, IX**, XII, B.C. No. 3	Accurate above 3,400 yards.
4.7-inch XI, using B.C. No. 1	Accurate above 1,500 yards.
4.7-inch XI, using B.C: No. 2	Accurate above 1,500 yards.

KEEPING TUNED TO EQUIVALENT FULL CHARGE RANGE.

58. A Vickers clock is set to the actual range of the target at open fire, and the equivalent full charge range is tuned on the clock range counter of the A.F.C.C. The rate is read off the A.F.C.C. and set on the Vickers clock.

At "Open Fire" the A.F.C.C. and the Vickers clock are started, and thereafter the Vickers clock operator calls out the actual range every 100 yards: this is converted to equivalent full charge range and the A.F.C.C.- kept tuned to this range. Two additional operators are therefore required, one to work the Vickers clock and the other to read off the E.F.C. range from the table provided and pass it to the range operator at the A.F.C.C.

The rate set on the Vickers clock must be kept up to date continuously.

Procedure when using Bombardment Charges and Smoke Shell.

59. The procedure when using smoke shell is laid down in B.R. 927.

(SO 2214 B4

CHAPTER III.
MECHANICAL DESCRIPTION.
See Plates 3 to 19 and Appendix III.

General.

61. The description of the mechanisms given in this chapter refer to the Plates at the end of the book.

The gear ratios for A.F.C.C. I are shown on the wheels in the Plates, the gear ratios for A.F.C.C. I* are not included but are shown in Admiralty Diagram D.N.O. 4247.

The colouring of the Plates 1 to 19 is similar. Thus a piece of mechanism or shafting that is light green on one Plate remains light green on the other Plates where it is also shown.

To Open and Close the Clock.

62. These are simple operations, but should, nevertheless, not be undertaken unnecessarily.

The top part of the clock is hinged at the rear. To open the clock, remove the two securing screws at the front corners (they screw up from below) and ship the two side links; the longer arm of each link is the upper arm.

These side links can only be shipped and unshipped with the clock closed. When shipping them, it is most important to see that the ends of the links are right home in their sockets before any attempt is made to jack up the top.

When the links are properly in place, jack up the top of the clock by means of the built-in jack in front. This will raise the top far enough to disengage the couplings in the spindles connecting the upper and lower parts, and also to give room to get hold of the top and lift it fully open.

63. Before closing the clock, first see the jack screwed up, the oil tray properly shipped, and no foreign matter in the way of closing or working the clock. Then lower the top on to the jack by hand, and finally lower the jack until the clock is fully closed and replace the two securing screws at the front corners to prevent the clock from opening due to shock.

The shafting and leads between the two parts of the clock are so arranged that the clock is not put out of adjustment by altering the settings or working the hunters while the clock is open. The connecting spindles are fitted with spring clutches so that the top can be lowered straight down on to the pedestal and, as soon as the shafts are worked, they should spring into engagement.

It is advisable, however, before finally closing the clock by means of the jack, to see that all the clutches are in line and, before finally lowering on the jack, see that they engage.

Always line up again after opening up and closing the clock, moving all shafts and handles to ensure that all are working freely.

Bearing. Diagram 2 and Plates 4 and 8.

64. Compass course (orange) is received from the gyro compass and through differential 9 on Plate 8 offsets the compass control hunter (red) which, by synchronous transmission works the compass control motor. This motor produces the power drive of compass course (green) which is added to table training (yellow) in differential 7 to give enemy compass bearing (blue). Enemy compass bearing is used to keep the gyro rings on the own and enemy dials set and is used as shown later in conjunction with inclination and wind direction. Compass course (green) also goes back to differential 9 to meet compass course as originally received (orange). These two are subtracted differentially and so recentre the hunter (red).

65. The own dial (yellow) is set for table training (yellow) by the table training drive from the training clutch. According to the position of this clutch this drive is either from the L.S.T. motor (blue) or from the bearing handle (light blue).

As a check on this table training drive, an emergency pointer (red) is provided, worked differentially by the table training drive (yellow) and by an emergency step-by-step L.S.T. receiver motor giving L.S.T. direct from the D.C.T.

Line of sight training from this emergency motor (pink) is subtracted from table training (yellow) in differential 4 on Plate 4. If the two are equal the pointer (red) will remain motionless on the fixed line of sight engraved on the top of the clock.

To the right of the own ship dial there is the own ship vernier dial with similar gyro ring and pointer. These are so geared to their corresponding parent dials that they indicate ten degrees of bearing in one revolution and enable accurate lining-up, following and reading off.

66. Line of sight training comes to the clock from the D.C.T. via the H.A./L.A. change-over switch on the T.S. bulkhead by means of synchronous transmission. This transmission works the L.S.T. motor which drives the shafting (blue) to the training clutch. When the H.A./L.A. change-over switch is put to H.A., director training is transmitted to the clock from the rangefinder director instead of from the D.C.T.

67. The training clutch has three positions:-

(i) Normal. Clutches "A" and "B" IN. Clutch "C" OUT. The L.S.T. motor, which is being worked by the hunter in the D.C.T., drives shafting (blue) through clutch "A" on to the skew gearing (pink) to (a) produce gun training and (b) recentre the hunter in the D.C.T. The drive also goes through clutch "B" to (a) operate the table

Normal is used when the synchronous transmission is working.

Hand is used for putting the D.C.T. on a bearing, for lining-up, when the target crosses the stern or when all the L.P. circuits fail.

Auxiliary is used when the synchronous circuits fail, and for lining-up.

A spring stop prevents the clutch handle being moved accidentally.

68. The drive from the inclination handle (light green) is added differentially to enemy compass bearing (blue) in differential 3 in Plate 4 to give enemy compass course (green) (read off against gyro ring) or inclination (read off against the fixed outer scale). The inclination will be kept up-to-date by the E.C.B. drive (blue) and only actual alterations in enemy's compass course need be set on by the inclination handle.

An alternative inclination handle is provided at the right-hand end of the clock.

69. In the same way the direction of the wind (purple) is added to enemy compass bearing (blue) in differential 2 in Plate 4, giving the direction of the wind relative to the line of sight (orange). The hand setting need not be changed unless the actual wind direction changes.

Own, Enemy and Wind Speed Settings. Plates 3 and 4.

70. These speed settings (purple) are together with table training (yellow) enemy compass course (green) and the wind direction by gyro (orange) resolved to produce own, enemy and wind speed across and along the line of sight.

Own and enemy speeds along are added to produce range rate (see Plates 10 and 11.)

Enemy and wind speeds along are added and used in the calculation of range correction (see Plates 10 and 12). Own speed across is required in the calculation of gun deflection (see Plates 5 and 6).

Enemy and wind speeds across are required in the calculation of both gun deflection and datum deflection (see Plates 5 and 6).

71. On the own element there is a central spindle (yellow), which carries at the top, a dial, which can be set to the bearing of the enemy by the table training drive (yellow), and, at the bottom a slide.

Working in the slide is a block (red) which can be offset from the centre of the disc an amount proportional to own speed.

On the block is a pin, sticking down through the two links. The "own speed along" link (shown in Plate 10) and, at right angles to it, the "own speed across" link (shown in Plate 5).

By setting own speed the sliding block (red) is offset from the centre by means of a spiral groove in the disc (purple) immediately above it. Normally when bearing is being set, this disc and the disc carrying the slider turn together, being connected through the double pinion (purple) shown on the right.

If the own speed setting handle (purple) is depressed, the lower pinion (purple) disengages from the lower disc, and the spiral groove can be turned relative to the link, so pushing the block out or in.

The own speed thus set is indicated through an aperture in the top dial. When own speed is not being set both discs of the own element (purple and yellow) will be moved together for table training.

72. The enemy element is similar to the own element, and Is shown on the right of Plates 3 and 4. In this case the central spindle (green) is moved by enemy inclination (see paragraph 68), and the slider (red) is offset from the centre for enemy speed by means of a spiral groove in the disc (purple) in exactly the same way as in the own element. When enemy speed is not being set both discs in the enemy element (purple and green) will be moved together for enemy inclination.

73. The wind element is again, in principle, similar to the own and enemy elements and is shown on the right of Plates 3 and 4 below the enemy element but this time the arrangement is different.

Wind speed (purple) is set through differential and moves the disc (light green) with the spiral groove, and so offsets the slider (red) for wind speed. Wind speed shows on a disc (purple) partially covered by a shutter. When wind speed is not being set the shaft (purple) is kept locked by the locking clutch (grey) and so both discs of the wind element (orange and light green) will be moved together for the direction of the wind.

74. The deflection gear is arranged so that either single ship or concentration firings can be carried out without changing clutches or any big change in drill.

75. DATUM DEFLECTION is deflection due to enemy and wind, and deflection spotting.

76. GUN DEFLECTION is datum deflection, plus deflection due to own ship. Enemy and wind deflections are calculated and offset pointers "A" and "B" in Plate 6. Own deflection is calculated and offsets pointer "C" in the reverse direction and also moves the datum deflection transmitter. Thus, pointers "A" and "C" are separated by the deflections due to enemy, wind and own speeds. When brought in line by the deflection handle, gun deflection is applied to the gun deflection counterdrum and transmitters.

Gun Deflection (orange) drives to:-

(i) Two gun deflection counterdrums (Plate 6). (ii) Two gun deflection transmitters (Plate 8). (iii) Differential 6 (Plate 6) to combine with drift to produce gun deflection plus drift. Datum deflection (pink) drives to a datum deflection transmitter (Plate 8).

77. When concentrating as master ship, datum deflection to signal can be read off the datum deflection receiver, whilst gun deflection shows on the gun deflection counterdrum and is transmitted to the guns in the normal manner.

When concentrating as consort, datum deflection received by signal is set on pointer "C" of the deflection dial by the deflection handle. This will apply gun deflection on the counterdrums and transmitters.

78. The amount of deflection required to allow for a certain enemy or wind speed across depends on the range. The number of minutes of deflection per knot of "speed across" at any range (known as the "deflection factor") is shown graphically in Diagram 8; the graph is explained in Chatter VII.

The enemy deflection factor graph has the same slope as that for wind, but its value is greater by a constant amount; thus enemy and wind speeds across can be corrected for range in a common link mechanism and the remainder of the enemy factor which is independent of range can be added uncorrected for range.

On Plate 5, enemy speed across (light green) and wind speed across (yellow) are added by a pinion (pink). The horizontal movement of this pinion angles the lower link (pink) which rotates about its right-hand end. The upper link (orange) is free to move across the line of fire, i.e., parallel to the enemy and wind deflection answer rack (blue). Gun range, led in through a splined shaft (purple), positions the block (red), in the upper slide (orange).

This block (red), is connected by a pin to a sliding block in the lower link (pink). Thus the lateral movement of the upper link (orange) is governed both by the range setting (purple) and by the sum of enemy and wind speeds across (pink).

This motion of the upper link (orange), is added to a proportion of the movement of the enemy speed across rack (light green) by the lattice (blue), the answer, which is deflection due to enemy and wind, being transmitted to pointer "A" on the deflection dial.

(It will be noticed that the lattice links are not equal in length. The movement imparted to the answer rack by either end of the lattice is inversely proportional to the length of the lattice links at that end.)

79. Referring again to Diagram 8, it will be seen that deflection due to own ship does not vary appreciably with range.

On Plate 5 a rack on the own speed across link (light blue) engages a pinion which, through differential 5 on Plate 6 drives pointer "C" (pink). The other side of this differential is worked by the deflection spotting handle (orange).

The deflection dial gear is shown in detail in Plate 6 and diagrammatically in Diagram 3.

80. The action of pointers "A" (blue) and "C" (pink), has been described above. Pointer "B" (light green) is normally locked to pointer "A" (blue), but, for convenience when applying deflection spotting corrections, it will spring into line with pointer "C" (pink), when the recentring push (yellow) is pressed. This is effected by means of the heart-shaped cam (light green) fixed to pointer "B," which is turned by a roller on a spring arm (pink), attached to pointer "C."

When acting as a consort it is convenient for pointer "B" (light green), to be locked to pointer "C" (pink), so that datum deflection is followed on the fixed scale (grey). This is effected by a locking device (red) which keeps the recentring push (yellow) pressed.

Stop gear is provided on the deflection spotting handle at 76 units right and left.

Drift. Plate 7.

81. Drift in minutes is equal to drift constant "A" multiplied by the tangent of tangent elevation in degrees(θ).

The block (red) also engages in the lower slide (green). This lower slide is set by the tangent elevation drive (green), so that the angle between slides is equal to tangent elevation (θ). At zero range the two slides are parallel. As the position of the block in the upper slide is proportional to drift constant "A," its lateral movement (light green) will be proportional to A tan. θ.

This drive (light green) is not powerful enough to help drive the gun training transmitters, so it is stepped up in the drift relay.

82. The drift relay consists of a gear wheel at the base (yellow) driven at constant speed by the timing drive. Two deep pinions (yellow), free to revolve on a common shaft, mesh with opposite sides of the gear wheel at the base and so revolve at a constant speed in opposite directions. There is just space between them for the central pinion (purple) whose lateral movement is controlled by the drift link (light green). This central pinion (purple) is in constant mesh with the long pinion (red).

When the central pinion (purple) of the drift relay is moved over by the drift link, it meshes with one or other of the constant speed pinions (yellow) starts to revolve, and so turns the long pinion (red).

The central pinion (purple) is mounted on a screw thread (light green), and, as soon as it starts to revolve, it screws its way back to a central position.

(In the rod connecting the drift link to the relay there is a spring box (light green). This prevents damage if the teeth of the central pinion (purple) do not mesh exactly when the drift link (light green) moves.)

The number of turns required to bring it back to the centre, idle position, depends on the amount it was displaced, which is proportional to drift. This motion shows on the DRIFT DIAL.(red) and is added to gun deflection (orange) in differential 6 on Plate 6 to produce gun deflection plus drift (green).

Cross Levelling. Plate 9.

83. Cross levelling comes to the Clock from the Cross Levelling Sight in the D.C.T. via the H.A./ L.A. Change-over Switch on the T.S. Bulkhead by means of Synchronous transmission. This transmission works the Cross Levelling Motor on the right of the pedestal. The drive from this motor (yellow) goes to the electro-magnetic brake which prevents the motor over-running, and to the cross levelling clutch.

84. The cross levelling clutch handle (red) moves the collar (light green) up and down the cross levelling shafting (light green). This clutch has three positions:-

(i) Normal. The collar (light green) is UP, making contact with the drive (yellow) from the C.L. motor. In this case the movement of the C.L. drive (yellow) is transmitted to the C.L. dial (light green) and via an adjustable clutch to differential 10 on Plate 8 where it is added to L.S.T. (pink). (ii) Hand. The collar (light green) is CENTRAL and free to revolve. The hand setting knob (blue) can be worked to put the drive (light green) to the zero position as shown by the cross levelling dial (light green). (iii) Locked. The collar (light green) is DOWN, making contact with the fixed portion of the clutch (grey).

Normal is used in L.A. fire when the C.L. gear is working and always in H.A. fire.

Hand is used for lining up and setting to zero in case of failure.

Locked is used in L.A. fire when the C.L. gear has broken down and has been moved by Hand to the zero position. A spring stop prevents the clutch being moved accidentally.

85. In H.A. fire the cross levelling synchronous circuit is utilised to transmit total training correction (T.T.C.) from the F.K.C. to the A.F.C.C. where it is added to L.S.T. to produce gun training. This change is achieved by the H.A./L.A. change-over switch and in H.A., the cross levelling clutch must be to Normal.

Gun Training. Plate 8.

86. Gun Training is produced in the transmitter gear box. If the training clutch is to Normal or Hand L.S.T. (pink) enters the gear box as driven by the L.S.T. motor (blue). If the training clutch is to Auxiliary this L.S.T. (pink) comes from the bearing handle (light blue) through the table training drive (yellow).

L.S.T. (pink) has cross levelling (light green) added to it in differential 10 and the resultant (purple) has gun deflection plus drift (green) added to it in differential 8 and the resultant gun training (red) is transmitted to the guns and to mechanical pointers (red) in the gun training repeat receiver. This receiver also has electrical pointers (blue) driven by a step-by-step receiver motor from the same transmission as is being sent electrically to the guns.

The mechanical pointers (red) on this receiver have a lining up knob which moves the pointer but not the shafting as the drive to the shafting works through a slipping clutch.

87. Own speed along (light blue) and enemy speed along (light green) are added by a lattice work (blue) on Plate 10 and the resultant combined speed along (blue) shows on a range rate scale (grey) on Plate 11. (Range rate and combined speed along are the same thing only the one is expressed in yards per minute and the other in knots, that is both are speeds).

88. This range rate (blue) is connected to the ball cage (blue) of a double ball rate clock (Plate 11).

The first ball (pink) bears on a steel-faced disc (yellow) which is driven from the timing drive at a constant speed of 180 r.p.m.

The resulting movement of integrated rate (pink) imparted to the first ball is transmitted through the second ball to the roller (pink) and thence through the clock range clutch to the clock range drive (light green).

The advantage of the double ball type of rate clock is that own and enemy speed can be set without damage to the disc face, even if the main drive is switched off.

The roller and ball cage are held in a bracket (green) which is pivoted about the outgoing shaft. Springs hold the bracket towards the face of the disc so that the steel balls are always bearing on the disc. The springs and gear are designed for a roller pressure of 15 lb., i.e., a pull of 10 lb. abreast the spring anchorage should just lift the rollers from the disc face.

89. The clock range clutch is fitted in the outgoing clock range drive (light green) for use in sub-calibre and reduced charge. As the speed scales on the own and enemy dials are adjusted to suit the range corrections, and equivalent full charge ranges are used to suit the R to E gear, so the rate clock speed ratio has to be changed to correspond.

The clutch is operated by a rod (purple) from the change charge knob (purple) on top of the clock. The clutch lever is spring-actuated so that the clutch can be disengaged independently of the charge setting by the range tuning handle (red) or by the gun range stop gear (light blue). Both these move the rod (light blue) for centring the clutch.

When the gun range reaches its limits, the stop gear (light blue) centres the clock range clutch (pink) so disconnecting the integrated rate drive (pink).

When the range-tuning handle is pressed in, the integrated rate drive (pink) is disconnected by a push rod (light blue) which centres the clock range clutch, and the range-tuning (red) is connected to the clock range drive (light green). At the same time a tally (red) indicating "Rate stopped" appears. When the range tuning handle is pulled out, the clutch slips back into gear by means of the spring, the. tuning handle is completely disconnected and integrated rate is again applied.

90. Clock range (light green) drives to:-

(i) The clock range counterdrum (Plate 11). (ii) The clock range transmitter (Plate 11) for the Radar range matching receiver. (iii) The datum range follower dial (Plate 19) to be converted into log datum range. (iv) Differential 14 (Plate 14) to be converted into gun range.

The clock range transmitter (light green) on Plate 11 transmits clock range to the Radar range matching receiver (Plate 16). One pair of pointers (light green) are moved for clock range and the other two pointers (red and light blue) are moved for Radar range. The inner Radar pointer (light blue) can be offset from Radar range for the amount of the straddle correction. This is done by a milled knob (light blue) on the outside glass front and a slipping clutch on the Radar pointer drive. A straddle correction scale shows at the opposite end of this pointer.

Range Spotting. Diagram 4 and Plate 13.

91. The range spotting handle (yellow) drives:-

(i) The range spotting drive to differential 14 on Plate 14. (ii) The outer range spotting pointer (yellow), on the range spotting dial. (iii) The inner range spotting pointer (pink) on the range spotting dial. This pointer will fly back in line with zero mark on range spotting dial (light green) when recentring push (blue) is pressed. (iv) The disc and pointer (yellow) of the range P.I.L. follower dial.

92. The range spotting dial (light green) itself is driven by the range correction drive, and the act of bringing the outside pointer (yellow) into line with the zero of the dial (light green) by means of the range spotting handle automatically adds the range correction and range spotting (yellow) to clock range (light green) in differential 14 to give gun range (purple).

To facilitate the application of range spotting corrections the inside pointer is provided. This pointer normally moves round with the outside one, but, if the recentring push provided is depressed, it will spring into line with the zero of the spotting dial.

This is effected by a heart-shaped cam (pink) fixed to the pointer spindle. Bearing against the cam is a spring loaded roller (light green) on a lever pivoted on the spotting dial. When the recentring push (blue) is depressed, the pointer spindle is raised and disconnected from the drive at the bottom. The roller bearing on the heart-shaped cam recentres the pointer. When the push is released, the pointer is pulled down by a spring and again engages the drive from the spotting handwheel.

A slipping clutch is provided in the range spotting handle spindle so that the hand is not unduly jarred when the gun range stop gear comes into operation at the limits of gun range.

93. The range P.I.L. follower dial is used instead of the range spotting dial only when a consort in G.M.S. concentration firing. Range P.I.L. (purple) moves the upper pointer. The lower pointer (yellow) is moved by the range spotting handle, and so range P.I.L. is added to give gun range (see also para. 117). A shutter is provided to cover up the range spotting dial or the P.I.L. follower dial, whichever is not required.

94. Collections due to temperature of cordite or loss of M.V. due to wear of guns are applied at the elevation receivers at the guns.

95. Corrections due to enemy and wind speed along (yellow) are evolved in the upper link gear and corrections due to change in the ballistic coefficient (blue) are evolved in the lower link gear of Plate 12.

The two corrections (yellow and blue) are added in differential 11, and the total correction (light green) moves the range spotting dial and the range correction indicator (Plate 13).

The range spotting operator, by following up the movements of the range spotting dial (light green) with the outside pointer (yellow), adds these range corrections, together with range spotting, to clock range to produce gun range.

The range correction indicator shows which way the dial has moved and is of use if the dial moves through 180° or more.

96. No correction is made for own speed along. This is omitted because, firstly, it would cause complications with datum range and, secondly, its maximum amount is only 105 yards, approximately 10 per cent. of each of the enemy, wind and ballistic maximum amounts.

97. Enemy speed along (light green) and wind speed along (yellow) are added by a lattice (green) on Plate 10, the centre of which moves one end of the lower of two links (green). The other end of this link is a fixed pivot.

The upper link (yellow) is constrained so that it can only move at right angles to the slot cut in it, that is, up and down the range.

In each slide there is a block (red), and the blocks are fixed together by a pin.

The block in the upper link is moved laterally for time of flight (light green) by a screwed spindle, thus the movement of the link (yellow) will depend on the sum of enemy and wind speeds along and on the time of flight.

This movement of the upper link is transmitted through a rack and pinion (yellow) to differential 11.

98. Air temperature (pink) and barometer (light blue) are set on two dials and added in suitable proportions in a differential 12 to produce ballistic correction (orange). The fixed index (grey) on both these dials has several positions which are used when firing shells whose percentage B.C. is not zero. (See para. 24.)

Stop gears are provided which limit the two dials and also a stop gear which limits the total setting. There are also locking nuts on each dial to prevent the settings being moved accidentally.

The total evolved in differential 12 sets a block (red) in the lower link (blue) through a splined shaft and screwed spindle (orange). This lower link is constrained to move at right angles to the slot cut in it, that is, up and down the range.

The upper link (purple) is turned about a fixed pivot by gun range, thus the movement of the lower link (blue) will depend on the ballistic corrections set and on gun range. This movement is transmitted through rack and pinion (blue) to differential 11 where it is added to the enemy and wind correction (yellow) to give the total range correction (light green).

Gun Range. Plates 5 and 14.

99. Gun Range (purple) is produced in differential 14 on Plate 14 by the addition of clock range (light green) and range spotting and range corrections (yellow).

Gun range (purple) drives to:-

(i) Two gun range counterdrums (Plate 5). (ii) The range to elevation gear (Plate 14). (iii) Differential 13 (Plate 14) to combine with tangent elevation to produce time of flight. (iv) Differential 17 (Plate 15) to combine with tangent elevation to produce dip. (v) Two gun range transmitters (Plate 14). (vi) The deflection link (Plate 5). (vii) The ballistic link (Plate 12). (viii) The gun range stop gear (Plate 14).

100. As a lot of the clock mechanisms are set for gun range (as shown above) positive stop gear is essential. The gun range stop gear consists of a nut on a screwed spindle (purple) which forms part of the gun range shafting on Plate 14. This nut reaches the end of its travel at 0 and 15,700 yards range (19,000 yards range on an A.F.C.C. I.*) and operates ratchet stop wheels (light blue) on both the range tuning (see Plate 11) and the range spotting (see Plate 13) handles. This gear also disconnects the integrated rate drive (pink) from the range rate clock by centring the clock range clutch (see Plate 11).

Tangent Elevation. Plate 14.

101. Gun range revolves the pinwheel (purple), the upper side of which is engraved with a range scale for testing purposes. Engaging in spiral of pins on the lower side of this pinwheel is a pinion (pink) fixed to a screwed spindle (pink). As gun range (purple) alters, the pinwheel turns and with it the pinion (pink) engaging in the pins (purple). The screwed spindle (pink) is so arranged that it screws itself along and always remains in mesh. Its rotation, transmitted through a hollow splined shaft (green) is made proportional to tangent elevation.

Tangent elevation (green) drives to:-

(i) Differential 16 (Plate 15) to combine with D.S. to offset the gun elevation hunter. (ii) Differential 13 (Plate 14) to combine with gun range to produce time of flight. (iii) Differential 17 (Plate 15) to combine with gun range to produce dip. (iv) The drift link (Plate 7).

102. Director setting is transmitted from the D.C.T. by step-by-step transmission and received in the clock in a receiver motor. The drive from this motor (light blue) drives through differential 15 to be added to tangent elevation (green) in differential 16 to offset the gun elevation hunter (see also paras. 103 and 104).

Dip. Plate 15.

103. Gun Range (purple) has tangent elevation (green) subtracted from it in differential 17 to produce a function of range (yellow) which revolves the dip cam (yellow). Movement of this dip cam offsets the contact gear of the gun elevation hunter.

If the dip cam were moved for gun range directly it would result in a very steeply cut cam at low ranges and a very flat curve at medium and high ranges. The function of range used instead gives a considerable movement to the dip cam at low ranges and a comparatively small movement at medium and high ranges. Dip is not correctly applied below 1,200 yards as the gear has to be arranged to give the correct elevation at the fixed sight and "Down 800" marks and zero elevation at zero range for lining up purposes.

Gun Elevation. Plates 15 and 16.

104. The gun elevation hunter controls the gun elevation motor in the Mark V synchronous unit on the T.S. bulkhead by synchronous transmission from the clock via the H.A./L.A. change-over switch. The synchronous unit also controls a gun elevation motor in the clock for recentring the hunter. The drive from this motor (light green) recentres the hunter via differentials 15 and 16. The amount of this drive is therefore equal to the total amount of offset, namely, T.E.+D.S.+dip.

Page 27. Insert new paragraph 105A:- 105A. The gun elevation repeat receiver originally designed and fitted as described in paragraph 106, did not show the correct director elevation and gun range in use, when switched to A.A. Control. It has since been authorised to modify the instrument so that it shows only gun elevation, both in A.A. and surface fire. The modification is carried out as follows:- (i) By disconnecting the leads to the director elevation motor. (ii) Removing the gun range pointer by disconnecting the stop gear, thus allowing this pointer to be slipped off the gun elevation pointer. (iii) Suitably covering the director elevation dial, including the director elevation index and the range scale. (G. 08388/48.-A.F.O. P.524/48.) (Previous amendment No. 2-A.F.O. P.846/45.)

One end of the pointer reads gun elevation against the fixed outer scale, and the other end, which slides in and out telescopically, reads gun range on a spiral scale on the director setting dial.

One revolution of the dial represents 20°, and, to read off larger angles than this and to prevent the possibility of lining up a whole turn out, another small scale with a director setting dial and gun elevation pointer is fitted beneath. This reads from 20° depression to 60° elevation.

The fixed outer scale is graduated in 3-minute steps. The director setting dial (light blue), similarly graduated on its perimeter, and with an arrow engraved on it at zero, is revolved by the director setting motor. The arrow reads "director setting" against the fixed outer scale.

The gun elevation pointer, driven by the gun elevation motor independently of the director setting dial, reads gun elevation against the fixed outer scale. As the dial has been revolved through an angle equal to director setting, the gun elevation pointer will read against the perimeter scale of the dial (gun elevation minus director setting). From the composition of gun elevation, the latter reading must be "Tangent elevation plus dip."

The spiral scale on the director setting dial is so graduated that the telescopic pointer reads gun range on it, corresponding to the "Tangent elevation plus dip" being shown by the gun elevation pointer. This gun range should always be the same as that on the gun range counters on the clock.

If these gun ranges are not the same, either the director setting motors in the gun elevation hunter section and combined repeat receiver are out of step with one another or the corresponding gun elevation motors are out of step with one another. The only other possible cause is range to elevation conversion gear being wrongly assembled. It is almost impossible, though, for it to go wrong when it has once been correctly assembled.

It is possible for there to be a fault in the director setting transmission and for the combined repeat receiver still to show the same range as the gun range counter. But this fault should be seen at once in the D.C.T. by the director setting repeat receiver pointers getting out of line.

The gun range pointer has an internal rack which engages with a wheel on the director setting dial, so that movement of the gun elevation pointer on which it slides, relative to the director setting dial, causes the gun range pointer to move in or out and keep on the spiral scale.

Stop gear is fitted to prevent the gun range pointer from running off the gun elevation pointer altogether. This stop gear has the indirect effect of making it necessary to line up director setting dial first if gun elevation pointer is showing elevation and the gun elevation pointer first if it is showing depression.

(SO 2214) c

107. It has been found that if tangent elevation and gun range are added together in the right proportions, the result is approximately proportional to time of flight. This is done in differential 13 in Plate 14, and the resulting time of flight evolved (light green) is transmitted to the time of flight clock (Plate 17) and to the range correction link (Plate 12).

108. The time of flight clock (Plate 17) consists of a pin wheel (yellow) driven at a constant speed by the timing drive. The direction of rotation is indicated by an arrow.

A pin striker (red) is carried on an arm below the pin wheel and its position relative to the hoot trippers (red and blue) (which are fixed) is governed by the time of flight drive (light green).

The push labelled "PUSH WHEN GUNS FIRE" energises the starting magnet (red) (above the pin wheel) which jerks the pin striker up. The striker pushes up a pin (yellow) making its top end project from the upper face of the pin wheel. The pin is held up by the friction of a spring behind it. The displaced pin travels round until it strikes first the warning hoot tripper (blue) and then, at the expiration of time of flight, the pitch hoot tripper (red). These trippers complete the hooter circuit (light blue) and so sound the hooter in the D.C.T.

When the pins have passed both trippers they are replaced by a fixed ramp (grey).

The pin striker (red) is carried on a pivot and is held vertical by springs. so that, if the push is kept pressed, no damage will be done. Also to ensure the striker lighting fairly on a pin, serrations on the lower face of the pin wheel engage a projection on the striker.

To avoid damage to the trippers (red and blue) a safety switch (purple) is fitted, operated by a projection on the time of flight setting wheel, which breaks the magnet circuits at about 2,000 yards gun range.

The operation of the time of flight clock can easily be watched by removing the right rear cover plate of the clock.

109. The salvo selector push energises two magnets, first the selector magnet (red.) which pushes the hammer arm (red) outwards radially, so bringing a wide part of the striker under the pins (yellow) and then the starting magnet (red) which operates as before, but in this case two adjacent pins are pushed up together.

When the two pins (yellow) meet the warning hoot tripper (blue), a long hoot is given followed by two short hoots when they reach the pitch hoot tripper (red).

Adjustment for M.V. can be made by setting a dial (light green) disclosed by removing the right rear cover plate of the clock. (In later clocks a small portable cover is fitted over the adjusting knob and dial.) This adjustment changes the speed of the pin wheel by means of two coned rollers (yellow).

Timing Drive. Plate 18.

110. The constant speed motor runs at a governed speed of 1,800 r.p.m. It drives all the timing shafting (yellow) on Plate 18, and also works the range rate clock (Plate 11), the time of flight clock (Plate 17) and the drift relay (Plate 7).

A "clock stopped" indicator on top of the clock shows whether the timing drive is running or not. There an alternative hand drive if the timing drive motor breaks down. This revolves a stop-watch carrier and stop watch anti-clockwise, and, by keeping the hand of the stop-watch in line with an adjustable hair line on the top glass of the clock, transmits the necessary timing (yellow) to the above-mentioned mechanisms.

To prevent the alternative hand drive having to rotate the constant speed motor in addition to these mechanisms a free wheel is fixed in the shafting from the constant speed motor to the timing drive.

Datum Deflection. Plates 6 and 8.

111. In differential 5 on Plate 6, the gun deflection drive (orange) has the deflection due to own ship (light blue) subtracted from it, and the resultant (pink) moves pointer "C" (pink) on the deflection dial showing datum deflection against the fixed sale on the dial (grey). This resultant drive (pink) also works the datum deflection transmitter on Plate 8, which transmits to a datum deflection receiver above the clock.

Datum Range. Plates 11 and 19.

112. Datum range being tuned on the clock works the clock range shafting and counter drum (light green) on Plate 11. This drive moves a pointer (light green) on the datum range follower dial on Plate 19. The other pointer (red) on this dial is moved by the log datum range follower handle (blue) working through the log datum range conversion gear which converts the log datum range drive (blue) into datum range (red.). The log datum range drive (blue) also operates:-

(i) The left outer sun wheel (blue) of differential (see also para. 115). (ii) The stop gearing, which ensures that datum range set is not less than twice the datum distance and that the log datum range limits are between 1,000 and 16,000 yards.

Bearing P.I.L. Diagram 5 and Plate 19.

113. The bearing P.I.L. correction is calculated by the link (yellow and orange) of the bearing P.I.L. element and is shown by the outer pointer (yellow) against the outer fixed scale of the datum angle follower dial. The geometric solutions performed by this mechanism are given in Appendix V.

The mechanisms are set for datum angle (orange), log datum range (blue) (see para. 112) and log datum distance (green).

(i) The datum angle follower drive also goes through the double differential 19 and bevel gearing to the datum angle follower dial (orange) and the link (orange) of the bearing P.I.L. element, and through differential 20 to the datum angle pointer (light blue).

(ii) To the right inner sun wheel (orange) of differential 19 and so to the inner planet wheel (red). The planet wheels (red) are on the same crosshead, but engage respectively with both inner and both outer sun wheels. In this case the outer planet wheel is held by the outer sun wheels and so the drive passes from the inner planet wheel to the left inner sun wheel (pink), and so rotates the cam plate (pink). Thus both the link (orange) and the cam plate (pink) arc rotated by the datum angle follower handwheel and there is no relative movement between them to disturb the setting of the slider (red) in the cam.

115. Datum distance is passed from the D.C.T. by telephone and set by the log datum distance handwheel (green) on a logarithmic scale (green) on right outer sun wheel of differential 19. This drive (green) operates:-

(i) The right outer sun wheel (green) of differential 19. The outer planet wheel (red) of this differential is driven by both the outer sun wheels, and therefore its resultant movement is proportional to log datum distance minus log datum range. This movement is taken from the inner planet wheel (red) to the left inner sun wheel (pink), the right inner sun wheel (orange) being held; and through bevel gearing rotates the cam plate (pink). The cam on this plate (pink) is of an anti-log form and so positions the slider (red) proportional to (datum distance)/(datum range). (ii) To the sub-calibre or reduced charge log datum distance scale (green) and through differential 18 where since the right sun wheel (orange) is held, the drive moves the left sun wheel (light green) and the cam plate (light green). The cam on this plate is also of anti-log form and so the slider (red) is moved out a distance proportional to datum distance. (iii) To stop gearing, which ensures that the datum distance set is not more than half the datum range and that the log datum distance limits are between 200 and 2,500 yards in full charge and proportionally less in reduced charge or sub-calibre.

116. The positioning of the slider (red) of the bearing P.I.L. element turns the lower link (yellow) through an angle equal to bearing P.I.L.

This drive (yellow) also operates:-

(i) The outer pointer (yellow) of the datum angle follower dial. (ii) Through a 2 to 1 gearing to move the parallel movement mechanism (yellow) through an angle of bearing (P.I.L.)/2

Range P.I.L. Diagram 5 and Plates 13 and 19.

117. The range P.I.L. correction is calculated by the links (yellow and orange) of the range P.I.L. element (Plate 19) and is shown by the pointer (purple) against the fixed outside scale of the range P.I.L. follower dial (Plate 13). The geometric calculations, performed by this mechanism are given in Appendix V.

On Plate 19 the lower link (yellow) of this mechanism is kept set at the angle of 90°-(Bearing P.I.L. / 2) to the rack (purple) by the parallel movement gear (yellow). The upper slider (orange), when set for datum angle plus bearing P.I.L. and for datum distance as described in paras. 114 and 115, moves the rack (purple) a distance proportional to range P.I.L. This drives out on gearing to the upper pointer (purple) of the range P.I.L. follower dial (Plate 13).

The upper pointer on the range P.I.L. follower dial (purple) is therefore moved for range P.I.L. and the lower pointer (yellow) is moved by the range spotting handle (Plate 13) and so when clock range (light green) is tuned to datum range signalled, and the range P.I.L. calculated followed up by the range spotting handle, then gun range will show datum range plus range P.I.L. which is own ship's gun range.

118-120.

(SO 2214)