-H.M.S. Hood Reference Materials-
ADM 186/249: Addendum to Manual for Power Worked Mountings. 15-inch Mountings H.M.S. "HOOD"
Updated 15-Mar-2007

This document is a modern transcription of a portion of Admiralty record ADM 186/249. The original record concerns the 15 inch / 381 cm main gun system used aboard H.M.S. Hood. The original file is held at the The National Archives at Kew, London. This Crown Copyrighted material is reproduced here by kind permission of The National Archives.

Note- This document is not yet complete. We plan to add the remainder as time permits.

Chainbar divider

Manual for Power Worked Mountings.
15-inch MOUNTINGS H.M.S. "HOOD."


Elevation 30°, pneumatic run-out, flash doors, cordite cage, telescopic sights, 30ft. rangefinders, etc etc. 9, 10
Armour, rangefinder hood, turntable rollers, turret buffers, etc. 10 – 12
Compound pumping engine, pump in working chamber ring pipes, walking pipes, squirts and heating pipes 11, 12
Slide, loading arm, cradle, recoil and run-out gears, 20° and 30° stops with values, pipes etc. 12 – 14
Dismantling of gears 15 – 17
Cylinder and valves with depression control gear 17, 18
Engine, worm gear with control and cut off gears 19 – 22
With notes regarding dismantling of same. 23, 24
Rails with runners, grabs, blocks, etc., traversing bogies, revolving bogies, shell doors etc. 24, 25
Cordite hopper, inspection doors etc. 25
Cage with buffers etc., the cordite portion of the cage, cut off gear and working valve. 25 – 27
Hoist interlocks 30, 31
Hoist telegraphs 31, 32
Operating gear 27 – 29
Interlocking gear 32
Operating and interlock gears 33
Interlocks and telegraphs 33
Catch gear in working chamber for G.L. cage. 34
General statement 34
Cage 34
Interlocks – cage, chain rammer, etc. 35
Interlocks – cage and breech 36
Press, compensating gear and intercepting valves 36
Exhaust tank 36
Buffer on floor of working chamber 36
Catch gear on floor of working chamber 34
Control valve 37
Shell stowage in working chamber 37
Shell handling in working chamber 37
Shell supply to working chamber 38
Shell supply to gun house 38
Cordite supply to gun house 38
Shell stowage in gun house 39
Radial crane, hand loading tray, hand rammers, etc. 39
Loading cordite 40
Sub calibre gun 40
Cylinder and intercepting valve 40
Interlocking gear 40
Action of the gear 41
Firing and night sight circuits 45
Percussion firing gear 46
Local fire control 46
Lighting 46
Rangefinder window cleaning gear 47
Lubricators 47
Director firing gear 47
Lifting jacks 47
Cordite drencher 48
Fire service 48

- Page 5 -


Where possible and convenient the plates have been coloured as follows:-

1. Main drive BLUE
2. Details next in importance GREEN
3. Bearings and important small gear separate from 1 and 2 above RED
4. Fixed structure YELLOW
5. Piping; Pressure RED
  Piping: Exhaust BLUE

- Page 6 -


    Vickers Drg. No.
1 General arrangement of mounting, longitudinal section (as drawn for Y mounting) 23649
2 General arrangement of mounting, transverse section (as drawn for Y mounting) 23650
3 General arrangement of mounting. Plan. 23651
4 General arrangement of working chamber. Plan 23651
5 Shell and cordite hoists in central trunk 23413
6 Shell bogie at base of trunk 21083
7 Lead pipes outside revolving structure. Pressure 22289A
8 Lead pipes outside revolving structure. Exhaust 22444A
8A Pumping engines, tanks, and suction pipes: forward, port and starboard 21464A
8B Pumping engines, tanks, and suction pipes: aft port 21479
8C Pumping engines, tanks, and suction pipes: aft starboard 21480
9 Pipes in working chamber, diagram of main pressure and exhaust 24231
10 Carriage and slide 22966
11 Front cradle with clip, etc., perspective view 24443
12 Run-out gear. Diagram 24232
13 Recoil cylinders, with run-out control gear. Diagram. 24521
14 Gear on loading arm 22930
15 Elevating gear. Diagram of pipes and valves 23570
16 Safety depression gear. Diagram 24348
17 Training gear. Diagram of pipes and valves 23591
17A Training gear. General arrangement 20866
18 Training gear. Hydraulic training engine. Section 15974
19 Training gear. Hydraulic training engine. Valve setting diagram 15974
20 Training gear. Arc of training cut off gear. Arrangement 22281
21 Training gear. Arc of training cut off gear. Diagram 24233
22 Hand securing bolts for turntable. Diagram 24439
23 Central ammunition hoist cage 22630
24 Central ammunition hoist cage. Diagram of gear locking shell cage to cordite cage. 24349
25 Central ammunition hoist cage. Shell door and tell-tale gear at bottom of trunk. 24383
26 Cordite hopper on trunk 23333
27 Cordite hopper and central hoist cage. Diagram of interlocks etc. 23485
28 Cordite hopper and central hoist cage. Diagram of interlocks etc. 23485
29 Cordite hopper and central hoist cage. Diagram of interlocks etc. 23485
30 Central ammunition hoist. Cordite cage locking bolt, etc. 24441
31 Central ammunition hoist. Inspection doors and interlocking gear in handling room. 23397
32 Shell waiting tray in working chamber 24407
33 Shell waiting tray in working chamber. Diagrammatic arrangement 24517
34 Shell waiting tray in working chamber. Diagrammatic arrangement 24518
35 Control standard, levers etc., for central hoist 18975
36 Rammers in working chamber. Diagram of interlocking gear. 24417
37 Central hoist and shell carrier in working chamber. Diagram of interlocking gear. 24444
38 Gun loading hoist and central hoist levers. Diagram of interlocking gear. 24501
39 Gun loading hoist. Diagram of catch gear in working chamber. 24537
40 Central hoist cage “up” and “not up”. Diagram of interlocking gear. 24533
41 Central hoist cage “up and “not up.” Interlocks and tell-tales in shell and handling rooms. 24554
42 Central hoist cage “up” and “not up”. Diagram of tell-tales, etc. Shell and handling rooms to working chamber. 24541
43 Gun loading hoist. General arrangements. Side and end views. 20849
44 Gun loading hoist. General arrangements. Plan view. 23320
45 Gun loading hoist. Cage. Front view and plan. 22471
46 Gun loading hoist. Cage. Back and 2 end views 22471
47 Gun loading hoist. Cage. Diagram of gear for cordite trays. 24505
48 Gun loading hoist. Diagram of cut off and compensating gear, also interlock with breech 24308
49 Gun loading hoist. Cage, rammer and cordite trays. Diagram of interlocks 24538
50 Gun loading hoist. Flash door. General arrangement 22751
51 Gun loading hoist. Flash door. Diagram of operating gear. 23742
52 20° stop and gear. General arrangement 20861
53 20° stop and gear. Diagrammatic arrangement 24345
54 Valve standard. Gun loading hoist and secondary shell hoist. 19694
55 Secondary shell hoist. Working chamber to gun house. General arrangement 23370
56 Secondary shell hoist. Working chamber to gun house. Arrangement of guide ropes. 23581
57 Auxiliary cordite hoist. General arrangement 22276
58 Auxiliary cordite hoist. Arrangement of gear at bottom of hoist 23238
59 Auxiliary cordite hoist. Diagram of the different positions the gear can take 24437
60 Breech operating gear. General arrangement (see also 65) 18395
61 Breech operating gear. (Also for air blast) Arrangement of sliding cylinder 24385
62 Breech operating gear. Diagram of operating gear 24346
63 Air blast gear. General arrangement 23541
64 Air blast gear. Diagram of piping 23621
65 Air blast gear. (Also for breech mechanism). Arrangement of piping etc., on gun and slide. 17590
66 Air blast gear. Diagram of piping etc., on gun and slide. 23542
67 Chain rammer intercepting valve. Diagram showing action 19006
68 Voice pipes. General arrangement 23178
69 Voice pipes. Diagram 23179
70 Firing and night sight circuits 21570
71 Open director sight. General arrangement 22454
72 Rangefinder window gear 23076
73 Lubricators in gun house and turntable. Diagram 24607
74 Lubricators in working chamber. Diagram 24608
75 Lubricators in truck etc. Diagram 24609
76 Revolving hood over conning tower. Diagram of training and control gear 23569
77 Aloft director tower. General arrangement 7017D
78 Aloft director tower. Section through variable speed gear. 17497

- Page 9 -

These mountings, known as "Mark II," are arranged generally on the same lines as those of "Mark I" for the "Queen Elizabeth" and "Royal Sovereign" classes, but they have certain new and distinguishing featured which may be enumerated as follows:-

1. The Maximum Elevation of the guns is 30 degrees, the gear being the same in principle as before with the elevating cylinder lengthened to suit, Further , the trunnion bearings for the elevating cylinder and the plate structures supporting these bearings have been greatly stiffened up. There is a hydraulically operated stop which prevents elevation beyond 20 degrees when the breech is open, and an intercepting valve to prevent the gun loading hoist cage being raised until the breech is fully open.

2. The "Run-Out" Gear is Pneumatic and the air pressure, 1,000 lbs. per square inch, is provided by means of suitable connections to the air blast system of the turret. "Run-Out" Control is by means of valves fitted into the pistons of the recoil buffers, and separate self-contained buffers for the end of the run-out stroke. "Run-in" can be obtained by reducing the pressure in the "Run-Out" cylinder and elevating the gun; under these conditions the gun runs in by gravity.

3. A "Flash Door" in the gun loading hoist well completely separates the gun house from the working chamber. The door is operated hydraulically in conjunction with the hoist and is arranged so that it must be fully open before the cage is raised or lowered and that it will close again after the cage has passed.

4. In the Handling Room a Cordite Hopper is fitted to the Trunk and the hopper is provided with buckets so arranged that when loaded they can be rotated immediately to a flash proof position. The buckets can only be completely rotated to discharge the cordite into the central cage when the cage itself is right down.

5. The Cordite Cage is also provided with rotating flash proof buckets and when the cage comes to the bottom of the hoist of the bucket are brought automatically to the receiving position. When the cage has been loaded the hand telegraph gear is put to "Cage Ready" and the buckets rotate to the Flash Proof Position. The cage ascends with the buckets flash proof and at the top of the hoist they automatically discharge the cordite into the waiting trays in the working chamber.

6. The bearings for the worm shaft of the training gear are fitted with forced lubrication.

7. The Pump in the Working Chamber is provided with electric drive only; hand gear is not fitted.

8. Telescope Sights are provided:

(a). In the centre position they are carried on a bracket and operated by a connecting rod secured to the trunnion arm, and
(b). In the side position they are carried in the trunnion pins and operated by a bracket bolted to the trunnion arm.

9. Anti-Surging Stops, adjustable to suit varying lengths of shell, are fitted to the hoist cages, bogies, and waiting trays.

10. In the case of the Auxiliary Shell Hoist, working chamber to gun house, there is fitted in the bottom of the gun well a hinged flash proof door, normally padlocked, which must be raised and secured in the open position when the hoist is in use. The traversing gear of the radial crane in the gun house is provided with a winch handle and a chain drive.

11. The Screened-in Officers' Position in gun house is constructed, as in the "Royal Sovereign" Class, of 120 lbs. armour and is provided, in addition to the usual gears, with a training handwheel and control valve for use in conjunction with the open director sight. The Rangefinder is a 30 ft. instrument.

12. The Revolving Shell Bogie in the shell room is entirely supported on the trunk, the weight being taken on a roller race machined on a cast steel ring which is bolted to the trunk.

PLATES 1, 2, 3, 4, 5, AND 6.

Plates 1, 2, 3 and 4 show the general arrangement of the mounting in side and end elevations and in plan. Plate 5 shows the hoists in the central trunk and plate 6 the revolving bogie in shell room. The principal new features of the mounting are enumerated above. Leading dimensions are given on the plates.

- Page 10 -

The approximate total Revolving Weight is 860 tons, and the approximate position of its centre of gravity is 5.7 inches forward of the centre of rotation and 45 inches below the centre of gun.

PLATES 1, 2, AND 3.

The Wall Armour of the shield consists of 6 K.C. plates, the centre front being 600 lb. (15"), the side front 480 (12"), and the rear plates 440 lb. (11").

The centre front plate is stepped into a heavy glacis plate of 680 lb. armour. This glacis plate is of K.C. quality but without carbonising or final hardening, and is provided on its lower surface with keys which engage in grooves in the floor plate of the shield.

The Roof is of three K.N.C. 200 lb. plates.

The Floor is of 120 lb. high tensile steel plate and where it overhangs the barbette wall it is protected underneath by an 80 lb. K.N.C. plate.

The officers' cabinet is of 120 lb. K.N.C. Plates, and the shield support in front of it is a 120 lb. high tensile steel plate structure.

The Rangefinder Hood is of cast steel armour quality.

Sight ports are cut in the front and the front side plates to suit the telescopic sights provided.


The turret revolves on 48 Double Flanged Rollers, 15" long between the flanges and 8k" diameter in the middle of their length.

To enable rollers to be withdrawn for examination and replaced, 8 removable sections are fitted in the lower roller path. These sections can be withdrawn into the working chamber through spaces cut in the plate work of the revolving structure.

To remove the roller the following procedure should be adopted

1. Train the turret until one of the removable sections of the lower rollerpath is opposite one of the withdrawing holes in the revolving structure and midway between two rollers.

2. Unbolt the section, withdraw it into the working chamber, and pack gap loosely with timber to flanges of rollers.

3. Train the turret until the axle to be removed is opposite a withdrawing hole in the ring plating.

4. Withdraw the axle into the working chamber.

5. Train the turret until the roller to be removed is over the gap in the lower roller path, and lower the roller.

6. Remove section, of outer roller ring and withdraw roller into the danger space.

- Page 11 -

PLATES 8A, 8B, AND 8c.

The Hydraulic Pumping Engines are of similar type to those fitted in the "King Edward VII,, class and onward. Four pumps are provided, two being placed forward, port and starboard, and two aft.


The diagrams show the positions of the Pumps and Tanks with the leads for the pressure and exhaust pipes, and positions of all stop valves. There is a ring pipe forward supplying pressure to A and B turrets, and a ring pipe aft for supplying pressure to X and Y turrets, these two rings being connected by a pipe led along the port side of the ship. The forward and aft pumps connect to the opposite sides of their respective rings. The pressure supply to each turret is In Duplicate, the arrangement of stop valves being such that pressure can be led to supply pipe for any turret, from any one of the pumps, if it should be necessary to shut off the others.

Main and duplicate pressure supply is led from the forward and aft rings to the respective shell rooms.

The forward and aft tanks are connected by the main exhaust pipe on the starboard side of the ship, branches from this main leading to the main and duplicate exhaust connections for each turret. The two forward tanks are at a lower level than the two aft, and each tank is fitted with an adjustable spring loaded non-return valve. These non-return valves cannot be used as stop valves.

A locked salt water cock is fitted on each tank.


The Main Walking Pipes are shown on Plate 1, the exhaust tank on Plate 2, arid the pipes in the working chamber, diagrammatically on Plate 9.


A pump is fitted in the working chamber for supplying pressure to the various machines in the turntable, for adjustment of gear, etc. It delivers into the pressure ring and is intended to be used for working one~machine only at a time, so that the stop valve for other machines should be closed. The pump is driven by an electric motor.


To absorb the shock, when the turret reaches its maximum angle of training, Buffers of the ordinary type are provided. They are secured to the underside of the floor of the working chamber, and take against stops on the fixed structure. Pressure is led to them from the ring in the working chamber.


Water Squirts are fitted on the loading arm, and the operating handle is conveniently placed for use by 'the ramming number. Against the rammer head Two Nozzles are fitted, one directed into the chamber of the gun and the other on to the mushroom head. A Third Nozzle is fitted on the loading arm, directly beneath the breech end of the gun, and is directed on to the underside of the mushroom head. Pressure for these nozzles is taken from the supply to the chain rammer control valve.


A double ring of piping is led round the outside of the working chamber. The piping is formed into loops so as to give extra heating surface, the loops being formed between the two rings.

- Page 12 -

PLATES 10, 11, 12, 13, 14, 52, AND 53.

The Slide is built up of solid forged beams, connected by front and rear transoms, and fitted with trunnion arms which are braced together at their upper ends by a strong cap.

The Loading Arm is also a solid forging and it is secured by bolts to the rear transom of the slide in the usual manner. Two securing positions are provided for the slide, namely at 1° and 5° elevation. The hand lever and securing bolts for these positions are carried on the slide, the sockets for the bolts being arranged in the fixed lateral guides on the turntable structure.

Pressure is taken to a junction box on the slide by means of a double walking pipe, which also takes the exhaust away. From this junction box, pipes lead along the slide to the breech and rammer gear, the water squirts, the gun loading hoist cage buffer, and the interlocks, etc.

As the stop valves for these machines must be opened from under the slide, an Order has been laid down in the Gunnery Drill Book respecting them, as follows

The order ' Free the Slides ' is never to be given ' unless the gun wells are clear,' and no man is ever to 'go into the wells with the slides unlocked.'

Constant pressure Buffers are fitted in the gun well to bring the slide gently to rest on the 300 stops.

- Page 13 -


The gun rests in two Cradles. The front cradle engages with forward collars of gun but is not secured to it by keys. It only serves to provide the necessary sliding surface for carrying the weight of the recoiling parts. Plate 11 shows a perspective view of the arrangement of the forward cradle A, trunnion cap B, and splinter protection Plates C, D, and E.

The upward lift of the gun, on recoil, is taken by lugs F1 formed on the saddle piece F, fitted over the forward collars on the gun, which engage suitable sliding surfaces B1 at each side of the cap B.

Surfaces B1 are adjusted by means of sheet brass packings G inserted between the top of the trunnion arm H and the flange of the cap. There are two of these packing plates on each trunnion arm and the clearance between the cap and the saddle clip at surface B should not be less than .025 in or more than .040 inch. To remove the cap for adjustment of liners. G or for other reasons, it is first necessary to take off the top splinter protection plate C. The cap securing screws are then removed and the cap is forced up by means of 'the two starting screws J and then lifted clear by means of eye bolts, for which two 1.5" tapped holes are provided in the top of the cap.

The Rear Cradle is keyed and strapped to the gun, and is fitted with Clips which engage the top flange of the gun slide. It is provided with a bracket engaging the run-out ram which is placed underneath, and it carries, at the sides, the two recoil cylinders. Each Recoil Cylinder is fitted with a piston, the rod for which is coupled to an extension rod passing through the trunnion arm and secured at its forward end by a nut. The port in the piston is controlled by a valve key of varying depth,. in the usual manner.

A Compensating Rod, separate from the piston and its rod, is placed eccentric in the cylinder so as to clear the large end of the gun, and in consequence it has been necessary to secure the rear cover for this cylinder by means of bolts. These are of bronze 1.5" in diameter and 12 in number, and with regard to their strength it should be noted.

"If cylinders with rods in position have to be tested to 6,000 lbs. Per sq. in.,. these bronze screws must not be used, specially treated nickel steel screws. being provided for 6,000 lbs. tests only."

A Leakage Pump and tank of the usual type are provided for keeping the cylinder full of liquid. This pump delivers into the cylinders through the compensating rod~ at the rear end of the cylinders. An instruction plate on the leakage pump gives the necessary directions for filling.

The rear end of the compensating rod is carried in a bracket bolted to the slide and packed up with thin brass liners to allow of adjustment for wear of the slide surface.

- Page 14 -


In addition to the limit stops and buffers at 300 elevation there are fitted, under the slide, Movable Stops to prevent elevation beyond 200 with the breech open. These stops are actuated by a Hydraulic Cylinder so connected up to the breech valve that at the first portion of the movement of the breech operating lever to "open breech," the stops are put to the "Engage" position, and at the last portion of the movement of the lever in closing," the stops are moved into a position which allows of the maximum elevation of the gun.

Plate 53 shows breech lever A moved toward breech "Open " sufficient to cause valve B in breech valve B1 to uncover special port B2 which admits pressure to the stop actuating cylinder D and thus puts the stops E to the "Engage" position.

Movement of the stops E withdraws interlocking bolt F which allows of breech lever being now put over to breech "open."

When nearing 20° elevation with breech open, cam G engages with and moves Throttle Valve C, gradually restricting the exhaust passage from the elevating cylinder, thereby checking the momentum of the gun before the 'movable stops E come into contact with the structure of the turntable.

To Close Breech, the lever A can be put right over in the quadrant without interruption; the movement to the position shown-on the plate is sufficient to close the breech and the final movement puts port B2 in valve B1 to exhaust. The Stops E are then withdrawn by the action of the constant pressure in cylinder D.

To prevent breech being opened with gun beyond 20° elevation a Rubbing Piece J is provided to retain stops E in the disengaged position, and the lever A is locked at "closed" by means of the bolt F.

The gear described above serves for the operation of the stops in relation to the breech in "Power." There is provided, in addition, gear so arranged that the stops are also operative when the breech is in "Hand."

If the breech is in hand gear the breech lever must be put to "close" before gun can be elevated above 20°. If pressure is oft the breech control valve the 20° stop is inoperative.


The Pneumatic Run-Out Cylinder, initially charged to 1,000 lbs. Per square inch, is placed below the gun and secured to the slide structure. The run-out ram is hollow, and is secured at about the middle of its length to the rear cradle, the front end being supported in a guide ring which is fitted into what was originally the run-in cylinder. This cylinder is now open to 'the atmosphere.

The Gland of the pneumatic run-out cylinder is provided with a Liquid Seal comprising 2 leathers and fluid under pressure from an Intensifier.

The forward end of the Intensifier is filled with thick black cylinder oil and mineral oil in equal parts, and the other end is connected to the pneumatic run-out cylinder.

An Indicator is fitted to show when the intensifier is full or empty, and replenishing of the intensifier is performed by means of a hand pump provided for the purpose.

The items described above are all clearly shown on plate No. 12.

The Valve for Controlling the Speed of Run-Out consists of a rectangular plunger D (see Plate 13), attached to a control piston E working in a cylinder formed in the recoil piston.

With the gun in firing position and also during recoil, the Plunger is retained Clear of the Valve Key, but when run out commences the pressure at the rear side of the recoil piston acts on the end of piston E and forces the plunger into the valve key aperture, thereby restricting the flow of liquid past the piston and controlling the speed of running out by forcing the liquid through an opening in the rectangular plunger D.

Two Buffers, one on each trunnion arm, bring the gun gently to rest at the end of the run-out stroke. (Plates 1, 3 and 10).

For use when it is required to "Run In," an air release stop valve is provided (Plate 12), and when the pressure is sufficiently reduced the gun may be run in by gravity by putting it to elevation.

- Page 15 -



In offering this Strap to Place see that the end marked “Front” is towards the muzzle of the gun, as otherwise the draft for its keys will be in the wrong direction.

The strap should be slung from its centre eyebolt and canted by means of a small pair of pulley blocks fixed between the eyebolt provided on the bottom surface of the side recess and the hook from which the strap is slung) until the opposite side of the strap can be entered into the pocket provided on the cradle. This side should then be drawn toward the centre of the cradle and also upwards until the key seatings of the strap and the cradle are adjacent. Then, by means of the small blocks, lower the opposite sides of the strap until it falls into its pocket in the cradle. Then lower the strap and drive in the keys.

In dismantling reverse the above operations, first removing the oil boxes from the cradle.


To dismantle the Trunnion Arms, unscrew the nuts, drive back the bolts, and, by means of the starting screws, force off the arms.


To Remove the Trunnion Arm Cap over Gun, take off the top splinter protection plate and then take out the cap securing screws. Force up the cap by means of the starting screws and lift clear by means of eyebolt for which tapped holes are provided.

When Replacing this Cap see that the end to suit the splinter protection plate is towards the front.


Care should be taken when assembling mounting to see that the Thrust Collars on both front cradle front and saddle clip are Towards the Muzzle.


To Dismantle the Sliding Cylinder: Disconnect the pipes at each end, then remove the supporting brackets at either end of the sliding pipes, and take out the five screws securing the cylinder to the cradle.


To Disconnect Recoil Pistons and Valve Keys: With cradle full fun out unbolt the supports at the ends of the compensating rods and remove rods and brackets. Remove the nuts, at the front ends of the trunnion arms, on the recoil extension rods, then force the cradle back for a distance of about two feet, remove the dowel screws from the nuts connecting the piston rods to the extension rods, and unscrew the nuts; remove the cylinder covers, forcing them off by means of the starting screws, then take out the pistons and valve keys.

When Replacing the recoil pistons and rods care should be taken not to place too many packing plates under the rear supports, and also, that when completing the assembly of the piston rod and the extension rod, the nuts on the latter are so screwed up and set as to still allow the extension rod to “float” in the trunnion arm.


To Remove the Cradle from the Slide: Remove the compensating rods and rear supports for same as described above ; withdraw the cradle clips (this operation is described in the next paragraph), force back as previously described to disconnect the recoil piston rod, take off the cap from thrust collar under cradle, turn thrust collar round and remove it. Disconnect the sliding cylinder as before described and then lift off the cradle from off the slide.

- Page 16 -


Outer side.

(1). Take out set screws securing clip to cradle.

(2). Remove connection for air blast on sliding cylinder.

(3). Disconnect filling pipe on tail rod of recoil cylinder and fourway connection to same.

(4). Remove quadrant for breech operating lever.

(5) Remove support bracket at rear of slide for tail rod of recoil cylinder. To remove nut securing tail rod to this bracket and support bracket itself it will be necessary to run the gun in a few inches.

Whilst the gun is run in clip can be started from the front end by means of a jack, or from the rear end by means of a strong back. To withdraw clip fully it will be necessary to run gun right out to its stops, there being only 1” clearance between the rear end of the clip and the end of slide when cradle is run out and clip is just entering cradle.

To replace clip gun must be run out.

To replace support bracket (5 above) and nut for same, gun must be partly run in,

Note: - If recoil cylinders are being opened out at the same time as above it would not be necessary to run gun in, for after withdrawing recoil cylinder cover, rear support should be slewed towards side girder until there is sufficient clearance to remove support bracket (5) from tail rod, provided always that clip can be started by means of a strongback on rear end of clip.

Inner side.

It is not necessary to run gun in as rear support bracket (5) can be easily removed provided that clip can be started at rear end by means of a strongbavk.


To Remove the Run-Out Ram:- Disconnect the cap and thrust collar on ram under cradle, then take off the bonnet from the end of the run-out cylinder, and slide the ram out.

To assemble reverse the operation.


To Remove the Run-Out Cylinder: Remove ram as above described, then take away the air connection pipe under the cylinder, remove the securing bolts from the feet, slide the cylinder forward so that it may be turned part way over to enable the feet to be passed through the top or bottom of the slide.

To assemble reverse the operations.


To Remove the Run-Out Ram Guide:- Remove the ram as above described, force the cradle back to the extreme recoil position, remove the screws from flange of guide and withdraw it.

To assemble reverse the operations.

- Page 17 -


To Remove the Run-Out Ram Guide Bush:- Withdraw the ram as above described, push the cradle back and take out the grub screws securing bush, unscrew and withdraw bush.

To assemble reverse the operations.


To Remove the Hinged Loading Trays:- Take out the three screws securing the gun metal bush in the supporting bracket, withdraw the bush, release the tension in the spring, take out the two spilt pins, and then draw out the shaft by means of the tapped hole in its end.


To Take out the Rammer Chain: - Remove the three covers from the rammer bracket and the chain will run right out.

To Replace the chain with all the covers in place except those on the rammer bracket:-

Thread wire rope through the casings and attach with small eyebolt to the tapped hole in the end of the chain, thread the latter over the sprocket wheel, replace the bracket covers and pull the chain through the casings by means of the wire rope and pulley blocks, the chain being supported in a horizontal line until the rammer head is right back.


To Take out the Crosshead Pin: Run the rammer out about four feet, take off the outer cover of chain casing and one back segment of casing, remove the securing plate of the crosshead pin and then withdraw by means of the tapped hole in the end of the pin.




The Elevating gear provides for a maximum Speed of elevating and depressing of 5° per second. The Limits of elevating are 5° depression and 30° elevation.

The elevating Cylinder is mounted on strengthened trunnion Bearings in the gun well and fitted with piston and rod, the crosshead for which is coupled direct to the slide by means of pins through each beam. No tail rod is provided for the cylinder.

The procedure in dismantling the fittings of the elevating cylinder is described on drawing No. 21074, being page 21 in Volume 1 of the book of drawings supplied for use of ships’ officers. This drawing also indicates the special apparatus for the purpose and the method of application.

The lead of Pipes from the elevating valves to the cylinder is clearly shown on the plates. Pressure is led into the gun house from the Main Ring in the working chamber by pipes 7 to the two servo-motor Control Valves A, in the central and side positions, through stop valves N and Q as shown; the stop valve to the control valve which is not in use being closed, the other being open. Pipe 6 takes pressure to the depression control valve.

If the side position is in use the action of the gear is as follows:-

On the elevating valve being moved, say, to elevate, pressure passes from the elevating valve by way of pipe 2 to the depression control valve which, being inoperative, allows it to pass on by way of pipe 4 to the trunnion connection for the elevating end of the cylinder. At the same time exhaust passes from the cylinder by way of pipe 3 through the depression control valve, to the elevating throttle valve C, and on by way of pipe 1 to the servo-motor elevating valve and thus to exhaust.


- Page 18 -

A Non-Return Valve is fitted in the pressure pipe 7 where it branches to the two elevating control valves, and there is a Non-Return valve in the exhaust pipe 5 connecting the control valves to the exhaust main. The use of these valves is to prevent the gun running down should the pressure suddenly fail.


This gear automatically operates to Prevent the Guns being Fired in Depression at angles which are dangerous to the ship’s structure when the guns are trained into a “danger zone.” It also operates to Throttle the pressure and exhaust connections to the elevating cylinder for reducing speed as the slide come on the 30° Stops. In addition, constant Pressure buffers are fitted on these stops to prevent shock.

The gear comprises roller H carried on the slide so as to engage towards the ends of its movements in elevation and depression, with bell crank levers F and G respectively. The levers F and G are pivoted on the turntable, lever F being connected by a link to the upper end of the safety depression valve B. Lever G is connected by means of a link and the floating lever E to the lower side of valve B, thus ensuring that the normal and most frequent movements of the valve are communicated as Thrust. This Removes the possibility of the valve bridle being strained and it is with the same object in view that the constant pressure to the valve is led from the system on the Remote side of the non-return valve.

The forward end of floating lever E is provided with a roller, and bears on the upper end of a guided bar K which is provided with a roller at its lower end to roll on a cam J, carried on the roller path supporting structure. The pipe connections between the control valve A, the safety depression valve B, and the elevating cylinder are made as shown.

A throttle valve C is interposed in the pipe system as shown, and is actuated to check the speed of elevating, by throttling the exhaust, when the gun is nearing 20° of elevation with the breech open. The valve is worked in conjunction with the 20° stop gear shown on plates Nos. 52 and 53.

The action of the gear is as follows:-

1. Assuming the Gun Being Depressed while the turret is trained Off the “danger zone.”

The roller H on slide, bearing against lever G will cause floating lever E to pivot about the end riding on the guided bar K which rides on the circular cam rail J, and so lifts the depression valve B. Pressure which had till then been passing by way of pipes 1 and 3 to the depression end of the elevating cylinder, and exhaust which had been returning from the elevating end of the cylinder by way of pipes 4 and 2, will thus be Cut off and gun will be brought to rest at maximum depression.

2. Now suppose the turret to be Trained.

As the turret enters the danger zone, and thus depression becomes dangerous, the bar K will be lifted by the circular cam J, causing the floating lever to pivot round the end connected to lever G and lift the depression valve thereby putting depression end of elevating cylinder to Exhaust through pipes 3 and 5 and at the same time will then be elevated until depression ceases to be dangerous. When this stage is reached the bar K will be lowered and the depression valve will follow under the influence of constant pressure. Elevating will Cease and as the turret is trained clear of the danger zone, the valve will be lowered completely, depression will take place, and in due course the gun will be brought up at Maximum Depression by the normal operation of roller H and lever C.

The gear operates to Cut off in about the last 2 ½ ° of elevation or depression, with the turret trained on a safe bearing.

The ports in the safety depression valve are cut so that pressure and exhaust are never quite closed. This allows the gun to be elevated after the gear has acted

- Page 19 -


Plates Nos 17, 17A, 18, 19, 20, and 21.


Each turret is fitted with Two 14-cylinder engines of the Swashplate type. The specified maximum training speed of one revolution in 3 minutes is obtained with the engine running at 267 revolutions per minute.

The engine may be described as follows:-

Plate 18. The Swashplate is a circular wedge A, which is forged solid with the engine Shaft B. One end of this shaft is attached by means of a Clutch to the worm shaft of the training gear, and the other end is fitted with the Gearing which operates the Rotary Valve.

The principle of the machine is that if pressure is exerted on each side of a circular wedge, guided at its centre, the pressure on the faces will produce rotation. The necessary pressure is exerted by two opposite sets of Pistons, the connecting rods from which bear on the rocking swashplates C mounted pivotally in the gymbal rings D. The trunnions T of the gymbal rings D are carried in bearings in the casing at right angles to those of the rocking swashplates C; they are free to move longitudinally in grooves in the casing and are connected to each other by springs.

To reduce the friction to a minimum three sets of Roller Bearings are provided, these being: -

Rollers E, between the working faces of the rocking and the revolving swashplates, these rollers being held in a cage F, and

Rollers G and H between the barrel part of the revolving swashplate A and

(1) the cage F.

(2) The rocking swash plate C.

Case hardened steel Roller Paths J and K are fitted into the revolvong swasplate A, and the springs referred to above ensure that rocking swashplates C are kept in contact with the rollers E.

Pressure enters the cylinders as shown on Plate 18, the opposite cylinders being connected so that they are both open to pressure and exhaust simultaneously, and only one port for each pair of cylinders is provided in the valve seating. Normally, of course, the stroke of the pistons is governed by the throw of the swashplate, but for safety and to prevent the pistons encroaching, as they might otherwise do, on the admission port, a Stop, just clear of the piston end, is formed on the cylinder closing plugs.

An air or drain cock for each pair of cylinders is shown at K on the plate.

Plate 19 shows the position of the Swashplate in relation to, and for a guide in the setting of, the Valve; also information concerning the direction of the running of the engine. The Rotary Valve L has 12 ports, 6 communicating with the outside and pipe N, and 6 (not shown) with the inside and pipe M. It is driven by gearing from the engine shaft (the drive being transmitted by an Oldham coupling), and rotates at 1/6 the speed of the engine, but, as it goes in the opposite direction, the necessary ratio between valve and engine of 1 to 7 gives the correct sequence in the opening and closing of the ports is thereby restored.

The colouring of Plate 19 shows Ports open to pressure and exhaust, red and dark green respectively, with the engines and valve running as per indicating arrows, i.e., the engine running Anti-Clockwise.

The spaces M and N will be to pressure and exhaust respectively for one direction of training and vice versa for the other.

- Page 20 -

The water-tightness between the outer ends of the Valve and the Valve Casing is obtained by means of leathers, pressure being admitted to these from the spaces M and N around the valve.

The arrangements for the Lubrication of the engine are as follows:-

The engine casing is filled with a mixture of mica grease and lard oil of about the consistency of treacle, and this is circulated to the rotary valve and gear by means of a Force Pump shown at X on Plate 18. This pump consists of a small spring plunger, carried in the engine shaft, with its end working in an eccentric groove in the cap of the spindle bush.

Each cylinder is provided with a small hole leading into a Drain, the hole being drilled in such a position that any water leaking past the leathers will drain off. This arrangement should prevent any water from mixing with the mica grease, but in the event of a leather failing, and when the faulty leather is being replaced, the Mica Grease should be Removed and the water evaporated from it.

Failure of any leather can be detected at once by the water squirting out of the drain at each stroke of the piston. A Drain is also fitted at the Valve so that in the event of the valve face becoming so scored as to allow water to pass, the fact will be noticed at once, or should the packing of the cylinder gland give way mica grease will be forced through the cylinder drain in a similar manner to which water is forced out in the case of a piston leather going. This forms an indication that the cylinder gland requires repacking.

The cylinders are fitted at their outer ends with readily accessible closing Plugs, and to remove a piston leather it is only necessary to drain the cylinder and remove the plug, screw the withdrawing adaptor into the piston, and pull it out to the rear.


The training engine should be Opened Out completely every six months, and the rollers examined for wear and scoring. The mica grease should be removed, and any water evaporated from it once every quarter, and, if possible, it should be tested for water once a month.

The following procedure should be adopted when dismantling: -

1. Remove lubricating material by taking out the drain plug in the casing.

2. Take out the bolts securing the two halves of the valve casing, and also the screws securing the valve box. Remove the pressure pipes and unclutch the motor. Take out the securing bolts and move the engine until shafts are entirely clear of each other.

3. Remove the valve casing.

4. Unscrew and take out the 14 covers of the cylinders, and withdraw the rams with their connecting rods.

5. Turn the shaft until the apex of the converging planes of the swashplate points upward and then remove the upper half of the casing. (The position of the swashplate can be seen through the observation hole in the casing).

The shaft with its gymbals and valve driving gear can now be removed complete.

For Re-assembling the above operations should be carried out in the reverse order. Care, however, should be taken when assembling the gearing for working the rotary valve, because if incorrectly assembled the engine will not work.

To Avoid Mistakes the teeth which mesh together are punch-marked, and parts which, in assembly, should come to the top, are marked "Top." Great care should be exercised in the use of these punch mark, etc.