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Rh 1 specially light torpedo was designed for aircraft purposes. When the World War broke out, it was realized that means would have to be provided to carry the torpedo planes into proximity to their

objectives, and H.M.S. " Engadine " and " Riviera " were fitted
 * out for North Sea operations. Later, in May 1915, H.M.S.

" Ben-my-Chree " was sent out to the Dardanelles as an air- craft carrier. She carried two torpedo seaplanes, in addition to

reconnaissance aircraft. In 1916-7 the first torpedo planes were [ produced capable of flying off a ship's deck. About this time

British naval authorities became convinced of the value of
 * torpedo aircraft, and a large number were ordered. Delivery

commenced in 1918 concurrently with special training of tor- pedo plane pilots, and in Oct. H.M.S. " Argus " embarked the first completed squadron of torpedo planes. In the first instance, experimental work was concentrated at Felixstowe in 1916, and in 1917 a torpedo seaplane school was established at Scapa Flow, which latter station was closed down after the Armistice. A torpedo seaplane school was also opened at Gosport, and ex- perimental work and training is now carried out from here, pilots being embarked from time to time on board the aircraft carriers attached to the fleet.

In Aug. 1915 an attack was made on a s,ooo-ton merchant

1 ship by a short torpedo seaplane from H.M.S. " Ben-my-Chree "

in the Dardanelles. A hit was obtained amidships, and spray

and flying fragments observed. A few days later three Turkish

ships at anchor were attacked, one being hit and subsequently

gutted by fire, though the hull was salved. In the early part of

1017, the Germans, who had a squadron of torpedo planes at

, Zeebrugge, made several attacks on British merchant ships in

the Downs. Three were sunk and one enemy aircraft shot down.

Construction. In the British service the l8-in. and 2i-in. torpedoes are the only sizes now made ; the former are supplied for use in sub- marines, C.M.B.'s and aircraft, and the latter in capital ships,

\ light cruisers and destroyers. _ Constructed of steel plating, except for the air chamber, and of

i circular cross section, the profile of the torpedo is cigar-shaped, with

.a blunt-shaped head, a parallel portion and a fine run aft to the tail.

i Commencing from the forward end, the torpedo is divided into six compartments: the head, the air vessel, the balance chamber, the engine room, the buoyancy chamber, the tail. These may be

'described as follows, (i) The Head. There are two types, the War- head containing the explosive and the Collision-head used for practice. The former carries a charge of T.N.T. which is detonated on contact by a device known as the pistol, through the medium of a de- tonator of fulminate of mercury and a suitable priming charge. The pistol itself consists of a metal body which is screwed into the War-head and carries a striker which has externally projecting arms. On one of these arms, coming into contact with any object, the striker is forced in against the resistance of a shearing pin (which is provided for safety), and the detonator is struck. This in turn detonates the " primer " and the main charge. In the case of the " net cutter," used when attacking ships protected by nets, the action is similar, but ^the cutter is provided in addition with sheering devices for
 * utting through the meshes and opening up a hole sufficiently large

to enable the torpedo to pass through. Nets are not now carried by modern capital ships of any nation, but the net cutter might be if use against net-defended bases. The Collision-head, used for prac- tice, is a_ steel shell partially filled with cork to insure buoyancy in
 * ase of impact with a target ship. It is brought up to approximately

War-head weight by filling it with water before practice running, ind is so constructed that, on hitting, the fore part collapses, thereby essening the blow on the plating of the ship and the shock on the
 * orpedo itself. To facilitate recovery, an indicating light is fitted

n a pocket in the Collision-head, consisting of phosphide of calcium n a tin container. On coming in contact with water this chemical us the property of spontaneously bursting into flame, which shows }n the surface, thereby indicating the position of the torpedo. [2) The Air Vessel. This consists of a special nickel-steel forging xmtaining the compressed air which provides the motive power of
 * he torpedo. It is closed at either end by special dome-shaped

nieces, screwed and sweated into place. To the sides of the vessel ire secured the lugs or brackets which take the weight of the torpedo n the case of above- water discharges and the stresses on the torpedo )n discharge from submerged tubes. (3) The Balance Chamber is ivetted and sweated on to the after end of the air vessel, and forms a vatertight compartment which contains the depth-keeping mechan- sm, the heater apparatus and the supply of fuel (either alcohol or letroleum in some form) in a special flask. In this compartment is ilso situated the charging valve and the stop valve in the main air )ipe, which enables pressure to be isolated when it is necessary to emove the after part of the torpedo for examination of engines, etc. The depth-keeping mechanism, Mr. Whitehead's secret, consists of a xxxn. 24

pendulum weight and a hydrostatically operated valve, linked together by rods in such a manner that the weight corrects depart- ures from the horizontal trim of the torpedo, whilst the valve keeps the torpedo at its set depth. Their joint action operates the hori- zontal rudders of the torpedo through the medium of a small air engine termed the servomotor. (4) The Engine Room is the next compartment abaft the balance chamber. It is not watertight, and together with the "buoyancy chamber," to which it is rivetted and sweated, forms what is known as the " afterbody." This portion of the torpedo is secured to the " air vessel balance chamber " por- tion by a number of screwed bolts, which allows of the torpedo being easily " parted " for examination of the mechanism in the engine room. This mechanism consists of: (a) the engines, which are of the single-acting four-cylinder Brotherhood type; (6) the steering engine or servomotor; (c) the starting valve and counter gear;

(d) the reducing valve, which maintains a constant reduced working pressure at the engines, irrespective of the air-vessel pressure, thus insuring an approximately constant speed throughout the set range;

(e) oil Dottles for lubricating various working parts. The starting valve is operated by an air-lever which projects through the shell of the torpedo and is thrown aft by a downward projecting bolt in the torpedo tube on discharge. In addition to opening the starting valves, the air-lever in its backward movement presses against a rod which releases the gyroscope. The counter gear,, which is mounted on the starting valve casing is a piece of mechanism driven off the engines for stopping the torpedo at a pre-determined range. Off the counter is also driven the ignition gear, whose func- tion is to fire the cordite igniters in the " heater " arrangement at a pre-determined moment, and start the combustion of the air and fuel. In the earlier torpedoes, the counter also operated the " sink- ing gear." This gear can be set to " float " for practice or " sink " for action and when set for the latter adjustment a small valve is lifted at the end of the run and water is admitted into the buoyancy chamber, thus sinking the torpedo, which might otherwise remain a dangerous floating mine. (5) The Buoyancy Chamber provides a large proportion of buoyancy of the torpedo, and consists of a thin sheet- steel shell, strengthened up by internal angle rings, to enable it to withstand external pressure, due either to immersion at great depths or to impulse pressures on discharge. To the foremost bulkhead of this compartment are secured the engines. Two watertight tubes run through it, one centrally carrying the propeller shaft, and the other to one side carrying the rod connecting the servomotor or steering engine, and the horizontal rudders. The sinking valve is on this bulkhead. The remaining fittings in this compartment consist of the gyroscope which is fixed to suitable brackets secured to the shell, and the gyroscope rudder rod, which passes through a watertight gland in the after bulkhead. A watertight removable door is also fitted at the bottom of the chamber to obtain access to the gyroscope. This piece of apparatus consists of a comparatively heavy bronze wheel, delicately mounted in ball bearings in an inner horizontal gymbal. This in turn is mounted in an outer vertical gymbal capable of rotational movement within the framework of the in- strument. The wheel is initially spun at a high rate of revolution about its axis in the inner gymbal, due to the release of a strong spiral spring in torsion. This release takes place when the air-lever is thrown aft on discharge, after which the whole system of wheel and gymbals is freed from external constraint. The design is such that all axes of rotation of wheel and gymbals meet in a common point at the centre of gravity of the wheel. Consequently, in theory, if the instru- ment is in adjustment there are no external forces acting on the wheel or system except friction and windage, and, following the well-known dynamical laws of rotating bodies, the spinning axis tends to main- tain its direction in space no matter how the apparatus is moved bodily. Practically, of course, slight errors do creep in, due to minute manufacturing differences, etc., but if the gyroscope is in good condi- tion, the effect of these is barely noticeable until the initial wheel speed has dropped considerably. It will therefore be seen that the axis of the spinning wheel provides a datum line, the direction of which is the direction of the gyro wheel on release, i.e. in the longitu- dinal axis of the tube and torpedo. Subsequent deviations of the torpedo from the correct line in a horizontal plane, cause relative movement of the spinning axis, and fore and aft line of the torpedo. These relative movements are communicated to a delicate rotary valve through the medium of a small pin mounted on the outer gymbal. This rotary valve controls the air supply to a small steering engine which operates rudders on the vertical fins, so bringing the torpedo back to its original direction. (6) The Tail is a non-water- tight conical steel shell carrying the horizontal and vertical fins and rudders. The fins are fixed to the tail and the rudders are carried in suitable brackets on their after edges. This portion of the torpedo also contains the gearing which enables the two four-bladed pro- pellers to be driven in opposite directions off the same engine. The provision of two propellers is necessary in order that the torpedo shall remain upright during the run, andjthese are so shaped that the turning effect of one is balanced by-that of the other.

The Director. The name of " director " is given to the sight by means of which the firing officer is enabled to fire the torpedo at the correct moment. This he does by pressing a key which completes the circuit of the electrical portion of the firing gear at the tube. There are a number of types of sight extant, each of which has been