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Design of the Torpedo

A formidable weapon in time of war, the modern torpedo is also a complex piece of machinery. It embodies many ingenious devices for the purpose of keeping it trained on its target and at a uniform depth below the surface of the water

TORPEDO TUBES on the deck of H.M. flotilla leader Kempenfelt

TORPEDO TUBES on the deck of H.M. flotilla leader Kempenfelt. This ship, built in 1932, has a displacement of 1,390 tons. Her geared turbines of 36,000 horse-power give her a speed in excess of 35 knots. The Kempenfelt has a length of 326 feet on the water-line, a beam of 33 feet and a mean draught of 8 ft. 8 in. She is armed with eight 21 in. torpedo tubes of the type shown to the left.

CREDIT for the torpedo as we know it to-day must be given to Captain Luppis of the Austrian Navy, and to Robert Whitehead, the English manager of a small engineering works in Fiume, on the Adriatic.

In 1866 Whitehead, assisted by his young son and one workman, built his first torpedo in conditions of strict secrecy. The torpedo was of steel, cigar-shaped, between 14 and 16 in. diameter and weighed 300 lb. In many ways it was similar in general design to those that followed in later years. In the forepart or head of the torpedo was packed 18 lb. of dynamite, arranged to explode on impact against a ship’s hull. Behind the head was a compartment, built of boiler-plate, containing compressed air at a pressure of 700 lb. per square inch. The compressed air drove a set of small engines coupled to a screw propeller. The speed of this first torpedo was only 6 knots, and it did not run at a uniform depth. The importance of the invention, however, was at once recognized by the Austrian Government.

During the next two years the vital problem of running below the surface at a uniform depth was worked out behind locked and guarded doors, and finally the famous “balance chamber” was designed.

By 1876 the Whitehead torpedo had attained a speed of 18 knots for a distance of 600 yards. It now carried a 26 lb. charge of guncotton, and was able to keep to a true path in the water. The weapon was re-designed in 1884 with more powerful engines, giving a speed of 24 knots, and it carried a heavier charge of explosive. A new type of Whitehead torpedo was introduced in 1889 with a speed of 28 to 29 knots, a range of 1,000 yards and an explosive charge of guncotton weighing 200 lb. A factory for the manufacture of Whitehead torpedoes was established at Portland.

One of the most important improvements (apart from the balance chamber) introduced in the design of the torpedo was the gyroscope control gear invented by Ludwig Obry, of Trieste, who sold the idea to Robert Whitehead. The gyroscope controls the path of the torpedo and keeps it dead on the target in much the same way as the famous gyroscopic “metal mike” keeps a ship steered on her true course. The depth at which a torpedo runs is controlled by its horizontal rudders (worked from the balance chamber), and if it rolls these rudders may stand upright and so alter direction to port or starboard. The gyroscope gear, attached to vertical rudders, overcomes this difficulty and also corrects any deflection due to dents in the torpedo hull or other causes. So marked is this tendency of the gyroscope to continue to spin in one plane that a torpedo can be pre-set to run at right angles to the path of a submarine, even if fired from a bow tube. After having left the submarine the torpedo will make a right-angled turn and run for its target.

The first successful use of the Whitehead torpedo in wartime was on January 25, 1878, when the Russian warships Tchesme and Sinope each fired one Whitehead torpedo at a Turkish revenue cutter in the entrance to Batum harbour. Both torpedoes exploded and the Turkish vessel was immediately sunk. On April 23, 1891, during one of Chile’s earlier revolutions, the insurgent battleship Blanco Encalada was torpedoed in Caldera Bay by two government torpedo-gunboats, the Lynch and the Condell. The battleship sank in 6½ minutes — the first battleship to fall a victim to the deadly new weapon. The torpedo was also used with telling effect in the war between China and Japan in 1895 and in the Russo-Japanese War of 1904.

By 1907 the British Whitehead torpedo had grown to a diameter of 18 in. with a charge of 205 lb. of guncotton. It had a speed of 33 knots for 1,000 yards declining to 19 knots at its maximum range of 4,000 yards. The

French Navy had adopted an 18 in. torpedo carrying 198 lb. of explosive and having a maximum range of 3,000 yards. The German torpedo of this period had a speed of 30 knots, and a maximum range of 2,500 yards, and carried 246 lb. of explosive.

An interesting torpedo of the time was the Bliss-Leavitt used in the United States Navy. This was an 18-in. or 21-in. torpedo carrying 300 lb. of guncotton, with a speed of 36 knots for 1,000 yards or 27 knots for 4,000 yards. Air, at a pressure of 2,225 lb. per square inch, passed through an alcohol heater to Curtis turbines running at 10,000 revolutions a minute, reduced at the propeller shafts to 900 revolutions a minute, and developing 160 horse-power. The gyroscope for the control gear was also turbine-driven, at 18,000 revolutions a minute.

THE LAY-OUT OF A TORPEDO is shown in this diagram

THE LAY-OUT OF A TORPEDO is shown in this diagram. Behind the head, which is charged with guncotton, is a chamber containing compressed air for driving the engines. The balance chamber contains the valve and weight controlling the rudders, and farther aft are the engine-room and buoyancy chamber.

Another important torpedo was the Davis-Whitehead torpedo, in which the head was provided with a vanadium steel gun barrel containing a shell charged with high explosive. On striking the target the shell was discharged through the ship’s hull into the interior, where it burst.

The Brennan torpedo, introduced by its inventor in 1877, was primarily intended for coast defence. Its driving mechanism comprised two drums on which were wound light steel cables. On shore was erected a 100-horse-power winding engine that hauled on the cables and caused the drums, attached to the propeller shafts, to revolve and drive the torpedo forward. The Brennan torpedo carried a charge of 200 lb. of guncotton and in the head was a Holme’s light, providing smoke by day and flame by night, so that the path of the weapon could be observed and its course directed against a hostile ship.

In addition to the 18-in. torpedo the British Navy used a 21-in. weapon during the war of 1914-18. This torpedo carried a charge of guncotton weighing 330 lb. and had a range of 11,000 yards (6¼ miles) at 30 knots. A speed of 45 knots was possible at a maximum range of 7,000 yards. The Germans used a 22-in. torpedo carrying 300 lb. of T.N.T. The speed was 30 knots and the range 8,000 yards. German U-boats used a 14-in. torpedo charged with 420 lb. of T.N.T. and having a speed of 40 knots at a range of 1,200 yards.

The body of a Whitehead torpedo resembles a steel cigar rounded at the fore end, and tapering off aft to the tail. The head is detachable and in peace time a special practice-head is used, generally made of copper and filled with water to bring its weight up to that of the explosive head used in war. During practice the collapsible head hits the target and crumples up, and the torpedo remains floating on the surface of the water. The torpedo is located by a chemical light carried in a perforated container, to facilitate recovery — an important consideration with a torpedo costing £2,000. The light canister contains phosphide of calcium that yields an inflammable gas on contact with water, thus providing flame and smoke for ready identification by night or day.

Pressure of 2,000 lb.

The war head, however, is by no means as harmless as its peace time counterpart. It is packed with guncotton — compressed cotton that has been soaked in nitro-glycerine and has the property, when detonated, of turning instantaneously into a gas at about 3,000 times its own volume. The explosion of the guncotton is brought about by detonating a small charge of fulminate of mercury — the content of rifle cartridge caps and the detonators of Mills bombs. The fulminate is detonated by a blow from a plunger in the “nose” of the war-head and there are three safeguards against premature explosion.

The most important safeguard is a miniature propeller screwed on the end of the firing plunger. This propeller or “fan” is further secured by a removable pin against inadvertent unscrewing. When the torpedo has travelled for about 50 yards through the water the safety propeller has screwed itself off the end of the plunger. The firing plunger is then free to be driven into the fulminate when the torpedo strikes an enemy’s hull. It is not free, however, to explode the charge on striking, say, a small piece of floating wreckage. The blow must be comparatively heavy, because the plunger is provided with a copper pin that must be sheared off before it can be struck home.

On striking the target the torpedo blows to pieces and leaves an enormous hole in the plating of the enemy ship, well below the water-line. Should the torpedo miss the target and the war head fail to explode, a special valve, required by international law, comes into operation and the missile sinks to the bottom of the sea.

Behind the head, and occupying about half the volume of the whole torpedo, is the air chamber, in which is stored compressed air at a pressure of over 2,000 lb. per square inch.

The air chamber is made of the finest steel about ⅜-in. thick, and so great is the pressure that an 18-in. torpedo will increase 1½ millimetres in diameter when charged with air. The compressed air is surprisingly heavy (the torpedo requires a buoyancy chamber) and it can also be highly dangerous. Practice torpedoes have been known to burst on heavy impact against a target, showering steel splinters far and wide.

The next compartment aft is the balance chamber, for long the hiding place of the Whitehead “secret” — the mechanism that enables the torpedo to run submerged on an even keel at any predetermined depth below the surface down to about 20 feet. In the balance chamber is a pendulum free to swing within limits in a fore and aft direction. Pivoted to the pendulum links is a

short lever, one end of which is connected, through a “servo-motor”, with levers that operate the horizontal rudders. The centre of the pivoted lever is connected to a hydrostatic valve that is forced outwards by a spring against the external pressure of the water. The balance, or hydrostatic, valve thus operates to ensure that the torpedo shall run at the predetermined depth, and the pendulum maintains the missile on an even keel.

A control gear is used in conjunction with the balance mechanism to keep the rudders fixed for a certain distance after firing. This overcomes the shock of discharge and of the initial dive.

How a torpedo is maintained on an even keel by the combined action of a valve and a pendulum weight

AFTER ITS INITIAL DIVE, a torpedo is maintained on an even keel by the combined action of a valve (H) and a pendulum weight (W). The first diagram shows the position immediately after the dive. The weight swings forward and the pressure of water forces in the valve, these actions combining to elevate the horizontal rudder (R).

The second diagram shows the conditions in which the torpedo runs on an even keel.

The third diagram shows the means of counteracting a tendency to run upwards towards the surface, the valve and the weight combining to depress the rudder and to restore the correct balance.

The balance chamber contains also the stop-valve that is used to cut off the air from the engines when the air chamber is charged or adjustments are made. A special spanner is screwed into this valve to turn it so that the torpedo cannot be loaded into the firing tube with its air supply cut off from the engines.

Next is the engine compartment, containing a three- or four-cylindered radial engine driving two propeller shafts, one within the other, in opposite directions. The inner shaft is hollow, and through it escapes the air from the engine’s exhaust. The engine-room also contains apparatus for heating the air before it enters the cylinders, a device that greatly increases the range and efficiency of the torpedo.

In this compartment is the charging valve, through which compressed air is supplied to the air chamber. The charging valve also incorporates a starting valve, which releases air from the air chamber, through an automatic reducing valve that controls the pressure, to the engines.

The Buoyancy Chamber

The starting valve is operated by a cam turned by a projection in the torpedo tube immediately after firing. This starting valve is closed by a special counter-mechanism, incorporating a set of ratchet wheels, when the torpedo has run a predetermined distance. A delay action valve, worked by a flat “watertripper” attached to the torpedo hull, slows down the engines until the propellers are revolving in the water.

The engine-room contains also the “servo-motor” that assists the balance chamber to control the horizontal rudders. The servo-motor is simply a cylinder containing a piston operated by compressed air and controlled by a slide valve. A pressure by the balance mechanism of, say, half an ounce on the slide valve will cause the piston to exert a pressure of 180 lb. on the rudder levers.

The next compartment aft is the buoyancy chamber containing the propeller shaft, diving rods, sinking valve, and the gyroscopic control. The gyroscope is a flywheel weighing nearly 2 lb. mounted in a frame in the lower part of the compartment. It is set spinning at over 2,000 revolutions a minute by gearing, similar to that on a bicycle bell, operated by a hand-wound spring that is released by a trigger on the torpedo tube.

The gyroscope operates the vertical rudders through a system of levers and servo-motors, and so checks any tendency on the part of the torpedo to deviate to port or to starboard. In some torpedoes the gyroscope is spun by a small turbine driven by compressed air.

Finally, at the tail of the torpedo are the wheel gearing that makes the propellers revolve in opposite directions, the perpendicular fins, the horizontal and vertical rudders and the screw propellers.

The torpedo has revolutionized the conduct of war on the high seas; it has shaped the foreign policies of great nations and has worked its influence on the political histories of empires.

You can read more on “The Battle of Tsushima”,  “Big Guns in Action” and “Undersea Weapons” on this website.