The steering apparatus is undoubtedly the most ingenious of the many clever contrivances packed into a Whitehead torpedo. Its function is to keep the torpedo on an even keel at a depth determined before the discharge. This is effected by means of two agencies, a swinging weight, and a valve which is driven in by water pressure as the torpedo sinks. When the torpedo points head downwards the weight swings forward, and by means of connecting levers brings the horizontal rudders up. As the torpedo rises the weight becomes vertical and the rudder horizontal. This device only insures that the torpedo shall travel horizontally. The valve makes it keep its proper depth by working in conjunction with the pendulum. The principle, which is too complicated for full description, is, put briefly, a tendency of the valve to correct the pendulum whenever the latter swings too far. Lest the pendulum should be violently shaken by the discharge there is a special controlling gear which keeps the rudders fixed until the torpedo has proceeded a certain distance, when the steering mechanism is released. The steering-gear does not work directly on the rudder. Mr. Whitehead found in his earlier experiments that the pull exerted by the weight and valve was not sufficient to move the rudders against the pressure of the screws. He therefore introduced a beautiful little auxiliary engine, called the servo-motor, which is to the torpedo what the steam steering-gear is to a ship. The servo-motor, situated in the engine-room, is only four inches long, but the power it exerts by means of compressed air is so great that a pressure of half an ounce exerted by the steering-gear produces a pull of 160 lbs. on the rudders.
The engines consist of three single-action cylinders, their cranks working at an angle of 120° to one another, so that there is no “dead” or stopping point in their action. They are very small, but, thanks to the huge pressure in the air chamber, develop nearly thirty-one horse-power. Lest they should “race,” or revolve too quickly, while passing from the tube to the water and do themselves serious damage, they are provided with a “delay action valve,” which is opened by the impact of the torpedo against the water. Further, lest the air should be admitted to the cylinders at a very high pressure gradually decreasing to zero, a “reducing valve” or governor is added to keep the engines running at a constant speed.
Whitehead torpedoes are fired from tubes above or below the waterline. Deck tubes have the advantage of being more easily aimed, but when loaded they are a source of danger, as any stray bullet or shell from an enemy’s ship might explode the torpedo with dire results. There is therefore an increasing preference for submerged tubes. An ingenious device is used for aiming the torpedo, which makes allowances for the speed of the ship from which it is fired, the speed of the ship aimed at, and the speed of the torpedo itself. When the moment for firing arrives, the officer in charge presses an electric button, which sets in motion an electric magnet fixed to the side of the tube. The magnet releases a heavy ball which falls and turns the “firing rod.” Compressed air or a powder discharge is brought to bear on the rear end of the torpedo, which, if submerged, darts out from the vessel’s side along a guiding bar, from which it is released at both ends simultaneously, thus avoiding the great deflection towards the stern which would occur were a broadside torpedo not held at the nose till the tail is clear. This guiding apparatus enables a torpedo to leave the side of a vessel travelling at high speed almost at right angles to the vessel’s path.
It will be easily understood that a Whitehead torpedo is a costly projectile, and that its value—£500 or more—makes the authorities very careful of its welfare. During practice with “blank” torpedoes a “Holmes light” is attached. This light is a canister full of calcium phosphide to which water penetrates through numerous holes, causing gas to be thrown off and rise to the surface, where, on meeting with the oxygen of the air, it bursts into flame and gives off dense volumes of heavy smoke, disclosing the position of the torpedo by night or day.
At Portsmouth are storehouses containing upwards of a thousand torpedoes. Every torpedo is at intervals taken to pieces, examined, tested, and put together again after full particulars have been taken down on paper. Each steel “baby” is kept bright and clean, coated with a thin layer of oil, lest a single spot of rust should mar its beauty. An interesting passage from Lieutenant G. E. Armstrong’s book on “Torpedoes and Torpedo Vessels” will illustrate the scrupulous exactness observed in all things relating to the torpedo depôts: “As an example of the care with which the stores are kept it may be mentioned that a particular tiny pattern of brass screw which forms part of the torpedo’s mechanism and which is valued at about twopence-halfpenny per gross, is never allowed to be a single number wrong. On one occasion, when the stocktaking took place, it was found that instead of 5000 little screws being accounted for by the man who was told off to count them, there were only 4997. Several foolscap letters were written and exchanged over these three small screws, though their value was not more than a small fraction of a farthing.”
The classic instance of the effectiveness of this type of torpedo is the battle of the Yalu, fought between the Japanese and Chinese fleets in 1894. The Japanese had been pounding their adversaries for hours with their big guns without producing decisive results. So they determined upon a torpedo attack, which was delivered early in the morning under cover of darkness, and resulted in the destruction of a cruiser, the Ting Yuen. The next night a second incursion of the Japanese destroyers wrecked another cruiser, the Lai Yuen, which sunk within five minutes of being struck; sank the Wei Yuen, an old wooden vessel used as a training-school; and blew a large steam launch out of the water on to an adjacent wharf. These hits “below the belt” were too much for the Chinese, who soon afterwards surrendered to their more scientific and better equipped foes.
If a general naval war broke out to-day most nations would undoubtedly pin their faith to the Whitehead torpedo for use in the open sea, now that its accuracy has been largely increased by the gyroscope, a heavy flywheel attachment revolving rapidly at right angles to the path of the torpedo, and rendering a change of direction almost impossible.
For harbour defence the Brennan or its American rival, the Sims-Edison, might be employed. They are both torpedoes dirigible from a fixed base by means of connecting wires. The presence of these wires constitutes an obstacle to their being of service in a fleet action.
The Brennan is used by our naval authorities. It is the invention of a Melbourne watchmaker. Being a comparatively poor man, Mr. Brennan applied to the Colonial Government for grants to aid him in the manufacture and development of his torpedo, and he was supplied with sufficient money to perfect it. In 1881 he was requested by our Admiralty to bring his invention to England, where it was experimented upon, and pronounced so efficient for harbour and creek defence that at the advice of the Royal Engineers Mr. Brennan was paid large sums for his patents and services.