Navies of the world

by Edward W. Very

LOCOMOTIVE TORPEDOES.

The Whitehead Torpedo.

The Whitehead torpedo consists of a projectile, or more properly speaking a boat, containing a heavy explosive charge, an engine driven by compressed air, screw propellers, and mechanism for regulating the speed, depth of flotation, distance of run, and security of firing arrangements. The general exterior appearance of the torpedo is that of a spindle of revolution, its greatest diameter being in the middle and the lines being so curved as to present a surface of minimum resistance to the water. The dimensions of the torpedo range from fourteen feet in length by sixteen inches in diameter to nineteen feet by seventeen inches. The speed ranges from seven knots for a distance of eight hundred yards up to twenty-five and a quarter knots for two hundred yards, the most powerful combination being fifteen and a half knots for one thousand yards.

Whitehead Torpedo and Firing-Tube.

This torpedo, if adjusted to run at any desired depth of water of from five to fifteen feet, and if it be projected from either above water, at the water-line, or below the surface, will rapidly attain the desired depth and maintain it throughout the run. If fired in still water, it will make a straight run in the line of projection, allowance being made for the sweep of currents. It can be adjusted to stop after having run any distance up to its extreme range, and after stopping, it will sink, float, or explode as desired.

The gun-cotton charge is placed in what is termed a cartridge-case, which is a wooden case similar in shape to the forward section of the torpedo, somewhat smaller, and held in place in its compartment by wooden wedges. This charge is ignited mechanically, the arrangement being as follows: Extending from the nose of the torpedo to the cartridge-case is a tube terminating in a copper case, in which is placed the priming charge and the detonating composition; within the tube is a steel rod, two feet long, fitted with a needle-point at its inner end and having its outer end screwed into a frame; this frame is capable of moving in and out, and is connected with a spiral spring which tends to force it, and consequently the steel rod, inwards, the action being similar to that of the firing-pin of breech-loading small-arms. By compressing this spiral spring, the inner end of the frame is brought forward to a catch and held retracted. If now this catch is disengaged in any manner, the rod flies back, acting like an ordinary firing-pin on the detonating composition. The extreme forward point of the torpedo, called the nose-piece, is so fitted that it is capable of being forced inwards, but in a position of rest its inner edge is just clear of the catch. This nose-piece is provided with short horizontal and vertical arms, so as to insure good contact with the body struck. The collision of the nose-piece against any resisting body forces it back and releases the firing-pin. In order to secure against accident, the nose-piece is provided with a safety-wedge and key. Before discharging the torpedo the key is removed, and after the discharge the wedge is withdrawn by the action of mechanism, and is so arranged that it may be replaced automatically and thus disarm the torpedo after its run, in case it is desired to recover it.

The arrangement for adjusting the length of range and for drawing and replacing the wedge is as follows: Two cog-wheels, a large one and a small one, are fixed on the upper part of the after-end of the torpedo, just in front of the propellers. The small wheel has thirty teeth, gearing in an endless screw attached to the propeller-shaft, and of such a pitch that one revolution of the propeller moves the wheel one tooth. The big cog-wheel is so arranged as to move one tooth for each revolution of the small wheel. In front of this gearing is a small stud that works fore and aft in a slot, being provided with a spring which tends to force it towards the after-end of the slot. This stud is connected by a rod to the valve which admits the compressed air to the cylinders of the engine. When the stud is in the forward part of the slot the valve is open, in the after part it is closed. By means of a lever the spring of the stud is compressed, and the stud is moved to the fore part of its slot; the big wheel is then moved around until a stud on its face is the desired number of teeth above the lever. Now for every thirty revolutions of the propeller, or one tooth of the big wheel, a certain known distance is travelled, varying according to the pattern of the torpedo, slip, etc. When the propeller has made the number of revolutions corresponding to the desired length of range, the stud on the big wheel presses against the lever of the spring and releases the latter, forcing the valve-rod back and closing the valve. Attached to the axle of the big wheel is a small brass arm which is connected by means of a brass rod to the safety-wedge, and is so arranged that after any required number of revolutions of the propeller the safety-wedge will be drawn out; or it may be drawn out at the instant of discharge. By means of an additional lever at the fore port of the torpedo, which is connected by means of a rod to the valve of the engine, and by arranging the attachment of the safety-wedge to the brass rod from the big wheel so that on the wedge being withdrawn it is released from the brass rod, the action of the closing of the valve after the run of the torpedo is completed, forces the wedge into its securing position again.

Naturally the torpedo would float at the end of its run from its difference of buoyancy, owing to the compressed air used in working the engines.

To sink the torpedo at the end of its run, a spiral-spring valve is placed in the after wall of the adjustment chamber, which can be attached to the brass rod working the engine-valve in such a way that when the latter valve is closed the spring-valve is opened, admitting water to the chamber and thus sinking the torpedo. If it is desired to explode the torpedo at the end of the run, the nose-piece is connected to the engine-valve, which, on closing, draws it violently back and releases the firing-pin. To adjust the depth of flotation, a small wheel, the face of which is marked in feet, is placed in the adjustment chamber, and is turned by means of a key until the number of feet desired comes under a pointer.

The secret of the Whitehead is in the mechanism by which the torpedo maintains a desired depth. The adjustment chamber, which is next abaft the explosion chamber, is connected by screw to the forward and after chambers in such a manner that by means of a number of small holes bored around the circumference the faces of the chamber are exposed to the pressure of the outside water, which varies with the depth to which the torpedo descends. Within the adjustment chamber is an endless strong spiral spring, attached to the after face of the chamber, and so arranged that after being set to a certain tension, capable of resisting an equivalent pressure on the outside of the face, any increase or decrease in this pressure will cause this spring to work a rod by which the horizontal rudders of the torpedo are regulated. Within this adjustment chamber is also placed an automatic balance, which assists in maintaining the torpedo at the desired depth by swinging forward on the torpedo’s descending or aft on ascending, and thus assisting the rudders.

The Whitehead may be discharged through a submerged tube in the stern or in broadside, from a carriage above the water-line, or from the surface.

For discharging under water a tube is fitted to an orifice in the stern or broadside, closed by a water-tight valve; the inner end is closed by a water-tight door. The torpedo, being prepared, is placed in the tube, the door is shut, water is admitted to the interior, and the valve is opened. The torpedo is then shot out and started by means of a piston bearing against its rear end and worked by compressed air. To prevent it from slipping out before the time, a stop is provided at the forward end of the tube, which is removed automatically at the same time that the compressed air is admitted to the piston. In the case of broadside discharge, the tube works inside an iron casing, through a stuffing-box at the inner end and in a shield at the outer end. The shield, placed on the forward side of the orifice, is of such a length as to protect the torpedo from the pressure of the water passing the vessel.

In projecting from above water, an iron carriage is used, which is fitted with a frame in which the torpedo rests. The outer end of this frame is provided with a lip a few feet long, by means of which the rear end of the torpedo is slightly canted up on leaving the frame, preventing undue strain on the extreme end. The frame is mounted in the carriage in such a way that it can be elevated or depressed by means of a screw, like a gun. The torpedo is ejected by means of a piston as before, the carriage being provided with a small reservoir of compressed air so that it may be moved to any point aboard ship.

To project from the surface, no tube is necessary; all that is required is to set it for the depth, point it, and turn back the lever by hand, when it starts off of its own accord.

For discharging from boats, the torpedo is either mounted on its carriage forward or carried in iron slings suspended from davits. In the latter case the davits are pivoted, so that normally the torpedo rests in a cradle on deck; but the cradle being removed, the davits are swung over, lowering it to about two feet below water, where it is held securely until discharged.

The propeller is worked by means of a pair of Brotherhood engines, working to 60 indicated horse-power and giving 1000 revolutions a minute. Weight of charge, 33 lbs. gun-cotton; weight of torpedo, 500 lbs.