1.—If adjusted for a certain depth, from 5 to 15 feet, and projected from above water, or if started from the surface, or if discharged from a submerged tube, it will rapidly attain that depth, and maintain it during the run.
2.—If fired in still water, it will make a straight run in the line of projection, provided that an allowance has been made for the deflection due to transverse currents.
3.—It can be adjusted to stop after having run any distance up to its extreme range, and after stopping to sink, float, or explode.
4.—Its range and speed vary considerably, according to the pattern of the torpedo.
| Whitehead Fish Torpedo. | Woolwich Fish Torpedo. | |||
| Yards. | 14' long, 16" max. diam. one screw. | 14' long, 16" max. diam. two screws. | 14' long, 14" max. diam. two screws. | 14·5' long, 14" max. diam. two screws. |
| 200 | .. | .. | 20 knots. | 25-1/4 knots. |
| 250 | 9-1/2 knots. | .. | .. | .. |
| 300 | .. | 12-1/4 knots. | 19-1/4 knots. | 24-1/2 knots. |
| 400 | 8 knots. | .. | 18 knots. | 23 knots. |
| 600 | .. | 11 knots. | .. | 20 knots. |
| 750 | .. | 10-1/2 knots. | .. | .. |
| 800 | 7 knots. | .. | 16-1/2 knots. | 18 knots. |
| 1000 | .. | 9 knots. | .. | 15-1/2 knots. |
Pressure of air in engines varies for distance and speed from 40 atmospheres to 140 atmospheres.
Placing the Charge.—The explosive is generally placed in what is termed the cartridge case, which case is similar in shape to the interior of the charge chamber (1), and is fixed thereto by means of wooden wedges.
Ignition.—The method of ignition is mechanical, and is arranged 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 detonating composition; within this tube is a steel rod some 2 feet long, fitted with a needle point at its inner end, and 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, or striker, inwards. By compressing this spiral spring, the inner end of the frame is butted against a catch, by which it is prevented from acting. On this catch being released, no matter by what means, the spring is brought into action and forces the frame and steel striker inwards, the needle point of the latter coming into contact with the detonator fires the priming charge, and so explodes the torpedo. The foremost extremity of the torpedo, which is termed 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. On a pressure being brought on the nose piece in a direct line with the length of the torpedo, it will be forced inwards, the result being the releasing of the catch and explosion of the torpedo. In addition to the nose piece, horizontal and vertical levers, or whiskers, may also be used, a slight pressure on either of which will similarly effect the explosion of the torpedo; also cutters for penetrating nets, &c., are fitted to the nose piece when desired.
Safety Wedge and Key.—For safety purposes a wedge is employed, which when in the safety position prevents the catch from acting; this wedge is so arranged that it may be withdrawn by the action of the machinery after the torpedo has run a certain distance, and also may be replaced by similar means in the safety position on the completion of the run. As an additional precaution a safety key is used, which is inserted in the head of the torpedo through the spring of the frame.
Description of Adjustment Apparatus.—For adjusting the length of range for withdrawing and replacing the safety wedge, &c., the following apparatus is employed.