Sulphuric-acid Fuse.
This fuse consists of a brass fuse-case containing the magazine and crowned by a thin lead cylinder containing the chemicals, which consist of a small closely sealed glass phial of sulphuric acid placed in the tube and packed with a mixture of potassium chlorate and loaf-sugar. A slight blow on the lead cylinder breaks the bottle, thus permitting a contact between the explosive mixtures.
Harvey’s Torpedo-Fuse.
The principle of this fuse is precisely similar. The bottom of the firing-rod is in this case hollowed and partially packed with the potassic chlorate and loaf-sugar mixture. Over it a small bulb containing a few drops of sulphuric acid is placed and packed carefully with raw cotton. The mouth of the hole is then sealed with a lead capsule. The firing-rod is itself suspended over a firing-pin against which it is driven by the levers on the top of the torpedo.
Electrical Fuses
depend upon the heating powers of an electrical current to ignite certain explosive substances, preferably gun-cotton. Although there are many modifications of the electrical fuse, they almost without exception agree entirely in general make. Two current wires are necessary, called terminals, and having their inner ends separated, in order that some substance offering a high resistance to the passage of the current may be inserted between them. The terminals are of copper wire; the resistance material or bridge is generally of fine platinum wire, although other substances are used in different types. The terminals are as a rule separated by a small block of hard wood which forms an insulator and a support. Around the bridge a wisp of gun-cotton is generally wrapped, although here again other explosives are used in modified forms. This combination is called an exploder, and it is inserted in a fuse-case or magazine containing powder or gun-cotton. The exploder and magazine together form the fuse. One of the terminals is generally attached to the exterior of the torpedo, which forms an earth; the other one is connected with an insulated wire or cable leading to the electrical battery. These fuses are made to explode either at will or on contact. If they are to explode at will, the firing circuit as a rule is not completed until the moment desired for explosion. If they are to explode by contact, the general manner of use is to insert in the circuit at some part a resistance-coil of sufficient force to weaken the current below the firing point. At the moment of contact, the resistance coil is automatically cut out and the torpedo is fired. Another way is to use what is called a circuit-closer, which normally leaves the circuit broken, but on being touched the circuit is closed and the torpedo is fired.
American Dynamo-
Electric Fuse.
English Dynamo-
Electric Fuse.