Clockwork Fuse.
McEvoy’s Fuse
consists of a percussion system in connection with a small propeller. As long as the torpedo drifts with the current the propeller does not revolve, but if it is brought up in any way the force of the current starts the propellers, which after a few turns release the firing-pin spring.
The torpedo by means of which the Albemarle was sunk ([see cut, page 335]) was exploded by a percussion fuse of still a different nature. The torpedo itself was attached to the end of a spar, but just before explosion it was intended to detach and capsize. A hollow tube passed through the axis of the torpedo, having at the nose-end an ordinary percussion-cap arrangement. The rear half of the torpedo formed an air-chamber, and at the rear end of the tube an iron ball, free to move along the tube, was held in place by a small pin to which a laniard was attached to be pulled by hand. The torpedo being thrust by the spar under a vessel was detached, and the air-chamber caused it to tumble bottom up immediately. The pin then being withdrawn by the laniard, the ball dropped on the percussion-cap and fired it.
McEvoy’s Propeller-Fuse.
English Dynamo-Electric Fuse.
Hill’s Fuse
consists of a brass body having a percussion anvil screwed into its lower end. A spiral spring surrounds this anvil, projecting slightly above it and forming a seat for a light case holding the fulminate, which is of a very sensitive composition. Covering the top of the fuse-case, and just clear of the fulminate-case, is a light copper dome. A slight blow on this dome presses it in and drives the fulminate down on the anvil.