The war between Russia and Japan has brought prominently before the public the necessity of being able to keep a war vessel well supplied with coal: a task by no means easy when coaling stations are few and far between. The voyage of Admiral Rojdestvensky from Russia to Eastern waters was marked by occasions on which he entered neutral ports to draw supplies for his furnaces, though we know that colliers sailed with the warships to replenish their exhausted bunkers. In the old days of sailing vessels, their motive power, even if fitful, was inexhaustible. But now that steam reigns supreme as the mover of the world's floating forts, the problem of "keeping the sea" has become in one way very much more complicated. The radius of a vessel's action is limited by the capacity of her coal bunkers. Her captain in war time would be perpetually perplexed by the question of fuel, since movement is essential to naval success, while any misjudged fast steaming in pursuit of the enemy might render his ship an inert mass, incapable of motion, because the coal supplies had given out; or at least might compel him to return for supplies to the nearest port at a slow speed, losing valuable time.
A TEMPERLEY-MILLER MARINE CABLEWAY COALING H.M.S. "TRAFALGAR" AT SEA
A carrier, from which are slung the sacks of coal, is hauled backwards and forwards by steel ropes stretching between the foremast of the transport and a mast rigged on the warship.
Just as a competitor in a long-distance race takes his nourishment without halting, so should a battleship be able to coal "on the wing." The task of transferring so many tons of the mineral from one ship's hold to that of another may seem easy enough to the inexperienced critic, and under favourable conditions it might not be attended by great difficulty. "Why," someone may say, "you have only to bring the collier alongside the warship, make her fast, and heave out the coals." In a perfect calm this might be feasible; but let the slightest swell arise, and then how the sides of the two craft would bump together, with dire results to the weaker party! Actual tests have shown this.
At present "broadside" coaling is considered impracticable, but the "from bow to stern" method has passed through its initial stages, and after many failures has reached a point of considerable efficiency. The difficulties in transferring coal from a collier to a warship by which she is being towed will be apparent after very little reflection. In the first place, there is the danger of the cableway and its load dipping into the water, should the distance between the two vessels be suddenly diminished, and the corresponding danger of the cable snapping should the pitching of the vessels increase the distance between the terminals of the cableway. These difficulties have made it impossible to merely shoot coals down a rope attached high up a mast of the collier and to the deck of the warship. What is evidently needed is some system which shall pay the cableway out or take it in automatically, so as to counterbalance any lengthening or shortening movement of the vessels.
The Lidgerwood Manufacturing Company of New York, under the direction of Mr. Spencer Miller, have brought out a cableway specially adapted for marine work. The two vessels concerned are attached by a stout tow-line, the collier, of course, being in the rear. To carry the load, a single endless wire rope, 3 / 8 inch in diameter and 2,000 feet long, is employed. It spans the distance between collier and ship twice, giving an inward track for full sacks, and an outward track for their return to the collier. On one vessel are two winches, the drums of which both turn in the same direction; but while one drum is rigidly attached to its axle, the other slips under a stress greater than that needed to keep the rope sufficiently taut. Since the rope passes round a pulley at the other terminal, pressure placed at any point on the rope will tend to tighten both tracks, while a slackening at any point would similarly ease them. Supposing, then, that the ships suddenly approach, there will be a certain amount of slack at once wound in; if, on the other hand, the ships draw apart, the slipping drum will pay out rope sufficient to supply the need. The constant slipping of this drum sets up great heat, which is dissipated by currents of air. As the sacks of coal arrive on the man-of-war they are automatically detached from the cable, and fall down a chute into the hold.
In the Temperley Miller Marine Cableway the load is carried on a main cable kept taut by a friction drum, and the hauling is done by an endless rope which has its own separate winches. In actual tests made at sea in rough weather sixty tons per hour have been transferred, the vessels moving at from four to eight miles an hour.
FOOTNOTES:
[19.] Cassier's Magazine.