Page:Popular Science Monthly Volume 91.djvu/774

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The Giant Crane of the Austrian Navy

It has a three-hundred-foot jib and while handling a load maintains its equilibrium by means of water let into the rear ballast tanks

��AT work in the Austrian Navy Yard at Pola is the largest floating crane in the world. A giant floating crane is this, with its normal lifting capacity of two hundred and forty tons. It thinks nothing of taking guns and turrets weighing sixty tons more than that and carrying them to the ships under construction about the yard.

Nothing about the ship is nearly as im- portant as this busy crane. The other cranes of one hundred and one hundred and fifty tons capacity — wonderful cranes a few years ago! — have been relegated to the minor jobs of the yard.

The barge crane is commanded by a captain who stands at the navigating bridge. From his point of vantage, he signals the engineer at the hoisting engine to run out the cable truck on the jib and to let down the cable to the wharf. When the load — gun, or whatever it may be — is secured upon the grappling hook, the captain has it raised to the top of the jib, one hundred and eighty-seven feet in the air. Before the load has ascended many feet, he will have signaled to the boiler room just below the deck, and the barge will be steaming away towards the ship it is to equip. There she drops anchor and "straightens to" on tightening her anchor cables by her modern steam capstans.

With her mighty three-hundred-foot jib, the crane can run her burden far over the side of the largest battleship. While this is going on, water is let into the rear ballast tanks of the barge. Finally, when the load has been deposited on the battleship, this water will be forced out again with compressed air to restore the equilibrium of the barge.

This diligent little ship keeps constantly in touch with the yard headquarters by means of the auxiliary patrol boat that is assigned to her. Instructions reach the barge captain through the wireless station on board the patrol. It is through these channels that orders come when a subma- rine meets with mishap during its opera- tions on the Adriatic Sea.

If the submarine has foundered within any possible reach of the land, the barge is ordered to drop whatever work it is doing

��and to follow the fast patrol boat to the scene of the disaster. Expert divers put off from the yard to meet the barge on its way to the sea. Reaching the point where the submarine has been reported to have gone down, the divers at once descend, carrying the two lifting cables with them.

If the divers are fortunate and find the submarine, the grappling hooks are at- tached to the emergency eyes at each end of the U-boat's hull. Then, with the two lifting cables working together, the U-boat will be raised towards the surface at the rate of about three feet a minute. The rear cable, which goes through the hole built into the front deck of the ship, cannot lift its end of the submarine entirely out of. the water. The front cable can, however, and it raises the boat until its conning- tower clears the water. In this way, the crew are enabled to escape.

American cranes are of a more specialized type, and of an extraordinary efficiency. Revolving jibs take the place of the station- ary ones of the Austrian craft. Instead of having to maneuver to aline the barge in order that a load may be lowered into exact position, the American cranes maneuver the jib around.

On our floating cranes, moreover, the driving machinery is electrical. The oper- ator is stationed in a house near the bot- tom of the jib. The house rotates with the jib so that the operator can overlook every motion. The electric motor controls, and even the distant-controls for the electric capstans are mounted on the switch- boards in this cabin. By co-ordinating his movements, one man can handle his barge with marvelous facility.

Hence, where Austria's cranes exceed ours in size, the American cranes excel in dexterity. Furthermore, the use of water ballast to prevent a barge from tipping frontward when a load is on the jib seems absurd to American engineers. Our barges are inherently stable. The crane is mounted so near to the center of the ship that twice the capacity load would not overturn it. No, we do not use water ballast — the cables might break some day and as the load falls off in front the ballast might tip the barge over at the rear!


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