Publisher's Synopsis
This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1896 edition. Excerpt: ... work she is designed generally to perform rendering her specially liable to sudden torpedo attack. To provide snpport and security for these cranes about 30 feet of the pillar lies buried, passing down through the upper, main, and protective decks to the bottom of the ship, which is specially strengthened and fitted to support the weight and allow rotation. The upper deck, which takes the canting strain, is specially strengthened and fitted with a heavy steel ring in which the crane rotates. Rollers are not provided to reduce the friction at this point, the crane being simply fitted with a plain disc, 5i inches in thickness, fitting easily in the deck socket. The lifting machinery, which is placed inside the pillar of the crane, and therefore being well down in the hold is fairly protected from gun fire, consists mainly of two hydraulic rams; the larger one 17 inches in diameter, the smaller one 5 inches, having a vertical stroke of 10 feet, giving a lift of 40 feet at the purchase, through the multiplying power of the fourfold pulleys, which the rams are constructed to operate in the usual manner. At the ordinary working pressure of 1,000 lb. on the square inch, the thrust on the crosshead carrying the pulleys is about 118 tons, which gives a lifting power at the gib of 20 tons, moving at the rate of 90 feet per minute. The small cylinder plays an important part in this mechanism, being designed to mitigate the danger which always attends the hoisting boats in or out in a seaway, and is the subject of a patent. Its special duty is to keep taut the slings after they have been hooked on to the boat until a favourable moment for hoisting presents itself. The valves are so arranged that the main lifting power cannot be applied until the...
