For several months past we have been preparing a series of Plates of the great ship and its machinery, and with the present number we give the first of the series. Plate lxxiv is a transverse section of the after part of the hull of the great ship, exhibiting the peculiarity of her construction, and showing accurately a side view of the engines and machinery for driving the screw propeller, the scale being 1/8-inch to 1 foot.
These immense and splendid specimens of marine engineering have been designed and constructed by Messrs. James Watt & Co., of Soho, near Birmingham. The following are the principal dimensions of the engines, boilers, screw propeller, &c., as furnished to us by the manufacturers. We have to observe that the drawings have been made by us from the detached details and working drawings of the engines, boilers and machinery, and the accuracy thereof may be relied upon. As to the details of the cessel and the peculiarities of her internal arrangements, we shall hereafter give accurate details.
There are four cylinders, 84 in. diameter by 4 ft. stroke, and ordinary speed is to be 45 strokes per minute, at which the nominal power is 1,700 H.P.; but at 50 strokes per minute, and at which the engines will go with steam of 25 lbs. pressure, the power will be quite 2,000 H.P. The weight of the engines alone is about 500 tons.
There are to be three sets of boilers to work the screw engines, each set having a surface of 8,500 sq. ft., say 1,680 brass tubes 3 in. diameter outside, and 5 ft. 6 in. long. The grate surface is 406 ft. The weight of each set is 190 tons, including 90 tons of water.
The screw is 24 ft. diameter,and 37 ft. pitch; the propeller shaft is 24 in. in diameter, and 48 ft. long, and weighs 35 tons. There is an ingenious arrangement by which the after screw bearing may be cottered up and adjusted at pleasure. This is effetcted by a separate chamber — in fact a "diving-bell" — and from which the air is expelled in the usual manner by pumps, thus allowing an engineer to descend and do what is necessary. This shown in the longitudinal section (plate No. 2 of the series), which will be given in our text.
The velocity of this ship was never intended to be of the highest class, because the possesion of capacity for storing sufficient fuel on board for a voyage to Australia and back, gives a great advantage in making a direct passage without stoppage of any kind usual with other ships of less capacity, and that therefore a less average velocity would answer all calculated purposes. Supposing, therefore, the draught of this ship to be (when loaded and ready for sea) 28 ft., the area of the midship section will be 2,000 ft.; and if we infer that the actual power exerted by the combined engines will be equal to 10,000 H.P.,and further supposing the power to increase as the cube of the velocities, we find, from experience in practice, the velocity under such circumstances will be 17 statute miles per hour. By the same rule we find the paddle engines will give the ship a velocity of 12.55 statute miles per hour, and the screw engines alone will give a velocity of 14 statute miles per hour.
But this supposes no drag to take place from the immersion of paddle wheels in the one case and of the screw in the other. To obviate the retention arising therefrom, it is arranged so that the paddle-wheels may easily detached from the engines, and be allowed to revolve freely in the water.
In the case of the screw, perhaps a more complete scheme has been devised for this purpose.
Two engines, each of 20 H.P. are to be fitted, and which can readily be attached and detached from the screw-shaft at pleasure, a self-acting clutch is also to be fitted to the large screw engines, by which they can be readily disconnected from the screw-shaft. It will then become the duty of the small engines to work the screw at a reduced veolocity equal to that given to the ship by the paddle engine alone. As a recapitualtion of the various steam power to be employed in this gigantic work, we may observe that in all there will be on board no less than twenty-two engines of various powers.
Say, the four engines for working the screw of . . . . . . . . . 1,700 H.P.
Four ditto, ditto, paddle wheel . . . . . . . . . 1,350 H.P.
Two engines for working the capstan, get-
ting up anchors, and pumping out ship, &c., . . . . . . . . 60 H.P.
Two engines for working screw alone, having
separate boilers ans services, . . . . . . . . . . . . . . 40 H.P.
Ten donkey engines for filling up boilers, not
to be used for other purposes, and each en-
gine of about 10 H.P. . . . . . . . . . . . . . . . . . . . 100 H.P.
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Total . . . . . . . . . . . . . . . . 3,250 H.P.
In all 22 engines of the aggreate power of 3,250 H.P.
The large screw engine will be fitted with a separate steam cylinder, by which
it is presumed these large masses can be started and reversed with the
greatest ease and certainty.
In presenting our readers with a series of plates of so interesting a work, we propose, in the course of the present and following numbers of The Artizan, to give a sketch of the origin and progress of the undertaking, as we feel that it is due to the talented designer of this bold experiment in, and gigantic specimen of, naval architecture, as also to those connected with him in practically working out the great problem to be solved, as also to those who, aiding and assisting the undertaking commercially, thus enable the engineering talent of this country to maintain its supremacy over the combined skill and talent of the whole world.
Originality of conception, boldness of design, and combined with the consideration and accurate arrangement of practical details, are but seldom combined in one man; but the name of Brunel has been so often associated with things original, bold, and practical in science, that whether we look to the great works of the father, or the more modern, and, perhaps, more commercial achievements of the son, we must confess to the feeling that whatever money can be provided for, the original mind, talent, enterprise, skill and practical ability of a Brunel can unfailingly work out, however bold and problematical such schemes may at first sight appear.
To Mr. Isambard Kingdom Brunel is due the credit of originating the bold design of which we have undertaken to give our readers a general description, illustrated by a series of expensive copper-plate engravings. It is now twenty years since Mr. Brunel's first Transatlantic steam ship, the Great Western, was designed. It was thought at the time a bold stride to increase the dimensions of that ship by 50 ft. in length and about 8 ft. in breadth over the largest paddle-wheel steamer then afloat, but the prophesied fate of the Great Western was proved to be unfounded and untrue upon her first voyage; and we have seen the progressive increase in the dimensions of our steamships which has gone on during the last few years. The giant of 1838 has become the pigmy in 1856. Omitting the Great Eastern ship, we can compare the Great Western, 236 ft. × 35 ft. 6 in., with the Great Britain, 322 ft. × 51 ft.; the Himalaya, 370 ft. × 43 ft. 6 in., and, lastly, the Persia, 390 ft. &tiems; 45 ft. But beyond these Mr. Brunel's ship shoots far ahead, being laid down at 680 ft. × 83 ft.
Mr. Brunel seems to have determined to settle the question of whether or not steamships are to maintain their well-earned superiority over clipper sailing ships when employed upon world-round voyages, as they have heretofore done on Atlantic, Mediterranean, and other voyages of similar extent. And in looking about for the cause of the failure of the steamers employed in the Australian route to make such voyages in less time than clipper sailing ships or vessels fitted with auxiliary steam power, and also to make such voyages commercially profitable, he saw that the views he held twenty years ago with reference to the Atlantic trade were applicable, in an eminent degree, to India and Australian voyaging, via the Cape, and determined to increase the carrying capacity for fuel to such an extent, as to make his new ship independent of supplies to be derived from coaling depots during her voyage, to which coaling stations the fuel has to be sent by many shps at a vastly increased cost per ton, and is much damaged by the transhipments and breaking of bulk necessary under such circumstances. The estimated quantity of 5,000 to 6,000 tons of coal necessary for the voyage out and home involved other increases of dimensions, calling in turn for the proper proportioning of strength or power to suit these new conditions of things, and admirably does Mr. Brunel appear to have considered the every detail and bearing of the question. And we look forward to the time when the succesful launching of this monster ship will be but the first of a series of triumphs for this great work; and we sincerely hope we shall be one of the first voyagers invited to give the world the best proof of their entire confidence in the skill and talent of the designer — in the excellence of the workmanship and materials of the contractors — in the perfect stafety of the ship at sea — and in the success of the experiment in a practical and scientific point of view.
In our next we shall give, in continuation, a sketch of the progress of the work, and our second plate will exhibit a plan of that portion of the ship containing the engines, boilers, and machinery for driving the screw-propeller. Of the details of these engines we intend hereafter to give minute description, possessing, as they do, many features of interest and novelty, and eminently creditable as they are to the celebrated firm of James Watt & Co., by whom they were designed and manufactured.
In our second plate of this series every dimension is accurately figured upon each part.
Transcribed by Lars Bruzelius
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