244 HALL'S PATENT REEFING PADDLE WHEEL. causes must always be in operation in the commencement of long voyages, when the vessel, being laden with a large quantity of coals, is necessarily deep in the water, and the wheel is consequently more immersed; the results are, increased resistance, increased oblique action, and a diminished number of strokes. The latter cause may operate at any period of the passage. Under either circumstance, it is evident that the engine is incapable of exerting its full power: if, for instance, a pair of engines, making twenty strokes per minute, be constructed of 500 horse power; and if, from either of the above causes, the number of strokes be reduced to ten, which is of no uncommon occurrence, half the power of the engines is lost, and the vessel is placed in the unfavourable condition of carrying engines of a considerable size, weight, and value, with an incapacity of exerting more than half their power. It has been stated, on good authority, that the largest pair of engines now in operation are frequently reduced in their speed from eighteen to six and a half strokes per minute, thus performing the duty of only 195 horse power instead of 540 horse power; and that this reduction of power generally takes place when the greatest possible power is required to contend against the mighty power of the ocean, and to enable the vessel to move, in spite of this resistance, away from the lee shores, rocks, and other dangers, instead of paddling away, nearly in the same place for hours, without making the least progress on her voyage, as is the case with the deeply immersed and unalterable common paddle wheels. 166. Mr. Hall's patent Reefing Paddle Wheel.—To obviate the inconveniences, above mentioned, several patents for a reefing paddle wheel have been successively granted to different engineers; these contrivances have, however, failed, chiefly from the want of simplicity in the machinery for moving the paddles, and the rapid corrosion of the moving parts by sea water. Mr. Samuel Hall, whose talent and ingenuity have been so successfully applied to various improvements in the steam engine, has proposed a simple and HALL'S PATENT REEFING PADDLE WHEEL. 245 effective plan for accomplishing this object, by which scarcely any more parts are exposed to corrosion than in the common paddle wheel, and by which, on the mere application of a hand lever, the power of the engine will, in less than a minute, without regard to weather, withdraw the whole of the paddles from the extremity close up to the boss of the wheel, or to any intermediate distance to suit the immersion of the vessel. This contrivance is not, however, confined to merely regulating the paddles, as above described, but admits of their being withdrawn entirely out of the water, or as nearly so as possible, when desirable to do so-as, for instance, when the wind is so favourable as to render it desirable that the vessel should proceed entirely under her canvas, and that the working of the engines should be discontinued; and, when that is no longer the case, of the paddles being returned to their proper situations in the water, for the renewed operation of the engines. A pair of Mr. Hall's Reefing Paddle Wheels of 14 feet diameter were subjected to experiment nearly a month, on board a new iron steam barge, the "Lee." The barge went from Blackwall to Rochester Bridge in 7 hours and 18 minutes, being empty, and drawing only 2 feet and 9 inches of water. On her return, she was deeply laden, and drew 5 feet 6 inches of water; she performed the same distance in 7 hours and 51 minutes, being, by means of the reefing wheels, only 33 minutes longer in doing so when deeply laden, than when empty. This experiment proves how important it is to employ reefing paddle wheels in vessels destined for long voyages, during which the immersion of the wheels in the water is necessarily subject to great variations of depth. Among the numerous advantages of these wheels, two may be here mentioned: viz. first, the instantaneous manner in which a steamer may, by them, be converted into a sailing vessel, and vice versâ; whereby the whole of the fuel expended during favourable weather is saved, being probably, upon an average, upwards of one-third of the whole consumption; and, secondly, the 246 ENGINES OF THE STEAM PACKET "RUBY." reducing of the time very considerably (one-third, it is supposed, at least) now required for performing long voyages.* The testimony in favour of this contrivance, given by Mr. Hawksley, Civil Engineer, is complete: first, it is extremely simple; secondly, it is strong; thirdly, it is generally applicable; fourthly, it is durable; fifthly, it may be entrusted to the management of men of the commonest capacity; and, lastly, it is comparatively inexpensive. ENGINES OF THE STEAM PACKET "RUBY." 167. Dimensions and Speed of the Engines.—The engraving which forms the frontispiece of this volume represents an elevation of one of the engines of the steam packet "Ruby," copied from Tredgold's atlas of plates. This celebrated vessel was built by Mr. Wallis, of Blackwall, in 1836, from the designs and specifications of Mr. O. Lang, Jun., of Her Majesty's Dock Yard, Woolwich; her engines were made by Messrs. Seaward & Co.; the packet belongs to the "Diamond" Company, and plies between London and Gravesend, between which places it has run four times a day for six months, making 48,600 miles—a feat which had never been equalled; the "Ruby" has, in fact, enjoyed the reputation of being the fastest boat in Europe, and perhaps in the world. The engines of this packet are of 50 horse power each; their weight, including the water in the boiler, is 90 tons, 5 cwt., being about 18 cwt. to the horse power; the diameter of the cylinder, 40 inches; length of stroke, 3 feet 6 inches; number of strokes per minute, 30; diameter of paddle wheel, 17 feet 6 inches; length of paddle board, 9 feet 2 inches, and depth, 15 *The Surveyor, Engineer, and Architect, No. IV. The Author regrets that the limits of this treatise prevent him from fully illustrating this ingenious piece of mechanism. Those who are interested in the subject will be highly gratified by inspecting a beautiful model of it at the offices of the patentee, in King's Arms Yard, London. 66 66 REMARKS ON THE RUBY" STEAM PACKET. 247 inches; dip or immersion, 15 inches. The speed of the 'Ruby" is 13.5 miles per hour, being about a mile more than had been performed by any vessel previously constructed. The pressure of the steam is only 31⁄2 lbs. above that of the atmosphere. 168. Remarks on the "Ruby" Steam Packet. - The following remarks are gathered from the description of the engine of the "Ruby," given in the work of Tredgold. It is a remarkable fact, that this boat has not varied her speed 1-12th of a mile per hour; she has neither increased nor lost her speed; this has been particularly attributed to the use of the patent slide valves on board of this vessel, which after two years' working were found as perfect upon their faces as when first put together. A further proof of their superior working is evinced by the vacuum in the condensers of the engines having never varied 1-4th of an inch, having remained constantly between 28 and 28. The safety valves are arranged on the plan of Boulton and Watt, a plan now generally adopted by the engineers of London; the engine man can open them at pleasure for the escape of the steam, but he cannot load them beyond the weight determined by the manufacturer, viz. 3 lbs. on the inch; and it is remarkable that, with this small pressure, the "Ruby" has attained its great speed, while, in numerous instances, vessels working with high-pressure steam, and with the safety valves loaded at the pleasure of the engine men, have never been able to equal her speed. This clearly proves, what the late Mr. Watt demonstrated long ago, that the most efficient, safe, and economical mode of working steam engines for marine purposes, is at a pressure of 2 to 3 lbs. on the inch. In this and other respects, the 'Ruby" is constructed on principles quite the reverse of those adopted by the Americans, who employ steam of very high pressure, with a very long stroke of the piston. The success of the "Ruby" is partly attributed to a most judicious arrangement in the form and construction of the vessel. From the method of planking which is adopted, 248 REFERENCES TO THE FRONTISPIECE. consisting of three thicknesses of oak placed diagonally and longitudinally, the vessel is completely trussed from end to end, and at once combines strength and lightness in an eminent degree. The form of her bow enables her to cut and divide the water, instead of gliding over it, as in the American vessels, her bow being shaped like a knife, and being as long on the keel as at the water's edge within two feet. REFERENCES TO THE FRONTISPIECE. A, Cylinder. D, Main gudgeon. K K, Side frames. M, Air-pump. N, Feed-pump. OO, Sleepers. a a, Steam nozle and valves. bb, Eduction nozle and valves. c, Steam pipe. d, Throttle valve.' e, Handle and rod of throttle valve. f, Starting lever. g, Spill of steam valve. k, Rod to connect levers. m, Snifting valves. n, Blow-through valve. o, Eccentric rod. p, Eccentric beam and balance. (1.) The general mode of applying the steam in the marine engine, including the action of the cylinder and its apparatus, the beam, the connecting-rod, and the crank, will be readily understood by referring to the figures, and the explanation of them, given in paragraph 145—to which the attention of the reader is particularly directed. The motion of the engine commences at the cylinder A. The |