Abbildungen der Seite
PDF
EPUB

MR. BOOTH'S RECIPROCATING VALVE PROPELLERS, AND NEW SYSTEM OF PROPELLING VESSELS.

Mr. Henry Booth, whose name is so honourably identified with the rise and progress of the railway system in this country, has recently been applying his active and sagacious mind to the kindred subject of steam navigation; and the result has been the discovery of what he considers to be an improved method of applying steam power to the propulsion of vessels through water, for which he has obtained letters patent, and a pamphlet now before us, (anticipatory of his specification,) in which the principles and details of that method are very fully, and we need hardly add, very cleverly explained.*

The pamphlet opens with an investigation of the received doctrine that the mechanical power expended in giving different degrees of velocity to bodies propelled through water is as the squares of that velocity. Mr. Booth "demurs entirely" to the correctness of this doctrine. He says it is not at all recognized on railways, where the established rule is, that "if five horse-power will accomplish five miles an hour, ten horse-power will effect ten miles an hour," and so on; and he endeavours to show, both by argument and by experimental evidence, that it comes all of grievous theoretical blundering, that it has been recognised anywhere else. With the high respect which we entertain for Mr. Booth, it gives us great pain to be under the necessity of saying at once that, so far, his pamphlet is a most signal failure. It is evident, in the first place, from his statement of the "rationale of the quadruple ratio," that he does not understand what he has undertaken to refute; and, in the next place, some of the comparative experiments which he cites, are admitted by himself to be entirely in favour of the quadruple ratio, while others are as diametrically opposed to it-a circumstance of opposition which indicates, of necessity, some great error in the conditions of the experiments; for, as he truly observes

The Theory and Practice of Propelling through Water, with Observations on the Comparative Resistance offered by Water to Bodies moving through it at different Velocities, comprising also a Description of an improved method of applying Mechanical Power to Steam Navigation.- By Henry Booth, 46 pp. 8vo. Banes, Liverpool; Weale, London.

"facts in natural philosophy never contradict themselves." If Mr. Booth will read and ponder well the "Experimental Equiry" (1794) of our first authority on this as on other mechanical subjects, John Smeaton, a work which we cannot believe he has ever seen-we are persuaded (such is our impression of his habitual candour) that he will himself acknowledge that he is altogether in the wrong, and in the hope that he will do so soon, and that such will be the happy result of his self-examination, we shall refrain for the present from entering more particularly into his very singular heresy.

We cannot, however, quit the subject -even for the present-without expressing by the way our extreme surprise, to see it asserted by so great an authority in railway matters as the treasurer of the Liverpool and Manchester Railway, that, to double any given speed on railways, all that is wanted is double the power. Seldom has there been a greater mechanical mistake promulgated. If this is to be taken as a sample of the received doctrines on railways, no wonder the received dividends are so unexpectedly, and hitherto so unaccountably, small. It is of the same class of fallacies exactly, as the oft-exploded one in political economy, that the product of 2 x 2 is always, and of necessity, 4.

What Mr. Booth's heresy in regard to the theory of the quadruple ratio has to do with his patented improvements in ship-propelling, he does not explain; and fortunately, perhaps, for the reputation of the latter, it is not easy to discover. In point of fact, there is no connexion between them. The one may be exceedingly erroneous (as we take it to be), and the other not in the slightest degree affected by it.

The patented improvements of Mr. Booth may be described generally as consisting in a concentration of the mechanical power employed in steam-vessels; and this concentration his pamphlet leads us to consider under two heads,first, a concentration of the power exerted by the paddle-wheels; and second, a concentration of the power produced by the steam-engines.

First, then, as to the concentration of the power exerted by the paddle-wheels,

[graphic][merged small][subsumed][graphic][subsumed][subsumed][graphic][graphic][merged small]
[graphic][subsumed]

the following is Mr. Booth's own explanation of the means he has contrived for this purpose :

"The principle, I suggest, consists in a concentration of nearly the whole force of the engine or moving power, into one-tenth or other small portion of each stroke of the piston; and I make use of such concentrated force to effect a proportionably powerful stroke with the propellers; the momentum of the vessel so gained carrying it onwards, through the water, till the next stroke. The moving levers or beams (B), through which the power is communicated, are worked by an engine or engines in the ordinary or most approved way. C No. 1 and 2, figure 1, are cam wheels, which I employ to communicate the power of the engine to an upright lever L, vibrating on its axis (A) at its foot, and connected at the top by rod and crank with the main shaft S, to which the propellers are attached. The crank or short lever, thus fixed to the main shaft inside of the vessel, corresponds in its movements with the propellers, fixed to the same shaft outside the vessel. P is the propeller-one on each side of the vessel-serving instead

of the paddle wheel; the portion of it to which the water offers resistance, and by means of which the vessel is propelled, consisting of a valve plate (V) working on hinges like a valve or door, kept close by a moveable cross-bar, when forced in the direction required to propel the vessel; and, on the return motion opening on its hinge or axis, and yielding to the water, so as to offer little or no resistance; the movement of the propeller or single paddle being vibratory, backwards and forwards, instead of the rotary movement of the ordinary paddle wheel.

"It will be perceived, that when the working beam is in motion, and the cam wheel No. 1 is made to revolve in the direction indicated by the arrow, the cam which occupies about one-tenth part of the wheel's circumference, and which is shaded dark in the drawing, communicates motion to the upright lever L, through the friction wheel F, which moves between and receives its motion from the two cam wheels, and thus causes motion to the crank and main shaft, and consequently to the propellers. The forward or principal motion is effected in onetenth portion of the whole revolution of the cam wheels (or double stroke of the piston),

the cam of wheel No. 1 occupying about one-tenth of the periphery of the cam wheel, while the return motion of the lever L, bringing back the propellers with the valves or leaves open (V figure 5), is effected slowly, by means of the extended cam, on the wheel No. 2, also shaded dark, which moves in the same direction, as indicated also by the arrows. This cam (No. 2) comes into operation when the other cam ceases to act, and occupies about nine-tenths of the periphery of the wheel No. 2. The return motion, therefore, of the lever (L), and consequently of the propeller, is about nine times slower than the primary motion effected by the cam of the wheel No. 1, the engine working equably throughout. The upper end of the lever L, we have stated, is connected with the main crank (M C) which is attached to the main shaft (S), and moves simultaneously, and in the same direction as the propellers, constituting mechanically a lever of the third class. But the crank being only 4 feet in length, to a propeller of 20 or 24 feet radius, the velocity of the extreme end of the propeller-that is, of the closed valve plate or paddle-board, is proportionably more rapid, and being also a great depth below the surface of the water, the effectiveness of the propeller is multiplied in a greatly increased ratio.

"Now, the mode of operation is as follows in the forward or ordinary movement of the engine:-The cam wheels, No. 1 and 2, are moved round in the same direction by cranks and connecting rods, communicating with the reciprocating beam in the ordinary way, regulated by the slow uniform speed of the engine piston, which I will suppose 2 miles per hour. The dimensions of the engine, cam wheels, levers, &c., must obviously vary with the size of the vessel and other circumstances. In this description, I suppose the engine or engines to have a five feet stroke-the cam wheels to be 10 feet diameter each, making one revolution with each double stroke of the engine. The cam attached to the periphery of the wheel No. 1 in the forward movement, extends along 3 feet of the circumference (about onetenth of the whole), and projects 15 inches from the circumference in its extreme action, which is consequently the extent of motion communicated to that point of the lever L, which forms the centre or axis of the friction wheel F. This point is half way between the pivot or axis A, on which the upright lever rests and vibrates, and the upper end E; consequently, the upper end E moves 2 feet 6 inches, while the cam communicates a motion of 1 foot 3 inches to the centre of the vibrating lever. The upper end of the lever being connected with the main crank MC, communicates to it a 2 feet 6 inch

vibrating or bell-crank motion. This crank, or short lever, I suppose 4 feet long, and attached to the main shaft, to which the propellers also are attached (one on each side the vessel), and the propellers I suppose to be 20 feet long from the main shaft to the centre of the valve plates, or paddle boards, or five times the length of the main crank, (10 feet from the shaft to the water, and 10 feet deep in the water); the paddles or valve plates, therefore, will make a stroke of 12 feet, while the crank end moves 2 feet 6 inches in the same direction. Now, this movement or stroke of 12 feet in the water, is effected while the cam wheel No. 1 moves one-tenth part of a revolution, or that portion of the revolution which effects the action of the cam No. 1 against the upright lever L, in the forward movement of the engine; consequently, the propelling stroke of 12 feet in the water is effected while the engine piston moves one foot, or one-tenth of a double stroke. If the piston, therefore, moves at the rate of two miles and a half an hour, the propellers will move through the water at the rate of 24 by 124, or 314 miles an hour; the increase of speed being effected by the quiet and smooth motion of the levers; the centre or bearing point of the lever L moving only 1 foot 3 inches in each direction, with each double stroke of the piston.

"The speed of the propelling valve plate is here stated at thirty-one miles per hour, but it is obvious that this may be varied by varying the size of the cam or the proportion of the levers or cranks; or by modifying the sweep of the cam, the velocity of the propeller may commence at 12 or 14 miles an hour, (a little below the supposed speed of the vessel, and therefore producing no shock), and gradually increase to 30 or 35 miles, and then diminish down to 15 or 20 miles an hour before the end of the stroke.

"Still further, to render smooth the motion of the propeller, a range of springs is placed on each side of the valve plate, to render the shutting action of the plate against the supporting cross-bar smooth and gradual, the springs assisting the opening movement of the valve plate on the return motion of the propeller. Thus, every thing like shock or percussion in the action of the propeller is to be avoided, and a smooth and nearly uniform motion imparted to the vessel.

"It is thus evident that the propelling movement is accomplished in about one-tenth of a revolution of the cam wheel, or one-tenth of a stroke of the engine piston. The duty of the engine during the remaining nine-tenths of the stroke being to bring back, at a slow speed, the propeller with open valve, to keep up the momentum of the heavy cam wheels, and quietly to raise the piston of the pneu

matic cylinder, which, by its descent is to assist the principal movement or rapid stroke of the propeller."―pp. 22—27.

Figs. 2, 3, 4, and 5, are separate drawings of the propeller, shown during the action of the valve-plate, and the mode in which it may be thrown out of gear or put into back gear, either on one side or both sides of the vessel-or it may be thrown out of gear on one side, and continued in gear on the other side-or be put in back gear on one side, and forward gear on the other side, when it is wanted to bring the vessel quickly round; the utility of all which operations will be obvious to nautical men.

"Fig. 2, is a front view of the propeller with the valve-plate closed, (V) the lower edge supported by the sliding cross-bar O. This bar has a motion up and down of about 3 inches, effected by a lever on deck, attached to the bar by two connecting-rods r r. When it is lowered down, the valve-plate is loose, and will move backwards and forwards on its hinge or axis A A, having no power to propel the vessel either backwards or forwards; but when the bar is raised 3 inches, the lower edge of the valve-plate is forced by the water against the cross-bar O, and the propeller comes into action-and it is evident that, according as this sliding-bar is raised at the front or back of the valveplate, the propeller will become efficient to move the vessel either forwards or backwards, which may be done in a second of time at the option of the engineer, on one side of the vessel or both, and either with or withour reversing the engine.

64

Fig. 3 is a side view of the propeller, showing the moveable bar and connectingrod, guided in a slot behind the bottom of the valve-plate-the connecting-rod (r) extending up to the deck, where it is worked by the lever as before explained, being lowered a few inches, when required to throw the valve-plate out of gear, or to allow the valve-plate to pass to the opposite side of the cross-bar, and so become efficient to move the vessel in the opposite direction.

"Fig. 4 is a side view of the propeller with the valve-plate open, and nearly invisible, the edge of it only being seen."

46

Fig. 5 is a perspeetive view of the propeller."-pp. 28-30..

The "great point" which Mr. Booth considers he has here accomplished "is the saving of fuel, and of expense, in the ordinary working of the vessel," for,

"The forward stroke being effected during about one-tenth of the double stroke of the engine, the remaining nine-tenths of each stroke of the engine having only to bring back at a slow pace the propeller with the

valves open, is principally employed in accumulating the reserved power, of which we shall speak hereafter-keeping up the motion of the heavy cam wheels, and thus preparing for the next great stroke of the propellers." -p. 32.

Mr. Booth illustrates this view of the efficacy of his reciprocating propellers by the following instances

"In thus concentrating the moving power into a short interval of time, with afterwards a respite during a longer interval, and so on alternately, we copy the natural movements of those animals whose element is the water. A fish, by the muscular exertion of the tail, is propelled rapidly forward by one strenuous effort, after which the momentum gained is sufficient to keep up the motion till the muscles have recovered their tone for another stroke. The same plan of operation is pursued in a fast-rowing boat where a rapid and powerful stroke is effected with the aggregate power at command, after which there is an interval occupied by the returning movement of the oar, during which the strength is recruited for another effort; the momentum gained, carrying the boat forward in the interval. The principle and general mode of operation which I propose appears thus to be sanctioned by the motion of fishes in their own element, and by the operation of our swiftest boats moved by manual power, in which latter case the alternate effort and relaxation is altogether optional; as in a boat of six oars, instead of pulling all together, the rowers might, if they pleased, pull -two, and two, and two, keeping up, almost without intermission, a multiplicity and continuous succession of small pulls, instead of a comparatively few vigorous strokes, with pauses or intervals between, as experience has proved to be the most efficient

course.

66

Perhaps the best popular illustration of the advantage, and in some cases, absolute necessity, of concentrated power, in the propulsion of vessels through water, may be found in the working of a life boat. These boats are fitted with ten or twelve oars, and their service being required in storm and tempest, every mechanical means that ingenuity and physical strength can supply is little enough for the accomplishment of the object.

Imagine a life boat departing for a shipwreck, three or four miles distant, with a hurricane blowing, as is too often the case, right on the land. The life boat has ten oars, with as many men to work them. Suppose the continuous plan of working to be attempted, with ten men pulling in quick succession, the effort, indeed, is almost con

« ZurückWeiter »