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difficulty to be encountered. At 10 miles, loose-some mistake in a figure, in the there must be double resistance from experiments. They are so contradictory " twice the number of impinging par in themselves, and so utterly at variance ticles ;" the power must therefore be with theory, established with mathematiagain doubled, resulting in the "qua cal certainty, and practice, as proved by druple ratio."
close observation, and the most elaborate Mr. Booth's experiments 1, 2, and 4, experiments, that I must be excused for confirm the received law; but 3, 5, and taking with distrust assertions in direct 6 present an extraordinary anomaly, for, opposition to my own assent to a Q.E.D., according to these, twice the distance and the authority of such men as Colonel and twice the speed are acquired by a Beaufoy and Mr. Seaward-indeed, of little more than twice the power; and all “engineers and men of science in the 5 lbs., by changing the mode of applying present day.” The resistance to a body the power, become as effective as 16, passing through the water is resolved by under the old system, which his other writers on naval architectureinto three disexperiments confirm. This astounding tinct causes - head pressure, lateral result Mr. Booth infers to be in conse friction, and stern pressure. The first of quence of the loss occasioned by the these, caused by the water impinging the more rapid falling of his weight, or mo bow of the vessel, must necessarily be in tive power, in the one case than in the the ratio of the number of particles im. other; and by changing its speed from pinging, and their velocity, and, of 15 feet in 6 seconds to 7 feet 6 inches in
course, must be quadruple at double the same space of time, he gains in the speed. It constitutes by far the greater ratio of 16 to 5. Now, it is perfectly portion of the whole resistance. Lateral true, as Mr. Booth
says, “ if you in- friction is caused by the water passing crease the velocity of descent, you dimi in contact with the sides and bottom of nish the effectiveness of weight as a the vessel, and will be in direct proporpower, and, carried to the point indicated tion to the number of particles so passby the law of gravitation as affecting fall- ing. By an inspection of the diagram, ing bodies, a weight has no power at it will be found that it constitutes but a all." But what is this law ? "A heavy small proportion of the resistance; the body falling freely will pass through a forms presenting the greatest surface space of 1,208 feet the first second, and for its action, from having a better enthen attain an increased velocity, in the trance, are those that move most easily inverse ratio of the square root of the through the water. Stern pressure height from which it falls: in 4 seconds being the tendency to a vacuum caused it will have acquired 16; in 9 seconds, by the passage of a body through a fluid, 24; in 16, 32; and in 25, the rate of 40 with the fine lines adopted for the after feet in a second. The highest velocity bodies of steamers, and at their slow in the experiments 1, 2, and 3 is 15 feet speed must offer but little obstruction. in 6 seconds, the lowest 7), making A cannon-ball, on first leaving the piece 7+ feet the difference, or one foot and a from which it is discharged, is much requarter per second to be deducted for tarded by it, its motion being so rapid, loss by the increased velocity of descent, that the air cannot rush in with sufficient from the average speed of a body falling speed to fill up the vacuum; but at 10, six seconds. This is hardly sufficient to or even 16 miles an hour, the water account for a gain of upwards of 300 per readily flows in-its ratio, no doubt, will cent! Would a body, falling through a be double at double speed. given space at the rate of one foot and a
Suppose, by way of approximation, quarter in a second, raise a greater weight we divide these resisting powers in the double that distance, the cord attached to following different proportions_head preit passing over a pulley of double size, sure, increasing according to the squares than it would passing through double of velocity, and friction and stern pressure space in the same time, both pulleys in direct proportion, following Col. Beaubeing alike? Or would the difference foy's table of actual resistance at difbe more than the smallest fraction, even ferent velocities. (See Table next page.] although the falling body should be fea At slow speed, it will be seen that friethers, and the one raised lead ?
tion and stern-pressure have a much There must have been some screw greater relative effect than at high, on
6 miles. 8 miles. 10 miles. 12 miles.
0.7802 &c. &c.
the velocity being increased to the prac one, and the remaining tenth for the tical desideratum of 12 miles an hour, other two, approximates very nearly to
the practical results, which it would otherwise be difficult to reconcile. It would thus appear, that “the force or resistance (from head-pressure) is as the quantity of particles struck, and the velocity with which they are struck,” and that friction and stern-pressure are fixed quantities, increasing in a direct ratio.
Having disposed of the “ Theory," I may be allowed a few remarks on the " Practice" as involved in the “improved method of applying mechanical power to steam navigation.”
To drive a boat at any given speed, say from 10 to 12 miles an hour, the calculation in ordinary steamers, is to allow a loss of one-third of the power applied. Let us suppose, however, that Mr. Booth's propeller possesses such advantages as to lose only one-fourth—to give 10 miles speed to the boat, it must therefore go through a space of 66,000 feet in an hour, or 18} feet in a second, which, whether given in short, quick strokes, or long, slow ones, must require about 90 percussions in a minute, 90 x 12} x 67=67500. But he says, the piston of his engine moving at the rate of 2} miles an hour, will give 314 miles speed to his propeller. Take, however, 30 miles speed as the average, and it is obvious that there must be a loss of more than half from the want of resistance; for unless the irregularities are such as to make a tremendous jerking motion, 15 miles is as much as can be expected at any one moment of time, and that subsiding to 8.30 times in a minute, will not be over-pleasant. The piston of an engine of 4 feet stroke moving 24 miles an hour, would give 33 revolutions in a minute; 33 x by 12}, the length of the stroke of the propeller, would give less than 5 miles an hour, whereas 12 would be required; the residuc must therefore be made by the “ concentration of power.” Few engineers will agree with the writer in his principles of concentration. Does he suppose that the power absorbed and concentrated in a fly-wheel is any greater when given out at a single impulse, than if divided into ten ? Or in other words, that any more power can in
any possible way be obtained from the rehead-pressure increasing four-fold, while cipient than is communicated to it? If the other causes of retardation are only this can be effected, we need look no doubled ; the division of nine parts for the further for perpetual motion. If his 200
1 mile. 2 miles. 3 miles. 4 miles. 5 miles.
* Thus, 75 per cent. of 0·2229 for head pressure = 1672 x 4 = 6688
for friction and stern pressure 557 x 2 = 1114 25 do.
horse engine can be made to give out vice. I should like to call the attention more than 200 horse power" by a slow of your scientific readers to the table of succession of rapid strokes,” or in any head-pressure, friction, &c. If the other manner, the effect must be greater principle be correct, the exact proporthan the cause, and perpetual motion the tions may easily be found. I bare not inevitable result. The writer does not the book at hand for references, but I appear to take into consideration the re think “Charnock on Naval Architecsistance and friction that will be opposed ture' will give the requisite information. to the returning frame-work and open
O. B. F. propelling-plate; 10 miles an hour is the speed at which the vessel is supposed to go; say 880 feet in a minute; the
THE JRON STEAMER “QUEEN." stroke must be repeated 33 times x by Sir,- As your valuable publication is 124 = 412, or 1292 feet speed for the almost the only means through which returning propeller : this, too, supposing any works of art, either of merit or each concentrated stroke of 121 feet to otherwise, can be brought fairly before drive the boat 261, in which I apprehend the scientific world, I beg the favour of he will be greatly disappointed : 1292 your inserting the following statement of feet, however, in a minute, on the oc the dimensions and performance of a new tuple ratio, which he must pardon me iron steamer recently started upon the for still believing in, would be no incon Thames. siderable drawback even from an open The vessel I refer to is named the valve-plate.
Queen; and, so far as a judgment may It is unnecessary to dwell upon the be formed of her capabilities from a carepractical difficulties that would be op ful inspection of her, inside and out, and posed to such an application of power. the few trials of speed that have yet been What material could possibly be made to made with her, (more than one of which I stand the shock of the concentration of a have had the pleasure of witnessing,) I 500 horse power into a single impulse of am of opinion that she will fully merit the 5000 ? The best iron, and the most per high name her owners have selected for fect workmanship, are already in requi. her. A more beautiful specimen of a sition for the cranks and shafts of engines light river steamer, whether as regards as now constructed, to meet an uniform design or workmanship, I hare never resistance. What reasonable belief can
before seen. there exist that the quality of the mate The vessel was designed by, and built rial can be so improved, or the quantity under, the immediate superintendence of so increased, and, necessarily, the skill to Mr. Edward Pasco, (a gentleman well forge such masses so much advanced, as known on the river, and of considerable to meet so great a demand for additional promise as a shipwright;) and the enstrength, as the conversion of an uniform gines, manufactured by the eminent enmotion of 500 into one of impulses of gineering firm of Messrs. George and 5000 would require ? The tremendous Sir John Rennie, of Blackfriars. She is friction on a cam-wheel, giving out this 160 feet long, between perpendiculars; power in the space of 1 foot 3 inches 38 of 16 feet 6 inches beam; 8 feet 9 inches times in a minute, must be apparent to deep; and draws about 4 feet 3 inches all; but how Mr. Booth arrives at the water. In her engines there is nothing conclusion that he has not half the resist. new, but they are constructed on certain ance to overcome, unless he intends to known and well-approved principles, monopolize the discovery that the power which have produced a most efficient reof 5 is equal to 16, I am at a loss to un sult; and I feel confident this will be at derstand. That his engine will not be once admitted, by all competent judges, of half the usual height," and his “coals when I state their performance. On of not half the quantity," will be the ne Saturday, (the 6th instant,) her owners cessary result of 5 x0=16.
were honoured by the Lords CommisYour obedient servant, sioners of the Admiralty using her as the
O. B. F. mode of transit from Deptford to Wool. P.S. I have written the above before I wich Dock-yards, when iheir Lordships saw your Number of 16th July. If you were pleased to express, in no measured think it worth insertion it is at your ser. terms, the high gratification they felt on
Mean Vacuum. 11.06. Highest 12-5.
witnessing her extraordinary speed, to of paddle-wheels, 16 feet 6 inches width
at what portion of the stroke the steam is After landing their Lordships at Wool cut off, and that the effect indicated was wich Dock-yard, her owners directed produced at an expense of about 64 cwt. that her speed should be at once tested, of coal per hour, being, I believe, less by putting her in competition with about than the average of steamers of her the fastest, if not the very fastest vessel class. on the River, namely, the Railway. I am, Sir, your obedient servant, This the party in command, (the well
L. P. known Captain Turner, for many years
August 9, 1842. commander of the Mercury,) at once proceeded to do. The Queen met the Railway about three miles below Wool. wich, turned round, and beat her con
6 siderably into Blackwall. She started again with her for Gravesend, at halfpast four, and it was soon evident that
8 the Railway had no chance; but as this was in some measure to be attributed to
9 the number of passengers on board the latter, the Queen went on to Gravesend, with the view of trying the Railway on
10 her return passage, conceiving that, at half-past six o'clock on Saturday evening, there would not be many going up.
11 So, in fact, it turned out; and the people of the Railway, which started from the Terrace Pier, when passing the Queen,
5 lying at the Town Pier, gave her the challenge of—"come on, we are ready
12 for you now.” The Queen started some minutes after the Railway, so as to give her time to call at Gray's Pier ; but
12 when the former got up to Gray's, the latter was about two miles ahead. The Queen then made all haste after her,
5.23 making from 34 to 35 revolutions per minute, and got into Blackwall neck and
5.75 neck with the Railway, thereby establishing, without question, her much superior speed.
6.5 Having stated so much, Mr. Editor, allow me to remark, that I have read,
6 75 from time to time, a great deal about the speed of this and that vessel ; but in no one instance do 1 recollect noticing any
7 statement whereby we might come at the cost of obtaining these high speeds,
7 which, after all, is the question of most interest to the scientific reader. The cylinders of the Queen are 29 inches in
7 diameter, and the length of stroke 4 feet 5 inches; the average number of strokes per minute, 34; pressure of steam in
10.25 boiler, 8 lbs.; the condenser vacuum, cqual 274 inches mercury; the diameter
INDICATION DIAGRAM OF “THE QUEEN," 16TH JULY.
Mean Steam Pressure, 386lbs. Highest 7.25.
head of the lift, by having a small cistern or some other vessel prepared for the purpose.”
PERPORMANCES OP WATER WHEELS.
The Midland Counties Herald contains a letter from "A Miner,” in which, adverting to a statement made at the Institution of Civil Engineers that Wheal Friendship and Wheal Betsy water-wheels were, in July 1841, performing 69, 51, 54, 56, 72, 67, and 57 per cent., or on an average 61 per cent. the writer makes the following remarks :-
“I have been frequently at these mines in the course of the last thirty years, and have paid particular attention to the duty performed by the wheels, in order to make correct calculations for erections of my own; but at no time, could the best of these pumping engines perform 40 per cent. A recent practical trial to a eel, proved that 200 gallons of water cannot be pumped 20 feet high with a 50-foot water-wheel, using 200 gallons to peform one revolution.
« The tables in the Practical Miners' Guide may be depended on, found on page 88, made up as follows, viz. :
18,750 lbs. of water performing a revolution on wheel 46 feet diameter will draw a 12-inch lift 113 fathoms 6-feet stroke. Thus-113 fms. of 12-inch pumps,
lbs. 33,280 x 6 = 199,680
Performed with 18,750 x 46 862,500
About 233 per cent. “I should be glad to know-How the water was measured ?
Particularly the • Old Sump Wheel,' 51 feet diameter, 10 feet broad, the water poured into its buckets 5,632 gallons per minute.
“ The mode of measuring running water by width, depth, and time, is not a satisfactory way. The most correct way for measuring water is to measure the contents of a reservoir in number of cubic feet, When ascertained—First, Fill the same with water, observing the required time by minutes and seconds, which will give the number of cubic feet per minute. Secondly, Work the water down by counting the number of revolutions performed by the wheel until the reservoir is empty, which will give the number of cubic feet to each revolution.
“ The water may also be measured by the contents of each bucket, and counting the number. There is nothing intricate in calculating the real duty of a wheel pumping water: the boxes or plungers applied for that purpose should be in good working order, and the water pumped should not only be measured by the area of the cylinder or piston and length of stroke, but also proved by measuring the stream discharged at the
THE CRANK QUESTION. Sir,--Although I feel much obliged to your correspondent, R. W. T., for saying he does not doubt my veracity, in relating the experiments made by me, connected with the inquiry into the action of the crank, particularly the last experiment; nevertheless, the nature of that experiment, the limitations within which it was confined - the very terms of it rendering a practical trial unnecessary-makes me doubt whether I am much indebted to his kindness for this cour. tesy. The more so, that I find he has not changed some of his bad habits, and does not hesitate, when it answers his purpose, to give garbled extracts from my papers, and make believe he cannot understand me (as I before had occasion to remark), when he thinks it more convenient to do so than to refute my arguments. For example, had he not unfairly stopped short in the extract which he makes respecting the first matter he touches on, it would have been seen that I contended for a loss of power equivalent to 20; and have not, as he alleges, abandoned that point, as untenable. Would it not have been more to his credit, to use his best endeavour to prove I was in error in doing
R. W. T. is beating a retreat, I perceive. He wishes, like some others of your correspondents, when hard pressed, to shift his ground, and to make it appear that there is some misunderstanding between us about the meaning of words. He pretends that we are not agreed on the proper meaning which should be given to the words “ Loss of power," when applied to the mechanical contrivance of a crank. Now, as the concluding part of his letter is altogether confirmatory of my views, it is very necessary, to prevent cavilling about words, to explain, in language which cannot be misunderstood, what my meaning of the term “ loss of power” is; and I shall expect equally as explicit an explanation from my opponent.
Let us suppose two steam-engines, one on the rotative principle, but, speaking theoretically, without friction, the other with a crank, also without friction; and let the boilers and daily consumption of coals be perfectly equal; and let the proportions of each engine (again speaking theoretically) be such that the quantity of work done by each with the given boilers shall be a maxi. mum.
Further, let the work required to be done be of the same description in both cases, and involve a considerable degree of fric.