832 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



QAl'GVST, 



mass of fluid, and consequently produced, unabridged, their legiti- 

 mate effects; while those on the other wheel — unusually small 

 (', or ^) as their number was, compared to those on the wheels of 

 steamers — -following so quickly in the wake of one anotlier, tlirew 

 it into an u])roar, causing eddies, ivhirlpools, and counter currents, 

 and thus interfering with each other, necessarily produced inferior 

 results. 



We thought 8 of fig. 4 would be equally valuable as 21 of fig. 3, 

 but the construction of our wheels prevented us from instituting a 

 series of similar comparisons. 



The numl)er of paddles now employed is, generally, greater than 

 formerly. For large vessels, 28 are usual; some have 24, and 

 others 32. The English rule, said to be a good one, is adhered to 

 by many American engineers, except when circumstances require 

 a deviation. By it, there is a paddle for every foot of a wheel's 

 diameter, which makes them stand 3 feet apart; there are boats 

 in uhich tliey occur every 2 feet. 



One object of their multiplication, is to equalise the jar of their 

 striking the water, by increasing the number of the blows. With 

 tiie same view, they are often split through the middle, lengthwise, 

 and the inner half — that next the shaft — removed to 

 the opposite side of the arm, as in the end view, fig. 

 26, thus doubling, in a manner, their number. All the 

 British steamers have their blades thus arranged. 

 The Hermann's 28 were thus made into 56; their 

 efficacy was found to be reduced about 9 per cent. 

 The value of their upper or inner halves has been 

 ascertained to be about the same, for, when wholly 

 removed, the lower portions have proved within 10 

 per cent, as effective as before. The blades of the 

 United States are split, and disposed as in the figure. 

 The ti-ue principle of breaking the jar of paddles 

 striking the water, seems to me to be indicated in 

 Fig. 20. the blades 4, 5, 8, 9, 10, 14, 15, 21, 22, 23, 24, 25. 

 Had the attention of engineers been led to it in the 

 early days of steaming, the popular jilan of avoiding the evil at 

 the expense of a greater, would not have been sanctioned ^o long. 

 I observed the blades of tlie last-named steamer, a week after 

 her recent return from Europe. Seven were submerged, or fourteen, 

 if those on both sides of the arms are counted. She sailed on the 

 4th inst., for New Orleans with 8 (or 16) under water. The Che- 

 rokee left on the 1st inst., for Savannah, with si.r of her undi\'ided 

 blades below the surface. The Washiiiyton came in on the 6th inst., 

 from Bremen, with ^ii'e similar ones fully immersed on each side — 

 four full ones and the halves of two others. The largest of our 

 Sound and River boats have equal, if not greater numbers under. 

 Tlie l^undcrijllt, 1,200 tons, has^^ue, or ten halves, immersed in each 

 wheel, when lying at her dock, and without passengers on board. 

 The Isaac Newton, 1,200 tons, has similar wheels, and the same 

 number of blades under water at once. 



As sea steamers have little occasion to go stern for- 

 wards, the backs of the acting faces are occasionally 

 di-essed off, as shown by the outline of fig. 27. As far as 

 the lower, or dipping, parts are concerned, this is an ad- 

 vantage; but, from the preceding experiments, it is seen 

 how much more beneficially such blades would act, were 

 those parts brought to a knife-edge, and their sections 

 Fig. 27. bounded by the dark part of the cut. 



Arms of Wheels. 

 The practice of making the arms of paddle-wheels of uniform, 

 (0- nearly uniform, dimensions throughout, is also wrong. They 

 may, without diminution of strength, be reduced towards their ex- 

 tremities, and ought to to be, since every inch of surplus material 

 submerged in them, detracts from the work done by the blades. 

 They should taper outwards, as Nature tapers tlie radial ribs in 

 her propellers. 



Coating Paddles with Materials that Repel Water. 

 If any substance can be found, durably to prevent ])addles from 

 being wetted, they would then carry over less water with them. 

 ^Ve coated one set with grease (suet), and, while the water 

 streamed uniformly over the faces of others, it adliered only in 

 narrow streaks to these. 



The lessons which the foregoing experiments teach us are: — 

 That, to render jiaddles oi^ steamers more effectual, they ought 

 to be fashioned, as far as circumstances sanction, after models fur- 

 nished by Nature, so as to conform to her general practice of con- 

 tracting surface when resistance is of little avail, and extending it 

 when the latter is greatest — to give the largest portions of blades 

 the longest strokes. 





That the fewer the jiaddles on a wheel the better, provided one 

 be ahv.ays kept in full ]day; — and hence, that it would be more ad-f 

 vantageous to point, or fork them, as pro|)Osed, to evade the jar o 

 their striking on tlie surface, tlian so perniciously to split and mul- 

 tiply them, as the popular practice is. 



That smooth and thin metallic plates should be substituted for 

 the usual massive, water-soaked planks. (At present, perhaps, 

 nothing better than boiler-plates, galvanised, could be adopted). 

 That holt-heads, nuts, cleats, straps, and every other projection, 

 upon, or about, them, should be provided against. That the arms 

 of wheels ought to be reduced at their outer extremities, and the 

 immersion of all superfluous material carefully avoided. That, 

 when wheels require balancing, or their momentum to he increased, 

 the weights to be attached to the arms above the surface of the 

 water. 



To coat paddles, and parts that plunge with them, with varnish, 

 or other substance that repels water, that tlie fluid, instead of being 

 dragged up in volumes by them, may roll from them, as from the 

 backs of diving birds. 



Some persons smile at the idea of machinists studying nature; 

 and such, on perusing the preceding suggestions, will deem it a 

 sufficient reply, to remind the proposer, that steamers are not 

 blackfish, nor paddles salmons' tails, nor petrels' feet. 



But minds differently organised, think a glance into her work- 

 shops is never amiss, and that the longer the visit, the better for 

 the visitor, since there is no art or contrivance, (and it is certain 

 that, through eternity, there never can be one), which has not its 

 pi'ototype in her collections. If we find them not, it is because of 

 inattention, or of an imperfect acquaintance with her stores. Per- 

 haps we know not at which of her ateliers to inquire, or are not 

 prepared to appreciate specimens laid before us when we enter. 



It would be wrong to close this paper, without acknowledging 

 many obligations to Mr. John Bell, of Harlem, by wliose assistance 

 the e.xperiments were conducted; a gentleman whose judgment on 

 general mechanics is not surjiassed; and to Mr. Mott, for the use 

 of a boat, and facilities for making the various paddles tested; to 

 Messrs. Morris and Cummings, also. 



Mr. Bell has matured a subtitute, which he proposes for paddle- 

 wheels, consisting of two reciprocating arms on each side of a 

 vessel. At their extremities are folding blades, or vanes, which 

 open when sweeping in one direction, and close in tlie other. He 

 dispenses with the cumbrous paddle-boxes, and leaves the deck 

 nearly clear; — at the same time increases the sweep of the blades 

 beyond what is practicable with wheels, by simply ele\ating (on 

 framework resembling that of beam engines) the points of their 

 suspension. 



A^ote. — Since the above paper was written, I have seen in the 

 Journal of the Franklin Institute for February, 1842, (3rd series, 

 vol. 3, p. 102), an extract from the Civil Engineer and Architect's 

 Journal, for October, 1841, by which it appears that Mr. Reniiie 

 was led. by his experiments, to substitute the diamond-shaped 

 paddle (fig. 8) for that of the ordinary form. It is there stated 

 that, "after a great variety of experiments, he found that a paddle- 

 wheel of one-half the width and weight, and with trapezium floats, 

 was as effective in propelling a vessel as a wheel of double the 

 width and weight, with tlie ordinary rectangular floats." This 

 agrees very well with my own results. Mr. Rennie states that 

 the Admiralty had permitted hini to fit H. M. ship African with 

 these wheels, "and he had perfect confidence in the success of the 

 experiment; but I have not been able to find any account of the 

 results of this trial upon a large scale. 



Measures have been taken to secure by patent, the improvements 

 developed by the preceding experiments. 



ON AVATER-WHEELS WITH VENTILATED BUCKETS. 



On Water-Wheels with Ventilated Buckets. By Williaji Fair- 

 bairn, Esq. — (Paper read at the Institution of Civil Engineers.) 



Since the time of Smeaton's experiments in 1759, little or no im- 

 provement has been made in the principle on which water-wheels 

 have been constructed. The substitution, however, of iron for 

 wood, as a material for their construction, has afforded oppoi'tuni- 

 ties for extensive changes in their forms, particularly in the shape 

 and arrangement of the buckets, and has given, altogether, a more 

 permanent and lighter character to the machine than had pre- 

 viously been attained with other materials. A curvilinear form of 

 bucket has been generally adopted, the sheet iron of whish it is 

 composed affording facility for being moulded or bent into the re- 

 quired shape. 



