ISi6.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



301 



Horizontal Water Wheels, esiieciall.j Turbives ; thrir history, 

 tonstruction, and Iheonj. By Moritz Ruhlhas. Edited bj Sir R. Kane. 

 Dublin : Hodijes aud Smilli, 1840 ; small quarlo ; pp. 70. Six lithogra- 

 phic platen. 



Notices of the coastruoti.in and power of the turbines, or horizontal 

 water-wheels, have appeared in this Journal in the volume for 1842, p. 203, 

 and in the volume for 1814, p. 85 and p. 32... The publication of the 

 work before us enables us to give some further information respecting the 

 practical results obiaiued from these machines. 



The present treatise is translated by the editor from the German, with 

 the adilition of some notes and an introduction. The translation was un- 

 dertaken on account of numerous inquiries from millwrights and engineers, 

 addressed to Sir Robert Kane, in consequence of his having directed atten- 

 tion to the turbine in his work on the " Industrial Resource.s of Ireland." 

 He has selected for translation the present treatise by Professor Riihlman, 

 as the most suitable for his purpose: at the same time he gives accounts 

 of several other treatise's on the same subject. From one of these, that by 

 M. Morin, we take what we consider a very important extract, because it 

 exhibits the general practical eft'ects of turbines as determined, not from a 

 doubtful theory, but from actual experience, and because these conclusions 

 are conOrmed by the authority of a commission consisting of MM. Arago, 

 Prony, Gambey, and Savary, appointed by the Academic des Sciences to 

 report on the subject. The following are the genei al results of the investi- 

 gation : — 



1. That the wheels are applicable equally to great and to small falls of 



2. That they transmit a useful effect, equal to from 70 to 78 per cent, of 

 the absolute total moving force.* 



3. That they may work at very different velocities, above or below that 

 eorresponding to the maximum effect, without the useful effect varying ma- 

 terially from that masimuni. 



4. That they may work from one to two yards deep under water, without 

 the proportion which the useful effect bears to the total force being sensibly 

 diminished. 



5. In consequence of the last preceding property, they utilize at all times 

 the greatest possible proportion of power, as they may be placed below the 

 lowest levels to which the water surface sinks. 



6. That thev may receive very variable quantities of water without the 

 relation of the useful effect to the force expended being materially less- 

 ened. 



Kiihlman's treatise is divided into three parts — I, a history and descrip- 

 tion of the turbine; II., rules of construction ; III., the mathematical 

 theory. We shall confine our attention chiefly to the first of these sections, 

 for the " rules" in the second section are derived from the " theory" in the 

 third, which theory, whatever may be its value as a speculative inquiry, 

 does not seem sufficiently well established to satisfy the wants of the prac- 

 tical mechanician. M. Ruhlman's calculation of the useful effects of the 

 turbine is founded on the principle of the Conservation of Vis Viva, aud 

 would perhaps be perfectly satisfactory if that principle held for fluids in 

 motion. But it does not : the theoretical effect calculated from this prin- 

 ciple is much greater than the effect really produced in practice; for it is 

 found by actual experience that a large portion of the force of water in 

 Eiotiou is absorbed by the mutual action of the molecules of water on each 

 other, and by various resistances far too complicated for calculation. It 

 is true that the results obtained theoretically may be modified by the in- 

 troduction of " practice-coefficients :'" but these coefficients, obtained from 

 experiments on one kind of water machines, are not necessarily accurate 

 when applied to another kind. Indeed, Sir R. Kane himself observes in 

 his introduction, that " the action of the turbine, considered as a problem 

 •f hydrodynamics, involves conditions to the discussion of which science 

 in its present state scarcely reaches." The value of the theoretical rules is 

 therefore very doubtful. The most prudent course in this, as all other 

 cases of practical mechanics where the theory is not fully settled, is to 

 trust principally to experience, not neglecting, however, the general sug- 

 jestions obtained from theory. 



To proceed, however, to that portion of the present treatise which is of 

 wore direct interest, we observe that the general result of experience and 

 of all that has been written on the subject tends to show that, of all the 

 forms of the turbine hitherto invented, that by Fournejron is by far the 



most useful, and to this, therefore, we may confine our attention. The fol- 

 lowing is a plan of a quadrant of a horizontal wheel erected on Fourney- 

 ron's principle in a cotton factory, at St. Blasien. The plan is drawn t« 

 a quarter the actual size. 



• From Smeaton'8 fiperimenta (Phil. Traua. 1759) it appears that In ordinary oversUut 

 water-wheels, nearly 80 per cent, of the original moving force U usefully applleJ: (uiJ 

 Jliat in undershot wheels, the useful effect la no more ttian 30 per cent, of the original 

 patrer.— Ed. C.E. and A. loiuaal. 



In order to understand the action of the wheel, the reader must imagine 

 the circles, of which the quarter only is drawn, completed. The machine 

 will then be seen to consist of two parts— an inner wheel fixtd, and aa 

 ouler or larger wheel revolring. The water comes from ihe centre, pro- 

 ceeds along the guide curves F, F, which cause it to impinge directly upon 

 the curved paddles D, D, attached to the outer wheel, which consequently 

 revolves in the opposite direction to the impulse of the water. 



The shaded parts x, x, are stops attached to a drum J J : the object of 

 these stops is to shut ofl' when requisite, the communication between the 

 inner fixed wheel and the revolving one. J J is capable of being raised 

 or lowered by external niaciiinery, and consequently x,jr, descending be- 

 tween the guide curves regulate the supply of water or shut it off allo- 

 gether. 



The next cut is a vertical section of the whole turbine, and shows the 

 method in which the water is supplied to the revolving wheel. 



■■{_J. 



20 



