SCIENCE AND FLYING MACHINES

New Zealand Times, Volume XXXVII, Issue 8346, 5 February 1913, Page 8

SCIENCE AND FLYING MACHINES

It took the engineering world a long time to learn that useful practical information could be gained _in a laboratory of applied mechanics, and that the laboratory experiments of ono period become the manufacturing processes and practical applications of tue next. The want' of useful and accurate knowledge in aerodynamics has onlj been felt during the last few years—since the aeroplane became a reality, consequently it is not surprising to find that research work in the laboratory has lagged somewhat behind, and that the practical aeroplane constructor can say with a clear conscience that he owe* little, if anything, to the laboratory experimentalist. How much of the rule-of-thumb of the last few years could have been avoided by guidance from laboratory investigations it is hard to say; probably but little, since tho first year** of mechanical flight have been spent in developing a machine that was able to fly with a fair degree of safety, regardless of efficiency or stability. That state is now past. The work accomplished at the National Physical Laboratory on large-scale apparatus is sufficiently suggestive of improvements when duo regard is had to the principles of similarity in aerofoils; and even if small-scale experiments cannot readily bo applied to the practical problems of design, they illustrate the complexity of the problem, and the curious results obtained on such points as pressure distribution serve to emphasis© the need for further study. The results of recent experiments have been so illuminating that one is inclined to believe that the solution of outstanding problems will rest with the laboratory experimenters. The writer has recently visited two great aeronautical laboratories in Paris —that of the University of Paris, at St. G'yr, founded by the munificence of M. Deutsche de la Heurthe, and under tho capable direction of M. Maurain; and the private laboratory of M. Eiffel, in the .Hug Boilean, Auteuil. As the methods of study in these two laboratories comprise the three ways by which the action of air currents on aerofoils may be studied by the help of apparatus designed on a large scale, it shows the importance attached to laboratory work, oven if it does not point to unanimity as to the best methods of achieving results. In the St. Cyr Institute, which is solely devoted to research, there is a track 400 metres long, along which a car may be driven at a high speed by electric' motors or by the reaction of the propeller of an aeroplane under test, which is fastened on the car. The electric motors are controlled from a cabin at one end of the line, and the car (chariot), with its aeroplanes, traverses the course without an observer upon it, all the necessary data being obtained by automatic apparatus. The braking Is effected by a series-parallel controller in the usual tramway style, so that the operator in the cabin on the top of the laboratory building is able to stop the oar when desired, and from his position he can see the entire track. The measurements of velocity and pressure are made automatically, the latter being taken at various points of the wing surface by the height of liquid in pressure tubes. Thqse manometer tubes are brought down side by side to a single board, and a camera is adjusted to photograph the heights of the liquid at the same time that the velocity is measured. Speeds comparable with aeroplanes in flight aro obtained, if only for a few moments, which is all that is necessary. A dynamometer for measuring the kinetic thrust of propellers is also carried on the car. The car is built of steel in a substantial manner. On calm days when the disturbing effect of the wind is absent this apparatus is used, but a whirling table, 32 metres in diameter, is now.almost completed for indoor experiments. The double arm of the tabic is a. steel lattice cantilever, and the apparatus is in a circular brick building forming one of the group of imposing structures comprising the institute. By the combination of the track and whirling table research can be carried on independently of the weather, and in the central hall or laboratory there is ample accommodation for many aeroplanes and a ma-chine-shop for constructing the apparatus. —“ Kngin eering.”