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Aviation History
1954
1954 - 3051.PDF
702 Fig. 2 left) Cayley's light wheel for aero plane undercarriages,the forerunner of the bicycle wire wheel. Fig. 3 (right) Solid of least resistance — a sketch by Cayley—with, below, N.A.C.A. aerofoil 63A016-LB N-0016. SIR GEORGE CAYLEY . . . model glider, with an adjustable tailplane and a movable centre of gravity, to test his results.* , In this paper Cayley briefly touches upon the helicopter, the principle of which he demonstrates with a model using two sets of contra-rotating airscrews made from birds' feathers. "For the mere purpose of ascent this is perhaps the best apparatus," he declares, "but speed is the great object of this invention, and this requires a different structure." He discusses the problem of the lateral and longitudinal stability of a fixed-wing machine and "aided by a remarkable circumstance that experiment alone could point out," shows that at very acute angles of incidence the centre of pressure moves considerably in front of the centre of gravity of a wing. This was the first statement made of the centre-of-pressure movement. Light construction, light engines, and minimum forward resist ance were the key features of all Cayley's ideas about heavier- than-air craft. "In thinking of how to construct the lightest possible wheel for aerial navigation cars," he wrote in 1808, "an entirely new mode of manufacturing this most useful part of locomotive machines occurred to me—vide, to do away with wooden spokes altogether, and refer the whole firmness of the wheel to the strength of the rim only, by the intervention of tight cording." In a later paper he pointed out that the wheel was an incum brance during flight, a cogent reason why it should be as light as possible. Cayley's next papers appeared in the famous Phil Mag. in 1816. In them he discussed airships: "A globe is by no means the best shape for obviating resistance; a greater extension in the line of its path, with a corresponding diminution in the section perpendicular to it, may be adopted with great advantage." In his notebook he made a sketch of what he called "the solid of least resistance" based on the measurements of the trout. Von Karman, in his Aerodynamics, draws attention to the astonishing fact that Cayley's outline "almost exactly coincides wim certain low-drag airfoil sections." The figure shows Cayley's sketch and his points superimposed upon the N.A.C.A. aerofoil section 63A016-LB N-0016. In his paper of May 1816 Cayley proposed an airship 432ft in length with a total lift of 163,000 lb. He allowed a weight of 160 lb/h.p./hr for a steam engine with coal and water, "and as die water is a considerable part of the whole, and can be recovered by permitting steam to pass within the double coats *Since this lecture was prepared, these experiments have been analysed by A. H. Yates ("Flight," October 22nd, 1954). He draws attention to the surprisingly good agreement of Cayley's results with modern theory as given by Flax and Lawrence at the 1951 Anglo- American Conference. Fig. 4. Sir George Cayley's designs for an "aerial carriage." FLIGHT of the balloon and to be thus exposed to so extensive a cooling surface it is probable that/200 lb per horsepower will be more than sufficient for working twelve hours without any further supply of water or fuel." This was a remarkable suggestion for water recovery in air ships. He had suggested an inner skin of oiled silk to conserve the hydrogen and lessen the danger from accidental damage to the outside skin. Cayley calculated the speed at 20 m.p.h. and the range in calm air, carrying 50 men, to be 960 miles. In his 1837 paper in the Mechanics Magazine he discussed other means of propelling an airship. One of these is of present- day interest: "Communicating centrifugal force to air by means of a hollow drum and fans by the steam engine is another means of getting a propelling power conveniently applicable in every direction that may be required; for by having a movable mouth piece, from which the air escapes, the re-action will always be in the opposite direction." Shades of the turbojet! One of his more remarkable papers appeared in 1843. In it Cayley outlined what would now be known as the convertiplane. There were revolving blades for the take-off and airscrews for horizontal flight: "The first may be termed the elevating fliers, to distinguish them from the two smaller ones, set at a very different angle with their axis, and used for propelling the machine, when the others are stationary; both sets will be put Jttecfcamcjj* 4ttaga?me, 2/3 MUSEUM, REGISTER, JOURNAL, ANL- GAZETTE. •No. 1026.] SATURDAY, APRIL 8, 1843. [Price M. SIR GEORGE CAYLEY'S AERIAL CARRIAGE. Pig. I. Kg. 2. xxxrm.
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