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Aviation History
1924
1924 - 0445.PDF
JULY 10, 1924 MILESTONES IN THE DEVELOPMENT OF THE METAL AIR-SCREW THE following brief and scattered extracts, which have been submitted to us from the correspondence and other documents of the Metal Air-screw Co., Ltd., covering a period of seven years, will, perhaps, record in as few words as possible, the story of the progress made in the development of the metal air-screw during that time. Starting with December 14, 1917, the Air Board wrote to Mr. Henry Leitner—who, in conjunction with Dr. Watts, is responsible for the production of the now famous Leitner-Watts metal air-screws—as follows :— . The first propeller has now been spun with very satisfactory results. The propeller was designed to run at about 65 h.p., and was run at 75 h.p. for half an hour without showing any signs of fatigue, this is satisfactory when one remembers that the majority of metal propellers fail by fatigue at the root after about two minutes' run. . . ." Then, in another letter from the Air Board, dated June 17, 1918, it is stated :— " . . . The first (metal propeller) ran for 30 hours at 1,150 r.p.m. on an engine mounted on a fuselage in the open ; the propeller was then examined and showed no signs of any creeks or opening joints. The result on the whole is very satisfactory. Technically, we may, there fore, say the proposition is proved. We then come to an extract from a letter to Mr. Leitner from the Ministry of Munitions of War, Air Group (Technical Dept.), dated August 21, 1918, which runs as follows :— " The other of the two propellers which had run a 30-hours' test, was spun at Farnborough ; it was run up to 1,635 r.p.m., at which speed it was absorbing 340 h.p. This power being the limit which could be obtained at the Roya! Aircraft Establishment, we were unable to carry out our intention of breaking the propeller." The following year, in 1919, the Metal Air-screw Co. was incorporated, and commenced operations in 1920, when a considerable amount of research work was carried out, mainly in connection with detachable blades and hubs, which enabled propellers to be made up with two, three or four blades, adjust able as to pitch, in lieu of the integral complete two-bladed propellers. The first of this new type was supplied to a " Bristol Tourer " (240 h.p. Siddeley " Puma"), a report on which, dated October 15, 1920, runs thus :— NOT FOR LIGHT 'PLANES ! A Leitner-Watts metal airscrew (for Rolls-Royce " Condor III " engine), 16 ft. in diameter and 16 ins. width of blade. A HYDRO-GLISSEUR FOR INDIA : The above craft was designed by Flt.-Lieut. O. G. Lywood, O.B.E., for H.H. the Nawab of Bahawalpur, India, for irrigation work on the Sutlej River. The engine, a 240 h.p. Siddeley " Puma," drives a 10-ft. Leitner-Watts metal propeller. With 16 passengers a speed of 30 m.p.h. has been made, and with half this number speeds up to 50 m.p.h. are possible. 445
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