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Aviation History
1914
1914 - 0341.PDF
on ball bearings capable of taking thrust as well as radial load. The outer rim of this ring is constrained to move within curved guides formed on or rigidly attached to the outer casing. Thus, as the cylinders and casing rotate about the central shaft, this inclined ring is also caused to move with them, and in so doing the outer rim of the ring oscillates to and fro in a longitudinal plane con taining the axis of rotation. The travel of the piston is, therefore, governed by the longitudinal displacement of the inclined rotary disc during its revolution. The makers of this engine desire that the motion of this ring should not be confused with that of the mechanism known as a " wobble gear." It will be seen from the accompanying drawing that the cylinders are " off-set" with respect to the outer universally-jointed end of the connecting rods, the object of this construction being to partially counteract the effects of centrifugal force upon the pistons. At the propeller end of the engine is situated the valve operating gear. The exhaust valves are operated by rocking levers and push rods, and the inlet valve directly by cams formed on a sleeve, mounted on ball bearings, concentric with the stationary central shaft and driven by planetary gearing carried by the casing to which the propeller is attached. The inlet valves are provided with counter-weights to balance centrifugal force, but the centrifugal force assists in closing the exhaust valves. The stationary central shaft serves as a conduit through which the lubricating pipes to the various parts are carried and also for the mixture from the carburettor to the cylinders. It will be seen that orifices are formed in the circumference of this shaft in the vicinity of the inlet valves, so that as the engine rotates and the inlet valves open in sequence, the mixture from the carburettor is drawn through these orifices into the various cylinders. The lubrication to the various parts is under pressure provided by a Bosch special three-throw pump, and a Bosch magneto is fitted at the end remote from the propeller—the leads to the plugs being carried in tubular rods, that also serve to bolt the parts in position, from a distributor plate that rotates with the engine. As we remarked in our issue for the 14th inst., the advantage* of this construction lie in the low resistance offered to forward motion through the air—since its shape readily lends itself to the applica tion ol a streamline covering ; while the power utilised in rotating the engine is reduced to a minimum value ; and since the effects The 40 h.p. Stat ax air-cooled rotary engine. produced by centrifugal force, that have proved to be so extremely detrimental to engines of a similar type in the past, have been, to a great extent, eliminated, there would appear to l>e great possibilitio in the future for these engines. Tests made at the makers' works arc stated to have deroonstiaied that the efficiency and reliability are all that could be desired, while the weight per horse power is also quite satisfactory. It will be interesting to hear of performances made under flying conditions. A 10-cylinder too h.p. model is now under consideration by this firm, in which a piston valve will replace e;ich pair of inlet and exhaust valves. ® ® ® ® RUST-PROOF STEEL FOR AIRCRAFT. AN exhibit of considerable interest to aeroplane constructors in general, and to manufacturers of hydro-aeroplanes in particular, was that of Messrs. Thomas Firth and Sons, of Sheffield, which was located on the Sopwith Aviation Co.'s stand. This well-known firm of steel makers have already an extensive market for their ordinary steels in sheet and bar form amongst aeroplane manufacturers, of whom Messrs. Sopwith may be specifically mentioned. These steels, of which there are many grades to suit the manifold uses to which they are applied, range from mild steel sheet of 26 tons ultimate tensile strength and 18 tons elastic limit with an elongation of 30 per cent, in two inches to a high tensile steel of 987 tons ultimate strength, 95*3 tons yield point, and 10 per cent, elongation in 2 ins. when heat treated. All of these materials may be readily machined and bent cold to sharp angles, and when such is likely to be necessary may also be welded, as the many samples of work exhibited bore ample testimony—several specimens being of very intricate shape, and others having been bent double and doubled a second time without showing any signs of fracture or damage. But a special feature of this exhibit, and one for which there is an undoubted future, was their new rust-proof steel. Three specimens of steel immersed in sea-water were shown on the stand—a 30 per cent, nickel steel (which has hitherto been considered as rust-proof), a mild steel and a sample of rust-proof steel—but whereas the two former were covered with rust, the latter was as clean as when first put in, a month back. This property of resisting corrosion is inherent in the metal, and is not due to any coating or after treat ment to which it may be subjected. The steel is a high tensile air- hardening material, and may be heat treated to give tensile tests ranging from 30 to 100 tons per sq. in., with correspondingly high yield points. The physical tests recorded by the manufacturers indicate that, in this respect at least, it is quite comparable to the more usual grades of steel. In its natural state all the grades are so soft that they can be readily machined, and may also be die or drop forged or worked cold, without fracture—one specimen of thin malleable sheet had been bent double, and then doubled again. The steels will acety lene weld with difficulty, but as where such a process is resorted to in aeroplane work, the weld is used lor locating the part, and is not usually subjected to stress, and because the welded joint would be likely to corrode at the weld, there is no point in adopting this pro cess. The manufacturers, therefore, suggest that the parts should be brazed, as this process would enable the rust-pioof qualities of the joint to l>e retained. Its usefulness may be illustrated by a short catalogue of the parts to which it may be applied. This includes—clips, lugs, brackets, engine plates, engine valves, strainers, complete pins and bolt* ; and we understand that it is hoped to pUce a wire upon the market which will lie suitable for such purposes as bracing very shortly, while no difficulty is anticipated in the production of stranded cables having an ultimate tensile strength of over 100 tons per sq. in. It should hardly be necessary for us to emphasize the importance of this new development, as many instances will recur to the minds of our readers where it might be advantageously substituted for the non-corrosive metals and wood that are now employed—some of which are suggested above—and quite apart from the greater pre ference that must be shown for a rust-proof steel than for the ordinary steels for parts where the latter are already used ; and, in the event of steel tubing becoming commercially possible, as we have reason to believe it is, its utility will be still further greatly enhanced. 8 ® ® ® AERONAUTICAL SOCIETY OF GREAT BRITAIN. Official Notices. 1. Elections.—Members: Capt. W. L>. Beatty, R.E., and G. K. B. Elphinstone. Assoc. Members: F. D. Brwoker, A. E. Steele, and C. H. Vickers. 2. Meeting.—The tenth meeting of the present session will be held on Wednesday, April 1st, at 8.30 p.m. Messrs. B. C. Hucks and E. Gordon Bell will read a paper, to lie followed by a di5Cussion, on "Three Years' Flying Experience." Members are reminded that, under the rules, they may introduce visitors to general meetings. Tickets for visitors, not introduced, may be obtained from the Secretary, II, Adam Street, Adelphi, W.C. B. G. COOPER, Secreary. 341
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