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Aviation History
1909
1909 - 0742.PDF
NOVEMBER 20, 1909. necting-rods and the big-end ; as but for this rigidity the big-end would be liable to rock upon the crank-pin and thereby interfere with the operation of the engine. The mixture enters the cylinder via the hollow stationary crank- shaft and atmospheric valves situated in the pistons. The con- struction and fitting of these valves shows great ingenuity, which is enhanced by the good workmanship that characterises the construc- tion of the Gnome engine throughout. An accompanying sectional sketch shows the arrangement of one of these induction-valves. The valve, A, itself has a very short stem mounted in a guide provided by a bracket forming an extension of the member, B, which makes the valve seating. Two lugs on the valve-stem guide serve as pivots for a pair of small counterpoised weights, C, the inner ends of which engage with a slot cut in the valve-stem. The object of these weights is to balance the effect of centrifugal force on the valve itself. Centrifugal force necessarily forms one of the most important factors to be considered in the design of any rotary engine. The valve-spring, D, consists of a couple of thin steel strips which are curved upwards at their extremities to partially embrace the balance weights. They are easily detached and replaced. The valve with its seating and attendant parts form a detachable unit. The seating is mounted on the top of the piston by being screwed into a lug which carries the gudgeon-pin. This latter member is, of course, situated inside the piston, and the two parts, when screwed together, clamp the head of the piston between them. A feather-key defines their exact position. Another very interesting p'lint about the Gnome engine is that it has no piston-rings of the ordinary kind, these having been tried and found unsatisfactory in practice. Their deficiencies were mainly associated with difficulty in proper lubrication. Instead of the usual piston-rings there is a com- pound ring of curious construction at the extreme upper end of the piston. The piston-wall at this place is recessed with a rather wide groove, in which lies the cast-iron piston-ring. Surrounding this ring is a thin brass band rolled into an L sec- tion, so that its narrow turned-up edge can engage under the cast-iron ring in order to retain the band in place. The band is, of course, split to enable it to be put in place, and its size is such that its ends just close when the surface of the band lies in contact with the cylinder wall. The split dividing the band is vertical. The action of the band is analogous to that of the leather ring in a pump-bucket; it expands against the cylinder-wall when fluid pressure is exerted on the top of the piston. This is the only method adopted in the Gnome engine for preventing leakage of gas past the piston and it is important to mention that the clearance between the piston and the cylinder-wall is rather large. The piston, like the cylinder, is made of steel. A portion of the lower end of the piston is cut away to clear the connecting-rod. Lubrication on the Gnome engine seems to have been satis- factorily accomplished by the use of castor oil. Farman has been in the habit of using a mixture of castor oil and petrol for this purpose. An objectionable feature of castor oil as a lubricant is the very unpleasant odour which it gives to the exhaust. The Gnome engine appears to be thoroughly adequate in its air cooling ; engines in practical use showing no signs of having been overheated. On one occasion, immediately after Farman had alighted from a flight which lasted for over an hour, we found it possible to touch all parts of the engine with the bare hand without discomfort. Prini and Berthaud. — Two-stroke 4-cylinder water-cooled engine. The mixture is drawn into the crank-chamber from which it is admitted to the cylinders when the pistons uncover the inlet- ports at the end of the stroke. There are of course no valves other PARIS FLIGHT SHOW.—View of the Prini-B^rthatid two-stroke engine, showing two of the copper water-jackets ramoviid to expose the cylinder-casting. As there are no valves the attachment of the copper jacket is considerably simplified. At the top it is merely held down by the ignition-plug. than the slots or ports in the cylinder, which are uncovered or closed automatically by the action of the pistons. Part of the exhaust is allowed to pass around the induction-pipe to warm the mixture. The cylinders are cast separately, and as there are no valve chambers it has been possible to fit a copper water-jacket to each in a very simple manner. These corrugated jacke ts are held down by a flange at the bottom, and by the ignition-plug at the top. Dimensions,—100 mm. by 110 mm. ; weight, 95 kilogs. ; h.p., 50 at 1,400 r.p.m. ; price, 5,000 francs. (The weight includes a radiator.) RULES FOR AVIATION MEETINGS. AT the last meeting of the Federation Aeronautique Internationale, held at Zurich, four rules were drawn up which should form the basis of all rules governing aviation meetings. By his entry for a certain event, a flyer is bound by the first rule to take part in that event, unless, of course, he is prevented from some extraordinary cause. Also no entrant may enter for more than one meeting during the same day or period under pain of disqualification. The entry must be made by the pilot, and he will personally gain all prizes and records. AH prize money and awards must be sent to the winners within fifteen days after the publication of the decision of the organising Committee, which must be ratified by the ruling body in each country representing the F.A.I. The decisions of the organising Committee can be appealed against to the National Club within fifteen days, and that is also the time allowed for entering protests. The last rule provides that the National Club shall enforce penalties against any competitor who makes a false announcement with regard to his performances. It also states that competing machines may bear no other trade announcement than the name of the constructor. "Pilote'Aviateur" Certificates. THE conditions for securing the Pilote-Aviateur certificate of the Ae.C. de France are to be made still more severe. After January 1st nextt candidates will be required to make three flights of at least 5 kiloms. each in a closed circuit. Before each flight the aviator will be required to name his landing place, and he must descend within 150 metres of it. For this certificate, which will constitute a card of identity, there will be no charge. The Ae.C.F. certificate will not be given to aviators in a foreign country represented in the F.A.I, without the authorisation of the national authority, but it will be obtainable in countries not represented in the F.A.I. 744
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