Variable Gear Research Articles

The Effect of Variable Gearing on Aeroplane Performance

It has been shown that considerable improvement may be made in the performance of an aeroplane by the use of an airscrew, the pitch of which can be varied. The matter was discussed by Mr. H. A. Mettam in R. and M. 577, Part II. There are, however, certain pratical drawbacks to the use of a variable pitch airscrew. Such an airscrew is expensive to construct and probably more liable to breakage or derangement in flight than the ordinary type. It also imposes on the pilot the necessity of making constant and accurate use of the variable pitch control, if the full advantages of the system are to be obtained.The present writer considered, therefore, that it might be worth while to inquire whether a similar improvement in performance could not be obtained by other and simpler means, namely, by the use of variable gearing between the engine and airscrew (the latter being of the usual fixed pitch type). The calculations have been made for the same machine as was used to illustrate R. and M. 577, the S.E.5 with Wolseley Viper engine. As in the variable pitch airscrew calculations, the weight has been increased from 1,976lbs. to 2,000lbs., thus allowing 24lbs. for the weight of the gearing.

Societies and Academies

DUBLIN. Royal Dublin Society, December 20, 1910.—Mr. R. Lloyd Praeger in the chair.—Dr. J. H. Pollok: The vacuum-tube spectra of the vapours of some metals and metallic chlorides (part i.). By the use of a new form of vacuum tube, made entirely of quartz, which the author has recently devised, he can readily obtain photographs of The whole of the vacuum-tube spectra of the vapours of metals and metallic chlorides. In the present paper the author gives a description of the quartz vacuum tube and photographs of the spectra of the vapours of mercury, zinc, cadmium, arsenic, and antimony, together with photographs of the spectra of their chlorides, under varying conditions. The vapours of the metals and their compounds, so far examined, show substantially the same line spectrum in the vacuum tube that they do when metallic electrodes are sparked in air. When a condenser is introduced in the circuit, the metal and its compound show precisely the same change of spectrum, which would seem to indicate that the changes take place in the vibrating atom. If a large amount of vapour of the chloride is present without a condenser, bands are seen in addition to the line spectrum of the metal, and these appear to be due to the particular compound present, and must therefore be connected with the vibrations of the molecule.—Dr. G. H. Pethybridge: Considerations and experiments on the infection of potato plants with the blight-fungus (Phytophthora infestans) by means of mycelium derived direct from the planted tubers. The theory recently advocated by Massee, that the potato crop becomes attacked with the “blight,” not by means of the “spores” of P. infestans, but by means of the mycelium of this fungus, which, after lying dormant for a long period, passes from the planted tubers into the nearly full-grown stalks, is criticised, and it is pointed out how difficult it is to reconcile this mode of infection with the well-known facts of the disease. It is shown that, owing to the absence of controls, the experimental evidence on which the theory is based is quite worthless. A repetition of the experiments, carried out by the author with the necessary controls, gave results exactly the opposite to those on which the theory is based.—Rev. H. C. Browne: Some suggested improvement in epicyclic variable gears. The improvement applies specially to the modern bicycle, and consists in effecting the complete separation of the epicyclic train from all the moving parts on the middle speed, so that the friction is reduced to the same amount as if the machine were a single-geared machine, i.e. so that there is no movement except that of the ball races at each end of the axle. The high and low speeds are also improved by getting rid of all friction due to over-running pawls or the unnecessary rubbing of parts. The middle speed is produced directly by the engagement of the driving member with the hub, the epicyclic train being completely detached and in no contact with any of the moving parts. The linking up of the gear train with the drive for the high and low speeds is effected in a simple manner by the use of spring trigger pawls. Some care has been given to the construction of the epicyclic train so that it may be a proper mechanical unit in itself instead of being a somewhat loose assemblage of wheels. With this object, the wheels of the train are provided with friction discs reaching to the pitch lines, and the friction between the elements of the train is thereby reduced to rolling friction.

On Vertical Compound Engines Fitted with Correy's Variable Expansion Gear

On Vertical Compound Engines Fitted with Correy's Variable Expansion Gear