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Aviation History
1909
1909 - 0031.PDF
JANUARY 16, 1909. THE FIRST PARIS AERONAUTICAL SALON. Continued from page 22, January qth.) ENGINES FOR AEROPLANES. Types. IT is generally said that the development of the motor car engine has been the one factor which has made aero- planes possible. Such, too, is indeed the case, but the truth of the saying applies to generalities only, and to the high-speed internal-combustion engine as a principle rather than as a definite machine. The motor car engine is light for the power it develops, wonderfully light com- pared with ordinary steam engineering practice, but it is not considered light enough for experimental work in these early days of flight. New designs, therefore, are to be seen on every side, and there is hardly an instance in which the motor car type of engine has been closely copied by the manufacturers of aeronautic machines. The one exception that there is happens to be none other than the Wright engine, made by the Bariquand and Marre firm, for it alone has four upright cylinders. All the rest are quite unorthodox, although some, like the Antoinette, have been sufficiently long in existence to have become a well-known type. The Antoinette has its cylinders arranged V fashion, and so too has the Renault, the E.N.V., and the J.A.P., the last named being the only British-built exhibit at the Show. A leading idea which has very largely controlled the design of aero motors has been the necessity of making the engines run properly with only so much fly-wheel effect as they can obtain from the momentum of the propellers. A fly-wheel would in itself be regarded as so much useless weight on a flying machine, and makers have in consequence felt called upon to dispense with it, at any rate at the present time. The propeller, mounted direct on the crank-shaft, is doubtless a fair substitute, but one driven through a transmission-chain cannot very well have any useful effect in such a capacity, owing to the slack of the chain intervening at the moment when the stored-up energy, represented by the momentum of the fan, is to be returned to the assistance of overcoming the inertia of the engine's moving parts. It is in order to overcome this initial difficulty that the majority of aero motors have a large number of cylinders, the object of this being to spread the impulses as evenly -as possible over the two revolutions which go to com- plete the Otto cycle. In the larger Antoinette engines there are as many as sixteen cylinders, but the more usual number is eight for engines of this pattern. Such a number gives a very even turning moment on the crank-shaft, and collectively they occupy but a moderate amount of space when arranged in this way. Economy of overall length is, of course, a valuable feature in a light engine, because a long crank-shaft will not only be heavy in itself but will need a large number of bearings to keep it from whipping, and these in turn will involve a big crank-chamber. It is very easy to understand, therefore, why an engine with radial cylinders should suggest itself as a desirable basis for the design of an aerial motor, inasmuch as with such an arrangement both the crank-chamber and the crank-shaft are utilised to their fullest extent. This type has been developed in the Clement-Bayard, Gnome, Farcot, and Gobron-Brillie engines, but not one of these four but has been modified in other directions as well. The Clement and the Farcot are arranged horizontally, the Gnome is a rotary engine—that is to say, its cylinders revolve bodily about a fixed crank-shaft—and the Gobron, instead of having its eight cylinders arranged radially in one plane, has them arranged in pairs, so that they form a cross in appearance. The Gobron engine, it may be mentioned here, has sixteen pistons in its eight cylinders, working on the usual Gobron principle. Other makers who have favoured the radial principle have been deterred from adopting it completely by fear of lubrication troubles in connection with those cylinders which are inverted, and this has, of course, in part accounted for the horizontal disposition of two of the engines mentioned above, which are in other respects of the pure radial type. In order to get over the difficulty of having inverted cylinders, while at the same time retain- ing certain advantages of the radial principle, M. Esnault Pelterie has adopted a design in which those cylinders which would ordinarily be inverted in such an engine are transferred en bloc to a position above the crank-chamber. Here they occupy a parallel plane, and assume positions which are midway between the other cylinders; they thus differ essentially—though not in effect—from engines PARIS AERO SALON.—View, from beneath, of the Antoinette Monoplane, showing the lattice-girder frame, which carries the tubular condenser near the front end. 33 B 2
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