FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1910
1910 - 0163.PDF
MARCH 5, 1910. (/JJGHT] THE ASTER FLIGHT ENGINE. A GLANCE at the accompanying photographs reveals what is apparently a twin-cylinder motor of unusual breadth ; in reality the illustration represents a 4-cyl. engine which is remarkably short. The design in question is the work of the Aster Company, and it has been applied to a 12-h.p. model (bore and stroke 80 x 100 mm.) which they have recently placed on the market. There is, as the photographs show, only one crankshaft, and the peculiarity of the system lies in the fact that the cylinders are bored on oblique axes, so that in reality they lie V fashion in pairs; the cylinder casting, however, has the external appearance of a vertical engine. The connecting- rods are coupled in pairs to two cranks, which are set 1800 apart, an arrangement which is analogous to an ordinary 4-cyl. engine. In the case of the Aster engine, however, the sequence of the cylinders is quite different from that of a 4-cyl. engine, for one transverse pair represents cylinders Nos. 2 and 3 on an ordinary 4-cyl. engine, while the other pair represents cylinders Nos. 1 and 4. The firing order follows the usual sequence of a 4-cyl. engine, the impulse being received by the two cranks alternately, as in a 2-cyl. engine. An explosion occurs every stroke, as with a 4-cyl. engine, but the oblique position of the pistons upsets the evenness of the periods between the explosions, that is to say, the dead centre of one piston occurs a little before (exactly 15°) the dead centre of the other piston, which is coupled to the same crank-pin, and there is consequently this difference between the points at which the two explosions take place. The wiring is so arranged that __^^ the firing order di vides the cycle up ^L into the following periods. The first '^3 period is 1800, and represents the transference of working stroke from one cylinder to, say, that immediately behind it in the longitudinal plane. The second period is 1950, and represents the transference of the working stroke to the View of the 4-cyl. Aster. The cylinders are arranged V fashion, and cast en bloc THE ASTER FLIGHT ENGINE.—End and side views of the new motor, which has the appearance of a twin-cylinder engine, but in reality has four cylinders arranged obliquely in pairs. The pistons are connected to a two-throw crank-shaft. cylinder which is diagonally opposite that last in action. It is here assumed that the sequence is being considered in the same sense as the engine rotates, and that the crank-shaft, therefore, has to make up 150 leeway before it brings the next piston into its firing position. The third period in the cycle is another of 1800 because the working stroke merely passes to the adjacent cylinder in the longitudinal plane, but the forth and last period in the cycle is only 1650, inasmuch as in transferring the working stroke diagonally once more to the opposite pair, there has this time been a gain of 150 on the crank-shaft in the operation, and the firing point for that piston will be reached correspondingly early. Although it might be expected that this discrepancy would be noticeable compared with the best results obtainable from a well- balanced 4-cyl. engine of the ordinary type, it must not be overlooked that a 2-cyl. motor is commonly designed to run with extremely unequal intervals, a period of 1800 being followed by another of 5400, and it is as a substitute for the twin-cylinder engine that the model has been designed. A more serious difficulty would appear to be the working of the ignition from a magneto, but even a battery circuit would, of course, require some form of specially synchronised contact-breaker in the primary circuit, in addition to a special spacing of the distributor quadrants. There is also a constructional difficulty in an engine of this type, which might not at first sight be foreseen, and that is the necessity of making provision for the pistons to clear one another when the cylinders are lifted. In this operation the effect is to bring the connecting-rods gradually together like the blades of a pair of scissors, until finally the trunks of the pistons overlap before they can be drawn clear. In order to allow for this, part of 159
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
