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Aviation History
1909
1909 - 0192.PDF
APRIL 3, 1909. with the realisation of such a wholly satisfactory result, but although it is mainly on the score of smooth running and simplicity that the two-stroke engine aims at gaining its laurels, there is, or at any rate there should be, a very appreciable increase in the power available from a given weight. In the case of the new N.E.C. aero-motor, the manufacturers state that they have secured about 25 per cent, more horse-power than they have been accustomed to obtain from four-stroke engines of the same dimensions. All the types which have been mentioned hitherto ibelong to the same main category of stationary engines, that is to say engines which have their cylinders and base- •chamber rigidly supported on the frame of the flyer while their crank-shafts revolve to operate the propeller. There is, however, the opposite principle to this, viz., the system in which the crank-shaft is held stationary •while the cylinders revolve round it. Two main advan- tages are claimed by the adherents of this method of operation, one being that use is made of the otherwise • dead weight of the cylinders by virtue of their fly-wheel •effect when revolving, and the other claim is that, while revolving, their passage through the air creates a sufficient cooling effect upon the walls to enable water cooling to be dispensed with. It is to the rotary class that the Gnome engine and International Rotary motor belong, the former being also a pure example of the radial system of construction. In one of its two types the International Rotary motor possesses the peculiarity of having a rotating crank-shaft as well as rotating cylinders, the two members revolving, of course, in opposite directions, and at half speed. The extreme development of the rotary principle is, of course, the turbine, and an example is not lacking even of this unusual class, although the little Tani model is perhaps scarcely convincing in its present state. In an accompanying table we summarise the leading dimensions and particulars relating to the aero-motors on view, and in order to make the table as complete as possible we have also included the full range of models manufactured by each exhibitor, even where an example of each size is not actually there. In addition to the price, it will be noticed that a column is included to show the nature of the guarantee, and the figures therein indicate the number of hours that the manufacturers are prepared to guarantee that their engines shall maintain the specified horse-power at the specified speed. Although every effort was made to obtain the correct weight for each engine, the information available is not always based on actual weigh-bridge figures, and it is, therefore, impos- sible to say for certain that these weights are exact in all cases. Commencing this week, we now proceed, having thus briefly summarised the exhibits collectively, to describe in greater detail the characteristics and leading features of each individual make of aerial engine at the Show. LEADING AERO-MOTORS ILLUSTRATED AND DESCRIBED. Simms AERO MOTORS, LTD.). V-type engine, peculiar in its class for having six cylinders, whereas the majority have eight. The cylinders are cast separately, but each is complete with its valve- chamber and water-jacket : the cylinders are bolted to a "Flight" Copyright Photo. SIMMS AERO-MOTOR.—This 6-cVl. V-type engine isfitted with Phillips' auto-mechanical inlet-valves. magnaleum base-chamber. The cam-shaft lies longi- tudinally above the crank-chamber, between the cylinders, and is exposedT#s also are the gear-wheels which drive it; the half-speed gear-wheel is made of magnaleum and fibre and weighs only 7 ozs. In spite of being arranged externally and exposed, the cam-shaft bearings are lubricated under pressure in the same way as the crank- shaft. Another special feature is the use of Phillips' "auto-mechanical " inlet-valves. These valves, as readers of The Automotor Journal are aware, are a combination of the mechanically-operated and the atmospheric types, the mechanical control being employed to relieve the pressure on the valve-spring for a certain pre- determined period, during which the valve is free to open under atmospheric pressure. If at the end of this period it has not opened of its own accord, it is positively lifted from its seat. The closing of the valve takes place in a similar manner. Green (GREEN'S MOTOR PATENTS, LTD.). Of the three standard models—designed by Mr. Green and constructed by Messrs. Aster—two are vertical 4-cyl. engines, while the other is an 8-cyl. V-type engine. All operate on the four-stroke cycle, and embody the same constructional features which in many cases are quite original, and in all instances have been very carefully thought out. The cylinders are separate steel castings machined all over so as to be as far as possible of even thickness, and to thereby give regular expansion and contraction. They have copper water - jackets, which are pressed from the solid sheet metal; and are fastened in place in a special manner which is one of the features of the Green engine. These copper jackets are simple cylindrical covers open at one end and closed at the other. At their open ends they are slightly bell-mouthed, so that each can slide easily into its place over a rubber ring which is carried in a grooved flange on the cylinder casting. This ring forms a water-joint, and at the same time that it prevents leakage it allows the copper jacket to expand and contract independently of the cylinder. Above the cylinder head, the water-jacket joint is formed by 194
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