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Aviation History
1910
1910 - 0335.PDF
APRIL 30, 1910. I/OGHT] THE "ALVASTON" FLIGHT MOTORS. SOME very interesting results have been obtained by the manufacturers of the Alvaston petrol motors from tests carried out at the Derby factory, where they are manufac tured. Apparently, in fact, an exceptional degree of freedom from vibration has been secured by taking full advantage of the horizontal opposed principle of con- Fig. 1.—The above 30-h.p, Alvaston petrol engine has cylinders of 132 mm. bore by 127 mm. stroke, and weighs, as shown, about 113 lbs. struction to produce a high grade design of extreme lightness and yet of ample strength for the required purpose. As may be observed from our first illustration, there is nothing radically novel about the general arrangement of the parts, inasmuch as the two horizontal cylinders are mounted on opposite sides of the central crank- chamber, and the valves are arranged in the cylinder- heads. Earlier practice is, moreover, followed in that a two-throw crank-shaft is employed in order to secure a good balance of the moving parts. But, firstly, it may be noticed that four steel rods are employed for securing the cylinders in place, and that these rods — which are of vanadium steel —are so disposed that not only do they re lieve the cylinders and the crank-cham ber of any severe strains, but that they also serve as a means for fixing the engine in place in the finished machine that is to derive its pro pulsive power from the engine. A pair of special bridge-pieces lie across the cylinder-heads, and are threaded over the bolts in question, while these bridge- pieces, moreover, carry the simple valve - operating mechanism whereby a single rocker serves to operate both the inlet and the exhaust-valves. Our illustration also indicates that auxiliary exhaust- ports are provided in the cylinder-walls, where they are uncovered by the pistons when at the end of their outward strokes. And equally clear, too, is the disposition of the external two-to-one gear for operating all four valves through a single pair of push-rods, as well as the high- tension Simms magneto, and the carburettor seated above the top of the crank-chamber. Water jackets are formed for each cylinder casting, and not only are the cylinders ground out true to size, but the inside surface of the combustion-chamber heads are machined internally, thereby permitting high compression to be employed, as well as ensuring a thorough balance between the two cylinders. Large inlet and outlet ways are provided by the nickel steel valves, and in order to secure long life for the valve-gear, the push-rods are ball-jointed with hardened and ground bearing - surfaces. Equal importance, moreover, has been laid upon first-rate materials and workmanship in connection with the crank-shaft and its bearings, the shaft itself being formed of a one- piece chrome-vanadium forging, subsequently bored out hollow, while the main journals are carefully ground so as to bed-in truly to the special phosphor- bronze main bearings. Provision is made for taking the thrust imposed by a tractor-propeller if fitted direct to the shaft, for there is a Hoffmann ball thrust collar on the inside of the crank-chamber for this express purpose. The illustrations that we give herewith relate more particularly to the 30-h.p. model, though motors of a similar design, both of 20-h.p. and of 40-h.p., are included in the standard series. That illustrated has a bore of 132 mm. (5Tsff in. approx.) by 127 mm. (5 in.) stroke, and as shown in Fig. 1, its weight is 113 lbs. As regards the 20-h.p. model, the bore and the stroke are both 114 mm. (4! in. approx.) while the bore of the 40-h.p. is 155 mm. with a stroke of 150 mm. -An Alvaston engine on a testing chassis, driving 6 in. fan at a speed of 1,500 revs, per min. A 3-second exposure was given to this photograph. Fig. 3.—A 30-h.p. Alvaston motor, fitted with its pronybrake on the Company's test chassis. Both our second and third illustrations represent a light testing chassis which has been equipped for running these engines under load out in the open, and it will be realised that the conditions thereby attained are quite different to what would pertain on an ordinary test-bench. In spite of that, and despite the further fact that a 3 sec. exposure was given when the photographs were 333
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