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Aviation History
1941
1941 - 1728.PDF
66 FLIGHT JULY 31st, 1941.J ANOTHER ENGINE LAYOUT Novel Cylinder Arrangement Patented by Daimler-Benz - THE quest for power continues.The ding-dong battle betweenthe air-cooled and the liquid- cooled goes on ; first one seems to be a little ahead, then the other. And in both classes the number of cylinders and their arrangement have been the cause of many a headache. We have had the 9-cylinder radial single-row, the 14-cylinder double-row, the 18- cylinder double-row, and various num- bers of cylinders in line behind one another in three rows ; this in the air- cooled class. In the liquid-cooled we have had the V-i2, the H-16, the H-24, and the X-24. And now German designers come along with yet another suggestion. It may be nothing more than that at the moment, or it may be undergoing tests; at any rate, the Daimler-Benz company has taken out patents on a 36-cylinder arrangement. Actually the patent does not limit the number of cylinders, but the 36- cylinder 4-stroke has been used as an example. The cylinders are arranged in six banks of six each, the banks be- ing arranged with an angle of 40 deg. between them, and a gap of 100 deg. between groups. The objects stated in the patent are mechanical balance, uniform torque, small frontal area, and a compact out- line suitable for installation in wings or fuselage (the major axis of the unit may be horizontal or vertical), and good accessibility. In the 36-cylinder unit illustrated, the firing interval is 20 deg. of crank angle. A conven- tional six-throw crankshaft is used with, presumably, two master rods and four auxiliary rods on each crankpin. The firing order may be ascertained by following the intersecting circles in the diagram. Starting from cylinder a, the piston of which is at top dead The cylinder lay-out and firing order of the proposed 36-cylinder engine. 180' IOC la 6b 2f 5a 2b 4f 3a 4b If 6a Ib 5F 2a 5b 3f 4a 3b 6f la 120* 240° 360° |480" 600° 4c 3d 4e Ic 6d le 5c 2d 5e 3c 4d 3e 6c Id 6e 2c 5a 2e centre on the firing stroke, the next explosion occurs in cylinder c after 140 deg. crank rotation; then succes- sively in e after 80 deg., / after 100 deg ; b after 80 deg., and finally d after 140 deg. to complete the cycle. The cranks receive their power im- pulses in the following order: 1, 5, 3, 6, 2, 4, and thus the sequence for the 36 cylinders at intervals of 20 deg. is as shown in the line diagram. In order to reduce as much as pos- sible the number of inlet and exhaust ducts, these are arranged to serve pairs of cylinders. On the drawing the inlet and exhaust manifolds are indicated by the letters I and E respectively. It is a little difficult to follow the argument of the Daimler-Benz com- pany. For instance, the frontal area will be the same whether the six banks of cylinders are arranged as in the patent specification or in the more usual symmetrical way, with 60 deg. between banks. For wing installation the '' natter '' D-B engine might make a slightly better fairing, although an engine of some 2,000 h.p. or more could not be buried in a wing of nor- mal thickness-chord ratio unless the aircraft were vastly larger than any- thing contemplated hitherto. For nose installation it might be an advantage to place the engine with the major axis vertical so as to give the pilot a better view. • , ALLISON 24-CYL. DOUBLE VEE ENGINE '"FHE Allison Company has developed a 24-cylinder liquid-cooled engine which consists essentially of two of their 12-cylinder V-1710 engines joined together in the form of a double Vee with an angle which appears to be 150 deg. between the two outer banks. The V-1710, which was described in Flight for June 19th, page 419, has an included angle of 60 deg. From the illustration of the V-3420, as the new engine is called, the angle between the two middle banks is 30 deg. There are two crankshafts geared to the one air- screw shaft through reduction gearing. The type number of both the engines comes from their capacity in cubic inches. Output of the 24-cylinder will be approximately twice that of the V-1710, which is rated at 1,150 h.p.
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