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Aviation History
1926
1926 - 0934.PDF
total swept volume, 8 litres ; compression ratio, 5-3 to 1 ;normal speed, 1,700 r.p.m. ; maximum, 1,870 r.p.m. ; normal power, 130 b.h.p. ; maximum, 140 b.h.p. ; petrol consump-tion at maximum power, 36 litres ; oil, 2-2 litres per hour ; petrol consumption at normal power, 27 litres per hour ; oil,1 -2 litres ; weight of engine, 150 kgs. The main data relating to the " Cherub " series III are :Type, two-cylinder opposed air-cooled ; bore, 90 mm. ; stroke, 96 mm. ; cubic, capacity, 1'228 litres; compressionratio, 5-5 to 1 ; normal power, 32 h.p. at 2,900 r.p.m. ; maximum power (for 5 minutes), 36 h.p. at 3,200 r.p.m. ;petrol consumption at normal power, 9 litres per hour ; oil, 0-57 litres; weight of engine, 45-36 kgs. It is regretted that conditions at the Grand Palais were suchthat it was found difficult to photograph the Bristol engines on the stand, but some very excellent photographs appearelsewhere in this issue of FLIGHT. BREITFELD, DANEK I SPOLTHIS Czechoslovak firm, of Prague, commenced the manufac- ture of aero engines as long ago as 1914, when the typesproduced were built under licence from the " Hieronymus " company. In 1922 the firm commenced original design,the first proprietary engine to be turned out being the " Blesk," a six-cylinder vertical water-cooled of 100 h.p., having abore of 120 mm. and a stroke of 140 mm. This engine was successful within the limits imposed by a low-power output,and further types were then developed. The outcome has been a scries of three engines, all of the high-compressiontype, designed to maintain their power up to an altitude of 3,000 m. The " Perun I " is a six-cylinder, vertical water-cooledof 190 h.p.^having a bore of 150 mm. and a stroke of 180 mm. Its normal speed is 1,400 r.p.m., and the petrol consumptionis 190 grs. per h.p./hour, while the oil consumption is 12 grs. per h.p./hour The weight cf the engine dry is 285 kg " Perun II " is a slightly more powerful version of thesame type, with a bore of 160 mm. and a stroke of 190 mm., developing 240 h.p. at a normal speed of 1,400 r.p.m. Itsweight is 315 kg., and the petrol consumption is 190 grs. per h.p./hour, while the oil consumption is 12 grs. perh.p./hour. The most powerful engine produced by this firm up to dateis the 500 h.p. " BD," a 12-cylinder water-cooled Vee type with a bore of 160 mm. and a stroke of 190 mm. The normalspeed is 1,400 r.p.m., and the weight of the engine is 550 kg. Whereas the smaller models have two valves per cylinder,the " BD " has four. This engine also is claimed to maintain its power up to an altitude of 3,000 m. THE "CAFFORT" ENGINE IN some ways the most interesting engine at the show, because it represents an attempt at solving the problem of engine-head resistance, is the new 500 h.p. engine designed and constructed by the French firm of Caffort Freres, which is exhibited at Paris next to the Bristol stand. This engine, which is apt to DECEMBER 9, 1926 be overlooked, is well worth an inspection, and, althoughrelatively little information is available concerning it—the engine having been but recently finished, and, in fact, wasrunning a couple of days before the opening of the Salon— the general principle is simple enough and easily followed.That some of the details may require modification before this engine becomes a practical proposition is, of course,more than likely. The firm that has produced it is, we understand, a very old French firm, but has had no previousexperience of aero-engine work, so that one should not be over-critical in judging detail. The main principle of the " Caffort " engine is that it hasits 12 cylinders disposed in two rows of 6 each, the two rows being horizontal and placed at an angle of 180°. In otherwords, the engine is of the horizontally opposed type. We gather that the object which the designer had in view wasto produce an engine capable of being tucked away neatly inside a thick wing, thus saving the head resistance offeredby the more orthodox types of engine. This being the object, water cooling was adopted as a necessary corollary,and there still remains the problem of the radiator and its head resistance. That, however, is a matter over whichthe engine designer has little or no control. It must rest with the aircraft designer, and, presumably, the wing-surfacetype of radiator would be the logical type to adopt in conjunction with the " Caffort " engine. It is regretted that the lighting arrangements of thisyear's Paris Salon were such that it was found impossible to take photographs of quite a number of interesting exhibits,and among these was the " Caffort " engine. The preliminary test runs of this engine were carried out so recently that thefirm has had no time to have photographs taken, and it is therefore impossible for us to place before our readers anyillustration of it. The following brief notes on its more important features will have to serve for the time being. As already mentioned, the " Caffort " engine is of thehorizontally opposed type. Each bank of cylinders lies horizontal, and the overall depth of the engine is very smallindeed. Thus, even when used in the ordinary way in the nose of a fuselage, the engine would give a particularlygood view over the top from the pilot's cockpit, and for this reason alone the type might be worth developing, quiteapart from its obvious suitability for mounting in the interior of a thick wing. The cylinders are water-jacketed in the normal way, andthe overhead valve gear is entirely enclosed in casings. It was pointed out that these casings could, in future engines,very easily be lightened since they do not have to take any stresses and in this way alone it is thought that about100 lb. could be saved in the weight. The crankshaft has three pairs of crankpins each pairbeing placed at an angle of 120° in relation to adjacent ones. Opposite cylinders have one connecting rod takingits big end bearing direct on the crankpin, its " opposite number " having an articulated connecting rod. The crank- ENGINES AT THE PARIS SHOW: Two Farman " broad-arrow " types, on the left the 500 h.p. and on the right the 700 h.p. 806
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