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Aviation History
1928
1928 - 0077.PDF
FEBRUARY 2, 1928 Power loading 7 877 Speed at 5,000 ft. (1,525 m.) Speed at 10,000 ft. (3,050 m.) Speed at 15,000 ft. (4,575 m.) 113 m. Climb to 5,000 ft. (1,525 m.) in 4-J- mins 10,000 ft. (3,050 m.) in 10 mins. =8-76 lb./h.p. = 3-98 kg./h.p. 125 m.p.h. (201 km /h )122m.p.h.(196-5km /h ) 11 m.p h (182 km '/hJ mi Climb to 15,000 ft. (4,575 m.) in 19 mins.Service ceiling 21,000 ft. (6,400 m.). " Everling Quantities High speed figure Distance figure (top speed) Altitude figure (ceiling) (Metric). 13 3 4-8 THE NAPIER "LION" RACING ENGINE 875 B.H.P. for a Weight of 835 lbs. Low specific weight and small frontal area are the two out- standing features of the Napier " Lion " racing engine fitted in the three British machines which took part, and of which two gained first and second place, in the race for the Schneider Seaplane Trophy at Venice. A detailed description of the engine cannot be given, but a few particulars will, perhaps, serve to show the enormous progress in aero engine design and construction which this Napier product represents. Like all the Napier " Lion " series, the racing engine has 12 cylinders, arranged in three blocks of four cylinders each, a formation variously known as the " W " and "Broad Arrow " formation. There was a time when not a few people held the view that an engine of this type would have too great a frontal area to enable really high speeds to be attained. That this view was incorrect was definitely established when Flight-Lieut. Webster won the Schneider Trophy Race at an average speed of 281-5 m.p.h. True, the racing engine presented a considerably smaller frontal area, than does the normal " Lion," but this reduction was made possible by a rearrangement of the engine accessories, rather than by any redesigning of the engine itself. How compact the Napier racing engine is will be realised when we point out that the height is 2 ft. 10| in., the width 3 ft. 21 in., and the length 5 ft. 6£ in. The bore, by the way, is 5\ in. and the stroke 5£ in., while the compression ratio reaches the remarkably high value of 10 to 1. Needless to say, this high ratio is only possible by using a special fuel composed, it was stated by Capt. Wilkinson at a lecture at the R.Ae.S. and I.Ae.E., of 75 per cent, petrol, 25 per cent. benzol, with a small percentage of " Ethyl " added. Sparking plugs were rather a problem, but in the end a special K.L.G. plug was evolved which proved capable of standing up to its extremely difficult task. The Napier racing engine is produced in two types ; direct drive and geared. By great skill in design and workmanship, it has been possible to run this engine at a speed of 3,300 r.p.m., when the power output is 875 b.h.p. The direct-driveengine weighs 835 lbs. complete, giving a specific weight of 0-954 lb./b.h.p. The geared engine is slightly heavier, buteven this has a specific weight as low as 1-05 lbs./b.h.p., weighing 920 lbs. The reduction gear of the geared type of engine is of thedouble-reduction spur gear type, which has the advantage for racing aircraft, that the airscrew shaft, instead ofbeing raised above the crankshaft, as is the case in the normal " Lion " engine, is coaxial with it. Thus the goodstreamline form of the nose of the fuselage is not interfered with. The fact that the Schneider Trophy Race was over a distanceof approximately 220 miles provided an opportunity for testing out the reliability of engines at full power, and in thisconnection it is worth remembering that the geared and direct- drive Napiers in the two Supermarine S.5 monoplanes whichgained first and second places, respectively, in the race, ran without a falter for the whole of that distance. Finally, it may be stated that the fuel consumption of theNapier racing engine is 50 gallons per hour, while the oil consumption is three gallons per hour. On a basis of 875b.h.p., these consumptions work out at (taking the fuel at 7 lbs. per gallon and oil at 10 lbs. per gallon), 0-4 lb./h.p./hourand 0-034 lbs./h.p./hour, respectively, a total consumption of 0-434 lbs./h.p./hour. It is now well known that sometime this spring an attemptwill be made to beat the world's speed record established by the Italian pilot, de Bernardi. To do this, it will be neces-sary for the Supermarine S.5, or Gloster IV, whichever is used in the attempt, to average rather more than 300 m.p.h. overthe 3-km. course. That the attempt will be successful there is good reason to hope, and if Great Britain should gain thedistinction of being the first nation to exceed the 300 m.p.h., the Napier racing engine will be able to claim a very large shareof the credit. THE BRISTOL "MERCURY" MARK I. 800 B.H.P. for a Weight of 680 lbs. ALTHOUGH a most unfortunate mishap at Venice denied the Carter-designed, Short-built " Crusader " monoplane a fair opportunity to demonstrate its capabilities, suffi- cient was learnt during practice flights to show that the machine was, to say the very least, a most interesting experi- ment. Whether or not the " Crusader " was as fast as the other Schneider machines does not, at the moment, matter, a great deal. The point to bear in mind is that it represented a serious attempt to prove that a really high-speed machine could be based upon a radial air-cooled engine. That engine was the Bristol " Mercury' " Series I, developed from the now famous " Jupiter " which it resembles to this extent that it is a 9-cylinder radial air-cooled engine. For fairly obvious reasons the " Mercury " cannot at present be described in detail but as the engine is likely to have a marked influence upon future design for service use, the following brief particulars of the Series I " Mercury will, we feel sure, be of considerable interest to our readers. . The " Mercury I " as already indicated, is a single-bank 9-cylinder radial air-cooled emgine, generally similar to, but differing in many respects from, the Bristol Jupiter which is now used so extensively in service and commercial aircraft in almost aU parts of the world. In order to reduce air resistance, and thus do away with what is really the only serious drawback to the radial engine, the overall diameter of the " Mercury I " has been very materially reduced, inis reduction has been made possible partly by employing ashorter stroke, and partly by a more compact cylinder design and rocker gear. As in the " Jupiter " there is a single-throw,two-piece crankshaft, with a connecting rod assembly con- sisting of one master rod and eight articulated rods. Thefact that the engine was designed for very fast machines per- mitted of running it at fairly high speed (2,500 r.p.m. normal).This fact, in conjunction with the use of an internal geared blower providing supercharging made possible the attainmentof very high power (800 b.h.p. normal) for extremely low weight (680 lbs. complete), thus attaining the astonishingspecific weight of 0-85 lb./b.h.p. As this figure represents the specific weight at normal power, and includes, of course, thecooling arrangements, it would appear that the " Mercury I " establishes a record for low specific weight. The main data relating to the " Mercury I " are as follows : TypeNumber of cylinders Bore Stroke Total swept volume Normal speed Normal power ..Propeller SuperchargerComplete weight Specific weight .. 65 Air-cooled radial racing engine. 9 5-75 in. 6-5 in. 1,519 cub. in. 2,500 r.p.m. 800 b.h.p. Direct drive left-hand tractor. Integral geared blower 680 lbs. 0-85 lb./b.h.p. c2
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