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Aviation History
1946
1946 - 0164.PDF
FLIGHT ROLLS-ROYCE MERLIJS WITH the advent of the new Series 130 it can truth-fully be said that the Merlin has carried progres-sive development of a basic type farther than any other aircraft engine in'the world, for within a period of lea years (the first Merlin was produced in 1936), not only has its power output been increased from less than 1,000 to more than 2,000 b.h.p., but, in addition, more Merlins have been built than any other type. The Merlin 130 and 131 are specially developed variants of the Series 100 engines, and have been specifically pre- pared for installation in the de Havilland Hornet, which is the first twin-engined British aircraft to have handed airscrews. This feature accounts for the designation 130 and 131, the former being a right-hand tractor unit for the port side, and the latter a left-hand tractor for. the starboard nacelle. As the airscrew on the 130 rotates in the opposite direction to that of the 131, it might at first sight appear that this would involve considerable comph- cation, and that it would be necessary for the crankshaft to rotate in the opposite direction—making the engine "handed" throughout. This, however, is not the case; all that is necessary on a liquid-cooled, in-line engine em- ploying a single spur reduc- • tion gear is the introduction of an idler wheel between the driving pinion and the main gear wheel. The advantage of this simple modification, which is clearly shown in an illustration, is that the two engines have 95 per cent, of spares in common, and to alter the engine from one " hand " io the other, it is only necessary to change the reduction gear ; the weight in- crease with the additional gear and bearings is prac- tically negligible and can be discounted. Although the Merlin 100s were the first of a new series of two - stage, two - speed," inter cooled types incorporat- ing many improved features, the series 130 and 131 have further new features which enable an improved installation to be effected for fighter aircraft. In fact, it would not be inapt to describe this latest Merlin as being "tailored" to suit the particu- lar installation; this has resulted in a very low frontal area per b.h.p. An illustration gives a curve of interesting comparisons of frontal-area : power, starting with the Eagle produced at the beginning of the first World War and end- ing with the Merlin 130 of to-day. From this curve it will be seen that a steady increase in power per square foot of frontal area was achieved during the inter-war years, every four years producing an increase of roughly 25 b.h.p./sq. ft., until 1936, and then, with the advent of the Merlin, there was a considerable improvement amount- ing progressively to 60 b.h.p./sq. ft. in 1940; 100 b.h.p./ sq. ft. between 1940 and 1944, until in 1945 the amazing figure of 340 b.h.p. /sq. ft. was achieved with the Merlin IOOS. History of Collaboration The Hornet is a good example of the excellence which can be obtained1 when close collaboration exists between Cf \ a: 3OO 275 2SO 22S 2OO 175 ISO 125 CO 75 SO 25 CONDOR - I92O 1922 B2*626 KESTREL S55 VULTURE "MERLIN B34 1936 I95T B.H.P./SQFT. OF FRONTAL AREA The Merlin 131 differs from the 130 only in that an idler wheel is inter- posed between the driving pinion and . the main gear wheel. the aircraft designer and the engine manufacturer, although sound basic design must obviously be the founda- tion if extensive developments are planned. In .this connection, when the design for the Mosquito was lakL-flL down in 1939/40, the decision was taken to use Merlin 20s, as they were then sufficiently advanced in design and development to ensure that the Mosquito would have a superior per- lormance to that of any equivalent enemy aircraft. Further, it was pre- dicted by Rolls-Royce that the Mer- lin 20 would be capable of much greater development, and thin would ensure the initial superiority being re- tained over a period of years. Even the most casual survey of the Mosquito's record is sufficient to illus- trate how well this long-term planning has succeeded, andiit is sufficient to
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