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Aviation History
1939
1939 - 1647.PDF
546 •fflgssv MAY 25, 1939 while in weight the new engine was only 8 lb. heavier. By 1928 further modifications were made, with the result that the Cirrus Mark III was introduced, developing 95 maximum b.h.p. for a total weight of 280 lb. These engines were used in many pioneering flights, such as Sqn. Ldr. Bert Hinkler's first solo journey to Australia, Lady Bailey's flight round South Africa, and Capt. Bentley's many return flights between London and the Cape. In 1933 the company became known as the Cirrus-Hermes Engineering Co., £.nd between that date and March, 1934, when Mr. Robert Blackburn became chairman, the company produced a whole series of Cirrus-Hermes from Mark I to Mark IV. Soon after; the works were transferred from Croydon to Brough, where new shops had been built and equipped with modern machinery and appliances for develop ing, constructing, and testing Cirrus engines. Recently the Cirrus-Hermes Engineering Co. was merged into Black burn Aircraft, Ltd., and became the Engine Division of Blackburn Aircraft, Ltd. A New Range At Brough a new range of engines was started. The first was the 90 h.p. Cirrus Minor, which is already fitted in twenty-five types of aircraft, operating with marked success in fourteen countries. This engine has a capacity of 3,605 c.c. and produces a maximum b.h.p. of 90 at 2,600 r.p.m. It is a straightforward inverted, air-cooled, four-cylinder unit following closelv on the lines of its elder brother, the Cirrus Major. Its weight, however, is only 227 lb., including a very complete speci fication. The latest Cirrus Major, introduced in 1935 and modified twice since then, is fully described in the following pages. Its performance when introduced was high for its type—it developed 135 b.h.p. at 2,350 r.p.m. In its latest form this engine develops 150 b.h.p. at 2,450 r.p.m., a remarkable figure for an engine of this class. External cleanliness in design is a feature of the new Cirrus Major, two end views of which are shown above. On the left of the rear view can be seen the method of mounting the generator, while on the right are the twin fuel pumps and filters. The Major is now in series production along with the Minor at Brough. It is being fitted to the Miles Magister as used by the R.A.F. for training pur poses, in the Percival Gull, the Black- . burn B.2, the G.A. Cygnet, and a number of foreign aircraft. Among the recent developments which have taken place in the Engine Section are the appointments of Mr. C. S. Napier as research and development engineer, and Mr. E. Mitchell (formerly chief en gineer of the De Havilland Aircraft Co.) to chief engineer of the Cirrus Engine Section. Mr. J. L. H. Bishop, formerly research engineer (materials). ;of the Bristol Aeroplane Co.'s engine depart ment, has taken up his duties as chi?E designer to the Cirrus Division ' £t Brough. Such a strong combination augurs well for the future success of /those two pioneering concerns—the Blackburn Air craft Co. and the Cirrus Engine Division. THE NEW CIRRUS MAJOR Light «Y" alloy heads, each with twelve studs and special steel valve seat inserts, are used in the Cirrus Major. THE Cirrus Major is a development of the original Cirrus and Hermes engines. The Major made its first ap pearance in June, 1935. It was intro duced as an inverted air-cooled four-in line, developing the maximum of 135 b.h.p. at 2,350 r.p.m. Since then various modifications in the design, and the use of new materials, have brought about a vastly improved performance, while its exterior has been cleaned up to the extent that there are now no external oil leads, except the usual services from and to the tank. Likewise all controls have been reduced to a minimum. Basically, the Cirrus Major 150 engine is an inverted air-cooled four-in-line, of simple but exceptionally robust design. It has a bore and stroke of 120mm. and 140mm. respectively, giving a capacity of 6,330 ex. Each of the four cylinders is retained to the crankcase by four long studs with Jin. distance pieces, to allow a cer tain degree of elasticity. The cylinders are wholly machined throughout from normalised billets of "55" carbon steel. From the base the skirt tapeis up to the first of 24 deep fins. The top flange is machined to fit into the spigoted "Y" alloy heads. The base of the cylinder is recessed into the crankicasevto the ex tent of approximately 2|in. A special oil-resisting rubber washer is used for the cylinder-to-crankcase base joint. Each cylinder head is secured to_ the cylinder flange by means of twelve deeply set studs, a gastight seal, be'ing obtained by the use of a plain circular laminated copper gasket. The head is machined from a casting roughly rect angular in shape and incorporating the upper half of the rocker box casing. While the inlet port is radiused into a horizontal plane, the exhaust is radiused in the opposite direction towards the vertical, so that when the exhaust stubs are fitted they point in a downward direction. Special valve seats are shrunk into the heads. A Monel seat is used in the" case of the exhaust, while nickel-chrome high-expansibility steel is employed for the inlet. In both cases the seats have slightly tapering walls and are pressed into the head after the latter has been subjected to a temperature of 300 ®e~ grees C. for twenty minutes. The metal
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