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From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Article on engine ramming effect and the Bristol Perseus X engine, with an advertisement for 'dag' colloidal graphite.

Identifier  ExFiles\Box 122\4\  scan0226
Date  25th March 1939
  
RM{William Robotham - Chief Engineer}
407

How Much Can Be Gained by “Ramming” an Engine?
(Continued from page 399)

sion in the past that the ramming effect would be a maximum if the ram were provided with a horn, or scoop, which would scoop up air and produce an additional ramming effect. From the results of the N.A.C.A. it would seem that the very opposite is the case and that the inlet to the ramming tube, instead of being expanded trumpet-like, should be contracted. This, of course, is on the supposition that the air velocity in the carburetor inlet pipe is less than the slip-stream velocity. In an automobile, however, the air velocity in the inlet pipe is considerably greater than the velocity of the vehicle. For instance, in a popular low-priced car the car speed in direct drive at the peaking speed of the engine is 5500 ft. per min., whereas if we assume the volumetric efficiency of the engine to be 70 per cent, the air velocity at the carburetor inlet is 16,500 ft. per min. or just three times as high. The flying speeds of modern aircraft are just about three times as high as the top speeds of modern low-priced cars, and in aircraft the carburetor and inlet passages are made relatively large to be able to get high outputs from the engines. It seems, therefore, reasonable to expect an increase in the ramming effect from a horn or entrance cone. For instance, if the air velocity at the carburetor entrance had to be three times the velocity of the vehicle, the entrance cone could be made with an area of opening three times as large as that of the carburetor inlet, and if the angle of the cone were made sufficiently small, there would be no pressure rise at the entrance and no consequent spilling of air over its edges.

Ramming of the carburetor would certainly seem to be worthwhile in the case of racing and record machines, such as Captain Eyston’s Thunderbolt, for at 315 m.p.h. the dynamic pressure of the air is approximately 1.75 lb. per sq. in. Of course, the engines of such cars are usually supercharged, but the ram can be used also with the super-charger, and will then reduce the power required to drive the latter, for a given ratio of supercharge.

A new method of securing cylinder heads of air-cooled aircraft engines to the cylinders has been patented in England by the Skoda Works of Czechoslovakia. These heads are usually screwed and shrunk on. In the Skoda design the top end of the cylinder is externally threaded, as usual, and a ring nut is provided. This ring nut has an internal offset or shoulder, and a turned flange on the cylinder head is clamped between the end of the cylinder and the offset in the bore of the ring nut.

THE Bristol Aeroplane & Motor Co., Bristol, England, announces the going into production of the Perseus X engine described as the first highly supercharged sleeve-valve aero engine. It is quite similar to the Perseus XII, details of which were released last year, but the supercharger has an impeller of larger diameter and turns at higher speed. In a special 50-hr., weak-mixture test the fuel consumption was 0.448 lb. per b.h.p.-hr., at an output of 520 b.p.h. The new design is a nine-cylinder, air-cooled, radial, sleeve-valve engine of 5¾ in. bore by 6½-in. stroke and 1520 cu. in. displacement. Its maximum output is 880 hp. at 15,500 ft. altitude.

TELEVISION
... and 'dag' play part

THE RCA MANUFACTURING CO. apply, 'dag' colloidal graphite to the interior walls of television's picture-taking and projecting tubes - thereby intensifying, shielding, and focusing the sensitive, image-forming beams. 'Getter' action is also provided.

The part 'dag' has played in the development of television is indicative of its versatility, permitting it to serve, for example, as a lubricant for steam cylinders, compressors, and internal combustion engines; as an impregnant of materials, to effect lubricity, opacity, or electrical conductivity as desired.

A request on your letterhead will bring a new 40 page booklet which outlines the 19 properties and 181 applications of 'dag' Brand colloidal graphite in industry.

ACHESON COLLOIDS CORPORATION
PORT HURON MICHIGAN

dag COLLOIDAL PRODUCTS

Automotive Industries
When writing to advertisers please mention Automotive Industries
March 25, 1939.
  
  


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