In the Spring 2008 Issue of
The Bristol Hercules
Part 1: Sleeve-valve Design and Operation:
Manufacturing the Cylinder and Sleeve
by J. A. Oates, A.M.I.E.I., Int.A.M.I.P.E.
This
article first appeared in the Volume 4, Number 40 (February, 1942) issue of
Aircraft Production magazine, and is presented here through the kind
permission of Flight International.
This is the first of a series of articles dealing with production processes in the manufacture of the Bristol Hercules radial sleeve-valve engine at one of the Shadow factories that acted on behalf of the Ministry of Aircraft Production during WWII. Years of patient research and experimental work by the Bristol Aeroplane Co. were necessary before the engine reached its high state of efficiency, and powered a number of famous military aircraft. Production was been brought to a state of perfection by the coordinated effort of the Bristol Aeroplane Co. and the Shadow Factory engineers. Skilful planning overcame the many difficulties.
Contra-Rotating Propellers
Part 1: Why, How, Rotol and the Wyvern
by Tom Fey
As
engine power increased towards the end of the 1940s and with the advent of even
more powerful turboprops, the ability of propellers to absorb the rising
horsepower became limited by diameter and blade loadings. Larger props mean
taller, more complicated landing gear, and propeller blades, like wings, have
structural and efficiency limits with respect to their loadings. Longer prop
blades also risk running into supersonic airflows at their tips, and blades of
increased chord are limited by structural and drag considerations. Another
alternative is to increase the number of blades, such as the five-blade Rotol
propeller on the Sea Fury, the six blades on the Dowty R391 propellers on
Lockheed C-130J, or the eight blades on the Hamilton-Sunstrand NP2000 props on
the Grumman E-2. More blades, however, tempt aerodynamic interference and wake
effects due to reduced spacing between blades.
A more complicated and fascinating remedy to power absorption is the use of
coaxial, contra-rotating propellers, which are props mounted on concentric drive
shafts, rotating in opposite directions. Besides offering a large increase in
blade area, the opposing rotation of these propellers eliminate the
airframe-swerving torque inherent in a single-rotation propeller.
Aero Engine Drawing
The Mighty Fiat AS6 Engine
Part 3: The AS6 Performance and Testing
by C. F. Bona
From the paper, I motori italiani per gli apparecchi di alta velocita, 1935.
Translated by S. Reiss, NACA, 1940. Transcribed and edited by Jerry Wells, 2007.
Preparation
and testing of an engine of the AS6 type required a huge number of trials which
lasted over a period of almost a year and a half.
Prior to testing the complete engine, investigations were carried out on the various parts, namely the cylinder, supercharger, carburettor and on the two engines with and without supercharger. For the tests on the cylinder alone, a section of the crankcase of the AS5 was utilized and a counterweighted crankshaft and a drive for the camshafts were constructed so that the height of the cylinder could be varied thus allowing changes in the compression ratio to be tried. Pistons and cylinder were those of the AS6. Compressed air from the laboratory was used for supercharging, the air being taken from a compressed air tank (provided with safety devices) and led to the carburettor intake. These tests were useful because they provided preliminary data on the fuel mixture, the effect of the degree of supercharging, measurements on the overall thermal balance and on valve temperatures.
The Merlin's Worst Enemy
by David Birch
Part
1 gave us a view of operating conditions in North Africa from the viewpoint of
the Packard field reps serving with American units operating the P-40F. Part 2
gives the British view from the head of maintenance operations in the Middle
East, Group Captain (later Air Vice-Marshal) Grahame Dawson. His report is
supplemented by an extract from a visit report by Cyril Lovesey, Rolls-Royce’s
Development and Research Engineer, who visited many of the maintenance and
operational units and bases of the RAF and USAAF.
Group Captain Grahame Dawson was Chief Maintenance Staff Officer in charge of the Royal Air Force’s aero-engine maintenance in the Middle East in the first half of World War Two. He was one of those people for whom the phrase “can’t do” was not in his vocabulary. Two thousand miles away from Britain and with supplies running the gauntlet of Axis air and naval attacks, it was more often the case of make do with what you have and think of something when you have nothing. His efforts to keep the RAF’s aircraft flying entailed methods of repair and re-manufacture that would make any respectable engineer wince, but under the circumstances there was no other way.
The First Aero Engine Made by Rolls-Royce Ltd.
(With Mercedes Digressions)
by Sandy Skinner
This
book is probably the best insight ever printed into the thought processes of a
great designer. It is a compilation of the memos sent at the start of WWI by
Frederick Henry Royce (henceforward R: see Appendix 2 on Rolls-Royce naming
conventions) from the south coast of England to the Derby works. They cover the
inception, design and development of the Eagle engine with passing mentions of
what became the Hawk and the Falcon. It is important not just for the insight it
gives into R’s thinking, but because it adds to our understanding of design and
production methods at a time when hand fettling was slowly giving way to batch,
if not mass, production. It also shows a more sympathetic and broadminded R than
the hire and fire autocrat of legend.
The book is often, if improperly, called the Rolls-Royce bible. If that great Company has one failing, it’s a tendency to be pompous. The cover bears the intimidating instruction:
CONFIDENTIAL
The Property of Rolls-Royce, Limited
Not to be shown to anyone without the
authority of the Directors
The preface is a classic of its time and worth quoting verbatim. “In the opinion of the Board of Directors, the Memoranda and Letters written by Mr. F. H. Royce, the Engineer-in-Chief in connection with the design, testing and manufacture of these Engines, are so admirable as evidence of extreme care, foresight, and analytical thought, that the Directors decided to have them printed and bound in order that copies may be available for study and as an example to all grades of Rolls-Royce Engineers, present and future.”
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