Interesting article on Pegasus engines for Short Empires
Dec 28, 2022 22:43:11 GMT 12
madmac and oj like this
Post by Dave Homewood on Dec 28, 2022 22:43:11 GMT 12
This comes from the Mew Zealand Herald, 2 May 1936.
NEW AIR LINERS
REMARKABLE ENGINES
WORLD'S LARGEST ORDER
FIFTEEN YEARS' DEVELOPMENT
[From our own correspondent] LONDON, April 8
Many hundreds of workpeople are engaged continuously day and night on the execution of the largest single order for aero engines ever placed by an air transport company. For the new Short monoplane flying-boats which are being built at Rochester for the Empire routes, Imperial Airways needs 116 engines and an additional 40 engines as "spares" for use when overhauls are in progress. In aggregate output these motors — Bristol Pegasus Xc air-cooled radials —account for more than 150,000 horse-power. They will drive the new boats at about 200 m.p.h., ranking them easily as the fastest commercial flying-boats in existence.
In less than 12 months the manufacturing area of the Bristol engine shop has been doubled, and in the midst of military orders on an unprecedented scale the company is dealing calmly with this record commercial contract.
Most Modern Thought
The Pegasus Xc engine represents the most modem thought in the design and building of poppet-valved aero engines. It is the latest in a series of nine-cylinder engines of basically similar type, having the same bore, stroke and swept volume, which have been in constant evolution, production and use for more than 15 years.
In spite of its increased power, the most recent Pegasus engine is lighter than any previous series. All kinds of new ideas are embodied in its design. The cylinder head and barrel has been redesigned to give more efficient combustion and much greater effective cooling area. The exhaust valves are cooled by sodium and "stellited" to protect them from the corrosive action of leaded fuel. Provision is made for installation of a controllable-pitch airscrew. The carburetter is improved. A new kind of exhaust-gas collector ring is also an efficient silencer. Special drives are embodied for working the accessories, including the supercharger, magnetos, electric generator and the fuel and oil pumps; between them these drives absorb 70 h.p., leaving a maximum of 900 h.p. to be delivered at the airscrew hub.
Development Running
Seven hundred thousand drawing office hours were spent in the evolution and design of the motor. Two thousand precision drawings were prepared for its manufacture in quantity. Special single-cylinder test runs totalled more than a thousand hours at powers representing maximum output on the main engine, though maximum power is normally used only for a few minutes at take-off. In addition, 3000 hours of normal development running and 1000 hours of "overload" running at powers greatly in excess of normal output were done on complete engines. This aggregate of more than 5000 hours of development running involved 500 million crankshaft revolutions and the burning of 130,000 gallons of fuel.
Figures such as these underline the complexity of the work of aero engine development, the tremendous organisation that is required and the vast expenditure involved. They explain why the design and building of aero engines, especially in the high-powered categories, must be a task engaging enormous technical resources and the highest standards of craftsmanship.
And the pace of development shows no signs of slackening. Research is proceeding on lines which may mean that the Pegasus Xc, marvel of engineering though it is, will represent the culminating point in development of the nine-cylinder air-cooled poppet-valved radial motor, to be succeeded by the sleeve-valved units that the Bristol Company has evolved in 11 years of arduous work to the stage of successful production. Some time in the near future the sleeve-valved motor, which constitutes yet another triumph of British engineering genius in a field where others have failed, will offer formidable competition.
NEW AIR LINERS
REMARKABLE ENGINES
WORLD'S LARGEST ORDER
FIFTEEN YEARS' DEVELOPMENT
[From our own correspondent] LONDON, April 8
Many hundreds of workpeople are engaged continuously day and night on the execution of the largest single order for aero engines ever placed by an air transport company. For the new Short monoplane flying-boats which are being built at Rochester for the Empire routes, Imperial Airways needs 116 engines and an additional 40 engines as "spares" for use when overhauls are in progress. In aggregate output these motors — Bristol Pegasus Xc air-cooled radials —account for more than 150,000 horse-power. They will drive the new boats at about 200 m.p.h., ranking them easily as the fastest commercial flying-boats in existence.
In less than 12 months the manufacturing area of the Bristol engine shop has been doubled, and in the midst of military orders on an unprecedented scale the company is dealing calmly with this record commercial contract.
Most Modern Thought
The Pegasus Xc engine represents the most modem thought in the design and building of poppet-valved aero engines. It is the latest in a series of nine-cylinder engines of basically similar type, having the same bore, stroke and swept volume, which have been in constant evolution, production and use for more than 15 years.
In spite of its increased power, the most recent Pegasus engine is lighter than any previous series. All kinds of new ideas are embodied in its design. The cylinder head and barrel has been redesigned to give more efficient combustion and much greater effective cooling area. The exhaust valves are cooled by sodium and "stellited" to protect them from the corrosive action of leaded fuel. Provision is made for installation of a controllable-pitch airscrew. The carburetter is improved. A new kind of exhaust-gas collector ring is also an efficient silencer. Special drives are embodied for working the accessories, including the supercharger, magnetos, electric generator and the fuel and oil pumps; between them these drives absorb 70 h.p., leaving a maximum of 900 h.p. to be delivered at the airscrew hub.
Development Running
Seven hundred thousand drawing office hours were spent in the evolution and design of the motor. Two thousand precision drawings were prepared for its manufacture in quantity. Special single-cylinder test runs totalled more than a thousand hours at powers representing maximum output on the main engine, though maximum power is normally used only for a few minutes at take-off. In addition, 3000 hours of normal development running and 1000 hours of "overload" running at powers greatly in excess of normal output were done on complete engines. This aggregate of more than 5000 hours of development running involved 500 million crankshaft revolutions and the burning of 130,000 gallons of fuel.
Figures such as these underline the complexity of the work of aero engine development, the tremendous organisation that is required and the vast expenditure involved. They explain why the design and building of aero engines, especially in the high-powered categories, must be a task engaging enormous technical resources and the highest standards of craftsmanship.
And the pace of development shows no signs of slackening. Research is proceeding on lines which may mean that the Pegasus Xc, marvel of engineering though it is, will represent the culminating point in development of the nine-cylinder air-cooled poppet-valved radial motor, to be succeeded by the sleeve-valved units that the Bristol Company has evolved in 11 years of arduous work to the stage of successful production. Some time in the near future the sleeve-valved motor, which constitutes yet another triumph of British engineering genius in a field where others have failed, will offer formidable competition.
