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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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#1
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The Rolls-Royce Crecy
Always woundered what whould happened if Rolls-Royce had developed the
utterly INSANE crecy engine, and shoehorned it into a spit! The Rolls-Royce Crecy was a 2-stroke 90 degree V12 liquid cooled aero engine of 26.1 litres capacity, featuring sleeve valves and direct petrol injection. Single cylinder development began in 1937 under project engineer Harry Wood. It was designed by Sir Harry Ricardo. The first complete engine was built in 1941 and produced 1400 hp. There were problems with vibration and the cooling of the pistons and sleeves. The firing angle was 30 degrees and 15lb supercharger boost was typical. Bore was 5.1" stoke 6.5" compression ratio 7:1 and weight 820 kg. The thrust produced by the 2-stroke exhaust was estimated as being equivalent to 30% of the power of the engine, and was exceptionally loud. Unlike most 2-stroke engines, supercharging or turbocharging was used rather than crankcase compression to force the charge into the cylinder. Stratified charge was used where the fuel was injected into a bulb like extension of the combustion chamber where the twin spark plugs ignited the rich mixture. Operable air/fuel ratios of from 15 to 23 were available to govern the power produced between maximum and 60%. The lean mixtures reduced detonation allowing higher compression ratios or supercharger boost. Supercharger throttling was used as well to achieve idling. The supercharger throttles were novel vortex types, varying the effective angle of attack of the impeller blades from 60 degrees to 30. This reduced the power required to drive the supercharger when throttled and hence fuel consumption at cruising power. The sleeve valves were open ended rather than sealing in a junk head. They had a stroke of 30% of the piston and were 15 degrees in advance. It was named after the Battle of Crécy, battles being the chosen theme for Rolls Royce 2-stroke aero engines. There were however no subsequent Rolls Royce engines of this type, and rivers were used for jet engine names. Sir Henry Tizard was a proponent of the engine as Chairman of the Aeronautical Research Council. The power of the engine being interesting in its own right, but also the exhaust thrust at high speed and altitude making it a useful stop gap between engines such as the Rolls-Royce Merlin and anticipated jet engines. Only six complete examples were built when the research was terminated in December 1945. An additional eight vee twins were built. Serial numbers were even, Rolls-Royce practice being to have even numbers for clock-wise rotating engines when viewed from the front. Crecy number 10 achived 2500 hp on 21 December 1944. Subsequently single cylinder tests achieved the equivalent of 5000 bhp ( holy shi**! ) for the complete engine. |
#2
Posted to rec.crafts.metalworking
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The Rolls-Royce Crecy
Other interesting engines were the Napier Nomad (12 Cylinder horizontally
opposed turbo-compound diesel - target HP 6,000!) and the H 24 (two rows of horizontally opposed 12's) Napier Sabre II, which developed 3,500 HP in later versions. The Nomad was never produced, but is considered by many to be the most complex aircraft engine ever attempted. -- Bob (Chief Pilot, White Knuckle Airways) "Hveem" wrote in message ... Always woundered what whould happened if Rolls-Royce had developed the utterly INSANE crecy engine, and shoehorned it into a spit! The Rolls-Royce Crecy was a 2-stroke 90 degree V12 liquid cooled aero engine of 26.1 litres capacity, featuring sleeve valves and direct petrol injection. Single cylinder development began in 1937 under project engineer Harry Wood. It was designed by Sir Harry Ricardo. The first complete engine was built in 1941 and produced 1400 hp. There were problems with vibration and the cooling of the pistons and sleeves. The firing angle was 30 degrees and 15lb supercharger boost was typical. Bore was 5.1" stoke 6.5" compression ratio 7:1 and weight 820 kg. The thrust produced by the 2-stroke exhaust was estimated as being equivalent to 30% of the power of the engine, and was exceptionally loud. Unlike most 2-stroke engines, supercharging or turbocharging was used rather than crankcase compression to force the charge into the cylinder. Stratified charge was used where the fuel was injected into a bulb like extension of the combustion chamber where the twin spark plugs ignited the rich mixture. Operable air/fuel ratios of from 15 to 23 were available to govern the power produced between maximum and 60%. The lean mixtures reduced detonation allowing higher compression ratios or supercharger boost. Supercharger throttling was used as well to achieve idling. The supercharger throttles were novel vortex types, varying the effective angle of attack of the impeller blades from 60 degrees to 30. This reduced the power required to drive the supercharger when throttled and hence fuel consumption at cruising power. The sleeve valves were open ended rather than sealing in a junk head. They had a stroke of 30% of the piston and were 15 degrees in advance. It was named after the Battle of Crécy, battles being the chosen theme for Rolls Royce 2-stroke aero engines. There were however no subsequent Rolls Royce engines of this type, and rivers were used for jet engine names. Sir Henry Tizard was a proponent of the engine as Chairman of the Aeronautical Research Council. The power of the engine being interesting in its own right, but also the exhaust thrust at high speed and altitude making it a useful stop gap between engines such as the Rolls-Royce Merlin and anticipated jet engines. Only six complete examples were built when the research was terminated in December 1945. An additional eight vee twins were built. Serial numbers were even, Rolls-Royce practice being to have even numbers for clock-wise rotating engines when viewed from the front. Crecy number 10 achived 2500 hp on 21 December 1944. Subsequently single cylinder tests achieved the equivalent of 5000 bhp ( holy shi**! ) for the complete engine. |
#3
Posted to rec.crafts.metalworking
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The Rolls-Royce Crecy
Bob Chilcoat wrote:
Other interesting engines were the Napier Nomad (12 Cylinder horizontally opposed turbo-compound diesel - target HP 6,000!) and the H 24 (two rows of horizontally opposed 12's) Napier Sabre II, which developed 3,500 HP in later versions. The Nomad was never produced, but is considered by many to be the most complex aircraft engine ever attempted. -- One of the engineers working for Lockheed designed a mulit-mode jet engine back in 1947, that we would have trouble building even with all the advanced technology we have today. It was a 47 stage tubojet that used automatic controls to convert to a scramjet based on aircraft speed and power needs. As the aircraft sped up and the dynamic pressure in the inlet increased, the engine would decouple a stage of compression and feather the tubine blades as well as the stator blades. This would continue until all stages were feathered and only a single stage in the hot section was turning, only to drive the accessory gearboxes. By this point the aircraft would be well into the supersonic regime of flight and the engine would be operating in the scramjet mode. The data that I've seen suggested somewhere around 20,000 pounds of thrust in an engine case of only about 20" in diameter. Craig |
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