Shortround6
Major General
Bristol had trouble making the sleeve valves come out 'round' within acceptable tolerances, or perhaps 'stay' round. Engines were often using unacceptable amounts of oil in under 20 hours of running. This could often result in oil fouled plugs so the answer was not just fit a larger oil tank and carry on.
Solution, so the story goes, was found when a workman used some grinding wheels out of sequence by mistake in the finishing process( Bristol had used several hundred combinations of alloy, heat treatment and finishing processes already).
Same problem beset the Napier Sabre before Bristol was forced to help Napier ( they were not happy to 'solve' Napier's problem with Sabre while trying to sell their own 2000hp engine to the Government). Napier went through several hundred combinations themselves.
The solution was never apprentices when you are trying to make hundreds of engines a month, if not thousands.
Hooker, when he went to Bristol after the war, is supposed to have said that the people at Bristol never understood airflow.
You also have the cooling problem with air cooled engines, power is limited by the cooling system (fins and baffles) and in many cases the ability to add as much fin area as was desired was limited by the foundry techniques (casting or forging) and machining ability. Wright went to machining groves instead of fins on the cylinder barrels and 'rolling' sheet metal fins into the groves on their later engines. The Hercules went through around 1/2 dozen different cylinder head designs with ever improving cooling ability.
I would note however that in 1940 nobody had a supercharger that offered a FTH of much over 17,000ft even in high gear of a two speed set up and that sometimes it took twice the power to drive the supercharger in high gear than in low gear. Picking the right supercharger gear was always a balance between altitude desired and the power needed to drive the supercharger ( and since 30% or more of the power just went heating the intake charge there comes a point of diminishing returns).
AS far as the R-2600 goes. please remember that it is a 1900lb engine that is 55in in diameter, it is NOT a 'plug in' replacement for anything but a Hercules and the 1940 1600hp for take-off version is only good for 1400hp at 11,500ft. (Merlin III at 12lbs was good for 1310hp at 9,000ft) and Wright only hit triple digit per month production in July of 1940. Production would double by Dec and double again by April/May 1941. First 1/2 of 1940 saw production numbers of around 70 per month most months.
Solution, so the story goes, was found when a workman used some grinding wheels out of sequence by mistake in the finishing process( Bristol had used several hundred combinations of alloy, heat treatment and finishing processes already).
Same problem beset the Napier Sabre before Bristol was forced to help Napier ( they were not happy to 'solve' Napier's problem with Sabre while trying to sell their own 2000hp engine to the Government). Napier went through several hundred combinations themselves.
The solution was never apprentices when you are trying to make hundreds of engines a month, if not thousands.
Hooker, when he went to Bristol after the war, is supposed to have said that the people at Bristol never understood airflow.
You also have the cooling problem with air cooled engines, power is limited by the cooling system (fins and baffles) and in many cases the ability to add as much fin area as was desired was limited by the foundry techniques (casting or forging) and machining ability. Wright went to machining groves instead of fins on the cylinder barrels and 'rolling' sheet metal fins into the groves on their later engines. The Hercules went through around 1/2 dozen different cylinder head designs with ever improving cooling ability.
I would note however that in 1940 nobody had a supercharger that offered a FTH of much over 17,000ft even in high gear of a two speed set up and that sometimes it took twice the power to drive the supercharger in high gear than in low gear. Picking the right supercharger gear was always a balance between altitude desired and the power needed to drive the supercharger ( and since 30% or more of the power just went heating the intake charge there comes a point of diminishing returns).
AS far as the R-2600 goes. please remember that it is a 1900lb engine that is 55in in diameter, it is NOT a 'plug in' replacement for anything but a Hercules and the 1940 1600hp for take-off version is only good for 1400hp at 11,500ft. (Merlin III at 12lbs was good for 1310hp at 9,000ft) and Wright only hit triple digit per month production in July of 1940. Production would double by Dec and double again by April/May 1941. First 1/2 of 1940 saw production numbers of around 70 per month most months.