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Serious losses were inflicted on Japanese airpower, not by fighters, but by bombers.
There are many theories about engines that have fundamental theoretical superiority over others, whatever the theoretical strengths of sleeve valves are or were, getting them to work reliably was another thing.It may well have had greater greater volumetric efficiency in general or especially over certain examples. However poppet valve engines have considerable variation in volumetric efficiency so unless we know what is being compared such a statement doesn't mean much.
That is to say that perhaps a sleeve valve cylinder shows a 2% increase over poppet cylinder A and a 10% improvement over poppet cylinder B.
Obviously the advantage over Cylinder B is substantial and even the difference between the sleeve valve and the average of the poppet valves is a noticeable one. However if the difference gets down to 2-3 % while the statement is still accurate does the cost/complication of the sleeve valve justify the development of engines using it?
I use the Typhoon as a guide, I don't know if they actually flew them back to the UK to scrap them, when the war ended. In poppet valve engines minor differences of machining can "bed in" on a sleeve valve engine everything is moving in circles and orbits rubbing things away. As you allude to, the pistons wear the sleeves and the sleeves wear the block or guides, it isn't an overhaul it is basically a new engine.They got them to work, what has never been answered is if the cost was worth it. Post war commercial Hercules and Centaurus engines were powerful, economical in fuel and had very hi times between overhauls. But if we don't know the cost of the engines or the cost to overhaul them, then we have no real basis for figuring out if they were better than the poppet engines which were posting overhaul times of well over 1000 hours.
Since we also have no ideas of the R&D costs leading up to WW II (or the first few years of WW II) we don't know if the they made enough engines to really justify the costs.
Trying to give the Sleeve valve the benefit of the doubt and there were a lot more Bristol radials built than Sabres.I use the Typhoon as a guide, I don't know if they actually flew them back to the UK to scrap them, when the war ended. In poppet valve engines minor differences of machining can "bed in" on a sleeve valve engine everything is moving in circles and orbits rubbing things away. As you allude to, the pistons wear the sleeves and the sleeves wear the block or guides, it isn't an overhaul it is basically a new engine.
In theory I can see the benefits, and with todays machining technology and metallurgy I could see it working, but poppet valve engines have moved on too.Trying to give the Sleeve valve the benefit of the doubt and there were a lot more Bristol radials built than Sabres.
It may well have had greater greater volumetric efficiency in general or especially over certain examples. However poppet valve engines have considerable variation in volumetric efficiency so unless we know what is being compared such a statement doesn't mean much.
That is to say that perhaps a sleeve valve cylinder shows a 2% increase over poppet cylinder A and a 10% improvement over poppet cylinder B.
Obviously the advantage over Cylinder B is substantial and even the difference between the sleeve valve and the average of the poppet valves is a noticeable one. However if the difference gets down to 2-3 % while the statement is still accurate does the cost/complication of the sleeve valve justify the development of engines using it?
This one notes the steady increase in Bristol Hercules TBO, right up to
3,500 hrs in Bristol Freighters working hard ferrying cars across Cook Strait
in NZ.
https://www.newcomen.com/wp-content/upl ... assell.pdf
& here below, Kevin Cameron describes some of the poppet valve problems encountered
by Wright R-3350 engines in hard-flown B-29's..
https://www.cycleworld.com/writing-abou ... y-davidson
A message I received from a former member....
They got them to work, what has never been answered is if the cost was worth it. Post war commercial Hercules and Centaurus engines were powerful, economical in fuel and had very hi times between overhauls. But if we don't know the cost of the engines or the cost to overhaul them, then we have no real basis for figuring out if they were better than the poppet engines which were posting overhaul times of well over 1000 hours.
Since we also have no ideas of the R&D costs leading up to WW II (or the first few years of WW II) we don't know if the they made enough engines to really justify the costs.
I wouldn't put any Napier powered MB fighter to advertise Napier engine, firstly Baker was killed in Napier Sabre powered MB 3 proto when its Sabre failed during a take-off. Martin & Baker had asked for a RR Griffon but had to be content with a Sabre. Secondly Dagger wasn't a good engine, look the service history of Handley Page Hereford, Dagger powered version of Hampden. Napier had made good engines earlier, like Lion, but in 30s it had not a good track record.
Napier engines had accrued a number of merits...
View attachment 489408
Napier engines powered the World Land-speed record holder in 1939,
& Sabre* power was selected for an attempt on the World Air-speed title too.
Nothwithstanding problematic mass-production issues, the Sabre was the sole 'hyper' type
to see useful wartime service, & was the most powerful aero-engine ever, to pass service
type tests in the early 1940's..
*That specially 'fettled' Sabre then went into a regular service Typhoon, but I'd reckon
the squadron C.O. would've scored that one, for his 'personal' use..
Juha, do you have a 'root cause analysis' which sheets home fault to the Sabre engine,
- in the case of Capt Bakers' fatal crash?