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On 12 September 1942, the aircraft made its 10th flight. Captain Baker had just taken off when the engine seized, a result of a sleeve drive crank failure. Low to the ground and without any options, Captain Baker put the MB3 down in one of the many small fields lined with hedgerows and other obstacles surrounding RAF Wing. The aircraft clipped a pile of straw and crashed through a hedgerow at high speed. The MB3 cartwheeled, broke apart, and caught fire. Captain Baker was killed instantly.
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?
Juha, do you have a 'root cause analysis' which sheets home fault to the Sabre engine,
- in the case of Capt Bakers' fatal crash?..
As for the dismal H-P Hereford - as I recall, the engine development writer LJK Setright likened
the use of the Dagger, ( which was intended for a fighter, such as the MB 2) in a medium bomber,
as akin to putting a Formula 1 racecar engine in a bus, & then expecting it - to do well at the task..
...
On Dagger Bowyer writes that attemps were made to persuade Supermarine to fit a 24-cyl Napier Dagger in their latest design, Type 300, but Supermarine strongly resisted. At least Supermarine trusted more on RR than Napier. IIRC in all books I have read Dagger suffered from reliability and maintenance problems. And Merlin worked well on fighters and bombers as did most of engines, Bristol Hercules, DB 60x series, BMW 801,R-1820, R-1830, R-2800, Jumo 213 etc. IIRC only on CC AW Whitley GR types there were significant troubles with early Merlins. So if Setright is correct, Dagger was fairly unique engine during late 30s early 40s, suited only for one type of aircraft.
Well, nobody outside of the UK put sleeve-valve aircraft engines into service, so I'd say most engineers of the era would say "no." Sleeve valves have some advantages, and at least as many disadvantages.
Much more to it than that.
Getting a new application working well is a big effort, so makers such as P & W & R-R, who certainly knew
that sleeve valve advantages were real, having tested their mettle, in metal - made a commercial
decision to stay with developments of their established, if old-fashioned designs - for mass-production.
Roy Fedden & Frank Halford both had experience with DOHC 4V poppet valve cyl heads,
& both well knew that sleeve valves had real advantages over them, let alone pushrod 2V cyl heads.
Much more to it than that.
Getting a new application working well is a big effort, so makers such as P & W & R-R, who certainly knew
that sleeve valve advantages were real, having tested their mettle, in metal - made a commercial
decision to stay with developments of their established, if old-fashioned designs - for mass-production.
Roy Fedden & Frank Halford both had experience with DOHC 4V poppet valve cyl heads,
& both well knew that sleeve valves had real advantages over them, let alone pushrod 2V cyl heads.
Still don't like auto-wrap?
The engineers at P&WA and Rolls Royce certainly knew the advantages of sleeve valves; they would have been reading the same journals and technical reports as Roy Fedden and Frank Halford, and they were all capable of doing the same sort of math. The engineers and the management at those companies also could look at their disadvantages and do a cost-benefit analysis, and conclude that sleeve valves were not worth the bother. Instead, they constructed highly optimized, very carefully designed engines that could sustain high outputs, be mass produced by subcontractors with no prior aviation experience, and perform reliably in service. Napier leapt onto the sleeve valve bandwagon and produced a complex engine that they couldn't manufacture without outside technical assistance and machinery that didn't exist in the UK.
From what I read the problem wasn't so much of the design of the Sabre but of mass producing it.
The engineers at P&WA and Rolls Royce certainly knew the advantages of sleeve valves; they would have been reading the same journals and technical reports as Roy Fedden and Frank Halford, and they were all capable of doing the same sort of math. The engineers and the management at those companies also could look at their disadvantages and do a cost-benefit analysis, and conclude that sleeve valves were not worth the bother. Instead, they constructed highly optimized, very carefully designed engines that could sustain high outputs, be mass produced by subcontractors with no prior aviation experience, and perform reliably in service. Napier leapt onto the sleeve valve bandwagon and produced a complex engine that they couldn't manufacture without outside technical assistance and machinery that didn't exist in the UK.
Yet, amazingly somehow, the backyard tinkerer, poor bloody Brits did get their 'Hyper' mill into combat,
& usefully so, unlke the mighty US military-industrial complex, which only produced the 'Hype', but not the engines..
What proves what point? The Typhoon was retired in October 1945, presumably before winter started because the engines had to be kept constantly warm and run up through the night in the previous winter. How many Sabre Tempests were in service post war?Yep, the fact that the RAF kept their Sabres flying hard ( the manner which suited them best) right up to the mid `50s
- indeed, proves that very point.