British Air Ministry rejects sleeve valve engines

IMO, sleeve valve radial aircraft engines were a technological dead end vs. poppet valve engines. In 1932 Bristol introduced their first sleeve valve engine, the Perseus. Up to this date Bristol was making poppet valve engines, such as the Jupiter and Mercury.

WI the British Air Ministry rejects all sleeve valve tech in 1930. How are RAF and FAA aircraft impacted in the interwar period?

What does Bristol make instead? Presumably they focus on the Bristol Pegasus? https://en.wikipedia.org/wiki/Bristol_Pegasus

Would they proceed with the Bristol Phoenix diesel design?
 
It is debatable whether sleeve valve tech was dead end, though it was said that it took way too much of money & time. However:
They might use Mercury's bore & stroke as basis. 38.9L of displacement in a 14 cyl engine warrants plenty of power, even on 87 oct fuel. 18 cly version = 50L of displacement, probably 1800+ HP on 87 oct.

Hercules was at 38.7L, BMW 801 at 41.8L, R-2800 was at 46L.
 
Good idea on a multi-bank Mercury.

We'll need something with 2,000+ hp for the Centaurus replacement. Perhaps a twin bank Bristol Pegasus?

What about the overhead cam Bristol Hydra? https://en.wikipedia.org/wiki/Bristol_Hydra Change the heads to four valves and you might have winner.

See model below. Notice the pistons are inline.

hydra0612_5.jpg
 
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At the time, Bristol Engines was manufacturing the engines designed by Roy Fedden. He had created the Cosmos Jupiter, sales of which were said to get Bristol through the depression in good shape financially. It was his opinion that poppet valves were becoming a dead end, and that sleeve valves were a solution to the limitations of poppet valves. In fact, several boffins of the era shared his opinion, spawning efforts by Rolls Royce and Napier. Some American firms also dabbled. Air Ministry officials were prone to listen to the boffins. Poppet valves lost some of their limitations, but the Nord Noratlas of the 1950s was powered by SNECMA-built Hercules engines producing just under 2100 hp. Some of the things that were a benefit to poppet-valve engines also helped sleeve-valve engines. Neither Hercules nor Centaurus used dynamic balancers. Considering the time it took Pratt & Whitney to adapt a balancer for the R-2800, finally adopting the Wright solution, one can only wonder how long it would take Bristol to do the same.
 
Good idea on a multi-bank Mercury.

We'll need something with 2,000+ hp for the Centaurus replacement. Perhaps a twin bank Bristol Pegasus?

The twin-bank Mercury should be able to do 1900 HP on early 100 oct fuel, fully supercharged (S/C in high gear in US parlance), so 2000+ HP should be available in low S/C gear. The 2000+ HP should be more than enough for mid-war needs.
Once Bristol has these engines up & running, they should recall their altitude records with Type 138A, that used two-stage supercharger system + intercooler, and get cranking on coming out with military-capable, 2-stage 14- and 18-cyl engines. Plus water injection for late ww2.

What about the overhead cam Bristol Hydra? https://en.wikipedia.org/wiki/Bristol_Hydra Change the heads to four valves and you might have winner.

The Hydra was a small engine, 25L. Looks like it was prone to vibrations, too. Due to the layout?
 
Start by stopping Harry Ricardo publishing his 1927 paper on sleeve valves and the limitations of poppet valves. Without this impetus maybe the research into sleeve valves never progresses. A double Mercury would be a good engine.
If you follow the development line of the Gnome Rhone 14n series engines then by 1940 you are at around 1500hp.
 
Once you get to a certain displacement per cylinder poppet valves have a very hard time filling the cylinder. Plus sleeve valves allow very accurate valve opening. Another plus for sleeve valves us the ability to design optimal cumbustion chambers unencumbered by the valves. Sleeve valves do have their downsides too. One is increased production costs vs poppet valve engines. Not so much in monetary costs but in terms of the additional skilled labor needed to produce the sleeves themselves. As I understand it these were heat treated steel that then ha to be ground and then honed in the inside diameter. Given 1940s manufacturing technology it will be a big soak of manhours. Add in the large number of gear wheels per engine that is another issue. With a poppet valve engine the valves even if forged can be produced largely with multi-spindle automatic lathes and centerless grinders. I can see that in the time it takes to produce one finished sleeve all of the valves for a R2800 or a R4360 being produced easily. I for one would like to see a comparision in terms of manhours for a finished R2800 vs the Bristol Hercules

Production problems aside the main reason to use sleeve valves is greater efficency in terms of lower fuel consumption per HP. Important for longrange patrol and transport aircraft. Combat aircraft not so much. Napier's Sabre eventually was developed into a great engine yet I personally think Britian would of been better served having Napier's build Merlins allowing Rolls Royce to switch over to Griffon production
 
Would be interested what you base your statement about sleeve valve engines on ?
AIUI, poppet valve engines, especially by the late 1930s were easier to make, gave equal to greater power, easier to seal, burned less oil and were easier to maintain than sleeve valve units.

I should qualify that with today's tech the above issues with sleeve valve engines are entirely solvable. Indeed, you can take nearly any technology that's been replaced and make it much better than it was in its heyday. Imagine a modern day triple expansion steam engine - you might argue that to say it was a technological dead end compared to the steam turbine was false. And you'd be right, throw enough money at it and you could make a fantastic TE engine. But, like how sleeve valves are rarely seen today, you'd have to ask yourself why bother.

This looks like a good article on the topic http://www.enginehistory.org/members/articles/Sleeve.pdf I haven't read it yet, got to get back to work.
 
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AIUI, poppet valve engines, especially by the late 1930s were easier to make, gave equal to greater power, easier to seal, burned less oil and were easier to maintain than sleeve valve units.

That's a lot of reasons, but do you have examples of direct comparisons, like AEHS's sample of Miss B. Shilling's direct comparison of Perseus/Mercury engines to determine volumetric efficiency? Easier to maintain?

I think you must be confusing Bristol's lack of efficiency with the sleeve-valve engine. It might have been better if the Air Ministry banned float-type carburetors and forward-facing manifolded exhausts.

The pity is that Bristols developed the direct-injected 3220 hp Centaurus in the age of the turbo-prop.
 

NoMommsen

Donor
But, like how sleeve valves are rarely seen today, you'd have to ask yourself why bother.
Don't wanna be offensive, but ... this sounds a bit like the 'flys argument' :
Why don' t you eat sh-t, trillions of flys can't be wrong.:p;)

This looks like a good article on the topic http://www.enginehistory.org/members/articles/Sleeve.pdf I haven't read it yet, got to get back to work.
That one ... read it some years ago.
Its conclusion IMHO : Sleeve valves were competitive, on the brink of surpassing poppet valves even though being 1 - 2 decades behind in development in which they lacked the pushing rivalry of a bigger number of developers when - sadly for piston engines at all - the jet-age began.
 
Good points. I don't have the necessary supporting info, so I'm not going to convince you otherwise. I can live with that.

Back to the OP, the Air Ministry rejects sleeve valve tech....
 
Maybe they don't but want a Plan B, so say to Bristol, if you are convinced that sleeve-valve is the way to go - then you won't mind Armstrong's having the drawings for the Pegasus, to enable them to do a 'double'!?
 
if the Air ministry can be persuaded to hedge their bets vis-a-vi sleeve valved engines perhaps in 1937 they order a number of aircraft fitted with the Alvis Pelides engine. At that time producing 1,050hp on 87octane fuel. These engines being an anglicized version of the Gnome et Rhone Mistral Major 14 series which were themselves derived from licensed built Bristol Jupiter and Titan engines. Then it is quite practical that by 1940 with the Mistral N being developed into the Mistral R series developing some 1500hp at take off that the Alvis engine follows the same development giving a viable alternative to the Bristol Hercules.

• The Gnome et Rhône 14 R Météore, a 14 cylinder double row radial air cooled engine issued from a complete redesign of the previous 14 N of 1050 hp. The new engine was of the 1,600 hp class.
o It was fitted with a 2 stage Farman CC1 supercharger with a first critical altitude of 2,000 m and a second critical altitude of 6,000 m.
o The maximum continuous power of 1,250 hp was obtained at 2,400 rpm.
o The combat power of 1,580 hp was obtained at 2,600 rpm, for 5 minutes during climbing or 15 minutes during horizontal flight.
o This engine had successfully flown since July 1939 with the twin-engined float sea scout-bomber Loire-Nieuport LN 10, allowing her a top speed of 430 kph, a very exceptional performance for a 14,000 kg seaplane, carrying a crew of six, two torpedoes and able to fly 3,300 km.
 
While the Pelides - would be a start, it's the Pelides Major that would be needed - that was to have had improvements to the supercharger.
 

NoMommsen

Donor
Would they proceed with the Bristol Phoenix diesel design?
Diesel engines - beside Junkers - weren't in much favor by anyoneelse beside the licensing of it by Napier (later becomming the Napier Deltic for locomotives and speed-boats). But afaik the napier variant didn't made it in countable sold engines in use.

The first notable, probably successfull aircraft diesel after Junkers was the Klöckner-Humboldt-Deutz 700 of 1937. Unfortunatly - for germany - it wasn't perceives well in terms of suuport from above.

Even the 'follow-up' development into the monstrous (?) Dz 710 seemed not to have any impact in the air ministry - even though on the nazi beloved route of B I G things. :D

Think the higher power levels promised by benzol-based fuels was just too tempting for going on the diesel road.
 

NoMommsen

Donor
Can you think of anyone in the Air Ministry or the Government, or the Government technical establishments, who thought they knew more about engines than Roy Fedden?
That would be a POD to be constructed :
Dunno about Roy Feddens personality, but perhaps just let him somehow ipss off some mayour guy in the ministry:p.
 
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