Advantages of sleeve valves for H-24 engines?

[Simon Thomas]

The Tempest had two engines available to it. If the Sabre was a "miserable failure" then surely they would have switched all to be powered by the Centaurus?

 

[Deleted member 68059]

The Tempest had two engines available to it. If the Sabre was a "miserable failure" then surely they would have switched all to be powered by the Centaurus?

At the time the Centaurus was itself absolutely excelling at being a failure, it was probably even further behind than the Sabre.

 

[J.A.W.]

Sabre, just over 5,000 built to end 1945, production continued through 1946, about another 200 built, plus there was a conversion program of II, IIA, IIB and IIC into VA

3,215 Typhoon plus 942 Tempest V and VI comes to 4,157. However the engine situation was so bad in 1943 several hundred Typhoons in storage were reduced to spares as they had little chance of ever receiving an engine. In 1945 even some Tempests were being reported as "slaved to purgatory storage", no engine fitted. Typhoons are over represented when it comes to numbers turned into Maintenance Airframes. So deduct about 10% from the aircraft figure.

The Tiffy was Pissy?

The Typhoon had a design flaw like the early Bf109F causing structural failure near the tail, in both cases the fix was simple once the problem had been understood. The main Typhoon problem was the engine performance and availability. Typhoon cumulative production was 227 by end June, 448 by...

ww2aircraft.net

The Tempest V finished production in August 1945, the 142 Tempest VI (July 1945 to June 1947) used the Sabre V, about 130 V and VA had been built by end 1945.

I've seen figures for 3,317 Typhoons, (did you include the Mk1a, & Hawker built units) plus weren't many of those 1943 Typhoons taken back
for airframe modifications, (sliding bubble-canopy/Tempest tailplane/4-blade prop/1000lb bomb shackles)?

There were also 20+ production Firebrands, plus numbers of prototypes/research aircraft flying with Sabre engines too, of course.
Hawker refurbished 80 odd Mk Vs to TT5 spec, for service use into the mid `50s.

 

[J.A.W.]

That is quite a novel approach to inferring engine reliability.

It is worth noting, that an aircraft which crashes and the airframe of which is destroyed or even just written off does not require a new engine for that airframe,
and that an aircraft which is lost over enemy terratory does not require a new engine for that airframe.

The RAF knew perfectly well what the Sabre was like and were inspecting them constantly and rebuilding them at tiny service intervals
once the sleeves started playing up to make sure they DIDNT blow all engines up. For a very long time whilst Merlin`s were
doing 200>400 hours between major overhauls, Sabre`s were being taken apart at 50/70 hours or less. None of that
requires a replacement engine for that airframe either, but is still a catastrophically bad position.

A slightly more solid viewpoint on what it was actually like is to be found if you read the Air Ministry files,
part of the reason for there not being so much effort put into rebuilding them at tiny intervals was
that there WERE no spare engines.

Even in 1943, the Air Ministry description of the Sabre was "from bad to worse" (see 4th page down)

"never likely to become a reliable engine" (see 5th page down)

"it was on balance a miserable failure" (see 6th page down)

- By the final 12months of the war it was just about there in terms of being reliable to a practical degree, but
that was far too late.

Please note I think its a fascinating engine, and it would be a good thing to get one running again now,
but - at the point in time back then, it was an immensely troublesome, difficult unreliable engine
for most of the war, these are simply recorded facts.

View attachment 759093
View attachment 759094

View attachment 759095

View attachment 759096

View attachment 759097

Note: This is hours between FAILURES IN FLIGHT, not T.B.O.

View attachment 759098


View attachment 759099


"Average engine life is 67 hours"

View attachment 759100

They are manufacturing, rather than design issues, & of course, like F1 drivers, the fighter pilots wanted its performance, it was up to the
makers to sort out their end of the stick. Even the very early Typhoon, rushed into service full of bugs, showed why the Merlin was passe`

See: http://www.wwiiaircraft.org/typhoon/Typhoon_AFDU_Tactical_Trials.pdf.

Ironically, at a meeting where the RAF brass were canvassing views as to whether the Typhoon/Sabre program should be cancelled,
there were many 'boffins' spouting exactly the kind of appraisal listed in the letters shown, but one Squadron Leader present,
(later a test pilot, of some note) R. Beamont piped up, & asked if the RAF 'expert' (who was an experienced Spitfire pilot) bagging
the Typhoon so heavily - had ever flown a Typhoon? & of course, he hadn't - which 'spiked his guns' rather...

 

[Deleted member 68059]

They are manufacturing, rather than design issues, & of course, like F1 drivers, the fighter pilots wanted its performance, it was up to the
makers to sort out their end of the stick. Even the very early Typhoon, rushed into service full of bugs, showed why the Merlin was passe`

See: http://www.wwiiaircraft.org/typhoon/Typhoon_AFDU_Tactical_Trials.pdf.

Ironically, at a meeting where the RAF brass were canvassing views as to whether the Typhoon/Sabre program should be cancelled,
there were many 'boffins' spouting exactly the kind of appraisal listed in the letters shown, but one Squadron Leader present,
(later a test pilot, of some note) R. Beamont piped up, & asked if the RAF 'expert' (who was an experienced Spitfire pilot) bagging
the Typhoon so heavily - had ever flown a Typhoon? & of course, he hadn't - which 'spiked his guns' rather...

Sure thing you go with whatever info you feel most comfortable with, here is what I feel comfortable with >

 

[Deleted member 68059]

If this doesn't lay it out for you I don't know what will.

 

[J.A.W.]

Sure thing you go with whatever info you feel most comfortable with, here is what I feel comfortable with >

View attachment 759241

Yes, IMECHE has some useful documents, some are viewable online, now too.

Edit: Corrected typo in title acronym of organisation.

 

[Shortround6]

The Sabre appears to have been oversold before it really entered production (not the only example by far), manufacturing difficulties were a real problem (and not just for Napier).

A lot of drawings/prototype planes were trashed because they couldn't make enough Sabres.

The Sleeve valve lost some of it's edge when the engine designers starting figuring out what 100-130 fuel could really do.
The sleeve valve would not stand up to high boost without bending/breaking the sleeves which stopped the engine pretty quick. It got better but not anywhere near quickly enough.
An engine using 18lbs of boost can move 27% more air than one using 11lbs of boost. Actually power needed to achieve that boost and the altitudes it can be done at change things somewhat.
Hercules didn't go over 8.25lbs of boost until the 100 series.

In 1935-1940 with 87 to 100 octane fuel the sleeve valve looked like it might provide some answers. In 1940-41-42 the better fuel allowed poppet valve engines to close up some of the difference with fewer problems. But the engine and airframe programs were too far along to cancel and bedsides "the solution" was just around the corner/a few weeks or months away

 

[J.A.W.]

If this doesn't lay it out for you I don't know what will.

View attachment 759246

Of course, it was the Bristol sleeve manufacture/finishing method that was needed.

Funnily enough, when Bristol presented their unconventional finish-machining method for patent approval,
it was rejected as being inexplicable by the examiners, 'til Riccardo wrote a supporting analysis...

 

[J.A.W.]

The Sabre appears to have been oversold before it really entered production (not the only example by far), manufacturing difficulties were a real problem (and not just for Napier).

A lot of drawings/prototype planes were trashed because they couldn't make enough Sabres.

The Sleeve valve lost some of it's edge when the engine designers starting figuring out what 100-130 fuel could really do.
The sleeve valve would not stand up to high boost without bending/breaking the sleeves which stopped the engine pretty quick. It got better but not anywhere near quickly enough.
An engine using 18lbs of boost can move 27% more air than one using 11lbs of boost. Actually power needed to achieve that boost and the altitudes it can be done at change things somewhat.
Hercules didn't go over 8.25lbs of boost until the 100 series.

In 1935-1940 with 87 to 100 octane fuel the sleeve valve looked like it might provide some answers. In 1940-41-42 the better fuel allowed poppet valve engines to close up some of the difference with fewer problems. But the engine and airframe programs were too far along to cancel and bedsides "the solution" was just around the corner/a few weeks or months away

Can you post some pix of boost bent/broken sleeve valves? Or is that apocryphal?

I'd note that the 1943 Sabre max boost of +7lb was a cruise rating by 1944, & by 1945 max boost was more than +10lb higher...

I'd also point out that the +15lb (dry) Sabre rating in 1945 was on 100/130 avgas, & the Merlin was restricted to +18lb on that juice.

 

[Simon Thomas]

Ricardo notes that the Sabre was capable of sustained outputs of 3600 hp.

THE HIGH-SPEED INTERNAL- COMBUSTION ENGINE, SIR HARRY R. RICARDO, Fourth Ed 1953, p310.

The boost and BMEP that sleeve valves could withstand was found by Ricardo to be rather high on a test rig.

THE HIGH-SPEED INTERNAL- COMBUSTION ENGINE, SIR HARRY R. RICARDO, Fourth Ed 1953, p343.

 

[J.A.W.]

The sleeve acting as an oil pump of sorts may be quite true.

Part of our problem in sorting out the sleeve valve situation is that often the reports are snapshots in time. What was true late in WW II was not true early in WW II, or what was true in the 1950s.

Oil consumption was quite problem with the early Hercules, to point of oil fouling the spark plugs, More than an annoyance in overwater flights. It was solved, but the claim that all the Sleeve valve problems were solved in 1933 or even 1938 doesn't hold up.

I don't have a good timeline for the later Hercules and Centaurus engines. The last engine types appear to have been built between 1953 and 1956 ( I don't have the 1954 and 1955 editions of Aircraft engines of the World) and the 663, and 673 (?) show up in the 1956 book but not the 1943 book. Also showing up in the 1956 book is a listing for the 373 and 873 which were intended for the Blackburn Beverly but never fitted (if indeed they were ever built?)

with around 10 years of development after WW II quoting performance specs needs to done carefully. On both sides.

If you check the differences for 1st & 2nd iterations in the Sabre VIII spec-sheets listed by Wilkinson, the later unit not only shows the uprated
boost capability*, but also the improvement in fuel & oil consumption, which was a result of Napier ring** development, aiding sealing of oil, &
pressure, while reducing friction-losses, even though an extra sleeve-seal ring had been added. Napier ran an ignition timing advance servo.

The Sabre moved large volumes of oil internally, and a fair % oil-cooled, the Tempest Mk VI using the same big oil-cooler as the radial Mk II.

*Depending on the tribological characteristics, excess oil which worked its way into the combustion chamber could be deleterious, of course.

**For 'Napier ring' hit link:

What Does The 2nd Piston Ring Do? Purpose And Function Explained! | Wiseco

Piston ring packages are as carefully engineered as any high-performance part. Here’s a look at the science that goes into second ring design.

www.wiseco.com

 

[Deleted member 68059]

Yes, IMEC has some useful documents, some are viewable online, now too.

They do not have "SOME useful documents" they are the custodians for the entire remaining Napier Archive material.

 

[J.A.W.]

They do not have "SOME useful documents" they are the custodians for the entire remaining Napier Archive material.

If that is so, is this box (MS/2056 - Sabre test reports & etc) held at the Science Museum, empty?

Records of D. Napier and Son Ltd. | Science Museum Group Collection

Comprisies calculations, diagrams and reports from the office of P.J. Wallace, Test Plant Department, mailny relating to the testing and development of Napier Sabre aero-engines and interconnected control box. Also photo album relating to Napier Research Station, Liverpool.

collection.sciencemuseumgroup.org.uk

 

[Deleted member 68059]

If that is so, is this box (MS/2056 - Sabre test reports & etc) held at the Science Museum, empty?

Records of D. Napier and Son Ltd. | Science Museum Group Collection

Comprisies calculations, diagrams and reports from the office of P.J. Wallace, Test Plant Department, mailny relating to the testing and development of Napier Sabre aero-engines and interconnected control box. Also photo album relating to Napier Research Station, Liverpool.

collection.sciencemuseumgroup.org.uk

Yes amazingly enough huge national scale projects have boxes in other places, Cambridge University archives are the official
holders of the Vickers Supermarine company archives, stunningly there are also copies of a few Supermarine reports about Spitfires at Kew.

 

[Geoffrey Sinclair]

I've seen figures for 3,317 Typhoons, (did you include the Mk1a, & Hawker built units) plus weren't many of those 1943 Typhoons taken back
for airframe modifications, (sliding bubble-canopy/Tempest tailplane/4-blade prop/1000lb bomb shackles)?

I have seen and cross referenced the production figures in British National Archives files AIR 19/524, AIR 8/278, AVIA 46/146, AVIA 10/315, AIR 20/1871, AVIA 49/229 . The Ministry of Aircraft Production (MAP) monthly Statistical Bulletin for 1942 to 1945, plus the 1945 Statistical Review. Ministry of Supply Monthly Statistical Bulletin reports from February 1946. Plus of course the published RAF serial listings, 3,317 is all Typhoon production plus the 2 prototypes P5212 and P5216

Hawker officially built 2 mark IA in March 1942, another 1 in April another 1 in June and the final 1 on March 1943, the Hawker built mark IB were 2 in September 1942, 3 in December, then 3 in March and 1 in April 1943.

From the URL I gave,

The first sliding hoods were actually rebuilds from older Typhoons which had been in store at Glosters, followed by introduction on the production line (intermittent to start with) and finally a mass modification program on Typhoons in service (around 400). Tempest tailplanes were introduced with MN307 in late February 1944 but only a small number could be initially fitted with 4-blade propellers which were not normal until around MN600 in mid April 1944. As far as I am aware the fitting of the Tempest tail was tied in with the 4 blade propeller. It looks like the first 1,000 pound bombs were dropped on 23 April 1944. (AIR 16/1036).

Plus the note on the 1942/43 Typhoons reduced to spares.

There were so many Typhoons in storage that they could be modified to the latest standard there without impacting squadron strength. End July 1944 there were 360 Typhoons in Air Storage Units of which 132 deficient in equipment, plus another 206 airframes. Means of the 566 Typhoons present 228 were complete. Total airframes in storage 588 (Including 146 Master III and 53 Battle), of the 1,364 aircraft deficient in equipment, Typhoons were number 1 in the deficient stakes, followed by 101 Spitfire IX, 100 Oxford I, 79 Swordfish, 77 Beaufighter X, 74 Mosquito VI, and 73 Anson

1 September 1943 the 16 Typhoon squadrons had 178 serviceable aircraft, the 4 Hurricane squadrons 53 (x4=212). The authorised strength of the Hurricane squadrons was 14 aircraft each, the Typhoons were 11 squadrons at 18 aircraft each, 5 at 14 each, average 16.75

There were also 20+ production Firebrands, plus numbers of prototypes/research aircraft flying with Sabre engines too, of course.

Yes, along with prototype Sabre which are not in the production statistics. Firebrand 9 mark I (5 from June to August 1943, 4 from May to October 1944) 12 mark II (June 1944 to February 1945) again ignoring prototypes. The mark II is reported to have used the Sabre III, of which 25 were built October 1942 to February 1944. The mark III used the Centaurus, over 2,900 produced to end November 1945

 

[J.A.W.]

Yes amazingly enough huge national scale projects have boxes in other places, Cambridge University archives are the official
holders of the Vickers Supermarine company archives, stunningly there are also copies of a few Supermarine reports about Spitfires at Kew.

View attachment 759328

Yes, certainly, but as well as Napier archive papers/pix - the Science Museum also holds an actual Napier Sabre engine, too.

 

[Tom Fey]

There is a scientific paper comparing sleeve versus poppet valves on the Aircraft Engine Historic Society Website. I am a member and read the document probably 10 years ago. I cannot locate it right now and I don't believe I can share it here anyways.

https://www.enginehistory.org/members/articles/Sleeve.pdf

 

[J.A.W.]

https://www.enginehistory.org/members/articles/Sleeve.pdf

Yes, Raymond really ought to have revised that article by now, certainly as a 'thesis' it would not been passed by an informed supervisor,
based on a number of cogent points.

 

[Deleted member 68059]

Yes, Raymond really ought to have revised that article by now, certainly as a 'thesis' it would not been passed by an informed supervisor,
based on a number of cogent points.

Go and write your own paper then.