Talk:Napier Sabre

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Cooling of rear cylinders

I think there's a minor error in this article; where it talks about "the rear banks proved to be impossible to cool properly", I think it means "rear cylinders", since of course in an inline H engine the banks are described as top/bottom and left/right. However, without checking a reference, I'm loathe to change it. Noel 00:37, 3 Oct 2003 (UTC)

White's "allied aircraft piston engines of world war II" doesn't seem to specify whether the sabre was two or four stroke, but "Jane's fighting aircraft of world war II" page 278 is quite explicit that it was a four stroke. I've just read Setright's "power to fly" and don't remember him saying the sabre was a two stroke. I think the only major two strokes were Junkers diesels like the 205. Kahl 24/7/2006

It's a four stroke. If it was a two stroke it would be like the Rolls-Royce Crecy and would be even more remarkable than it already is. PeterGrecian 13:27, 24 July 2006 (UTC)[reply]

The statement that the forces from opposing pistons balance is only true where the pistons move in opposition - one moves left as the other moves right. In many flat-12s, including the H-24 Sabre, the two pistons move together - both left or both right and so the forces add rather than cancel. Peter R Hastings 13:31, 26 February 2007 (UTC)[reply]

- To add a little to Peter's remarks above, the way that an engine like this balances is that the secondary forces within one plane of four cylinders (eg one slice of the engine) all balance out. The four pistons effectively all move together, with the two crankshafts revolving in opposite directions. The primary forces then balance along the engine, in this case in the same way as the primary forces would balance along a six cylinder motor. This gives excellent primary and secondary balance, without the need for any balance weights. Also the crankshafts are simpler than a boxer style opposed engine would need since two cylinders each share a crank, and they can use a standard forked rod arrangement. John — Preceding unsigned comment added by 122.62.95.56 (talk) 07:08, 1 January 2014 (UTC)[reply]

Time for an update?

I just had a quick read through, lots of good text but there are many claims and statements that lack references even if they are true (which they most probably are). The lack of references is holding it off of B class. The one web reference used would almost certainly not be accepted at FAC review (from very recent experience of this!) despite it being apparently 'straight as a die'. Will have a look through my books. Nimbus (Cumulus nimbus floats by) 00:16, 2 October 2009 (UTC)[reply]

There is some confusion over the variants of the Sabre; for example several of my sources confirm that the Sabre II was used in at least two early production batches of Hawker Typhoons, yet, according to Lumsden (which is the primary source), it appears to be an experimental version from 1940. This article should have been properly cited as it was being written, instead of needing all this effort to untangle conflicting information. Poor show! Minorhistorian (talk) 01:54, 9 November 2009 (UTC)[reply]

The Tempest became the principal destroyer of the V-1 flying bomb (Fieseler Fi 103), since it was the fastest of all the Allied fighters at low levels.

I know I've seen test reports of Mustang MkII's going the same speed at Sea level as the Tempest, which is why it (and the F-6A and B) were used into 1945. ^[1] JetMec (talk) 22:43, 2 January 2013 (UTC)[reply]

Your point being? ◆Min✪rhist✪rian◆MTalk 00:16, 3 January 2013 (UTC)[reply]

There's also the issue of range. The Mustang, owing to its particularly efficient wing, had (especially with drop tanks) a longer range and so remained in demand as an escort fighter. Tempests were fast and available. Andy Dingley (talk) 00:42, 3 January 2013 (UTC)[reply]

The Tempest V was the fastest Allied fighter at low level, approx 436 mph at sea level.

Test aircraft may achieve such speeds but the test needs to be performed with all the operational equipment installed, and with a representative load of fuel and ammunition, and so the test referred to above may not be relevant. — Preceding unsigned comment added by 95.149.172.235 (talk) 09:56, 9 November 2018 (UTC)[reply]

References

^ http://www.wwiiaircraftperformance.org/mustang/mustang-I.html

5500 hp

Is this documented - is it a fact or merely wishful thinking? 86.178.21.163 (talk) 04:26, 4 January 2010 (UTC)[reply]

3,500 hp is the highest power output that I could cite for a production engine, the text does note that this was for late prototypes running at +45 lb boost so it's not entirely unreasonable. Problem is, like the rest of the important facts in this article, it is unreferenced. Hopefully someone will get round to it in 2010. Nimbus (Cumulus nimbus floats by) 06:08, 4 January 2010 (UTC)[reply]

The Sabre did not receive the attention in supercharger development that the smaller Merlin did, until later in its life. The later Sabres had more advanced superchargers and could achieve over 5,000hp. The UK could get more power out of an engine than anyone else in the world, which is why they dominated Formula One motor racing for so long. —Preceding unsigned comment added by 213.40.253.12 (talk) 12:40, 27 January 2010 (UTC)[reply]

This sort of false logic is not really the basis for a reference-standard article. Comparisons between Formula 1 and 1940s aero engines are pretty pointless since the demands are totally different. Flanker235 (talk) 23:31, 9 August 2014 (UTC)[reply]

The Sabre was used as a low-rated engine (i.e., for low altitude use) for most of the war, and so did not get the attention in supercharger development that the Merlin did. Thus the Sabre only had a single-stage supercharger for most of this time. Later test Sabres had two-stage and three-speed superchargers like the final Griffons, and had much greater power.

This is highly unlikely. The Sabre had a cubic capacity about the same as that of the Griffon and unless it showed massive improvements in Brake specific fuel consumption or Volumetric efficiency, it's highly unlikely the difference would have been that great. Piston aero engines were pretty much at the limit of their development at that time, irrespective of layout. Flanker235 (talk) 10:00, 9 August 2014 (UTC)[reply]

Did the three-stage ever fly, or was it just Napier playing with compressors, as part of their increasing focus on gas turbines? Andy Dingley (talk) 10:54, 27 April 2010 (UTC)[reply]

IIRC I don't think so - apart from the 'unusual' types of engine such as the Nomad (which was intended for a long-range maritime reconnaissance aircraft such as the Shackleton), Napier's attention had shifted over mostly to Gas Turbines by then. I think also any likely orders for a 5,000hp Sabre had probably disappeared by around 1945-6 and the experiments were discontinued along with any further development of the engine. The Sabre weighed about a ton and was complicated and it was becoming fairly obvious by then that it would soon be possible to get 5,000hp from a turboprop of around that weight, e.g., the later Tyne and the Proteus.

BTW, the 45lb boost figure for the final Sabres is extremely high and shows the amount of supercharging this engine could take, IIRC, the highest figure for a Merlin was around 32lb, in the final military Merlin 130/131s in the de Havilland Hornet.

Er...are the two paragraphs starting with "IIRC I don't think so..." and ending "de Havilland Hornet" to be read as being from Andy Dingley, or is that someone else's comment? Otherwise it looks very much like A-D is replying to himself. 'Tis confusing ;-) Minorhistorian (talk) 10:56, 29 April 2010 (UTC)[reply]

Fixed.

Is this documented - is it a fact or merely wishful thinking? if you want some idea of the sort of powers the British could get out of a piston engine then I suggest a look at the BRM page which includes the 1949 BRM V-16 of 1.5 litre and around 600 hp, as well as the later BRM H16. The power obtained from the 1.5 litre BRM V-16 was around the same power as that of the turbo-engined 1,500cc Group B Rally cars of the 1980s that were eventually banned as being too dangerous. So 5,500 hp from a 36 litre Sabre doesn't seem excessive.

Perhaps not but it's not really the basis for reference-grade material, which this is supposed to be. Remember that aero engines are generally under greater stress than even racing engines, since they are required to run at around 80% of their rated power for long periods. Even racing engines are not at 100% for all that long. What seems simple enough from a motoring point of view is not always so from an aviation point of view.

Without wishing to pour any scorn upon L.J.K. Setright, from whose book "The Power to Fly" the claim comes, anyone who has read any of his material will know that he was primarily a bit of an entertainer. A combination of slightly outrageous, stiff-upper-lip and public school clown, he could be very funny and engaging but sometimes played a little fast and loose with the truth. To be fair to him though, I have not read the book (it's far too expensive for what it is, costing several hundred dollars for a copy in very ordinary condition) and I suspect he was probably being rather more serious about his topic than was usually the case. He took his work seriously. Your reasoning, while not readily provable, would certainly have found favour with him. Flanker235 (talk) 09:46, 9 August 2014 (UTC)[reply]

The claim of '5500 hp' has now been uncited for two whole years - I think it's high time to move to something along the lines of 'type-tested at 3000-odd hp at the end of the war; see 1945 Flight article' etc. 86.185.70.237 (talk) 13:52, 3 January 2012 (UTC)[reply]

While not actually denying the claim, the late Bill Gunston certainly poured cold water on it in the introduction to his book "Piston Aero Engines" (Patrick Stephens Ltd, 1993, p.8 ISBN 978-1-85260-619-0), when he said:

"When you are going from engine to engine there are no great problems in trying to present a fair assessment, though I suppose even the most objective author has his likes and dislikes. (I shall never forget Setright's belief that the Napier Sabre was good for 5,500 hp!) On the other hand, when you are trying to explain basic principles it is almost impossible not to let personal opinion creep in. Inevitably, you 'know' certain ideas worked well while others didn't, and in no time you are using words such as 'better' and 'worse'. On reflection, it may be that such sweeping assessments are not justified. Sometimes particular ideas or design features were never properly tried out, or they were tried out in half-baked immature form in a very harsh environment."

Gunston's background is noteworthy and for that reason (true to his above quote!), I would have to rate him higher than Setright. Gunston was a former RAF pilot and editor of "Jane's Aero-Engines" for 12 years. However, it's probably not entirely fair to Setright to dismiss his claim on that basis. The trouble is that there is no other source for it and I'm not sure it fits the criteria for verifiability. I think it should probably be removed. Flanker235 (talk) 09:26, 9 August 2014 (UTC)[reply]

Possibly the highest published approximate performance for a Sabre is the "Nearly 4,000hp on test" for the Sabre VIII intended for the RAF Hawker Fury, here: [1] Official support for further development of the Sabre VIII was almost certainly stopped with the cancellation of the RAF Fury requirement, the naval version using the Bristol Centaurus instead. Napier may well have continued on their own however.

I would expect the "Nearly" to refer to around 3,900hp or thereabouts. IIRC, this would have been achieved with a boost pressure of around 45 lb/sq in. or higher. I suspect that would have been on 150 Grade (150 octane) fuel.

What it achieved on a test bench and what it achieved in service are two different things and for clarity's sake, unofficial figures should be left out. Otherwise people start talking about the "Hawker Fury with its 4,000 hp engine" which obviously didn't happen. This is supposed to be reference grade material and needs to be verifiable. "Almost 4000 hp" isn't reference grade, even with that citation. It certainly isn't a pointer to service engines, nor is it a validation of Setright's claim. Flanker235 (talk) 04:45, 25 January 2016 (UTC)[reply]

Setright's claim is almost certainly the theoretical maximum that could be obtained from the engine based on its cubic capacity and estimated rpm limit. FWIW, Rolls-Royce engineers reckoned the 1.5l BRM V16 was 'good for 1,000 hp with special fuels'. Rolls-Royce themselves more than doubled the horsepower of the Merlin during its six years of wartime service and had obtained 2.160 hp from a test engine as early as 1938. OTOH, at the time the Sabre was cancelled it was still in a relatively early stage of development.

I suspect Setright was basing his statement on the Sabre being sufficiently robust as to allow ever increasing levels of boost during development over time without suffering mechanical failure.— Preceding unsigned comment added by 95.149.172.235 (talk) 12:00, 9 November 2018 (UTC)[reply]

Deleted - after more than ten years of disbelief, for the most part.

Worth noting exactly what Gunston said (quoted above): I shall never forget Setright's belief that the Napier Sabre was good for 5,500 hp!

Not 'Setright's claim that it did . . .' but 'belief that' it could, conceivably - by no means the same thing.

31.51.219.150 (talk) 03:48, 9 November 2021 (UTC)[reply]

Double-counting

< Another important effect of increasing the number of cylinders is that the piston area increases (for a given capacity and bore/stroke ratio) and this also aids higher power.[citation needed] >

This is only a rewording of the concept described in the previous sentence. No 'other important effect' that 'also aids higher power' can be claimed.

86.3.108.41 (talk) 15:02, 30 September 2011 (UTC)[reply]

Comparing the very similar displacement engines - Griffon and Sabre - the piston area of the Sabre is 471 sqin and the Griffon's 339. But, the piston circumference, an indicator of internal friction, is also much more - 377 vs 226 inches. 162.157.224.171 (talk) 06:52, 4 October 2015 (UTC)[reply]

Sabre's also a sleeve valve though, so assumptions about comparable relations for friction and ring length break down a bit. Andy Dingley (talk) 10:09, 4 October 2015 (UTC)[reply]

Not to mention the fact that ultimately, each design is a different way of trying to do the same thing: to extract the maximum energy from the fuel at the greatest efficiency possible. The differences between competing designs, as long as they remain reciprocating piston engines, are not that great. If anyone has any information on things like the Sabre's fuel flow rate or SFC, I'd be interested in running some calculations. The most important figures I need are torque and fuel flow rate. My brother-in-law builds dynamometers so I'm well placed to do it. Of course, Wiki doesn't allow primary research as a submission for reference material but sorting these things out is not as hard as you think, provided we have the right information. Flanker235 (talk) 06:58, 26 January 2016 (UTC)[reply]

The use of more cylinders of smaller diameter gives lower inertial forces on the piston/con rod/crankshaft assembly, thus lower stressing of these components. This, in conjunction with sleeve valves, allows for greater rpm to be attained as there is no problem with valve bounce. The Sabre was of the same cubic-capacity as the Griffon - 36 litres - and as the Sabre has 24 cylinders as opposed to the Griffon's 12, the Sabre's pistons were in fact smaller and lighter than those of the Griffon. The Griffon was rev-limited to around 2,700 rpm, whereas the Sabre was red-lined at around 3,900 rpm. The corresponding figure for the smaller 27-litre Merlin was around 3,000 rpm.

The downside to this is greater internal friction which makes the engine more difficult to turn over when starting, a factor that became important in cold weather with the engine oils available at the time. In cold weather the oil thickens and sometimes the starter cartridge would not give enough 'oomph' to turn the engine over through sufficient revolutions to allow firing on more than one or two cylinders before the initial impetus provided by the starter had subsided. A temporary solution for this was to run the engines up every four hours during cold nights, a practice that IIRC caused much annoyance to the local residents around RAF Manston when Typhoons were based their in order to counter low-level Fw 190's raiding the UK.

The philosophy behind Halford's engines was to obtain as high as possible rpm for greater powers from a given displacement. This same philosophy was also used by BRM's Peter Berthon for the post-war BRM V16. — Preceding unsigned comment added by 95.149.172.235 (talk) 09:51, 9 November 2018 (UTC)[reply]

Performance In Aircraft Engines

This article seems to place great importance on the HP/CID that the engine produces. That is not a good measure of an engines performance. The important figures are the ratio of power to weight (HP/LBS) and of efficiency as expressed as the ratio of power produced to the amount of fuel burned. An engine of lighter weight is a better engine than one of the same power producing the power from fewer cubic inches but with more weight. In general the HP/LBS ratio is a much more meaningful one than HP/CID. Also in this article there seems to be a tendency to default to figures for power which are from seldom used or unproduced engine types. This is not very useful in comparison.--Corumplex (talk) 07:05, 17 November 2013 (UTC)[reply]

Agreed. Although there are many parameters by which the performance of an engine can be judged, Brake specific fuel consumption does not seem to rate a mention in this article. I would have thought it an imperative. Flanker235 (talk) 09:52, 9 August 2014 (UTC)[reply]

For an RAF fighter of the period the only important engine performance parameters were power-to-weight ratio, minimum frontal area, and reliability. Fuel consumption was mostly irrelevant, provided an endurance of around an hour was still possible while cruising on the available internal fuel.

The fighters were specified for intercepting attacking enemy bombers, and with RAF airfields located all over the UK, and an effective Early Warning system and Ground-controlled interception in place, long range or endurance for RAF fighters was neither required, nor specified.

That, BTW, is why RAF fighters since around 1939 were often criticised for their lack of range or endurance. Used as-intended, for the defence of the UK, there was no pressing need for it.— Preceding unsigned comment added by 95.149.55.0 (talk) 20:14, 18 August 2017 (UTC)[reply]

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What restoration projects can be including in the "Restoration project and engines on display" section?

The title of this section is a bit vague to me. Does it mean "(restoration project and engine)s on display" or "(restoration project) and (engines on display)"? The former would require a restoration project to be on display to be included in the list whereas the latter would allow all known restoration projects to be included (and therefore should probably have the section title corrected to say "projects"). There was a news article on March 26 2023 about a group in British Columbia - https://www.typhoonlegacy.com/index.php/project/ - having acquired a Napier Sabre as part of their Typhoon restoration project: https://www.cbc.ca/news/canada/british-columbia/vancouver-island-second-world-war-hawker-typhoon-fighter-bomber-rebuild-1.6791024 Their intention is to restore the plane and engine to flying condition. - Wikkiwonkk (talk) 03:59, 28 March 2023 (UTC)[reply]

[1] ttp://www.wwiiaircraftperformance.org/mustang/mustang-I.html

[1]