Jumo 213 vs. Napier Sabre

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Minor typo - should be Napier Sabre VA has 2,300hp @ 3,850rpm, +12psi for take-off, 2,600hp @ 2,500ft, 3,850rpm, +15psi boost in low gear, and 2,300hp @ 12,750ft, 3850rpm, +15psi boost in high gear.

This aligns with Lumsden for the VA.
 
re Sabre use after the war

I may be wrong, but I have always assumed that the reason for the rapid fade out of the Sabre was the British intent for adoption of turboprops in the power range of the larger piston engines, and the ending of the RR Eagle 22 program. The British seem to have begun a serious push for turboprops in 1945-46? Gannet and Wyvern being their first(?) military types, both introduced to service in 1953.

The US stayed with large piston engines (R-2800/3350) because they already had them in large numbers, with the R-4360 available soon after WWII. The US seem to have begun serious development of turboprops about the same time as the British (maybe 1-2 years later?) but put them on the back burner for combat aircraft types - the first military use by the US being the 4-engine aircraft Hercules and Orion(?) introduced to service in 1957 and 1962 respectively.
 
Longevity of the Merlin was likely helped by its use as tank engine (Meteor) with an ample supply of spare parts produced into the 1970s(?)
 
Denniss said:
Longevity of the Merlin was likely helped by its use as tank engine (Meteor) with an ample supply of spare parts produced into the 1970s(?)
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Another good point.

In April 2022 I visited the RAF Museum in Hendon, London. Here's my photo of their Typhoon. The Sabre and its scoop look impressive.

IMG_20220331_1324490.jpg


They had a Tempest there too, you can just see it to the left of the Bf 109.

IMG_20220331_1328048.jpg
 
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View: https://www.youtube.com/watch?time_continue=5&v=Hk1-P5iksIc&embeds_referring_euri=https%3A%2F%2Fwww.secretprojects.co.uk%2F&source_ve_path=Mjg2NjY&feature=emb_logo

I wonder how a four Sabre, four blade prop, HA-optimized Lancaster, HP Halifax or Short Stirling would have done. With all engines working it would have been quick. When up to three engines predictably failed, you might still get home. Here's a Sabre-equipped Vickers Warwick. Without the chin scoop, a FAA Typhoon would have benefited from this layout. If only reliable.

bddbed5389fcab6c950925075559d618.jpg
 
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The 4-e bombers likely would have required a lot more fuel, giving up some bombload for a questionable speed gain.
 
Simon Thomas said:
Getting back to the Napier Sabre producing 5000 hp.

In the Aeronautical Journal volume 79, Issue 777, September 1975 there is a review of the book "Some Unusual Engines" by Setright. The reviewer is Air Commodore F.R. Banks, and he states this about the Sabre:
"Further, the Sabre never achieved 5500 bhp. The maximum (quoted by the reviewer [Banks] in his James Clayton lecture of 1951) was 3000 bhp on 100/130 grade fuel plus water/methanol injection."​

Ricardo in "The High-Speed Combustion Engine" Fourth Edition states:
"It gave a take-off and combat power of no less than 3050 B.H.P. when running at 3850 r.p.m. and had shown itself capable of a sustained output of 3600 H.P."​

I suggest that:
  • 5000/5500 hp is a myth dispelled by a very well respected figure in Aircraft engines
  • 3600 hp could be squeezed out in the Napier test bay during a long term test but with plenty of cooling water. I would consider Ricardo a dependable source.
  • 3050 hp with ADI is the real maximum figure. I expect there is a type test somewhere to verify this, although I have never seen it.


I have attached Banks James Clayton lecture. It doesn't say much that we don't know.
Click to expand...
Hi Simon,

First off, a caveat - I'm only providing Setright's text - like you, I find the 5500hp pretty hard to believe.

But I thought I would add what I could from L.J.K. Setright himself, regarding the Sabre. He published a slightly earlier book "The Power To Fly" in 1971, and I quote the following:

[Discussing a Sabre-engined racer project in 1941, a monoplane built by Fairey he states - the Heston racer, page 134]

"The colossal size of the propeller that was specially built for the Heston racer was due simply to the incredible power that it had to absorb, for the Sabre had been brought to such a state that it could deliver a reliable 5500 h.p. at 4200 rev./min., running at about 45 lb/in2 boost and a b.m.e.p. of 467 lb/in2.
By any standards these figures strain the bounds of credibility. In those days the Rolls-Royce R was still considered quite exceptionally highly tuned, in giving 76 b.h.p. per litre at a little less than 300 lb/in2 b.m.e.p., by all those who were not aware of the output of the Daimler-Benz 601 Rekordmotor which mustered 82 b.h.p. per litre at a about 350 lb/in2. Yet here was the Sabre bettering 150 b.h.p. per litre at a b.m.e.p. more than 15 per cent higher than was to be achieved for a matter of minutes only in the Rolls-Royce Merlin some years later, and doing it with complete reliability. In fact this was not the end of the matter, for the Napier engine was run frequently up to 500 lb/in2 and only began to show signs of strain when taken up to 4500 rev/min."

Elsewhere in the same book (page 129) he quotes the Sabre as 3750 h.p @ 4200rpm and 318 lb/in2 b.m.e.p. (in what appears as a more standard rating, comparing it to RR, DB603 etc. He talks of this rating able to be "sustained" on page 136).

Straight talks about a 16' four-bladed airscrew for the Heston racer. While I haven't checked the engine sums, and don't claim the HP figures are accurate one way or the other, this is at least one source of the information you have. In Setright's later book "Some Unusual Engines" (1975), he doesn't repeat the claim in as much detail. He discusses the Sabre, and Napier, in some detail in the earlier book

Would love to know what others can add to confirm or deny plausibility (i.e.: does the quoted bmep match the power/rpm?), or what survives at Napier/RR regarding any of the reported development.

Anyway, my (and Setright's) two cents worth for the day ;) ..... should make for some amusing armchair reading in the responses, if nothing else.....
 
brianwnz said:
But I thought I would add what I could from L.J.K. Setright himself, regarding the Sabre. He published a slightly earlier book "The Power To Fly" in 1971, and I quote the following:

[Discussing a Sabre-engined racer project in 1941, a monoplane built by Fairey he states - the Heston racer, page 134]

"The colossal size of the propeller that was specially built for the Heston racer was due simply to the incredible power that it had to absorb, for the Sabre had been brought to such a state that it could deliver a reliable 5500 h.p. at 4200 rev./min., running at about 45 lb/in2 boost and a b.m.e.p. of 467 lb/in2.
Click to expand...

Firstly, Heston built the Napier-Heston racer.

Secondly, the Sabre for that was rated at 2,450hp (according to Wiki), when normal Sabres were rated at ~2,000-,2,200hp.


brianwnz said:
By any standards these figures strain the bounds of credibility. In those days the Rolls-Royce R was still considered quite exceptionally highly tuned, in giving 76 b.h.p. per litre at a little less than 300 lb/in2 b.m.e.p., by all those who were not aware of the output of the Daimler-Benz 601 Rekordmotor which mustered 82 b.h.p. per litre at a about 350 lb/in2. Yet here was the Sabre bettering 150 b.h.p. per litre at a b.m.e.p. more than 15 per cent higher than was to be achieved for a matter of minutes only in the Rolls-Royce Merlin some years later, and doing it with complete reliability. In fact this was not the end of the matter, for the Napier engine was run frequently up to 500 lb/in2 and only began to show signs of strain when taken up to 4500 rev/min."
Click to expand...

Yes, those numbers seem to be beyond incredible.


brianwnz said:
Elsewhere in the same book (page 129) he quotes the Sabre as 3750 h.p @ 4200rpm and 318 lb/in2 b.m.e.p. (in what appears as a more standard rating, comparing it to RR, DB603 etc. He talks of this rating able to be "sustained" on page 136).
Click to expand...

3,850 rpm seems to be the normal maximum engine speed.



brianwnz said:
Straight talks about a 16' four-bladed airscrew for the Heston racer. While I haven't checked the engine sums, and don't claim the HP figures are accurate one way or the other, this is at least one source of the information you have. In Setright's later book "Some Unusual Engines" (1975), he doesn't repeat the claim in as much detail. He discusses the Sabre, and Napier, in some detail in the earlier book
Click to expand...

The Napier-Heston racer had a 3 blade prop.
 
Ahhh yes, just remember I'm merely repeating Setright's words...... never claimed they were accurate.

However, I wouldn't like to claim Wiki is accurate either ;), and yes, I checked the Heston with the three-bladed prop there too.

I agree that 5500hp is stretching credibility; what I'm interested in is the detail Setright has regarding boost and rpm - where did he get it from?

And I also think it likely that this was far from a 'normal' Sabre - it's a one-off racer to regain the world speed record; why wouldn't Napier soup it up? So any list of available/approved ratings would be very unlikely to list it.

A pity the man is no longer here to ask; perhaps he made it up, perhaps he made (quite a few) typo's, perhaps we'll never know.....
 
brianwnz said:
Ahhh yes, just remember I'm merely repeating Setright's words...... never claimed they were accurate.

However, I wouldn't like to claim Wiki is accurate either ;), and yes, I checked the Heston with the three-bladed prop there too.

I agree that 5500hp is stretching credibility; what I'm interested in is the detail Setright has regarding boost and rpm - where did he get it from?

And I also think it likely that this was far from a 'normal' Sabre - it's a one-off racer to regain the world speed record; why wouldn't Napier soup it up? So any list of available/approved ratings would be very unlikely to list it.

A pity the man is no longer here to ask; perhaps he made it up, perhaps he made (quite a few) typo's, perhaps we'll never know.....
Click to expand...
They did soup it up, it gives the power for the Heston racer plane in the list above, which I also have and is an official Napier company document.

No intended slight to Setright, but I think people don't realise how poor the overall level of research was in almost all post-war books written on WW2 planes and
engines until after about the mid 70`s when most of the real documents were declassified/opened by the major state/national archives.

So many well regarded books are full of things the author just saw once in a magazine article, or were told at the pub after several beers by someone
who once worked at the firm concerned and similar kinds of things.
 
Brian,

I understand where you are coming from. Undoubtedly Setright wrote "The Power to Fly" with the best of intentions. He obviously visited some of the players involved (there was an amusing quote from S. D. Heron, but I can't recall it at the moment) It is very hard to believe that he would have deliberately written any errors but as Calum has said, the information back then was hard to find and near impossible to verify. I wonder if he spoke to a few Napier employees who totally led him up the garden path. With the bad blood between Rolls and Napier (the Bentley takeover and the Air Ministry "theft" of the Sabre & data to give to Rolls), I would not put it past someone to inflate the Napier data to make Rolls look average.

Heston Racer:
4200 RPM:
My calc tells me that a 16' prop being turned by a Sabre at 4200 rpm will hit sonic tip velocity at about 330 mph. (Note the prop dia is not actually 16' - Setright has pretty much every detail of this aeroplane wrong) The highest published operating speed of a Sabre is 4000 rpm. The highest diving speed I have seen for a Sabre is 4050 rpm. (Flight Nov 22, 1945 p 552). I expect that in a test bay then possibly 4200 rpm could be achieved in a low boost/fine pitch test, but it will take far more sources than just Setright for me to believe it could be achieved in flight. (Note the BMEP/Power/RPM quoted all make sense mathematically)

BMEP of 467 psi:
This is certainly an outlier compared to other engines around the same time. Just for reference, a Continental IO-550 gets a peak pressure of around 900/1000 psi, and it has a BMEP of 143 psi on 100LL. If the Sabre pressure curve is of similar proportions, that would put the peak pressure in the Sabre around 2900 psi.

Power of 5500 hp:
I would find it hard to believe that Napiers had a test bay in 1940 that could test up to 5500 hp. I have no idea how to determine what the prop shaft was, and if it could accommodate the 25,000 ft.lb of torque (someone check my math - 5500 hp, 4200 engine rpm, prop gear ratio of 0.2742)

I check the next edition of the journal that Banks review was published in, and I could not find a response from Setright. If the 5500 hp was real, I would have expected some form of response.

3750 hp:

I could believe 3750 hp in a test bay. I find no reason to doubt Ricardo who claimed 3600 hp. That kind of percentage increase over the type tested number sounds similar to Pratt & Whitney, Rolls Royce and Wright test bay figures.

One of these days I will visit IMechE in the UK and spend far too long reading every Napier document they have. I have started making a 3D solidworks model of the Sabre with the hope of doing a dynamic analysis on the sleeve, but the rate I get things done will be decades before I finish. (Has anyone got a clear copy of the crank drawing – the one on the web is rather blurry?)
 
Snowygrouch said:
They did soup it up, it gives the power for the Heston racer plane in the list above, which I also have and is an official Napier company document.

No intended slight to Setright, but I think people don't realise how poor the overall level of research was in almost all post-war books written on WW2 planes and
engines until after about the mid 70`s when most of the real documents were declassified/opened by the major state/national archives.

So many well regarded books are full of things the author just saw once in a magazine article, or were told at the pub after several beers by someone
who once worked at the firm concerned and similar kinds of things.
Click to expand...
Thanks Calum,

That does put Setright's comments in perspective - I never thought about the state of archive documents back then.

The one thing he had was that some of the people involved might still be alive back then - but as you say, that would still be relying on very human memory.....

I've appreciated the documents people have provided, as I have nothing on Napier petrol engines, and I agree original documents are the best source.

Thanks and regards,

Brian W.
 
Simon Thomas said:
Brian,

I understand where you are coming from. Undoubtedly Setright wrote "The Power to Fly" with the best of intentions. He obviously visited some of the players involved (there was an amusing quote from S. D. Heron, but I can't recall it at the moment) It is very hard to believe that he would have deliberately written any errors but as Calum has said, the information back then was hard to find and near impossible to verify. I wonder if he spoke to a few Napier employees who totally led him up the garden path. With the bad blood between Rolls and Napier (the Bentley takeover and the Air Ministry "theft" of the Sabre & data to give to Rolls), I would not put it past someone to inflate the Napier data to make Rolls look average.

Heston Racer:
4200 RPM:
My calc tells me that a 16' prop being turned by a Sabre at 4200 rpm will hit sonic tip velocity at about 330 mph. (Note the prop dia is not actually 16' - Setright has pretty much every detail of this aeroplane wrong) The highest published operating speed of a Sabre is 4000 rpm. The highest diving speed I have seen for a Sabre is 4050 rpm. (Flight Nov 22, 1945 p 552). I expect that in a test bay then possibly 4200 rpm could be achieved in a low boost/fine pitch test, but it will take far more sources than just Setright for me to believe it could be achieved in flight. (Note the BMEP/Power/RPM quoted all make sense mathematically)

BMEP of 467 psi:
This is certainly an outlier compared to other engines around the same time. Just for reference, a Continental IO-550 gets a peak pressure of around 900/1000 psi, and it has a BMEP of 143 psi on 100LL. If the Sabre pressure curve is of similar proportions, that would put the peak pressure in the Sabre around 2900 psi.

Power of 5500 hp:
I would find it hard to believe that Napiers had a test bay in 1940 that could test up to 5500 hp. I have no idea how to determine what the prop shaft was, and if it could accommodate the 25,000 ft.lb of torque (someone check my math - 5500 hp, 4200 engine rpm, prop gear ratio of 0.2742)

I check the next edition of the journal that Banks review was published in, and I could not find a response from Setright. If the 5500 hp was real, I would have expected some form of response.

3750 hp:

I could believe 3750 hp in a test bay. I find no reason to doubt Ricardo who claimed 3600 hp. That kind of percentage increase over the type tested number sounds similar to Pratt & Whitney, Rolls Royce and Wright test bay figures.

One of these days I will visit IMechE in the UK and spend far too long reading every Napier document they have. I have started making a 3D solidworks model of the Sabre with the hope of doing a dynamic analysis on the sleeve, but the rate I get things done will be decades before I finish. (Has anyone got a clear copy of the crank drawing – the one on the web is rather blurry?)
Click to expand...
Cheers Simon,

I was hoping someone could fact-check some of the sums; the boost and bmep figures looked very high to me when I read them.

Thanks to yourself & Calum for laying this myth to rest, I appreciate the work you've put in.

Thanks and regards,

Brian W.
 
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