Jumo 213 vs. Napier Sabre

[J.A.W.]

Care to post some docs that show Sabre's boost with 100/130 + ADI?



IIRC Fedden didn't design neither Sabre nor Jumo 213.


As noted by the above member, swept volume was not what was propelling the aircraft.
On the p/w basis, a host of other engines were doing at least as good. What Sabre was not good was power at higher altitudes, but that somehow ends swept under the rug when people talk about the Sabre as it was the next best thing after the sliced bread.

The table in Wilkinson's book, refer to the Sabre section, the final production unit he lists notes the output at ~70" Hg (+20lb) on 100/130.

Fedden led a British Engineering/Technical appraisal of German aero-engine developments in 1945, he examined the Jumo 213,
and expressed his incredulity at the notion of such a long-stroke engine running reliably at 3,700rpm, per basic stress limitations.

Swept volume is the fundamental dimensional metric of a piston engine as a fluid working machine.
Altitude compensation is an add-on, the Sabre could hack hard running (unthrottled) at sea-level as a measure of how robust it was.

One of the Napier engine charts available on Calum's ('snowygrouch' here) site shows the Sabre with turbo-altitude compensation,
as was intended for US production (with Typhoons built by Bell Corp, & the Sabre built by Chrysler Corp - in the event, Stalin's need
for the P-39, & the top priority US B-29 program, with its big, troublesome Wright mills - built/remediated by Chrysler, killed this).

 

[Deleted member 68059]

The Napier idea of a high speed short stroke engine was a good one, very forward thinking, I wish they`d made it a poppet valve though. I did a rough scheme for the increase in engine width using some period DB 605 valves as "representative". Its not as bad as you might think...and could probably be even more compact with a rocker format OHC instead of cam/buckets. In fact it can even be improved further because since the bottom of the liner doesnt go up and down without a sleeve, you can probably shorted the con-rods without the crank banging into the bottom of the liner, which is always the choke point.

 

[tomo pauk]

The table in Wilkinson's book, refer to the Sabre section, the final production unit he lists notes the output at ~70" Hg (+20lb) on 100/130.

Unfortunately, the primary sources disagree with him, at least what is posted on this thread.

Fedden led a British Engineering/Technical appraisal of German aero-engine developments in 1945, he examined the Jumo 213,
and expressed his incredulity at the notion of such a long-stroke engine running reliably at 3,700rpm, per basic stress limitations.

Okay, roger that.

Swept volume is the fundamental dimensional metric of a piston engine as a fluid working machine.
Altitude compensation is an add-on, the Sabre could hack hard running (unthrottled) at sea-level as a measure of how robust it was.

Altitude power was an important thing (as eg. Luftwaffe pilots experienced on their own skin from mid-1943 on), unfortunately Sabre lagged badly behind the top cop of the engines of the day.
Swept volume is not end-all metric of an engine, let alone of an aircraft's performance. Sabre was many things, robustness was not one of these, as seen here (contribution of Calum Douglas).

One of the Napier engine charts available on Calum's ('snowygrouch' here) site shows the Sabre with turbo-altitude compensation,
as was intended for US production (with Typhoons built by Bell Corp, & the Sabre built by Chrysler Corp - in the event, Stalin's need
for the P-39, & the top priority US B-29 program, with its big, troublesome Wright mills - built/remediated by Chrysler, killed this).

As-is, Sabre was not doing well at high altitudes. Both P&W and RR made engines that were very good/excellent at high altitudes without resorting to turboes.
Typhoons built by Bell, Sabre built at Chrysler - I guess we can dream all day. Real-world questions: a) how is that earlier than P-47 production, and b) how is that better than P-47 production and use?

 

[J.A.W.]

Unfortunately, the primary sources disagree with him, at least what is posted on this thread.



Okay, roger that.



Altitude power was an important thing (as eg. Luftwaffe pilots experienced on their own skin from mid-1943 on), unfortunately Sabre lagged badly behind the top cop of the engines of the day.
Swept volume is not end-all metric of an engine, let alone of an aircraft's performance. Sabre was many things, robustness was not one of these, as seen here (contribution of Calum Douglas).



As-is, Sabre was not doing well at high altitudes. Both P&W and RR made engines that were very good/excellent at high altitudes without resorting to turboes.
Typhoons built by Bell, Sabre built at Chrysler - I guess we can dream all day. Real-world questions: a) how is that earlier than P-47 production, and b) how is that better than P-47 production and use?

Actually, its pretty clear that Wilkinson's tables were copied from the type-test records, as they match the figures supplied to 'Flight',
and included in their articles.

Altitude performance was important if you wanted to stop turbo'd USAAF bombers, & contest their fighter escort likewise, but by
1943, that was not really a primary business for the RAF, & even the LW, from mid 1944, when it was redirected to anti-JaBo work,
against the Allied tactical airforces, as being a more tenable use of its limited resources - was operating below 20,000ft.

Ironically, the USAAF's expensively turbo-optimised P-38 & P-47 were also redirected to operate in TAF roles, too.

The Turbo-Typhoon was not a dream, it was designed/tested but not productionised, as noted.

The USAAF themselves recognised the P-47 was not as good at low-level, or for A2G as the Typhoon, but its what they had...
(The Soviet VVS tested their Lend-Lease P-47s & found the idea of using them for A2G 'Ludicrous', & sent them to air defence units)

 

[J.A.W.]

The Napier idea of a high speed short stroke engine was a good one, very forward thinking, I wish they`d made it a poppet valve though. I did a rough scheme for the increase in engine width using some period DB 605 valves as "representative". Its not as bad as you might think...and could probably be even more compact with a rocker format OHC instead of cam/buckets. In fact it can even be improved further because since the bottom of the liner doesnt go up and down without a sleeve, you can probably shorted the con-rods without the crank banging into the bottom of the liner, which is always the choke point.View attachment 759192

Couple of things there Calum, cam boxes/drives to add, plus it clearly shows how those poppets crowd the combustion chamber,
introduce problematic hot-spots, coolant/oil circulation issues, & obtund ports to restrict volumetric efficiency.

 

[tomo pauk]

Actually, its pretty clear that Wilkinson's tables were copied from the type-test records, as they match the figures supplied to 'Flight',
and included in their articles.

You will hopefully understand me not buying the +20 psi and 3500-3550 HP figures, in light of the docs available now.

Altitude performance was important if you wanted to stop turbo'd USAAF bombers, & contest their fighter escort likewise, but by
1943, that was not really a primary business for the RAF, & even the LW, from mid 1944, when it was redirected to anti-JaBo work,
against the Allied tactical airforces, as being a more tenable use of its limited resources - was operating below 20,000ft.

Since Germans tried to stop the high-flying bombers and their escorts during the 2nd half of the ww2, I'd say that altitude performance was very important. It was for Germans, for Americans, and also for the RAF, who were the 1st people to push for 2-stage superchargers in military engines in Europe, and, with P&W, in the world. RAF were also the 1st to provide some sort of escort for the 8th AF.

Ironically, the USAAF's expensively turbo-optimised P-38 & P-47 were also redirected to operate in TAF roles, too.

No irony there - Americans have had money to buy stuff, and were using the stuff in the way they saw fit, even gifting them to the Allies.
If you think that turboed Sabre will come in cheap, I have the Brooklyn bridge on sale, real cheap.

The USAAF themselves recognised the P-47 was not as good at low-level, or for A2G as the Typhoon, but its what they had...
(The Soviet VVS tested their Lend-Lease P-47s & found the idea of using them for A2G 'Ludicrous', & sent them to air defence units)

Any source that describes the P-47s being considered for A2G by Soviets, the same Soviets whose fighters were hopeless in A2G? Any sources describing USAAF wanting the Typhoon?
The P-47s surely killed a lot of Axis ground assets for not being good at low level.

 

[Deleted member 68059]

Couple of things there Calum, cam boxes/drives to add, plus it clearly shows how those poppets crowd the combustion chamber,
introduce problematic hot-spots, coolant/oil circulation issues, & obtund ports to restrict volumetric efficiency.

The 2nd last poppet valve engine I worked on used 4 bar boost on fuel you can get from a normal petrol station. A well designed set of
poppet ports gets you over 100% volumetric efficiency with no boost at all. Trust me, these issues you mention stopped existing about 1935
once the valve alloys improved.

 

[Simon Thomas]

You will hopefully understand me not buying the +20 psi and 3500-3550 HP figures, in light of the docs available now.

I thought was the 4000 hp figure from Setright that was discredited. Both Ricardo and Bingham state that the Sabre achieved 3500/3600 hp.

 

[tomo pauk]

I thought was the 4000 hp figure from Setright that was discredited. Both Ricardo and Bingham state that the Sabre achieved 3500/3600 hp.

See here (two posts, one after another).
Also this.

 

[J.A.W.]

I thought was the 4000 hp figure from Setright that was discredited. Both Ricardo and Bingham state that the Sabre achieved 3500/3600 hp.

That "4,000hp" figure was duly noted in 1950s era 'Flight' article, which was a reputable journal, FWIW.

 

[Deleted member 68059]

As Tomo posts accurately above, 3050 bhp is the absolute peak power figure which is currently known in actual Napier documents. I`ve been to the archive,
and this is the highest power rating I`ve found for an engine which actually existed. The higher figures all seem to be from the Sabre VIII (which never existed
except on paper and was re-designated E.122 at some stage to be a completely different engine, which appears to be a sort of half way house to a Nomad).

(17.25lbs boost & water methanol, no higher boost exists in any papers I have ever seen)

 

[Deleted member 68059]

As Tomo posts accurately above, 3050 bhp is the absolute peak power figure which is currently known in actual Napier documents. I`ve been to the archive,
and this is the highest power rating I`ve found for an engine which actually existed. The higher figures all seem to be from the Sabre VIII (which never existed
except on paper and was re-designated E.122 at some stage to be a completely different engine, which appears to be a sort of half way house to a Nomad).

(17.25lbs boost & water methanol, no higher boost exists in any papers I have ever seen)

View attachment 759224

Thats from HERE by the way > note, post war, 1946.

 

[J.A.W.]

The 2nd last poppet valve engine I worked on used 4 bar boost on fuel you can get from a normal petrol station. A well designed set of
poppet ports gets you over 100% volumetric efficiency with no boost at all. Trust me, these issues you mention stopped existing about 1935
once the valve alloys improved.

Sorry Calum, but seeing the flow comparison of cylinder porting to poppet valves (check out how Toyota tried to run one of its DOHC 4V
engines on a 2-stroke cycle & quickly ran into flow-capacity poppet valve limitations) gives me trust in actual results...

See the final test figures for a Sabre test in the link below - scroll to bottom - showing 22 bar (321lb/sq.in) BMEP @ +1.37 bar boost (+20lb)

http://www.wwiiaircraftperformance.org/Aircraft_Engines_of_the_World-Napier_Sabre.pdf

 

[J.A.W.]

You will hopefully understand me not buying the +20 psi and 3500-3550 HP figures, in light of the docs available now.



Since Germans tried to stop the high-flying bombers and their escorts during the 2nd half of the ww2, I'd say that altitude performance was very important. It was for Germans, for Americans, and also for the RAF, who were the 1st people to push for 2-stage superchargers in military engines in Europe, and, with P&W, in the world. RAF were also the 1st to provide some sort of escort for the 8th AF.



No irony there - Americans have had money to buy stuff, and were using the stuff in the way they saw fit, even gifting them to the Allies.
If you think that turboed Sabre will come in cheap, I have the Brooklyn bridge on sale, real cheap.



Any source that describes the P-47s being considered for A2G by Soviets, the same Soviets whose fighters were hopeless in A2G? Any sources describing USAAF wanting the Typhoon?
The P-47s surely killed a lot of Axis ground assets for not being good at low level.

I have no reason to doubt the veracity of Wilkinson, esp' since the figures listed interrelate, so cannot be a mere typo/proof error.
Where are the Air Ministry Acceptance records - relating to 'Official Type Tests'? That would be the clincher.

The high-altitude war was an outlier, primarily due to the USAAF strategic bomber doctrine, most everywhere else, tactical air-power
was the thing, & certainly after the advent of the turbo-jet fighter, high-altitude capability for piston engine fighters wasn't a big deal.

As noted here recently, the US Services (& rightly so, IMO) put their own interests 1st, inc' Lend-Lease.

IIRC, the Soviet assessment of the P-47 (perhaps a member here, more up on VVS matters - can link it) was like a more extreme
reaction but essentially similar to the Eagle Squadron pilots who climbed out of diminutive, dainty Spitfires into the mighty 'Jug',
as going from a Yak to a P-47 would be, naturally enough. (The VVS were told P-47s were used for A2G).

The USAAF assessment had warned P-47 pilots to be aware of LW advantages over them below 20,000ft. Of course if the P-47 had
to drop its A2G ordnance early to contend with interception, that was 'a win' for the Germans not bombed as a result.

The figures for 9th AF tactical P-47 losses are pretty sobering stats, plus when redirected as escorts for mediums, they suffered too,
check the infamous B-26/P-47 attack during the German Ardennes offensive, when they were decimated by a LW interception.

 

[Deleted member 68059]

Sorry Calum, but seeing the flow comparison of cylinder porting to poppet valves (check out how Toyota tried to run one of its DOHC 4V
engines on a 2-stroke cycle & quickly ran into flow-capacity poppet valve limitations) gives me trust in actual results...

See the final test figures for a Sabre test in the link below - scroll to bottom - showing 22 bar (321lb/sq.in) BMEP @ +1.37 bar boost (+20lb)

http://www.wwiiaircraftperformance.org/Aircraft_Engines_of_the_World-Napier_Sabre.pdf

You realise that "Aircraft Engine of the World" is an annual periodical ? To whom manufactures send sales info to to print
and that the issue that is taken from is four years after the war ended ?
I think we all agree that the Sabre is not a 2-stroke.

I have the Sabre VII performance booklet right here, which I held and copied myself >

 

[J.A.W.]

Yes, but doubtless the data wasn't simply 'made up' back in 1947.
Hawker were still test flying the most highly developed Sabre in VP207, the 2nd Sabre-Fury prototype,
a Swiss delegation checked it out at Langley, but chose the DH Vampire jet for their needs, I recall reading
a Neville Duke memoir (Spitfire ace/Hawker test pilot) wherein he reckoned it was the most potent piston job.

(Sabre was originally envisaged as CI 2-stroke, as it happens, & given high performance 2-strokes must breathe effectively,
it may well've contributed to the Sabre's volumetric efficiency)

Good effort to find & show the surviving Napier tech-notes
(or what was left after R/R had razed Acton in the early `60s).

Edit: Added Neville Duke bit.

 

[Deleted member 68059]

Yes, but doubtless the data wasn't simply 'made up' back in 1947.

I suspect as is always the case, there is a lot of difference between projected (i.e. sales figures) and test bed figures, if it is real, where is the power curve ?

Nobody likes finding obscure WW2 aero engine power curves more than I do (literally nobody) - and I cant find it in the Napier archive.

 

[J.A.W.]

I suspect as is always the case, there is a lot of difference between projected (i.e. sales figures) and test bed figures, if it is real, where is the power curve ?

Nobody likes finding obscure WW2 aero engine power curves more than I do (literally nobody) - and I cant find it in the Napier archive.

Yeah, that is much appreciated - so can you ask BAE - if they still have the Hawker flight test archive from 1940s Langley?

 

[J.A.W.]

Yeah, that is much appreciated - so can you ask BAE - if they still have the Hawker flight test archive from 1940s Langley?

I suspect as is always the case, there is a lot of difference between projected (i.e. sales figures) and test bed figures, if it is real, where is the power curve ?

Nobody likes finding obscure WW2 aero engine power curves more than I do (literally nobody) - and I cant find it in the Napier archive.

A wee bit more, Ol' Len Setright claimed to have read through the Napier Engineering docs back in the `60s, & discussed them with
the ex-Napier men, I heard FWIW (hearsay, I know) from another who'd spoken with Setright, that those extreme figures were done when blowing a test engine was no longer a big deal, and was in the very sophisticated (English Electric built) test cell with "unlimited boost & cooling available) and as such can be fairly compared with the extreme figures made by ex-aero engines in hydroplane/tractor pulling...

(That is, akin to the Chrysler Engineers in the `60s - working their 'Hemi V8' from a 500 mile NASCAR engine - into a top-fuel dragster mill).

 

[Shortround6]

There is supposed to have been a P & W engineer that got an R-2800 B series to around 3500hp for a few seconds on test stand using copious quantities of water/methanol, and well over 100in/hg pressure.
He may have been egging on the R-4360 engineers .
The engine survived. everybody knew it wasn't practical. Does sort of show the bottom end strength though.

Wilkinson just collected data/information sent to him. Maybe he did see a test run or two? but he did no independent testing.
Some of the data he has for French engines at times is a bit suspect, what he had for Japanese engines is almost laughable now and what he had for Soviet engine is no better than what you might expect at the time. By the way, I have twelve volumes of his work from 1941 to 1966/67.