Napier Sabre engines

[JFC Fuller]

Mods might want to split this out as we seem to be drifting off-topic,

Nick Sumner,

I just found this in relation to the Sabre E.122: http://www.flightglobal.com/pdfarchive/view/1946/1946 - 1443.html?search=Tempest annular

This tailless fighter was to have the 3,350hp Sabre E.122 engine.

I do wonder whether the E.122 was the Sabre VIII.....?

Link to another post in the previous Martin Baker thread: http://www.secretprojects.co.uk/forum/index.php/topic,11784.msg113902.html#msg113902

Another musing, given that the Sabre VI was basically a V modified to take the Napier annular intake (tested on a Typhoon, a Tempest and a Warwick) is it possible that the VIII was a VII modified for a similar intake? With the addition of the full three-speed, two-stage supercharger?

 

[Nick Sumner]

(All this from memory as I'm meant to be working )

I believe the VIII was another single stage 2 speed job. It was intended for the Hawker Fury fighter and for once Napier felt that with the Fury they were getting access to the best quality propellers. (A consistent complaint from Napier was that the Typhoon and Tempest didn't get the best quality propellers because they were seen as essentially low altitude fighters. They were seen as low altitude fighters because their engines only had single stage superchargers. Circular logic from the powers that be. The Fury too was forced into the ground attack niche so a two stage blower was not deemed to be necessary. Hawker was annoyed by this lack of imagination from the powers that be too but by this time the point was moot because the jet had come along and made piston fighters obsolete.)

IIRC not much is known about the E118 development stage. It was run in 1941 with a three speed two stage charger and a contra prop but at the time the Sabre had many production and service difficulties and there was a serious question as to whether or not the engine would 'come good'. This is part of the reason for Britain's Merlin (Rolls-Royce) engine monoculture and the marginalisation of Napier.

The other part of the reason was that Napier were fantastic engineers but the management couldn't get sh*gged in a brothel. Unlike Rolls-Royce the task of mastering the difficulties of going from small-scale handbuilt manufacture of small numbers of aircraft engines to mass production in shadow factories was completely beyond them. The mess wasn't sorted out until they were forced into a shotgun marriage with English Electric. This was so successful that by the end of the war reliability had improved so much that there was a huge surplus of Sabre engines IIRC there was something like 3000 surplus to requirements because the engines they were supposed to replace simply hadn't worn out/broken as they had been expected to and were still in the airframes of Typhoons and Tempests.

There is a persistent rumour that a model of Sabre reached 5000 hp on the test bench. I believe the origin of that rumour was from the author LJK Setright, an almost rabid proponent of the Sabre's virtues, but I am not aware of any confirmation of this so I have to treat it sceptically..

 

[JFC Fuller]

If that is the case then the E.118 and E.122 seem to be from different time-frames with the former being early war and the latter being late war as a sort of combination of all the various great ideas Napier had for the Sabre- annular intake, contra-prop and three-speed, two-stage supercharger.

Interestingly it seems like a couple of Sabre VII's have survived.

The question then becomes, did Napier ever perfect the three-speed, two-stage supercharger?

 

[Nick Sumner]

Had a look in Lumsden, British Piston Aero Engines The E122 development stage became Sabre VII - the last full scale production variant. The book only mentions E118 in passing as having a 2 stage 3 speed supercharger but implies that one was fitted in a Folland Fo108 Frightful.

To make life confusing White in Allied Aircraft Piston Engines says E122 was merely a design with a 2 stage blower that wasn't built. He doesn't mention E118.

 

[JFC Fuller]

Well that is curious as the Flight Global article from 1946 distinguishes the Sabre VII from the E.122 which is why I wondered whether the E.122 became the Sabre VIII. I was working on the assumption that the E.118 was a relatively early model, however the E number is relatively late suggesting it might be mid rather than early 40s?

 

[Johnbr]

I read ed that the E.118 it got the axe in 1943 by air ministry.

 

[Nick Sumner]

Johnbr - do you recall where you read that?

 

[Johnbr]

http://en.wikipedia.org/wiki/Napier_Sabre

Here is one of them.I thought it was here can not find it now sorry.

 

[Nick Sumner]

I've emailed Napier Power Heritage looking for some leads on this issue - I hope perhaps we can track down original Napier documentation on the subject to learn more.

Here is Setright again waxing lyrical.

http://www.hawkertempest.se/GreatestEngines.htm

 

[JFC Fuller]

Nick,

It would certainly be interesting to see what could be unearthed, the Sabre never really seems to have fulfilled its potential and Napier seems to have had allot of irons in the fire for the type, contra-props and a three stage supercharger being the big two whilst annular cowling actually flew. The Hawker tempest page link suggests that three-stage supercharger was tested towards the end of the Sabre programme on a bench; that increasingly makes me wonder whether it was intended for the E.122.

Further reading the piece by LJK Setright it is apparent that the big power figures achieved (5,500 hp) came via massively increased boost. The 3,055hp Sabre VII ran at 17.5psi max whilst the Sabre V ran at 15psi, the 5,500 hp version supposedly ran at 45psi which is incredibly high. The life of the engine at that pressure must have been reduced?

This website states that when rated at 20psi with water/methanol injection the Sabre VII could make 3,500hp;

http://www.enginehistory.org/buckel_galleries.htm

That 3 stage supercharger is certainly curious, as is the Sabre VIII designation which still seems like it could be anything. Designed for the Fury unfortunately does not narrow it down.

 

[Nick Sumner]

Further reading the piece by LJK Setright it is apparent that the big power figures achieved (5,500 hp) came via massively increased boost. The 3,055hp Sabre VII ran at 17.5psi max whilst the Sabre V ran at 15psi, the 5,500 hp version supposedly ran at 45psi which is incredibly high. The life of the engine at that pressure must have been reduced?

This website states that when rated at 20psi with water/methanol injection the Sabre VII could make 3,500hp;

http://www.enginehistory.org/buckel_galleries.htm

Depends, engine wear is directly related to piston speed which for a Sabre at 4000 RPM is about 16m per second. At 4200 RPM that's still under 17m per second. Now while that's fast for engines of this era there were certainly others that turned faster - the experimental DB603N turned at 18m per second and the Jumo 613E at 17.9m per second.

 

[JFC Fuller]

With that in mind it certainly seems that, depending on the nature of the supercharger, these late variant experimental Sabres, possibly with lower boost could have been viable high altitude fighter power units. It further leads me to believe that perhaps the E.122 had this curious 3 stage supercharger..?

Certainly the E.122 in the linked Flight Global article uses both an annular intake and a contra-prop.

 

[Rickshaw]

Further reading the piece by LJK Setright it is apparent that the big power figures achieved (5,500 hp) came via massively increased boost. The 3,055hp Sabre VII ran at 17.5psi max whilst the Sabre V ran at 15psi, the 5,500 hp version supposedly ran at 45psi which is incredibly high. The life of the engine at that pressure must have been reduced?

This website states that when rated at 20psi with water/methanol injection the Sabre VII could make 3,500hp;

http://www.enginehistory.org/buckel_galleries.htm

Depends, engine wear is directly related to piston speed which for a Sabre at 4000 RPM is about 16m per second. At 4200 RPM that's still under 17m per second. Now while that's fast for engines of this era there were certainly others that turned faster - the experimental DB603N turned at 18m per second and the Jumo 613E at 17.9m per second.

What is the "m" after the number measuring? Obviously not metres.

 

[Arjen]

What is the "m" after the number measuring? Obviously not metres.

It is. Metres, that is.

Classes

low speed diesels
~8.5 m/s for marine and electric power generation applications
medium speed diesels
~11 m/s for trains or trucks
high speed diesel
~14 m/s for automobile engines
medium speed petrol
~16 m/s for automobile engines
high speed petrol
~20–25 m/s for sport automobile engines or motorcycles
competition
Some extreme examples are Nascar Sprint Cup Series and Formula one engines with ~25 m/s and Top Fuel engines ~30 m/s

http://en.wikipedia.org/wiki/Mean_piston_speed

 

[Rickshaw]

What is the "m" after the number measuring? Obviously not metres.

It is. Metres, that is.

Classes

low speed diesels
~8.5 m/s for marine and electric power generation applications
medium speed diesels
~11 m/s for trains or trucks
high speed diesel
~14 m/s for automobile engines
medium speed petrol
~16 m/s for automobile engines
high speed petrol
~20–25 m/s for sport automobile engines or motorcycles
competition
Some extreme examples are Nascar Sprint Cup Series and Formula one engines with ~25 m/s and Top Fuel engines ~30 m/s

http://en.wikipedia.org/wiki/Mean_piston_speed

Ah, so the time measurement was missing. Thanks for the explanation. What is travelling these metres a second? The engine, what is mounted in or the pistons?

 

[Arjen]

What is travelling these metres a second?

The piston inside the cylinder. At the same rpm, short-stroke engines have a lower piston speed compared to long-stroke engines of the same displacement + number of cylinders. Lower piston speed reduces engine wear; it also makes it easier for short-stroke engines to operate at high rpm. Which generally means more power. Long-stroke engines tend to deliver more torque.

More on wikipedia: http://en.wikipedia.org/wiki/Long_stroke

 

[JFC Fuller]

Armstrong Siddeley AS.56: http://www.flightglobal.com/pdfarchive/view/1951/1951 - 0354.html

Projected single seat fighter with Napier Sabre VI engine and four 20mm guns

Note that the VI is the annular intake version flown on a Tempest and a Warwick.

I would love to know about the three-stage supercharger that LJK Setright mentions...?

Apparently it was Folland PI 778 that test flew the ducted radiator for the E.118, is there an image of that particular airframe anywhere?

 

[Nick Sumner]

Here is the text of an email from Roy Gasson, Chairman of Napier Power Heritage replying to an email of mine about the E118 and E122

I hope the following answers your questions, apart from ploughing through
Flight & Aircraft Production magazines of the era I am not sure what to
suggest for research.
The "Sabre E118" was a "Twin Contra-prop, 2 stage 3 speed supercharger"
design of November 1941, that never held a Series No. during its wartime
development.
The final design had a similar spec. the "Sabre E122" engine of 1946, by
then with a bulk injection carburettor, but this was not even tested, and
was to have 3350 bhp max. @ 3750 rpm. It was taken over by Rolls-Royce in
1947 by command of the Engine Production Ministry, to become their much
larger capacity "Eagle 2" which I believe they did not pursue into
production .
The Setright output figures are nonsense, of course, as the highest test
house power from a "Sabre" was 3500 plus bhp @4500 plus rpm. before it
broke-up and wrecked the dynamometers (via R.Silva)
The "Sabre 7" (E121) had 3050 bhp for take-off @ 3850 rpm, 17 psi boost,
and flew at 490 mph in the Hawker "Fury Mark 1" prototype.


Sigh, but that 5000bhp figure was really just too good to be true wasn't it?

 

[JFC Fuller]

Nick,

Thank you for posting the reply. That sits with what the Flight Global article relating to the Sabre VII says in relation to the E.122 and confirms my theory that the E.122 was Napiers effort to roll all the ideas they had for the Sabre into one final variant. The only question directly related to this topic that really remains is whether the Sabre VIII was to be the E.122, given that the VII was the E.121 it rather suggests that perhaps it was...?

The other question being, where on earth did Setright get his figures from!?

 

[Arjen]

I could not find Folland Fo.108 P1778. There are several pictures of Fo.108s with Sabres here: http://www.airwar.ru/enc/xplane/fo108.html

I have found some pictures of an annular cowling Tempest and Typhoon, and a ducted spinner Tempest.
From "WW2 Aircraft Fact Files: RAF Fighters Part 2" by William Green & Gordon Swanborough, Macdonald and Jane's 1979.

Are there any pictures of the Sabre-Warwick?

 

[JFC Fuller]

Arjen,

Based on what I have read so far the annular intake was a Napier rather than Hawker concept with the engine, cowling and intake being produced as a single power unit. This was then bolted onto the Tempest and two units with extended exhaust pipes were put on the Warwick, see these two for pictures of the Warwick;

http://www.flightglobal.com/pdfarchive/view/1946/1946%20-%201439.html?search=Napier%20Sabre%20Warwick

http://www.flightglobal.com/pdfarchive/view/1946/1946%20-%201442.html?search=Napier%20Sabre%20Warwick

Personally I find the engine a very elegant solution, and apparently it did result in a performance increase as well.

Another picture from the Institute of Mechanical Engineers;

http://picturegallery.imeche.org/ViewLarger.aspx?PID=484&RAID=30

 

[robunos]

Are there any pictures of the Sabre-Warwick?

From Aeroplane Monthly, February 1989, page 82.

"Vickers Warwick C MkIII HG 248 fitted with Sabre VI engines; January 1947"


cheers,
Robin.

 

[Arjen]

Thanks, both of you

 

[Arjen]

More on the Folland Fo.108:

In all, twelve airframe serial numbers, P1774-P1785 inclusive, were allocated in November 1938, under contract no. 953635/38, to the Folland 43/37 engine testbeds. Known installations were:
- P1774 - Sabres and Centaurus IV,
- P1775 - Hercules VIII and Centaurus IV,
- P1776 - Sabre I and Centaurus I,
- P1777 - Sabre I and Centaurus I,
- P1778 - Centaurus I, Griffon and DH propeller tests,
- P1779 - Sabres and Hercules XI,
- P1780 - Hercules XI, Sabre I, V and VIII,
- P1782 and P1785 - Hercules XI.

From "The British Aircraft Specifications File" by KJ Meekcoms and EB Morgan, Air Britain 1994, p.256.

 

[Nick Sumner]

In further emails with Roy Gasson he informed me that work was begun by Napier on a 32 cylinder version of the Sabre.



Sadly nothing other than this is known about the project. I would assume that it would be 4 banks of 8 cylinders in configuration and the main difficulty in development would be vibration in the long crankshafts required.

 

[Arjen]

I would assume that it would be 4 banks of 8 cylinders in configuration and the main difficulty in development would be vibration in the long crankshafts required.

Porsche had a similar problem with the flat-12 engine of their 917 racer. They solved it by having the power take-off in the middle of the crankshaft, not at the end.

 

[Nick Sumner]

Chrysler tried that with the IV 2220 but couldn't get the engine to work well. Both Daimler Benz and Porsche designed V16 aircraft engines but DB started theirs in September 42 and didn't expect to have it ready until 1947. It was the DB609, essentially a V16 DB603.

The Porsche engine was a 19.7 litre designed in 1936 but I've no other info apart from a small drawing.

 

[Arjen]

Nick Sumner:

The Porsche engine was a 19.7 litre designed in 1936 but I've no other info apart from a small drawing.

Nice. I didn't know about that one.

To avoid possible confusion: the Porsche 917 racer I'm referring to is the one in the picture.

 

[red admiral]

Chrysler tried that with the IV 2220 but couldn't get the engine to work well. Both Daimler Benz and Porsche designed V16 aircraft engines but DB started theirs in September 42 and didn't expect to have it ready until 1947.

There are also the Fiat engines AS.8 and A.38 from pre/early WWII.

The AS.8 was an upright V16 intended for the CMASA CS.15. The configuration may be the same as the attached patent. Power take off was at a single end.

The A.38 was originally intended for the G.55 and changed configuration a few times. The pictured engine on the test bench is the inverted V16 configuration, with contra-rotating propellers and centrally mounted supercharger.

 

[Nick Sumner]

The Fiat V16 - two separate crank shafts - interesting.

Is there any more info about this engine around?

 

[JFC Fuller]

Tempest with an Annular Radiator:

http://picturegallery.imeche.org/ViewLarger.aspx?PID=478&RAID=30

 

[Yellow Palace]

Depends, engine wear is directly related to piston speed which for a Sabre at 4000 RPM is about 16m per second. At 4200 RPM that's still under 17m per second. Now while that's fast for engines of this era there were certainly others that turned faster - the experimental DB603N turned at 18m per second and the Jumo 613E at 17.9m per second.

What is the "m" after the number measuring? Obviously not metres.

Why not? At 4200 rpm, that's 70 up strokes and 70 down per second; with a mean piston speed of 16 m/s, that's a stroke of 0.23 metres (9 inches) as near as makes no difference.

 

[tartle]

15.2 metres/sec is 3,000 ft per min... which is the rule of thumb used by aero engine designers to get a reasonable service life potential in the engine. Napier, or rather Halford's design team pushed over the limit and then the team at Napier and Halford, who became one team at DeHavilland leaving Napier to get on with it, were too busy pursuing power rather than life. As late as mid-1944 the MAP planning expert Ely Devons was having to find ways of doubling production as at that time Napier could only supply enough engines to keep existing service aircraft in the air as tbo was pitiful.. but at least they worked for a few hours... which was an improvement. Their engineering was too ambitious for the technologies they understood and so RR willingly and, Bristol unwillingly had to supply technical secrets to EE to get Napier off its knees. Also the prod cost was quadruple a Merlin and double a Hercules. To be hard headed the pursuit of supercharger technology when the base product was not right seems crazy, especially in the middle of a war... RR knew how to concentrate talented resources whilst still allowing a little fat for 'serious play".

 

[tartle]

The title of this picture from the Napier Archive preserved by IMechE is
Napier Sabre V (series VII) aero engine, 1946, scale model Other Sabre pics are under this search
Hope this helps to move the speculation on a little bit.
Bare in mind when RR were asked to look at a high power backup to the Sabre they considerably simplified the complexity and the Eagle II was born ...with a lower mean piston speed of course! Of course there is considerable scope to increase mps for low-life sprint and looking at today's F1 racing car engines shows how duty can be traded off against performance.. I wonder what would happen if F1 were a single journey over the Alp?

 

[tartle]

A plot of mps for various engines...

 

[Nick Sumner]

Tartle, first of all thanks for all the great information you are posting, particularly on turbofans.
Do you have any info on the Napier E.118 development stage of the Sabre? The one with the two stage three speed blower and critical alytitudes of 32,000 and 40,000 feet. It is mentioned in Lumsden and because he includes it that seems to imply that it was actually built. He even implies that it was installed in a Folland Frightful. It was swept away by the Sabre's manufacturing problems - or so I assume.

 

[tartle]

I'll certainly dig in my files.. it may take a while! .... in the meantime an unidentified Sabre in a Frightful....

 

[Nick Sumner]

[quote author=tartle Bare in mind when RR were asked to look at a high power backup to the Sabre they considerably simplified the complexity and the Eagle II was born ...with a lower mean piston speed of course!
The eagle 22 had an unimpressive P/W ratio compared to the Sabre or the Merlin. I've always wondered if RR planned to push up the piston speed incrementally for higher power outputs. That might explain the weight; ie weight = strength - to handle the increase in stresses with higher piston speeds.

 

[Hobbes]

Extra weight also works against higher piston speeds (more rotating mass=greater forces), I'm not sure what the net effect is but generally you see a move to stronger materials (titanium) when high piston speeds are required.

The extra weight could also be in preparation for higher boost pressures (the way to increase power without increasing piston speed). But that leaves the question of fuel: increase the boost pressure too much and you invite detonation or backfires, if your fuel isn't of sufficient quality.

 

[tartle]

Nick,
The starting power of a RR engine (other companies too maybe) was usually conservative.. take the Merlin in 1939=1000hp, 1944=2100hp. So I guess the Eagle would have followed in its footsteps.
Hobbes:
Forces exerted on engine critical components, e.g. pistons, pins, con rods, crankshaft, bearings and engine block, are directly related to piston acceleration. Force is mass times acceleration so lighter weights = less force; as GeorgeA points out the specific strength is also important, hence the advanced manufacturing techniques for steel manage to produce a thinner piston of sufficient strength a deformation resistance without a weight penalty. Making an identical piston in aluminium would probably mean the strength/deformation resistance would not be high enough without dropping metal temperature... by oil cooling, which was the way the Sabre's critical components survived.