Kermit Weeks Napier Sabre

[DogTailRed2]

Interesting video regarding Kermit's Napier Sabre.
MiniPix UK V24 16x9 Vo1 (youtube.com)
The obvious question is, are those restorations using an early Napier Sabre doomed to failure?

[Jhieminga]

I would say 'doomed to a path with lots of challenges'. As there aren't all that many Sabres lying about, having one in your possession is a step closer to the ultimate goal and as mentioned in the video, having an early model could also be the starting point for a swap. Also, it's not impossible to get an early one running, but seeing as Kermit has two Sabres available, I can see Richard's point in selecting the later model.

Edit: I have uploaded a cutaway image here: https://www.vc10.net/div/NapierSabre_cutaway.jpg It shows a bit of the complexity of the engine. It's an impressive beast.
https://live.staticflickr.com/65535/53559970632_f39332a0bd_c.jpg
NapierSabre by Jelle Hieminga, on Flickr

[VictorGolf]

Every time I look at the cutaway example at IWM Duxford I wonder at how the groundcrews kept them running in the field during WW2.

[GeeRam]

Interesting video regarding Kermit's Napier Sabre.
MiniPix UK V24 16x9 Vo1 (youtube.com) (https://www.youtube.com/watch?v=LVm7jCRARD0)
The obvious question is, are those restorations using an early Napier Sabre doomed to failure?

My personal view is they are going to struggle, depending on who else they can find with the right credentials who may be prepared to take on rebuilding an early Sabre to flight standards. It sounded like that the guy Nick has lined up (would guess its whoever is doing the Centaurus engines for him?) turned down doing the older one for one of the Typhoon projects...?
There's not exactly a large list of sleeve valve experienced engine shops around that might be willing to do it. I remember Kermit was struggling to find any engine shop 30 odd years ago willing to take it on, back when Paul Coggan did a feature on it for Warbirds Worldwide.

[Downwind.Maddl-Land]

Every time I look at the cutaway example at IWM Duxford I wonder at how the groundcrews kept them running in the field during WW2.
My father was 'Q'ed on the Sabre. He said it was a beautiful piece of engineering, but a bastard to maintain. If the ignition timing wasn't 'just right', one bank of cylinders would end up 'driving' the other, with concomitant demise of the gearbox an inevitability. TBO between major servicings was 25 hrs and a plug chage was a complete pain in the tender parts. It was also a bit of an oil slinger too.....

[DHfan]

I would guess that all sleeve-valve engines are a bit oily with effectively twice as many cylinder oil films required. One between the sleeve and the block and another between the piston and sleeve.

[longer ron]

I would guess that all sleeve-valve engines are a bit oily with effectively twice as many cylinder oil films required. One between the sleeve and the block and another between the piston and sleeve.

'A bit oily' is a master of understatement DH - I 'waved in' a couple of Sea Furies over the years and the wing roots were slick with oil from the exhaust pipery (also with oil dripping out of said pipery) - looked like a total loss oil system :)

[Jhieminga]

At some point in the video Richard mentions that sleeve valve engines have a chart in their manual that shows how much oil it should consume per hour. If you're below that, you're out of oil.

[ShyTorque]

I remember my father showing me a manual of a sleeve valve engine after explaining the basic principles of the four stroke cycle using a Merlin engine workshop manual (which I still have over sixty years later), when I was about five or six years old. It was difficult for me to imagine how such a thing was ever designed and built. He explained that the weak spot of these engines was ensuring sufficient lubrication of the sleeve itself.

[longer ron]

ISTR that from a previous S Fury accident report - the normal oil consumption figure was 12 - 20 imp pints per hour depending on power setting.
That is a lorra lorra oil to pay for :)

My Austin Apache that I drove whilst working in zimbabwe was almost as bad :)

[DHfan]

I had a '62 Vauxhall Cresta that used nearly as much oil as petrol.

I've just remembered the first time I ever heard of a sleeve-valve engine. It was in the middle sixties and an article in Motor Sport about the original Daimler Double Six, with a Knight principle V12. Obviously paraphrasing, it's nearly sixty years ago, but it was something along the lines of: "proceeding silently along the road, followed by a cloud (or haze) of blue smoke."

[longer ron]

I had a '62 Vauxhall Cresta that used nearly as much oil as petrol.



Absolutely - my Austin Apache (which was basically an 1100 with a triumph style front end and saloon/boot) had an engine leak (cannot remember where from).
But I took 2 friends up to Harare from Thornhill AFB (about 170 miles) - pulled into petrol station in Gatooma which was approx half way - they said ''need petrol ?'' not really says I but we will need some oil :).
My main use of the Apache was across town to the gliding club so the oil consumption was not normally a big deal :)

[treadigraph]

The Centaurus prefers a particular grade of mineral oil as I recall, which is more or less unobtainable now; haven't some of the failures been attributed to other oils used instead doing damage? Think it's been discussed on here before...

Always an absolute pleasure listening to Richard talking about such matters, he is so clear in his explanations as the storehouse of knowhow in his mind pours out at a digestible rate!

[DHfan]

Yes, it's a particular grade of AeroShell, which Shell will make, but understandably there's a minimum order of about a grillion* gallons.

It seems that in theory a specified substitute is suitable, but not necessarily in practice.

*Copyright Douglas Adams.

[longer ron]

Always an absolute pleasure listening to Richard talking about such matters, he is so clear in his explanations as the storehouse of knowhow in his mind pours out at a digestible rate!

It is but I thought he was being brave describing Kermies engine as a 1000 Hr TBO engine - I have always wondered what the highest actual TBO time a Sabre ever got to in service,I would imagine a lot less than 1000 hrs

[treadigraph]

True but, as he says, Kermit would really to go some to reach 1000hrs on it, even if Richard gets the thing airborne in the next year or two. :) A trip up to Oshkosh and back from Polk City probably would only amass 10 to 15 hours I'd imagine.

I trust Kermit will fly the thing at a UK display or two before shipping it home. Assuming it does come here for restoration. Roll on Part 3...

Interspersed with his purchase and relocation of The Cosmic Muffin... anyone got some B-17 wings to spare? How come I didn't see that when I went on a boat tour of the Fort Lauderdale waterways 30 years ago...

[GeeRam]

Yes, it's a particular grade of AeroShell, which Shell will make, but understandably there's a minimum order of about a grillion* gallons.

It seems that in theory a specified substitute is suitable, but not necessarily in practice.


Yep.
There's a rumour that the last batch of it left was sitting in one of the storage tanks that went up with the Buncefield oil terminal explosion......but I suspect there's no truth in that though.

[Jhieminga]

It is but I thought he was being brave describing Kermies engine as a 1000 Hr TBO engine - I have always wondered what the highest actual TBO time a Sabre ever got to in service,I would imagine a lot less than 1000 hrs
I don't know... the Sabre got a bad reputation due to the problems with the early versions. The servicability of the later versions, such as in the Tempest TT.5, was fine according to several sources (just don't ask me to list these right now...).

[stevef]

I read something in Group Captain Desmond Scott's Typhoon Pilot about the Typhoon's Sabres being susceptible to engine rapid failure in Normandy due to ingestion of sand on the forward airstrips damaging the cylinders. Apparently an efficient air filter was designed in a matter of days to fix the problem.

[sycamore]

I`m sure I read some yrs ago on the `real` Flypast` forum that `someone had found that there were some Sabres being used as water pump engines` in S.California..Don`t recall if it was verified,as it was at the time `Flypast` changed hands.....So ,who knows....

[treadigraph]

I have feeling an article I saw about Mike Nixon at Vintage V-12s mentioned he'd acquired a load of Packard Merlins from water pump useage in California; hydroplane racing might have been another source for his stock of spare bits 'n' bobs...

[DogTailRed2]

In the video the Sabre is described as a total loss oil system and that the green engine has the fuel delivery system which is missing on others.
Just two points of interest others may find interesting.
Keeping fingers crossed to seeing and hearing a Typhoon at some point.

[WB627]

ISTR that from a previous S Fury accident report - the normal oil consumption figure was 12 - 20 imp pints per hour depending on power setting.
That is a lorra lorra oil to pay for :)

My Austin Apache that I drove whilst working in zimbabwe was almost as bad :)

My wife's Austin Allegro (donated by my mother) was a pint to the mile :uhoh:

[DHfan]

My wife's Austin Allegro (donated by my mother) was a pint to the mile :uhoh:

I've no idea of how many miles I did now but I used to buy a 99p gallon of oil a week for my 1962 Vauxhall Cresta.

So far, I think you've got the winner.

[VM325]

Episode 3 just dropped.

Quite an emotional ending…

https://youtu.be/D7n7-4e0lm4?si=W-jwSKvWGwhqQRjP

[DHfan]

Dropped?

[VM325]

[QUOTE=DHfan;11615278]Dropped?[/QUOTE

From ‘drag and drop’…

[Jhieminga]

The green Sabre turns out to be a Sabre V, the correct type to put in a Tempest V. The other engine is a Sabre III which is a Firebrand engine. Looks like the Tempest V project will move into a higher gear... that is interesting news!

[DogTailRed2]

Is there much commonality between the Sabre Tempest and Typhoon?

[Jhieminga]

They look similar, but as to commonality, I doubt that there is much you could easily swap out between them. The Tempest used a completely new, thinnner, wing. The front fuselage was lengthened to accomodate an extra fuel tank (to cover for the loss of fuel storage in the wings) and because of this a new tail (with more surface area) was needed too. They use similar construction techniques, with a steel tube fuselage cockpit section mated to a semi-monocoque rear fuselage and tail.

Edit: just to illustrate the development path a bit more, this is the Hawker Tornado, an early parallel development version of the Typhoon. This airframe was built up from two airframes that were in production when the order for Tornados was cancelled. It was re-engined with a Centaurus CE.4S engine and used as a testbed for various Centaurii, leading to the later Tempest II.
https://live.staticflickr.com/7561/15833937541_1d673b6813_c.jpg
15_002600 Hawker Tornado HG641 by SDASM Archives (https://www.flickr.com/photos/sdasmarchives/), on Flickr

[sycamore]

J, that `Tornado` looks like it has a `Mercury` fitted,with the front cowling exhaust ring,and 3 bladed prop...

[DHfan]

As Jhieminga, stated, it's an early Centaurus.

If an aeroplane is designed for 2000+hp, it's hardly likely to be fitted with an engine with around a third of the power.

The same picture is in Putnam's Hawker book, along with another one of the same aircraft with a later Centaurus and a four-bladed prop.

[Jhieminga]

There is a comprehensive history of the Tornado here: https://oldmachinepress.com/2020/12/20/hawker-tornado-fighter/. According to that story it was a Centaurus engine with three bladed prop and common exhaust. This is the same airframe with a different prop and cowling configuration:

https://cimg0.ibsrv.net/gimg/pprune.org-vbulletin/512x249/image_16_86e62e7a464128bad0a6678897909c685c591eb0.png

[Geriaviator]

Don't know about the Centaurus but the approved beverage for the smaller Hercules in the 202 Sqn Hastings was OMD-270. It so happened that this heavy lubricant was well suited to our 1936 Hillman Minx, giving oil pressure of 35psi instead of 5. And Dad just happened to be serving on 202 Sqn.

[kenparry]

My understanding is that the Centaurus is much more picky about its oil than the Hercules, though I don't know why.

[DHfan]

I found an ancient post on the FP forum which said the oil for the Centaurus was AeroShell 100 U, apparently specially formulated for the engine.
One squadron or flight used OMD-270 instead in the Centauruses on their Beverleys in the middle east. Possibly because of high ambient temperatures?

Much to my surprise, it also said the TBO for the civil Centaurus was 3000 hours.

[Geriaviator]

Sounds very optimistic, I would think 1000 hrs would be closer. Back to the Sabre, and the 1946 editions of Flight (can be seen online) carry Napier's adverts for the Sabre rated at 5000bhp -- yes five thousand) for civil use. But by then it was clear that the future lay with jets. A brilliant design whatever way you look at it.

[DHfan]

I agree it seems unlikely, but I'm only repeating what was posted, eight years ago, and it's not a user name I recognise although he was a regular poster,

He also said the civil Merlin TBO was 1000 hours.

Presumably they are documented somewhere?

[Downwind.Maddl-Land]

The common factor between the 2 engines covered by this thread (Sabre and Centaurus) is the Bristol Aeroplane Company Ltd - Aero-engine Department. When the Sabre first entered service it was equipped with sleeve-valves (S-Vs) manufactured and machined by Napier; it was these that were the cause of many of the early S-V failures, even during 2-hr acceptance tests. It was only when help was requested from Bristol, who were by now well-versed in the production of S-Vs for their family of S-V engines, that the problem was solved as Bristol Taurus S-Vs could be adapted for use in the Sabre. Napier's own S-Vs usually lasted 20 to 30 hrs before wear caused excessive oil consumption (hence the 25 hrs TBO I referenced above) whereas Bristol S-Vs lasted 120 hrs without trouble.

[VM325]

I thought this might be of interest, it's from Flight March 1944...

[India Four Two]

Great article, VM325.

What mind-boggling complexity!

https://cimg1.ibsrv.net/gimg/pprune.org-vbulletin/898x1326/sabre_gears_cd1e33c953c94c08ed69adf8e858ee2e3774460e.jpg

"OK chaps, let's design an engine with more mechanical complexity than anyone has dreamt of!"

[DHfan]

Frank Halford obviously gave Napier ideas. This is the gear train for a Napier Deltic engine.
Nothing to do with Halford actually, it was developed from a Junkers opposed-piston design.

For those that aren't familiar with the engine, it's an 18 cylinder, 36 piston, 3 crankshaft, supercharged 2-stroke diesel.


https://cimg7.ibsrv.net/gimg/pprune.org-vbulletin/1000x747/delticgeartrain_6ecd72eaa33873a3ab20d723ad41f2a90f16583c.jpg

[sycamore]

`OY,mate,you`re missing 2 studs at the bottom..`

[VM325]

Frank Halford obviously gave Napier ideas. This is the gear train for a Napier Deltic engine.
Nothing to do with Halford actually, it was developed from a Junkers opposed-piston design.

For those that aren't familiar with the engine, it's an 18 cylinder, 36 piston, 3 crankshaft, supercharged 2-stroke diesel.



There's a chap here who's built a running model Deltic (https://craftsmanshipmuseum.com/artisan/clen-tomlinson/)
along with a Napier Sabre... (https://craftsmanshipmuseum.com/artisan/clen-tomlinson/clen-tomlinson-photos/) :eek:

[dfv8]

Another interesting viewpoint of the Napier Sabre, and other aviation related engines.

https://youtu.be/Hk1-P5iksIc?si=4iz-j4ZPpqCTvicH

and continued in part 2

https://youtu.be/Ej7TixxfmMs?si=CUZAqon2iIySHjNl

[treadigraph]

I gather Kermit has crated up all his Tempest V bits and attached a label addressed to Air Leasing at Sywell... :ok:

[DHfan]

Couple of pictures on the Key.Aero/FlyPast forum...

https://www.key.aero/forum/historic-aviation/hawker-tempest-incoming-florida-sywell