The notorious Centaurus

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Member for

23 years

Posts: 352

I´m aware that it´s common practise, at least in the USA, to substitute a Wright Cyclone R-3350 for the original Bristol Centaurus in Sea Fury rebuilds. This is said to be due to the unreliability of the BC and, though realizing that it´s a complex design, I´ve always wondered what causes the unreliability.

In the thread about fighter-bombers Phil mentioned this problem and I quote:
"The Centaurus is notorious for its intense sevice requirements, i was talking to someone recently who had worked on both Napiers and Centaurus whilst in sevice and hated the Bristol. He also reckoned the recent engine failure of the RNHF Fury was due to lack of engine knowlege !!"

Phil, would You care to elaborate on this, historically as well as the recent engine failure of VR930.
I always wanted to know and anyone else with insight into the subject is also most welcome to enlighten me!

Regards,
Christer

Original post

Member for

23 years

Posts: 3,553

RE: The notorious Centaurus

From what I understand - and I have to say I'm NOT an engineer, so this may not be entirely accurate - the big problem with the Centaurus (and the Hercules for that matter) is the sleeve valve system.

On most normal engines, the valves are the standard push-rod type, with a normal up-down motion cycle which is contained within the cylinder head. The stresses and loads that the valves are subjected to act in a straight line, and therefore are easier to manage. Also, a push-rod valve failure will result in limited damage, definately the valve concerned, possibly some of the others, and maybe the cylinder head and a piston.

A sleeve valve is in effect a large tube which fits inside the cylinder, but which contains the piston. I *THINK*, from looking at the insides of a Hercules engine recently, the sleeve valve turns and oscillates inside the cylinder in order to shut off the inlet / exhaust holes, AND also has the piston thundering up and down inside it. So the loads and stresses on a sleeve valve are vastly different to a normal one. The sleeve has to cope with turning and oscillating friction on the outside face (against the inside of the cylinder), and also has to deal with the up-down friction of the piston against it's inside surface. Factor in the combustion stresses, and you've got a heck of a lot of different forces acting on that valve.

Because of the layout of a Centaurus / Hercules, when a sleeve valve lets go, it will most probably pull the whole engine apart; a normal valve will just get slapped up against the head of it fails, whereas a sleeve valve is an integral part of the cylinder as it is in constant contact with the piston, therefore when it fails, the piston will come to a dead stop, seizing the whole engine and causing all sorts of damage within the other cylinders.

As I said, I'm NOT an engineer, and so if anyone is, and wants to put me straight on this, please feel free! I'm going to be up close to a sectioned Hercules tonight, so I'll have a look and ask some knowledgable people whether my ramblings are correct, and I'll let you know...

Member for

23 years

Posts: 352

RE: The notorious Centaurus

Steve,
thanks for Your reply!
I know a little bit about how it works.
Someone said sleeve valve engines are simpler than poppet valve engines. No push rods or valve gear at the top of it but, to me the Centaurus seems like a Swiss watch churning out 2,500 Hp!? Just look at that gear train for the sleeve drive!

I´m still hoping for a comment from Phil about what he learned from the "service time guy"!

Regards, Christer

Member for

23 years

Posts: 341

RE: The notorious Centaurus

Hi folks, I'm new to this computing game, but I'm an old hand RAF engineer who's worked both the Centaurus and British and American poppet valve radials. The simple fact is that sleeve valve engines were developed to get over all of the problems that were encountered on poppet valve engines! The sleeve valve mechanism may look complex, but in reality it's not. Poppet valve engines require much more routine maintenance than sleeve valves, checking and adjusting the valve clearances on an 18 cyl engine is one of the real pain jobs you have to do on a regular basis. On balance though, provided both types are operated within the design limits there should be little difference in overall reliability. I suspect however that with racing engines, they spend a lot of there running time near to, or over the limit! The problem is that running a sleeve valve engine at extended high temperature has a tendency to distort the sleeves, and this leads to problems. The most likely explanation for the Centaurus being replaced is probably that there is a greater availability of American engines, and that American engineers feel more comfortable with them. But to my view putting an American engine in a Fury is like hanging furry dice in your Ferrari!

Member for

23 years

Posts: 352

RE: The notorious Centaurus

Keith,
thanks for Your input!
Obviously people have different opinions, the other guy, to whom Phil referred, hated it whereas You and the Centaurus agreed with eachother.
I liked Your analogy with furry dice and a Ferrari! Can I assume that putting a Centaurus in an American fighter would be like hanging a pair of horses balls in the window of a Fiat?
(Sorry, couldn´t resist it!)

Regards,
Christer

Member for

23 years

Posts: 341

RE: The notorious Centaurus

Absolutely!!

Member for

23 years

Posts: 924

RE: The notorious Centaurus

Sorry Guys,
I was trying to track down the guy i was speaking to about the Centaurus so as i could get the facts straight, unfortunately i have not ben able to speak to him yet. I am an engineer but not unfortunately on aero engines. I if remember rightly the cahp was telling me about the difficulty in timing the cylinders individually on 18cyl radials, in particular the Centaurus.He said that in his opinion RNHFs Fury was exhibiting all the signs of not getting the timing correct, ie the damage to a sleeve which has resulted in metal particles being ingested further down the engine.
I will try again to track the chap down as he was very intersting, i met him whilst giving a talk at a club where i showed slides of Fury amonst others.
Phil

Member for

23 years

Posts: 352

RE: The notorious Centaurus

Phil,
thanks for Your efforts.
I´ll check the thread at least every other day!

Regards,
Christer

Member for

23 years

Posts: 74

Christer Bergstrom ?

Are you the Black Cross, Red Star co-author ?

TTFN
Inquisitive Mick

Member for

23 years

Posts: 352

RE: Christer Bergstrom ?

No Sir!

Just click the profile icon, some nuts state their full and real names there.

On another forum I´ve recently been referred to as Indiana Christer. I guess we´ve "met" there!?

Member for

6 years 7 months

Posts: 16

I know that his is an old topic but I felt some things were missing.

I have had vast experience on both the R3350 a lovely engine but with its faults, and also the Centaurus and Hercules engines. They are complicated , for example there are 49 gears in the front gear housing to drive the sleeve mechanism in the Hercules..

A good read is By Jupiter and live story of Sir Roy Fedden and the delevopment of the first sleeve valve engines and the trials and tribulations of development.

as the JUpiter, Pegasus, Hercules and Centaurus engines evolved wear was a problem, this was taken up with Shell Aero division who formulated a hi spec Mineral oil for the engines. Aero shell 100 U. This was a winner and wear reduced and a longer engine life.
Any Engine if mishandled will fail somewhat, take a Bog Standard R3350 and exceed 3000RPM by a little and standard Articulating rods will get a .010" bow. Centaurus engines will display faults I am sure.

Now back to the exchanging of the Centaurus with R3350 turbo compound engines , in my mind, is the shortage of the Bristol engine and a POSSIBLE nil availability of Aeroshell 100 U which is essential for smooth running of the sleeve valve engines.

SOme years ago I visited Oshkosh a had casual talks with some engineers/Mechanics working on ex RAN Sea Furies and asked them why the exchange. all answered , more engines and availability of spare parts. Nothing else came into the equation. I may have missed some things but have written to the best of my recollections.

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18 years 10 months

Posts: 3,902

Welcome to the forum nennrita.

As a rule ,we generally start a new thread rather than revive an old one, but you weren't to know that !

!5 years old, might be a record. We have lost a few since then. RIP Steve Young.

Member for

17 years 4 months

Posts: 554

Must have missed this thread first time round.
Trained on Hercules 100 at RAF Halton in the fifties, during our last term sectioned a Centaurus. Posted to RAF Seletar worked on No. 34 Sqdn. Beverley's fitted with Centaurus 173 for two and a half years. Returned to UK posted to RAF Colerne, No. 36 Sqdn. equipped with Hastings, Hercules 216 engines. Flew as ground engineer for five hundred hours in both types. The Beverley operated all over the Far East including supply dropping during the Borneo confrontation. I remember one engine failure at Labuan where a cylinder poked its nose out of a top cowling, holding down studs had sheared. Powers that be had increased max boost by 1 lb, that was quickly changed. The major problem was the rubber dynafocal engine mounts, they could not stand the heat, especially when reverse was selected and there was no cooling air.
Three and a half years on Hastings recall one failure, a split sleeve.
Great engines.

Member for

8 years 6 months

Posts: 584

As has been posted, the Centaurus was a more reliable engine than other British ones. When built properly.
Typical examples of reliability:
Civil Centaurus max TBO (Time Between Overhaul) was 3000 hrs and Civil Merlin max TBO 1000 hrs.
Setting up the valve timing was intensive work though. The good thing being that you didn't have to adjust them anymore.
I would imagine fitting American engines was due to their availability of spares. The swept volume of the 3350 is slightly higher (1 ltr) and being turbo-compound, more power available. It is also slightly more reliable, the figures given being in the range of 3500 hrs TBO.

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11 years 2 months

Posts: 277

Still don't sound as good as a Centaurus at high power though.

Member for

8 years 6 months

Posts: 584

I'll give you that. Many moons ago I did some work at Duxford and helped out with a Sea Fury. That engine was really hard compared to Merlins and Griffons.

Member for

23 years

Posts: 352

Hello nennrita, well, the thread starter is still around and waiting for further insights ... :eagerness: ... but fifteen years is a long time. It's amazing that you found the thread!

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17 years 3 months

Posts: 472


Now back to the exchanging of the Centaurus with R3350 turbo compound engines , in my mind, is the shortage of the Bristol engine and a POSSIBLE nil availability of Aeroshell 100 U which is essential for smooth running of the sleeve valve engines.


A good few years ago I knew the last Rolls Royce inservice support engineer officially charged with supporting the Bristol Sleeve valves. He told the same story relating to oil and limited spare availability but added the following;-

The really significant retirement of the Bristol sleeve valve fleet was pretty advanced in the early 70’s so demand for the Shell oil ceased. Because the oil was deemed necessary for the safe operation of the engine and there were still a few operators (mainly Noratlas and Bristol Freighter) determined to continue, Rolls Royce (& Snecma) brokered a deal whereby Shell would still produce the oil to special order but only with a commitment to buy a minimum quantity. Right into the mid 80’s he organised several operator syndicate purchases which enabled some of these types to linger on, providing commercial/military service into the late 80’s, early 90’s.

When I asked about the private Sea Fury operators in the 70’s & 80’s he was less than complimentary about their attitude. They refused to accept the Rolls Royce instructions, declined invitation to join oil purchasing syndicates, and preferred to believe rumours that other oils would work just as well. The gotcha was that an engine filled with an alternate oil which would appear to being doing fine but was liable to very, very rapid deterioration and would inevitably destroy the engine, leading frequently to the loss of aircraft and sometimes the pilot. Of course when this happened the operators would always blame the engine and arrogantly never admit their wilful neglect of the manufacturers directives.

It’s a great shame that the ignorance of a few has left a perceived poor reputation on what was a magnificent piece of engineering.

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12 years 11 months

Posts: 194

IIRC my father (an X rated licensed engineer, who had great experience on Hercs, 'big' Hercs & Centurii from the late 40's until his death in '79), said the biggest danger was a sleeve pinching if the power was suddenly reduced after a climb for example, & hence creating fast temperature reduction.
Keith

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13 years 8 months

Posts: 1,020

I still have memories of a Centaurus failing very shortly after take off in a Brigand. This was put down to an oil leak, but the engine stopped pretty abruptly. Being in the crash,/take off/landing position sat on the floor down behind the cockpit with back against the rear? spar, I saw nothing. The pilot did a great job in wandering round a sloppy circuit and landing safely.

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13 years 7 months

Posts: 85

The best man to talk to by a country mile in this country is a chap called Jeff Rushen who I believe is down working for Weald Aviation