Thread: Spitfire celebrates 75th anniversary

Originally Posted by 85 county

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The British Bristol Centaurus, is was and always will be a dog. The advantage of a sleeve valve motor was better air flow. This was good up until sodium filled valves became available, which allowed overlap in valve timing and (eventually multiple valves) which increased the performance of valve motors past that of the sleeve valve motor. Ease of manufacturing wasn’t in the sleeve valves favor either. The real disadvantage was cooling, having a sleeve and a liner meant that there was so much metal between the hot stuff and the cold stuff. Distortions of the sleeve and excessive wear of the sleeve both lent to in-flight failures with disastrous effect for such a heavy air craft with a high over the fence speed.
Its use was a political one, since all the other manufactures had been post war supported with other projects or products. Bristol had to be given some thing.

Besides all that, they are the absolute top of piston powered fighters. And to me the best sounding aircraft ever. uumm that would make a Bristol freighter twice as good ????

The Bristol Centaurus was not a dog - it was very successful both as a military and civil engine. Its use was not political, except perhaps in the sense that it had to be used in Britain instead of US-built engines for currency exchange reasons. Compared to the comparable Pratt and Whitney or Wright radials, the Centaurus gave a smaller overall diameter (no rocker gear) and lower specific fuel consumption. Overhaul intervals were comparable as was reliability (If there had been problems in this regard, I think you would have seen the engines in the Bristol Freighters in Australian service in the sixties and seventies being replaced by P&W).

I think the early sleeve failures you are thinking of relate rather to the Napier Sabre sleeve valve engines, where the failures were eventually traced to incorrect field maintenance (of the gadget that set rpm and boost from a single power lever) allowing overboosting at low rpm. By the time the Centaurus came out, Bristol had been working on sleeve valve engines for nearly twenty years, and had had the very successful Perseus in production for ten. Most people who are not very familiar with sleeve valves are frightened of them simply because they are unfamiliar, but while as you point out there are heat dissipation problems with sleeve valves, these are nothing compared to the heat dissipation problems with poppet valves - these problems have largely been solved today, but read any of the early aviation accounts and you realise how hard this was. As an example, in the early flights to Australia, every overnight stop, someone spent the night doing a top overhaul on the engine(s), often barely mentioned, simply because it was assumed you had to do this. An advantage of sleeve valves rarely mentioned is that because the sleeve is moving, the piston never stops moving relative to it, unlike a poppet valve engine, where the piston stops moving relative to the cylinder twice every revolution, allowing static friction to take over, increasing wear and power loss.

The reason most piston airliners of the post-war period used American engines was that most airliners were American, partly as a result of the US/UK agreement in 1941 that the UK would concentrate on military aircraft development and buy US transport aircraft. Also, outside the USA, most new designs were looking at turboprops or jets (HS748, F27, Comet - even the flops such as the Brabazon and Saro Princess were designed for turboprops)

John

Originally Posted by JDNSW

The Bristol Centaurus was not a dog - it was very successful both as a military and civil engine. Its use was not political, except perhaps in the sense that it had to be used in Britain instead of US-built engines for currency exchange reasons.

It was political, patriotic and just British, as you said

Originally Posted by JDNSW

Compared to the comparable Pratt and Whitney or Wright radials, the Centaurus gave a smaller overall diameter (no rocker gear) and lower specific fuel consumption. Overhaul intervals were comparable as was reliability (If there had been problems in this regard, I think you would have seen the engines in the Bristol Freighters in Australian service in the sixties and seventies being replaced by P&W).

there is the swept volume debate, a bit like the 2 cycle vers the 4 cycle, this leaves the swept volume questionable, weight was another factor when compared to a American radial. There fuel consumption was due to there ability to run quite lean comparatively speaking.

Originally Posted by JDNSW

I think the early sleeve failures you are thinking of relate rather to the Napier Sabre sleeve valve engines, where the failures were eventually traced to incorrect field maintenance (of the gadget that set rpm and boost from a single power lever) allowing overboosting at low rpm.

Quite correct. There was also the problems in making the chrome molly sleeves and getting them to stay round. they were actually manufactured not round when cold, this was for the Napier sabre. The Centaurs only gave similar problems when over heated a little.

Originally Posted by JDNSW

By the time the Centaurus came out, Bristol had been working on sleeve valve engines for nearly twenty years, and had had the very successful Perseus in production for ten. Most people who are not very familiar with sleeve valves are frightened of them simply because they are unfamiliar, but while as you point out there are heat dissipation problems with sleeve valves, these are nothing compared to the heat dissipation problems with poppet valves - these problems have largely been solved today, but read any of the early aviation accounts and you realise how hard this was. As an example, in the early flights to Australia, every overnight stop, someone spent the night doing a top overhaul on the engine(s), often barely mentioned, simply because it was assumed you had to do this. An advantage of sleeve valves rarely mentioned is that because the sleeve is moving, the piston never stops moving relative to it, unlike a poppet valve engine, where the piston stops moving relative to the cylinder twice every revolution, allowing static friction to take over, increasing wear and power loss.

Quite correct but i get the feeling that you are spreading over time.
The sleeve valve had great advantages over poppet valves, as you stated, due to the reduced maintenance and its ability to flow cleaner air. then with the advent of sodium filled valves this advantage was eroded away since poppet valves now became more reliable and it allowed the introduction of valve overlap ( timing) which improved a poppet valve motors over all performance. The last stage was supercharging, this is where the sleeve valve became a disadvantage, the heat retention of the sleeve, distorting and tendency to fail would have been the nail in the coffin of the sleeve valve motor. but we will never relay know if a solution would have come because as you stated below the advent of the jet age.

The maintenance hours of the Centaurs was about twice that of the P&W powered Andersons. As a comparison.

Originally Posted by JDNSW

The reason most piston airliners of the post-war period used American engines was that most airliners were American, partly as a result of the US/UK agreement in 1941 that the UK would concentrate on military aircraft development and buy US transport aircraft. Also, outside the USA, most new designs were looking at turboprops or jets (HS748, F27, Comet - even the flops such as the Brabazon and Saro Princess were designed for turboprops)

Good knowledge John.

I thought the Brabazon was built with 2 griffons driving a single prop shaft though a strange angled gearbox arrangement but with a view of replacing it with turbo props when and if ever available

Originally Posted by 85 county

I thought the Brabazon was built with 2 griffons driving a single prop shaft though a strange angled gearbox arrangement but with a view of replacing it with turbo props when and if ever available

The Brabazon, as with the Princess, was designed to use the Bristol Proteus turboprop, in this case in pairs driving four sets of contra-rotating props. In the one specimen that actually flew, the planned Proteus gas turbines were replaced by eight Centaurus engines, as the Proteus at this stage was having serious problems. The Proteus eventually was a reasonably satisfactory engine in the Britannia, but that was much later.

John

Well that sparked an intersting conversation, I am not a fan of any radial engine in particular I was just relaying a quote I heard from an old bloke about 30 years ago. Re the "Pratt and Whitney would have made them that way"

The Corsair (F4U) was the first to crack 400mph in level flight and Goodyear produced them with the Wright Cyclone 4360 (cu) which had 28 cylinders - and if you are think of picking one up, that's 56 spark plugs at about $110 ea....

Anyway, if you're interested in the Goodyear FG-1, have a look / search for Race 57 - THAT is a beast.

Also platinumfighters.com for the Hawker Fury for sale....couple of Spitfires too and my favourite, the P-40!

Matt

[ame=http://www.youtube.com/watch?v=r5-1HS7Qylg]YouTube - Spitfire buzz reporter[/ame]

The old reporter getting buzzed by the Spitfire video. I'm sure many have seen it before, but it still brings a smile to my face when I see it. **LANGUAGE WARNING**

MMMM they have a Spitfire 1A for a mere $4,900,000.00
I could sell the deefer then I would only need to find $4,890,000.00, what do you reckon

Check out the Griffon in a Fairey Firefly, camera work is a bit ordinary but sound is good
[ame=http://www.youtube.com/watch?v=MiGtlP6wzQc&feature=related]YouTube - RNHF Fairey Firefly display[/ame]