Bristol Orion aero engine.

Here is the text on the Orion

“The team at Somerdale was enlarged, and work began on what Fedden had finally concluded must be started at the earliest possible date: a new engine much more powerful than the Centaurus. Under the revived name Orion, a study was made for an 18-cylinder radial with a bore of 6’/a in and capacity of 4,140 cubic inches. It incorporated several features planned for future models of the Hercules and Centaurus. One was an exhaust system with the pipes discharging straight to the rear from aft*facing ports. Another was a new design of head consisting of a close-finned copper base, with nickel-plated flame face, shrunk into a steel body. The Orion was drawn in detail by Butler in early 1941, and promised to be a superb engine rated at an initial power of about 4,000 hp. Several airframe constructors welcomed it, and Arthur Gouge (Short Brothers) and Rex Pierson (Vickers) began projects for large bombers and flying boats using four or even six. Such very big machines appeared certain to be needed – in peace, if not during the War – and the one thing Fedden wanted to avoid was having to couple together groups of smaller engines.

“With the Centaurus he had what appeared to be the most powerful aero engine in the world. With the Orion added at the top end of his family he considered the Bristol company would be able to offer an unbeatable range of engines, not only to win the War – which he said in 1941 would probably last until 1946 – but also to win the fierce commercial battles of the ensuing peace.

“Fedden was frankly and totally committed to the sleeve-valve piston engine, which he was certain would be needed up to at least 1955 and probably later. He had no doubt his company could – if it had the strategic judgement and motivation – be the world leader in piston aero engines during the whole of this period, providing the foundation for a world-beating series of British aircraft. It is characteristic of Fedden that, in early 1941, in the grimmest period of the War and long before the formation of any Brabazon Committee to study the problem, he was deeply engaged in considering the design of the aircraft for the post-war period. It was partly because of this that he appreciated the importance of the Orion.”

Here at last is some info from gunston’s ‘Fedden’.

Pages 244 – 248 has information, diagrams and comparative drawings of both the Orion and a 4 row 28 cylinder 5 3/4 in bore by 7 in stroke engine.

The Orion was basically a bigger Centaurus, ie 18 cylinders in two rows of nine, 6 1/4 in bore and 7 1/2 in stroke. It was expected to achieve 4000hp.

The unnamed 28 cylinder does not appear to be a ‘corncob’ design from the diagram, it looks similar to the BMW 803 layout – ie row 3 is directly behind row 1 and row 4 is directly behind row 2. However, although it has Centaurus bore and stroke, 28 cylinders means 4 rows of 7 rather than 4 rows of nine so there is more room for the air to circulate. It is also noticable that the cowling outline is well clear of the cylinder heads – again giving more circulation room – whereas Hercules, Centaurus and Orion were (or were to be) very closely cowled.

Here are links to the drawings of the Orion, 28 cylinder engine and a couple of other interesting tidbits from ‘Fedden – The Life of Sir Roy Fedden’ by Bill Gunston. A fascinating book, I recommend it.

I apologise for the large file sizes but there is a lot of detail and some tiny printing I thought might be useful.

http://i115.photobucket.com/albums/n291/nsumner/PP246top.jpg

http://i115.photobucket.com/albums/n291/nsumner/PP246lower.jpg

http://i115.photobucket.com/albums/n291/nsumner/PP247top.jpg

http://i115.photobucket.com/albums/n291/nsumner/PP247lower.jpg

http://i115.photobucket.com/albums/n291/nsumner/PP255.jpg

Obviously this is copyright material so personal use only! 🙂

I’ve contacted the Bristol Branch of the Roll Royce Heritage Trust at Filton, if and when they reply I’ll post the info here.

It’s a shame that nobody has written/published a genuinely useful book on the history of Bristol engines. Lumsden’s “British Piston Aero Engines” is useful on the detail but not the big picture, Binghams “Major Piston engines of World War II” oddly ignores the Mercury but devotes many pages to the Centaurus (and the Brabazon), Graham Whites “Allied Aircraft Piston Engines” is genuinely useful, but inevitably can only cover Bristol briefly. The only other work we’re left with is Gunston’s deeply ludricous hagiography of the works of St. Roy Fedden which even in its moderated second version is an appallingly slack attempt at documenting an important piece of history.

NiallC

Bristol Orion radials

In Bill Gunston’s “By Jupiter – the life of Sir Roy Fedden” TWO Bristol Orion radial engines are described. The following is extracted from the book.

The first was a development of the Jupiter VI incorporating an RAE turbocharger and ran in 1928. Although getting a Gamecock to 20,000 ft in 12 3/4 mins there were cooling problems plus distortion on the turbocharger impeller casing and the programme was abandoned.

The second Orion was an 18 cyl radial with a bore of 6 1/4 ins and capacity of 4,140 cu ins. Detail drawing was done in 1941 and it promised to be a superb engine with an initial rating of 4,000 hp and, like the smaller Centaurus (at that time the most powerful radial in the world) was sleeve-valve. Despite the internal political battles at Bristol (which came to a head when Fedden received his Knighthood) an Orion single cylinder rig was run in 1942 but it seems the design died with the departure of Fedden from Bristol Engines in October, 1942.

A good source for further information might be the Bristol Branch of the Roll Royce Heritage Trust at Filton.

Roger Smith.

There is a brief mention of the Orion on page 152 of Bill Gunston’s “The Development of Piston Aero engines”. This was to be an 18-cylinder monster of 67,929 cc (4,142 cu in) providing 4,000 hp initially. It never ran, however.

As I understand it the original Bristol Orion was a piston radial that was designed around 1942-43, I should have mentioned that I didn’t mean the 50s turboprop – sorry!

Does anyone have, or can they point me too, any information on a projected Bristol radial aero engine called the Orion which was supposed to follow the Centaurus? Like many other piston projects it was abandoned in favour of jet engines.

Host of refs on Google – try

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

😉