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The other Bristol Mercury engines

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AVTUR:
Edit Jo: I have extracted this very interesting discussion from Vixen's Bristol Mercury build so it is not lost and to let his thread focus on his excellent modelling:
 


--- Quote from: Vixen on September 06, 2019, 11:33:18 PM ---Sir Roy Feddon, Bristol's chief engineer, had an entirely different view, he loved complexity and elaboration in his engines. He could not leave a design alone, he always wanted to change and 'improve' it. He nearly bankrupted the Bristol Aircraft Company, before they eventually sacked him. I have always been fascinated by the man and his over complex engines. That's why I build so many of them.

Mike

--- End quote ---

Feddon designed another Mercury. It was a 14 cylinder radial with seven conrods and bigends on each crankpin (unlike a master rod).  The two banks of cylinders were arranged helically around the crankcase. It flew in 1918 in a Bristol Scout and could have been a successful engine if the Ministry of Munitions had not ordered the ABC Dragonfly (probably one of the two worst engines of all time).

AVTUR

Vixen:
Hello AVTUR,

Me? I'm strictly AVGAS.

Thanks for reminding us of the earlier 14 cylinder Mercury.

I just happens that I have some full size blueprints for the Brazil-Straker 14 cylinder Mercury dated June 1918. Feddon was the design genius and Butler was his brilliant design draftsman who converted Feddon's dreams into reality. That partnership lasted for over 25 years. You may be able to see the parts callout; all start with FB.

The BS Mercury was unusual in as much as the conrods were lined up one behind the other on the two crankpins. The 14 cylinders were arranged in a double helix rather than in two rows. Apparently the BS Mercury performed well and 200 were ordered for the Royal Navy Air Service. The order was subsequently cancelled, later that year, after the Armistice.

I also have blueprints for the ABC Dragonfly. It looked to be a reasonable engine on paper. In fact it was ordered straight off the drawing board before the first engine was built. By all accounts, it was a dreadful engine, very unreliable with the ability to cook itself almost every flight.

Mike

PS I have no intention of building one.



Brazil-Straker Mercury

AVTUR:
Vixen

We, RRHT at Bristol, know it as the Cosmos Mercury. It looks far more complicated than the Jupiter. I am not sure where I got the idea it had 14 cylinders. The only pictures I have seen of it is in the Scout. Can I request a clearer, more in-focus, picture please?

The Dragonfly ran at a critical speed of its crankshaft.

AVTUR

Vixen:
Hello AVTUR,

You are quite correct it was 14 cylinders and I have gone back and corrected my typo.

The aviation interests of Brazil Straker were purchased by Cosmas Engineering in 1919.  With the ending of the war, Cosmos had no production orders, and their engine repair work was quickly dwindling. The company was soon insolvent. The Cosmos company was then purchased by Bristol's in 1920.

Feddon and Butler joined Cosmos from Brazil Straker and went on to the Bristol Aircraft Company. Together they designed and built many notable radial engines, the Jupiter, Mercury and Pegasus poppet valve engines. Then later, the sleeve valve Hercules and Centaurus engines. And many others besides.

I am also a RRHT (Bristol Branch) member but live too far away to get there regularly.

Mike

PS. I will try and find a better camera to get a better photo of the blue print.

Art K:
Mike,
Sorry I just caught up with this one. Impressive engine and stand to display it, wow. I was trying to find out more about the Brazil-Straker Mercury, you wouldn't believe all the garbage you find when you are looking for one particular thing. I finally found a fuzzy photo on wiki, I'm not picturing the engine layout, does anyone have other photos. I mean it's not even mentioned in Hirschel Smiths book which is sort of the bible of piston aircraft engines, intriguing.
Art

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