Why so few single engine Hercules applications?

[Admiral Beez]

Most of us have seen claims online that the Bristol Hercules were optimized for multi engined, tractor-like bomber hauling rather than the rapid changes in throttle, supercharger, manifold pressure, attitude and altitude seen in single seat fighters. But there are many potential single engine application for the Hercules that were not fighters. There's also the case that in the Merlin and Griffon, Britain had two superlative liquid cooled inline engines. Is that it, is this why we see so few single engined aircraft powered by the Hercules? The Hercules' predecessors and its successor the Centaurus certainly made it into single engined aircraft. Considering how frequent Bristol motors were used in FAA aircraft, from the Flycatcher to the Skua and Albacore it's noteworthy that the Hercules never saw fleet service.

Twin engined fighters-bombers, like the Beaufighter would have made demands upon the Hercules similar to those of a single engined fighter. Though perhaps that's why the Beaufighter was considered for Merlin engines.

 

[Shortround6]

Main problem was simply carburetor type and location. It used a downdraft carb that was mounted high, inlet of the carb was almost the height of the cylinder heads.
Air scoop would have been right in front of the pilot.
This was not insurmountable. Other engines had either a downdraft or updraft carb. A different, shorter carb might have been designed that allowed side (or 1 o'clock/11 o'clock) inlets.
But Bristol was having trouble in the very beginning of the war mass producing the sleeves. They were also having cooling issues as they attempted to increase the power of the engine.
They may not have had enough engineering capacity to modify that part of the intake system while fixing other things?
Just an opinion.

Those may be oil coolers hanging under the fuselage.

 

[Koopernic]

Most of us have seen claims online that the Bristol Hercules were optimized for multi engined, tractor-like bomber hauling rather than the rapid changes in throttle, supercharger, manifold pressure, attitude and altitude seen in single seat fighters. But there are many potential single engine application for the Hercules that were not fighters. There's also the case that in the Merlin and Griffon, Britain had two superlative liquid cooled inline engines. Is that it, is this why we see so few single engined aircraft powered by the Hercules? The Hercules' predecessors and its successor the Centaurus certainly made it into single engined aircraft. Considering how frequent Bristol motors were used in FAA aircraft, from the Flycatcher to the Skua and Albacore it's noteworthy that the Hercules never saw fleet service.

Twin engine fighters-bombers, like the Beaufighter would have made demands upon the Hercules similar to those of a single engine fighter. Though perhaps that's why the Beaufighter was considered for Merlin engines.

BMW 801 Diameter: 51 in (1,290 mm) Displacement: 2,560 in³ (41.8L)
R-2800 Diameter: 52.8 in (1,342 mm) Displacement: 2,804.5 in³ (45.96 L)
Hercules II Diameter: 55 in (1,397 mm) Displacement: 2,360 in³ (38.7 L)
R-2600 Diameter: 55 in (1,397 mm) Displacement: 2,604 in³ (42.7 L)

The clear out winners here in terms of frontal area, displacement and power for frontal area are the R-2800 and BMW 801 and this is probably why both engines were used on fast fighter aircraft (Fw 190, P-47, Hellcat, Corsair) or high speed bombers (Ju 88 S-1)

The BMW 801 is actually the heaviest, much heavier than the R-2800 but I believe this is because of the armoured oil ring and gearbox.

In terms of P/W ratio the Hercules is good but it does have a large diameter. He Beaufighter was very fast at low altitude when hauling a load.

 

[A.G. Williams]

Bristol Type 153, intended for the cannon-fighter spec won by the Whirlwind, but never built.

Picture by John Dell: John Dell's Aviation Art

 

[A.G. Williams]

BMW 801 Diameter: 51 in (1,290 mm) Displacement: 2,560 in³ (41.8L)
R-2800 Diameter: 52.8 in (1,342 mm) Displacement: 2,804.5 in³ (45.96 L)
Hercules II Diameter: 55 in (1,397 mm) Displacement: 2,360 in³ (38.7 L)
R-2600 Diameter: 55 in (1,397 mm) Displacement: 2,604 in³ (42.7 L)

It does seem odd that the Hercules is so wide, given that one of the advantages of sleeve valves is that you don't have the bulky poppet valve gear sitting on top of each cylinder. Other things being equal, the Herc should have been appreciably narrower.

 

[Shortround6]

Unfortunately reality got in the way of theory.

Perseus engine but shows the problem. The sleeve rises higher than the ports to help close them off. Plus you still need a LOT of fin area in the head to cool the cylinder.
Hercules went through a number of cylinder heads with ever increasing fin area as the power went up.

 

[pbehn]

It does seem odd that the Hercules is so wide, given that one of the advantages of sleeve valves is that you don't have the bulky poppet valve gear sitting on top of each cylinder. Other things being equal, the Herc should have been appreciably narrower.

That is what I used to think until I saw a rotating cutaway engine at the Yorkshire Air Museum, the sleeves move side to side and up and down, so the sleeve and its support go well above the piston at TDC, it gives the illusion of the piston only going half way up the cylinder.

lols S/R beat me to it.

 

[Koopernic]

It does seem odd that the Hercules is so wide, given that one of the advantages of sleeve valves is that you don't have the bulky poppet valve gear sitting on top of each cylinder. Other things being equal, the Herc should have been appreciably narrower.

The latter versions got a little narrower and much more powerful, I used rubbish data, as it turns out, from Wikipedia which doesn't mention latter versions.

From the Hercules VI the diameter was only 52 (being 3 inches less than the 55 of the Hercules I ) so quite competitive with the R-2600 and even 801D2 at 1.42ata.

The large diameter of the early versions (Hercules I from 1939) It might have deterred early development of certain aircraft.

I suspect the sleeve increases diameter of the cylinder which must be compensated by a combination of either superior aspiration or a longer stroke.

The Hercules II may have been quite 'open' inside and perhaps the pressure loss experience by the cooling flow was less than dense engines like the R-2800 or 801.

 

[Shortround6]

Some of the data may come from Lumsden but his data is for a power egg, Much like the confusing data on the BMW 801 where you have th ebare engine and the power egg diameter.

Early Hercules didn't make enough power to compensate for the drag (crappy high drag cowling) and Bristol was behind RR in supercharger design.

 

[Admiral Beez]

That is what I used to think until I saw a rotating cutaway engine at the Yorkshire Air Museum, the sleeves move side to side and up and down, so the sleeve and its support go well above the piston at TDC, it gives the illusion of the piston only going half way up the cylinder.

Makes me wonder if Bristol would have been bettter off to skip the sleeves and instead develop a larger/powerful ohv Mercury or Taurus.

BMW 801 Diameter: 51 in (1,290 mm) Displacement: 2,560 in³ (41.8L)
R-2800 Diameter: 52.8 in (1,342 mm) Displacement: 2,804.5 in³ (45.96 L)
Hercules II Diameter: 55 in (1,397 mm) Displacement: 2,360 in³ (38.7 L)
R-2600 Diameter: 55 in (1,397 mm) Displacement: 2,604 in³ (42.7 L)

But the better diameter comparison is between Bristol's ohv and their own sleeve. Perhaps Bristol engine were all uncompetitively wide, regardless of valve train.

 

[Koopernic]

Makes me wonder if Bristol would have been bettter off to skip to she sleeves and instead develop a larger/powerful ohv Mercury or Taurus.
But the better diameter comparison is between Bristol's ohv and their own sleeve. Perhaps Bristol engine were all uncompetitively wide, regardless of valve train.

Roy Fadden, a relative of Harry Ricardo no less, ended up being sacked by the board of management in 1943 over the issue. It seems sleeve valves may have worked but were not profitable. Bristol were masterful in poppet valves at the time. The Centaurus was a fine engine though.

 

[Deleted member 68059]

If its a single engine, its pretty much either a trainer, or an interceptor fighter, nobody is going to bother with the expense of a Hercules in a single-seat trainer, so that leaves fighters. If you read the tech reports that the Air Ministry made of the Fw190, its clear the prevailing attitude was "radial fighters ought not to be able to be this fast". So its pretty clear that for high performance single-seat applications that the liquid cooled V12 was basically the only choice to be taken seriously in Britain in the 30`s as far as the air ministry was concerned.

 

[MIflyer]

Well, let's face it, folks. When the first PBY purchased by the British arrived in the U.K. a reporter attending the event said that it could not have flown very far because the nacelles were not covered with oil.

When the Short Sunderland Mk V came out the crews were delighted to find they could complete one of their long missions and come back with all four engines still running.

British radials often did not inspire confidence.

 

[Admiral Beez]

Well, let's face it, folks. When the first PBY purchased by the British arrived in the U.K. a reporter attending the event said that it could not have flown very far because the nacelles were not covered with oil.

When the Short Sunderland Mk V came out the crews were delighted to find they could complete one of their long missions and come back with all four engines still running.

British radials often did not inspire confidence.

I suppose that's why the Blenheims were crated and shipped to Malaya rather than flown there, despite Britain having the necessary airfields. Here's the route, just ignore the stop in Lisbon needed to force the route to avoid Spain. Total 10,000 miles, at 198 mph cruise speed will require about fifty hours of flight time. Any reliable and well designed radial would handle fifty flight hours without needing a tear down at the final destination.

No British engine inspires confidence. I had a 1969 Triumph twin, and while over 11 years of I loved that bike, I could never trust it.

 

[MIflyer]

In contrast the DH Comet flew all the way to Australia. Although they did lose an engine along the way, and a DC-3 powered by American radials came in 2nd.

Also note that when Canada copied the DC-4 they used Merlins but apparently did not give a moment's thought to British radials.

There was a TV commercial a while back featuring a man saying that when he went to his first job, in Scotland, he borrowed a car from his parents. During the trip there he refilled the gas tank once and the oil tank twice.

An additional factor may have been that many of the smaller aircraft Britian sent overseas did not have radios. They were using battery powered short range radios in Spits and Hurris in the BoB and even in P-40's in the Western Desert, so no radios for others makes sense. GB was a world leader in electronics and in some ways still is - I just bought an aircraft radio made by an outfit in Scotland - but did not have anything like the production capacity required. After designing the revolutionary SCR-522 and the even more revolutionary microwave radar sets, they left building them to the Americans.

 

[Koopernic]

I suppose that's why the Blenheims were crated and shipped to Malaya rather than flown there, despite Britain having the necessary airfields. Here's the route, just ignore the stop in Lisbon needed to force the route to avoid Spain. Total 10,000 miles, at 198 mph cruise speed will require about fifty hours of flight time. Any reliable and well designed radial would handle fifty flight hours without needing a tear down at the final destination.

No British engine inspires confidence. I had a 1969 Triumph twin, and while over 11 years of I loved that bike, I could never trust it.

Britain went through some difficult times in its manufacturing industry in the 1970s, 80s and 90s. Not sure what caused it. Industrial Relations problems were clearly there and the vestiges of class warfare but I think the problems were also driven by the economic situation, high interest rates which made capital investment difficult. I went for an MBA a few decades ago (before they were as brain washy and PC as gender studies) and there I found that many of the quality control systems and manufacturing techniques were in fact developed and used by the British in WW2. For whatever reason they just couldn't keep it up post war. Possibly also the discovery of North Sea Oil caused a decline as oil wealth tends to push the currency up and therefore make exports expensive and imports cheap. I think British problems are over now and British quality is excellent now, especially in bespoke products, though western elites, indifferent to any sense of loyalty, have outsourced much production to China.

 

[MIflyer]

though western elites, indifferent to any sense of loyalty, have outsourced production to China.

They are a bunch of touchy feely types who know nothing of any real use and have found that you can avoid having to understand what is happening on the shop floor if the shop floor is in Red China.

 

[Admiral Beez]

Britain went through some difficult times in its manufacturing industry in the 1970s, 80s and 90s. I went for an MBA a few decades ago (before they were as brain washy and PC as gender studies) and there I found that many of the quality control systems and manufacturing techniques were in fact developed and used by the British in WW2.

If you read up on the failures of the British automobile and motorcycle industries you'll see a repeated claim that there were too many MBAs (sorry there) and business school graduates in upper management and not enough engineers. The Germans had the inverse experience, with their industrial giants being run by engineers. Perhaps that's part of the difference. I wonder if Bristol's engineers were hobbled by management directives on cost, resources or company direction.

There's also the issue of The City, where much of British industry was run or beholden to financiers in London who didn't care about industry, just profits. At Honda, almost every dime of profit was reinvested into engineering, production, process and product improvements, while profits in Britain went almost entirely to divideds to the shareholders, resulting in WW2 equipment and methods languishing into the 1970s. Even today, the inverse to Britain in Italy can be seen in motorcycles. In Britain today Triumph motorcycles have moved all production to Thailand in order to chase profits for its City financeers, meanwhile in Italy, Moto Guzzi produces all its bikes domestically, because the company is owned by the very industrialists that supply the parts, rather than banks in Milan.

 

[Deleted member 68059]

If you read up on the failures of the British automobile and motorcycle industries you'll see a repeated claim that there were too many MBAs (sorry there) and business school graduates in upper management and not enough engineers. The Germans had the inverse experience, with their industrial giants being run by engineers. Perhaps that's part of the difference. I wonder if Bristol's engineers were hobbled by management directives on cost, resources or company direction.

There's also the issue of The City, where much of British industry was run or beholden to financiers in London who didn't care about industry, just profits. At Honda, almost every dime of profit was reinvested into engineering, production, process and product improvements, while profits in Britain went almost entirely to divideds to the shareholders, resulting in WW2 equipment and methods languishing into the 1970s. Even today, the inverse to Britain in Italy can be seen in motorcycles. In Britain today Triumph motorcycles have moved all production to Thailand in order to chase profits for its City financeers, meanwhile in Italy, Moto Guzzi produces all its bikes domestically, because the company is owned by the very industrialists that supply the parts, rather than banks in Milan.

Dont underestimate personal hostility and petty bitterness. Just about the entire Air Ministry absolutely hated Fedden on a personal basis, he was very rude, stubborn and abrasive and loathed administrators. It wasnt enough that the firm sacked him, the Ministry then got him out the country by sending him off to America on the "Fedden Mission" to look at US industrial practises, which, whilst useful - is hardly a realistic use for one of Britains greatest aero engine designers. They wanted rid of him, and would do almost anything to ensure he was out of their hair.

 

[MIflyer]

Where did Sir Frank Whittle go to live after the war? And von Ohain came to live about 20 miles from where I am now.

For that matter. Martin quit building airplanes because after the B-51 was rejected in favor of the Canberra he was told there was no way they would ever buy one of his designs.

I am told that Harley Davidson now builds reliable motorcycles. For years, Bike Week in Daytona Beach was known as "Trailer Week" because of the preponderance of Harlys and how they got there.