RR Merlin, competitors and alternatives before 1941

[tomo pauk]

Guess I'd have this discussion moved here, lest we don't clog another thread with aero engine pr0n:

Even the storied Merlin was a deeply flawed engine and obsolete in many respects by the time it entered service.

To what i replied: Compared to what?

[the fuel injected DB 601 was suggested]

Next post by the fellow forum member on that topic:

Hispano-Suiza 12Z is another - sadly killed off by the fall of France. The Allison V-1710 was a much more modern engine too - one-piece block, quad cams, just hamstrung by its inadequate supercharger. Then there was the Ford GAA which should really have replaced the Packard Merlin in American service.

V-1710 was a SOHC engine, not DOHC. Inadequate supercharger is not a minor issue, nor it is the availability of the V-1710, that being mid-1940, by what time the superlative Merlin XX is in service by the RAF. V-1710 have had a two-piece block (countries onther than UK called that feature: 'head is detachable from the block' - as we take for granted now). Even the Merlin X was earlier available that the service-grade V-1710.
Further to go 'by the time it [Merlin] entered service'. There was no HS 12Z in 1936, when Merlin I was introduced (flawed as it was). The 1st DB 601A entered the service in late 1938, almost a year later than the non-flawed Merlin II. Best what DB had to offer in winter of 1937/38 was the DB 600C and D, good for 900 HP at 4 km (vs. Merlin's 1030 at 5 km - even better than the vaunted DB 601A).

Ford GAA, for all it's on-paper qualities, never materialized as an aero engine. Not even as a test mule.
Henry did a disservice to the Allies with cancelling the contract to the British, but we can forgive him that since his brand-new factory manufactured thousands of R-2800s. Obviously, GAA is not an answer to the British questions, Merlin is/was.

 

[Broadwoodwidger]

Sorry, I forgot the V-1710 was SOHC, getting it mixed up with the GAA and the H-S 12Z and its Klimov cousins. Yes, the head is detachable from the block, but with the Merlin, you have two heads, two blocks and a separate crank-case. It's an obsolete construction which caused no end of trouble with gaskets leaking and loss of oil pressure. There is no such thing as a non-flawed Merlin, they just range from merely troublesome to downright disastrous. The GAA was a far more modern design, and was cancelled for purely political reasons.

Rolls-Royce as a company had a hugely inflated view of themselves and their expertise, from engineering design (they were still making side-valve engines after they scrapped the tooling for the Bentley straight six!) to production (they seriously thought they had finer engineering tolerances than mass-produced Ford engines...) - how a company was able to build such global fame on such abject mediocrity has always bewildered me. They were only able to make the Avon reliable as a result of absorbing Armstrong-Siddeley (the Avon 200 is closer to a Sapphire than to an early series Avon), they needed French help to sort out their reheated version of the Bristol Olympus, and after the useless "variable noise constant thrust machine" Viper, it was the French who came to their rescue again with the Adour. That either the car brand or the engine-maker survives at all today is largely thanks to BMW... and really, the Phantom VII was the first Rolls-Royce car to live up to the hype. Alas, I am not quite possessed of the funds required to run one, but I do own a very used example of its "little" brother, a 2005 760Li, and that car absolutely beats the pants off any Rolls-Royce I've ever been in. But I digress...

Don't forget that it was also Rolls-Royce who buggered up the Fairey Battle. It was originally supposed to be powered by a large 24-cylinder engine of Fairey's own origination (a prototype was built and flew reliably throughout the war), then as the various Rolls-Royce big engine projects fell apart, they ended up lumbering the bloody thing with a grossly inadequate Merlin instead. The result was to turn a good aeroplane into a suicidal death-trap.

 

[Bougnas]

What thread did this discussion come from? I'm curious.

 

[tomo pauk]

Sorry, I forgot the V-1710 was SOHC, getting it mixed up with the GAA and the H-S 12Z and its Klimov cousins. Yes, the head is detachable from the block, but with the Merlin, you have two heads, two blocks and a separate crank-case. It's an obsolete construction which caused no end of trouble with gaskets leaking and loss of oil pressure.

Every ww2 V12 (and most of other Vee engines) was with two heads, two blocks and a separate crankcase, so I'm not sure why you've singling out the Merlin.

There is no such thing as a non-flawed Merlin, they just range from merely troublesome to downright disastrous. The GAA was a far more modern design, and was cancelled for purely political reasons.

Sources for both sentences? Real sources, not fanboy articles.
Boy, if Merlin was that flawed, than the BMW 801, Bristol Taurus, A-S Tiger, DB 603, Napier Sabre, VK-107 or R-3350 should've been left on the drawing board.

(they seriously thought they had finer engineering tolerances than mass-produced Ford engines...)

What tolerances were used by RR aero engines, what were the ones used by Ford?

Don't forget that it was also Rolls-Royce who buggered up the Fairey Battle. It was originally supposed to be powered by a large 24-cylinder engine of Fairey's own origination (a prototype was built and flew reliably throughout the war), then as the various Rolls-Royce big engine projects fell apart, they ended up lumbering the bloody thing with a grossly inadequate Merlin instead. The result was to turn a good aeroplane into a suicidal death-trap.

I forget, in a hartbeat, the urban legends, myths and opinions not backed up by facts.

What thread did this discussion come from? I'm curious.

Started here.

 

[ArtosStark]

Not sure if it can be considered a competitor since it was never a viable flying engine, but the AS Deerhound was at least in the right hp range.

 

[CV12Hornet]

Don't forget that it was also Rolls-Royce who buggered up the Fairey Battle. It was originally supposed to be powered by a large 24-cylinder engine of Fairey's own origination (a prototype was built and flew reliably throughout the war), then as the various Rolls-Royce big engine projects fell apart, they ended up lumbering the bloody thing with a grossly inadequate Merlin instead. The result was to turn a good aeroplane into a suicidal death-trap.

I'm going to have to ask you to cite that, because none of the histories I can find mention this and the aforementioned 24-cylinder, the Fairey Monarch, only first ran in 1939, a good two years after the Battle was introduced.

 

[Cryhavoc101]

Don't forget that it was also Rolls-Royce who buggered up the Fairey Battle. It was originally supposed to be powered by a large 24-cylinder engine of Fairey's own origination (a prototype was built and flew reliably throughout the war), then as the various Rolls-Royce big engine projects fell apart, they ended up lumbering the bloody thing with a grossly inadequate Merlin instead. The result was to turn a good aeroplane into a suicidal death-trap.

Are you referring to the Fairey P.24 Monarch?

It was never going to power the Battle aircraft - other than using a Battle airframe as a test bed - it flew for the first time in 1939 in one for trails and had it been successful and brought into production then it would have powered subsequent designs such as the Hawker Tornado and not the Battle.

However into 1940 it had a number of issues and was dismissed in favour of other engines such as the Sabre and Vulture (which was also cancelled)

The Battle was well into its production and service and being slaughtered over the Meuse (as any bomber of the day would have been under the same circumstances) while the Monarch was still in prototype status.

 

[marathag]

Keep RR working on the Buzzard.
If that fails, go with a close competitor in that size class that was just a bit less efficient

Packard finds the funds to do more with their big V12, and do more than just power PT Boats in the War, keep the focus on Aero engines.
Marine version got to 1500HP by wars end. Don't let that 'low' HP rating fool you, that was continuous rating, not a WEP for a couple minutes.

From the Wiki

Specifications (1A-2500)​

General characteristics

• Type: 12-cylinder V engine
• Bore: 6+3⁄8 in (161.9 mm)
• Stroke: 6+1⁄2 in (165.1 mm)
• Displacement: 2,489.7 cu in (40.799 L)
• Dry weight: 1,120 lb (510 kg)

Components

• Valvetrain: Four valves per cylinder, overhead camshaft
• Fuel type: Petrol
• Cooling system: Liquid-cooled

Performance

• Power output: 850 hp (630 kW) at 2,500 rpm
• Specific power: 0.33 hp/in³ (15.2 kW/L)
• Power-to-weight ratio: 0.76 hp/lb (1.25 kW/kg)

 

[marathag]

Oh, and from earlier discussion on the Ramp Head Merlin

Hawker Hurricane even more prolific and versatile?

The main problem with no Beaufort is no Beaufighter. However, it might be possible to develop the Hampden into a heavy fighter ("Hampfighter" or "Hampdestroyer") by fitting more powerful engines and modifying the fuselage. The Blenheim and the Beaufighter aren't much different in size - is...

www.alternatehistory.com

 

[marathag]

What tolerances were used by RR aero engines, what were the ones used by Ford?

Stanley Hooker's autobiography, Not Much of an Engineer,

"In my enthusiasm, I considered that Rolls-Royce designs were the ne plus ultra, until the Ford Motor Co. in Britain was invited to manufacture the Merlin in the early days of the War. A number of Ford engineers arrived in Derby, and spent some months examining and familiarizing themselves with the drawings and manufacturing methods. One day their Chief Engineer appeared in (Merlin development head Cyril Lovesey's) office, which I was then sharing, and said, 'You know, we can't make the Merlin to these drawings.'

"I replied loftily, 'I suppose that is because the drawing tolerances are too difficult for you, and you can't achieve the accuracy.'

"'On the contrary,' he replied, 'the tolerances are far too wide for us. We make motor cars far more accurately than this. Every part on our car engines has to be interchangeable with the same part on any other engine, and hence all parts have to be made with extreme accuracy, far closer than you use. That is the only way we can achieve mass production.'"

 

[Cryhavoc101]

Stanley Hooker's autobiography, Not Much of an Engineer,

"In my enthusiasm, I considered that Rolls-Royce designs were the ne plus ultra, until the Ford Motor Co. in Britain was invited to manufacture the Merlin in the early days of the War. A number of Ford engineers arrived in Derby, and spent some months examining and familiarizing themselves with the drawings and manufacturing methods. One day their Chief Engineer appeared in (Merlin development head Cyril Lovesey's) office, which I was then sharing, and said, 'You know, we can't make the Merlin to these drawings.'

"I replied loftily, 'I suppose that is because the drawing tolerances are too difficult for you, and you can't achieve the accuracy.'

"'On the contrary,' he replied, 'the tolerances are far too wide for us. We make motor cars far more accurately than this. Every part on our car engines has to be interchangeable with the same part on any other engine, and hence all parts have to be made with extreme accuracy, far closer than you use. That is the only way we can achieve mass production.'"

This is the only source I've ever seen for the oft repeated "Ford tolerances being better than Rolls Royce because Ford mass produce stuff!" claim

My Great Aunt and others like her were mass producing RR Merlin's at Crewe during the war and she was an Irish book keeper before coming to England in 1939 not an engineer hand building the things.

RR mass produced them in their 10s of thousands

For me its up there with Garand ping totally getting GIs killed!

 

[marathag]

This is the only source I've ever seen for the oft repeated "Ford tolerances being better than Rolls Royce because Ford mass produce stuff!" claim

Had been looking for that source for a really long time, and finally tracked that down last year

 

[Llewwyy]

I seem to recall something I read regarding why Packard was chosen to make Merlins in the U.S. It was because they were the only manufacturer who met Rolls Royce quality control. If Rolls Royce made such terrible products then why were the WWI armoured cars still being used at the start of WW2? Normally one gets rid of things that are costly to maintain. I seem to recall also, that during development Merlins were run until they broke, got fixed then were run again to try and break the engine, then again fix the flaw. Sounds like a terrible engine, let's not build it and lose the war.

 

[Llewwyy]

Did not the Germans test their brand new fighter, the BF 109 with another terrible RR product, the Kestral because their motor was not ready yet? I believe the Merlin was in production at the time as well.

 

[PhilKearny]

I seem to recall something I read regarding why Packard was chosen to make Merlins in the U.S. It was because they were the only manufacturer who met Rolls Royce quality control. If Rolls Royce made such terrible products then why were the WWI armoured cars still being used at the start of WW2? Normally one gets rid of things that are costly to maintain.

Just because RR armored cars made for WW I were used in WW doesn't mean they were particularly good or easy to maintain. Rather, it suggests that the users couldn't afford to replace the RR armored cars with anything better, so they had to scrape by with worn-out, obsolete armored RR armored cars.

 

[sonofpegasus]

I have a copy of the three volume 'official' history of Rolls Royce, when I have the time I will try and look up what is says in there about the tolerance issue.
The RR factories at Crew and Glasgow ere set up with machines tools for mass production whilst the Original RR factory at Derby was based on more traditional British artisan engineering system making it more adaptable for engine development and starting production of new variants based on a very skilled work force. The combination of the two different methodologies was IMHO a winning formula.

 

[Broadwoodwidger]

@tomo pauk it is not correct to state that all WW2 V12s had the same construction with separate blocks and crank-case. Rolls-Royce persisted with it to the bitter end, as did the Allison, but the Ford V12 had a one-piece block, as did the H-S 12Z, the old 12Y used a one-piece block and head per bank with a separate crank-case, so again, only two gaskets to worry about (four if you include the cam covers). The DB601 was identically constructed - just three main castings. Rolls-Royce, in using five, caused no end of trouble with loss of oil pressure...

Re the Fairey Monarch, the reason that its development was so delayed was because of Rolls-Royce's assurances to the Air Ministry that the Merlin would meet all their needs. It didn’t. Those early Merlins had to be derated down to 880bhp as their reliability at the initial stated 1030bhp proved so poor. Eventually R-R got it back up to 1030bhp, but it was still nowhere near enough, and even that was an extrapolated gross figure from bench testing with no ancillaries. On high octane fuel and with additional boost, you could crank them up to around 1300bhp but only for a minute or two before the engine would grenade. It wasn’t until 1939 that they were able to provide a continuous rating of 1280bhp, and even that was nowhere near sufficient.

 

[fastmongrel]

Meteor tank engines often used refurbished parts from life expired Merlin's. Packard, Ford and RR parts could be used interchangeably.

As for obsolete well the Merlin was state of the art at the time the draughtsmen were sharpening their pencils. By the time it was in service more advanced designs were on the drawing board thats how design works. How many more advanced designs got into service before wars end.

As for the DB fuel injection that's typically German design. "We need tens of thousands of these engines let's fit them with complicated fuel injection that requires hundreds of high quality parts, hundreds of man hours and costs a fortune. Everyone else let's fit a carburettor that uses 20 parts and can be serviced with a screwdriver.

 

[Broadwoodwidger]

I have a copy of the three volume 'official' history of Rolls Royce, when I have the time I will try and look up what is says in there about the tolerance issue.
The RR factories at Crew and Glasgow ere set up with machines tools for mass production whilst the Original RR factory at Derby was based on more traditional British artisan engineering system making it more adaptable for engine development and starting production of new variants based on a very skilled work force. The combination of the two different methodologies was IMHO a winning formula.

R-R had to turn to Ford to implement those mass production techniques at Crewe and Glasgow, Derby was stuck in the dark ages (W. O. Bentley had been manufacturing to a much higher standard of precision and was not at all happy with what he found at Crewe, quite aside from the disgusting way Rolls-Royce took over Bentley and destroyed all its tooling, parts stock etc).

@fastmongrel at no time was the Merlin ever state-of-the-art. The design was obsolete the day the PV12 drawings were produced. In some respects it was actually a step back from the old WW1 V8s. The French had also turned to fuel injection, the Germans weren't alone in doing that, and the Merlin's carbs were junk.

 

[ArtosStark]

I'm going to have to ask you to cite that, because none of the histories I can find mention this and the aforementioned 24-cylinder, the Fairey Monarch, only first ran in 1939, a good two years after the Battle was introduced.

Are you referring to the Fairey P.24 Monarch?

It was never going to power the Battle aircraft - other than using a Battle airframe as a test bed - it flew for the first time in 1939 in one for trails and had it been successful and brought into production then it would have powered subsequent designs such as the Hawker Tornado and not the Battle.

However into 1940 it had a number of issues and was dismissed in favour of other engines such as the Sabre and Vulture (which was also cancelled)

The Battle was well into its production and service and being slaughtered over the Meuse (as any bomber of the day would have been under the same circumstances) while the Monarch was still in prototype status.

The only hints I have read on the Battle being built for a larger engine than the Merlin say it was originally intended to be powered by the originally proposed RR Griffon. This was basically a straight militarization of the R racing engine, rather than the later Griffon that had more Merlin lessons learned. RR stopped work on this engine to focus on the PV-12. So I suppose in a case way RR did mess up the Battle, by not building another engine as well as the Merlin. Practically traitorous bunch, weren’t they?