WW2 Without the Merlin: Options for the British

Bearing in mind that the Merlin, in its original "ramp head" form was a failure.

Rolls-Royce redesigned the head along the lines of the Kestrel, as they had experience with that type and knew it would work.

Shortround6 said:

Peregrine used the same bore and stroke, same layout (V-12 with 4 valves/cylinder with overhead cams,etc) but was about 140lbs heavier and turned more rpm.

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Interesting that the Peregrine was rated for 3000rpm, whereas the Vulture, using the same bore and stroke, was rated for 3200rpm (before, of course, the troubles). I would imagine that given time and development the Kestrel would have ended up turning at 3200rpm. And a Merlin at 3000rpm is equivalent to a Peregrine turning at 3272rpm.

And the myth perpetuates:

Four Kestrel/Peregrine cylinder banks attached to a single crankcase and driving a single common crankshaft would produce the contemporary Rolls-Royce Vulture, a 1,700-horsepower (1,300 kW) X-24 which would be used for bombers.

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Though Wiki cites Rubbra for this claim, it is incorrect. The bore spacings were:
Vulture – 6.1in
Kestrel/Peregrine – 5.625in
Merlin – 6.075in
Griffon – 6.9in

So, though the Vulture shared bore and stroke with the Peregrine (and possibly items like pistons), its bore spacings were closer to that of the Merlin.

History of the 12Y/M-100/M-105 series goes something like this.

1932, the 12Y is placed on the Market.

1933 the Russians enter into negotiations with Hispano- Suiza for licence production. Jan, 1934 sees an engine drawn from a French contract set up for a 100 hr test run, it breaks it's crankshaft in the 11th hour and develops cracks in the cylinder block jackets. Hispano-Suiza adds counter-weights to the crankshaft. Con-rod ends, cylinder blocks and crankcase are reinforced, diameter of gearbox shaft increased. Weight is increased to 475kg. Tests are completed to the Russians satisfaction but but long running at max power still resulted in malfunctions. tests finished March of 1934. A member of the purchasing commission proposed accepting the engine in the original form but derated to 750hp at which level it's service life was long enough to be acceptable.
June 14, 1934 the contract is signed with a provison that Hispan-Suiza keep the Russians informed of all changes to production engines until the contract expired March 26 1938.
1935, March sees the first Russian M-100s leave the shop with many French supplied parts. Max rating is 750hp.
1936, March sees the introduction of the M-100A with strengthened blocks, modified valves, higher supercharger pressure and a max rating of 860hp. Work starts on M-103 model.
1937 sees th estart of the M-105 project.
1938 sees the introduction of the M-100AU with increased service life. It also sees the introduction of the M-103. Increased compression ratio, changes supercharger drive ratio, boosted rpm, strengthed cylinder blocks, new gas seals, crankshaft with caps(?) new pistons. Max power is 1000hp and weight is now 495kg.
1939 sees the M-103A introduced with the same power rating but cylinders of decreased diameter, strengthened crankshaft, crankcase, cylinder blocks sand cylinder liners. M-104 is introduced, a M-103 with 2 speed supercharger, basically it picks up it's 1100hp max rating by using less supercharging at low altitude ( less power to drive the supercharger and less heating of the intake air) The end of 1939 sees the start of M-103U production which is a M-103A with longer service life. This year also sees the first M-15s flying in prototypes. Russian accounts are confusing, July 1939 is supposed to be the start of production but Oct 1940 is when the last of 50 of the first production batch is completed with a number of changes.
1940 is the year that the M-105 is really showing up, with (again) strengthened crankshaft, crankcase, cylinder blocks, con rods. three valve heads and two speed supercharger drive. first versions weigh 550kg and have a max rating of 1100hp. This goes to 570 kg very quickly as improvements are made to stop cracks in the valve boxes and main crankshaft journals and burned exhaust valves. The M-105P is also "introduced" during 1940 (May 1940 officially) although flying earlier. Max rating is still 1100hp but weight is now 600kg.
1941 sees the M-105PA introduced with the same nominal weight and power rating but described as having a strengthened crankcase and stiffened con-rods in addition to other changes.
May of 1942 sees the M-105PF introduced with boosted supercharging. The change increases power at low levels but decreases power at higher altitudes. Power is now 1260hp for 600kg. later series engines have strengthened crankshafts. Engines in training units and flying schools have the pistons modified for lower compression and power but longer service life.
The summer of 1943 sees prototypes of the M-105PF-2 and 1944 full production at a max power of 1290hp.

Basically it took the Hispano/Klimov series until 1943/44 to get to where the Merlin III was with 100 octane fuel in 1939/40 and with dubious reliability. In 1939/40 the Hispano/Klimov series was about 100-200hp behind the Merlin III on 87 octane depending on altitude. The Peregrine is about 100-200hp behind the Merlin III depending on altitude.

Talking of the Peregrine:

Topic: Peregrine Engine Work in Progress - Whirlwind Fighter Project

Many thanks for the Hispano -> M-105 time line, SR6. About the M-105PF:

The change increases power at low levels but decreases power at higher altitudes.

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Don't think that (bolded part) was the case, the power at higher altitudes remained the same (same drill as when Merlins got more boost, or V-1710 received WER) :

Basically it took the Hispano/Klimov series until 1943/44 to get to where the Merlin III was with 100 octane fuel in 1939/40 and with dubious reliability. In 1939/40 the Hispano/Klimov series was about 100-200hp behind the Merlin III on 87 octane depending on altitude. The Peregrine is about 100-200hp behind the Merlin III depending on altitude.

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For a Hispano to work for the RAF in BoB, the fighter based around it must, again, be smaller lighter than the Spit Hurri duo. It would be able to carry a cannon with minimal drag weight penalty, though. So in the worst case we would've seen something like MS-406, in the best case something like VG-33. In between fall the Historic Avia, IK-3 and D.520 - far easier for things to go wrong with lower HP engine around, rather than with high HP one.

Thank you Tomo. Just going by the text in the book but the translation is not the best. You have to guess sometimes what they mean as the English doesn't make 100% sense.

The problem with the Hispano is that it works (but only just) for 1939-40 and then starts crapping out in 1941. Even with smaller airframes you are hitting performance problems pretty soon. Using the historic superchargers the FTH was seldom over 4000 meters. The range is only going to be enough longer than a Spitfires to win a bar bet, not have any real impact on operations, and the smaller airframes will NOT have the adaptability. Hurricane II's may not have been very good fighters but what does a Hispano powered VG-33 get you for a ground attack plane? Chances of a VG-33 carring even one 500lb bomb (Spitfire) let alone two is not good and the VG-33 is carrying about 1/2 the guns for strafing.
Yaks worked, inpart, because they were often carrying 70KG of guns not including ammo. The ShVAK weighed 8 kg less than a Hispano and the Hispano needs either a drum or or belt feeder running the weight up even more. The 12.7mm UB was about 25kg. The Russian ammo was about 71% of the weight of Hispano ammo. The VG-33 (or British clone) may wind up carrying more weight in guns-ammo than a Yak very easily.
Adding armor/BP glass and self-sealing tanks to a VG-33 sized fighter may not degrade the speed that much but it will screw up both turn and climb to a greater degree than the larger planes as the wing loading takes a bigger hit (percentage wise) as does the Power to weight ratio ( again, percentage wise).

The D520 and the 109 Emil weighed pretty much the same so I dont see an issue here.
As a pure interceptor range and bombload are very secondary. European fighters 1930s did have short range and that was the way it was.
I certainly agree that a small Hispano fighter would be limited but its better than no fighter. A lot better. The D.520 should have gone Merlin early on but Klimov only copies Rolls Royce jets and not V12s.

For pure interceptors gun load is important even if bomb load is not. Many contributors to this forum complain about about the eight .303s in the BoB fighters that had around 17 seconds worth of ammo. The 20mm Hispano gun available in 1940 had 6 seconds worth of ammo, then you are down to 2 or 4 .303 guns. without the 20mm gun through the prop hub the smaller fighter will be limited to 4 or 6 .303 guns. If eight is not enough why are 4-6 ok?

My point is that both the Hurricane and Spitfire were able to do other jobs after the BoB. Jobs that a small fighter like the VG-33 or D 520 either cannot do or would be rather poor at. This requires replacement fighters sooner. The Hispano fighters with small wing 180-190sq ft or less) are going to be lousy fighter bombers. Their ability to operate as photo-recon planes is going to be rather limited. Their ability to be up gunned is limited.
The Typhoon/Tornado is needed even sooner than it was historically as the Hispano has very limited ability to be upgraded without a total redesign.

R-R specialised in in-line, Bristol in radial - had problems with sleeve-valve technology, Armstrong - had the Tiger which on the Whitley was replaced by the Merlin, Napier had the Dagger - but on the Hereford was not successful. Avis had a licence to produce Gnome-Rhone engines, but this wasn't utilised - thought to be too heavy!
Then there is Pratt Whitney whose R-1830 engine , perhaps, could've helped, so which Aero-engine company, is the most likely/plausible to take on licence production - e.g. Wasp Twin-Wasp, Armstrong, Fairey, or who??

Wouldn't be Fairey - they didn't have an engine factory.

I don't think the R-1830 gives you too much more than a Bristol Pegasus, frankly.

Austin motor's had an engine plant that had built aero engines and had production line experience. Alvis had built imperial measure Gnome Rhone 14 radials that passed tests in 1936 give them a contract to develop it for 100 octane and particularly the supercharger for better altitude. Give Austin a shadow factory contract to build a production line. Get Hawkers to modify the Hurricane to take the Alvis 14 and a decent fighter should be in service not much later than the original Merlin Hurricane

Aaaaggghhhh!!!!

The engine (among others in the G-R range) Alvis got the license for is the 14N with no middle crankshaft bearing. Same fault that doomed the Armstrong-Siddeley tiger and Kept the Russian M-88 engine at 1100hp or less.

The engine would not stand increased boost pressures due to crankshaft flex. All you need to "fix" it is a new crankshaft and crankcase. And then add more cylinder and head finning to handle the higher heat load and then.........

Reading a bit about Fokker XXI, seems 5 examples were furnished with Bristol Pegasus aboard. Anyone has more informations about how those performed?
The Perseus-equipped version (never built), but also with retractable U/C should be on par with Hurricane I?

fastmongrel said:

Austin motor's had an engine plant that had built aero engines and had production line experience.

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When did Austin have an aero engine factory?

What result would bolting the Merlin's supercharger to the Peregrine give?

More power?

Or merely a higher critical altitude/FTH?

wuzak said:

Interesting that the Peregrine was rated for 3000rpm, whereas the Vulture, using the same bore and stroke, was rated for 3200rpm (before, of course, the troubles). I would imagine that given time and development the Kestrel would have ended up turning at 3200rpm. And a Merlin at 3000rpm is equivalent to a Peregrine turning at 3272rpm.

And the myth perpetuates:



Though Wiki cites Rubbra for this claim, it is incorrect. The bore spacings were:
Vulture – 6.1in
Kestrel/Peregrine – 5.625in
Merlin – 6.075in
Griffon – 6.9in

So, though the Vulture shared bore and stroke with the Peregrine (and possibly items like pistons), its bore spacings were closer to that of the Merlin.

Click to expand...

Good post - there are lots of myths about the Vulture, including the idea that the cylinder banks were from the Kestrel or Peregrine - the crankcase, pistons and heads were derived from, but different to, the earlier engines while the "star-rod" design, which drove four pistons from one crankshaft bearing was completely new, and badly thought out:


(From Robert Kirby Avro Manchester: The Legend Behind the Lancaster page 83) Apparently there were doubts about developing the Vulture in early 1938.

Superchargers provide two things.
1. airflow, usually measure in mass like pounds per minute or the metric equivalent.
2. pressure.

the two can be traded off some but superchargers usually have a narrow 'sweet spot' at which they give a good but not max airflow at a good but not max pressure at good efficiency, least amount of power needed. Max air flows or max pressures are at lower efficiency levels. lower efficiency levels also raise the intake charge temperatures.



Granted this is for a modern turbo-charger compressor but the same principles apply. Using too big a supercharger as far as air flow goes can put you too close to the surge line/limit. When the supercharger surges airflow breaks down, think of the impeller blades "stalling" and then grabbing more air, repeatedly, very quickly. The higher airflow supercharger may or may not give you the pressure ratio you want. In the late 30s nobody had a supercharger with a pressure ratio of over about 2.8:1 outside of a lab.

It might have worked but there is a good chance it might not. When they went for the two stage supercharger Hooker used a supercharger from the Vulture as a 1st stage but the Vulture enough enough air for around 1000hp at 30,000ft which was the target for the two stage Merlin so the mass airflow was close. Since they were using two stages the pressure ratio didn't need to be very high for either stage. Total pressure ratio was around 5.6 I think? since you multiply the pressure ratios they could get 5.6 with a pair of 2.36 pressure ratio compressors or some variation.

Hello Shortround6.

I stand by my view that the 12Y would be acceptable in the 1930s for a fighter.
Not as 1940 so much but 1937 oh yeah.

8 guns or 6 is 1940s concepts. The D.520 was well armed in my opinion and the French origin of the engine was a handicap as the French went into hibernation for a spell mid 30s just when they shouldnt. So the 12Y could have been more.

The Bf 109B was small with an underpowered engine and 2 MG17s so Dewoitine D.520 would have given that a hard time plus the 20mm nose cannon which makes a good bomber destroyer.

And I never minded 8 303s in my Spitfire because it could have been 4 and the Italian and Japanese had far less
It is the fact that aviation changed so violently that a 1930s concept has no place in 1944.

wuzak said:

When did Austin have an aero engine factory?

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They didnt Whoops I meant Morris, Morris and Austin amalgamated in the 60s thats probably where the slip up came from. Morris had an engine plant that built motor car engines but it had also built Wolsley aero engines (Wolsley was part of Morris motors) though they gave up in iirc 1936 when they had had enough of the Air Ministry.

From Wiki
Wolseley engine

All Airspeed aeroplanes under manufacture or development in 1936 were to use a Wolseley radial aero engine of about 250 horsepower (190 kW) which was under development by Nuffield, the Wolseley Scorpio. The project was abandoned in September 1936 after the expenditure of about two hundred thousand pounds when Lord Nuffield got the fixed price I.T.P. (Intention to Proceed) contract papers (which would have required re-orientation of their offices with an army of chartered accountants) and decided to deal only with the War Office and the Admiralty, not the Air Ministry.

According to Nevil Shute Norway it was a very advanced engine (and the price struck Shute as low; much lower than competing engines on the basis of power-to-weight ratio), so its loss was a major disaster for Airspeed (and Britain). But when he asked Lord Nuffield to retain the engine, Nuffield said "I tell you, Norway ... I sent that I.T.P. thing back to them, and I told them they could put it where the monkey put the nuts!" Shute wrote that the loss of the Wolseley engine due to the over-cautious high civil servants of the Air Ministry was a great loss to Britain. Shute said that "admitting Air Ministry methods of doing business ... would be like introducing a maggot into an apple .. Better to stick to selling motor vehicles for cash to the War Office and the Admiralty who retained the normal methods of buying and selling.

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

The 12Y would have been a good engine IF the war had started in 1936-38.

The 12Y needed a total redesign to be a good engine in 1940 or beyond. It's construction was fine for 80-87 octane fuel. The block and crank and connecting rods were too weak to stand up to the higher pressures that 100 and 100/130 fuel allowed.
The cylinder head was an abomination. A two valve head for a 3 liter cylinder? and the valves were not angled. The intake ports are Siamesed and both intake and exhaust are on one side of the head ( to free up the inside of the V for the cannon).
The 170mm stroke limited RPM, and the 6 carburetor intake system was a headache waiting to happen. It also offered the worst of two worlds. Some of the problems of carburetors (but not all, no carb icing)but lacking the benefit of cooling the intake charge like the Merlin or Allison. It's supercharger was pretty lousy but so was everybody else's at that time.

Please note that ALL of the improved Hispanos (French Z, Spanish Z, Russian and Swiss) changed cylinder heads, gained 200-400lbs in weight, changed superchargers, and changed to fuel injection when they could.
Spanish 12Z in 1947 was claiming 1300hp for take-off at 2800rpm/47.2in( 8.6lbs) on 92 octane fuel. 1400hp at 4500meters single speed supercharger and a weight of 1410lbs and had fuel injection.
Swiss YS-2 in 1947 was claiming 1300hp for take-off at 2800rpm/41,4in( 5.7lbs) on 93 octane fuel. 1410hp at 4800meters single speed supercharger and a weight of 1510lbs and had fuel injection.
The Klimov-107 maxed at 1650hp in it's 3rd version but weighed 1687-1695lbs.

The British 8 gun concept dates from around 1934. In 1940 it was found to 'adequate?' much like the Americans found six .50 cal guns "adequate" on 1944/45. Adequate being far from ideal but not really failing. AS for your 109 to D 520 comparison you are comparing planes that went into service a few years apart. First flight of a D 520 prototype is about 1 1/2 years after "the Bf 109B was small with an underpowered engine and 2 MG17s" is flying combat in Spain. The first 109Es with DB 601 engines are coming of the production line before the first production order is placed for the D 520. Granted these 109s use just four MG17s.