# WW2 Without the Merlin: Options for the British



## wuzak (Aug 29, 2013)

To go along with the thread about no V-1710, what would be the alternatives had the Merlin not been in production?

There were alternatives - but not necessarily appetizing ones.

Rolls-Royce:

Kestrel XXX - tops out at about 720hp. Hurricane and Spitfire would seriously lack performance.
Peregrine I - same size as Kestrel. Not developed in deference to the Merlin. Also 3-4 years behind the Merlin. 885hp around 1940, but could have eventually been developed to c.1500hp.
Exe - solid lump of metal, makes 1150hp, expected to top out at around 1500hp. Not developed in deference to the Merlin.
Vulture - troubled development with numerous issues that had to be solved. Showed potential, but engineering time was precious, so was dropped to concentrate on Merlin and Griffon.
Griffon I - detuned version of the Rolls-Royce R, which was a racing version of the Buzzard. 36.7l should give c.1500hp at the start of WW2. With special fuels and no regard for longevity, 2900-3000hp could be possible (with 1 hour life!). Not proceeded with in deference to the PV.12/Merlin.
Griffon II - new 36.7l engine, started only in 1938. Would be late for the start of WW2.

Bristol:

Hercules - usually an alternative engine for the Merlin in proposals and production aircraft. Problematic production at the start of the war led to fears of under-supply (hence the Merlin Beaufighter). Had good development potential, but lagged the Merlin early on.
Taurus - Hercules's little brother. SImilar issues plus the added one of insufficient cooling.
Centaurus - initial developments pre war, but lagged while Bristol sorted the Hercules. Good engine, but not necessarily a Merlin alternative, or available early enough.

Armstrong Siddeley:

Deerhound - under development at the start of the war, it needed a couple of redesigns before it was making anywhere near the required power. Cooling issues also held it back. Air cooled, though AS wanted it to be liquid cooled. 

Napier:

Rapier - too small, not enough power.
Dagger - promising power output for its size, but it was too small. Also quite an earful, apparently.
Sabre - powerhouse under development at beginning of WW2. Production issues and reliability held it back. Different class to Merlin

Fairey:

P.12/P.12S Prince - between Merlin and Kestrel in size, around Kestrel power levels. Not proceeded with.
P.16 Prince - 1500hp class H-16, 34l. Quite heavy (according to Wiki) at 2180lb. Each half could operate separately. Not proceeded with.
P.24 Monarch - 2200hp H-24, also weighing 2180lb, according to wiki. Quite wide and tall (3" wider and 6.5" taller than a Sabre). Each half could operate seprately, and had its own two speed, single stage supercharger (not a 2 stage 4 speed as it is often described. Alos slow and late in development. Not proceeded with.


For mine, the short term solution for Spitfire/Hurricane class of fighters would have been the Griffon I, with the Griffon II replacing that at a later stage.


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## Shortround6 (Aug 29, 2013)

considering that you need 3-4000 engines by the summer of 1940 (minimum) the only practical one on the list is the upgraded Buzzard/Griffon I. You also need the engine for Battles, Whitley's and some other odd bombers (Wellington IIs ?) 

Unless your "what if" includes sorting out _production_ sleeve valves about 2 years earlier than historically.


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## wuzak (Aug 29, 2013)

True.

Most on that list were late or had development difficulties.


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## tomo pauk (Aug 30, 2013)

How about using US engines (P&W, Wright), either from the USA or license produced (UK, Canada)?


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## wuzak (Aug 30, 2013)

tomo pauk said:


> How about using US engines (P&W, Wright), either from the USA or license produced (UK, Canada)?



Like?

I suppose the R-2600 would have been an acceptable substitute for the Hercules. R-1820 and R-1830 really don't give you that much.

R-2800 is a bit late, R-3350 is a lot late.

V-1710 is later than the Merlin in timing. Though it would have been interesting if Rolls-Royce had got their hands on it in '39/'40.


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## GregP (Aug 30, 2013)

If Rolls-Royce had gotten the Allison and put on the 2-stage supercharger, it could have been a VERY good unit. Didn't happen but could have been a real player. I would be loathe to lose the mighty Merlin to posterity. It just sounds too good to miss out on. If the Merlin AND the Allison had been failures, what would WWII fighters have sounded like?

Hopefully not 47 Briggs Straton lawn mower engines on a common crankshaft!

The R-1820 and R-1830 might not have bought you much power, but it would have bought a load of reliability, historically speaking. It would have been a good, reliable choice ... that probably would have produced planes of average performance.

The Wright R-2600 could have been developed a bit more, especially with a Sir Stanley Hooker supercharger setup. It might have rivaled the later R-2800 had that happened. One can wonder.

I'm not all that sure the Griffon would have been proceeded with had the Merlin failed. Maybe ... matbe not. If it HAD, it would have been the engine of choice, as indicated above, for non-radial power.

What about the Eagle 22 for later in the war? Certainly showed promise, power-wise, but of course would have been a non-starter for the 1939 - 1943 crowd.


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## wuzak (Aug 30, 2013)

I would prefer a developed Vulture over the Eagle 22 - lighter and more compact, if a little less powerful.

Or a Vulture with Merlin sized pistons and a short stroke - 5" stroke. That would give about 2750-2800ci. And should give 1hp/ci from the start.

The Pennine had 5.4" bore and 5" stroke and made 2750hp at the start of development. But that was an air-cooled engine with sleeve valves. Still, a good looking engine, but way too late for WW2 (was aimed for post war civilian market).


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## GregP (Aug 30, 2013)

There were a LOT of engines with promise, possibly developed as fall-back positions in case a primary choice failed. 

Ditto with planes. The US B-32 Dominator was a safety fallback in case the B-29 failed.

Whatever engine the Brtis chose if the Merlin had not worked out, I'm sure it would have done the job. Though, with the Sabre, I'd probably have bagged it and gone with something else. British planes were at the forefront of development and they surely would not have simply given up ... it's not in the British makeup to do that in the face of a threat. Possibly in peacetime when it seems too costly ... but the Brits are always up for a good scrap when it is looming on the horizon.

They like nothing better than to go into a good Spitfire fight with 40 Messerschmitts and come back to base, land, get some tea, and say, "It was a bit dicey up there, eh, what chaps? But the buggers ran low on fuel and had to go home to use the loo just as we had 15 of them cornered! Pity, that. I almost fell asleep in the landing circuit, though. Only the thought of a pint kept me awake and able. I say, anyone for a pint?"


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## tomo pauk (Aug 30, 2013)

wuzak said:


> Like?
> 
> I suppose the R-2600 would have been an acceptable substitute for the Hercules. R-1820 and R-1830 really don't give you that much.
> 
> ...



The R-1820/1830 can substitute Merlin in early bombers, so we save 2000+ Merlins here. R-1830, even in sigle stage version, can make a fighter do 350 mph, without 'trick' aerodynamics. Of course, the fighter's size should be closer to Bf-109, rather than to Typhoon's.
The R-2800 can come in handy from late 1941 on, powering a fighter anywhere between Fw-190's and Typhoon's size.

V-1710 might've powered a fast, unarmed bomber...


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## Shortround6 (Aug 30, 2013)

Once again timing has a lot to do with this. The Merlin was in production by late 1936/early 1937 and in the MK II form in 1938.

Possible replacements have to be considered in that light. And this points to part of the Merlin's "greatness" It was available in numbers at the _start_ of the war making competitive power and it was capable of being modified/developed to be making competitive power at the end of the war. 

You may be able to replace with another engine at a given point in time but few, if any, engines could replace it (without some "What if" development work) for the entire duration of the war. 

Now it may have been a bit passed it's prime and being pushed to a ragged edge in 1945 and beyond but it was still hanging in there. And in this it was in company with a few other piston engines that required a fair bit of TLC to operate at some of the post war power levels even in commercial service. 

You may consider what could have replaced it in 1938-40, 1941-42, and 43-45 or some other time break down. 

Even the R-2600 is a bit late in timing as it doesn't exceed 100 engines a month until the Fall of France. 

Also consider that 100 octane fuel was by no means universal in British service in the summer of 1940 let alone earlier. Fighter command certainly had it but bomber command and coastal command saw a LOT less of it.


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## tomo pauk (Aug 30, 2013)

When considering Merlin in fighter airframes, we can note that both Hurricane and Spitfire were quite large airframes too (compared with mainstream Soviet, German, Italian and Japanese fighters, or even when compared with P-39/40) - hence much of the engines power was wasted to lug around extra bulk. Spitfire got away with that with extra thin wing, size permitting to accept Griffon without problems; Hurricane was not in that position. My point is that a fighter designed around Kestrel, then upgraded with Peregrine, Taurus, Twin Wasp and maybe V-1710 (fighters license produced in Canada?), should be sized akin to MC.202, Bf-109 or Yak-1, if we want it to be competitive as the war progresses. 

Both Cyclone and Twin Wasp developing more HP for take off in 1940 than Merlin III, and similar to Merlin X?


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## Shortround6 (Aug 30, 2013)

tomo pauk said:


> When considering Merlin in fighter airframes, we can note that both Hurricane and Spitfire were quite large airframes too (compared with mainstream Soviet, German, Italian and Japanese fighters, or even when compared with P-39/40) - hence much of the engines power was wasted to lug around extra bulk. Spitfire got away with that with extra thin wing, size permitting to accept Griffon without problems; Hurricane was not in that position. My point is that a fighter designed around Kestrel, then upgraded with Peregrine, Taurus, Twin Wasp and maybe V-1710 (fighters license produced in Canada?), should be sized akin to MC.202, Bf-109 or Yak-1, if we want it to be competitive as the war progresses.
> 
> Both Cyclone and Twin Wasp developing more HP for take off in 1940 than Merlin III, and similar to Merlin X?



Going the small route doesn't work very well. You can't scale the pilots, cockpit, radios and such to the engine. and the MC.202, Bf-109 or Yak-1 scaled the armament down, not a good option for the British _unless_ they can change guns along with the engines. 

Please forget the Taurus, it was a near failure as an engine. Any time spent on it is at the cost of the Hercules or Centaurus. Why the British were fooling around with a 25.4 liter 14 cylinder engine is beyond me. They wanted sleeve valves? Use the 24.9 liter Perseus, at least it used Hercules cylinders. 

The two American radials had a lot more power for take-off than a Merlin III but then they didn't have as much power at 15-16,000ft. The First engines used in Beauforts ( and rated on 87 octane) had 1050hp for take-off and Military at 7700ft but had a Military rating of 1000hp at 11,500ft. They also weigh about 500lbs more than a Kestrel. Granted the Kestrel needs a cooling system.


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## tomo pauk (Aug 30, 2013)

Shortround6 said:


> Going the small route doesn't work very well. You can't scale the pilots, cockpit, radios and such to the engine. and the MC.202, Bf-109 or Yak-1 scaled the armament down, not a good option for the British _unless_ they can change guns along with the engines.



There is no need to scale down stuff - all of these smaller fighters have had the listed items. As far as the weaponry goes - the P-40 was able to carry 6 HMGs and 6 x 280 rds in the wings that were both thinner and of less area than Hurricanes. It was also carrying almost 50% more fuel than Hurricane (greater part in the wings). Hurri went from 8 to 12 LMGs without troubles - sign that wing was really of generous proportions.
So an 8 gun fighter should not be such hard thing to pull on a smaller airframe. According to Wikipedia, even if the plane has less than 150 sq ft of wing area:
_Unlike the Hurricane and Spitfire, the Venom was fitted with full armament from its first flight_



> Please forget the Taurus, it was a near failure as an engine. Any time spent on it is at the cost of the Hercules or Centaurus. Why the British were fooling around with a 25.4 liter 14 cylinder engine is beyond me. They wanted sleeve valves? Use the 24.9 liter Perseus, at least it used Hercules cylinders.



Perseus (9 cyl) was featuring 20% greater diameter than Taurus (2x7 cyl), or ~40% greater front area. Not a great thing for the fighter engine, or so I'm told  I agree that Taurus saga was not something British needed in early 1940s, but it was there.



> The two American radials had a lot more power for take-off than a Merlin III but then they didn't have as much power at 15-16,000ft. The First engines used in Beauforts ( and rated on 87 octane) had 1050hp for take-off and Military at 7700ft but had a Military rating of 1000hp at 11,500ft. They also weigh about 500lbs more than a Kestrel. Granted the Kestrel needs a cooling system.



I was thinking of the US radials more as bomber engines, the R-1830 also as fighter engine. Again, the fighter need to be tailored accordingly, ie. no big thick wing.


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## Readie (Aug 30, 2013)

We had the Griffon that probably would as near to the Merlin as we could get developed and in production by 1939. 

Design work on the Griffon started in 1938 at the request of the Fleet Air Arm, for use in new aircraft designs such as the Fairey Firefly. In 1939 it was also decided that the engine could be adapted for use in the Spitfire. However, development was temporarily put on hold to concentrate efforts on the smaller Merlin, and the engine did not go into production until the early 1940s.

If RR's resources were just put into the Griffon then there is no reason to think that it wouldn't have been in service. 

John


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## stona (Aug 30, 2013)

tomo pauk said:


> hence much of the engines power was wasted to lug around extra bulk. Spitfire got away with that with extra thin wing,



And, for a Mark I, being a similar weight to, for example, a P-39. According to figures in "Spitfire the History" and "America's Hundred Thousand." 
In fact, the P-39 seems to have a greater all up weight, loaded, if I'm reading the figures correctly.
Steve


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## Shortround6 (Aug 30, 2013)

> There is no need to scale down stuff - all of these smaller fighters have had the listed items. As far as the weaponry goes - the P-40 was able to carry 6 HMGs and 6 x 280 rds in the wings that were both thinner and of less area than Hurricanes. It was also carrying almost 50% more fuel than Hurricane (greater part in the wings). Hurri went from 8 to 12 LMGs without troubles - sign that wing was really of generous proportions.
> So an 8 gun fighter should not be such hard thing to pull on a smaller airframe. According to Wikipedia, even if the plane has less than 150 sq ft of wing area:
> _Unlike the Hurricane and Spitfire, the Venom was fitted with full armament from its first flight_



They had the listed items but they take up a greater percentage of the load and with less power available things get weird real quick. 
Now _WHY_ was the P-40 such a dog at 20,000ft and above? It was _underpowered_ and _overloaded_. The P-40B/C had 1040hp at 14,300ft which is 2,000 ft less than the Spitfire I but trying to lug more fuel and guns ammo killed the performance. The P-40B/C carried about 599lbs of guns and ammo and the E carried 893lbs. A Spitfire with eight .303s and 350 rpg carried 439lbs. Weights do NOT include mounts, reinforcing, ammo boxes, chutes, heaters, charger's etc. Just because you have the room to fit guns doesn't mean you can/should. Drop the power to 86% of a Merlin (Peregrine) and you better be cutting more than just wing area if you want both speed AND climb. Weight of guns and ammo in the MC.202, 109 and Yak-1 didn't come close to the weight of guns/ammo in a P-40. 



> Perseus (9 cyl) was featuring 20% greater diameter than Taurus (2x7 cyl), or ~40% greater front area. Not a great thing for the fighter engine, or so I'm told  I agree that Taurus saga was not something British needed in early 1940s, but it was there.



It was 46in to 52in diameter. Frontal area was 11.7 to 14.7 sq ft or about 25-26% more frontal area. Considering that the two production planes they used it on were the Albacore biplane and the Beaufort a few extra sq ft of frontal area on the engines wasn't going to make that big a difference. Pratt Whitney had wised up and stopped development on the R-1535 twin wasp junior. 





> I was thinking of the US radials more as bomber engines, the R-1830 also as fighter engine. Again, the fighter need to be tailored accordingly, ie. no big thick wing.



No big and thick wing helps speed. Climb, acceleration (recovering speed after a maneuver) have a lot more to do with power to weight. Cut the power and you better be cutting weight or you wind up with a fast plane that can't turn and can't climb.


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## gjs238 (Aug 30, 2013)

GregP said:


> If Rolls-Royce had gotten the Allison and put on the 2-stage supercharger, it could have been a VERY good unit. Didn't happen but could have been a real player.



From Wiki:
_The Allison Division of General Motors began developing the ethylene glycol-cooled engine in 1929 to meet a US Army Air Corps need for a modern, 1,000 hp (750 kW), engine to fit into a new generation of streamlined bombers and fighters. To ease production the new design could be equipped with different propeller gearing systems and superchargers, allowing a single production line to build engines for various fighters and bombers._

I suspect that what started out as a good idea (this modularity that was designed into the engine) made it difficult later on to incorporate a 2-stage supercharger.
I suspect the Merlin and DB supercharger designs were easier to make 2-stage.


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## Shortround6 (Aug 30, 2013)

stona said:


> And, for a Mark I, being a similar weight to, for example, a P-39. According to figures in "Spitfire the History" and "America's Hundred Thousand."
> In fact, the P-39 seems to have a greater all up weight, loaded, if I'm reading the figures correctly.
> Steve



A P-39D clean, but loaded weighs more than a MK IX Spitfire with two 20mm guns and four .303s clean and loaded. 

It had speed but a 7500-7700lb pound plane with 1150 hp at 12,000ft or under 1100 at 15,000ft is going to have pretty bad altitude performance.


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## wuzak (Aug 30, 2013)

gjs238 said:


> I suspect that what started out as a good idea (this modularity that was designed into the engine) made it difficult later on to incorporate a 2-stage supercharger.
> I suspect the Merlin and DB supercharger designs were easier to make 2-stage.



The modularity should have made it easier to build a 2 stage version.

Unbolt the standard single stage module and bolt up the 2 stage module.

But, Allison had a different 2 stage concept than Rolls-Royce. In effect it mimicked a turbo compressor, in that the auxiliary or first stage supercharger varied its speed with altitude. Unlike the turbo the power did drop off as altitude increased.

On some models they used an aftercooler like that of the 60-series Merlins. But most of their 2 stage engines did without, as that meant that the core engine could be built as a standard unit, with the auxiliary supercharger bolting on after that, or being installed with a turbocharger.

Wright Field (IIRC) tested a V-1710 with a Merlin 2 stage supercharger, though it was not bolted to the back of the engine. Performance figures were near identical to the Merlin, but the bearings failed due to the compressor not being fixed to the engine, so lacking the heat and causing clearences to be wrong.

Not sure about the idea that the DB engines were easier to change to 2 stage. In the Allison you take a single stage engine and bolt up some new bits. DBs were somewhat more complicated, owing to their side mounted superchargers.

Not sure with the Merlin, but I suspect that it just required unbolting the single stage supercharger and bolting on the two stage supercharger. If the single stage engine being converted has the strengthened components required o be run as a 2 stage engine.


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## wuzak (Aug 30, 2013)

tomo pauk said:


> Perseus (9 cyl) was featuring 20% greater diameter than Taurus (2x7 cyl), or ~40% greater front area. Not a great thing for the fighter engine, or so I'm told  I agree that Taurus saga was not something British needed in early 1940s, but it was there.



Some comparisons:


```
Engine         Dia    Area  power  weight
                in     in²    hp      lb 
Taurus        46.25   1680   1050    1301
Pegaus        55.3    2402    965    1111
AR 126 RC.32  55.3    2402   1350       ? (based on Pegasus)
R-1820        54.25   2311   1000    1184 (start of war)
R-1830        48.03   1812   1200    1250
```

I believe the Alfa Romeo was based on the Pegasus, and was developed further than the Pegasus as Bristol were concentrating on the sleeve valve engines.

I don't think that the Wright and Pratt Whitney engines offer anything much better than the Bristol engines, except production capacity.


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## fastmongrel (Aug 31, 2013)

I have often wondered if Bristol should have tried developing a twin Mercury as a Bomber and heavy fighter engine. It might have been Britains R 2800 given enough time.


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## wuzak (Aug 31, 2013)

fastmongrel said:


> I have often wondered if Bristol should have tried developing a twin Mercury as a Bomber and heavy fighter engine. It might have been Britains R 2800 given enough time.



Kind of like the Alfa Romeo 135

Alfa Romeo 135 - Wikipedia, the free encyclopedia


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## tomo pauk (Aug 31, 2013)

Shortround6 said:


> They had the listed items but they take up a greater percentage of the load and with less power available things get weird real quick.
> Now _WHY_ was the P-40 such a dog at 20,000ft and above? It was _underpowered_ and _overloaded_. The P-40B/C had 1040hp at 14,300ft which is 2,000 ft less than the Spitfire I but trying to lug more fuel and guns ammo killed the performance. The P-40B/C carried about 599lbs of guns and ammo and the E carried 893lbs. A Spitfire with eight .303s and 350 rpg carried 439lbs. Weights do NOT include mounts, reinforcing, ammo boxes, chutes, heaters, charger's etc. Just because you have the room to fit guns doesn't mean you can/should. Drop the power to 86% of a Merlin (Peregrine) and you better be cutting more than just wing area if you want both speed AND climb.



My talk about P-40 weaponry carried was not aimed to show it as a good example (low HP plane carrying heavy armament), but to show that one can pack plenty of guns without having a wing suitable for 1500-2000 HP fighters. Hurricane's wing WAS too big for a 1000-1200 HP fighter, as shown when it swallowed 50% more LMGs, or 4 cannons without a hiccup. Or, looking at Spitfire - basic design proved suitable to lug around twice the powerplant weight, twice the fuel and twice the armament weight, comparing 1944/45 with 1940. My point - if the plane still looks good with such weight increase, then the basic design might've been smaller in the 1st place and perform better when introduced (or same with less power). Both RAF's fighters were using the wing with about same area as twin engined Whirlwind, or just a tadd smaller than Typhoon.
The weight is saved when choosing Peregrine (we'll skip the engines reliability for now), not only the bare engine, but also the oil cooling system, prop etc. Further saving is with lighter airframe and undercarriage. With smaller airframe we also cut the drag.



> Weight of guns and ammo in the MC.202, 109 and Yak-1 didn't come close to the weight of guns/ammo in a P-40.



Of course, but the MC.202 with additional 7.7mm, the Bf-109 with cannon(s) aboard and Yak-1 are pretty close in weight to the RAF's 8 gun battery in Spits Huris during BoB.



> It was 46in to 52in diameter. Frontal area was 11.7 to 14.7 sq ft or about 25-26% more frontal area. Considering that the two production planes they used it on were the Albacore biplane and the Beaufort a few extra sq ft of frontal area on the engines wasn't going to make that big a difference. Pratt Whitney had wised up and stopped development on the R-1535 twin wasp junior.



It was 55in for the Perseus, noted both by Wiki and wuzak. I agree that with Perseus aboard bot those two wouldn't loose anything, while gaining on reliability.



> No big and thick wing helps speed. Climb, acceleration (recovering speed after a maneuver) have a lot more to do with power to weight. Cut the power and you better be cutting weight or you wind up with a fast plane that can't turn and can't climb.



Agreed - I've elaborated about weight savings above in the post.

Further on topic - with Merlin out of the picture, Peregrine and Vulture get more resources, so we can have better Whirly, along with Tornado?


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## fastmongrel (Aug 31, 2013)

wuzak said:


> Kind of like the Alfa Romeo 135
> 
> Alfa Romeo 135 - Wikipedia, the free encyclopedia



Hopefully without the problems. Possibly Bristol having more radial experience than just about anyone else might have had more success, though doubling up radials wasnt the easy fix some believe. If Bristol started a twin Mercury at the same time as historically they started the Sleeve valve programme it should be in service at the same time as the Hercules, hopefully with a better supercharger earlier than the Hercules got a good supercharger.


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## yulzari (Aug 31, 2013)

Whilst it wouldn't have been my first choice, Bristol's Taurus did give years of service in the Beaufort and Albacore in some numbers.

I have to go for Bristol avoiding sleeve valves and thus being able to get a double Mercury and/or a double Pegasus out in a Merlin timescale. Let the backroom boys play with a sleeve valve Centaurus in the background.

There is always the RR Peregrine in the Whirlwind and having the shadow factory programme devoted to Whirlwinds early enough in quantity. We know the Peregrine worked and we know it could be developed further and we know the Whirlwind worked (yes it could be improved in some details).


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## Shortround6 (Aug 31, 2013)

> My talk about P-40 weaponry carried was not aimed to show it as a good example (low HP plane carrying heavy armament), but to show that one can pack plenty of guns without having a wing suitable for 1500-2000 HP fighters. Hurricane's wing WAS too big for a 1000-1200 HP fighter, as shown when it swallowed 50% more LMGs, or 4 cannons without a hiccup. Or, looking at Spitfire - basic design proved suitable to lug around twice the powerplant weight, twice the fuel and twice the armament weight, comparing 1944/45 with 1940. My point - if the plane still looks good with such weight increase, then the basic design might've been smaller in the 1st place and perform better when introduced (or same with less power). Both RAF's fighters were using the wing with about same area as twin engined Whirlwind, or just a tadd smaller than Typhoon.
> The weight is saved when choosing Peregrine (we'll skip the engines reliability for now), not only the bare engine, but also the oil cooling system, prop etc. Further saving is with lighter airframe and undercarriage. With smaller airframe we also cut the drag.



Part of the size of the wing of the Hurricane and Spitfire was to get the short field performance desired. The Flaps on these planes did _nothing_ for take-off and acted as speed brakes for landing. Big wing was needed, especially with the fixed pitch props. in another couple of years flaps could do a lot more. Please also remember that ALL British military aircraft were restricted at the time to things like a max of 35lb pressure in the tires to prevent ruts in the grass fields. Several planes were granted exceptions before WW II ( Whirlwind was allowed 42lbs after a bit if arguing) and once the shooting started a LOT of these restrictions were "forgotten". If you start design of the "mini" fighter in 1937 you can use a whole bunch of tricks that were not available in in 1934-35. 





> Of course, but the MC.202 with additional 7.7mm, the Bf-109 with cannon(s) aboard and Yak-1 are pretty close in weight to the RAF's 8 gun battery in Spits Huris during BoB.



Weight of Spitfire MK II battery about 439lbs, MK I and Hurricane cared a bit less ammo.
Weight of M 202 battery 373lbs not including links for 12.7mm ammo.
Weight of Bf 109E-3 Battery 328lbs including drums.
Weight of Yak-1B battery (0ne 12.7mm instead of two 7.62 guns) 264lbs not including links. 
These may be off a bit and DO NOT include gun heaters, ammo boxes (eight for the British planes, gun chargers and firing mechanisms in most cases. 




> It was 55in for the Perseus, noted both by Wiki and wuzak. I agree that with Perseus aboard bot those two wouldn't loose anything, while gaining on reliability.



We have ONE source that says 55in for the Perseus. Wiki and Wuzak both quoting Lumsden. 
3 different editions of Jane's say 52in, Two editions of Wilkinson's "Aircraft Engines of the World" say 52" as does "Aircraft Engines" by A. W. Judge. I will note that Lumsden gives the same exact diameter for the Pegasus which has a 1" longer stroke and the poppet valve head. Perseus used Mercury cylinder dimensions and one of the selling features of the sleeve valve was the "supposedly" smaller diameter of the engine because it _didn't_ have the overhead valve gear on top of the cylinder. Most sources give 51.5in diameter for the Mercury so even at 52in the Perseus doesn't quite live up to the claim but 55 or 55.3 in???


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## wuzak (Aug 31, 2013)

Shortround6 said:


> We have ONE source that says 55in for the Perseus. Wiki and Wuzak both quoting Lumsden.



For the record, I quoted Wiki but only for the Pegasus, not the Perseus.


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## Shortround6 (Aug 31, 2013)

My apologies.


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## wuzak (Aug 31, 2013)

Not a problem. 

Just looking pictures of the Perseus in Lumsden, it would appear to have a larger diameter crankcase than the Pegasus.

Lumsden has the Hercules, which used 14 Perseus sized cylinders, at 52" diameter for early versions and 55" for later versions (which may or may not include the cowling as part of a "power egg").


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## The Basket (Sep 1, 2013)

Hispano Suiza 12Y


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## tomo pauk (Sep 1, 2013)

The Hispano engine enables easy installation of a cannon, so LW bombers would've had far harder time above UK. The LMG battery might be only half of historic one, so LW fighters might have easier time?

I'll apologize too for making a confusion, should have purchase Wilkinson's book(s) by now.



Shortround6 said:


> Part of the size of the wing of the Hurricane and Spitfire was to get the short field performance desired. The Flaps on these planes did _nothing_ for take-off and acted as speed brakes for landing. Big wing was needed, especially with the fixed pitch props. in another couple of years flaps could do a lot more. Please also remember that ALL British military aircraft were restricted at the time to things like a max of 35lb pressure in the tires to prevent ruts in the grass fields. Several planes were granted exceptions before WW II ( Whirlwind was allowed 42lbs after a bit if arguing) and once the shooting started a LOT of these restrictions were "forgotten". If you start design of the "mini" fighter in 1937 you can use a whole bunch of tricks that were not available in in 1934-35.



Ideally, a non-Merlin, mid 1930s fighter should be sized maybe like Re.2000 (Hurricane replacement), and late 1930s one somewhere along the lines of Macchi or FFVS fighters (Spitfire replacement). 




> Weight of Spitfire MK II battery about 439lbs, MK I and Hurricane cared a bit less ammo.
> Weight of M 202 battery 373lbs not including links for 12.7mm ammo.
> Weight of Bf 109E-3 Battery 328lbs including drums.
> Weight of Yak-1B battery (0ne 12.7mm instead of two 7.62 guns) 264lbs not including links.
> These may be off a bit and DO NOT include gun heaters, ammo boxes (eight for the British planes, gun chargers and firing mechanisms in most cases.



Thanks for the effort to find and type out the numbers. The MC.202 battery is without additional 7.7mm? 
We have a difference between ~75 and ~175 lbs (~35 to ~ 80 kg) on 6000+ lbs airplanes.



> We have ONE source that says 55in for the Perseus. Wiki and Wuzak both quoting Lumsden.
> 3 different editions of Jane's say 52in, Two editions of Wilkinson's "Aircraft Engines of the World" say 52" as does "Aircraft Engines" by A. W. Judge. I will note that Lumsden gives the same exact diameter for the Pegasus which has a 1" longer stroke and the poppet valve head. Perseus used Mercury cylinder dimensions and one of the selling features of the sleeve valve was the "supposedly" smaller diameter of the engine because it _didn't_ have the overhead valve gear on top of the cylinder. Most sources give 51.5in diameter for the Mercury so even at 52in the Perseus doesn't quite live up to the claim but 55 or 55.3 in???



Many thanks for clearing out the issue. Perseus now looks like an really usable fighter engine, not only for the Skuas


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## yulzari (Sep 1, 2013)

tomo pauk said:


> Many thanks for clearing out the issue. Perseus now looks like an really usable fighter engine, not only for the Skuas



The diameter difference may be between the original Perseus and the later enlarged capacity Perseus 100? That could put out @1,200bhp. The early Perseus were much of a muchness with the Mercury. Hence they were both put into Lysanders with much the same performance.


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## Shortround6 (Sep 1, 2013)

tomo pauk said:


> Thanks for the effort to find and type out the numbers. The MC.202 battery is without additional 7.7mm?



No, it includes the 7.7mm MGs and 500 rounds per gun. 

The "payload" of an Eight gun Spitfire is about 1486lb, guns, ammo, pilot, radios, fuel, oil, oxygen cylinders dinghy, etc. 

Since about the ONLY things you can cut from the "payload" if you use a lower powered engine are fuel and an armament you run into the small, cheap fighter problem. 

The Spitfire carried about 358lbs worth of NON-fuel and armament "stuff" (counting the pilot as "stuff") BUT not including armor/bulletproof glass. This weight is pretty much _fixed_ no matter which engine you use. 

Cut the engine power by 14% ( Merlin III to Peregrine) and what can you cut to keep the power to weight roughly the same? 14% reduction in payload is 207lbs or just over 28 imp gallons of fuel. You want the Peregrine fighter to have just 57 Imp gallons of fuel? 

This is assuming you can scale down the engine/ prop and airframe by 14%.

If you cut the guns to six you can get back about 15 gallons of fuel. 



> Many thanks for clearing out the issue. Perseus now looks like an really usable fighter engine, not only for the Skuas



Well, For a real "what if" what happens _IF_ you could run a Perseus at the same levels as a Hercules on 100 octane fuel  

Unfortunately you still have an under 1000hp engine at altitude. But then the Taurus was going to be under 1000hp too at altitude ( 12-16,000ft).


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## Shortround6 (Sep 1, 2013)

yulzari said:


> The diameter difference may be between the original Perseus and the later enlarged capacity Perseus 100? That could put out @1,200bhp. The early Perseus were much of a muchness with the Mercury. Hence they were both put into Lysanders with much the same performance.



I am not sure if the Perseus 100 was ever flown or even built. But Little , if anything was done with the original Perseus to take advantage of 100 octane fuel.


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## tomo pauk (Sep 2, 2013)

Shortround6 said:


> No, it includes the 7.7mm MGs and 500 rounds per gun.



Okay, thanks.



> The "payload" of an Eight gun Spitfire is about 1486lb, guns, ammo, pilot, radios, fuel, oil, oxygen cylinders dinghy, etc.
> Since about the ONLY things you can cut from the "payload" if you use a lower powered engine are fuel and an armament you run into the small, cheap fighter problem.
> The Spitfire carried about 358lbs worth of NON-fuel and armament "stuff" (counting the pilot as "stuff") BUT not including armor/bulletproof glass. This weight is pretty much _fixed_ no matter which engine you use.
> Cut the engine power by 14% ( Merlin III to Peregrine) and what can you cut to keep the power to weight roughly the same? 14% reduction in payload is 207lbs or just over 28 imp gallons of fuel. You want the Peregrine fighter to have just 57 Imp gallons of fuel?
> ...



The 'Spitfire replacement' should've featured the wing of circa 180 sq ft, so we save weight here too. Airframe needs to be tailored to support smaller lighter wing, ditto for complete powerplant. U/C gear also needs to be lighter. I've listed the items a page ago. Lighter, less draggy less powerful fighter needs less fuel for same endurance/range, maybe down to 75 imp gals. 
Plenty of 900-1500 HP fighters were featuring the similar dimensions - Bf-109, Macchi Yak fighters, IAR-80, J-22, French fighters. We know that Yak-1 was better combat airplane than LaGG-3, and that MC.202 was able to out-perform the Re.2001 - same generation engine aboard, but smaller lighter fighter wins here. 
Dictating that a ~900 HP fighter would've still needed the 250 sq ft wing bigger fuselage only saddles the engine with superfluous chunk of airframe to lug around.



> Well, For a real "what if" what happens _IF_ you could run a Perseus at the same levels as a Hercules on 100 octane fuel
> 
> Unfortunately you still have an under 1000hp engine at altitude. But then the Taurus was going to be under 1000hp too at altitude ( 12-16,000ft).



The Perseus was only 1in of greater diameter vs. Piaggio XI, used in the Re.2000. Would've made 'Hurricane replacement' make 310-320 mph?


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## OldSkeptic (Sep 3, 2013)

Been watching this thread, on and off. No Merlin then Britain lose the BoB and, quite possibly gets invaded, at least sues for peace.

There is no alternative for the Merlin of that size/weight/power/growth. 

Yes, one of those, rare, unique things, unreplaceable by any alternative. No Merlin then no Mustang, Hurricane, Spit, Mossie, Lanc, et al.

Thank you Sir Henry Royce and Hives and ....


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## swampyankee (Sep 3, 2013)

Rolls Royce had tested a de-rated version of the "R" engine in 1933. I suspect that it would be practical to resurrect this engine if the Merlin turned into dust. It would be bulkier and heavier, but likely more powerful. Also, the failure of RR's 24 cylinder engines was probably due as much to reducing the resources devoted to them as to intrinsic shortcomings..


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## tomo pauk (Sep 3, 2013)

OldSkeptic said:


> Been watching this thread, on and off. No Merlin then Britain lose the BoB and, quite possibly gets invaded, at least sues for peace.
> 
> There is no alternative for the Merlin of that size/weight/power/growth.
> 
> ...



For such a defeatistic attitude people were been sent to Siberia in previous century 
BTW, the Royal navy would've simply sail to, say, Canada?


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## fastmongrel (Sep 3, 2013)

OldSkeptic said:


> Britain lose the BoB and, quite possibly gets invaded,



Only if the German Army can march to Britain


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## swampyankee (Sep 3, 2013)

fastmongrel said:


> Only if the German Army can march to Britain



You mean that the Teutonic übermensch couldn't? Looking at some of the posts here, one would think that the Germans must have won the war because they were so much better at everything.


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## stona (Sep 3, 2013)

swampyankee said:


> You mean that the Teutonic übermensch couldn't? Looking at some of the posts here, one would think that the Germans must have won the war because they were so much better at everything.



They could swim across......oh, hang on, Vice Admiral Assman of the German naval staff actually specifically said that they couldn't simply swim over, the defeatist nincompoop 
Cheers
Steve


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## The Basket (Sep 3, 2013)

The Hispano Suiza 12Y replace the merlin. Maybe not perfect but adequate. Get 20mm cannon as well


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## Shortround6 (Sep 3, 2013)

Adequate for 1940, after that it is a liability. 

It needs major re-work just to get to 1200-1300hp _below_ 4000 meters let alone above that. 

Rolls, from the end of WW I on, always had 2 engines on offer and often 3. The Merlin was their 6th V-12 production aircraft engine. If had been shown to be a dead end in 1936, they had 2-3 years to come up with something else like the Griffon I.


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## swampyankee (Sep 3, 2013)

stona said:


> They could swim across......oh, hang on, Vice Admiral Assman of the German naval staff actually specifically said that they couldn't simply swim over, the defeatist nincompoop
> Cheers
> Steve



I thought the plan was for them to march along the bottom of the English Channel. They just couldn't get big enough seahorses for their artillery.


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## wuzak (Sep 3, 2013)

The Basket said:


> The Hispano Suiza 12Y replace the merlin. Maybe not perfect but adequate. Get 20mm cannon as well


 


Shortround6 said:


> Adequate for 1940, after that it is a liability.
> 
> It needs major re-work just to get to 1200-1300hp _below_ 4000 meters let alone above that.
> 
> Rolls, from the end of WW I on, always had 2 engines on offer and often 3. The Merlin was their 6th V-12 production aircraft engine. If had been shown to be a dead end in 1936, they had 2-3 years to come up with something else like the Griffon I.



The Buzzard was good for ~800-900hp, at a weight of ~1100-1200lb. It was slightly taller than the Merlin, but otherwise was similar dimensionally. 

With a couple of hundred pounds of strengthening it would weigh the same as a production Merlin, and one would think capable of similar power levels.

The R weighed about the same as a 2 stage Merlin ~1650lbs. A detuned R should have been good for at least ~1300-1500hp by 1940, considering in full sprint trim in 1931 it was capable of >2900hp. he interesting thing about the R was that it was able to rev to 3400rpm, whereas the Griffon was stuck at 2750rpm. I suppose that was all about longevity.


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## tomo pauk (Sep 4, 2013)

Wonder if the Peregrine would've went to 3200 rpm, some time mid war? It is not hard to visualise the two speed, 'Hookerised' Peregrine, too. And then a two stage unit. Griffon and Vulture following suit some time in 1943? 2000 HP for Tempest, but at 25000 ft - 470 mph?

The Hurri and Spit 'replacements' getting Hercules (FAA gets those too?) and V-1710 (380-400 mph in 1943?)?


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## Shortround6 (Sep 4, 2013)

I like the Peregrine and I like the Whirlwind and think both got a bum rap but sinking too much time or money into the Peregrine is a loosing deal. A two speed Merlin XX type supercharger and a little beefing up is about as far as it should go.

Increasing the RPM is questionable. Maybe it will work and maybe it won't. If you increase the pressure in the cylinders by 10% you should get 10% more power (minus the extra power needed to drive the supercharger) and you may have to strengthen certain parts to handle the 10% increase in strain. If you increase the RPM 10% you increase the strain on the reciprocating and rotating parts by 21%. You increase the friction in the engine by 21% and you do need a bit more power to drive the supercharger to flow 10% more air. Your _net_ power gain is lower than increasing the BMEP 10% and you may need more modifications depending on the original strength of the parts.
If you have another, larger engine in the works ( Buzzard/Griffin) then the research and development of any but the simplest of improvements should go to that engine. A single stage Griffon II was about 73% of the weight of a single stage Vulture (about 650lbs ?) which can certainly affect the size/choice of airframe.


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## Shortround6 (Sep 4, 2013)

duplicate post.


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## tomo pauk (Sep 4, 2013)

Shortround6 said:


> I like the Peregrine and I like the Whirlwind and think both got a bum rap but sinking too much time or money into the Peregrine is a loosing deal. A two speed Merlin XX type supercharger and a little beefing up is about as far as it should go.



The 'Peregrine XX' making some 940 HP at 18500 ft, 1150 at 11800 ft (12 lbs boost?) in late 1940/early 1941 - comparable with 'plain vanilla' V-1710s (8.8:1 and 9.6:1 superchargers) and DB-601A/Aa/N? Later versions making 150-200 HP more, at lower altitudes of course? 



> Increasing the RPM is questionable. Maybe it will work and maybe it won't. If you increase the pressure in the cylinders by 10% you should get 10% more power (minus the extra power needed to drive the supercharger) and you may have to strengthen certain parts to handle the 10% increase in strain. If you increase the RPM 10% you increase the strain on the reciprocating and rotating parts by 21%. You increase the friction in the engine by 21% and you do need a bit more power to drive the supercharger to flow 10% more air. Your _net_ power gain is lower than increasing the BMEP 10% and you may need more modifications depending on the original strength of the parts.



Okay, thanks for assessment. The increase in RPM should allow for greater power at all altitudes, vs. greater boost allowing greater power at altitudes under current FTH?



> If you have another, larger engine in the works ( Buzzard/Griffin) then the research and development of any but the simplest of improvements should go to that engine. A single stage Griffon II was about 73% of the weight of a single stage Vulture (about 650lbs ?) which can certainly affect the size/choice of airframe.



Again, well put. 
Without Merlin around, Supermarine might start their own 'new, 2000+ HP fighter', to compete with Hawker?


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## The Basket (Sep 4, 2013)

Not sure what the issue with the Hispano 12Y as its timeframe is right where you want it and plus you get a 20mm cannon included. It certainly could have put fighters in the air during the Battle of Britian and this is certainly not a 'what if' as it is fully viable. Of course it would be developed to new power ratings to keep up with the latest tech and obviously would be replaced by something better such as the Griffon and Sabre and Hercules in good time.

Klimov got a bit of extra life out the 12Y so it certainly would have been good enough and available.


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## The Basket (Sep 4, 2013)

/


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## Shortround6 (Sep 4, 2013)

Klimov got a bit of extra life out of the 12Y by reducing the bore, adding several hundred pounds, changing the cylinder heads, using a 2 speed supercharger with a low gear to allow more power at low altitudes ( he didn't improve power at 4-5000 meters that much) and over revving the engine and accepting a much shorter time between overhauls. 

The 12Y was designed a number of years before the Merlin ( 12Y was on sale in 1932) and was NEVER intended to run at the BMEP level of a Merlin or Allison or DB 601 even on 87 octane fuel. 

It would put fighters in the air but without an extensive redesign ( and lighter armament than the British planes carried) you are putting up targets, not viable fighters. 

The _BEST_ production Hispano (not Prototype) was the 12-Y-51 and if offered 1100hp for take off and 1000hp at 3260 meters (10,760ft), with little or no possible improvement by using 100 octane fuel. The Swiss built YS-2 engine used a crankshaft that was about 30kg heavier than the one on the 12-Y-51. 
And the 12-Y-51 used bigger intake valves, stronger camshafts and reinforced upper and lower crankcases compared to the -45 and 49 models.


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## wuzak (Sep 4, 2013)

Shortround6 said:


> The _BEST_ production Hispano (not Prototype) was the 12-Y-51 and if offered 1100hp for take off and 1000hp at 3260 meters (10,760ft), with little or no possible improvement by using 100 octane fuel. The Swiss built YS-2 engine used a crankshaft that was about 30kg heavier than the one on the 12-Y-51.



I would think that the Buzzard could match that performance with not much work.

That said, the Hispano was given as an option for a number of British projects in the 1930s.


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## Shortround6 (Sep 4, 2013)

The Hispano was a good engine in 1932-36. In 1934 it was offering 860hp at 4000 meters. The Problem was that it was built light (470kg/1034lbs for the 1934 860hp version) and had no real reserve of strength to either increase RPM or boost pressure.
It doesn't take a rocket scientist to figure out that a 36 liter engine that weighs 32kg more than a 21.2 liter Kestrel might be lacking a little in either strength or durability. 
By 1938 it was falling behind and minor tweaks (like the -51) were not enough to keep it competitive. The Z series _might_ have done it but they don't show up as flying prototypes until the Spring of 1940 which is too late.


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## Shortround6 (Sep 4, 2013)

duplicate


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## The Basket (Sep 4, 2013)

The Dewoitine D520 was certainly as good as a Hurricane with the 12Y and so were the Yaks.

I agree that the 12Y was not as good as the Merlin and certainly nowhere near as expandable but at a pinch with a no viable alternative...it would have been ok.


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## Shortround6 (Sep 4, 2013)

The Basket said:


> The Dewoitine D520 was certainly as good as a Hurricane with the 12Y and so were the Yaks.



Yaks didn't use the 12Y, they used the M-105 engine _derived_ from the 12Y but had 3 valve heads instead of 2 valve heads, the above 2 speed supercharger drive with a low altitude gear ( both engines used a 10:1 drive for altitude but the Russians added a 7.8:1 gear that takes less power to drive and heats the intake air less for Low altitude (2000-2500meters and less). The M-105 alos gained about 100kg of weight between the new heads, the supercharger drive, the stronger crankshaft and the stronger crankcase. 



The Basket said:


> I agree that the 12Y was not as good as the Merlin and certainly nowhere near as expandable but at a pinch with a no viable alternative...it would have been ok.



Unless you license the -51 version (which is too late) or spend a couple of years redesigning the 12Y it actually doesn't offer a whole lot more than the Peregrine would offer if you changed supercharger gears on the Peregrine.


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## fastmongrel (Sep 5, 2013)

Would it have been case that if the Merlin was a failure then the Peregrine would also have been a failure as they were pretty much the same design.


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## The Basket (Sep 5, 2013)

M-103 as well.

Just saying that for a mid 30s engine the 12Y would have been adequate and the prototypes of the Hurricane and Sptifre could have been flying. 

Not saying the 12 was as good as a merlin and as an Englishman I never would! But Klimov got the ball game with it so overall it was ok although not auper.


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## Shortround6 (Sep 5, 2013)

fastmongrel said:


> Would it have been case that if the Merlin was a failure then the Peregrine would also have been a failure as they were pretty much the same design.



Well, the Buzzard was a scaled up Kestrel and the Peregrine was a "Merlinized" Kestrel, whatever that means. R-R built 4750 Kestrels which isn't bad for a Between the wars engine so we can assume that the Kestrel was fairly well sorted out. 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. Chances of the Peregrine having a fatal flaw seem pretty slim.


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## wuzak (Sep 5, 2013)

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.


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## wuzak (Sep 5, 2013)

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.



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.



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.


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## Shortround6 (Sep 5, 2013)

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.


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## wuzak (Sep 5, 2013)

Talking of the Peregrine:

Topic: Peregrine Engine Work in Progress - Whirlwind Fighter Project


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## tomo pauk (Sep 5, 2013)

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*.



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.



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.


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## Shortround6 (Sep 5, 2013)

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).


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## The Basket (Sep 5, 2013)

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.


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## Shortround6 (Sep 5, 2013)

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.


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## merlin (Sep 6, 2013)

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??


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## wuzak (Sep 6, 2013)

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.


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## fastmongrel (Sep 6, 2013)

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


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## Shortround6 (Sep 6, 2013)

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.........


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## tomo pauk (Sep 6, 2013)

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?


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## wuzak (Sep 6, 2013)

fastmongrel said:


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



When did Austin have an aero engine factory?


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## wuzak (Sep 6, 2013)

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

More power?

Or merely a higher critical altitude/FTH?


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## Aozora (Sep 6, 2013)

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:
> 
> ...



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.


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## Shortround6 (Sep 6, 2013)

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.


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## The Basket (Sep 7, 2013)

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.


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## fastmongrel (Sep 7, 2013)

wuzak said:


> When did Austin have an aero engine factory?



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


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## Shortround6 (Sep 7, 2013)

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.


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## tomo pauk (Sep 8, 2013)

I'll agree with SR6, the 12Y would be adequate until Germans introduce the Friedrich. So, for 1941 we need something better to propel RAF fighters.Hercules as a prime choice? Twin stage Twin Wasp? Updated Peregrine? C series V-1710?


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## Shortround6 (Sep 8, 2013)

Well,

Merlin 45-------1230hp at 18,000ft
Herc XI-------- 1510hp at 11,250ft
Herc VI---------1545hp at 15,500ft
R-1830---------1000hp at 19,000ft
1710 C---------1040hp at 14,300ft. 

Peregrine needs a 17% increase to get in the game and a 39% increase to equal the Merlin 45. The first _may_ be doable, the second is highly doubtful (think 1500hp Merlin in high gear at 15-18,000ft). 

Now you have the weight/drag problem of the Hercules. 1700-1800lbs ( granted the Liquid cooled engines need radiators) and 52in in diameter and British cowlings in 1940-41 were a far cry from ideal. Exhaust thrust from radial engines at this point on time was _usually_ pretty minimal and the Hercules, with it's exhaust ports halfway down the cylinder is going to be harder (not impossible ) to arrange.












The early units used the leading edge of cowl as a collector ring.






The exhaust from a Merlin XX could be worth around 120hp to a Hurricane II.


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## tomo pauk (Sep 8, 2013)

Shortround6 said:


> Well,
> 
> Merlin 45-------1230hp at 18,000ft
> Herc XI-------- 1510hp at 11,250ft
> ...



The two stage Twin Wasp might not even be available to the British until some time in 1942, judging by the variety of engines Grumman had installed in Wildcat? 
The 1710 'C' is in the ballpark with DB-601A/Aa and Merlin III (though we might never know just how much power was the V-1710 'C' able to make when over-boosted at lower altitudes, and the external spur reduction gear was an obstacle on it's own for anything above 1200 HP?). My proposed 'Spitfire replacement' should be able to perform as good as MC.202/Spit V/Bf-109F0-1-2/Ki-61?



> Peregrine needs a 17% increase to get in the game and a 39% increase to equal the Merlin 45. The first _may_ be doable, the second is highly doubtful (think 1500hp Merlin in high gear at 15-18,000ft).



Even if we don't have Merlin, mr. Hooker is still at RR  For the 39% increase in Peregrine's power, we need two stage supercharger, and that's not the 1941 stuff. The 17% increase brings us to 1030 HP at, presumably, 18000 ft, once Hooker gets it's job done?




> Now you have the weight/drag problem of the Hercules. 1700-1800lbs ( granted the Liquid cooled engines need radiators) and 52in in diameter and British cowlings in 1940-41 were a far cry from ideal. Exhaust thrust from radial engines at this point on time was _usually_ pretty minimal and the Hercules, with it's exhaust ports halfway down the cylinder is going to be harder (not impossible ) to arrange.
> 
> The early units used the leading edge of cowl as a collector ring.
> The exhaust from a Merlin XX could be worth around 120hp to a Hurricane II.



Thanks for the feedback. The 'Hurricane replacement' with Hercules, combined with 200-210 sq ft wing makes it an useful fighter-bomber. It should also out climb many of other fighters - useful (not only) once Japan attacks?


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## Shortround6 (Sep 8, 2013)

tomo pauk said:


> The two stage Twin Wasp might not even be available to the British until some time in 1942, judging by the variety of engines Grumman had installed in Wildcat?



You may be right. 98 two stage engines delivered in 1940, 507 in 1941 (over 5,000 single stage engines) and 2,129 in 1942 (over 8,000 single stage by P&W alone). earlier tooling of a 2nd factory? The licencee factories never built the 2 stage version. 




> My proposed 'Spitfire replacement' should be able to perform as good as MC.202/Spit V/Bf-109F0-1-2/Ki-61?



Using what for armament? Using historical armament (20mm Hispano, .50 cal Browning is iffy, or .303 Brownings) you have a problem, no center line cannon means you need two minimum and 1040hp (or even 1200 using over boost) isn't enough. Now you are down to 2-4 .50s (un-historic for the British at this time but plausible) or mix or a 6-8 gun .303 battery. By 1941 the .303 battery is slipping in the ETO even if adequate in other theaters. 





> Even if we don't have Merlin, mr. Hooker is still at RR  For the 39% increase in Peregrine's power, we need two stage supercharger, and that's not the 1941 stuff. The 17% increase brings us to 1030 HP at, presumably, 18000 ft, once Hooker gets it's job done?


 And you are 100-200hp down on the 109F? 
A 2000hp Whirlwind makes a nice replacement for the Typhoon but a 1030hp single engine fighter is not where you want to be in 1941/42.






> Thanks for the feedback. The 'Hurricane replacement' with Hercules, combined with 200-210 sq ft wing makes it an useful fighter-bomber. It should also out climb many of other fighters - useful (not only) once Japan attacks?



Useful fighter bombers are only useful if they have other fighters flying top cover for them. At least some of the success of the Kitti-bombers and Hurri-bombers in NA can be attributed to the Spitfires flying top cover for them. Take away the Spitfires and where are you? 

A Hurricane II with a Merlin XX had 1186 hp (both shaft and exhaust ) at 20,000ft and 335mph. A Hercules XI is going to be down to about 1200hp (shaft) at 20,000ft with an unknown exhaust thrust/power.
A Hurricane II with a Merlin XX had 1067 hp (both shaft and exhaust ) at 25,000ft and 330mph. A Hercules XI is going to be down to about 1030hp (shaft) at 25,000ft with an unknown exhaust thrust/power.

Exhaust thrust on those front collector ring engines is going to pretty low. 
A Hercules XI is rated at 1325HP at 2500ft max continuous (30 min climb) in low gear. A Merlin XX is rated at 1125hp at 9500ft. Granted while climbing the plane is moving slow and drag isn't quite as important but how much more drag does the Hercules have than a Merlin in a single engine plane? 12-20%?

The Hercules can be used as as substitute if you _have_ to but you are NOT going to pick up much of anything over the Hurricane II or Spitfire in terms of performance ( speed/climb/ load carrying ability) in an _all round_ airplane.


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## tomo pauk (Sep 8, 2013)

Shortround6 said:


> ....
> Using what for armament? Using historical armament (20mm Hispano, .50 cal Browning is iffy, or .303 Brownings) you have a problem, no center line cannon means you need two minimum and 1040hp (or even 1200 using over boost) isn't enough. Now you are down to 2-4 .50s (un-historic for the British at this time but plausible) or mix or a 6-8 gun .303 battery. By 1941 the .303 battery is slipping in the ETO even if adequate in other theaters.



Agreed, 2 cannons and 4 LMGs seem like a hefty weapon pack, comparable with US '1200 HP fighters' (F4F-4, P-39, P-40E) were carrying; fuel carried is far less, as is the fighter's size - keeping weight and drag lower than those had. The weaponry is, however, lighter than what Hurricane IIC was carrying, granted on more HP, but also on a draggy airframe. It would be, though, not an easy task to pack that sort of battery into 180 sq ft wing (Hurricane replacement might be a better platform for that).



> And you are 100-200hp down on the 109F?



I've specified F-0, F-1 and F-2 (DB-601N), and those were featuring some 1050-1060 HP at 18000 ft (1 minute rating), 1250 HP at 6800 ft (same rating). That would be a maybe 50-100 HP deficit, if the upgraded Peregrine is to have 80% HP of the Merlin XX/45; such a Peregrine being able to make full boost for 5 minutes instead of 1 min for the 601N? Smaller size weight of the 'replacement' fighters (vs. historical ones) again should play it's part, performance-wise.



> A 2000hp Whirlwind makes a nice replacement for the Typhoon but a 1030hp single engine fighter is not where you want to be in 1941/42.



Depends what part of 1941/42 we talk about, what fighter we talk about, and what is the altitude those 1030 HP are achieved. Once F-4 arrives (summer of 1941), RAF indeed needs a true performer, as historically. Even more emphasized once Fw-190 arrives, and finally when the F-4's engine is cleared for Notleistung (Feb 1942?). If the RAF's fighter has 1500 HP, but can do only 350-380 MPH, the RAF is, as historically, in great jeopardy. The V-1710 'C's 1040 HP at 14300 ft are worth less than other V-12s 1030 HP at 18000 ft (size weight being comparable).
Hopefully the RAF will, by late 1941/early 1942 field a fighter with Griffon, or Vulture; the 2000 HP Whirly making 380 MPH? RAF actually fields turbo P-38? Historically, the RAF did not have had parity in performance from summer of 1941 till summer of 1942 anyway.




> Useful fighter bombers are only useful if they have other fighters flying top cover for them. At least some of the success of the Kitti-bombers and Hurri-bombers in NA can be attributed to the Spitfires flying top cover for them. Take away the Spitfires and where are you?



We should have the equivalents of MC.202 around. Spitfire arrived in Africa when much of the mauling was over, though - Hurricanes and P-40s were on their own some 2 years.



> A Hurricane II with a Merlin XX had 1186 hp (both shaft and exhaust ) at 20,000ft and 335mph. A Hercules XI is going to be down to about 1200hp (shaft) at 20,000ft with an unknown exhaust thrust/power.
> A Hurricane II with a Merlin XX had 1067 hp (both shaft and exhaust ) at 25,000ft and 330mph. A Hercules XI is going to be down to about 1030hp (shaft) at 25,000ft with an unknown exhaust thrust/power.
> 
> Exhaust thrust on those front collector ring engines is going to pretty low.
> ...



Many thanks for the numbers. Just equaling what Hurricane and Spitfire were able to do, but now with Merlin out of picture, is a task on it's own. I was thinking more of a bomb-carrying ability of the fighter with Hercules aboard, especially vs. historical Spitfire and P-40 - eg. the Re.2002 (1175 HP engine) was able to carry 1400 lbs of bombs.


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## Aozora (Sep 8, 2013)

Shortround6 said:


> Klimov got a bit of extra life out of the 12Y by reducing the bore, adding several hundred pounds, changing the cylinder heads, using a 2 speed supercharger with a low gear to allow more power at low altitudes ( he didn't improve power at 4-5000 meters that much) and over revving the engine and accepting a much shorter time between overhauls.
> 
> The 12Y was designed a number of years before the Merlin ( 12Y was on sale in 1932) and was NEVER intended to run at the BMEP level of a Merlin or Allison or DB 601 even on 87 octane fuel.
> 
> ...



An Hispano given to Rolls-Royce and redesigned and adapted to using R-R alloys, manufacturing techniques and supercharger technology would probably have performed a great deal better than the Klimovs, which didn't have the R-R metallurgy backing them. The two stage R-R supercharger used on the Merlin was an adaptation of a French Farman design, so there's probably no good reason why it couldn't have been used on a R-R 12Y.

One thing people are forgetting is that the French aviation industry was inefficient and in a great deal of trouble during the 1930s, which is another reason for the 12Y's patchy development and production.


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## wuzak (Sep 8, 2013)

Aozora said:


> An Hispano given to Rolls-Royce and redesigned and adapted to using R-R alloys, manufacturing techniques and supercharger technology would probably have performed a great deal better than the Klimovs, which didn't have the R-R metallurgy backing them. The two stage R-R supercharger used on the Merlin was an adaptation of a French Farman design, so there's probably no good reason why it couldn't have been used on a R-R 12Y.



The Farman bit is the supercharger 2 speed gear drive.

A Merlin type supercharger precludes a motor cannon - because it is in the way.


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## Shortround6 (Sep 8, 2013)

Aozora said:


> An Hispano given to Rolls-Royce and redesigned and adapted to using R-R alloys, manufacturing techniques and supercharger technology would probably have performed a great deal better than the Klimovs, which didn't have the R-R metallurgy backing them. The two stage R-R supercharger used on the Merlin was an adaptation of a French Farman design, so there's probably no good reason why it couldn't have been used on a R-R 12Y.
> 
> One thing people are forgetting is that the French aviation industry was inefficient and in a great deal of trouble during the 1930s, which is another reason for the 12Y's patchy development and production.



The 12Y was an old engine. The cylinder head/valve train design is little different than the WW I V-8s. It is not just metallurgy, The 12Y was very close to a Griffon in displacement (or a Buzzard) but was several hundred pounds lighter than a Merlin, in fact it was about the weight of Peregrine. Given that fact I doubt very highly that R-R Metallurgy can make a 36 liter engine for the same weight as a their own 21 liter engine and have any reserve of strength. 

All you are going to "save" from the Hispano is the V-12 60 degree layout. *EVERYTHING* else needs to be changed. 

Using the 12Y _ONLY_ makes sense if you already have one or more factories _already_ tooled up for it. Then you are trying to save your tooling investment and time to retool (lost production). 

Rolls already has some minimal tooling for the Buzzard and "R" racing engines. It is an engine with more potential and they know an awful lot more about it.


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## Aozora (Sep 8, 2013)

Shortround6 said:


> The 12Y was an old engine. The cylinder head/valve train design is little different than the WW I V-8s. It is not just metallurgy, The 12Y was very close to a Griffon in displacement (or a Buzzard) but was several hundred pounds lighter than a Merlin, in fact it was about the weight of Peregrine. Given that fact I doubt very highly that R-R Metallurgy can make a 36 liter engine for the same weight as a their own 21 liter engine and have any reserve of strength.
> 
> All you are going to "save" from the Hispano is the V-12 60 degree layout. *EVERYTHING* else needs to be changed.
> 
> ...



I doubt if R-R would have bothered redesigning a foreign engine anyway...just some thoughts as to how the 12Y might have been better with R-R type metallurgy. As it is I doubt whether Rolls-Royce would have given up on the idea of designing a decent V-12, even if the Merlin had failed for whatever reason, and chances are what became the Griffon would have emerged earlier than it did, most likely as an extrapolation of the R or Buzzard series updated and improved in much the same way the Kestrel evolved into the Peregrine. Just imagining a Spitfire with (say) 1,500 hp, and developing c. 1,800 hp up to 10,000 ft with increased boost and 100 Octane in 1939 - 1940...


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## tomo pauk (Sep 8, 2013)

I'm a little bit puzzled about the Buzzard - Wikipedia says it was an '800 HP engine', however there were some 100 examples produced that were capable for ~950 HP, again according to the same source. Any better info?


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## wuzak (Sep 8, 2013)

tomo pauk said:


> I'm a little bit puzzled about the Buzzard - Wikipedia says it was an '800 HP engine', however there were some 100 examples produced that were capable for ~950 HP, again according to the same source. Any better info?



I don't have access to Lumsden at the moment, so I can't give you answers.

It may be that the 800hp was "normal", 950hp for take-off?

In any case, strengthened Buzzards were capable of well over 2000hp. Nearly 3000hp, in fact, in 1931. (Rolls-Royce 'R'.)


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## Shortround6 (Sep 9, 2013)

tomo pauk said:


> I'm a little bit puzzled about the Buzzard - Wikipedia says it was an '800 HP engine', however there were some 100 examples produced that were capable for ~950 HP, again according to the same source. Any better info?



It was about 800hp at 2000rpm and 925-955hp at 2300rpm. FTH was about 5,000ft. These engines used fixed pitch props so the 800hp is sort of a max cruise power level. Engine was also rated on 70-77 octane fuel. Weight may have been a bit over 1500lbs rather than the number Wiki gives.


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## wuzak (Sep 9, 2013)

Lumsden gives:

Buzzard IMS - 825hp @2000rpm t/o. 955hp @ 2300rpm @ 2000ft

Weight 1540lbs.

Rolls-Royce R (1929) - 1900hp @ 3000rpm, +13.5psi boost t/o / sea level. Weight 1530lb.
Rolls-Royce R (1931) - 2350hp @ 3200rpm, +17.5psi boost t/o / sea level. Weight 1640lb.
Rolls-Royce R (1931 record) - 2530hp @ 3200rpm, +17.6psi boost t/o / sea level. Weight 1640lb.

That was on special fuel, obviously, allowing for the increased boost. But it would seem that the ultimate version of the R was only 100lbs heavier than the base Buzzard. But was capable of taking boost in excess of +18psi and rev to 3400rpm (in later uses). So it should take +12psi with 100 octane fuel comfortably, but the revs would have to be dialled back for longevity. I could see it make 1hp/lb by the BoB.


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## tomo pauk (Sep 9, 2013)

Many thanks for the feedback. 
Some strengthening and a good supercharger needed for 1939-41?


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## Shortround6 (Sep 9, 2013)

Depends on how much of the "R" you use. The "R" being basically a reinforced/modified Buzzard with a _*BIG*_ wacking supercharger on it. 






A 1939 supercharger may be better than the 1930-31 supercharger even before Hooker gets to it.

Please note the Buzzard was being listed in Nov 1930 Flight Magazine at 662KG dry weight.


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## tomo pauk (Sep 9, 2013)

Thanks again. 
Buzzard seem like a potentially outstanding and timely tank engine - plenty of torque from a 36.7 liter engine? The known diesel V-2 (V12 cylinders, of course) engine from Soviet Union was just a tad bigger, 38.8L.


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## Shortround6 (Sep 9, 2013)

If the British had wanted a tank engine they could (and did) do much worse than just using the Kestrel. 21.2 liters compared to the 21.35 liters in the Early Tigers and 23.01 in the later Tigers, Panthers and Royal Tigers. 

It may have been a bit expensive but it would not be lacking in power right up until the Centurion (and even then?)


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## Aozora (Sep 9, 2013)

Shortround6 said:


> Depends on how much of the "R" you use. The "R" being basically a reinforced/modified Buzzard with a _*BIG*_ wacking supercharger on it.
> 
> View attachment 242507
> 
> ...



The Merlin II was listed at 605 kg dry (1,335 lbs) in 1937, so a Buzzard variant with Kestrel/Merlin type refinements would probably have a better power-weight ratio than the original design, depending on the supercharger. R-R already had two speed superchargers in 1938

View attachment Rolls-Royce Merlin 1937.pdf


Had the Buzzard/R series been seriously pursued Rolls-Royce might have been able to ditch the Vulture, and the Avro Manchester might have had more powerful, reliable engines right from the start - a Manchester with two-stage, two-speed supercharged Buzzard variants. Better still a Manchester variant with four two-stage, two speed Buzzard variants...
View attachment Rolls-Royce R Oct 1931.pdf


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## OldSkeptic (Sep 10, 2013)

Oh I will stick by my original argument. Britain would have fallen (or more likely the upper classes would have kicked out Churchill and made a deal). 
Britain would have had a 'special relationship' with Germany. British troops would have fought against the Soviets alongside it's 'natural allies' Germany. 
Until a bitter stalemate. And a deal with a split between the respective empires.

But the German empire with all of Western Europe and a lot of eastern Europe would have ended up a superpower. The US would have won a bit of the Pacific war, because the British were on the side of the other 'Axis' member, Japan (at the price of losing some of its Empire .. sorry Australia).

Germany would have gotten all the nuclear, radar, etc stuff from Britain (without the Tube Alloy project there would have been no Manhatten one).

British ships (and subs) would have joined into 'isolating' the US, given the USN's hate (at that time and now) of anti sub stuff. then its Pacific war against Japan would have died real fast.
Without the technical stuff from Britain the US remained a .. great place to make a good refrigerator.
No radar, no nuke stuff, no jet engines ... and so on.

A totering balance would have been struck until the US invades Canada (post Roosevelt) and the Axis supports it with troops. The US reels against that attack, well planned. British' shock troops' thrust towards Washington (at the cheers of many Americans no less). LiftwafeRAF (new name for the combined Luftwaffe and the RAF) combined airpower strikes deep into the US. Under the new Doctrine of 'lie to the indigenous until you have won .. then exterminate them later', a British innovation to Axis planning, German, Italian (though not Irish or Jewish) Americans flock to the cause of being 'liberated'. This is a war of 'liberation 'from 'plutocrats'.

The US North falls, aided by long term deals with the American 'South', promised total control of their areas and their 'race issues' and 'promises to 'help' them expand' further south.

Wall Street is untouched since it, as always, funds all of them. Though New York, for many, especially the rich, becomes better (unless you were Irish, Jewish, homosexual, etc in which case it becomes a lot, lot worse). 


And then, the rump of the Soviets, basically the pure Russians, when the Axis is so stretched.. attack, starting with massive nuclear attacks on Berlin, Paris, London and the Russians sweep though the near east and into the (totally undefended) Germany and western Europe.

In the end a smashed, destroyed (and very glowing) World (you could sit on Mars and look at it .. wow it is bright, even without sunlight).

And all because there was no Merlin engine.......8)


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## The Basket (Sep 10, 2013)

There were alternatives to the Merlin which could have powered fighters in the battle of Britain.

For sure. 

And win. ..but as good as the merlin is the question


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## parsifal (Sep 11, 2013)

There is no question the absence of a Merlin would have been a great loss for the British war effort. Except if the resources poured into the merlinhad been diverted into other engine projects and tangible results obtained to compensate for the non-development of the merlin.

This scenario then means we have to estimate how much effort (even design resources constitute a finte resource, difficult to quantify, but finite just the same) would be released if the Merlin was not developed. 

If the scenario is re-defined, such that resources are poured into the merlin, and such efforts are a failure, then Britain's war making potential sufferes a major setback.

The parameters of the scenario need to be more sharply defined....are we looking at a failed design efort, or a design effort never attempted?????

On the assumption that a design effort is never attempted, and that resources are instead poured into other projects, then one has to assume that from the gaggle of protoypes that werent developed because the Merlin was a success

Thinking out of the box, I dont see it as all that difficult to envisage a development of something like the Britol Mercury along the same lines as the P&W R1340 Single Wasp was developed. The American engine served as a the basis for the R1830 twin Wasp, and was more or less a contemporary of the Bristol engine. In fact a comparison of the two is worth undertaking

The R1340 had the following chracteristics (from Wiki)

Type: Nine-cylinder single-row supercharged air-cooled radial engine
Bore: 5.75 in (146 mm)
Stroke: 5.75 in (146 mm)
Displacement: 1,344 in3 (22 L)
Diameter: 51.75 in (1.314 m)
Dry weight: 930 lb (422 kg)

Performance
Power output: 600 hp (447 kW) at 2,250 rpm at 6,200 ft (1,890 m)
Specific power: 0.45 hp/in³ (20.3 kW/L)
Compression ratio: 6:1
Power-to-weight ratio: 0.65 hp/lb (1.05 kW/kg)

It was developed into into the R1830 twin Wasp. which started as a 750hp engine, but by 1939 had been developed into an engine capable of 1200hp. It eventually was uprated to deliver 1350hp. Both respectable power outputs

Wiki gives the following characteristics for the Twin Wasp

Type: Fourteen-cylinder two-row supercharged air-cooled radial engine
Bore: 5.5 in (139.7 mm)
Stroke: 5.5 in (139.7 mm)
Displacement: 1,829.4 in³ (30 l)
Length: 59.06 in (1,500 mm)
Diameter: 48.03 in (1,220 mm)
Dry weight: 1,250 lb (567 kg)

Performance
Power output:
1,200 hp (895 kW) at 2,700 rpm for takeoff
700 hp (522 kW) at 2,325 rpm cruise power at 13,120 ft (4,000 m)

Specific power: 0.66 hp/in³ (29.83 kW/l)
Compression ratio: 6.7:1
Specific fuel consumption: 0.49 lb/(hp•h) (295 g/(kW•h))
Power-to-weight ratio: 0.96 hp/lb (1.58 kW/kg)

The Bristol Mercury has characteristics remarkably similar to the Single Wasp in its key feratures....weight, dimensions, and power output. 

The design development of the Bristol Mercury was the Hercules. The Hercules was again a remarkable equivalent of the twin Wasp, if somewhat less reliable (more correctly, it was a development of the Bristol Perseus sleeve valve configuration). I can easily envisage, with more resources spent on its development, acting as a very reliable, somewhat uprated version and adequate substitute for the Merlin in the early war period. 

For the later war, if additional resources were made available by the non-development of the Merlin, I see the long term engine needs of the British being met by the Bristol Centaurus. This engine, like all the Bristol interwar engines, has a link back to the Jupiter of 1919. 

The Centaurus was type tested in 1938 but production was not started for two reasons....it suffered some reliability issues, and quite simply, early in the war it was not needed. Production did not start until 1942 mostly because priority was given to the more useful Hercules and as stated the need to improve the reliability of the entire engine line. Nor was there any real need for the larger engine at this early point in the war, when most military aircraft designs were intended to mount engines of 1,000 hp or a little more. The Hercules' approximately 1,500 hp was simply better suited to the existing airframes then in production.

Provided we are not talking about a total failure of the merlin program (ie, it was never attempted, rather than attempted, but failed), there are plenty of alternatives available to the British.


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## Shortround6 (Sep 11, 2013)

The problem for fighters is the difference in drag between the liquid cooled v-12 and the air-cooled radial. This difference changed as time went on. The P-36 (with a _Twin Wasp,_ Double Wasp was the R-2800) had 22% more drag than the XP-40. By the fall of 1942 P &W had gotten the difference down to 8%. By the end of the war who knows? 

Bombers, with their fat fuselages, multiple engine nacelles, fat wings and projecting turrets have a much lower percentage of total drag caused by the engine installations. 

One reason for the _dominance_ of the Merlin on the early war British aircraft scene was the near failure of the Hercules to make it into production. 

Bristol built their first sleeve valve test rig in 1926-7, design work started on the Pereus in 1932. While hand built (or hand finished) engines built in small numbers worked OK, manufacturing sleeves in quantity was a stumbling block that was only solved at the last minute and then, as the story goes, by accident. A worker used grinding wheels out of sequence. 
No fault in the _design_ of the engine, like under sized bearings or a harmonic vibration but a major production obstacle. And one that the solution to was counter intuitive to knowledge at the time. 

Bristol superchargers were somewhat less than stellar also, despite their setting a world altitude record with a two stage Pegasus in 1938. 

Rolls Royce would much more likely have spent their resources on other Rolls Royce engines rather than working on Bristol engines in the years from 1932 to 1938-39 in the absence of the Merlin. 

Don't get me wrong, The Hercules was a good engine and got better as the war went on, the post war 100 series and higher were very good engine indeed but are a bit late. But the hercules was also a bit late in the 1930s and was NOT avialable for the thousands of aircraft powered by Merlins from 1936-1940. Granted the British might have gotten by without quite as many Battles and Defiants


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## tomo pauk (Sep 11, 2013)

Looking at speed figures for the French fighters with Hispano 12Y engine, the MS-406 ends up as a really slow airplane. Not surprisingly, it was lacking ejector (rear facing) exhaust stacks - that alone making 10-15 mph difference in speed here? Swiss license-built examples received ejector exhaust stacks in 1944.

The Napier Dagger would be another interesting, but controversial choice, to power RAF planes between 1939-41?


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## Shortround6 (Sep 11, 2013)

Could be. Could aslo be the Ms 406 was kind of high drag. Could also be that the engine used in the 406 had a FTH of 3250 meters (860hp), or 1674 meters lower than a Merlin III. The engine in the D 520 had a FTH of 4200 meters (920hp). The HP difference isn't that great but the difference in altitude means that the air is about 6-7% thinner for lower drag. 

The Dagger is a terriable choice. It's FTH was 8,750ft (2650 meters). It's 1000hp will drop to less than the Peregrines 885hp at 15,000ft. 

All it needs is better cooling, a better supercharger, less drag, and...........
It is a 16.9 liter engine running at 4200rpm full throttle. 48 spark plugs to change.


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## tomo pauk (Sep 11, 2013)

Shortround6 said:


> Could be. Could aslo be the Ms 406 was kind of high drag. Could also be that the engine used in the 406 had a FTH of 3250 meters (860hp), or 1674 meters lower than a Merlin III. The engine in the D 520 had a FTH of 4200 meters (920hp). The HP difference isn't that great but the difference in altitude means that the air is about 6-7% thinner for lower drag.



Many thanks for pointing out the difference between FTHs. 
The quick overview of the Hispano variants can be seen here, and more detailed data is in our 'Engines' subforum - many thanks to siboh who provided it. The 406 used the 12Y-31 variant, the D.520 used the 12Y-45.



> The Dagger is a terriable choice. It's FTH was 8,750ft (2650 meters). It's 1000hp will drop to less than the Peregrines 885hp at 15,000ft.
> 
> All it needs is better cooling, a better supercharger, less drag, and...........
> It is a 16.9 liter engine running at 4200rpm full throttle. 48 spark plugs to change.



Not an easy task, filling Merlin's shoes


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## OldSkeptic (Sep 12, 2013)

The problem with asking these sort of questions (thought experiments) is that you have to go through the details. Like WHY there would be no Merlin.
It was a logical development of previous engines (inspired by Royce himself and ordered by him to make it, hence the PV tag .. Private Venture they used their own money at first and they were not a rich company at that time by any means), brought to life by the great Hives.

So for it not to be available then something (ah lah the Allison 1710, 10 years of development) had to go seriously wrong within RR. They had to go broke, or Royce died earlier, or Hives was never in the company ... or whatever. Given their technical ability (and the Merlin only took 4 years to get into full production and RR had fought for the 'shadow' factories right from the beginning) then to have a zero Merlin scenario you basically have to assume RR went bust some years before.

But the lack of it (to be serious for a moment) meant there would be no Spit or Hurricane or Mossie or Merlin Mustang, at least as we know them. In the case of the first three their designs were built around the Merlin. For the Spit and Hurri it was an official requirement.

If for some reason they couldn't do the Merlin, then the Griffon has to be assumed as a dead duck too (basically RR is gone). And their earlier engines as well. Therefore the British only have, in the big engine league of the time, the Bristol ones. Given how long it took them to get the Hercules into production (and it was always a low altitude engine), then you can quite sincerely say that the British lose the BoB, in fact they will surrender before then as they have no aircraft that can even get close to the 109/DB 601 in performance. Whatever they put in the air will be slaughtered and the Luftwaffe can bomb Britain (even if it does not invade) into total submission in the day.

Now you have no US involvement in the European war, even if they wanted too how could they? Worse, there is no way to predict the outcomes of the British/German peace treaty. Maybe the RN does agree to defend Germany???

The Merlin is one of those cardinal points (in Dr Who terms a 'fixed point in time') . While many different things could have happened or been done in WW2 and had little effect on the eventual outcome certain things are 'fixed', without which there are zero options and the whole outcome can change. 

The classic is, what if Roosevelt had left MacArthur in the Philippines .. some would argue the US would have won the Pacific war earlier, at the very least it would have made zero difference.

WW2 was winnable by the Germans, though Hitler would have had to be killed to achieve it post France. The Allies won by a slim margin, much slimmer than most people realise. If Hitler hadn't been distracted by Greece and the Balkans and invaded the USSR a month earlier (as planned) then...?. 

If the Germans had done the, correct, south thrust first, the Med, North Africa. Middle East, Iraq and Iranian oil and an another springboard for an attack at the USSR later, Britain surrenders, the US is powerless, the USSR later (with Germany with all that oil) is attacked from multiple thrusts .. game over.

All those are 'what if's' are interesting, as is the other one, what of the British had consolidated, forgot about Greece and kicked the Italians out of NA, then the Med would have remained a British 'lake' and many, many shipping issues would never have happened and the Western Allied invasion of France *could* have happened in 43 (because of shipping it was impossible).


But the Merlin is one of those cardinal points. There literally is no alternative, not if you want a Spit or Hurri in 1940.

Funny thing these cardinal points, applies to people too. Take out Dowding or Park then the war is lost as well. No Dowding, no FC, no radar network, C&C and Spits/Hurris (or with 8 guns).
No Park, the Bob is lost in a couple of weeks.
No Mitchell and no Spit. 
No Royce or Hives and no Merlin.
No Merlin and no Spit, Hurri, Mosquito, or Lancaster.
No Merlin (or even RR push, they disobeyed the Air Ministry which had, thanks to Portal, zero interest) and no Merlin Mustang.

The old 'For a want of a nail ...' argument.


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## Shortround6 (Sep 12, 2013)

You are assuming that the rest of the British aero engine industry does nothing different.
While the Air Ministry discouraged Fairey from becomeing an engine manufacturer that was with Rolls in existance. It was Fairey's importation of the Curtiss V-12 that got the AIr Ministry to ask Rolls for something better, the Kestrel. 
A J Rowledge, who had designed the Napier Lion went to Rolls Royce in 1921 (?) contributed quite a bit to most Rolls-Royce pison engines from the Condor on. No Rolls-Royce, does he retire to the south of France?
Halford had taken over as chief designer at Napier ( actual an indepentent contractor for quite a few years) by the Very early 30s. 

IF the Air Ministry had issued a reqirement for a liquid cooled V-12 _something_ would have been built by another company than Rolls Royce and given the improtance of the liquid cooled V-12 that requirement would have been made either in the 1920s or shortly after the R-R _bankrupcy_ in your scenerio. It wouldn't be a Merlin but it would be something. 

With every major country in the aircraft industry making one or more V-12s (the US in the 20s had 2 different sized Curtiss and two diffierent sized Packards) the idea that Britian would ignore that type of engine _without_ Rolls Royce doesn't hold up.


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## parsifal (Sep 12, 2013)

> The problem for fighters is the difference in drag between the liquid cooled v-12 and the air-cooled radial. This difference changed as time went on. The P-36 (with a _Twin Wasp,_ Double Wasp was the R-2800) had 22% more drag than the XP-40. By the fall of 1942 P &W had gotten the difference down to 8%. By the end of the war who knows?



No argument that a radial was more draggy than an inline, and the designs around which the aircraft for which the merlin was designed were about as good as they were in the 1930s as far as reducing drag was concerned.

Thanks for the correction about Double wasp and twin wasp. i did know, but suffereed some sort of brain melt down when i wrote my original post. 



> One reason for the _dominance_ of the Merlin on the early war British aircraft scene was the near failure of the Hercules to make it into production.
> 
> Bristol built their first sleeve valve test rig in 1926-7, design work started on the Pereus in 1932. While hand built (or hand finished) engines built in small numbers worked OK, manufacturing sleeves in quantity was a stumbling block that was only solved at the last minute and then, as the story goes, by accident. A worker used grinding wheels out of sequence.



I have no problem in describing the hercules as problematic. Its the main reason the Australians settled firstly on the single wasp for their licence built engines at the GAF works, and then the twin wasp from 1941. The reason the Australians switched to the American engines was that the hercules that they planned to build under licence for their beaforts was not ready for production in 1939, and then the British slapped their emargo on technology from 1939. Australia was already making single wasps in 1939, faced with the British embargo the GAF retooled in 1940 to build the twin wasp and rolled the first twin wasps out by May 1941. they had converted their factory in less than twelve months with virtually no expereience to call on, and not much in the way of investment either.

If more money had been poured into the finishing of the hercules, i dont see any reason why its bugs could not have been ironed out 1936-7 when they were supposed to. i get the near miraculous way the solution to the sleeve valve problems were solved, but in reality thet merely confirms that the design was suffering from a lack of investment and proper R&D. All clear inidications of not enough money. more money means a more thorough development, means an earlier completion of the design, means earlier entry into quantity production. Same applies to the Centaurus, which suffered similar problems really 



> No fault in the _design_ of the engine, like under sized bearings or a harmonic vibration but a major production obstacle. And one that the solution to was counter intuitive to knowledge at the time.



But surely you would agree, if more money had been available for the development of this engine, these issues could have been solved far earlier. 



> Bristol superchargers were somewhat less than stellar also, despite their setting a world altitude record with a two stage Pegasus in 1938.



Ive read about this as well, and accept that it was a bit of a problem. What I dont know, is the precise nature of these problems. I dont suppose yopu have any knowledge you would like to share. I would be very interested to know. 



> Rolls Royce would much more likely have spent their resources on other Rolls Royce engines rather than working on Bristol engines in the years from 1932 to 1938-39 in the absence of the Merlin.



I agree entirely, but its here we have to get creative as to why the Merlin would not be designed or developed. There are not a lot of options, and all of them are really quite "out there" as far as plausibility is concerned. one might be that Rolls royce was bought out by one or more of its rivals. The only way I can see the Merlin not being produced, is if there is no RR to build it. in that scenario, where does the RR expertise go....to its rivals of course....the engineers would be dispersed to these other companies  as required. Bristols R&D capability gets bigger, because there is no RR R&D team..... 




> Don't get me wrong, The Hercules was a good engine and got better as the war went on, the post war 100 series and higher were very good engine indeed but are a bit late. But the hercules was also a bit late in the 1930s and was NOT avialable for the thousands of aircraft powered by Merlins from 1936-1940. Granted the British might have gotten by without quite as many Battles and Defiants




The Herc was not abvail;able because it wasnt ready, and it wasnt ready because it had insufficient R&D poured into it. It could have, if the effort poured into the merlin was put into it instead. There is no reason to surmise otherwise. as you say, there was nothing inherently wrong with the design. 

The question then arises, what sort of design would be built around the Hercules. Probably not a Spitfire or hurricane. possible a development of Spec F5/34. This design had just 840 HP when designed, had more range than a Hurricane, could climb faster and a top speed of 316 mph. Obviously it would lose some of this performance when kitted out to combat requirements, but what could the design have done with a 1200 hp donk instead.


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## Shortround6 (Sep 12, 2013)

Bristol spent around 2 million pounds and 5 years on the sleeve valve project to get a workable engine, the Perseus. The _initial_ R-2800 (A series) may have cost 8 million dollars. 

The Hercules started with a sand cast single piece cylinder head with 540in2 and was changed to a die cast single piece cylinder head with 581in2 by the first production model. The main war time models used two piece heads, die cast for at least one part, with 728in2 of cooling area. Improved casting technique allowed an increase to 777in2 and a reduction of of 15 degrees C in CHT. Several more head designs were tried and finished, post war, with a machined copper based head. 
This is one example of the development and this piece of the engine had no moving parts. 
Literally hundreds of combinations of alloys and finishing proccess had been tried before the "solution" was discovered. Please note the trouble Napair had with sleeve valves before Bristol was "persuaded" to share their knowledge ( Taurus sleeves) with , again, hundreds of combinations of materials and finishing processes. How many were duplicates I don't know.
The sleeve valve came very close to bankrupting Bristol. 

I don't know what the Problem was with Bristol superchargers but I believe when Stanley Hooker left Rolls-Royce and went to Bristol he is supposed to have thought that the Bristol designers didn't really understand airflow. Granted they were working on jets at the time but in 1949 a great many of the men involved had worked on the wartime piston engines. 
A good supercharger needs 3 things, mass airflow, pressure ratio (not the same thing) and efficency. Mass airflow is the easy one, just keep making the whole thing bigger. Getting a good pressure ratio at a good efficency is the hard part. Poor efficency even with a good pressure ratio means more power to get the same effect and most of the extra power goes into heating the intake charge which lowers the density/airflow and pushes the intake mixture closer to the detonation limits.


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## wuzak (Sep 12, 2013)

parsifal said:


> I agree entirely, but its here we have to get creative as to why the Merlin would not be designed or developed. There are not a lot of options, and all of them are really quite "out there" as far as plausibility is concerned. one might be that Rolls royce was bought out by one or more of its rivals. The only way I can see the Merlin not being produced, is if there is no RR to build it. in that scenario, where does the RR expertise go....to its rivals of course....the engineers would be dispersed to these other companies as required. Bristols R&D capability gets bigger, because there is no RR R&D team.....



The Merlin did fail. The original design with the "ramp heads" didn't work as well as predicted from single cylinder testing.

At that point Rolls-Royce had three options:


cancel Merlin development and use the resources on other projects being developed - Peregrine, Vulture and Exe.
cancel Merlin development and start a new project/ This could be all new, or could be new developments of old engines. eg Buzzard+/production R/Griffon I
redesign Merlin and make it work

History will show that the third option was chosen. But they could equally have gone in the other directions.

Maybe they could have started again and used their own sleeve valve research (Kestrel RR/P and RR/D) to design a new liquid cooled V-12 of 27-37l.


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## The Basket (Sep 13, 2013)

My memory maybe playing tricks but wasnt the spitfire designed originally for the Goshawk engine?

That woukd suck as the Goshawk was 700bhp and the Spit would have been well rubbish. Stupid evaporative cooling malarkey. 

The 1,000bhp merlin alternative would have to be about 1934 so that the Spitfire can be designed and fitted for it. Spitfire is a big old thing for 700 horses. Again the 12Y just fits nicely here and holds the fort for something to appear down the line.


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## fastmongrel (Sep 13, 2013)

I think that was the Supermarine Type 224 Supermarine Type 224 - Wikipedia, the free encyclopedia


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## The Basket (Sep 14, 2013)

The bent wing? For sure.

But the leading edge of type 300 was designed for evaporative cooling. Sure of it.


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## fastmongrel (Sep 14, 2013)

Possibly the Merlin was originally to be steam cooled RR and the Air Ministry seemed to be quite keen on it. Pretty sure the Spit was designed around the Merlin possibly some of the early drawings were for a Goshawk/Kestrel sized engine installation. Mitchell seemed to be a great doodler turning out countless iterations of a basic design till it looked right.


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## Shortround6 (Sep 14, 2013)

The Basket said:


> The 1,000bhp merlin alternative would have to be about 1934 so that the Spitfire can be designed and fitted for it. Spitfire is a big old thing for 700 horses. Again the 12Y just fits nicely here and holds the fort for something to appear down the line.


The 12Y in 1934 was 860hp and even then none too reliable( Russians had it down rated to 750hp). Unless R-R goes bust in 1929-31 they had the Buzzard which gave 800hp MAX continuous on 70-77 octane. 

Octane is not a liner scale. the PN (performance number) scale may not be liner either but it is a lot closer.

octane..........70............77...........80............87.........91............100
PN number.....48.28........54.90.......58.33.......68.29......75.68.......100

Feed a Buzzard 87 octane instead of 77 octane and _IF_ (mighty big if) you could raise the manifold pressure with NO increase in temperature you could get about 25% in power from the engine.

Kestrel V would give 640hp at 14,000ft. 740hp at 11,000ft. 745hp for take-off. It was a bit lighter than 1934 12Y.


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## stona (Sep 14, 2013)

The Supermarine Type 224 was built to AM specification F7/30. It featured a Kestrel engine and evaporative cooling. It was specifically the Kestrel S, developing 535 bhp at 2500 rpm and 13,000ft. It first flew 20th Feb 1934 and performance was disappointing.

Subsequently the prototype was extensively modified and fitted with a Goshawk engine. The aircraft in this form appeared at the RAF pageant at Hendon on 30th June.

The Air Ministry wrote asking for an alternate proposal for the specification using the Napier Dagger engine. On 6th November Supermarine declined the proposal, officially they thought the Napier powered version would be slower than that with the Goshawk engine. Unofficially Supermarine had a long standing relationship with Rolls Royce and were anticipating the new PV12. This is first mentioned in Supermarine Report TD 1232, dated 13th October, _before_ the AM request for a Dagger engine proposal.

The next proposal from Supermarine was illustrated in design submission 425A and is starting to look like a Spitfire, though without the elliptical wing. This was to be powered by a Goshawk II.

The Type 300 was a result of an on going process and it was decided in December 1934 that it would be powered by the PV12 and retain the evaporative cooling of its predecessors.

On 9th January 1935 Mr Ross of Supermarine visited Rolls Royce in Derby to discuss re-rating the PV12 and agree figures for the fully supercharged version now known as Merlin. This just six days after AM contract 361140/34 which led to the Spitfire. 

The Type 300 was designed around the Merlin and Mr Ross' Derby visit also arranged for delivery of the engines to Supermarine for the Type 300 prototype. The figures provided by Rolls Royce to Supermarine in January 1935 for the Merlin engine were; Rated 950 bhp at 2600rpm and 11,000ft. Maximum 1045 bhp at 3000rpm and 15,000ft. 

Cheers

Steve


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## Aozora (Sep 14, 2013)

The Basket said:


> The bent wing? For sure.
> 
> But the leading edge of type 300 was designed for evaporative cooling. Sure of it.



Definitely: the Merlin was intended to use evaporative cooling and the D shaped wing leading edge was to house the condensers, plus there would be a retractable auxiliary radiator behind the cockpit. This is the design in 1935 (Price_ The Spitfire Story_ 2010 p 19):


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## OldSkeptic (Sep 15, 2013)

Shortround6 said:


> You are assuming that the rest of the British aero engine industry does nothing different.
> While the Air Ministry discouraged Fairey from becomeing an engine manufacturer that was with Rolls in existance. It was Fairey's importation of the Curtiss V-12 that got the AIr Ministry to ask Rolls for something better, the Kestrel.
> A J Rowledge, who had designed the Napier Lion went to Rolls Royce in 1921 (?) contributed quite a bit to most Rolls-Royce pison engines from the Condor on. No Rolls-Royce, does he retire to the south of France?
> Halford had taken over as chief designer at Napier ( actual an indepentent contractor for quite a few years) by the Very early 30s.
> ...



You make a mistake ... *individuals count*. Without Royce and Hives (always forgotten about, though he dominated things so much during the war) there is no Merlin. Royce made the decision, Hives made it ... and fought for the 'shadow' factory system so the mass production was in place very early on. Even by 39 RR was producing more Merlins than there were aircraft for it.

None of the other British engines were in place then. None of the others got the same mid/high/very high altitude performance out of their engines. And there is another individual that counts, Hooker. Without his work the Merlin would probably topped out at about the 1,300bph level even with 2 stages, and probably only 600-700bph at 30,000ft, not enough to be competitive against the ever lager, lower supercharged, higher comp ratio, radically cammed, power boosted German engines.

To put it in perspective that would have gotten the Merlin Mustangs into about the 410mph class at 20,000ft, and Spit IXs into about 380. Not nearly enough to hold their own.

The fact that the Merlin was up to 2,000bph in operational use in 44 was amazing (as was the 2,600bph type approved RM-17). The other fact was that the 130's (RM-16s) used in the Hornet were 2,000bhp ... at 20lb boost on 100 grade fuel was also amazing ... as it was, by that time a tiny engine of 'only' 27 litres compared with all the other 33, 36, 42, 56, etc litre engines.

But Hooker was another Hives 'creation', as he admitted himself. A truly 'great man'.


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## Aozora (Sep 15, 2013)

OldSkeptic said:


> You make a mistake ... *individuals count*. Without Royce and Hives (always forgotten about, though he dominated things so much during the war) there is no Merlin. Royce made the decision, Hives made it ... and fought for the 'shadow' factory system so the mass production was in place very early on. Even by 39 RR was producing more Merlins than there were aircraft for it.
> 
> None of the other British engines were in place then. None of the others got the same mid/high/very high altitude performance out of their engines. And there is another individual that counts, Hooker. Without his work the Merlin would probably topped out at about the 1,300bph level even with 2 stages, and probably only 600-700bph at 30,000ft, not enough to be competitive against the ever lager, lower supercharged, higher comp ratio, radically cammed, power boosted German engines.
> 
> ...



And Hooker claimed he was "Not Much of an Engineer"...Not Much of an Engineer: Sir Stanley Hooker: 0800165000736: Amazon.com: Books

Here's an article on Merlin development by A.C Lovesey, who also played a role in its development:

http://www.wwiiaircraftperformance.org/merlin-lovesey.pdf


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## swampyankee (Sep 15, 2013)

I think this and the V-1710 failure thread are somewhat predicated on the Rolls Royce and Allison engineers and managers being so completely stupid that they run down a blind alley and then try to butt through a thick reinforced concrete wall with their heads. While managers can be ridiculously enamored of failed and flawed projects, especially when somebody else* is footing the bill, they're usually** not stupid. 

Looking at the likely points of failure in a quite conventional liquid-cooled V-12s, even in the 1930s, and I think that it's hard to see what potentially insurmountable problems either engine had: poppet valves were well-known technology, with sodium cooled valves already in commercial use, V-12 crankshaft torsional vibration issues were known, if not well understood, the monoblock Curtis D-12 was well known to the engine community, overhead camshafts were commonplace, etc: the Merlin and the V-1710 were not bleading-edge designs, instead, they were advanced designs based on existing practice. Bristol's sleeve valve designs were certainly much riskier, as were Napier's H-engines. Indeed, P&WA's R-2800 and Curtis-Wright's R-3350 were probably riskier developments than the Merlin or the V-1710.


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* Whether the money comes from shareholders or taxpayers, project managers rarely write checks from their own bank accounts. 

** They obviously are sometimes. They do, after all, remain human, and stay the course way too long, even endangering company survival. Examples? Convair CV880/CV990 and the Ford Edsel.


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## wuzak (Sep 15, 2013)

OldSkeptic said:


> as was the 2,600bph type approved RM-17



Just to be technical, the RM.17SM was rated at 2200hp MS and 2100hp FS - can't recall the altitudes.

The RM.17SM was also flight cleared for 2380hp @ 3300rpm, +30psi boost.




OldSkeptic said:


> The other fact was that the 130's (RM-16s) used in the Hornet were 2,000bhp ... at 20lb boost on 100 grade fuel was also amazing



I believe that the 130 series were RM.14SM rated.

But you are correct - an engine originally designe for ~1000hp to be stretched to over 2000hp is impressive.


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## Shortround6 (Sep 15, 2013)

You are pretty much right. The Merlin was R-R's 6th or 7th V-12 aircraft engine (depends if you count the Buzzard and "R" together or separate). For there to be no Merlin R-R has to go out of business. 
Then you have to assume that the air ministry decides they don't want a V-12 built by another company. And assume that the R-R people who worked on the previous engines don't find jobs with the other British engine companies. 
Fairey wanted to become and engine maker. The Air Ministry already had Armstrong, Bristol, Napier, and R-R so they 'discouraged" him. If R-R had gone bankrupt would the Air Ministry just accept 3 suppliers or would they encourage Fairey to take up the slack? 
R-R pretty much had the British V-12 market sewn up. The other companies, while competing with R-R did so not by building competing V-12s but by building alternative engines. If there are no R-R V-12s then do one of more of the existing companies build a V-12 rather than some of the engines they did build? 

AS for the Merlin topping out at 1300hp without Hooker?
The engine for the Speed Spitfire was running at over 1800hp on the test stands before Hooker went to work for R-R. Most of the 2000hp Merlins had about zero effect on the war. 

The two things that allowed the Merlin to go from 1000hp to 2000hp were the better superchargers and the better fuel. without the better fuel the supercharges could only do so much and in fact, without the better fuel there is little point in designing the two stage superchargers. 
It is kind of a chicken and egg thing.


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## OldSkeptic (Sep 15, 2013)

Even with poorer fuel (ie 87 octane) the advantages of increasing the full throttle height with 2 stages would have been worth it, but the boost and hence the power levels would have been lower. Instead of the (approx) 1,700/1,500bhp for the max 1st and 2nd FTHs (most Merlins 60 with 18lb boost) might have been around 1,300 levels with water, 1,150 levels without it.

The estimate of 1,300bhp (and I should have stated that this was the 2nd stage FTH, you would have had more for the lower FTH of course and at 18lb boost) is inferred by comparing pre and post Hooker supercharger Merlins at the same boost. His work added about 150bph at 12lb boost. The gap would have gotten a bit bigger with higher boost levels, because of the better efficiency levels (as you work the supercharger more) and the FTH would have been a bit lower.

Maybe 1,400bhp, as I said an estimate.

Efficiency counts, you compare the 100 series to the 60 series (on a like by like basis), even on the same boost and supercharger size FTH was raised by 1,000ft, just due to the better efficiency.

And Wuzak you are perfectly correct it was the RM-14SM. But they tested the RM-17SM at 2,632 bhp, 3,150 rpm, 36lb boost and water injection.

All of them are amazing numbers of course.

But of course RR's genius was to make an engine capable of those mechanical and thermal loads. All the superchargers in the universe would have been useless if the engine couldn't take that power and be reliable.

North American found that out when testing (post war I think) a very late model 2 stage Allison (forgotten the model number) which had terrible misfiring issues, finally traced to the inlet manifold (unchanged since the first one) being unable to handle the airflows at such pressures and volumes. So there was a lot of work by a lot of people in many different areas getting everything right.


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## wuzak (Sep 15, 2013)

OldSkeptic said:


> And Wuzak you are perfectly correct it was the RM-14SM. But they tested the RM-17SM at 2,632 bhp, 3,150 rpm, 36lb boost and water injection.



And special fuel.




OldSkeptic said:


> But of course RR's genius was to make an engine capable of those mechanical and thermal loads. All the superchargers in the universe would have been useless if the engine couldn't take that power and be reliable.



RR did a lot of testing and strengthening to make it capable of such power.

Another amazing thing, to me, is that lat war Merlins coudl cruise at power levels which were 5 minute ratings in the BoB.


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## OldSkeptic (Sep 15, 2013)

No the 2,600bhp test was on 150 octane, RDE/F/290 (115/150 grade), water injection of course.

Sorry forgot to add the source. The Merlin 100 Series, RR Heritage trust.


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## tomo pauk (Sep 16, 2013)

Good options for the FAA with Merlin absent, anyone?


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## parsifal (Sep 16, 2013)

well the ultimate prop engine for the FAA was the Centaurus, which was ready by 1942 and offered a LOT of power


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## Shortround6 (Sep 16, 2013)

OldSkeptic said:


> Even with poorer fuel (ie 87 octane) the advantages of increasing the full throttle height with 2 stages would have been worth it, but the boost and hence the power levels would have been lower. Instead of the (approx) 1,700/1,500bhp for the max 1st and 2nd FTHs (most Merlins 60 with 18lb boost) might have been around 1,300 levels with water, 1,150 levels without it.



The fuel limits the amount pressure inside the cylinders. with 87 octane the engine was limited to 1030hp at 16250ft _plus_ the power to turn the engine over (friction and pumps) _plus_ the power to run the supercharger. Adding a second stage increases the power to run the supercharger at higher altitudes. The higher the compression of the air, even if limited to 6lbs in the intake manifold heats the intake charge more (6lbs boost[42in] requires the air to be compressed about 2.5 times at 16,000ft. at 23,000ft the air needs to be compressed about 3.5 times) and intercoolers do NOT remove _all_ of the heat. the power to run the second stage has to be subtracted plus the lower density of the intake charge has to be figured in. 
That gives you the "power" of the engine. Now add the weight and bulk of the two stage system and the actual improvement in performance of a fighter is not that great.


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## Aozora (Sep 16, 2013)

I have read somewhere that it took about 200 hp to drive the F.S stage on the Merlin 60/70 series - can anyone confirm this?


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## Shortround6 (Sep 16, 2013)

It depends on the gear ratio.

For the Merlin XX in high (F.S.) it took 219hp at 15,000ft to get 48.24in pressure. 225hp at 20,000ft 48.24in, 202hp at 25,000ft for 42.12in and 167hp at 30,000ft for 34.30in. for the single stage. 

Power required changes with the square of the speed of the impeller. changing from the 6.39 low gear to the 8.03 high gear on some of the two stage engines requires about 57% more power. Changing impeller size without changing gear ratio changes power requirement. 

200hp certainly doesn't seem out of line depending on gear ratio ane model of engine ( The first stage on the P&W R-2800s could take close to 350hp to drive in high gear or caused a 350hp power loss.


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## swampyankee (Sep 16, 2013)

One of the advantages of turbo-chargers is that there is no mechanical connection to the engine, which should, hypothetically, result in greater net output at a given level of boost. While there was an increased pumping loss due to the back pressure resulting from the presence of exhaust turbines, this would probably result in less power loss than the mechanical supercharger.


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## tomo pauk (Sep 16, 2013)

parsifal said:


> well the ultimate prop engine for the FAA was the Centaurus, which was ready by 1942 and offered a LOT of power



Centaurus was indeed a powerful machine, though we need something to propel the fighters (mostly) in the rough 1st half of the ww2. The Peregrine, even if it is updated, would be hard pressed to serve in a 2-seat fighter, so it's either Hercules (from mid 1940?), or updated Buzzard (late 1930's)?


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## Glider (Sep 16, 2013)

I am sure something could have been designed around the Hercules.


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## parsifal (Sep 16, 2013)

Glider said:


> I am sure something could have been designed around the Hercules.



I mentioned this before, but the F5/34 was designed as a long ranged single seat fighter with just 840hp, and a max speed of 316mph. Its almost unfathomable that the RN did not ressurrect this design in 1937 when it finally got control of its own procurement again.

The F5/34 with a Hercules powerplant would have been a formidable carrier fighter. Whilst the hercules was being brought up to speed, it would have been possible to substitute the twin wasp using imported engines until domestic product was developed. 

As I said, it defies logic that this pathway was not followed. The RN convinced itself that it needed a multi role fighter recon which was the basis of the Fulmar. I would defend the Fulmar anytime against its detractors, but 1st line material it was not. A Hercules/twin wasp powered f5/34 would have been as good or better than a Zero if it had been developed.


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## fastmongrel (Sep 17, 2013)

I still think an Alvis Pelides (modified Gnome Rhone 14K) could have been a decent alternative for the Merlin for 1940 and it would have been a good fit for a Glster F5/34. If boot can be applied to Bristol backside pre war then maybe the Hercules could be the Merlin alternative from 1940 but I dont think its going to be any earlier thats why I think the Alvis engine can help hold the fort till the Hercules is ready with a decent supercharger.


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## Shortround6 (Sep 17, 2013)

fastmongrel said:


> I still think an Alvis Pelides (modified Gnome Rhone 14K) could have been a decent alternative for the Merlin for 1940 and it would have been a good fit for a Glster F5/34. If boot can be applied to Bristol backside pre war then maybe the Hercules could be the Merlin alternative from 1940 but I dont think its going to be any earlier thats why I think the Alvis engine can help hold the fort till the Hercules is ready with a decent supercharger.



Alvis Pelides is NOT a substitute for the Merlin. It is may be a substitute for the Armstrong-Siddeley Tiger but that is about it. It needs a total redesign to become a decent engine by 1941-42 standards keeping ONLY the bore/stroke and 14cylinder layout, EVERYTHING else needs to be changed. 

AS for 1940? the engine was rated at 1050hp/ 2150 rpm/37.0in for take off and 1050hp at 2150rpm at 5000ft on 87 octane. It would have offered under 850hp at 15,000ft. 100 octane would have very little effect on power, with no center bearing on the crank it is going to suffer from crankshaft flex if you try boosting the pressure. The same problem that the Tiger suffered from. With the Bristol Mercury already offering 840hp at 14,000ft at 400lbs less weight I don't know why ANY fighter designer would pick the Pelides. The Pelides had passed a 50hr Civil test but only 15 were made and none may have flown. 
The Tiger had passed tests and was used in a several aircraft but had a lot of trouble with it's crankshaft. Perhaps the "boot" should have been applied to Sir Siddeley to put a center bearing in the engine and give Britain the rough equivalent of the R-1830.


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## fastmongrel (Sep 17, 2013)

I wasn't proposing an imperial GR14K as a replacement for the Merlin in 41 that should be a Hercules with a decent supercharger but an engine is needed for 39 and 40 and I think the GR14K could do the job sufficently to hold the line. The best figure i can find for the GR14K weighed 1,190 pounds and put out 1,065 hp at 8,530 feet on French 87 octane. The best pre war Mercury I can find is the Mercury XV weighing 966 pounds and putting out 825 at 14,500 on British 100 octane. Neither engine is a true Merlin replacement but needs must and without something the RAF is stuffed.


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## Aozora (Sep 17, 2013)

fastmongrel said:


> I wasn't proposing an imperial GR14K as a replacement for the Merlin in 41 that should be a Hercules with a decent supercharger but an engine is needed for 39 and 40 and I think the GR14K could do the job sufficently to hold the line. The best figure i can find for the GR14K weighed 1,190 pounds and put out 1,065 hp at 8,530 feet on French 87 octane. The best pre war Mercury I can find is the Mercury XV weighing 966 pounds and putting out 825 at 14,500 on British 100 octane. Neither engine is a true Merlin replacement but needs must and without something the RAF is stuffed.


 
Just found a Flight article from 1937 describing British aero engines British Aero Engines December 2 1937 Flight Archive 
including a rundown of vital statistics: Specifications Flight Archive 

and another 1937 article on the Alvis radial engines 1937 | 0981 | Flight Archive I didn't know they were also working on an 18 cylinder radial, the Alcides. 

Adapting the GR14K to use 100 octane would have potentially yeilded more power; one question is how efficient was the supercharger compared with that of the Hercules? There were two versions with low and medium rated superchargers.


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## Shortround6 (Sep 17, 2013)

The GR14K can't do the job and any attempt to use it means the RAF is stuffed anyway. The Gnome-Rhone company themselves were developing the "N" series engine from 1935 onward and were flying the First "R" series engines in 1940. 
The Alvis engine was sort of a "imperial" mish-mash of the K and N. The N used beefed up crankshaft, crankcase and more fins on the cylinder heads. 

Sources are rather contradictory on the K and N engines but weights generally run between 1200-1500lbs. Engine life at the higher powers is suspect. Please remember that best the Russians got out of this line (the M-88 series) was 1100hp for take-off and _perhaps_ 1000hp at 6000meters using 95 octane fuel and a weight of 1500lbs. Compared to earlier versions the M-88 the 88B had increased ribbing (finning?) on the cylinder barrels and heads, strengthened connecting rods and pistons, modified drives to the units (accessories?) a carburetor with economizer and oil injectors on the crankshaft (?). Of course ALL M-88s used a two speed supercharger drive instead of the single speed used on the parent engines. It took until Nov 1939 for an earlier, lower powered version to pass it's 100 hour test but problems dogged the M-88 (about 100 engines had to be removed from aircraft after flight testing at the aircraft factories) and it's production was suspended in and then resumed in late 1940. Designer Tumanskiy was removed from his post and replaced by E.V. Urmin. 
British quality may well have been better but the basic design seems to have had some fundamental flaws that would take a lot of modification to change. The "K" may have been a decent engine in 1931 when it was introduced (not design started) at 626hp but trying to push the design to 1000hp may have been asking too much. 

The Mercury could pull 840hp at 14,000ft using 87 octane gas from 1935 on (VIII). With 100 octane it couldn't do any better at altitude but picked up power at lower altitudes.


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## Shortround6 (Sep 17, 2013)

Aozora said:


> Adapting the GR14K to use 100 octane would have potentially yeilded more power; one question is how efficient was the supercharger compared with that of the Hercules? There were two versions with low and medium rated superchargers.



The G-R series had the flaw of no center bearing on the crankshaft between the two cylinder rows. Increasing the force acting on the pistons (higher boost and cylinder pressures) is going to result in more crankshaft flex and failed crankshafts or failed bearings or both. The structure of the engine is limit on power with this engine. Please note that the G-R "R" series engine being flown in 1940 DID USE and center bearing but it needed a new crankshaft and crankcase and picked up several hundred pounds in weight.


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## tomo pauk (Sep 17, 2013)

SR6, many thanks again for the great insights. Ditto to aozora.


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## merlin (Sep 17, 2013)

parsifal said:


> I mentioned this before, but the F5/34 was designed as a long ranged single seat fighter with just 840hp, and a max speed of 316mph. Its almost unfathomable that the RN did not ressurrect this design in 1937 when it finally got control of its own procurement again.
> The F5/34 with a Hercules powerplant would have been a formidable carrier fighter. Whilst the hercules was being brought up to speed, it would have been possible to substitute the twin wasp using imported engines until domestic product was developed.
> As I said, it defies logic that this pathway was not followed. The RN convinced itself that it needed a multi role fighter recon which was the basis of the Fulmar. I would defend the Fulmar anytime against its detractors, but 1st line material it was not. A Hercules/twin wasp powered f5/34 would have been as good or better than a Zero if it had been developed.



I agree that the Gloster f.5/34 wold be a prime candidate to take the Twin-Wasp - not different in size weight. However, IMHO I'm not at all convinced it could take the Hercules - both longer and heavier, which will shift the CofG!

I think it's a better aircraft for the Far-East than the RN - see my entry in the Poll for Allied Aircraft in the Far East - last entry goes back to May!


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## Aozora (Sep 17, 2013)

Shortround6 said:


> The G-R series had the flaw of no center bearing on the crankshaft between the two cylinder rows. Increasing the force acting on the pistons (higher boost and cylinder pressures) is going to result in more crankshaft flex and failed crankshafts or failed bearings or both. The structure of the engine is limit on power with this engine. Please note that the G-R "R" series engine being flown in 1940 DID USE and center bearing but it needed a new crankshaft and crankcase and picked up several hundred pounds in weight.


 
No centre bearing?  I can see why the engine wasn't even flown, let alone accepted because the 1937 article doesn't mention that Alvis added a center bearing. So essentially the Pelides might have been a comparative lightweight and used better engineering and materials than the G-R, but it was still seriously flawed. If Alvis continued the practice with the 18 cylinder Alcides. 

Another 1937 Flight article shows how much effort Alvis put into the engines Alvis Engine Testing 1937 Flight Archive


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## Shortround6 (Sep 17, 2013)

The same flaw doomed the Armstrong-Siddeley Tiger, the first production engine to use a 2 speed supercharger. Even the earlier and smaller Jaguar and Panther had problems but what you can get away with in 400-600hp 14 cylinder engines is not what you can get away with when you try for 900-1100hp. 

I would also note that the 1190lb weight given in some of these tables is for a direct drive engine, Prop turns the same speed as the engine.


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