WW2 Without the Merlin: Options for the British

[wuzak]

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.

 

[Shortround6]

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.

 

[wuzak]

True.

Most on that list were late or had development difficulties.

 

[tomo pauk]

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

 

[wuzak]

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.

 

[GregP]

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.

 

[wuzak]

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).

 

[GregP]

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?"

 

[tomo pauk]

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.

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...

 

[Shortround6]

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.

 

[tomo pauk]

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?

 

[Shortround6]

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.

 

[tomo pauk]

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.

 

[Readie]

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

 

[stona]

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

 

[Shortround6]

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.

 

[gjs238]

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.

 

[Shortround6]

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.

 

[wuzak]

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.

 

[wuzak]

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.