WW2 Without the Merlin: Options for the British

[fastmongrel]

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.

 

[wuzak]

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

 

[tomo pauk]

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?

 

[fastmongrel]

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.

 

[yulzari]

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).

 

[Shortround6]

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???

 

[wuzak]

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.

 

[Shortround6]

My apologies.

 

[wuzak]

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").

 

[The Basket]

Hispano Suiza 12Y

 

[tomo pauk]

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.

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

 

[yulzari]

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.

 

[Shortround6]

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).

 

[Shortround6]

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.

 

[tomo pauk]

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?
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.

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?

 

[OldSkeptic]

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 ....

 

[swampyankee]

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..

 

[tomo pauk]

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 ....

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?

 

[fastmongrel]

Britain lose the BoB and, quite possibly gets invaded,

Only if the German Army can march to Britain

 

[swampyankee]

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.