Early Mustangs-performance/experience?

Shortround6 · Dec 13, 2017

Tomo is correct. The Merlin fell into a most useful size/catagory of engine. The only other large piston engine engine to be made in larger numbers was the P & W R-1830.
The Allison, Merlin, DB 600/1 and Jumo 211 all being similar in size, weight and power in the late 30s.
Most radial engine makers were trying for 1000-1300hp at the time. Engines like the R-2600 and R-2800 were sort of the exception.

The British were in a bit of bind, They had a bunch of 800-1000hp engines which were too small to do the jobs wanted (even in 1938-39) and the "super" engines (1800-2000hp) were too far in the future. Only other medium engine was the Hercules and a discreet veil will be pulled over it's suitability for mass production in the late 30s, as well as the suitability of the 3 super engines.

I would also note that the Merlin was being made by the hundreds when the Allison was only a bit better than tool room samples.
14 engines delivered in 1938 and 46 in 1939. They did build 1175 in 1940.

pbehn · Dec 13, 2017

tomo pauk said:
I hear what you are saying.
However, IMO, there is quite a long distance between statement 'The UK went from planning to phase out the Merlin to making the MErlin the main engine on most front line bombers and fighters' and 'The Typhoon prototype had already been delayed by then, the Halifax had already had its engines re specified in 1937.' I'd like to know who said that UK was planning to phase out Merlin, and in what year.
The Air Ministry of the UK knew before the war that they will eventually phase out the Merlin, but with commitment to mass production much before BoB, that phasing out was not a matter of months, but years.

The Manchester was to have Vulture engines, which it did, replaced by the Lancaster with the Merlin.
The Halifax was to have Sabre engines, redesigned with the Merlin
Along with the Stirling no UK heavy bomber was originally due to have Merlin engines,
The Hurricane was only seen as a stop gap, the Typhoon Tornado were to replace it.
In 1940 the Mosquito was a design project as was the Mustang.

Prior to war being declared the Merlin had no future in long term planning but the failure of other engines declaration of war quickly changed things. The UK was obviously planning to phase out the Merlin because in 1937 all its new designs used other types. In 1939 a total 1960 Tornados were ordered only 1 flew. The Typhoon was delayed due to problems with the Sabre engine then pushed into service too quickly. The Merlin factories you describe in UK would certainly have been making Vultures and possibly Sabres if they could have been proved to work, they were financed by the UK government. This is a different issue to my original point that the Merlin was designed in peacetime for orders of 100s for the Defiant Battle Spitfire and Hurricane.

pbehn · Dec 13, 2017

Shortround6 said:
Tomo is correct. The Merlin fell into a most useful size/catagory of engine. The only other large piston engine engine to be made in larger numbers was the P & W R-1830.
The Allison, Merlin, DB 600/1 and Jumo 211 all being similar in size, weight and power in the late 30s.
Most radial engine makers were trying for 1000-1300hp at the time. Engines like the R-2600 and R-2800 were sort of the exception.

The British were in a bit of bind, They had a bunch of 800-1000hp engines which were too small to do the jobs wanted (even in 1938-39) and the "super" engines (1800-2000hp) were too far in the future. Only other medium engine was the Hercules and a discreet veil will be pulled over it's suitability for mass production in the late 30s, as well as the suitability of the 3 super engines.

I would also note that the Merlin was being made by the hundreds when the Allison was only a bit better than tool room samples.
14 engines delivered in 1938 and 46 in 1939. They did build 1175 in 1940.

My point was the production figures the Merlin was built around, if Rolls Royce had known that they were designing an engine that would be produced in 150,000 units they would have designed it in a different way, as car manufacturers they were and are high cost/ low volume it only passed producing 4000 cars per year in 2015. Allison made 1175 engines in 1940, what was the size of the order because at that time the P40 was one of the few US planes in the game and at the time the USA was not actually at war.

Shortround6 · Dec 13, 2017

pbehn said:
Allison made 1175 engines in 1940, what was the size of the order because at that time the P40 was one of the few US planes in the game and at the time the USA was not actually at war.

Of those 1175 engines, 833 went to the British (British had taken over ex French orders in addition to their own) 342 went to the Americans.

Americans had ordered over 837 in June of 1939. They deferred some deliveries of both engines and airframes to speed up the delivers to the British.

Point is that the Allison, despite being started in 1930, was in terms of production, a later engine than the Merlin. Allison had 3 factories, #1 was little more than an experimental shop. #2 was in started 1936 and dedicated May 30th 1937 with an production capacity of 100 engines a YEAR (perhaps only one shift?).
#3 broke ground on May 30th 1939 with a planned capacity of 75 engines a month. Plant #3 was to comprise 390,000 sq ft. By June 1943 Allison was using over 3 million sq ft of plant area and this does not include the sub contractors.

Please note that all was NOT smooth sailing. They redesigned the crankshaft in March 1940 and then the lubrication system in April 1940 in order to solve connecting rod bearing failures. Until already produced engines could be brought back to the factory and reworked they were derated to 950hp.

Please note that RR was getting the Merlin XX into production at this time which may also explain the US interest in the Merlin engine just a few months later.

I would also point out that the Allison was also an interim engine. Army projects being designed around the Continental 1430 engine, the P&W X1800 and the Wright R-2160 Tornado in 1938-41. Unfortunately for the Army these all crapped out worse than any of the British engines.

wuzak · Dec 13, 2017

pbehn said:
The Manchester was to have Vulture engines, which it did, replaced by the Lancaster with the Merlin.
The Halifax was to have Sabre engines, redesigned with the Merlin
Along with the Stirling no UK heavy bomber was originally due to have Merlin engines,
The Hurricane was only seen as a stop gap, the Typhoon Tornado were to replace it.
In 1940 the Mosquito was a design project as was the Mustang.

Yes, the Manchester was designed around the Vulture. Other Manchester versions were to have the Sabre or the Centaurus.
The HP.56 was supposed to have the Vulture. None were built. HP lobbied to change to the 4 engine HP.57 Halifax, which was designed for the Merlin from the outset.
Note that at that time the Vulture was early in its development life.

The Hurricane was not seen as a stop gap. It was the front line fighter, development starting in 1934. The Typhoon/Tornado development was started in 1938 and was intended to replace the Hurricane and Spitfire. It was not uncommon for the RAF/Air Ministry to look for a successor to an aircraft just entering service.

The Lancaster program came together as quickly as it did because Rolls-Royce had developed the power egg for the Beaufighter.

Note that the Griffon was a supplement to the Merlin, not a replacement. The Griffon may well have dropped off the production list in 1940/41 if someone hadn't figured out that it could fit in a Spitfire.

This is a list of prototype or production aircraft using the Merlin that were developed before 1940 and flew before, or during 1940.
Armstrong Whitworth Whitley
Boulton Paul Defiant
Bristol Beaufighter II
Fairey Barracuda
Fairey Battle
Fairey Fulmar
Fairey P.4/34
Handley Page Halifax
Hawker Henley
Hawker Hotspur
Hawker Hurricane
Supermarine Type 322
Supermarine Spitfire
Vickers Wellington Mk II and Mk VI

Note also that one of the compeitoprs to the Hawker Typhoon/Tornado were the Supermarine Type 324/325/327, which was to use, as first choice, two Merlins.

pbehn · Dec 14, 2017

The Merlin was designed in peace time as a private venture. Other RR engines like the Kestrel sold 4,750 units while the Peregrine sold 300. Other successful designs between the wars like Bristols Mercury sold 20,000. There was simply no basis for designing or modifying an engine for production of 150,000 units especially since Rolls Royce themselves were working on its replacement. Things moved increasingly quickly as war loomed and contingencies were made, factories built etc but things really changed in 1939 when war was a fact. They changed still further in 1940 when France fell after the RAF lost a lot of Hurricanes there. Then the Battle of Britain started and the Ministry of aircraft production was formed. Despite a massive increase in production losses to all causes meant front line strength rose slightly. This combined with Lancaster and Halifax production starting meant a huge and uncertain rise in the need for Merlin engines, and a panic in case a factory was hit.

wuzak · Dec 14, 2017

pbehn said:
The Merlin was designed in peace time as a private venture. Other RR engines like the Kestrel sold 4,750 units while the Peregrine sold 300. Other successful designs between the wars like Bristols Mercury sold 20,000. There was simply no basis for designing or modifying an engine for production of 150,000 units especially since Rolls Royce themselves were working on its replacement. Things moved increasingly quickly as war loomed and contingencies were made, factories built etc but things really changed in 1939 when war was a fact. They changed still further in 1940 when France fell after the RAF lost a lot of Hurricanes there. Then the Battle of Britain started and the Ministry of aircraft production was formed. Despite a massive increase in production losses to all causes meant front line strength rose slightly. This combined with Lancaster and Halifax production starting meant a huge and uncertain rise in the need for Merlin engines, and a panic in case a factory was hit.

The Vulture was not a replacement for the Merlin - they were in two different power classes.

The Griffon was not a replacement for the Merlin. It was a supplement, originally intended for naval aircraft. Its design only started in 1938.

pbehn · Dec 14, 2017

wuzak said:
The Vulture was not a replacement for the Merlin - they were in two different power classes.

The Griffon was not a replacement for the Merlin. It was a supplement, originally intended for naval aircraft. Its design only started in 1938.

The Spitfire and Hurricane were to be replaced by the Typhoon/Tornado that is no Merlins in fighters All heavy bombers were originally specified with engines other than the Merlin. All the cases quoted where other uses were found were as a result of the Sabre and Vulture running into problems.

At the time of the Merlins original design no one could have foreseen a situation where the Merlin could have the same power output as the Vulture but that is approximately what happened with the de rating of the Vulture and the introduction of the Merlin XX. That was my original point.

Shortround6 · Dec 14, 2017

That may be true but that is the case in many other nations. Most engines of the early to mid 30s were considered too small by even 1940.
However most of the replacements failed. Some more spectacularly than others. Also France was knocked out of the race early and Italy didn't have the engineering capacity to bring any of the large engines to production status (at least in reliable form).

A lot depended on fuel and in the 1935-38 time period a lot of companies/designers were trying to design engines that would make big power on 87 octane fuel. Some were working with 100 octane (but not 100/120 let alone 100/130) and a lot of the engine designs reflect that. Without the ability to use high boost they were left with either large displacement or high rpm or a combination, lots of cylinders for displacement and small cylinders for High RPM.

Once the fuel supports more than 6-8bs of boost (and the 7-8lb level needed small cylinders and/or sleeve valves) a lot of these complicated engines lost their appeal.
The problems with vibration, lubrication and heat dissipation were vastly underestimated with most of these engines.
Even the Merlin XX as originally produced was not a substitute for the Vulture. That took uprating that depended on better fuel.

pbehn · Dec 14, 2017

Shortround6 said:
That may be true but that is the case in many other nations. Most engines of the early to mid 30s were considered too small by even 1940.
However most of the replacements failed. Some more spectacularly than others. Also France was knocked out of the race early and Italy didn't have the engineering capacity to bring any of the large engines to production status (at least in reliable form).

A lot depended on fuel and in the 1935-38 time period a lot of companies/designers were trying to design engines that would make big power on 87 octane fuel. Some were working with 100 octane (but not 100/120 let alone 100/130) and a lot of the engine designs reflect that. Without the ability to use high boost they were left with either large displacement or high rpm or a combination, lots of cylinders for displacement and small cylinders for High RPM.

Once the fuel supports more than 6-8bs of boost (and the 7-8lb level needed small cylinders and/or sleeve valves) a lot of these complicated engines lost their appeal.
The problems with vibration, lubrication and heat dissipation were vastly underestimated with most of these engines.
Even the Merlin XX as originally produced was not a substitute for the Vulture. That took uprating that depended on better fuel.

I am sure there is a library of books on the situation political, military and technical on the situation as it developed between 1936 and 1940. Even on Wikipedia there is a change on almost all types in this period. For me I believe that the performance of the "Racing Merlin" in the "Speed Spitfire" pointed another way. That is that it is the volume of gas/fuel mixture that is important not the swept volume of the engine. There were changes to the Merlin engine block as it developed but they were of little importance compared to the developments in fuels and supercharging. None of this could or was foreseen at the start of the Merlin programme, for an engine in that period to be developed and used for a front line fighter (Hornet) more than a decade later was unprecedented.

wuzak · Dec 14, 2017

The changes to the Merlin block were of high importance,as they allowed greater reliability and the strength to cope with boost levels.

And while it is true that the air flow was important, there is only so much boost an engine can take without combustion issues. Then the engine's rpm has to be increased to keep up with the airflow requirements, and this too had its natural limits (and why crankshafts and rods, for example, were evolved).

pbehn · Dec 14, 2017

wuzak said:
The changes to the Merlin block were of high importance,as they allowed greater reliability and the strength to cope with boost levels.

And while it is true that the air flow was important, there is only so much boost an engine can take without combustion issues. Then the engine's rpm has to be increased to keep up with the airflow requirements, and this too had its natural limits (and why crankshafts and rods, for example, were evolved).

That again was my point, the changes to the engine block were for reliability, the ability to develop more power was from fuel and supercharger improvements. This was an ongoing issue in engine development. A few decades later 1.5 Litre turbo engines would be developing 1,350 BHP in formula1 However that was just in qualification, a maximum of 6 minutes running time.

Shortround6 · Dec 14, 2017

The Speed Spitfire and the Racing Merlin used one of Rod Bank's special "brews" but the ability to run at 1600hp for ten hours on the test stand pointed to the fact that should better fuel become available the basic Merlin engine could handle a much higher power level than was being used in service engines without extensive work ( something that could not be said for some other engines). This must have been some comfort (or provided some breathing room) as the replacement engines stumbled and fell.
Again I am not picking on the British.
The two American hyper engines depended on high rpm to try to make up for small displacement. The Continental was enlarged to 1430 cu in (still too small) and the Lycoming company gave up and stuck two engines together to make a 2470 cu in 24 cylinder engine. The Wright Tornado use 42 cylinders to get 2160 cu in but went to 4150 rpm for peak power. The small cylinders kept the piston speed down but still?????
Many US aircraft projects had to switch from engine to engine as these "wonder" engines slid down the slope of Thomas Crapper's device.

pbehn · Dec 14, 2017

Shortround6 said:
The Speed Spitfire and the Racing Merlin used one of Rod Bank's special "brews" but the ability to run at 1600hp for ten hours on the test stand pointed to the fact that should better fuel become available the basic Merlin engine could handle a much higher power level than was being used in service engines without extensive work ( something that could not be said for some other engines). This must have been some comfort (or provided some breathing room) as the replacement engines stumbled and fell.
Again I am not picking on the British.
The two American hyper engines depended on high rpm to try to make up for small displacement. The Continental was enlarged to 1430 cu in (still too small) and the Lycoming company gave up and stuck two engines together to make a 2470 cu in 24 cylinder engine. The Wright Tornado use 42 cylinders to get 2160 cu in but went to 4150 rpm for peak power. The small cylinders kept the piston speed down but still?????
Many US aircraft projects had to switch from engine to engine as these "wonder" engines slid down the slope of Thomas Crapper's device.

I didn't suggest that you were picking on the British, I wouldn't because I have read your posts for a long time. I remember in when Honda were trying to develop a 500cc four stroke racer to compete with the two strokes they had a V4 eight valve per cylinder that revved to 22,000 RPM and an engineer said "It is OK getting the engine to rev up to that speed but the problem is getting it to produce power". In some respects the tuning a supercharged engine runs counter to the technology and science of conventionally aspirated engines.

Honda NR500 - Wikipedia

wuzak · Dec 14, 2017

pbehn said:
My point was the production figures the Merlin was built around, if Rolls Royce had known that they were designing an engine that would be produced in 150,000 units they would have designed it in a different way, as car manufacturers they were and are high cost/ low volume it only passed producing 4000 cars per year in 2015.

When the Merlin was initially designed it was for British military aircraft, At that time (early '30s) there wasn't going to be a huge market for aero engines.

The Vulture, Peregrine and Griffon, all of which made production, were designed along much the same principles as the Merlin.

They were not designed with any more consideration for quantity production.

Factories were being built for the Merlin. Licence production suppliers were sought for the Merlin.

Changing these in favour of the Vulture or Sabre would not be a simple thing to do, and it would certainly cost many months of production.

As far as I know, no additional facilities were sought or obtained for the Vulture or Sabre.

pbehn · Dec 14, 2017

wuzak said:
When the Merlin was initially designed it was for British military aircraft, At that time (early '30s) there wasn't going to be a huge market for aero engines.

The Vulture, Peregrine and Griffon, all of which made production, were designed along much the same principles as the Merlin.

They were not designed with any more consideration for quantity production.

Factories were being built for the Merlin. Licence production suppliers were sought for the Merlin.

Changing these in favour of the Vulture or Sabre would not be a simple thing to do, and it would certainly cost many months of production.

As far as I know, no additional facilities were sought or obtained for the Vulture or Sabre.

As far as I know it was the other way around, if it wasn't the other way around then the whole Typhoon Tornado Manchester programme makes no sense. The Vulture and Sabre were supposed to replace the Merlin but couldn't so the Merlin was developed further. No additional facilities were sought for either engine because they didn't deliver, they were both de rated at the start, the Vulture in service and the Sabre in its prototype version. That is purely in power output, the comparison in reliability was another issue.

Shortround6 · Dec 14, 2017

I would note that at the time. late 1930s, many aircraft engines exceeded the power to weight ratio of many car racing engines.

For instance the Mercedes 1939 Grand Prix engine was a 3 liter (181 cubic in) engine that made 485hp at 7,500rpm but weighed 603lbs.
It used two stage supercharging at 2.31 Atm manifold pressure and the fuel was 86% methanol, 4.45 nitrobenzol 8.8%acetone and 0.8% sulphuric ether.

Granted there is some economy of scale but most large aircraft engines were in a pretty high state of "tune" considering their weight.

pbehn · Dec 14, 2017

Shortround6 said:
I would note that at the time. late 1930s, many aircraft engines exceeded the power to weight ratio of many car racing engines.

For instance the Mercedes 1939 Grand Prix engine was a 3 liter (181 cubic in) engine that made 485hp at 7,500rpm but weighed 603lbs.
It used two stage supercharging at 2.31 Atm manifold pressure and the fuel was 86% methanol, 4.45 nitrobenzol 8.8%acetone and 0.8% sulphuric ether.

Granted there is some economy of scale but most large aircraft engines were in a pretty high state of "tune" considering their weight.

I agree, which is why producing 150,000 F1 engines was a considerable achievement considering they were used in aircraft and needed a major overhaul after 250 hours, that is more than a Grand Prix season.

EKB · Dec 20, 2017

Re: Rolls Royce Merlin XX / Merlin 45 / Packard V-1650-1 / Allison V-1710-81/85

A P-40F with a Packard Merlin XX engine was heavy, at about 8,500 lbs. for take-off. The Kittyhawk II with British spec changes weighed about 9,000 lbs. with a normal service load. Either way the rate of climb was poor and service ceiling was below 35,000 feet during U.S. and U.K. government trials.

That does not read like a missed opportunity.

In any case a Mustang with a Merlin XX would have been heavier still, and would not have climbed higher than a P-39N, P-40N or P-51A.

The supposed performance gain of the Merlin XX was brought into question after the A&AEE used a Hurricane for trial installation with the Merlin 45 engine. This airplane easily out-climbed a standard production model with a Merlin XX. Hurricane P3157 (Merlin 45) climbed to 20,000 feet in 7.1 minutes, compared to a best time of 8.5 minutes by Hurricane Z3564 (Merlin XX). The take-off weights were 6,685 lbs. (P3157) and 7,397 lbs. (Z3564).

The Merlin 45 weighed less, consumed less fuel, had fewer moving parts, and returned a lower build and maintenance cost than the Merlin XX. It's no surprise that the RAF made the Merlin 40 series standard for Spitfires until the 60 series was available.

The Allison engine held a big advantage at forward airstrips because of the down draft carburetor, with the air scoop being on top of the engine nacelle. The RAF Desert Air Force and USAAF reported that the V-1710 ran dependably with the air cleaner removed, for the purpose of increasing power.

The Merlin used an updraft carburetor setup that ingested dirt and sand like a vacuum cleaner. Taking out the air cleaner was attempted, but doing so ruined the Merlin quickly. The engine nacelles of many RAF planes were retrofitted with tropical air intakes but the Kittyhawk II was not one of them.

Shortround6 · Dec 20, 2017

EKB said:
The supposed performance gain of the Merlin XX was brought into question after the A&AEE used a Hurricane for trial installation with the Merlin 45 engine. This airplane easily out-climbed a standard production model with a Merlin XX. Hurricane P3157 (Merlin 45) climbed to 20,000 feet in 7.1 minutes, compared to a best time of 8.5 minutes by Hurricane Z3564 (Merlin XX). The take-off weights were 6,685 lbs. (P3157) and 7,397 lbs. (Z3564).

Well something doesn't smell right about this.
According to most sources the difference in weight between the Merlin 45 and the Merlin XX was about 25-30lbs not 700lbs. Hurricane Z3564 was used for a number of tests but it was a IIb with 12 machineguns.
Was Hurricane P3157 similarly equipped? (roughly 200lbs for the extra 4 guns and ammo over a MK IIa)
One book claims a 490lb difference between a IIa and IIb just at empty weight (tare) without guns installed and both would have Merlin XX engines.

In Fact Hurricane P3157 seems to be a Hurricane I from Gloster's first production block of 500 aircraft. Not saying it wasn't later used for test purposes but
something seems a bit dodgy comparing these two aircraft.

Early Mustangs-performance/experience?

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