Me109F vs Spitfire MkV

[Lunatic]

Also there is an advantage in being able to feel your way to the target, firing at longer range and working the guns onto the target.

The 20mm of the 109 had further range than the M2HB.

That is just flat wrong Schwartz. Tell me how does a round fired at 765 m/s (or even 800), with sectional density of about 2.6 g/sq-mm and a blunt nose have longer range than a round fired at 915 m/s with a sectional density of 3.83 g/sq-mm and nearly perfect ballistic shape? Answer: It can't.

A tactic used was to stand-off from the B17's (sans escorts!) lobbing cannon rounds.

This was tried, but not with the MG151/20. The MK103 30mm and BK50 50mm cannon were tried for stand-off attacks, but this proved ineffective. First the interceptor could not hit the target at that range. Second, .50's firng backwards toward the trailing fighter could indeed reach it even at ranges exceeding 3000 feet. The stand-off attacking fighter was usually a Bf-110 or similar aircraft and it was making no attempt at evasion as it was aiming.

The 20mm German round is used in high-end modern sniper rifles, I doubt it was so bad.

Where do you get this from? The MG151/20 ammo is not used in any modern gun, and was never used in any sniper rifle.

Anyone who has any experience with firing a .50 at vehicles can just imagine what 8 x .50's would do to the wing of a B-17.

With API yes, but not without.

Why? Even with ball ammo the P-47 puts out a wopping 100-120 rounds per second. This is more than enough to rip the wing right off a B-17. And Ball ammo was never used in combat, it would either be M8 API or a mix of M1 Incendiary and M2 AP rounds depending on the year.

Or the Merlin, radar etc

US radar was not derived from British radar. In the end, the British used mostly American designed radar equipment. The USN developed by far the best radar in the world and it was not based upon British help of any kind.

The Packard Merlin was produced as much for the Britiish as for the USA. Lancasters and Spitfires were powered by Packard Merlins, and even many of the later RR Merlins were built partially from US parts. Had the Merlin not been produced the odds are either a 2nd supercharger stage or a turbocharger stage would have been added to the Allison powered Mustang, or the Hyper-Engine would have been completed. Or the P-51 would have been bypassed in favor of an R-2800 powered design such as the P-47N (earlier) or the F4U for Europe.

Against bombers... well it's hard to argue against the MK108!

What about the MK103, MK213 and R4M?

The MK213 is a revolver-cannon which never saw service in WWII, and thus is irrelevent to this discussion.

The R4M was of qestionable value in actual combat. Hitting bombers with undguided rockets was very difficult.

The MK103 RoF was just too slow (360-420 rpm), it was too heavy (141 KG, the .50 M2 by comparison weighed 29KG), and the recoil made it ineffective when mounted on a single engine fighter (only a handful of FW's were tried with this armament). It was found that a fighter could carry twice as many MK108's as MK103's, and these would put out 3 times as many rounds per second without the recoil problems of the MK103, and would land more hits on target per attack run. So the MK108 beat the MK103 in actual practice.

=S=

Lunatic

 

[DerAdlerIstGelandet]

I was thinking about the Incendiary part, for the fuel tanks.

I think normal rounds have less range?

IIRC the .50 was developed from a Boys-type anti-tank rifle round?

No actually regular Ball ammo will do just fine in tearing through the skin of a B-17 and in fact will do the same in igniting the fuel tanks.

 

[Hop]

US radar was not derived from British radar. In the end, the British used mostly American designed radar equipment. The USN developed by far the best radar in the world and it was not based upon British help of any kind.

Magnetron?

The vast majority of US radar sets were based around the British cavity magnetron.

Had the Merlin not been produced the odds are either a 2nd supercharger stage or a turbocharger stage would have been added to the Allison powered Mustang

Allison continued to develop a second stage for the V-1710, it wasn't ready until the end of the war.

 

[Nonskimmer]

True enough about the cavity magnetron. It was a British development. Developed at Birmingham University in 1940 I believe, under the supervision of an Australian physicist. But the first magnetron was actually American.

 

[Hop]

The first magnetron was developed in the early 20s by an American named Hull. A German radar researcher called Holmann also patented his designs in the mid 30s.

But none of these were much use for radar. Indeed Hollmann and several German teams worked for years to develop centimetric radar using magnetrons, they eventually gave up. It wasn't until an RAF bomber carrying H2S radar crashed near Rotterdam, and it's magnetron recovered, that they restarted their work. Germany simply copied the British magnetron and used it in some of their late war radars.

Likewise the Americans didnt have any way of generating high power microwaves for radar, until they were given a British magnetron.

Just because there were earlier magnetrons, doesn't mean they were capable of generating short wavelengths at sufficient power, with sufficient stability.

Certainly during WW2, the only successful centimetric radars were all built around Randall and Boot's magnetron design.

 

[Lunatic]

US radar was not derived from British radar. In the end, the British used mostly American designed radar equipment. The USN developed by far the best radar in the world and it was not based upon British help of any kind.

Magnetron?

The vast majority of US radar sets were based around the British cavity magnetron.

And the cavity magnitron was based upon American inventions in the field.
And the cavity magnitron was also independantly developed in the USA, I believe in 1934 or so. The tech was there already, and if you investigate it you will see there was very little of British orgin in the USN radar program.

I posted in detail on this subject last spring sometime. The idea that the US was beholding to Britian for radar is largely a myth. Tech in this arena went back and forth fairly freely between the two countries in the 30's and the likelyhood is neither would have developed radar w/o the other. It's kind of hard to make a cavity magnitron without a magnitron

One thing is totally clear, by 1943 the US had the lead in radar tech and never lost it.

Had the Merlin not been produced the odds are either a 2nd supercharger stage or a turbocharger stage would have been added to the Allison powered Mustang

Allison continued to develop a second stage for the V-1710, it wasn't ready until the end of the war.

Yes but that is because Allision had to do it w/o the enthusiastic support of the War Department. W/o the Merlin, the situation would have been very different. And the turbo-supercharger stage was ready in 1940 anyway.

In genral, by 1944 the US had determined that radial engines were the better choice for fighters anyway. And for these both the turbo supercharger and 2 stage superchargers were well developed.

=S=

Lunatic

 

[Soren]

Oh dear.... the Bias on this page is very present...

 

[schwarzpanzer]

That is just flat wrong Schwartz. Tell me how does a round fired at 765 m/s (or even 800), with sectional density of about 2.6 g/sq-mm and a blunt nose have longer range than a round fired at 915 m/s with a sectional density of 3.83 g/sq-mm and nearly perfect ballistic shape? Answer: It can't.

The .50 was developed from a WW1 German round, the German enineers didn't work backwards?

I'm pretty sure the Me109 cannon had a super-long barrel?

This was tried, but not with the MG151/20. The MK103 30mm and BK50 50mm cannon were tried for stand-off attacks, but this proved ineffective. First the interceptor could not hit the target at that range. Second, .50's firng backwards toward the trailing fighter could indeed reach it even at ranges exceeding 3000 feet. The stand-off attacking fighter was usually a Bf-110 or similar aircraft and it was making no attempt at evasion as it was aiming.

It was a Me109, so I'd reckon so?

I'll try and find an article.

Where do you get this from? The MG151/20 ammo is not used in any modern gun, and was never used in any sniper rifle.

Don't be so sure!

These two versions had slightly different applications: 20mm version, built around WW2-era German MG-151 aircraft gun round, can deliver high explosive, fragmentation or incendiary shells with good accuracy, so a relatively "soft" targets could be disabled by the blast and / or fragments. When the long range and armor penetration is an issue, the 14.5mm version comes into the play. It is built around another WW2-era round, Soviet 14.5mm high velocity, armor-piercing cartridge, developed for PTRD and PTRS anti-tank rifles

http://world.guns.ru/sniper/sn55-e.htm

I kinda see your point, however as an aircraft armament:

While probably not so accurate as the specially developed .50BMG (12.7x99mm) rifles, mostly due to unavailability of the "match grade" ammunition in the 14.5mm and 20mm, NTW-20 offers significantly more terminal effectiveness than any .50BMG rifle / round combination. 20 mm version could be most effective against targets like parked aircrafts and helicopters, command and communications equipment, radar cabins, fuel dumps, unarmored cars.

So given the choice, I'd have the 20mm.


Thanks for all info on the big-fifty ammo, was there any rounds similar to the German APHE?

R-2800

Nice engine! 8)

Had the Merlin not been produced the odds are either a 2nd supercharger stage or a turbocharger stage would have been added to the Allison powered Mustang

May not have been so easy...

e.g how big were the inlet ports etc?


Thanks for the info on the Mk103 also.

In genral, by 1944 the US had determined that radial engines were the better choice for fighters anyway. And for these both the turbo supercharger and 2 stage superchargers were well developed.

Yes and in general, by 1944 the UK had determined that jet engines were better for fighters!

 

[wmaxt]

Had the Merlin not been produced the odds are either a 2nd supercharger stage or a turbocharger stage would have been added to the Allison powered Mustang

May not have been so easy...

e.g how big were the inlet ports etc?

They, Allisons, were already turbo charged which is actually harder than mechanical supercharging. The Merlin was never successfuly turbocharged.

I do object to the hyped up Mustang, which had actualy been dropped from production for three months. The timing of the Merlin prototypes only gave it a limited reprive through early '43. If the realization that its range could be extended both allowing it to be an escort and that escorts were required, had come as little as two months later the P-51 as we know it would never have existed.

wmaxt

 

[Lunatic]

That is just flat wrong Schwartz. Tell me how does a round fired at 765 m/s (or even 800), with sectional density of about 2.6 g/sq-mm and a blunt nose have longer range than a round fired at 915 m/s with a sectional density of 3.83 g/sq-mm and nearly perfect ballistic shape? Answer: It can't.

The .50 was developed from a WW1 German round, the German enineers didn't work backwards?

Huh? First off I've never seen anything that indicates the .50 was developed from a German round. Second, German engineers had to make compromises - if they wanted an explosive round they needed to put a fuse in the round, preferably in the tip. If they put a fuse in the tip (using the tech available at the time) the tip would have to be flat. If they wanted to maximize the capacity of the round for a given projectile length it would have to be fatter futher forward than the optimal ogive shape used in the .50. Trade-offs are common in engineering.

I'm pretty sure the Me109 cannon had a super-long barrel?

No. The ShVAK engine cannon did have a longer barrel, but the MG151/20 did not.

This was tried, but not with the MG151/20. The MK103 30mm and BK50 50mm cannon were tried for stand-off attacks, but this proved ineffective. First the interceptor could not hit the target at that range. Second, .50's firng backwards toward the trailing fighter could indeed reach it even at ranges exceeding 3000 feet. The stand-off attacking fighter was usually a Bf-110 or similar aircraft and it was making no attempt at evasion as it was aiming.

It was a Me109, so I'd reckon so?

I'll try and find an article.

Good luck

Where do you get this from? The MG151/20 ammo is not used in any modern gun, and was never used in any sniper rifle.

Don't be so sure!

These two versions had slightly different applications: 20mm version, built around WW2-era German MG-151 aircraft gun round, can deliver high explosive, fragmentation or incendiary shells with good accuracy, so a relatively "soft" targets could be disabled by the blast and / or fragments. When the long range and armor penetration is an issue, the 14.5mm version comes into the play. It is built around another WW2-era round, Soviet 14.5mm high velocity, armor-piercing cartridge, developed for PTRD and PTRS anti-tank rifles

http://world.guns.ru/sniper/sn55-e.htm

Umm... nowhere does this indicate the mine type round is being used. Nor does it indicate that the rounds have not been updated to use more modern fuse technology (which allows a pointed tip).

I kinda see your point, however as an aircraft armament:

While probably not so accurate as the specially developed .50BMG (12.7x99mm) rifles, mostly due to unavailability of the "match grade" ammunition in the 14.5mm and 20mm, NTW-20 offers significantly more terminal effectiveness than any .50BMG rifle / round combination. 20 mm version could be most effective against targets like parked aircrafts and helicopters, command and communications equipment, radar cabins, fuel dumps, unarmored cars.

So given the choice, I'd have the 20mm.

Sure, if you only can shoot one round! But tell me, would you rather have one shot with that 20mm, or 6-7 shots with the .50? Lets suppose the odds of hittng on any given shot are about 1:3, and the odds of destroying the target with the 20mm are 1:1 and the odds of destroying it with the .50 are 1:2. ????

Thanks for all info on the big-fifty ammo, was there any rounds similar to the German APHE?

Yes there were some experiments with HE rounds. However, the amount of HE that can be packed into a ~13mm round is insufficient to do much damage, and because the weight of the HE is so much lower than that of steel or lead the mass (and thus ballistic properties) are greatly effected. In the end it was determined that the IM11 incendiary metal composition was the best choice, as a small amount would do the trick. The cost to go from BALL/AP ammo to API ammo in terms of mass is only about 10% at the .50 calibur level.

The German 13mm HE/I rounds were generally not very effective. The very small HE payload just wasn't enough to do serious damage.

Had the Merlin not been produced the odds are either a 2nd supercharger stage or a turbocharger stage would have been added to the Allison powered Mustang

May not have been so easy...

e.g how big were the inlet ports etc?

If it could accomodate a Turbo-supercharger it could accomodate a two stage supercharger.

Thanks for the info on the Mk103 also.

In genral, by 1944 the US had determined that radial engines were the better choice for fighters anyway. And for these both the turbo supercharger and 2 stage superchargers were well developed.

Yes and in general, by 1944 the UK had determined that jet engines were better for fighters!

Neither Britain nor Germany could build jet engines for war in 1944 or 1945.

BTW: I was mistaken, the best case MV of the MG151/20 mine round was 785 m/s, not 765 m/s as I stated before. However, the typical case velocity (as presented for the Hispano and .50 BMG) was only 755 m/s.

Here is my old gun page. Actually, it's not complete, somehow long ago it got messed up and I've posted it only for the tables. Note most of the discussion has to do with the ShVAK cannon, prior to my discovery that there was a different version of this gun for the Yaks when mounted through the spinner. Anyway, the Estimated Ballistics chart is the only part of this page that is relevant to this discussion. I'm fairly confident the values are accurate.

http://members.cox.net/rg_lunatic/gunpage/

The chart gives the ballistics performance for the most of the guns we are discussing.

=S=

Lunatic

 

[Hop]

And the cavity magnitron was based upon American inventions in the field.

Which were in turn ased on other countries inventions.

Inventions do not come out of the blue. Nobody invents a new device, the basic theory behind it, the manufacturing process that make it possible, the other components that make the final device possible, etc.

And the cavity magnitron was also independantly developed in the USA, I believe in 1934 or so. The tech was there already, and if you investigate it you will see there was very little of British orgin in the USN radar program.

Again, the magnetron. The US and Germans might have had various magnetron designs, none of them was suitable for radar use. As shown by the fact none of them were used to make usefull radars, whereas the British design was, by the British, by the Americans, then by the Germans.

Neither Britain nor Germany could build jet engines for war in 1944 or 1945.

Derwent?

 

[Lunatic]

No I think the cavity magnetron was also invented. The inventors simply failed to see its significance and like many other inventions it was shelved.

And both the key components of the CM were invented in the USA, not just the magnetron. The magnetron was a fairly basic invention, however the klystron was not so obvious.

Certainly Churchill's decision to provide the CM to the USA sped up US shortwave radar development (US longwave radar development was quite well along already). However given the increase in expenditures for war related research occuring in 1940 and 41 I'm pretty sure even without this US researchers would have come up with the technology quickly on their own.

Neither Britain nor Germany could build jet engines for war in 1944 or 1945.

Derwent?

Huh? Note I didn't say they could not build jet engines, simply that they could not build them suffiently well to support the war effort.

=S=

Lunatic

 

[Parmigiano]

I remember I read somewhere that even the chin mounted 20mm of the SA Rooivalk helicopter is derivated from the MG151: anybody can confirm or knows a bit more?

 

[schwarzpanzer]

Sorry, I can't help you Parmigiano.

I'll be rooting through my archives, if I find anything, I'll let ya know.

Is it a minigun-type?

If it is, it may be the MK203?


wmaxt:

They, Allisons, were already turbo charged

The correct name for a Turbo is an 'exhaust turbine driven supercharger'

- Sorry, just being annoying!

A turbo is not difficult, but on the Jug the US engineers screwed the piping totally!

I think the scrolls (snails) were vastly inferior to UK ones also.

The scrolls can be inter-changeable between super turbo-chargers.

The RAF didn't need Turbos as above 300mph the exhausts can give a degree of thrust that is superior to the Turbo's, offsetting any gain.

Also with a twin-scroll supercharger (a bit like a like a Toyota Supra's Turbo's) the Turbo isn't needed.

The only advantages I see for the turbo are in fuel economy and noise, so for bombers?...

However power for take-off could easily suffer...

I think some Lancs were Turbo'ed?

I'm almost certain at least one RAF plane was if not?


The Turbo-compounder was a good US idea, used in the R-2800 IIRC? 8)

The Allison seems a nice engine, still being made in Russia!


Lunatic:

Huh? First off I've never seen anything that indicates the .50 was developed from a German round.

I'll have to find that too!

It was the K bullet IIRC?

Umm... nowhere does this indicate the mine type round is being used. Nor does it indicate that the rounds have not been updated to use more modern fuse technology (which allows a pointed tip).

I'd say it is the minenschoss, the fuses? - you may well be right there.

But tell me, would you rather have one shot with that 20mm, or 6-7 shots with the .50?

Very valid point, I'd have the one 20mm.

Thanks for the info on the API round, I can't remember there being one! I'll have to check.

If it could accomodate a Turbo-supercharger it could accomodate a two stage supercharger.

From what I hear the Allison is the best for low-level, turbo's etc just don't seem to suit it?

- I'd need the specs, particularly port sizes, valve sizes and bore/stroke info vs the Merlin.

Anyone got that please?

Neither Britain nor Germany could build jet engines for war in 1944 or 1945.

Derwent?

Huh? Note I didn't say they could not build jet engines, simply that they could not build them suffiently well to support the war effort.

Jumo 004?

The German type jet was better for mass-production and, I think, power. But the UK ones were inherently more reliable.

 

[DerAdlerIstGelandet]

The Jumo 004 suffered from many problems and only had a life span of about 10 hours.

 

[schwarzpanzer]

Yes but it could be changed a lot quicker than the Derwent and could use crappy metals (could the Derwent?)

 

[Lunatic]

wmaxt:

They, Allisons, were already turbo charged

The correct name for a Turbo is an 'exhaust turbine driven supercharger'

- Sorry, just being annoying!

Hmm that's a new one on me. Supercharging refers very specifically to forced air/fuel induction by means of tapping power directly off the crankshaft to drive the pump. Turbocharging refers to tapping power off spent exhaust fumes to drive the pump. Turbo-supercharging refers to using a combination of both a turbocharger and a supercharger, one feeding into the other, to derive even more compression of the air-fuel mixture. Dual superchargers just use two superchargers, one feeding into the other to achieve the same goals.

A turbo is not difficult, but on the Jug the US engineers screwed the piping totally!

Not really. Turbo-supercharging was new and the intercooler requirements were complex. They needed a long pipe to make the thing work.

I think the scrolls (snails) were vastly inferior to UK ones also.

The scrolls can be inter-changeable between super turbo-chargers.

What the hell are you talking about??? :8 What are "scrolls" and "snails"?

The RAF didn't need Turbos as above 300mph the exhausts can give a degree of thrust that is superior to the Turbo's, offsetting any gain.

As far as I know Britain never sucessfully developed a turbo-supercharger which could be mass produced. I know Germany was never able to do so.

Umm... thrust from exhaust stacks was good for only a tiny amount of power - in the best cases adding only about 5 mph to the top speed of the plane and adding no increase in climb rate. The Turbo stage in a turbo-supercharger added considerably more power for climb and speed to the plane, and unlike the supercharger did not sap so much power from the engine to do so.

Also with a twin-scroll supercharger (a bit like a like a Toyota Supra's Turbo's) the Turbo isn't needed.

The only advantages I see for the turbo are in fuel economy and noise, so for bombers?...

However power for take-off could easily suffer...

Your knowlege of turbocharging seems to be based upon modern automotive tech. For aircraft things are quite different. For aircraft, altitude changes must be considered. Super chargers involve gears, normally one stage of a WWII fighter two-stage supercharger is at a fixed gear ratio, and the other either has one or two gears, plus neutral. The maximum pressure (usually called boost) is limited by various considerations, but in English measurments was generally limited to 18, 21, or 25 lbs of boost. With a two speed two stage supercharger, maximum boost can be achieved at two altitudes (called critical altitudes).

With the turbocharger things are different because the boost is regulated by the speed of the turbine input shaft which is variable. Therefore, full power can be sustained over a wide range of altitudes. This means that while the P-51 was producing peak power at about 16,000 and 26000 feet, with less than peak power at all other alititudes, the P-47 could produce peak power right up to about 31,000 feet where the maximum speed of the turbo input shaft is reached.

So turbo-charging had a huge advantage over supercharging for WWII fighters. The disadvantage was mostly the complexity of the intercooler stage and the ducting which had to be done to accomodate it.

I think some Lancs were Turbo'ed?

Not as far as I'm aware. If there were, they were likely test planes powered by P&W or Wright engines.

I'm almost certain at least one RAF plane was if not?

I believe there were some RAF bombers powered by US made radial engines with turbo-superchargers. ???

The Turbo-compounder was a good US idea, used in the R-2800 IIRC? 8)

The Turob-supercharger was used on Wright Cyclones, P&W Wasps and double wasps (R-2800's), as well as the Allison (on the P-38).

The Allison seems a nice engine, still being made in Russia!

The Allison was smoother and sturdier than the Merlin, but the Merlin made better power, mostly because of its integrated supercharger stage. This meant that only one supercharger (or turbo-charger) stage needed to be external to get two-stage power, allowing the Merlin to be retro-fit into the P-51 which was designed to accomodate only one supercharger stage (as per it's P-40 heritage).

But tell me, would you rather have one shot with that 20mm, or 6-7 shots with the .50?

Very valid point, I'd have the one 20mm.

For no valid reason. In the scenario I presented you'd have less than a 1 in 3 chance of killing the target with the 20mm, but it would be almost a sure thing with the .50 caliber.

The point is it all depends on the target. If the target is a deer, shooting it with anything bigger than a 30/06 is pure over-kill and buys you practically nothing. Shooting it with a 50 caliber would simply tear it in to multiple pieces, but it would be just ad dead either way.

Thanks for the info on the API round, I can't remember there being one! I'll have to check.

The M8 API round entered service in mid-1943 and was the standard round by 1944, used almost to the exlusion of all other sorts of ammo in US fighters.

If it could accomodate a Turbo-supercharger it could accomodate a two stage supercharger.

From what I hear the Allison is the best for low-level, turbo's etc just don't seem to suit it?

The late P-38J and the P-38L were fine up high. Eariler models had few problems with the engines up high, however there was no heating for the cockpit which made high altitude difficult for the pilot. On the J and L series this was rectified. In the Pacific the P-38 operated at altitude frequently.

Neither Britain nor Germany could build jet engines for war in 1944 or 1945.

Derwent?

Huh? Note I didn't say they could not build jet engines, simply that they could not build them suffiently well to support the war effort.

Jumo 004?

The German type jet was better for mass-production and, I think, power. But the UK ones were inherently more reliable.

Germany built something like 15,000-20,000 Jumo jet engines, of which a mere 800 or so saw combat service. Most failed quality checks or self destructed during testing. Even when they did work, they were good for less than 10 flght hours, including intial flight testing. The jet engine was just beyond Germany's ability to mass produce. The same was true for Britain.

=S=

Lunatic

 

[FLYBOYJ]

Your knowlege of turbocharging seems to be based upon modern automotive tech. For aircraft things are quite different. For aircraft, altitude changes must be considered. Super chargers involve gears, normally one stage of a WWII fighter two-stage supercharger is at a fixed gear ratio, and the other either has one or two gears, plus neutral. The maximum pressure (usually called boost) is limited by various considerations, but in English measurments was generally limited to 18, 21, or 25 lbs of boost. With a two speed two stage supercharger, maximum boost can be achieved at two altitudes (called critical altitudes).

With the turbocharger things are different because the boost is regulated by the speed of the turbine input shaft which is variable. Therefore, full power can be sustained over a wide range of altitudes. This means that while the P-51 was producing peak power at about 16,000 and 26000 feet, with less than peak power at all other alititudes, the P-47 could produce peak power right up to about 31,000 feet where the maximum speed of the turbo input shaft is reached.

What is being omitted it the amont of "Boost" (which is actually manifold pressure) is also based on engine RPM. If you're pulling 25 pounds (or inches in US terms) and have the engine runing at 1000 rpm due to a course prop pitch setting, chances are you are going to destroy that engine.....

 

[wmaxt]

[quote="FLYBOYJ
What is being omitted it the amont of "Boost" (which is actually manifold pressure) is also based on engine RPM. If you're pulling 25 pounds (or inches in US terms) and have the engine runing at 1000 rpm due to a course prop pitch setting, chances are you are going to destroy that engine.....[/quote]

True enough, The P-38 in the pacific esp after Lindberg commonly ran 1700/1900 rpm and 42". This combination was very economical and increased the heat in the cockpit enormously as the heating system was a radiant heat type off the exaust manifold. Had they run this combination in the ETO many of the problems encountered there would have never existed.

BTW: the Allisons were tested up to 110" and 2,300+hp without major dificulties.

The inner parts of a Turbo and a mechanical supercharger are NOT interchangeable, turbo's run much to fast and also run hotter (the heat expansion is where they get their power from). P-38s ran in the low 20,000rpm range with 26,400rpm as absolute max.

The reason they did not use two stage superchargers on the Allisons is that the AAF did not allow their use or development from the early '30s relying on the use of Turbos because of their superior performance above 25,000ft.

wmaxt

 

[FLYBOYJ]

The inner parts of a Turbo and a mechanical supercharger are NOT interchangeable, turbo's run much to fast and also run hotter (the heat expansion is where they get their power from). P-38s ran in the low 20,000rpm range with 26,400rpm as absolute max.

wmaxt

They were manufactured in "matched sets." Great info wmaxt!