Which country designed the best engines for WWII?

[swampyankee]

Getting the cooling system right for a piston-engined aircraft is very difficult, and a lot of aircraft showed just how difficult. A major reason for the P-51's success was probably its superbly well-designed cooling system, even if it did not achieve negative cooling drag (it may have under conditions of high power and high mach number, but, if so, it would be on the order of ten pounds of thrust)

Negative cooling drag is certainly possible with both air-cooled and liquid-liquid cooled engines, by using ejector exhausts.

 

[Guchi]

I'm surprised that Germany has been rated better that the US - or even Japan!! (Must be true - Anything with a swastika will sell!!)

Germany was the only country of GB, USA, Japan and Germany that never managed to build a truly 2000hp engine. Even Japan managed that.

GB had a couple of "stars" like the Merlin and the Napier-Sabre, but the rest were oil-leaking troublemakers.

USA had (apart fron the Allison) good, reliable, powerful, non-spectuclar engines that did everything - and then some.

Japan had good, but lower powered engines in the begining and powerful but (due to war shortages) un-reliable engines in the later years.

Germany had highly engineered, un-imaginative and stagnated engines that were always in short supply!!

 

[fastmongrel]

I'm surprised that Germany has been rated better that the US - or even Japan!! (Must be true - Anything with a swastika will sell!!)

Germany was the only country of GB, USA, Japan and Germany that never managed to build a truly 2000hp engine. Even Japan managed that.

GB had a couple of "stars" like the Merlin and the Napier-Sabre, but the rest were oil-leaking troublemakers.

USA had (apart fron the Allison) good, reliable, powerful, non-spectuclar engines that did everything - and then some.

Japan had good, but lower powered engines in the begining and powerful but (due to war shortages) un-reliable engines in the later years.

Germany had highly engineered, un-imaginative and stagnated engines that were always in short supply!!

What was wrong with the Allison and if you want a nightmare engine look at the R3350 which probably killed more B 29 crew than the Japanese did.

I wouldnt call the Sabre a star either it became a decent engine capable of fantastic power to weight ratios but a star no dont think so. As for the rest of the British oil leaking trouble makers like the Griffon, Centaurus, Hercules, Mercury, Pegasus, Cheetahs, Kestrels, Perseus (possibly a contender for the most reliable engine of the war though not many were built) and all the other rubbish engines that flew millions of hours.

German engineers were very clever and produced excellent engines in the face of shortages of materials, fuel and often the lack of a roof on the factory. There was never a shortage of engines in Germany (apart from DB engines at times) but there was a shortage of good decision makers in the Ministry who kept moving the goalposts on the designers and manufacturers.

 

[tomo pauk]

Can we see some numbers to back up the claims, Guchi?

 

[wuzak]

Note that the 1,730hp was maximum cruise and was at 8,500ft and was 1,570hp @ 17,000ft.

The Griffon's international rating, which would be close to maximum cruise, is just under 1,500hp @ 17,000ft.

The Griffon also has ~1,150hp in its cruise rating (I'm guessing most economical) at 30,000ft while the Sabre is dipping under 1,000hp.

 

[wuzak]

In terms of maximum output, the Sabre VI and the Griffon 130 are roughly the same at 20,000ft - 2,000hp.

At 25,000ft the Griffon has ~150hp more - 1,750hp vs 1,600hp.

At 30,000ft the Griffon has 1,450hp vs 1,300hp.

You may also notice that the Griffon's LS gear (low supercharged) is used on cruise up to 17,000ft, which is the point at which the Sabre's peak maximum cruise power in FS (fully supercharged) gear.

Adjusting the gear ratios for the Griffon would bring more low down power for both combat and cruising conditions at the expense of high altitude performance..

 

[wuzak]

Correct W, but that is solely a matter of supercharger tech..

The Sabre VII in its final rated form was capable of 3,500 hp for take-off,
so, 'bout a thousand more than the low-level rated, ADI equipped Griffon in the Shackleton.

& as the test bench dyno showed, if the supercharger limitations are removed, the Sabre was certainly
capable of outputs over extended periods - which would've give the long-stroke Griffon mill conniptions, if attempted.

( As for Greg P 'disliking' the facts.. as if 'like' comes into it..).

No doubt that the Griffon would not match the Sabre for power.

But Rolls-Royce invested in that supercharger "tech", Napier didn't (or couldn't - they were going broke, see).

In the prior post I was pointing out the difference between relative cruise performance and maximum performance, and how the supercharger gearing affected that.

 

[BLine22]

Somehow I don't think 'going broke' comes into it in wartime, not when HM Gov't is the sole customer.

There certainly was a politico-economic play, hence the Centaurus going to the Sea Fury,
( even though the Griffon was ostensibly an FAA mill) & the Griffon getting the Shackleton gig,
yet it would've been a natural fit for the Centaurus, being a low-level long-range patrol bomber).

R-R it seems, certainly had the political clout to resist the pressure to share tech, ( that Bristol had to share)
& so they kept the high-altitude performance fighter band via the Griffon Spit/Spiteful,
leaving the low-level FB zone to Hawker using its Napier/Bristol power.

The other matter is, look at the 'climbing power' a permitted high out-put rating for an hour,
( & which would burn the ops worth fuel, if used) , this indicates the Sabre's robust duty capability.

Since the Shackleton was base on the Lincoln/Lancaster, the Griffon was a easier replacement for the Merlin. After using Wildcat, Hellcat, and Corsair, FAA must have realized the Radials were more suited for shipboard ops.

 

[wuzak]

I dont think so, Griffon was certainly used by FAA shipboard in later Seafire, Firefly & the loser to the Sea Fury, the Sea Fang.
The Hawker Fury was tested with the Griffon, but performed better with the Centaurus.

Lancaster IIs had Bristol Hercules engines, but the Halifax needed them more, so R-R Merlins predominated in Lancs.

And the fact that the Lancaster performed better with Merlins than it did Hercules.

The opposite seems to be true for the Halifax.

 

[wuzak]

Actually James, from what I remember, the Beaufighter II had a higher performance than the contemporary Hercules version. However, it caused a decrease in stability, leading to the dihedral tailplane, which was kept for subsequent versions.

The Merlin Beaufighter was built in case there was a shortage of Hercules, and the Lancaster II was built in case of a shortage of Merlins.

Edit: Seems my memory fails me: Bristol Beaufighter - Variants and Stats

 

[ChrisMcD]

To give it another slant, I rate them England, USA, Germany and Japan - in order of leading edge research.

England
Rolls-Royce - good V12's (Merlin and Griffon) plus superb supercharging development.
Bristol - innovative sleeve valved radials that could compete with the best from the USA - not so good on supercharging and crap with turbocharging!
- Napier - only company to make an H24 work - and how! Again, not great supercharging experts. Probably too innovative for their own good - how else do you explain the Nomad!

USA
Wright and Pratt & Whitney show everyone else how to make big radials (ie the Germans and the Japanese)
Allison - good V12, let down by the US services preoccupation with turbocharging that only got fitted to the P-38

Germany
Daimler Benz - good V12's but dry liners and roller main bearings? Some great ideas on supercharging (hydraulic drive)
BMW - the BMW132 was a P&W Hornet made under licence, the BMW 139 was two 132's put together, then the 801 was a more serious rethink to get a more compact engine. All very good, but not what I would call innovative.

Japan
I do not know enough to have a proper fight, but I gather that all(?) of the major Japanese manufacturers evolved their designs from licenses taken out in the 30's from P&W, Bristol, Gnome Rhone etc. For example I understand the Nakajima Sakae was based on the Gnome Rhone 14K
Most of this is based on reading Herschel Smith's "Aircraft Piston Engines"

 

[Deleted member 68059]

Germany:

Germany conducted the most in depth research on almost every single engine system.
I can state that I believe their supercharging work is stunningly good (see attached pic SC), and were the only ones
towards the end who started developing engines which were on the truly modern path philosophically,
of radically increasing crankshaft speeds, and having flexible valve timing controls; which with the
possibilities of direct injection are really knocking on the door of all modern engines, in terms
of control possibilities.

However they utterly failed in the task of taking all this research and putting it into one, or two
engines which would actually be able to be mass manufactured in time to have any useful
war impact.

The Jumo 213J and DB603N, were in several respects light years ahead of their time, due to
design features like hydraulic VVT, swirl throttling and mean piston speeds over 66fps well over 4000rpm, bu due to pitiful organization and planning - were militarily, non-events. If you see the list of engines DB developed you will never believe it, its like an engines menagerie.

Germany gets a gold-star too in my book for having carried out all this research and work
under horrific conditions, which really makes it a wonder they did anything useful at all.

Their greatest failure was not getting a two-stage supercharged engine with charge-cooling
into service. Which was really criminal, as their drawing offices and test stands were littered
with them.


Britain:

Generally made very "simple" engines (ignoring Napier...) and the only country I think which
understood not only what it needed to do, but understood its own strengths and weaknesses.

Unlike the Germans, Rolls-Royce brutally culled engine projects before they dragged on draining resources
from the critical work (eg Vulture being cancelled, dramatically increased the resources available for Merlin development according to Geoffrey Wilde).

Understanding the limited time and people they had, Britain more or less conducted its entire war
effort on one engine series, and would have (sorry to Bristol and Napier fans) been entirely able to
have finished in the same circumstances with only Merlins. Which I dont think you can really
say about any other nation. The "stick with what you`ve got and develop it" pragmatic approach
probably won the war for Britain in the air.

I think the Merlin 60 series, two-stage with charge-cooling was really the ubiquitous liquid
cooled V12 of the war (in terms of mass produced operationally significant engines, that
were fitted across several aircraft platforms). The significance of the introduction of the Merlin 61
is very apparent from reading German technical intelligence reports, and internal DBenz reports,
no other Allied engine is really mentioned much, but the 61 and V1650 had them quite panicked;
although they did meticulously take apart and test every other engine the Allies made too, as did we.

I think Britain's great failure was an embarrassing reliance on carburetors, which in view
of the problems it caused, and the open possibilities to change it early on - was really very very bad,
and I`m sure cost many pilots their lives until the pressure carburettors were put on by Packard.


USA:

The Americans clearly got their act together with Turbocharging and fuels research in a way
that nobody else did (although plenty of behind the scenes stuff credit on fuels has to go to
Brits like F.R.Banks). However turbo setups in the 1940`s were horribly heavy and gigantic in
size, which did mean that without a really good two-stage mechanically blown engine, their
smaller fighters were a bit limited, which is really why the P51 was a little hamstrung for a while.

I think the big Wasp radials with turbo`s were amazing engines. I think their greatest failure was
not developing a really good supercharger for the V1710, which was in many respects a
better basic engine than the Merlin. The combustion chamber shape of the Allison is much
better than that of the Merlin, and is very similar to a modern engine, inclined 4 valve narrow-valve angle
pent roof, and splitting the crankcase down the crank centre-line, then using the whole sump as a
main bearing ladder-frame is very modern in concept, it makes for an extremely strong and stuff
crankcase structure and bearing alignment.


Russia:

I am not knowledgeable on Russian engines yet, but I do know that we can credit them for the very clever
introduction of the supercharger swirl-throttleon the AM35 engine. Which was quickly copied by Werner Von Der Null at the DVL
and eventually pressed into service on the Jumo 213 and DB603L & N.


Overall

Its very open to interpretation, but your question was "which country DESIGNED the best engines", I`m going to
vote Germany. The fact they never really managed to actually put many of them into a plane is a second thread !

The best DESIGNS, were I think the DB603N (which went to wet-liners, and conventional bolted head joints) and
the Jumo213J, which was really the only engine of the war to move seriously towards very high speed crank speeds.

According to internal german comparisons, which compared all the major engines, Sabre, Cyclone, AM35, AM38, Merlin, Griffon, DB`s, Jumo`s, BMW`s - the Jumo 213 scores first place in just about all categories, only loosing
out to engines like the P240 which was never used (developed by the Mercedes Silver Arrows automotive
racing dept !).

Kg/PS Kilograms engine weight per PS (basically a horsepower) (see pics 1,2,3,4 - sorry they are so blurry!)
PS/m^2 Engine frontal area
PS/m^3 Engine package volume
MEP Mean Effective Pressure
MPS Mean piston speed

Of course you can invent other categories in which it scores very little, such as was it introduced
early enough and in sufficient numbers to actually matter.....probably not really. I`ve attached a couple of snippets on the Jumo213EB, which even ended up in a real aircraft, amazingly...haha, the amazingly
flat power vs altitude curves can easily be mistaken for a turbocharged engine, but are in fact due to
the Swirl Throttle (copied from the Russian AM35). Which dramatically lowers pumping losses below rated heights.

I`d also say that the DB624 turbo-twin-supercharged engine would have been superb, and Benz had completed
their 100hour tests on turbocharged DB`s in 1941. So while USA deserves tremendous credit for getting not only
the science right, but ALSO the scheduling, and production - German turbo research has laid it all on the plate
for their country too. They just never got their act together to make proper use of much of it (we can all thank
Ernst Udet & Göring for that).

In terms of things that were actually made in enough volume to be war-influential, then I think I can only pick the Merlin, because if you waved a magic wand and said "ok its 1939 and you only get to have ONE engine for the
rest of the war for ALL your planes" I think its the only one that really could have done that well, and for
Britain more or less actually did...but I dont think its necessarily a particularly advanced engine, it was just
developed very well to do one thing, using a simple proven layout. Therefore it really stops being an aircraft engine
and starts being just, a useful mass produced, reliable war-machine - and I think Germany spent rather too much
time trying to build clever engines, and forgot about the fact they needed war-machines.

But all this was very strongly tied in with fuels, and strategies, Germany never really managed to figure out what it was
supposed to be doing with their engines, and the fuels situation was also catastrophically poorly planned, and run. So
I think its really very very difficult to compare like for like, every country had their own constraints and targets, although it was the same war, very few in Germany were really trying to do what the Allied designers were trying to do, and visa-versa, its not as if each side had to just make an engine that could reach 30,000 feet first, or use least fuel
and so on. Its really hard to say what "best" is without knowing the background to each.

I am also "cheating" with this post, because its the topic for a book I`m writing which should be finished in the next few months. So I get unfair advantage of having piles of stuff right at my desk. I would post alot more info, but its all copyrighted and I cant upset the people and places who gave me this stuff, by just posting it all verbatim.

("Umfangsgeschwindigkeit" means "supercharger impeller tip speed" in the pic SC and the last pic means "German Aeronautical Research Institude - Berlin Aldershof, Institute for Turbomachinery report by Dietrich, Report on the Analysis of the two-stage, two speed supercharger system from the high altitude engine Merlin 61 with after-cooling & housing cooling").

 

[ChrisMcD]

Ah yes the Jumo 213!

Apologies for missing out the Junkers Jumo series

I can only plead guilty to accepting the slander that the 211 was a "bomber engine" - by implication heavy, economical and slow to respond to throttle movements - so not any good for a dogfight. And the Avia S-199 rather confirms that verdict.

But it is very clear that when Jumo got their act together they produced a very fine engine in the 213.

One other thing worth mentioning is that Junkers were the only manufacturer (AFAIK) who managed to cast both cylinder banks and the crankcase in a single casting (unlike RR!).

Mind you, I remain to be persuaded about the virtues of three valve heads and I think the Sabre compared well on rpm.

 

[wuzak]

Mind you, I remain to be persuaded about the virtues of three valve heads and I think the Sabre compared well on rpm.

The Sabre pushed the rpm envelope before the 213 did. But it had much less piston speed.

I am very doubtful that the 213 spent much, if any time, at 4,000rpm. I believe the maximum was 3,250rpm, which was rather high for an engine with such a long stroke.

Wasn't the best of the Jumo 213s using a 4 valve head?

 

[Piper106]

QUOTE="wuzak, post: 1278794, member: 42564"]

I am very doubtful that the 213 spent much, if any time, at 4,000rpm.

Wasn't the best of the Jumo 213s using a 4 valve head?[/QUOTE]

Ah yes, the near mythical (or is that unicorn-like) stories of the Jumo 213J. I have read many time, four valves per cylinder, and emergency rating at 3700 rpm. I even read once that the bore was increased to 155mm from the 150mm used for the Jumo 211, and Jumo 213 up to that point.

But beyond those few interesting words... nothing, nada, zip.

Was the 213J ever hardware (even if only on a test stand) or was it just another feverish dream in the crumbling last days of the Reich?? Without pictures of the Jumo 213J, without cross section drawings, without perforance vs. altitude curves, or proposed applications, and with no 213J captured by the Allies and examined, I think it was a 1945 version of vaporware.

 

[wuzak]

Rolls-Royce went a different route to increasing rpm - they increased boost.

With increased boost it was less necessary to chase higher rpm.

 

[Shortround6]

A better indication of the stress in an engine that rpm is the "corrected piston speed".
This is calculated by dividing the mean piston speed by the square root of the stroke/bore ratio.
Engines with a bigger bore than stroke wind up with a higher number than the mean speed (due to heavier pistons) and engines with a smaller bore than stroke get a lower number.

For instance the Merlin has a mean piston speed of 3000fpm and a corrected piston speed of 2856fpm.
The Sabre has a mean piston speed of 3048fpm and a corrected piston speed of 3129fpm.
A Junkers 213 has a mean piston speed of 3521fpm at 3250rpm and a corrected piston speed of 3353fpm.

Now just for comparison a 1938 Auto-Union Grand Prix engine had a corrected piston speed of 3207fpm at 7000rpm and the 1939 Mercedes Grand Prix engine had a corrected piston speed of 3370fpm at 7500rpm.

Granted they did make a lot of progress in bearing technology, piston ring technology and lubrication in just a few years but running aircraft engines at piston speeds of Grand Prix engines (or significantly higher) probably wasn't going to work very well.

A Jumo 213 running at 3700rpm would have corrected piston speeds not seen until the early to mid 50s in race cars.

 

[Shortround6]

Rolls-Royce went a different route to increasing rpm - they increased boost.

With increased boost it was less necessary to chase higher rpm.

Given fuel that allows you to do it it is certainly simpler. The stress on the engine goes up with rise in combustion pressure. While with rpm the stress goes up with the square of the speed. Increase combustion pressure by 20% and you get (roughly) 20% more power and 20% higher stress. Increase rpm by 20% and you get 44% higher stress.
Of course if you don't have the fuel that allows the higher combustion pressure you start running out of options real quick.

 

[Deleted member 68059]

Hi,
I have quite alot of info on the 213J, although far less than I`d like.

The best info I have so far is that the drawings were got to by the French team first, and so likely are going to be
very difficult to locate (although maybe not impossible).

It was designed 4000rpm, with margin for 4400rpm, which involved radically light-weighting all the moving parts.

Allied tech intel. reports say that around 10 physical engines were built, but that testing was not finished (ie quite possibly
there were no performance curves finished).

I have a rough drawing of the connecting rod, and a very complete set of supercharger schematics and layouts from British intelligence interrogation of one of the jumo designers. The connecting rods are very clever, and look almost identical to those i used from a Cosworth indy car engine few years ago. Anyway, I think I'll leave it at that on this thread.

 

[Shortround6]

The French either got the Jumo drawings and quite a bit more or were building Jumo 213s (or major parts for them) during the war as they tried to market the Jumo 213 after the war. Not the J model. In addition to the "normal" Jumo 213 they did market (and built enough engines to power 26 flying boats for the French Navy) and which was fitted with water injection for take-off, they were marketing one version with contra-rotating propellers, one with a turbo compound unit and had tried putting 4 cylinder banks on one crankcase (two crankshafts) as a vertical 24 cylinder H engine. This engine is reported to have 4 valves per cylinder but run at 3250rpm. Misprint on the valves or?????
"Ownership" went through Arsenal and then S.F.E.C.M.A.S.
The 1953 "specs" are for a 3 valve 12 cylinder Version with 2300hp at 3250rpm for take-off using 11lb boost wet and 2100hp at 3250rpm/11lbs boost dry. Normal power (max continuous??) is given as 1720hp at 3000rpm at 5900ft and 1500hp/3000rpm/16,400ft, boost not given, Fuel is given as 100/130.
In the late 40s and early 50s the only real market for large piston engines was the long range transport or patrol plane market and engine durability was as important as peak power. P & W and Bristol getting over 2000 hours between overhauls on some models/installations if not higher.
It is easy to specify certain performance limits/goals, achieving them is more difficult and achieving then with decent engine life is quite another thing.