Jumo inverted vee's vs. Daimler-Benz inverted vee's - Pros and Cons

cherry blossom · Jan 4, 2021

Fortunately, you haven't specified understand but since I received my copy today, it might be worth mentioning the comments in the summary 1939 (page 127), which argues that the DB600 series should have adopted the crankshaft oil feed system from the Jumo 211 and that the Jumo should have adopted the DB 600 series superchargers. One might add that the spark plugs are better positioned in the Jumo 211, especially before the DB 601E, whilst having 4 valves helped the DB series in comparison to every Jumo up to 213J.

Koopernic · Jan 4, 2021

cherry blossom said:
Fortunately, you haven't specified understand but since I received my copy today, it might be worth mentioning the comments in the summary 1939 (page 127), which argues that the DB600 series should have adopted the crankshaft oil feed system from the Jumo 211 and that the Jumo should have adopted the DB 600 series superchargers. One might add that the spark plugs are better positioned in the Jumo 211, especially before the DB 601E, whilst having 4 valves helped the DB series in comparison to every Jumo up to 213J.

I suspect that 4 valves versus 3 is not a big improvement in aspiration at the kind of speed both the DB versus Jumo engines were operating at (initially both under 3000rpm) probably added some difficulties in head and valve cooling. When Junkers Jumo decided to push the Jumo 213J to 3700 RPM it made sense to go to 4 valves.

xylstra · Jan 5, 2021

tomo pauk said:
I will not comment on 'well thats really not quite true' line.
Also I'm not sure from where the one-speed S/C drive popped out here - neither DB 601/605 nor the Jumo 211 were with the 1-speed drive.

The power graph posted there is at odds vs. the power graph posted here, or here, or here - where the effects of throttling under ~2 km are obvious. The 1st two charts are from the engine manuals.
The data sheets also show 1100 PS for take off, like this one here.

I'm sure that you know about DB 603. Some other people might not know about it's throttle plates.

My thinking is also along similar lines to yourself Tomo but what amazes me is that there seems to be a tunnel-vision phenomena going on. Everyone seems fully absorbed in German engines vs British engines. You all seem to forget the numerous American and Russian engines and the particular example of the Allison variant with hydraulic-coupling driven supercharger vs it's fully gear-driven siblings. If there was inherent superiority in the use of a hydraulic coupling then everyone would be using it. I doubt very much that its efficiency losses will be insignificant over it's normal fight profile.

tomo pauk · Jan 5, 2021

xylstra said:
My thinking is also along similar lines to yourself Tomo but what amazes me is that there seems to be a tunnel-vision phenomena going on. Everyone seems fully absorbed in German engines vs British engines. You all seem to forget the numerous American and Russian engines and the particular example of the Allison variant with hydraulic-coupling driven supercharger vs it's fully gear-driven siblings. If there was inherent superiority in the use of a hydraulic coupling then everyone would be using it. I doubt very much that its efficiency losses will be insignificant over it's normal fight profile.

With a risk of sounding harsh - I regard the 'you all seem to forget' as being too cocky for my taste. Ditto for 'then everyone would be using it' - if one does not have it, then one can't be using it.
The thread is about two lines of German engines, not about British engines, nor about American engines.

Shortround6 · Jan 5, 2021

Sometimes the best was the enemy of good enough.

Some sources claim for instance that the British didn't want to spend the man hours (and machine time) making fuel injection like the Germans used.

It is also claimed the examined the MG 151/15 and thought it too was excessive in man hours/machine time for what it may have offered over the Hispano (already in production)

Hydraulic couplings were not new. They had been used in cars, They had been used a few experimental railroad locomotives, They had been used as far back as just before WW I in a few ships so that the diesel or heavy oil engines of the time could run at more nearly steady speeds and the ships speed (propeller) controlled by the hydraulic coupling.

The only practical effect of the hydraulic coupling is that it eliminates the saw tooth dip in the power curve of a two speed engine. It doesn't allow for any higher altitude performance than a gear driven supercharger (of the same design) using the the same drive ratio.

Other countries/companies may have looked at the hydraulic coupling and decided it wasn't worth the effort for a number of reasons. Many of which might have nothing to do with the engine performed with it.

xylstra · Jan 5, 2021

Shortround6 said:
Sometimes the best was the enemy of good enough.

Some sources claim for instance that the British didn't want to spend the man hours (and machine time) making fuel injection like the Germans used.

It is also claimed the examined the MG 151/15 and thought it too was excessive in man hours/machine time for what it may have offered over the Hispano (already in production)

Hydraulic couplings were not new. They had been used in cars, They had been used a few experimental railroad locomotives, They had been used as far back as just before WW I in a few ships so that the diesel or heavy oil engines of the time could run at more nearly steady speeds and the ships speed (propeller) controlled by the hydraulic coupling.

The only practical effect of the hydraulic coupling is that it eliminates the saw tooth dip in the power curve of a two speed engine. It doesn't allow for any higher altitude performance than a gear driven supercharger (of the same design) using the the same drive ratio.

Other countries/companies may have looked at the hydraulic coupling and decided it wasn't worth the effort for a number of reasons. Many of which might have nothing to do with the engine performed with it.

I quite agree, but that old efficiency number seems forever elusive and slippery yet ironically the 'ground-hugging' auto-industry is the best source for the efficiency evaluation of fluid transmissionss with numerous SAE papers published. They aren't shy about complicating matters by the incorporation of lock-up mechanisms to ameliorate their inherent inefficiency.
I'm not necessarily sure that British aero-engine manufacturers wanted to avoid investing resources into home-grown F.I. It may be simply as prosaic as closely following the American development of the Bendix-Stromberg injection carburettor and realising that it made no sense to re-invent the wheel. Just sit back, let them do the hard work then licence the design. Eventually, that's pretty much what Rolls-Royce did.

Deleted member 68059 · Jan 6, 2021

xylstra said:
I quite agree, but that old efficiency number seems forever elusive and slippery yet ironically the 'ground-hugging' auto-industry is the best source for the efficiency evaluation of fluid transmissionss with numerous SAE papers published. They aren't shy about complicating matters by the incorporation of lock-up mechanisms to ameliorate their inherent inefficiency.
I'm not necessarily sure that British aero-engine manufacturers wanted to avoid investing resources into home-grown F.I. It may be simply as prosaic as closely following the American development of the Bendix-Stromberg injection carburettor and realising that it made no sense to re-invent the wheel. Just sit back, let them do the hard work then licence the design. Eventually, that's pretty much what Rolls-Royce did.

Not "elusive", the loss of the Föttinger coupling is directly proportional to the speed ratio its running at. Use a 10% slip, and 10% of the driven power will be converted to heat.

Both the British and Americans knew perfectly well how to make petrol injection almost a decade before the war broke out.

Please provide a citation for Rolls-Royce not bothering to develop their own technology because they were waiting for the Bendix to solve the problem for them>
(Hint, what they were working on was their own singlepoint fuel injection, which was implemented on the Merlin 100 series onwards - and I can assure you
that they were frantically scrambling to sort out their carburettor problems, having read the letters).

In the meantime, something to un-derail the thread, Junkers-Jumo training manual page, showing a nice section of the different bearings used between
the 211 and 600. You need a more sophisticated oil supply system to make best use of plain bearings, as Daimler discovered to their cost later on when
they had to convert to them.

Koopernic · Jan 6, 2021

xylstra said:
My thinking is also along similar lines to yourself Tomo but what amazes me is that there seems to be a tunnel-vision phenomena going on. Everyone seems fully absorbed in German engines vs British engines. You all seem to forget the numerous American and Russian engines and the particular example of the Allison variant with hydraulic-coupling driven supercharger vs it's fully gear-driven siblings. If there was inherent superiority in the use of a hydraulic coupling then everyone would be using it. I doubt very much that its efficiency losses will be insignificant over it's normal fight profile.

I wondering if the hydraulic coupling on the Allison (or even DB) wasn't more like a torque converter or variable speed drive than a clutch in which any speed difference is slippage that is wasted energy. The hydraulic power recovery turbines on the turbo compounds R3360 were surely like this.

xylstra · Jan 7, 2021

Snowygrouch said:
Not "elusive", the loss of the Föttinger coupling is directly proportional to the speed ratio its running at. Use a 10% slip, and 10% of the driven power will be converted to heat.

Both the British and Americans knew perfectly well how to make petrol injection almost a decade before the war broke out.

Please provide a citation for Rolls-Royce not bothering to develop their own technology because they were waiting for the Bendix to solve the problem for them>
(Hint, what they were working on was their own singlepoint fuel injection, which was implemented on the Merlin 100 series onwards - and I can assure you
that they were frantically scrambling to sort out their carburettor problems, having read the letters).

In the meantime, something to un-derail the thread, Junkers-Jumo training manual page, showing a nice section of the different bearings used between
the 211 and 600. You need a more sophisticated oil supply system to make best use of plain bearings, as Daimler discovered to their cost later on when
they had to convert to them.

View attachment 607753

I recall reading in "SPITFIRE, The History" that R-R test-flew examples of B-S's injection carburettor adapted to the Merlin.

xylstra · Jan 7, 2021

Koopernic said:
I wondering if the hydraulic coupling on the Allison (or even DB) wasn't more like a torque converter or variable speed drive than a clutch in which any speed difference is slippage that is wasted energy. The hydraulic power recovery turbines on the turbo compounds R3360 were surely like this.

A big factor in slippage losses is how the variability is actually achieved.

Deleted member 68059 · Jan 8, 2021

xylstra said:
I recall reading in "SPITFIRE, The History" that R-R test-flew examples of B-S's injection carburettor adapted to the Merlin.

Thats a good book, but what you`ve quote from the book about a flight test bears little relation to your first claim.

xylstra · Jan 8, 2021

Snowygrouch said:
Thats a good book, but what you`ve quote from the book about a flight test bears little relation to your first claim.

You lost me there, are we still talking injection carb's or back to hydraulic couplings?
This site has some very authoritive articles on aircraft powerplant and an especially good one on the R-R Merlin:
WWII Aircraft Performance

Deleted member 68059 · Jan 8, 2021

xylstra said:
You lost me there, are we still talking injection carb's or back to hydraulic couplings?
This site has some very authoritive articles on aircraft powerplant and an especially good one on the R-R Merlin.

Life is too short for this, you know perfectly well what we were talking about, I know there are articles here which are good, I wrote some of them, those; and the 3000 copies of a huge book Rolls-Royce themselves just described as: "a masterpiece of research and will undoubtedly become classic reference material."

But what do I know.

bdefen · Jan 10, 2021

I started this thread, and am glad to see the robust discussion.

Were the Jumo inverted vees able to accommodate through-the-propeller-hub guns like the DB engines?

Shortround6 · Jan 10, 2021

The Jumo 210 could.

The Jumo 213 (at least some versions) could.

The 211??? Some versions may have been able to but since the 211 was seldom, if ever (prototypes?) used in a single engine fighter the feature was never used.
The Germans never put guns through the propeller hubs of twin engine aircraft in service, drawings and proposals may be a different matter.

Hardrada55 · Jan 10, 2021

Would the Japanese have been better off licensing the JJ 211 instead of the DB601? I have read that lubrication system was superior in the JJ 211 and many of the Japanese problems with the DB601 were caused by problems with lubrication. A JJ 211 powered Kawasaki Ki-61 might have had less performance than a DB-601 powered version, but there might have been more servicable airplanes available.

tomo pauk · Jan 11, 2021

bdefen said:
I started this thread, and am glad to see the robust discussion.

Were the Jumo inverted vees able to accommodate through-the-propeller-hub guns like the DB engines?

Jumo 210 was flown with a cannon in that position, so that should be a 'yes'.
Jumo 211 B, D and H have had the 'tube' to where the gun barrel was to pass through as well as the cannon mounting attachment point (guns/cannons were not mounted directly to the engines, but via mountings).
It is very much possible that Jumo 211A have had provision for the prop gun.
On Jumo 211 F, J, N P, the space for gun barrel was blocked.
Jumo 213C and subsequent have had the ability, the Jumo 213A (known as the engine for theFw 190D-9) didn't.

Hardrada55 said:
Would the Japanese have been better off licensing the JJ 211 instead of the DB601? I have read that lubrication system was superior in the JJ 211 and many of the Japanese problems with the DB601 were caused by problems with lubrication. A JJ 211 powered Kawasaki Ki-61 might have had less performance than a DB-601 powered version, but there might have been more servicable airplanes available.

Timing is probably the key. Japanese DB 601A engines (Ha 40) were coming in service well after the Germans moved on, while other countries haven't stayed in the same place with regard to the engine power, either.
IMO - Japanese (Kawasaki for Army A/C, and especially Aichi for the Navy A/C) would've best to avoid licencing the engines from Germany, and carry on with production of radials. Both Kawasaki and Aichi were making radial engines under licence before the V12 saga anyway; Kawasaki was still making radials well after the Ha 40 production started.

FWIW (engine production at Kawasaki):

tomo pauk · Jan 11, 2021

Engine production at Aichi:

Koopernic · Jan 12, 2021

bdefen said:
I started this thread, and am glad to see the robust discussion.

Were the Jumo inverted vees able to accommodate through-the-propeller-hub guns like the DB engines?

Jumo 213A could not carry a motor canon since the engine lacked the fittings for the appropriate hollow shaft propeller and canon mounting. Hence the Fw 190D9 did not have one. The Jumo 213A engines having come from planed bomber production
.
The planed Jumo 213C could have, it was an improved Jumo 213A specifically developed as a fighter engine with both a motor canon and emergency boost. It never saw production.

As it was the Jumo 213E (Ta 152H0/H1) and Jumo 213F (Fw 190D12 and D13) that did have the mountings and had a motor canon. These had two stage superchargers, the Jumo 213F lacked the intercooler. I think all subsequent engines did as well, the Jumo 213EB, Jumo 213S and Jumo 213J.

The motor canon allowed the deletion of the cowling guns on the Few 190D12/13.

bdefen · Jan 12, 2021

Koopernic said:
Jumo 213A could not carry a motor canon since the engine lacked the fittings for the appropriate hollow shaft propeller and canon mounting. Hence the Fw 190D9 did not have one. The Jumo 213A engines having come from planed bomber production
.
The planed Jumo 213C could have, it was an improved Jumo 213A specifically developed as a fighter engine with both a motor canon and emergency boost. It never saw production.

As it was the Jumo 213E (Ta 152H0/H1) and Jumo 213F (Fw 190D12 and D13) that did have the mountings and had a motor canon. These had two stage superchargers, the Jumo 213F lacked the intercooler. I think all subsequent engines did as well, the Jumo 213EB, Jumo 213S and Jumo 213J.

The motor canon allowed the deletion of the cowling guns on the Few 190D12/13.

The Fw 190D10 prototype tried a motor cannon with some variant of the Jumo 213, but there were problems with it. The D11 deleted the motor cannon, deleted to cowl machine guns, and mounted and additional cannon in the outer wing.

Jumo inverted vee's vs. Daimler-Benz inverted vee's - Pros and Cons

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