"Jumo 222" and "DB 606/610" made in H16 form instead of being 24 cyl types - what gives?

[tomo pauk]

Tomo, having looked at a few other threads, I realize your interest in an H16 is long lasting. There is a reason that there was only one production H16, that was installed in only 70 aircraft. Wuzak, Shortrounds and a few others have already commented on the difficulties of creating an H16. The largest unknown is the resonance from the firing order and that impact on the gears that connect the crankshafts and the prop speed reduction unit. The alternative is to have more primary order vibration. As the 18 cylinder radials showed, vibration was the great bugaboo of WW2. There is no guarantee in 1939 that an H16 would be buildable on schedule at specification. An H24 would be significantly easier to develop. It is not just history that tells us that, but a pair of flat crankshafts are not going to make a smooth engine.

There is certainly no guarantee. However, this is a what-if scenario, and like most if not all such scenarios, there are trade-offs in play.

"The H16 will be providing no worse power-to-weight ratio than the BMW 801 or the coupled engines"
This seems to be a bit tenuous.

My cunning idea is that German mass-produced engines were already with the worse power-to-weight ratio than the Western or Japanese types, so achieving the similar unimpressive p/w ratio would've been achievable.

I have no problems with people - especially SR6 and wuzak - trying to poke holes in my ideas, after all this is what the forums are for.

 

[sotaro]

A H16 would have the same frontal area as a H24 if they are based on the same design.

An H16 will have two crankshafts, each with 4 rod journals. They will use fork and blade type rods.

Only if they went for a boxer type engine would they need 8 throws per crankshaft

Agreed on the frontal area similarities, as I stated.
No doubts that H engines have two crankshafts.

", each with 4 rod journals" This I believe to be in question. Have you seen an H16 crankshaft? This is the only photographs I have seen, and it is of the BRM H16 Grand Prix engine. Yorkshire Ferret

I believe the first version is on the left and the second version the right. The first version had 4 rod journals, the second had 8. The second was not a boxer type engine. This crankshaft design change was to reduce vibration and resonance issues. Still BRM had to replace components very often, "ruthlessly" due to their rapid fatiguing. It is much easier to find discussion of the BRM H16 than the Napier H16.

Have you seen any photos of the Napier Rapier crankshafts?

 

[sotaro]

There is certainly no guarantee. However, this is a what-if scenario, and like most if not all such scenarios, there are trade-offs in play.



My cunning idea is that German mass-produced engines were already with the worse power-to-weight ratio than the Western or Japanese types, so achieving the similar unimpressive p/w ratio would've been achievable.

I have no problems with people - especially SR6 and wuzak - trying to poke holes in my ideas, after all this is what the forums are for.

Tomo, no one I have seen on this thread has posted in support of an H16 being able to beat vibration and resonance issues. The folks that seem most knowledgeable have cautioned against the idea. Geared together crankshafts always have some issues to be resolved. The fewer the cylinders geared together the greater the problems. Then it has to go thru the prop speed reduction unit (PSRU). So, what about turning to something that seems less problematic, the W18? Far less resonance issues, less frontal area, easier to predict its completion of engine trials. more history for the type.

 

[don4331]

So, what about turning to something that seems less problematic, the W18? Far less resonance issues, less frontal area, easier to predict its completion of engine trials. more history for the type.

I don't know if I want to derail tomo pauk 's H16 thread with a W18 offshoot or not...well, here goes:

I too was original thinking of proposing the W18 as an alternative:

The multiple "straight 6s" of W-18 have primary and secondary vibration issues that are less than most other engine configurations (not as nice as a straight 6 or v-12 but better than any odd number of cylinders in a bank e.g. V-10)​

The master rod has both slave rod connections in "upper half" so the bolted connection is easier than an "X" engine. However, the slave rods increase side loads on the pistons/cylinders which would need to be accounted for. The master/slave rod balance also doesn't follow the nice concentric path that the V-12 blade and fork does - it won't be as bad as a radial, but the crank will see higher stresses.​

It needs unique magnetos/fuel injection and custom camshaft drive. A supercharger of 50% more capacity for which the discharge locations aren't nicely symmetric, so balancing boost is going to be a challenge​

The W18 tends to be a tall engine - but I'm not sure if that is too great of an issue if we assume inverted engine for the German applications.​

Like a radial, there won't be any opportunity for a centerline cannon.​

And its going to run a generation behind the V-12 assuming you are reusing as much as possible i.e. cylinder blocks, heads, pistons, etc.) But maybe the 50% extra capacity will keep it enough ahead of the V-12 to justify its existence.​

 

[tomo pauk]

Tomo, no one I have seen on this thread has posted in support of an H16 being able to beat vibration and resonance issues. The folks that seem most knowledgeable have cautioned against the idea.

I'm okay with people not throwing themselves in support of my ideas. And Good knows I've had loads of them in the last 20 years of being a member of different forums.

Geared together crankshafts always have some issues to be resolved. The fewer the cylinders geared together the greater the problems.

Definitely something for the engineers to work on.

So, what about turning to something that seems less problematic, the W18? Far less resonance issues, less frontal area, easier to predict its completion of engine trials. more history for the type.

IIRC S Shortround6 was not a fan when I've tried to pitch them years ago

 

[sotaro]

I am sure there are reasons to dislike the W18. However, compared to the H16 they are a walk in the park. The solutions engineers may come up with may take a long time, may be expensive and will be heavier. The result could be not worth the effort, which is exactly what the historical record for the H16 has shown us. The Napier Rapier had 6 versions developed between 1929 and 1936 before it was installed in 66 production aircraft. If your H16 were successfully developed twice as fast as the Napier it would be 1942-43 before it could be in production. A W18 would have to have a lot of problems before I would be tempted to throw my development money at the H16. Your question does allow a lot of speculation given the paucity of actual information on H16s.

I'm okay with people not throwing themselves in support of my ideas. And Good knows I've had loads of them in the last 20 years of being a member of different forums.



Definitely something for the engineers to work on.



IIRC S Shortround6 was not a fan when I've tried to pitch them years ago

 

[tomo pauk]

I am sure there are reasons to dislike the W18. However, compared to the H16 they are a walk in the park. The solutions engineers may come up with may take a long time, may be expensive and will be heavier. The result could be not worth the effort, which is exactly what the historical record for the H16 has shown us. The Napier Rapier had 6 versions developed between 1929 and 1936 before it was installed in 66 production aircraft.

There is not enough of historical records about the H16 to begin with. One H16 that made it to a meager production numbers is the too small a sample, especially when compared with the V12s or R14s that were made by many companies and in many thousands.
We can recall that Napier Dagger was in the same category of reliability as the Rapier - perhaps a lot had to do with what company was making the engines, and that air cooling was not a recommended way to go on the engines with many rows of cylinders.

If your H16 were successfully developed twice as fast as the Napier it would be 1942-43 before it could be in production.

From the German point of view - excellent.

Your question does allow a lot of speculation given the paucity of actual information on H16s.

A reason why we're discussing this in a what-if forum

A W18 would have to have a lot of problems before I would be tempted to throw my development money at the H16.

Don't get me wrong, I kinda like the W18s.
From the Italian and French PoV, it would've meant a 1200-1300 HP engine on tech and fuel of the second half of 1930s (ie. using the HS 12Y and I-F Asso XI as starting points, respectively), with an engine that is not too heavy. Both companies actually made the W18 engines, but you know that already.
For the Germans, this means 2000 HP in 1942, and still with 87 oct fuel.

 

[mack8]

I'll just say that whatever keeps the germans away from the very advanced hence impractical in wartime Germany Jumo-222 and DB-604, with their very high rpm and other advanced features hence needing the best materials, and of course any welded engine disasters like DB-606/610, is a good thing.

So all that design time is invested instead into the DB-616 and Jumo-216, using existing cylinders, down to earth rpm etc. They might get 2000 HP out of them by the size route, rather than rpm/advanced features route, which perhaps has more chances of success.

In this ATL i'm in two minds about the high rpm/advanced features Jumo-213 which took ages to get ready. By all account it was an excellent engine, but would it have worth putting that time into the notional Jumo-216 instead? By all means incorporate the best features of the Jumo-213 like the swirl throttle supercharger and so on, but into a 2600-2700 rpm engine. Maybe it will be ready 1 or even 2 years earlier, a long time in WW2.

 

[Reluctant Poster]

Agreed on the frontal area similarities, as I stated.
No doubts that H engines have two crankshafts.

", each with 4 rod journals" This I believe to be in question. Have you seen an H16 crankshaft? This is the only photographs I have seen, and it is of the BRM H16 Grand Prix engine. Yorkshire Ferret

I believe the first version is on the left and the second version the right. The first version had 4 rod journals, the second had 8. The second was not a boxer type engine. This crankshaft design change was to reduce vibration and resonance issues. Still BRM had to replace components very often, "ruthlessly" due to their rapid fatiguing. It is much easier to find discussion of the BRM H16 than the Napier H16.

Have you seen any photos of the Napier Rapier crankshafts?

The website you reference is the best history of the ill starred BRM H-16 I have found. As you point out the H-16 had terrible torsional vibration issues which were somewhat cured by 8 journal crankshaft and a revised firing order. Porsche also used the 8 journal crank in their flat eights of the 60s. As such I think that fork and blade or articulating connection rods are a non starter in an H-16. Here's all four parts of the history

The BRM H16 engine – part 1: Concept

New rules for Formula 1 engines were introduced for 1966 which stipulated that normal pump petrol was to be utilised in either 3 litre nat...

yorkshireferret.blogspot.com

The BRM H16 engine – part 2: Engine layout

The H16 was a clear descendent of BRM’s 1.5 litre V8 engine. The H16 utilised the same valves, springs, tappets and cam forms. It was origi...

yorkshireferret.blogspot.com

The BRM H16 engine – part 3: Performance and development

Given that the H16 utilised effectively 16 cylinders from their 1.5 litre V8 engine, BRM had anticipated that the H16 would produce approx...

yorkshireferret.blogspot.com

The BRM H16 engine – part 4: The quest for reliability and conclusions

It is fair to say that the development of the BRM H16 suffered due to numerous reliability issues. Vibration and resonance issue was by fa...

yorkshireferret.blogspot.com

 

[z42]

If one wants a 16-cylinder engine using the same bore&stroke as the 605 & 211, what about a V-16? Yes, you'd need a comparatively heavier and stiffer crankshaft and casing than the V-12, but would that really be heavier than the H-16? Additionally, you'd get to keep the same frontal area as the V-12, much smaller than a H layout.

 

[wuzak]

Porsche also used the 8 journal crank in their flat eights of the 60s.

Porsche's flat 8s were, like their 6s, boxer engines.

That can only be achieved with 8 crankshaft throws.

 

[Reluctant Poster]

Porsche's flat 8s were, like their 6s, boxer engines.

That can only be achieved with 8 crankshaft throws.

In his excellent book "Classic Racing Engines" Karl Ludvigsen has chapters on the Porsche 753 1.5 litre Flat-8 and the BRM P75 3 litre H-16.
For the H-16 he writes:
" Severe torsional vibrations affected the output gear train's centre gear and bearings, which received twisting impacts from both crankshafts at alternating intervals and in opposite directions. As a palliative the mass of four of the crank counterweights was increased by 2lb (0.9kg) apiece by bolting and welding a steel inertia ring to each one. "This modification, crude though it was, proved effective' recalled Tony Rudd,' and it was then possible to install the engine in a car."
"A major change allowed the H16 to run as a sequential 16, with one cylinder firing every 45 degrees of output shaft rotation. This required new crankshafts with eight individual throws to give a firing order that allowed tuned scavenging exhaust pipes to be used."

 

[z42]

As you point out the H-16 had terrible torsional vibration issues which were somewhat cured by 8 journal crankshaft and a revised firing order. Porsche also used the 8 journal crank in their flat eights of the 60s.

Should the H engine with 8 journal crankshafts (or generally, one journal per cylinder) then properly be called a h (h-bar) engine?


(Unless you're a physicist or chemist, you probably didn't get this. Don't worry about it. Hint: h-bar=h/(2*pi))

 

[Shortround6]

IIRC S Shortround6 was not a fan when I've tried to pitch them years ago

Don't get me wrong, I kinda like the W18s.
From the Italian and French PoV, it would've meant a 1200-1300 HP engine on tech and fuel of the second half of 1930s (ie. using the HS 12Y and I-F Asso XI as starting points, respectively), with an engine that is not too heavy. Both companies actually made the W18 engines, but you know that already.

There were several other W-18s in the 1920s and early 30s. 4 companies ?.

As you point out they were based on using the tech and fuel of the time (20s/early 30s). Something to be looked at is the weight for power.
Part of the "tech" of the time is that some of the engines were direct drive (or reduction gears were optional) which limited the rpm. Adding displacement could make up for lower rpm.
The other thing was the fuel, which was bad enough that many of the 20s engines were not using superchargers. Which also limits power compared to later engines.

A number of the engines were 'race' engines which means we should be comparing them to 'race' Napier Lions or RR "R" engines for output/weight and engine life.

Commercial (or military)interest seems to have (nothing in writing) gone away with geared and supercharged V-12s offering similar power to weight. Like a W-18 Hispano being around 100kg heavier (about 20%) than 12Y engine but running at 2000rpm and offering about 25% more power than the V-12 for it's 50% extra displacement. There is a few years difference bey perhaps the W-18s were seen as a dead end?

RR was using a supercharger and exotic fuel to make a 36.7 liter V-12 engine make record setting power.
The Hispano W-18 was 54.1 liters.
The Farman T-18 was only 24.4 liters but was supposed to hit 3700rpm. They were also planning on using two of them in the racer.
The Isotta engines were for commercial use and were 47.1 liters. There was a race version with 10mm more bore and 10mm more stroke for 57.3 liters. later become a commercial engine.
Most of engines in the late 20s/early 30s were not supercharged.
Larraine had made the 18K of 36.6 liters but the 120mm bore X 180mm stroke both limited rpm but also piston area. There was a later 18Ga with many improvements and a bore of 125mm for a displacement of 39.8 liters. In 1934 a supercharged version was shown but few details are available.

 

[Shortround6]

If one wants a 16-cylinder engine using the same bore&stroke as the 605 & 211, what about a V-16? Yes, you'd need a comparatively heavier and stiffer crankshaft and casing than the V-12, but would that really be heavier than the H-16? Additionally, you'd get to keep the same frontal area as the V-12, much smaller than a H layout.

This gets a little dicey. There have been successful V-16s built, but generally luxury car engines or diesel railroad locomotives or marine engines. Applications were weight was not a primary concern.
The Chrysler V-16 aircraft engine 'solve' the torsional vibration problem by separating the engine into two V-8s and taking the propeller drive from a gear mounted midway on the crankshaft and routing the drive though a shaft located under the crankshaft of the forward 8 cylinders. This was rare (maybe only instance?) of this being used on a V-16 but it was not uncommon for straight eight racing engines to be built as a pair of fours with cam drives and other accessories mounted between the blocks even if the crankshaft was one piece with the drive going off one end. The Chrysler V-16 and these 'split' 8s also had an extra main bearing on the crank. A bearing on each side of the gear in addition to the ones in the normal locations.

Shows the 5 main bearings on this 1/2 of the engine with the drive gear just visible on the left side of the pictures.
Not saying it was the only way to make a hi-performance V-16.
BRM used the same basic layout for their 1 1/2 liter 1951 Grand Prix car. Two crankshafts joined by a gear section, the gears running up to the 8 cams (two cams in each head and two heads on each bank of cylinders. Drive taken off the central gear and a shaft run under the engine to the clutch/transmission.

Maybe both teams would have been better not trying to be quite so clever and just designing a heaver crankshaft and crankcase to begin with?
But this might mean new connecting rods to fit the larger diameter crankshaft journals.

 

[sotaro]

This gets a little dicey. There have been successful V-16s built, but generally luxury car engines or diesel railroad locomotives or marine engines. Applications were weight was not a primary concern.
The Chrysler V-16 aircraft engine 'solve' the torsional vibration problem by separating the engine into two V-8s and taking the propeller drive from a gear mounted midway on the crankshaft and routing the drive though a shaft located under the crankshaft of the forward 8 cylinders. This was rare (maybe only instance?) of this being used on a V-16 but it was not uncommon for straight eight racing engines to be built as a pair of fours with cam drives and other accessories mounted between the blocks even if the crankshaft was one piece with the drive going off one end. The Chrysler V-16 and these 'split' 8s also had an extra main bearing on the crank. A bearing on each side of the gear in addition to the ones in the normal locations.
View attachment 784046
Shows the 5 main bearings on this 1/2 of the engine with the drive gear just visible on the left side of the pictures.
Not saying it was the only way to make a hi-performance V-16.
BRM used the same basic layout for their 1 1/2 liter 1951 Grand Prix car. Two crankshafts joined by a gear section, the gears running up to the 8 cams (two cams in each head and two heads on each bank of cylinders. Drive taken off the central gear and a shaft run under the engine to the clutch/transmission.

Maybe both teams would have been better not trying to be quite so clever and just designing a heaver crankshaft and crankcase to begin with?
But this might mean new connecting rods to fit the larger diameter crankshaft journals.

How much did the crankshaft of an V12 aircraft engine of 27-36 liters weigh? I vaguely remember reading that an X engine was one crankshaft lighter than an H engine and the crankshaft weighed about 330 lbs (though that seems like too much). I would anticipate that the weight of a V16 is going to be much more than just one third more than a V12 crankshaft.

 

[sotaro]

In his excellent book "Classic Racing Engines" Karl Ludvigsen has chapters on the Porsche 753 1.5 litre Flat-8 and the BRM P75 3 litre H-16.
For the H-16 he writes:
" Severe torsional vibrations affected the output gear train's centre gear and bearings, which received twisting impacts from both crankshafts at alternating intervals and in opposite directions. As a palliative the mass of four of the crank counterweights was increased by 2lb (0.9kg) apiece by bolting and welding a steel inertia ring to each one. "This modification, crude though it was, proved effective' recalled Tony Rudd,' and it was then possible to install the engine in a car."
"A major change allowed the H16 to run as a sequential 16, with one cylinder firing every 45 degrees of output shaft rotation. This required new crankshafts with eight individual throws to give a firing order that allowed tuned scavenging exhaust pipes to be used."

Great find Reluctant. After reading that, it is apparent that the H16 would need a lot of amazing engineering to make a reliable aircraft engine. It is not a good choice of lay outs.

 

[Reluctant Poster]

How much did the crankshaft of an V12 aircraft engine of 27-36 liters weigh? I vaguely remember reading that an X engine was one crankshaft lighter than an H engine and the crankshaft weighed about 330 lbs (though that seems like too much). I would anticipate that the weight of a V16 is going to be much more than just one third more than a V12 crankshaft.

R Raymond has several papers on crankshaft design on the AEHS website:

Crankshaft Design Evolution

https://www.enginehistory.org/members/articles/V-12TV.pdf

https://www.enginehistory.org/members/articles/CrankpinBearings.pdf

 

[Shortround6]

How much did the crankshaft of an V12 aircraft engine of 27-36 liters weigh? I vaguely remember reading that an X engine was one crankshaft lighter than an H engine and the crankshaft weighed about 330 lbs (though that seems like too much). I would anticipate that the weight of a V16 is going to be much more than just one third more than a V12 crankshaft.

You may be right. But there was a lot of stuff going on and sometimes studies or comparisons are done for engines of the same power. The 16 cylinder engine/s that Tomo is proposing has 1/3 more power than the V-12 which makes things a little more difficult, Much like most people would not want to use the same weight crankshaft in a 36 liter engine as they would in a 27liter engine assuming both engines were making the same power per liter.
H-S used a rather light crankshaft for a 36 liter engine (about 50KG) but then they were only getting around 900-1000hp out of the engine in it's 1930s forms. Sauer changed to an 80 kg crankshaft when they tried to get 1400-1500hp out of the engine.
Not only were they putting a greater load on the crankshaft with more pressure in the cylinders (more force on the piston per firing impulse) but they were running the crankshaft at a higher speed. Going from 2400rpm to 2600rpm is 8.33% faster but the rotational loads go up with the square of the speed (so do the loads on the connecting rods just from stopping and then going back in the opposite direction hundreds of times per second) so these forces go up 17.3%. Junkers was pulling a miracle getting the 213 over 3000rpm
V-16 also has a crank about 1/3 longer which means more flex and for torsion that extra 1/3 length can mean a lot with the last pair of cylinders trying to twist the crankshaft and then unloading.
Our intrepid engine designer can opt for the H-16 and dodge the V-16 problems and pay for it with the 2nd crankshaft/crankcase and came drives. It might actually not wind up that different as far as weight goes. I don't know. But there is no getting away from the increased frontal area. This aspect had greater and lesser importance over the years.
1919 and the 20s it didn't really matter what shape the engine was (mostly), This 60.3 liter X-16 engine was huge

Don't even want to figure out the firing order on that thing
But they hid it well two of these

Another Blackburn product so frontal area was not a consideration. Fuselage was over 11ft deep.
In the 1930s size of the engine became a lot more important. During WW II it became a little less so, with 1700-2300hp engines and the fuel to operate them the planes hade gotten larger and with added length and decent streamlining a fairly large engine could be put in a fast plane with good streamlining (Do 335, a 13.8 meter fuselage can hide a lot of "stuff").

An H-16 engine may have been very useful as a bomber engine even if it would have given the 109 boys conniptions.

 

[sotaro]

R Raymond has several papers on crankshaft design on the AEHS website:

Crankshaft Design Evolution

https://www.enginehistory.org/members/articles/V-12TV.pdf

https://www.enginehistory.org/members/articles/CrankpinBearings.pdf

Thank you!!! I just read parts of the first link, but clearly a crankshaft in an H 24 engine would not weigh 330 lbs. Seems like the crankshaft itself would weigh from 100-176 lbs (though the data shown does not include the Griffon). Perhaps including the extra bearings and crankcase strength and the gears that unite the two cranks of an H24 would add up to 330 lbs, but that would seem to be a stretch.

After reading that one article, the idea of an H16 seems like it would face very significant resistance from those tasked with funding and creating it. From a crankshaft/case design perspective, the multiples of six offered a path to success. Considering the difficulties facing the 60 degree V12s, a decades old configuration, caution is the byword. Nonetheless, the H engines did have the advantage of a very strong crankcase which kept the crankshaft from bending it too much and allowed the bearings to work better. To a lesser extent, the W would also have some of that advantage, though I am guessing the the 80 degree W18 would have a more flexible crankcase than the 160 degree W18 (like the W18 that made it into commercial service!).

I will try to read the articles carefully, they are not for the faint of heart...