"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 hight 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))