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

[tomo pauk]

My argument is that focusing on H, X, W or whatever exotic layouts you can come up with is a distraction from solving the problems that are making their V-12's noncompetitive. Solve those, and the 603 and 213 are more than good enough until jets take over. And without solving those issues, the hypothetical H-16 won't be particularly good either.

We can take a look at DB.
It was probably not their own original idea to implement the, let's say, high capacity 'central' oil feed to the crankshaft, but something that was brought by Jumo, whose people were installing that on the 211s years before it was applied to the DB engines. Or, chrome plated valves - that came from BMW, not from DB.
(BMW was 'fighting' with the oil supply issues themselves by the time of the switch from the 139 to 801 )
My point is that a H16 engine by DB will not be taking much from solving the issues, that were solved by other companies in the 1st place. It will take a far better degree of cooperation and oversight by the RLM, not by DB, to make a debugging happen months earlier.

Further, the H16 engine drawing from existing types can immediately take advantage of the things like better valves, while a new type of the V12 will need separate debugged items. So, as noted before, DB needs to design & develop basically 1.5 engine lines for the 1940s if the H16 replaces both the double engines and the DB 603 on their production lines, whereas they were developing 2+ lines of engines historically (without counting the X or V16 types).

With so much of resources and the design talent freed, there is no reason to not make a H16 engine with a high capacity supercharger.

But I suspect if you can't fit a bigger V-12 like the 603, you won't be able to fit a H-16 either. And the V-12 is a much less riskier proposition.

In my mind, the H16 should be seen as an upgrade vs. the BMW 801, and fit on the same aircraft as the 801, with benefits of making the better power on 87 oct fuel even if restricted as it was the case with the DB 605.
If the H16 cannot fit, use the DB 601/605/Jumo 211.

 

[tomo pauk]

The issue I see with an H-16 - there isn't enough difference between the 'sorted out' H-16 and 'current' V-12 to justify the extra weight/frontal area:

Date	V-12	H16
1937	Jumo 211A, 1,000 hp	prototype
1940	Jumo 211D, 1,200 hp	H16A 1,335 hp
1941	Jumo 211F, 1,350 hp	H16D 1,600 hp
1943	Jumo 211F, 1,500 hp	H16F 1,800 hp
1944	Jumo 213A, 1,750 hp	H16P 2,000 hp

H16 should be making a 33% better power than it's 12 cyl sibling.
So:
1200 HP V12 -> 1596 HP H16
1350 -> 1796
1500 -> 2000
1750 -> 2328

 

[don4331]

H16 should be making a 33% better power than it's 12 cyl sibling.
So:
1200 HP V12 -> 1596 HP H16
1350 -> 1796
1500 -> 2000
1750 -> 2328

The 1940 1,350 hp prototype H16 is equivalent to the 1937 prototype V12 in power per cylinder. You can't be developing the H16 and V12 concurrently or you will never get either finished, so the H16 is always a generation behind.

 

[tomo pauk]

The 1940 1,350 hp prototype H16 is equivalent to the 1937 prototype V12 in power per cylinder. You can't be developing the H16 and V12 concurrently or you will never get either finished, so the H16 is always a generation behind.

You can be developing the V12 and H16 in the same time if something else is not also being made.
For Jumo, there is no 222 in this scenario.

 

[TM06]

Beyond the bombers, there's the possibility to fit a Jumo H-16 / DB H-16 into the Do 335, Fw 190 / Ta 152, Ta 154, Ju 188, Ju 388, He 219 and maybe the Series 6 Fighters or the BV 155.
I'd wager that the twin-engined fighters would appreciate the boost in power, and it gives my beloved G.56 and even greater capability to outperform the Bf 109.

 

[z42]

We can take a look at DB.
It was probably not their own original idea to implement the, let's say, high capacity 'central' oil feed to the crankshaft, but something that was brought by Jumo, whose people were installing that on the 211s years before it was applied to the DB engines.

You're probably correct that the crankshaft nose oil feed wasn't their original idea. But so what? The point is having the engineering resources to be able to implement good ideas, wherever they may originate from. And the way to do that is to focus on improving a good enough base engine rather than flailing crazily in a hundred directions all at once.

As an aside, IIRC from Calum's book the bearing problems with the 605 originated with failing to increase the bearing oil supply when they switched from the roller bearings on the 601 to plain bearings on the 605. A really WTF level mistake from experienced engineers, and one entirely of their own doing. (the switch itself was per se probably a correct decision)

Again, something which may have been avoided by better focusing on what was going to become their main product rather than being distracted by a zillion other projects.

Or, chrome plated valves - that came from BMW, not from DB.

Understandable that BMW were the first to be seriously impacted by the sparmetall valve issue considering the hotter conditions in a radial.

And yes, big egg on the face of the RLM for not disseminating these findings to other companies. However, DB figuring this out was IIRC delayed by their test engined using the pre-sparmetall valves, again a mistake entirely of their own doing. Which might not have happened had they focused more on their main product rather than being distracted by all kinds of other engine projects.

My point is that a H16 engine by DB will not be taking much from solving the issues,

I suspect you're underestimating the effort to design a new engine of a layout the company has no previous experience with.

I mean, look at the Vulture. Just take the cylinder blocks from the Kestrel and smash four of them together on the same crankshaft. Easy peasy, what could go wrong? Granted a H engine is probably less risky than a X, but assuming it would be smooth sailing sounds wildly optimistic.

 

[tomo pauk]

You're probably correct that the crankshaft nose oil feed wasn't their original idea. But so what? The point is having the engineering resources to be able to implement good ideas, wherever they may originate from. And the way to do that is to focus on improving a good enough base engine rather than flailing crazily in a hundred directions all at once.

I'm all for improving the base engine, not just because it is using the idea that is materialized in mass production (be it at at another company, or the indigenous one), but also because it is applicable on the sibling engine.

I suspect you're underestimating the effort to design a new engine of a layout the company has no previous experience with.

I mean, look at the Vulture. Just take the cylinder blocks from the Kestrel and smash four of them together on the same crankshaft. Easy peasy, what could go wrong? Granted a H engine is probably less risky than a X, but assuming it would be smooth sailing sounds wildly optimistic.

Note that I'm avoiding, like a plague, the idea that the many-cylinder-engine should be with the single crankshaft, at least if the companies that don't make the radials are in question.
(FWIW, Vulture was using bespoke cylinder blocs due to the increased cylinder spacing vs. Kestrel/Peregrine)

The H16 can be considered, with a bit of salt, as two 180 degree engines one atop of another (or one next to another). Unlike the X engines, that required going with the master/slave rod arangement - can be done, but it is yet another step for a company to design/make/solve. So perhaps the H16 is not all the way a smooth sailing experience, but probably if not certainly more smooth than making an X engine.

 

[don4331]

Beyond the bombers, there's the possibility to fit a Jumo H-16 / DB H-16 into the Do 335, Fw 190 / Ta 152, Ta 154, Ju 188, Ju 388, He 219 and maybe the Series 6 Fighters or the BV 155.
I'd wager that the twin-engined fighters would appreciate the boost in power, and it gives my beloved G.56 and even greater capability to outperform the Bf 109.

A Jumo H16 isn't going to a fighter or a fast twin - based on the Arsenal 24H the engine is 1.5m tall (59") and its going to have frontal area of ~1.8 m^2 (19 ft^2) compared to ~0.7m^2 (7.7ft^2) for V12 or even 1.3m^2(14ft^2) for a BMW801. Compare how much slower the Fw190A is compared to the Fw190D; the H16 engine powered Fw190 is going to be that much slower.

We will also note that the Arsenal 24H was 1,850kg (4.080lbs) so an H16 might weigh as much as 1,250kg (2.700lbs)!

If you want and H16 for your fighter, you start with a short stroke, which allows you shorter rods and the whole engine becomes narrower. Then with your short stroke the crankcase becomes narrow enough that you can have a single head for both rows ala Sabre (and that stiffens the whole engine). But that throws tomo pauk 's concept of reuse of Jumo 211/3 development/parts out the window.

Note that I'm avoiding, like a plague, the idea that the many-cylinder-engine should be with the single crankshaft, at least if the companies that don't make the radials are in question.
(FWIW, Vulture was using bespoke cylinder blocs due to the increased cylinder spacing vs. Kestrel/Peregrine)

The H16 can be considered, with a bit of salt, as two 180 degree engines one atop of another (or one next to another). Unlike the X engines, that required going with the master/slave rod arangement - can be done, but it is yet another step for a company to design/make/solve. So perhaps the H16 is not all the way a smooth sailing experience, but probably if not certainly more smooth than making an X engine.

And yes, between concept and prototype analysis showed that there wasn't sufficient beating surface using Kestrel blocks and spacing had to me increased to almost Merlin level. (And it also ruled out using 2 blade and fork connecting rods as per the Eagle XVI (1925 version)

I would suggest a V-16 ala Chrysler/FIAT AS.8/DB609 engine; I do like the idea of center takeoff ala Chrysler/FIAT AS.6 and I would go with 90* to simply balance. An extra 35cm (14")* in length is a lot easier to fit into existing airframes.

*The length increase may be even reduced slightly by using 2 mirrored superchargers rather than single large one.

Clarification added to which Eagle I was referring to as RR used the name.

 

[tomo pauk]

We will also note that the Arsenal 24H was 1,850kg (4.080lbs) so an H16 might weigh as much as 1,250kg (2.700lbs)!

Arsenal 24H was based on a very heavy engine - Jumo 213. Thus the weight of the 24 was as it was - more than 400 kg heavier than the DB 606.
The run-on-the-mill Jumo 211s and Db 601/605 were much lighter than the 213, being tailored for a considerably lower RPM and power.

A Jumo H16 isn't going to a fighter or a fast twin - based on the Arsenal 24H the engine is 1.5m tall (59") and its going to have frontal area of ~1.8 m^2 (19 ft^2) compared to ~0.7m^2 (7.7ft^2) for V12 or even 1.3m^2(14ft^2) for a BMW801. Compare how much slower the Fw190A is compared to the Fw190D; the H16 engine powered Fw190 is going to be that much slower.

As a next step in the evolution, shortening of the stroke might've been worthwhile, talk down to 150-155mm (from original 160-165mm, for DB and Jumo respectively)? Making the engine slightly less tall, while allowing the increase of RPM = not unlike what Bristol did with when making the Mercury from Pegasus.
190A was slower due to several factors than the 190D - greater engine-related drag, greater guns' related drag, less power, worse air intake. The "190-16" should be with more power, not less, and with 87 oct fuel in use vs. 100 oct fuel for the 190A, so there is a way to get even more power.

 

[wuzak]

And yes, between concept and prototype analysis showed that there wasn't sufficient beating surface using Kestrel blocks and spacing had to me increased to almost Merlin level. (And it also ruled out using 2 blade and fork connecting rods as per the Eagle.

Using 2 fork and blade connecting rods was under cnsideration for improving the Vulture had it continued.

The late/post war Eagle had 2 crankshafts, so had one fork and blade rod set per crank throw.

The Pennine was an X-24. It used a single piece master rod with a built-up crankshaft - as was used in several high powered radial engines.

The problem with the Vulture was not that it used the master/slave rod configuration, it was that the master rod design was poor.

 

[Shortround6]

The H16 can be considered, with a bit of salt, as two 180 degree engines one atop of another (or one next to another). Unlike the X engines, that required going with the master/slave rod arangement - can be done, but it is yet another step for a company to design/make/solve. So perhaps the H16 is not all the way a smooth sailing experience, but probably if not certainly more smooth than making an X engine.

This is quite true.
But with the H-16 we loose some of the commonality of the H-24 engine, or X-24 engine. An X-16 engine also looses some commonality with the 12 and 24 cylinder engines using cylinder blocks that at 6 cylinders long.
The W-18 was more popular than the 4 bank (16 cylinder) engines.
Some of this was that they had an idea of what to expect from the 6 cylinder "bank" of cylinders. 6 cylinder engines were smoother running than 4 cylinder engines. When you add banks this do get smoother but the four, eight, W twelve and sixteens vibrate differently than sixes, twelve, eighteen and twenty fours. Some are better than others but they do vibrate differently.

Then we have engine construction. The two failed American 12 cylinder engines (and the H-24) were built in a way that minimized tooling, the separate cylinders. If you have tooling for an engine that uses en bloc construction for 6 cylinders You can't just lop off two cylinders. You often have to take out the 2 middle cylinders or design new parts that use the same bore and stroke and basic dimensions of the cylinders and heads in new castings. You can use the same rocker arms/valves. You need new cams. The cam profiles will be the same but you need to arrange the cam lobes differently to suit the different firing order.
Maybe you can machine the 4 cylinder heads on the same machinery, maybe you can't. You need to do the same things but it depends on the jigs/fixtures holding the heads. Maybe the 4 cylinder head fits in the Jigs/fixtures (clamps, locating surfaces, hold down bolts) and maybe they don't.

An H-16 can probably be made into a smooth running engine. Perhaps very smooth. But it needs a new path than the V-12 or H-24.

We are still skating right by the frontal area problem. Maybe we can mount the H-16 in place of the V-12 and figure out what to do about the weight. We have not figured out what to do about size/bulk/frontal area. V-12s are usually tapered in shape, skinny at the front and bigger at the back, this does not show up in a quick look at the width and height

Allison V-1710 from a P-38. The sump tapers to the rear, most (all?) of the accessories are hanging out the back or off to the sides at the rear. But that does give you 4-5 ft to taper the nose from the prop to the wide part at the back. even a Napier Dagger

Is a pretty blunt engine at the front. And it is a small engine, 16.8 liters, 3.75 in (95.25mm) stroke 45in overall height. Maybe it is a little taller at the back but it is huge at the front of the cylinder blocks compared to a Merlin or Allison.
The taper is important as it not only affects streaming (gradual taper can cover a lot of sins) but it helps with the downward view over the nose.

 

[Shortround6]

As a next step in the evolution, shortening of the stroke might've been worthwhile, talk down to 150-155mm (from original 160-165mm, for DB and Jumo respectively)? Making the engine slightly less tall, while allowing the increase of RPM = not unlike what Bristol did with when making the Mercury from Pegasus.

Mercury to Pegasus is a 25mm change in stroke. For some reason (rounded off numbers?) this was only worth 47mm in listed diameter
Bristol may have cheaped out and used the same rods on both engines? Sometimes you can shorten the rods but you do want to keep the same proportion (ratio) of rod length to stroke or the angles at 90 degrees get a little odd.

You might not get quite the reduction in stress you want from the shorter stroke in any case.
Using the Jumo 211 as an example at an RPM of 2500 it is rated at 2708fpm piston speed but that raw. Corrected by the Lanchester formula (correction factor 1.048) that gives a corrected piston speed of 2583fpm.
Now if we cut the stroke down to 155mm from 165mm and keep the same bore, that changes the correction factor to 1.016 and at the same 2500rpm it cuts the corrected piston speed to 2501fpm. Better but not the difference that the 155mm stroke shows in the raw figure, 2541.6 fpm
Our 167fpm advantage from the short stroke as shrunk to about 41-42 fpm.
Granted this is a calculated formula.
On a Napier Sabre engine things flip. For a stroke to bore ratio of 4.75in to 5.00 the correction factor is 0.975 and that boosts the corrected piston speed at 3850rpm from 3048 fpm to 3127fpm.

If you can make your pistons lighter you may get enough reduction in stress to allow for the rpm without shorten the stroke.
Cutting your displacement by 6.5% means you have to make that up increasing the rpm to around 2660 from 2500rpm, everything else remaining equal.

 

[wuzak]

Mercury to Pegasus is a 25mm change in stroke. For some reason (rounded off numbers?) this was only worth 47mm in listed diameter

Maybe the stroke wasn't the limiting factor for the engine diameter, but the space required between cylinder barrels at their base.

 

[wuzak]

Also want to mention that the synchronising gears and reduction gear may be a higher proportion of the weight of an H16 compared to an H24.

 

[Frank Stewart]

Basically, both engines are designed in the shape similar as the Napier or Fairey engines, where we can take about the separate engines one atop of the other (or one aside to the other - whatever floats your boat), that share supercharger and propeller, as well as other bits and pieces so that pilot, for all intents and purposes, directs the power of just one compete engine.
Engine bore and stroke are shared with the mass-produced types, Jumo takes from the 211, DB takes from the DB 601/605. Contemporary advantages and disadvantages of German engines are present here, like the direct fuel injection, can make decent power on 87 oct fuel due to the engines being of reasonably big displacements, while the lack of nickel and, with DB , quirky oil system are also in play. Both engines are obviously liquid cooled
Development of both engines start as it was the case historically, in the late 1930s, with the DB contender making the 1st flights in the early 1939, and the Jumo's engine doing the same in the early 1940.

What changes to the German design and purchase might've unfolded with these engines available in good numbers, both wrt. the next-gen aircraft and next-gen engines?

Again, why bother? The DB-603 is already in the works and can, or has made 2,500 HP on higher octane gas, for the Silber Vogle record car. The Turbocharged Version made 2,930 HP IRC. If Germany had had high temp alloys, the TA-152 would have ruled the roost! In real life there are really only two types of economical powerful piston engines. Big V-12s and Radials! Any other type is a can of worms and not worth the effort. In reality all inline engines were dead ends, Only Radials had the growth potential to provide the next generation of aircraft power. Look at the R-R Merlin and Griffon. both were developed past their reliability point and had to be dialed back to meet reasonable durability limits! Look up the history of the R-R Merlin in the Horet! This long after radials were making bigger power for more hours at lower costs!

 

[Frank Stewart]

The issue I see with an H-16 - there isn't enough difference between the 'sorted out' H-16 and 'current' V-12 to justify the extra weight/frontal area:

Date	V-12	H16
1937	Jumo 211A, 1,000 hp	prototype
1940	Jumo 211D, 1,200 hp	H16A 1,335 hp
1941	Jumo 211F, 1,350 hp	H16D 1,600 hp
1943	Jumo 211F, 1,500 hp	H16F 1,800 hp
1944	Jumo 213A, 1,750 hp	H16P 2,000 hp

I agree you have to go to more cylinders as the DB603 has same issue - the bigger cylinders/longer stroke means it never makes sufficient additional power to justify its increased weight.

And that's effectively the issue with the Vulture, by the time it makes 1,750 hp reliably, so is the Griffon. At least the Sabre makes 2,200hp (we can debate how reliably), so between not wanting to get locked into sole source supplier and Typhoon/Tempest being designed for Napier's engine, it soldiers on.

The DB-603 was lighter than the much smaller Griffon and made significantly more power, if run on better gas. No Griffon passed it's type test at more than 2,500 HP during the war and were dialed back significantly post war to meet longevity requirements. The DB-603 turbo made and passed at 2,930 HP in 1944!

 

[z42]

Again, why bother? The DB-603 is already in the works and can, or has made 2,500 HP on higher octane gas, for the Silber Vogle record car. The Turbocharged Version made 2,930 HP IRC. If Germany had had high temp alloys, the TA-152 would have ruled the roost! In real life there are really only two types of economical powerful piston engines. Big V-12s and Radials! Any other type is a can of worms and not worth the effort. In reality all inline engines were dead ends, Only Radials had the growth potential to provide the next generation of aircraft power. Look at the R-R Merlin and Griffon. both were developed past their reliability point and had to be dialed back to meet reasonable durability limits! Look up the history of the R-R Merlin in the Horet! This long after radials were making bigger power for more hours at lower costs!

I agree that Germany had been better off just concentrating on the 603, 213, and turbines.

That being said, I think the post-war dominance of radials is mostly due to the industrial and economic dominance of the USA and their liking radials for transports and bombers (post-war fighters were largely a lost cause for piston engines for well-known reasons, except a few Hail Mary's for carrier use).

As I've mentioned before, I think had turbines been delayed we'd have seen a fusion of inlines and radials in a sort of liquid cooled radial engine. A bit like the Vulture, but why stop at 4 banks? 9 banks of 6 Griffon cylinders each would give a 54 cylinder engine with 165L displacement.

 

[tomo pauk]

Again, why bother? The DB-603 is already in the works and can, or has made 2,500 HP on higher octane gas, for the Silber Vogle record car. The Turbocharged Version made 2,930 HP IRC. If Germany had had high temp alloys, the TA-152 would have ruled the roost! In real life there are really only two types of economical powerful piston engines. Big V-12s and Radials! Any other type is a can of worms and not worth the effort. In reality all inline engines were dead ends, Only Radials had the growth potential to provide the next generation of aircraft power. Look at the R-R Merlin and Griffon. both were developed past their reliability point and had to be dialed back to meet reasonable durability limits! Look up the history of the R-R Merlin in the Horet! This long after radials were making bigger power for more hours at lower costs!

I was trying to type out the reply, but the density of exclamation marks convinced me that there is no point.
Cheers.

 

[don4331]

The DB-603 was lighter than the much smaller Griffon and made significantly more power, if run on better gas. No Griffon passed it's type test at more than 2,500 HP during the war and were dialed back significantly post war to meet longevity requirements. The DB-603 turbo made and passed at 2,930 HP in 1944!

Prototypes don't count, Germany never had a working turbocharger; Numbers below are from Jane's

Engine	Weight	Power
Rolls Royce Merlin 130/131/134/135	1,645lbs	2,080hp MS (150 octane, +25lb boost)
Rolls Royce Griffon 65	1,980lbs	1,720hp MS (100 octane, +15lb boost) 2,220hp MS (150 octane, +25lb boost)
Rolls Royce Griffon 130	2,165lbs	2,420hp LS
Daimler Benz 603A	2,002lbs	1,726hp (B4)
Daimler Benz 603E	2,035lbs	1,775hp (C3)
Daimler Benz 605D	1,665lbs	1,900hp(C3 +water)

I'm not seeing significant differences in weight and/or power between Griffon and 603. And the smaller Merlin/605 hold their own.

 

[z42]

Prototypes don't count,

Why should prototypes not count? The entire thread is a what-if scenario about some engine types that weren't even on the drawing table AFAIK. If we're thinking about potentially better resource allocations, it seems only fair to compare these entirely fictional engines with variants of actual engines that just were too late.

Had they not put the 603 on hold for several years (while spending resources on things like those coupled engines), the much improved 603N might very well have seen service. No turbo though, but generally improved performance and a two-stage supercharger doesn't seem completely unfeasible.