Alternate Jumo-213

[mack8]

This is inspired by a post elsewhere, where an alternate Jumo-213 is proposed. So let's suppose that instead of developing the admitedly very good OTL design with it's high rpm and other which pretty much resulted in a new egine compared to the Jumo-211, the Jumo people borrow a trick from DB and go for an incremental upgrade, they bore it out to 155x165 and 37.4 litre capacity, raise the rpm to say 2700, or 2800 rpm if possible, and adopt a 4-valve head. Basically Jumo's equivalent to DB-605.

The idea being that the development should take less than the OTL Jumo-213, so this engine is available earlier, ideally about the same time as DB-605 so 1942. Based on the power levels of the Jumo-211P/N, this ATL Jumo-213 should make about 1600 PS intially at 2700 rpm? It's basically much like a Jumo-211N/P but bored out and with 4-valve head. Is it difficult to implement a 4-valve head on the Jumo-211 design? Of course, the advances in supercharger design such as the swirl throttle etc will be incorporated.

Further evolutions with MW boost, C3 fuel and 2-stage superchargers happens as in OTL. Is it feasible to further increase rpm to 2800 in later models for more power? Also preferably a motorkannone shaft from the start.

If the evolution of the DB-605 is mimicked, then this Jumo-213 should be quite a lot lighter that the OTL design, maybe around 800 or not much over kg? So it's lower power will in part be compensated by lower weight. Possibly if used on FW-190D it may not need the fuselage extension, thus easing design and production?

Assuming the production switching is as relatively straightforward as on DB-605, then this ALT Jumo-213 should account for a big chunk of Jumo's production from 1942 onwards, say at least 20,000 will be made, maybe even considerably more, even possibly approaching DB-605 numbers.

So what changes? 1600 PS in 1942 is better than 1750 PS in 1944, many midwar designs OTL using Jumo-211 (Ju-88, 87, He-111 etc.) would get a welcome power boost, while possibly a FW-190D powered by this engine appears much earlier, say 1943, more or less instead of the planned FW-190C. Armed with 3 cannon and no cowl guns to keep weight down, and without the tail extension, this should be lighter than the OTL FW-190D, while offering almost the same performance, but of course over a year earlier? Presumably the increase boost kits could be adopted on this ALT Jumo-213 as well? And then later MW-50 and C3 fuel.

 

[tomo pauk]

Nothing much to add, bar the addition of the 2-stage supercharger by late 1943.

 

[Shortround6]

Development often means changing one thing at time.

You are looking for at least 3 and probably 4

The Change in displacement is worth abut 7% but it is a bit risky. It was the 4mm change in bore that 'helped' Screw the DB 605 up for while. Bigger bore means harder cooling, both from the volume to wall area ratio but in the longer (slightly but it is there) distance from the piston center to the piston skirt to dissipate the heat before piston failure.

By the end of 1940 they were expecting the Ju 211 J running at 2600rpm. It ran late. 2600rpm to 2700rpm is worth 3.8% if everything else goes well.
Increasing rpm means the loads on the Crankshaft goes up with the square of the speed.
Changing rpm can also (but maybe not?) mean changing the counterweighting on the crank or changing a vibration damper. They were looking for all kinds of vibrations, from 1st order to out 7th or 8th order and a number of 1/2 orders, like 4 1/2 order (vibration occurs at 4 1/2 times the speed of the crankshaft) so a lot vibrations shift a bit and a few new ones show up.

Changing the bore size changes the piston weight and the balance.

Can't find a picture of a Jumo cylinder head/combustion chamber.
If they have an idea of what they want to the change to 4 valves to do all is fine, changing it just change it just creates problems. Does the 3 valve flow enough air to make the power you want or do you need 4 valves to really get the flow, not just a little more.
How good is your porting? How good is you manifold?
Junkers was making pretty crappy supercharger impellers in 1939-40.

Change the valves and don't change the impeller doesn't get you much.

Aircraft engines were supposed to last for 100 hours or a more, some didn't make it (I am looking east here). Using race engine tricks from engines that last a dozen hours or less?
The whole ramp head problem with Merlin was because the heads were cracking under the stress, either from valve to valve or from valve to other surface/stess point in the head.


I am not saying it can't be done, it was. But the paths for some changes can be short or they can be long. Taking a lot of paths at the same time is often hard.

 

[z42]

Also preferably a motorkannone shaft from the start.

If the evolution of the DB-605 is mimicked, then this Jumo-213 should be quite a lot lighter that the OTL design, maybe around 800 or not much over kg? So it's lower power will in part be compensated by lower weight. Possibly if used on FW-190D it may not need the fuselage extension, thus easing design and production?

While lighter than the historical 213, it's still a long engine, so unclear whether the fuselage extension can be omitted. What if the motor cannon is omitted in addition to the cowl MG's, would that allow the engine to be mounted further back, improving balance?

And, if omitting the motor cannon, what about using the motor cannon tube for the engine air intake and filters? That would get rid of the need to have the air intake sticking out in the airflow as in the historical FW190D or Bf 109. Would need to reposition the SC though.

Without the motor cannon nor cowl MG's, only two MG 151/20's in the wing roots is a bit weak. So keep the wing mounted MG-FF's from the FW 190A.

 

[z42]

It was the 4mm change in bore that 'helped' Screw the DB 605 up for while.

I thought it was largely the switch from ball bearings to plain bearings, as well as the switch to the 'sparmetall' valves that were the main issues with the initial 605? Both introduced to alleviate material and component shortages, and only incidentally introduced at the same time as the bored out cylinders?

 

[mack8]

While lighter than the historical 213, it's still a long engine, so unclear whether the fuselage extension can be omitted. What if the motor cannon is omitted in addition to the cowl MG's, would that allow the engine to be mounted further back, improving balance?

And, if omitting the motor cannon, what about using the motor cannon tube for the engine air intake and filters? That would get rid of the need to have the air intake sticking out in the airflow as in the historical FW190D or Bf 109. Would need to reposition the SC though.

Without the motor cannon nor cowl MG's, only two MG 151/20's in the wing roots is a bit weak. So keep the wing mounted MG-FF's from the FW 190A.

I was going by the example of the planned FW-190C-1 which it seems it didn't have the fuselage extension. Though it may be that they would have found out they need the fuselage extension if the 190C-1 was produced.

Both the OTL Jumo-213 (2,26m) and DB-603 (2,6m) are considerably longer than the Jumo-211 (1,74m), so since this TL supposes relatively few changes to the basic Jumo-211, the length should remain about the same? This coupled with the expected lower weight, say 100kg less than OTL, should alleviate any changes needed to the airframe or altering the armament, other than dropping in the inline power egg. So there will be little disruption to production. That's the idea anyway.

Imo removing the cowl guns is only worth it if a motorkannone can be fitted instead, so the armament will be either 3 x MG-151, or 1x MK-108 and two MG-151s.

They did try the tunnel intake as you suggest on FW-190V13 with the DB-603, it didn't work, reduced the ram and critical altitude way too much. So they got back to the external intake.

 

[z42]

I was going by the example of the planned FW-190C-1 which it seems it didn't have the fuselage extension. Though it may be that they would have found out they need the fuselage extension if the 190C-1 was produced.

Both the OTL Jumo-213 (2,26m) and DB-603 (2,6m) are considerably longer than the Jumo-211 (1,74m), so since this TL supposes relatively few changes to the basic Jumo-211, the length should remain about the same? This coupled with the expected lower weight, say 100kg less than OTL, should alleviate any changes needed to the airframe or altering the armament, other than dropping in the inline power egg. So there will be little disruption to production. That's the idea anyway.

Imo removing the cowl guns is only worth it if a motorkannone can be fitted instead, so the armament will be either 3 x MG-151, or 1x MK-108 and two MG-151s.

They did try the tunnel intake as you suggest on FW-190V13 with the DB-603, it didn't work, reduced the ram and critical altitude way too much. So they got back to the external intake.

Sorry, I meant long compared to the BMW 801. Indeed there is no big difference in length between the different inline options.

As for the tunnel intake, that's interesting they tested it and it didn't work for them. Seems there's no fundamental issue with the approach, as long intakes going from the nose to behind the engine were successfully used e.g. on the P-40 and P-51?

 

[Shortround6]

I thought it was largely the switch from ball bearings to plain bearings, as well as the switch to the 'sparmetall' valves that were the main issues with the initial 605? Both introduced to alleviate material and component shortages, and only incidentally introduced at the same time as the bored out cylinders?

I have seen claims of piston failures or burnt pistons, could be wrong. Since one of temporary fixes was to reduce the manifold pressure from 1.42 to 1.30 that may not have been bearing problem. Again I could be wrong but I would think for a bearing problem you would limit the rpm?

Things don't always go according to plan but plain bearings usually stand up to higher impact loads better than roller bearings. Assumes that your plain bearings are good to begin with though.

 

[tomo pauk]

I have seen claims of piston failures or burnt pistons, could be wrong. Since one of temporary fixes was to reduce the manifold pressure from 1.42 to 1.30 that may not have been bearing problem. Again I could be wrong but I would think for a bearing problem you would limit the rpm?

DB messed, and messed big time by not employing the oil de-aerator and by not employing the central lubrication via the crankshaft that starts on the end of a crankshaft. That left the lubrication at higher revs to be insufficient.
Corroding valves, again at high settings, were a cause of premature detonations, that were wrecking the pistons. Valves were corroding since they were not coated by some resistant material, like stellite (needs cobalt) or nickel.

It took retrofit of the oil system with a better one (basically a copy of what Junkers was doing several years prior?), and introduction of chrome-plated valves in order for the DB engines work reliably on the 'book' settings from 1942 (but now we're in late 1943, and air war is as good as lost).
DB was proudly noting the presence of the oil de-aerator on the data sheets of their engines in 1944-45.

DB 605A was not the only DB engine that was bad when run at 'book' settings, the DB 603A was also unreliable in 1943.

 

[Shortround6]

Thank you.

 

[tomo pauk]

Both the OTL Jumo-213 (2,26m) and DB-603 (2,6m) are considerably longer than the Jumo-211 (1,74m), so since this TL supposes relatively few changes to the basic Jumo-211, the length should remain about the same? This coupled with the expected lower weight, say 100kg less than OTL, should alleviate any changes needed to the airframe or altering the armament, other than dropping in the inline power egg. So there will be little disruption to production. That's the idea anyway.

The 'Jumo 212' (tm) installation will probably not require the tail 'plug'. BMW 801 was not some small and compact engine, being 2m long with prop shaft and more than 1000 kg heavy, dry.
Jumo 211 was indeed at 1.74/1.75m, but that is without the prop shaft, so perhaps another 20 cm for it? Jumo 213 was 205 cm long without the prop shaft.
The smaller cooler will require a smaller armor for the cooler, so there is another few kg to be saved well away from the CoG.

 

[z42]

I have seen claims of piston failures or burnt pistons, could be wrong. Since one of temporary fixes was to reduce the manifold pressure from 1.42 to 1.30 that may not have been bearing problem. Again I could be wrong but I would think for a bearing problem you would limit the rpm?

Things don't always go according to plan but plain bearings usually stand up to higher impact loads better than roller bearings. Assumes that your plain bearings are good to begin with though.

DB messed, and messed big time by not employing the oil de-aerator and by not employing the central lubrication via the crankshaft that starts on the end of a crankshaft. That left the lubrication at higher revs to be insufficient.
Corroding valves, again at high settings, were a cause of premature detonations, that were wrecking the pistons. Valves were corroding since they were not coated by some resistant material, like stellite (needs cobalt) or nickel.

It took retrofit of the oil system with a better one (basically a copy of what Junkers was doing several years prior?), and introduction of chrome-plated valves in order for the DB engines work reliably on the 'book' settings from 1942 (but now we're in late 1943, and air war is as good as lost).
DB was proudly noting the presence of the oil de-aerator on the data sheets of their engines in 1944-45.

DB 605A was not the only DB engine that was bad when run at 'book' settings, the DB 603A was also unreliable in 1943.

So the DB 601 used roller bearings, but for the 605 they switched to plain bearings. There were two big issues with the initial DB 605 ones:

• A plain bearing needs several times more lubrication than a comparable roller bearing. However in their hurry to get the 605 out of the door DB had neglected this and not upgraded the oil supply system. As Tomo notes, this was eventually fixed by introducing a crankshaft nose oil feed system and de-aerator (and IIRC beefier oil pumps as well).
• German plain bearings were traditional lead-bronze bearings. Problem is that the oil in the crankcase corrodes this bearing material leading to short bearing life. The US Vandervell company had figured out a solution using Indium plating which led to a very strong and corrosion resistant bearing surface. This solution was also adopted by Britain.

 

[mack8]

Very interesting to see the simple explanations of why the DB-605 had so many problems. Presumably, the increased volume engine further demanded increased oil debit as well, thus stressing even more the oil system?

I guess this kind of lapse from DB goes in the same vein as general lapses such as not bothering to test whether a C2 fuel engine actually works properly with C3 or not, or not bothering to test whether ersatz materials actually work in the engine before producing them, or not bothering to share critical data and troubleshooting beween companies, etc. etc.

About the DB-601E as i understand it was cleared for full power as of spring 1942, so presumably it didn't have the kind of issues the 605 had, but did it have valve problems as well? If not, why not, were it's valves made with better materials?

Diverting a bit from the Jumo-213 yes, but interesting details to be discussed nevertheless.

PS: were the DB-603 reliability issues the same as for the 605, ie with oil system, valves, spark plugs etc.?

 

[tomo pauk]

About the DB-601E as i understand it was cleared for full power as of spring 1942, so presumably it didn't have the kind of issues the 605 had, but did it have valve problems as well? If not, why not, were it's valves made with better materials?

I don't know.
The 601E was rated to 2700 rpm max, vs. the 605A to 2800 rpm max - that, couple with over-boring the engine, perhaps meant that DB 605A had more going against it when fully rated? My guess, anyway.

PS: were the DB-603 reliability issues the same as for the 605, ie with oil system, valves, spark plugs etc.?

There are probably good reasons that the 603A suffered due to the same shortcomings, being of similar construction and made by same company.

 

[special ed]

Somewhere in my stack of stuff in a magazine article about the D-9 sent to Minnesota or Wisconsin for engine overhaul. The engine rebuilders reported babbitt bearings requiring the rods and crankshaft to be ground to accept modern bearings. Their comment was the original bearing life was 25 hours.

 

[tomo pauk]

They did try the tunnel intake as you suggest on FW-190V13 with the DB-603, it didn't work, reduced the ram and critical altitude way too much. So they got back to the external intake.

As for the tunnel intake, that's interesting they tested it and it didn't work for them. Seems there's no fundamental issue with the approach, as long intakes going from the nose to behind the engine were successfully used e.g. on the P-40 and P-51?

I've took a peek on the actual and relative dimensions of the ram air intake. Already eyeballing it here shows that the tunnel for the motor cannon was of a too small cross section, especially when aimed for the high-altitude engines where any restriction of the airflow is not wanted, period.

IIRC the pre-set internal diameter of the tunnel for motor-cannon installation was 70mm, while the diameter inducer of the impeller on the DB 601E was some 150 mm (the widest, outer diameter was 260mm) - that is less than more than 4 times the cross section required. Basically, even the modest engine, like the 601E, will be starved for air if the fresh air is to be routed via the tunnel, let alone some more capable engine like the Jumo 213, where the 213A was with roughly 150 x 250 mm cross section at the ram air intake.

 

[z42]

I've took a peek on the actual and relative dimensions of the ram air intake. Already eyeballing it here shows that the tunnel for the motor cannon was of a too small cross section, especially when aimed for the high-altitude engines where any restriction of the airflow is not wanted, period.

IIRC the pre-set internal diameter of the tunnel for motor-cannon installation was 70mm, while the diameter inducer of the impeller on the DB 601E was some 150 mm (the widest, outer diameter was 260mm) - that is less than more than 4 times the cross section required. Basically, even the modest engine, like the 601E, will be starved for air if the fresh air is to be routed via the tunnel, let alone some more capable engine like the Jumo 213, where the 213A was with roughly 150 x 250 mm cross section at the ram air intake.

Fair enough.

As a slight aside, one may also want a diffusion plenum for the air intake (similar to a 'Meredith effect' radiator) to convert the air velocity to pressure. This would of course require even more volume for the intake system.

 

[mack8]

I've took a peek on the actual and relative dimensions of the ram air intake. Already eyeballing it here shows that the tunnel for the motor cannon was of a too small cross section, especially when aimed for the high-altitude engines where any restriction of the airflow is not wanted, period.

IIRC the pre-set internal diameter of the tunnel for motor-cannon installation was 70mm, while the diameter inducer of the impeller on the DB 601E was some 150 mm (the widest, outer diameter was 260mm) - that is less than more than 4 times the cross section required. Basically, even the modest engine, like the 601E, will be starved for air if the fresh air is to be routed via the tunnel, let alone some more capable engine like the Jumo 213, where the 213A was with roughly 150 x 250 mm cross section at the ram air intake.

Correct me if i'm wrong, but my understand is the V13 intake was an aperture in the oil cooler then running on the side of the engine under the cowling to the impeller. sort of like on Ju-88? Nothing to do with the motorkannone tunnel.