MESSERSCHMITT ME309 Development and Politics. Dan Sharp & Calum Douglas

[Holtzauge]

There are also still Swedish built DB 605's in circulation: Saw one myself a few years back in the hangar of a Swede I know who has ambitions to build his own Bf 109 eventually. Sweden secured the licensing rights to build these during WW2 in exchange for all the steel and ball bearings they supplied to the Germans during the war. These engines were used in a rather unusual SAAB pusher design called the J21. Supposedly these surviving engines are of quite high quality given that Sweden did not have the same raw material problems the Germans did and that they were produced by Sweden's leading aero engine facility in Trollhättan under peacetime conditions.

 

[Snautzer01]

There are also still Swedish built DB 605's in circulation: Saw one myself a few years back in the hangar of a Swede I know who has ambitions to build his own Bf 109 eventually. Sweden secured the licensing rights to build these during WW2 in exchange for all the steel and ball bearings they supplied to the Germans during the war. These engines were used in a rather unusual SAAB pusher design called the J21. Supposedly these surviving engines are of quite high quality given that Sweden did not have the same raw material problems the Germans did and that they were produced by Sweden's leading aero engine facility in Trollhättan under peacetime conditions.

That would be nice.

 

[cammerjeff]

There are also still Swedish built DB 605's in circulation: Saw one myself a few years back in the hangar of a Swede I know who has ambitions to build his own Bf 109 eventually. Sweden secured the licensing rights to build these during WW2 in exchange for all the steel and ball bearings they supplied to the Germans during the war. These engines were used in a rather unusual SAAB pusher design called the J21. Supposedly these surviving engines are of quite high quality given that Sweden did not have the same raw material problems the Germans did and that they were produced by Sweden's leading aero engine facility in Trollhättan under peacetime conditions.

I had forgotten that Sweden produced DB 605's, they were also used on the 2nd version of the SAAB B-18 if I remember correctly.

 

[Holtzauge]

I had forgotten that Sweden produced DB 605's, they were also used on the 2nd version of the SAAB B-18 if I remember correctly.

Yes, the B18 A-version used the Twin-Wasp copy which was copied without a license AFAIK , while the B-version had the DB 605.

In this video Swedish aviator Mikael Carlson flies Hangar 10's Bf 109G6. Listen to the "music" when the Bf 109's fly over at about 3 min in. Would not be surprised at all if that DB 605 harks from Trollhättan.

 

[Engineman]

There are also still Swedish built DB 605's in circulation: Saw one myself a few years back in the hangar of a Swede I know who has ambitions to build his own Bf 109 eventually. Sweden secured the licensing rights to build these during WW2 in exchange for all the steel and ball bearings they supplied to the Germans during the war. These engines were used in a rather unusual SAAB pusher design called the J21. Supposedly these surviving engines are of quite high quality given that Sweden did not have the same raw material problems the Germans did and that they were produced by Sweden's leading aero engine facility in Trollhättan under peacetime conditions.

Yes, I am including Swedish engines, and Italian etc in my estimation of how long the regular flying of DB 601/605 engines might go on before major parts are needed from new manufacture. Of course, some items are already remade, and some of the magnesium cases have been reproduced.
As regards the Swedish produced DB 605 B, it is very much the German original but, the material specifications are better for the steel, particularly. The Swedish worked to the original German metal specification as it was before the Wartime economy versions.

Eng

 

[Holtzauge]

Yes, I am including Swedish engines, and Italian etc in my estimation of how long the regular flying of DB 601/605 engines might go on before major parts are needed from new manufacture. Of course, some items are already remade, and some of the magnesium cases have been reproduced.
As regards the Swedish produced DB 605 B, it is very much the German original but, the material specifications are better for the steel, particularly. The Swedish worked to the original German metal specification as it was before the Wartime economy versions.

Eng

I'm currently reading Calum Douglas excellent book on WW2 engines, and reading about the detonation problems the Germans battled with due to the scaling on the exhaust poppet valves was a revelation to me. I always thought it had more to do with the Allied fuel being so much better even than the German C3 grade but apparently the biggest problem they faced was the chrome and nickel shortages. Wonder if the Swedish made exhaust valves for the DB 605 was more like the Allied quality or something in between those and the German stuff....

 

[Engineman]

I'm currently reading Calum Douglas excellent book on WW2 engines, and reading about the detonation problems the Germans battled with due to the scaling on the exhaust poppet valves was a revelation to me. I always thought it had more to do with the Allied fuel being so much better even than the German C3 grade but apparently the biggest problem they faced was the chrome and nickel shortages. Wonder if the Swedish made exhaust valves for the DB 605 was more like the Allied quality or something in between those and the German stuff....

So, the Swedish generally used the original material specifications that the original German DB designs specify. These were good materials before the German material production went to lower standards. However, some things did change. You might be able to help. The Swedish later specified a different sparkplug, the "BG RB 697". This is possibly a different sparkplug than the later German wartime Bosch DW 250 ET 7/1A or 7/1D that was common on later DB 605 A engines without MW50. If you can discover what sparkplug make and type the Swedish BG RB 697 Tändstift is exactly, it would be interesting.

Eng

 

[Holtzauge]

The Swedish later specified a different sparkplug, the "BG RB 697". This is possibly a different sparkplug than the later German wartime Bosch DW 250 ET 7/1A or 7/1D that was common on later DB 605 A engines without MW50. If you can discover what sparkplug make and type the Swedish BG RB 697 Tändstift is exactly, it would be interesting.

About the sparkplug, maybe Mikael Carlson will know. However long time since I last spoke to him but I will keep it in mind if/when I do next time.

Seeing you did the Me 309 book review, perhaps you could provide some details about the radiator? I just can't understand how they thought they would get low drag with that design?

Even without having seen the innards, the intake and exit are so close to each other that it's hard to envision how they could have fitted a decent diffusor in there. By that I mean there has to be a gradual expansion before the entry into the radiator core and after that a gradual compression before the exit to get any decent so-called Meredith effect.

But how on earth could that be accomplished seeing how short the "tray" is? I'm here assuming that this "tray" is lowered and raised to control the airflow through radiator?

Then there is no boundary layer diversion by the looks of it. So whatever boundary layer that has built up on the lower fuselage before the intake goes straight into the radiator system which would not have improved things either.

 

[Engineman]

About the sparkplug, maybe Mikael Carlson will know. However long time since I last spoke to him but I will keep it in mind if/when I do next time.

Seeing you did the Me 309 book review, perhaps you could provide some details about the radiator? I just can't understand how they thought they would get low drag with that design?

Even without having seen the innards, the intake and exit are so close to each other that it's hard to envision how they could have fitted a decent diffusor in there. By that I mean there has to be a gradual expansion before the entry into the radiator core and after that a gradual compression before the exit to get any decent so-called Meredith effect.

But how on earth could that be accomplished seeing how short the "tray" is? I'm here assuming that this "tray" is lowered and raised to control the airflow through radiator?

Then there is no boundary layer diversion by the looks of it. So whatever boundary layer that has built up on the lower fuselage before the intake goes straight into the radiator system which would not have improved things either.

I just thought you might be able to easy find out about that sparkplug in Sweden?

The retractable cooler for the Me 309 remains a bit of a mystery. However, if you understand some of the theory and read the information in the book, I think you can get the picture.
It seems that in 1941 Messerschmitt really still thought along the lines of a retractable cooler for high speed, the engine cooling then relying on "boiling", with loss of coolant for short periods.
This is a very limited method of cooling, unsuitable for service use. It would seem that a definitive system for the Me 309 is not in the records available, the prototype versions were mostly fixed or with limited positions. The Me 309 book covers this. As you should know from Calums' book TSHR, the Germans were behind on high temperature cooling, which is a little strange. They seem to me to have been mesmerised by zero cooling drag from their success with record breaking, while unable to really move forward with more workable methods.
The later German designs with annular nose mounted radiators seem somewhat better, but only really appeared late in the war in high-speed applications.
So, the Me 309 retractable radiator system remains a question. Possibly, it might have been OK but, it was not going to be miraculous IMO.

Eng

 

[Holtzauge]

I just thought you might be able to easy find out about that sparkplug in Sweden?

The retractable cooler for the Me 309 remains a bit of a mystery. However, if you understand some of the theory and read the information in the book, I think you can get the picture.
It seems that in 1941 Messerschmitt really still thought along the lines of a retractable cooler for high speed, the engine cooling then relying on "boiling", with loss of coolant for short periods.
This is a very limited method of cooling, unsuitable for service use. It would seem that a definitive system for the Me 309 is not in the records available, the prototype versions were mostly fixed or with limited positions. The Me 309 book covers this. As you should know from Calums' book TSHR, the Germans were behind on high temperature cooling, which is a little strange. They seem to me to have been mesmerised by zero cooling drag from their success with record breaking, while unable to really move forward with more workable methods.
The later German designs with annular nose mounted radiators seem somewhat better, but only really appeared late in the war in high-speed applications.
So, the Me 309 retractable radiator system remains a question. Possibly, it might have been OK but, it was not going to be miraculous IMO.

Eng

Alas, the only info I have on the "Flygmotor DB 605" regarding ignition is that it was dual magneto, Bosch ZM12-CR22 with two 14 mm short reach spark plugs per cylinder and that's it.

About the Me 309 radiator: Yes, that the Germans had not picked up on pressure radiator systems is surprising. OTOH they did very well with the annular radiator systems on the late Fw-190's and Ta-152's which were really low drag designs. However, the Me 309 radiator looks bad as far as one can tell from the external pictures I've seen which was why I asked about it. I can understand if you are reluctant to post whole side view images, but a detail of the radiator or a verbal description would be helpful. I have seen one image which could be interpreted as the radiator core being angled at about 20 deg (from the horizontal) and the idea being that the air is pushed up through the core and then flows backwards to exit at the rear. If this were true, it looks like a very rapid expansion of the intake air just aft of the nosewheel well and not a very good channel on top of the radiator either. But that may just be me misinterpreting the drawing.

 

[Engineman]

Yes, Bosch ZM12 CR8 Magneto. Strangely, the sparkplugs are not referred to in detail in the Swedish manual, only quoted as the type BG RB 697, which may be a Swedish type?
I think you might find that it is best to buy the book if you have great interest in the radiator. As I wrote, this subject seems to not have been fully sorted by Messerschmitt. There is a fair amount of detail in the book but, the story is not simple and I don't feel that Messerschmitt ever finalised this.

Eng