German Rohrbach Ro XII 'Roska' Long-Range, Heavy Bomber

[Pioneer]

Hello Gents

I have finally got around to buying myself a copy of ‘Luftwaffe Secret Projects – Strategic Bombers 1935-1945.

I was surprised to see an early, yet advanced design - the Rohrbach Ro XII ‘Roska’ Long-range, Heavy bomber.
I have never heard of the Rohrbach aircraft company before, let alone the Ro XII design.

Does anyone have anymore info on this promising bomber design of 1926?

Regards
Pioneer

 

[richard]

Hello
A part of "Rochbach" work can be seen on the site "histaviation"
It's work continues then in" Weserflug" on "histaviation" and "luftarchiv" sites
The only source I know for the 1926 Ro XII Roska is the book you mention.
The other name was Ro XII Ro Na Bo for Romar Nacht Bomber for it stemmed from the Romar flying boat

 

[joncarrfarrelly]

According to Rob Mulder's European Airlines site the Ro XII, also listed as Ro VIII Mb, was the rebuilt Rohrbach Ro VIII Roland I c/n 18, D-991 which was returned to Rohrbach in August 1928 and was then converted to a bomber configuration. The airplane had been used by both Luft Hansa and Iberia.
His info comes from John Stroud's 'European Air Transport 1919-1965', and not having seen the 'Luftwaffe Projects' book I don't
know if this info jibes with what is in that volume.

Here is an illustration from Robert Craig Johnson's 'Chandelle' online magazine.

...and a 3-view of the Ro VIII airliner:

..a pic of D-991 in Luft Hansa livery:

BTW the British Beardmore 'Inflexible' bomber prototype was a Rohrbach design.

Cheers, Jon

 

[Pioneer]

Thanks guys
Its far more than what I knew about this aircraft

Regards
Pioneer

 

[Jemiba]

With the clue "Ro VIII" I've found it in Helmut Stützers book "Die deutschen Militärflugzeuge
1919-1934", very good for those, who like good 3-views.
Who's interested in a higher resolution scan, just tell me.

 

[joncarrfarrelly]

Excellent Jemiba.
I for one would like a high res scan.

j.c.farrelly@comcast.net


Cheers, Jon

 

[hesham]

very good my dear Jeimba.

 

[airman]

i don't know more about Roska !

 

[Jemiba]

Someone, who owns "Luftwaffe Secret Projects : Strategic Bombers 1939-1945" by
Dieter Herwig and Heinz Rode perhaps could help ? At least the Roska seems to be
mentioned there.

 

[airman]

Someone, who owns "Luftwaffe Secret Projects : Strategic Bombers 1939-1945" by
Dieter Herwig and Heinz Rode perhaps could help ? At least the Roska seems to be
mentioned there.

Yes, of Rohrbach Ro XII Roska , at moment, is mentioned on Luftwaffe Secret Projects , a model in scale : simply a heavy bomber with four engines ( seems it)

 

[malcolm]

From Luftwaffe Secret Projects - Strategic Bombers 1935 to 1945

In 1926 the Rohrbach factory in Berlin developed a four engined bomber, designated RoXII, to meet the specifications of the Heereswaffenamt (Army Ordnance Directorate). With a winspan of 38.3M (125ft 7in), a length of 20.5M (67ft 3in), four seperate engines, a fixed undercarriage and a bomb load of 700kg(1540lbs), its range was to be 1200 kilometers (745 miles).
In layout the "Roska" was a cantilever shoulder wing monoplane of all metal construction.
Due to the limited power output of the four engines, estimated speed was only 260km/h (162mph), which was below the specified requirements.
In all other respects the "Roska" met all the criteria of a standard heavy bomber of the period.But that alone did not suffice for the Air Department of the Heereswaffenamt to recommend production.
The "Roska" did not progress beyond the model stage, and in May 1927 the Reichswehr withdrew development of the contract.
Other sources quote the wingspan as 43.05M (141ft 2in) and the length as 21.6M (70ft 10in). Powerplant was to have been four 600hp in-line engines.

 

[Jemiba]

Probably just a wild theory, but I compared data of the Roska with the Tupolelv TB-3.
The latter was designed and built around 1930, the design of the Roska was from 1926,
the technical data meet quite well, I think ....
Could it be, that the TB-3 was somehow influenced by the R.XII Roska, maybe because the
Germans had allowed to give this design, which already was regarded as not good enough for
the German airforce, to the Russians ?
There were other examples, where designs were handed over, due to the very special relations.

 

[Avimimus]

The ANT-4/TB-1 first flew in 1925 - so the basic layout of the TB-3 was already in place prior to the Ro XII (although only be a few months). However, Rohrbach was already producing designs a few years earlier. So, they are basically contemporary. It may just be that designs from a similar era tend to get similar performance out of the same concepts.

If I were looking for influence - I'd look at the possibility that Junker's influenced both: Junkers was already using corrugated steel and monoplanes with thick high-lift wings during WWI.

My two cents. I can definitely see the similarities though.

 

[Jemiba]

Yes, you're certainly right, I didn't remember the close relation to the TB-1.
It's just annoying, that a lot of energy is spent for researching late WW II German
projects, that often just may have been crackpot ideas, fired by desperation and the
will to stay in the relatively safe design offices, whereas somewhat older projects are
finding only very limited attention !

 

[Silencer1]

Vladimir Kotelnikov in his article about TB-3 mentioned, that aircraft has been so complex and large, that certain people thinks, that Soviet factories would unable to build it in mass production - so its should be transfer this order to "Rohrach" factories. However, the production preparation has started in 1939 at Factory 22,near Moscow.


At this moment I couldn't find the source of this statement (somewhere in magazine, I think), as well my translation is beat rough.
IMHO, Rohrbach company hasn't have the necessary factory power for such mass production - perhaps, Junkers (as already proven manufacturer) has been planned?


Anyway, as one of the enthusiasts of all-metal, stressed skin, cantilever monoplanes Adolf Rohrbach could made great influence on any designers and Air Force officials of that era.
Even E 4/20 looks futuristic, and his owns designs under "Ro" mark looks impressive, excluding the number of series-built ...


It should be noted, that even TB-1 has been born in time, when the ordering of such type in England (Short, probably) has been considered.
Ostekhburo (Special Technical Bureau, headed by Bekauri) ordered heavy aircraft for their purposes - for torpedo-bombing and mine-laying.
So, conventional bombing historically became just the second role of TB-1.
TB-3 design also has been ordered by Ostekhburo.


It could be a situation, that Rorhbach has been secretly ordered to design such heavy aircraft, or - in turn, Soviet intelligence knew something of it's work. This only my speculation.


I think, that after building of ANT-1 and ANT-2 prototypes, establishing of ANT-3 all-metal aircraft and TB-1 as well, Andrey Tupolev have all necessary to design and build such 4-engined monoplane.


One important difference between Rorhbach and Tupolev was structure of their aircraft - stressed-skin against the corrugated one.
Basic dimensions of "Roska" and TB-3 looks very close, as they both planned to use 4x600 hp engines.

 

[Jemiba]

A skin made of corrugated sheet may unload the basic structure, but there aren't principal
differences, I think. And a foreign design given into the hands of Andrey Tupolev probably
wouldn't have been used unmodified. But again,it's only a very vague theory, based on the
similarity between those two designs.

 

[Silencer1]

A skin made of corrugated sheet may unload the basic structure, but there aren't principal
differences, I think. And a foreign design given into the hands of Andrey Tupolev probably
wouldn't have been used unmodified. But again,it's only a very vague theory, based on the
similarity between those two designs.

In my humble opinion, there has been a great difference between corrugated skin and smooth skin, in case, that second one used as integral part of wing structure, bringing load along with spar booms and stringers.
But this design has been widely adopted in 1930th - like on DC-3 etc.


Concerning the Roska and TB-3 - do anyone remember any other similar aircraft or projects of the same period?
There have been not so much 4-engined monoplanes in the end of 1920th...
And definitely no on military service. Not in France, UK, USA as far as I remember.


By the way, did you knew anything about Rorbach' role in design of E 4/20 monoplane?

 

[Jemiba]

As I said, a skin made from corrugated sheet can unload ribs and stringers, so they
can be somewhat lighter. But principally the structure isn't really different to that, of
an aircraft with a smooth skin, maybe recognisable in the attached cutouts from two
cutaways, showing the ANT-20 on the left and the Ju 52 on the right
(cutaways from http://www.fiddlersgreen.net/aircraft/Tupolev-Ant20/IMAGES/Tupolev-Ant-20-Maksim-Gorki-Pre-WWII-Russian-Giant-Transport-Cutaway.jpg
and http://aviadejavu.ru/Site/Crafts/Craft20218-6.htm )

 

[Silencer1]

Dear Jemiba, thank yo for the illustrations - although, as far as I knew, ANT-20, like Ju-52 has been build with corrugated skin.


I would for the moment cease our discussion of smooth and corrugated skin usage in 1920, don't you?
This is interesting subject, and I at least want refresh my knowledge about it.


Are there were any others sources about Roska, other then already mentioned in this topic?


Article in Luftfarht International 4-1974 (about bomber version of Roland -Ro VIIIMb) has mentioned Rorbach type XII under name "RoKa".
No other information yet.




P.S. By the way, one of the late-produced TB-3 has been sequentially modified with a additional smooth skin over various part of aircraft - each time with greater area covered. Some other aerodynamic improvement have been also made. As result the speed increased by 4,5 %... Not to much.
And another bomber - deep modification of TB-3 - DB-A has been built with stressed skin on most surfaces with the nearly similar overall dimensions of predecessor.




I hope, sometime we found new details about "Roska" project *-)