Talk:Rohrbach Ro VII Robbe

Robbe II was originally planned to use BMW V straight-6s, but actually used BMW VI V12s.
On my talk page, you remarked:

That spurred me to double-check the Robbe II. While I found conflicting information at first, I'm now sure that Gütschow is correct. The Robbe II was originally intended to have BMW V engines, but it was eventually built with much more powerful BMW VI engines.

The most definitive source I've found on this is a French-language brochure published in October 1928 by the Rohrbach company itself, which I found on a web page dedicated to Rohrbach's history. Page 5 of the brochure states, "Un autre perfectionnement important pour l'hydravion d'outre-mer apparaît dans le »Rohrbach-Robbe II«, destiné à servir à expérimenter les nouvelles ailes effilées Rohrbach qui sont prévues pour le »Rohrbach-Romar«. Ces machines, qui, pour des raisons d'ordre commercial de la part de la Firme fournissant les moteurs, portent 2 BMW VI, au lieu des 2 BMW V primitivement envisagés, ont démontré par de nombreux vols l'évidente supériorité de l'aile effilée pour les grands hydravions de 20 tonnes et davantage. (Another important development for the overseas seaplane appears in the "Rohrbach-Robbe II", intended to be used to test the new Rohrbach tapered wings planned for the "Rohrbach-Romar". These machines, which, for business reasons on the part of the firm supplying the engines, carry 2 BMW VIs, instead of the 2 BMW Vs originally envisaged, have shown by many flights the obvious superiority of the tapered wing for large seaplanes of 20 tons and more.)"

Some other sources I've found which confirm the Robbe II as having BMW VI (or VIa) engines:


 * Jane's All the World's Aircraft (1928), p. 244
 * "The Development and Construction of the Rohrbach Airplane", in Foreign Aeronautical News, 4 October 1929, no. 163, p. 4 (published by the U.S. Department of Commerce)
 * Das Buch der Deutschen Luftfahrttechnik (1970), vol. 1, page 352 (this also says that the BMW V was originally planned, but the snippet I see cuts off most of the explanation)
 * Kurt Tank—Konstrukteur und Testpilot bei Focke-Wulf (1980), p. 20 (also available in English as Kurt Tank: Focke-Wulf's Designer and Test Pilot (1998))
 * Wasserflugzeuge: Flugboote, Amphibien, Schwimmerflugzeuge (1994), p. 133

Several photos of the Robbe II show cowled engines which look like V12s rather than straight-6s. In particular, note one I found in L'Aéronautique, December 1927, p. 407: the photo at the bottom right corner of the page (zoom in for maximum detail).

BMW's own archives don't say much about the BMW V and Va, but they do mention that the original BMW V was an experimental engine with four valves per cylinder and a single common water jacket, and that only a few test samples were built; it didn't go into series production. The Va, which did go into production, was an engine with two valves per cylinder and individual water jackets for each cylinder. This may explain why the Robbe II was initially planned to use the V (presumably the four-valve-per-cylinder V) and switched to the VI.

The source you found which claims the Robbe II used the BMW V, L'Aéronautique, October 1927, pp. 326–327, is the only such source I could find. I now believe this was reporting the original plans for the Robbe II with the four-valve BMW V before that engine was abandoned.

--Colin Douglas Howell (talk) 11:42, 4 October 2018 (UTC)


 * That's a fine piece of very convincing detective work. The l'Aéronautique article, the only one I found saying BNW Vs, has the Robbe as "under construction" which fits as well. Do you want to make the edit and add a source or two or shall I? I'm easy either way. Cheers,TSRL (talk) 19:35, 4 October 2018 (UTC)


 * Thanks. :) Feel free to make the edit yourself, if that's OK with you. --Colin Douglas Howell (talk) 19:52, 4 October 2018 (UTC)


 * Willdo and thanks for your analysis.TSRL (talk) 20:22, 4 October 2018 (UTC)