Oberursel UI, UII, URII and Le Rhone 9J

[Greybeard]

I was impressed reading what follows (from
http://www.hydroretro.net/etudegh/mo...de_lerhone.pdf
"En Suède, pays neutre pratiquant allègrement
la contrebande, malgré le blocus imposé par les
alliés, la société Thulin fabrique pour l'Allemagne
des moteurs 9J sous le type Oberursel UII dès
1916. La société allemande Oberursel Motoren,
qui détenait déjà la licence de construction du
moteur 9C avant la guerre, produit le 9J sous le
type Oberursel UI en 1916 (650 en Allemagne et
200 en Suède). Ces moteurs équipent des Fokker
DR1, E5 et D8."

Indeed, what were really Oberursel "umlaufmotoren" has been never much clear for me; if copies of french engines or original designs, or both.

On a german source Oberursel UI is quoted having 125x150 bore x stroke, so not matching with a copy of the 112x170 Le Rhone 9J. On the other hand, UR2 has exactly same dimensions of its french counterpart and develops same horsepower (120 PS). About Oberursel UII, I have still to understand if it really existed, since no german sources did mention it (and, if existed, in what differed from URII?).

What do you think about?

GB