Abstract: In a rotodynamic cross flow machine at least one vane (4) is positionably fixed in the rotor (40') so as to be able to pivot about two axes which are at least approximately perpendicular one to another, and of which at least one subtends an angle between 5.degree. and 85.degree. or between 95.degree. and 175.degree. with a plane comprising the rotational axis (1) of the rotor and the pivot point (14, 15) of the respective vane. Thereby is achieved, among other things, that the position of the vane can be set during operation in a simple way with the aid of a stationary setting means (18) which changes the inclination of an end element (5) of the rotor to which end element the vane is connected in said manner. The invention is applicable among other things to the construction of water turbines which have to work with a small head.