The swashplate (2) on a rotor (1) uses a cylindrical part (3) of the rotor to centre itself with respect to the main axis of rotation (8). More compact, more robust and with fewer parts, this device in which the ball joint-ring (4) bears at its centre a rotation device here represented by a rolling bearing (5) and the internal part of which bears an internal plane which is operated at at least three points, forms the swashplate (2) assembly (ball joint-ring, rolling bearing, and the internal part), this part which drives the swashplate assembly is represented here by the triangular ring, it can be moved in the direction of the axis of the rotor, and also in such a way that its plane is free to move angularly relative to this axis and thus allows a cyclic influence on the pitch angle of the blades through connections between the ball joint ring and the blade roots, all rotary wing manoeuvres being provided for.