Rotor assemblies

A rotor assembly comprising a rotatable shaft, first and second annular discs axially spaced on the shaft and rotatable with the shaft, a plurality of rotor blades located between the discs and angularly spaced around the axis of the shaft, and means urging the discs against the blades so that a root portion of each blade is trapped between the discs with the remainder of the blade projecting from the discs, each root portion being shaped so as to be non-complementary with the portions of the disc between which it is trapped, and each disc being shaped so as to present to each root portion first and second surfaces which, when the shaft is rotated in use, engage first and second spaced regions respectively of the root portion so that the root portion is held respectively against movement radially outwardly relative to the axis of the shaft and against axial movement relative to the shaft, said first surface of each disc presented to a respective root portion being curved about the axis of the shaft and the associated first region of said respective root portion being defined by a further surface which is similarly curved about the axis of the shaft, but which has a radius less than the radius of the curve defined by said first surface so that there is point contact between the surfaces.