Patent ID: 7874806

Claim:
A turbomachine rotor assembly comprising a turbomachine rotor and a plurality of turbomachine rotor blades, the turbomachine rotor having a plurality of firtree shaped slots in its radially outer periphery to form a plurality of rotor posts, the turbomachine rotor blades having correspondingly shaped firtree roots to fit in the firtree shaped slots in the turbomachine rotor, the firtree roots of the turbomachine rotor blades comprising circumferentially spaced flanks, a plurality of radially spaced lobes on each of the flanks and a radially inner base, the rotor posts of the turbomachine rotor comprising circumferentially spaced flanks, a plurality of radially spaced lobes on each of the flanks and a radially outer periphery, a radially inner lobe of at least one of the turbomachine rotor blades having reduced stiffness such that the load on the radially inner lobe of the at least one turbomachine rotor blade is shared with the other lobes of the at least one turbomachine rotor blade, the radially inner base of the firtree root of the at least one turbomachine rotor blade has a recess such that the load on the radially inner lobe of the at least one turbomachine rotor blades is shared with the other lobes on the at least one turbomachine rotor blade, or a radially outer lobe of at least one of the rotor posts having reduced stiffness such that the load on the radially outer lobe of the at least one rotor post is shared with the other lobes of the at least one rotor post, the radially outer periphery of the at least one rotor post has a recess such that the load on the radially outer lobe of the at least one rotor post is shared with the other lobes on the at least one rotor post.