A base includes bearing socket B having hemicylindrical case and inner socket A placed therein. Bearing socket has the blades 7 wherein the openings 8 are executed. A lattice consisted of radially disposed assembly openings 3, to connect sockets to each other, is placed on case bases. Metallic webbing of rigidity 4 is fastened inside of socket. Bearing socket openings are disposed straight on the blades; and assembly openings executed on the base are oval-shaped.
