A fly wheel arrangement includes a rotatable axle (1), a ring (4) essentially forming the rotating mass of the fly wheel and a connecting member (5) made from fiber-reinforced plastic connecting the ring (4) with the axle (1) or with a part rotating therewith. The connecting member (5) is connected to the ring (4) at its outer end portion and to the axle (1) or a part connected thereto at its inner end portion. The connecting member (5) has essentially the shape of a cylinder or a conical shell