WELLENSTABILISATOR

A load transfer arrangement is provided to act as a stabiliser for utilisation in centring rotational instabilities which may occur in rotor devices such as those within a gas turbine engine 10. By providing a fixed screw thread path 31 which comprises a groove having channels 39 to 43 and having constrictions 44 to 46 and which define clearance crowns 60, 61, 62 an acceptable eccentricity range it is possible to slow screw thread driving motion and therefore load transfer only to the positions where the rotational eccentricity enters tapers leading to the constrictions 44, 45, 46. In such circumstances an orbit thread 32 is then progressively brought into confinement and continuous engagement with a fixed screw thread 31 defined by crowns 63, 64 of channels 42, 43 of the fixed screw thread path 31 defined by the continuous groove through the channels 39 to 43. In such circumstances wide eccentricity is allowed initially but as rotational speed reduces greater and more continuous driving motions are provided whilst avoiding excessive loading during early stage operation. High loads on final rundown contact are controlled by a diaphragm mount, the whole serving to restore the support stiffness of the rotor post fusing.