of each pad and is utilised as follows a plurality of arcuate strip members 26 are formed equal in number to the number of blades 16 on the rotor 10 the radius of arc formed on their concave surface 28 corresponds with the radius of arc of the bottom of the peripheral groove 18 and the width of the strip portion of each member 26 is such as to make it a sliding fit in the peripheral groove 18 and each foot groove 20 the thickness of the strip portion of the member 26 is such that it will fit under each blade foot 14 when the blade 16 is in its operation loaded position and its accurate length is such that when positioned with its mid length centrally of the width of the respective groove 12 it spans the groove 12 its end extremities overlapping the side walls of the peripheral groove 18 thus when in the position just described if the strip member 26 attempts to move longitudinally of its groove 12 its end extremities will abut one or other of the opposing sidewalls of the peripheral groove 18 each strip member 26 has a projection 30 formed about mid length on its convex side the projection 30 is proportioned such that when the member 26 is positioned as described hereinbefore it lies in.