increasing distance from shoulder 216 the pitch of the rotor blade also varies with increasing distance from shoulder 216 with the absolute value of the pitch being set by the angular position of the shoulder 216 on its pivot axis preferably the blade is curved helically through an angle of about 15 u00b0 20 u00b0 and the blade is set by rotation of shoulder 216 so that the angle of attack of the leading edge 230 is optimum for the prevailing wind velocity with reference to fig5 the angle of attack is defined as the angle between one line running from leading edge 230 to the pivot axis of the blade and a second line running from the pivot axis at a right angle to the support ring 202 the length of the rotor blades is such that the outer ends of the rotor blades lie close enough to the stator casing ring 18 so that substantially all of the air which passes between the inlet stator blades must pass between the rotor blades but far enough from the stator casing ring that the rotor blades may be removed from the rotor assembly while the assembly is mounted in the turbine flange 234 is attached to support ring 204 preferably via bolts 236 and is provided with a hub 237 surrounding a tapered center bore 238 flange 234 is sized so that its center bore is somewhat larger than the diameter of shaft 102 and the outer diameter of its bore shoulders form a tight fit with the inner wall of support ring 204 the rotor assembly is normally preassembled as a unit and then mounted in the turbine the rotor assembly is mounted to shaft 102 by means of a wedge type bushing arrangement first shaft.