of stops 28 the blades 3 are then free to pitch to a 45 degree pitch angle the aerodynamic braking effect keeps the rotor speed within a structurally safe range this is a fail safe system of rotor protection the lower end of the main shaft 2 is supported by two bottom bearings 44 and 45 as shown in fig8 the main bearing or upper bearing 44 is mounted to the main support cross beam 46 above the gearbox 10 and the foundation the shaft system includes the main shaft 2 and a drive shaft 47 this shaft system can pivot about the main bearing 44 both bearings are self aligning the shaft system including main shaft 2 and drive shaft 47 teeters because the guy cables 7 can stretch under load the bottom bearing 45 must be able to move in the horizontal plane to relieve bending stresses in the drive shaft 47 bearing 45 is smaller than the main bearing 44 the drive shaft is stepped at the bottom to accommodate bearing 45 and so that bearing 45 can share thrust loads with the main bearing 44 the lower bearing rests on plate 48 which rests on a roller bearing surface 49 shown in fig1 the roller bearing surface 49 allows the bearing support plate 48 to move freely in the horizontal plane to relieve bending on the drive shaft 47 all of these plates are supported by the foundation 50 through several plates that are held in place horizontally.