the rotor members non rotatably thereon the lower end of the stack of rotor members abuts rotor spacer ring 64 which seats against the upper end 65 of splined connecting member to be subsequently described at the upper end of rotor shaft 44 there is positioned a cap or makeup screw member 66 which is internally threaded at 67 and forms a tight threaded connection with the threaded end portion 46 of rotor shaft 44 when cap member 66 is tightened in position its lower end portion 68 abuts the uppermost rotor member 48 and compresses the stack of rotor members tightly on rotor shaft 44 cap member 66 is closed at its upper end and has one or more threaded apertures 69 in which there are positioned set screws 70 to secure cap member 66 against loosening during operation upper spline member 71 has its upper end portion 65 abutting rotor spacer ring 64 as previously described spline member 71 is internally threaded and forms a threaded connection 72 with the lower end portion 47 of rotor shaft 44 spline member 71 is hollow and has an exterior surface 73 spaced from the inner surface of stator makeup sleeve 30 to define an annular passageway therebetween the lower end portion 75 of spline member 71 abuts ring shaped spline spacer 76 spline member 71 has a plurality of grooves 77 in the lower or box portion 75 thereof which receive spline pins 78 a lower spline member 79 has upper pin portion 80 provided with grooves 81 which receive the other side of spline pins 78 spline member 79 has a peripheral.