This was built in to address some of the issues found with the Mark 1
version. The main differences are:
The main axle of 10mm stud is replaced with length of 10mm steel rod, threaded at both ends. The components (hub bearings, alternator, body, etc) are clamped along the length of the axle spaced with sections of 12mm steel tube. The steel rod is a much better fit on the bearings and the tube spacers allow the components to be more accurately positioned.
The hub is redesigned based on a piece of aluminium tube that is a push fit over the outside of the bearings.
The alternator is changed from 3 phase to single phase. While the 3 phase alternator is smoother it seemed over complicated for a turbine of this size.
The shape of the PVC tube blades is calculated to give a more efficient shape.