Almost completely finished my center power transfer shaft, with it being such a complex part I am really glad I didn't make enough critical mistakes that I had to redo it. Here's how it looks now: The flat sides in the middle suit a 22mm spanner to help with dissassembly. I still need to remove the small shoulder on the right middle, otherwise it's complete. View from the end, I took this metal out to save weight as it wasn't needed. Looking inside, there's a 25mm long straight section that's machined to be exactly 20mm before coming to a 20 x 1.5 L.H thread. The uni joint & outer bearing support shaft will locate on this section and transmit the torque using this internal thread. The sprocket cluster wound on: and in place on the frame: Notice how the main spine and crank boom are misaligned, this is how it's meant to sit. I purposefully offset the crank shell 3mm off to one side, that added to the ftattened section and the different in pipe sizes adds to the illusion of being way out of alignment.