The picture below shows of the rotor stacks up into an assembly. The magnets get embedded into the magnet housing, and is covered by a laser cut sheet metal cover. The sheet metal cover prevents magnetic flux of the powerful magnets from going out of the generator, and also makes the flux stronger on one side of the Magnets.
The rotor brace prevents the powerful magnets from collapsing into each other ( THE MAGNETS ARE FREGGIN POWERFUL), as well as provides a way to mount the drive shaft. Use M3x16 CSK screws to mount everything together.