I just got another idea that takes out the limitations of the homopolar generator.
It consists of two big toroid magnets or electromagnets facing each other in opposing manner (not attracting)!!! bucking field.
In the middle will spin a toroidal coil it may be rectangular in cross section...
The coil could be mounted in a disk of brass or plastic or something that may be reliable for giving rotation to it.
As the magnetic field inside a toroid remain inside the toroid this beauty will create high unipolar voltage without reaction... that may be take out by brushes...
Its all about the geometry of the generator coils and the magnetic fields... the lines of magnetic field must be accounted for determining the better performance by creating strange new coil geometries...
Other way is to use electromagnets pulsed to induce ac voltage instead of dc. This allow the system to be brushless by resonant transformer action using another coil on the rotor...
THe magnets can also be flat... and can also rotate with the rotor if needed.
The toroid may be made mix with spiral design presented earlier...
