SRSG

["Steve" <Steve-at-g8cyerichmond.freeserve.co.uk> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

I have a number of motors, varying in power and type. The local mains is 230V
50Hz. I want  to build an SRSG, what should I ideally be looking for? At
present I am thinking of a disk in the range of 5-10". Alternatively does
anyone know of a good source of info on synchronous gaps, remembering this will
be a first for me? By the way I have a reasonably well equipped metal work shop
available, and someone who has expressed an interest in helping me with the
actual machining of components.
Steve