Original poster: "K. C. Herrick" <kchdlh-at-juno-dot-com> I've worked up a dwg of the prospective commutator assembly for http://hot-streamer-dot-com/temp/tspk17s1.pdf. See http://hot-streamer-dot-com/temp/tspk17a1.pdf. Notice that the commutation configuration is a bit different from the schematic. Also that I show a tungsten rod for the gap element. KCH