Here is our 12" Tesla Coil, operating at the Y2K Texas Teslathon in Ft. Worth, Texas. The coil was drawing approximately 40A @ 240V at the time, an input power of roughly 10kVA. An arc welder was used for current limiting, and input power was controlled by our homeade power controller. Our controller features a huge variac, voltage and current metering, SCR controlled start/stop switching, and a mains power ON keyswitch for safety. The secondary coil is 12" x 54", wound with #16, sealed with polyurethane. The primary is 3/8" copper with a 3/8" t-t spacing, tapped at the seventh I believe. Capacitor was purchased from Dave Wightman, and is .1uF @ 30kVAC. Spark gap was running 240BPS synch, motor RPM of 3600. Toroidal topload major O.D. is 52", minor O.D. is 20". Construction of toroid is chicken-wire stapled to 3/8" ply, screwed-in 1x2's for strength. This coil reliably produces 10.5 foot arcs @ 10kVA in its current configuration.