Original poster: "Peter Terren" <pterren@xxxxxxxxxxxx>It is used to shape the direction of the sparks. Avoid primary strikes by using a small toroid below a larger one. Eg
http://tesladownunder.com/Tesla_7ft.JPG Otherwise this happens http://tesladownunder.com/T6_5ft.JPGNeeded if you are pushing the spark length/secondary length ratio towards 3 in my experience. May not be too important otherwise.
Peter
Original poster: "Todd Reeve" <todd.reeve@xxxxxxxxxxxx>While checking out pictures of coils different sites on the Tesla Coil Ring, I noticed that some of the coils that use flexible aluminum ducting for a toroid sometimes have 2 stacked toroids while the coils that have a spun aluminum toroid have only one. I surmise that this is to increase the capacitance of the top load. Is this needed when using ducting since the wall thickness of ducting is thin compared with a spun toroid?