Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx> Thanks Alex.The coil is about what I expected in size. Smooth toroids are always in search of. The easiest way to buy one from John Freau whenever he brings up the offer on the list. Dr. Resonance also periodically provides a bulk buy. I purchased a 9 x 30 for a larger coil on a long gone bulk buy several years ago. On my 4.5" coil, I always just used al ducting tape over a corrugated tubing, but even that can be difficult to make perfectly smooth. So, I finally bought some plaster of paris and some other similar patching compound which I mixed 50/50. I basically took a corrugated tube and turned it into a perfect toroid after a little sanding and topped it off with some heavy duty foil. Works real good.
Here are pics of a similar size coil (4.5" x 21") with the toroid mentioned using a 12/60 NST (a repaired NST with 1/2 shunts removed and a lowered output voltage at 10600 volts; to be accurate).
http://www.classictesla.com/photos/ba45/ba45.html Take care, Bart Tesla list wrote:
Original poster: "Alex July" <julez06@xxxxxxxxxxxxxx> The secondary is 4" x 20", and the tubing is 1/4", I have smoothed out my toroid a bit whilst I wait for some HVAC ducting which looks a lot smoother than what I had, I had it running at full and suddenly the sparkgap stopped firing, on further inspection there was a huge ammount of corroded copper. I've just finished removing it and hopefully I will be able to power it up soon. However smoothing out the toroid has helped a lot, less little ones and some nice lingering sparks. I'm on my outer most tap so it looks like I might have to make a larger primary. Thanks for the compliments, going to have to add casters on the bottom though!