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Re: crazy secondary coil arcs

Original poster: Thomas DeGregorio <tommacs@xxxxxxxxxxxxx>

Wow to my surprise I was actually getting measurements of impedance, though it varied in different sections of the pvc pipe. The impedance range was about 10M Ohm to 2M Ohm with my DVM probes about 1 cm apart.

Yes the inner and outer layer of the PVC pipe are separating.

The distance from the primary coil and secondary coil is about 1 inch (horizontally) and i raised it up 2 inches (about 3 inches part now) and this still occurred.

On Jan 25, 2005, at 6:48 PM, Tesla list wrote:

Original poster: Daniel Hess <dhess1@xxxxxxxxxx>


I've never heard or seen the type of PVC pipe you've described but it sounds like some sort of special purpose, special application material. Personally, I try to avoid any black material anywhere on a coil because carbon is frequently used to make black things black; Black paint, black rubber, black plastic and so on. Do you have a VOM meter and can you measure any resistance along the inside surface of your secondary? If you can then this material is unsuitable for use as a secondary coil for the obvious reason.

Coil materials such as fiberglass or styrene are considered optimum but are also pricey. I've used white schedule 40 and the blue/green sewer pipe (available at construction sites usually for the asking). Some opinions claim that PVC is lossy at TC frequencies but I've been very satisfied with my results and you can't beat the price (free!)

I'm not sure I fully understand your 'bumpy' description. It sounds like you've developed blisters from where the inner and outer layers are separating? That in itself may make this material unsuitable for coiling even if the black inner lining isn't conductive.

The vertical arcs you describe are called 'racing' arcs and can also be caused by your coil being slightly out of tune and/or by being too tightly coupled to the primary coil. Also, I install insulating discs inside the secondary form at the 1/3 and 2/3 points, as well as the top and bottom of the coil, to prevent inner arcs from occuring. Any sort of plastic is usually suitable for this. I've used discs made from Plexiglas, polyethylene and styrene; Whatever is handy and plentiful at the time I'm building a secondary. The discs are glued in place with silicon RTV. I've used wood for end caps before but make sure they're sealed with multiple coats of polyurethane before they're installed.

Good luck,

Daniel Hess

[]"Tesla list" <tesla@xxxxxxxxxx>

Original poster: Thomas DeGregorio <tommacs@xxxxxxxxxxxxx>

I just finished my 6" dia tesla coil, which is in a 1:4 ratio, but it's
exhibiting rather an odd behavior in which the secondary is internal arcing
and is arcing to itself. My secondary coil when running is arcing to the
base of my coil's table. It's arcing from the bottom of the secondary coil
to it's self higher above, the arcs are travel along the surface of the
secondary coil. Most of all it's arcing internally. I can literally hear it
arcing inside the coil.

Is the black inner layer of my secondary conductive? I'm going to buy a different PVC pipe, but I just want to hear from someone else before I do so.