From: "Barton B. Anderson"
Date: Wed, 15 May 2002 00:13:00 +0000
Subject: Re: [TSSP] racing arc thought
Hi Bert, Just FYI: The spar varnish goes on pretty thick. It's glass smooth and I use the gloss. Interesting observation about the dust magnet issue. I never see that. Looks the same from top to bottom and never even noticed dust on it. I think the write up showed harder coatings like Behr contain more metallic dryers than the spar type varnishes, so actually, your's should be more conductive? That's why I was hypothesizing about a capacitance between windings and coating. Maybe the insulation serves as the dielectric? Just a thought. Take care, Bart Bert Hickman wrote: > Hi Bart, > > It just may be that your coating is slightly conductive - it probably > wouldn't take very much dielectric leakage to bleed off the excess > charges. Some of the satin spar polyurethanes contain silicon dioxide > (quartz?) to help dull the surface, but this additive is probably not > very conductive. Maybe your varnish does contain some other proprietary > (and slightly conductive?) additive that's not specifically spelled out. > > The conformal dielectric coating on my coil is likely much thicker that > yours - perhaps a thicker dielectric layer can retain a higher voltage > for a longer time(?). And, Behr Build50 appears to be a very excellent > dielectric - I can feel the hairs rise on my secondary for many hours > after a run. And since the coil is housed in a screened-in porch, it > also acts like a dust magnet, rapidly attracting a film of dust that's > mainly concentrated at the top of the coil. Wiping this accumulation off > becomes a somewhat hazardous exercise - no problem as long as I remember > to continuously touch the toroid with one hand while wiping the coilform > off with a rag with the other. And, the coil never fails to remind me > lest I forget...:^) > > Best regards, > > -- Bert -- > -- > Bert Hickman > Stoneridge Engineering > Coins Shrunk Electromagnetically! > http://www.teslamania.com > > "Barton B. Anderson" wrote: > > > > Hi Bert, > > > > I haven't thought about the windings affect. I'm glad you mentioned this. What is > > dissimilar between our coils is the coating. Last night, after running the coil > > for tests, I walked up to the secondary and placed my arm to the top area of the > > coil, but couldn't even feel a hair move, even to the point of just touching the > > hairs of my arm to the coil. > > > > I just read something interesting about the coatings we use. Seems all are oil > > based. The oils are cooked and blended with resins, solvents are added to thin it, > > and "metallic" dryers (cobalt and zinc) are added to speed up curing time. It also > > discusses long and medium oils, where long is more oil, thus it takes longer to > > dry but is more flexible (such as spar varish). This makes me wonder if there is > > more metallic properties in the harder coatings. If so, maybe there's a sufficient > > capacitance for storing a charge? Anyway, the page is a simple write up and kind > > of interesting: > > > > http://members.aol.com/woodinfo1/varnish.htm > > > > Take care, > > Bart > > > > Bert Hickman wrote: > > > > > Bart and all, > > > > > > I agree with you re: static build up for grounded resonators being > > > mostly a phenomenon of the outer coating. If there were stranded charges > > > trapped on the coil former itself (a possibility with an excellent > > > insulators such as PVC), the grounded secondary winding should shield > > > most of the internal charge trapped on the former from appearing outside > > > except past the ends of the winding where the former is uncovered. > > > However, this would not be the case for a highly insulating outer > > > conformal coating. > > > > > > My 10" coil uses a relatively thick (1/16" to 3/32") coating of Behr > > > Build 50 (which I think is a two-part clear epoxy resin) on a 10" PVC > > > former. The coating build up a very substantial (read "painful!") > > > charge, particularly near the top of the resonator. I can easily feel > > > the strong E-field with the hairs on the back of my hand, and hear the > > > snapping of partial discharges as they spark to my fingertips as I > > > approach and touch the highly charged regions of the conformal coating. > > > And, if I'm wearing rubber soled shoes, my entire body gets charged up > > > in the process - I can get zapped quite nicely by then touching the > > > grounded toroid. The first time this happened it was with my forehead... > > > OUCH! The charging/discharging sequence can be repeated many times > > > before the charge is finally reduced. > > > > > > All bets are off when the secondary ground is removed... stranded > > > internal former charges may then contribute to coilers getting nailed > > > even more strongly while carrying loose formers. BTW, getting "nailed" > > > from a charged resonator is an official rite of passage for novice > > > coilers to graduate to "experienced" coilers... :^) > > > > > > Best regards, > > > > > > -- Bert -- > > > -- > > > Bert Hickman > > > Stoneridge Engineering > > > Coins Shrunk Electromagnetically! > > > http://www.teslamania.com > > > > > > > > > "Barton B. Anderson" wrote: > > > > > > > > Hi Marc, > > > > > > > > For coils which do contain a charge, I have to believe it's either in the > > > > former or coating. It may be the makeup of the poly. I use marine spar > > > > varnish and never get a static build up. From all the posts on the list > > > > regarding this subject, I've often wondered if it was the former. Before > > > > this last coil, I used sonotube. This last coil I used pvc. In both formers, > > > > a static charge still is not detectible (at least without a sensitive static > > > > meter). Because of this, I would suspect it is the coating itself. Materials > > > > such as nylon will remember and build a charge easily. It's possible some of > > > > the coatings others are using contain similar property's. This might explain > > > > why I haven't experienced a static charged secondary. The reason I chose > > > > marine spar varnish was due to running in freezing temps in MN (I wanted a > > > > flexible coating that wouldn't crack under extreme weather changes). > > > > Although I'm in CA now, I still use it. > > > > > > > > Take care, > > > > Bart > > > > > > > > marc metlicka wrote: > > > > > > > > > hello all, > > > > > I have some thoughts in the back of my mind about those thick poly > > > > > coatings over the windings on most coils, you see, I never saw a acing > > > > > arc until the very first coil that i coated with many layers of spray > > > > > polyurethane? Most all my coils are a "moto finish" red, this is because > > > > > i tended to coat the windings in layer after layer of insulating > > > > > varnish. I liked the 2kv per mil. of dielectric property and the color > > > > > is nice too. > > > > > > > > > > I did wind a very small coil onto a "creamora" bottle (polystyrene" i > > > > > believe) This coil would race up down and sideways even with a 530 nst > > > > > turned low. This was also the first coil that gave me the "extended > > > > > charge" zap after a run, since i coated it in moto finish, I tend to > > > > > believe the charge was in the former? I have a "gut" feeling that those > > > > > thick coats of poly can build a static charge that at the very least, > > > > > cannot help guard against racing arcs. > > > > > Just a thought of mine that i'd be interested in hearing other opinions > > > > > on. > > > > > Take care, > > > > > Marc
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.