From: Bert Hickman
Date: Wed, 15 May 2002 00:01:51 -0500
Subject: Re: [TSSP] racing arc thought
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.