Re: Primary coil configuration

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Yurtle Turtle <yurtle_t@xxxxxxxxx>

Are you saying that with a good coating, racing arcs
cause no damage? My experience has been different,
though mine were on the backside, so I may have let
mine go a few seconds longer. I don't see how a
spark/arc can occur without causing at least pinhole
damage. If stopped soon enough, I agree the damage is
minimal and can easily be fixed, but I don't want to
downplay the risk of secondary damage. I've trashed a
secondary or two, and have sucessfully repaired them,
but I don't think they're ever as good as new.

http://www.hot-streamer.com/adam/burnt_secondary.jpg

Adam

--- Tesla list <tesla@xxxxxxxxxx> wrote:

> Original poster: "Dave" <dgoodfellow@xxxxxxxxxxxxxx>
>
<snip>
>     I became convinced at that moment that it was
> better to loose a
> little q by applying a coating then to completely
> kill a secondary if
> you are a little off in your coupling. Since that
> coil, I have only
> used low q components and they work fine. I don't
> like PVC pipe, so I
> use kraft phenolic tube. Strong and light weight.
> Once wound, I coat
> the secondary with water based Minwax Polycrylic. I
> have been told
> that this would be marginally better than winding my
> coil on a soaked
> rain barrel. Again, my coils perform fine. On the
> occasions that I
> have had racing arcs, they usually glide along the
> outer coating in a
> light manner, and have done no harm. In my more
> recent coils, I have
> used only flat primary coils, and started the first
> turn of the
> secondary an inch or so above the plane of the
> primary. I don't know
> that I have the coil putting out as much as
> possible, but I do get
> very good performance. My last coil with this
> arrangement used a
> 9/60nst, a 4" x 20" phenolic secondary coil form
> wound with 30 gauge
> magnet wire,  a 4" x 13" toroid on top, and 12.5
> turns on the flat
> primary. The coil at 120 volts pushed out 36" sparks
> with a nice
> steady tone. Spark gap set at 13/64"
>
> The bottom line: If you cross the line of max
> coupling, a good coil
> coating may save your coil from non-repairable
> damage.
>
> Dave Goodfellow
>
> ----- Original Message ----- From: "Tesla list"
> <tesla@xxxxxxxxxx>
> To: <tesla@xxxxxxxxxx>
> Sent: Friday, April 21, 2006 4:31 PM
> Subject: RE: Primary coil configuration
>
>
> >Original poster: "Lau, Gary" <Gary.Lau@xxxxxx>
> >
> >Increasing the coupling until racing sparks occur,
> then backing off, is
> >the only way I have ever heard of to set the
> coupling.  Since the exact
> >mechanism responsible for racing sparks is still
> unknown, we are unable
> >to predict the coupling threshold at which they'll
> occur.  As setting
> >the coupling much lower than that threshold will
> degrade performance, we
> >strive to keep it as high as possible.  Some may
> consider it "horrible
> >engineering", but it's the best that can be done.
> How do you propose
> >to determine that threshold without ever crossing
> it?
> >
> >I agree that running a coil with racing sparks with
> reckless abandon
> >will permanently damage the secondary, but I think
> most of us have
> >briefly coupled too high, seen the sparks, backed
> off, and have had no
> >further trouble.  Or are you suggesting that a
> brief racing spark will
> >permanently lower the critical coupling threshold?
> An interesting and
> >reasonable suggestion, but very difficult to prove.
> >
> >I don't know that it's ever been conclusively
> demonstrated that any
> >secondary sealing technique will render it
> invulnerable to racing
> >sparks.
> >
> >Regards, Gary Lau
> >MA, USA
> >
> > > Original poster: "D.C. Cox"
> <resonance@xxxxxxxxxx>
> > >
> > > Someone advocated adjustment until racing sparks
> occur and then
> > > backing off. This is horrible engineering.  Once
> a spark punctures a
> > > solid insulation it does not "cure" or repair
> itself.  Once the
> > > damage is done it is permanent unless the coil
> is rewound.  You can
> > > back off the coupling to reduce sparkover, but
> then you always have a
> > > weakest link in your coil system. Properly
> sealing the sec coil and
> > > then not puncturing it will produce a long
> lasting coil.
> > >
> > > Dr. Resonance
> >
> >
> >
>