Re: Conductive paint?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Metlicka Marc by way of Terry Fritz <twftesla-at-uswest-dot-net>" <mystuffs-at-orwell-dot-net>

duncan,
response interspersed below, no argument intended, just something i've
thought about
Tesla list wrote:
> 
> Original poster: "Dr. Duncan Cadd by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <dunckx-at-freeuk-dot-com>
> 
> Hi Marc, All!
> 
> >i've tried spray graphite lube on a couple toploads with pretty good
> >success? even though the graphite megs out real high resistance in a
> >half inch distance, the streamers didn't seem all that much shorter,
> >just many more at once.
> 
> Now *THAT* I find fascinating.  It implies that the spark length is
> simply controlled by the total net charge and that, if there's
> sufficient resistance on the surface, breakout at one spot can't drain
> all the charge fast enough to regain equilibrium.  So you get more
> breakouts in order to reach equilibrium between the charging rate and
> the discharging rate.  Are the individual streamers from a
> graphite-coated topload less intense than the fewer sparks you get
> from a metallic topload of the same size?

yes individually they are slightly thinner and somewhat more active.
dancing around and seeming to slide across short areas of the toroid.
the toroid was fairly smooth to start with and after a few coats of the
graphite, was almost perfect. 

> 
> >i've often wondered if the dc resistance really comes into play with
> the
> >topc charge being at such a high frequency?
> 
> Don't see why not.  It's a thin coating, so the skin effect isn't
> going to alter much, and Ohm's law is still Ohm's law.

right, but is the charge actually flowing through any amount of
thickness at any given time? the charge being distributed over the
complete surface of the topload, i was wondering if it really only
travels through the thickness of a cross section of the material that it
is made of. in other words, only the .010" from inside surface to
outside surface? i can see what your saying above that once one streamer
breaks out, the resistance over the surface may prevent most of the
charge from traveling to that discharge point, this is interesting. i
will try it again and see if i notice any streamers actually connecting
above the surface, if they do this over a short space then the
resistance could be why they seem to dance around more.

> 
> >is the charge of the topc
> >being held on the conductor or in the dielectric?
> 
> Gauss' theorem suggests on the conductor, when the conductor is
> outside the dielectric as in a coated topload.

but the coating is conductive itself, so i would think the air between
it and the ground would be the dielectric? it is just my thinking as i
have read about lightning only so far. so if the charge is distributed
over the full surface of the toroid, the rate of curvature actually
gives a more uniform surface contacting the dielectric, allowing more
charge to build up before at some point a minor imperfection or bump
starts to develop a corona, and at that instant charge is dumped into
the streamer, or leader.
if the charge wasn't built up in the surrounding dielectric then
bringing a grounded object in any vicinity wouldn't force breakout at
that point, am i correct in this? the grounded object produces a leader
that forces a pull from the charge in the dielectric. i've read much on
lightning and the leaders are the deciding factor to what is actually
struck, in the last fifty or sixty feet to ground. i've seen photos of
several objects producing leaders at once stretching to intercept one
bolt.
though the dynamics of lightning are far different then the discharge of
a tc, lightning still travels along stepped leaders to the ground. so
the charge of the dielectric is being channeled into the main bolt from
what we see as forks extending outward to thin air, are actually charge
being channeled inward to the main bolt allowing it to jump the next
step distance.
in the tc charge, there are many differences, but the main one that the
charge is actually being produced in a somewhat bubble that is
compressed in the center, top to bottom. this forces the charge to
travel from the opposite side to a streamer in that short time, i don't
think all charge can make it that fast? i'll stop here before i really
misunderstand, i'll wait for comments.

> 
> >i wondered if the
> >hf\hv wouldn't just jump across the points of all the fine graphite
> >particles?
> 
> I would assume it does, but if they're in contact anyhow, there may be
> little jumping involved.  Also, particles in contact will "cohere"
> very efficiently considering the circumstances!

i agree with this, i see what your saying as the cohesion of the
particles being tight enough to form a sheet. but the charge only
travels from the center outward, over the conductor? well through it
somewhat.

> 
> >the spray graphite never flaked off but i did notice that
> >once in a while the clear poly spray i put over one, seemed to burn
> in a
> >fine point as one streamer would get stuck there, showing a very
> bright
> >pinpoint at the base. i never could see a pinhole on it though?
> 
> Maybe it carbonises a mini-breakout spike in the poly coating.

i think it is doing this, the pinhole is so small that i have looked
right at the spot were i know a streamer was stuck, to small for my
eyes, maybe i will try a magnifying glass and see if it might increase
in size?

> 
> >just thinking again,
> 
> Dangerous that!  What manner of spray-on goop is this?  I know you've
> mentioned it before, but it sounds like a specialised sort of product.
> Where might you find it?

yes i have often been told i think to much? the product i use is from:
superior graphite co., it is called "SLIP PLATE" GRAPHITE DRY FILM
LUBRICANT. i use it on my hay cutter bar and baler knotting units,
chutes. i get it at "tractor supply" or "quality farm and fleet"
if you're interested in trying this i will send you a can.

> 
> Dunckx