RE: Primary to primary sparking?

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

Original poster: "Ian McLean" <ianmm-at-optusnet-dot-com.au> 

Hi Chris,

I may be wrong, but I thought the rubber used in tires and tire tubes was
somewhat conductive because the black colour is made by adding fillers to
the rubber such as carbon black.  I believe rubber can also contain other
metallic oxides such as titanium dioxide and zinc oxide as reinforcing
agents.  Might this be a problem ?

It is just that I have not heard too much about using rubber as insulation
for high voltages, and it seems that it is usually bad to use anything that
is black.

Regards
Ian

 > -----Original Message-----
 > From: Tesla list [mailto:tesla-at-pupman-dot-com]
 > Sent: Friday, 2 April 2004 1:28 am
 > To: tesla-at-pupman-dot-com
 > Subject: Re: Primary to primary sparking?
 >
 >
 > Original poster: Chris Roberts <quezacotl_14000000000000-at-yahoo-dot-com>
 >
 > Well, it's a 9/120 NST with a TCBOR gap which has some red
 > plastic at the
 > top. When the gap is sparking, the light shines through, and
 > it gives it
 > that neat glowing look. The primary is .25 inch tubing with
 > .25 inch gap,
 > and it rests on rubber cut from an old tire tube to prevent
 > any problems. I
 > guess I just may have had the tap too close. But I am still
 > confused as to
 > why it would want to do that in the first place... Oh well. I
 > guess the
 > coil must've been bored with just running as it should, and
 > decided to have
 > some fun with me. =D
 >
 > Tesla list <tesla-at-pupman-dot-com> wrote:
 > Original poster: "John Richardson"
 >
 > Hi Chris,
 >
 > I've got a few thoughts, which may or may not help. I am
 > going to guess
 > that you are tapping at a relatively small number of turns,
 > and that your
 > turn to turn spacing is on the small side, say under a 1/4
 > inch. I've found
 > this to be a big mistake. Try to keep turn spacing 3/8 or
 > better. It seems
 > at higher power levels, when tapped at low turn numbers, that
 > the easiest
 > path for energy dissipation can sometimes be the next turn as
 > opposed to the
 > secondary. This will especially be pronounced if you are out
 > of tune, which
 > the lack of streamers leads me to believe. Are you sure that
 > your tapping
 > mechanism isn't coming within a hair's width of the adjacent
 > turn? This
 > will also cause your problem. BTW, what is your power source,
 > and what type
 > of gap are you using? All I can make ! out from the picture
 > is a glowing UFO
 > type of deal, and I'm thinking it's a TCBOR style gap.
 >
 > John Richardson
 >
 >
 >
 > -Chris
 >
 >
 >