RE: Ground box

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

Original poster: "Ray Robidoux by way of Terry Fritz <twftesla-at-uswest-dot-net>" <robidoux-at-basystems-dot-com>

Hi Malcolm,

Thanks for your explanation, but I am still confused.
My experience does not agree. I am using an 8" piece of
braid right now in my primary. It is the wire that
forms the connection for my tap on the primary down
to the SG. I have touch this many times, while tuning
for example, and have found this piece of braid to be
STONE COLD. I have NEVER found this braid to be even
the slightest bit warm, but ALWAYS as I have said above
"stone cold".

Also your explanation of how current, "has to hop from
one strand to another", makes me wonder about stranded
wire in general. In a standed wire don't those strands
have to "duck and dive under each other along the length",
as well. That would seem to put stranded wire in the same
category as braid. But I have heard of coilers who say they
have used STRANDED wire for their PRIMARY coils, without I
assume excessive heating.

I would be curious to get more of your data on the subject.
I use braid quite a bit and if it is detracting from the
final objective (Long Sparks) I want to know so that I
can go on a seek-and-destroy mission if necessary.

Ray

> -----Original Message-----
> From: Tesla list [mailto:tesla-at-pupman-dot-com]
> Sent: Sunday, April 08, 2001 5:54 PM
> To: tesla-at-pupman-dot-com
> Subject: RE: Ground box
> 
> 
> Original poster: "Malcolm Watts by way of Terry Fritz 
> <twftesla-at-uswest-dot-net>" <m.j.watts-at-massey.ac.nz>
> 
> Hi Ray,
>          I can help explain this braidophobia very succinctly:
> 
> On 6 Apr 01, at 12:18, Tesla list wrote:
> 
> > Original poster: "Ray Robidoux by way of Terry Fritz
> > <twftesla-at-uswest-dot-net>" <robidoux-at-basystems-dot-com>
> > 
> > Hi All,
> > 
> > I am very confused as to why this list has such a dislike
> > for braid. I have seen many comments like this against the
> > use of braid in TC work. My experience with braid is
> > that for the same amount of copper (and 90+% optical
> > coverage) the braid is an order of magnitude better than
> > solid wire at conducting RF energy. The reason for this
> > is exactly why we use refer tubing in the primary of a
> > TC. It is the skin effect, the fact that the center of
> > a conductor is useless in conducting RF currents. Therefore
> > you want to increase surface area in the conductor to
> > decrease current density. When using braid the most
> > important feature to examine is the so called
> > "optical coverage". This is the amount of light blocked by
> > the strands of braided wire (strand density). Braid comes
> > in all sorts of optical coverage(OC), from 10-% to 90+%. One
> > can imagine that 20% OC braid is useless, and in fact is
> > typically used in conjunction with aluminum foil to make it's
> > shielding and conducting properties better. I would not use
> > any braid with less than say 90% OC. If you look at the pics
> > that Terry has shown, which is going to be the better conductor,
> > I find it hard to believe its the center wire which has maybe
> > 1/10th the amount surface area than the braid. I would like
> > to hear others thoughts on this matter.
> > 
> > Ray
> 
> Unfortunately, it is precisely the skin effect that works against 
> braid. There can be no doubt about how poor it is - I have measured 
> it in a carefully crafted expt. I then went and proved the point by 
> running a high current primary with a foot of it included. It got 
> hotter than the brass blocks holding the gap electrodes.
>       The strands duck and dive under each other along the length. 
> Since skin effect is trying to keep current near the outer surface of 
> the braid, the current has to hop from one strand to another at every 
> point. Result: to RF, braid is like including thousands of 
> connections in series, and contact connections are generally less 
> than perfect. Braid was the standout worst performer in my tests by a 
> country mile.
> 
> Malcolm
> 
> 
>