Re: Ground, etc. (Re: A few Q's)

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

Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>" <evp-at-pacbell-dot-net>

Tesla list wrote:
> 
> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<jim-at-jlproduction-dot-com>
> 
> Hi all
> DWP I am left a little confused by your comments. Are you saying that
> the cement will conduct enough to cause harm or that it is ok just
> laying there?

	Even dry concrete is a good enough conductor to cause problems when
attached to high voltage circuits.  If you run a wire from a NST and
touch it to the ground you'll usually see quite a discharge.  The
driveway of a house down the street from me has large holes and glazed
areas left over from when the power line above it (only 2200 volts)
broke in a wind storm and arced and jumped and sizzled for almost an
hour.  That was 30 years ago!  Don't let HV lines touch the ground!  By
the way, there's a very old myth that storage batteries have to be
insulated from the ground/concrete to keep them from discharging. 
That's not true.

> Also of note is that I too have seriously debated the Variac's ground
> point.
> I think that maybe after all I should just use the mains ground and
> leave the other item for the RF ground.
> 
> The secondary part I pretty much had decided to do something with anyway
> so I will secure that somehow.
> 
> Thanks for anyone who can set me straight on this. I really want to make
> sure that I (nor anyone else) gets hurt.
> 
> Jim L

> 
> > I glass beaded (like mild sandblasting) the entire head to it is
> > scale/oxidation free but it is dull in appearance.
> 
>         Al, in air, is NEVER oxidation free.  It oxidizes
>         Immediately.  (The oxide is clear, so it may look
>         shiny, and 'clean'.  The Oxide is fragile enough
>         so that tightening a screw, etc will disrupt it.
>         THAT gets a metal to metal joint, which, if tight,
>         excludes the oxygen.  (typically, toughing with
>         an ohmmeter probe will break the oxide: which appears to
>         conduct...)

	If the surface is polished well enough to start with, even the oxidized
appearance will still be nice and shiny; waxing helps preserve the
shine.  The oxide isn't that fragile (the stuff is aluminum oxide, which
is pretty hard), and making a good connection isn't easy.  Note that the
use of anodized aluminum "insulators" is a common to provide a thermal
path to ground for transistors and other power semiconductor devices.

Ed