RE: Metal Screws and Salt Water Caps

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

Original poster: "Lau, Gary by way of Terry Fritz <teslalist-at-qwest-dot-net>" <Gary.Lau-at-hp-dot-com>

My coil has morphed considerably since the experiment, but the (active) 
primary diameter was approximately 18"-19".  I would say that an 
NST-to-primary spacing rule of thumb is more like a primary radius or more, 
and even then, there is some leeway.

Regards, Gary Lau
MA, USA


Original poster: "Paul Benham by way of Terry Fritz <teslalist-at-qwest-dot-net>" 
<paulb-at-woodanddouglas.co.uk>

One question Gary,

What was the overall diameter of the primary? (the part with the current
flowing through it, not including the outer turns after the tap point).

Maybe we can get a general rule from this, eg keep large metal objects at
least the primary diameter's away from it when directly under the coil.  As
you say, the spark gap is probably still the greatest loss, but I like the
idea of keeping losses to a minimum if it is easy to do from the outset of
design.  I have set my primary's height to its diameter above the floor to
try and minimise any eddy loss.

Cheers,

Paul Benham.

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Friday, January 10, 2003 2:33 AM
Subject: RE: Metal Screws and Salt Water Caps


  > Original poster: "Lau, Gary by way of Terry Fritz <teslalist-at-qwest-dot-net>"
<Gary.Lau-at-hp-dot-com>
  >
  > In my experiment, I only looked to see how much the equivalent primary
tank
  > resistance in Ohms, i.e. losses, was affected by objects places near the
  > primary.  No attempt to see actual operating performance differences were
  > made.  See http://www.pupman-dot-com/listarchives/2000/November/msg00359.html.
  >
  > Regards, Gary Lau
  > MA, USA
  >
  >
  >
  > -----Original Message-----
  > From: Tesla list [mailto:tesla-at-pupman-dot-com]
  > Sent: Thursday, January 09, 2003 8:33 PM
  > To: tesla-at-pupman-dot-com
  > Subject: RE: Metal Screws and Salt Water Caps
  >
  >
  > Original poster: "Chris Roberts by way of Terry Fritz
  > <teslalist-at-qwest-dot-net>" <quezacotl_14000000000000-at-yahoo-dot-com>
  >
  >
  > Gary,
  >
  > How badly did the NST affect performance? Our NST is located really close
  > underneath the primary and we have been getting sub-par sparks from it.
  > (9kv, 120ma, only 20" sparks) Serves me right I guess for trying to make
  > the coil compact and good looking =).
  >
  >
  >
  >    Tesla list <tesla-at-pupman-dot-com> wrote:
  > Original poster: "Lau, Gary by way of Terry Fritz "
  >
  > There is no reason not to use metal screws unless they're so close to the
  > primary that they may cause a short between turns. Very large metal
  > objects are more problematic. A large metal-encased NST will contribute to
  > losses if it is closer than 6"-9" below a large primary coil (I did this
  > test with a 20" diameter primary, not sure how a mini coil-class primary
  > would behave).
  >
  > Bleeder resistors are commonly used on MMC caps because shorting the end
  > terminals won't guarantee that individual caps are discharged. Since a SW
  > cap is not a series array, shorting the terminals WILL discharge the
  > cap. However, situations may arise where a charge could be left on a SW
  > cap (i.e. if the primary tap is loose), and SW caps are not that lossy
that
  > the charge wil! l bleed off by itself. A series array of resistors would
be
  > a wise addition.
  >
  > Gary Lau
  > MA, USA
  >
  >   >Original poster: "Centauri by way of Terry Fritz "
  >
  >   >
  >   >Hello everyone,
  >   >
  >   >I'm assembling the base into which I will place all the components of
my
  >   >coil, and I was wondering if I need to avoid using metal screws, bolts,
  >   >etc.. in certain places? Specifically, is it alright to use metal
screws to
  >   >attach the legs. The head of the screw would be directly below the
primary
  >   >coil with a separation of approx. 1". Is this acceptable? Also, what
other
  >   >places should metal be avoided?
  >   >
  >   >Second, do I need resistor(s) across the terminals of my salt water
bottle
  >   >cap or is it too lossy to matter? If I do, could I just wire a number
of
  >   >small resistors in series?
  >   >
  >   >Thanks,
  >   >Alan
  >
  >
  >
  > -Chris
  >
  > "Learn from the mistakes of others. You won't live long enough to make all
  > of them yourself."-unknown
  >
  >
  >