RE: Metal Screws and Salt Water Caps

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

Original poster: "Steven Ward by way of Terry Fritz <teslalist-at-qwest-dot-net>" <srward16-at-hotmail-dot-com>

Here is a related story:

When at the 2002 cheesehead teslathon, my coil somewhat failed:(.  I have a 
setup with 15/120 NST bank 27.5nf MMC and a 13 turn primary with a 6.3" 
sec....  I had the pair of rebuilt 15/60s about 8" below the primary coil.
Everytime the sparks hit the strike rail, my NST core would short to the 
primary on the NST!  I had no idea why.  And furthermore, i wondered "WHY 
NOW!!!".  D.C. and some others mentioned that the primary could be inducing 
some current onto the large nearby cores of the NST.  So that ended my 
running for the day:(

When i got home, i rebuilt the NSTs, again(!) and put them in a seperate 
enclosure mounted about 10' from the coil.  I ran some heavy cables to my 
nice insulator connection points.  The coil worked wonderfully, but not any 
better than before.  The sparking didnt happen with the NST core.  Then 
about 5 run periods latter at a friends house, it started arcing again.  I 
have no clue as to why.  It appears that it does occure less often, but 
then again, there is insulation in there.

Make of this story, what you will.  I realize its inconclusive.  But if i 
did it over again, i would have just re-insulated and put the transformers 
back in the coils base.  My setup time is MUCH longer now, but then again, 
it looks more impressive/technical to the average joe.

IF anyone knows why the primary core or coil is generating enough potential 
to form an arc through at least 600v of insulation, please let me know!  I 
do not have any protection but a safety gap.  Maybe i need an RC type filter?

Steve Ward.






>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: RE: Metal Screws and Salt Water Caps
>Date: Thu, 09 Jan 2003 19:33:48 -0700
>
>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


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