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Any hope here?


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From:  FutureT [SMTP:FutureT-at-aol-dot-com]
Sent:  Sunday, January 25, 1998 10:04 AM
To:  tesla-at-pupman-dot-com
Subject:  Re: Any hope here?

In a message dated 98-01-25 00:25:55 EST, you write:

<< 
> Well, I am feeling a little defeated.. I think I got a bit ambitious.
> Fired up my new coil today after rebuildng the primary, and building
> a new topload, and could not get breakout to save my life. With
> a bump on the outside edge I did mangage to get regular 30" arcs.
> I'd love to have this beast firing without the bump tho-
> So I am open for suggestions!!!
 
>snip
 >I am wondering if my topload is just too big, and if I should make a
> 4" based one? or if there is some trick of tuning I could use to get
> breakout without the bump?
> [Note that this same coil, with a 12"x3" torid produces several
> 18" arcs at the same time.]
  >>

Michael,

There's always hope, esp I believe in this case.  I must admit I have not
tried your particular parameters, but I have no trouble getting breakout
on a 5" toroid with no bump at 12kV, 30ma, with a .007uF cap.  This
seems to suggest to me that 12kV, 60ma, with the .0135uF you're
using should break out well.  In fact, my 15kV,60ma does break out
well using a 6" by 26" alum. duct toroid.  However, my 6 x 26" toroid
has quite a few rough edges which may be acting like bumps of sorts.

One thing you could try...and may have already tried...is to raise the
toroid about 2" to 3" above the secondary which should increase the
coils spark-length capability by unshading some of the top turns.  I
often find that this can increase the spark length by 3" or more.  You'll
probably need to re-tune (outward) after this.

Another possibility is that the gap is just not quenching adequately
for whatever reason?  In general, a large, hard-to-break-out-of toroid
will make the spark gap harder to quench.  A gap that quenches
adequately with a small toroid may fail to quench properly with a
larger toroid.  This effect can be seen nicely using an oscilloscope.

Another possiblity is that the spark gaps are too narrow, preventing
sufficient cap charging voltage.  Of course if you widen the gaps, then
the danger of neon destruction is increased.  I like to have extra neon
trannies on hand, so if a few burn up, it's not a big deal.  This way,
you find out your system's capabilities by pushing it to the max.  This
is the way rocket engines (etc.) are tested.  Push it 'til it blows, then
cut back 10% or so.  This gives max bang for the buck in the long run
(but not the short run).  But a lot of this is personal philosophy.
Personally if I don't blow out some components occasionally, then
I feel like I'm not really testing things properly.  Over the years, I've
only blown out two neon trannies, and I've unpotted them, and they
still work great.  So my destructive testing techniques have not really
cost me much cash.  I've blown out a number of vacuum tubes by
running them at 3 times their rated plate voltage, but I had gotten them
for free, so it's a matter of judgement.  The tube experiments served
many valuable purposes in learning about this exciting Tesla coil
hobby.

I usually use higher inductances in both the primary and secondary
of my coils, but I'm not sure how much it helps my results.  

In any case, good luck with the system, and let us know what 
happens.

John Freau