Re: S.s. info...re: differing secondaries

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

Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <FutureT-at-aol-dot-com>

In a message dated 2/14/01 7:44:10 PM Eastern Standard Time, tesla-at-pupman-dot-com 
writes:

> Original poster: "Kennan C Herrick by way of Terry Fritz 
<twftesla-at-uswest-dot-net>
> " <kcha1-at-juno-dot-com>
>  
>  S.s. coilers may be interested in the following:
>   
>  As I've previously reported, my s.s. system utilizes an untuned primary and
>  also a means for making the excitation frequency always exactly that of the
>  secondary's resonant frequency.  I have now made two secondaries, both
>  according to "HERRICK'S RECIPE..." posted in 8/00, one 52" high and the 
> second,
>  36" high.  Fr's are ~100 KHz and ~125 KHz respectively.  I use the 
Landgren 
> 6"
>  x 24" toroid with no added breakout-point.

Ken, all,

I consider your coil to be an impressive accomplishment, and
that you get breakout from a toroid of that size is impressive in its
own right.  Have you tried using a breakout point, or smaller toroids,
to see what effect it has?  I seem to remember that you mentioned
in the past that the sparks looked somewhat disruptive in appearance?
They must be very fierce and thick though.  Are there any photos
available?  I seem to remember you saying you were going to offer
these at a price?  (or that may have been someone else.)

>   
>  I find that, while the 52" coil yields very satisfactory sparks, those 
from 
> the
>  36" coil are markedly less so.  It might be that the driving impedance for 
> the
>  spark is diminished, away from optimum, by going to the lower turns-ratio
>  (~2:760 vs. ~2:1100).  But then, the operating frequency increases with the
>  shorter coil, so one might expect the driving impedance to be higher due to
>  that.

The impedance may be shifting more than the frequency, when all is
considered?
You say the sparks from the shorter coil are less impressive, but can
you give us some idea of what's different about them, and their sizes?
Are the sparks mostly shorter, or thinner, or branched differently, etc.?
>   
>  Manually sweeping the two coils with a signal generator shows that their 
Qs 
> are
>  essentially the same--around 100.  So with a Q of 100 and with only 760 
> turns
>  in the secondary, I am finding that spark breakout still occurs from the 
6" 
> x  24" toroid.

I assume your generator is low enough impedance to give a true Q reading?
I would have thought the Q would be higher, but that's a guess because
I don't know the details of the secondary.
>   
>  I also notice the following:  1.  The electric field, as measured by a
>  partially-shielded scope probe placed ~4' away from the coil c.l., is
>  essentially the same with both coils--both at the peak of the envelope 
when 
> the
>  spark breaks out (as expected since it's the same toroid) and also during 
> the
>  remaining ~5 ms spark duration.  And 2:  The input line (mains) current,
>  directly equal to average primary current in my case, is essentially the 
> same. 
>  It should be noted that, during the entire pulse-burst time, the secondary 
> is
>  driven at its instantaneous self-resonant frequency.
>   
>  So I tentatively reach this conclusion:  The factor that mostly caused the
>  decrease in spark energy was the increased operating frequency since a) Qs 
> were
>  the same, b) primary power was the same and c) the turns ratios in the two
>  cases were sufficiently high to allow spark break-out from the same 
toroid. 
>  Thus I would conclude that one wants to employ a secondary construction
>  technique that minimizes Fr while at the same time providing a Q vs.
>  turns-ratio condition such that spark break-out reliably occurs from the 
> toroid of choice.

I'm very surprised that such a small difference in frequency would make
much difference.  In work I've done, I've run at double the frequency
or more, and not seen very much difference, although my tests were
somewhat poorly controlled, and may not be valid.  I wouldn't be surprised 
if something else is the cause.  Then again, I have no idea how much
shorter or less impressive the spark is from the 36" secondary.  
It can be a real bear to track down the causes of spark differences in
these systems because of the many variables.  I suspect something
is the area of impedances perhaps.  It will be interesting to see what
others have to say about this.
>   
>  My next task will therefore be to construct another 36"-high secondary, 
also
>  with 20 ga. wire but close-wound instead of spaced ~.05" center-center.  
> That
>  will bring the frequency down substantially while maintaining ~1100 turns,
>  although Q will diminish due to the lack of spacing.  But the lower Q will 
> be
>  compensated for by the higher turns-ratio, in bringing the toroid voltage 
to
>  break-out potential.  So, we'll see...

That does seem like a good test.
>   
>  Comments, anyone?  Am I missing something?

I'm glad to see the interest lately in VTTC and SSTC work.  These
coils are often shunned by coilers, I doubt if even 1 out of 10 coilers
have built one.  They are powerful tools for investigating spark 
behaviour, and fascinating in their own right.  The ongoing
investigations in this area should provide important coiling insights.

Truly the internet as a communication tool is showing its power these
days, in helping to speed up the advancement of true TC understanding.

John Freau

>   
>  Ken Herrick
>