Bart,
That's some interesting observations that I never really
considered. Not too sure my observations have matched the certain
"power window" that you state where the pri-
mary strike frequency seems to spike. As you stated, when the sparks
are allowed to emanate freely from the smooth (or relatively smooth)
toroid surface, they tend to start from the horizontal center region.
With this in mind, I have found that the primary/strike rail hits can
be significantly reduced by setting a breakout point closer to the top
of the toroid, thus forcing spark propagation
from the upper part of the toroid, well above the hori-
zontal center. But even then, I will still get an occasional
strike to the primary region. I guess you have to expect
that with a 240 volt, 90 amp power feed into a coil
that doesn't quite top 8 ft. in total vertical height!
This past Friday when P. Slawinski and C. Prince came for a visit, we
tried elevating the whole tank
circuit assembly of the Green Monster about 18" with my 4 jack stands.
This is what allowed for more
numerous sparks in the >12 ft. range, in my opinion,
although this did NOT change the toroid to primary
coil/strike ring clearance and consequently, the pri-
mary strike frequency remained pretty much status quo.
David Rieben
----- Original Message ----- From: "bartb" <bartb@xxxxxxxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Tuesday, July 15, 2008 8:51 PM
Subject: Re: [TCML] Strike Rail Hits Was: Stacking vs Large Diameter
Hi David,
I've used my old primary on many coils and refitted it with inner
turns as necessary (started big and then started building smaller
coils). I was just thinking the Green Monster would look pretty cool
with a small ribbon primary resonantly driving the secondary. Yes,
the sparks do go where they want. But then, their going there for
reason (because they can) ;-) . What I don't like is giving the coil
"just enough power" to hit the primary. I have some extra turns and
thus a little auto-transformer action occurring which I don't like.
This seems to add to primary hits, but I'm not sure if it's the
auto-transformer action or simply power. A smaller 4.5" coil I run
can hit the primary as well all day long if I only give it just about
enough juice to do so. But if I increase power enough, I rarely hit
the primary. I can also reduce power and achieve the same thing of
course (but that's no fun).
I think some coils will hit the primary quite often and some won't.
Some coils are geared up just enough to do so and no more. Sparks
start in the horizontal center of the toroid as we all know. It
always starts out horizontal (or say emitting directly outward from
it's origin). After the spark begins it's length increase, then it
begins to bend. With higher power, it seems that initial thrust
outward heads out far enough to stay away from the primary or
whatever. But with just the right power, it can bend right down and
then there's the primary or strike ring willing and ready to accept
the connection. The spark "should" actually head upward due to
heating. And at first it does, but then the fields overtake the
heating affect and drive the spark downward as the spark progresses
further from it's origin. Easy to see in just about everyone's spark
photo's (from big coil to little coil).
As coilers start increasing power to attain longer sparks, they
eventually cross the primary strike bridge. Coilers may wonder why
(did they do something wrong, did tuning go south, what happened?).
Well, they simply reached that threshold. It's time to boost power
further to get over the hurtle (or reduce power, or even maybe change
the top load height and/or size).
Take care,
Bart
David Rieben wrote:
Hi Bart,
Cameron Prince uses a flat ribbon primay design
for his primary on his big coil, too. It would have
been easier for me to employ the flat ribbon if I
had started the design with a flat ribbon primary to begin with, as
"retroing" from a copper tube
design back to a flat ribbon design would pret-
ty much require a complete dismantle and reas-
sembly of the system. It's funny too, because sometimes I can hurl
multiple streamers for
a minute or so non-stop without hardly a single primary primary
strike and then the
next 30 seconds the streamers may hit the
primary area 30% of the time! They seem to
do what they want to do ;^)
David Rieben
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