Primary Thoughts

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

Original poster: "Ray Robidoux by way of Terry Fritz <twftesla-at-uswest-dot-net>" <robidoux-at-basystems-dot-com>

Hi All,

I was musing about primaries on my long commute
home one day. My current TC is a 2.5" x 13" with
a 45 degree conical primary using 1/4" refer pipe.
The Primary is tapped at turn 10 out of 13 turns.
So I got to wondering just what those extra turns
are doing electrically to the TC circuit. They
would seem to resemble an auto-transformer if
looked at schematically:

 To the CapPrim______
                     )
                     )
                     )   Lprim
                     )
 To the Spark G______)
                     )
                     )   Lextra
                     )
 Floating_end   -----

But because the "Floating_end" 'floats' there is "no"
current flow in Lextra so maybe it does not contribute
to the circuit of the TC. But wait, it is an inductor
immersed in a magnetic field, just like the secondary,
so it must have some effect. So the question is not does
it have an effect, but rather is this effect positive or
negative with regard to spark length. So I thought about
an experiment to find if Lextra can be used to help in a TC.
What would happen if I were to put a Cap in parallel with
Lextra (CapExtra) such that:

                  CapPrim x Lprim  ==  CapExtra x Lextra

Then I would have another tank circuit at the same resonance
as the Primary tank, that might increase energy delivered to
the secondary.

So when I got home I tried it right away. But what I found
was that I suddenly had NO output from my secondary. :(
Obviously the Lextra part of this arrangement is directly
opposite in phase as the Lprim tank. To further verify what
is going on, I tried a different Cap value that would not
be at the same resonance. And when I powered up I was getting
sparks of about the same length as my TC would normally give. :)

So I concluded that the Lextra CAN effect the output of a TC.
But the question remains as to how much does it detract from
spark length (if at all). One thought to test this would be
to design a primary that can be added to in stages. Then one
could make the primary just the exact length for proper tuning
and no longer, measure the spark length. And then add several
extra turns on the primary and measure again. This sounds like
a job for a flat spiral, because the form to hold this primary
would accommodate such a modular primary without too much trouble.

Like all of us I am busy and would have to add this to the bottom
of a very long to-do list. If anyone out there is willing to spend
some time and would be able to go on with this idea, I for one would
be curious as to the outcome. After all we all put extra turns on our
primaries "just in case". Well if they are detracting from our main
goal (BIG SPARKS) then lets rethink this a little.

Looking forward to all comments:
Ray.