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Re: A Puzzle


From: 	richard hull[SMTP:rhull-at-richmond.infi-dot-net]
Sent: 	Tuesday, September 02, 1997 6:57 PM
To: 	Tesla List
Subject: 	Re: A Puzzle

At 06:45 PM 9/2/97 -0500, you wrote:
>
>From: 	Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
>Sent: 	Tuesday, September 02, 1997 6:03 PM
>To: 	tesla-at-pupman-dot-com
>Subject: 	A Puzzle
>
>Greetings All,
>               This is a genuine enquiry (no, I don't know all the 
>answers regrettably). Last night, I replaced the large resonator in
>my work system with a much smaller one with the same sphere on top.
>I am using the same primary but k would be somewhat different.
>
>      The large resonator is a 10" x 44" space wound job (Ctot about 
>26pF). The small resonator is 4" x 17" and with the same topload 
>resonates at exactly the same frequency as the large one. This coil 
>has around 1800 turns of wire one it and consequently its inductance 
>is much higher (which it would have to be to resonate at 146kHz as 
>its Ctot is much less than the larger coil). OK, I know the wire 
>losses are a lot higher in the small one so on to the next bit of 
>information.
>
>     Under single shot conditions, the spark length is pretty much 
>the same as the large resonator so that implies that output voltage 
>is pretty much the same. Now that is reasonable because of higher 
>losses and possibly reduced k probably compensated for by reduced 
>total capacitance.
>
>    The cruncher: The large resonator has created those rare long 
>sparks measured well over 4 feet p-p. The little one is struggling to 
>get to two feet p-p. This is with exactly the same primary coil and 
>cap, energy and gap setting. This situation echoes someone recently 
>switching from a 3" (?) coil to a 6" one. The air discharges from the 
>terminal are a bit shorter with the small one suggesting the reduced 
>capacitance might be a factor. I have not as yet taken any real 
>measurements but will sometime today.
>
>    The question: why?  Any input sought, Ideas welcome from all. 
>I'd like to hear from anyone, no matter how trivial you think your 
>contribution might be.
>
>Regards All,
>Malcolm
>
Malcolm,

I spite of all things in the primary circuit appearing to be the same, there
are a number of alterations and shifting values other than the secondary.
You already noted the coupling (very complex and nasty business indeed)  the
4" coil has lotsa' wire wound in a small area on the small tube and located
rather far from the primary.  The big coil must be quite close to the
primary coil but is sparsely wound in the main area of the mag field from
the primary.  Our own Dave Sharpe has noted a possible role for capacitive
coupling in the primary/secondary electrical dance.  This would be
considerably altered.  The smaller coil with high inductance should have a
higher voltage using the old L di/dt saw.  Back in the primary circuit, is
the gap doing better at quenching the lower K coupled coil's arc and thus
yeilding lower losses?

Sorry your question was not answered, but many other questions are posed in
search of possibilities.  Some careful measurements are needed like those K
values.  What were the form materials for the secondaries?  Different or
same material.  On one of our tapes, we graphically show the reduction in Q
using wood, paper, cardboard or any pourous material for a coil form.

I'd like to give you a difinitive answer or even a proposed quess but there
is a lot of data needed to compare them effectively.

Richard Hull, TCBOR
>
>