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Re: New guy questions (fwd)

---------- Forwarded message ----------
Date: Thu, 19 Jul 2007 16:54:38 -0700 (PDT)
From: G Hunter <dogbrain_39560@xxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: New guy questions (fwd)

Hi Dan,

--- Tesla list <tesla@xxxxxxxxxx> wrote:

> ---------- Forwarded message ----------
> Date: Wed, 18 Jul 2007 21:54:10 -0400
> From: Dan/Elaine G. <degargel@xxxxxxxxxxx>
> To: tesla@xxxxxxxxxx
> Subject: New guy questions
> Hi all,
> I wanted to introduce myself by way of asking a few
> questions.
> I started getting interested a few months ago, doing
> some research, starting
> a design, scoring some hardware, and joining the
> List. Thought I stop
> lurking and ask-away.
> I have also been following the recent FAQ thread
> btw, and I can understand
> the difficulty such an undertaking might offer,
> since some of my questions
> focus on some well intentioned yet mildly
> contradictory input I collected
> from browsing various sites.
> 1) How critical is the Secondary HD ratio?  I found

Not very.  4.5:1 is a useful guideline, but it is not
law.  Slender secondaries often exceed this ratio, and
very large diameter coils often fall well short.  In
my case, I like to wind 24" of wire on a 4" PVC
secondary, just in case I want to over drive the thing
a bit.  The slightly longer H/D ratio gives me a
little better HV standoff, hence longer maximum
sparks.  I admit my ideas about secondary length are
mostly just intuition.  For example, I once pushed 45"
sparks out of a 4" x 18" PVC secondary (28 AWG wire). 
I fired it many times for longish runs.  It held up
fine, and probably could have tolerated even longer
sparks had I cared to push the issue.

> some guidance, but I
> also see some folks seem to ditch the convention -
> for example, maintaining
> an HD of 4 to 4.5 for a 4" coil form. (I haven't run
> any what-if analysis
> since I've been waiting for the math refresher to
> hopefully sink into my
> brain).
> 2) If I can afford an acrylic/plexiglas over a PVC
> Sec form, is it worth it?

Nah.  PVC pipe is cheap and readily available.  It is
easy to glue, and it can be drilled, cut, shaped, and
sanded using ordinary woodworking tools.  Also, most
common wood varnishes & sealers adhere well to PVC. 
The only good thing I can say about clear acrylic or
plexiglas coil forms is that they look really cool.

> (considering dielectric, looks, ease of using an
> adhesive, etc)
> 3) Best place to score some Cornell Dubilier caps
> for an mmc: does the Geek
> Group really sell them? to non-members? Should I try
> eBay or another source?
> 4) One curiosity question, in my past acquaintance
> with circularly polarized
> antennae, I was just wondering if there was a
> winding-sense convention (left
> or right-handed) that applied to coils as well. I've

No.  Winding direction doesn't matter.

> found no such advice
> (probably for an obvious reason). Does it help or
> not matter at all?
> Too many questions? Reply here or to my address -
> whatever is better,
> Thanks tons,
> Dan in PA
> I got a variac(!) and a 15/30 NST.



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