RE: Why the primary is a flat spiral?

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

Original poster: "terry oxandale by way of Terry Fritz <twftesla-at-qwest-dot-net>" <toxandale-at-cei-dot-net>

In a recent tests of two primaries (one flat 1/4" copper tubing vs one
cylindrical AWG 8 softdrawn), I expected the flat to out perform the
cylinder (2x the secondary diameter) type being ALL other parameters of the
systems being identical. To my surprise, there was no difference in the
performance of the two. Nor were there any difference in the frequency of
strikes between the two circuits. The only advantage drawn from all this was
the flat spriral type was indeed shorter by about 6" vs the cylinder type.
These comparisons were done with a 5.5" x 30" coil, 32nF, and based on a 60"
discharge max reach power setting. No other changes where made to the coils
other than the primary swap, and consequently the need to raise the
secondary up by several inches.

(Un)Terry

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Tuesday, April 09, 2002 1:25 PM
To: tesla-at-pupman-dot-com
Subject: Re: Why the primary is a flat spiral?


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

In a message dated 4/9/02 10:17:22 AM Eastern Daylight Time,
tesla-at-pupman-dot-com
writes:


>
> the primary is in its flat form to
> 1.   keep coupling to a minimum value



Scot, all,

The coupling can be kept just as low by using a wide diameter
cylinder primary.  Instead I would say that using a flat primary,
the coupling usually just "happens" to work out closer to a
correct value, without using a computer program to pre-calc
the k value.  With a cylinder pri,  the secondary may need to
be raised a lot, which may not give as nice an appearance.
I suspect that much of the appeal of flat primaries is in
the appearance too.

>
> 2.   to reduce the height to minimize strikes to it



In some sense, the wider diameter of a flat primary makes
strikes more likely rather than less likely.  Although I agree
in a way.

>
> 3.   to make adjustments a bit easier when tuning



cylinder primaries are easy to tap and tune.

>
> 4.   and its a bit easier to mount a primary in this configuration...



I agree.

The answer I would have given the group, is that the primary
doesn't have to be flat, but flat is better in certain ways, but
other shapes are valuable too, and will work fine.

cheers
John