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Re: SMALL SPARKS: PLENTY OF POWER- NO TIME

Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

Hi Ralph,

I agree with David and would add that on average, it is less troublesome, especially for new coilers to use flat primary's. IMHO, the benefit to helical primary design is space savings. The downside is that if the proximity is not thought out ahead of time, coil 1 ends up in a position relative to coil 2 that is far from desired. As I see it, the following will occur:

1) They may get lucky
2) They will think it through and equate mutual inductance before winding
3) They will live with what they have
4) Rewind and try again.

But a good learning experience usually. In any event, there has been a great deal of new coiling success and some of that can be contributed to flat primary design because unless it's really "off the wall", it's easy to compensate proximity with little effort.

With that said, I see nothing wrong with helical primary design. They've been around 100+ years and keep the coil compact in most cases. I would actually like to see more helical designs from a cosmetic point of view.

There are limits to both as far as how high k can be attained. Helical's can achieve much tighter k than Archemedes design. With both, the upper limit is when the primary is center to the secondary and the helical has the advantage of tightening up the proximity (not including coil to coil arcing problems). But with TC's requiring such loose k, performance is neither gained or lost with either design. At least, nothing I've measured (I've only built 2 helical primary's).

Take care,
Bart




Tesla list wrote:

Original poster: DRIEBEN@xxxxxxxxxxxxxxx
Ralph, all,

I too used helical primaries in the early days of my
coiling (nearly 20 years ago). I used like #4 insulated
cable and this too worked well without racing sparks
once properly coupled. The insulation made it more
difficult to tune though. I don't think there's really
a question of IF a helical primary can work but it's
more of a question what works best and is more practical.


David Rieben

----- Original Message -----
From: Tesla list <tesla@xxxxxxxxxx>
Date: Wednesday, October 26, 2005 0:05 am
Subject: RE: SMALL SPARKS: PLENTY OF POWER- NO TIME

> Original poster: "Ralph Zekelman" <gridleak@xxxxxxxxxxxxxx>
>
> Gary,
>
> I regularly use helical coils with the half-wave twins and bi-
> polars.  I
> wind 1/4-inch Cu tubing to allow around 2-inch spacing to a 3 or 4-
> inchdiam secondary. There is no problem with racing sparks. I do
> not understand
> why the helical primary seems to be in disfavor with many coilers
> sincemany of the historical *Tesla era* photos show a helical coil.
>
> Ralph Zekelman
>
>
> -----Original Message-----
> From: Tesla list [mailto:tesla@xxxxxxxxxx]
> Sent: Monday, October 24, 2005 8:43 PM
> To: tesla@xxxxxxxxxx
> Subject: RE: SMALL SPARKS: PLENTY OF POWER- NO TIME
>
> Original poster: "Lau, Gary" <Gary.Lau@xxxxxx>
>
> Hi Jeremiah:
>
> I would also suspect that the primary tap may not be optimum.
> With a 15
> turn primary, one can vary 1-2 turns and not see a world of
> difference,but since you say you use only six turns, it may be
> very sensitive to
> fractional turns.  It looks like it wouldn't be too difficult to
> replacethe insulated wire you have with solid bare wire, at least
> temporarily,or ideally 1/4" copper tubing, to permit quick and
> easy tapping at
> arbitrary points.
>
> It's curious that you've not reported racing sparks.  It's always
been
> said that the use of a helical primary will result in too-high
> couplingand racing sparks.  Maybe no one's ever actually tried it?
> I hope so,
> yours is very compact!
>
> I don't think that 20 Amps is at all out of line; I use at least that
> much with my 15/60, and that's with PFC caps.
>
>
>