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Re: Fine Tuning a Spark Gap



Hi Bill, Mike,
I would have to also agree that aluminum in the primary LC will work, and will
work ok. I know first hand because my first rotary was an aluminum flywheel
with
8 copper electrodes and two stationary electrodes on each side (same side) of
the disk for 120bps operation. Yes, it did work. But I have to wonder, without
the aluminum, would it have worked better? I don't know and may never know
because I've since dismantled it and am working on a variable break system.

I think what D.C. is telling us is if capacitor current peaks are
suppressed at
RF frequencies, than why use aluminum and wouldn't this be a poor choice to
something else better? He didn't say it wouldn't work, he just said there's no
"electrical" reason to use it. Sometimes availability of the part (free
aluminum
disk) changes this perception. As for Q, if conductance is decreased, well...
It may not be enough to be of any real concern.

What my post was questioning was, if Reinhard's increase in performance is due
to the aluminum standoffs, then is it the aluminum helping the gap quench?
Very
likely, it has nothing to do with the aluminum and possibly copper
standoffs of
equal positioning and size would do the same thing. But if performance
decreases
with copper standoffs, I would have to suspect the aluminum itself is
playing a
role which copper cannot and then, is it due to RF frequency effects on the
aluminum regardless of how small this effect may be. I think only Reinhard
could
answer this with a similar comparison described above.

Bart



Tesla List wrote:

> Original Poster: "Wysock, William C." <Wysock-at-courier8.aero-dot-org>
>
> To Mike, D.C., All.
>
> I have to agree with Mike's statement below.  If one has an aluminum
> conductor in a (Tesla coil) tank circuit, that is of sufficient surface
> area,
> I see little (if any) degredation in the performance of the circuit.  People
> have been using aluminum rectangular strip for flat spriral primary
> inductances, for many years, with very good success.  Moreover, if
> aluminum is so poor a conductor at radio frequencies, then how come
> all the commercial capacitor manufactures use this material in their
> extended foil construction?  The high end polypropylene capacitors
> using this foil exhibit very low ESR and ESL numbers, and very high
> Q's.
>
> Of course, the conductivity of aluminum is not as good as copper.
> In coil designs where every precious joule of input energy must be
> conserved (at any cost,) then clearly, copper is the superior choice.
>
> Granted, you wouldn't want to use aluminum wire for a secondary
> inductance, but where a primary inductance is concerned (typically
> say less then 100-150 feet in length and a strip width of say, 2",)  I
> know of a number of very effective and efficient coils that have been
> built, using this material.  One common trick has been to use 4 to 5
> strips of equal width, and sandwich them together, then wind the
> flat spiral.  Using this method, each individual strip had a thckness
> of around 0.020 to 0.030"; therefore a composit thickness of 0.100" to
> 0.150".
>
> Bill Wysock.
>  --------------------------------------------
> Tesla Technology Research
>
>  ----------
> From: Tesla List
> To: Tesla List
> Subject: Re: Fine Tuning a Spark Gap
> Date: Thursday, October 29, 1998 7:59AM
>
> Original Poster: Hollmike-at-aol-dot-com
>
> In a message dated 10/28/98 9:43:43 PM Mountain Standard Time,
> tesla-at-pupman-dot-com writes:
>
> >
> >  Mike,
> >  What I've heard has been from this list. Aluminum at RF frequencies is a
> > poor
> >  choice for a conductor. The conductance is affected by the frequency and
> >  the Q of
> >  the conductor drops. That's what I meant by RF suppression. I didn't mean
> > the
> >  frequency was suppressed.
> >  Bart
> >
>
> I didn't think that the frequency could be suppressed as mentioned in your
> last sentence.  I am not sure I can agree with the statement that aluminum
> is
> a poor conductor at TC  frequencies.  Chip uses a primary made from a strip
> of
> aluminum(about two inches wide) cut from a roll of flashing.  His coil does
> quite nicely with it.  Perhaps it would do even better with a copper strip
> of
> identical size, but as far as I can tell, aluminum works just fine.  Maybe
> this is simply due to the large surface area of the conductor.  Whatever the
> case, I wouldn't hesitate to use a similar design.
> Mike