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RE: [TCML] primary material? (interview)
I agree with every word. Yes, the myth that aluminum is unsuitable for use at RF frequencies is a stubborn one. The oxide layer on aluminum is too thin to affect the skin effect at high frequencies. As long as the DC resistance is compensated for, I don't believce there would be any significant difference.
Regards, Gary Lau
MA, USA
> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of bartb
> Sent: Saturday, July 19, 2008 2:27 PM
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] primary material? (interview)
>
> I don't know if DC has tried it or not, but there is certainly truth to
> higher resistance, peak currents, heating. Ed Phillips did measure Al
> and Cu wound coils for Q, R, etc. TCML archives (final report). What was
> found was expected. There is a an overall blanket myth with aluminum and
> Tesla coils when it comes to the electrical properties. It is true that
> Al has higher R of a ratio in the neighborhood of 1.6, but these
> properties are linear and increasing conductor size will bring it up to
> par with Cu (these functions are linear).
>
> The real problem I think for Al primaries is oxidation and the effects
> this has with tap connections, galvanic corrosion, etc.. With some
> maintenance, that should be manageable. Given the prices of metals these
> days, I suspect we will see more and more use of aluminum and we will
> also see "how" to use it in the correct application as experience
> unfolds. For example, if one were to use Al as a spark gap electrode
> material, then you would have some real issues (none of which are
> electrical but rather mechanical such as heat, pitting, quenching, etc.).
>
> The overwhelming losses are in the gap. The losses in the tank are small
> in comparison. The use of Al and it's electrical properties requires
> putting the coil itself as a whole into perspective. There is no doubt
> that copper is a better choice electrically size for size. But that
> isn't the issue. The issue is if it is a viable alternative if material
> costs force it's use for some coilers.
>
> Even for super coils where the cost of material is substantial, it may
> be a significant cost savings, or similar if manufacturing a high number
> of coils. Let's see, 35" sparks versus 40" at Al versus Cu cost ratio of
> 2.67? Maintain margins and move the savings to the customer (quantity of
> sales increase, profits increase). So, did I talk anyone into it? :-D
>
> Regards,
> Bart
>
> dr.hankenstein@xxxxxxxxxxxxx wrote:
> > Have you actually tried comparing the two materials side by side?
> >
> >
> >
> >> [Original Message]
> >> From: DC Cox <resonance@xxxxxxxxxxxx>
> >> To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
> >> Date: 7/18/2008 2:34:41 PM
> >> Subject: Re: [TCML] primary material? (interview)
> >>
> >> Bart & Gary are correct --- alum is not the best choice. Alum can be used
> >> for high voltage transmission lines cross country because it's resistance
> >>
> > is
> >
> >> reasonable low at the 60 Hz frequency, but at RF frequencies that Tesla
> >> coils operate at, it's a very poor choice. In the primary it will cause
> >> excessive resistance at operating frequency frequencies which reduces the
> >> overall peak currents. Remember high peak currents in the primary (which
> >>
> > is
> >
> >> why we used pulse caps -- to get a high peak current) produce powerful
> >> magnetic fields which encompass the secondary coil. When this magnetic
> >> field collapses rapidly, a high voltage pulse is produced in the sec coil.
> >> With a weaker pri current, the sec coil will not receive as much energy
> >>
> > thus
> >
> >> producing a weaker spark --- certainly not as bright as copper.
> >>
> >> Happy sparkin' with copper,
> >>
> >> Dr. Resonance
> >>
> >> On Fri, Jul 18, 2008 at 12:11 PM, John Matok <jmatoknoon@xxxxxxxxx> wrote:
> >>
> >>
> >>> What affect would aluminum have on my performance? If it's cheaper, why
> >>> wouldn't everyone use it?
> >>>
> >>> Nicholas
> >>>
> >>> On 7/17/08, bartb <bartb@xxxxxxxxxxxxxxxx> wrote:
> >>>
> >>>> Hi Nicholas,
> >>>>
> >>>> Yes, all metals are up in price everywhere. It makes choices more
> >>>> difficult. Copper is up about 50 cents/lb as well as aluminum. The
> >>>> difference is $4/lb with copper versus say $1.50/lb with aluminum
> >>>>
> > (just
> >
> >>>> looking at scrap rates). Anyway, you could build the primary with
> >>>>
> >>> aluminum
> >>>
> >>>> tubing. It's sold in the hardware stores also and is certainly an
> >>>> alternative.
> >>>>
> >>>> Take care,
> >>>> Bart
> >>>>
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