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Re: Electrical Properties of Brass
Original poster: "Jeremy Scott by way of Terry Fritz <teslalist-at-qwest-dot-net>" <supertux1-at-yahoo-dot-com>
The brass i was thinking about using
was alloy 260, the kind mcmaster-carr
sells. I looked this stuff up and it's
approximately 70% copper and %30 zinc.
The zinc increases it's rigidity and
helps the copper resist corrosion, but
unfortunately it increases resistance.
I would say that if anyone wants to
make things out of brass, design for
copper and then increase it by 30%
size if you plan on using brass.
P.S. Where do you get that 2" braided
copper strap? My design calls for some.
--- Tesla list <tesla-at-pupman-dot-com> wrote:
> Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>
>
> Hi Jeremy,
>
> At 10:27 AM 4/21/2003 -0700, you wrote:
>
> >Thanks Terry,
> >
> >I think I am going to use copper strips instead.
> >I'm more worried about loss of power in the tank
> >circuit than I am about the eventual oxidation
> >of the circuit. (You can always sand copper, but
> >you can't easilly modify the electrical properites
> >of brass... :) )
>
> I guess you noticed that were really are unsure
> about things like this
> ;-)) Copper is the "safe" choice we all know will
> work... Unless you live
> in a really humid place, oxidation should be a very
> minor problem. If a
> contact wipes the surface, it should stay very
> clean. I would look at
> copper plumbing pipe inside houses in your area to
> judge how bad corrosion
> will be. There are tuner cleaners and such that
> have oil in them that will
> really help resist corrosion too. Automotive
> switches have grease on the
> switch contacts but I am not sure what that actually
> is.
>
>
> >I'm glad Finn replied to this thread, I am
> >designing a primary similar to his that allows
> >the tap to be adjusted as the coil is running.
> >I was worried that after time, the copper would
> >oxidize and make the sliding tap less effective.
> >I could probably attach a small bit of sandpaper
> >to the side of the tap so it clears oxidation
> >as it moves :)
> >
> >I've already designed the thing in AutoCad and
> >pspice, so others can build it as well.
>
> Cool!!
>
>
> >I'm just now beginning to fabricate the parts. The
> >rotating primary tap support has been partially
> >manufactured. The whole thing is made of red oak,
> >which will look really nice when finished with a
> few
> >layers of PU varnish.
> >(Primary supports are HDPE)
>
> It sounds really cool!!
>
>
> >Another thing, I was browsing through the archives
> >on hot-streamer and I came across your "ground box"
> >which basically provides ground points for the
> >secondary coil and saftey grounds for lower voltage
> >parts. The box is then connected to a pipe ground
> >via RG-8U cable, at which point the sheild and
> center
> >conductor are connected to each other.
> >I was wondering, what is the maximum length of the
> >cable, what sorts of things are acceptable to
> connect
> >to the saftey ground, and finally what level of
> power
> >is this thing effective to?
>
> I used it about 1000 watts. It is about 20 feet
> long. I used to know the
> inductances and all that...
>
> >I haven't yet designed a ground connection into my
> >system, other than 1" dia copper pipe that extends
> >down from the bottom of the coil to the ground. (If
> I
> >had a
> >6' ground rod in the middle of the lawn I could
> >theoretically plop the whole mess on top of it :)
>
> I would do the ground rod. Like the copper vs. Al
> thing, We "know" the
> ground rod will work were fancy cables do have some
> questions. Nowdays, I
> have 2 inch copper braid going to two ground rods
> six feet away ;-)
>
> Cheers,
>
> Terry
>
>
>
>
> >--- Tesla list <tesla-at-pupman-dot-com> wrote:
> > > Original poster: "Terry Fritz"
> <teslalist-at-qwest-dot-net>
> > >
> > > Hi Jeremy,
> > >
> > > Resistance = Resistivity X Length / Area
> > >
> > > The numbers I have here are all in meters.
> > >
> > > Copper = 1.7 x 10E-8 Ohm-Meters
> > > Brass = 6.39E-8 Ohm-Meter
> > >
> > >
>
>http://www.matweb-dot-com/search/SpecificMaterial.asp?bassnum=MBRASE
> > >
> > > So brass is about 4X more resistive than copper
> at
> > > DC.
> > >
> > > Skin Depth = 1 / SQRT(pi x f x Resistivity x
> > > Permeability)
> > >
> > > Permeability = pi x 4e-7 H/m X Ur
> > >
> > > Ur copper = 1
> > > Ur brass = 1.05
> > >
> > >
>
>http://www.npl.co.uk/electromagnetic/dclf/magnetics/lowpermeabilitylc.html
> > >
> > > So the skin depth is about 1/2 that of copper
> since
> > > the resistivity is 4X.
> > >
> > > The skin depth of copper is 2.602 / SQRT(F)
> inches.
> > > At 154kHz that is
> > > 0.00663 inches. So brass is roughly 0.0033
> inches.
> > > Your 16mil brass is
> > > perfect. At 2 inches wide, it is about the
> > > equivalent of 0.159 inch copper
> > > tubing.
> > >
> > > So I will say your brass strips will be about
> 50%
> > > more lossy than 1/4 inch
> > > copper tubing. Lots of "if, ands, ors, and
> buts"
> > > too all this... but the
> > > brass will work "ok" for a 15/120 NST system.
> You
> > > may loose about 2 to 4
> > > inches as compared to 1/2 inch copper tubing or
> > > something but probably not
> > > a big deal.
> > >
> > > Cheers,
> > >
> > > Terry
> > >
> > >
> > >
> > > At 04:28 PM 4/18/2003 -0700, you wrote:
> > > >Hi!
> > > >
> > > >I was wondering if anyone has any experience
> with
> > > >building primaries out of brass instead of
> copper?
> > > >I want to use brass since I'm worried about
> copper
> > > >oxidizing over time.
> > > >
> > > >I have a design in mind that is going to use
> > > >brass strips for all connections in the tank
> > > >circuit. (Including the primary)
> > > >
> > > >The brass strips I have in mind are
> approximately
> > > >.016" thick by 2" wide.
> > > >
> > > > >From calculations I have done with JavaTC,
> > > >the tank current at gap conduction is going
> > > >to be approximately 800 Amps.
> > > >
> > > >(15KV/120mA NST .03 uf LTR primary cap)
> > > >(154kHz resonant frequency)
> > > >
> > > >I am concerned that the brass strips I've got
> > > >are too thin to handle this current load.
> > > >Unfortunately, anything thicker is tough to
> work
> > > >with and bend into the proper shapes I require.
> > > >(Doubling up the thin strips is an option but
> > > >I don't want to do it if i don't have to.)
> > > >
> > > >On the otherhand, since the tank current will
> be
> > > >oscillating at RF frequencies, skin-effect
> tells
=== message truncated ===
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