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Re: the mechanical engineering problem
Original poster: Terrell Fritz <terrellfone@xxxxxxxxxxxxxxxxxxxxxxx>
Silver will tarnish fairly quickly and look bad in this
application. It will still do fine electrically since the silver
sulfide tarnish is very conductive. I have not worked out the skin
depth of silver at 9kHz but that layer would probably have to be so
thick that it might flake off the copper as well. Electrical silver
coatings have to be fairly thin or the silver will fall off!! Don't
let them us nickle or other intermediate layers...
Gold would be perfect just as a layer to stop corrosion while still
giving great electrical conductivity and looking nice. The cost of
the plating would probably be too much though.
The best thing to do is to "polish" the coil to a mirror shine with a
buffer and appropriate polish (rouge I think?) and clean it with say
(acetone). Then coat the coil with your favorite coil coating paint
like you used to coat the secondary. Best to use a pneumatic paint
gun and hire a good auto body guy to do it "right".
For the joints, beware that solder is a terrible conductor and might
like to heat up at the joints. I have seen copper high current
inductors melt the solder joints even though the copper was stone
cold, but the frequency was 1000X higher... We went to something
"secret", but at lower frequencies it might not be a problem.
The fire hose connectors sound very nice for the connections!!!
Be aware that if heat is the only real concern, you can "think" about
water cooling the copper and using far smaller tubing. That is
actually pretty easy to do and goodness knows that RF inductors carry
thousands of amps in copper smaller than your finger as a rule
everyday... I know a LOT about that, but if a told you, I would have
to kill you ;-))
At 10:37 PM 1/10/2007, you wrote:
Original poster: Mike <megavolts61@xxxxxxxxx>
I'd be happy to silver plate your primary, as I am well versed
in that. I used to work in a research lab doing all kinds of
electrochemisty, including once even fixing an induction furnace
who's silver plating had tarnished away over the years and quit
working. I put a better plating on the parts than the original
manufacturer did. That's beside the point.
I deleted the earlier emails on this thread but seem to
remember you planned to run this monster at about 20kHz. Let me
point out a lil something I thought about. From the information I
have, The skin depth (based on copper, but probably close) at 10
kHz is 0.66 mm. So for fun, I did a lil caclulation based on an
assumption that the skin depth for silver at 20kHz is about 0.5
mm. I know I should be more precise, but I'm lazy tonight.
First of all your perimeter of the bus bar is (5 + 1/4 + 5 +
1/4) * 2.54 cm/ in. or 26.67 cm. Then, 1 ft length is 12 *
2.54 or 30.48 cm, giving you an area of 812.9 sq. cm. per foot
of bus bar. Now multiply that by 0.5 mm (or 0.05cm), you get
40.645 cu. cm per foot if you wish to have ALL silver
conducting. At a diameter of 26 ft, this leads you to
need pi*26*40.645 cu. cm of silver. Multiply that by the
density of 10.5g/cu. cm and divide by 31.1 grams/troy oz. This
shows you will need over 1100 troy oz of silver just for that first
turn. I think you might gain about 5% better conductance for
your $$. This was just an estimate....but you see where I'm
coming from....might be a lot cheaper to go to six inch bus
bar. It also depends on how thick you want the silver plating to
be. I honestly can't say at this moment if there's really
anything to be gained by plating the bus bars.
Original poster: Yurtle Turtle <yurtle_t@xxxxxxxxx>
You may know this already, but when you go to silver
plate the bus bars, you can do it in your shop for a
fraction of the cost of having it electroplated, by
using Cold Amp. It's a powder and real easy to use.
We've used it in medium voltage (12,470) switchgear.
--- Tesla list <tesla@xxxxxxxxxx> wrote:
> Original poster: "D.C. Cox" <resonance@xxxxxxxxxxxx>
> Thanks to everyone who submitted ideas for the big
> primary coil. I
> have several ideas now and will resolve the issues
> Several members suggested internal primary, but if
> there are any
> flashovers they would not be visible unless fiber
> optics were
> employed to watch for them.
> The idea I think we will employ (actually suggested
> by several
> members) is to use 5 inch wide x 1/4 inch copper
> ribbon buss bar and
> then silver plate it.