Electrode holder material for a high-power RSG

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Mark Broker by way of Terry Fritz <twftesla-at-uswest-dot-net>" <broker-at-uwplatt.edu>

Hello, all

I am making an RSG that I hope to one day (years away) use with a big TC
(25kVA) at 3600RPM (thinking 5kRPM *MAX*), though I'll be starting with a
1200RPM motor (min speed).  Since I have the resources literally at my
fingertips until this May, I thought I'd build this puppy now.

An AutoCAD drawing of the whole rotor can be seen at:
<http://mbroker.tripod-dot-com/TeslaCoil/SRSG.jpg>http://mbroker.tripod-dot-com/Tes
laCoil/SRSG.jpg

That's a 12" Dx1/2"thick G-10 rotor with 12 electrodes on a 10"D circle.  the
idea is that the electrode assemblies will be precisely the same lenght (from
electrode tip to electrode tip) and as symmetric as possible.  They can be
removed from the rotor by removing the single set screw, and replaced just as
easily.

A picture of my prototype electrode assembly can be seen at:
<http://mbroker.tripod-dot-com/TeslaCoil/Electrode_holder_Prototype.jpg>http://
mbroker.tripod-dot-com/TeslaCoil/Electrode_holder_Prototype.jpg

(turns out the elctrode is 8mm, not 5/16", so they won't fit into the brass w/o
using a hammer, which I don't want to do just yet.)

The holder is 1"Dx 2.10"long brass (don't know what kind - but it wasn't an
"easy machining" type - lots of tool chatter).  The  "spacer" between the two
"fins" is .50"D.  FTR, I'm going to remove the 45deg taper on the first "fin"
of the holder.  I also have to tighten up the lathe a bit - too much play which
led to much imprecision.

So, anyways, I was concerned about the .5"D brass being a weak point in the
system (copper is about 5 times more conductive than brass).  I fear that if
I'm operating a high power TC with a high bang size that the resistivity of the
brass will cause undue heating and I^2R losses.  I did some searching
throughsome catalogs, and found at McMaster Carr a copper alloy that appears to
be the ticket item:  Copper Alloy 182.  It's virtually lead free, and contains
.6-1.2%by wgt chromium, which adds a lot of strength and high temperature
stability.  The down side is that it's a LOT of money.  Alloy 172 also seems to
be a good bet as it's supposed to be spark-resistant, and even harder than
182.  I uploaded the PDF file explaining the alloys here:
<http://mbroker.tripod-dot-com/TeslaCoil/3238.pdf>http://mbroker.tripod-dot-com/Tes
laCoil/3238.pdf

What are you thoughts on my design?  What are your thoughts on using this
material for this purpose?

Thanks, guys!

Mark B