On Thu, 30 Oct 2003 22:13:47 -0000, (Dave Platt)
wrote:

In article ,
jakdedert wrote:

I've also seen several places in my old houses where iron piping
was screwed directly into brass fittings. [ snip ] When finally
I got down to it, there was practically nothing of the threaded
end left, although the rest of the pipe was in good condition.

This is more the fault of the iron pipe. Not the bronze/brass
fittings. When you thread the end of a pipe, you remove the
galvanized coating. Exposed metal pipe = weak spot.

That might be the case if every iron pipe also exhibited this effect. The
only place I've found it was when an iron pipe was mated with a brass
fitting.

The hardware stores around here sell special unions, with insulated
threaded fittings, for mating iron/steel pipes to brass. I've
pondered whether these might be useful for making certain forms of
(non-DC-connected) copper-tubing J-pole antennas.

We used similar fittings when building water-cooled RF coils, used in
plasma deposition vacuum systems. Since the skin effect means that
most of the RF is transmitted on or near the outer surface anyway,
there was little loss compared to a solid copper rod. We could have a
complete plumbing circuit with an electrical discontinuity.

Happy trails,
Gary (net.yogi.bear)
------------------------------------------------
at the 51st percentile of ursine intelligence

Gary D. Schwartz, Needham, MA, USA
Please reply to: garyDOTschwartzATpoboxDOTcom