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.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

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

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

Dave Platt wrote:
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.

Those are specifically mating up old iron piping with new copper.
For the prevention of galvanic action.

Jeff

--
"They that can give up essential liberty to obtain a little temporary
safety deserve neither liberty nor safety." Benjamin Franklin
"A life lived in fear is a life half lived."
Tara Morice as Fran, from the movie "Strictly Ballroom"

Dave Platt wrote:
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.

Those are specifically mating up old iron piping with new copper.
For the prevention of galvanic action.

Jeff

--
"They that can give up essential liberty to obtain a little temporary
safety deserve neither liberty nor safety." Benjamin Franklin
"A life lived in fear is a life half lived."
Tara Morice as Fran, from the movie "Strictly Ballroom"

jakdedert wrote:

You can tin the edge of the PCB and avoid this for the most part.

-Bill


Probably, but the object was to eliminate heating the copper board. Other
coatings would work, as well. Zinc chromate primer is what they use in
aircraft construction.

jak

I jumped in at the "make them removable" part. Doing a bit of tinning
wouldn't really qualify as heating the board enough for the copper to
peel up.
Actually I think that would be preferable to "paint on" coatings that
might flake/chip around the screw holes in this case.
But we have now made a simple everyday PCB board box into a home project
that meets FAA specs.
:-)
-Bill

jakdedert wrote:

You can tin the edge of the PCB and avoid this for the most part.

-Bill


Probably, but the object was to eliminate heating the copper board. Other
coatings would work, as well. Zinc chromate primer is what they use in
aircraft construction.

jak

I jumped in at the "make them removable" part. Doing a bit of tinning
wouldn't really qualify as heating the board enough for the copper to
peel up.
Actually I think that would be preferable to "paint on" coatings that
might flake/chip around the screw holes in this case.
But we have now made a simple everyday PCB board box into a home project
that meets FAA specs.
:-)
-Bill

"--exray--" wrote in message
...
jakdedert wrote:

You can tin the edge of the PCB and avoid this for the most part.

-Bill


Probably, but the object was to eliminate heating the copper board.
Other
coatings would work, as well. Zinc chromate primer is what they use in
aircraft construction.

jak

I jumped in at the "make them removable" part. Doing a bit of tinning
wouldn't really qualify as heating the board enough for the copper to
peel up.
Actually I think that would be preferable to "paint on" coatings that
might flake/chip around the screw holes in this case.
But we have now made a simple everyday PCB board box into a home project
that meets FAA specs.
:-)
-Bill

LOL...but, naah...the original idea would work with just a quick squirt of
z.c. primer (from a can) on the inside of the aluminum angle stock, I
guess...not that much trouble, in order to avoid further troubles down the
line. If the assembly never got wet--or stored/used in a humid
environment--those problems would likely never show up. OTOH, probably best
to avoid problems in the first place.

jak

"--exray--" wrote in message
...
jakdedert wrote:

You can tin the edge of the PCB and avoid this for the most part.

-Bill


Probably, but the object was to eliminate heating the copper board.
Other
coatings would work, as well. Zinc chromate primer is what they use in
aircraft construction.

jak

I jumped in at the "make them removable" part. Doing a bit of tinning
wouldn't really qualify as heating the board enough for the copper to
peel up.
Actually I think that would be preferable to "paint on" coatings that
might flake/chip around the screw holes in this case.
But we have now made a simple everyday PCB board box into a home project
that meets FAA specs.
:-)
-Bill

LOL...but, naah...the original idea would work with just a quick squirt of
z.c. primer (from a can) on the inside of the aluminum angle stock, I
guess...not that much trouble, in order to avoid further troubles down the
line. If the assembly never got wet--or stored/used in a humid
environment--those problems would likely never show up. OTOH, probably best
to avoid problems in the first place.

jak