> 1 Is there a specific flux that is required or just works
> better for this procedure? If so, a maker and part
> number would be appreciated.
> 2 Is there a specific type of brazing rod that is required
> or just works better for this. I asked my welding jobber
I think you will find that plain old brazing using brass rod which is
already flux coated will work as good as any other method with the exception
of cad welding (TM)
I say this for several reasons. First you need something easy to apply and
that will stand up to the weather and ground conditions.
When brazing two materials with quite different melting points, "heat
conduction" and mass become important.You have to take into account how much
of each material has to be heated and how fast that heat is carried away as
well as the heat required to melt the brazing rod.
Welding copper to steel is melting two materials with quite different
melting points together which means you not only have all the points taken
into account when brazing, but they are much more critical.
Silver soldering is really a form of brazing rather than solder unless the
melting point is very low. Typically the melting point of silver solder is
a bit lower than brazing rod.
However in both brazing and silver soldering both materials must be clean.
It's very easy to melt of burn the copper even when silver soldering. It
really helps to first wet the end of the steel rod with the brazing rod or
silver solder, but then you have to be careful not to burn that.
I see no real advantage to silver soldering over brazing plus it's a lot
If possible I'd use a One Shot Cad Weld (TM) which is by far the easiest
although considerably more expensive than brazing.
> for "silver bearing" brazing rod and got a blank stare in
> response. If so, a maker and part number would be
> 3 I'll be using stranded #2. Any special precautions, advice
That is what I used. 33 eight foot ground rods cad welded to over 600 feet
of bare #2 stranded.
> or "tricks of the trade" would be welcomed.
Keep it clean and bright. Do not let it get dirty, or wet. The more like
shiny new the easier it will be to work with and the better it'll take
either the silver solder or brazing rod.
If it does get dirty, wash it thouroughly. A pressure washer to clean the
specific area, then acid etch that area and wash again. Don't use too
strong an acid or the surface will become rough. You might even have to
take some of the twist out of the cable to get at the internal strands.
Use lots of flux when brazing. Use as large a tip as possible (one where you
can control the heat) to heat a large area controlably with a relatively
soft flame. I prefer a flame slightly on the carbonizing side. IE, adjust
to neutral and either back off on the Oxygen or increase the Acetylene
*slightly* to lengthen the feather to the point where it is pronounced but
not overly long. I know that's a generalization, but it's about as close as
I can come to describing it.
If the copper and steel are not clean and bright the brazing rod/silver
solder will not stick properly and the copper will most likely end up burnt
while trying to get the brazing rod or silver solder to flow.
Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2
> Thanks to all.
> Tim Colbert K3HX
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