On 8/7/2015 2:25 PM, David Gilbert wrote:
For grounding, safety or lightening, I avoid mechanical connections like
the plague. Much depends on the soil PH, but here, I've never had a
mechanical clamp last a year, including the ones installed by the
electricians to "meet code" on the panel ground.
With their history, at close to a year, I dug up the 3 ground
connections for the 200A panel. I was able to slide all 3 clamps up and
down the ground rods. They were actually loose. These were clamps that
were accepted by the electrical inspector who told me they were plenty
good enough as they wouldn't fail. We are right on the edge of an area
that has a high concentration of peat.
From Wikipedia : *Brazing* is a metal
<https://en.wikipedia.org/wiki/Metal>-joining process in which two or
more metal items are joined together by melting and flowing a filler
metal <https://en.wikipedia.org/wiki/Filler_metal> into the joint, the
filler metal having a lower melting point than the adjoining metal.
Brazing differs from welding <https://en.wikipedia.org/wiki/Welding> in
that it does not involve melting the work pieces and from soldering
<https://en.wikipedia.org/wiki/Soldering> in using higher temperatures
for a similar process, while also requiring much more closely fitted
parts than when soldering. The filler metal flows into the gap between
close-fitting parts by capillary action
<https://en.wikipedia.org/wiki/Capillary_action>. The filler metal is
brought slightly above its melting (liquidus
<https://en.wikipedia.org/wiki/Liquidus>) temperature while protected by
a suitable atmosphere, usually a flux
<https://en.wikipedia.org/wiki/Flux_%28metallurgy%29>. It then flows
over the base metal (known as wetting) and is then cooled to join the
work pieces together.^[1]
<https://en.wikipedia.org/wiki/Brazing#cite_note-Groover-1> It is
similar to soldering <https://en.wikipedia.org/wiki/Soldering>, except
the temperatures used to melt the filler metal are higher for brazing. A
major advantage of brazing is the ability to join the same or different
metals with considerable strength."
A large area silver solder/brazed joint (done properly) should require
no additional mechanical force for strength. A one inch Copper strap
silver brazed to copper sheet of the same thickness should be strong
enough that the copper would tear before the solder/brazing would give
way. Where the copper is heated just shy of glowing, it will become
"dead soft", making the copper the weak mechanical link.
I always use exothermic welds under grade if possible..
Having worked with a lot of grounding in industry, "a long time ago" (I
quit in 87) I think you will find that most Silver Solder, whether it's
solder or brazing, (many boxes list it as Silver Solder) is lower
resistance than the copper.. Be that as it may, Silver soldering, or
brazing is working near the melting point of copper. It takes a
relatively large, but soft flame to heat a relatively large area to the
melting point of the rod/stick. Still the silver solder, like all
solder will tend to flow toward the location where the heat is applied.
This applies what ever the solder and heat source, be it flame, iron, or
gun so keep that in mind when doing any soldering or brazing.
I do not use lead free solder except under grade and there I use the
exothermic bonds if the connection will support it. It has been my
experience, that RHOS solder (lead free) has been the primary source of
problems in commercial equipment as in headphone connections on TV sets.
That's the only problem we've had with today's TV sets. As they were
under warranty, the fix was free and the repairman's experiences with
RHOS solder paralled mine, although he had many more experiences than I
with RHOS solder. He used good old 60/40 solder.
73
Roger (K8RI)
I'm not sure I'd rely on any "solder" for strength of the connection
for radials. The solder would be there only to preserve the
electrical connection and I'd rely on some sort of mechanical
connection for the strength. For that purpose, the primary
consideration would be that the solder be lead free (it leaches out in
moist environments) and almost any silver solder (like that used to
meet plumbing codes and commonly available at Lowes, HD, etc) ) should
work. The key is that it not have lead ... not how much silver it has.
For lightning protection (or any high current application), solder
seems to me to be a very poor choice. Solder, including silver
solder, almost invariably will be the highest resistance element (and
the weakest thermally) in the system and will act like an explosive
fuse if it takes a hit. As Jim says, clamps or welds are the way to
go for this.
73,
Dave AB7E
On 8/7/2015 9:51 AM, Jim Lux wrote:
On 8/7/15 9:24 AM, mike stokes wrote:
Hello
I need to improve my radials and lightning protection. What Silver
Solder
is best for the job and where is a good place to purchase it ?
I'm not sure silver solder (called silver brazing these days) would
be appropriate for lightning protection. It's certainly not what the
code requires for grounding (approved clamps or exothermic welds),
although I think it's a reasonably workable solution.
For RF purposes (e.g. your ground radials), though, silver brazing
isn't a bad idea. It's rugged, it's easy (assuming you have the right
equipment).
I doubt that the specific alloy makes a lot of difference. What
you're really looking for is that the melting point is higher than
that of tin/lead, and that it's mechanically more rugged. I've used a
variety of "hard solders" from the local hardware store. Typically,
they are around half silver (price varies with silver content).
Pretty much anything will work with copper/brass (if you're brazing
steel, you need to be a bit more careful in material selection). A
typical alloy is something like Silvaloy 355 which is about half
silver, 1/5th copper, and the rest zinc and tin. No cadmium. At
least that's what I found out in the garage that still has a label on
it.. I'm not a pro welder, with ovens to keep my rods dry, records of
material certs, etc.. Others on this list ARE much more knowledgeable
and may have some recommendations on the best alloys.
As with all "melt metal to stick metal together" things, the right
flux and the right heat source is probably more important than the
actual metal you're melting.
I use the solid white paste flux, and I've used both a oxy-mapp rig
(one of the ones with the two "propane torch" sized bottles) and a
oxy-acetylene rig (with a fine tip on the torch). Either works. The
bigger rig (with big bottles, either oxy mapp or oxy acetylene) is
nicer because you don't worry about running out of gas. If you could
borrow or rent the rig, life is easy.
Silver solder alloys melt around 1000F (compare tin-lead at <400F),
but lower than bronze brazing rod (typically >1500F). Note that
1000F is "red heat"
I'd say that in a few hours, if you've got experience soldering
(especially if you've done plumbing) you can crank out perfectly
serviceable electrically and mechanically brazed joints. They may
not be pretty, they may not be something you'd trust your life to for
mechanical reasons, but they'll work fine.
I find brazing, in general, MUCH easier than doing good plumbing
fittings with soft solder and a propane torch, and MUCH easier than
real fusion welding.
With real welding, you have to worry a lot about the metal you're
welding, and getting the temperature right, and getting just the
right penetration (whether gas or arc), and it's a lot hotter. With
soft solder and plumbing, there's a real art to getting the right
flux, and the right temperature on the whole joint (not too cold, not
too hot) so that you get a nice even solder layer with no pinholes
and no globs. And with plumbing there's always the whole "wet pipe"
and "don't light the wall on fire" thing.
A small oxy-gas torch has a nice small hot flame that's easily
adjustable and not too bright, and there's a big temperature range
over which a good joint can be made (iron and steel melt at >2500F,
copper melts at 2000F, the brazing filler melts 1000F less, so lots
of room between), and the overall lower temperature means you don't
need as much eye protection, so you can *see* what's going on.
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73
Roger (K8RI)
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