[TowerTalk] Silver Solder

[Paul Christensen]

> "For lightning grounds with a few connections, a proper mechanical
clamp or an exothermic weld, both of which are readily available to
hams, are as good or better than brazed connections using materials and
equipment that are not as readily available."

Brazing with silver-solder rods (or Cadwelding) allows for the burial of the 
finished work without concern for things like inspecting, tightening, and 
cleaning mechanical clamps over time.  Five, ten, or twenty years after an 
installation, I don’t want to worry about the integrity of a mechanical 
clamp.  For underground connections, inspection wells are useless if the 
connection is buried down several feet.  The silver-solder braze is every 
bit as solid and maintenance-free as an exothermic weld.

Cadwelds are great when the application calls for it but they're of no value 
when trying to join say... #2 copper wire to a 4-inch ground strap.  Or, 
when joining two pieces of #2 when they not part of a ground rod weld. 
Sure, you can start paying even more money for an Erico wire joiner, but you 
have a better connection by using a pair of split-bolt connectors to 
mechanically stabilize the brazing joint, then apply silver-solder between 
the split bolts.  The result is faster, equally strong with excellent 
conduction, and is less expensive.  So, it's often easier to silver-solder 
in some cases and get the same result as a Cadweld.  Where Cadwelds really 
work well is a situation where you need to join multiple copper wires onto a 
ground rod.  Several versions exist to join from 1 to 4 wires onto a rod 
head.

Earlier this year, I stated here on the list that acetylene-air (without O2) 
brought the right working temperature for silver-solder -- and it does 
unless the connection is substantially "heat-sinked."  The other issue is 
that acetylene without O2 results in an extreme amount of carbon soot.  I 
cannot imagine how I relied on this almost 30 years ago, but I must have 
forgotten about the carbon.  MAPP gas temperature is close to acetylene-air.

After using oxy-acetylene (O2A) at the suggestion of a few list members, I 
would never again use either of the other gas types alone.  Once the 
acetylene valve is brought up to pressure and gas ignited, the O2 valve is 
then slowly turned to mix with acetylene to obtain a perfect blue cone; all 
other color and gas emission disappears.  It's an interesting experience to 
see for the first time.  With O2A, you can braze the silver bars with zero 
difficulty, even in a high heat-sink application.

I purchased a small Lincoln Electric portable torch set for about $200 at 
HD.  The tanks are empty when purchased and are noticeably small compared to 
what the pros use.  However, we finished a complex job with just one tank 
charge to make over 50 connections and still had about 50% gas remaining.

Paul, W9AC