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Re: [TowerTalk] Silver Solder

To: <towertalk@contesting.com>
Subject: Re: [TowerTalk] Silver Solder
From: "Paul Christensen" <w9ac@arrl.net>
Date: Fri, 7 Aug 2015 19:15:30 -0400
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
"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
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