That's not how solder joints fail. Solder has a higher resistance than
copper so it drops more voltage due to any current through the
connection. Ironically, the better the copper conductor, the more heat
the joint could possibly see since it will suffer a greater percentage
of the total volt drop (assuming the impulse isn't a constant current
source). The pipe doesn't heat up ... the solder itself does. If the
heat is high enough it vaporizes the solder in a runaway condition (as
some of the solder leaves it forces the rest to sustain the connection)
that ultimately creates a localized plasma for a nice arc.
In industry, soldered connections are a no-no for critical high current
applications (also for connections requiring high thermal
conductivity). Bare metal to bare metal is much preferred. Solder
might give a more consistent connection over time (it sort of protects
the joint from corrosion in some environments), but it doesn't provide a
truly good joint.
73,
Dave AB7E
john@kk9a.com wrote:
> My tower has had a number of direct lightning strikes and I have never seen
> a soldered connection fail. I am assuming that Pete is referring to using
> copper water pipe or refrigeration tubing as a ground conductor for his
> shack and I find it hard to believe that a strike would raise the pipe
> temperature to 400 degrees or so and melt the solder from the fittings.
>
> John KK9A
>
>
>
> Subject: Re: [TowerTalk] inductance of tubing vs bar or strip
> From: "Dick Green WC1M"
> Date: Tue, 18 Aug 2009 13:31:11
>
> I don't know about the inductance, Pete, but my understanding is that
> soldered connections are not a good idea -- a lightning surge can melt the
> joints. I think you would need to use a mechanical clamp or something like
> Cadweld.
>
> 73, Dick WC1M
>
>
> To: TowerTalk <towertalk@contesting.com
> Subject: [TowerTalk] inductance of tubing vs bar or strip
> From: Pete Smith N4ZR
> Date: Tue, 18 Aug 2009 08:16:36
>
> Can anyone suggest where I can find a calculator for the inductance per
> foot of copper tubing compared to the same length of copper bar or
> strip? I'm looking to understand the potential utility of using
> soldered copper tubing for a ground bus, as compared to copper strip/strap.
>
> _______________________________________________
>
>
>
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>
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