Re: Further to power over steel wire.

In article <vu6g14tsjkstsutbt89acmp7epv3vbo6vv@xxxxxxx>,
Bruce L. Bergman <blnospambergman@xxxxxxxxxxxxxxxxx> wrote:

On Wed, 30 Apr 2008 11:25:46 +1200, grumpyoldhori
<grumpyoldhori@xxxxxxxxx> wrote:
Don Foreman wrote:

37 ohms per km of 4 mm iron/steel wire strongly suggests  a splice
that may be mechanically strong but has poor conductivity due to
corrosion.

Yes, good point, I will put 4 mm copper wire jumpers
across all splices.
What figure should I be looking for on a km of 4 mm
steel wire in ohms ?

No, you should get a portable torch rig with some horsepower (Oxy-
Acetylene or Air-Acetylene or MAPP) and go silver-braze or silver
solder all the splice points - or even 60/40 lead/tin solder if you
don't worry about RoHS, but no acid flux unless you clean it up.

I would soft solder it, using whatever is used on copper pipes, to avoid
overheating and de-galvanizing the wires, promoting faster rusting.
Tinners flux (zinc chloride in HCl) will be needed. Plumbers grease
flux will not work on steel wire. Wash the joint off when done.

The splice joints are probably already too corroded and dirty to solder,
but there is no reason one cannot add jumpers around the existing
splices. Starting with open wire allows one to polish down to bright
metal before making the mechanical connection that will be soldered.
The splice should be the same kind of wire as the wire, to avoid setting
up a galvanic couple at each splice.


Get the resistance down enough, and 24V (AC or DC) at the bottom of
the hill will be enough to get 12VDC at the top (after regulating,
filtering and surge/lightning arresting).

I still say AC is better for longer distance work at low voltage,
but as always Your Mileage May Vary.

Another reason to prefer AC is to reduce corrosion. With DC, one strand
will soon be eaten away at the fence posts by galvanic corrosion due to
the inevitable leakage currents. With AC, the leakage is still there,
but there is no net transport of material.


Joe Gwinn
.

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