[TowerTalk] Aluminum radials

[K8RI on Tower talk]

> Aluminum has several characteristics that make it a bad choice for any 
> current carrying conductor.
>  First is the fact that when placed in soil under even the smallest 
> current it wants to return to the state it was >as a ore. Hence you get a 
> nice white powder/scale like the bauxite it was refined from.
>  Second you always have a problem with migration out from under any 
> setscrew connection.(That's why its >not a common housewireing practice 
> after the fiasco in the early 70's and all the fires traces to connections 
>  >that loosen up after a year) Thermal cycling with the large coefficient 
> of expansion and its natural softness of >wiring

I think you will find that it has again become common practice to use 
Aluminum at least from the meter to the breaker panel.  I couldn't even find 
00 Sopper and had to settle for 0000 Aluminum. The feed for the house 
reminded me of the old #6 feed for mobile homes except it was 0000.  2 
conductor plus ground with an overall wrap with insulation.  The outside of 
the stranded conductors appear to be swedged smooth so they appear as if 
they are a solid conductor until you take a closer look.

The feeds in the shop from the meter to the panel are individual 0000 
Aluminum that also have the smooth outter appearance.  The go into the meter 
and panel with lots of antigalvanic compound and those connectors (allen set 
screws) are torqued down really tight.  After they were as tight as we could 
get them by hand we used an Engineers 5# hammer on the over size allen 
wrench to finish tightening them.  IMO 0000 Aluminum is terrible to work 
with compared to 00 Copper. We had to use pipe benders to prebend most of 
the cables as far as we could and still get them through to the connectors 
at the other end.


>grade Al explains all. When used in electrical services they either use a 
>special crimped lug of if setscrew it >must be re-tightened on a yearly 
>biases. The lack of yearly checks on Al wire is the most common service 
> >failure.

They have to be checked on a yearly basis, but after five years we've not 
found one yet where the wrench would even move.  OTOH I sure wouldn't want 
to use the stuff for the wiring after the breaker box. In addition to the 
other problems the wire has to be twice the physical size of copper and I 
doubt you'd find many outlets that would even take that size wire.  I don't 
belive "wire nuts" for splicing, or junction boxes would be acceptable 
either.

>  Third is that Al will form aluminum oxide in minutes on freshly bared Al. 
> This is the black stuff you get on your hands putting your antennas 
> together. It is a very poor conductor and is more of a problem with 
> plumbers delight type of construction as compared with antennae that use 
> insulated from the boom elements.
>
>  Aluminum is a wonderful metal, they just haven't yet figured out how to 
> make it hard and corrosion resistant

There are indeed some very hard alloys of Aluminum, but unfortunately you 
either settle for hard OR good corosion resistance. Like a high performance 
airplane that can come down or slow down you can't do/have both.  Aircraft 
use alloys that are quite hard, but they are alodyned before paining. 
Alodyne works very well, but it is thin and fragile.  It's not all that 
difficult to do, but it does take time and can be messy.  As the first step 
is a Phosphoric Acid etch I'd not want to do it on stranded Al.  The process 
it basically treat and wash, treat and wash, treat and was and this is after 
the etch. When you finish the Al should be a nice Gold color that looks 
almost transparent.

> and still high conductivity. The smelter that produced the purest Al for 
> wire was shut down due to a buyout >by competitor wire manufacturer from 
> overseas. Go figure?

Unfortunately, although pure Al is the most corosion resistant it is soft 
and has, I believe, the highest coefficient of expansion making it poor for 
connections.

Both Anodizing and Alodyining do a good job of corosion proofing, but both 
are fragile.



Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2
www.rogerhalstead.com
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>  WB7PEK
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