JAMES_S_WALLACE@HP-Canada-om1.om.hp.com wrote:
>
> Well, I can't really comment on the overdrive, except, I'd really like
> one in my car!
> As far as the copper/aluminum mix: If a connection gets a little
> loose, a galvanic reaction occurs, generating heat.
> This is why, if you have aluminum wiring in your house, it is
> recommended that you periodically go around and tighten the screws on
> your receptacles and switches. Around here, it used to be a big deal
> when buying a house if it had aluminum wiring. You could just about
> argue the price down by the cost of re-wiring the place in copper.
> Haven't heard much of this lately though. Maybe there aren't any of
> those houses left..
> Now my galvanic reaction theory's a little rusty, so to speak, so
> perhaps someone can elaborate (Trevor?)..
> Regards,
> Jim Wallace
> '60 TR3 TS81417
>
> ______________________________ Reply Separator
>_________________________________
> Subject: Re: wiring and OD tranny for TR6
> Author: Non-HP-van (van@nucmar.physics.fsu.edu) at HP-USA,mimegw5
> Date: 7/28/97 3:58 PM
>
> > "re-engineered" with lamp cord. The centre of the fire seemed to be
> > coming from a Marrette, and when I took it apart - guess what - one of
> > the lamp cords was copper, and the other was aluminum!
> >
> > My personal conclusion: don't do this.
> >
> > Jim Wallace
> > miraculously still alive in Canada.>
>
> Two questions:
> 1) Why the objection to the mixed conductors?
>
> 2) What is the story on TR6 overdrives. They seem to be precious
> objects. What was the ratio (ball park) of OD's to non OD
> TR6's. I have a '76 that has the overdrive eblem on the back but
> someone has nicked the original unit and replaced it with a non-OD..
> No sig file, Van
Hey, I have aluminum wiring in my house. I've lived in it for 13 years
without any spontaneous electrical fires. You just have to convert your
high current outlets and switches to aluminum compatible components.
The problem stems from alumumin's (aluminium for the Brits)
characteristic to form to the joint (soft metal). I would suspect as the
joint gets sightly warm, it expands by a small amount and eventually
becomes loose. The joint now oxidizes and creates an "ohmic" contact. In
other words, it has resistance. When current passes through the
connection, it gets warm due to the resistance. Remember Ohm's Law?
Dependent on the amount of resistance and cuurent the joint can get to
the point of melting insulation, smoke, and fire. I've heard of a joint
compound that you can put on aluminum wiring connections for A.C wiring
but have never had the need to use it in my house (or car for that
matter).
I believe the problem in the Marrette was due to the same type of
situation. A sightly loose joint and a little oxidation or corrosion
will result in the heat build-up when current is flowing.
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