Alt-BEAM Archive

Message #13813



To: beam@sgiblab.sgi.com
From: Jeffrey D Spears jspears@engin.umich.edu
Date: Fri, 21 Apr 2000 21:32:56 -0400 (EDT)
Subject: On the importance of good solder connections



Greetings BEAMers;

Sometimes we look at equations and so on, but really can't see
what is going on. Im an EE student so this happens to me--Big Time!
Here is an experience that hammered home a simple electrical
concept for me.

I worked on a couple of ships during a ten year stint in the Coast
Guard. One day I was walking down the corridor, and all these
electricians were standing around an electrical junction panel. It
was basically a box inside the wall where wires came in from one
side and connected directly to wire on the other side. No big deal
except these were high current lines. One of the fellehs had some
contraption that looked like a camera. So I asked one of the other
joe's who was standing around what he was doing. Apparently, the
camera looking thing was actually an infrared camera, similiar to
what fire-fighters use to see where the fire is through all the
smoke. What they were doing was looking at the connections under
full load--for heat. They could see the bad connections from the
heat they generated. So, this team of folks were looking at all
the junction panels and tightening down the terminals if they
were hot.

Over a years operating time, the generator fuel savings gained
by these fellehs was probably substantial. Couple thousand
bucks maybe?

BEAM experimenters who are new at soldering should bear this in
mind. Solder is a very poor conductor of electricity. If we
solder two elements together with just a gob of solder holding
them, then we are effectivly adding a resistor (small space
heater) between these elements. Resistors cause voltage drops
which cannot be reclaimed. Make GOOD SOLID ELECTRICAL CONTACT,
and then solder to maintain that good contact. Whereas ships have
generators that can generate unlimited sources of charge--plenty
to waste--the beam designer has a very limited source of charge.
I imagine good careful electrical contact at solder joints could
provide significant performance differences to typical SE's.

Here is a simple test. If before soldering you can wiggle the
connection and then everything looks okay in terms of good
contact afterword, then go ahead and solder it. If you are
making a connection and think to yourself--man, thats pretty
flimsy--better get solder on their before it falls apart! Well
then the time taken providing better connection is probably
worth while.

Frankly, I wish gold was cheap enough to use as solder! Low
melting point, excellent conductivity, no oxidation.

ok..jef

Jeffrey D. Spears
University of Michigan
College of Engineering

``Double-E, can't spell gEEk without it!''
-Captain Gerald M. Bloomfield II, USMC
(my brother)

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