RE: (ET) cable terminals

["Chris Tromley" <chris_t microtrac com>]

David Roden wrote:

> ...  In most electrical work, 
> solder normally 
> augments and seals an already-sound mechanical connection (a good old 
> Western Union splice, for example).  The solder strengthens 
> the connection 
> and excludes air and contaminants.  But generally solder alone isn't 
> considered to be strong enough to make a secure connection.

I still have a copy of a Machine Design article from May 1989 about this
topic, because my employer at the time learned this lesson the hard way.
The article is about solder strength as it applies to electronics 
packaging,
but the concepts apply equally well to larger joints.

Basically, solder really stinks as a means to make a mechanical joint.  The
situation is made worse under conditions of temperature cycling, 
*especially
with slow cycles*.  Kind of like what you get when high current draws 
slowly
heat up the post/terminal connection (because there's so much metal there)
and then slowly cools down when the load and current are reduced.

If you have a large copper cable hanging cantilever-fashion off a terminal
as you bounce along over rough ground, you're putting a significant load on
the cable/terminal joint.  You want that joint to be anchored in a way that
does not rely on solder.  The *only* thing solder should be asked to do is
to make an electrical connection.

Chris Tromley
near Philadelphia  PA  USA

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