On 12/29/2013 12:21 PM, Pat Horne wrote:
> In the 60s, while in the Air Force, I attended a soldering school that
> taught us to solder to NASA specs. The problem with soldering wire to
> that level was with the solder wicking up under the insulation,
> basically making the stranded wire a solid wire. We used anti-wicking
> tweezers, which was basically a heat sink that kept the solder near
> the connection, allowing for more flexibility of the wire.
>
> Either a high quality crimper, spot welding, or minimal amounts of
> solder would be my choice, in that order.
>
When I worked at the big bus company, we had large customers that put
crimped soldered connections in their specs, and there was no way to
avoid soldering. Now, on balance, soldering is more likely to provide a
positive electrical and physical connection--initially. What we found,
over time, is that vibration (this problem became more acute once the
industry changed over from six- cylinder 2-stroke diesels to
four-cylinder four-strokes) would eventually affect the joint pretty
much no matter how the joint was soldered (because the problem would
invariably start at the junction between the soldered joint and the
unsoldered wires), and the fix was to add support and vibration damping
to as much of the wire and joint as possible. We ended up using
adhesive-coated shrink tubing to about two inches behind the terminal
and extended over as much of the terminal as possible without
interfering with the electrical connection, with double layers of tubing
over heavier wires. This didn't completely end the problem, but it did
greatly extend the time to failure.
Engine vibration caused no end of troubles--on one model, we identified
one maximum amplitude vibration behind the front door which over time
would crack the vertical structural member horizontally, travel through
the side destination sign and crack the forward vertical member
horizontally, crack the upper door header vertically, then travel down
through the a-pillar and crack it horizontally about halfway down.
Couldn't change the vibration, so the only fixes were fishplates and
internal bracing in the a-pillar. And that's nothing compared to the
havoc wreaked by vibration on military aircraft. Once knew a guy who did
avionics repair on carrier F-14s and he said it was a losing battle
trying to keep the avionics running while on a cruise because the
vibration would cause the connectors to literally crumble, and there
never were enough spares.
Cheers.
--
Michael Porter
Roswell, NM
Never let anyone drive you crazy when you know it's within walking distance....
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