Scott Davis wrote:
>
> Thought I would add my two cents worth, as I used to build race car
>looms and am in the middle of building a set of Spitfire looms.
>
> The major problem with soldering is that the joint becomes very
>brittle. In aerospace applications (and hence race cars as well) solder is
>NOT used. Vibration from the road and engine are considered harsh enough that
>a soldered joint, no matter how well supported, will not have the longitivity
>and reliability that the application requires. The MilSpec components that we
>use are all the 4 or 8 indent crimp type. Load carrying for each circuit
>ranges from 7.5A to 25A.
This issue comes up periodically with some customers for our buses. One
large transit agency insists on having crimped and soldered terminals at
several places in the bus, even though we try to tell them that the
longevity of those connections will be lower. (One of such properties is
the largest transit agency in the country, and they have an engineering
staff many times larger than ours, so they tend to bully us. <smile>)
Myself, I'm of two minds about soldering crimped connectors, since
practical experience indicates that in high-vibration areas, with a
soldered joint, the joint does become more brittle, but also, for a
while, anyway, prevents the wire and joint from flexing, but the joint
will eventually fail. Unsupported wire after an unsoldered connection is
an equally large problem, since vibration causes the wire to flex back
and forth, and can fatigue-crack the strands, sometimes fairly quickly.
This is most often a problem with single, small-gauge wires.
Ultimately, best practice would be to support the wire for about three
inches after the connection, but with single wires, or small pairs, this
isn't always possible. In those cases, the answer is probably to add
layers of heat-shrink tubing to the connector and wire for the three
inches, to help limit movement of the wire after the terminal and
connector. And, wherever possible, bundle wires together to limit
flexing and provide more clips, closer together.
As an alternative to MilSpec metal connectors, Scott, you might consider
Deutsch DT or DTM connectors--these are mil spec rated, have internal
seals which have been dependable in commercial vehicle use, and are not
horribly expensive. The downside of occasional use of them is in the
cost of the crimping tools, which are not cheap.
We've actually had a lot of problems with AMP multi-pin connectors,
related to two specific areas--terminal pins backing out of the
connectors from vibration, and connectors eventually crumbling from
vibration. Depends, of course, on the terminals and connectors chosen,
but, overall, much less trouble with the Deutsch connectors than the
AMPs.
Cheers.
--
Michael D. Porter
Roswell, NM (yes, _that_ Roswell)
[mailto:mporter@zianet.com]
The gulf between content and substance continues to widen....
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