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Old December 13th 07, 02:53 PM posted to rec.aviation.soaring
jcarlyle
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Posts: 522
Default Wiring a Sailplane

Thank you, Darryl and Todd, for your replies. Thanks also to John for
his off-line message.

Darryl, my experience has been with coaxial cables having BNC, UHF,
microdot and LEMO connectors. It's interesting that one of the URLs
you provided, http://www.aeroelectric.com/articles/bnccrimp.pdf, shows
the exact BNC crimp connector that has proven most troublesome in the
field. I've seen many of these connectors be electrically noisy
straight from the factory. But also, there's no true strain relief on
this connector, so the ground braid tends to break in a completely
invisible manner. A soldered BNC connector (the type with the
compression nut on the bottom) doesn't seem to have this problem, and
especially so if it's been fitted with a strain relief boot.

I thank you for this URL, http://www.aeroelectric.com/articles.html. I
was aware of Mr. Nuckolls' site, but somehow I had missed this page.
He appears to be a no nonsense, practical man, and as far as I can
tell he doesn't have a preference for either solder or crimp - as long
as they are done properly, that is!

One thing he points out is not to tin a wire you'll use a crimp
connector on, nor should you solder a crimped connector. You shouldn't
do the second because it destroys the strain relief, and you shouldn't
do the first because the connection loosens over time. Very, very
interesting, because Tefzel wire is pre-tinned...

I'm not a member of IEEE, so references to their journal won't do me
any good. But I take the point that there are indeed unbiased studies
favorably comparing crimp to solder in a production environment.
Manufacturers of course care a lot about unskilled labor being able to
make quick connections, as it maximizes their profit. And I don't
doubt that connector manufacturers take considerable design care so
that their connectors can approach the reliability of a good solder
joint. But speed and skill isn't generally an issue when it comes to
you yourself wiring your own glider. Personally, I'll take the time to
make a good solder joint having proper strain relief. YMMV, but I've
seen too many bad crimp connections to rest easy with having them in
my own plane.

Todd, the fact that car and aircraft manufacturers use crimp
connectors doesn't really sway me. Look at Consumer Reports and you'll
see that the major source of complaints for reliability in cars is
electrical systems. And don't overlook the fact that the Space Shuttle
flight has just been scrubbed because of intermittent connections. As
I said above, I think manufacturers' prime motivation is assembly
speed using unskilled labor. Reliability is also important, don't get
me wrong, but I think they're more interested in minimizing their cost/
benefit ratio. And as Jerry Pournelle of Chaos Manor fame likes to
say, "better is the enemy of good enough".

-John

On Dec 12, 4:44 pm, "
wrote:
On Dec 12, 11:04 am, jcarlyle wrote:



On Dec 12, 11:51 am, ContestID67 wrote:


- Solder - Is to be avoided in liu of crimp connectors. However,
sometimes you just can't avoid it.


Why do you make this statement, John? I've dealt with tens of
thousands of cables professionally for over 35 years, and during that
experience I've found that if a connection is crimped, it's crap. By
that I mean it's highly likely to be either electrically noisy or
mechanically weak.


I did a Google search, and basically discovered that crimping vs
soldering discussions are, in some quarters, a quasi-religious war. I
don't want to add fuel to that fire, but are there authoritative,
unbiased studies (eg, not from connector manufacturers) that bear out
your assertion?


-John


I'm not sure what sort of cable you are talking about. Some cables
e.g. professional audio cables are probably going to fail regardless
of how they are done just form the handling they get. Similarly I've
spent many hours repairing RF and microwave coax cables in research
labs and I'm sure most failere are from gross abuse (peopel pulling on
the cables etc.) and these have had all times of connections,
soldered, crimped, spot welded, exotic super conducting connections,
etc. For my money in my glider I'll take properly done crimp
connections.

There are quite a few research papers that demonstrate superiority of
crimp connectors in production environments - ie. where both solder
joints and crimp connections are performed properly. Even with good
control and technique solder suffers from dry joints and surface
contaminatation issues amongst others and in general take a lot more
skill to do properly than an equivalent crimp joint. Most of the
papers I recall are in IEEE publications not from vendors, if you are
an IEEE member or have access to their publications I'll try to find
them for you. Crimping may be faster and lower cost in production
environments but automotive and aerospace company also do not want to
pay for the cost of failed connections in the field - if soldering was
superior you would see it being used more in these applications.

It seems many people's experience with crimp connectors is using some
no brand PVC jacketed connector from the local hardware or auto parts
store with a cheap single action crimp tool. All bets are off if that
is the case.

Getting back to the original request, there are some interesting
articles on general aviation wiring etc. athttp://www.aeroelectric.com/articles.html
I've not looked through them all but some seem to have a good
perspective from a professional A&P who does this stuff for a living.
He seems to have lots of practical examples of good tools and
workmanship, eg. -

http://www.aeroelectric.com/articles...s/bnccrimp.pdf

Cheers

Darryl Ramm




On Dec 12, 5:44 pm, Todd wrote:
I would suggest you take a look inside your car. You wont find
anything but crimped connectors EVERYWHERE. And the continue to
function even when corroded by the road salt the local highway
departments love to spread around here.

High quality connectors applied with the correct tool gives a very
reliable and repeatable connector. Look inside your next B787, you
wont find any soldered connectors there either. The technology is
quite well proven.