Date: Sun, 31 Jan 1999 12:43:01 EST
Reply-To: CarlMarin@AOL.COM
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Carl Turner <CarlMarin@AOL.COM>
Subject: Re: Soldered Connections...Not!
Content-type: text/plain; charset=US-ASCII
David Writes:
<<<<<<<
Subject:Soldered Connections
I think you are missing the point with soldering - or you have never seen
it done correctly. Your examples of failing solders are not from a wire to
wire connection but a wire to a component / circuit board connection. If
you are soldering two wires together you must do what is called a "western
union" connection first. This is where you strip the wires say 1.5 to
2.0cm and put them parallel to each other so the cut end of one wire is
next to the begining of the plastic covering of the other. Then twist the
wires so they make a mechanical connection first. The wires should be able
to hold together without solder. The next step is to do a propper
soldering job where you heat the wire and not the solder thus advoiding a
cold solder. Use decent solder that contains a very small amount of flux.
I use the Radio Shack stuff. After you make this connection I will bet
anyone one hundred bucks that it will NOT break. If you waterproof it with
lithium greese and seal it with very snug heat shrink it is almost as good
as an uncut wire - just a little stiffer where the connection is made.
Crimps do have their place and work well when done with the right tools.
They do tend to leave some part of the connection open to the atmosphere
which makes it prone to rust and eventually failure.
<<<<<<<<<
I'm afraid you'd loose that 100 dollars David! Soldered connections used on
equipment subject to vibration, cars, airplanes, rockets are especially prone
to fatique failure. The type of soldered joints used on connectors and
splices in the mil-spec environment are highly speciallized and the specs for
how these wires are then harnessed and strain relieved are very specific. The
wiring on our Vanagons doesn't even come close to this standard. Most wiring
on General Aviation aircraft and most experimental homebuilt aircraft (as Ken
W. alluded to) is done with proper solderless crimp connections.
A proper solderless crimp connection fits a proper size crimp fitting to the
gage wire, is compatible in material, ie copper on copper wire, aluminum on
aluminum wire and so on. The joint is then "sealed" as it were with a
generous length of shrink wrap that not only keeps out corrosive environment
but also serves to strain relieve the joint. One problem common to us all I'm
sure is working with the crappy crimp connectors they sell down at the local
flaps. They usually have some plastic cover with huge water catching cups on
the ends. I never really figured out what the point of those were. I often
just cut the plastic cover on these type of crimps off, slide one or two
lengths of shrink wrap on the wire before crimping, do the crimp thing, slide
the heat shrink over the joint and warm it up ( proper heat gun, not a hair
drier or a match please!) Resulting joints stay dry, and maintain the
ductility of the base wire and should not corrode if you used the proper
material crimp (remember dissimilar metals corrosion?) If the wire you are
connecting is grubby, it should be cleaned with some scotchbrite before
crimping. Really, the key to neat and tidy crimp connections is using shrink
wrap over top of them. Those blue and yellow plastic covered things they sell
at the auto parts store do not make for neat connections unless modified as I
described above .
Now to the problems with soldering. Soldering can be used to solve connection
problems certainly. For example, you can't get a good fit for a crimp
connection or you are joining wires of different gage or you can't get the the
store to buy the right crimp connections (I've been there, believe me!). So
what you want to do is try and create a solid mechanical connection before you
solder by twisting the wires together or whatever (or dare I say...use a crimp
sleeve) You then want to use a minumum amount of solder, not so much that you
coat the joint with a shiny blob of metal (I know, it looks good but its a bad
idea). What happens is the multistranded wire wicks the solder up along the
length of wire well away from the joint making that length of wire very
brittle and prone to fatigue failure. The flux gets wicked up even further
into the wire where it can have a corrosive effect over time (even rosen
flux). Just take a bit of wire scrap and solder a really big blob of solder
to the end and really burn that baby in. When cool you'll be able to actually
feel how the wire has been stiffened under the insulation where the solder
wicked up. So if solder you must, practice on some scraps till you can get
the 1/4 inch at the end soldered but can still flex the wire beyond the
soldered bit. You're on the right track now for an acceptable soldered
connection. The joint should now be shrink wrapped, maybe a couple of layers,
each a little longer than the one underneath, to give a nice strain relief to
the wire. The wire should now be strain relieved with proper clamp in the
installation so it isn't buzzing as you roll down the road or fly through the
wild blue yonder (depending on your personal conveyance of choice). As
further argument in favor of my assertion, notice that all automotive wiring
used multistranded wire rather than single solid wire conductors. This is for
flexiblility and thus longer fatique life. By soldering your multistranded
wire and binding up the strands for a significant length you are creating
something that looks like solid single conductor wire. Anybody wiring their
cars with Romex?
Carl Turner
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