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Date:         Sun, 31 Jan 1999 23:17:29 -0500
Reply-To:     Frank Miller <fmiller01@SPRYNET.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Frank Miller <fmiller01@SPRYNET.COM>
Subject:      Re: Soldered Connections...Not!
Content-Type: text/plain; charset="us-ascii"

Ok people, I wasn't going to add more fuel to the fire, but what the heck.. back in a former life I worked for a car company in their wiring division. The production terminals aren't soldered because it costs more money to do it, not because it degrades the connection. Always remember that every little piece on your car is there because the manufacturer determined that it had to be there. If they can leave something out and save even a fraction of a cent per vehicle and still get performance that "meets specification", they will. Every terminal is designed for the standard gauges of wiring and certified to meet a "design life" under an accellerated testing program for "crimp-only" applications. The design life, BTW, is usually 10 years or 100,000 miles. When the terminals are assembled to wires in production, a precise set of dies makes the crimp to assure that the crimp is the same as what was certified. Crimp heights are measured and "pull-off" tests are performed periodically on samples to assure the quality. For hand-assembly for prototypes, a set of hand crimpers are used and the connections are always soldered because the hand crimping process is so variable, even with the ratcheting type of hand crimpers. The soldering isn't done with your Radio Shack soldering iron. It's a pair of resistance electodes the concentrates the heat in the crimp area. That's probably more than anybody wants to know. Me, I always solder my connections - been let down too many times by connections that weren't.

Frank Miller

At 12:43 PM 1/31/99 EST, you wrote: >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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