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How to properly splice wires

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  • How to properly splice wires

    Developed during the heyday of the telegraph, the Linemanís splice is designed for connections that will be under tension. It is commonly claimed that, properly made, a Linemanís splice is stronger than the wires of which it is composed. In any case, it is a time-proven method, and, coolest of all, one of NASAís Required Workmanship Standards. To wit, in a NASA-approved Linemanís splice:
    1. The conductors shall be pre-tinned.
    2. There shall be at least 3 turns around each conductor and the wraps shall be tight with no gaps between adjacent turns.
    3. The wraps shall not overlap and the ends of the wrap shall be trimmed flush prior to soldering to prevent protruding ends.
    4. Conductors shall not overlap the insulation of the other wire.
    Though the Linemanís splice was originally used without solder, today soldering is common. And NASA insists on it:
    1. Solder shall wet all elements of the connection.
    2. The solder shall fillet between connection elements over the complete periphery
      of the connection.
    This material comes from page 84 of NASA-STD 8739.4 (PDF), which is a great reference if youíre interested in best practices for interconnecting cables and wires.
    Doing it all wrong since 1966

  • #2
    Like you, I do it all wrong...and my stuff works...strange.

    You should see the fun discussions folks get into about wiring methods, on the robot forum. I like to occasionally mention that there are many ways to make a good connection, also many ways to make a bad connection. More important than the type of splice you use, is that you do it well. Crimped, soldered, whatever, all work if done properly. All of them can fail if done wrong.

    My fabulous web page

    "If it don't go, chrome it!" --Stroker McGurk

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    • #3
      I wonder what the coiling of the conductor does to the electric flow.. I'd think that area would be warmer than the rest of the conductor..
      Seems over kill in a vehicle that the wire needs to viberate.. and not be clamped down so it doesn't move.. as movement tends to break wire at the solder joint end.

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      • #4
        I see they did it like I usually do - Step back to have a look at that beautiful splice and solder and then notice the piece of heat shrink tubing sitting next to the wires. Kind of like flare nuts next to a perfect flare.

        Flying south, with a flock of bird dogs.

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        • #5
          you would think they would have the first step of putting heat shrink tubing over one of the wires.

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          • #6
            Lineman's splice was invented decades before heat shrink tubing was invented.

            My fabulous web page

            "If it don't go, chrome it!" --Stroker McGurk

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            • #7
              That lineman's splice, one of many techniques I'm sure NASA has a specified method for, would be most useful for...linemen. I don't know where an automotive harness has room for that big knot and nothing in a car should have tension on it anyway. In an application where there was tension, there is a distinct disadvantage in soldering over that also in that stress becomes concentrated at the ends of the soldered area and not spread through the intertwining of it all. I could see solid-core or very thin-gauge wire that could still be bent after pre-tinning being done that way, that's probably where they would use it.

              I used to do a coarser version of that splice anyway, not tinned, just a few twists and soldered after, and then tape or whatever to get kinda an ugly little wad of mass in the middle of wires. These days on anything thicker than 20-gauge I strip the insulation back a little and just stick them together so that the strands mesh (maybe with some rosin in there), clamp with a little home-made thing made from aluminum piano hinge, solder, and have the heat-shrink tubing on there first of-course. What you end up with is not all that thicker than the base wire and with the solder in there it will never pull apart. You still have the problem of stress concentration as with any soldering, it's not something to put in the middle of a wire that has to flex much in use.

              Last edited by Loren; August 7, 2016, 11:02 AM.
              ...

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              • #8
                I don't depend on solder, If I can help it...I do a less graceful version of the lineman's splice when splicing wires in a car. I try not to have to splice wires, if possible. Stranded wire makes it more interesting, of course. And solid wire is not really that good in a car, which moves around. House wiring techniques are not really applicable.
                My fabulous web page

                "If it don't go, chrome it!" --Stroker McGurk

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                • #9
                  thought i'd show how i splice multi strand wire. have used this in the marine industry for many years wear we have to pull wires through pipe ect.
                  first figure your cut area, slip on heat shrink, then split the wire in 2 halfs.
                  Last edited by redneckjoe69; August 7, 2016, 05:55 PM.

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                  • #10

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                    • #11
                      pics are easier than words.

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                      • #12
                        bend over, solder, use pliers to make sure no sharp edges, heat shrink and electric tape. gaurantee you cant pull the wire apart at the splice even before solder.

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                        • #13
                          Originally posted by squirrel View Post
                          Lineman's splice was invented decades before heat shrink tubing was invented.
                          well, you are talking about an article from NASA, who probably invented heat shrink tubing.

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                          • #14
                            My question is how old is this article, 1960's? I recall reading an article a few years ago where the auto manufacturers do not recommend soldering but use pressure connections. It had to do with the heat and solder having an adverse affect on the copper as I recall.
                            Tom
                            Overdrive is overrated


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                            • #15
                              For building my old stuff, like it was done in the 60s, soldering is fine

                              My fabulous web page

                              "If it don't go, chrome it!" --Stroker McGurk

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