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Is there a end fitting for rope that develops the full strength of the rope?

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  • Is there a end fitting for rope that develops the full strength of the rope?

    Something sorta like this:


    The one shown is made of nylon with a stainless screw. The description in McMaster says it's "strong", but I doubt it is as strong as the rope itself. The rope is 3/8" double braided Dacron.

    I want to put it in a recess in an aluminum fitting so it will not be able to expand. There's no room for an eye splice or stop knot.

    I'm a little worried about the stainless screw. It doesn't say anything about the threads on the screw, but it seems like sharp threads would be a bad idea.

    Roger
    Any products mentioned in my posts have been endorsed by their manufacturer.

  • #2
    A splice can get you close to the full strength, but any time you distress the fibers, even with a small radius bend, you weaken the connection. I'm pretty sure that any mechanical fitting is going to be substantially worse than a splice.

    By the way, do you have room for a backsplice? It would smaller diameter than a stop knot, but probably longer.
    .
    Mike

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    • #3
      Epoxy should work if you get it into the fibers and then wrap nylon string or fiberglass over it with more epoxy to get the diameter you need. Of course you can't dismantle it afterwards...

      If you need it a specific size you could make a plastic mold or a metal mold with Saran Wrap as a release agent.

      John

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      • #4
        I'm thinking about making an aluminum sleeve with a tapered bore and a matching tapered plug. The plug would fit into the core, and the rope would be seized with wrapping to keep the plug from slipping out. Then the rope would be pulled into the sleeve to compress the fibers around the plug. It wouldn't be too hard to make. Any opinions on how it would work?

        The backsplice would be too long.

        Roger
        Any products mentioned in my posts have been endorsed by their manufacturer.

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        • #5
          Roger,

          The item mentioned in your original post is just used to keep the rope ends from fraying.

          The only thing I know of that will be able to utilize the full tension capacity of the rope is a "sock". This is a wire mesh that tightens as tension is applied to the rope. For full development of the rope it may be necessary for the "sock" to be several feet in length.

          I don't have time right now to do an internet search but companies that construct power lines use these.


          Okay, I found some...




          These are for cable but they work just as well on rope!

          http://www.h-lift.com/cablesock.htm

          .
          Last edited by Mike Burdick; 10-09-2008, 01:32 PM.

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          • #6
            Open braid rope Roger?

            Open it up like a chinese finger, slip the "bullet" inside, tape it all down. THE harder it pulls the Harder it locks in..

            Is this on a winch drum? I've braided lots of kevlar-and other ropes with loops, bullets, ties.. a loop is only strong with a thimble inserted.. otherwise the fibers break.

            I was somewhere and a rope broke.. Open braid.. I slipped the one through the other a couple times in a few feet and the pull was back on.. unfortunately.. the electricians being the lazy bastiches most are were all gone off in different directions. Like children it took a hour to get everyone back on the job in the pull corners.
            Excuse me, I farted.

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            • #7
              It's not an open braid, but it can be spliced using a fid. I only have 1.5" lengthwise to work with. I want the rope beyond that point to be the original diameter. That's why I wanted something so short.

              The plug and sleeve works for wire rope, and it's approved for lifting:



              Should be good enough for Dacron in a non-lifting application, I'd think.

              Roger
              Any products mentioned in my posts have been endorsed by their manufacturer.

              Comment


              • #8
                Something like this?


                http://images.google.com/imgres?imgu...icial%26sa%3DN

                It's designed for wire rope and may be what your after
                "To invent you need a good imagination and a pile of junk" Thomas Edison

                Better to have tools you don't need than to need tools you don't have

                73's KB3BFR

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                • #9
                  Possibly this would work, not sure of the outer diameter of the various sizes.

                  http://splicingnut.com/

                  Designed for an eye splice, but a very small eye splice could be managed.

                  Had someone come up while I was on the boat and try to sell me on them, couldn't see the point if you have a boat you should be able to splice a line, but in your application it may work.

                  Ken.

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                  • #10
                    Two more ideas.

                    If you go with the plug and sleve design, I would use delrin for the contact parts. You want something with a little give so you don't crush the fibers.

                    If you make a stopper knot like a double or triple overhand knot, work it down carefully, and snug it almost tight, you can roll it between two boards and reduce the diameter. Then pull it into the sleve, and tighten it down. It depends on how tight the rope is woven. It might reduce it enough.
                    .
                    Mike

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                    • #11
                      Originally posted by mwechtal
                      A splice can get you close to the full strength, but any time you distress the fibers, even with a small radius bend, you weaken the connection. I'm pretty sure that any mechanical fitting is going to be substantially worse than a splice.

                      By the way, do you have room for a backsplice? It would smaller diameter than a stop knot, but probably longer.
                      What he is saying here is absolutely true. Any disturbance to the fibers will produce a weaker point. The socks like the power companys use are probably the best in terms of strength. The stress on the cable/rope is distributed over the length of the sock, highest near the fastened end and lowest at the cable end of the sock. This applies a gradually increasing force on the cable/rope as it goes further into the sock. They are probably close enough for most breaks to happen at a weak spot in the original rope, not at the sock.

                      Splices (properly woven splices that is) are designed to produce the least bends and are therefore probably the next best. After that, perhaps the epoxy and string idea but the strength could vary with application technique. Knots suck because they produce stress riser points at every curve.

                      Anything you do will produce a weaker spot. It will never be as strong as the original rope. The crimped splices used on steel/metal cable can weaken the cable as much as 50% if used as a single overlap splice: they are better used to form loops.
                      Paul A.

                      Make it fit.
                      You can't win and there is a penalty for trying!

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