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  • cable attachment

    I have a project where there's a 1.5 inch diameter shaft which will turn and wind up four 1/8 diameter steel cables. This is a piece of threaded rod, and the cables will lay in the groove. A fixed nut is attached to a machine and as you turn the rod the cables wind on and the shaft moves through the nut, keeping the cables in the same position. In other words, they doesn't move sideways as more turns go on- instead the shaft moves sideways.

    In any event, the cables needs to be attached to the shaft, and there is very little room for an attachment device. What I propose is to drill crosswise into the shaft and jb weld the end of the cables into those blind holes. I can tolerate two winds around the shaft that will remain in place, so I can jb those two turns as well.

    I don't much like the idea of a sharp bend in the cable where it would go into the hole, but I don't have to drill the hole directly towards the center of the shaft- I could use some angle so the bend isn't so severe. Perhaps I could cross drill into that hole and use a setscrew to pinch the cable- still filling the hole with jb weld.

    I could pinch a stopper onto the cable- then I would have to enlarge the 'back end' of the hole to take the diameter and length of the stopper. Still use jb weld.

    The blind hole with set screw would be the most space-saving, and is what I'd prefer if no better option comes up. One of the problems is limited space on the threaded shaft- two of the windings will come right up to the beginning of the other of that pair. I don't want an anomaly in the threads that the cables would drop into as they pass over it.

    So that's it- how to secure the end of a steel cable to the side of a shaft without taking up any space with clamping devices. As I see it, I have two options- pinch on a stopper and pull that into a blind recess big enough to put it below the surface of the shaft, then smooth out the 'evidence' with jb weld so the cable will wind right over it- or jb weld the cable into a blind hole and help it out with a set screw, probably smoothing that over with jb too.

    Third option- put up with a sharp bend in the cable and drill cross-wise through the center of the shaft, but do this at a 45 degree angle so the exit hole is 1.5 inches further along the shaft than the entry hole. That way one unbroken length of cable can be used for each pair, still using jb weld to secure the center point of the cable into the hole. While this idea is kind of elegant in its own right, I don't relish the idea of trying to drill through the shaft like that.

    Just fishing for ideas again.
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  • #2
    How much load or tension is each cable holding? Most cable drum applications like that don't reach full load capacity till there are at least a couple wraps on the drum. Gonna be hard to hold the end in place if it takes the full load right at the start...
    Keith
    __________________________
    Just one project too many--that's what finally got him...

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    • #3
      How about drill hole in center, or offcenter, then die grind a nice lead in into the hole so the cable is not bent so sharply.
      I would consider making the hole exit shallow tapered and ram a matching tapered pin in the center of the steel wire. Or maybe off to the side.

      The other option is you weld/pin/whatever a small disk on the shaft, cut a notch in the disk at an angle, pass the wire through the notch then crimp a ferrule onto the end of the wire to prevent it passing back through. This way the wire hardly has to bend at all.
      Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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      • #4
        There will be two turns permanently in place for each wind. How much tension- a good guess would be 500 lbs maximum for each cable. This is a lamination press, so if something breaks it might mean one wrecked layup- no danger.

        I like the lead in to the hole idea- that's certainly do-able. A tapered hole with a tapered pin- trickier but do-able also.
        Last edited by darryl; 02-18-2015, 01:48 AM.
        I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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        • #5
          Originally posted by darryl View Post
          There will be two turns permanently in place for each wind. .
          If this is the case, you probably don't need to worry about bending it sharply where it comes out of the hole. With 2 permanent turns, the anchor point won't see but a relatively small percentage of the tension placed on the cable.

          Dave

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          • #6
            You might take a look at the cable drum used on the end of the torsion rod on a roll-up garage door. I think they have a swaged ball that fits into a notch.



            I like the previously suggested idea of drilling the hole off-center and easing the angle with a die grinder. You could slide the cable through the hole and just fray the end to secure the cable.
            Last edited by winchman; 02-18-2015, 02:46 AM.
            Any products mentioned in my posts have been endorsed by their manufacturer.

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            • #7
              Originally posted by winchman View Post
              I like the previously suggested idea of drilling the hole off-center and easing the angle with a die grinder. You could slide the cable through the hole and just fray the end to secure the cable.
              Soldering is also used to secure steel cables to brass ferrules. See: old motorcycle brake, clutch and throttle lines.
              Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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              • #8
                Originally posted by Black_Moons View Post
                Soldering is also used to secure steel cables to brass ferrules. See: old motorcycle brake, clutch and throttle lines.
                If you can fray the end of the cable you could also use a slightly tapered hole opposite where the cable enters, and anchor it with solder or epoxy. This is the same method that is used to anchor elevator cables

                Pertinent info extracted:
                Potted ends or poured sockets

                Poured sockets are used to make a high strength, permanent termination; they are created by inserting the wire rope into the narrow end of a conical cavity which is oriented in-line with the intended direction of strain. The individual wires are splayed out inside the cone, and the cone is then filled with molten zinc, or now more commonly, an epoxy resin compound.[15]

                paul
                paul
                ARS W9PCS

                Esto Vigilans

                Remember, just because you can doesn't mean you should...
                but you may have to

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                • #9
                  Thru drill the shaft. Counterbore one side and and radius the other side. Swage a stop onto the cable and feed it into the counterbored side and let it exit on the radiused side. The radius will ease the cable's exit.

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                  • #10
                    Depending on whose numbers one believes, the shear strength of JB Weld is 700 to 1040 psi. For a 500 pound load, that's roughly half to three-quarters of a square inch of contact area required.

                    I suggest a sliver bearing solder or brazing. The solder is several times as strong as the JB Weld and brazing is several dozen times as strong. You could just braze a wrap and a half and be done with it - no drilling required.

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                    • #11
                      Pictures would help..........

                      JL......

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                      • #12
                        Are you using threaded rod or radiused grooves, if grooves I see no problem but a thread is an angle which is not good for the lay of cable.

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                        • #13
                          I'm using threaded rod. The cable does lay inside the thread flanks, not on top, so at least that is the better of the two situations- not as good as a half-round groove though. I had in mind to turn the shaft in the lathe and work along the groove with a round file. Unless I want to spend all day I won't be removing much material, but at least I'll be making a smoother spot where the cable will touch.

                          Just out of academic interest, I wonder which of these two situations would be better for the cable- winding up on a smooth shaft, or winding up in thread grooves- . I have in mind that the thread grooves would be better since the cable would not ever wear against itself. In this particular situation, the cable is 1/8 and the threaded rod is 6 TPI. There should be 25 thou between the wraps.

                          I'll post a pic tomorrow.
                          I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                          • #14
                            Yes, v-shaped threads would be way better than winding on the flat.

                            The whole purpose of "scoring" is to prevent the cable from crushing against the drum under load, which is what happens when it is wrapped on a smooth surface or on top of other layers of cable.

                            Dave

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                            • #15
                              If you're going to use the nut as a bearing block it will wear fast and cause a lot of drag. I suggest making a plastic or bronze nut and not using it as a support for the shaft - have a bush or bearing to do the support and use the nut only for axial loading. A 6tpi ballscrew would make for a smooth running setup.
                              Peter - novice home machinist, modern motorcycle enthusiast.

                              Denford Viceroy 280 Synchro (11 x 24)
                              Herbert 0V adapted to R8 by 'Sir John'.
                              Monarch 10EE 1942

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