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Bolts used in controls, including those with bushings

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  • Bolts used in controls, including those with bushings

    Seems like a dumb question, but I can't find the answer anywhere.

    When bolts (or clevis bolts) are used in controls that rotate (no bearings), you obviously couldn't torque the whole thing tight as it would not be free to move. I thought about using a bolt that is slightly too long, and torquing the nut till it stops but the hole for the cotter key would be several threads outside the castellated (or clevis) nut.

    So my assumption is you just leave the nut slightly loose, and insert the cotter pin. I can't find any other answer, or any answer. Since clevis pins work the same way, This is my assumption.

    Also, some of the thimbles used require bushings (flap drive). I think I remember reading here that the bushings should be slightly proud of the thimble, and then torque down the bolt onto the bushing. I couldn't find that in AC43, or anywhere else, either.

  • #2
    Since joints that rotate require castellated nuts I haven't given much thought to torquing those to a value, for the reasons you describe. The nut only serves to retain the bolt and you wouldn't want to affect the rotation of the joint. At least that's my take. Haven't worked flaps yet, but I've wondered since all the control cables are under fairly good tension if bushing is really necessary. The elevator control horn/turnbuckle joint comes to mind.
    Dave B.


    • #3
      The plans call for oversized (an4 bolt) thimbles on the flap drive, and you need them because smaller ones bind against the actuating arm. Actually the oversize ones still bind, just a lot less.
      I think not using the bushing would oval out the hole fairly quickly.

      There are a few others as well. I was planning on using slightly too long bolts and tighten the nut up to the shank but it doesn't work unless you drilled new holes. The holes for the cotter pin would be a few threads outside the nut.


      • #4
        You are over-thinking it, AN#-## bolt and a castle nut. Do them all up to the lower spec torque - which is VERY LOW. Everything will rotate smoothly, but if not, back off one notch in the castle nut.


        • svyolo
          svyolo commented
          Editing a comment
          Yeah. I thought there might be some spec for it.

        • Battson
          Battson commented
          Editing a comment
          Yes it never hurts to ask - I had to ask about 10,000 questions during the build. I am so happy we can use a form now instead of a Yahoo group!