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Technical Main cap safety wire

Discussion in 'The Hokey Ass Message Board' started by Chappy444, Aug 16, 2020.

  1. hello all,
    In the process of inspecting a 39 or 40 59ab engine. I pulled a main cap to check the bearing and it looked great so I am putting it back together.
    Spec is 80-90 ft. lbs
    On one of the studs 85 lines the safety wire hole up perfectly, on the other stud 85 blocks the hole perfectly.
    My question is do I add or remove torque to make the hole line up?
    Thanks for the input.
    Chappy
     
  2. rusty valley
    Joined: Oct 25, 2014
    Posts: 3,883

    rusty valley
    Member

    if you really want to be fussy you try a different nut, or go tighter until it lines up. generally speaking, never go backwards
     
  3. Thanks,
    I was really concerned about going beyond the max torque spec as this is on a main bearing.
    Below is a picture of what i was dealing with. At 85lbs there was no way I was going to tighten or loosen enough to clear the hole without being way over or way under the spec.
    I ended up swapping nuts side to side and was able to get the holes to line up enough to get a safety wire installed...
    However one nut is now at the lower end of the torque range and the other is at the upper end.
    64337.jpeg
     
    lothiandon1940 likes this.
  4. Truck64
    Joined: Oct 18, 2015
    Posts: 5,325

    Truck64
    Member
    from Ioway

    Generally speaking anytime a fastener won't line up within the torque range, technically the answer isn't "go ahead - exceed the torque spec." I mean, duh, right? Technically.

    Try a different nut, a new one. Those look pretty trashed. Or use a peelable shim. This is a fancy name for a thin washer. Magic!

    I'd wonder what if something hasn't stretched or buggered. They taught us the alternate nut or peelable shim method in aviation school, but I don't recall having to use it very often, and I de-installed and re-installed a shitload of fasteners like that. Is your torque wrench calibrated?
     
    Last edited: Aug 17, 2020
    VANDENPLAS likes this.

  5. blowby
    Joined: Dec 27, 2012
    Posts: 8,661

    blowby
    Member
    from Nicasio Ca

    Run the nut over sandpaper a few strokes maybe. Or spin it if you can chuck it up.
     
  6. Stueeee
    Joined: Oct 21, 2015
    Posts: 305

    Stueeee
    Member
    from Kent, UK

    Why not use self locking nuts. Nylocs or Aerotight/Aeroloc if you are concerned about the Nylocs' locking ability failing at temperature -never had that problem yet myself.
     
  7. SEAAIRE354
    Joined: Sep 7, 2015
    Posts: 537

    SEAAIRE354
    Member

    I’m with blowby. Fine sandpaper on a flat surface move nut in a figure 8 pattern to thin the nut. It doesn’t take much. You may not get it the first time but will quickly get a feel of what you need. I’ve done it hundreds of times and I learned this from someone in the aircraft field with a licensed airframe mechanic.


    Sent from my iPhone using H.A.M.B.
     
    blowby likes this.
  8. dreracecar
    Joined: Aug 27, 2009
    Posts: 3,476

    dreracecar
    Member
    from so-cal

    That design/assembly is for a "cotter key" and not for safety wire
     
    Truck64 likes this.
  9. RmK57
    Joined: Dec 31, 2008
    Posts: 2,659

    RmK57
    Member

    Clean up the threads nicely and use red loc-tite.
     
  10. The stud itself might have moved a little,,,,a fraction of a turn would do it .
    Then the nut would not line up when reassembled .
    I am assuming it lined up correctly when you took it apart ?

    Tommy
     

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