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Thread: Torque & Friction Drag ?

  1. #1
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    Default Torque & Friction Drag ?

    A question about torqueing…

    In CCK-1865 AMM (PAGE 20-00 1of2) Cubcrafters provides a very well presented “Torque Values” table, and it states: “NOTE: ADD FRICTION DRAG TO ALL VALUES”.

    In the WING MANUAL they give a little table (page 20) for bolt torque and states: “unless noted in the build section”. Later, at page 43, they ask for a 180 inch.lbs for 5/16” bolts. This value is well above the values indicated in the AMM.

    My question: does the values indicated in the WING MANUAL includes the “FRICTION DRAG” ?

    Rgrds
    Y.

  2. #2
    Senior Member Andy's Avatar
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    Default Re: Torque & Friction Drag ?

    Quote Originally Posted by PBY Catalina View Post
    My question: does the values indicated in the WING MANUAL includes the “FRICTION DRAG” ?
    I can't answer your question but the torque table in AC 43.13 may perhaps be helpful. These tabulated values exclude friction drag torque.
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  3. #3
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    Default Re: Torque & Friction Drag ?

    Answer: probably 'no', but maybe.

    The torque in the manual is correct. You are attaching the wing connection fittings to the spars (note this is also a reamed hole indicating a machined tolerance hole). Also notice that on these bolts are very duty MS self locking nuts that come pre-lubed (dry film) due to their intense locking ability.

    Not all nuts in a design will have the AC43.13 'RECOMMENDATIONS' called out.

    In regards to friction drag; my technique is to bring the torque up slowly with a constant motion until the torque value is achieved. Then I let the bolt/nut relax for a while and then retorque. This technique includes any friction drag and also reduces the chance of torque values relaxing from the bolt stretching.

    Enjoy the build, but flying the build is even better! Have fun.
    Last edited by aeroaddict; 04-02-2021 at 03:21 PM.
    Dan Arnold
    KEUL

  4. #4
    Senior Member Andy's Avatar
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    Default Re: Torque & Friction Drag ?

    If I was still in any doubt I would measure the friction/prevailing torque of these nuts, subtract it from the specified torque, and attempt to reconcile the resulting value with AC 43.13 or the AMM.

    I'm surprised the assembly instruction would leave this in any doubt. Isn't there some other place in the kit instructions that says whether the specified torques are final target values?

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