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  • preload torque

    xun

    Member

    Updated: Oct 26, 2024
    Views: 1.1K
    I've been working on designing a scissors lift jack, but stucking when it leads to the calculation of torque as I have no idea what preload torque is and how it is calculated. I'm kinda frustrated now as the assignment has to be submitted within 2 weeks though I have tried hard to look for information of preload torque on web.😔 Does anyone have any idea on it?
    Any help is kindly appreciated 😀
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  • suhasvd

    Member • Apr 18, 2010

    Hi Xun,

    If I have understood correctly you are trying to calculate the preload for the fastener which are used for the mechanical joints (mainly flange joints)

    Follow the following steps
    1) Calculate the load coming on the each fastener (consider max f0r calculation)
    2) Select the material (based on the yield strength) and the diameter of fastener ( these are initial assumption)
    3) Find out the maximum force based on the cross section and Yield strength.
    4) Consider 20-30 % load will be taken by the preload ( based on the experience)
    5) Approximately 40% load coming from the mechanical loading will be absorbed in fasteners after pretension.(exp)
    6) Hence summation of (4) & (5) should be less than the allowable yield stress.
    7) Once the cross section area and the material is finalized based on the (6), calculate the force I,e preload.
    8) Calculated the Torque = 0.2 * Initial preload * shank diameter.

    Suhas
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  • suhasvd

    Member • Apr 18, 2010

    Hi Xun,

    If I have understood correctly you are trying to calculate the preload for the fastener which are used for the mechanical joints (mainly flange joints)

    Follow the following steps
    1) Calculate the load coming on the each fastener (consider max f0r calculation)
    2) Select the material (based on the yield strength) and the diameter of fastener ( these are initial assumption)
    3) Find out the maximum force based on the cross section and Yield strength.
    4) Consider 20-30 % load will be taken by the preload ( based on the experience)
    5) Approximately 40% load coming from the mechanical loading will be absorbed in fasteners after pretension.(exp)
    6) Hence summation of (4) & (5) should be less than the allowable yield stress.
    7) Once the cross section area and the material is finalized based on the (6), calculate the force I,e preload.
    8) Calculated the Torque = 0.2 * Initial preload * shank diameter.

    Suhas
    Are you sure? This action cannot be undone.
    Cancel

  • xun

    Member • Apr 23, 2010

    thank you suhas, it does help me and i really appreciate your help 😀
    i feel myself like a small calf, trying to learn more in this forum 😉
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