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Anti Wrap Bar

Discussion in '1982-Present GM Diesel' started by René, Dec 22, 2002.

  1. René

    René 1/2 ton status

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    What’s a „Anti Wrap Bar“?I saw some photos in Rene's album, but the effect isnt clear.
     
  2. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    When using soft rear springs they can deflect into and 'S' shape under acceleration and then snap back to their normal shape in a rapid cycle. This causes the tires to hop if they lose traction and also damages the springs. The rotational torque on the rearend housing causes this. With stiffer springs it would not be as much of an issue...but then the suspension wouldn't flex as well either.

    The bar triangulates the diff housing so it cannot deflect the springs, but allows the suspension to still move in the ways we want it to without binding.

    One example of axle wrap is under heavy braking. On my truck as I apply moderate to heavy brake the pinion wants to rotate forward and down as the tires try to lock, this motion turns the front half of the spring into a mild 'S' shape until the spring overcomes that force and snaps back. It will do this several times per second and eventually the tires will lock and hop up and down. Obviously this reduces the effective braking of the vehicle.

    Axle wrap is an inherant characteristic of leaf spring suspension, the degree of axle wrap is based on the stiffness of the springs.

    This is a good article that explains a lot better than I can:

    http://www.4x4wire.com/jeep/tech/susp/axlewrap/

    Rene
     
  3. René

    René 1/2 ton status

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    Thanks now I can understand it in such a way.
    Because a mobile Shakel is installed in the proximity of the Transfercase, the rear axle can still vary the wheel base, so the springs further are able to make waves. In addition, the bar is fastenedt nearly in the center and can’t resist side working forces of the rear axle. Also the axle can steer uncontrolled. I can’t believe in a large effect of this construction. According to my opinion semi-trailing arms on the left and the right would be the better choice. But they should be geometrically correct fited.
     
  4. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Well I don't want the axle to be controlled laterally...this would create bind when the suspension flex's. The bar is made to stop housing rotation only.

    If I wanted a road car or drag car type suspension then a rigidly designed 4 link rear with coils would be my choice.

    Rene
     
  5. René

    René 1/2 ton status

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    >If I wanted a road car or drag car type suspension then a rigidly designed 4 link rear with coils would be my choice.<

    That would be the best. But why for a roadrocket only. A similar construction you can find in both models of Landrover (with a reaction triangle) and it works great in offroad terrains. My Dream for my Burb is accurately led axles with pneumatic springs and enough spring travel.
     
  6. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    As the axle articulates the center of the diff moves laterally. To try and stop or limit that is to induce bind. This applies to leaf sprung suspension. I have no plans to redesign my suspension as it works incredibly well as it is. I'm sure I have as much or more articulation as any land rover out there...check the signature picture. My goal was to keep the super soft rear springs I have and eliminate the axle wrap...goal accomplished.

    Rene
     

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