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Technical shackles

Discussion in 'The Hokey Ass Message Board' started by flatheadgary, Oct 31, 2019.

  1. flatheadgary
    Joined: Jul 17, 2007
    Posts: 845

    from boron,ca

    i never really thought about it before but i am putting twin elliptical rear springs on a car i am building and was wondering what degree to put the rear shackle at. i know when putting a straight or dropped axle on the front they should be at a 37 degree angle. i have looked at a few cars and trucks and the rears seem to be straight up and down. does this have to do with the front axle ones are on the front of the spring and the rears are at the rear of the spring? now that i think about that, do you put the shackle straight up or on an angle when they are on the rear of the front spring? my head is starting to hurt thinking about this.
  2. Mimilan
    Joined: Jun 13, 2019
    Posts: 842


    90 deg to the datum line when the spring is loaded.
    The datum line between the 2 eyes.
    Note: This drawing is a typical incorrect trailer set up [but shows the datum line]
    Leaf Spring Angle, Incorrect.gif
    Shackle angle can be used as a tuning tool [dirt racers do this] by making the angle more acute will dynamically soften the stiffness because the spring eye arcs upwards as the spring compresses upwards.
    Making the angle less acute [as above] will dynamically stiffen the stiffness because the spring eye arcs downwards as the spring compresses upwards.[ the spring will compress more than the suspension movement]
    Last edited: Nov 1, 2019
    alanp561 and VANDENPLAS like this.

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