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3/4 link Q's

Discussion in 'The Garage' started by Geargrinder, Jun 3, 2005.

  1. Geargrinder

    Geargrinder 1/2 ton status

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    OK, I'm gona 3 link the back of my trail rig (F150) and this will be my 1st link suspension. I know this is not on a Chevy, but the set up is similar for all trucks.
    I will be going with a "wishbone" upper, and 2 lowwers, my Q is: Do I need the lower links to be triangulated, or can I run them forward @ 90* to the axle?
    And any info (from exp.) on this would be great. I am learning all I can BEFORE I start to build :) Problem is all the info I find is on 4 link only, and I'm not sure how that will difer from a 3 link set up.
     
  2. Triaged

    Triaged 1/2 ton status

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    A "3-link w/ A-arm" can be thought of as a 4-link with the ends of 2 links mearged. With that you will be able to do as much searching as you want on 4-links and be able to use all that info to help you design a 3-link w/ A-arm.

    Download my (and Gred72's) 4-link calculator (also called ExcelCAD by some)
    http://home.earthlink.net/~triaged/Files/4BarLinkV3.0.zip

    If you do not triangulate the lowers you will have a lot of rear axle steer (steep roll axis angle). For this reason alown you should triangulate the lowers.

    When you make the A-arm use a spherical bearing (or one of those rebuildable joints without a shank). Don't use a spherical rod end (sometimes called a "heim" by people that don't know better). This will keep you from having the threaded shank of the rod end loaded in bending from side loads. You should also have the axis of the bolt pointing vertical so the spherical bearing is loaded in the radial direction (the way they were designed to be used) and not in the axial direction (have about 10% strength in this direction).

    Run the lower links at the axle end on top of the axle to keep the angles down (so you can get low anti-squat values close to 50%). This will put a large load on them but the lower links need to be strong to keep them from bending over rocks so might as well use their strength.

    Run the axle end of the upper links as high as you can (within reason). 12" higher then the lower links should be a good starting point. I can't think of any reason that more wouldn't be better. This will help take some of the stress out of the lower links because you put them on top of the axle tube. You will have to build a tall/strong axle truss (rectangular tubing cut to fit around the axle and center section works good for this) to make this happen.

    There is some good info on here in the Center of Gravity forum as well as on Pirate. Some people on pirate are full of themselves...others just full of 'it'. Most all of the info you find on here is good (but there is less of it :( ).
     
  3. Geargrinder

    Geargrinder 1/2 ton status

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    Thank U! that thing is cool :cool1: And thanks for the info. too.
    I am a dumb @$$, I never even looked around @ the other aeras of this site :o I know where to post this type of thing now.
     
  4. Triaged

    Triaged 1/2 ton status

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    The CoG forum is a bit different. You can't just make a new post in there. You have to make it somewhere else and if it is "good enough" it will get moved there. If you really want to see how much went into the calculator go to the vector calculations page and click "Ctrl+`" the ` key is the one on the top left with the ~ over it.
     

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