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Lower link separation in dbl triangulated rear

Discussion in 'The Garage' started by 8_YOUR_H2, Jun 5, 2006.

  1. 8_YOUR_H2

    8_YOUR_H2 1/2 ton status

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    I have been checking out other rigs to try and get some real world ideas on setting up my 4 link. It seems that on most of the rigs I have looked at have the lower links at 8-12" of separation at the frame as opposed to the upper links which have 3-4" of separation at the diff.

    It would seem that this gives better side hill stability but are there any other reasons for this?
     
  2. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    The triangulation is the only thing locating the axle on a true 4-link design (no panhard).... so the bigger angle you can get in the converged "V", the better you'll control the axle and keep it from being forced out sideways.

    IIRC there was someone quoting a minimum of 40* as a target. If you keep your links short, this is generally not too hard to accomplish. Personally, I'd get the "V" links as close to each other as practical (to still get the bolts into the heims) and on the other end I'd get the open end of that "V" as wide as my vehicle would allow.


    :usaflag:
     
  3. BoondocK5

    BoondocK5 1 ton status Author

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    So Im following what you guys are doing, and Greg your stuff looks great, I'm actively cosidering using 1/2 ton furd front coil springs, to get this working, My only concern would be about rear axle "Walking" without a pan hard bar, Greg, how does yours hold up? is there any appreciable movement?
    Also I saw in your specs that you were using DOM tubing in the link fab. is this just to save weight? I'm going to use 1.5 in. cold rolled steel bar. I've looked at the specs when I purchased some for my steering arms and this stuff is waaaayyyy stronger than anything else I could come up with, but, it's fairly heavy too. any thoughts?
     
  4. 8_YOUR_H2

    8_YOUR_H2 1/2 ton status

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    The traingulation centers the axle and prevents it from moving side to side so technically you should have no walking. I would not suggest 1.5" DOM for lower links. You would be ok using them for upper links but you need something stronger for lower links. I bought 1.75" DOM with a .75 wall for my lowers.

    As for the solid steel stock for CA arms, I have cold rolled solid steel 1 5/8th on my Jeep TJ and I have never had any problems with them in any way. They are extremely heavy and adjusting them is difficult since they came with right hand threads on both ends.
     
  5. ntsqd

    ntsqd 1/2 ton status

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    Solid bar is WAY too heavy, unnecessarily heavy, for linkage. If you only loaded it in shear then maybe, but you won't hardly be able to put shear loads in it.
    Roughly speaking the middle third of any diameter is only weight and doesn't do much for strength.
     
  6. marv_springer

    marv_springer 1/2 ton status

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    Do you mean "horizontal" separation...?? [left to right] :dunno:

    I've seen 4 links setup all different ways. Some triangulated to the max on the lowers, some just mildly triangulated. I think what you mean is "can you have the lowers meet right next to each other at the frame mount?"

    Sure.... The triangulated lowers always seem to keep the rear steer down. Only drawback I've seen is that all the load is concentrated in the middle of a crossmember that usually spans the inner framerails.... and if not built tuff enuf.... it can cause a failure here...:eek1:

    I've seen this happen out on the trails twice....

    Marv
     
  7. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Your material selection should be based on a few factors:


    1. Calcs - Use the Material Selection page of ExcelCAD to look at the Factors of Safety for your lower links....especially the Bending FS. The longer a link is, the more easily it will bend when it's stuck on a rock with the vehicle's weight crushing down on it.

    2. BTDT advice - There are a decent number of guys here with link suspensions that can tell you what wall thickness seems to hold up to "real world" abuse. Anything less than 1/2" doesn't seem to last long on a full-size K5.

    3. Heim Selection - This will somewhat dictate both diameter and wall thickness, since you have to fit your ends into whatever material you choose...too thin and you won't have the strength to retain the heim, or to cut proper threads in it.


    BTW -> My "link suspension" exists only in my mind, in 1/4-scale models and on numerous ExcelCAD printouts.... :D One of these days it will be built the way I've planned.....but there's still some more obstacles to overcome first.


    :usaflag:
     
  8. 8_YOUR_H2

    8_YOUR_H2 1/2 ton status

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    Sorry, I was refering to horizontal separation.
     

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