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4 Link and coils in the rear, whos done it, advice?

Discussion in 'Center Of Gravity' started by K5MONSTERCHEV, Mar 4, 2004.

  1. K5MONSTERCHEV

    K5MONSTERCHEV 1/2 ton status

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    Ok so in a few years Im putting my truck on 4 link with coilovers, and going bigger, and gonna go to school to learn about custom suspension fabrication. But for now, im pondering the idea of putting coil springs in the rear.

    I have a few questions:

    How big of tube should I use? I was thinking 2" diameter, but what wall thickness?

    How big of Heims? Wheres a good source for the parts?

    I was thinking about using Dodge coils, How would I figure how big of coils id need, and where to get them, and buckets?

    Last, any tips or coments? All help GREATLY appreciated! /forums/images/graemlins/thumb.gif
     
  2. sled_dog

    sled_dog 1 ton status

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    the size of the tube isn't as important as wall thickness. I used 1 3/4" DOM cause thats all the supply store had, but 1.5" is what most use. With a .250 wall. I'm running 3/4" heims, some people think this is a mistake I am gonna say wait and see. Dodge coils will be far too stiff I would say. They are designed to hold up a full size truck with a heavy old v8 up there, the rear of your rig weighs a lot less than that.
     
  3. willyswanter

    willyswanter 1/2 ton status GMOTM Winner

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    I'd not recomment heims if you drive your truck on the street alot. They will wear out rather quickly. If you do go heims I run 1-1/4's, I don't think I could ever break one, wear it out yes, but not break or bend it. On the other end I use large RE joints to add some give into the system for the street.

    For link tube, I went with 1.75" OD DOM with .25" wall thickness then with a 2" .120" wall sleeved over that. So in total .375" wall. I think I may add another .120" wall to the lowers due to the weight of my truck.
     
  4. Greg72

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

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    [ QUOTE ]
    Ok so in a few years Im putting my truck on 4 link with coilovers, and going bigger, and gonna go to school to learn about custom suspension fabrication. But for now, im pondering the idea of putting coil springs in the rear.

    I have a few questions:

    How big of tube should I use? I was thinking 2" diameter, but what wall thickness?

    How big of Heims? Wheres a good source for the parts?

    I was thinking about using Dodge coils, How would I figure how big of coils id need, and where to get them, and buckets?

    Last, any tips or coments? All help GREATLY appreciated! /forums/images/graemlins/thumb.gif

    [/ QUOTE ]




    Hey....I've got a great idea! You should find a program called ExcelCAD. /forums/images/graemlins/whistling.gif


    ExcelCAD will let you plug in whatever values you want for tubing diameter and wall thickness. The results are given as FS numbers (Factors of Safety) and you can keep playing with numbers until you get values that are acceptable.

    The same goes for link ends. All you need to do is plug in the values from the manufacturer for maximum load, and the program will tell you what your safety factors are.


    The "catch" is that the answers change depending on your suspension design (longer links need to be THICKER to achieve similar strength) ...

    /forums/images/graemlins/deal.gif
     
  5. K5MONSTERCHEV

    K5MONSTERCHEV 1/2 ton status

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    Thanks you guys!

    [ QUOTE ]
    Dodge coils will be far too stiff I would say. They are designed to hold up a full size truck with a heavy old v8 up there, the rear of your rig weighs a lot less than that.

    [/ QUOTE ]


    Your right, I didnt even think about that. Then, what coils should I use? Or should I just leave the leafs (as much as id rather not) until I go coilovers?
    /forums/images/graemlins/confused.gif
     
  6. dhdescender

    dhdescender 1/2 ton status

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    I've seen some having good luck with stock or lift XJ coils...
     
  7. Greg72

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

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    [ QUOTE ]
    Thanks you guys!

    [ QUOTE ]
    Dodge coils will be far too stiff I would say. They are designed to hold up a full size truck with a heavy old v8 up there, the rear of your rig weighs a lot less than that.

    [/ QUOTE ]


    Your right, I didnt even think about that. Then, what coils should I use? Or should I just leave the leafs (as much as id rather not) until I go coilovers?
    /forums/images/graemlins/confused.gif

    [/ QUOTE ]



    I think it's more complicated than that.....

    The effective spring rate of any coil is a function of where it is located relative to the force being applied to it. A spring mounted more "inboard" on the axle should be more easy to articulate than a coil at the very outer edge of the tube...since there's a stronger lever acting against it.

    I know I've seen a post about how to calculate this somewhere... /forums/images/graemlins/thinking.gif
     
  8. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    Greg-

    Any idea where I could find that calculation on coil spring rates? I have been reading up on link systems, and this is one of the last pieces in the puzzle. The very last piece is to decide if I want to link the K5, or just go all the way and build a buggy from the ground up... /forums/images/graemlins/hack.gif

    -Dan
     
  9. Triaged

    Triaged 1/2 ton status

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    Try this
    http://home.earthlink.net/~triaged/Files/CoilSprings.xls

    If you want the equation to punch into a little calculator when you are at the j/y it is:

    30000000 * wire_diameter ^4 /( 8 * mean_diameter ^3 * #_active_coiles)

    # active coiles depends on "end condition". Just use how many coils you "think" do the work...it doesn't have to be a whole # (i.e. you can use 4.75). Mean diameter is just the OD - wire diameter. Of all these #'s the coil diameter matters the most (because it is to the 4th power)...so you need a good measurement (either with a micrometer or a caliper if you don't have a mic). Mean diameter is also important but not quite as much as the wire diameter (it is only cubed)...using a caliper or getting to the closest 64th of an inch should be close enough. As you can see the # of active coils isn't rased to any power...this is why a guess is good enough.
     
  10. owen

    owen 1/2 ton status

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    [ QUOTE ]
    [ QUOTE ]
    Thanks you guys!

    [ QUOTE ]
    Dodge coils will be far too stiff I would say. They are designed to hold up a full size truck with a heavy old v8 up there, the rear of your rig weighs a lot less than that.

    [/ QUOTE ]


    Your right, I didnt even think about that. Then, what coils should I use? Or should I just leave the leafs (as much as id rather not) until I go coilovers?
    /forums/images/graemlins/confused.gif

    [/ QUOTE ]



    I think it's more complicated than that.....

    The effective spring rate of any coil is a function of where it is located relative to the force being applied to it. A spring mounted more "inboard" on the axle should be more easy to articulate than a coil at the very outer edge of the tube...since there's a stronger lever acting against it.

    I know I've seen a post about how to calculate this somewhere... /forums/images/graemlins/thinking.gif

    [/ QUOTE ]

    So why wouldnt you put coils closer to connection point (on lower arms) as well as in board? wouldnt that allow for more flex with less spring height? I thought the down-side of coil springs was the spring being able to "pop out" when it wasnt compressed? If you moved the springs in and up, as the newer Toyota, it would allow greater flex with less spring- what is wrong with this idea? sorry about hi-jack /forums/images/graemlins/tongue.gif
     
  11. KRAZIE87K5

    KRAZIE87K5 1/2 ton status

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    My guess is that it would allow the weight of the truck to have too much leverage on the coils. I would guess that you would have to run a heavier coil to support that. /forums/images/graemlins/dunno.gif
     
  12. owen

    owen 1/2 ton status

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    true, but since the leverage also works in the other direction, the weight of the housing would stretch the spring easier. So you wouldnt have to have a soft or long coil spring. In theory, the wheel could move twice as far as the spring moves if it were positioned half way up the lower arm. /forums/images/graemlins/thinking.gif
     
  13. owen

    owen 1/2 ton status

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    ok, ok- sorry about the hi-jack. But I still would like to know. Anyone?
     
  14. miniwally

    miniwally 1/2 ton status Premium Member

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    You can put the springs on the control arms to gain rear wheel travel. Look a serious desert racing stuff.
    Most of those trucks use beefy lower links with the coil over, and shocck or shocks mounted to them at some piont in their length. This is how they get 36" of wheel travel out of an 18" or less shock.
    The down side to this is heaveir spring rates, although you really don't feel it because of the leverage, and extra strong lower control arm. These are now holding the vehicle up and transfering axle input to the chassis.
    At the same time you can "Inboard the springs" to gain flex. The down side to this is more body roll because the springs only have side to side leverage on them not front to back leverage. They are still attached to the axle and the frame. The same amount of vertical wheel travel with increase articulation because of the inboard springs.
    We prefer to keep all of the shock and spring forces acting as close to the wheel as possible for Rock crawling.
    Hope this helps
     
  15. owen

    owen 1/2 ton status

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    looks like the weight of a massive 14ff and the beefy lowers would keep it on the ground without added force of the spring being out by the wheel. I guess if it was such a great idea, someone would be doing it already?!
     

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