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linked suspension design

Discussion in 'The Garage' started by bigbluesuburban, Nov 1, 2006.

  1. bigbluesuburban

    bigbluesuburban 1/2 ton status

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    I want to one day build a linked suspension under my '69. So I want to start now with the learnin' how to design it properly.

    I am interested in ANY & ALL information sources.

    If this is a book... post it up
    If this is a web page... post it up
    If this is a forum post... link it up.

    If this thread is good enough I think it might be a good sticky.

    Ok, school me on linked suspensions
     
  2. spoolnaround

    spoolnaround 1/2 ton status

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    time to search COG and surf Pirate.
     
  3. ntsqd

    ntsqd 1/2 ton status

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    X ad nauseum.

    Search my posts. I posted a list of books on chassis design. They're all road racing oriented, you won't find one pointed at off roading.
     
  4. spoolnaround

    spoolnaround 1/2 ton status

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    ?? are you saying, good luck?? :p: There is some info out there, everyone has their own design and reasons theirs is better or what have you. There are a couple of guys here that are linked up with coils or 1/4 elip. Just the only source I know to find any info on the subject. I have though about it myself but I barely have the time or $$ to wheel my junk the way it is.
     
  5. bigbluesuburban

    bigbluesuburban 1/2 ton status

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    Here is what I am thinking...

    I want to keep the leaf springs. BUT... I will not attach the axle to them. Instead I will build a complete linked suspension and ONLY when the suspension compresses will it interact with the springs. I am thinking that limiting straps will stop the droop and I don't have to invest in expensive coil overs.

    So what is wrong with this theory? Am I missing something here?
     
  6. 55Willy

    55Willy 3/4 ton status

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    part of that idea Lee is to use a shackle at each end of the spring to eliminate all binding and to link the axle and only use the spring for dampening.

    if you do wanna coil the front. get all the measurements off of a 94+ dodge fullsize.
     
  7. bigbluesuburban

    bigbluesuburban 1/2 ton status

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    So you think I should keep the axle attached to the leaf springs? I guess I don't see the benefit if I am going to design a proper 3 or 4 link.

    Is there some other reason to keep the two attached?

    EDIT: I didn't read your post thoroughly. You suggested that would be some DAMPENING of the axle movment by keeping it attached to the axle. And I can see that. Especially in fast droop situations. But I also think that a quality shock should be able to do this without any problem.
     
  8. 55Willy

    55Willy 3/4 ton status

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    there wouldn't be droop without counter presure from the other spring. also a shock wouldn't cushion the axle enough if it did drop away from the springs.

    basicly nothing would be making that axle droop...well unless you were wheeling a 39.5 bogger that had weight.
     
  9. bigbluesuburban

    bigbluesuburban 1/2 ton status

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    Well how about a D60 or 14BFF with a 35" Bogger.

    I get what you are saying. I think that you are inferring that I would get droop, but not articulation. And I am not sure if I agree or not.

    If the left side of the front axle were at full droop. NOT attached to the leaf springs and limited by a strap, while the right side were stuffed into the wheelwell, making contact with the spring... wouldn't that be the definition of articulation, but without the additional drag of having the axle attached to the leaf on the other side.

    However, I do see your point about the shock. It would need MONSTER valving to stop that much weight from dropping to the end of the limiting strap.

    I suppose that there is a reason that the rock crawlers don't do this. If it were feasable they would buy the huge and expensive coil over shocks that seem to be at the corners of every moon buggy out there.

    So I guess I go with a double shackle, and perhaps put johnny joints at the frame end of the shackles and I was even thinking of a jointed connection from the spring to the axle.

    Now I have to learn more about linked suspensions so I know what length and such they have to be to get optimum travel and limit things like squat and droop stear.

    So Mr Brain, how about you teach me about that stuff then... hahahaha
     
  10. 55Willy

    55Willy 3/4 ton status

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    if I can find a soucre for good steel, ie dom. I shall be constructing a long arm kit for my cherokee and brain storming for the rear set up. There are some simple ideas I have seen on here. I think greg72 or triaged had the 4 link calc program in the CoG.


    I'll send ya a PM to not confuse everyone at once.
     
  11. Greg72

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

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    You've got plenty of learnin' to do....:D

    CoG has hours worth of reading about linked suspensions...If you get over to Pirate4x4 it's more like DAYS of reading.

    Download ExcelCAD and start messing with that too.

    The problem you will find immediately is that almost nothing in books you'll find is related to 4x4 applications....and once you start talking to 4x4 enthusiasts you won't find too many people agreeing about the "best" way to develop a multilink suspension system. You'll be forced to develop your own opinions in a hurry if you want to make any forward progress.

    There are lots of compromises that must be made, and YOU are the one that has to decide what is most important and what tradeoffs you are willing to make. Regardless, it will take plenty of time and money to build what you want.

    Quality rod ends cost good money, strong link arms cost money. coilovers certainly cost money.... and unless you REALLY understand what you are doing, odds are that you'll create something less capable that the leaf springs you are trying to replace.

    STUDY STUDY STUDY.....the reason I created ExcelCAD in the first place was to teach myself about link suspensions (and I learned plenty) you aren't going to find anyone around who will simply "spoon feed" you the answers to such a broad question.


    :usaflag:
     
  12. shane74

    shane74 1/2 ton status

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    Couldn't have said it better myself :D
     
  13. ntsqd

    ntsqd 1/2 ton status

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    What I'm saying is that any books he finds, & I posted the known to me titles and brief descriptions some time ago, are going to be road race oriented. I do not know any book on chassis design written with off road applications in mind.

    Leaf springs have some built-in damping due to their internal friction, but damping is supposed to be the job of the damper ("shock") and not the spring.

    The opposite spring doesn't push down on the near tire. The opposite spring, in resisting compression, becomes a fulcrum point for the opposite tire use the axle housing as a lever to force the near tire down.

    B4 long travel C/O's became easily available one springing method was to use a 1/4 elliptic leaf spring. The Center pin was usually anchored to the chassis with the main leaf on the bottom and the rear axle pushed against the main leaf. Sometimes shackles were used, but it was more common to see a pair of guides and a roller attached to the top of the axle housing. W/o a limiting strap/chain/cable the hsg could fall away from the spring. In that application the "re-connecting" of the two could be quite violent and travel was usually limited to avoid this.
     
    Last edited: Nov 2, 2006
  14. Txchevy18

    Txchevy18 1/2 ton status

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    So you want to build a set of links and keep the leaf springs but, have them unatached to the frame and use the limit straps and control droop and a heavily valved shock or air shock to control the down force aplied?

    Correct me if im wrong but I always thouh the reason with goin to links was to delete axle wrap and do away with the heavy leaf spring in favor of a more resonsive and lighter coil spring, as well as gain more suspesion travel . I think that with a leaf spring still attached to the axle that when it articulates or you jump it, just theres goin to be a space between the spring and the frame and when everything comes back together it could be rather violent unless you can get ur shock dialed in to be progressively harder as they compress. That could be solved by a dual or even triple spring rate col over that was properly tuned.
    I could picture frame failure, snaped main springs, u-bolt failure not to metion a possible rollover. Just seems like a bit of a pointless idea. I have seen 1/4 elipticals in action and wow those are sweet when set right but still have there downfalls as does every other option as well.

    Btw if I got your idea wrong as I described above plz try and re explain and disregard what I just posted.
     

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