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3 link designing?

Discussion in 'Center Of Gravity' started by sled_dog, Nov 19, 2003.

  1. sled_dog

    sled_dog 1 ton status

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  2. willyswanter

    willyswanter 1/2 ton status GMOTM Winner

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    I hope that guy plans on cutting the tubing off there past the frame or else is lower links are gonna get up close and personal with it...

    Thats actually a 4 link design but utilizes a single link attachement point at the axle, but I guess technically it's a 3 link I guess... That bushing attachement on the upper link at the axle is going to be binding like no other when that thing gets twisty.

    I just took two vicodin and I am in mucho pain so I'm not going to start on proper 3 and 4 link design tonight. Maybe someone else will but I'm sure I'll be in the mood in the morning.
     
  3. sled_dog

    sled_dog 1 ton status

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    yeah I don't get the bushing mount on the top link. Thats Steve Sharp's yellow K5. Seen action shots of it so I guess he got it going without trouble.
     
  4. blazinzuk

    blazinzuk Buzzbox voodoo Premium Member GMOTM Winner

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    It looks like a well thought out design you guys gotta remember everyones link suspension is gonna be different a bit depending on how much anitsquat you want how long you want your links what type of wheeling you do etc. I know a guy here in town that has a four link front and rear He has awesome approach and departure angles but worse breakover than I do because his links are so long. Sorry kind of getting off the subject. Anyway what I am saying is do alot of asking around then muesuring then do it all again until you think you are close then think about ordering stuff and if some one could give a disertation on link style suspensions that would be great /forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif
     
  5. Greg72

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

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    Let's take a closer look at the photo:

    [​IMG]


    I'm going to cast my vote that we're looking at a 4-link. From what I've seen, TRUE 3-link setups use either a single lower link and two uppers (or vice versa) and a panhard bar for lateral location of the axle. This particular setup has no panhard, and the upper links are merely converged to a single point on top of the axle. If those links were even 1" apart, everyone would call it 4-link..... /forums/images/graemlins/grin.gif


    So here's the million-dollar question you asked: "What are the fundamentals in designing a 3-link (or in this case 4-link)"

    Well it should be obvious in a HURRY that you'll never hear the same answer twice. The primary reason is that once you start to understand the relationships of the links and the way they will affect handling, and offroad driveability, etc the "choices" get tough....

    This photo is a great example:

    1. Lower links are bent to provide really good ground clearance (Drawbacks: the effective link angle is quite steep which is going to dial in a LOT of anti-squat. Also those bent arms are going to be travelling up inside the cab of the truck substantially, so rear storage will be minimal)

    2. Rear link converged on top of pumpkin also provides good ground clearance (Drawbacks: Probably is going to travel up inside the cab also. I see a lot of bushing-style endlinks on it too, which I suspect will cause binding as it tries to flex)


    In this example....it's clear that the objective is suspension travel over interior room, or storage space, etc. and it looks like he's going for maximum ground clearance (breakover angle) too.

    There are a lot of ways to plan a link suspension, but the amount of available solutions becomes smaller once you decide which criteria are most important to you, and how efficiently you want to package everything.


    FUN STUFF!! /forums/images/graemlins/thumb.gif
     
  6. BIGJ

    BIGJ 1/2 ton status Author

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    I think he's running johnny joints at the axle link ends to prevent binding. It looks like it has some decent flex from the trip pics on their site.

    [​IMG]

    BIGJ
     
  7. sled_dog

    sled_dog 1 ton status

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    Alright my main concerns are this, I want get a better departure angle, with a good breakover angle, and storage is not a major factor. So I'm thinking this setup may be useable for me. I don't think I would go as steep on the low link angle though. I want a good flexy suspesion(not talking monster crazy stuff) just good flex with really good departure angle. 4 link would allow maximum bobbing. The k5 will not be a road vehicle, I will drive it once in a while when I feel like taking a cruise through town but that won't be a frequent event, otherwise it will be trailered everywhere.
     
  8. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    One thing to think of with that setup is the roll axis. It must be kept high so that the axle moves to the stuffed side or it will drive the outer arms into the frame... This is how he gets away with the arms up beside and close to the frame, the roll axis is just barely below the frame…
     
  9. 88K5Jimmy

    88K5Jimmy 1/2 ton status

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    I think he designed it pretty well.
    [​IMG]
    [​IMG]
     
  10. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Oh, I know his works very well. I was talking to others who might try to duplicate without realizing the importance of that one piece of data...
     
  11. 88K5Jimmy

    88K5Jimmy 1/2 ton status

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    Yeah I gotcha, I didn't mean to seem harsh. I get the opportunity to wheel with him every now and then and its always amazing to see that rig in action.
     
  12. Greg72

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

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    Have you got any other pics?......specifically of the rear suspension flexing.

    Most of what's showing in those is front flex...the rear isn't being "challenged" much in those shots.
     
  13. 88K5Jimmy

    88K5Jimmy 1/2 ton status

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    I sure don't. There are a couple more pics here

    I do remember Steve (the owner) sying that his current coils in the rear were to soft.
     
  14. weisel

    weisel 1/2 ton status

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    there was an excelent two part article in one of the 4x4 mags about how to 4 link a rear axle. Good enough info in order to get started with your project. It discuses the factors also, ie. anti-squat, roll axis, ect. I will get the months and mag title tomarow.
     
  15. Stephen

    Stephen 1/2 ton status Moderator Vendor

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    It's pretty hard to ignore the benefits of putting the lower link arms on top of the axle tube. I've been really happy with the flat roll axis and ground clearance with my rear suspension. Plus it's on a stock K5 frame with good room for the exhaust, nice cargo area (heck, it had a full bed floor to start with) and apparently is strong enough to do what I want to do with it. The drawbacks are higher forces on the lower arms (build them stronger) and possible problems with link separation.
     
  16. weisel

    weisel 1/2 ton status

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    ok, it its petersons june and july 2003. I am going to scan them so I can have a computer copy. I may put them online.
     
  17. mainiac

    mainiac Registered Member

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    Please let me know when you get them scanned. I would like to see what they have to say.
     
  18. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    It's not bad, but overly simplistic. Think about the Petersons article as Elementary school level discussion on links. What you have discussed here on CK5 about link suspensions is mostly High School level. Solid information, but generally boiled down and targeted. For College Level general discussion you'll need to read books, get an ME and/or dig through the juvenile BS on PBB.
     

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