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!!! 3-Link Discussion - Feasibility of lower Wishbone... (!! NEW PICS !!)

Discussion in 'Center Of Gravity' started by Greg72, Sep 2, 2003.

  1. Greg72

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

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    OK Guys,

    That last discussion thread was GREAT! I appreciate all the input so far. From my research and experiments, it's becoming clear that a "panhard bar" based solution is going to have some limitations. So I'd like to put that solution aside for a while and explore another design that could potentially solve the "axle shifting" issue....

    Wishbone-based Lower Link(s) -

    I think this is considered a "4-Link" technically speaking, but it may still have merit depending on how I/we can solve the binding issues.

    My current thought is to take the last design of the links (the ones where they are offset from the axle 8" vertically and parallel to the ground) and add a lower wishbone to that design. Here's the NEW pic:

    [​IMG]


    Now I've got a few more to share too.... (it's been a busy weekend)

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]



    The setup shown here has about 129% anti-dive. The lower links are 46" long, and the uppers are 32". This setup has a LOT of uptravel (close to 12"!) though I'll be limiting that to probably 8".

    The nice part about this setup (from what I've seen so far) is that the axle-shifting that happened with the previous panhard bar setup is very minimal....about 1" at full stuff! That's substantially better.

    Other issues, like driveshaft and steering still need to be worked out....but since this is all "experimental" at this point, I'm not going to do much with those except take a look at whether they look do-able or not. So far, they look OK.

    I've spent a lot more time in front of the PC, doing calcs and understanding the geometry....that's why there doesn't seem to be as much "progress" in the photos lately! /forums/images/graemlins/tongue.gif
     
  2. marv_springer

    marv_springer 1/2 ton status

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    Re: !!! 3-Link Discussion - Exploring feasibility of lower Wishbone !!!

    [ QUOTE ]
    At this point, I'm unclear whether the wishbone would be better with the convergence point under the tranny pan (roughly) or converging under the front axle??


    [/ QUOTE ]

    Greg,

    From an analytical standpoint, you only have one choice here... that is to have the converged end of your wishbone at the tranny. Reason is... if you converge it under the axle, then this point defines your roll center for the front suspension and you don't want your CG that far above your roll center.. .or it's always gonna want to flop over! /forums/images/graemlins/blush.gif

    From a practical viewpoint though.... I've seen a couple of rigs that have acutally made this setup work with the converged end at the axle. Walker Evans ran something like this on the front of his S-10 Comp buggy for a while, but then he went on to other things (like IFS.. /forums/images/graemlins/rolleyes.gif)... Probably the most successful rig I've seen run it is a little orange 1 seater buggy built by FourWheeler's here in Phoenix.

    Still these examples of making it work have all been light buggies, and I think it would be tuffer on a fullsize to get away w/ it...

    Marv
     
  3. Greg72

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

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    Re: !!! 3-Link Discussion - Exploring feasibility of lower Wishbone !!!

    Gotcha!

    From a purely "wild guess" I was thinking it needed to converge under the tranny....just needed to be reminded "WHY" again.... /forums/images/graemlins/thumb.gif

    I'll be drawing some of this up on graph paper and applying a few calcs for roll center, instant center, etc. And let those numbers help to guide me towards the mounting points and angles I should be using... /forums/images/graemlins/deal.gif
     
  4. Greg72

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

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    Re: !!! 3-Link Discussion - Exploring feasibility of lower Wishbone !!!

    One more quick question:

    When solving this equation, is Theta expressed in "degrees" or some other unit of measure (radians?, etc)


    [​IMG]




    /forums/images/graemlins/ears.gif
     
  5. Burt4x4

    Burt4x4 3/4 ton status

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    Re: !!! 3-Link Discussion - Exploring feasibility of lower Wishbone !!!

    Who Are You???
    What did you do with my Buddy Greg??
    Give him BACK!!!!!
    hahhaaha
    J/K /forums/images/graemlins/usaflag.gif /forums/images/graemlins/ignore.gif /forums/images/graemlins/ignore.gif
     
  6. Donovan

    Donovan 1/2 ton status

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    Re: !!! 3-Link Discussion - Exploring feasibility of lower Wishbone !!!

    Greg sorry I have to ask but what are your design goals? Like street and offroad or trail only rig? I think that we are making the panhard rod out to be way to difficult. Look at all the front ends that use them like the Dodge truck, jeeps and Landcruisers I don't think it is that hard. /forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif
     
  7. m j

    m j 1/2 ton status

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    x

    x
     
  8. Greg72

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

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    Re: !!! 3-Link Discussion - Exploring feasibility of lower Wishbone !!!

    [ QUOTE ]
    go limit your 3 link susp travel to the 'possible' and see how bad your PHB shifts the axle.
    it seems like you are looking at the extremes and panicing

    [/ QUOTE ]


    Not sure I'd use the word "panicking"....really the first discussion thread got me a pretty solid understanding of how the panhard bar works, and that (like all things) it has some weaknesses as well as strengths.

    That is not to say I have abandoned it as a solution....I'd really like to explore the triangulated lower links with the same "skeptical eye" and see what weaknesses it has, and what strengths it offers....

    Ultimately, the decision about which solution is best will come down to the one that has "weaknesses" that I can either live with, or plan-around. Or maybe it will simply be the one that lets me fit all the "other" stuff into the equation too (driveshaft, idler steering /forums/images/graemlins/thumb.gif, etc) The best suspension design in the world won't help me much if I can't connect any steering linkage.... /forums/images/graemlins/grin.gif

    As for a "real" objective....how about a suspension that can do between 7" and 8" of bumptravel (up) and a similar amount down? That would put me in the 14" to 16" shock realm and would be a significant improvment over the roughly 5.5" of bumptravel I currently have.... not that this is the PRIMARY reason for the suspension change. As most of you already know, I am enjoying the challenge of it all....the planning, the calcs, the fabrication. This is the essence of the "Built Not Bought" philosophy to me. /forums/images/graemlins/thumb.gif



    Besides.....I just KNOW that you guys want to see some photos of an articulated wishbone suspension to compare to the panhard bar stuff I've already done..... don't you?? /forums/images/graemlins/deal.gif
     
  9. Triaged

    Triaged 1/2 ton status

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    Re: !!! 3-Link Discussion - Exploring feasibility of lower Wishbone !!!

    Theta is in what ever you want it to be...just make sure you have your calculator (or excel) in the right mode to make it what you want.
     
  10. Stephen

    Stephen 1/2 ton status Moderator Vendor

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    Re: !!! 3-Link Discussion - Exploring feasibility of lower Wishbone !!!

    And how exactly would you steer this?

    Triangulating the front can work OK but the packaging is weird and the steering is really weird. We put a panhard on my bro's buggy even given a wide open sheet of paper. Triangulating the front got caught between the roll center requirements, the front driveshaft on the high pinion axle, the belly clearance, etc. And this is not even considering steering since it's using hoses instead of linkage.

    Put a panhard bar on it and be done. That's my call, it does work OK, I'm down to about 14" of travel now and the panhard works fine. It's a little funky to get it all in there but it works. Steering is where the triangulated front becomes a problem.
     
  11. Greg72

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

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    Re: !!! 3-Link Discussion - Exploring feasibility of lower Wishbone !!!

    [ QUOTE ]
    And how exactly would you steer this?

    Triangulating the front can work OK but the packaging is weird and the steering is really weird. We put a panhard on my bro's buggy even given a wide open sheet of paper. Triangulating the front got caught between the roll center requirements, the front driveshaft on the high pinion axle, the belly clearance, etc. And this is not even considering steering since it's using hoses instead of linkage.

    Put a panhard bar on it and be done. That's my call, it does work OK, I'm down to about 14" of travel now and the panhard works fine. It's a little funky to get it all in there but it works. Steering is where the triangulated front becomes a problem.

    [/ QUOTE ]


    Two words......Rope Steering!!


    ...just like the old wooden go-cart I built as a kid!



    In all seriousness, I didn't know if the rest of the stuff would "fit".....mj has me thinking about a really weird-sounding "front to back idler arm steering" setup, that seemed to move a lot of the stuff out of the way.

    This image was posted up in the OTHER 3-link thread:

    [​IMG]


    Anyway, I'm not sure if that will solve the packaging of the steering setup. Maybe once I start actually laying in the wishbone on my "mock up" it will become obvious that I can't fit everything.... /forums/images/graemlins/thinking.gif
     
  12. willyswanter

    willyswanter 1/2 ton status GMOTM Winner

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    Re: !!! 3-Link Discussion - Exploring feasibility of lower Wishbone !!!

    Greg, your steering drag link that runs from the idler to the axle needs to have it's pivot points in the same planes as the pivot points of the suspension link it is running parallel to. If not as your suspension cycles your steering wheel will be doing all kinds of fun stuff...

    I think your best bet is going to be a regular crossover setup with a panhard bar running parallel and the same length as the drag link and mounted in the same plane vertically and horizontally as the drag link when steered straight ahead...
     
  13. jimmy88

    jimmy88 1/2 ton status

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    Re: !!! 3-Link Discussion - Exploring feasibility of lower Wishbone !!!

    In case your intrested in the October 4 Wheel & Off-Road mag, page 96 "Tube Car K5" looks to have a front 3 link very similar to what you have mocked up.
     
  14. Donovan

    Donovan 1/2 ton status

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    Re: !!! 3-Link Discussion - Exploring feasibility of lower Wishbone !!!

    Greg there was that same steering setup on one of the Avalanche rigs. It was on there website before the two companies spilt. Maybe you could Ask Clifton at Poison spyder about that setup.
     
  15. Greg72

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

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    Re: !!! 3-Link Discussion - Exploring feasibility of lower Wishbone !!!

    Thanks for the tip.....I will try a little "sleuthing" to see if I can find any pics.

    Anyone familiar with PBB feel like looking over there? /forums/images/graemlins/thumb.gif
     
  16. willyswanter

    willyswanter 1/2 ton status GMOTM Winner

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    Re: !!! 3-Link Discussion - Exploring feasibility of lower Wishbone !!!

    I take it your in the pbb band? /forums/images/graemlins/rotfl.gif

    I have gotten all my knowledge on this stuff from there and thats reading maybe 5% of the posts on the subject over there... I've got a thread going right now over there on my rear 4 link design and I don't know what I would do without all the help from them.

    Heres the latest:

    [​IMG]
     
  17. Greg72

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

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    Re: !!! 3-Link Discussion - Exploring feasibility of lower Wishbone !!!

    Jason,

    I can still "lurk" over on PBB, it's just that I spend so little time there that I don't even know which forums are the most useful (for tech).... mostly it looks like a lot of "flipoffs" and "fag comments"....

    Anyway, that suspension diagram is GREAT! I followed the link back to your site, and grabbed the other ones there too (the early designs perhaps? /forums/images/graemlins/wink.gif) Being able to compare the link positions you chose, and the effects that those choices have on the IC, roll centers, and anti-dive are going to be a great learning tool for me.

    BTW -> What are you using to draw those? Is it some multi-thousand dollar software I'll never own, or maybe something a little more "wallet-friendly"???? /forums/images/graemlins/grin.gif
     
  18. willyswanter

    willyswanter 1/2 ton status GMOTM Winner

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    Re: !!! 3-Link Discussion - Exploring feasibility of lower Wishbone !!!

    Thast autocad 2004, runs in the neighborhood of 3,728.39

    Here is the entire thread:

    http://www.pirate4x4.com/forum/showthread.php?s=&threadid=173230

    The General 4x4 Discussion forum is by far the best for general tech like this, it's pretty much the only one I hang out in other than the chevy forum but it's not heavily traveled.

    Everyone always complains about pbb and how harsh everyone is but if you make a nice post and don't ask stuff like how much stronger did the chrome plating make my diff cover you'll be ok /forums/images/graemlins/rotfl.gif
     
  19. Stephen

    Stephen 1/2 ton status Moderator Vendor

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    Re: !!! 3-Link Discussion - Exploring feasibility of lower Wishbone !!!

    Interesting you mention Zach's tubecar K5, it's a pretty well executed rig overall. The front suspension would be a good one to study, it works well. I've had a ride in it and it handles pretty well at high speed (60+ sideways in a sandwash felt good) and he has it tuned to the gnat's ass for climbing steep slickrock.
    Your front to back idler steering isn't a bad idea, the best setups I've seen like this run the steeringbox under the seat and either use a "V" drive box to redirect the shaft, or in Randy Ellis's "toy" jeep he basically ujointed the shaft around the corner.
    Watch tire clearance to your idler, my link arms run under the frame and get hit HARD by the tire. This is with a 42 on 5" backspace. You'll also need to pay close attention to the idler angles and lengths to make it all happy, and I can tell you that multiple draglinks like that can introduce a good bit more play and it had to have added a good bit of weight on my truck and will on yours too.

    Once again, I'd encourage a relatively simple panhard bar using the crossover steering you already have. RED's conversion on Juan's K5 would be a good example to look at also.

    A few days perusing the PBB would be well spent, there's plenty of good tech and creative thinking there, you just have to sift it a bit. I guarantee all this has been covered there at some point in time.
     
  20. Greg72

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

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    TTT - New pics and commentary are now in the opening post. /forums/images/graemlins/thumb.gif
     

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