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Can you help make my triangulated 4 bar work?

Discussion in 'The Hokey Ass Message Board' started by MeanYellowZ, Feb 6, 2011.

  1. MeanYellowZ
    Joined: Jan 10, 2007
    Posts: 59

    MeanYellowZ
    Member

    In a stock Mustang it isn't bags, but the springs are mounted on the lower arms. The uppers and lowers are shorter than in my setup since they weren't designed to have as much suspension travel as I am aiming for. The Mustang uppers are 43* apart and start out on the center of the rearend and aim outward. This is made possible by the brackets that are part of the rearend and center section and the wider frame mounting point. The only thing really adapted from the stock Mustang design is placing the "spring" (bag or coil) on the lower bar at a point between halfway and the rear of the lower arm. This is also similar to a 58-64 Impala rear setup.
     
  2. Ned Ludd
    Joined: May 15, 2009
    Posts: 5,025

    Ned Ludd
    Member

    Remember that, hypothetically, a triangulated four-bar can work upside-down. In fact there might be some dynamic advantage in it. It's not the conventional way, but there is no reason you can't have a pair of very long angled lower bars (fronts close together) and a pair of relatively short parallel upper bars. The difference in bar lengths in absolute terms would be greater than the other way around, as the ratio of lengths as seen side-on is what is important.

    It depends on what your frame does over the axle (I can't see your latest photos as I'm on a cellular modem and the reception is awful where I am; they're taking forever to load :mad:)
     
  3. Francisco Plumbero
    Joined: May 6, 2010
    Posts: 2,533

    Francisco Plumbero
    Member
    from il.

    Yes, there it possibly is, no one says that the bars need be straight on the top do they? They simply need to attach at given angles and across a given distance. Therefore if the bars are fabricated with an s curve within then to gain a length advantage will that work? You could then connect at the 60 degree angle as well.
     
  4. LaidoutRivi63
    Joined: Apr 21, 2009
    Posts: 193

    LaidoutRivi63
    Member

    First of all, depending on the size of the air bag you use, you can duplicate the ride characteristics of having the bag on the bar with a bag mounted out back, but it would have to be a much softer spring rate bag. You will, however lose that lift. This is assuming you know the load your airspring will see on the bar, and have figured how stiff or soft it will be at ride height.

    You may have to if you want a certain setup to work. Not to criticize but when it comes to setting up something like this four-link, planning is the most crucial stage. When I did our 40 merc, the front bridge pieces didn't get fabbed until all the links were in place and in their correct places. If you design as you go, this is the learning curve you will face.
     
  5. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,263

    gimpyshotrods
    ALLIANCE MEMBER

    Box the frame rails ahead of the bridge notch, run the upper bars parallel to the lowers inside the frame rails, and run a panhard bar or watts-link. Call it done.

    It is not a crime to change your mind.
     
  6. designs that work
    Joined: Aug 29, 2005
    Posts: 411

    designs that work
    Member

    Been following this thread and all the ideas. I am not a expert and I did not stay at a Holiday Inn. You are very concerned about the highth of the top bars, would it be possible to move the angeled upper bars to the front of the axel tube. Right now the brackets set on top of the tube,could you rotate them to the front of the axel tubes and make it work?
     
  7. langy
    Joined: Apr 27, 2006
    Posts: 5,730

    langy
    Member Emeritus

    What the Tinman said, sorry


     

  8. If you can find the picture i would love to see it. Please pm me it if you would i dont wanna hijack the thread anymore, unless MeanyellowZ would like to see it. Thanks

    Justin
     
  9. MP4/8
    Joined: Dec 5, 2004
    Posts: 90

    MP4/8
    Member

    I do a lot of air ride work. Let me clarify that statement for you... If you use a bag that is to large (as in weight capacity), mounting the bag on the bar will soften it due to the leverage. What that really means is that if you make a poor selection in the purchase of your bags, this is the way to get by. A smaller bag, specifically a firestone F9000 bag, mounted behind the axle like some have suggested, will give you around 8-9" of lift, along with the nice ride your lever system will.
    What you are trying to do, isnt uncommon in the minitruck & sporttruck world. That doesnt mean it is good. It also appears you have bought your parts and got all your info from that same group. These guys here are giving you some good advice. But it appears you waiting for an answer you want to hear. If that is the case, go back to the minitruck forums, and they will tell you how to do it. But if you want it right, listen to some of the advice you have been given.
    And last, early chev truck frames are to narrow to really run a triangulated properly. And by early, that goes to pre 88 chevs.
     
  10. LaidoutRivi63
    Joined: Apr 21, 2009
    Posts: 193

    LaidoutRivi63
    Member

    This is false. Not trying to find holes in your arguments, but if you are going to put a suspension system together, it is best you know the physics of it all. If you mount a 'bag on a four link bar, if it is between the axle and the pivot point, the mechanical advantage is given to the rearend. In other words, the bag "sees" more weight than the car is really applying. Therefore it takes more air to reach a given height than if the same size 'bag is mount atop the axle, which applies a 1:1 or near 1:1 load depending on positioning. This makes for a better ride with a big bag due to the stiffer spring rate of the increased air pressure in the bag. If you do what the previous poster suggested, and use a smaller, sleeve type 'bag, it will accomodate your setup much better, and provide the same results. Smaller 'bag can lift less weight, but mounted out back of the axle, is given the mechanical advantage, and and the spring rate is applied in the same manner, only reversed. Thats a vague and generalized but it gives you an idea of what you are dealing with. pickups are especially light in the rear, so too big of a bag, even mounted on the bar in the location you are suggesting, will produce a very soft, bouncey, ground-pounding ride.
     
  11. Francisco Plumbero
    Joined: May 6, 2010
    Posts: 2,533

    Francisco Plumbero
    Member
    from il.

    Can you effectively dampen out some of the bouncey ground pounding ride characteristics of this situation with an adjustable shock?
     
  12. MeanYellowZ
    Joined: Jan 10, 2007
    Posts: 59

    MeanYellowZ
    Member

    Well that sure doesn't agree with 90% of the information you can find on the net and my personal findings. Using a larger bag to get the same amount of lift with less pressure has also always been a nice improvement over a small bag with 90psi in it just to maintain ride height. I have bagged a handful of cars and they always ride better with the bag on the bar versus the rearend and are way less bouncy. This seems to work well except for heavy load/ haul/ tow situations. I would never place the bags on the bar in a dually for instance. In many setups where the bags have been moved from the rearend to the bars it always takes less pressure to raise the truck to the same level which results in a better ride.

    Do a google search on bag on bar versus bag on rearend and a multitude of sites and threads come up with the majority all for moving the bags to the bar. This is also what has brought on a huge amount of bag on bar suspension setups over the last few years by most of the major suppliers.


    At the end of the day the purpose of this thread was to look into different ideas for my upper bar dilemma with this narrow frame setup. Some good ideas were brought up and I am looking into how to put them in action on this setup. I appreciate those who were able to stay on track and help me with some ideas for that.
     
    Last edited: Feb 8, 2011
  13. 17rattycaddy
    Joined: Sep 3, 2010
    Posts: 12

    17rattycaddy
    Member

    Fairly new on here but just an idea, Take a look at the rear suspention on a dirt track car. They tend to use very short linkage and some builders disconnect by use of "tube floaters" or birdcages the rear housing from the suspention. This is done usually to take braking forces out of the picture but it does a nice job of controlling pinion angle.
     
  14. CharlieLed
    Joined: Feb 21, 2003
    Posts: 2,463

    CharlieLed
    Member

    Here is the design I worked up for my 53 F100 and had built by Jason Thorbecke...
     

    Attached Files:

  15. LaidoutRivi63
    Joined: Apr 21, 2009
    Posts: 193

    LaidoutRivi63
    Member

    If the spring rate is incorrect, a shock will only bandaid the problem. Its like when you take a torch to a spring to lower a car, and the springrate is reduced. The spring may still suspend the car, but the soft nature of the spring will cause it to travel very far, regardless of the valving of the shock. The shock may slow down the occilations to some degree, but it will not be the ideal situation. A bag on bar scenario can be nice if you know the weight of the rear of the car, the rate of the airspring (or the force applied at a certain height/psi), and have a correct understanding of how the force is being applied to the bag depending on the location of the 'bag on the bar.
     
  16. tmoble
    Joined: Dec 30, 2010
    Posts: 20

    tmoble
    Member

    MeanYellowZ,

    suggest to re-read LaidoutRivi63's post #70 that starts with "This is false" He's right. To see why, just imagine a case where there's a long lower bar with the bag or spring mounted on the front half. The closer to the pivot point it gets the more spring rate/air pressure it's going to take to support the weight of the car.
     
  17. swissmike
    Joined: Oct 22, 2003
    Posts: 1,297

    swissmike
    Member

    Quote: In many setups where the bags have been moved from the rearend to the bars it always takes less pressure to raise the truck to the same level which results in a better ride.


    You must live in a parallel universe where physical principles apply in reverse....
     
  18. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,263

    gimpyshotrods
    ALLIANCE MEMBER

    Uh, no. I have a Master's Degree in Mechanical Engineering to back this up, and from an Ivy League school, at that.

    It may take less volume, but that volume will have to be at a higher pressure.
     
  19. I second that . You could hide a Watts linkage very easily on the uprights of the notched section behind the axle.
     
  20. swissmike
    Joined: Oct 22, 2003
    Posts: 1,297

    swissmike
    Member

    I completely agree with your last statement, but it obviously is the exact opposite of your previous statement.
     
  21. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,263

    gimpyshotrods
    ALLIANCE MEMBER

    Could you elaborate?

    My second-to-last post was about running the upper links parallel inside the frame rails as a solution to rescue this setup, already partially welded.

    My last post was about how the closer a bag is to the pivot point, the more pressure (but at a lower volume) it requires to lift the same weight, and not less pressure, as some have stated previously in this thread.

    I am not clear how these are the opposite of each other, unless I am missing it.
     
  22. KrisKustomPaint
    Joined: Apr 20, 2007
    Posts: 1,107

    KrisKustomPaint
    Member

    Finished the bed floor before the suspension huh? Here's what you do. Take your 4 link throw the whole works in the garbage. Go to the junk yard get truck arms off of the 63-72? Chevy trucks.

    Problem solved.
    You can stick your bags in the middle of the truck arms with out worrying about bending the lower tube.
    No upper links to get in the way of your bed floor.
    Most importantly easy to understand geometry.
     
  23. Jim Lohman
    Joined: Dec 20, 2008
    Posts: 99

    Jim Lohman
    Member
    from Colorado

    Weld uppers to diff housing, below top of diff housing so as to not hit bed.
     

    Attached Files:

  24. I_am_who_I_am
    Joined: Apr 16, 2008
    Posts: 194

    I_am_who_I_am
    Member

    Is that a welder series 4 link?
     
  25. Jim Lohman
    Joined: Dec 20, 2008
    Posts: 99

    Jim Lohman
    Member
    from Colorado

    No, 32 Ford kit from Ebay.
     
  26. cain
    Joined: Nov 28, 2006
    Posts: 153

    cain
    Member
    from riverside

    lotsa good advice. i know its probably to late but a 2 link system would of left a lot of room to work with. theyre ez to install, leave alot of room for double convaluted bags, shoks, coilovers, shockwaves or whatever you choose. jimenez bros customs sells the kit. call us @ 951 781 1268
     

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