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Thread: Home built independent suspension?

  1. #1
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    Jan 2008
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    Default Home built independent suspension?

    Just wondering if any one has successfully designed and built their own independent trailer suspension? Looking through my trailer supply catalogs I can buy the spindles with the brake flanges and I'm tempted to try my hand at this.

    I know that AT has their kit available, but it is a lot of fun to design and build my own stuff. In another post I shared the following picture of a trailer frame that I was modeling, but I thought I would start a thread specific to the suspension. If I try to go this route then I'll probably be looking at using air bags as well.

    What are your thoughts guys?


  2. #2
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    Oct 2007
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    yorba linda ca.
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    At's arms are adjustable.....If it were me I would buys an axle that is straight NOT. the kind with the bow in it.mount it where you want make sure it it straight, add your arms, air bags then cut the center section out of the axle. JMO.
    Overland XT

  3. #3
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    Cool... another Rhino user. NURBS rocks!

    As far as the trailer goes, I don't think that it would be all that difficult, and I've actually entertained the idea of building my own as well. However, I have a little different idea about the suspension from the days where I was building racecars,but that'll wait 'till another post.

    Words of advice from someone in the trailer business (hoggdavis.com):

    Measure twice, weld once.

    Make sure that you do all the math. The last thing that you want is to throw a bunch of money at a project that works crummy when you're done.

    Also, I'd maybe do a stress analysis with whatever CAD program you're going to use for the final drawings. Figure out where your weak spots will be, and make sure you beef 'em up a bit.

    Get creative- There are a lot of different ways that the suspensions for trailers made for off-road use can be improved upon.

    Again... Do the math before fab (looks like you have this under control so far), and measure again and again before melting steel. Think "Alignment"!


    Good luck with it, and make sure to keep us all posted on your progress.

  4. #4
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    Guest of the northern barbarians Aberdeen
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    mmm stress analysis....that'll be fun..........

    D = P x l^3 / 48EI

    for those who like math..........me I'd go by experience.....

    Now the arms would be only around 18"-20" Long...so 1/8" wall would be fine....if not overkill as there are two.

    with one or two braces between the arms

    looking at the design, from a fabricating view point, I'd miss out the cut and bend on the inner piece and go at an angle from the bushing to the spindle.

    the inner mount really only limits the twisting of the outside bushing, the spindles available on the web are usually only 8" long, unless you do the mount and cut method....expencive in parts.......

    But if you know of long spindles as per your design let me know....I'll be doing something similar soon.....basic frame is done and I'm working on the upper boxes right now
    whilst I juggle the suspension plans....trailing arms or the more standard triangular yoke hinged from the center of the trailer.

    Another thing I'm looking at is replacable spindles......as its a wear part long term...

    spindle mounting inside a 1/4' thick 2" tube and bolted through.

    a plate wrap welded from the arms around the tube and back on the arms would make a stronger joint than an angled butt weld.......especially if making in the garage rather than a factory angle cut ....ie I know I'll have weak points if I just butt weld

    I guess your talking about using these too, as the bushings ?

    http://www.ruffstuffspecialties.com/...eve-p-148.html

  5. #5
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    Prescott, AZ, USA
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    The difficult thing about trailing arms is that each weld makes the tubing bend in a given direction. Once all the welds are completed you pray it's all square. You pray it's square even when the assembly is clamped on a welding table in a template.

    Adding to the issue is getting the spindle welded into the tube at 90' to vertical and horizontal. Did I mention that nasty internal seam on the tubing that needs to be addressed?

    We have a 15 - 20 % rejection rate on trailing arms. And before anyone asks we dont sell the rejects.

  6. #6
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    Gig Harbor, WA (originally from Morenci, AZ)
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    Find an old IRS VW Beatle, and use the rear suspension from it. You could buy one of the aftermarket torsion tubes to save weight. All the suspension parts mount to the torsion tube. Then fabricate the shock mounts, and you are good to go.

    All of the parts are available in the aftermarket, and you wouldn't need to find an old VW. These parts are much lighter weight also.

    Shouldn't have any alignment issues either.

    Just an idea, since you are still in the design phase.

    Either way, it should be a fun project.
    Brian

    2004 Toyota 4Runner Sport, 3" OME lift, 255/75R17 Goodyears, Super Sliders, communications, GPS, Black Widow roof basket, Truck Vault, 400 watt inverter, Scion stereo with iPod cable. 2009 Roadtrek 190 with 5" lift.

  7. #7
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    Quote Originally Posted by Photog
    Find an old IRS VW Beatle, and use the rear suspension from it. You could buy one of the aftermarket torsion tubes to save weight. All the suspension parts mount to the torsion tube. Then fabricate the shock mounts, and you are good to go.

    All of the parts are available in the aftermarket, and you wouldn't need to find an old VW. These parts are much lighter weight also.

    Shouldn't have any alignment issues either.

    Just an idea, since you are still in the design phase.

    Either way, it should be a fun project.

    Now thats an original idea!

    70'sType 2 (bus) and Type 4's (wagon and fast back) are coil rear suspension. They have the coil buckets in the A-Arm. Easy to convert to air bags.
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  8. #8
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    Aug 2007
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    Quote Originally Posted by Martyn
    The difficult thing about trailing arms is that each weld makes the tubing bend in a given direction. Once all the welds are completed you pray it's all square. You pray it's square even when the assembly is clamped on a welding table in a template.

    Adding to the issue is getting the spindle welded into the tube at 90' to vertical and horizontal. Did I mention that nasty internal seam on the tubing that needs to be addressed?

    We have a 15 - 20 % rejection rate on trailing arms. And before anyone asks we dont sell the rejects.
    I've been thinking about this too and that's my biggest concern. You would have to have a very good jig for setting all this up. If not you'd be going through a lot of tires and bearings.

  9. #9
    Join Date
    Nov 2007
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    62
    Can the alignment issues be addressed by fabricating with a single tube at the bottom (as in axle) and another where it connects to the frame? The tubes could be cut after everything is welded up. A good jig will still be needed.

    Good luck!

  10. #10
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    Welding relatively thin material, like .125" wall tubing for instance, will warp, no matter how hard you try to keep it in place. From what I have read, controlling the warping is the hardest part of any suspension fabrication as it jacks around everything that started out square.

    Leaving tubes in and cutting them out might help a little, but any of the "warping load" that is carried by that peice has the potential to come loose as soon as you cut away the material.

    Leafs and shocks... or AT airbags/trailing arms, are the only logical choices for me.

    I'd love to see someone try it though, and see if they can do it within an acceptable spec.
    Drew F.

    '76 FJ40... 4" lift, 35" MT/R's, ARB Snorkel, Warn 8074, Power Steering, Saab Seats, Custom rear tire carrier, soon to be scratch built expedition trailer.

    My rig... "Maude"

    My camping trailer build up thread.

    "Make a life, not a living..."

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