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Technical Split rear rods - open driveshaft

Discussion in 'Traditional Hot Rods' started by chopt49, Sep 12, 2020.

  1. chopt49
    Joined: Jul 5, 2006
    Posts: 945

    chopt49
    Member

    OK so I’ve looked through past threads I notice topic has been talked about a lot but I could not find the answer specific to my question.

    I have a 1935/36 Ford banjo rear end with the stock long radius rods (trimmed down some for frame attachment) —- currently I have them split. I am going to be running an open driveshaft and a 1940 flathead with Ford 3 speed top loader

    I was originally going to run the rear radius rods to the frame. After researching and realizing that it’s better to have the radius rods triangulated back almost to where they attached to the stock torque tube I am changing my plans.

    I have fabricated an idea to use the Model A stock crossmember and build a platform to mount the radius rods to (see attached photos). Cardboard will be 1/4” plate. I plan to use the tie rod ends and 7degree fittings as seen in photos.

    Do you think this application will work and keep the rear end just as happy as Henry had intended minus the torque tube?

    thanks.
     

    Attached Files:

    dana barlow likes this.
  2. trey32
    Joined: Jul 27, 2014
    Posts: 287

    trey32

    Gonna need a third link up top to stop the twisting that the torque tube used to take care of...
     
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  3. badshifter
    Joined: Apr 28, 2006
    Posts: 3,344

    badshifter
    Member

    You need an upper link. The 35/36 radius rods won't last without triangulation.
    IMG_2353.JPG IMG_2359.JPG
     
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  4. chopt49
    Joined: Jul 5, 2006
    Posts: 945

    chopt49
    Member

    So then why can I not just run these to the outer frame and then add the 3rd “panhard” link? Be a heck of lot less fab work.
     

    Attached Files:


  5. badshifter
    Joined: Apr 28, 2006
    Posts: 3,344

    badshifter
    Member

    Don't think of less fab work, think of correct fab work.

    What you're saying building is one big sway bar, without the flexibility of a sway bar. You will just break the tubes or brackets off as the rear end twists. Do a search, it's fact. They will break eventually Usually close to or at the axle end. A panhard bar keeps the rear end centered side to side and will do nothing for rear end rotation. The third bar (or 4th as some do) keep the rear end from rotating while under acceleration or braking. The radius rods being triangulated (front being as close together, or attached) minimizes the stresses of the rear end twisting. The rear spring keeps the axle centered side to side. If you don't run a transverse leaf spring, and opt for coil overs, then you need a triangulated 4 link , or a parallel 3 or 4 link and a panhard bar.
     
  6. trey32
    Joined: Jul 27, 2014
    Posts: 287

    trey32

    Panhard controls lateral or side to side movement.
    If you remove the torque tube there is nothing from keeping the housing from rotating forward under acceleration.
    Nothing to do with a panhard bar, just needs a simple third upper link is all...
     
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  7. gimpyshotrods
    Joined: May 20, 2009
    Posts: 18,359

    gimpyshotrods
    ALLIANCE MEMBER

    You'd be attempting to turn your rigid rear axle housing into a giant anti sway bar.

    Since it won't twist, your links will simply bend.

    That is why you want the leading ends of the links as close together as possible.

    That allows the rear suspension to follow the road, and articulate over bumps/potholes that are under just one wheel.
     
    chopt49 likes this.
  8. krylon32
    Joined: Jan 29, 2006
    Posts: 7,410

    krylon32
    Alliance Vendor
    from Nebraska

    As gimpy said put them as close together as possible. I'm going to do some 36 bones on a chassis and I'm planning on using a pair of adjustable Johnny Joints at the front along with a torque arm. I've done a lot of buggy spring rear ends and have never used a panard bar. I am careful to make sure the shackles are at 45 degrees loaded
     
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  9. chopt49
    Joined: Jul 5, 2006
    Posts: 945

    chopt49
    Member

    Thanks guys, I knew you all would be the voice of reason. I wil go with the original idea and try to get the bars as close together as possible and build a torque bar off the rear to center.

    Again thanks!
     
    X38 likes this.
  10. 19Fordy
    Joined: May 17, 2003
    Posts: 7,231

    19Fordy
    Member

    Read up on TORQUE ARMs.
     
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  11. 421-6Speed
    Joined: Dec 10, 2011
    Posts: 695

    421-6Speed
    Member

    This is how I did my 33 coupe. I didn't have room on top and didn't want to cut my mint original floors so i put the torque arm on the bottom. Used a 37-40 radious rod cut the end off and made a attachment out of 3/8" plate that runs up into the radius rod about 18". 20200723_170610.jpg 20200723_170626.jpg 20200724_160823.jpg
     
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  12. 19Fordy
    Joined: May 17, 2003
    Posts: 7,231

    19Fordy
    Member

    Is that torque arm you made using a radius rod strong
    enough when compared to the size of the stock torque tube? Radius rods
    are not very beefy.
     
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  13. gimpyshotrods
    Joined: May 20, 2009
    Posts: 18,359

    gimpyshotrods
    ALLIANCE MEMBER

    That is on the same plane as the radius rods, and thus provides no triangulation.

    It simply adds another thing to bend.
     
  14. trey32
    Joined: Jul 27, 2014
    Posts: 287

    trey32

    Yeah, you really need an upper link...
     
  15. Fortunateson
    Joined: Apr 30, 2012
    Posts: 4,129

    Fortunateson
    Member

    Would flipping that link be enough to create the triangulation?
     
  16. The upper link and triangulation is sort of a New-stalgia thing. It works well, perhaps is more sound building practice from an engineering standpoint, but the bones were just split and landed on the frame for decades.

    I am not saying that the triangulation and the torque stay is not a good idea but in actual practice it was not done as a common practice in the era that we normally shoot for. IE either will work you just have to decide what is acceptable for you.

    I like both setups personally. But you have to remember I like a lot of different suspension setups. :D
     
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  17. trey32
    Joined: Jul 27, 2014
    Posts: 287

    trey32

    I'ma guessing it would interfere with the bottom of his floor...
     
  18. Jmountainjr
    Joined: Dec 29, 2006
    Posts: 1,364

    Jmountainjr
    ALLIANCE MEMBER

    I think the split rear bones survived in the flathead era. When the OHV stuff came along and some found their way into a hot rod with a later trans and open drive line probably was the end of safely running split bones on the rear without reinforcements.
     
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  19. chopt49
    Joined: Jul 5, 2006
    Posts: 945

    chopt49
    Member

    Thanks everyone for the feedback.

    Few more question:

    Can I use Tie Rod ends to attach the Radius arm to the underside of the frame or are they too weak?
    Are 4 bar ends better suited for this? Yet the give no articulation...

    I plan to run the Torque arm as stated by a few here.
     
  20. chopt49
    Joined: Jul 5, 2006
    Posts: 945

    chopt49
    Member

    I agree and was under the same thought when I started this project.

    I will be running a almost stock Flathead and 3 speed top loader. So I assumed (I know what that can do) it would not be a earth twisting set up yet since I will have an open driveline now this opens challenges.
     
  21. neilswheels
    Joined: Aug 26, 2006
    Posts: 934

    neilswheels
    Member
    from England

    Some not so great shots of mine.
     

    Attached Files:

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  22. neilswheels
    Joined: Aug 26, 2006
    Posts: 934

    neilswheels
    Member
    from England

    ..and heres a few other ideas, not saying they're all good, just pics I found when i was deciding what to do with mine.
     

    Attached Files:

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  23. chopt49
    Joined: Jul 5, 2006
    Posts: 945

    chopt49
    Member

    Great pictures, thanks for sharing.

    Did you fabricate the Torque Arms system or was it a kit?
     
  24. chopt49
    Joined: Jul 5, 2006
    Posts: 945

    chopt49
    Member

    Update, I mocked it up (Tack-welds only)
     

    Attached Files:

  25. I would gusset the tie rod end tabs.
     
  26. chopt49
    Joined: Jul 5, 2006
    Posts: 945

    chopt49
    Member

    I plan to add side gussets to tab they mount on, to add side stability. Then I will construct the Torque Arm.
     
    X38 likes this.
  27. PotvinV8
    Joined: Mar 30, 2009
    Posts: 133

    PotvinV8
    Member

    Make sure the output shaft of the trans and the input of the rear is in "sync" at ride height before you finalize anything. Looks good.
     
  28. So no split bones from '49 on?

    split bones are still working fine they are just not cool if you are a Monday morning engineer.
     
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  29. Andy
    Joined: Nov 17, 2002
    Posts: 4,765

    Andy
    Member

    If you make a mounting plate for the radius rods that drop them down a couple of inches or more you will have no problems. You would not need the extra torque arm. The math is tricky but if the rods are centered on the axle and you move them down half the distance to the ground, the bending loads are cut in half. I did that when I put a set an a friends car. He ran a 383 sbc and 350 trans. He drove it hard for years. I would check on them every so often. They stayed straight.
    The thing that is hard to get your mind around is that the math says that if they were all the way to the pavement, there would be NO bending loads!!
    Dropping them down also helps a bunch for clearance to the frame sides.
     
    HemiDeuce likes this.
  30. eicke
    Joined: Jul 30, 2012
    Posts: 63

    eicke
    Member

    Yea but your messing with driveline angles.
     

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