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Technical Violent front end shaking

Discussion in 'Traditional Hot Rods' started by spillaneswillys, Jul 22, 2016.

  1. There is one other thing is just thought about. I had jacked the front end up to get underneath and tighten up the oil and trans pan. Just wondering if knocked something out that way.
     
  2. F&J
    Joined: Apr 5, 2007
    Posts: 13,219

    F&J
    Member

    I think I mentioned earlier, that maybe you clipped the tie rod with the jack, but that I doubted it. If your alignment guy set the toe, he would have spotted a bent tie rod as soon as he turned it to adjust it.

    any bend on a tie rod is food for a wobble. As one wheels hits the bump, it tries to "push" the tie rod against the caster of the other wheel. So a slight bend would then make the rod flex, which helps to start a chain reaction
    .
    .
     
  3. DeucemanLt1
    Joined: Aug 15, 2014
    Posts: 145

    DeucemanLt1

  4. manyolcars
    Joined: Mar 30, 2001
    Posts: 8,389

    manyolcars

    When you split the wishbones, you must measure the wheelbase on both sides of the car. Make sure both sides are the same
     
  5. F&J
    Joined: Apr 5, 2007
    Posts: 13,219

    F&J
    Member

    Not to beat a dead horse on "scrub radius" and "too much caster" issues...but ..

    If you have a weak tie rod, or a slight bend on any hotrod with those long I beam tierods.. If your scrub radius is wrong and the tire is outwards too far from the king pin line, hitting a bump or hole will greatly increase the "pushing force" on the tie rod. It's more leverage. Then if the caster is too positive, that opposite wheel resists steering as easily, because the caster makes the wheel want to stay straight.

    so, you are trying(with increased leverage) to shove a "more unmovable object" with a weak or bent rod. It will flex a lot more....not to mention the forces now increased to other things like poor shackle angles, etc.

    incorrect caster and scrub can't be ignored...but they can be side stepped by doing other things to offset the problems they can cause.

    The entire car needs looking at, as was mentioned by others.

    .
     
  6. Atwater Mike
    Joined: May 31, 2002
    Posts: 10,347

    Atwater Mike
    ALLIANCE MEMBER

    This reminds me of the prescribed Magoo panhard rod. "You BETTER have one..."
     
  7. The problem is you guys understand what you are saying. I am a carpenter and dont. Is there anyone near Johnstown Pa that is a pro at this. I will trailer somewhere if I have to.
     
  8. Kerrynzl
    Joined: Jun 20, 2010
    Posts: 2,284

    Kerrynzl
    Member

    A panhard bar is a really good add-on with split bones .
    I asked the OP to post a photo of the front spring and shackle angle [I'm still waiting]

    With split bones the shackles need to be almost horizontal at ride height or you end up with shackle wobble [ the bones parallelogram themselves as the axle shifts sideways ]
    The arc of the shackles and caster both are height correcting [or height sensitive]
    If the shackles are in the approx 45degrees to vertical range, a panhard bar is the best remedy
     
  9. dana barlow
    Joined: May 30, 2006
    Posts: 4,152

    dana barlow
    Member
    from Miami Fla.
    1. Y-blocks

    Photos of your frontend will help a lot,very often a good eye can pick out the prob in a photo that lots of talk can't. always cover.
     
  10. Had that on my F-500. Tire shop found a bent rim ,replaced that & no more wobble. Not saying that is your problem but you might check your wheels for running true.
     
  11. OK here are some new pics. I adjusted the steering as F&J said. It made the steering better but didn't fix the wobble. So I came home and looked at the wheels and the drivers side is angled as the passenger side appears straight. It's getting dark so the pics might be hard to see.
     

    Attached Files:

  12. I just checked the tilt of the wheels and they both appear to be plumb no tilt at all
     
  13. F&J
    Joined: Apr 5, 2007
    Posts: 13,219

    F&J
    Member

    I've been fooled by optics on cameras before, but I see what you are talking about, so it's not all just camera. Driver side sure does look odd

    Something is very wrong, because that is a repro axle from what little I can see. If it is repro, you'd not expect to see that camber problem. (an old home done dropped axle might come out wrong, but not a forged or cast repro IMO)

    Next thing is to see if the king pins went bad? That would let the wheels do that. Jack it up, squat along side of tire, and grab top and bottom of tire and see if it will move like the pin is sloppy.

    You said you are a carpenter...get levels and a square. Check the floor across the front, if level, use the carpenters square along the tire. That will show what it has for tilt. If the floor is wavy, run a long level or straight edge in front of both tires.

    I see other things.... but start with the angles and check the king pins for slop first
    .
     
  14. The axle was a new Super Bell. All the suspension parts are new, 1500 miles, probably not even that. I did x check the kingpins when this first started. I will square up the wheels tomorrow, thanks for all the help, I just don't know what to do and I am scared to drive it.
     
  15. F&J
    Joined: Apr 5, 2007
    Posts: 13,219

    F&J
    Member

    Can we get some input from other builders here? The OP said in his first thread, first post; "been driving it 1.5 yrs, greased it and noticed brake dragging"

    I don't use repro axles or spindles, and is it crazy to ask if anyone ever had a repro spindle snout bend? If so, could that be why the camber is wrong now, and might explain brake drag? I can't see how, but I ask anyways.

    .
    Yes double check the pins and try to get a level surface for the square. We don't need a measurement of the angle, we need to know if the top of tire is tipped IN, towards the motor/rad

    .
     
  16. AmishMike
    Joined: Mar 27, 2014
    Posts: 497

    AmishMike
    Member

    A repro axle is always perfect? I believe another HAMB site someone posted they found camber differed from one side of axle to other. OEM always perfect - have an air bag recalled? how about ignition switch? or maybe you drive a VW diesel?
     
  17. F&J
    Joined: Apr 5, 2007
    Posts: 13,219

    F&J
    Member

    The crappy part about talking on the net, is that it's not like talking to a person standing there. In person, you'd question what I said and I'd explain further..

    I did not make it clear enough. What I was getting at, is that several members in the other thread agree that something has changed since it was first built and driven 3000? miles.

    I find it hard to believe that Koz, who built it, would not have seen it when he assembled it. Yes I saw a repro on here shipped to Scandinavia, and the guy asked about the severe positive camber after he installed it, but it was equal, both sides.

    crazy that this car was just looked at by a shop?...and all they found was toe adjustment?

    .
     
  18. David Chandler
    Joined: Jan 27, 2007
    Posts: 1,101

    David Chandler
    Member

    Isn't a "Super Bell" a cast ductile axle? If that it true, then it's possible it is bent, seeing how this started with hitting something. Like everyone else said check everything!
    Good luck!
     
  19. 53 ford
    Joined: Apr 8, 2012
    Posts: 143

    53 ford
    Member

    In post 48 the shackle looks to be almost straight up. The spring may have settled over time and relived tension on the shackles. I would start with a dead perch on one side and not worry about a pan-hard bar. I would redo the steering arm to level the drag link. Shorten the radius rods to the center of the steering box and that will eliminate most if not all bump steer. My hillbilly opinion, Harley
     
  20. Kerrynzl
    Joined: Jun 20, 2010
    Posts: 2,284

    Kerrynzl
    Member

    That is why I requested photos of the front end showing the spring shackle arrangement ,The OP responded with photos of the grill, so I guess he doesn't really want our help [he even started a 2nd thread]http://www.jalopyjournal.com/forum/threads/death-wobble-update.1027731/
    You and myself have both guessed the same predicament [ I dont think photos in post #48 are clear enough to be conclusive ]
    It has a geometry issue, but not caster/camber geometry. I personally think it is shackle angle geometry caused by the spring eyes being too far apart [reverse eyed/flattened spring]
    The axle is shifting sideways [shackle wobble] and the split bones are not helping.
    The OP needs to shorten the spring or shackles or add a long panhard bar [this can be added to one of the bones]

    Lets see if we can keep the guessing game going to 200+ posts Flogging a Dead Horse.jpg
     
    Last edited: Jul 31, 2016
  21. Mart
    Joined: Mar 3, 2001
    Posts: 4,287

    Mart
    Member

    Ok, I'll chip in here. The geometry is not as Ford intended. The drag link is heading uphill to the steering arm at the spindle. This gives a conflict of arcs between the drag link and the radius rods. You need to modify that steering arm to lower the front of the drag link as much as possible.

    I think that you have a severe bump steer issue which triggers the death wobble.

    I had the same bump steer issue on my 33 coupe and modified the steering arm to lower it. I also made an adjustable length drag link so I could get the steering box in it's sweet spot when the wheels are straight. These mods made a real perceptible improvement over bumps.

    You say going over the railway tracks sets it off. It's bump steer initialising the problem.

    Here's a before pic:
    [​IMG]
    And an after pic:
    [​IMG]

    Mart.
     
  22. F&J
    Joined: Apr 5, 2007
    Posts: 13,219

    F&J
    Member

    These threads are a learning/sharing tool, useful to all of our future builds.

    "guesses" are part of sharing knowledge.

    By the way, the only car I have ever owned with true low speed violent DW that I mentioned way back, was a 50's built, 1930 Mopar fullfender roadster with a later 30s Dodge wavy tube axle on parallel leaf springs. Kinda, sorta, blows the theory of transverse spring shackle angles being the likely suspect of DW events.

    The only other car I have ridden in that had violent low speed DW; a 50s built 33 Ford that was perfect until an automatic trans swap forced the bones to be split, but discs were added at the same time.(scrub changed). He claims he tried different caster by raising/lowering bone ends, but gave up and added a damper. DW was gone, but he says he can still "sense" the original unknown problem on that "perfect" bump.

    That makes me "think" that caster and scrub can induce much more sideways forces on transverse or parallel springs. So, what comes first?, the chicken or the egg

    .
     
  23. F&J
    Joined: Apr 5, 2007
    Posts: 13,219

    F&J
    Member

    The reason I like reading all the input from all of the posters, is that it makes me think more.

    Reading about what was just said about drag link angle/bump steer, makes me sit here and wonder what exactly happens to the OPs car at that same railroad track crossing; Does the DW event start because one wheel hits a rail and shoves the other wheel/and-or front springs, or is it the left front tire lifting or dropping to cause a bump steer which then moves the other wheel/and-or springs?

    there is always a certain initial movement of something, that starts the chain reaction. We are jumping all around trying to either find a way to stop the chain reaction that is starting(P-bar or damper), or is it lessening the forces that actually start the chain reaction (geometry)
    .
     
  24. manyolcars
    Joined: Mar 30, 2001
    Posts: 8,389

    manyolcars

    Follow instructions. Measure the wheelbase on both sides of the car. They must be the same.
     
  25. Drivers side
     

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  26. Pics
     

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  27. More
     

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  28. More
     

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  29. How would I modify the drag link to make it more level? This is much to take in that is why I started another post,
    I squares both wheels and they both tilt in a few degrees
     
  30. If you have the room flip your upper steering arm 180 degree's to where it's a dropped arm. You would also have to spin the tie rod end 180 degree's as it would now be on top of the arm rather than underneath it. Looks like this would get the drag link much more level, again only if you have the room/ clearances to do this.
     

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