Death Wobble - Explanation - Page 2





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  1. #21
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    Quote Originally Posted by Jean Kotze View Post
    Why is this not a sticky yet?
    Rich

  2. #22
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    Was thinking about this a bit more today - our 1930 Graham Paige sometimes gets a death wobble at low speeds - you have to stop to make it go away

    Thankfully when it happens we might be going at about 30-40km/h

    I don't wanna know what it's like at a higher speed.

    PS. We have no idea why it does that
    '65 Jeep Wagoneer
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    Richard, the higher the speed, the more energy the beast has to feed from, the bigger the in your pants.
    '89 LR 110 V8

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    Mike, it's a good thing defenders are too scary to go over 80 or more people would understand the death wobble!

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    Quote Originally Posted by RichardMiddelmann View Post
    .......PS. We have no idea why it does that
    The maths for an exact solution is complicated, but the principle is simple. It is a resonance with positive feedback due to the interplay of axle lateral location stiffness and steering mechanism layout. At the "correct" speed, any small shimmy disturbance on the front wheels set the resonance in motion, the DW rapidly build from there. Theoretically a perfectly healthy set-up will also run into a DW, but the design parameters should ensure that it lies at an unatainable speed, even for a Jeep :-)
    Last edited by Mike N; 2012/01/27 at 10:04 PM.
    '89 LR 110 V8

  6. #26
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    Quote Originally Posted by Mike N View Post
    Actually quite common on Defenders, happens at lower speeds though, around 80 km/h (the road speed at which DW happens depends on the natural frequency of the front axle system, Jeeps have pressed plate light duty components not weighing much, therefore natural frequencies tend to be higher, Landies have proper solid heavy duty components, therefore the natural frequency is lower. )
    Had it four times in one day, at an ever decreasing speed. First one at 80km/h, second one at 65km/h, third at 60km/h. last one at 40km/h. That was in one trip trying to get home! Did the last few km's at 10km/h, to scared to go any faster.

    89 110 3.5 V8

  7. #27
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    Quote Originally Posted by Combrink View Post
    Had it four times in one day, at an ever decreasing speed. First one at 80km/h, second one at 65km/h, third at 60km/h. last one at 40km/h. That was in one trip trying to get home! Did the last few km's at 10km/h, to scared to go any faster.
    Chicken
    Rich

  8. #28
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    So this only happens with cars with solid axles??
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  9. #29
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    excellent post.
    WJ V8 4.7L, 2inch IronMan Suspension, 30mm spacers ,Maniac front diff truss, Iron Rock Adj TrackBar, Zone Steering Stabilizer, Bulli Prop, DIY BumpStops, 16" steelies with 265-75-16 Mud BF's
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  10. #30
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    Although it is not complete and not completely true on actual causes.

  11. #31
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    Quote Originally Posted by andre` View Post
    Although it is not complete and not completely true on actual causes.
    Andre, feel free to add. The benefit of this thread is that if something else is found, the user can add their experience/knowledge and everybody benefits.
    Rich

  12. #32
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    Can anyone say if the death wobble is more prevalent on coil sprung suspensions than the older leaf sprung setups. I'm working on a SFA for the Sani and this has been something that has bugged me for a long time.

    I have been through a death wobble on a Army Samil 20 that ended me in the bushes next to the road, and a 1983 Safari that would cause it's EFI ECU to reset due to the violence and the action. Both of these were leaf sprung.

    Most my research on the net (youtube) shows the problem on Coil and Panhard rod setups. Only found one on leaf type and nothing yet on 4 link.
    David/Hillbilly - 1997 SFA Nissan Sani 2,7 TD - 5" lift on 33" tires - Dual Transfer with 4.1 gears

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  13. #33
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    Quote Originally Posted by Jeep Luvva View Post
    Andre, feel free to add. The benefit of this thread is that if something else is found, the user can add their experience/knowledge and everybody benefits.
    I will do a complete write up on my experience in conjunction with Shane JKA. I had the whole whammy last month and there is a lot more involved.

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    Quote Originally Posted by andre` View Post
    I will do a complete write up on my experience in conjunction with Shane JKA. I had the whole whammy last month and there is a lot more involved.
    What lift kit did you fit to your Jeep??

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    Quote Originally Posted by HeinrichC View Post
    What lift kit did you fit to your Jeep??
    Whether the vehicle was lifted or not is also an important factor. When relaying your experience and solutions state whether the vehilce was lifted or not.

    Mine for instance is a standard WJ. Will post once the problem is solved.

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    Quote Originally Posted by andre` View Post
    I will do a complete write up on my experience in conjunction with Shane JKA. I had the whole whammy last month and there is a lot more involved.
    That would be great
    Rich

  17. #37
    andre` Guest

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    Quote Originally Posted by HeinrichC View Post
    What lift kit did you fit to your Jeep??
    I have an AEV kit that has been installed 2 years ago. My deathwobble was caused by everything on the front suspension and steering except the control arms failing at the same time. My ball joints had serious play, the one actually fell apart when it was pressed out, Tie rod, track bar, steering box. The steering box was reconditioned 3 times and eventually I decided to buy a new one. Even with everything new, if I fit the old OME damper, the death wobble is back. I have a standard damper now and I can feel the force of the 37" on the steering components. Will hopefully have a Fox damper by tomorrow.

  18. #38
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    Nice one Rich, finally a sticky \m/\m/
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  19. #39
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    Quote Originally Posted by andre` View Post
    I have an AEV kit that has been installed 2 years ago. My deathwobble was caused by everything on the front suspension and steering except the control arms failing at the same time. My ball joints had serious play, the one actually fell apart when it was pressed out, Tie rod, track bar, steering box. The steering box was reconditioned 3 times and eventually I decided to buy a new one. Even with everything new, if I fit the old OME damper, the death wobble is back. I have a standard damper now and I can feel the force of the 37" on the steering components. Will hopefully have a Fox damper by tomorrow.
    37's wow, now that's big

  20. #40
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    Quote Originally Posted by bfreesani View Post
    Can anyone say if the death wobble is more prevalent on coil sprung suspensions than the older leaf sprung setups. I'm working on a SFA for the Sani and this has been something that has bugged me for a long time.

    I have been through a death wobble on a Army Samil 20 that ended me in the bushes next to the road, and a 1983 Safari that would cause it's EFI ECU to reset due to the violence and the action. Both of these were leaf sprung.

    Most my research on the net (youtube) shows the problem on Coil and Panhard rod setups. Only found one on leaf type and nothing yet on 4 link.

    on a leaf spring set up, the leaves provide the transverse location (i.e. stop the axle shifting left to right) thus there is no possibility of serious death wobble.

    On most front axles with springs, axle location is by means of a panhard rod, so it's pretty much specific to the panhard rod (track bar for the 'mericans) systems, however, while I've never heard of watts linkage or 3 link location fitted to a steering axle, I am sure it could happen with any transverse link type locating system.

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