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Re: A case of death wobble today

You got it. I was referring to the REALLY old stuff, vintage 30's
and 40's, 2 cylinder, no power anything. JD A's & B's, and
similar. Any kind of cyliner will be naturally limited by fluid
viscosity and port sizes.

L.W.(ßill) ------ III wrote:
> The hydraulic ram use for the power steering of old trucks and
> wheel tractors is a good substitute for the tie rod dampener.
> God Bless America, ßill O|||||||O
> mailto:-------------------- http://www.----------.com/
>
> Roy J wrote:
>
>>Actually, since you see the stabilizers on most later model 4x4's
>>(but not most other vehicles) I would SPECULATE that they are
>>there to cut the shock loading to the steering wheel and driver
>>when you hit a rock or pot hole. Without one, the steering wheel
>>will spin violently, the front wheel will twist up against it's
>>stop. Not a good thing at any kind of speed. The old tractors
>>commonly had a steering knob bolted to the steering wheel, quite
>>a few broken wrists as a result. Power steering calms this down a
>>lot, but you still can get quite a bit of feed back from the wheels.
>>
>>Oh, and I can easily block the virus loads with a decent anti
>>virus. The problem was that I do not have 'always on' ISP
>>service, my ISP would shut down my account when it hit 15mb worth
>>of files. As in about 4 hours. A guy has to sleep sometimes.

Re: A case of death wobble today

Since this seems to be the argument of the week, I went off and
did some calculations. Sigh. I hate being an engineer.

A while back there was a guy from the east coast, helicopter
pilot, etc that had a built TJ (sorry I can't pull up his name)
and we got into the discussion of DW on the TJ. He finally
convinced me that big tires need LESS caster than stock tires
(say about 5 degrees) rather than the 6 to 7 degrees on the
various shop specs. And that the toe in on big tires needs to be
as close to zero as you can get and still be toe in.

The OP stated that he has the 1" lift Confer shackles (that are
2" longer than stock) Sin (2"/45") is 2.56 degrees. So the OP is
shorting himself 2.5 degrees on the caster (unless he has added
the appropriate shims of course) Every inch lowering in the front
shaves another .6 degree off the caster. So if he hits the brakes
and gets 3" of front dive, he shaves another 2 degrees off the
caster. If he has any permamanet spring wrap, he will shave off
some more. (35" tires and a D60 probably means he pushes it a
little!)

The OP stated that he has high mileage on his 35" tires. Most of
us have not solved the problem of perfect wear on big tires so
I'll assume that they are not worn evenly. He did not state if he
had balanced them lately but even then, did he shuck a wheel weight?

The OP has the reversed tie rod , this changes things from what
most of us run.

Th OP told Dynatrac about his vehicle, did he indicate he was
going to use the Confer shackles? And does Dynatrac set up the
axle for a specified caster angle??? Ie do they do factory stock
or what works??

When we tackle a harmonic vibration problem (and this is a
special case of the general theory) we have 4 basic methods to
deal with things:
1) change the freqeuency of the system
2) "Stiffen" the system to move the harmonic up higher.
3) Dampen the system
4) Reduce the input energy at the vibration frequency to keep if
from going off.

In a Jeep, #1 is tough, it has to move through a range of
frequencies (speeds)

#2 involves tightening up the slop in the system (tie rod ends,
ball joints, heavier tie rod, etc) Plus you need enough toe in to
keep the system preloaded one direction.

#3 is the infamous steering stabilzer.

#4 is mostly from the tires. They need to be dynamicly balanced
at the frequency in question (about 60 mph) AND they need to be
round and straight. Keep in mind that 35" tires run almost 100
pounds a piece, I have seen them worn down with up to 1/4" cups
and waves in them. Lots of side energy available here.

Net: I'll sit here and speculate that the actual caster is way
less than the OP thinks it is, that the tires are worn and out of
balance (not a lot but enough!), that he hit the brakes and a
bump with a bit of a turn, the whole works started to shake, and
the steering stabilzer was not up to the job of getting control
back. Take your choice of fixes, I personally prefer naturally
stable systems to ones that are subject to failure from the
fatigue of a single component.

Cheers.

CRWLR wrote:

> Think of how the forks on a motorcycle are raked. A chopper goes straighat
> ahead really good, but can be a bitch to turn, and a racing bike can turn on
> a dime, but the steering is very twitchy. The most significant difference in
> these examples is the rake of the forks, and this rake is similar to the
> Caster angle.
>
> As I said earlier, caster typically does not play a large role in the
> adjustments of the front end geometry because it is pretty much set during
> manufacturing of the axle. The spring perches define the caster angle.
> Assuming the axle is the right one, the caster angle should be right. Of
> course, with custom modifications - lift - the caster angle can change
> enough to become a player in DW.
>
> Caster angle is the imaginary line through the upper and lower ball joints,
> and the center of the spindle. Properly set, the caster angle should be
> about 7° towards the rear of the vehicle. That is, the upper ball joint
> should trail the lower by about 7°. Perhaps the number is a little bit
> different in your case, but greater angles will be more stable than lesser
> angles. When the angle drops to about 4° or less, then the tires willsearch
> for the straight ahead position, and this sets up the DW symptoms. There is
> an easy test for Caster angle ... Go to an open area and make a Uturn, or a
> manuver that simulates what you might do when backing from a parking stall.
> Turn the steering wheel fully to one stop, then begin going and see if the
> wheel returns to center on its own, or if it remains in Turning Mode and
> requires you to physically turn back to center. If you have to drive itback
> to straight ahead, then your caster is not great enough, but if it wants to
> go to center on its own, then the caster is probably OK.
>
> In my motorcycle analogy, there are other geometry forces at play, so the
> analogy breaks down pretty quickly, but in general terms, it works pretty
> well. I am certain that my analogy will be corrected, but it works for now.
>
> My FSM says the spec for Caster angle is 6°.
>
>
>
>
>
> "Terry Jeffrey" <twjeffrey@hotmail.com> wrote in message
> news:a5SZb.4126$aT1.454@newsread1.news.pas.earthli nk.net...
>
>>The ball joints appear to be good. I did the push-pull-raised-tire test
>
> and
>
>>it checked out Ok. All the rod ends are tight and lubed. I'll get the
>>caster checked out next week. Explain, if you will, why caster would be a
>>player in DW. This could be my problem. If the caster angle is off,
>>wouldn't this only cause the vehicle to pull to one side or the other?
>>
>>It was suggested to move the steering stabilizer from the drag link to the
>>tie rod. When I did this, I still got the same DW. I thought I felt a
>>little air in the stabilizer at the extended end while testing it, and
>
> will
>
>>replace it as soon as I can find one.
>>
>>Your track bar comment is noted. I'd like to leave it off all together
>>because real estate up front is a premium right now with the Dana60. But
>>will put it back on nice and tight and put the DW to the test again.
>>
>>Thanks again,
>>Terry.
>>
>>
>>
>>
>>"CRWLR" <CRWLRJEFF@YAHOO.COM> wrote in message
>>news:103foc9kj445236@corp.supernews.com...
>>
>>>If all of that stuff is new, I would not think the steering stabalizer
>>
>>would
>>
>>>be so significant. Did you attempt the tests that I described? (If I
>>>described something incorrectly, did you try what might have been
>>
>>suggested
>>
>>>to correct me?)
>>>
>>>If you suspect the track bar is worn, and causing a problem with
>>
>>looseness,
>>
>>>then removing the trackbar altogether is not much of a confirmation
>
> test.
>
>>If
>>
>>>yo had no trackbar, and complained of DW, then put the bar on to see if
>>
>>the
>>
>>>DW went away, then you would have a reasonable diagnostic test. Taking
>
> the
>
>>>trackbar off is the same thing as having one on that had worn bushings.
>>>

Re: A case of death wobble today

In <1Yf_b.131$pT1.86178@news.uswest.net> Roy J wrote:

> A while back there was a guy from the east coast, helicopter=20
> pilot, etc that had a built TJ (sorry I can't pull up his name)=20
> and we got into the discussion of DW on the TJ. He finally=20
> convinced me that big tires need LESS caster than stock tires=20

That sounds like Harry B.

----------------------------------------------------
Del Rawlins- del@_kills_spammers_rawlinsbrothers.org
Remove _kills_spammers_ to reply via email.
Unofficial Bearhawk FAQ website:
http://www.rawlinsbrothers.org/bhfaq/

Re: A case of death wobble today

As an engineer, you will notice the TJ uses control arms that form
a radius, mounted behind the front axle so the higher the lift the more
castor he looses as the axle swings down and towards the back of the
car. So in a braking dip he would in temporally gain some of those
degrees back. Of course, Terry here, has Real Jeep leaf springs, that
are not effected by height.
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/

Roy J wrote:
>
> Since this seems to be the argument of the week, I went off and
> did some calculations. Sigh. I hate being an engineer.
>
> A while back there was a guy from the east coast, helicopter
> pilot, etc that had a built TJ (sorry I can't pull up his name)
> and we got into the discussion of DW on the TJ. He finally
> convinced me that big tires need LESS caster than stock tires
> (say about 5 degrees) rather than the 6 to 7 degrees on the
> various shop specs. And that the toe in on big tires needs to be
> as close to zero as you can get and still be toe in.
>
> The OP stated that he has the 1" lift Confer shackles (that are
> 2" longer than stock) Sin (2"/45") is 2.56 degrees. So the OP is
> shorting himself 2.5 degrees on the caster (unless he has added
> the appropriate shims of course) Every inch lowering in the front
> shaves another .6 degree off the caster. So if he hits the brakes
> and gets 3" of front dive, he shaves another 2 degrees off the
> caster. If he has any permamanet spring wrap, he will shave off
> some more. (35" tires and a D60 probably means he pushes it a
> little!)
>
> The OP stated that he has high mileage on his 35" tires. Most of
> us have not solved the problem of perfect wear on big tires so
> I'll assume that they are not worn evenly. He did not state if he
> had balanced them lately but even then, did he shuck a wheel weight?
>
> The OP has the reversed tie rod , this changes things from what
> most of us run.
>
> Th OP told Dynatrac about his vehicle, did he indicate he was
> going to use the Confer shackles? And does Dynatrac set up the
> axle for a specified caster angle??? Ie do they do factory stock
> or what works??
>
> When we tackle a harmonic vibration problem (and this is a
> special case of the general theory) we have 4 basic methods to
> deal with things:
> 1) change the freqeuency of the system
> 2) "Stiffen" the system to move the harmonic up higher.
> 3) Dampen the system
> 4) Reduce the input energy at the vibration frequency to keep if
> from going off.
>
> In a Jeep, #1 is tough, it has to move through a range of
> frequencies (speeds)
>
> #2 involves tightening up the slop in the system (tie rod ends,
> ball joints, heavier tie rod, etc) Plus you need enough toe in to
> keep the system preloaded one direction.
>
> #3 is the infamous steering stabilzer.
>
> #4 is mostly from the tires. They need to be dynamicly balanced
> at the frequency in question (about 60 mph) AND they need to be
> round and straight. Keep in mind that 35" tires run almost 100
> pounds a piece, I have seen them worn down with up to 1/4" cups
> and waves in them. Lots of side energy available here.
>
> Net: I'll sit here and speculate that the actual caster is way
> less than the OP thinks it is, that the tires are worn and out of
> balance (not a lot but enough!), that he hit the brakes and a
> bump with a bit of a turn, the whole works started to shake, and
> the steering stabilzer was not up to the job of getting control
> back. Take your choice of fixes, I personally prefer naturally
> stable systems to ones that are subject to failure from the
> fatigue of a single component.
>
> Cheers.
>
> CRWLR wrote:
>
> > Think of how the forks on a motorcycle are raked. A chopper goes straighat
> > ahead really good, but can be a bitch to turn, and a racing bike can turn on
> > a dime, but the steering is very twitchy. The most significant difference in
> > these examples is the rake of the forks, and this rake is similar to the
> > Caster angle.
> >
> > As I said earlier, caster typically does not play a large role in the
> > adjustments of the front end geometry because it is pretty much set during
> > manufacturing of the axle. The spring perches define the caster angle.
> > Assuming the axle is the right one, the caster angle should be right. Of
> > course, with custom modifications - lift - the caster angle can change
> > enough to become a player in DW.
> >
> > Caster angle is the imaginary line through the upper and lower ball joints,
> > and the center of the spindle. Properly set, the caster angle should be
> > about 7° towards the rear of the vehicle. That is, the upper ball joint
> > should trail the lower by about 7°. Perhaps the number is a little bit
> > different in your case, but greater angles will be more stable than lesser
> > angles. When the angle drops to about 4° or less, then the tires will search
> > for the straight ahead position, and this sets up the DW symptoms. There is
> > an easy test for Caster angle ... Go to an open area and make a Uturn, or a
> > manuver that simulates what you might do when backing from a parking stall.
> > Turn the steering wheel fully to one stop, then begin going and see if the
> > wheel returns to center on its own, or if it remains in Turning Mode and
> > requires you to physically turn back to center. If you have to drive it back
> > to straight ahead, then your caster is not great enough, but if it wants to
> > go to center on its own, then the caster is probably OK.
> >
> > In my motorcycle analogy, there are other geometry forces at play, so the
> > analogy breaks down pretty quickly, but in general terms, it works pretty
> > well. I am certain that my analogy will be corrected, but it works for now.
> >
> > My FSM says the spec for Caster angle is 6°.
> >
> >
> >
> >
> >
> > "Terry Jeffrey" <twjeffrey@hotmail.com> wrote in message
> > news:a5SZb.4126$aT1.454@newsread1.news.pas.earthli nk.net...
> >
> >>The ball joints appear to be good. I did the push-pull-raised-tire test
> >
> > and
> >
> >>it checked out Ok. All the rod ends are tight and lubed. I'll get the
> >>caster checked out next week. Explain, if you will, why caster would be a
> >>player in DW. This could be my problem. If the caster angle is off,
> >>wouldn't this only cause the vehicle to pull to one side or the other?
> >>
> >>It was suggested to move the steering stabilizer from the drag link to the
> >>tie rod. When I did this, I still got the same DW. I thought I felt a
> >>little air in the stabilizer at the extended end while testing it, and
> >
> > will
> >
> >>replace it as soon as I can find one.
> >>
> >>Your track bar comment is noted. I'd like to leave it off all together
> >>because real estate up front is a premium right now with the Dana60. But
> >>will put it back on nice and tight and put the DW to the test again.
> >>
> >>Thanks again,
> >>Terry.
> >>
> >>
> >>
> >>
> >>"CRWLR" <CRWLRJEFF@YAHOO.COM> wrote in message
> >>news:103foc9kj445236@corp.supernews.com...
> >>
> >>>If all of that stuff is new, I would not think the steering stabalizer
> >>
> >>would
> >>
> >>>be so significant. Did you attempt the tests that I described? (If I
> >>>described something incorrectly, did you try what might have been
> >>
> >>suggested
> >>
> >>>to correct me?)
> >>>
> >>>If you suspect the track bar is worn, and causing a problem with
> >>
> >>looseness,
> >>
> >>>then removing the trackbar altogether is not much of a confirmation
> >
> > test.
> >
> >>If
> >>
> >>>yo had no trackbar, and complained of DW, then put the bar on to see if
> >>
> >>the
> >>
> >>>DW went away, then you would have a reasonable diagnostic test. Taking
> >
> > the
> >
> >>>trackbar off is the same thing as having one on that had worn bushings.
> >>>