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.
> >>>

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.
> >>>

Re: A case of death wobble today
 

On Sun, 22 Feb 2004 21:44:14 -0800, L.W.(ßill) ------ III
<----------@cox.net> wrote:

> 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.

They would be if some of the height is gained by using the lift
shackles. I was looking at these as a cheap way to lift my YJ, but it
didn't take an engineer to tell me that lifing one end of the springs
is going to rotate the axle and thus change the castor angles.

--
Old Crow
'82 Shovelhead FLT 92" 'Pearl'
'95 Jeep YJ Rio Grande
ASE Certified Master Auto Tech + L1
TOMKAT, BS#133, SENS, MAMBM, DOF#51

Re: A case of death wobble today
 

On Sun, 22 Feb 2004 21:44:14 -0800, L.W.(ßill) ------ III
<----------@cox.net> wrote:

> 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.

They would be if some of the height is gained by using the lift
shackles. I was looking at these as a cheap way to lift my YJ, but it
didn't take an engineer to tell me that lifing one end of the springs
is going to rotate the axle and thus change the castor angles.

--
Old Crow
'82 Shovelhead FLT 92" 'Pearl'
'95 Jeep YJ Rio Grande
ASE Certified Master Auto Tech + L1
TOMKAT, BS#133, SENS, MAMBM, DOF#51

Re: A case of death wobble today
 

On Sun, 22 Feb 2004 21:44:14 -0800, L.W.(ßill) ------ III
<----------@cox.net> wrote:

> 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.

They would be if some of the height is gained by using the lift
shackles. I was looking at these as a cheap way to lift my YJ, but it
didn't take an engineer to tell me that lifing one end of the springs
is going to rotate the axle and thus change the castor angles.

--
Old Crow
'82 Shovelhead FLT 92" 'Pearl'
'95 Jeep YJ Rio Grande
ASE Certified Master Auto Tech + L1
TOMKAT, BS#133, SENS, MAMBM, DOF#51

Re: A case of death wobble today
 

Have you tried going to your webmail site and using SPAM/VIRUS blocking
there? If you do that, your unwanted emails will get automatically
deleted and won't clog your acct up. There is no reason to change email
addresses in most cases.

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.

--
__________________________________________________ _________
tw

03 TJ Rubicon - Rubicon Express 4.5"
01 XJ Sport

There is a very fine line between "hobby" and "mental illness."
-- Dave Barry

Pronunciation: 'jEp
Function: noun
Date: 1940

Etymology: probably from g. p. (abbreviation of general purpose)
A small general-purpose motor vehicle with 80-inch wheelbase,
1/4-ton capacity, and four-wheel drive used by the U.S. army in
World War II.

(Please remove the OBVIOUS to reply by email)
__________________________________________________ _________

Re: A case of death wobble today
 

Have you tried going to your webmail site and using SPAM/VIRUS blocking
there? If you do that, your unwanted emails will get automatically
deleted and won't clog your acct up. There is no reason to change email
addresses in most cases.

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.

--
__________________________________________________ _________
tw

03 TJ Rubicon - Rubicon Express 4.5"
01 XJ Sport

There is a very fine line between "hobby" and "mental illness."
-- Dave Barry

Pronunciation: 'jEp
Function: noun
Date: 1940

Etymology: probably from g. p. (abbreviation of general purpose)
A small general-purpose motor vehicle with 80-inch wheelbase,
1/4-ton capacity, and four-wheel drive used by the U.S. army in
World War II.

(Please remove the OBVIOUS to reply by email)
__________________________________________________ _________

Re: A case of death wobble today
 

Have you tried going to your webmail site and using SPAM/VIRUS blocking
there? If you do that, your unwanted emails will get automatically
deleted and won't clog your acct up. There is no reason to change email
addresses in most cases.

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.

--
__________________________________________________ _________
tw

03 TJ Rubicon - Rubicon Express 4.5"
01 XJ Sport

There is a very fine line between "hobby" and "mental illness."
-- Dave Barry

Pronunciation: 'jEp
Function: noun
Date: 1940

Etymology: probably from g. p. (abbreviation of general purpose)
A small general-purpose motor vehicle with 80-inch wheelbase,
1/4-ton capacity, and four-wheel drive used by the U.S. army in
World War II.

(Please remove the OBVIOUS to reply by email)
__________________________________________________ _________

Re: A case of death wobble today
 

Yep!

Del Rawlins wrote:

> 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
 

Yep!

Del Rawlins wrote:

> 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/