Home » Public Forums » GMCnet » Re: [GMCnet] New RV Buddies article
| Re: [GMCnet] New RV Buddies article [message #112730] |
Sun, 23 January 2011 09:59  |
Gary Casey
Messages: 448
Registered: September 2009
Karma: 0
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Senior Member |
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Hardie,
I think you have the right general idea. I'll comment on your points below:
Previously posted: "With the new 6-wheel rear suspension
and disc brakes, you can now stop on a dime."
Hardie: Has anyone actually done any braking distance runs? 60-0 in how many
feet? And where are the two extra wheels mounted?
My comment: You must be confused about the "two extra wheels." No extra
wheels. I guess the 4-wheel rear suspension and the 2-wheel front suspension
make up the "6-wheel" suspension. "Stop on a dime?" I think the shorter
stopping distance that is usually quoted is a result of running out of pedal
force capability with the standard system. Once the rears lock, at about 0.6
G's the pedal force increases disproportionately and I assume it reaches a point
that the driver runs out of ability to push harder. My rough estimate is that
it might take 150% as much pedal force than "expected" to get all 6 to lock.
Even with the new system I doubt that the fronts will ever lock. There have
been stopping distance tests done, but I don't recall ever reading about what
the limit was: Is the stopping limited by pedal force? Which wheels lock
first? The standard system will lock the rears at about 06 G's, well below the
ultimate limit of about 0.9 G's. How close does the "new" system come to that
limit? I have no idea.
Previously posted: "The “Chuck Aulgur Rear Anti-Skid Kit” prevents the back
rear wheels from skidding and having
the rear of the RV move in front of you.
It also eliminates torque on the center bogie arms
which provides for more effective braking on
all four rear wheels. Translation: Your coach is safer
and you won’t end up with four bald spots on
your tires after a panic stop."
Hardie: Does this overstate the case?
My comment: Yes. The rear wheels skidding (locking) does NOT dramatically
reduce stability, since the middles still have plenty of downforce. It's not at
all like a 4-wheel vehicle where rear lockup dramatically reduces stability.
And of course, you don't end up with "four bald spots", only 2 :-).
Hardie: If the rear wheels cannot be locked up (isn't that what it means if
they do not skid?) has anything been improved?
My comment: Hopefully, they can still be locked up - after all, that's the
purpose of a braking system; to provide as much braking effort as the driver
commands. Yes, it has been improved - the "torque link" suspension lessens the
tendency for the rears to lock and better balances the braking between the
middles and rears. Definitely a good thing.
Hardie: Clearly this text describes the effect of some sort of ABS technology,
which I do not think it actually implements, does it?
My comment: You're right - as far as I know, a real anti-lock, or Adaptive
Braking System (ABS) has never been implented in our coaches.
Hardie: If one pair locks up then retarding force would be reduced, but if the
other pair would continue to roll that would reduce the tendency to skid. I
thought that was the behavior we have with the stock system?
My comment: You are exactly correct.
Hardie: Does it 'eliminate torque' as he writes, or just change the way the
reaction forces influence the chassis? Eliminating the torque from brake
reaction is of course impossible. Changing how it affects the chassis and the
wheels, maybe.
My comment: Again, exactly correct. The "torque" on the bogie pins has
nothing to do with braking. What it does is reduce (not eliminate) the lifting
effect from the fronts and the down load from the rears. During braking it
effective "lengthens" the swing arm, a very good thing.
Hardie: The new system may well be better, but it would be helpful if someone
actually quantified this.
Hardie: Certainly in the last 30 years a lot has been learned about suspension
action under braking and acceleration, anti-dive and anti-squat are common
considerations for geometry these days, and if anyone has stepped up to the
plate for our coaches it is Jim and Chuck.
My comment: Just a slight correction - I think all the things we talk about
today were known in 1973. The difference, I think, is in the priorities
attached to the several factors involved: Production cost, ride control, ease
of height control for campsite leveling, brake wear, and of course finally,
braking performance. It's my opinion that braking performance to a back seat to
some of the other factors. Today we have a different perspective and braking
performance would be higher in the rankings.
Hardie: I am not saying the system is an ineffective use of time, money, and
effort, just it seems the level of rhetoric about the advantages is escalating.
Numbers would help.
My comment: I agree completely.
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| Re: [GMCnet] New RV Buddies article [message #112733 is a reply to message #112730] |
Sun, 23 January 2011 11:15  |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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I only pose one question. Why would any reasonable, thinking, person want to
"lock up the brakes" on a 12.000 pound vehicle? The shortest stopping
distances are achieved at some point before wheel lock up occurs.
Jim Hupy
Salem, Or
78 GMC Royale 403
On Sun, Jan 23, 2011 at 7:59 AM, Gary Casey <casey.gary@yahoo.com> wrote:
> Hardie,
> I think you have the right general idea. I'll comment on your points
> below:
>
> Previously posted: "With the new 6-wheel rear suspension
> and disc brakes, you can now stop on a dime."
>
> Hardie: Has anyone actually done any braking distance runs? 60-0 in how
> many
> feet? And where are the two extra wheels mounted?
>
> My comment: You must be confused about the "two extra wheels." No
> extra
> wheels. I guess the 4-wheel rear suspension and the 2-wheel front
> suspension
> make up the "6-wheel" suspension. "Stop on a dime?" I think the shorter
> stopping distance that is usually quoted is a result of running out of
> pedal
> force capability with the standard system. Once the rears lock, at about
> 0.6
> G's the pedal force increases disproportionately and I assume it reaches a
> point
> that the driver runs out of ability to push harder. My rough estimate is
> that
> it might take 150% as much pedal force than "expected" to get all 6 to
> lock.
> Even with the new system I doubt that the fronts will ever lock. There
> have
> been stopping distance tests done, but I don't recall ever reading about
> what
> the limit was: Is the stopping limited by pedal force? Which wheels lock
> first? The standard system will lock the rears at about 06 G's, well below
> the
> ultimate limit of about 0.9 G's. How close does the "new" system come to
> that
> limit? I have no idea.
>
> Previously posted: "The Chuck Aulgur Rear Anti-Skid Kit prevents the
> back
> rear wheels from skidding and having
>
> the rear of the RV move in front of you.
> It also eliminates torque on the center bogie arms
> which provides for more effective braking on
> all four rear wheels. Translation: Your coach is safer
> and you wont end up with four bald spots on
> your tires after a panic stop."
>
> Hardie: Does this overstate the case?
>
> My comment: Yes. The rear wheels skidding (locking) does NOT
> dramatically
> reduce stability, since the middles still have plenty of downforce. It's
> not at
> all like a 4-wheel vehicle where rear lockup dramatically reduces
> stability.
> And of course, you don't end up with "four bald spots", only 2 :-).
>
> Hardie: If the rear wheels cannot be locked up (isn't that what it means
> if
> they do not skid?) has anything been improved?
>
>
> My comment: Hopefully, they can still be locked up - after all, that's
> the
> purpose of a braking system; to provide as much braking effort as the
> driver
> commands. Yes, it has been improved - the "torque link" suspension lessens
> the
> tendency for the rears to lock and better balances the braking between the
> middles and rears. Definitely a good thing.
>
> Hardie: Clearly this text describes the effect of some sort of ABS
> technology,
> which I do not think it actually implements, does it?
>
> My comment: You're right - as far as I know, a real anti-lock, or
> Adaptive
> Braking System (ABS) has never been implented in our coaches.
>
> Hardie: If one pair locks up then retarding force would be reduced, but
> if the
> other pair would continue to roll that would reduce the tendency to skid.
> I
> thought that was the behavior we have with the stock system?
>
> My comment: You are exactly correct.
>
> Hardie: Does it 'eliminate torque' as he writes, or just change the way
> the
> reaction forces influence the chassis? Eliminating the torque from brake
> reaction is of course impossible. Changing how it affects the chassis and
> the
> wheels, maybe.
>
> My comment: Again, exactly correct. The "torque" on the bogie pins has
> nothing to do with braking. What it does is reduce (not eliminate) the
> lifting
> effect from the fronts and the down load from the rears. During braking it
> effective "lengthens" the swing arm, a very good thing.
>
> Hardie: The new system may well be better, but it would be helpful if
> someone
> actually quantified this.
>
> Hardie: Certainly in the last 30 years a lot has been learned about
> suspension
> action under braking and acceleration, anti-dive and anti-squat are common
> considerations for geometry these days, and if anyone has stepped up to
> the
> plate for our coaches it is Jim and Chuck.
>
> My comment: Just a slight correction - I think all the things we talk
> about
> today were known in 1973. The difference, I think, is in the priorities
> attached to the several factors involved: Production cost, ride control,
> ease
> of height control for campsite leveling, brake wear, and of course finally,
> braking performance. It's my opinion that braking performance to a back
> seat to
> some of the other factors. Today we have a different perspective and
> braking
> performance would be higher in the rankings.
>
> Hardie: I am not saying the system is an ineffective use of time, money,
> and
> effort, just it seems the level of rhetoric about the advantages is
> escalating.
> Numbers would help.
>
> My comment: I agree completely.
>
>
>
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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| Re: [GMCnet] New RV Buddies article [message #112739 is a reply to message #112735] |
Sun, 23 January 2011 12:05 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
|
Senior Member |
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|
Hardie, not only the pickups and trucks but the Aerostar and E line of full
size vans and perhaps others as well had rear wheel ABS. There were wheel
rotation sensors on both the front and rear wheels that were compared by the
computer. When the rear wheels would lock up as weight transferred to the
front end during hard braking, the ABS would come into play by rapidly
applying, then releasing the rear brakes, also turning on a red warning
light labeled ABS on the instrument cluster. The pickups and perhaps other
vehicles also had a valve that had a plunger on it that operated between the
axle housing and the frame the purpose of which was to sense the extent that
the vehicle was loaded. I think that the valve was a non electronic device.
So to answer your question, "was it mechanical or electronic?" Yes, some of
each.
Jim Hupy
Salem, OR
78 GMC Royale 403
On Sun, Jan 23, 2011 at 9:48 AM, Hardie Johnson <hardie.j@gmail.com> wrote:
>
>
> James Hupy wrote on Sun, 23 January 2011 12:15
> > I only pose one question. Why would any reasonable, thinking, person want
> to "lock up the brakes" on a 12.000 pound vehicle? The shortest stopping
> distances are achieved at some point before wheel lock up occurs.
> > Jim Hupy
> > Salem, Or
> > 78 GMC Royale 403
> > <>
> > > Hardie: If the rear wheels cannot be locked up (isn't that what it
> means if they do not skid?) has anything been improved?
> > <>
>
> Yes, that is correct, we do not want to skid to a stop, but if you can't
> lock them up then you can't get close to lockup and some braking is lost. It
> would be great if we could actually develop an ABS system. Ford pickups used
> to have rear wheel only ABS; does anyone know how that worked? Was it
> mechanical or electronic?
> --
> Hardie Johnson "Crashj"
> 1973 26 foot Glacier, White Thing
> Raleigh NC
> _______________________________________________
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| Re: [GMCnet] New RV Buddies article [message #112764 is a reply to message #112730] |
Sun, 23 January 2011 15:40 |
 |
USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Gary,
I wonder if someone should forward this email to RV Buddies! ;-)
Regards,
Rob M.
USAussie - Downunder
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Gary Casey
Sent: Monday, January 24, 2011 2:59 AM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] New RV Buddies article
Hardie,
I think you have the right general idea. I'll comment on your points below:
Previously posted: "With the new 6-wheel rear suspension
and disc brakes, you can now stop on a dime."
Hardie: Has anyone actually done any braking distance runs? 60-0 in how
many
feet? And where are the two extra wheels mounted?
My comment: You must be confused about the "two extra wheels." No
extra
wheels. I guess the 4-wheel rear suspension and the 2-wheel front
suspension
make up the "6-wheel" suspension. "Stop on a dime?" I think the shorter
stopping distance that is usually quoted is a result of running out of pedal
force capability with the standard system. Once the rears lock, at about
0.6
G's the pedal force increases disproportionately and I assume it reaches a
point
that the driver runs out of ability to push harder. My rough estimate is
that
it might take 150% as much pedal force than "expected" to get all 6 to lock.
Even with the new system I doubt that the fronts will ever lock. There have
been stopping distance tests done, but I don't recall ever reading about
what
the limit was: Is the stopping limited by pedal force? Which wheels lock
first? The standard system will lock the rears at about 06 G's, well below
the
ultimate limit of about 0.9 G's. How close does the "new" system come to
that
limit? I have no idea.
Previously posted: "The "Chuck Aulgur Rear Anti-Skid Kit" prevents the back
rear wheels from skidding and having
the rear of the RV move in front of you.
It also eliminates torque on the center bogie arms
which provides for more effective braking on
all four rear wheels. Translation: Your coach is safer
and you won't end up with four bald spots on
your tires after a panic stop."
Hardie: Does this overstate the case?
My comment: Yes. The rear wheels skidding (locking) does NOT
dramatically
reduce stability, since the middles still have plenty of downforce. It's
not at
all like a 4-wheel vehicle where rear lockup dramatically reduces stability.
And of course, you don't end up with "four bald spots", only 2 :-).
Hardie: If the rear wheels cannot be locked up (isn't that what it means
if
they do not skid?) has anything been improved?
My comment: Hopefully, they can still be locked up - after all, that's
the
purpose of a braking system; to provide as much braking effort as the driver
commands. Yes, it has been improved - the "torque link" suspension lessens
the
tendency for the rears to lock and better balances the braking between the
middles and rears. Definitely a good thing.
Hardie: Clearly this text describes the effect of some sort of ABS
technology,
which I do not think it actually implements, does it?
My comment: You're right - as far as I know, a real anti-lock, or
Adaptive
Braking System (ABS) has never been implented in our coaches.
Hardie: If one pair locks up then retarding force would be reduced, but if
the
other pair would continue to roll that would reduce the tendency to skid. I
thought that was the behavior we have with the stock system?
My comment: You are exactly correct.
Hardie: Does it 'eliminate torque' as he writes, or just change the way
the
reaction forces influence the chassis? Eliminating the torque from brake
reaction is of course impossible. Changing how it affects the chassis and
the
wheels, maybe.
My comment: Again, exactly correct. The "torque" on the bogie pins has
nothing to do with braking. What it does is reduce (not eliminate) the
lifting
effect from the fronts and the down load from the rears. During braking it
effective "lengthens" the swing arm, a very good thing.
Hardie: The new system may well be better, but it would be helpful if
someone
actually quantified this.
Hardie: Certainly in the last 30 years a lot has been learned about
suspension
action under braking and acceleration, anti-dive and anti-squat are common
considerations for geometry these days, and if anyone has stepped up to the
plate for our coaches it is Jim and Chuck.
My comment: Just a slight correction - I think all the things we talk
about
today were known in 1973. The difference, I think, is in the priorities
attached to the several factors involved: Production cost, ride control,
ease
of height control for campsite leveling, brake wear, and of course finally,
braking performance. It's my opinion that braking performance to a back
seat to
some of the other factors. Today we have a different perspective and
braking
performance would be higher in the rankings.
Hardie: I am not saying the system is an ineffective use of time, money,
and
effort, just it seems the level of rhetoric about the advantages is
escalating.
Numbers would help.
My comment: I agree completely.
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] New RV Buddies article [message #112775 is a reply to message #112740] |
Sun, 23 January 2011 16:15 |
 |
mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
Karma: 0
|
Senior Member |
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| storm'n wrote on Sun, 23 January 2011 10:06 |
Fords had some type of valve hooked with a linkage to the back axle that regulated the brake pressure, heavy load, more pressure,no load , light pressure. I don't think there was any ABS involved. ...
|
Late 70's Audi 5000s had the same type set-up. (Front wheel drive.) It was a valve like object connected to the rear axle by a spring. It worked very well. That car was extremely well behaved even under panic braking. Saved me more than once.
I do not see the "need" to be able to skid the wheels on clean dry pavement. This isn't a sports car and doesn't need to driven on "the edge." But the brake system should be able to put out enough "braking ability" to skid the wheels on something like a gravel road. If it can't then it isn't stopping you (on normal pavement) as well as it could.
If you know the subject, you need to take articles like RV Buddies with a grain of salt. SO... Makes you wonder about how much stock to put into articles on subjects you do not know much about...
I did notice that the reaction arm system shown in the article is the older style. (Not the sway-bar based version.) Are both types available?
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
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| Re: [GMCnet] New RV Buddies article [message #112877 is a reply to message #112848] |
Mon, 24 January 2011 03:59 |
|
USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
|
Senior Member |
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Larry,
If you watch the video of their drive up the coast from LA (?) to Fremont
one of those bozos says "we'd tell you where we're going if they were
sponsoring us!"
I trust the inscrutable Ornamental didn't give away the farm er rice paddy!
Regards,
Rob M.
USAussie - Downunder
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of LARRY L CALHOUN
Sent: Monday, January 24, 2011 3:15 PM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] New RV Buddies article
I have been over to Trueline RV and had a look at it. some interior work but
slowed do to lack of funds, said 11k owed and so they stopped work. that was
3-4 months ago. :?
--
Larry Calhoun GMC Cascader 76 Glenbrook Osburn ID.
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
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_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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