Shock mount failure - Printable Version

wrote:
> > >
> > > I'm the latest victim of a driver's side front shock mount
failure.
> > It took out the brake line when it went. I was not far from home
on
> > the way back from Q, so I limped on in (I know, in retrospect it
was
> > too dangerous, but I kept a lonnnng following distance!)
> > >
> > > I've used the local Detroit dealer in Arcata (Trinity Diesel) a
> > couple of times now for service, so I called them, and the service
> > manager said he would swing by for a look, no charge. He ended up
> > removing the shock and the air line, and said that he would come
by
> > the next time he was this way with a new airline. A new shock will
> > have to be ordered (the top bent/caved in) and they will schedule
an
> > appointment to get it welded after they have that. Shock was 17
> > months old.
> > >
> > >
> > > Don Bradner
> > > 90 PT40 "Blue Thunder"
> > > My location: http://www.bbirdmaps.com/user2.cfm?user=1
> > >
> >
> >
> > ------------------------------------------------------------------
------
> >
> > No virus found in this incoming message.
> > Checked by AVG.
> > Version: 7.5.552 / Virus Database: 270.10.23/1952 - Release Date:
2/13/2009 6:29 PM
> >
>

Shock mount failure - David Brady - 02-19-2009 02:57

My mistake Greg, I thought you were talking about the shock
swinging out of plumb in the plane of the steer axle. Email
communication is sometimes difficult.

David
'02 LXi, NC

Greg wrote: ----------------------------------------------------

I think the lack of flex of the frame adds a greater stess to the
pivioting points . when absorbing the shock of a pothole all the
stress is on the two pins so I guess the violent action and reaction
must be a big force on the cantilivered pin. if you ever see slow
motion footage of a pickup truck off road, you can see the frame and
fenders flexing major. Your "inverse sine" calc sold me, you are
probably right with your theory. (I wrote that down for later use)
Greg ofTim&Greg
94ptca

Shock mount failure - Pete Masterson - 02-19-2009 06:11

I'm inclined to agree that the left shock mount was a less robust component than is ideal, possibly due to a Ridewell error or miscalculation of stresses. The tear starts at the top and works down. That suggests that the force causing the stress is the fully extended shock absorber. This is in the opposite direction of stress caused by lowering the jacks when the air bags are deflated. Indeed, in that situation, the bumper stops ought to be taking the brunt of the weight rather than the shock mount, if the shock is of the correct length.

I noticed the 'popping' noise (that apparently was indicative of impending failure) whenever Itraversed dips or undulations in the road. Unfortunately, many freeways and highways in the SF Bay are built on fill or unstable clay soils, and undulations caused by ground subsidence is common and occurs frequently. Even a small bobble, crossed at 50 or 60+ mph results in a rather severeporpoisingincident. With the frequency of these undulations in the area with the heavy, fast moving traffic, it is rarely possible to spot the undulation and take protective action before you're upon it. (It's so perverse, that one lane may be affected while other lanes are not.) Indeed, there have been several studies (over the years) that suggest that the condition of Bay Area highways may be costing drivers $billions each year in additional repairs to their vehicles. Naturally, living in a near-bankrupt state, there is little chance that there will ever be significant improvement.

So, my feeling is that the most likely source of stress comes from super extension of the shock, rather than compressive stress caused by lowering the jacks before the suspension is aired up. I note that the shock can't be longer, since then it would not be able to compress sufficiently in the opposite direction. Further, between the time of the first repair and the second failure, my coach did not go through all that many jack raise/lower cycles and I've rarely lowered the jacks without sufficient air in the suspension. (I'd say never, because I have a 'get ready to go' procedure that I'm quite careful to follow -- but I admit the possibility of a distraction or memory lapse where lowering the jacks without air in the suspension is possible once in a while.) In contrast, I probably had many porpoising events for each jack lowering with or without air in the suspension.

I also speculate that the second failure after the first repair I encountered is due to the particularly large number of porpoising events encountered in Bay Area traffic (and the generally poor condition of many California freeways). Of course, if the first repair were more robust, I may not have had the second failure. I further note that it did take a dozen years and more than 125,000 miles before the fracture was first found. While we should expect better, that's quite a few miles on the chassis without a failure, so one might conclude that the part is only just short of being "strong enough."

Pete Masterson

'95 Blue Bird Wanderlodge WBDA 42 (For Sale)

<http://www.aeonix.biz/BBforsale.html>

El Sobrante CA

"aeonix1@mac.com"

On Feb 18, 2009, at 7:45 PM, david brady wrote:

Greg,

I don't think the axle tilt puts undo stress on the shock. If you
consider the steer axle in full droop on one side and full bump on
the other. The angle of the axle is roughly 5 deg to the horizon,
and this turns out to also be the angle of the shock.
(inverse sine of (8 inches / 96 inches)). The rubber bushings
in the shock can easily comply without transferring
excessive forces to the mounts. I'm sure Ridewell did this basic
calculation. If this were the cause then we'd be seeing similar
failures on the drive axles. The cause could be shocks that bottom
before bump stops (shocks too long), folks retracting their
HWH jacks w/o first airing up the suspension, folks raising the
front off the ground w/o first dumping air, or simply and inferior
Ridewell design. After year 2000 or so, I was informed by
the engineering staff at Ridewell that all their suspension systems
underwent finite element analysis and subsequent redesign;
consequently the LXi uses a different shock mount system than
the WB's. Could be that Ridewell addressed an inherent weakness.

David Brady
'02 LXi, NC

timvasqz wrote:

I think the crack was there from off-camber HWH jack parking in the
past. looks like the temper of the weld proved a brittle spot that
under normal conditions would not have issue. Then the new shock
absorbed more bounce but reacted equally agressive causing much more
stress on the mount. I think the mount post should have less strength
and be a point that can bend at failure. the tripod gussettes are a
bad idea.

I think problems arise when the bus air bags are dropped to be
leveled but the spot is too off camber. the HWH push one side up
and tilt the axle too much. at that point raising the front is
effortless and and the 30 foot lever post all the stress on the
tucked tire.

If I was to repair that mount I would remove two bolts and make a
trapazoid shape cut and replace the plate with a butt weld then build
the post mount back no better than before.

If you lose an airline and must drive. there is a screw set in the
maxicam to turn off the parking brake. you can then plug the airline
and fold it over then tape it.
Greg ofTim&Greg
94ptca

..--- In"WanderlodgeForum%40yahoogroups.com", "Don Bradner"
...> wrote:
>
> I'm the latest victim of a driver's side front shock mount failure.
It took out the brake line when it went. I was not far from home on
the way back from Q, so I limped on in (I know, in retrospect it was
too dangerous, but I kept a lonnnng following distance!)
>
> I've used the local Detroit dealer in Arcata (Trinity Diesel) a
couple of times now for service, so I called them, and the service
manager said he would swing by for a look, no charge. He ended up
removing the shock and the air line, and said that he would come by
the next time he was this way with a new airline. A new shock will
have to be ordered (the top bent/caved in) and they will schedule an
appointment to get it welded after they have that. Shock was 17
months old.
>
>
> Don Bradner
> 90 PT40 "Blue Thunder"
> My location:www.bbirdmaps.com/user2.cfm?user=1
>

No virus found in this incoming message.
Checked by AVG. Version: 7.5.552 / Virus Database: 270.10.23/1952 - Release Date: 2/13/2009 6:29 PM

Shock mount failure - David Brady - 02-19-2009 06:50

Pete,

I note that Koni shocks have zero or close to zero dampening
in the bump direction. All of the dampening control is exerted
on the rebound. I had discussions with Justin at Koni regarding
this and he said this is how they are able to achieve the ride
that Koni's known for.

In the case of rebound where the front end is bobbing over
Ca roads, the accelerations and velocities of the shock body
are such that Koni calculated 4000 pounds of force that can be felt
by the shock mount at the frame. Mostly in the downward direction.

When I spoke with Ridewell, they were most concerned about
folks lifting a tire off the ground, via hwh jacks, while still having
air in the air bags. They calculated a force of up to 13000 lb in
the downward direction in this case.

So, the forces are predominantly in the downward direction,
unless the shock is too long, and the issue seems to be metal
fatigue of a Ridewell component that is probably underdesigned,
or mounted incorrectly. I say this cause just one additional bolt
adjacent to the brake air line and next to the shock mount might
have been a good idea.

David Brady
'02 LXi, NC

-----Original Message-----

From: Pete Masterson

Sent: Feb 19, 2009 1:11 PM

To: WanderlodgeForum@yahoogroups.com

Subject: Re: [WanderlodgeForum] Re: Shock mount failure

I'm inclined to agree that the left shock mount was a less robust component than is ideal, possibly due to a Ridewell error or miscalculation of stresses. The tear starts at the top and works down. That suggests that the force causing the stress is the fully extended shock absorber. This is in the opposite direction of stress caused by lowering the jacks when the air bags are deflated. Indeed, in that situation, the bumper stops ought to be taking the brunt of the weight rather than the shock mount, if the shock is of the correct length.

Shock mount failure - Jon - 02-19-2009 06:54

--- In WanderlodgeForum@yahoogroups.com, David Brady
wrote:
>
> My mistake Greg, I thought you were talking about the shock
> swinging out of plumb in the plane of the steer axle. Email
> communication is sometimes difficult.
>
> David
> '02 LXi, NC
>
>
>
> Greg wrote: ----------------------------------------------------
>
> I think the lack of flex of the frame adds a greater stess to the
> pivioting points . when absorbing the shock of a pothole all the
> stress is on the two pins so I guess the violent action and reaction
> must be a big force on the cantilivered pin. if you ever see slow
> motion footage of a pickup truck off road, you can see the frame and
> fenders flexing major. Your "inverse sine" calc sold me, you are
> probably right with your theory. (I wrote that down for later use)
> Greg ofTim&Greg
> 94ptca
>

Just wondering after reading all this technical stuff what will be
the fix???? And how do you guys know that your shock mount is not
going to rip oft like Don's? Seems like to me this should be a
factory recall item or at least some type of notice given to all
owners of these bigger units. Can you beef up this area to make it
more stronger???? I sure would be bothered to know that such an item
exist and the factory not notifing owners. Jon

Shock mount failure - Pete Masterson - 02-19-2009 07:10

It affects coaches built some time ago -- apparently the flaw was addressed when the LXi models were introduced. Of course, it would be nice if there were a recall -- but who'd do the recall? The coaches were built 3 or 4 company owners back. Still, it's wise to inspect the left front shock mount from time to time.

The repair done to my coach, with added gussets across the break, is probably along the lines of how the repair should be made. It appears to have strengthened the component significantly.

Ideally, a "better" mount subassembly would be nice -- but it's a piece that includes the top air bag mount forward of the shock mount. It's obvious that the frame rail (used to mount the subassembly) is considerably more robust than the airbag/shock mount piece. Had it been made of slightly heavier steel, it might have proved strong enough to take the loads.

It's entirely possible that a technical bulletin went out suggesting periodic inspection -- but so much time has past and so many coaches have moved on to new owners that any such notice (or the technicians that new about it) may be long gone. For all I know, there might even be a notice hidden somewhere in the 35 lbs. of documentation I have in my blue box. I will say that the folks at Henderson's seemed to be aware that it was a "known issue" and inspected the component as they prepared to align the suspension.

Pete Masterson

'95 Blue Bird Wanderlodge WBDA 42 (For Sale)

<http://www.aeonix.biz/BBforsale.html>

El Sobrante CA

"aeonix1@mac.com"

On Feb 19, 2009, at 10:54 AM, Jon wrote:

---<snip>

Just wondering after reading all this technical stuff what will be
the fix???? And how do you guys know that your shock mount is not
going to rip oft like Don's? Seems like to me this should be a
factory recall item or at least some type of notice given to all
owners of these bigger units. Can you beef up this area to make it
more stronger???? I sure would be bothered to know that such an item
exist and the factory not notifing owners. Jon

Shock mount failure - Leroy Eckert - 02-19-2009 08:46

Thanks for the info. I checked mine out today and it looks solid.
Leroy Eckert
1990 WB-40 Smoke N Mirrors
Dahlonega, GA
Royale Conversion

--- On Thu, 2/19/09, Pete Masterson wrote:

From: Pete Masterson
Subject: Re: [WanderlodgeForum] Re: Shock mount failure
To: WanderlodgeForum@yahoogroups.com
Date: Thursday, February 19, 2009, 1:11 PM

I'm inclined to agree that the left shock mount was a less robust component than is ideal, possibly due to a Ridewell error or miscalculation of stresses. The tear starts at the top and works down. That suggests that the force causing the stress is the fully extended shock absorber. This is in the opposite direction of stress caused by lowering the jacks when the air bags are deflated. Indeed, in that situation, the bumper stops ought to be taking the brunt of the weight rather than the shock mount, if the shock is of the correct length.

I noticed the 'popping' noise (that apparently was indicative of impending failure) whenever Itraversed dips or undulations in the road. Unfortunately, many freeways and highways in the SF Bay are built on fill or unstable clay soils, and undulations caused by ground subsidence is common and occurs frequently. Even a small bobble, crossed at 50 or 60+ mph results in a rather
severeporpoisingincident. With the frequency of these undulations in the area with the heavy, fast moving traffic, it is rarely possible to spot the undulation and take protective action before you're upon it. (It's so perverse, that one lane may be affected while other lanes are not.) Indeed, there have been several studies (over the years) that suggest that the condition of Bay Area highways may be costing drivers $billions each year in additional repairs to their vehicles. Naturally, living in a near-bankrupt state, there is little chance that there will ever be significant improvement.

So, my feeling is that the most likely source of stress comes from super extension of the shock, rather than compressive stress caused by lowering the jacks before the suspension is aired up. I note that the shock can't be longer, since then it would not be able to compress sufficiently in the opposite direction. Further, between
the time of the first repair and the second failure, my coach did not go through all that many jack raise/lower cycles and I've rarely lowered the jacks without sufficient air in the suspension. (I'd say never, because I have a 'get ready to go' procedure that I'm quite careful to follow -- but I admit the possibility of a distraction or memory lapse where lowering the jacks without air in the suspension is possible once in a while.) In contrast, I probably had many porpoising events for each jack lowering with or without air in the suspension.

I also speculate that the second failure after the first repair I encountered is due to the particularly large number of porpoising events encountered in Bay Area traffic (and the generally poor condition of many California freeways). Of course, if the first repair were more robust, I may not have had the second failure. I further note that it did take a dozen years and more than 125,000
miles before the fracture was first found. While we should expect better, that's quite a few miles on the chassis without a failure, so one might conclude that the part is only just short of being "strong enough."

Pete Masterson
'95 Blue Bird Wanderlodge WBDA 42 (For Sale)
<http://www.aeonix. biz/BBforsale. html>
El Sobrante CA
"aeonix1@mac.com"

On Feb 18, 2009, at 7:45 PM, david brady wrote:

Greg,

I don't think the axle tilt puts undo stress on the shock. If you
consider the steer axle in full droop on one side and full bump on
the other. The angle of the axle is roughly 5 deg to the horizon,
and this turns out to also be the angle of the shock.
(inverse sine of (8 inches / 96 inches)). The rubber bushings
in the shock can easily comply without transferring
excessive forces to the mounts. I'm sure Ridewell did this basic
calculation. If this were the cause then we'd be seeing similar
failures on the drive axles. The cause could be shocks that bottom
before bump stops (shocks too long), folks retracting their
HWH jacks w/o first airing up the suspension, folks raising the
front off the ground w/o first dumping air, or simply and
inferior
Ridewell design. After year 2000 or so, I was informed by
the engineering staff at Ridewell that all their suspension systems
underwent finite element analysis and subsequent redesign;
consequently the LXi uses a different shock mount system than
the WB's. Could be that Ridewell addressed an inherent weakness.

David Brady
'02 LXi, NC

timvasqz wrote:

I think the crack was there from off-camber HWH jack parking in the
past. looks like the temper of the weld proved a brittle spot that
under normal conditions would not have issue. Then the new shock
absorbed more bounce but reacted equally agressive causing much more
stress on the mount. I think the mount post should have less strength
and be a point that can bend at failure. the tripod gussettes are a
bad idea.

I think problems arise when the bus air bags are dropped to be
leveled but the spot is too off camber. the HWH push one side up
and tilt the axle too much. at that point raising the front is
effortless and and the 30 foot lever post all the stress on the
tucked tire.

If I was to repair that mount I would remove two bolts and make a
trapazoid shape cut and replace the plate with a butt weld then build
the post mount back no better than before.

If you lose an airline and must drive. there is a screw set in the
maxicam to turn off the parking brake. you can then plug the airline
and fold it over then tape it.
Greg ofTim&Greg
94ptca

..--- In"WanderlodgeForum%40yahoogroups.com", "Don Bradner"
wrote:
>
> I'm the latest victim of a driver's side
front shock mount failure.
It took out the brake line when it went. I was not far from home on
the way back from Q, so I limped on in (I know, in retrospect it was
too dangerous, but I kept a lonnnng following distance!)
>
> I've used the local Detroit dealer in Arcata (Trinity Diesel) a
couple of times now for service, so I called them, and the service
manager said he would swing by for a look, no charge. He ended up
removing the shock and the air line, and said that he would come by
the next time he was this way with a new airline. A
new shock will
have to be ordered (the top bent/caved in) and they will schedule an
appointment to get it welded after they have that. Shock was 17
months old.
>
>
> Don Bradner
> 90 PT40 "Blue Thunder"
> My location:www.bbirdmaps. com/user2. cfm?user= 1
>

No virus found in this incoming message.
Checked by AVG.
Version: 7.5.552 / Virus Database: 270.10.23/1952 - Release Date: 2/13/2009 6:29 PM

Shock mount failure - david brady - 02-19-2009 09:26

Leroy,

How many miles on your coach?

David

'02 LXi, NC

Leroy Eckert wrote:

Thanks for the info. I checked mine out today and it
looks solid.

Leroy Eckert

1990 WB-40 Smoke N Mirrors

Dahlonega, GA

Royale Conversion

--- On Thu, 2/19/09, Pete Masterson com>
wrote:

From:
Pete Masterson com>

Subject: Re: [WanderlodgeForum] Re: Shock mount failure

To: WanderlodgeForum@yahoogroups.com

Date: Thursday, February 19, 2009, 1:11 PM

I'm inclined to agree that the left shock mount was a less
robust component than is ideal, possibly due to a Ridewell error or
miscalculation of stresses. The tear starts at the top and works down.
That suggests that the force causing the stress is the fully extended
shock absorber. This is in the opposite direction of stress caused by
lowering the jacks when the air bags are deflated. Indeed, in that
situation, the bumper stops ought to be taking the brunt of the weight
rather than the shock mount, if the shock is of the correct length.

I noticed the 'popping' noise (that apparently was
indicative of impending failure) whenever Itraversed dips or
undulations in the road. Unfortunately, many freeways and highways in
the SF Bay are built on fill or unstable clay soils, and undulations
caused by ground subsidence is common and occurs frequently. Even a
small bobble, crossed at 50 or 60+ mph results in a rather
severeporpoisingincident. With the frequency of these undulations in
the area with the heavy, fast moving traffic, it is rarely possible to
spot the undulation and take protective action before you're upon it.
(It's so perverse, that one lane may be affected while other lanes are
not.) Indeed, there have been several studies (over the years) that
suggest that the condition of Bay Area highways may be costing drivers
$billions each year in additional repairs to their vehicles. Naturally,
living in a near-bankrupt state, there is little chance that there will
ever be significant improvement.

So, my feeling is that the most likely source of stress
comes from super extension of the shock, rather than compressive stress
caused by lowering the jacks before the suspension is aired up. I note
that the shock can't be longer, since then it would not be able to
compress sufficiently in the opposite direction. Further, between the
time of the first repair and the second failure, my coach did not go
through all that many jack raise/lower cycles and I've rarely lowered
the jacks without sufficient air in the suspension. (I'd say never,
because I have a 'get ready to go' procedure that I'm quite careful to
follow -- but I admit the possibility of a distraction or memory lapse
where lowering the jacks without air in the suspension is possible once
in a while.) In contrast, I probably had many porpoising events for
each jack lowering with or without air in the suspension.

I also speculate that the second failure after the first
repair I encountered is due to the particularly large number of
porpoising events encountered in Bay Area traffic (and the generally
poor condition of many California freeways). Of course, if the first
repair were more robust, I may not have had the second failure. I
further note that it did take a dozen years and more than 125,000 miles
before the fracture was first found. While we should expect better,
that's quite a few miles on the chassis without a failure, so one might
conclude that the part is only just short of being "strong enough."

Pete Masterson

'95 Blue Bird Wanderlodge WBDA 42 (For Sale)

<http://www.aeonix.
biz/BBforsale. html>

El Sobrante CA

"aeonix1@mac.com"

On Feb 18, 2009, at 7:45 PM, david brady wrote:

Greg,

I don't think the axle tilt puts undo stress on the shock. If you

consider the steer axle in fulldroop on one side and full bump on

the other. The angle of the axle is roughly 5 deg to the horizon,

and this turns out to also be the angle of the shock.

(inverse sine of (8 inches / 96 inches)). The rubber bushings

in the shock can easily comply without transferring

excessive forces to the mounts. I'm sure Ridewell did this basic

calculation. If this were the cause then we'd be seeing similar

failures on the drive axles. The cause could be shocks that bottom

before bump stops (shocks too long), folks retracting their

HWH jacks w/o first airing up the suspension, folks raising the

front off the ground w/o first dumping air, or simply and inferior

Ridewell design. After year 2000 or so, I was informed by

the engineering staff at Ridewell that all their suspension systems

underwent finite element analysis and subsequent redesign;

consequently the LXi uses a different shock mount system than

the WB's. Could be that Ridewell addressed an inherent weakness.

David Brady

'02 LXi, NC

timvasqz wrote:

I think the crack was there from off-camber HWH jack
parking in the

past. looks like the temper of the weld proved a brittle spot that

under normal conditions would not have issue. Then the new shock

absorbed more bounce but reacted equally agressive causing much more

stress on the mount. I think the mount post shoud have less strength

and be a point that can bend at failure. the tripod gussettes are a

bad idea.

I think problems arise when the bus air bags are dropped to be

leveled but the spot is too off camber. the HWH push one side up

and tilt the axle too much. at that point raising the front is

effortless and and the 30 foot lever post all the stress on the

tucked tire.

If I was to repair that mount I would remove two bolts and make a

trapazoid shape cut and replace the plate with a butt weld then build

the post mount back no better than before.

If you lose an airline and must drive. there is a screw set in the

maxicam to turn off the parking brake. you can then plug the airline

and fold it over then tape it.

Greg ofTim&Greg

94ptca

..--- InWanderlodgeForum@
yahoogroups. com, "Don Bradner"

wrote:

>

> I'm the latest victim of a driver's side front shock mount failure.

It took out the brake line when it went. I was not far from home on

the way back from Q, so I limped on in (I know, in retrospect it was

too dangerous, but I kept a lonnnng following distance!)

>

> I've used the local Detroit dealer in Arcata (Trinity Diesel) a

couple of times now for service, so I called them, and the service

manager said he would swing by for a look, no charge. He ended up

removing the shock and the air line, and said that he would come by

the next time he was this way with a new airline. A new shock will

have to be ordered (the top bent/caved in) and they will schedule an

appointment to get it welded after they have that. Shock was 17

months old.

>

>

> Don Bradner

> 90 PT40 "Blue Thunder"

> My location:www.bbirdmaps.
com/user2. cfm?user= 1

>

No virus found in this incoming message.
Checked by AVG.
Version: 7.5.552 / Virus Database: 270.10.23/1952 - Release Date: 2/13/2009 6:29 PM
No virus found in this incoming message.

Checked by AVG. Version: 7.5.552 / Virus Database: 270.10.23/1952 - Release Date: 2/13/2009 6:29 PM

Shock mount failure - Leroy Eckert - 02-19-2009 11:15

117,000. Fortunately, my coach does not have any evidence of significant rust anywhere, even on the chassis. The area around the shock mount is clean and black. There is some minor surface rust on the steering rods, but extremely minor. Virtually nothing on the axle's front or rear. It is really clean. That is what I paid for when I purchased the coach. The engine has about 25,000 on an in frame. I re-sprayed the insulation on the bottom of the coach with undercoating. It is shiny and clean.
Leroy Eckert
1990 WB-40 Smoke N Mirrors
Dahlonega, GA
Royale Conversion

--- On Thu, 2/19/09, david brady wrote:

From: david brady
Subject: Re: [WanderlodgeForum] Re: Shock
mount failure
To: WanderlodgeForum@yahoogroups.com
Date: Thursday, February 19, 2009, 4:26 PM

Leroy,

How many miles on your coach?

David

'02 LXi, NC

Leroy Eckert wrote:

Thanks for the info. I checked mine out today and it
looks solid.

Leroy Eckert

1990 WB-40 Smoke N Mirrors

Dahlonega, GA

Royale Conversion

--- On Thu, 2/19/09, Pete Masterson
wrote:

From:
Pete Masterson

Subject: Re: [WanderlodgeForum] Re: Shock mount failure

To: WanderlodgeForum@ yahoogroups. com

Date: Thursday, February 19, 2009, 1:11 PM

I'm inclined to agree that the left shock mount was a less
robust component than is ideal, possibly due to a Ridewell error or
miscalculation of stresses. The tear starts at the top and works down.
That suggests that the force causing the stress is the fully extended
shock absorber. This is in the opposite direction of stress caused by
lowering the jacks when the air bags are deflated. Indeed, in that
situation, the bumper stops ought to be taking the brunt of the weight
rather than the shock mount, if the shock is of the correct length.

I noticed the 'popping' noise (that apparently was
indicative of impending failure) whenever Itraversed dips or
undulations in the road. Unfortunately, many freeways and highways in
the SF Bay are built on fill or unstable clay soils, and undulations
caused by ground subsidence is common and occurs frequently. Even a
small bobble, crossed at 50 or 60+ mph results in a rather
severeporpoisingincident. With the frequency of these undulations in
the area with the heavy, fast moving traffic, it is rarely possible to
spot the undulation and take protective action before you're upon it.
(It's so perverse, that one lane may be affected while other lanes are
not.) Indeed, there have been several studies (over the years) that
suggest that the condition of Bay Area highways may be costing drivers
$billions each year in additional repairs to their vehicles. Naturally,
living in a near-bankrupt state, there is little chance that there will
ever be significant improvement.

So, my feeling is that the most likely source of stress
comes from super extension of the shock, rather than compressive stress
caused by lowering the jacks before the suspension is aired up. I note
that the shock can't be longer, since then it would not be able to
compress sufficiently in the opposite direction. Further, between the
time of the first repair and the second failure, my coach did not go
through all that many jack raise/lower cycles and I've rarely lowered
the jacks without sufficient air in the suspension. (I'd say never,
because I have a 'get ready to go' procedure that I'm quite careful to
follow -- but I admit the possibility of a distraction or memory lapse
where lowering the jacks without air in the suspension is possible once
in a while.) In contrast, I probably had many porpoising events for
each jack lowering with or without air in the suspension.

I also speculate that the second failure after the first
repair I encountered is due to the particularly large number of
porpoising events encountered in Bay Area traffic (and the generally
poor condition of many California freeways). Of course, if the first
repair were more robust, I may not have had the second failure. I
further note that it did take a dozen years and more than 125,000 miles
before the fracture was first found. While we should expect better,
that's quite a few miles on the chassis without a failure, so one might
conclude that the part is only just short of being "strong enough."

Pete Masterson

'95 Blue Bird Wanderlodge WBDA 42 (For Sale)

<http://www.aeonix.
biz/BBforsale. html>

El Sobrante CA

"aeonix1@mac.com"

On Feb 18, 2009, at 7:45 PM, david brady wrote:

Greg,

I don't think the axle tilt puts undo stress on the shock. If you

consider the steer axle in fulldroop on one side and full bump on

the other. The angle of the axle is roughly 5 deg to the horizon,

and this turns out to also be the angle of the shock.

(inverse sine of (8 inches / 96 inches)). The rubber bushings

in the shock can easily comply without transferring

excessive forces to the mounts. I'm sure Ridewell did this basic

calculation. If this were the cause then we'd be seeing similar

failures on the drive axles. The cause could be shocks that bottom

before bump stops (shocks too long), folks retracting their

HWH jacks w/o first airing up the suspension, folks raising the

front off the ground w/o first dumping air, or simply and inferior

Ridewell design. After year 2000 or so, I was informed by

the engineering staff at Ridewell that all their suspension systems

underwent finite element analysis and subsequent redesign;

consequently the LXi uses a different shock mount system than

the WB's. Could be that Ridewell addressed an inherent weakness.

David Brady

'02 LXi, NC

timvasqz wrote:

I think the crack was there from off-camber HWH jack
parking in the

past. looks like the temper of the weld proved a brittle spot that

under normal conditions would not have issue. Then the new shock

absorbed more bounce but reacted equally agressive causing much more

stress on the mount. I think the mount post shoud have less strength

and be a point that can bend at failure. the tripod gussettes are a

bad idea.

I think problems arise when the bus air bags are dropped to be

leveled but the spot is too off camber. the HWH push one side up

and tilt the axle too much. at that point raising the front is

effortless and and the 30 foot lever post all the stress on the

tucked tire.

If I was to repair that mount I would remove two bolts and make a

trapazoid shape cut and replace the plate with a butt weld then build

the post mount back no better than before.

If you lose an airline and must drive. there is a screw set in the

maxicam to turn off the parking brake. you can then plug the airline

and fold it over then tape it.

Greg ofTim&Greg

94ptca

...--- InWanderlodgeForum@
yahoogroups. com, "Don Bradner"

wrote:

>

> I'm the latest victim of a driver's side front shock mount failure.

It took out the brake line when it went. I was not far from home on

the way back from Q, so I limped on in (I know, in retrospect it was

too dangerous, but I kept a lonnnng following distance!)

>

> I've used the local Detroit dealer in Arcata (Trinity Diesel) a

couple of times now for service, so I called them, and the service

manager said he would swing by for a look, no charge. He ended up

removing the shock and the air line, and said that he would come by

the next time he was this way with a new airline. A new shock will

have to be ordered (the top bent/caved in) and they will schedule an

appointment to get it welded after they have that. Shock was 17

months old.

>

>

> Don Bradner

> 90 PT40 "Blue Thunder"

> My location:www.bbirdmaps.
com/user2. cfm?user= 1

>

No virus found in this incoming message.
Checked by AVG.
Version: 7.5.552 / Virus Database: 270.10.23/1952 - Release Date: 2/13/2009 6:29 PM

No virus found in this incoming message.
Checked by AVG.
Version: 7.5.552 / Virus Database: 270.10.23/1952 - Release Date: 2/13/2009 6:29 PM

Shock mount failure - Don Bradner - 02-19-2009 12:01

I'm at around 131,000. There is not a lot of rust except on the break itself.
One thing to not about that rust is that it was driven in rain the day it broke,
and it sat through 10 straight days of rain and high humidity after being parked
before I looked at it. No way of knowing what the break looked like at the point
it actually gave way.

On 2/19/2009 at 3:15 PM Leroy Eckert wrote:

>117,000. Fortunately, my coach does not have any evidence of significant
>rust anywhere, even on the chassis. The area around the shock mount is
>clean and black. There is some minor surface rust on the steering rods,
>but extremely minor. Virtually nothing on the axle's front or rear. It is
>really clean. That is what I paid for when I purchased the coach. The
>engine has about 25,000 on an in frame. I re-sprayed the insulation on the
>bottom of the coach with undercoating. It is shiny and clean.
>Leroy Eckert
>1990 WB-40 Smoke N Mirrors
> Dahlonega, GA
>Royale Conversion
>
>--- On Thu, 2/19/09, david brady wrote:
>From: david brady
>Subject: Re: [WanderlodgeForum] Re: Shock mount failure
>To: WanderlodgeForum@yahoogroups.com
>Date: Thursday, February 19, 2009, 4:26 PM
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>Leroy,
>
>
>
>How many miles on your coach?
>
>
>
>David
>
>'02 LXi, NC
>
>
>
>Leroy Eckert wrote:
>
>
>
>
>
>
> Thanks for the info. I checked mine out today and it
>looks solid.
>
>Leroy Eckert
>
>1990 WB-40 Smoke N Mirrors
>
>Dahlonega, GA
>
>Royale Conversion
>
>
>
>--- On Thu, 2/19/09, Pete Masterson
>wrote:
>
> From:
>Pete Masterson
>
>Subject: Re: [WanderlodgeForum] Re: Shock mount failure
>
>To: WanderlodgeForum@ yahoogroups. com
>
>Date: Thursday, February 19, 2009, 1:11 PM
>
>
>
>
>
> I'm inclined to agree that the left shock mount was a less
>robust component than is ideal, possibly due to a Ridewell error or
>miscalculation of stresses. The tear starts at the top and works down.
>That suggests that the force causing the stress is the fully extended
>shock absorber. This is in the opposite direction of stress caused by
>lowering the jacks when the air bags are deflated. Indeed, in that
>situation, the bumper stops ought to be taking the brunt of the weight
>rather than the shock mount, if the shock is of the correct length.
>
>
>
> I noticed the 'popping' noise (that apparently was
>indicative of impending failure) whenever I traversed dips or
>undulations in the road. Unfortunately, many freeways and highways in
>the SF Bay are built on fill or unstable clay soils, and undulations
>caused by ground subsidence is common and occurs frequently. Even a
>small bobble, crossed at 50 or 60+ mph results in a rather
>severe porpoising incident. With the frequency of these undulations in
>the area with the heavy, fast moving traffic, it is rarely possible to
>spot the undulation and take protective action before you're upon it.
>(It's so perverse, that one lane may be affected while other lanes are
>not.) Indeed, there have been several studies (over the years) that
>suggest that the condition of Bay Area highways may be costing drivers
>$billions each year in additional repairs to their vehicles. Naturally,
>living in a near-bankrupt state, there is little chance that there will
>ever be significant improvement.
>
>
>
> So, my feeling is that the most likely source of stress
>comes from super extension of the shock, rather than compressive stress
>caused by lowering the jacks before the suspension is aired up. I note
>that the shock can't be longer, since then it would not be able to
>compress sufficiently in the opposite direction. Further, between the
>time of the first repair and the second failure, my coach did not go
>through all that many jack raise/lower cycles and I've rarely lowered
>the jacks without sufficient air in the suspension. (I'd say never,
>because I have a 'get ready to go' procedure that I'm quite careful to
>follow -- but I admit the possibility of a distraction or memory lapse
>where lowering the jacks without air in the suspension is possible once
>in a while.) In contrast, I probably had many porpoising events for
>each jack lowering with or without air in the suspension.
>
>
>
> I also speculate that the second failure after the first
>repair I encountered is due to the particularly large number of
>porpoising events encountered in Bay Area traffic (and the generally
>poor condition of many California freeways). Of course, if the first
>repair were more robust, I may not have had the second failure. I
>further note that it did take a dozen years and more than 125,000 miles
>before the fracture was first found. While we should expect better,
>that's quite a few miles on the chassis without a failure, so one might
>conclude that the part is only just short of being "strong enough."
>
>
>
>
> Pete Masterson
> '95 Blue Bird Wanderlodge WBDA 42 (For Sale)
> <http://www.aeonix.
>biz/BBforsale. html>
> El Sobrante CA
> aeonix1@mac. com
>
>
>
>
>
>
>
>
>
>
>
>
> On Feb 18, 2009, at 7:45 PM, david brady wrote:
>
>
>
> Greg,
>
>
>
>I don't think the axle tilt puts undo stress on the shock. If you
>
>consider the steer axle in fulldroop on one side and full bump on
>
>the other. The angle of the axle is roughly 5 deg to the horizon,
>
>and this turns out to also be the angle of the shock.
>
>(inverse sine of (8 inches / 96 inches)). The rubber bushings
>
>in the shock can easily comply without transferring
>
>excessive forces to the mounts. I'm sure Ridewell did this basic
>
>calculation. If this were the cause then we'd be seeing similar
>
>failures on the drive axles. The cause could be shocks that bottom
>
>before bump stops (shocks too long), folks retracting their
>
>HWH jacks w/o first airing up the suspension, folks raising the
>
>front off the ground w/o first dumping air, or simply and inferior
>
>Ridewell design. After year 2000 or so, I was informed by
>
>the engineering staff at Ridewell that all their suspension systems
>
>underwent finite element analysis and subsequent redesign;
>
>consequently the LXi uses a different shock mount system than
>
>the WB's. Could be that Ridewell addressed an inherent weakness.
>
>
>
>David Brady
>
>'02 LXi, NC
>
>
>
>
>
>
>
>timvasqz wrote:
>
>
> I think the crack was there from off-camber HWH jack
>parking in the
>
>past. looks like the temper of the weld proved a brittle spot that
>
>under normal conditions would not have issue. Then the new shock
>
>absorbed more bounce but reacted equally agressive causing much more
>
>stress on the mount. I think the mount post shoud have less strength
>
>and be a point that can bend at failure. the tripod gussettes are a
>
>bad idea.
>
>
>
>I think problems arise when the bus air bags are dropped to be
>
>leveled but the spot is too off camber. the HWH push one side up
>
>and tilt the axle too much. at that point raising the front is
>
>effortless and and the 30 foot lever post all the stress on the
>
>tucked tire.
>
>
>
>If I was to repair that mount I would remove two bolts and make a
>
>trapazoid shape cut and replace the plate with a butt weld then build
>
>the post mount back no better than before.
>
>
>
>If you lose an airline and must drive. there is a screw set in the
>
>maxicam to turn off the parking brake. you can then plug the airline
>
>and fold it over then tape it.
>
>Greg ofTim&Greg
>
>94ptca
>
>
>
>...--- In WanderlodgeForum@
>yahoogroups. com, "Don Bradner"
>
> wrote:
>
>>
>
>> I'm the latest victim of a driver's side front shock mount failure.
>
>It took out the brake line when it went. I was not far from home on
>
>the way back from Q, so I limped on in (I know, in retrospect it was
>
>too dangerous, but I kept a lonnnng following distance!)
>
>>
>
>> I've used the local Detroit dealer in Arcata (Trinity Diesel) a
>
>couple of times now for service, so I called them, and the service
>
>manager said he would swing by for a look, no charge. He ended up
>
>removing the shock and the air line, and said that he would come by
>
>the next time he was this way with a new airline. A new shock will
>
>have to be ordered (the top bent/caved in) and they will schedule an
>
>appointment to get it welded after they have that. Shock was 17
>
>months old.
>
>>
>
>>
>
>> Don Bradner
>
>> 90 PT40 "Blue Thunder"
>
>> My location: http://www.bbirdmaps.
>com/user2. cfm?user= 1
>
>>
>
>
>
>
>
> No virus found in this incoming message.
>Checked by AVG.
>Version: 7.5.552 / Virus Database: 270.10.23/1952 - Release Date:
>2/13/2009 6:29 PM
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>No virus found in this incoming message.
>Checked by AVG.
>Version: 7.5.552 / Virus Database: 270.10.23/1952 - Release Date:
>2/13/2009 6:29 PM