Shock mount failure

[Kurt Horvath]

I also believe that the stress cracking comes from extension not compression of
the suspension. When my coach was lifted up on the front end the broken piece
pulled away when lowered it you could barely see the fracture lines on the
mounts. I just basically reseated itself in it's original position. I doubt that
anything we could do intentionally would cause such a fracture. Air in or out of
the airbags lifted with the jacks or not. A constant pressure of 13000 LB is not
the same as 13000lb rebounding and extending at 60 MPH. Perhaps dropping the
jacks on empty airbags could do it, when it hits bottom it hits hard, real hard.

Kurt Horvath
95 PT 42
10AC



--- In WanderlodgeForum@yahoogroups.com, Pete Masterson wrote:
>
> If I understand correctly, that raises the front of the coach. If the
> air bags are inflated, it can put 13,000 lbs pressure on the shock
> mount (from the air pressure in the bag) with the maximum pressure
> achieved if the front tires are lifted completely off the ground (as
> sometimes is the case).
>
> Pete Masterson
> '95 Blue Bird Wanderlodge WBDA 42 (For Sale)
> <http://www.aeonix.biz/BBforsale.html>
> El Sobrante CA
> aeonix1@...
>
>
>
>
> On Mar 10, 2009, at 12:30 PM, Dan Williams wrote:
>
> > Pete, I may be getting in on this late, but how does lowering the
> > leveling jacks with the suspension still aired up put stress on the
> > front shocks and mounts?
> > Dan Williams, 88WB38, Jackson, MS
> >
> > From: WanderlodgeForum@yahoogroups.com
[mailto:WanderlodgeForum@yahoogroups.com
> > ] On Behalf Of Pete Masterson
> > Sent: Tuesday, March 10, 2009 12:20 PM
> > To: WanderlodgeForum@yahoogroups.com
> > Subject: Re: [WanderlodgeForum] Re: Shock mount failure
> >
> > There is a sub-frame that holds the shock mount, air bag, and other
> > parts of the front end. It's a piece that's about 24 to 30 inches
> > long. That piece comes from Ridewell. (Although Ridewell might claim
> > that Blue Bird provided the specification.) The speculation is that
> > the Ridewell piece is not thick enough (or otherwise not
> > sufficiently strong) to take the constant hammering.
> >
> >
> > Awhile back on one or the other WL lists, someone reported that
> > lowering the leveling jacks with the suspension still aired up puts
> > an unusually large stress on the front shocks and mounts. That may
> > start the weakening process. However, I know that it was rare for me
> > to forget to dump the suspension before I leveled the coach.
> >
> > Before the complete failure of my shock mount, I'd noticed a
> > 'popping' noise in the front end when encountering the porpoising
> > movement that occurs after passing over one of the multitude of
> > ground subsidence undulations that are frequently found on the
> > freeways, especially in the SF Bay Area where the highways are
> > frequently built on fill (near the bay) or unstable clay soils
> > (nearly everywhere else in the area). Later I realized that the
> > noise was cause by the flexing of the split (and eventually broken)
> > piece of the Ridewell sub-assembly. (The acoustics caused it to
> > sound like it came from the opposite side.)
> >
> > Pete Masterson
> > '95 Blue Bird Wanderlodge WBDA 42 (For Sale)
> > <http://www.aeonix.biz/BBforsale.html>
> > El Sobrante CA
> > aeonix1@...
> >
> >
> >
> > On Mar 9, 2009, at 7:40 PM, Don Bradner wrote:
> >
> >
> > Did your tear look at all like mine (mine looks almost exactly like
> > Pete's)? Presumption is that the slamming downward when the wheel
> > bottoms into a pothole or similar is the issue. Countless slams, and
> > the metal gives way. Note that it is not the frame, but rather the
> > steel mounted to the frame - that steel is a part of the axle
> > assembly and was presumably not welded by BB.
> >
> > The repair done on mine comes close to matching the original
> > assembly, making it possible/likely that sometime in the next 20
> > years it will fail again. I'm going to try to remember to stick a
> > camera in there for photos every few months (more often to begin
> > with!) that it is driven.
> >
> > On 3/10/2009 at 2:22 AM Eric Perplies wrote:
> >
> >
> > My front left shock mount broke just before the Q rally in 08. CCW in
> >> Riverside fixed mine shortly after the Q rally. On my coach the
> >> shock
> >> mount ripped out a chunk of metal on the frame. A piece of steel
> >> about
> >> 1/2" x 8" x 6" was welded onto my frame. A hole was drilled in it to
> >> accommodate the brake air line. The original shock mount with it's
> >> three
> >> gussets were removed from the broken out piece. That original
> >> shock mount
> >> was then welded back onto the 1/2" plate mentioned above.
> >>
> >> The welds made during the repair were VERY thorough. There was an
> >> indication that the original BB welds may not have been as through
> >> as they
> >> could have been. (One side of one of the gussets had not been
> >> welded onto
> >> the frame.) That having been said this could not be the reason for
> >> the
> >> failure. After all the frame on my coach had a section ripped out
> >> of it.
> >> The shock mount itself did not fail.
> >>
> >> A far more interesting question is: What causes the failures on
> >> the shock
> >> mounts?
> >
> >
> >
> >
> >
>