Shock mount failure

[Pete Masterson]

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 theporpoisingmovement 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@mac.com"

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?