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What is the reason for the left front shock mount failures on 90's buses?
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What is the reason for the left front shock mount failures on 90's buses?
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What is the reason for the left front shock mount failures on 90's buses?
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03-09-2009, 16:12
Post: #1
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What is the reason for the left front shock mount failures on 90's buses?
When I discovered my front left shock absorber mount had failed just before the
Q rally in 08' I thought my experience was unique. Evidently it was not. There seems to have been several similar failures on 90's vintage buses. All of them appear to have occurred on the left front shock mount. It might be both interesting as well as useful for all of us that have experienced the failure as well as other interested parties to discuss what had caused the failures. If there is a design flaw we know we are on our own, of course. Right now it continues not to be clear to me what caused the problem. I realize that some of you have already discussed your failure. I do hope you can participate in what may be on line troubleshooting. Let me start out by discussing my failure. Just before the Q rally in 08' the left front shock absorber mount on my coach failed. The whole piece of metal on the frame of my bus was pulled away from the frame, leaving the shock mount still connected to the chunk of metal that was pulled away from the frame. CCW in Riverside repaired the problem. They had extensive discussions with the engineers at Ft. Valley. I will tell you that CCW was less that fully communicative with me about what they discussed in their multiple phone calls to Ft. Valley. Always say they "discussed the problem and solution." The fix was to weld a 1/2" plate to the area ripped out of my frame and re-weld the still good shock mount back in position. (Caution: what I am about to say is unreliable  It looked to me as though the repair shock mount was re-weldedback in position just slightly lower than it may have originally been located. When I asked CCW about the location of the mount they said something like: "We put it back in where it should have been." Never saying that they relocated it. When I strongly suspect that the failure occurred on my bus is when I traveled a poorly maintained road (US 30) between Chicago and Ft. Wayne, IN. While along that roadway my bus developed a "squeak" coming from what I thought was the right front of my bus. I could not see anything wrong with the underside of the coach. I did not look at the left upper shock mount. I was looking for at problem on the right side of my coach. I took my coach to a big rig shop in Ft Wayne that did among other things, front end work. They said everything looked fine. On my trip from Ft. Wayne to Las Vegas I did a lot of inspections, greasing and spraying of lubricate on the front right of the coach. I even removed the Steer Safe. By the time I got to Sante Fe the noise had stopped. When I went to put my Steer Safe back on in Las Vegas, just before the 08 Q rally, I discovered the failed shock mount on the left side of the coach. (By the way, sorry for the long post.) The question still remains in my mind: What caused the failure. I have been on many bad road in my life with this coach. The road I was on when the "squeak" started was bad but not ridiculously bad. I would hate to think that every time I might ride a bad road that I may be replacing a shock mount. Eric Perplies 96' 42' WBWL |
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03-09-2009, 16:35
Post: #2
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What is the reason for the left front shock mount failures on 90's buses?
Did you look at the picture(s) I posted links to? Pete's CCW repair pictures can
be found here: http://homepage.mac.com/aeonix1/PhotoAlbum11.html No before pictures there, only after. Had your shocks ever been replaced? A lot of us seem to have the issue soon after shock replacement, for whatever that is worth. Don Bradner 90 PT40 "Blue Thunder" My location: http://www.bbirdmaps.com/user2.cfm?user=1 On 3/10/2009 at 3:12 AM Eric Perplies wrote: >When I discovered my front left shock absorber mount had failed just >before the Q rally in 08' I thought my experience was unique. Evidently >it was not. There seems to have been several similar failures on 90's >vintage buses. All of them appear to have occurred on the left front >shock mount. It might be both interesting as well as useful for all of us >that have experienced the failure as well as other interested parties to >discuss what had caused the failures. If there is a design flaw we know >we are on our own, of course. Right now it continues not to be clear to >me what caused the problem. Don Bradner 90 PT40 "Blue Thunder" My location: http://www.bbirdmaps.com/user2.cfm?user=1 |
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03-09-2009, 17:34
Post: #3
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What is the reason for the left front shock mount failures on 90's buses?
Hey guys
I have posted several pics of the shock mount repair. I have outlined the new weld in red in pics 22 & 44. They are in my album BUMPERSBIRD it's at the end on page three. As I recall now, when the front end of the coach was lifted up to install new airbags it just kinda pulled away and when we dropped her back down it just went back into place with, It was very hard to see when we lowered the front end it just laid back into the broken area and was not obvious it was broken, the guys at Prevost just welded it back in place. I was told at the time by my BB Guru, "that's a known problem," the fix, "weld it back together boy!" From the pictures I've seen here it looks as if they are failing mostly on the plate the stud is welded to that supports the shock is the problem, The plate is either too thin a material or inferior steel. Compounded by a similar event that has happened to each of us. Letting the jacks drop on empty airbags, over travel in the suspension ???????Replacement shocks incorrect size?????? I don't know, mine broke after installing new shocks. It's now on the pre-trip, during trip, and post trip inspection list. A camera does a great job for a great look and detailed veiw. Kurt Horvath 95 PT-42 WLWB 10AC --- In WanderlodgeForum@yahoogroups.com, "Don Bradner" > > Did you look at the picture(s) I posted links to? Pete's CCW repair pictures can be found here: http://homepage.mac.com/aeonix1/PhotoAlbum11.html > > No before pictures there, only after. > > Had your shocks ever been replaced? A lot of us seem to have the issue soon after shock replacement, for whatever that is worth. > > Don Bradner > 90 PT40 "Blue Thunder" > My location: http://www.bbirdmaps.com/user2.cfm?user=1 > > On 3/10/2009 at 3:12 AM Eric Perplies wrote: > > >When I discovered my front left shock absorber mount had failed just > >before the Q rally in 08' I thought my experience was unique. Evidently > >it was not. There seems to have been several similar failures on 90's > >vintage buses. All of them appear to have occurred on the left front > >shock mount. It might be both interesting as well as useful for all of us > >that have experienced the failure as well as other interested parties to > >discuss what had caused the failures. If there is a design flaw we know > >we are on our own, of course. Right now it continues not to be clear to > >me what caused the problem. > > Don Bradner > 90 PT40 "Blue Thunder" > My location: http://www.bbirdmaps.com/user2.cfm?user=1 > |
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03-09-2009, 17:38
Post: #4
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What is the reason for the left front shock mount failures on 90's buses?
Eric, There's been a whole lot of discussion on this Forum relative to the shock mount failure. You may want to search the archives for "shock mount". David Brady '02 LXi, NC Eric Perplies wrote:
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03-10-2009, 01:33
Post: #5
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What is the reason for the left front shock mount failures on 90's buses?
Dave this kinda supports your "shock stroke too long theory" if BB moved the
mount farther away from the other mount. pot holes are violent at 70 mph. if you ever see a slomotion of a PU truck hitting them the entire truck frame twists. In the bus there is no twist so the only place the equall reaction force is felt is in the suspension (and tile grout) Greg of Tim&Greg --- In WanderlodgeForum@yahoogroups.com, david brady > > Eric, > > There's been a whole lot of discussion on this Forum > relative to the shock mount failure. You may want to > search the archives for "shock mount". > > David Brady > '02 LXi, NC > > Eric Perplies wrote: > > > > When I discovered my front left shock absorber mount had failed just > > before the Q rally in 08' I thought my experience was unique. > > Evidently it was not. There seems to have been several similar > > failures on 90's vintage buses. All of them appear to have occurred on > > the left front shock mount. It might be both interesting as well as > > useful for all of us that have experienced the failure as well as > > other interested parties to discuss what had caused the failures. If > > there is a design flaw we know we are on our own, of course. Right now > > it continues not to be clear to me what caused the problem. > > > > I realize that some of you have already discussed your failure. I do > > hope you can participate in what may be on line troubleshooting. Let > > me start out by discussing my failure. > > > > Just before the Q rally in 08' the left front shock absorber mount on > > my coach failed. The whole piece of metal on the frame of my bus was > > pulled away from the frame, leaving the shock mount still connected to > > the chunk of metal that was pulled away from the frame. CCW in > > Riverside repaired the problem. They had extensive discussions with > > the engineers at Ft. Valley. I will tell you that CCW was less that > > fully communicative with me about what they discussed in their > > multiple phone calls to Ft. Valley. Always say they "discussed the > > problem and solution." > > > > The fix was to weld a 1/2" plate to the area ripped out of my frame > > and re-weld the still good shock mount back in position. (Caution: > > what I am about to say is unreliable It looked to me as though the> > repair shock mount was re-welded back in position just slightly lower > > than it may have originally been located. When I asked CCW about the > > location of the mount they said something like: "We put it back in > > where it should have been." Never saying that they relocated it. > > > > When I strongly suspect that the failure occurred on my bus is when I > > traveled a poorly maintained road (US 30) between Chicago and Ft. > > Wayne, IN. While along that roadway my bus developed a "squeak" coming > > from what I thought was the right front of my bus. I could not see > > anything wrong with the underside of the coach. I did not look at the > > left upper shock mount. I was looking for at problem on the right side > > of my coach. I took my coach to a big rig shop in Ft Wayne that did > > among other things, front end work. They said everything looked fine. > > On my trip from Ft. Wayne to Las Vegas I did a lot of inspections, > > greasing and spraying of lubricate on the front right of the coach. I > > even removed the Steer Safe. By the time I got to Sante Fe the noise > > had stopped. When I went to put my Steer Safe back on in Las Vegas, > > just before the 08 Q rally, I discovered the failed shock mount on the > > left side of the coach. > > > > (By the way, sorry for the long post.) The question still remains in > > my mind: What caused the failure. I have been on many bad road in my > > life with this coach. The road I was on when the "squeak" started was > > bad but not ridiculously bad. I would hate to think that every time I > > might ride a bad road that I may be replacing a shock mount. > > > > Eric Perplies > > 96' 42' WBWL > > > > > > ------------------------------------------------------------------------ > > > > No virus found in this incoming message. > > Checked by AVG. > > Version: 7.5.557 / Virus Database: 270.11.9/1990 - Release Date: 3/8/2009 5:17 PM > > > |
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03-10-2009, 05:14
Post: #6
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What is the reason for the left front shock mount failures on 90's buses?
And BB knew all along. The shock could "just fit" with the air dumped. But when owners drop their birds off the jacks, the front goes crashing down, the bump stops compress, and the shock mounts take a huge impulse. It's a good theory. The rough road scenario doesn't fit for me. You'll never find a road rough enough that will cause the air springs to bottom on their rubber bump stops. The air springs are enormously progressive. At full compression they can support something like 4G's. That's equivalent to dropping the bus in free fall from 15 feet (give or take). David '02 LXi, NC timvasqz wrote:
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03-10-2009, 06:28
Post: #7
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What is the reason for the left front shock mount failures on 90's buses?
Yes ... that is exactly what occurred to me. The noise (in my case, more of a popping sound) seemed to be coming from the curb (right) side of the coach. It never occurred to me to look at the street (left) side suspension.
I had the failure twice -- first time it was discovered at Henderson's Lineup in Grants Pass Oregon. The repair they made (bending the partially failed piece back and welding the split) did not last 6 months. The piece completely failed (fortunately for me) at the CCW repair facility. Since it cut the air line to the left front wheel, it was quickly found. I've subsequently driven 8000+ miles since the CCW repair and I can see no degradation of their repair. I had driven about 10,000 miles on the Henderson's repair before it failed the second time. Pete Masterson '95 Blue Bird Wanderlodge WBDA 42 (For Sale) El Sobrante CA "aeonix1@mac.com" On Mar 9, 2009, at 8:12 PM, Eric Perplies wrote:
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03-10-2009, 06:50
Post: #8
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What is the reason for the left front shock mount failures on 90's buses?
Since the failure is at the TOP of the mounting plate, it seems like its the EXTENSION of the shock, not the compression that's the problem. I invite you to drive the Nimitz (I-880) from Oakland to San Jose -- you will hit _many_ road undulations that will fully extend your shocks, no matter how carefully you watch for the bad spots. Even at 55 (the official speed limit for 3 axle vehicles) you'll get full extension on some of the undulations. The road passes over clay bay fill and subsides, expands, and contracts with the seasons. (I -hate- to pass over that area -- but it's unavoidable if I'm going south to the coast...)
Pete Masterson '95 Blue Bird Wanderlodge WBDA 42 (For Sale) El Sobrante CA "aeonix1@mac.com" On Mar 10, 2009, at 9:14 AM, david brady wrote:
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03-10-2009, 07:31
Post: #9
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What is the reason for the left front shock mount failures on 90's buses?
I lived in the Bay Area for 11 years. I know of what you speak. True,
if you are lifting the tires off the ground; i.e., complete front end unload and shock hyper extension, well neither the shock nor the mounts are going to last very long under those conditions. The shock is designed to hold 8500 lb under full extension. Lifting the front wheels off the ground with the HWH jacks and the air dumped results in the axle being suspended by the fully extended shock; this scenario is easily within the 8500lb limit. Add air to the airbags and you're easily loading the shocks to 13000lb. Take in to account the angle of the shock and the loads are even higher. "Get air" while driving down an undulating highway... the shocks and mounts are likely to survive even a couple of oscillations. If this is truly happening, then you need to install straps or chains or something else to limit suspension travel cause the shock/mounts aren't even close to being strong enough. David Brady '02 LXi, NC -----Original Message----- |
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03-10-2009, 13:26
Post: #10
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What is the reason for the left front shock mount failures on 90's buses?
I do believe that one of the issues with the failure on the shock mounts is the
quality/mass of the steel in the frame of the coach. The center of the upper left shock mount is about 2"- 3" from the edge of the modestly thick frame. The webs or gussets on my coach had to be turned in the "hold water" position to keep them from projecting above the frame member. I didn't measure the thickness of the frame steel but I would guess it's 1/4" +/-. But even if the problem is the location/thickness of the upper mount it doesn't answer the question about why this failure has ALWAYS happened on the left shock mount. The right shock mount is built the same way. The right shock mount should be extended even more because of the camber in the road coupled with the leveling system on the bus. Finally, road damage is typically much more prevalent on the right side of the road. What's up with the left side?? Just too make my previous discussion complete. (My post on the Don's shock mount post 'disappeared'. A regular occurrence for me on this site.) When CCW repaired my upper shock mount they welded a 1/2" x 6" x 8" plate to the damaged area on my frame. They drilled a hole in the plate to accommodate the air line. They were on the telephone a lot with Ft Valley engineers discussing the problem. It took them 4 days of telephone conversations before they started the work. But it was very difficult to get CCW to relate what there discussions were except to say "we were trying to find out from Ft Valley how to repair the problem." Eric Perplies 96' 42' WBWL |
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