Shock mount failure
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02-19-2009, 12:15
Post: #31
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Shock mount failure
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02-19-2009, 12:22
Post: #32
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Shock mount failure
You might try looking at the curb side shock mount for ideas. That
shock mount appears to be trouble free. Earlier Don took a picture of it. There appeared to be a rectangular cross section tube welded vertically to it. Something like that or a vertically placed angle iron might do the trick. I know what you mean though, any fix is simply moving the center of stress around, and possible causing stress raisers elsewhere, that's why looking at the curb side might be informative. David Brady '02 LXi, NC -----Original Message----- |
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02-19-2009, 12:22
Post: #33
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Shock mount failure
--- In WanderlodgeForum@yahoogroups.com, Pete Masterson
wrote: > > 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@... > > > > > 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 Were this coaches chassis used in the commercial buses for transporting people? If so than there should be something out there I would think. Not only are these coaches made for private owners but like I said for business that transported people > |
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02-19-2009, 12:54
Post: #34
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Shock mount failure
On my street side mount, the gussets coming off the stud are much larger and fan out to a much greater area. Plus its orientation is reversed from the WB's with the 2 gussets at the top at 10:00 and 2:00 and one at the bottom at 6:00, and there's a bolt between each gusset. The metal also appears to be thicker, but this is difficult to tell thru a photograph. You may consider moving over to the LXi style. I have 97,000 miles so far with no trouble. My curbside is totally different from the picture that Don took. David Brady '02 LXi, NC David Brady wrote:
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02-19-2009, 13:28
Post: #35
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Shock mount failure
This chassis was sold as the Blue Bird "Express" as a luxury airporter and for some other intercity service. To be honest, I don't think it was a huge seller (the primary purchaser seems to have been the U.S. Government, probably due to 'buy American' rules in the government agency purchasing regulations).
However, in passenger service, these coaches would not have the HWH jack system (which may have played a role in the stress in certain situations). In addition, the weight of the passenger version might be considerably less than the RV version, since the holding tanks, roof mounted appliances, and interior fixtures would not be present. The lower weight might have reduced the stress. Or, a completely different suspension may have been used on the intercity bus version of the chassis. Then, again, perhaps the intercity passenger version were all sidelined with various difficulties with the shock mount ... there's actually no way of knowing. Ridewell is still around -- they may have new components available or newer design components that could replace the existing subassembly that has the shock and airbag mount. However, replacing that component might prove to be difficult, requiring considerable disassembly of the suspension and steering system for access -- and the component itself is likely to be expensive. This would tend to make it quite expensive to implement as a repair -- and it simply is unlikely to be cost effective compared to a field repair where some thoughtful welding and adding some means of strengthening the mount. It would be nice if Ridewell took an interest and perhaps could make some suggested field repairs to adequately strengthen the mount with some engineering calculations behind the procedure. (It's not likely that they'd be willing to do this, however, legal liability, etc. being what it is.) While (apparently) a fair number of 89 to 2000 (?) wide body units are subject to the problem, it also does not seem to "get" all of them, so the cost effective solution is to be aware of the potential for a problem, and if there are no other immediate symptoms, it's probably a good idea to inspect the mount annually -- or semi-annually. Effecting repairs if any stress fractures should develop. Clearly, the fracture takes some time to develop (possibly several years if it's going to appear) so it's likely to be observed during an inspection before any serious damage results. I observed a bit of rust on the bare metal edges of the fracture on my coach when it was first observed. I assume that the fracture exposed metal to the elements that was not protected with the paint or other rust resistant coating used on the intact frame and suspension components. The rust was quite obviously not part of the issue (the fracture wasn't related to a rust issue), but simply a little surface rust that collected on the exposed bare metal. Pete Masterson '95 Blue Bird Wanderlodge WBDA 42 (For Sale) El Sobrante CA "aeonix1@mac.com" On Feb 19, 2009, at 4:22 PM, Jon wrote:
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02-19-2009, 13:38
Post: #36
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Shock mount failure
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02-19-2009, 16:10
Post: #37
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Shock mount failure
when I weld in a triangle gussett, I first cut out the right angle or
just dont weld to the point. On the redesign David has I would think the gussets are not top and bottom in line with the shock???? Gussetts off to the side of the line of the force would allow for some distortion in place of total metal failure. When you beef one thing up the next weak link becomes evident. first thing I do when I crack an arm on a bobcat is realize the proven limit then weld it back to spec. I just think the problem is not in the ride dynamic. "You can jack a bus up.... by jacking a bus up" Greg of Tim&Greg 94ptca --- In WanderlodgeForum@yahoogroups.com, david brady wrote: > > On my street side mount, the gussets coming off the stud are much > larger and fan out to a much greater area. Plus its orientation is > reversed from the WB's with the 2 gussets at the top at 10:00 and > 2:00 and one at the bottom at 6:00, and there's a bolt between > each gusset. The metal also appears to be thicker, but this is > difficult to tell thru a photograph. You may consider moving over to > the LXi style. I have 97,000 miles so far with no trouble. My > curbside is totally different from the picture that Don took. > > David Brady > '02 LXi, NC > > David Brady wrote: > > > > You might try looking at the curb side shock mount for ideas. That > > shock mount appears to be trouble free. Earlier Don took a picture > > of it. There appeared to be a rectangular cross section tube welded > > vertically to it. Something like that or a vertically placed angle iron > > might do the trick. I know what you mean though, any fix is simply > > moving the center of stress around, and possible causing stress > > raisers elsewhere, that's why looking at the curb side might be > > informative. > > > > David Brady > > '02 LXi, NC > > > > > > -----Original Message----- > > From: Leroy Eckert > > Sent: Feb 19, 2009 7:15 PM > > To: WanderlodgeForum@yahoogroups.com > > Subject: Re: [WanderlodgeForum] Re: Shock mount failure > > > > Yes, I understand Don. There is a plate there and water can get > > behind it. I really do not know how to evaluate that. I looked at > > it closely and think a doubler plate could be placed there with > > through bolts which might create a weak point at the shock mount > > pod weld..Gotta think about that. That is tentative of course, it > > was cold and windy today so I did not spend much time looking. I > > will look again when it warms again. I have done those types of > > mods on aircraft with rivets and it works well. > > Leroy Eckert > > 1990 WB-40 Smoke N Mirrors > > Dahlonega, GA > > > > --- On *Thu, 2/19/09, Don Bradner / > > wrote: > > > > From: Don Bradner > > Subject: Re: [WanderlodgeForum] Re: Shock mount failure > > To: WanderlodgeForum@yahoogroups.com > > Date: Thursday, February 19, 2009, 7:01 PM > > > > 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 > > >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" > > > > > > > > > > > >> > > > > > >> 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 > > > > > > > > ------------------------------------------------------------------ ------ > > > > 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 > > > |
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02-19-2009, 17:06
Post: #38
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Shock mount failure
One thing to keep in mind is that these shocks don't act vertically. My shocks are canted over to almost 45 degrees, give or take (probably take a bit, I haven't measured the angle). That's part of the problem. The mount has an almost 2:1 mechanical lever disadvantage. On the LXi, along the axis of the shock, which is how the forces are acting, there's a gusset in line with the shock. call it 10:00, then there's the 2:00 and 6:00 gussets with the bottom of the shock pointing at 4:00. I'll see if I can dig out a pic. If you look at the WB version, you'll see that there isn't a gusset in line with the shock opposing the rebound forces. The WB gussets are at 12:00, 4:00 and 8:00. With the shock acting on 10:00. Pete's pic in particular shows how that weld bead flowing between the 12 and 8:00 gusset broke, right where the forces are the strongest. I believe it broke first at this weld bead and then ripped the rest of the metal off to the direction of the brake line. Check for cracks at that weld bead. Wire brush the paint off, then repaint. Now that it's 12:00 I think I'll go to bed... David '02 LXi, NC timvasqz wrote:
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02-20-2009, 04:14
Post: #39
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Shock mount failure
if there are four gussets and two are inline with the shock the side
two do nothing. In that case the top gusset that sees compression transfer more force on the bottom gussett that feels tension. if they place two gussets one each on 22 degrees of the center line from the shock across the bottom and two at 22degrees off center line at the top, the force of the shock(action) will be shared equally by each gusset reducing the stress at the end of either weld. I have loader arm gussets that have a crease in them that allow the gussett to flex some. that takes advantage of metals ability to absord some and not crack. the mods that have been done strengthen the post which isnt failing. the plate fails. the point where plate first fails is the part that allows the metal to peelup. welding the plate to the frame at the top has no advantage either. Greg ofTim&Greg 94ptca --- In WanderlodgeForum@yahoogroups.com, david brady wrote: > > One thing to keep in mind is that these shocks don't > act vertically. My shocks are canted over to almost > 45 degrees, give or take (probably take a bit, I haven't > measured the angle). That's part of the problem. The > mount has an almost 2:1 mechanical lever disadvantage. > > On the LXi, along the axis of the shock, which is how the > forces are acting, there's a gusset in line with the shock. > call it 10:00, then there's the 2:00 and 6:00 gussets with > the bottom of the shock pointing at 4:00. I'll see if I can > dig out a pic. > > If you look at the WB version, you'll see that there > isn't a gusset in line with the shock opposing the rebound > forces. The WB gussets are at 12:00, 4:00 and 8:00. > With the shock acting on 10:00. Pete's pic in particular > shows how that weld bead flowing between the 12 and > 8:00 gusset broke, right where the forces are the strongest. > I believe it broke first at this weld bead and then ripped > the rest of the metal off to the direction of the brake line. > > Check for cracks at that weld bead. Wire brush the paint > off, then repaint. > > Now that it's 12:00 I think I'll go to bed... > > David > '02 LXi, NC > > > timvasqz wrote: > > > > when I weld in a triangle gussett, I first cut out the right angle or > > just dont weld to the point. On the redesign David has I would think > > the gussets are not top and bottom in line with the shock???? > > Gussetts off to the side of the line of the force would allow for > > some distortion in place of total metal failure. > > > > When you beef one thing up the next weak link becomes evident. first > > thing I do when I crack an arm on a bobcat is realize the proven > > limit then weld it back to spec. I just think the problem is not in > > the ride dynamic. > > > > "You can jack a bus up.... by jacking a bus up" > > Greg of Tim&Greg > > 94ptca > > > > > |
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02-20-2009, 04:35
Post: #40
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Shock mount failure
Hi Greg, Three gussets, 120 deg apart. On at the top inline with the shock in tension, two at the bottom are in compression with each contributing 50% when projected along the axis of the shock. David '02 LXi, NC timvasqz wrote:
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