| Author | Message | ||
| Ken Turner (Pipesusmc)
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http://www.sunherald.com/mld/thesunherald/10907926.htm | ||
| James Maxwell (Jmaxwell)
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600-700 lbs. of sikaflex???????????????????? Give me a break. What else involved in a new roof skin would add that much weight. And, find me any skin replacement job that does not involve drilling some new holes. The rusty side wall structure I can buy but the rest of it sounds like typical government agency bs. What the hell do these people expect when u slam a 35k# box into a ditch @ 70MPH! | ||
| captain ron (Captain_ron)
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I think they said "Misalined holes" which would mean they had some egg shaped holes in which case would not properly hold. either way it's a tragedy. | ||
| Marc Bourget Rating: N/A |
Not wanting to add holes to the new skin, I predict that when the skin holes didn't quite match the structure holes, they drilled thru the skin holes, usually resulting it two oval holes. Not good by itself but what contribution was made with the sikkaflex? I also disagree with the 600# unless they added some type of baggage rack which was included in the total. | ||
| Sojourner (Jjimage)
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Driver’s speed thru turn at 70 mph & sleeping I believe is reason of mishap. It show in photos of grassed tire path verge gradually off after beginning of exit’s curve and roll onto side of drop embankment. About Sikaflex glue; It very strong but it can not be use without same number of rivets from factory. MCI’s mona-coupe depends on rivet for diagonal reaction. New MCI E series & Prevost H series are Sikaflex glued panel onto SS “trusses” wall frame. About new rivet holes misses to old one & glue; Garage’s roof fire perhaps was hot enough warp and weakens MCI roof’s structure. It appears MCI’s roof assembly broke loose from side posts and side skin were not adequacy riveted. Skin (aluminum) with proper & sufficient rivets is more pulling strength then vertical post. However MCI’s window post is weak point but photos shows below window side skin were peal loose. I believe a very poor workmanship of repairing a fire damage roof. Who knows, if driver had maintain proper control and knowing the repair is weaker than normal, it still be on road today. I wonder how many similar conditions on road now? FWIW Sojourn for Christ, Jerry | ||
| Sojourner (Jjimage)
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More Links with photos http://www.nbc5.com/news/3797582/detail.html on photo # 19 show tire mark on grass before drop bankment. http://www.ncsbs.org/crash_reports_2004/arkansas.htm http://abclocal.go.com/wls/news/101304_ns_tourbus_crash.html# http://cbs2chicago.com/topstories/local_story_285112451.html Sojourn for Christ, Jerry | ||
| Jim (Jim_in_california)
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B'Gawd. The pictures of that roof ripped clean off are just mind-numbing. You know...every single time I've seen pics of people doing roof-raises on various websites, I get this little shudder. And that's been going on since I first heard about such roof lifts many months ago. Ain't. No. Way... ...I'm ever getting involved in something like that. Give me a good original design, be it MCI, Crown, GMC, whatever, in good shape and *intact* structurally. If I have to live with a ceiling 2" shorter than I am, so be it. A lot of bus crashes are survivable even without seatbelts because the sucker DOES NOT come to a complete halt all at once unless you drive it clean off a cliff or straight into the side of a mountain. But that only holds if the basic structure does. Here, that structure failed utterly.  | ||
| Marc Bourget Rating: N/A |
On thing that concerns me about roof raises I've seen is that they employ a straight cut across the vertical. This concentrates stress. I plan on making a chevron cut. Tougher to make and will require some custom fitting if my plan of a custom guide for a plasma cutter doens't work out. But it'll be much closer to virgin metal and more than sufficient for a sturdy roof raise. Note that Galey points out raising the roof actually strengthens the chassis. | ||
| Brian Brown (Fishbowlbrian)
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Yup, Marc, the add'l. height of a raised roof will make for a deeper "beam"... more rigidity, less deflection across the "span" (coach length) IF everything else is kept the same or made better. However, the lateral and axial loads on the vertical members themselves become much greater, because of their additional span. And you're right, the splices certainly don't help! "Sistering" on a full length adjoining member might be overkill or simply sound engineering. We all need to know when making alterations and adulterations to a monocoque or semi- we must put back both the outside AND the inside stress panels on the walls and roof. Likewise, the rivets must be the same or better than "factory". Does Sikaflex have the same shear strength as a rivet? No way. A few hundred psi vs. a few million. The sides and roof are essentially a box beam and require the "flanges" of the beam, the skins, to be intact on both sides. Otherwise it's a compromised structure. One can easily mock something up out of basswood or balsa from the hobby store and readily see and feel the stiffness of a "sandwich" vs. the alternatives. Without both skins, it's a house of cards. And luan and other plywoods just don't cut it. Everybody, "do it your way." Just do it safe! Me? I'll stick with stooping a little. FBB | ||
| Phil Dumpster Rating: N/A |
You think roof raises have the potential to compromise a coach? What about slideouts? Those scare the hell out of me. Yet people do it so often and claim there is no cause for concern. Altering the shell in such ways without proper knowledge of what you are doing puts your bus into the same class as the sticks and staples when it comes to crashworthiness. | ||
| Marc Bourget Rating: N/A |
Phul said: " . . . puts your bus into the same class as the sticks and staples when it comes to crashworthiness." Structurally - maybe, but there's alot more to crashworthiness with a bus than that portion of the structure - making a bus still preferable to a S&S, especially a S&S with slideouts! So I agree with you but point out [without running the list] the unspoken attributes to the newby's. Onward and Upward | ||
| truthhunter@shaw.ca
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I can not think of a better place to expire than in a bus. This does not negate saftey first! Mayabe some day someone with engineered & proven plans (model specific)for slides and raised roofs will roll over (on trade secrets and liability) and offer them to others, if it is distributed free then their is only residual liability. Hell even the Manhatin Project is common knowledge in this era of information enlightenment. | ||
| Steve Padgett Rating: N/A |
Hi Guys, This is Steve from Sika. Just to give you guys some background, I'm a technical service specialist at Sika and I'm also a bus driver. Not a certified busnut since I don't have one, but I do hold a CDL with passenger and air brake endorsement and regularly drive a 4107 and MCI-9 running kids to a Christian camp in Michigan's Upper Peninsula (from Detroit) It's sad that this incident occurred. As a driver who routinely has 40 or more lives in my hands, I hoppe to never be in a similar circumstance. However, I'm concerned that our product (Sikaflex) has been ID'd by some people as having some involvement. Tha article mentioned that the roof skin had been riveted and glued together. As everyone knows, there are many products used (some correctly, some incorrectly) for this operation. The Sun Herald article pins the root cause on corrosion of the frame work. On a properly treated frame, an adhesive like Sikaflex is certainly strong enough to handle just about anything you can throw at it. True, a rivet has tremendous strength at the rivet point, but an elastic adhesive has great strength all along the bond line, often resulting in a greater distribution of energy and no chance of failure due to rounded rivet holes or fatigue. Most of the newer smooth side buses use Sikaflex adhesives to bond the skins on with very few rivets. In a couple of bad crashes I've heard of, the biggest problem was in removing the skin. It doesn't just fall off. If you look close at the photographs, this bus appears to have failed at the bottom of the window frames, not the roof skin. Steve | ||
| Marc Bourget Rating: N/A |
Steve, Thanks so much for weighing in with a reasoned and experienced observation regarding this thread! Well Done! | ||
| DMDave Rating: N/A |
Maybe they got really cheap and lazy and added new sheet metal to the roof. If it was new steel over the old aluminum it could add pounds. But it dident cause the accident, nor did pre exsisting cracks in bulkheads. | ||
| John Rigbyj
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The bus turned over at 70 mph, no wonder the roof came off. John | ||
| BrianMCI Rating: N/A |
In reading the story, it apears to me that they added steel panels over the existing roof which certainly would have added 600 lbs if that is the case... it certainly would have been the fast and dirty way to do it! In any case if the NTSB says there was an added 600 lbs I'd have to think that was the case. Metalurgy is a tricky thing... that this coach was in a fire and got so hot it required it's roof be repaired makes me suspect that the metal of the roof pillars probably were compromised add an extra 600 pounds to that equation and it isn't surprising that the roof sheared off during the accident. Brian | ||
| Sojourner (Jjimage)
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Good to hear you Steve. Please always feel welcome to update and correct any question regarding to SikaFlex 252. I know your a tech. on this product and many of us have wonder about how to use it and where to apply and still do the job without future problem. I talk to you on phone in MI. We need your technical support from the horse mouth. Thank you Sojourn for Christ, Jerry | ||
| James Maxwell (Jmaxwell)
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Steve: Since I was the 1st to mention the Sika name in this thread, be assured that I intended no implication of the product as a cause or any involvement. I was merely questioning the amount of it as implied by the 600-700# added weight and I used a Brand name in a generic context. My apoligies. | ||
| steve padgett Rating: N/A |
James, No apology needed. Actually, it's kind of cool to have Sikaflex become a generic term for a great adhesive. I just wanted to clarify my thoughts on this tragic event. Steve |