CharlieC Posted September 8 Share Posted September 8 On a motorway transit yesterday evening, I had the unpleasant experience of the mount attaching the bottom of the rear (left) suspension arm to the DeDion tube become disconnected, necessitating a quick stop (scraping the floor of the car along the road) and continuning the rest of the jounrney on the back of a low loader. The attached photo shows the situation today - the attaching bolt has been lost, along with the fitting and washers (possibly sheared flush with the DeDion tube). There was also some grease around the ant-roll bar arm and the inside of the wheel. I have also attached a photo of the 'good' (right) side for comparison. So my question is: What to do? Is this a simple case of reattaching the suspension arm with a new bolt (too good to be true, I suspect) or something that requires the removal and servicing (replacement) of the DeDion tube? or something else? All help/advice welcome from the knowledgeable club membership! Many thanks, in advance Link to comment Share on other sites More sharing options...
OldAndrewE Posted September 8 Share Posted September 8 Not familiar with this set up (as I have a live axle car). I assume that is a threaded boss in which case there is probably a bit of sheared bolt left in there. That will need some careful work with drills and screw extractors to remove it. Make sure you have the correct grade of bolt when you replace. Re the grease did the driveshaft boot get damaged in the incident? Link to comment Share on other sites More sharing options...
CharlieC Posted September 8 Author Share Posted September 8 (edited) With a bit of poking around, there does appear to be part of the sheared bolt remaining inside the DeDion tube, so will need to be removed. Thank you - good spot. Regarding the grease and the driveshaft boot - possibly. Is that where you think the grease will have come from? Edited September 8 by CharlieC Link to comment Share on other sites More sharing options...
Jonathan Kay Posted September 8 Share Posted September 8 Please let me know if you'd like a copy of the appropriate Assembly Guide. Jonathan Link to comment Share on other sites More sharing options...
OldAndrewE Posted September 8 Share Posted September 8 18 minutes ago, CharlieC said: Regarding the grease and the driveshaft boot - possibly. Is that where you think the grease will have come from? It is one of the main sources of grease in that area, certainly worth checking 1 Link to comment Share on other sites More sharing options...
Wrightpayne Posted September 8 Share Posted September 8 I wonder if there is anyone with metallurgy knowledge on the forum. With a photo of the end of the bolt they might be able to tell if overtightened. When I read the post I thought it was going to be about dedion tube failure, which used to be a thing, but yours is the later design. I’d also check all the suspension bushes for play to see if any unusual twisting of the dedion is happening. I know of one owner who’s car entered the scenery when a dedion tube failed (its in the archives). Scary stuff!! Link to comment Share on other sites More sharing options...
Wrightpayne Posted September 8 Share Posted September 8 Also, is the ARB fitted correctly - looks very low to the road? Link to comment Share on other sites More sharing options...
Wrightpayne Posted September 8 Share Posted September 8 #3 the brake disc wear looks very different on the collapsed side. Is that preceding the incident or caused by it? Something else to check IMHO Link to comment Share on other sites More sharing options...
CharlieC Posted September 8 Author Share Posted September 8 (edited) That is my conclusion too! Lots of angles/aspects to look into .... The irregular disc wear preceded this and is a known issue. Thanks Edited September 8 by CharlieC Link to comment Share on other sites More sharing options...
Gridgway Posted September 8 Share Posted September 8 Needs a good inspection to check for any damage apart from the sheared bolt. Left to my own devices, I'd want to get the DD tube out to get the remains of the bolt out and to check it was all ok. 1 Link to comment Share on other sites More sharing options...
CAT170 Posted September 9 Share Posted September 9 I'm not a metallurgist but once a Rolls Royce stress engineer (albeit over 35 years ago) and had some experience of tests to failure of components during development (some planned, some not so planned! but always before production🙂). The start of this article has excellent photos of failed bolts and some failure modes. https://smrp.org/News/Solutions-Archive/Member-Written-Articles/Bolt-Failures-Why-Learn-to-Recognize-Mechanical-Failure-Modes If you are able to see details of remaining bolt face it might give away its secrets. They haven't shown another common failure which occurs due to a poor quality bolt's small crack or inclusion at the thread root and a series of shell like lines grow around it as a crack spreads, often worsened as rust sets in but yours looks too new for rust effects. For what it's worth, my guess is the bolt was probably fine but insufficiently torqued allowing some movement that tends to worsen and a sudden impact sheared it off. Could also have been overtightened and sudden added shear impact was just too much. 1 Link to comment Share on other sites More sharing options...
Area Representative Geoff Brown Posted September 9 Area Representative Share Posted September 9 (edited) When building my car & the subsequent back end rebuild post diff repair I found that the shocker rear face & the DD mount do not align parallel to allow easy insertion of the bolt. With a bit of fiddling the faces can be aligned but it is tight. Maybe the two faces were not lined up sufficiently to allow easy insertion & turning of the bolt. If so then the threads could have been easily & sufficiently crossed in the mounting. Torque loading then possibly assisted in putting the bolt in failure mode. I quote the engineering mantra: 'do it up till it shears then back half a turn'......😖 Edited September 9 by Geoff Brown 1 Link to comment Share on other sites More sharing options...
Jonathan Kay Posted September 9 Share Posted September 9 3 minutes ago, Geoff Brown said: I quote the engineering mantra: 'do it up till it shears then back half a turn'...... I'd guess that you've heard the bomb-aimer's joke a few times... Jonathan 1 Link to comment Share on other sites More sharing options...
Leadership Team Andrew 21 Edney Posted September 10 Leadership Team Share Posted September 10 (edited) 18 hours ago, Jonathan Kay said: I'd guess that you've heard the bomb-aimer's joke a few times... Jonathan Is it like the one on the train? "See where I get off, your station is the one before." Edited September 10 by Andrew 21 Edney Link to comment Share on other sites More sharing options...
Jonathan Kay Posted September 10 Share Posted September 10 1 minute ago, Andrew 21 Edney said: 19 hours ago, Jonathan Kay said: I'd guess that you've heard the bomb-aimer's joke a few times... Jonathan Is it like the one on the train? "See where I get off, your station is the one before." Precisely, but with added shouting. Jonathan Link to comment Share on other sites More sharing options...
Jonathan Kay Posted September 10 Share Posted September 10 By popular demand... the bomb-aimer's joke... Spoiler Left a bit, left a bit, right, right, right... BACK Jonathan Link to comment Share on other sites More sharing options...
CharlieC Posted September 11 Author Share Posted September 11 Thanks all for your inputs, although it seems to have veered off target a bit (sorry). Car is now in the capable hands of Andy at PGM, sent the Club's assembled wisdom attached. Link to comment Share on other sites More sharing options...
OldAndrewE Posted September 11 Share Posted September 11 54 minutes ago, CharlieC said: although it seems to have veered off target a bit (sorry). A bit like the bomb aimer 2 Link to comment Share on other sites More sharing options...
Nigel Blandin Posted Thursday at 07:13 Share Posted Thursday at 07:13 On 08/09/2024 at 16:22, Wrightpayne said: Also, is the ARB fitted correctly - looks very low to the road? The car is on stands on the chassis, so the dedion is on full drop. 1 Link to comment Share on other sites More sharing options...
Ainsley Posted Thursday at 07:25 Share Posted Thursday at 07:25 I would replace the other bolt as well. 1 Link to comment Share on other sites More sharing options...
Area Representative Geoff Brown Posted Thursday at 08:17 Area Representative Share Posted Thursday at 08:17 A Frame rear mounting bolt, check A Frame for distortion the list is not endless but comprehensive. Link to comment Share on other sites More sharing options...
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