Dave_H Posted April 24, 2003 Share Posted April 24, 2003 I’ve just had a failure of my cars de-dion tube. At the weekend I noticed that the rear suspension had sagged on one side. After jacking up the back of the car, it was clear that the de-dion tube had split virtually all the way round both sides of the shock mounting boss. Luckily for me, I just noticed it before it had gone all the way around – I hate to think what would’ve happened if I hadn’t spotted it sooner. ☹️ The car was built August 1999, and I’ve only ever done 2 ½ track day’s - never riding kerbs. The de-dion tube has been substantially strengthened since then, so If your car is newer than this you should be OK. If your car is of a similar vintage to mine I’d seriously think about having a good look at the tube, especially the shock mounting bosses – even if you never do any track days. This tube was clearly not up to the job and its recent modifications prove this. There’s a (not very good) picture here Just don’t expect any comeback from Caterham – according to them it’s an installation fault. 🙆🏻 Dave If anyone’s got a decent tube for sale let me know! Link to comment Share on other sites More sharing options...
stevefoster Posted April 24, 2003 Share Posted April 24, 2003 I check mine often, ooh er. I'm no mech engineer in the theory of metal stess and weld alteration of a metals properties BUT, Looks like a stress failure in the metal around the welds due to way the weld has affected that metal. I reckon a good old pot holey road is worse for your suspension than any track day (kerb crashing excluded perhaps). We talked earlier about jacking the car on the A frame possibily causing tube failures. Any views on this particular one? Seems a long way from the jacking point but you are lifting the car on these points and making the tube droop doing this. Trouble is it's hard to use a quicklift on the diff quickly. Jason B has done some 55K+ miles on his tube 1996 car. Are you running the progressive springs or very stiff ones? My racing pics, 7 DIY, race prep. Updated often here Photo's of the year here Hants (North) and Berkshire Area club site here Link to comment Share on other sites More sharing options...
Dave_H Posted April 24, 2003 Author Share Posted April 24, 2003 Steve, I've always jacked the car up under the diff. As for springs, I'm using the SV/21 progressive's - they are quite stiff but not overly stiff. I agree that bumpy roads must put a lot of stress on the suspension, surely it should have lasted longer than 3 years though Dave Link to comment Share on other sites More sharing options...
Mark Durrant Posted April 24, 2003 Share Posted April 24, 2003 Dave Sorry to hear about your tube failure ☹️ but it would help to know how many miles your car has covered. Thanks Mark D Su77on Se7ens Avoiding the Kerbs Link to comment Share on other sites More sharing options...
stevefoster Posted April 24, 2003 Share Posted April 24, 2003 Dave, You could have had a dodgy or too hot weld. How can it be installation? My racing pics, 7 DIY, race prep. Updated often here Photo's of the year here Hants (North) and Berkshire Area club site here Link to comment Share on other sites More sharing options...
Dave_H Posted April 24, 2003 Author Share Posted April 24, 2003 Mark I've actually done about 30k miles shameful I know, but that's what I bought it for 😬 I believe I met you at Heyford just before you had your “incident”!? I was with Jon who picked up your spare radiator. Steve I don't know, but thats what they said. Maybe it's the fact that you have to pack the shock absorber out with washers to alow the adjustable platform to clear the tube - I always thought that seemed a bit dodgy Dave Link to comment Share on other sites More sharing options...
stevefoster Posted April 24, 2003 Share Posted April 24, 2003 I wanted the shorter dampers as they go through the tube on long bolts but even the M1 Race dampers are long and bolt on to these after thought weld on's. I think the Freestyle dampers are the shorter ones though... My racing pics, 7 DIY, race prep. Updated often here Photo's of the year here Hants (North) and Berkshire Area club site here Edited by - stevefoster on 24 Apr 2003 10:54:09 Link to comment Share on other sites More sharing options...
AMMO Posted April 24, 2003 Share Posted April 24, 2003 Basically I think it is a design fault. Nobody in their right mind would mount a shock that way. It almost eems like the shock was too long and it was decided to put the mount under the tube. The mount is always trying to pull away from the tube. I have the earlier De Dion where the shock mount goes through the tube. This is a much better solution in my opinion. Better still would be an even shorter shock (think of the weight saving) mounted with brackets in double shear above De Dion tube. Stuff like this scares the crap out of me. Good job it didn't fail while you were doing any speed. AMMO Link to comment Share on other sites More sharing options...
Dave_H Posted April 24, 2003 Author Share Posted April 24, 2003 AMMO I totally agree. I think it’s only a matter of time before someone is seriously injured or worse. I’m just so glad that I found it when I did. Dave Link to comment Share on other sites More sharing options...
stevefoster Posted April 24, 2003 Share Posted April 24, 2003 So why don't we gang up on Caterham and get this sorted? My racing pics, 7 DIY, race prep. Updated often here Photo's of the year here Hants (North) and Berkshire Area club site here Link to comment Share on other sites More sharing options...
Dave_H Posted April 24, 2003 Author Share Posted April 24, 2003 Steve, I've been in contact with Caterham, basically it's my fault not theirs - even though this part has been substantially strengthened recently. I’ve given up with them to be honest, they just don’t want to know – they seem to be only interested in new car sales these days 🙆🏻 Dave Link to comment Share on other sites More sharing options...
greg Posted April 24, 2003 Share Posted April 24, 2003 without wishing to stir up a hornets nest: How long do manufactures need to be liable for thier products - correctly installed or not? If this is an install issue why have we all not been warned that it is possible to install them wrongly? Have I got the wrong end of these posts. Greg, Q 86 NTM (Green 185BHP XF) Link to comment Share on other sites More sharing options...
stevefoster Posted April 24, 2003 Share Posted April 24, 2003 I agree with the above. It will not be good for Caterham, the club or the person that sufferes the worst from one of these failures. How is it best to act as a body of blatchatters? My racing pics, 7 DIY, race prep. Updated often here Photo's of the year here Hants (North) and Berkshire Area club site here Link to comment Share on other sites More sharing options...
greg Posted April 24, 2003 Share Posted April 24, 2003 Steve, I assume you agree with me? I would have though the best way would be for someone to double check the evidence and then write a letter outlining some concerns and then await Caterhams writen response. This could open another tin of worms as what other bits can be incorrectly assembled resulting in a safety critical failure? I would have thought the list could be quite long ..... Greg, Q 86 NTM (Green 185BHP XF) Link to comment Share on other sites More sharing options...
westy Posted April 24, 2003 Share Posted April 24, 2003 You could do with getting that wall repointed while your off the road to (at least it's in focus 😬) Link to comment Share on other sites More sharing options...
Dave_H Posted April 24, 2003 Author Share Posted April 24, 2003 Cheeky git!! Dave Link to comment Share on other sites More sharing options...
Mark Durrant Posted April 24, 2003 Share Posted April 24, 2003 Dave I now have a new tube, radius arm and ears fitted and the car is back on the road. The impact did not break the tube but bent one of the mounts for the ear so better safe than sorry I replaced it. As for the old tube I intend to recycle this as a tyre rack in the garage. My brother, although he doesn't know it yet, will make me some brackets that can be bolted to the tube enabling me to fix it to the wall. An expensive tyre rack but better than just chucking it away. I do find Caterhams attitude to these failures very disappointing, they could at least make a good will gesture of supplying it at cost! Mark D Su77on Se7ens Avoiding the Kerbs Link to comment Share on other sites More sharing options...
Dave_H Posted April 24, 2003 Author Share Posted April 24, 2003 Mark Sounds like you’re gonna have quite a cool tyre rack. Make sure you don’t damage it though – you’ll probably need it one day! Yes, I was very disappointed, it’s just there typical attitude though. A new tube at cost would have been a nice gesture – all I got was stubborn refusal to accept blame in any way, shape or form. I could understand it if I’d been tracking it every weekend or the car had a big powerful engine, its only a 1.6 SuperSport. Dave Link to comment Share on other sites More sharing options...
R2D2 Posted April 24, 2003 Share Posted April 24, 2003 This problem with Dedion tubes keeps coming up and it seems to me that there are just too many failures. To be simplistic the failures must be stress related as the component has broken and as far as I know the only way to break any material is to apply a stress. It is also quite common to have failures occur in the heat affected zones of welded parts and any reduction in a material's property that may occur should be allowed for or the component should be designed so that a weld is not in a region of high stress relative to the rest of the component. The calculation of the stresses needed to cause a catastrophic failure are not too complex and I don't really think that this is the issue. It is much more likely that the failure is fatigue related and esimates of fatigue life can be quite complex with major/minor fatigue cycles also influencing component life. It sounds as if Caterham's basic attiude isn't too helpful and they should be prepared to answer some basic questions. If you are designing any fatigue rated component you must start with an estimate of the service loads that can be applied and hence the stresses that are being developed in the component. Automotive designers then commonly use a Goodman Diagram to estimate fatigue lives and it is in this area that it is easy to under estimate particularly in a situation where loading is fairly complex. It would be useful to know the stress levels that Caterham estimate in the region of the failure and to try to model the fatigue life based on these assumptions. It would also interesting to know what increase in stress they believe occurs when the component is incorrectly installed as this seems to be a standard response but I think more detail is needed. If anyone has a broken dedion tube that they are scrapping rather than repairing I wouldn't mind having a look at the failure. Link to comment Share on other sites More sharing options...
Dave_H Posted April 24, 2003 Author Share Posted April 24, 2003 Chris, You're more than welcome to have a look at mine, YHM. Dave Link to comment Share on other sites More sharing options...
Paul D Jones Posted April 24, 2003 Share Posted April 24, 2003 Is it the weld that has failed or the perant material Is it TIG or Mig welded as I have said before Mig is Crap in this application and it should be tig welded. Paul. See My Car Here Link to comment Share on other sites More sharing options...
stevefoster Posted April 24, 2003 Share Posted April 24, 2003 Hard to say where the crack started from the photo... If one did as you say Chris then they would be a service item or have to be designed for the reasonble life of the vehicle. Longer than 3 yrs / 30000 miles at any rate I would think. Can we def say that the tube with the shorter damper bolted through it is less failure prone? I would change my dampers tomorrow if that were the case. My racing pics, 7 DIY, race prep. Updated often here Photo's of the year here Hants (North) and Berkshire Area club site here Edited by - stevefoster on 24 Apr 2003 15:15:38 Link to comment Share on other sites More sharing options...
R2D2 Posted April 24, 2003 Share Posted April 24, 2003 Steve, I have never heard of a road car that has a component designed for a finite life, this would be an insurance nightmare. It is common to do this on race cars and fighter aircraft but this is usually backed up by fairly extensive component testing. If these tubes only fail on track cars with sticky tyres it may be worth trying to "life" the component but I would think driver ability could be aq significant variable. Depending on the load spectrum it may only need small changes to provide a component with infinte life, which would be the happiest solution. I think we really need to draw it out and start some basic stress analysis with some reasonable estimates of loading. Link to comment Share on other sites More sharing options...
V7 SLR Posted April 24, 2003 Share Posted April 24, 2003 When was the redesigned de Dion implemented and what was the redesign? I lightly tapped my original one (which Rob Grigsby's now using) causing a very minor toe-in when my car was new. That was early in 2000. That particular de Dion harks from late 1999 but I had a new de Dion simply because it was my new car and I wanted it back as new again. I need not have done so because it was only very lightly damaged. I could have shimmed the ear a half degree really. Anyway, from April/May 2000 my (new) de Dion has had approx 14,000 hard miles. I've run with big wide sticky ACB10s since new and with 200bhp also from new. It's done about a dozen track days in that time. After reading Steve F's original post warning us all to check our tubes, I spent an educational few minutes on my back in the garage investigating mine which appears to be OK. My dampers are mounted underneath on those tacked-on brackets. I appear also to have holes in the tube itself to which shorter dampers could attach, which I agree looks a far better solution. I hadn't realised until reading this that those holes were intended for damper mounting. Another reason to buy Freestyle dampers next year I think. 😬 Now, if my new de Dion is of the old design (tell me what to look for) then I would have expect mine to have failed IFF the the design is at fault (the sticky tyres and power ought to have caused a failure) but if the failures are because of manufacturing inconsistencies then I would have expected the failures to be a bit more random. Either way it seems a bit hard-nosed of Caterham to insist it is an installation problem. How on earth can you install it wrong? In fact, did Caterham explain what it was that was wrong and why wasn't it picked up at the PBC? I wouldn't necessarily expect Caterham to pay for a new one, or to even give it away at cost but I would expect them to be a bit more forthcoming with information about why it failed... unless that directly implicates them as having supplied inferior components. Their lack of openness recently (R300/400 maps) is quite concerning. Anyway, Rob G ought to keep an eye on his new tube. I'll provide a full refund if it fails. Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours Link to comment Share on other sites More sharing options...
Dave_H Posted April 24, 2003 Author Share Posted April 24, 2003 V7 SLR This is the latest revision to the tube I believe: here Dave Link to comment Share on other sites More sharing options...
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