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Summary of Dedion tube failures


Ian B

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Why not get the strengthening bits welded on and it will be as good as a new one
Not necessarily, depending on it's age it could be the thinner gauge tube.

 

BTW, all info is useful, but can we please keep the thread on subject to provide a record of failures. Maybe we need another thread for 'fixes'? *wink*

 


Ian - Slightly Vider SVelte SuperVeloce model 😬 - Joint AR for North Kent - Area details and calendar here
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A somewhat understated notice from VOSA here *rolleyes* (thanks tweeky).

 

It's widely know, and by CC, that the failures don't only relate to "race cars", and there are more than "38" affected! *nono* 😔

 

Keep checking yours - pay special attention to the front edge weld of the undertube shock mounts 🙅🏻‍♂️

 

.

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Quoting Guy Lowe: 
Quoting Smithy7: 
Maybe this sort of subject should be stickied to the top of ChitChat.
Oh no, that would upset Caterham Cars and the managementwouldn’t dare do that *nono*I couldn't possibly comment *wink* but it would be a good idea if this was better publicised, before anyone (else?) gets hurt *eek*

 

 

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Great.just putting my BDR back on the road..and we have the DD Question.

She has done 33000 miles and the tube looks , but that seems to be no protection. I wouldnt mind so much if cc facilitated swops without charging the massive 300 pound price tag. This adds insult to injury. I did ask last time.

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1997 S3 1600K Superlight 138bhp.

Type 3, standard Bilsteins.

33K miles (road and track).

Spotted small crack around front edge of n/s damper mount weld during annual check.

Many thanks for prompting me to check through this thread!

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Has anyone done analysis of what is causing the failures? Is it a brittle failure or a plastic one?

 

Without having seen one in the flesh I would expect it to be fatigue with the straw that broke the camel's back being a pothole or high-speed corner loading the suspension.

 

From the pictures here it looks like it's a failure at, or very close to the weld, which to my (inexperienced, but interested) eye points to a manufacturing fault rather than a design fault. The heat involved in welding introduces stress to static components, which can drastically reduce their critical stress.

 

I find it very hard to believe that a car manufacturer lacks the knowledge and skills to assess load-bearing characteristics vs. requirements of an alteration to a component as simple and vital as the rear-axle. Perhaps CC had intended the under-tube mounts to be welded with pre-heating, or stress relieved after welding and this was not done?

 

If that's the case, I'd be a bit sceptical about the validity of repairing with ANOTHER weld as this is only likely to increase the internal stresses of the component...

 

 

I'm currently on the last module of my (Mech) BEng: 'Fracture analysis' - can you tell?

 

 

 

Edited by - charlie_pank on 27 Jun 2013 13:30:40

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Is this the longest running thread in here?

 

Ok, had the delight of my DD tube fail last Sunday, at Scammonden Dam hillclimb. I appear to have V2, and this has snapped almost completely in two, just after the central buttress. I was flat out, just changed up into 3rd gear, and chasing a class record needing only another half-second! The 'wiggle' from the rear was interesting!

 

Anyway, as luck would have it, I had a newer V3 tube in the garage, and have fitted this, only to discover the wider buttress bottoms out on my two inner chassis rails.

 

Do I cut and shut the chassis rails further apart, heat the rails and flatten them so the buttress doesn't butt them, or can I order a replacement tube with smaller buttress and through-tube mounts that is an improved design?

 

All advice greatly appreciated!

 

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Quoting LesG: 
.....

Do I cut and shut the chassis rails further apart, heat the rails and flatten them so the buttress doesn't butt them, or can I order a replacement tube with smaller buttress and through-tube mounts that is an improved design?

 

Ask Bruce Robinson at Arch.

 

Peter

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Ok, having had another look, I can see it's the A-frame bush mount catching on the chassis rail which the outer skin wraps around.

 

I will check with Bruce before I do anything else, cheers *thumbup*

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Ouchh!!!  - still quite a new 7 owner - and stumpled across this posting. Now I am worried! Went under my 1995 car and the dedion tube does not look like it has been replaced. More worries...

So onto caterhamparts. They only have the narrow buttress type, item 79016 available - not the later/wide type, which I understood was better. Should I just buy the narrow type? And can I replace i myself without disconnecting brakes and everything?

Thanks for any advice!

 

 

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Were are you, Morten?
Happy to look over your rear end (ooerr) if you are nearish, or a local member will probably offer too :)

It's not always obvious if a dedion has been changed, but it's pretty normally obvious if it is failing.

I've also a spare/good dedion if you get stuck...

Cheers - Simon

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