De Dion tube broke

[Janza]

I got new but I'm thinking Why this happening:



Car got little racing history (hill climb). But now only daily drive and sometimes trackday.

Car is 1991

[damdy-cash]

that problem is well-known, have a look here http://www.blatchat.com/t.asp?id=94283

cheers Volker

[one eyed mick]

If that is the standard of caterham welding I'm glad I've not got one ,pigeon crop is'nt init

[BertBert]

well that was what it looked like 20 years ago, but maybe not now!
Bert

[Dave J]

jacking the car on the A frame bush .

[BertBert]

Dave J said:

jacking the car on the A frame bush .

Yep, agreed.

[Purespeed]

Learnt something new tonight. I always jack from the A frame bush but I wont now.

Jason

[Incorrigible]

You can jack on the bush with the newer style de-dion (still not recommended though)

The old ones have a much narrower "tower" which is the bit where the a-frame bush sits (when you put the old one and new one side by side it will be obvious). Also there are 2 models of the newer ones which are slightly different lengths, if you've bought it new then you'll be fine. However if it was second hand check the clearance between the brake caliper and the radius arm

[mickrick]

Spray some waxoil inside the new one before you assemble it.
I bet the handling was fun untill you realised what had happened!

[downsman]

The recent "Get to know your Seven" articles in Low Flying said that the best place to put a trolley jack at the rear of the car is under the A frame bush.

Looking at the chassis design, I can't see a better place to place the jack to raise both rear wheels. Where do you put the jack if not under the De Dion tube?

[BertBert]

The DD tube does not take the weight of the rear of the car in the middle in any circumstance other than jacking. If you look at how it bears weight in normal operation, the distance between the load point (shock mount) and support point (the end) is pretty small for roughly half the weight of the rear.

So I never jack on the middle of the tube.

You can jack under the end of the tube or on the rear towing eye.

Bert

[Dave J]

I jack under the diff

maybe , just maybe the low flying articles are incorrect ?!

[DCL]

Look at the failure in the photo, this has been caused by fatigue through flexing of the A frame mount where it joins the tube - but I doubt there have been enough jacking 'cycles' to cause it. I would suggest that too light a gauge of metal in the tube has just not coped with the cornering forces imposed by the A frame.

Edited by DCL on Friday 19th August 22:16