Thanks for this. I was aware of some of the previous failures and can see that the newer cars, eg metric chassis, appear to have a further strengthened underslung mounting point. My car (late 1996) has the later de-dion with the wider lower triangular section to take the A frame bushing, which I would like to keep, if ever I need to change it. I think the photograph you show is the earlier pre-1996 de-dion, which also has the central mounting point, but probably lacks the lower one.
I've has reassurance from a reputable source that the only difference in the nitron dampers for either mounting is the length of the interchangeable lower mounting on the damper, so there are always options.
It is probably more difficult for a low volume manufacturer to eliminate all potential failure modes early in production runs I guess, though I would rather have a de-dion that is a few kg heavier and doesn't fail!!
On the first DD tubes with underslung mounting point i have seen some very poor welding, besides that there are better ways and easier to manufactor to fix an underslung mounting point that doesn't compromise the tube it's strength, some people may think that when something is welded it's strong but in fact get it wrong and it becomes weaker.
I've seen another tube fail like that on a track day. It has been suggested jacking the car up on the dedion tube can cause this.
Hi Ian, yes I have also heard that so I always jack under the diff. Don't want to hijack this thread but briefly the story from the thread linked above is:
"At about 35mph, rear of car suddenly stepped out to the middle of the road and crabbed along with no prior warning. Earlier in the day I had done some 'hot' laps of Hethel, and this happened on the way home 36 miles later. The car is a 1991 and had done about 16,000 road miles. Arch sand blasted and re powder coated the chassis including the tube in 2004 when I did a ground up rebuild. At no time did they or I notice anything wrong. Always jacked from under the diff, but previous owner could have used the tube as a jacking point."