-Chassis failure

[coltishall pete]

 

Dear all

 

I have notices over the last few days various noises coming from the rear of the car. I removed the rear wheel and found to by horror that the crossmember rear axle has cracked through where it meets the main chassis, just below the rear damper mounting bracket. I have attached a drawing showing the position, although it is the offside and not as shown.

 

The edges of the crack are bright and I cannot see any rust.

 

I realise that I can get this welded up and that it is important that some additional reinforcement is used.

 

However, something has caused this fatigue failure can any body help who has had a similar problem.

chassis_2.bmp

chassis_2.bmp

[marvmul]

That's very unusual, I suppose. If it is not a manufacturers fault, then is it fatigue? By flexing of the chassis because of rust in the neighbourhood?

[Richard Crawley]

Pete

Not that it helps much but I’ve not seen a failure in that area before. I would say it’s almost certainly associated with stress from the action of the shock absorber; what type do you have, original lever arm or telescopic with a conversion bracket? I suppose running rock hard suspension settings coupled with hard nylon bushes would increase the stresses in this area considerably but I’m still surprised it’s cracked! How long have you had the car, does it have any history of restoration work? Do you know if a previous owner raced or seriously abused the car?

[coltishall pete]

Pete

Not that it helps much but I’ve not seen a failure in that area before. I would say it’s almost certainly associated with stress from the action of the shock absorber; what type do you have, original lever arm or telescopic with a conversion bracket? I suppose running rock hard suspension settings coupled with hard nylon bushes would increase the stresses in this area considerably but I’m still surprised it’s cracked! How long have you had the car, does it have any history of restoration work? Do you know if a previous owner raced or seriously abused the car?

 

 

Richard

 

Thanks for the reply.

 

The car has the original lever arm shock absorbers.

 

The car was body off restored I think about about ten years ago.

 

Perhaps its down to just one too many pot holes in the Norfolk Roads

[Guest ron]

Hi Pete, like the others I've not seen cracking at that point, surprisingly as it does look very vulnerable due to the action of the shock absorber. I wouldn't be surprised if a few cars have unknown cracks there and this is probably an area worth checking in the future as the chassis get older.

I think it might also be worthwhile checking the diff mounts as the design looks as if it uses the diff as a support for this crossmember to stop it flexing backwards under the action of the shock absorber.

As you suggested in your original post it is important that it is reinforced as it will just crack again beside the weld if it isn't.

Ron