D.A.,
if these stress cracks are at the top edge of the A panel, more likely than not that they're the result of folk leaning on them when working in the engine bay.
Strong favourites for the culprits would be Kw~k#it or similar outfits, who never quite got their heads around the concept of removing the wings to replace an exhaust...

ken.

( p.s. @ oolong.
Hemispherical?
Are you quite sure about that? )

Ever seen one fail? I don't think they are poorly welded at all, what you see is just the excess from the welding process, it's not sloppy workmanship as such.

Agree
the arms appear to have had a zigzag edge to them before they were clamped and induction welded what you see on the arm is the slaggy deposits that were squeezed out during the weld

if you clean them up with a grinder there is a perfectly formed fusion all the way up

on older Mig or gassed arms ive seen the two halfs so out of register that supplimentary welds were laid to fill the gap there was a batch doing the rouds of all the fleamarkets 10 yrs ago

only arms I've ever seen let go were ALWAYS because someone thought srengthening them would help.
had to weld up a rear arm at the 24hr this year....with the driver still in situ
Sean

Ken - ah, of course!

Found myself doing that the very first time I opened the bonnet for a look-see .

At least neither Kwik-Fit nor anyone else will be getting near it from now on...

Haha, brain fade. The only vaguely hemispherical areas on an orig chassis are where clumsy garages/MoT testers have jacked under the wrong spot.

Semi-circular, I think I meant to say. Thanks Ken.

Although I live in Orstralia where the chassis are upside down (and so is the whole country) I have been very interested in this thread. However, I have also been confused as I don't know one chassis from the other (brand wise). Perhaps Roy and Viking can help me.

Roy, what is the brand of chassis that you stock at ECAS?

Viking, what is the brand of chassis that I bought from you when you lived in Perth. I have an idea that they were sourced from the Netherlands.

Club Cassis stock Plateformes Origines and cheaper Plateformes Adaptable, which look identical.

For Australian 2CV owner the above plus Das Franzose in Germany would probably be the source for a new chassis. How different are they?

Daffy Duck

There are no more original chassis around or produced.
Cassis claim that they manufacture so called original chassis most likely on tools from Citroën France. The other chassis are from Argentina also supplied to the Dutch where many 2cv businesses get them from including us.
The chassis are galvanized in the country where they sell from either cold around 90 or hot dipped at around 400 degrees. The 90 degrees are cataphoretically painted afterwards (blank). These chassis are very well made and fit like a clove. You got one underneath Daffy Duck.
Der Franzose is producing their own, I don’t know anything about them but I’m sure the Germans are spot on with the quality.
The English are also making their own chassis and here it is a completely different world. The way I read it is that the English are keen on ‘’strong’’ chassis made with thicker material mainly galvanized. Some outlets are offering the South American produced chassis. In my book only time will tell which chassis are good? Of cause word of mouth is also an indicator which chassis to buy or which ones to avoid but sometime fact and/or reality is not always mentioned. To me a chassis is just another part which will rot away in time no matter what you do. I prefer a chassis that can flex in response to the road. My choice for my own cars is the 90 degrees cataphoretically painted. Will also recommend this chassis to customers but if their choice is for something else, I’ll help them getting what they want.

Hi again Viking,
a few comments necessary, I'm afraid...

Any chance of more info on this 'cold' galvanizing?
As far as I can make out, this is actually electroplating, which is nowhere near as good as hot dip galvanizing for corrosion protection.
The following links may be relevant.
< http://www.hdgasa.org.za/infoSheet/sheet1.pdf >
& < http://www.mechanicsupport.com/galvanize.html >

As regards your preference for a 'flexible' chassis, I'm (almost) lost for words.
< http://en.wikipedia.org/wiki/Body_flex >

ken.

Thanks Viking. I had suspected that this was the case and presume the the Cassis Plateformes Adaptables come from the same source.

For Australian conditions, the black painted ones are fine as the drier climate reduces rust. I did squirt in a litre of anti rust penetrating oil through each of the 9 compartment plugs. Much of this slowly seeped through the seams on the bottom edge of the chassis. I guess in the UK, using Waxol liberally would preserve a new chassis for a long time.

The 1986 2CV (last of the French builts) still has its original chassis. Hugh Rhys-Williams (Tunbridge Wells) had maintained the car up to 1993 when I bought it. He used to pour sump oil into the chassis which helped. Seems to be OK, but one front arm has been bent up slightly due to a very heavy hit in a washout. The triangular panel has a widening gap from top to bottom. The other side is fine. One day I'll look at it.

Daffy Duck

We can go back in time, what I write here is shear speculation and what I hear from other folks. Original chassis 50’ 60’ 70’ are made from top quality steel. My AK 400 chassis from 1975 lived in salty and humid condition (Viking country) up to 2001 where after Viking Van went down under. 2005 on a raid survey I broke the chassis the usual place underneath the steering rack. It folded nicely just like all chassis do. After the survey, I opened the chassis and found large amount of rust solution floating around mainly underneath where you rest your feet. The good news was that the chassis had not rusted at all but it simply bend from hitting a washout at 30 km per hour.
Should mention that the Van have never been off road before.
This to me proves how ‘’flexible’’ the chassis is or how soft the metal is maybe also suggestion that the chassis design makes the chassis bounce around. Back to the speculations. When Citroën France decided to end A-model production sometimes beginning of 1980 chassis was made from recycle metal. Look around and see whole cars made in Portugal they rust away by just listening to the weather report.
Thanks to all this folks are turning to galvanized chassis and may also look for solid build chassis. My reason for wanting a flexible chassis is based on raid cars breaking parts attached to the chassis. I believe that a stiff chassis will transfer the stress on to the suspension and other parts. Comparing original standard (soft) chassis to solid galvanized ‘’stronger’’ chassis and you see more bits on the stiffer chassis breaking. That is fact when we talk raiding maybe not the case on street cars. It is common knowledge that 430 degrees hot dip will make the metal more brittle, correct me if I’m wrong.
The 2 links from Ken does explain very well the difference between cold or hot dips.