Help - Cracks In S-s Welds :o

[Guest projectinsane]

Hi all,

 

After leaving 'da tin' (as its known) over the winter months, Ive returned to get it ready for this years summer only to discover a slight crack in three of the structural welds on the corners inside the engine bay .., only god knows how they got there

It is an Exmo kit collected from Robin Hood in 1996, which was not built until 2 years ago. I am only running a 1600 pinto so I doubt the engine torque would have made a differnce, it has not been involved in any crashes which would have stressed it and since sva, has only just done over 1200 miles.

 

Nevertheless, can anyone suggest anything that would sort it?

 

- I only have a MIG welder which I believe can not be used on stainless steel.

 

- Im worried that getting it road legal and/or driving it somewhere to have it repaired might stress the fractures more.

 

- If its started to crack structurally then what would stop it happenning again and what damage could be done to the chassis?

 

I have considered making some 'braces' to help ease the load out of 5mm x 8'' mild steel and bolting them through to try and reduce stress and stop the same thing happenning in the future.

 

Any help, advice or information all gratefully recieved as obviously Id rather not go messing about too much with the cars original structure.

 

 

Thanks people

[steve_wilson]

theres been a lot of thread about this in the past, quite a common problem i think.

 

have a search and im sure you'll find the solution

 

cheers, steve

[Jamiep]

can you post some pics of the cracks with reference to where they are as I haven't found any on mine but would like to check in same areas.

as for repair,I'm no expert but if possible drill the ends of the crack the reweld and possibly weld a patch too.

 

mig welding works fine on stainless but remember to use stainless wire and if possible argon gas to reduce discolouration and impurities in the weld.

 

if your not confident in welding stainless try looking for a local food equipment manufactures/ fab shops as they will weld it on a daily basis.

[Guest projectinsane]

Yea, I will do but the cars in a lockup 15miles away from where I live. I wll try to get some pics up fri evening/saturday for you to reference from. Thankfully they are not large cracks.., yet, but obviously I want to catch them sooner rather than later.

 

After having a search on this site I reckon Im going to grind the offending bit out, reweld as best I can then brace the joins as best I can with some 6mm plates bolted through chassis/shell and see how I get on.

 

Wish me luck people, and I will let you all know how I got on.

 

Thanks

[Longboarder]

A welded repair is best. If adding strengthening it would also be best welded in by someone who knows what he's doing. Bolted in braces means more holes drilled in the monocoque around an area that is already weak.

I would advise take a little more time to carefully examine all the front end welds, including the engine bay floorpans. Also wait while other owners add more comments and advice. Then think through and plan repairs with the help of a good welder and without rushing.

 

Nigel

[Snapperpaul]

I am keeping a look out for the very same problem on my S3, if the problem hits me I will drill either end of the crack, grind and reweld then patch over and weld.

[Guest mower man]

I have had minor probs with cracking on my s7 in the same area not so much welds as the engine bay floor ,drilled the ends and plated also put a stiffener in the return using aircraft bond and rivet techniques I know there was some disscusion about the spec of the metal used a while ago ,anybody know any more info? .I personaly think spring rates for the front susp are too heavy [factory spec on inboard susp was 180 lbs ] and this does not help ,my car handled like a tea tray until I fitted 120lb srings and tie bars ,the improvement was enormous ,any other comments? mower man

[Guest projectinsane]

Longboarder - I understand what you mean by stressing the shell with holes for the bolts, that was something I was worried about too. If, 'theoretically' I was to plate both sides with 6mm and add some hollow tubing between the rolled strengthening beam to stop the bolt torques compressing the beam inwards...., (thus the technique I was told best while building subframes for my 4x4 Puma) Admittidly the beams are not solid box section, but the 4mm tubing should add strength around the holes and the 6mm plates will strengthen the shell.

 

I have considered welding the plates on, although am worried that in time the plate welds could also crack so am trying to prevent, rather than cure again in future. Maybe to be safe I could do both, then, if the welds did split it would be held together without any major surprises when driving about one summers afternoon???

 

Its definatly looking like this weekend will be going over every single weld with a torch and a fine toothcomb.

 

Thanks for everyones advice, its all useful and gratefully recieved

[Jamiep]

there are some very good bonding adeasives available for stainless but would have to be a clean flat area and you would have to be able to clamp an even pressure over the whole patch for 24hrs.

 

I was involved in a test using such a bond which we could not split using about 1000kg but we also had one that failed after 10kg due to the sheets not being cleaned properly.

 

I think mowerman is probably on the right track ref: the stiff front end as it's repetitive shaking that does in stainless.

[Guest gdc]

from what i can gather stress cracks are almost expected on the stainless monocoques ,

and reported through posts .

welded repairs are poss the best , but need to be done compitently.

 

graham

[geoff shep]

Yes, these were very common on the monocoques - stainless and steel alike. We used to stop-drill and re-weld. Also, I bolted on some extra stiffening in the form of 1" square heavy tube.