stitch welding on cars

[optima21]

when cars are made the panels are normally spot welded together, and if you increase the performance of a car it is often recommended that you should stitch weld the panel joints together to increase the rigidity of the shell. anyone know the reasoning behind stitch welding as opposed to continuous seam welding of the panels.

a generic picture off the net to show what I mean

i've heard it said that the the stitch welding is less prone to cracking than a continuous weld, but I've have thought that the stresses would have made them at the end of the welds.

 

[the snooper]

if you make a structure too rigid it will start to crack because there is no give in it

 

[God mode restorations]

They are normally stich welded every other inch in high stress areas where panels over lap. Stitch welding helps reduce panels warping.

 

[piman]

Hello all,

I think it was Mo Nunn that used to prepare Ford's rally car shells and he brazed the seams?

Alec

 

[keeny]

we all know there is alot of movements in a car thats reason i think anyway they spot welded manufacter
as if they were seam welded it would be a problem it would break, so what i cant understand is
when a car faild mot on welding why now its got to be fully welded doesnt make sence .....

 

[Richard.]

if you make a structure too rigid it will start to crack because there is no give in it

Exactly this. By strengthening something to the point there is no give you can encourage stress points and cause a break where a bit of flex would be a bit of relief.

 

[PhillipM]

Less warping, less weight for similar stiffness improvements, and if a crack starts it can only cross one stitch before stopping, not a whole seam weld.

 

[Rocketman]

we all know there is alot of movements in a car thats reason i think anyway they spot welded manufacter
as if they were seam welded it would be a problem it would break, so what i cant understand is
when a car faild mot on welding why now its got to be fully welded doesnt make sence .....

But it doesn't need to be fully welded, it depends what you are doing - replacing a panel or putting in a patch for instance.