To Seam Or Not To Seam

[andy_twincams]

just been debating between a few friends of the advantages of seam welding??i personally dont think its worth seaming 1-inch on 1-inch off,though i am going to weld round suspention mounts etc just to strenghten it up a touch.wot do you guys think??

[215 compressor]

just been debating between a few friends of the advantages of seam welding??i personally dont think its worth seaming 1-inch on 1-inch off,though i am going to weld round suspention mounts etc just to strenghten it up a touch.wot do you guys think??

THINK SEAM WELDING LOOKS A LOT TIDIER IF GOOD WELDING

[andy_twincams]

carpets are probly going back down though??

[cfc1]

MOT states that any welding has to be seam welded... IIRC.

[dawesy]

think that only applys to repair work although i have never had a car fail using the plug weld method.

seam welding is very good especialy on an older car where the welds have a level of fatigue.

i have done the rolla and can say it does feel a fair bit more ridgid.

the reason for leaving and inch gap then inch weld is to stop any weld cracks from running up the seam. never do one long run as you'll comprimise the structure of the car.

[andy_twincams]

wot plug or seam on your rolla dawesy??

[dawesy]

seam, inch weld, inch gap

[nrgizerbunny]

problem with welding is invariably getting full penetration. I would seam weld and not leave the gaps. if you leave gaps you increase the stress where you have seam welded it so its more likely to fail.

[dawesy]

yes but the same stresses will still be there with a gfullseam exept the crack will not stop untill it reaches the end of the weld, which cdould mean a very long crack!!! thats why when repairing a split panel you drill out the ends of the split to stop it going any further

[nrgizerbunny]

the reason why you drill the ends of the cracks is to reduce the stress concentration. where the crack finishes you get a sharp point which is an area of high stress, by making the edges blunt instead of sharp this reduces the stress.

This is why aeroplane windows are all rounded and not square at the corners.

Someone has misguided you with regards to stress. if you weld a greater area then there is a larger amount of material for the forces to travel through, so the stress gets smaller.

read here

http://en.wikipedia.org/wiki/Tensile_stress

[dawesy]

well next time your near a rally car have a look at the seam welding in there!

seam welding is done in addition to the std production spotwelds so they take the most of the strain. the stich weld is there to provide extra support

[nrgizerbunny]

you'll find the spot welds there because they are quick and easy for a robot to do. seam (butt) welding is preferential but costs more.

the seam welding in a performance car is more to stiffen it up than anything else. the loads would be adequately carried by the spot welds unless you are planning on having rock hard suspension. However because they are there, they also take some loading.

if you want to reduce the risk of crack growth, do your full pen weld then put a fillet weld on the outside.

[andy_twincams]

as much fun as you to are having(no offence)is it worth going for it bearing in mind it will do a quater mile and a few track days not driving it trough a forest(optionally anyway)

so will it tighten up the Shell or is a waste of time and money??

[dawesy]

it has mine andy. the rolla can now be jacked up at the front or rear and the doors still open and close cleanly. before the would catch a little due to Shell twist.

the whole point of seam welding IS to stiffen the Shell. to make it stronger a roll cage is needed, however a lot of insurers dont like em on road cars.

[andy_twincams]

it has mine andy. the rolla can now be jacked up at the front or rear and the doors still open and close cleanly. before the would catch a little due to shell twist.

the whole point of seam welding IS to stiffen the shell. to make it stronger a roll cage is needed, however a lot of insurers dont like em on road cars.

cheers big fella :D