Another Welding Question

[manta88]

I have started doing some welding an my A series front chassis rails and jacking points . For the MOT does the welding have to be a continuous seam ? i can remember some years back (opel2000) saying his car failed for this reason,is this right.

[mantadoc]

As a general rule look at what the manufacturer had done.

For instance where a car originally had a seam, joining it in the same manner is acceptable. Where it didn't is isn't.

For example where a full sill goes onto the rear quarter and you would not normally have a seam I would expect that to be seam welded. Where spot welded originally, along the sill to floor and door apature I have plug or stitch welded (not continuous) and never had any problem. Where it deviates from the manufacturers seam I have seam welded.

That help?

[mantasrme]

I think the fully welded rule is if its a patch stuck over a rusty bit

So more for what back street garages and mot stations do.

If you're replacing a panel or part of panel then it can be welded as the original one was.

Plus to be honest once its treated and painted/undersealed the mot tester won't be able to see what sort of welding was used.

Normally i seam weld most things on chassis rails for the extra strength

[opel2000]

General rule of thumb for any welded repairs as far as MOT man is concerned:-

"All welded repairs should be fully seam welded"

Although the area that I had repaired had not been fully seam welded, due to not being able to get the car high enough to clear welding torch and me with helmet on, the original area was only spot welded together anyway, in fact aren't the cars spot welded together pretty much everywhere from the factory anyway.

As MantaDoc says though, stitch welding a sill should be perfectly acceptable, and many areas can lend themselves to plug welding.

When fabricating stuff in the real world "All joints must be fully seam welded" as basically any open seams lends themself to a weak point where stresses can induce cracks along the joint,,, or something like that.

[manta88]

Thanks chaps ,i will seam weld the lot ,i now have a new welder that works alot better than the old Clarke welder i had from Machine mart.

[mantadoc]

The companies that remove cars from the V Car register after doing tests and reports on them MARK YOU DOWN IF YOU SEAM WELD A SEAM THAT WAS FACTORY SPOT WELDED.This is because the car may not behave the same way in an accident as when originally built.

[upk]

seam welding rally cars adds strength to the shell!

however if you have a knock its a bigger job to repair as they don't always pull back the same on the jig!

so if its a road car don't overweld it.

[manta88]

Ok, thanks for the advice ,i will seam weld the floor plates in and stitch weld the chassis rail cover plates in as close to as it was originally.

[opel2000]

The companies that remove cars from the V Car register after doing tests and reports on them MARK YOU DOWN IF YOU SEAM WELD A SEAM THAT WAS FACTORY SPOT WELDED.This is because the car may not behave the same way in an accident as when originally built.

That is all well and good, but not having access to a spot welder means I shall always either have to plug weld or seam weld to satisfy MOT man, further to the fact that as cars were built in a set spot weld sequence it isn't always a good idea to dismantle half the shell of a car just to put in the original spot welds, should you of course have access to a spot welder.

however if you have a knock its a bigger job to repair as they don't always pull back the same on the jig!

so if its a road car don't overweld it.

On a personal note I would rather have the strength added from any repair rather than live with the thought of how hard my car would be to jig back into place if I crash it.

I'd rather crash in a stronger car over one that has not had too much strength put back into the repairs any day.

[upk]

On a personal note I would rather have the strength added from any repair rather than live with the thought of how hard my car would be to jig back into place if I crash it.

I'd rather crash in a stronger car over one that has not had too much strength put back into the repairs any day.

total agreement on this one, only caution point is the car will fold in a certain way during impact......modern cars absorb alot of the impact forces.

don't think we need to worry about that!

as always its down to personal preference...basically provided its done to a high standard there shouldn't be an issue.

[mantadoc]

I think the points here, before we get upset with each other are:

1) Do whatever you like to your own car, but bear in mind you do need to satisfy the MOT man.

2) The part about seam welding repairs is to do with joints in panels not to do with existing seams. In fact things like wheel arches etc or non structural parts aren't even required to be seam welded BUT what's structural and what isn't is open to interpretation. rusty holes are allowed as long as they are more than x from suspension pickup points or load baring parts (if that's changed apologies, not read motor vehicle constructions and use regs along with the MOT stuff in 15 / 20 years)

3) "Seam welding" for rallying does not mean unbrokencontinuousweldsasstresscrackscanrunendtoendso is often stitch welds with gaps

4) Repairs are best guess anyway. Seam welding might give added strength but a seam welded localised repair might just mean that crumple zones don't work as intended and you pop your passenger safety cell. Not likely, but possible. That said we're driving cars designed in 1975 so we're probably not into safety as the highest concern.

5) DVLA say stuff about cutting your bodyshell calls a cars identity into question. It is claimed this is nothing new and has been the case for 27 years. However, it is common bodyshop practice to use only sections of original panels where that is apprpriate.........

No warranty of any kind implied or given

[manta88]

Some good points there to bear in mind. The other thing that i have been thinking about is making up some front jacking points from some box section, will this cause any problems with the MOT man or worse still will it have to have an SVA test or what ever it's called now ?

[mantadoc]

Some good points there to bear in mind. The other thing that i have been thinking about is making up some front jacking points from some box section, will this cause any problems with the MOT man

Unlikely / no, not if done properly

or worse still will it have to have an SVA test or what ever it's called now ?

Technically probably, in reality unlikly, but it's your resposibility to make sure it has one if it needs one...... it's all a can of worms

Oh yeah, no warranty implied or given, it's your job to find out.