Newbie MOT Questions

[tonytiger]

Hi all.

I need to repair the chassis on my Saxo, as I've just inspected it ready for its MOT next month (and it's worse than I thought).

I've done a bit of reading on this site for MOT/chassis repairs but I'm still not entirely certain about some points, so....

I know I need to seam weld the repairs (which makes sense to me, can't see why you wouldn't on a chassis). But, can I just clean it up back to good metal and plate over the damaged areas, so that it's welded with an overlap, or does it have to be flush and butt welded? I'm not bothered about appearance!

Also (not quite sure how to explain this) can I plate in several pieces and weld those pieces together, or do I have to use a single u-shaped (channel) piece?

Finally, can anybody suggest what thickness metal I should use - would 1.6mm be sufficient, or should I be using 2mm?


Thanks for any advice.

 

[rikrobson]

if you overlap you must seal up the flap that is left or its going to rust again. as long as you has a good seam on one side it should be ok, but loose jagged metal is a fail iirc. Better to butt weld
It's better to use a single section rather than welt bits together, top job is to cut a section from original or pattern parts so the shape of the original is correct and keeps as much of the original car.
second would be to make the u section if that is what is requires by bending and shaping the metal and thirdly to weld bits together to make the correct shape.
The metal should be what the car was made of originally, being a french car it probably tin foil, but to be serious i would have thought 1mm without knowing which bit need welding

 

[tonytiger]

Thanks. Yes - you're right about tin foil!

The bit's I need to weld are the rail type (box?) sections running front to rear. Wasn't sure if would be easier to bend the metal to the channel shape in one piece, or just use 3 pieces welded together - so was hoping I could use either.

Cheers.

 

[rikrobson]

I'd do whatever was easier. option 4 would be to scrap it and buy an new car

 

[Chickenjohn]

On a modern car- use 0.8-1mm at the most!

2mm is only found on some classic cars such as the inner sils on a Morris Minor.

For your channel box section you can weld three bits together as long as the welding between then pieces is continuous, i.e either a seam (or more likely) pulsed thin metal technique style welding.

see the tutorial on this site http://www.mig-welding.co.uk/thin-metal.htm

 

[Howburn]

Why not put it in for the MOT and see what the inspector fails it on, you then have 10 working days to do the repair before the re-test.
Doing it this way you will save doing repairs that may be unnecessary for the MOT, in other words area's that you may think are a fail may not be in the eyes of your MOT tester, or vice versa.
MOT's are very subjective; with deferent testers from deferent stations or levels of experience having often quite different opinion of what is acceptable.

 

[xantica]

According to my MOT tester the following applies.
If you replace a complete panel then you may spot weld it on as was original from manufacture. If you weld on like say a skin sill then it must be fully seam welded as these kind of repairs are deemed a "patch" up.

Hope this is of help.

 

[TGR]

Hi Tonytiger,

The choice of gauge needs to match the gauge of the material used on the chassis. if you use lighter gauge then its can be classed as an "unsatisfactory repair affecting structural strength" it can be butt welded or overlap aslong as its seam welded its fine.

 

[tonytiger]

Thanks for the replies.

I was intending to use material thicker than original to be on the safe side - in the end I've got 1mm and 1.2mm to patch with.

Unfortunately since starting I've now found that one of the sills is in need of work. And I really don't think I'm going to master arc welding for that. So I'm now seriously thinking about buying a cheap (but not too cheap) mig. If I can do all the welding myself, then that pays for the mig. But if I still can't manage the welding, then it'll cost me twice!

Of course I could just make life real easy and set fire to the car!

Seriously though, I'm looking on this as practice - and if I can do it all myself, all well and good!

 

[Flathead_Dave]

Get your self a mig welder and set it up with refillable bottle,using argon/co2 mix.Practice welding on the bench and try and get an old wing etc from a body repair shop.
If you jump straight in and try and weld the car with the welder just out the box,it will break your heart.When you know you can weld,then working on the car will just be a case of adapting to the conditions.

 

[bluebobtail]

Hi there. where abouts in the north east are you?

 

[rhubarb7]

wasting your time with an arc welder mate, you need a mig..

The 1mm sheet will be more than thick enough..

Try and make the chassis sections out of one piece, saves time and welding wire, and will look neater