Chassis repair question

[MartinH]

Hi Guys,
I've got a mitsubishi l200 that is in need of a few repairs on the chassis, I have a mig welder which I am competent in using, I have some suitable thickness repair material but just have a couple of questions about the best way to carry out the repair.

Now aesthetically the best way (I think) would be to cut out the rotted section (which will happen either way I do it) cut a piece of plate so that it is a tight fit in the cut out hole and seam weld the piece in then grind back flush, seam sealer/waxoyl etc job done!

or

Should I cut out the rotted section cut a piece of plate oversized and seam weld around it, grind back/seam sealer/waxoyl etc job done?!

Basically I would like to know which will be the strongest method as being a chassis leg strength is more important than appearance but it would be nice to have a balance between the 2!

Here's what I'm faced with, the second picture is the kind of area I propose to cut out (or go bigger till I find something solid but you get the idea!) and carry out either option 1 or 2!




Or option 3 is I'm completely barking up the wrong tree and I'm open to suggestions on what the most structurally sound way of doing it is!

Thanks in advance.
Martin

 

[God mode restorations]

Hi.the problem is that what does not look to bad usually is..it's when you start cutting back to good metal..you finally see the extent of the repair needed..if it was me I would cut out and replace rather than plate over..just my opinion the. .

 

[MartinH]

Thanks for the reply, thats the only really bad bit, the area around it has had a good battering with a hammer and screwdriver, I know what you mean though, once I start grinding who knows. Ive had several fords in the past including a mk2 fiesta and a transit so am aware how things can spiral out of control!!

 

[Justme]

That is going to be much bigger than you think.

Prob even a box section.

If I am wrong then both your methods will work but dont grind back the weld as that is reducing strength.

 

[God mode restorations]

Yes you no..especially ford stuff..but yes I think cut out to good clean metal..make new section/sections..and weld back in..it's a better finish and should be as strong as it originally was.

 

[Bill Edwards]

There's nothing wrong with a good butt weld, just don't go too enthusiastic grinding the welds back and end up eating into the metal and making it thin - I suggest leaving a little bit of the weld proud.

I think you'll be cutting out a much larger chunk that you've outlined though!

 

[MartinH]

Thanks for all the advice, the outlined area is what I'm hoping for, I fully expect to be disappointed but got to think positively! Ill go with cutting a plate that fits tightly in whatever hole I end up with, tack, seam weld, seam seal and a top coat then. Wish me luck.......

 

[RonA]

That is going to be much bigger than you think.

Prob even a box section.

If I am wrong then both your methods will work but dont grind back the weld as that is reducing strength.

I agree totally in my experience rust holes are like icebergs you can only see 1/3 of the problem.
RonA

 

[normspanners]

A 'little' bit of welding I have just done on a landrover chassis I always cut out and butt it if I can

 

[Coo]

cut out and butt weld t...no need for a tight fit you'll need a wee gap.
If you are still concerned about strength after, you could put a plate over your patch extending well past it and seam weld (and drill and plug weld it on)

Good luck !

 

[Screwdriver]

Or option 3 is I'm completely barking up the wrong tree and I'm open to suggestions on what the most structurally sound way of doing it is!

Thanks in advance.
Martin

I have some experience now with a rotten chassis and despite it being my first time, even I can see that whole piece is rusted. While there might be a crinkly layer of solid metal inside the shell of rust (and iron phosphate), as soon as you start to weld it, it will blow into wet tissue paper. Ideally find a donor vehicle and cut out a section to replace the whole lot, back to good solid metal. Your only other option is to fabricate a beam from scratch and forget "project Binky" for a moment, that's a LOT more difficult than it looks!

Good luck.

S.