Spot welding upside down

  1. amazighman Member

    Messages:
    53
    Location:
    Tamworth
    Hello.
    .i have discovered some rust damage on My BMW E39 at the rear of the sills where it meets arches plz see pic.. i was tempted to tackle it myself but then i thought i ll see if i can get a pro to do it . Unfortunately most welders dont seem to want to do a small patch, most want restoration work and big jobs, so i am again left with no option but to tackle it myself.

    I can put the car on axle stands high enough but i am not very familiar with upside down welding, certainly never has to spot weld underneath a car either.

    Any leads and advice very welcome.
     
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  2. slim_boy_fat

    slim_boy_fat Forum Supporter

    You're going to have to strip out anything remotely combustible from above the area [+ a bit], or have a fire watcher on hand, so you might as well weld from above in that case.

    It'll help [maybe] to make templates before you start in with the grinder. Check carefully when you've cut out ALL the metal back to sound that the rust doesn't extend as far as the jacking point.

    I'm sure others with 'Australian' welding experience ;) :D will be along to help and advise.
     
  3. amazighman Member

    Messages:
    53
    Location:
    Tamworth
    It is not very far from fuel tank which is behind rust affected area. I am planning to leave the tank alone as it is a big job to remove especially when working outside on axle stands but I will remove all that Underseal and paint with a grinder before cutting it out and have the wife around as watcher.
    The rust doesn't extend to the jack points and the weakened rotten metal is just around that hole...
     
  4. henry Kadzielski Member

    Messages:
    845
    Location:
    Australia Wollongong
    Luckily there are people in Australia where welding is always done upside down:laughing:. so this is not even a challenge. Welding down hand, now that requires some skill:thumbup:
    From a strictly welding point, if you can tack in the down hand position then you can tack upside down, actual welding upside down is a different matter. Welding upside down is 'positional welding' and is done in the short arc mode. Generally speaking wire speed and voltage is less than in the down hand positions, (there is no spray transfer). All machines are capable to de this, however it is up to the operator to get it out of the machine in setup.
     
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  5. daedalusminos Member

    Messages:
    850
    Location:
    Norwich
    Very good advice, you need to know what's the other side of the panel, could be a wiring loom or some nice flammable sound deadening. A partial strip down inside is required then hit it as much as possible from above.

    If they're hydraulic or fuel lines then watch the angle grinder.
     
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  6. slim_boy_fat

    slim_boy_fat Forum Supporter

    Oh Oh......
    .
    @henry Kadzielski makes an excellent point re the possibility of damage to stuff before it's even visible. No-one I know can run faster than fuel igniting.

    My [former] B-i-L was very badly burned when working under a car. He was in a pit and had drained the fuel from the tank but overlooked the residual fuel fumes in there with him. Fumes are heavier than air so will sink to ground level. Struck up a match to light the OA torch and.........whoosh :flame:[literally]. It took him longer to get out than usual because of the car overhead.........:(

    That was 50+ years ago and I've never forgotten it.

    Please take care.
     
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  7. amazighman Member

    Messages:
    53
    Location:
    Tamworth
    What you see there is brake lines and they are well away from my rusty patch.
    I had a look inside that box section with my endoscope and there is nothing inside and there is no need to chop all that box section, i will drill out any spot welds, make a surface cut and remove first layer and see what i have got.
    I will be very careful and only weld in short bursts
     
    slim_boy_fat likes this.
  8. colnerov

    colnerov Member

    Messages:
    3,457
    Location:
    Nr Gatwick UK
    Hi, I hate pits for the very reason you state. Not just for fire but any other mishaps where gravity is present.

    Colin
     
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  9. p0689109 Member

    Messages:
    1,727
    Location:
    stoke on trent,england
    Don't forget the photos for us to peruse!
     
  10. You wouldn't be welding this thickness material in spray, regardless of the position. Settings are a thing of personal preference to a degree but I tend to find on thin material you will be using pretty much the same settings as in the flat your original query was regarding spot welding, I would go with either seam or plug welds, spot welding on this type of repair isn't really an option
     
  11. amazighman Member

    Messages:
    53
    Location:
    Tamworth
    I cleaned the wheel arches today and i am going to tackle this rust soon if health permits.

    Like you guys said i will strip anything remotely combustible and i will put a fire blanket between tank and sill, i will also invest in a powder fire extinguisher .

    This rusty area is made out of two pieces spot welded together and i have to drill out the spot welds before trying to cut the outer skin , hopefully i can manage that without cutting the inner skin too.After that I will inspect the inner skin for any rust which i will wire brush then use rust remover few times untill metal is clean, then weld through primer to protect the inner skin, the fabricate and hopefully weld it, any reapir i will do is better than rust and rot.

    I tried to get somebody pro to weld it but they all say, oh it is 20 miles away, too far for me, i am fully booked and so on, nobody wants to do a patch ,they all seem to want big resto jobs imho.
     
  12. Burdekin

    Burdekin Chief Bodger

    Messages:
    5,091
    Location:
    Aberdeen
    Earth clamp right at the weld location also.
     
  13. slim_boy_fat

    slim_boy_fat Forum Supporter

    Or, there may just be another reason......
     
  14. Lufbramatt

    Lufbramatt Member

    Messages:
    275
    Location:
    Rochester, Kent UK
    Did this exact repair on my e39

    http://www.mig-welding.co.uk/forum/threads/an-e39-bmw-530i-with-rusty-floors.67914/

    Drop me a pm if you want any pointers!

    I did it the "hard" way and dropped the tank, although think it was easier in the long run than working round it.

    That sill closing panel is about £12 from BMW, I'll find the part number if you want.

    It's an empty void behind the panel although there is a wiring loom under the carpet not far away.
     
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  15. amazighman Member

    Messages:
    53
    Location:
    Tamworth
    You did a fantastic job.. I wish i was half as good
     
  16. amazighman Member

    Messages:
    53
    Location:
    Tamworth
    Can anyone help with the correct technique for plug welding upside down underneath a car?

    I shopped out the rusty metal and luckily the bottom skin is intact with any surface rust removed with acid all looks clean, it ll get a coating of weld through zinc primer before the top skin patch is welded on.

    Wanted to take some pictures but was getting dark, will update soon.
     
  17. PSweeney Member

    Messages:
    245
    Herts
    my procedure is to get in all my gear, in position then try to strike an arc but forgetting the earth clamp. I them crawl back under, reattach clamp, strike an arc and remember I haven't turned the gas on. I then crawl out, turn on the gas, crawl back under, put a few tacks on shooting spatter into every nook and cranny including my boot, down my ear, down my back etc. I then roll around on the driveway swearing like a sailor until the burns subside. I then peer under the car for a bit wondering if cars were built to rust on purpose, I drag my fat **** back under, run a couple of beads, few more burns and expletives, slap some underseal on, then throw all my tools back in the garage vowing never to weld up old bangers again.
     
  18. Lordspectre

    Lordspectre If it aint broke, tinker with it anyway

    Messages:
    201
    Location:
    Ireland
    Think PSweeney said it all...despise tacking/welding compeltley upside down as get that horrid smell of burning hair from spatter on the head or down the front of the overalls
     
  19. outofthefire

    outofthefire Member

    Messages:
    2,255
    Leeds
    Pretty much every reply to this thread explains why nobody wants to do this professionally or why if they do the price they quote is so high. It's not a two minute job and it's a pain in the ar*e even with a ramp or pit.
     
  20. wookie Member

    Messages:
    2,597
    Location:
    .
    I prefer CO2 rather than powder, powder makes a hell of a mess.... been there, done that and turned the garage into a winter wonderland.

    Nowadays I tend to keep the hosepipe on standby as well as a CO2 extinguisher, it's less hassle to dry out a car than repair fire damage and there is nowt worse than your extinguisher running empty before the fire is out.

    As for clothing wear a hat under your welding lid and I always use welding sleeves on top of weld proof overalls, if you have a cold please don't do it, I knew a guy who ended up with 3rd degree burns when the petrol vapours that he couldn't smell because of his cold ignited.
     
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