One thing I always found when designing welded devices was that you should never try to weld a thick piece to a thin piece. For example, welding a flange to a tube, I always put a weld prep groove in the flange, so the weld joined two thin cross sections. The heat has to dissipate evenly away from the weld through both pieces, as they both expand and then contract. So you try to equalize cross sectional area in both pieces, working away from the weld.
Just checked and it’s either ER4043 or 5356. The former for sure on fresh aluminum, not sure if 5356 was what I used on the older stuff. I’ll know for sure when I get around to doing some aluminum welding during the next few months.
For body work? I would have said to use ER1100 for sheet aluminum.
Do we know what alloy the bonnet, doors and boot lid were made of?
Rob,
The “famous” XK 120 LT’s with bodies produced by Abbey panels, were made of “Birmabright” aluminium. Standard available Birmabright alloys could be supplied with up to 7% Magnesium (grade BB7).
The standard XK bodies also used Birmabright for doors and bonnets. Don’t know whether these all had the same Magnesium content. The Mg content could vary from 0.6% to 7%. Would that affect the “weldability” and the choice of filler rod?
See also https://en.wikipedia.org/wiki/Birmabright
Bob Knynenburg.
Although when welding engine pipes to the flanges one has to do this. We always use oxy welding so as not to have abig build up of weld where one will need the spring washers to seat.
Dad found that out, when welding up the Silverstone’s (LT-2) nose!!
And so did David Cottingham when he restored the body of LT1.
Again, I don’t know what the impact is of increasing the Magnesium content in an Aluminium alloy with regard to weldability and the choice of filler rods!. Although Cottingham believes the bodies were made of an Magnesium alloy (like the “Elektron” alloy used on some comtemporary Continental sportscars) I still believe what Abbey Panels used was an Aluminium alloy with a higher Magnesium content. Any welding experts out there?
Bob K.
Well, my first guess would have been 1100 which is known for its easy formability. In which case weld with 1100 rod.
Lots of deep drawn commercial products are made from this stuff. But it has no magnesium.
So if you think there was magnesium, maybe they used something like 5052 which has 2.2-2.8% Mg, and is also rated high in formability. In which case 1100 rod would be ok but if you have a choice you would want to weld with 4043 (preferred, more ductile) or 5356 (higher strength but less ductile, more likely to crack).
Not particularly relevant but Bugatti Atlantiques had the panels made of magnesium [ Possibly called Electron , in those days and rather than weld the sections were riveted together by way of the distinctive fins running the length of the roof and guards.
I near drove off the road, when I was driving by Ralph Lauren’s ranch, in Stn Colorado, and saw his Atlantique going the other direction!!!
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If there is a better place for this question please feel free to move it.
Re: 679265
Has anyone replaced 120 FHC sills (one side at a time) without adding any extra bracing in the way that is necessary on an open car?
Is the roof structure enough to be sure that the door frame will remain steady without any warping?
679265 is rust free apart from the sills so it isn’t really necessary to remove the whole body for any other reason. I have seen in old forum notes, etc, that this job is possible and my very experienced welding friend is happy to proceed provided we check whether bracing is necessary or not. Obviously bracing can be put on but it limits access for work and there’s no point if it isn’t necessary.
I welded in new sills in my OTS without bracing so it’s certainly do-able on a coupe, assuming the body is still on the frame. The door hinge panel is bolted to the hinge boxes which are bolted to the dash side structure, so it’s not going to go anywhere. The shut panel is welded to the shut pillar box section, which is very rigid and isn’t going anywhere either. The hinge and shut panels are 16 ga while everything they’re attached to is 18 ga. The usual approach to welding light sheet applies - tack welds to get everything positioned, checking alignment as you go along, then finish with short stitches, moving around and allowing brief cool down between welds. Best if you leave the doors on but the rear wings removed.
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Really good descriptive advice, many thanks
Yw. A particularly important part of doing the job well is cutting out the old sills while preserving as much of the steel sections they’re welded to as possible. You will find that some remedial welding to the attachment points is required so take your time and solicit your welder friend’s advice from time to time as you go along - before you even begin, even.
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I’m been trying to teach myself TIG Welding, Aluminum is my kryptonite. I just can’t seem to figure it out, granted I’ve only been doing it on scrap pieces of Aluminum. I seem to work better with steel. I’m trying to read all the comments so this may be redundant but if you guys have any tips / tricks I would greatly appreciate it.
Youtube is your friend, and lots of practice. Still, tig welding steel is much easier.
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One thing you need to consider is the quality of your machine. It became very clear to me when my old cheap machine died and I bought a new miller. My welding ability jumped immediately just because of the superior machine. If you already have a quality setup ignore this.
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TIG welding aluminum is difficult even for some professionals. We had one guy at my lab that everybody said don’t give him any aluminum jobs because they’ll come back warped.
I did a little bit on my cylinder head, and I found I had to have super clean freshly ground metal exposed, use Argon and the correct alloy rod, clean the weld with a new stainless steel wire brush between passes, and let it cool off between passes.