Welding old cars

As an apprentice welder with a MIG I can tell you that bit's easy. I can do a near perfect bead down a sheet of steel. What defeated me was a butt joint - the one thing I really wanted to do.

Consider a blowtorch and BRAZING. Its more than strong enough for bodywork. I wouldn't do it on a chassis,but it is fine on a wing or something.

That would be a disaster! With a blowtorch you'd feed so much heat into a large area of metal that it would warp and buckle like a bugger (and prolly set the vehicle alight!) The only real way to braze car body is with oxy-acet, but then you'd (normally) be better off with steel filler rod and weld the joint.

BTW there are issues with braze repairs WRT MOT's. Older vehicles must be welded IIRC. However, I believe that new vehicles are increasingly using boron steel in their construction, and a Thatchem approved repair must be MIG brazed - welding is unacceptable because the temperatures reached destroy the steel's heat treatment.

Julian.

I don't think this is acceptable for MOT anymore, it must be continuous welds. Apart from that brazing with gas tends to put a lot more heat into a sheet compared with mig, so more distortion and damage to adjacent paintwork.

AJH

Not suitable where an MOT man might be interested. And very difficult to prevent distortion on a panel due to the general heat needed.

Probably why most small migs are pants.

Has anyone tried one of the new inverter welders that can be used with stick, tig or reel feed? I suppose they use electronics to mimic the droop characteristics of each mode?

I'm still hunting for a small portable mig with a decent wire feed/control.

AJH

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Andy Dingley saying something like:

Looks like the site is run by Malcom Vardy and nothing to do with this Tony geezer, afaics.

I've got a 200A inverter welder that does only stick. It's fantastic and welds as smoothly as the old 'Oxford' oil cooled transformer welders. The rod doesn't stick, striking up is easy and it is happy at the end of a long extension lead - something that my old buzz box welder wouldn't really tolerate. I think it is also more efficient, because I haven't had to substitute the 13amp fuse with a 5/16'' bolt yet when on 3.2mm rods :-)

Julian.

I don't think that applies to non structural repairs. Certainly I wouldn't braze a sill box member..but I am fairly sure brazing is fine for making good holes in e.g. skins. I mean, if you canu se car body filler...;-)

Solder then, :-)

That's more like it! I've got a car full of it. (lead-loading - just like a wiped joint on a lead pipe) So much better than resin filler....

Julian.

I'm not sure it is - corrosion tends to start between the lead and steel.

================================== Didn't you find it difficult to sand to a decent finish? When I tried it it clogged the paper constantly even using 'wet and dry'. Standard body filler seems to be the modern way.

Cic.

Not on sheetmetal it isn't. Although there are brazed "birdcage" tube chassis around, brazing alone on a thin sheet monocoque is a _terrible_ idea. It'll hold together, it'll even be strong when first made. However any cracking that does develop (and it will) has a huge risk of truning into an instant "zipper" fracture and the whole seam splitting.

If you're going to braze to waterproof, then at least stitch weld it first.

There's also the issue (crazy as it might be) that it's an instant MOT failure.

This is a Beetle we're talking about. Although it does pretty much have a "chassis" (you can rip the floorpan out of a Beetle and use it as a separate chassis without too much trouble, hence the plastic bathtub beach bugy), it's still a major structural component that's designed around an integral monocoque of thin stressed sheetmetal.

You're getting to be as bad as Drivel...

read the tester's handbook or STFU

You don't sand lead-loading, you use a rasp.

A _clean_ rasp (otherwise it pins), which from time to time you clean with gunshop lead fouling remover.

Even though the some old Astons had steering linkage fabricated by brazing....

Julian

I suppose if you're using to slap over rust then yes, it prolly does. But I'll bet you a £ to a penny that in similar circumstances corrosion will bleed through a 'repair' with resin almost overnight.

But the above is purely theoretical of course, nobody here would slap the stuff straight over a rusty hole or scabby metal - would they!

Julian.

As has been pointed out you need a rasp or file.

Just a small word of warning, (and I try hard to distance myself from the modern phenomenon of the safety Nazi culture) sanding lead produces dust which is not too good for health if you breath enough of it in.

Julian.