Are you working on a wooden top build table? As the heat from the weld sets fire to the timber it causes contaminants in the weld by pushing the gas away. You can get round this by using a 50mm+ hole saw where the joints are then you can run straight down the joint. Hollow section or black realy needs to be weld preped with a 45' grind and it's worth taking the material back to clean steel where the earth clamp is too. If your using a small shroud or hobby type torch it might pay to take it off and clean it every 5-6 welds as it gets blocked with splatter it reduces the gas flow.

:) as talon says, and also check the condition of your welding wire thats assuming your using a mig :p

Thanks people, had a play this morning and I ended up knocking back the power a little and the wire speed alot also checked the welding shroud which I think was also contributing. Welds are now nice with no bubbles although I need to work on being a little more economical with my welds. Yes I'm migging and am using a wooden table. Letting the gas flow for a few seconds before starting to weld has helped get a clean start to the weld too. I have a lot to learn.:) Including not welding in a vest (it was warm), I got a little UV burnt! Doh!:D

Oh a deeper V cut has helped get a solid weld too.

Found this for people's reference.

http://www.welding-technology-machin...distortion.htm

Procedure at Complex Joints?
 

This is a very nice thread and the photos and commentary make it crystal clear in terms of flat plates and T-joints. However, one if the things I've worried about is how to do a complex joint. I'm thinking both of the distortion issues and also the best sequence in terms of welding strength and perhaps grinding flat after each fillet or butt weld is completed?

An example in my mind is the joint where BR1, D1, U3, BR3 and D3 all meet.

I'd guess the only practical way to test a practice piece with similar joint would be to cut through it and see how it looks on the inside?

I found this site usefull.



http://www.mig-welding.co.uk/tutorial.htm

Tig welding
 

Very useful posts! When I first though about building a Roadster I took an evening course in welding and found that I was most comfortable with Tig - maybe because I've done quite a bit of soldering/brazing in the past. I've also done some commercial courses and am booked in for testing end November. Then I discovered that most people use MIG welding and this seems to be what most of the posts cover.
Couple of questions - does anyone have any experience of tig welding a chassis? Any tips would be most welcome! Secondly is it necessary to produce any test pieces or results for the IVA? I've had a reply to a different post saying that it's likely the IVA inspector will look very closely at any visible welds (to be expected), I was wondering if people generally have some form of welding test results to hand.

Thanks

Hi If you are comfortable using a TIG welder go for it, there is no real reason as to why the chassis can't be TIG welded.

That said, There are a few places on the chassis that may be very awkward to get to with a TIG torch ( Very acute angles )

If you are intending to use the TIG take care to keep yor joint gaps to an absolute minimum, this will make the task of welding much easier )

I had originally intended to TIG my chassis but soon got bored with the time it was taking & reached for the MIG :D

As far as I am aware, you will not need to provide any paper evidence to prove your competence as a welder when it comes to the IVA test.

It is a visual inspection only, as a general rule of thumb, if a weld looks poor, the IVA tester is likely to pick you up on it. ( A horrible looking weld is seldom a strong one )

I would have thought none of the IVA guys would be qualified to inspect welds in an official capacity and they would need NDT and in reality its not going to happen.

First impressions will go a long way.

i have a tig and a mig 90% of my chassis and bits are mig'ed
tig's are a two handed job, real sensitive to dirt,oil and drafts, more prep is needed and gas and filler wires would be more expensive also take an age to do. if your not skilled in tigging there is a chance you might not get full penitration of the joint.
too meny cons and not enough pros tbh
on the plus it would be ideal to tack up chassis as heat is kept to a minimum befor migging it fully