car welding

[Badbusboy]

Hello all,
I have come to the conclusion that my trusty french car will need welding soon. It appears to be just to the rear of the front wheels on the chassis of a citreon zx. Have been told before it is double skinned though! What is 1) the things I need to disconnect for safety/saving components 2) the best way to tackle this rusty isssue of chassis? Thanks BBBoy.

 

[ChrisJohnsSculpture]

Disconnecting the battery and alternator and making sure you have a good earth connection as close as possible to where you are welding should stop you damaging any electronics.

Obviously extra care is needed welding near thinks like fuel and brake lines, if necessary use a piece of sheet metal and/or wet towels to shield heat sensitive parts.

Where you're patching metal cut away all the rust so you are welding onto sound, clean metal. If you have to make up odd shapes then it helps enormously to first make templates from thin cardboard (eg cereal boxes) to check the fit.

For weld repairs on vehicles try to replace like with like as far as possible ie use the same gauge steel and where you're putting in patches they should be finished with a continuous weld seam. If you're replacing a whole panel which was originally spot welded on then a series of plug/puddle welds equivalent to the spot welds will be fine.

Hold parts in place with plenty of tack welds and check fit from multiple angles before you put any permanent welds in. If at all possible it's usually best to clamp the patch or replacement panel in place before you tack it. Try to get as close a fit as possible.

Most car bits are relatively thin so the biggest issue is usually avoiding burning through the metal and distortion.

For seam welds work in a series of short sections, spaced apart, maybe 30mm long (usually between two tack welds) and gradually fill in the whole seam alternating from one side/end to the other, allowing a bit of time to cool if necessary. 'thin metal technique' may also be useful this involves a series of continuously overlapping spot welds which gives adequate penetration without building up too much heat in the weld, this is especially useful for vertical and overhead welds.

 

[Badbusboy]

Thanks

Thank you very much for the very informative advice. I shall pay very close attention to your pointers.

 

[outofthefire]

I personally wouldn't disconnect anything, I always use a surge protector. Have a read here http://www.mig-welding.co.uk/forum/showthread.php?t=34397&highlight=surge

 

[Badbusboy]

Thanks outofthefire,
I shall look at getting one of those when funds allow. Just have to disconnect for now!.
BBboy