welding tips please

Post by **grainger** » Tue Nov 16, 2004 10:40 am

hi

ive got to bite the bullet and become a welder !! ..

ive spent the last 6 months getting my traveller sorted, the timbers all treated and varnished (im just finishing the doors), all the floor and sills hammerited, window channels replaced, the engines been rebuilt ... the only major problem left is welding. firstly the sliding windows had been leaking on the passenger side and its rotted the wheel arch from the inside (about an in inch from where it screws into the timber, over almost 75 % of it) ... now remembering this is the side with the petrol tank and i presume its quite a structural panel (holding the frame to the car) is it the sort of thing someone should try if theyve never welded before ?

... im willing to have a go unless i could end up wrecking it

there is a very handy repair panel available that includes the flange to bolt to the timber arch attached to a big triangular piece to cover the wheel arch

well to begin with i would need to buy a welder i presume ... whats the smallest i could get away with to do this sort of repair ? ive worked out i need a gasless mig, whats the best place to get one ? any good sites for info ? all words of wisdom gratefully received ...

theres a couple of little patches needed in the floor and there is also a small repair on the same side on the front inner wing where the bump stop has caved in the top a bit, so i could have a go at these afterwards ..

cheers
grainger

Post by **rayofleamington** » Tue Nov 16, 2004 11:16 am

I would recommend a mig, but not gasless - if you don't have to weld the whole car, then the disposable bottles are good enough.
I use a 130 amp mig which cn do everything you would need on a Minor - for the 'lowest' you can get away with, hopefully somone will have experience of smaller equipment.

Post by **Cam** » Tue Nov 16, 2004 1:31 pm

now remembering this is the side with the petrol tank

Well, the petrol tank filler! It should not be a problem because if you are welding near the tank (which you are) then you should remove the tank anyway.

im willing to have a go unless i could end up wrecking it there is a very handy repair panel available that includes the flange to bolt to the timber arch attached to a big triangular piece to cover the wheel arch

If you use the proper panel then it's much easier than fabricating your own repair sections. We all have to start somewhere so you will only wreck it if you are not careful and don't use a bit of common sense!!

well to begin with i would need to buy a welder i presume ... whats the smallest i could get away with to do this sort of repair ? ive worked out i need a gasless mig, whats the best place to get one ? any good sites for info ? all words of wisdom gratefully received ...

Smallest would be a 90 amp, but you are best going for a 130 really as it will handle much thicker stuff like crossmembers etc. Gassless MIGs are not very good. A conventional gas one is much better (as Ray says).

Machine mart do a good range: http://www.machinemart.co.uk/

This is the one I have (150TE (Turbo) MIG Welder):

Currently £211.44 inc VAT.

I have had mine for a few years now and it's pretty good.

Post by **grainger** » Tue Nov 16, 2004 5:07 pm

thanks

yes maybe i should get something bigger if im going to do any more ... well i know its had one chassis leg replaced so probably the other would need doing at some point. but other than that, all the other chassis welding has been done including a new x member so if its the difference between one or two hundred quid at the moment ill have to go for the cheaper option.

why is the gas mig better ?

oh and i really dont think im going to be able to get this petrol tank out, i can see all the screws, but theyve been coated in underseal or something

..

cheers
grainger

Post by **Cam** » Tue Nov 16, 2004 6:38 pm

why is the gas mig better ?

The non-gas has a 'flux' type material inside the wire which creates an inert gas shield around the weld. The gas type blows inert gas (CO2, Argon or a mix of the two) at the weld as you make it.

It's just that the gas type gives a better (stronger) shield than the non-gas type and so a better neater weld.

The only advantage with the non-gas types is that they don't suffer from poor welds if you weld outside in the wind and the gas shield blows away.......

oh and i really dont think im going to be able to get this petrol tank out, i can see all the screws, but theyve been coated in underseal or something ..

You might be surprised. Clean the screw heads out with a fine thin screwdriver and then use a correctly fitting screwdriver with plenty of pressure and they usually crack off and come out ok. Does not really matter if you snap a couple off as there is about 15 or so anyway to hold it down.

Post by **bigginger** » Tue Nov 16, 2004 7:34 pm

and please don't do any welding, gasless or not, without taking the tank out

Post by **Chris Morley** » Tue Nov 16, 2004 11:13 pm

and please don't do any welding, gasless or not, without taking the tank out

That's not always true and you certainly don't see professional welders refusing to touch a car with the fuel tank still in it. A fuel tank explosion will only happen if a spark develops in the petrol vapour or if the temperature rises significantly (and oxygen is present).

If the electrical circuit is completed between the torch and return wire there's no reason for a spark to occur in the tank unless you're daft enough to fix the return wire to the tank itself

or you try to weld the tank! However I've always been very wary of heat build up so I take the tank out if I weld anywhere within 18 inches of it.

Incidentally, welding a fuel tank is not something I would ever try at home - professionals attempting this will usually flush the tank out with water first, test the atmosphere for flammable gas vapours and then fill the tank with an inert gas such as Argon or Co2 before welding it. Even so, it's not unknown for tanks to blow up when being repaired, especially large industrial fuel tanks.

Post by **rayofleamington** » Wed Nov 17, 2004 8:28 am

If you are using a mig welder and have an alternator - remember to replace the alternator and battery on the hard shoulder in rush hour 6 months later when you brake down. (:lol: or make sure the alternator is fully diconnected before you turn the welder on)

Post by **bigginger** » Wed Nov 17, 2004 11:02 am

and please don't do any welding, gasless or not, without taking the tank out

That's not always true and you certainly don't see professional welders refusing to touch a car with the fuel tank still in it.

Fair point, and the one I was trying to make. I thought we were talking about welding near the tank... Jeez, but you have to be precise on this board.

Post by **grainger** » Wed Nov 17, 2004 11:29 am

thanks for all your concerns for my safety ! makes me feel like someone cares !!

... cam, i think i WILL try to take the tank out it makes sense, all the back is out so ive only got to get the (15!!!) screws out ... but if i cant, i cant and to start cutting off screws will make it even more dangerous, so i will have to do it with the tank in place. so chris, any tips to make it less likely to explode, my tank is in good condition, no smell of petrol in the back, the cap is very tight (it hisses when i take it off) ... all the windows and doors will be open obviously ... what if i cover it with duvets etc ...

oh and ray thanks for the tip about the electrics, im still on a dynamo, will the welder affect this ? i will disconnect it all anyway ...

cheers
grainger

Post by **Cam** » Wed Nov 17, 2004 11:57 am

what if i cover it with duvets etc ...

Not dry ones or they will catch fire!!! Make sure they are soaking wet.

Post by **ericwork** » Wed Nov 17, 2004 12:14 pm

I was talking to somebody who repairs cars and breaks minors a few weeks ago about this very subject. he even welds petrol tanks in place. His tip, which i haven't tried so can't confirm its effectivness, is to run exhaust gas into the tank tor 15 min before doing any work. He emptys the tanks first and sticks a hose from the exhaust, from another car, into the tank. He says he has been doing this for years and he is still here to tell the tale. He said he once tried dropping a lit match into a tank after this treatment and it just went out. You have got to be either brave, foolish or confident to do that.

Eric.

Post by **Kevin** » Wed Nov 17, 2004 3:13 pm

he even welds petrol tanks in place.

each to his own I suppose

but replacement tanks dont cost that much in the 1st place.

Post by **ericwork** » Wed Nov 17, 2004 3:44 pm

I agree Morris tanks don't cost much but he has worked on some very old and interetsing vehicles in the past, Allards, Fordson, even a very huge and very ugly french thing, which he loved, but nobody else seems to have heard of, the name of which escapes me.

Post by **rayofleamington** » Wed Nov 17, 2004 4:20 pm

im still on a dynamo, will the welder affect this

well -i've never disconnected a dynamo, and rarely even disconnect the battery either. I would certainly not recomment using the battery earth lead to ground the welder tho!! (in case it makes a bad connection to the body, you will put a few thousand volts to the cars electrics instead

)

Post by **Chris Morley** » Wed Nov 17, 2004 6:29 pm

Eric's friend has method in his madness. There's almost no oxygen left in a car's exhaust (it's been used up by the combustion) and it's an inert collection of gases!

I always try to remember to disconnect the positive battery lead but I did forget to do so once. It didn't harm my dynamo or the immobilser.

Grainger, in theory if the tank's full up then there's no room for vapour. However if the theory's wrong then the explosion will be even bigger! Does this advice make you feel more confident?

Post by **Alec** » Wed Nov 17, 2004 8:36 pm

Hello all,
there is no problem with dynamos, it's the solid state bits in an alternator that does not like the relatively high voltage of the welder. As for petrol tanks, my personal prefered method is to fill them to the brim with water then weld, with the area to be welded at the top.

Alec

Post by **brixtonmorris** » Thu Nov 18, 2004 10:14 am

"I would certainly not recomment using the battery earth lead to ground the welder tho!! (in case it makes a bad connection to the body, you will put a few thousand volts to the cars electrics instead "

not if u disconect the battery

Post by **Alec** » Thu Nov 18, 2004 10:44 am

Hello Brixton,

what sort of welder are you using?

"you will put a few thousand volts to the cars electrics instead"

welding voltage is typically 90 volts open circuit and less while the arc is sustained. It is, however, good practice to put the earthing clamp adjacent to the area being welded. Things that do get damaged by welding current (apart from solid state devices) are bearings and bushes so that is a point worth thinking about.

As I use gas to weld I don't have these problems but as earlier discussions on this forum has proved it is not a popular option to the almost universal MIG. I would say though, that I still believe it is a better system due to it's flexibility and the variety of jobs it can tackle.

Alec

Post by **Cam** » Thu Nov 18, 2004 12:37 pm

Gas is better in some respects as the welds are a lot less brittle than MIG and you can use the welding gear for cutting, heating, brazing etc.

BUT it distorts the metal a lot. MIG is much better because it's faster, easier and does not distort the metal as much.