| Author | Topic |
|---|
Location:
Brisbane
Registered:
November 2002
|
|
Seam Welding & Stitch Welding
|
Mon, 09 August 2004 13:41
|
 |
Hi Guys.
Before anyone says anything, I've had a search and managed to find only >one page< with any real information on the topic. This is one of the few topics I haven't got 2c to contribute on, so I was hoping you could help me out.
I've currently got a car that's stripped to buggery, and was thinking I might take the opportunity to complete a a cheap upgrade. I've had a look into it, and with the limited information I've found, seam welding appears to be "the go" for any car, particularly an older one. The cheapest way to stiffen it up, basically free, and invisible too.
I was wondering if anyone could offer any information of experience on the topic, or point me in the direction of any such details. The car in question will have approximately 3 times the factory power output and will be used for street driving, occasional drag racing and 6-weekly circuit sprints.
Thanks guys,
Leigh
|
|
|
Banned user
Location:
ADELAIDE - The Drift City
Registered:
July 2002
|
|
Re: Seam Welding & Stitch Welding
|
Mon, 09 August 2004 13:48
|
|
basically you want to be seam wealding the structual parts of the car, and then the joins in the chassis where the factory spot welds are, now you also idealy want to be focusing on the front half of the car since this where most opf the forces and twisting is, With all that torque, braking cornering going on!
now take into consideration when seam welding a car that heat can distort things, So wire wheel the seam that you will weld and be sure to remove all the factory seam sealant. you may have to use a chemical of some kind.
then, when you have cleaned it you're ready to weld, run a smooth seam of weld about 5cm long, then move to a cooler part of prepared seam and weld there, then rotate between the to as to not focus too much heat in one area
appart from that, thats really all i can offer! Laos take the opportunity to weld in some extra bracing under the car 
|
|
|
Location:
Eskilstuna, Sweden
Registered:
May 2002
|
|
Re: Seam Welding & Stitch Welding
|
Mon, 09 August 2004 13:58
|
|
Hi,
Well I have stitch welded and seam welded on my car. It is importnat not to get carried away with the seam welding as you don't want a car that can't be straighted after a little dingle.
That said I completely seam welded all load baring junctions and the like. Though I did talk to some guys who could point me to wear all these places really were - it's common sense now that I look back at it.
Some people stitch or seam weld all around the front windscreen area and the like as well (windscreen is out of course), but I thought that was going a bit far for a road car!
I have just done the floor pan\unitary part of the car.
Cheers
|
|
|
Location:
Rosanna, Melb
Registered:
June 2002
|
|
Re: Seam Welding & Stitch Welding
|
Mon, 09 August 2004 15:32
|
|
I have read a story on the build up of a seam welded Jap AE86 racecar. Basically is as the above two have said. They would weld a bit in one area, then move to the other corner of the car and weld a bit there. This meant thermal stresses didn't build up in one area at any time.
I have also heard it said that stitch welding is good because it gives most of the strength of seam welding, but if a crack forms in the weld it can only propagate through one stitch.
Always wanted to do this to a car some time, but never have had a suitably stripped car to use.
Hen
|
|
|
Location:
Brisbane
Registered:
May 2002
|
|
Re: Seam Welding & Stitch Welding
|
Mon, 09 August 2004 23:26
|
|
| Henn wrote on Tue, 10 August 2004 01:32 |
I have also heard it said that stitch welding is good because it gives most of the strength of seam welding, but if a crack forms in the weld it can only propagate through one stitch.
|
Yup, all the rally guys I've spoken to have said use stitch welding, NOT seam welding. Maybe not so much an issue for a street car, but it seems to make sense anyway.
|
|
|
Location:
Canberra
Registered:
May 2002
|
|
Re: Seam Welding & Stitch Welding
|
Tue, 10 August 2004 01:38
|
|
|
One trick is that you really need both an oxy and a mig to do it nicely. You need to point the oxy under the seams and run over them with a wire brush to get all the impurities out of the seam before you hit it with the mig.
|
|
|
I supported Toymods
Banned User
Location:
Brisbane
Registered:
May 2002
|
|
Re: Seam Welding & Stitch Welding
|
Tue, 10 August 2004 07:40
|
|
I agree with what was said above. You should not seam weld anything on the car, everything should be stitched welded.
If a crack appears in a seam weld it will continue to crack through all of the weld. Whereas with a stitch, the crack will only go as far as the one stitch it formed on.
|
|
|
Registered:
May 2004
|
|
Re: Seam Welding & Stitch Welding
|
Tue, 10 August 2004 10:46
|
|
|
I don't know what happens on a car without a cage to give it stiffness, but we have fully seam welded rally cars and have had no hassles with cracks forming in seams. We also welded it in one go, not in small welds to let it cool, we did however do all our seam welding after the cage was installed so this may make a diference. Agree with cleaning the seams out as much as you can though and use a little burner or an oxy to burn and then pick the filler out of the seams before you wire wheel them. Only weld from strut tower to strut tower though, 'cos any small front or rear end bingles will be easier to pull out without the welds. Interesting theory on only doing stitch welds though, it sounds reasonable to me, has anyone out there had full seam welds fail?
|
|
|
I supported Toymods
Banned User
Location:
Brisbane
Registered:
May 2002
|
|
Re: Seam Welding & Stitch Welding
|
Tue, 10 August 2004 10:51
|
|
| paddles wrote on Tue, 10 August 2004 20:46 |
has anyone out there had full seam welds fail?
|
Yes! However not on a car. But on boats this is a common problem.
|
|
|
Registered:
May 2004
|
|
Re: Seam Welding & Stitch Welding
|
Tue, 10 August 2004 10:56
|
|
|
Alloy or steel?
|
|
|
I supported Toymods
Banned User
Location:
Brisbane
Registered:
May 2002
|
|
Re: Seam Welding & Stitch Welding
|
Tue, 10 August 2004 10:58
|
|
|
Both.
|
|
|
I supported Toymods
Banned User
Location:
Brisbane
Registered:
May 2002
|
|
Re: Seam Welding & Stitch Welding
|
Tue, 10 August 2004 10:59
|
|
|
Although alloy is more prone to crack around the weld than through it.
|
|
|
Registered:
May 2004
|
|
Re: Seam Welding & Stitch Welding
|
Tue, 10 August 2004 11:08
|
|
|
Yeah? wow, we've had cracks start in bizarre places like down the firewall from where the brake booster bolts on, and creases form through the floor/tunnel and wacko stuff like that but have been lucky and never had a seam weld split. Why does the alloy split around the weld? is it cos the heated section of alloy goes brittle?
|
|
|
I supported Toymods
Banned User
Location:
Brisbane
Registered:
May 2002
|
|
Re: Seam Welding & Stitch Welding
|
Tue, 10 August 2004 11:13
|
|
|
I'm not sure if its because of the alloy being heated or just simply that the alloy is soft and flexes under less vibration that what the weld does.
|
|
|
Location:
Canberra
Registered:
May 2002
|
|
Re: Seam Welding & Stitch Welding
|
Tue, 10 August 2004 22:14
|
|
| paddles wrote on Tue, 10 August 2004 21:08 |
Why does the alloy split around the weld? is it cos the heated section of alloy goes brittle?
|
Electric welding causes farily large increases in hardness in aluminium. The only way to weld aluminium without increasing hardness is by using a gas welder..
|
|
|
Banned by his request
Location:
moved to tamworth
Registered:
July 2002
|
|
Re: Seam Welding & Stitch Welding
|
Wed, 11 August 2004 02:12
|
|
really not much point without a cage but if you want to just stich between all seams and use a tig as it burns the drip-check out from between the joins. it will take you a couple of full days to do it properly. once the car has been done make sure you clean and under coat everywere you weld. just finnished doing an misushitty evo7 for circuit,had a week to seem weld it and make a cage for it, thank god it was only 16 point cage. got to love plasma cutters for notching in a hurry!
mick
|
|
|
Location:
Madrid - Spain
Registered:
August 2002
|
|
Re: Seam Welding & Stitch Welding
|
Wed, 11 August 2004 03:28
|
|
|
Welding alloy locally heat treats it, so the area around the weld will be harder than the nominal alloy properties. This creats a hard point which will actually attract load. it will normally crack around the heat affected region, not in the weld itself.
|
|
|
