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View Full Version : Spot welding chassis. How long did it take you?



bleach8484
05-12-2005, 08:13 PM
Ive read as many post as I could get ahold of dealing with this topic, on several sites. Im just curious about how long it took YOU, personally to do spot weld the entire car. I started stripping the shops FC and started spot welding the trunk area today. I know its a long tedious job, and its worth it in the long run.

Its a strictly track car, and i would just like to hear how long you guys took and your process of doing it. Like what methods you used to remove the seam glue and undercarpet sound deadner

Thanks, Brandon

gunluvS14
05-12-2005, 11:24 PM
i thought u read enough http://forums.freshalloy.com/images/graemlins/laugh.gif
use dry ice... those tar come off a lot easier with the "freezing" method.

MATT_BACK_VASS
05-13-2005, 12:35 AM
did any of you REALLY notice a difference when stitch welding the chassis?

When I removed a body panel and unibody section of a 240, there were about a bazillion spot welds I had to drill out to remove it... It's pretty well held together from the factory.

Flybert
05-13-2005, 01:01 PM
did any of you REALLY notice a difference when stitch welding the chassis?

When I removed a body panel and unibody section of a 240, there were about a bazillion spot welds I had to drill out to remove it... It's pretty well held together from the factory.





That is the same reason why I didn't spot weld mine when I had my motor out. It just didn't seem like it was worth my time and effort.

bleach8484
05-13-2005, 04:40 PM
I know about the dry ice method, I didnt know if it just flakes off with a scraper perfectly or should i just blast it with a wire brush on my angle grinder.

On a few of the threads I read, people stated that they already had a full cage in their cars. A few said they placed there hands between the cage rail, and the roof, And lets say they were climbing a drive way at an agle or something, They could feel the flex of the body and the roof tighten their hand between the two. And after seam/spot welding, the flex was gone.

Im sure i worded that horribly, and after all thats just internet stories I read about. Either way, we have time to blow, and I like getting familiar with my welder.

Remember...Im dealing with a Mazda (FC) I havent ran across that many welds thus far. I seriously doubt i will do this on my S14

mattmartindrift
05-15-2005, 07:55 PM
hammer and a chisel...that's what I did, it comes up in big sheets
if you go along the chassis with a hammer after dry icing, then use the hammer and chisel. I think it works really well.

thoraxe
05-17-2005, 10:48 AM
did any of you REALLY notice a difference when stitch welding the chassis?

When I removed a body panel and unibody section of a 240, there were about a bazillion spot welds I had to drill out to remove it... It's pretty well held together from the factory.



Depends on which panels you're talking about and along what lines of stress you're reinforcing them.

I've had spot welds pop on me just driving around. There may be a lot of them, but they're not designed with 100% chassis rigidity in mind. There are plenty of other criteria that determine where the welds go.

Especially in S13s, over time the chassis will begin to bend/tweak, and of course more-so if you are abusive of it. My roof is bent on the chicken in several places and the chassis is definitely not straight anymore. Had the car been seam/stitch welded from the beginning it probably would've held up much better.

Just watch still images of your car cornering/drifting and make some relative measurements. You'll see how much the body flexes. A lot of that is in the panels.

aaronyoung
05-17-2005, 11:03 AM
The biggest problem is the seam putty. It is in between the panels and boils out when you go to weld, contaminating the weld. You can try a propane torch to burn it out before welding but it never seems to all come out.
The absolute best way to do it would be to acid dip the whole chassis, but I have only heard of a few people in my life that have gone to that extent.

I personally would like to see some one use a tig and continuously weld the entire seam, as opposed to spotting with a mig. Not that there is any thing wrong with a mig it is just impossible to control the heat on as opposed to a tig.

bleach8484
05-17-2005, 04:31 PM
The only reason people do not continuously run a bead all the way down the seam is, if some how it starts to crack or break the weld, it will more than likely keep going down the line. But if its only spot welded it will only break that particular weld.

asad
05-17-2005, 04:59 PM
The other reason is because a continuous bead will put a lot more heat into the metal than a series of spot welds, potentially weakening the base metal in the heat-affected zone.

Asad

aaronyoung
05-17-2005, 06:54 PM
The other reason is because a continuous bead will put a lot more heat into the metal than a series of spot welds, potentially weakening the base metal in the heat-affected zone.

Asad



Your right, there is potential there for metal fatigue on a continuous weld.

thoraxe
05-18-2005, 12:57 PM
Just do whatever Prodrive does. If their rally cars hold up, our weenie drift cars sure will http://forums.freshalloy.com/images/graemlins/wink.gif

digitalpimp
05-18-2005, 05:25 PM
the few chassies i've helped build for racing (which were either volvo touring cars or rally impreza's) we mostly used a 30mm long stitch weld with a 40mm gap between welds. older cars (such as a mk2 escort) you can go as far as seam welding the chassie, durring witch it is quite easy to warp everything if you arn't carefull. new cars (like a wrc spec new focus) you only really need to bother with certain junctions in the chassie, around frame rails and such. car unibody construction has come along that far, that the rest of the regidity needed is supplied by a good cage design.

sealer inbetween the panels is right, it can be a real pain in the ass. we've used a torch to burn it out, but it still dosn't yeild a super good weld. we've also had problems on shells that were acid dipped, because they were diped in tanks with old acid. the gunk at the bottom of the tank made it really hard to weld on some parts of the car (that were closer to the bottom of the tank). from what i've seen, stitch welding a whole unibody would take about 3 solid days of JUST welding, after having all of the prep work done. obviously less if you skip over the areas that arn't that imporntant.

the difference it makes is simply amazing. i watched some volvo shells being carried around with a fork lift, plain shells would shake, and stiched shells (that didn't have a cage yet) were totally rigid, it was very easy to see the difference.

http://img.photobucket.com/albums/v93/wanganps13/Untitled-73.jpg

bleach8484
05-18-2005, 07:33 PM
Man thats awesome. Nice info. Ive been having good luck with removing seam putty with a grinder and a steel brush atatchment. then just burning off the excess with a torch.

How many LBS of dry ice do you guys usually buy for a project? Ive heard around 15 LBS will do it. I would say im about 1/4 of the way through, but im just working on the car inbetween coustomers cars. Ive been doing the 1-2" strips under the car and main joining. But body panels inside ive just been spot welding

digitalpimp
05-18-2005, 10:16 PM
the volvo GT touring car shell pictured above (that runs in the speed world series, poorly, but within the last few weeks some HUGE transmission bugs were worked out) was shiped right from the assembly line in sweden before any coatings were put on the metal, needless to say sound deadening. http://forums.freshalloy.com/images/graemlins/grin.gif

personally, i think for any "street" car stitch welding is not nessesary. a *GOOD* cage design gos a long way twards stiffening the car, while making it more safe to. on the rally cars it helps so they don't tear apart. but at that point there is a obvious difference between a pro welder doing the work and a "normal" welder.