90KAcoupe

im sorry but u fail ... i think we have all came to the conclusion that stitch welding doesnt effect crumple zones.. crumple zones are places that bend.. not welds that break loose..

i wish people would read.. cause they always seem to over look the educated post..

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GSXRJJordan

link em. I have no idea what you mean, unless he added metal to the car for extra stiffness.

Hahaha. Have you even seen a stitch-weld how-to?

In order to stitch weld, you have to prep the car. First you remove all the interior/engine pieces in the way, then you strip the factory glue shit off of the seam to be welded. That shit weighs WAY more than the tiny bit of welding wire I'm adding to the car. Get real.

exactly.

It doesn't get softer, but it can become more brittle with oxidation/etc, making it crumple unpredictably anyway. His point is that you're changing very little as far as how the car reacts in a crash, as far as we can tell. Read the rest of the thread.

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twistedsymphony

Nope, I've never seen a stitch welding how to... I do know the general premiss though yes. If you read my other comment I noted that stripping the car and removing the seems was necessary.

as for the weight... I have no first hand experience but as I said I "HEARD" it added weight. I heard this from some member of my local car club who had just recently finished stitch welding an s13 hatch for use as a Time Attack vehicle. They said they weighed the chassis before and after and it added a little over 100lbs to the car in the process. Maybe they were wrong, maybe they did it wrong. Maybe they added some other kind of bracing as well which is where the weight came from... I don't know.

I make no claims that I'm an authority on stitch welding I'm simply repeating what I heard from someone who had first hand experience.

track_s13coupe

Im interesed in stich welding my 92 coupe for track use, but do you have to worry about warping the metal from heat when welding??

twistedsymphony

that all depends how good you are at welding...

track_s13coupe

Ive just heard horror stories about panels warping tryn to stich weld and not letting the welds cool off. Im a novice welder....

gerson408

is it better to stitchweld your car while its on stands or when its on a garage floor??

Flybert

You obviously have no clue what you are talking about so don't even post next time. First thing you need to do is weigh a roll of wire for a wire feed welder. Then go weld up a car and see how many rolls you use. My dad stitched my car up, top and bottom, and I don't think we used more than 2 rolls. We were welding a ton of other stuff so I'm not exactly sure how many we used on stitching alone but those rolls only weigh about a pound or two.

s14kouki44

i stitched it on the ground cuz that's the way the car is going to sit, if you weld it while it's up in the air, there could be the possibility of gravity pulling the panels down ever so slightly that it's not the perfect stance as if the car was sitting on the wheels. it shouldn't matter too much though

spoolandslide

i feel a some argument in this forum

so tell me so i can get the exact answer i am looking for, i understand everything everyone has said about crumple zones and such but then some people say that they would only stitch a track car so...
there may have been something i have overlook though that will probably be brought up with a quote but...

does stitch welding your car make it any less unsafe on public roads?
yes or no?

thats all i need because between the different posts im kinda confused
and without any experience on the topic, this is how i learn for sure

gerson408

ok so also i wanna know if you can rent a welder or do you have to buy one and also whats a good price for one my budgets like 200 for a welder

gerson408

GSXRJJordan

Do any of us fucking work for the Department of Transportation? How the fuck could any of us tell you, with authority, that it's completely safe?

Do you trust your life to a goddamned internet forum?

I think we're dealing with deeper issues here.

I can tell you, in my engineering experience and from what I've seen while building multiple cars for track and street, I felt like it is perfectly safe for my street-driven S14. I don't know if that's enough for you or not.

About welders: the fabrication thread is a great place to look, because I asked this exact question before I started. The welder linked from Home Depot is very similar (if not the exact model) to the one that they rent, and that's what I used to do mine. Took me two full days to do it, but the welding alone is the fast part - the prep is what takes the majority of the time.

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spool_sample

This thread = SIGH.

People are making it seem that stitch welding the chassis is going to make it 100% rigid and that you will die IMMEDIATELY upon impact. I don't think that's going to happen. In that case, why stiffen up the car at all, even if it's a DD? Take off your fender braces and tower braces and lower arm bars, then.

For some reason, people are confusing the structural integrity of stitch welding to be near that of a proper cage, but really, it's pretty marginal.

I think it's funny, though, that some of the people who get worried about the "safety" of stuff like that have cars with aftermarket steering wheels and buckets, and run stock brakes and bald all-seasons with 350+hp motors... get serious.

gerson408

how much did you get charged to rent it??

gerson408

what exactly should i do before i start this im gonna start at the back of the car so i know that your suppost to skip and not do a continuos weld please fill me in

guitaraholic

From what I have read on the subject, don't you mostly just stitch weld from the firewall back, and from the gas tank forward (ie mostly the cabin area). Yes, I know you weld under the body and so forth, but if you do the cabin I don't think it would effect crumple zones what-so-ever. Again, I would think the crumple zones are mostly ahead of the firewall and behind the rear passenger compartment. Though, if you stitch weld past that for maximum rigidity, I would not be sure what it would effect. I do not have enough knowledge on the placement/functionality of crumple zones to validate anything on the subject. Just merely stating what I have read.

GSXRJJordan

^^^ Not complete.

Home Depot rents the welder and mask for $40/day, or $25/4hrs. It took me two full days. The wire was about $10.

Stitch weld every seam you see, from strut tower to strut tower - everything after that is marginally effective, if you've got strut tower bars installed.

Start in the passenger compartment with everything taken out. Like I said earlier, you'll need a wire wheel or lots of sandpaper ('coarse' wire wheel on a corded drill works WAY better than anything else) to get the "glue" shit and paint off of the surfaces. Then I wiped it down with acetone/denatured alcohol.

When I did the welding, I was worried about heat warping the metal (its very thin). I did single, pea-sized beads about an inch apart, and only 6 inches at a time or so. This worked out well because I'd wire wheel a section, clean it up, weld it, and repeat, making sure that I was never welding in one area too much. I saw no signs of warping on any of the panel ends, which would curve/warp first (before the panel itself).

Afterwards, I cleaned the area with acetone again, then sprayed it with automotive primer to seal it.

In the engine bay: Firewall seams, strut tower->fender tops, strut tower->inner fender bottoms-> frame rails. Basically, anywhere you see a seam, grind the glue off and weld it.

In the passenger compartment: Footwells -> firewall (you can do the whole seam if the dash is out), "seat hump" up and over the tranny tunnel, from side to side, front and back, door seams (all the way around), rear seat side area seams.

In the trunk: Strut towers all around, and the seams on the top near the trunk lid.

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gerson408

so just grind down to bare metal clean up the area then boom spot weld?? that easy

derek_s13

agreed. hard.



jixerjordan knows what he's talkin about.

fabrik8

I forgot I was a member here, and I came across this thread completely accidentally through Google.

So first and foremost: Where do some of you people come up with this stuff?

Ever seen a WRC car hit a rock, ditch, tree, etc? They're all stitch welded. They crumple, quite a lot, and they have full cages and braces and everything.

Stitch welding only makes the sheet metal seams not shift, but sheet metal is really easily overloaded and buckles very well. It's going to absorb impact no matter what, and the crumple zones will do their job no matter what. So when you get into an accident, you'll still have very, very buckled sheet metal. You'll just have stiffer seams where the metal attaches, because the sheet metal can't move as much with relation to the other pieces of sheet metal. This doesn't affect accident performance at all. Like whoever said earlier, you're not breaking welds in an accident, you're buckling (crumpling) sheet metal. If anything, stiffer stitch welded seams should transfer force more effectively into the sheet metal, turning force into buckling instead of shifting the seams around. Basically, you can have incredibly stiff seams, and the sheet metal will still buckle because it's much weaker than the seam itself.

Crumple zones are box sections that are preformed to deform in a very controlled way under impact, and changing to a stitch weld isn't going to affect that deformation more than a little (if at all). Again, the sheet metal in the crumple zones will buckle way before the seam type becomes a factor.

Assuming that stitch welding will make the whole chassis into an infinitely stiff, solid block of steel ready to turn you into a cloud of red mist on impact is a very wrong assumption. Sheet metal doesn't work that way.

Imagine welding two pieces of thin sheet metal together at a seam, and punching/riveting two more pieces together. All the pieces are going to buckle somewhere in the middle (not the joint) when you overload them, completely independent of the type of joint used to attach them together. However, until you reach the yield point of the sheet metal (and it's the pretty much the same point regardless of the joint), the welded seam will be much stiffer because it won't allow the pieces to move with respect to each other.

Don't put the slightest amount of paranoia into stitch welding; if you're worried about safety you need to learn a lot more about materials and basic chassis concepts.

There are only two drawbacks to stitch welding: Time, and repair. It takes a long time to weld an entire car. If you need to repair a panel that has been stitch welded on, it will take a lot longer to remove and replace. Other than those two things, there are no downsides.

Stitch welding the whole car should add less than 10 pounds of weight, you're not adding anything but tiny filler rod or MIG wire unless you add other reinforcing braces, plates, gussets, etc.

Use a good paintable seam sealer when you're done, it's easy to find (body repair supply shops) and easy to use, and will eliminate corrosion and noise problems.

And please, do an actual stitch welding job, with inch (or two) long stitches and then skip someplace else to keep the heat distortion down, then come back to where you were.. You can prep the entire car before you even think about welding, and then spend a few days welding without doing anything else. If you properly stitch weld, you can do a few welds, move to another seam, do a few there, move somewhere else, etc. You don't need to weld, prep, weld, prep, weld, prep because you can just move where you're welding instead. This is a better method because you're progressively increasing stiffness all over a little at a time, instead of locally stiffening one area at a time.

Put the car on something very solid, and make sure the height from the ground is as even as possible. Shim it if you have to so twist preload is minimum during welding. If you keep the car on the suspension and wheels, the chassis is going to twist depending on where in the car you are and how much the suspension sags under your weight.. Not good, but probably not a big deal. It's easy enough to put it on jackstands or something like that, so better safe than sorry.

Don't do the little bitty round spot weld every 2" thing, it doesn't do much overall compared to actual stitch welding.. It might be fine for a street car, but you've already got everything prepped, and you're already welding, so why not do a higher performing weld type that will give a stiffer chassis?
You should end up with a continuous or near-continuous weld seam when you're done, not a dotted line of 700 little round tack welds. Those little tack welds still allow the sheet metal to rotate around the weld, and if you overload it in some off-plane direction it will wrinkle between the welds. Remember, the whole unibody is assembled with spot welds (from a resistance welder) and if you do a lot more spot/tack welding, you're just making many more of the same welds, not better types of welds.

Remember: Making spot/tack welds along all of the seams is not stitch welding, and it doesn't work as well. And you're not going to die a horrible death because your chassis is stitch welded.