turbo-polak

a friend that has been into rallying for years now, and drifting also, told me that i should spot weld my frame to stiffen it up..... he had done it with his subaru and said it did a world of a difference...

anyone had any experience with this?

what are the reccomended spots for welding exactly?

the car will be used for daily driving, and drifting... occasional grip car on the local track....


cheers,Dan.

TrentO

Your friend is refering to seam welding the frame. I've got some pictures of my tub on my website and you can see where I seam welded the chassis. http://www.rxracing.com
Seam welding is a very involved step and takes a great deal of time.

-Trent

turbo-polak

he specifically said spot welding and said to me not to seam weld it as the chassis wong last long for some reason?

maybe because it would be toooooo rigid for the street?

peejay

Are you sure he didn't mean stitch welding?

The body is already spot-welded. Spot-welding is how 99.9% of all cars are put together, because it's so quick and repeatable: Pinch the metal together with big tong-looking things, apply current through them for a given amount of time (very short!), and the metal is welded together.

Stitch welding is what most people mean when they talk about seam-welding a car. You go to a given body seam and weld an inch, skip an inch, weld an inch, and so forth.

You don't really want to weld up the seams 100% because you can induce stresses in the body because the metal wants to expand and contract when you weld it. (Also why you don't want to weld all in a line, but jump around all along the seam until the whole thing is done)

There's no such thing as "too rigid", but there are heat issues inherent to any kind of welding. Welding is like driving, just when you think you know what you're doing, you realize you haven't even scratched the surface (pardon pun).

turbo-polak

ya, im pretty sure thats what he meant.... stitch welding... not welding the frame 100% all the way across, but every inch or two...that will help a lot, right?

where do you guys reccomend doing this??

strut towers?

Speed Raycer

The last car that I seam welded, I had over 60 hours in it, and that was just from the rear struts to the firewall (drivetrain was still in the car... rest will be done at a later date). You're looking at a good 80+ hours of work to do it like your buddies rally car.

Seams and surrounding metal have to be very clean otherwise you'll spend 90% of your time burning through the metal and cussing when globs of metal run down the back of your neck.

peejay

EVERYWHERE.

As others mentioned it's not something you typically "just do", you have to get the seam sealer (if any) out, and you *will* have to repaint anyway, so might as well dig out the sandblaster and do the job *right*....

As a rule of thumb, anywhere two big pieces of sheetmetal are spotwelded by the factory, stitch that sucker. (On the "fold" side of the factory seam, not the "edge", if it's a pinch type joining, but you don't always get to choose) Areas between the front and rear suspension should get the highest priority.

DougFD3S

When I asked about seam welding my car, a guy told me what he learned from the GT guys. I guess they spot weld their cars as opposed to stich welding. It involved drilling out the first layer of sheet metal to get to the second and then welding those points.

turbo-polak

first off, i dont have a sandblaster.... but i do have a bunch of different tools for sanding, grinding, cutting and such..

i was planning on borrowing a mig welder for a day or two, and tack welding a spot every 2 inches or so...

but i would be sanding/grinding off the paint first, de-greasing, welding, then primering and painting over..

i dont see what would be so hard about it? some of the places are hard to reach?

i also dont have a hoist in my garage, so only sections that are reachable w/out a hoist will be done, at least for now..

the silicone comes off pretty easy, i peeled some off already,.....

my friend that did it to his subaru will be with me for advice...


i said strut towers because when i was in portland and saw the Formula D cars, they all had them spot welded...

NasaPro7

Do as much as possible. Don't tack weld every couple of inches, but lay an inch bead or so... leave an inch of two, then do it again. Listen to Scott (Speed Raycer).
here is a shot of the number of welds it will take:
http://www.simulationinformation.com/durability2.jpg

another photo, halfway down:
http://mummbrothers.com/T2_Stuff/Tec...nstruction.htm

Marcus

NasaPro7

one more...
http://www.rally.subaru.com/rally/se...?part=1&page=1

turbo-polak

hhmm... seems like a LOT of damn work... only for the car to be crashed likely what will happen to me.... haha

which areas are the easiest/most effective to do?

i was considering doing this whole seamwelding thing not in having the car on a rotisserie...but more just welding areas that i can do while my interior is stripped and i have stripped it of the sound deadening TAR from the factory, which is the state it is in right now...

DriftingB26RX7

iTrader: (4)

WOW i wish i could do that to my car thats ****** awesome

speedturn

iTrader: (1)

As the above guys have been telling you, it is going to take a few weeks. Much more time than the "I was planning on borrowing a mig welder for a day or two"

If racing was easy, then anybody could do it.

If you want to make your chassis stronger, get a roll cage designed and welded in by a professional.

peejay

But that is what you're building it for!

One saying I really like about race cars is that you have to be mentally and financially prepared to be able to just push the car off of a cliff.

Seam welding *is* a lot of work. It also has great benefits, too. Like the extra body strength even with a rollcage thrown in.

Look at it this way: You wreck a non seam welded car. A hit on one corner can bend, fold, spindle, and generally mangulate MOST OF THE CAR. The 'cage protects you but the car around it gets all tweaked. Fully seam welded, it's more likely that the damage will be more localized and it might be easier to repair than start over with a new bodyshell.

Of course if you turn the car into a crumpled beer can, there's no hope for it anyway, but now you can do the next one faster because you have more experience.

Finish taking the interior apart first if you are still thinking about doing it. Ideally you shouldn't see anything but metal.

Boswoj

Absolutely incorrect - seam welding is used to make the body a single structural unit, instead of allowing local deformation. Go to the local bodyshop and take a look at the deformation that happen along seam lines in an accident. That allows crumple zones that are localized - and those seams allow a breeaking point to replace damaged areas. Seam welded cars are quite a bit stiffer, but accidents affect the entire unit as forces are transferred right through the whole shell. That means in low speed bumps less damage is likely to occur becasue you are dealing with a much stiffer stronger shell. Those forces have to go somewhere though, and the deceleration on the driver will be greatly increased. Crumple zones on street cars are a carefully thought out feature for YOUR protection. High speed impacts like those typically found in racing accidents on the other hand, will distort the WHOLE shell instead of in localized zones. Cars become tanks instead of pillows, so don't assume you will not be writing off the whole shell in an accident! Everything in engineering has a tendancy to have tradeoffs. Racing is a specialized, narrow focus case where some things (comfort, reliablity, wide parameters of use) are traded for others that better fit the activity (speed, consistency, predictabilty, tunability). Safety is always a relative term when you discuss racing. It is always SAFER to decide not to race at all, but that doesn't stop those of us who are passionate about it.

DriftingB26RX7

iTrader: (4)

I bet you that you can seam weld that car in a 1 DAY if the car was preped and ready. Everything sanded down and what not, I think i could do it if i really wanted to and had the time.

peejay

Makes sense...

But welded up cars seem to retain their "shape" better in a wreck.

Crush zones only work if the area they are meant to protect is stronger than the zone itself, if it's all relatively weak then *everything* gets damaged. Or, at least, a significant chunk of everything.

For simple situations, like a hit to the right front causing damage to the left front due to a strut brace, then yes adding strength hurts.

I'm not so convinced for situations like off-angle quarter hits.

Speed Raycer

Not to get into this fray, but if you seam weld a car, any crash damage to a seam welded area becomes much worse to repair. As Boswoj stated, you've removed the crumple zone that absorbs the impact. That offset front ender that normally would have stopped before the strut tower now goes all of the way back to the firewall. Time for a new shell!

Do yourself a favor, and dont seam/stitch/spot weld any further fore/aft than the shock towers to retain *some* crumple zone.

Remember, BOTH sides of the weld have to be clean. That means you'll be grinding underneath the floorpan as well.

Yes, if the moons all aligned and you had the seams down to bare metal and every ounce of seam sealer and other gunk removed (not likely), you could do from the firewall back to the rear shock towers in a day.

aussiesmg

iTrader: (1)

Exactly right, seam/stitch welding is done to stiffen the chassis so that it can be tuned more effectively, it does not make the car safer but makes it handle better if tuned properly. This process has no safety implication at all and as mentioned removes some of the factory (albeit 20 year old technology) safety features.

A roll cage is for safety and any handling improvement is purely coincidence.

NasaPro7

ageed, to a point. your statement is contradictory.
If the process removes the crush zone ( 20 year old safety features), which is does, with little argument... then it has safety implications.

I believe when discussing these implications we are at the noise end of the spectrum, well into theory and "what-ifs", but ya know...

Marcus, who hopes the hans he just bought (against his better wishes) doesn't harm him.

Boswoj

The crumple zone design becomes substantially less effective for racing cars anyway, as they are designed for speeds and conditions that are typically found on the road and not on the track. Crumple zones on street cars are primarily designed to absorb the energy expended in 30 to 60 mile an hour crashes which probably comprise 80% of all road use accidents. Race cars musst be made safe for substantially higher forces, and particularly to absorb energy from being struck by other high speed vehicles, immovable objects like armco, hills, and walls, and to prevent intrusion. Crumple zones will always help to reduce deceleration loads on drivers, but racecars are operated in kinetic energy situations that quickly overwhelm the amount that the crumple zone was intended to absorb.

speedturn

iTrader: (1)

I believe in keeping the areas ahead of front strut towers and behind rear shock towers as crumple zones. I have done that on my GT car; no extra tubes added ahead of the struts. On a first gen, there is about 3' from the tip of the nose back to the struts. Three feet of deacceleration can greatly reduce the G's felt in a crash. I have been there and done that.

cagedruss

The GCR also does not allow any stich welding for most classes for the same purpose, they say it is for cost, but a National tech said it is for overall safety of the drivers. Stitch where you have a roll bar or cage to help stiffen the platform. Let everything else be, that is what the engineers are paid for.

Boswoj

Very much agree with speedturn and cagedruss from an engineering standpoint. Most people don't realize how much safer cars have become in the last 30 years. Cars used to be built like tanks so they didn't deform in accudents. Transferred very high deceleration loads directly to the driver. Humans are NOT designed for high decel loads - take a look at some of the data that is avalable on Hans and Isaac websites - it's pretty interesting. Now the body acts as a shock absorber by soaking up energy while it deforms. The energy that is soaked up by the car may cause it to be a total, but saves the driver from being totaled. Just a few milliseconds of time can make the difference between a stiff neck, and a broken neck. Sacrificial bodywork provides that time to slow down deceleration.