Frame rails... Options

[Jeroen]

last one...

Targa/roll bar inner reinforcement

[Eric_Shea]

At the seam marked "C" the long has a small lip (aprox 1/4") that is folded to the inside of the long. This lip is spotwelded to part "A" from the outside (shocktower side).  They must have done that before the shocktower was welded in place.

OK... That's the answer I was looking for. It is welded, just not very well. Thanks.

I've looked at Gint's tub again this morning. Here's some things I'll throw out there as was my discussion with Gint a few hours ago:

1. Brad is right. (first time for everything (IMG:style_emoticons/default/laugh.gif) ). The factory stiffening kit gets welded to a cover plate not to the actual longitudinal and shock tower area. This is an area of sheet metal that is pressed into the inner fender well and it sticks up about 1/8" to 1/4" depending upon the area. Those who have been there know what I'm talking about.

After looking at that area, I believe there is a fix for this that will make the factory kit "VERY" useful. That fix is this:

Tack weld the ends of the factory piece or use clamps to hold it in place (this is the long piece that ties the longitudinal into the shock tower). It is drilled rosette. With the appropriate drill, drill out all the rosettes in the "outer layer" that Brad talks about. Next, rosette weld through both pieces to the actual longitudinal and shock tower.

2. I'm not sold on the need for seam welding the shock towers. After looking at this car and Jeroen's recent photo I believe the factory was simply chasing after whatever they thought might solve their problem. The seam in the shock tower has "2 rows" of spot welds and we've never seen one split there.

I do believe that Brad, Jeroen whomever "did" find the problem area and I think we've found another way to strengthen it "IF" you so care to do so without the surgery seen here (not that that's bad... just that some application would probably forbid this method). This is it...

3. Using a die grinder and a burr from the "inside" of the shock tower that seam can be accessed (seam marked C). A bead can then be applied from the backside and closed upon itself all within the shock tower.

So...

The factory kit can be made to work (I think, and so does Troy who would be doing the welding). I really think that a factory kit installed this way (weld the rosettes through to the actual longitudinal and shock tower) would do away with the need for most of this welding and reinforcing.

Seam welding the shocktowers looks like it wouldn’t be that effective based upon the massive amounts of spot welds there.

Most of the elusive "seam marked C" can be welded from the inside of the shocktower if you have a stockish vehicle and want to preserve the cosmetic integrity while strengthening that area.


Thoughts?

[Gint]

Thanks Eric...

[SpecialK]

Great pics guys! 'Saved' them all!!

I had no idea that there were that many double-walled areas on our cars.......looks like I'll be needing another gallon of Ospho! (IMG:style_emoticons/default/huh.gif)

[nsyr]

Anybody have any pics of the shock tower seperated or damaged?

[hargray2]

rosette weld through both pieces to the actual longitudinal and shock tower.

(IMG:style_emoticons/default/agree.gif) This is what I've had in mind for a while.

[Jeroen]

Ok, maybe this is more clear
The pic below shows how I think it is best to weld "seam B" if you leave the firewall in place
Weld a bead from each side of the firewall over the width of the long

To get to "seam C" it's best to do it the way Brant did
Cut a small section of the inner wall of the firewall (inner = looking from the engine bay)
Weld up "seam C" and close the firewall back up

[Brett W]

Guys,
Something to keep in mind. Seam welding can actually make a part weaker by creating a stress point along the line of the weld. You are much better off running small short "plug" welds. These would be about 1-2 inches in length seperated by the same length. This will be much stronger.

[Eric_Shea]

To get to "seam C" it's best to do it the way Brant did

Why?

I'm asking because I was told by an "very" experienced fabricator that it's 6's at that point, meaning a toss up. That rear firewall piece "is" your rear shock tower brace and an intrigal part of the backbone of the car as you have pointed out. By cutting it with a torch and then rewelding it you fatigue and harden the metal.

He also said "exactly" what Brett just said about the seam welding. Same thing goes there. With literally dozens of welds (double spot rows) on the shock towers he looked at me like I was crazy when I said we wanted to seam weld there (sorry Brandt, not panning on your ride... it's absolutely beautiful. Actually, it's buttfuckingugly and I hate your guts! Had to have a reason for Miles to chime in here (IMG:style_emoticons/default/w00t.gif) ).

Jeroen, I like your idea about the welds into the seams at the back of the shock tower. I wondered about that area myself.

If there is a real reason that "it's best" to do it that way, please let us know now because Gint's tub is going into paint in the next week or two. Gint, correct me if I'm wrong here but this is a street car that will be driven hard at a couple DE events per year. I'm guessing it will get "spirited" driving on the street as well (based on the way you abused my poor little car with me right there in the passengers seat! (IMG:style_emoticons/default/laugh.gif) ).

Thanks!

E.

[Brad Roberts]

Remove the cover. Weld stiff kit to frame rail. Weld cover back on. This also leaves you more room for TIRE. I hate seeing comp cars with the kit installed and the tires rubbing the stiff kit. It ads material and takes away space if you do it the way the factory did.



B

[Gint]

If there is a real reason that "it's best" to do it that way, please let us know now because Gint's tub is going into paint in the next week or two. Gint, correct me if I'm wrong here but this is a street car that will be driven hard at a couple DE events per year. I'm guessing it will get "spirited" driving on the street as well (based on the way you abused my poor little car with me right there in the passengers seat!).

Here's what I said on page 1 of this thread:

I hear ya, but if I want to do it, now is the time.

I don't baby my cars.

This car will see the track, even if it isn't much for the first few years.

It will get Mueller bearings which may necessitate stiffer springs.

It may also get much more motor and some point in the future.

And it could very well see significant track time after the shine of the resto wears a bit.

I only want to do this once. After the investment involved with this resto, I'll be keeping this car for a long time. I can seriously see a larger engine and more track time in it's future later on down the road. If nothing else, I want to do some more auto-X in the very near future as well.

[larryp]

I am consistently amazed by the effort you people put into these 30+ year old cars. Amazing.

[Brad Roberts]

I'm betting we wont be doing this to Boxsters in 30 years.



B

[Eric_Shea]

I'm betting a Boxster couldn't take 30 years of this type of abuse. (IMG:style_emoticons/default/w00t.gif)

Now get back to your friend rice!! (IMG:style_emoticons/default/slap.gif)

[Brad Roberts]

I'm done. Couldnt eat all of it. I'm down to 190lbs now. Feeling pretty good. Ready for some seat time next year.



B

[Jeroen]

That rear firewall piece "is" your rear shock tower brace and an intrigal part of the backbone of the car as you have pointed out. By cutting it with a torch and then rewelding it you fatigue and harden the metal.

I don't see how cutting a small piece out of the (already very strong) firewall and patching it back up would hurt the strength of it so much that it would cause trouble

I guess the pics of how the end of the framerail is attached to the shocktower don't do it justice
If you'd see it for real, you'd be scared shitless...

[J P Stein]

I got an idea, let's take a bunch of "facts" and come to a conclusion.

1) The weakest part of any weld is the heat effected zone (HAZ) in the base metal.......this assumes the weld is done properly.

2) Low carbon steel can be made harder/more brittle....but not much. Air quench keeps this to a minimum.

3) Any weld metal applied to low carbon steel is gonna be
harder, stronger, and *maybe* tougher than the base metal. When overstressed, the base metal will fail first.

4) Any joint is only as strong as it's weakest link.

5) A skip weld joint is not as strong as a continious fillet weld....really!!

6) Welding the toe of an L shaped joint doesn't do much for the strength of the joint, but it keeps the water & "stuff" out. Welding the heel is much better *IF* you can get at it.

I worked bout 20 years in the steel fab biddness. I *may* be (tho I've had plenty of exposure to weld engineers) short on theory, but long in emperical data. Draw your own conclusions.....I did mine.

[brant]

Eric,
no offense taken on my car.

THIS IS ONLY MY OPINION, I'm sure others will disagree... but I wanted to throw out a few more thoughts...

1) The ONLY thing that these shock towers do is hold the spring from traveling upwards... The brace between the towers is really only necessary for positioning and is not necessary for reinforcement.. The shock towers do not move sideways in normal suspension travel. Therefore if the brace between the towers is weakend it is relatively irrelevant....

2) Correct me if I'm wrong here... But I don't think even 1 singe street car has ever popped the tower tops. NOT ONE. It is not a common failure. It is not necessary for a street car. It might not hurt anything, but probably not necessary. I ran 250lb rear springs for 10 years on the track (in a 2 driver car) and did not have problems.

I think the cars with racing slicks, downforce, and over 300lbs of rear spring might be suseptable. Those cars all have a bar from the roll cage to address the issue. Even on my car, I did it as a "while your there" kinda thing. The cavity I opened up is probably more important than all of the attempts I made at seam welding, but even it may be unnecessary.

this sounds like a rant.
I didn't mean for that effect.
I just meant to say that its all a very interesting conversation about theory that is probably not applicable much to steet cars.

brant

[hargray2]

Forget everything so far. I wanna see a pic of a shock tower that actually broke from
stress. <_<

[bob91403]

Guys,
Something to keep in mind. Seam welding can actually make a part weaker by creating a stress point along the line of the weld. You are much better off running small short "plug" welds. These would be about 1-2 inches in length seperated by the same length. This will be much stronger.

Reminds me of a good one. The Israeli airforce was testing it's first Israeli built fighter jet. They had a problem. Every time they got the plane up to mach 1, the wings would fly off. An old rabbi was watching as they continued to eject out of their failing aircraft. He went over to the engineers, and said, "You should drill holes in the wing along the point where they're breaking, trust me." The engineers thought he was crazy, but had tried everything else, so, they said what the hell, and drilled the holes in the wings. The plane made mach 2 with no problems. When they asked the rabbi how he knew it would work, he replied, "50yrs. I've been breaking matza, it never breaks at the holes." (IMG:style_emoticons/default/biggrin.gif)