Frame rails... Options

[Gint]

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

No one in this thread or any other has ever said (to my knowledge anyway) that the shock towers break or the tops of them pop off. That's not the issue that's being discussed. It's the longitudinal to shock tower junction and the associated crack that forms on the inner fenderwell area because it's a weak point. Especially if you're creating a race car and removing the firewall.

I just meant to say that its all a very interesting conversation about theory that is probably not applicable much to steet cars.

Which is exactly what I wanted to accomplish by resurrecting this thread. A discussion about theory and perhaps even actual experience regarding the frame rail to shock tower junction. You have an opinion about whether not this was applicable to a street car. I didn't until now. This thread so far is the best discussion I've seen on the subject on this site or anywhere else for that matter. With pictures too. Ultimately I will make a decision how much of this to apply to my tub. Now at least I can make a reasonably informed decision.

I will probably also move this to the Classics section when it all plays out. Great info here. The best yet regarding this subject IMO.

[Eric_Shea]

Draw your own conclusions.....I did mine.

OK. But I don't have all that steel fabricator experience so, once again, I got professional help. (IMG:style_emoticons/default/wacko.gif) This time there was a retired Boeing airframe engineer hanging around to add his $0.02. Here's what they both said.

1) The weakest part of any weld is the heat effected zone (HAZ) in the base metal

Correct. That would be the metal that runs along side the weld affected by the heat.

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

Correct. Proper voltage, wire speed, metal inert gas etc. can minimize this. E.G. A good welder with the proper MIG settings can weld up a turn signal hole without warping your fender beyond repair.

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.

Correct. The key word being "weld" metal. The weld would rarely break. It would break exactly where JP suggested is the "weakest part" in his first point... right "next" to the area welded.

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

Correct.

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

Correct. The key word being "weld" again. The weld is strong. The metal around it (I believe you call it HAZ metal in your first point) is fatigued. For reinforcement support they suggest "IF YOU FEEL THE NEED" you should go with Brett's stitch (or skip) welding that allows the strong factory metal area some relief. Especially in an area such as the shock tower where there are two rows of factory spot welds (which is what I think hargray2 is eluding to). I think that's exactly what Brett mentioned when he stated "Seam welding can actually make a part weaker by creating a stress point along the line of the weld" (that would be the HAZ metal that JP refers to) E.G.: (f=fatigued metal, w=weld, r=relief)

Continuous Weld
FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF (HAZ)
WWWWWWWWWWWWWWWWWWWWWWW (Weld)
FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF (HAZ)

Skip or Stitch Weld
FFFFFF RRRRRR FFFFFF RRRRRR FFFFFF RRRRR
WWW RRRRRR WWW RRRRRR WWW RRRRR
FFFFFF RRRRRR FFFFFF RRRRRR FFFFFF RRRRR

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.

Correct.

Looks like JP nailed it... (IMG:style_emoticons/default/smilie_pokal.gif)

Brant... that didn't sound like a rant at all. Excellent input all around. (IMG:style_emoticons/default/beerchug.gif)

[Gint]

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.

I need some pics Brad. In looking at all of this, I can't see a "cover" and it looks as if the long is only three sided and open faced towards the innner fender wall. There is a 1/4" or so flap along the top of the long (and probably the bottom) that tack welds to the inner fenderwell sheet metal. So the "cover" you refer to appears to be the inner fenderwell lining itself.

Have you ever actually removed the "cover"?

[URY914]

My car currently has the "firewall" (the sheetmetal 'teen the trunk and the engine), but no trunk floor and I added a 1" bar tween the shock towers.

I'm in the process of cutting the firewall out completly and only having the 1" bar holding the shock towers apart. I'm also going to clean away all that seam sealer crap so it is as clean as the pictures above.

The next step will be to add 1" bars from the shock towers down to the rear tranny mounts. Thus removing all original sheet metal from the just behind the shock towers. Sort of a bob-tailed 914.

I've got a few other ideas that I'll post pics of as I go. (IMG:style_emoticons/default/wink.gif) (IMG:style_emoticons/default/happy11.gif)

Paul

[J P Stein]

My personal jury is still out on the shock tower/frame rail interface. IMO, there are a couple other places that need help
much worse.

The inner ear ....something along the lines of what Brant did would be gud.

The whole area outboard of that ear .....above the swing arm pivot. The factory welds are gross AND incomplete.....this is "skip welding" (the actual term is intermittent fillet welding) at it's worst. I know an old weld inspector (that would be me) who damn near shit when he looked at those welds. (IMG:style_emoticons/default/w00t.gif)

The pinch seam all along the bottom of the longs. I have seen pics of cracks developing from the spot welds/lower edge. Some spot welds actually overlaped this edge on my car.

I'm going to stiffer rear springs...again.....and slicks. One AX season outta about do the old shitbox in, tho I'm hoping to get thru it. Then we drop the motor & get after this other stuff.

We all do what we *think* is right & proper. The more input we get helps make these decisions. (IMG:style_emoticons/default/idea.gif)

[Eric_Shea]

(IMG:style_emoticons/default/agree.gif) with Ricky Racer!!

There's a lot of great input in this thread.

That being the case I don't want to pollute it. I'm going to take back my "thingy" on the procedure to weld the factory stiffening kit on. After a few more hours of eyeballing his tub, I now agree with Gint regarding the outer area being the actual longitudinal.

In my earlier post I was thinking there was a 3rd wall behind that skin you see as you look under your rear fender. There is not. Meaning: This is the longitudinal. If you drilled through it you would be hard pressed to find backing to weld to behind it other than the other side of the longitudinal.

I've made up my mind (so far) (IMG:style_emoticons/default/biggrin.gif) as to what I believe is the best was to strengthen this area in a 914 that will retain it's engine firewall and it's trunk floor (threw that in there because if I was build a tube frame I would probably go similar to what Jeroen has done.)

After talking with the fabricator and airframe engineer I believe the factory kit is, by far, the best solution.

One bizarr coencidence was when the old Boeing guy literally drew the factory kit on the car without every seeing it. He was pointing out stress areas to strengthen.

Here's my take and then I'll bail on this (unless you guys really flame me and piss me off) (IMG:style_emoticons/default/w00t.gif)

1. The largest piece in the factory kit spans and ties in the areas (passengers side, left to right) where the transmission mount ladders across the longitudinals (keep in mind, this is still the outer longitudinal whether you like it or not). The transmission mount transferes load and stress as well. Next, it ties in the shock tower and firewall, as it moves toward the front of the car it ties into the longitudinal that is the door sill, floor of the hell hole and the piece we see terminating in Jeroen's photo.

2. It does one hell of a job addressing what JP just mentioned... "The suspension ear and pivot point." It wraps them (not the ear but the consoule) in steel and ties them into the longitudinal as well. (that's only 1/6th of an inch so if your tires are going to rub on that, they'll rub on the longitudinal anyway.)

3. The infamous "Seam Marked C" "is" spot welded to the shock tower along the top, bottom, and all of the inside (the seam area visable in Jeroen's photos). The outside of that area is where the factory piece welds. Along with that... the firewall closest to the engine, that also forms a brace across the shock towers, is spot welded 1" away from that seam for added rigidity.

So... if I were to build a Jeroen project, I would do what Jeroen did and add a factory kit. If I were to leave the firewall and floor in, I would (and will) put on a factory stiffening kit.

I've got things to do (IMG:style_emoticons/default/beer3.gif)

[hargray2]

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

No one in this thread or any other has ever said (to my knowledge anyway) that the shock towers break or the tops of them pop off. That's not the issue that's being discussed. It's the longitudinal to shock tower junction and the associated crack that forms on the inner fenderwell area because it's a weak point.

Yes, I completely understand what is being discussed here, but maybe I was unclear.

I want to see a picture of a car after the tower has separated from the long causing the crack to form.

[Gint]

I want to see a picture of a car after the tower has separated from the long causing the crack to form.

Yeah, me to. I've heard of it happening enough that I believe it does occur, but I'd really like to see pictures of it.

[URY914]

I started today.
Cut out the firewall and ground off the left over sheetmetal.

[URY914]

vvv

[URY914]

ee

[URY914]

Before

[Gint]

Still waiting to hear from BRAD! with regard to my last question about "the cover".

[Brad Roberts]

I'm looking it over right now.. hang on.


B

[Brad Roberts]

I removed the "cover" on Chris Reales car a few months back. Hang on whilst I find the pics.

The frame rail is 3 sided with the cover on the outside.


B

[Gint]

Gracias.

Need pics

[Brad Roberts]

I dont have "arrows" I can use on this computer.


B

[Brad Roberts]

OK. First off. The late cars have ribs and the early tubs dont. So be careful and KNOW what year tub pics your are looking at.

I'll revisit this tonight and explain more. I need to get cracking here at the shop.


B

[Gint]

Please do.

L8R

[TimT]

Hmmmmm Paul, you car weighed 15XX and you still had these panels in?

Damn and I though it was at light as it could be

(IMG:style_emoticons/default/beerchug.gif)