Seam Welding Works! Before and After Testing Video

[tperazzo]

My car is a good candidate to seam weld because I bought it as a stripped shell and it's going the hot rod route anyway. Another Porsche fan suggested the RS America workshop manual regarding how to seam weld the chassis and I thought I should give it a try. To be honest I was a little bit skeptical that the results would would be as significant as they were but here's what I did on my 1974.

I welded a bar across the front suspension pan suspension points and sat on it with a dial indicator below.

Then I went to town seam welding the front compartment only

I repeated the test under the same conditions and measured a 18% increase in torsionally rigidity over the entire car (I only welded the front).

Cool huh? The whole project is on YouTube...
https://youtu.be/RfDPUD-RhMM

Sorry I couldn't get the pictures to upload this morning.

[Rodney Nelson]

I appreciate your videos and am still in the process of watching them all. This was some great information on chassis strength and very timely for me as I'm welding up my trunk area.

Definitely would like to see the strut bar test!

[tperazzo]

Welded in strut bar brace brackets are done now. I also added strengthening plates to the top of the strut tower for good measure. This isn't a common failure area on G body cars, but I like to overkill things.

Here's the video of the install if you're interested:

https://youtu.be/OESBUGJyPuU

Next week, I'm going to doing some structural tests to determine how these bars improve the chassis integrity. Stay tuned.
Tom

[786]

Sub’d, very interested in this.

[jkuntze]

ok tom i've been good and kept my mouth shut but seems to me we are avoiding block sanding and body work jes sayin

btw have started the 928 bumper cover, front spoiler and fender liners off and repaired
stripping like 100 coats of paint and bondo off the bumper cover fun stuff

joe

[tperazzo]

Hi Joe,
What procrastination you speak of? Today, I was feeling a little tired and I think I'm coming down with a cold....so no sanding. Did I mention that my air compressor died and the new one isn't wired up yet,,,,,,no sanding. How about the football playoffs are this weekend and my dog ate my homework???no sanding. It's raining outside, no sanding.
When are you coming to socal for a visit? I'm available because I won't be sanding, ha ha.

Theoretical topics of strut bar loading is so much more stimulating than sanding. I could go on all day, but I should be sanding.

[icarp]

Ahh, the sand dance!

[Frog76S]

Originally Posted by tperazzo

Hi Joe,
What procrastination you speak of? Today, I was feeling a little tired and I think I'm coming down with a cold....so no sanding. Did I mention that my air compressor died and the new one isn't wired up yet,,,,,,no sanding. How about the football playoffs are this weekend and my dog ate my homework???no sanding. It's raining outside, no sanding.
When are you coming to socal for a visit? I'm available because I won't be sanding, ha ha.

Theoretical topics of strut bar loading is so much more stimulating than sanding. I could go on all day, but I should be sanding.

I bet your wife’s name is Sandy?

[ChrisHoover]

Dude, your hot rod video made it to Bring a Trailer and to Reddit! You're an interweb star!

[tperazzo]

Originally Posted by ChrisHoover

Dude, your hot rod video made it to Bring a Trailer and to Reddit! You're an interweb star!

Whoo hoo! That video was made on the plane ride home from vacation as a filler video for my channel and did way better than my usual DIY stuff, ha ha. I think this proves that most guys just wanna see the finished product and how much $$$

This weeks video will be techie data about strut bar braces which I think is way more entertaining, but that's just me.

[jjeffries]

Tom, nice welds. What kind of machine are you using? Thanks, John/CT

[tperazzo]

Originally Posted by jjeffries

Tom, nice welds. What kind of machine are you using? Thanks, John/CT

Thank you! Those are MIG welds from my Miller 110V machine. It's nothing special and about 15 years old. My other welder is a TIG Miller diversion 180 which I prefer in almost all cases.


https://amzn.to/2MeMOVI

[lateapex911]

I have ALWAYS wanted to do this. I cooked up ideas on how best to accomplish it, and essentially it was the same setup. In my case I was going to bolt the rear to the surface (floor or surface plate) so it couldn't budge, and use a scale and hydraulic pressure instead of body weight. (or known weights once the amounts were figured out.)

Fun to see it done.

Thanks! Saves me the effort. In reality, I have a pedal cluster to media blast and powdercoat and rebuild, and carbs to clean and....and.... LOL

[tperazzo]

Thanks Jake, maybe I'm not out of my mind.
Well maybe I am, because I just repeated this test for this week's video.
This time I did before and after testing with the front strut brace installed in both the two point and three point attachment configuration.
The results might surprise you???

On top of that I instrumented the strut bar so I know what the internal forces are.

Question for the driven hard group here:

Can you tell for certain if a front strut bar changed the feel of your car or reduced lap times, cornered better etc.

Inquiring minds want to know.

[crashmy911]

Do you guys push your cars hard enough to warrant doing these modifications? My car is tracked pretty hard with out this stuff and I haven't been able to break suspension stuff yet. My car is modified pretty hard too just not structurally except the cage.

[lateapex911]

Seam welding has been a good idea forever. Depends on the org, and the class rules, but lots of classes outlaw it. (In an attempt by rulesmakers to keep expense and time investment down)

If it's allowed, racers will want to do it, often ignoring it's actual benefit on that particular chassis.

Why is it good? Well, it makes the suspension more tunable. I always chuckle a little when people in restricted classes where cages are the type that don't allow suspension tie ins etc, put a damper package thats $6K on a car. Why? Because the body/chassis IS flexing, and it's undamped. So crazy dampers aren't as effective.

So, the answer is...it depends.....at least in racing. I've seen cars where they put springs and sphericals and dampers on it that were so stiff that the spot welds were failing. Seam welding, obviously, would help, but not if the rules forbid it.

For a street car, with normal street car suspension tuning and rubber bushings, it's probably overkill, at least with 911s. Other chassis? MAYbe it helps, assuming the chassis is made of wet noodles held together with butter.

Then there's the question of feel.
A- guys will swear it feels stiffer. Sometimes they believe it in their head, because they want to believe it, but lets face it- MOST of our butts aren't THAT accurate. I know mine isn't. (And I'm not Patrick Long, but I hold a few track records in my old race car so I'm not completely useless either)
B- guys will want to believe it, but they can't feel a difference, but they SAY it feels better......CYA, LOL... but, no harm keeping the legend going....it can't hurt, right?
C- guys will do it just because, they like doing stuff like that, but they are fine knowing they don't know if it really is effective.

In the end, as the OP has shown, marginal gains were made. I think a cage (properly done) would make a much bigger improvement. Or, a limited pickup point cage with seam welding in the front and back where the cage doesn't tie in, is an effective mod. (But it's unlikely a rules org would come up with such an odd cpmbo)


For street guys and guys who track and aren't chasing lap records, it's cool, but you need to think hard about the tradeoffs, vs the benefit.

Time, effort, and the need to properly finish the area (and the impossible to get to backsides) so corrosion is controlled, have to be balanced.

Interesting thread--and nice welds with that little Miller. I've always been interested in doing this.

But I also agree with a lot of what Jake said, especially with respect to a street car. I spent a lot of years building cars from road into full-on track cars, or as my wife put it, "ruining them." Now I like feeling my old 911 flex a bit as it works.

[tperazzo]

The results are in regarding the front strut bar test. I created a new thread because this one is mostly about the seam welding. Here it is:

http://forums.pelicanparts.com/porsche-911-technical-forum/1018553-strut-bar-benefit-testing-before-after.html#post10322679

Here's this weeks video:

[lateapex911]

Great vid. You need a good surface plate! Or a fixture.

[tperazzo]

For those of you who are curious how I rust proof these stitch welded areas especially the hollow cavities please have a look at this video. Skip forward to 7:00 for this part.

https://youtu.be/bO9VwLFCqyg

1. First I blow the cavities with compressed air
2. Then I peek inside with a boroscope
3. clean with a bit of wax and grease remover using the same technique in the video
4. coat with liberal amounts of epoxy primer
5. spray cavity wax after everything is painted. I haven't done this step yet.