Okay, some of you may think this is neat, most of you will probably think I'm nuts. I bought a 1991 Trans Am convertible last summer. Love the car, hate the wet noodle-like flex, so I decided to do something about it. The SFC's I was most impressed by were the Kenny Browns, so I bought them but discovered that there was potential for much greater reinforcement with just some additional work. Basically, the idea was to create a "boxed frame" out of the rockers. I wasn't satisfied with having such a stout looking piece weld in at just the rocker seam weld. So, with some 1/8"X 3" X 3' steel and some time (and guts; I had to cut the entire length of the floorpan for this), I added a 1/8" thick plate of steel that welds to the inboard side of the SFC tube (approx. 180 degrees from the rocker seam weld) at the bottom, and welds to the factory rocker reinforcement topside. I cut away about an inch or two of floorpan away, this gap will be filled with some 0.040" steel properly formed and spot welded. I should have taken a picture of the actual 1/8" piece before I put it in, but didn't think of it. If there is sufficient interest I will document the driver's side better (that is still to come.) Pictures should help, forgive me though, I'm definitely not cut out to be a photographer.

Sorry for the novel; enjoy!

 

Ahhh, I guess I should have learned how to make the photos 102500 bytes or less; I'm having trouble posting them as they are all around 250KB. I can either:

1. email them to anyone who knows how to manipulate them and they can attach, or

2. attach them this evening/tomorrow when I can get someone here to help

Sorry for the delay!!

 

To get your pictures within the space contraints, go to your editing program and resize them until the 100KB is met. Don't worry about the size because I have found that thirdgen.org makes the pictures plenty big to see.

I am interested in your work. That sounds similar to what I built for a guy's IROC a few years ago. We used 2 x 3 box steel and cut the length of the rocker panel area from the area next to the forward LCA mount to the firewall. The SFC is welded to the rocker panel and floorboard its entire length. We used round 1 3/4 tubing to connect the SFC to the factory subframe. At the rear we boxed the area around the LCA mount. It really works great and the car now has a perimeter frame, more or less. Unfortunatly I have no pictures either. MY car has a similar design SFC except with mine we used 2 x2 box tubing and did not cut through the floorboards more than we had to. My system works great as well. No pics either.

Sorry to write so much, but I love talking about frame work!!

 

Download Paint Shop Pro.

http://www.jasc.com/

Save the file as a .jpg. The default compression for jpgs is very good. You can modify the compression easily from the save menu.

Also, there is a resizing tool, which can maintain the aspect ratio of the picture (as to not distort it when resizing)

I am interested in seeing this, please post!

 

if you have trouble, shoot me an email at num116@psu.edu i'll post them for you

 

sorry for the delay; here come the pics

 

another; this shows the the Kenny Brown "outrigger" that goes over the cat

 

more

 

from the bottom

 

more from bottom; welds are much better than they look; I'm not a great photographer, so shadows make them look crappier than they are

 

last one for now. The passenger side is actually finished now; I closed the gap with 0.040 steel already, and it is ready for POR 15 and some seam sealer. Will take some final pics and post them later; I also will take more detailed, better pictures for the driver's side. In this pic you can see the rocker seam weld on the right side of the connector, and the ASC installed reinforcement cut away to access the actual rocker seam. I will bridge the gap from the cut away portion to the SFC tube with another sheet of 1/8" thick steel. Comments welcome.

 

One more thing--I ordered Alston SFC's; the way they mount allows them to coexist with connectors that mount at the rocker seam. I want to see just how stiff I can get this car; depending on how it feels when I'm done with these mods I will consider installing a 6 pt. roll bar with low front bars similar to the Kenny Brown super street cage. I definitely will be installing a wonderbar and STB this summer. I know I'm adding weight here, but I can't stand a flimsy feeling car.

 

My car is about how you want yours to be!! I fabed a 6 pt cage with "easy entry" front bars. I'll take some pictures of it in the morning and post them here if you like.

I also fabed my own STB, LCAs, Panhard, and SFC. I probably added almost two hundred pounds (guess!?) to the car and I don't regret one ounce of it. THere is no substitute for a tight, safe car.

All you need to do is add some cubes under the hood and its like the pounds were never added! Truthfully, in stock trim, my car felt faster after all the frame modification, it was probably just me pushing harder because I felt safer and more confident to plow through corners.

 

I'd be very interested in seeing your work with not only the 6 pt cage but the SFC's as well!! I want to see how you got the front bars around the seat belt anchor next to the seat. Did you start with a rollbar kit or custom make it from scratch?

The T/A convertible is my "guinea pig," its in good condition but not so good that I'm afraid to touch it--anything I do will pretty much make it turn out better. My '91 Z28 however is pretty much spotless, so I will only mod that when I'm REALLY confident.

I understand you put the 2x3 steel on the inboard side of the rocker pinch weld right? I was orignally looking at completely removing the gay ASC rocker reinforcement, cutting open the at the bottom of outboard side of the rocker pinch weld and welding in 1x4 or 1x5 box steel, but I was really afraid of having the car collapse. I like your idea better as you can itegrate the ends to the rest of the car better (like at the structure under the kick panels). I can't wait to finish so I can see what difference this will make--I'm hoping it will make a big difference because the few convertible people I've seen here have been pretty impressed with standard installations--hopefully mine will be stiffer. I completely agree about the cubes under the hood; I just bought an LT1, though it will wait until next fall for an install (I want to enjoy the summer) and will stay stock at first.

If anyone has pics of additional stuff like this please share, I love new ideas. I'll be ready to start the driver's side this weekend; do you guys want me to take pictures from start to finish to get the full idea (i.e. a pic of: before I start, what I cut away, the SFC welded in, the 1/8 fabbed plate before it goes in, etc)?

Sorry for the novel, and I'll start a new thread for the driver's side if people are interested...

 

I'll get some pics up soon. I have to go to class in a little while!! We actually used 2x2 for my car because I didn't want to cut up the floor. On my friend's, we used the 2x3. Either way there is a huge improvement!!

I did not use any kits for anything I fabed on my car. It was all designed and fabed from scratch. I liked the idea of the Kenny Brown street cage, but my front bars are, I think, a little more rigid in design.

BTW this car was also my first fabrication ordeal. There are some mistakes here and there, but altogether, I think I did a pretty good job considering it was a first try!! I was a little conserned about my car because when I bought it it was a gem. All stock except a cat back. Everything worked, interior was spotless, paint was good, not anymore though.

I get you some pics so you can see what I did. Easier than trying to explain it!!

 

Okay, got some. Let me know what you think.

 

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#4

 

#5

 

Hope you find them useful. Like I said this was my first cage!! When I do another in a 3rd Gen, I will do some things differently. I am happy with my work and mostly the structural integrity of my car. Good luck.

 

Very useful thank you, I like it. looks like you could use your back seats if you had to which I like. I was thinking very similarly witht the way you made the front bars attach to the main hoop--with that "triangle" I think little if any strength is sacrificed for the sake of clearance. I think I'll try to do the same only have the front bar go a little lower, like say: have the triangle come to a point right behind the seat belt anchor pod and have the forward bar go between the seat and the seat belt pod and gradually onto the SFC. I don't know if this would fit though, and once I'm done with the SFC's I'm going to put it back together and drive it for a few months (its been off the road waaay too long).

What would you do differently if you did it again?


P.S. I love Fla., used to live on Singer Island 8 years ago. Ever go to Moroso?

 

I used to go to Moroso often with my old car, it was a 71 Monte Carlo.

I would have taken the rear down bars all the way to the back as far as I could get them. Maybe a X brace also. If the car was a hardtop, I would go full halo, 10pt style. Make an actual roll CAGE instead of the roll BAR. Depends on what the car would be for. Absolutely, if I could go back and redo this project I would have made it NHRA legal from the beginning. If you are thinking about doing any drag racing or autoXing, maybe you want to look into a legal roll cage.

When I built this cage I had a 72 nova that was almost a racecar, body work and touch up stuff remained to be completed. So I decided to keep the interior complete. THis was almost 3 years ago. Now the Nova has gone away and I want to do some racing with my Camaro. Unfortunatly the cage is not legal for NHRA. I have been thinking about cutting out the front bars and redoing them legal, but I don't think I will. I think that would be more work than the initial building of the cage!!

Post some of the pics when you get your SFC all complete.

 

I think it because I have just had a really long day, but I'm not quite getting what you did...I'm sure if I look at it again & if I read it some more! Anyway...The point is that I would love to see a more detailed account...Esp the before, so I can get an idea what you saw & corrected with the additional boxing!

I'm doing a targa conversion and any extra strength I can find is apprieciated...I'm going with the spohn subframe conectors, and I was thinking of adding the MAC/Alston Style for more support. But I'm doing a dual side exhaust set up and I have no idea if the additional subframes will cause a clearance issue on a lowered car with this exhaust!

 

Unfortunately my pictures are pretty terrible; the surfaces are difficult to distinguish. Unfortunately I didn't take more pictures so I'll have to describe it; but if you look at these drawings I made it should be clear, and when you begin tearing into the car you'll definitely understand. The first is a drawing for reference; if you were to take the car and cut it in half this is what you'd see (a cross section, if you will). I'm not 100% sure what it looks like in one area (which is labeled on the drawing), but the important stuff is correct for my car. I'm not sure how the lines in blue look in all cars, it may only look like this on t-top cars (& convertibles of course). Anyway, here's the first sketch (hopefully it will come out well, I'm REAL bad with this computery stuff):

 

This second drawing shows the ASC installed riveted in reinforcement in red (convertibles only). Here you can see how the rivets tie into the blue rocker extension thing in the passenger compartment and the outside of the rocker. This is the only convertible specific addition to the car in terms of reinforcement. All the ASC cars marketed by GM had ground effects to hide this.

 

I think the ASC reinforcement concept was gold, but the execution was ****-poor. RIVETS? Yes, I know 747's and a lot of other precision things are riveted together, but this looked like a sloppy backwoods job to me (gotta love the abuses of mass production). I started by cutting away the section where the Kenny Browns would touch the rocker.

 

Here, the Kenny Brown SFC tube is represented by the green circle. This is how they (and the Sphoons) touch the rocker pinch weld. I stitch welded mine all along the pinch weld.

 

Next, I took 1/8" thick 3" wide steel plate to weld to the SFC 180 degrees from where the SFC attaches to the pinch weld. Then, the other side of this plate (shown in green, coming off the green SFC tube) welds to the thicker metal rocker piece on the inside of the passenger compartment (the blue lines). This goes along the entire length of the SFC. To do this, the floor needed to be cut open along the entire rocker. This is what you see in the pictures I originally posted. Notice that from the pictures taken from above, all the welds you see are where the plate attaches to the rocker below the upper pinch weld. The pictures from the bottom are where the plate attaches to the SFC at the bottom. The gap shown in the pictures was closed up using 0.040" sheet.

 

Finally, the gap from the ASC piece to the SFC will be bridged with another plate. This is the only thing I have not done yet. I had considered removing the ASC piece completely but to remove the rivets I cut them flush and knock them out (pulling the whole thing isn't practical) and there would be no way to remove the ends from inside the rocker. Also, they get more complicated in the front under the back of the front fender (in front of the door hinges). I just don't see these ASC pieces as contributing much. I don't think I added more than 50 lbs, I love a solid car, and since this is a convertible street cruiser (as opposed to street/strip), I don't need to loose every last ounce. Check out this drawing, now the lines shown in blue are one structure that not only resist force in tension and compression (like regular SFC's) but are one boxed structure that resists bending (i.e. like a sag in the middle) as well. Compare this drawing to the original. Should be a bit stronger.

 

I did take the car for a short spin last night, and it seems stiffer; I'll have to take it for a longer drive to really see. Also, top down weather would help as the top itself rattles a good bit when its up so its hard to distinguish between noises (still in the 50's in Chicagoland). Of course, if I'm not satisfied, I have a plan for next winter. Cut open the rocker on the outboard sides and weld in a 1" X 5" or so box steel piece. Shown in red in the attached image. Or a 6 pt. cage. or...

 

OK I got it now! thanks!

 

Since its FINALLY warmed up here in Illinois, I've been driving it now for a while. I have since also added Alstons, and the car is definitely a lot stiffer with the two SFC's. It no longer feels like it will fall apart when the wind blows.

There are still some types of surfaces (like things that twist the car back and forth) that still make the car feel a bit wobbly. However, and I think its because there is untapped potential here--I think the cowl and the part behind the doors need to be tied in better, and the front "framerails" need to be connected (by adding a custom X-brace under the trans area). I know for a fact that the rear is an issue, because when the car is jacked up and the rear is placed on stands under the control arm mounting points, the gap at the back of the door gets larger.

May plans are:
1) Fabricate a bolt in X-brace under the front of the trans. While I'm at it I'll see just what can be done to also utilize the trans crossmember as a structural piece. This shouldn't add much weight at all and will further limit how much the sides of the car can move with respect to each other.

2) Create a more positive connection the rear end of the SFC's to the 'C pillar' area. I still need to figure exactly how I'll do this, but it shouldn't be too hard.

As it is summer, I may be slow about this as I need to fix up the winter car.

 

Its good to hear you had some good results from your chassis stiffening. I too felt like I was driving a different car after the SFC, roll bar, and STB. I made and installed them all at once.

As for your next modifications, an x brace sounds like a good plan, but I wonder about ground clearance. I don't know if you did already but it might be worth something if you did not. I tied my SFC to the stock "framerails" under the seats. I also used .125" plate to make some bigger mounting surfaces to attach to. In the rear, I tied the SFC to the rear "framerail" and boxed the mount area for the LCA. Like I said you may have already done all this, but I don't know/remember.

I recently got myself a new TIG welder and am dying to redo the front down bars of my roll bar. Maybe after I get the engine work done...

Good luck!