Need Pics of RSR rear shock reinforcements

[collier]

Dear Friends,

Friday I am pulling my engine/tranny out of the car, and starting the reinstall process. In a seperate link, I took a poll about what I should do while the engine is out. I appreciate all that everyone has mentioned, and will be incorporating alot of what was suggested. Thanks.

One of my ideas was to add the reinforcements to the rear shock towers, like in the RSR's.

Does anyone have some good pics, or links to pics showing these gussets?

thanks,

chris

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chris collier
collier@iglou.com

72 911T
stock and ok with that, for now

[Bill Verburg]

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Bill Verburg
My Home Page My Pelican Gallery page My Porsche Owners Gallery Page


[This message has been edited by Bill Verburg (edited 11-07-2001).]

[turbo dave]

I hope my friend Chris doesn't mind my sharing his photos, here's his RSR mods (done with an original, stripped bare RSR right beside for inspiration-don't ask)





Good luck!

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David Schultz
1973 911T 2.7
http://home.earthlink.net/~kineticdg/Porsche1.htm

[BRAINIAC]

The October 2001 issue of "European Car" has an excellent article on chassis reinforcement for racing. It's on page 116.

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Tyson Schmidt
72 911 Cabriolet
92 C-2 Cabriolet

[70SWT]

Anybody got this issue of European Car handy, and could possibly fax it or scan and email it?

I will be addressing some rust damage on the 72 imminently and want to throw in some reinforcement while I'm at it. I also wonder about how to best reinforce the torsion bar area, seems a potential area of high stress.

[Britain Smith]

I am also on the path of doing these structural changes...can I get a copy also.

-Britain

[Shuie]

There was a good article in one of the magazines detailing a lot of the structural changes made to either a RSR clone track or a POC race car recently. I just went through my stack of 'excellence' and 'porsche 911' magazines and I cant find it.

Heres one of the 'Builidng a Better Black Beauty' threads that details the changes made to Jacks car.

Building a better Black Beauty #3: Reinforcing the Chassis

[70SWT]

Yep, awesome series of pics - I had been fortunate enough to find that one already when "data mining" the archives...

[Shuie]

The article is in the Feb '04 issue of Excellence.

[Ove]

Try this website: http://www.albertweb.de/

Here are some pictures of their work (see "Aktuelle Projekte").

[Peterfrans]

There was a series of articles by Sam Rossi, in European car in which he described the rebuilding of his 911S. This is the text on chassis strenthening:

Project 9115: Part 13: Phase 11-strengthening the chassis. Author/s: Mitchell Sam Rossi
Like the Porsche 356 before it, the 911 is based on a uni-body chassis design the frame is an inseparable part of the car. Floor boards, sills and roof all create the 911's inherent rigidity. The benefit of this type of construction is apparent by the sheer number of early 911s still dashing about the highways, most without the squeaks and squawks related to conventional body on frame vehicles. As long as the car is in good order, with its suspension points sturdy and straight, upgrading an early 911 for autocross and slalom events requires little if any changes to the chassis. On the other hand, performance improvements such as polyurethane bushings, stiffer torsion bars and anti-sway bars will certainty roughen the car's ride characteristics and stress the various anchoring points. As a car edges closer in its evolution from slalom runner to a dedicated track competitor, the chassis must be strengthened to handle the extreme conditions and mechanical forces working to tear it apart.
Prior to having the project car's undercoating removed by sandblasting (July 01), there were several modifications and repairs done by Mark Spraker of Euro-Tek, a fabrication and restoration shop in Costa Mesa, Calif. Working in both fiberglass and metal, Spraker specializes in top-dollar Porsches. The first upgrade Spraker tackled was removing the 911S's original battery boxes. In the factory's efforts to improve handling, the 911 was equipped with two batteries placed in forward boxes mounted outside, but accessed through, the trunk. These were removed in order to run the brake duct air hoses directly from the spoiler to the front brakes. During the work, Spraker spied signs of damage along the floor pan and tank support cross member. This was not a complete surprise. In 1979, in an overly exuberant dash toward a parking slot at my girlfriend's dormitory room, the front of the 9115 inadvertently made contact with the right rear fender of a 1967 Chevrolet Impala. As one might guess, the Impala won the day. As the wound from the Impala/Porsche merger was never properly repaired, corrosion managed to work its evil way into the front suspension's pickup points. This is an extremely critical location, so we decided it was best to replace the entire front pan and gas tank support brace (Dec. '00) with new reproduction pieces from Performance Products in Van Nuys, Calif. The premise of Phase II of the project was to take the 9115 beyond slalom and time trial levels and assemble it with some of the best components currently available to Porsche Cup-racing competitors. But, to garner the full potential of these upgrades, such as a complete coil over suspension system and massive anti-sway bars, the chassis had to be fortified. Knowing plagiarism is the highest form of flattery, and as Weissach had already performed most of the research and development needed to improve the 911, we scrutinized the factory's well documented progression through the RSR, IROC and 935 race cars looking for tactics we could assimilate into the project car. To be certain the 9115 would not only benefit from Porsche's past racing experience but also from current techniques being employed, Steve Alarcon of Johnson's Alignment Service in Torrance, Calif., was contacted for suggestions in preparing the chassis. As one of the premier suspension specialists in Southern California and an active competitor in the Porsche Owners Club, Alarcon has not only prepared the suspensions of some of the club's hottest 911s but on several occasions has also co-piloted these cars into the winner's circle. Following Alarcon's counsel for the chassis' upgrades, we first addressed the rear cross brace that houses the shock towers. When using rear coilovers, many club racers duplicate the factory's RSR efforts to strengthen the towers by simply welding in vertical gussets. For the project car, we took this a few steps further by installing a length of tubing that not only supported the towers but also reinforced the brace's attachment point at the chassis' linear beams. Bolstering this seam is an upgrade often overlooked when converting the early 911 to coil over suspension. "This is absolutely necessary," Alarcon said. "From the factory, that brace was not designed to support the car's weight. It has to be reinforced whether it is an early car or a later one. With the original suspension system, the duty of the cross brace was simply to hold the shock absorbers in place while the torsion bars shouldered the car. Implementing rear coil-overs transfers nearly 60 percent of the car's weight to this brace. Spraker fabricated reinforcement pieces from 1/4-in, steel plates, extended them to the towers, and then stitch-welded the pieces in place. The project car's previous exchange of steel trailing arms for aluminum units now became a potential problem as larger tires and a more powerful motor increased the lateral forces imposed on the rear end. The arms, which are both lighter and stronger, have less tendencies to flex during hard cornering, and as the polyurethane bushings were to be replaced with solid monoball cartridges, the pressures working against the suspension arms would now be transferred directly to the rear pickup points on the torsion tub. Alarcon noted that some of the factory welds did not penetrate the seams around these suspension points and suggested inspecting them for cracks. And while he did not think it was critical, we decided to strengthen the area by connecting the pickup points to the underbody with 1/8-in, plating. The next step was to upgrade the front of the chassis. Unlike the rear, the relative lightness of the trunk area and the stronger design of the strut towers made reinforcing this area subjective. Leaning toward prudence, I had Spraker wrap the towers with 3/16-in, steel. As it turned out, the extra plating around the towers was needed for the following improvement. Under severe cornering, lateral forces working against the suspension can pivot outward the strut tower that bears the loaded wheel, thus changing the car's camber and reducing the tire's footprint on the track. For cars involved in slalom and time trailing events, this problem is readily solved with aftermarket strut braces, such as those from Performance Products or Weltmeister. "A strut brace is useful on a later car, but the early cars absolutely have to have them," Alarcon said. "Especially if they are racing." To keep all four tires firmly planted to the ground, the 1970 911S came equipped with 15mm anti-sway bars. The rear bar was mounted under the chassis, while the front was a through-the-body type extending into the fender wells via rubber bushings and brackets bolted to the chassis' sheetmetal. Trying to plan for later changes, we decided to install a 12-indiameter piece of tubing between the towers. This would later become an intricate part of the front crash zone, as we wanted to encircle the car's fuel cell with additional bracing. This mounting was sufficient for the original bars, but with the project car scheduled to be equipped with Wrightwood Racing's prototype anti-sway bars measuring 1.3 in. diameter, Alarcon suggested we strengthen the fender wall. "We've seen some cracking in the sheetmetal after a couple of years of time trialing," Alarcon admitted. From the back of his shop, he retrieved an oddly shaped piece of cardboard. "Now is the time to install these," he said, offering what I realized was a template from which to make his front anti-sway bar reinforcement plates. "You want to alleviate any potential problems beforehand," he said, noting that if the 1-in. bars damaged the sheetmetal, the 1.3-in, rods were sure to do the same thing. For the rear anti-swaybar, it was sufficient to simply add a second piece of sheetmetal to the 911S's original mounting brackets. This enclosed the units, creating a much stronger boxed bracket. Beyond reinforcing the suspension points, one of the most fundamental ways to improve the chassis' rigidity is to (ink the rollcage to the front and rear shock towers. This is often referred to as through-bulkhead-bracing. But, at the club racing level, it has its drawbacks. "Through-bulkhead-bracing can put you in a totally different class," Alarcon said. "Anyone thinking about that kind of modification should check with the competition officials of their particular club." This was, in fact, the very reason I chose not to make this improvement. At least, not at this stage. In the Southern California region of the Porsche Owners Club, attaching the project car's suspension points to the cage would have bumped the old S into a class dominated by RS Americas and a few lightweight cars sporting monster motors. Of all the changes the project car has undergone, strengthening the chassis has been my steepest learning curve. "The whole thing is in the planning," Alarcon said. "So the steps you take now, you don't have to do over again. And obviously, taking the right steps so you spend your money wisely." It has quickly become apparent that the preparation of a race car, even on a professional level, is not simply an exercise in mechanical theory. The undertaking is more art than engineering, and no matter how much experience you take to the track, you always come away with a bit more.

Also these are two scans (of a bad picture) from the book 911 R-RS-RSR by John Starkey. They come from the FIA homologation form (I realy would like a better cope, anybody??).

[70SWT]

Awesome info. Let's see if I can dig up that old copy of Excellence...

[Par911]

bump......great stuff in this thread!

Can anyone post some more photos of welding done for chassis strengthening ?

[dsfnctn]

[randywebb]

Wierd... Just today, I was thinking about starting a post on what welding could be done to the unit body to strengthen it for purely street use ....

I boiled down the salient points in the above quoted text:

Rear:
1. Strengthen the rear shock towers by welding in vertical gussets.

2. Strengthen the rear shock towers by installing a length of tubing that not only supported the rear shock towers but also reinforced the brace's attachment point at the chassis' linear beams.

3. Strengthen the unit body area (where?) by connecting the (which) pickup points to the underbody with 1/8-in, plating.

4. For the rear anti-swaybar, add a second piece of sheetmetal to the 911S's original mounting brackets to create a much stronger boxed bracket.

Front:
Unlike the rear, the relative lightness of the trunk area and the stronger design of the strut towers made reinforcing this area subjective.
1. Wrap the towers with 3/16-in, steel.

2. Install a strut brace – they are useful on a later car, but the early cars absolutely have to have them… especially if they are racing."

3. Install a 12-in diameter piece of tubing between the towers to accommodate later changes (in sway bars?). This can form part of the front crash zone, and help encircle the fuel cell with additional bracing.

4. For large (> 1” dia.) anti-sway bars, strengthen the fender walls to prevent cracking.

5. Tie the rollcage to the front and rear shock towers (aka through-the-bulkhead-bracing).

[randywebb]

There have also been threads devoted to welding chassis seams and to ways to reinforce the rear shock towers.

The track junkies amy want to stick the links for them here...

[Porsche Doc]

Here is how we do it here up in the hills.

[tom1394racing]

Here's some shots of the stiffening work done on my RSR clone

Front shock towers


Rear shock towers


Welded roll bar (made to look like the bolted bar on the original RSR)

[JimCulp]

Tom,

I'm trying to do similar strengthening on my rear shock towers and I'm going to do a half cage as well. Why did you not tie the cage into the rear towers? Is it not needed?

Regards,

Jim

[JohnJL]

Here's how I did mine. I'll paint the firewall/bulkhead after I've welded on the dzus backplates for the ignition/ECU panel thats mounting on the passenger compartment side.

The welds weren't that pretty (i'm a novice) but I had good penetration all around. The plates are 3.5mm thick and the crosstube is 3mm wall steel.












I'm not actually installing the coilovers yet but I dont want to have to drop the engine again when I do. With the supercharger/intercooler and everything else dropping the engine becomes that much more of a PIA.