Roll Bar Supports

[_gonbau]

With the comments on the "kremer de 1970" post, I have resumed the investigation on my car 576 regarding the installation of roll bars, as mentioned by the second owner of this vehicle. I noticed back then that there were no welding marks in that location indicating the presence of a plate for the cage support. However, there were holes, two on each side of the vehicle, corresponding to the location where these cages would go.

Given this, I set it aside and continued working on other things with the vehicle... In recent days, I wanted to examine the area more thoroughly because it seems strange to me that someone would buy roll bars and "attach them improperly" to the vehicle. I researched the screws used for these bars (information present in numerous posts on this forum), so I tried using an M8 screw in those holes. They screw in; the size and thread match, making it a bit more peculiar.
Based on this, I begin to inspect the area more closely to try to see if the hole is indeed threaded (something unusual as I understand that threading something there is a weak point unless it has its respective reinforcement). Looking at the image, I try to distinguish whether what I see is the "thread" or another plate in that location. I am unaware of the thickness of the metal sheet in that spot; I must understand that it would be this entire panel:


So, I would like to know if anyone knows the thickness of this panel or would be able to discern if in these images, the "thickness" is apparent or in line with the normal thickness of this panel.


Also, these "pieces" are present, and I'm unsure if they were used to anchor the bars at some point. I believe I've seen something similar in some photos on this forum, on a "Kremer" vehicle.

example no kremer:

https://www.early911sregistry.org/forums/showthread.php?106860-1971-911-S-east-african-safari-race-car-discovered-in-Germany

On the other hand, I would like to inquire about the types of anchor points for roll bars. I'm already familiar with the "official" ones, but I would like to know (as in the case of Matter) how bars were anchored in those locations if the "Porsche hoop mounting plate" was not available. Has anyone ever seen any work from the inside of the piece?

[70SATMan]

Looks like only one or two threads in those holes so, I’d say it’s only into that reinforcement panel and that it’s of the nominal thickness of the rest of the chassis. Not a secure mount at all.

The other pictures look like harness attachment bosses to me. Not, roll bar mounting points.

[_gonbau]

That response is helpful to me! Thank you! So, I continue with the same initial approach, but knowing that the holes are threaded. I have tried to think about how he placed the Fend bars, but I can't figure it out. Taking into account that there is a racing history for this gentleman and that he spent good money on our car (assuming he would use it in events), why would he improperly anchor a safety device he paid for and is crucial? Incorrect anchoring or anchorages that I am unfamiliar with... Hence the question of whether we know more examples of anchorages or ways that could match my anchorages. Regarding the threaded holes... Would any of you tie bars there? I think not, which makes it difficult for me to understand why this gentleman chose to do it that way. In the rear part, I did not find holes or supports, so I understand (it wouldn't carry Matter bars), but then what? The second owner told me that he removed them because the car felt small to him, of course, he is not a small person...

[928cs]

I don't think that you understand how things have changed regarding the perception of safety from the early 70's.
It's only in 1971 that roll cages became mandatory, and the first ones were not as strictly defined as they are now. At first, it was perceived as aditional weight, and you don't want that in a racing car.

Now, it's perceived as an important safety device, and a way to improve the rigidity of the car's body.

Don't you have a way to find the original cage of your car?

[sanders]

I have seen, what I believe is a factory installed roll bar using lag bolts. This creates the threaded sheet metal. However, there were four holes on each side.

[70SATMan]

My 70S came with holes (previous owner made) in the floor and rear engine firewall for the mounting of harnesses. No roll bar mounts though. I’ve seen examples of early period bars fabricated to bolt through the floor which passed scrutiny back then but would fail inspection today.

For sure, we can’t make determinations on the historical decisions without the context of the period. It’s more than likely that your missing bar was fabricated locally and not sourced from Porsche.they may have copied the Porsche bar and the approximate mounting locations but were unaware of the Porsche mounting plates for install. In which case, might have used the rear seat belt bosses as per the factory bar.

[68S_SK2]

Here the earliest paper about the Matter roll cage I found, issued 18. March 1971, provided by DMSB (Deutscher Motor Sport Bund).
BR
Claudius

[_gonbau]

I don't think that you understand how things have changed regarding the perception of safety from the early 70's.
It's only in 1971 that roll cages became mandatory, and the first ones were not as strictly defined as they are now. At first, it was perceived as aditional weight, and you don't want that in a racing car.

Now, it's perceived as an important safety device, and a way to improve the rigidity of the car's body.

Don't you have a way to find the original cage of your car?

You're right, until now I thought roll cages were more "antiquated," so the point you're making is important for me to grasp this topic. Thank you for that basic clarification! I consider it fundamental to understand why they were referred to as "the first Matter bars," for instance. I understand it was around '70/'71 when manufacturers or "local" producers began making true roll cages. As for our cage, there's a 0% chance right now. The second owner removed them here in Tenerife, so if they weren't thrown away, they must be installed in some vehicle I'm unaware of... The second owner doesn't remember! I still have a pending conversation with him because it's always a pleasure talking to "those kinds of people." Sometimes, I get the feeling that the more I talk to him, the more he tells me! But... what kind of bars could have only two support screws in that spot?

[_gonbau]

I have seen, what I believe is a factory installed roll bar using lag bolts. This creates the threaded sheet metal. However, there were four holes on each side.

It would be interesting for me to see a photo of what you are saying, although the comment helps me perfectly to get an idea of ​​what you are saying! Factory... that's more interesting!

[_gonbau]

My 70S came with holes (previous owner made) in the floor and rear engine firewall for the mounting of harnesses. No roll bar mounts though. I’ve seen examples of early period bars fabricated to bolt through the floor which passed scrutiny back then but would fail inspection today.

For sure, we can’t make determinations on the historical decisions without the context of the period. It’s more than likely that your missing bar was fabricated locally and not sourced from Porsche.they may have copied the Porsche bar and the approximate mounting locations but were unaware of the Porsche mounting plates for install. In which case, might have used the rear seat belt bosses as per the factory bar.

That's something that seems strange to me, but perhaps it could be, as you say. I'm not familiar with the local scene, but I raise my doubt that someone who invests that much money in a car and is the founder and president of the Porsche club... would turn to a third party (not Porsche) to replicate a Porsche product (knowing that the Porsche ring existed at that time, so they'd be "replicating" its measurements). It seems odd to consider, but maybe it was a common method among racers since each might have had their own mechanic... Or did private racers who owned vehicles often go to Porsche dealerships for inspections and adjustments?