psychoideas

I've been toying with the idea of a roll bar for my car but as you can imagine suppliers are limited down here in Oz. And so is cash being unemployed

I really like the look of the 997 GT3 RS bar and have done quite a bit of research on them and other bar types for the 911, including DAS, Matter, Heigo, and Techquipment, to name a few.
I wanted a bolt in bar so I decided to have a go at making a copy of the RS one that would bolt in and out of my 76.

The pattern that I have started, is out of light walled seamed tube. There is a company about 45min drive from here that has a "million dollar" tube bender so I intent to take this pattern with my pre cut lengths of tube, (either cold drawn seamless with a wall thickness of 3mm or chrome molly with a wall thickness of 2.4mm. Price and availability will dictate which tube I use) and have them copy it exactly. I can then weld it all together myself. (TIG)

The mounting brackets I have made are out of 5mm (3/16) steel and will be used in the final application. The pictures below are just one of the trial fit ups. I can’t tell you how many times this thing has been in and out of the car.
As yet I have not cut or put any of the rear stays on as I am busy making up the rear mounts for these. In one of the pics you can see my cereal box template sitting on the rear seat pivot. I also took a pic with the rear quarter trim in place.
I will post more pictures as I get things made / installed.

psychoideas

couple more

psychoideas

Ok that's it for a while

mo_gearhead

Frank, I am certainly no "structural engineer" so perhaps others will comment but I have helped build roll cages in some drag cars over the years. I believe the "bends" you have in the lower "X brace" create a potential failure point. Would hope you never get the car on its roof, but IMO the bar would fail at those areas. The "x brace" bars should be straight. JMO

psychoideas

Hi JMO,

Thanks for the feedback, I appeciate comments, positive or negative. How else would we know if we've made a mistake?

I can see your concern
I've been in the steel fabricating game more than 20 years and that's the first thing I thought of when I saw this style of bar.

As stated in my first post this is just a template or pattern for the "bending" people to follow.

However, in saying that, I think I should show you a picture of the current 997 GT3 RS roll bar. They also have a bend low in the diagonals. These give the main hoop added strength while placing the bars far enough back so as not to interfere with the seat.

I'm guessing being on the roof with this style of bar is preferable to being on the roof with no bar

spence88mph

Wow, you're a nutcase frank!!!

psychoideas

Yes, some say that all of my ideas.........are.......................psycho?

mo_gearhead

Frank, So true that there are as many ways to construct roll bar/cages as there are people. Consider
a simple soda straw: Straight, you can press down with force, it supports. But put even a slight bend in that same straw and as soon as force is applied, the straw fails (at the bend). Just because that bar is in a GT3 RS (and looks pretty) doesn't mean its the ultimate design.

My only reason for commenting was; if I was going to the trouble of adding a roll bar/cage structure, I would want it to be as strong as possible given the physical constraints of the interior dimensions. And I can see no physical reason why the X member (the main support for the main bar) could not be made straight in either car? There is nothing for it to have to bend around.

Just always keep the shiny side up!

keith

In fact, that roll bar in the GT3 is pretty bad. Scary actually, as is the one posted in this thread. Just before the kinks fold, the base plates will.

psychoideas

Hi JMO,

I fully understand the straw concept and I know that just because it's in a GT3 and looks pretty, it isn't the ultimate design for a roll bar.
However we are talking about Porsches here and I'm sure I'm not the only owner that chooses their accessories based on functionality and aesthetics.

I imagine that the ultimate designed roll bar for occupant protection would be a full cage consisting of numerous triangulated sections including side intrusion bars. It’s just not the sort of thing I would want in my car.

The reason the X member has a bend in it is to allow the seats to travel back further on their rails. It actually puts the X an inch or so behind the main bar.

I have looked at many designs and it’s difficult to find a bar that doesn’t have a bend in its main legs. They nearly always bend in before they meet the floor. (Talking about ‘bolt in’ bars) The exception being a DAS bar that has straight legs on the main bar that bolts to a cross bar at rear seat height. I’ve seen bars with just a main bar and the rear stays, right up to a full cage, and everything in-between.

I know where you’re coming from and I fully intend to keep the shiny side up, I’m just of the opinion that any reasonable well constructed roll bar is better than no bar at all.
I’m just trying to make something that will provide some level of roll over protection, something that I like the look of, and something that I can make myself to save a bit of money.

Remember, any money saved can be used on other projects!

psychoideas

I've used a similar base plate to what the DAS bar uses, bolted to the same location, maybe I should bolt in a cross piece like the DAS bar has. What do you think?

Graufuchs

Make me one tooo

keith

the cross brace is better, but since you can weld and bend tubing, this is a much better arrangement (and still bolt in- the nutplates are welded to the chassis):

psychoideas

Hi Keith,
Thanks for the positive feedback,
I do like that one you have posted, especially that it ties into the seatbelt upper points as well. Also that the rear legs are as far back as possible. These wider legs give it a much stronger stance.
I know that welded plates to bolt to, would be a far better arrangement than I am going with, and I did think long and hard about it. I decided for my particular application that I would not weld plates to the car.
Thanks again for the sugestions, I think I will try and incorporate a horizontal between the monting plates.

964russ

that roll bar is spot on. i want sumthing like that for mine..