roll cage design

[eugene]

I wonder if this has been done before; I've never seen it. All of the roll cages I've seen have seemed to be a compromise between structural integrity and interior comfort/appearance. Due to the fact that they can be viewed as an independent structure that is built within the confines of the cabin. For safety reasons I would like a cage in my 280, but since it will be a daily driver, I really don't want it restricting interior space. I was wondering if I could construct a cage that was completely integral with the body; for instance, the main hoops would actually be completely welded to the pillars, the roof, the firewall, and the frame rails. All efforts would be aimed at finding a sound design that would transfer loads properly, without invading cabin space by more than the diameter of the tubing. Basically you would be building an inner support structure for the existing body, which would seem to make it stronger than a support structure that is mostly within the body. But the main reason for this idea is that most of the cage could be out of view, and you could go so far as to build a custom interior that covered most of it up. There's still the problem of side impact support impeding entry and exit, I also have no idea if this kind of design would be approved for different racing events, but I'm curious if it's been done before. I know it would be A LOT more labor intensive, but seems like it would be worth it in the end!

[Guest AlsoRanFPrepared]

Unfortunately, to obtain all of the structural benefits of a well designed roll cage some interior interference is required. Specifically the diagonal running from the upper drivers side to the lower passengers side of the main hoop and the bar running across the main hoop. In addition the door bars which to be of benefit will need to be above the sills. The other typical members of the cage may be subject to the method you described. Additional safety can indeed be gained through the method you mentioned but the compromises you must make will either make the bar significantly less effective or will require such a vast increase in weight that it may be counter productive.

 

-Mark

[Dp351zcar]

I have just done a mockup to see where my bars are likly to go and my question is. Without putting a hinge in the door bar. HOW do you get in the car gracefully?

Or am I just too old and fat to get in, 42 5'10" @200

It's a 71 240 will be with 8pt roll bar.

 

Don

[johnc]

> I was wondering if I could construct a cage

> that was completely integral with the body;

> for instance, the main hoops would actually

> be completely welded to the pillars, the

> roof, the firewall, and the frame rails.

 

If you're intent is to build this kind of structure for a street car, then it can be done but it will be very expensive and take a lot of time. If you're intent is to also put this car in a sanctioned race, buy the rule book first. There are limits to the number of bends on the main and front hoops and there are limits to the number of points the cage can attach to the body.

[Mikelly]

Don, welcome to middle age!

 

I'm with ya except for the age! I'm 36 and Rollcage Gymnastics SUCK!

 

Mike

[ZR8ED]

As others have commented it can be done. By what you are describing what you are trying to accomplish, it sounds like you are trying to do what I have had done to my car.

 

My rollcage is A VERY tight fitting 12 point, custom made chromemoly cage. It is not obvious to see, except for the diagonal brace from the drivers to the passengerside. None of my interior panels were removed, and now most can never be removed. My A pillar bars go around and under my dash down into the foot wells, with approx 1/2 inch clearance of the dash. The cage was built properly, and is mounted in the proper critical structural areas. I had it professionally installed and designed by a Z car racer/chassis/engine builder. I had it kinda easy though. I was given a free, full tube chassis 240z race car (rolling chassis) I used this pro built chassis as my donor so to speak. We chopped it up and installed/further customized it into my 78 280Z street Z.

 

Not an easy chore, and cost me 20 hrs labour.. With me helping cut up the race car. He did an awsome job welding it all in with most of the interior installed (minus seats/carpet) Not one burn mark on any of the panels. All seam welded and reinforced with gussets where required.

 

I still have not installed the side impact bars either. I figure it is not required for structural integrity.. except in a car accident (T bone) I may dismantle my doors and put in additional side bars inside the doors to save space, and to ease entry/exit. (280 has side impact beams standard)

 

Good luck if you go for it. Take your time, creative solutions are neccessary to maintain the strength of the cage and keep it tight fitting to the body... also becareful about racing rules if you are going to be racing this car.. if it is a street machine (like mine)you have more leaway...just don't underbuild it...Mine may not pass all racing bodies tech inspection, but I guarrantee it is stronger than what they require!

 

PS I have an additional 14 points of bracing that is mostly addjustable, and not technically considered part of the cage.

 

Total weight gain was less than 250 lbs... no match for turning up my boost to compensate.

[Pop N Wood]

ZR8ED

 

Have you ever posted pictures? I would be EXTREMELY interested in studying details of your design. I am particularly interested in how the cage clears the dash and whether you have a bar traversing the dash and connecting to the front strut towers. Plus any ideas on how to build a cage with stock interior panels would be appreciated.

 

I want to stiffen the chassis without doing a total dukes of hazards to the car.

[ZROSSA]

If Chassis stiffness is the main goal and you dont need to meet racing regs. then there are other ways to do this then a roll cage. The sub frame joiners are a good start. I Like the idea of a back bone chassis running along the trans tunel and then joining up with the front suspension trough the fire wall and also picking up the rear, very much like a strut brace. I would build it like a space frame with lots of little light bits of steel tube. You could then hide all of this under your carpet.

 

As i said, This wont help you meet any roll cage regs but if done right it would be easy to do and would really stiffen up the car. Early lotus's and TVR's have a chassis like this.

 

Cheers

 

Douglas

[ZR8ED]

Drop me an email. if you want some pics.

 

It is pretty hard to take good interior shots, and it usually takes many shots just to get an idea of whats in the car. Because of this, I have only 1 or two shots @ zdriver.com I do however have several pics of most of my cage saved on my computer for just these kinds of instances.

 

Hehehe some of you who have received Z car vids from me (VHS copies) have had some bonus stuff at the end, when I did a tour of the Mosport racetrack upgrades, and a few minutes of me walking around my Z with the video camera shooting as much of the cage as I had in the car at that time. (it is more extensive now)

[Guest]

Cyrus,Check with Tim240z,He is a member.E-mail him,he is easy to find roaming around the site. Hes real cool and Im sure hes willing to share info.I liked his setup because it is a comp. between sreet and race.He does have his own site with pics of progress.

[Guest JAMIE T]

I tlaked to a guy at a car show that said his car(mid 90's Mustang GT) had a "hidden" roll bar. Well turns out he did what you want to do. He used 1" tubing throughout perimeter of the interior of his car. Obviously it wont pass ANY racing sanctioning bodies rules, but according to him it stiffened the chassis. Honestly, I thought the guy was full of $hit, and if actually did all that work to that car, he wasted a bunch of money and time on it. If you want to put a cage in YOUR car, do it right. Strip the interior, and take it to a professional chassis builder and tell him you requirements. He should have no problem tucking the bars close to the roof and out of your way. Get the side bars removable if you like the space and ease of entrance. My wife has crawled in and out of my caged Mustang Convertible plenty of times. She didn't care much for it . Since she has her own car now, I get to do with the Z as I please, so that means full SCCA legal rollcage . Honestly, unless you have welding skills and tubing bending dies then installing any cage is going to be expensive.