Functional Roll Bars for Convertibles?
 

In light of the recent accident that hurleysurf24 had with his vert (https://www.rx7club.com/se-rx-7-forum-35/rx7-t2-vert-totalled-708249/), I was wondering who makes a stout functional roll bar? Not just one for looks. I was planing on buying one from Kirk Racing, but am not convinced that the upper seatbelt anchor points that they utilize as a mount point are entirly sound. What are your opinions and what other options are out there?
Keep in mind, I want the top to be completly functional which pretty much negates the use of rear angled bars.

There's also the Autopower one available through I/O Port Racing. As you say the top negates the possibility of having any rearward bracing. The only other feasable thing is a petty bar which goes from the middle of the bar to the passenger side footwell. This won't be as good though. You can also add door bars, but that won't really help support the top of the bar.

It'll be better than nothing, but obviously not as good as a full cage or a proper bar with rear legs.

You may not be able to escape those rear bars and keep functionality. You need cross bracing to prevent the roll bar from folding forward or backward in the event your car is sliding at a good clip when it flips over. A workaround might be possible but I don't know the interior dimentions of a vert well enough to offer any ideas outside of linking two roll bars, one in the back and one behind the windshield, which wouldn't be very pleasant to look at when the top is down.

I wouldn't worry about the seatbelt mounting points, they should be really solid. at least more solid than the freaking windshield. i always wondered how it would fair in a rollover situation, and know i know. sucks that hurleysurf had to find out the way he did though :( but at least he is alive and not missing any limbs.
do you have a link to the kirk racing ones?

You will NOT be able to have a truly functional roll bar and maintain full functionality of the top. It simply cannot be done. The only things you can do are buy the kirk bar and add door bars and additional bracing like what RX-Heven did.


Kirk racing does not show them on their site. I have emailed them over the last couple days and have just purchased a roll bar from them. I plan to mimic the setup that RX-Heven has in his car, but I want to try to have a similar harness bar for the passenger side as there is on the driver side. I dunno if that will work out though.

Images thanks to RX-Heven:
https://www.rx7club.com/forum/attach...d=185536&stc=1

https://www.rx7club.com/forum/attach...d=185537&stc=1

https://www.rx7club.com/forum/attach...d=185538&stc=1

https://www.rx7club.com/forum/attach...d=185539&stc=1

https://www.rx7club.com/forum/attach...d=185540&stc=1

https://www.rx7club.com/forum/attach...d=185541&stc=1

Kirk offers 2 flavors of roll bar for the FC vert. One which is just the hoop, and one which has a horizontal bar in the middle. RX-Heven started out with the Hoop with no horizontal brace. I asked Mark at kirk racing if they had pictures of the hoop + horizontal bar but he said they didn't have any. The Hoop is $250, and the Hoop with the horizontal bar is $295.

Thanks for the input guys and for the pics Juiceh. I have seen the amazing work that Rx-Heaven did with his bar setup. I too would like to integrate a harness bar for the passanger side seat as well as the driver. Perhapse a continuous harness bar without the diagonal brace? That would act similar to a standard horizontal bar.
As for the addition of the door bars, (correct me if I'm wrong) they don't offer any protection from upper hoop colapse in a roll-over situation. They are only there for side impact protection and lower cage support, correct? ( think I just answered my own question)
A petty bar is another option, but this is a street car with full interior that often has my wife in the passanger seat. I would rather not loose the use of it.
What about reinforcing the upper (seat belt) anchor points of the Kirk roll bar? Or perhapse the "B" pillars themselves?

Mine was custom made by Mitch Piper at www.pipermotorsports.com. He does superb work. The rollbar was SCCA Solo I legal when he did it (1997), but not race legal. So far, I've been able to use it at D/E events sponsored by NASA and others. His original design limits passenger seat travel a bit, so you can't date any tall girls, but my wife says I can't do that any way. She's 5'3", and the allowable seat travel is OK for her. The president of the Mazda Sportscar Club of Washington, DC had the first rollbar, and his 5'7" wife couldn't handle the lack of leg room. Mitch modified that rollbar to allow more seat travel, though he complained about the loss of strength compared to the original design.

http://www.cris.com/~Asam/20B.html for pictures.

George, it's a bit hard to see the roll bar in most of those pics. Where do the rear legs attach to the floor? It also appears that you had to make a custom boot cover to allow for the targa top sitting on said legs. Is this correct? If you could post any detailed pics of this setup that Mitch crafted, I would greatly appreciated it.

Yes, more pics please.


Without the diagonal brace you lose the protection from hoop collapse. So having a single harness bar may prove difficult.


Yup, side impact and lower cage support. I can't see them helping the rest of the hoop much.

Same here. Must be able to keep passenger seat, and as much passenger seat mobility as possible.


Thats an idea, dunno what can be done there except welding the anchor points themselves though, and that may not be a good idea..

Custom is the way to go. Try a shop that can make a bar that meets Sanctioned racing regulations.

You could have a cross bar on the rear legs to free up some room and still have some rigidity, but it's best to have one on the main hoop.

and make sure you're buying a ROLL BAR and not a STYLE BAR

Im pretty sure you could get some rearward triangulation while maintaining full function of the roof by running possibly two thinner (1 or 1 1/2" dia) tubes in parallel (one on top of the other) down around the edges where the hard tonneau cover sits, and then tie them into the rear shock mounts where the extra shock tower bracing in the verts already attaches. Depending on where you choose your attachment points, a slight kink may be necessary, and you'll need to cut some of the panels that cover the motors and stuff, but there should be room.

wouldnt rotormind be NotM this time?

I have a vert chassis outside my shop, and a tube bender inside. If anybody wants a custom bar without risking having welding done in their car PM me.

The area for mounting the shoulder point of a stock belt is VERY strong. There is always a few extra layers of steel and the metal with the threads for the bolt is usually thick and covers about 6-8 sq. in. around the hole. I have cut up quite a few cars to see this.

One of my first race cars was a FIAT X1/9 that I ran in IT. My rear hoop supports were triangle shaped plates that followed the length of the tube axis and bolted to the shoulder harness bolts. It passed anual tech for years in SCCA(early 90's) I don't know about current rules.

post up the pics. NOt everyone is as lucky as hurleysurf.

By saying "hoop collapse", do you mean the sides being drawn into the middle of the car from the force of the harnesses pulling forward? If so, wouldn't the fact that the harness bar being tied in near the seat belt anchors prevent this from happening?

This wouldn't be possible unless you had the ability to install rear legs. But I do agree with you.

toplessFC3Sman- I'm not quite following you. Can you please elaborate on what you were describing?

This is reasuring. As for triangle gussets to support the hoop above the seatbelt anchors; I don't think it would work in this instance due to how close the bar is to the anchors (i.e.- too acute of a triangle), but I may be wrong.

phoenix7-- The actual customization of the bar isn't the issue. Personally, I know a few people who have more then enough skill to build a proper bar/cage. It is the issue of designing a bar that is unobtrusive and still functional. As I mentioned, my particular car isn't, nor will it be, for track use; So meeting sanctioned racing regulations isn't a top priority. But those regulations are a good set of standards to shoot for if at all possible, I agree.

true, but as you mentioned : if it meets their criteria then it's more than enough for rollover protection. That's just my line of reasoning.

What I did forget was that some RACE vert cages are too large, at least to the point that the top is no longer usable.

tough cookies with the vert.

If you are doing a weld in bar you could go to the support beam across the width of the car instead of the floor.(you can always cut it out flush with the mounting plates later) Then you might be able to move the hoop behind the belt mounts. From the pics above it looks like the top function may be an issue, I don't know. I never saw the vert race car we have when it was a complete car with a roof.

i highly recommend john, the roll bar that he made for my coupe was totally awesome, beefy as hell
hopefully i'd never have to test its strength tho

fuck i cant find any pics

The problem with no diagonal bracing is that it can collapse sideways in an accident, sort of like how the rear legs help stop it from bending over when sliding along the ground. I know that cross bracing on the rear legs won't work with the top, but it's just to show that there can be other options. Miata bars do it that way.

A bar bolted to the seatbelt towers will be better than nothing, but having rear legs and a cross bar is much better.

Damn! After seeing Hurlesurfs' accident, I'm afraid to to drive my car without a fully functionable roll bar. I'm going to look into the Kirk roll bar like mentioned. My car is more like a... weekend warrior type thing (when its running). The passenger seat doesn't need to be all that functional. I figure if someone wants to ride in it. They'll make the sacrifice of not having much room! :)

Be sure to post up what you do decide to go with lov-2-rev.

^Ditto. I'd wondered about one a few times but now I think I might quit wondering and get thinking. If someone comes up with a working answer there's probably more than enough of us now who would be interested!

Yep, if they want it enough, they will accordian themselves in. You should have seen me in my uncle's Caterham 7. I'm 6'2 and there wasn't enough room in the footwell for my legs, so I had to put me knees up on the dash. Fun stuff!

Ahh. Got it. I had the whole "mouse trap" thing picture in my mind, but didn't consider it collapsing sideways, as in a rollover. Is it possible to connect the diagonal brace through a full width harness bar(i.e.-out of plain with the hoop) and still have it structural? If that doesn't make sense, think of it this way. A diagonal brace that angles backwards slightly, intersects with a full width harness bar, and has its own seperate mounting point just behind the passanger seat. I know it would be stronger if it tied back into the hoop at the bottom, but it would allow for a 2 seat harness bar, would offer some lateral stiffness and still allow full top and seat opperation. Or even make it a X-frame instead of a single diagonal.

I was planing on a bolt-in setup.
Hmm... If The hoop was moved farther back, wouldn't that give you less protection for your noggen? As for Rx-Heavens pics above........I know the top is still full opperational including the articulation of the targa top. It only clears the harness bar by about 1/8", but it works.

I'm starting to get the "thinkies". My brain is working overtime on this one and is starting to shut down. I'll come back to this with a fresh mind tomorrow.

it should be called the hurleysurf roll bar.

Yes and no.

Whereas in this case, the main hoop does tie into the shoulder belt attachment point to prevent movement of the bar, the design as was only provided very minimal support with the given tab, no matter what the strength of the seatbelt attachment point was. The bar was still capable of folding forward or rearward over itself at the seat belt point, ripping from the seatbelt point and pivoting at its base forward or rearward and finally, buckling sideways from lateral loads.

The diagonal brace in particular, and to a lesser degree the harness bars, help prevent the sideways buckling from lateral loads and reduces the likelihood of the bar folding rearward or forward over itself at its highest support point; in this case, at the seatbelt attachment point. The door bars help strengthen the position of support at the seatbelt attachment point helping to provide MORE support against the main hoop pivoting forward or rearward at its base. Notice they also meet up with the harness bar on the main hoop. The door bars also improve the stiffness of the chassis, especially in the vert since there is no roof to provide any support.

While this is not an ideal setup for racing, my car is a street car (sort of), and my goal was to:
1. Maintain normal operation of the top.
2. Add a diagonal support bar with an integrated harness bar.
3. Add some unobtrusive door bars that will help secure the main hoop.
4. Gusset the tab that attaches to the seatbelt support.
5. Maintain clearance around my head.

I know the pics make it look like the bars are right next to my head but in fact there is ample clearance, even with a helmet on and padding on the bars. The seat is all the way back and I do not drive with it that way.

There is only a cunt hairs clearance between the targa top when it folds down and the drivers harness bar.

If I was to do it again and did not already have the main hoop from Kirk Racing, I would start with a custom main hoop and secure it to the floor several inches back from its current position. This would make the main hoop more perpendicular to the ground.

I've been trying to get Attila to post more pics of his bar for years now. Still waiting.
He has told he has to remove the targa top to put the top down.
FWIW, his car has been my inspiration all these long years, even preceding this forum.

OK I lied. I couldn't let this rest for the night just yet.

Rx-Heaven-- Very good point about the entire bar pivoting forward on the floor. Makes the door bar idea much more desirable.
So in your opinion, the seatbelt tabs are inadiquite, even if the anchor points of the body are sound...... interesting. In what way did you gusset them?

As for my goals, I would have to agree with 1,2 and 5. If I use the Kirk bar, I will also plan on gussetting (or boxing with a bolt access hole) the seatbelt anchor tabs. If I can find a way around using door bars, I would like to for easier access.

Going back to my idea of a full width harness bar and such. I made a quick visual aid. This is what I came up with in a few minutes time. (don't laugh, I know it's crude)
(Disregard the copper as it is just there to hold everything in place.)

http://i219.photobucket.com/albums/c...5Image0003.jpg
http://i219.photobucket.com/albums/c...5Image0004.jpg

If the black legs were to intersect the harness bar at the same point, do you guys think something along these lines is viable? Perhapse anchoring at the floor behind the seats on either side of the tunnel, or on top of the chassis brace behind the seats?

There'll be very minimal support there due to the very small angle between the main hoop and the other supports.

You can do a full width harness bar behind the diagonal brace, a number of roll bars do that, it's not really needed to tie them together, but if you want you can put in a little bit of tube there to bridge the gap.

ask www.awrracing.com if they make anything for the vert.

Anybody have the bar from Sneed Speed Shop? It is supposed to allow for full seat travel. I am 6' 3" and have my seat slid back all the way, then tilted back as far as I can in my vert. I still don't like the idea of having to remove the targa every time you drop the top with all these bars. I also was hoping to put a subwoofer in the spare tire area, but the Sneed bar won't allow that either. Here is a link:

http://www.sneedspeedshop.com/store/...idProduct=1074

I not the biggest fan of how a roll bar looks on our verts. I'm also not big on cages in street cars. What percentage of the time will you have a helmet on while street driving? Suppose you crash, and knock yourself out on the bar. Then during the crash, the bar fails and folds at the seat belt mounting bolt like we all dread. Now you are unconcious and unable to "pull a hurley" so your head cheese-graters the pavement. I ain't goin out like that yo....

yay i have a rollbar named after me :)

Here's a pic from their website for quick reference.
http://i219.photobucket.com/albums/c...ertiblebar.jpg

Nice bar but I agree, not having complete top opperation isn't an option. That is why a modified single hoop design like Rx-Heaven's is what I'm going for.

You're right, no one will be wearing a helmet during street driving. But personally, I'd rather knock myself out on a padded bar during a crash then to have no bar at all. Hurleysurf was very lucky, but what's to say you dont knock yourself out on any number of other things in an accident (i.e.- windshield frame, door edge, seatbelt anchor, etc...). Then you are upside down and unconscious without the protection of a framework above you. Seams like a no brainer to me (pardon the pun). The point of this thread has morphed to coming up with a design that is FUNCTIONAL and won't collapse during an accident, but still allows for complete roof opperation. That way, even if you are unconscious, the bar and harness system protects you; And you can still "flip the lid" for a sunday drive without issue.

Lets face it, driving a convertible is inherently dangerous, more so then driving a vehicle with an enclosed cabin. We all accept that fact every time we go out, turn the key and pull out of the drive. But regardless of weather you are 6'6" or 5'1", a little extra protection in a convertible is a good idea. Period, amen.

True enough, but my thought was to allow for more passanger seat movment. Having the diagonal brace on the same plain as the hoop limits the seat from sliding back and reclining. Although it probably is the only viable option.

Dude, you're an inspiration to us all :D

I don't know if any of you have hit your head on a "padded" bar before, but it hurts almost as much as no padding. In a bad accident, even a padded bar can give you a concussion or kill you. For a street car, if there is any remote possibility of you hitting your head on the bar, I wouldnt go for that design.

One question for lov-2-rev, when you say you want functionality of the top, would you be opposed to the idea of having to take the targa section out every time you put your top down? For a roll bar in the vert to even have the possibility of rear legs, I don't see it happening with the targa piece still attached.

If you have the diagonal in the right place it'll cross behind the seat lower than the harness bar so it won't limit the seat travel as much.

hell, take the targa part off when you go anywhere. The top frame should help with the rollover too.

Gotcha. :icon_tup:

as for the question from Bronze:
I am opposed to removing the targa top everytime I open the roof. My spare tire is relocated to my trunk and there is a subwoofer being mounted into the origional spare tire well cover. No room to stash the targa in the car really. So then my only option would be to take the targa off and leave it at home. Not very convienent if I want to go topless while on a cruise somewhere. No, the targa needs to be able to stay on the top when folded down.

Phoenix- Have you ever seen the frame of the vert top? It isn't all that beefy. Won't provide any real support in the event of a roll over.

Ah i gotcha. my radio doesnt even work, and the spare tire is in my storage shed. plenty of space for me. But with trunk space at a premium, i see where you're coming from though. nothing else is fitting in that trunk with the targa in it.
how about an outer cage? one that runs from the trunk, over the top and to the windshield? yeah nevermind, i'll go sit in a corner now...

:uhh:


:rlaugh:

No. I was talking about the top of the main hoop collapsing in a rollover situation. The diagonal bar to the top of the hoop helps reinforce it to reduce the hoop collapsing.

I was wondering about this as well.

i was looking at porsche Boxster rollbars. I was gonna post last night but my wife shut the computer down before I could.


look into it though.

^ Damn womanfolk runnin' our lives for us. My wife does it to me too. haha

Funny you mention it though. I was following a Mini Cooper convertible yesterday and thought the same thing. The double arch design is less obtrusive visually, but I wonder how solid they are. I'm gessing they are more for style then for protection.
I then thought about two individual cages similar to those used in 50's and 60's era rail jobs, but ruled that out because of how close you are to the bars.

The brainstorming continues..........

seriously, look up porsche boxster roll bars, it's not the same design as you're sescribing but it looks like it might save your head.

Getting a concussion is much better then becoming decapitated or scraping your head against the asphalt until the contents of your head leak out on to the road. Your chances of hitting the bar in such a manner are slim to none, as when you get into a frontal are sideway collision, the car stops but your body continues to move forward. Even if you somehow manage to hit someone while going 50mph in reverse ... the bar SHOULD still be high enough to prevent you from hitting it. After all the point of a roll bar is to protect you .. and if itsnt atleast 3" higher then your head, then it becomes worthless and sholdnt be installed to begin with.

If anyone can see this one you may be interested .. I use to have pictures of the car with the top down, but they took it down.

http://redlineunlimited.com/Images/clpd.rx7.medium.gif

To Phoenix
 

No, you and I are on the same page. It is 2 head hoops instead of a single hoop bar. I know exactly what you are talking about. But the fact that the main/lower structure is triangulated, is intreeging(spelling?). If one was to design something similar, that also attaches to the seatbelt anchor points, it would reduce or eliminate the bar structure from hinging at the floor. Then just beef the hell out of the hoops and tie into a full width harness bar.......... I think we're onto something here...........

http://i219.photobucket.com/albums/c..._rollbar01.jpg
http://i219.photobucket.com/albums/c..._rollbar02.jpg

i like that design .. and think it shld work very well.

Hurleysurf24-- It is tough to see but I think it is a variation of what Phoenix and I are talking about.

**Goes back to scrap bin for more wire**

I don't like the design because in a rollover the forces will likely cause the middle to collapse inward/downward. A single hoop will protect you better.

Design #2
 

http://i219.photobucket.com/albums/c...rdesign2-1.jpg
http://i219.photobucket.com/albums/c...rdesign2-2.jpg

Once again, pardon the crudeness.

The lower tape pieces represent gussets. The upper tabs represent seatbelt anchor points.

The rear bar would double as the harness bar and anchor just in front of the top motors. The hoop braces should transfer downward force to the rear legs.
I suppose additional legs could be put in between the inboard part of the hoops to the floor or something. That would prevent the center section from colapsing. Just a thought.