Roll Bar Connected to Windsheild
 

I am swapping roll bars with the person who purchased my old Miata (they didn’t like the diagonal) and I plan on powder coating it before reinstalling (black). While researching things to do while bar is out, I have come across a few pictures of Miata's with a couple additional braces running centered from the top of the roll bar to the top of the windshield. I have a few questions:

1. Will this help noticeably with vehicle rigidity? I have no qualms about adding 10 lbs of metal to alleviate some of the body flex. I was looking into door bars, frog arms, and frame rails. How would it compare to these?
   
2. Is this something that must be done with the bar in the vehicle? It doesn’t make sense to powder coat the roll bar if this job is done after the bar is installed (mismatching coloring with new bracing/welds). Does the soft top fit back on? Is it welded or bolted to the top or bottom of the windshield frame?
   
3. I currently run in SSM in my local SCCA auto-x region. I know the frame rails and other braces would bump me out of that class, but would this?
   
4. Does anyone have any opinions after having this done to their car? Regrets, things to do differently? Cost? Pictures?

My car: 97 with Old School Sebring and additional this and that’s. It is my DD during the summer and the wife and I like to take a couple three day weekend road trips with it. I plan on attending a track day or two at Miller Motorsports Park this summer. Drive to auto-x events, which I do for fun. I am not top 10 pax competitive (mostly among friends).

yes
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1-guy with a mariner blue car

Thank you for the quick reply, but was looking for a bit more detail.

Flipsidecustoms

Watch your noggin if you plan to drive on the street....thats the only reason I'm not going to cage my car....

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That's very badass!

Looks cool as hell, but I just know I'd take a hacksaw to it the first time I smacked my head on it.

You're going to put a big moment on those welds for the top bar if you ever do roll it over. There isn't much strength in the windshield and it will still want to crush. Seems like a good chance the top bar would break too.

I highly doubt that. Since its boxed in there is a far less chance of total collapse. The load will be distributed across the roll bar and the windshield. Only way its breaking is if it gets thrown off a building (as long as it has a full strength weld)

Maybe if there was a hoop welded alongside the windshieldframe where this bar would connect. Make it real close to the frame and remove the trim pieces so you can get it welded in properly. This will allow you to still use the latches and it wont be so intrusive. Then you're only a few pieces of tubing and some doorbars away from a full cage.

i agree... thats just going to add a point load to the middle of the windshield frame and crumble the windsheild.

I was planning on doing this to my car as well! mainly to get rid of the vibrating of the window thingy (that shit annoys the piss out of me when the top is down!

+1 Looks like the worst designed roll bar I've ever seen; but what do I know, I thought building a splitter from plywood sounded like a good idea.:laugh:

Examine the first picture

Then examine the second


I agree there is a better design but its far better then just a roll bar.

What door bars are those in the red car? ^

Kirk Racing.

I can't see how in a roll over those bars wouldn't just fold down into the cabin. That would be a really bad day if those bars came down onto your shoulder.
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To me it looks like an unsuccessful attempt to bridge the gap between roll bar and roll cage. It may work better than I think; but I don't like it and would rather just have a well designed roll bar.

I agree. In a mild roll over, I could see it working. but in a catostrophic crash, those bars could be curtains to the driver. They could literally spear the driver. I would never put that in my car, unless there were test results that would prove it was beneficial and safe. Assuming that system is safe is ridiculous.

That setup looks like it would cost as much as a full cage.

I don't completely agree with your stress analysis of it. Any force in the connecting bar will get brought back straight to either the windshield or the roll bar. It is still the same basic scenario. It might add a little strength, but if the car rolls, the windshield is still collapsing.

The windsheild will crush either way.

It (roll bar) wasn't designed to keep the windshield in mint condition if you had a rollover.

Don't forget something, even a terrible rollover with a roll bar still has a solid structure supporting the car. The point isn't to keep the windscreen from crushing, its to keep YOU from crushing by supporting the mid/rear point of the car.

http://www.bethania-garage.com/image...h_m2sport6.gif

Even if the windscreen frame still collapsed during the crash I don't see the extra added bars doing any harm, but speculate it might add just a tiny bit of extra structure. However with that said I'm not an engineer so my speculation is worth basically nothing.

the sphincter is connect to the...colon.

I've had this discussion with a friend of mine, who was looking for increased rigidity & safety while trying to avoid the full cage (he really like my bolt-in front cage section), and, while looking into center roofline bars, several people told him that the windshield WILL fold in during a rollover, most likely taking the roofline bars along with it.

Now, if you had installed bars along the windshield, running down into the floorboards, THAT WOULD be a slight improvement, which WILL keep the roofline bars from collapsing, but, the corners of the windshield will still fold in in a rollover, hurting the driver.

Agreed.

The weight is on the front in a rollover (motor). To me, it looks like that bar will act as leverage on the mounting points and pull the bar towards the driver or maybe tear out the bolts. 6 point or no roof bar.

+1

Do not want.

One more thing to hit your head on in a street car, for minimal benefit, and a track car is better off with a full cage.

Since it is a boxed off section it may hold up better, as the longitudinal bars would technically be in compression, and not see a bending moment until the A-pillars buckle. In reality buckling cannot be assumed to happen uniformly, and the front welds would like not hold.

Even if it stays together, when the windshield frame is compromised the bars may actually push back on the roll bar, making it more likely that the rear mounting points would puncture through the chassis.

For street driving, you must have dual durometer padding on your rollbars. Not really necessary behind the seat, but, crucial for any metal bar that your noggin' might come in contact with.

The niggin might not get crushed in that pic, but it has a decent chance of being in its non-crushed state about 100 yards up the road.

Most rollbars are designed to preserve your head by supporting the weight on the nose of the car, and the rollbar hoop.

If you dray a line from the front cross member to the top of the bar you get the idea. Every flipped Miata I've seen has looked exactly like that. No one is expecting the windshield frame to do anything.

EDIT: Tall people may not fare so well...

That is what I'm afraid of when I get a roll bar, my head will still be on the ground, but it is better than crushed all the way to the body line i guess.

Roll bars aren't made so much to protect your head, or scalp. Even at 5'11'' I'd expect to get a concussion and abrasion from being thrown around by tangential force.

Roll bars protect your spine from compression, ergo they carry half the weight of the car instead of your weak, never-seen-a-gym, puny back.

You can fix scrapes, and live through several concussions and still be fully functional. Spinal injuries usually leave folks in wheelchairs.

My question is: How likely are you to get sliced up by that windsheild? Contact with the ground is unlikely sure, but that windsheild is pointed right at your face. If you plant that sucker right into a tree stup it looks pretty easy to slide it right into your face or neck and off it goes. Yeesh.

Didnt someone make a "bends only" kit for a roll cage in the NA?I cant seem to find it anymore
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