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also, do you guys do the NASCAR style door bars for safety reasons only? it doesnt seem like it would cut any weight.
Pound for pound, NASCAR bars are not as strong as an X brace. They give you a little more room to work. X braces will also stiffen the chassis more.
The failure mode of NASCAR bars is to bend inside the cockpit. For an X brace to fail it must literally be ripped from the rest of the cage since it would take incredible force to stretch a bar along its length.
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George Roffe
91 SE-R (well modded)
84 944 SCCA ITS race car under construction
http://www.nissport.com
gotcha. so, you think i should keep the stock door bars and use x braces? thanks for the info Sr Roffe.
Well, like so many things.... That depends.
Some folks who cannot gut the door unless they have NASCAR bar(s) sometimes use an X and a single NASCAR bar to force removal of glass and regulators. In my case, I chose to retain the glass and regulators to make locking and towing in inclement weather less of a hassle.
One alternative I looked at was to use an X and two NASCAR bars that are tilted to meet with no verticle bars, just a weld horizontally where the tow bars meet. That would keep the weight down a bit and provide a little buffer zone.
Again, in my case I chose however to just use an X. Despite the fact there is almost no buffer zone, the X is more stout, lb for lb.
arent nascar style bars used for ease of entry instead of the x braces?
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Blair
93 P10
"For I know the plans I have for you," declares the LORD, "plans to prosper you and not to harm you, plans to give you hope and a future." - Jeremiah 29:11 (NIV)
NASA mandates that you retain the stock side impact beams in your car, or if you remove them, you must put in NASCAR style bars, per NASCAR rules and regulations. NASA rules require either that, or an "x brace" in the cage along with the stock side impact bars, giving you that all important "buffer zone."
the only problem is, you couldnt really do both, as entry would be a serious act in contortionism, so you pick. i was going to go the NASCAR style route (despite my extreme revulsion to the actual "sport") when i started thinking (uh oh, here i go doing THAT again). the NASCAR style side beams would more than likely add more weight than removal of the side impact beams and as George pointed out, would not really add that much to the structure of the car.
well, nm. i re-read the rules. you can only gut the door if you install the nascar style door bars. this seems kind of lame, as it says you cant remove the window or anything.
strange, though. i see that will goo's car has totally gutted doors on both sides, and i know his car passed tech... can anyone clarify this for me?
well, nm. i re-read the rules. you can only gut the door if you install the nascar style door bars. this seems kind of lame, as it says you cant remove the window or anything.
strange, though. i see that will goo's car has totally gutted doors on both sides, and i know his car passed tech... can anyone clarify this for me?
NASCAR bars are only required on the driver's side. If you have a passenger X you can gut the passenger door, too. I'd re-re-read the rules You can always remove the glass.
Maybe an X is stronger pound for pound, but my NASCAR bars have a lot more mass than your X. I like having that extra mass and crumple zone when it is my body on the line. Plus, getting in and out is SOOOO easy... like if the car is on fire and I have to get out quickly.
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-Jim
SE-R Cup Hooligan
Last edited by Jim #98NX : 06-28-2004 at 11:48 AM.
Maybe an X is stronger pound for pound, but my NASCAR bars have a lot more mass than your X. I like having that extra mass and crumple zone when it is my body on the line.
But that is the point. The X brace can provide as much or more protection for less mass (weight).
But that is the point. The X brace can provide as much or more protection for less mass (weight).
I just remember seeing a Pro-7 with an X that got t-boned at Buttonwillow. They took the drive away in an ambulance. The X only had an inch or two before it was in to the driver.
After I saw that I was all for building as much crumple zone as I can. I kinda view door bars like helmets- this isn't the place you want to cut corners or cheap out. I'll take the weight out somewhere else.
Like most things in racing, there is never a right or wrong answer, just what is right or wrong for you. Don't make the mistake of thinking either way is permanent... its only metal
But with the NASCAR bars, you have to consider the placement of the a-pillar tube and main hoop carefully so a viable door bar can be made. Mine go through the door jamb.
Unfortunately, that would be illegal in SCCA Improved Touring. Yep, I know, this is a NASA forum, but if you ever want the ability to run your car in, or sell your car to, SCCA ITA specs, plan ahead.
This was our compromise. I like the structure of the X-bars much better, as it's stronger than horizontal/vertical curved bars. Curved tubes is Newton's way of saying, "Bend Here." Straight tubes is much preferred. I also wanted a bit more intrusion protection, I wanted to be able to remove the door glass and mechanisms, and I wanted to be able to get in and out easily. This works. In case you can't tell, the X is entending into the door:
I just remember seeing a Pro-7 with an X that got t-boned at Buttonwillow. They took the drive away in an ambulance. The X only had an inch or two before it was in to the driver.
Did the X fail or bend? If not, we cannot assume the driver was taken in the ambulance because of the X. He/she may have suffered something that would have happened with NASCAR bars as well. If the X failed, we have to ask why. If it did and the welds were good, it's also possible that with that much force the NASCAR bars could have collapsed into the seat and killed him/her.
My point is that we don't know if there is a causal relationship here.
I fully understand your desire for space. Just remember that the same thing that gives you space could also be the thing that kills you (curved bars).
I'm interested to see information you have regarding X's being stronger/better in a side impact than NASCAR bars because I've heard the opposite.
Well Greg was the one who explained it to me, but here's the gist of it....
As Greg said, bent tubes are Newton's way of saying "Bend Here." Basically, you have tubes that are longer than they need to be, so they have room be bend inward (since they are assembled bent outward, they can also be bent inward) without collapsing the main hoop or the front down tubes. In fact they can be bent inward at least as far as they start out bent outward.
The strength of NASCAR bars is their mass. But, for the same mass, the X is still stonger. Here's why....
The tubes in the X brace are as short as they can be (the shortest distance between two points is a straight line). In order for the tubes in an X to bend one of two things have to happen.
The first is the impact would have to collapse the main hoop and or the front downtubes. But without that happening, the only way for the tubes to bend is to stretch along their length and that would take truly significant force, even for a crash. Think about it this way... Take a drinking straw and hold it tightly at both ends. Try to deflect it in the middle. A tube firmly attached at both ends will be incredibly strong.
The other way to bend the tubes of an X brace or otherwise make them fail is to literally rip them from the main hoop and/or front down tubes. Any impact that can make that happen can also rip a NASCAR bar from the cage as well. But most likely it would bend into the cockpit first, then rip from the rest of the cage.
Now, towards that end, here's a photo of my cage:
To prevent the collapse of the main hoop, notice I have two horizontal tubes at the base of the main hoop and at shoulder height. At the front I have one that goes across the dash.
Now, to critique my own cage, the dash bar is bent on both ends, weakening the tube. But, I made this compromise due to the dash area of the 944 being so shallow and tight that it couldn't run behind the dash and a straight bar above the dash was not going to connect to the load path of the X bars. So, the solution I came up with is probably my only decent choice. In my mind, it was that or no dash bar at all.
So, does this explain it well enough? If not, perhaps Greg can elaborate.
What fire system are you running Greg and what capacity?.
I don't recall offhand; it's an England-sourced Halon system I've had for a while. Its capacity is in kg, but it's just over ten pounds.
We're looking for a system for the Miata, and we're going to buy the new FireCharger systems (http://www.firecharger.com/). It uses water and a surfactant, propelled by CO2 cartridges (same as used in paintball guns). It's field-serviceable.
No additions to the cage comments. Just keep in mind short, straight tubes as much as possible. To that end, you'll notice on my cage what appears to be a second main roll hoop on the driver's side (just over the driver's left shoulder). It is actually a second vertical member to support the long, curved front cage leg.
Unfortunately, that would be illegal in SCCA Improved Touring. Yep, I know, this is a NASA forum, but if you ever want the ability to run your car in, or sell your car to, SCCA ITA specs, plan ahead.
This w
You can always remove the glass.
