X Style Door Bars

[johnc]

Some real world results:

 

http://www.improvedtouring.com/forums/showthread.php?t=24806

 

Door Opening "X" Bars as Side Protection

 

I know we've hashed this out here in the past; I tried to find the relevant topics but could not. However, we had one hell of a troubling incident this weekend that I wanted to relate, and to caution.

 

At yesterday's NARRC Runoffs at LRP, ITA Integra driver Richie Hunter spun in West Bend, a very fast sweeper corner leading up to the bridge. He stopped driver's right (normal line is driver's left), with the passenger side of the car facing oncoming traffic and the two front wheels in the grass. As he sat there, perpendicular to the traffic, two or more cars passed by safely before another car t-boned him directly in the middle of the passenger door.

 

For reference, most fast ITA cars are going about 80-85 through that section.

 

The damage was sobering. Richie managed to drive the drive the car back into the pits, but you could hear a pin drop except for the mass sharp inhales and "oh my gods" and "holy shits" as he drove by: his passenger door was COMPLETELY driven into the car, bent in half, and up against the exhaust tunnel and his right arm. A casual observer would note the right door was simply missing altogether.

 

Richie's OK; he got his bell rung good, and he said he was momentarily knocked unconscious (I think he was just knocked silly, but it's really hard to tell with him anyway...) He also complained of right arm pain, but he's been checked out and I personally saw him as we were packing up and he looks fine.

 

But post-race we all got a good look at the car. As described the door was completely destroyed, hammered well into the car. The passenger-side rollcage/intrusion protection had completely failed.

 

Richie had the venerable "X" bar on the passenger side, one diagonal tube, with two other tubes welded to that to make an "X". That structure failed. Your first thought is probably that the welds failed, but you would be wrong: all welds seemed to hold. The primarily structural failure was on the first main diagonal bar, which simple tore apart at its center in tension. Then, the two triangular "halves" of the X-bar system hinged inwards where they were welded to the main the front hoops, tearing the two tubes partially off. To imagine this, think of the old Western saloon doors that swing to each side; the X-bar tube separated in the center, then allowed the other car to penetrate in the middle, tearing each half at the vertical tubes they were attached to. The door then came off of its hinges and latches, bending as it penetrated through the "swinging door".

 

The forces of the crash were so hard that the main hoop, front legs, and main plane diagonal bar were bent as well.

 

And lest you think this was some big heavy car, it was a Miata, I believe a SMMAITAC. So, what, 2380#...?

 

Similarly to my Watkins Glen incident two weeks ago, the Miata punched right through the center of the door, almost leaving the rocker panel completely intact. Because of the design of the nose of the Miata and the significant lowering one can do with an Integra, the main side structure of the car, the rocker panel, was ineffective at providing crash protection.

 

I bring up this subject as a point of interest for current and future builds. I've been a proponent of the X-bar system in the past, as I believe a well-built one can work. However, this incident was sobering. Richie has the "standard" multi-tubes-with-verticals-NASCAR-bars on the driver's side, but for that and 180 degrees of rotation I firmly believe Richie would not be alive today. I certainly could not see a passenger surviving a crash like this on the street: there was just no place for a breathing human to be.

 

From this I take three main points.

 

First, the basic x-bar system by itself may not be adequate. Since there is only one whole diagonal bar in that design the tensile forces are only resisted by one tube. I would recommend one of two directions if you pursue the X-bar: either bend two tubes in "U" shape and weld them together at the center, or weld plates completely across the intersection to increase the cross-sectional area of the main point of tension. Or both. I've linked a (poor) photo of our Integra from the Watkins Glen wreck to demonstrate what I mean.

 

Second, creating a single-plane x-bar is probably not a good idea. This x-bar is subjected to bending and tensile forces; tubing works better in compression. If this x-bar had extended outwards in a "pup tent" type of fashion into the door, it may have withstood the punching forces better.

 

Third, we need to give serious consideration to design based on who we race with. As noted, the only thing between Richie and the nose of that Miata was his factory door and his rollcage x-bar. The 'Teg's rocker panel was nothing more than a footnote in that crash, as the Miata with its shark nose drove up and over it.

 

Finally (yes, I know this is four), there was door glass everywhere inside that car. Richie got showered by it. I am a clear proponent now of recommending - possibly requiring - removal of door glass. Fortunately, Richie was wearing a face shield with eye protection.

 

We have no photos, at Richie's request. But I hope I've described this satisfactorily to you. This si something we need to hash over; while I hope no one is subjected to this in the past, we need to prepare for it.

 

Greg

[JMortensen]

I'm seeing a couple main issues pointed out by the author:

 

1. Bars are in tension. Bending the bars into the door means that when they get hit they are now in compression.

 

2. No rocker bar.

 

3. In the case of his own crash, it sounds as though the door bars were very low in the car and the Miata that hit him drove over the X.

[johnc]

I got the impression that the Miata rode over the rocker panel and hit the door bar basically square in the center of the X.

 

Similarly to my Watkins Glen incident two weeks ago, the Miata punched right through the center of the door, almost leaving the rocker panel completely intact. Because of the design of the nose of the Miata and the significant lowering one can do with an Integra, the main side structure of the car, the rocker panel, was ineffective at providing crash protection.

[JMortensen]

I guess I don't read too goodly on Monday morning.

[bjhines]

This is why I did this.

 

 

 

 

and not this!!!

 

 

 

I have seen others do this

 

 

 

 

I realize that this is considered safe, but what does it do for weight and stiffness?

 

 

 

 

...

[johnc]

I've got a call into Dow regarding their IMPAXX energy absorption foam. I've got a 240Z door I'm going to cut up and see how that foam can be positioned inside relative to a various types of door bars.

[jeffer949]

John i would just like to thank you for your past couple threads regarding roll cage construction, and the wrecks that have brought alot of attention lately. I am no where near needing a full cage but these past few threads have opened my eyes to how crucial they are when you actually start racing. i raced motocross for 13years and did a bunch of track days on sport bikes and have even gone down at 120mph on an R6. So I always kind of thought of a steel box around me as good enough. Honestly I always thought of Roll cages as a little over kill but I dont any more. Its amazing how much more damage is created with the additon of the mass of a vehicle.

 

On a side note i think its kinda childish that he doesnt want pictures of his car posted. Let people learn from how his cage was constructed so every one can be safer

[Clifton]

 

On a side note i think its kinda childish that he doesnt want pictures of his car posted. Let people learn from how his cage was constructed so every one can be safer

 

Me too. I would love to see what happened. Others could learn from it and make theirs safer. Could save someone else.

[jeffer949]

I read the original thread and it looks like we might get some pics. The cage builder(the guy that build the guys cage) is going to get in contact with him.

[johnc]

Here's a video of the wreck, from the Miata:

 

[Clifton]

Scary watching. It looks like the Miata driver was on the brakes too. The hit e was lucky they weren't facing the other way. A hit on the driver door and fire is my biggest fear.

[Rustyfriend]

reading up on all of these safety threads and road racing, it is making me very nervous for my first track day

[tube80z]

Some more reading for the safety minded, https://dspace.lib.cranfield.ac.uk/bitstream/1826/2282/1/Corrected_Roll_Cage_Thesis.pdf

 

Rally car side impact protection.

 

Cary

[Mayolives]

Johnc,

Afetr looking at Dow's web site regarding IMPAXX energy absorption foam and I think a number of us are looking forward to hearing more about it. Hopefully you will share information about IMPAXX and how we could use it. Most of us are making plans to go fast without providing adequate protection from the "what ifs" that can ruin the day.

[johnc]

Update on IMPAXX...

 

Dow is negotiating distribution agreements with two or three companies to make IMPAXX available to normal people like us. Right now its only available to OEMs and approved professional race teams. I'm trying to get some samples backdoored to me so I can mock something up in a 240Z.

[JMortensen]

Some more reading for the safety minded, https://dspace.lib.cranfield.ac.uk/bitstream/1826/2282/1/Corrected_Roll_Cage_Thesis.pdf

Is that paper really stating that Prodrive runs two non-parallel door bars that don't intrude into the door space and that's it? And the thickest tube in the cage is 38.1mm x 1.6mm??? Did I read something wrong there? That's 1.5" x .062". If that is right that means that any ITS Z car has substantially more side impact protection than a WRC rally car. I feel like I must be missing something.

[tube80z]

Is that paper really stating that Prodrive runs two non-parallel door bars that don't intrude into the door space and that's it? And the thickest tube in the cage is 38.1mm x 1.6mm??? Did I read something wrong there? That's 1.5" x .062". If that is right that means that any ITS Z car has substantially more side impact protection than a WRC rally car. I feel like I must be missing something.

 

I don't think you read anything wrong. I'm still going through a lot of this myself and was interested in seeing what was proposed as a better solution. There's more info that's being released in this area as the FIA has made it a hot topic.

 

With regards to the Subarus I'm pretty sure FIA regulations require the door bars not to protrude into the doors (all mechanisms must work etc.) and the doors may have the stock safety beams in place too. So the cage may be a secondary safety device designed to work with the shell.

 

To be quite honest I only found the link and it appeared it had some decent data and passed it along before looking very deep. I'm currently pretty messed up on pain pills so if what I'm writing isn't making sense you've been warned.

 

Cary

[JMortensen]

Well one issue is that the tubing is apparently 4130. Still, that is smaller than would be allowed in an ITS car. I guess I had this idea that rally cars were pretty much indestructible, and now I'm finding out that this is not the case. I hope your pain isn't so bad that you can't enjoy the pills.

[heavy85]

 

I have seen others do this

 

 

That looks hella stout both to aid in chassis stiffness and side impact protection.

 

Cameron

[bjhines]

The neat thing is that it is only a modified version of the classic fishmouthed-X-bar.

 

I used 2 V-bars with gussets for an even stronger connection. I saw no need in the center down-tube except for jacking the car from the middle.