Door Opening "X" Bars as Side Protection

[Greg Amy]

Which X bar was continuous?

From the photo, lower left to upper right.

With the information provided the tubing failed at the weld, which shouldn't be the case with proper welding.

The weld did not fail; that's apparent from the photo. The material immediate adjacent to the weld failed. - GA

[zchris]

Lets watch the mud slinging. That is one of my cages. And yes it fit properly pryor to welding and yes I have been welding for 36 years. The bar that tore was the continuos bar and was bent out maybe an inch to meet the door panel. So the curve the bar out theory goes in the trash. Its just a single bar at the intersection that as it tries to deform, has the weld area that is stronger and tears away from the weld. A .090" taco gusset would greatly help. These always go into my Rally cages. The club racer is just generally to unable(kind way of saying it) to pay for the additional work.
Interestingly the offending car in both cases is the same black Miata. Tom Kelly quickly put a new clip on the front after it killed Richies Acura. It then proceded to kill the Flatout rental car. Different driver in both cases. Unfortunately the driver of the miata this time did not walk away unharmed. What are the friggin odds of one car damaging 2 other cars in the same way with 2 different drivers.
Chris Howard

[Ed Funk]

Needs to be exorcized!

[Greg Amy]

What are the friggin odds of one car damaging 2 other cars in the same way with 2 different drivers.

I had the same Miata/driver combo hit me while I was in two different cars/events...does that count?

[rsportvolvo]

Lets watch the mud slinging. That is one of my cages. And yes it fit properly pryor to welding and yes I have been welding for 36 years. The bar that tore was the continuos bar and was bent out maybe an inch to meet the door panel. So the curve the bar out theory goes in the trash. Its just a single bar at the intersection that as it tries to deform, has the weld area that is stronger and tears away from the weld. A .090" taco gusset would greatly help. These always go into my Rally cages. The club racer is just generally to unable(kind way of saying it) to pay for the additional work.
Interestingly the offending car in both cases is the same black Miata. Tom Kelly quickly put a new clip on the front after it killed Richies Acura. It then proceded to kill the Flatout rental car. Different driver in both cases. Unfortunately the driver of the miata this time did not walk away unharmed. What are the friggin odds of one car damaging 2 other cars in the same way with 2 different drivers.
Chris Howard

The tubing did fail around the heat affected zone. That is not mud slinging, just an observation. Do you carry a current AWS certification?

No offense intented. I'm just playing devil's advocate. Many folks are too trusting with fabricators. Having fit up cages myself I can say that I've seen some cages at the track, both Pro and Club that make me cringe.

Porsche uses a pyramid x-brace with 4 gussets. Have you looked into that?

[Andy Bettencourt]

That is not a good picture of the failure (I know the door is smashed and most likely

With the information provided the tubing failed at the weld, which shouldn't be the case with proper welding.

This is not one of our cages but I diagree that it failed @ the weld. The weld did not fail - and can be seen intact. Just 'below' the weld failed. I (and others) hypothisize that this area is the most weak section...due to the position of impact and maybe from being heated by the welder.

I think the basic allowance of an X bar is what is wrong here.

[rsportvolvo]

This is not one of our cages but I diagree that it failed @ the weld. The weld did not fail - and can be seen intact. Just 'below' the weld failed. I (and others) hypothisize that this area is the most weak section...due to the position of impact and maybe from being heated by the welder.

I think the basic allowance of an X bar is what is wrong here.

Just to clarify I didn't mean the weld failed, it didn't. It failed at the weld's heat affected zone.

[Knestis]

From the outside of this particular case looking in, to say "the weld failed" intimates that it was somehow done incorrectly. If "weld failed" actually means that the material adjacent to a perfectly reasonable weld was changed in predictable ways, and those changes allowed the structure to fail in an impact that can fairly be expected to happen once in a while during our normal (mis)use of these cars, that's semantically a very different thing.

One takeaway here then, is that we ought to understand and accept the limitations of typical construction of cages. If we're going to use these materials and these manufacturing processes, we should maybe require that the weak point of the structure be more than one tubing diameter in cross section.

I completely support Greg's suggestion that the requirements be beefed up.

K

[dickita15]

I agree that we should consider raising the standards on the driver’s side. I would not require upgrades on the passenger side. I do not think the risk is high enough to require tech to bounce cars for Xs on the passenger side.

[RexRacer19]

I support Greg on this initiative as well. I re-read the latest version of the GCR as a refresher before hand. Some things I find interesting, and reasons for me supporting what Greg wants to do are as follows:

IIRC not long ago only a single door bar was required for the passenger side of the car. Basically that is the same thing as a bisected X bar with the difference being where the point of failure would likely occur. With a single continuous door bar, the fail point would move to the area adjacent to one of the welds. This would be either on the front down tube or the main hoop.

Initially I did not have as much concern as Greg over the tubes failing on the passenger side. Mainly because of the fact that they are adsorbing energy that would get transfered to the driver. However, as the rule reads, the minimum requirement is the same for BOTH sides of the car. It is obvious that a bisected X on the driver's side suffering the same impact would yield a much worse result as far as the driver is concerned.

One other thing troubles me about the rule as well. Specifically, it states that only two gussets per joint may be added for Showroom Stock and Improved Touring cages. That limits the strength that can be added to an X style door bar system. That should be looked at as well.

How do we make it better? I personally do not want to see the X style door bars being banished altogether. I am a strong believer in their benefits to the overall rigidity of the cage. There was some language discussed a while back that some folks may remember about this rule with another sanctioning body. The gist of it, and probably a very good solution for folks that want to run an X style door bar is this: Two continuous door bars must be utilized in the construction. If an X style door bar system is used then, at any point, there must be at least the cross sectional area of two tubes at any point along it. Basically, the way the Kirk has his done (and Xian's now as well) where they are bent to meet in the middle, welded together and then gusseted. That is two continuous door bars that form an X. Alternatively, if using a bisected X then an additional door bar must be added to make up the missing cross sectional area from the bisection (See the pictures posted earlier of my former CRX).

There is my $.02 on what to change if we want to change it.

[trhoppe]

Greg/Kirk,

So with your "new proposed" rules, something like my passenger and drivers bars would be considered acceptable correct? I feel they are very safe. The X bar structure is reinforced with a gusset and there is a bar running along the bottom. Also the drivers Nascar bar has a running to the front hoop to distribute any force there.

Gussets on passenger side X bars


Drivers side nascar bar and in the top right of the picture, the bar running along the bottom of the passenger side X bar


-Tom

[Greg Amy]

Well, I haven't written/proposed anything yet (probably won't get a round tuit until after the 13 Hour, as I'd like to speak face-to-face with several folks during the day for feedback, as well as review other cage deisgns that are there), but I'm going to propose a minimum requirement of two whole bars; definitely on the driver's side, undecided on the passenger side (Richie's wreck really spooked me, though).

But, to answer your question, I'd tentatively say "yes".

First note: what I'm seeing on your tubes is not what I'd call a "gusset". In my mind, a "gusset" is a plate welded within and in the same plane as the angle of the tubes, and its purpose is to strengthen the tubes between each other in a bending moment. What I would describe your cage as having is a "reinforcing plate". I just read the GCR definition of "gusset" (see below) and I suggest it concurs (though I recognize this interpretation can differ among reasonable people).

If we require two tubes in the door, a problem arises with reinforcing plates, as in yours: there's really no way to verify that there's two tubes in there. Further, even if there is only one continuous tube in there, I believe that adding those plates does reinforce the structure to be at least as strong in tension as two tubes. As a result, the proposed rule will need to be worded such that these reinforcing plates are allowed in lieu of two bars, or the plates must not be allowed at all to visibly obscure the existence of two bars. Just something to think about prior to submission.

Greg

GCR Definition (emphasis mine):

Gusset - A brace generally formed by attaching, by welding, a plate at near the junction of two structural beams or tubes, providing reinforcement particularly in the plane including the tubes and the plate.

[Knestis]

>> ...there's really no way to verify that there's two tubes in there.

That's precisely why I took pictures and put them in my race binder.

At the time we built Pablo II, the "two bar" rule was just coming online and there was conversation suggesting that the kind of X in question here didn't actually MEET that rule. I personally don't think that it does.

K

[seckerich]

Just remember to balance safety and reasonable methods of change. We do not need a bunch of cars cutting out their cage to get legal. This club can not afford the losses that would cause. It is very reasonable to require plating or gussets as a structural fix. Two continuous tubes are not required to be strong. Ever seen a GT3R factory Porsche cage? X with plates and it is 3 tubes. Don't go getting too carried away here.

[Knestis]

Absolutely agree, Steve. One possible solution would be a minimum x-sectional area requirement, a sum of all areas at the smallest point between the dash and main hoop.

K

[chuck baader]

Gentlemen, if you will look at the pictures I posted of the right side of my car, the solution is there. I have NASCAR bars on the passenger side in addition to the regular bars. This gives extra intrusion protection with the allowance of removing the door glass. Problem solved:026: Chuck

[Racerlinn]

Gentlemen, if you will look at the pictures I posted of the right side of my car, the solution is there. I have NASCAR bars on the passenger side in addition to the regular bars. This gives extra intrusion protection with the allowance of removing the door glass. Problem solved Chuck

But not all of us want to remove the glass. Problem not solved.

I had already planned on some cage and seat changes over the winter, and the fact that I have an X on both sides of the car has this whole subject as an obvious concern for me. I was looking at adding gussets at the X as well as two shorter tubes above and below the cross-section of the X, but this would not satisfy a "two tube" rule as these shorter sections would not reach all the way to the rear roll or front down tubes.

[dickita15]

Wording is important here, as I am sure Greg knows. It should be made easy for anyone with a driver’s side X bar to upgrade without major surgery on your cage.

[Andy Bettencourt]

After having seen these two cars (Richie's Integra and our rental car) and the way the X's held up under impact, I can say for sure that I would NEVER race in a car with an X on the drivers side. Dang tube has the potential to go THROUGH the driver.

[DavidM]

I'll be getting a cage in the new tub over the winter and am also following this thread with interest. The plan was NASCAR bars on the driver's side with either NASCAR bars on the passengers side or some from of X like Xian's. I also plan on getting the seat frame attached to the cage like Hoppe's.

One design of the NASCAR bars I found interesting was shown on the first or second page of the thread. Where the higher bar was out further with the vertical bars angled inward. It was mentioned that the thought was to try and deflect the front of the impacting car downward. I don't know how well this would work on the driver's side as you don't have a whole lot of room for intrusion, but on the passenger side trying to deflect the impacting car downward towards the frame rail may work. That would allow the frame rail to absorb some of the energy vs the doorbars/cage taking it all.

I gotta think somebody has done a scientific analysis of cage structures. With all the modeling tools available these days it seems like you could do a fairly detailed analysis of cage structures and how they fair in various impact scenarios.

David