Door Opening "X" Bars as Side Protection

[trhoppe]

Unfortunately, it is contrary to the IT regulations (i.e., "mounting points").

GA

Wait what? How would that add an additional mounting point?

back of the seat


front


-Tom

[JoshS]

Tom, where does that underseat assembly attach to at the right-front corner of the seat?

Most of them that have been proposed on these forums suggest that the lateral bars that support the seat should attach to the trans tunnel ... that would be the extra point. If yours somehow doesn't attach to the unibody at another point, then you're good with respect to the rules.

[trhoppe]

It doesn't attach. It is up against the trans tunnel and "rests" on the stock seat "hump", without being physically attached to it via a weld or bolt.

Basically, its a big steel rectangle that sits on top of the stock seat humps and then is tied into the roll cage in the back and the left site via 4 points. (legal)

I agree that welding it into the trans tunnel as well would be great, but that would be an IT/SCCA illegal 9th point.

-Tom

[spnkzss]

It doesn't attach. It is up against the trans tunnel and "rests" on the stock seat "hump", without being physically attached to it via a weld or bolt.

Basically, its a big steel rectangle that sits on top of the stock seat humps and then is tied into the roll cage in the back and the left site via 4 points. (legal)

I agree that welding it into the trans tunnel as well would be great, but that would be an IT/SCCA illegal 9th point.

-Tom

Couldn't "you" take some 1x1 tubing from teh dash bar down to make a better connection? A free floating point kinda scares me.

[Dave Patten]

This type of seat mounting is designed to keep the driver in position with the cage. In a a side impact, if the door bars move the idea is the seat moves with them, keeping the cage from colapsing onto the driver.

[Greg Amy]

It doesn't attach. It is up against the trans tunnel and "rests" on the stock seat "hump", without being physically attached to it via a weld or bolt.

In a a side impact, if the door bars move the idea is the seat moves with them, keeping the cage from colapsing onto the driver.

Doesn't this pretty much eliminate all crush zones with regards to the car and driver? I'm not sure I like the idea of the driver moving with no crush...of course, it's the same idea as a tube-frame car, so....

[rsportvolvo]

One benefit is that spending mega bucks on dampers is pointless, as the chassis is an undamped spring of sorts....

Very true about the chassis is an undamped spring. That is why so much time is spent by top teams making the chassis stiff. Having a stiff chassis will allow you to reap the benefits of a better damper, not to mention a more consistent handling car.

[lateapex911]

Very true about the chassis is an undamped spring. That is why so much time and money is spent by top teams making the chassis stiff. Having a stiff chassis will allow you to spend a bazillion dollars on better dampers, that raises the bar for everyone.

Fixed that for you.

Few realize that the limits to the cage are actually one of the brilliant parts of the IT ruleset. We get into arguments about remote res. dampers, and those against cry foul that allowing such things will increase the cost by huge margins. Well, it COULD increase the cost, just like paying somebody $100 an hour to lick the undercoating off the car, but with a 2 adjustment limit, and an undamped chassis, the gains will be debateable, at best, and the actual costs difference to a high end non remote res. damper is rather non existant, anyway.

That's why I resist allowances that increase cage connection points.

[Knestis]

...particularly since it's possible to build a pretty substantial cage inside of the points already allowed - more substantial than most IT racers currently build.

One area where I think we can do a better job in this respect is not listing cars so light that there exists an inducement to skimp on cage structure in the name of weight. A large portion of the amount that Pablo the Golf is overweight is in optional cage tubes. I didn't worry about that because (a) I'm kind of a safety geek, and (b) because our focus was endurance racing, but I've had conversations with other MkIII owners - and others - who talked about "minimal cages" when talking about meeting weight.

If it gets that close, the car in question might be better placed a class lower at a higher minimum weight.

K

[lateapex911]

......agreed!

But, two monsters rear their heads there.

1- If that class is ITC, many will resist building because of lack of competition in their area, or perceived "extinction" issues, and...
2- Determining what a car CAN get down to, and finding the "break" point on that weight.

#1 is tricky because we are making it heavy to increase safety, ease of building and therefor popularity, but the questionable class placement kills it on the last point. Certainly it's a method worthy of implementation for the upper classes.

[Greg Amy]

Back to the original point, I've gotten word of another failure of a pure-X design. Same situation, where there was a single-diagonal-with-braces design, and it failed in the same manner: the single tube failed in tension. Welds were all good.

Fortunately, this last time was also to the passenger side; it didn't fail as far into the car as Richie's did, but the potential was still there.

I am now completely opposed to the approval of "X" bars, when they are designed such that there is a single tube across the door with two tubes welded to it to form that "X". It is now my opinion that there be an area of AT LEAST two whole tubes between the main the front legs of the cage, in order to resist vehicle intrusion and subsequent driver injury. I originally supported this "X" when it came up last year, but incidents this year have changed that. I plan to send a letter to the CRB, with photos, requesting the rule be changed.

If you already have this in your car - and, for reference, I did in the NX and the Miata - my recommendation is to add a horizontal tube at the bottom of your "X". - GA

[seckerich]

My suggestion for modification to the X bar rule would be to require the joint be gusseted. Minimum of 4" gussett on 3 sides. Would have the same structural area as a solid tube. Two solid tubes (high and low bent in arcs) plated in the middle just seperate and open like a shark mouth. It still comes down to surface area connected in the middle.

[Andy Bettencourt]

Back to the original point, I've gotten word of another failure of a pure-X design. Same situation, where there was a single-diagonal-with-braces design, and it failed in the same manner: the single tube failed in tension. Welds were all good.

Example. Glass if from side mirror.

[spnkzss]

Example. Glass if from side mirror.

So is that failure from the heat generated in the weld, or bad design, or bad design because you will always have heat form the weld? Would it have been any different if the center of the X was off plane out towards the door?

Personally, I like my full on NASCAR bars on BOTH sides, I've never been a proponent of the X. I actually would like to add a third bar running lower behind the sill. Maybe in my next build, which will probably be never

[Andy Bettencourt]

Example. Glass if from side mirror.

And I don't want to UNDERdescribe the force of the hit. Here is what it looked like from the OUTSIDE.

[lateapex911]

Ouch! When and where did that happen???

It's seems like it's certainly a good idea to have two continuous tubes, perhaps crossed in an X bar manner, and perhaps welded together with gussets of some form.

[raffaelli]

Andy, is that the 04? Everyone OK?

[Andy Bettencourt]

No, that is the #91 rental car. Driver is fine.

[RexRacer19]

So is that failure from the heat generated in the weld, or bad design, or bad design because you will always have heat form the weld? Would it have been any different if the center of the X was off plane out towards the door?

It is probably reasonable to assume that the failure was because of the HAZ from the weld...not just one weld but two in that same area where the X gets formed.

To answer your second question...the section would have been stronger if it were pushed out into a pyramid shape. As mentioned before, those tubes are stronger in compression than tension. The tension part is really what is contributing the most to these things fail at the joints. I don't want to speculate as to if it would or would have not failed with the design change, but from a design standpoint, it would be stronger for sure.

[rsportvolvo]

Example. Glass if from side mirror.

That is not a good picture of the failure (I know the door is smashed and most likely prevents opening for a better view).

Which X bar was continuous?

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

This leads me to another thought. We are all concerned with tubing layout, but what about the connection design. How was the tube fitment? Where there gaps that the welder filled (metal cement truck method)? Was the welder certified? What filler wire was used? What was the MIG welder set at?, etc., etc. Basically was it a craftsman or someone burning wire.

Having researched the FIA standards I find it interesting how they (FIA) require approved roll cage installers. SCCA seems to have more relaxed regulations for the installation by leaving the responsibility in the hands of the car builder/owner/driver.

With that in mind how many folks request the credentials of their roll cage installer? A friend had a non-SCCA club cage installed by a guy who claimed to install ALMS Porsche cages. Unfortunately my friend didn't know that Porsche Motorsport installs those ALMS roll cages. So what did that roll cage installer have experience with? Not sure, but the $4k price tag was a rip off.