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Greg Amy
09-28-2008, 11:23 AM
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

http://www.improvedtouring.com/gallery/displayimage.php?imageid=233

Mike Guenther
09-28-2008, 11:47 AM
By your description of the force of impact, it sounds like the cage did a good job of absorbing the energy. Is there really a design that's practical in weight and material cost that can withstand any possible impact ? And how should it look after an incredible impact ? I wouldn't expect it to look like it did before the accident.:shrug:

The bending and breaking is absorbing energy that would otherwise transfer to the driver. Had the bar broke upon a 20 mph impact, I would look to see if inferior materials were used. But at 80 mph, what would you expect ?

The design you show does appear to be a stronger way to make an X. I'm sure that at an 80 mph direct impact there would be some failure somewhere in that construction too.

pdqracer
09-28-2008, 11:51 AM
Perhaps a 16ga. cover welded to the complete permiter of the door bars to act as onr giant gusset ala NASCAR would help. It would add a lot ostrength to that area.

tnord
09-28-2008, 11:59 AM
my car had seen it's share of impacts, a couple pretty solid side ones as well.

it's not just miatas that impact much higher than the rocker panel, a VW got into my drivers door once, completely destroyed the door, got into the door bar, but left the rocker panel untouched.

as i get ready to possibly build another car, i'll be real interested in where this discussion goes. i'm no structural expert by any means, but isn't it a "rule" that the bigger the bend you put in a bar, the weaker it becomes at the point of the bend since you have to stretch/thin the metal to make the larger outside radius? with that in mind, the x-bar pictured above looks like a pretty big bend relative to the traditional nascar bars. the plates welded at the intersection counter this, as the bars are pushed inward the stress is placed upon 4 whole rows of welds, but is it enough? either way, i see the quality of the welds and material used in those plates to be the key to safety in that design.

travis
-who had a "traditional" x-bar on the passenger side, but nascar bar on the drivers side.

raffaelli
09-28-2008, 12:18 PM
Greg, I was in T&S when Hunter’s car drove down pit lane. We were all laughing at the hay bail stuck to the front of the car, and then the air left the room as we realized the car was caved in and the door was against the driver. In a room full of jolly ladies, there were certainly a lot of holy shits going around.

I am glad to hear he is OK. I have always thought the glass in the door was a dumb idea. I have the X bar you describe with the three pieces. I had planned on added a diagonal across the roof and gussets elsewhere this winter. I will add an upgrade to the x bar also.

Good topic.

RSTPerformance
09-28-2008, 12:43 PM
The thought of the passenger side collapsing is interesting, but we would never want this to happen on the drivers side... I am now thinking about what I should do to upgrade my drivers side bars...

Raymond

Sandro
09-28-2008, 12:48 PM
My biggest fear has always been getting T-boned, mainly only the driver side, since I always thought I had crush space on the passenger side but from this example its pretty obvious thats not enough space.

http://www.improvedtouring.com/gallery/displayimage.php?imageid=234

My cage has the standard X plus a horizontal bar at the bottom, but as you mentioned due to the height of the miata the horizontal bar wouldn't have done anything. If I had a vertical bar on each side of the X, say about a foot from the center on either side, with taco gussets, how effective do you think that would be in a situation such as this? I think it would be fairly efficient because you would have two continuous bars(horizontal and one of the x bars) plus the two half bars of the x all having to bend in unison.

red = bars, blue = gussets

http://www.improvedtouring.com/gallery/displayimage.php?imageid=235

DoubleXL240Z
09-28-2008, 01:20 PM
This is one of the three dimensional x braces that I did. It was then gusseted. It seems like what Greg was talking about.

Knestis
09-28-2008, 01:49 PM
Thanks for bringing this up again, Greg. It's a big issue.

Submitted for consideration...

http://www.it2.evaluand.com/gti/images/mk3.2/cage07.jpg

http://www.it2.evaluand.com/gti/images/mk3.2/cage08.jpg

K

EDIT - Those bars project outward a couple of inches...

tom91ita
09-28-2008, 02:12 PM
Sandro has excellent photos that basically shows typical configurations of both the nascar and the x style.

i have the nascar type on both sides and i think they go deeper into the door than Sandro is showing but that may just be perspective. mine go right up to the reinforcing bar in the door and you have to give a good slam to latch the door. i do not have as many cross braces as Sandro is showing. that looks quite well done.

with regards to the more bends, i think you need to look at how the hit takes place and what happens. i am not a structural engineer either but i know if if i put a 2x10 on its side, and i walk over it, it will bend a lot. if i put it on edge and walk on it, there is no deflection noticed.

when we bend a bar into the door, there is a lot of compressive forces that come into play when it is hit, for the x-bar, there is lot more tension forces taking place. i think the bent bars spread the force into the rest of the cage/hoop as well.

and for the extreme example, how much force would it take to "ben" a 1.5" bar that is 36" long when laying on its side vs. to compress it from its end?

now i will freely admit that i have no idea which is better at dissipating the force of impact to lessen the g's felt by the driver. Sandro's cage may be the best of both worlds. give up energy in all the space you can on the passenger side cause you can give up the space and lessen the g's felt by the driver. and where space is a major premium, you need the prevent intrusion on the driver side and know that you will feel more g's in the impact.

greg, thanks for a detailed description of what happened and let us know he was alright.

dickita15
09-28-2008, 03:03 PM
We did a nascar style on both side though much less than Sando. The upper bar lines up perfectly with the stock anti intrusion bar.

Sandro
09-28-2008, 03:34 PM
my bar goes all the way into the door and touches the door beam in a spot or two, have to slam the door to get it closed. Whole goal was to get the bars as far away from me as possible, allowing for the most crumple room.

http://www.improvedtouring.com/gallery/displayimage.php?imageid=236

I had considered doing the same on the passenger side, but thought I would have enough crumple room. Now I wish I at least had a little protrusion into the door, only for the sake of being able to remove the glass, for the reason Greg mentioned above.

splats
09-28-2008, 03:34 PM
As an EX-circle tracker, I've had my share of T-bones & got hurt several times. And those were less than 60mph. Turn 1 at Sebring is a blind, 100mph turn. We built as strong door bars as we could. You can't see from the pics, but there are as many triangles in the bars as could get. All three horizonals are bent different. And the center bar will HOPEFULLY deflect front bumpers down. As with any cage, you can find a weak point with mine. If you see something that we overlooked, please let me know. When people talk about the cage adding weight, consider this..... my car is just 50lbs over the minimuim WITH 3/4 tank of gas (stock) & the spare tire still in the trunk. I'm glad that Richie is OK. But I'm supprised that no-one has gotten hurt because of building to the rules. If you can just open your door & STEP into your seat, IMO you don't have enough protection. I'm more worried about WALKING away from a crash than walking away with a placque. Sorry about the soapbox, but we just had this talk at our district meeting recently.

zchris
09-28-2008, 07:07 PM
Well I am glad Richie is OK. I am the one who built the cage in Richies car. I wish Rich had let poeple photo the damage as that is the only way we all learn. I think the Taco shell idea would solve that failure mechanism. I also think that foam filling the door would be the lightest and safest fix. The foam would absorb the energy and distribute the load over a larger area. I think this is common in Rally cars in Europe. All my Rally car customers have the Taco shell setup as they are required to have an X brace on both sides. Ultimately, Nascar bars on both sides would be best. Most of you guys just do not want the extra weight and cost. The other thing to remember is that you want the car to absorb energy in the impact, not you. Nascar got to the point that the cars were built so well that the car survived most any crash. Unfortunately the drivers were not. Its a balancing act between rigidity and crash worthyness. In one of Dick Shines early cages I built, the driver hit the wall in the oval at NHIS and rolled down into oncoming traffic. He was rearended so hard the drivers floor tore under the seat. We had built the rear to be so rigid it transfered to much energy into the drivers area. From the rear shock towers to the back of the main hoop was fine. Not a great design in that application. As always I am happy to build what the customer wants. Unless its a real disaster. Lets all try and learn from this. I wish crash testing was not so expensive.
Chris Howard
HowardMotorsports

raffaelli
09-28-2008, 07:14 PM
Chris, glad you posted here. I am pleased to hear that you built Rich's cage. You built my cage and I am very confident in it. The design, from what I saw, in Rich's car is the same as mine. I now see that your work will allow a driver to walk away under such severe conditions. Kudos. I'll be ringing you this winter for some 'extra' bars.

RSTPerformance
09-28-2008, 08:58 PM
Chris built our cages in the Audi's as well.... Very well built IMO.

We have the standard "X" bars like sandro does in both drivers side and passenger side. Many other people I know have the same thing... I think that it is obvious we need to make an upgrade or two. One thing we have wanted to do forever as put in a petty bar. Now I am also thinking that we should weld in a few "Taco's" (is that the real name for the sheet of metal reinforcing the area where the X is formed?). Do you think this would do the trick, or do people really think that it is necessary to take out what is already in the cars and put in NASCAR bars?

Raymond

Sandro
09-28-2008, 09:16 PM
[quote=RSTPerformance;274129is that the real name for the sheet of metal reinforcing the area where the X is formed?
Raymond[/quote]


thats just what I call them because when done like the picture below they look like a taco

http://www.rally.subaru.com/building/b27.jpg

rsportvolvo
09-28-2008, 11:00 PM
I think something here is being overlooked. We are looking at the car's damage and thinking it's bad to see a car THAT damaged, even though the driver escaped without injury. We should be looking at the car as a sacrificial anode in that the structure successfully absorbed the force of impact which allowed the driver to survive.

The X-brace and stock sheet metal deformed (I don't like using failed here as it really did it's job) during the impact. During impact the structural pieces deformation absorbed a significant amount of energy. That energy absorbed was not transferred to the driver.

Now if said driver had NASCAR bars on the passenger side the structure, in theory, would have deformed much less (that is the arguement here, right?). That means the load would be transferred elsewhere and ultimately to the driver. Not a good scenario either.

I want a structure that protects me from intrusion, but not at the expense of my bodies G-loading. The FIA has performed a lot of impact studies and requires impact test on as raced monocoques and shells as part of vehicle homologation. I should look into getting more information on this.

I'm actually a fan of impact absorbing structures and foam as used on FIA cars, Rolex Daytona Prototypes, and NASCAR COT. It is unfortunate that this safety technology has not trickled down to the club level yet, at least not here in the USA.

Unfortunately I don't know anyone besides Crawford Composites or DOW making such structures and foam, respectively.

Also, I spoke with the RaceTech folks last year at the PRI show about their seats with the integrated seat back bracing mounts (I think this is the Viper seat). They tested the seat to @ 45 G load where the FIA only requires something in the 20 G range. Customers have sustained upwards of 85 G impacts without significant driver injury. Something to think about.

rsportvolvo
09-28-2008, 11:04 PM
thats just what I call them because when done like the picture below they look like a taco

http://www.rally.subaru.com/building/b27.jpg

Gusset is the correct term.

They should match better too, e.g. make a rectangle or square.

Speed Raycer
09-28-2008, 11:38 PM
Yes, gusset is the correct term, but there are a WIDE variety of gussets out there. That style is commonly referred to as a Taco Gusset because of the shape/form.

Kudos to Chris for building a great cage that kept the driver safe. The chassis' are expendable. Glad the driver came through it OK

I'll reiterate (sp?) what Chris said... it is sometimes close to pulling teeth to get guys to upgrade from the minimum. PLEASE stop trying to save money on the cage end. I've had guys request that I NOT put any gussets in because they didn't want to spend the money. How about using those HoHo's for 2 weekends instead of new shoes every race ;)

It's a shame there aren't any pics as they would have taught us something.

dickita15
09-29-2008, 06:13 AM
To Chris’s comment about the drivers wanting weight savings of the X bars, I saved plenty in gutting the right door to make up for the small about of extra tubing.
It is somewhat bothersome that this incident took the force in the door alone rather than using the crush structure of the rocker and floor. Given IT cage rules I do not know how to change that.

Wreckerboy
09-29-2008, 08:25 AM
I'm glad that Rich Hunter is okay. Does anybody know anything about the driver that hit him? Chris built the cage in my Miata as well (which I unfortunately crash tested a few weeks later at LRP). I can't say enough good things about the quality of his work.

Earlier it was mentioned about drivers wanting the weight savings of x bars in the right side doors. When we discussed this as Chris was putting my cage together last summer, I thought (please correct me if I am wrong) that he mentioned that one of the advantages to NOT doing so was the straight load path gained from front to rear.

I understand that everything is a tradeoff, but but perhaps the best solution is a combination of the two or three approaches: the traditional X bar style arrangement as well as the NASCAR anti-intrustion design, as well as tacos. Yes, this will impart a weight penalty. The other thing to consider is the expanding foam mentioned here. The NASCRAP COT uses attenuating foam in the doors now. Does this sort of thing exist for our adaptation? I'm thinking that spritzing the inside of the tubes with the conventional expanding foam available at Lowe's is not a good idea... :D

Greg Amy
09-29-2008, 09:38 AM
I'm re-quoting Sandro's photo, because this is a good illustrative example of Richie's/Chris' build. Note the driver's side full-up "NASCAR" on the left side; right side is a single-tube bar bisecting another bar to create an "X". Richie did not have a horizontal bar at the bottom.

http://www.improvedtouring.com/gallery/displayimage.php?imageid=234


I think something here is being overlooked. We should be looking at the car as a sacrificial anode in that the structure successfully absorbed the force of impact which allowed the driver to survive.

By your description of the force of impact, it sounds like the cage did a good job of absorbing the energy. Is there really a design that's practical in weight and material cost that can withstand any possible impact ? And how should it look after an incredible impact ? I wouldn't expect it to look like it did before the accident.:shrug:

I suspect you don't understand the full scope of what happened to Richie's car. If Richie had been 180 spun around with the x-bar on the driver's side, he would be dead today.

Period.

There was absolutely ZERO space between the passenger side door and the exhaust tunnel. Zero. The passenger side door was halfway into the car, and only inches from hitting the driver, thankfully on the other side of the car.

A lot of people like to get into a discussion of "crush zones" and "energy absorption" and the like, but we don't have the tools to be able to quantify that. As such, it becomes more an "art" than a science. And without a survival cell, absorbing energy kinda doesn't matter. Granted, dying of a detached brain is just as dead as being crushed, but given the choice I think I'd rather take my chances with g-forces.

Finally, while this discussion centers around a crushed passenger side, my focus is how we should design a proper driver's side crash structure.


The design you show does appear to be a stronger way to make an X. I'm sure that at an 80 mph direct impact there would be some failure somewhere in that construction too.Of course. But this particular door structure failed in tension, and failed in a way we cannot accept.

Let me make this clear: I am not hammering Chris' work. In point of fact, my Nissan NX2000 has a (highly more structural) x-bar design on the driver's side. But, my point is that the design as illustrated above in Sandro's photo can withstand exactly half the tensile forces of a true double bar.

Think of it this way: let's say you cut that "X" out of there and hang a car from it; how much force can it withstand? Only as much force as one tube. Why only one tube, you ask? Because its weakest place is in the middle, where there's only the cross-sectional area of one bar. If, however, you were to weld a plate across the face of that "X" it could withstand twice the load, because it's now being distributed among two tubes.

A "taco" gusset would not do the same thing, unless it were also welded across the face. The purpose of gussets is not to increase tensile strength but to support the tubes in a bending moment. For the purposes of the discussion at hand, two plates welded across the back and face of the "X" would be just as effective.


It is somewhat bothersome that this incident took the force in the door alone rather than using the crush structure of the rocker and floor. Given IT cage rules I do not know how to change that.

Well, as you know, the best thing would to be allowed to weld to the rocker panel. But trying to get that IT rule changed would be Sisyphian. As a compromise, I'm envisioning using the plate are rule to extend the plates as far towards the center of the door as possible, then welding tubes to that. Kessler always added a longitudinal bar at the bottom on my cars (similar to Sandro's photo, above) but I think we might expand upon that a bit more.


Does anybody know anything about the driver that hit him?
I saw Richie talking to him in impound, looked fine. Front-end damage on the 'Ta didn't seem significantly worse than other bad SM wrecks...that car seems to handle hits pretty well.


I am the one who built the cage in Richies car. I wish Rich had let poeple photo the damage as that is the only way we all learn.
I chatted with Richie about it, but he wanted to discuss it with you first. If you can talk him into letting one of his guys take some photos to post here (or you take some when you see it), I think we can all really learn from it.

Honestly, Chris, there was really nothing you could have done differently to the passenger side to affect a significantly different result; it was that hard a hit. All I'm offering here is a detailed discussion of the failure mode and how we might apply that to our driver's side going forward.

This is timely, as we've got a new car build going to happen this winter. I'm personally no longer a fan of the pure "X" bar on the driver's side, though I'm not clear exactly how far towards the "NASCAR" I'm wanting to go...:shrug:

lateapex911
09-29-2008, 09:58 AM
I looked at it closely. The bar (as Greg described) sheared, as did all the other failure points, near to, but not at the welds. The door pillar/upper rocker area was pushed in nearly a foot. The cage had significant deformation at the cross car horizontal.

The points being made regarding the car deforming so that the energy being transferred to the driver is less are good ones. When we see a cage sheared, we get all amazed. In and of itself, the shearing isn't the end of the world, unless it happened at very low velocities. I'd GUESS this impact had a car that was initially traveling at 80, then locked them up, and hit in the 50MPH range, which is significant as Richie was not moving at all.

On the passenger side, I think "weaker" isn't bad, as it allows more deformation, which takes energy out of the driver impact. On the drivers side, such intrusion would be catastrophic. That said, I think a lower bar wouldn't be a bad idea, with a vertical bar linking it to the center of the X.


EDIT: I see Greg posted as I was writing, making my comments redundant. Oh well!

tom91ita
09-29-2008, 10:12 AM
how are the "taco" gussets being formed for around a bar? i see the formed hole as more optional for further weight savings.

i think i will add some sheet metal to my driver door bars as some insurance. not for this type of incident but there are still suspension pieces, etc. that can penetrate the door/cage.

and my car/logbook is old enough that the plate rules do not apply, iirc.

edit: that went away, i guess. haven't looked lately cause i was not changing anything. here is an excerpt from 2008 GCR.



3. Mounting Plates
a. Mounting plates welded to the structure of the car shall not be less than .080 inches thick. The maximum area of each mounting plate in the American Sedan, Improved Touring, Showroom Stock, Spec Miata, and Touring classes shall be 144 square inches. Plates may be on multiple planes but shall not be greater than fifteen inches on any side.

chuck baader
09-29-2008, 10:56 AM
I see the addition of door bars on both sides as extra intrusion protection. I designed my own cage and I like to be as far away from harm as possible. Attached are the pictures of both sidfile:///C:/Documents%20and%20Settings/Charles%20Baader/Desktop/TEMP/DSC_0027.JPGes of my car. Chuckhttp://www.improvedtouring.com/forums/../gallery/files/7/4/6/0/dsc_0027_thumb.jpg (http://www.improvedtouring.com/forums/../gallery/showimage.php?i=237&c=12)http://www.improvedtouring.com/forums/../gallery/files/7/4/6/0/dsc_0028_thumb.jpg (http://www.improvedtouring.com/forums/../gallery/showimage.php?i=238&c=12)

RexRacer19
09-29-2008, 10:57 AM
This is timely, as we've got a new car build going to happen this winter. I'm personally no longer a fan of the pure "X" bar on the driver's side, though I'm not clear exactly how far towards the "NASCAR" I'm wanting to go...:shrug:

Hey Greg,

This thread has lured me out of lurking...

That is a tough question/quandary that you have posed there. I am not sure if there is an ultimate solution here that is not a compete tank of a roll cage. My thoughts have always been "build it as best you can within reason, but there comes a point when, no matter what you do from a safety standpoint, the crash is just going to be too bad."

From the two schools of thought...The X style bar is structurally more efficient and increases the overall strength of the cage IMO. There is however, less metal there right next to the driver. The NASCAR style bars add more metal to the area adjacent to the driver, but are generally full of dead load paths. In nearly every example of a NASCAR bar shown in this thread, there is a nice mesh of tubes forming the side impact. BUT, that mesh of tubes gets attached to a single vertical tube in the front, and a single vertical tube in the rear mid-span. When having to take on an impact such as Richie's, The tubes that the NASCAR bars are attached to will be the first to deform/fail in a massive impact. Just like in Richie's crash, they will be in tension, which is less than ideal.

-Jeff

Speed Raycer
09-29-2008, 11:17 AM
IThat said, I think a lower bar wouldn't be a bad idea, with a vertical bar linking it to the center of the X.

Possibility of becoming a spear in the same situation.

I've been toying with going with a 1 bend X lately. Single straight bar ala the traditional X then the second bar bent out around it, then gusseted together.

I have to wonder if the car had had a NASCAR setup on the side that took the hit and had the same results what the discussion would be.

Why isn't anyone bringing up 4130 as an option to the 1020 used? 4130 isn't all that much more expensive anymore. Maybe 1-1.50 pf

Edit... reason I bring up 4130 is because this seems to me to be a case of the materials properities being exceeded during the impact... not necessarily of the "design"

ekim952522000
09-29-2008, 11:22 AM
<----Mike who is very interested in the discussion is getting a cage put into his ITR ITR next month and has to be worried about getting hit by 3200lb Supra's:wacko:

I am thinking that a 3 bar door bar setup plus lower bar is going to be necessary on the drive side.

tnord
09-29-2008, 11:36 AM
Possibility of becoming a spear in the same situation.

I've been toying with going with a 1 bend X lately. Single straight bar ala the traditional X then the second bar bent out around it, then gusseted together.

I have to wonder if the car had had a NASCAR setup on the side that took the hit and had the same results what the discussion would be.

Why isn't anyone bringing up 4130 as an option to the 1020 used? 4130 isn't all that much more expensive anymore. Maybe 1-1.50 pf

Scott -

is 4130 just a type of steel "alloy?" i'm not terribly knowledgeable in this area, but i am interested in this topic as i'll likely be building a new car this winter that should have plenty of room for extra weight in the cage.

is chromoly any stronger than the "regular" stuff? if you were to strategically place some stronger tubing (being chromoly or 4130 or whatever) that might cost and/or weigh more, where would you suggest that be used? the main hoop and the driver door bars perhaps?

ddewhurst
09-29-2008, 11:41 AM
***The bar (as Greg described) sheared, as did all the other failure points, near to, but not at the welds.***

Very ^ interesting. Jake, how far would you remember the failures are with respect to the edge of the welds. Do we know what tube material was used & what weld process was used?

chuck baader
09-29-2008, 11:44 AM
4130 has greater ultimate strength than DOM, but it brakes whereas DOM bends more before it brakes. Chuck

RexRacer19
09-29-2008, 11:48 AM
4130 has greater ultimate strength than DOM, but it brakes whereas DOM bends more before it brakes. Chuck

I would add that the welding process would be more difficult as well. For this application, I think that TIG welding would be the only good way to do it to keep it from becoming too brittle at the joints.

Speed Raycer
09-29-2008, 12:46 PM
(Random ramblings while I'm at work....)

First, I'm not a metalurgist but I did get some sleep last night ;)
2nd, I'm a much bigger fan of 102x in wheel to wheel cages than I am of 4130 due to the nature of the two materials.

It doesn't surprise me at all that the Mild Steel material failed *away* from the welds. The impact exceeded the materials properties. The welds *when done properly (and it sounds like they were well done)* end up being stronger than the base material. Its the nature of the material.

4130's (chromoly) yield (bending) point is greater than 1018's (mild steel) yield point (75kpsi vs 70k). Ultimate strength is 95kpsi vs 82kpsi. It's tensile strength is higher which leads to the "break before bend" reputation. For the same tubing size and thickness, the two materials weigh the same.

There's a ton more work/time involved with using 4130. It likes to be welded slowly. Same joint, a MIG weld might take 2-3 minutes, a TIG joint can take 3x as long. The pre/post weld heat treatment process adds time. I won't get into the debate on whether or not the heat treatment is necessary at our required thickness' nor will I get into the TIG/MIG/OXY debate either. 4130 & 1020 shouldn't really be mixed as the materials "wash" together during the weld making wierd things happen to the material properties of the 1020 tube.

A good free read from our buddy Mr. Smith:
http://books.google.com/books?id=5a8937Pc6uEC&pg=PA63&lpg=PA63&dq=1020+vs+4130+psi&source=web&ots=QzHyqwAj6j&sig=FseF382i4ZqRH1bfCmRpKqvmgRA&hl=en&sa=X&oi=book_result&resnum=8&ct=result#PPA66,M1

I liken 4130/10XX to a Hershey bar. 4130 is a bar kept in the freezer. 1020 is one kept in a cabinet. Feel free to do the experiment on your own ;)

Sandro
09-29-2008, 01:38 PM
The NASCAR style bars add more metal to the area adjacent to the driver, but are generally full of dead load paths. In nearly every example of a NASCAR bar shown in this thread, there is a nice mesh of tubes forming the side impact. BUT, that mesh of tubes gets attached to a single vertical tube in the front, and a single vertical tube in the rear mid-span. When having to take on an impact such as Richie's, The tubes that the NASCAR bars are attached to will be the first to deform/fail in a massive impact. Just like in Richie's crash, they will be in tension, which is less than ideal.

-Jeff

agree with what you are saying, but when I designed mine, I thought that bending, of the main hoop and a pillar bar would allow for some absorption.(the main hoop only has about a 2ft span where it isn't reinforced in another direction, and even less on the a pillar as I have a bar going to the firewall.) If I had added additional bars in line with the nascar bars to say the rear or the opposite b pillar, their would be zero absorption and in a hard blow my brain would probably fly out the passenger window.

My nascar bar also only has two bends( /-----\ ) on each bar not four as I see many do ( _/---\_ ), so a blow on the nascar bar will push the a and b pillars at 45*, not even relying on the welds to hold them in place, cause the bar will be forced into the a and b pillars, as opposed to the bars with four bends that you are now relying on the welds to hold the nascar bar to the pillars, putting the welds in shear when hit. Which as someone mentioned even when the welds are done properly the metal around them ends up shearing.

Please don't think I am trying to say my cage is perfect, just trying to give some insight to the thoughts I put into it, especially as I said my biggest fear is being T-Boned.

I personally think the passenger side should be able to give a little, so it reduces the g load in an accident but on the driver side you don't have that much room for it to give, until the driver begins to be crushed. So as Greg said I think on the driver side you need to accept the higher g load, instead of being crushed. That is also the reason I have a fully bolstered seat to reduce the chance of snapping my neck.

jerestahl
09-29-2008, 01:42 PM
A friend of mine did a steel tubing failure research program 29 years ago. I believe the results were published in Stock Car Racing Magazine at the time. The bottom line he says unless you pre-heat every weld to at least 300 degrees you will have parent material failure when the loads are high enough. I have some frightening photos taken of a SM at Summit Point last year that has multiple tubing failures. The attached photo was my interpretation of how to build some protection into a door bar and to meet the idiotic SCCA 8 point cage attachment rule which is the 1st rule that needs to be changed to improve driver safety.

Dave Patten
09-29-2008, 02:04 PM
Guys,
4130 (chrome moly or for the old timers,”Shelby Tubing”) is stronger than mild steel (1020) but if not properly welded and the welds “normalized” after welding it is significantly weaker than mild steel.

The welds on 4130 steel need to be normalized once completed. Basically this means the whole weld area must be heated and allowed to cool slowly, all at the same rate. This is very hard to do and something an average hobbyist does not have the talent to do. I never have used and will not use 4130 in anything structural that I weld just because I lack the expertise required to do the job properly.

On another note, welding creates a change in the metallurgic structure of the metal from the heat of welding. The fact that the weld joints didn’t fail in Richie’s cage is a good sign that it was properly welded. The breaks adjacent to the welds are as a result of the weld processes and not a fabrication failure. These weak points are just a matter of the process, nothing more. To limit the amount of heat during the welding process, tight fitting tube joints are needed. Filling gaps with filler rod or MIG wire will make the metal adjacent to the weld joint even weaker because of the added heat it introduces.

Also when doing a NASCAR style door bar, if you stagger the vertical tubes so they are offset from the bars above and below the whole assembly will be stronger because the weld process heat will be dispersed on the horizontal tubes and not concentrated top and bottom at the same point as when they are directly aligned. See this article in Stock Car Racing magazine http://tinyurl.com/544ogk

RexRacer19
09-29-2008, 02:07 PM
Please don't think I am trying to say my cage is perfect, just trying to give some insight to the thoughts I put into it, especially as I said my biggest fear is being T-Boned.



I don't want to come across as a know-it-all either. As I have told some others, there is more than one way to skin a cat when it comes to these things. Both design types have merits and drawbacks. The important thing is to build/buy a cage that YOU will feel safe in and meets the standards of the GCR. These discussions are generally healthy and provide some insight for folks going through that process.

spnkzss
09-29-2008, 03:46 PM
I don't want to come across as a know-it-all either. As I have told some others, there is more than one way to skin a cat when it comes to these things. Both design types have merits and drawbacks. The important thing is to build/buy a cage that YOU will feel safe in and meets the standards of the GCR. These discussions are generally healthy and provide some insight for folks going through that process.

I have to agree. I find it humorous that the first cage I had in my C car worked just how I needed it to. Then when I built the A car I had a whole different mentality of what I that was right and modified accordingly. THen I saw what you and Xian were doing and have another completely different mentality. :shrug:

Xian
09-29-2008, 07:12 PM
I have to agree. I find it humorous that the first cage I had in my C car worked just how I needed it to. Then when I built the A car I had a whole different mentality of what I that was right and modified accordingly. THen I saw what you and Xian were doing and have another completely different mentality. :shrug:

Very true... I saw some nifty things on Jeff's cage that I liked :)

FWIW, back to the question about side impact penetration... here is "my" solution to it:


http://www.raceconover.com/images/shipp/cage7.jpg

By "my" I mean "Chris Schimmel at Competition Cages" ;) Similar to Kirk's cage, my door bars project out into the door cavity and should end up in compression in the instance of a side impact.

Christian

Racer Chris
09-29-2008, 08:14 PM
...
Honestly, Chris, there was really nothing you could have done differently to the passenger side to affect a significantly different result; it was that hard a hit.
...
In the past, the simple X door bar design was not allowed in any SCCA road race car. The reason was that the perception of greater strength from this design is inaccurate. As noted, the door bars failed at the weakest point - a single bar crossing the center of the assembly. The rule should never have been changed, or at least only allowed such designs if significant reinforcements were added accross the weak point. I think the rule was probably changed due to lobbying of competitors who already had such door bars that had been overlooked for years, and one day ran afoul of a wise tech inspector who gave them grief. :shrug: The X design may add a high level of stiffness to the chassis but doesn't provide good intrusion protection by itself.
Adding "taco" gussets would have significantly reduced the likelihood of complete failure of the door bar assembly, but only if the gusset material was in the range of .080" thick, similar to the minimum welded mounting plate thickness. An assembly with such gussets would have provided appropriate g-force attenuation, which is what we want to happen. The "taco" gussets shown with bell mouth lightening holes are not sufficient IMO, since the material thickness is not suitable for the forces involved in what happened to RH's car.

Knestis
09-29-2008, 08:25 PM
More examples, all from Euro rallying...

http://www.it2.evaluand.com/gti/downloads/Kaari1_iso.jpg

This was the primary inspiration for the Pablo II-spec cage

http://www.it2.evaluand.com/gti/downloads/Polo4-rollcage-4.jpg

This one has an additional bar that I wish in hindsight I'd added - from the rear terminus of the top door bar back to the strut tower.

http://www.it2.evaluand.com/gti/downloads/photo9gEwTF.jpg

A US-prepared rally car, pre-gussets.

K

rsportvolvo
09-29-2008, 09:15 PM
For folks looking for impressive safety cages for production based cars I suggest looking at the Australian V8 SuperCar roll cages. There is a lot of good ideas, one being cross bracing the floorpan. We all assume the floorpan is stiff and only really pay attention to the side and top sections.

I keep a file on roll cages that I see pics of on the net. Many of them have influenced the design on my Volvo 240 (cage goes in this winter, finally).

rsportvolvo
09-29-2008, 09:21 PM
The attached photo was my interpretation of how to build some protection into a door bar and to meet the idiotic SCCA 8 point cage attachment rule which is the 1st rule that needs to be changed to improve driver safety.

I couldn't agree more. I'm not sure what the logic is with limiting the number of roll cage attachment points. It only seems to limit safety by reducing load paths.

Greg Amy
09-29-2008, 10:07 PM
In the past, the simple X door bar design was not allowed in any SCCA road race car.
Chris, I don't necessarily disagree with your technical points, but you are mistaken on the history of the rules. Prior to the 2007 change there was not even a requirement for a right-side tube. This is from the 2005 GCR spec for Showroom Stock:
A side tube connecting the front and rear hoops across the driver’s door opening is mandatory and across the passenger’s door opening is allowed (recommended).
It wasn't until the 2007 GCR that passenger side bars were mandated:
Effective 1/1/07 and permissible 10/1/05 two (2) side tubes connecting the front and rear hoops across both door openings are mandatory.
Finally, it wasn't until the 2008 GCR (per a 2007 Fastrack) that x-bars were approved as "two side tubes", precisely for the reason you describe (others had already gone beyond the prior rules requirements and built an x-bar where none was required, and didn't want it to be made illegal) :
NASCAR-style side protection or one bar bisecting another to form an “X” is permitted.
Greg

tnord
09-29-2008, 10:26 PM
http://heddev.com/miata/product_info.php?cPath=21&products_id=35&osCsid=b354913a13d93cf9668b15f21405e1d9

i'd be most interested in a critique of this cage. it's the only "cage kit" i'm considering for my next car.

Sandro
09-29-2008, 11:38 PM
Solution:

mount a F1 monocock within an 8pt cage, its IT legal too

6. Any number of additional tube elements is permitted within the boundaries of the minimum cage structure.

http://i48.photobucket.com/albums/f231/Kanoa9321/rabbitmonocock.jpg

RexRacer19
09-29-2008, 11:54 PM
Since we are full on show and tell mode now...here are my last two IT car cages.

This is from my former, would be ITA CRX now driven by AJ Nealey.

http://www.project-seven.goof.com/images/Dscn1646.jpg

http://www.project-seven.goof.com/images/Dscn1648.jpg

http://www.project-seven.goof.com/images/Dscn1652.jpg

RexRacer19
09-29-2008, 11:55 PM
Had to split this up because of image rules...

This is the ITB Civic that I am currently building for myself.

http://www.project-seven.goof.com/images/DSCN3138.JPG

http://www.project-seven.goof.com/images/DSCN3141.JPG

http://www.project-seven.goof.com/images/DSCN3144.JPG



I was happy with, and felt perfectly safe in the CRX cage. I wanted to try some things differently on the new car and made some changes in the door bar and rear bracing areas to both add some extra strength and maybe loose a little weight in the right places. My philosophy has always matched what the pictures that Kirk posted of the euro rally guys. (The GT cars are similar too). That is, to try my very bestest to make all the tubes connect at nodes that are supported by at least one tube in another plane with no dead load paths. Also, I feel that the cage itself should be its own structure that can completely be strong on its own without being welded into the car. That way, any energy from an impact, regardless of where it occurs, gets distributed throughout the cage and it's mounting points. This is easy to do in the rear half of the car, but it gets hard up front due to the rules as they are written. The cages are safe, I think, but could be a little better up front with more attachment points.

lateapex911
09-29-2008, 11:58 PM
I couldn't agree more. I'm not sure what the logic is with limiting the number of roll cage attachment points. It only seems to limit safety by reducing load paths.

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

RexRacer19
09-30-2008, 12:01 AM
http://heddev.com/miata/product_info.php?cPath=21&products_id=35&osCsid=b354913a13d93cf9668b15f21405e1d9

i'd be most interested in a critique of this cage. it's the only "cage kit" i'm considering for my next car.

Travis,

I am a fan of that cage kit. Having done a Miata myself, I really like how it mounts in and the configuration of the bars. I would maybe customize the driver's side door bar to suit me a little, but would hold judgement until I had all the pieces sitting in front of me.

$.02

ScottL
09-30-2008, 12:04 AM
This may be a naive point, but does everyone here expect that it is possible to build a cage that can protect an occupant from a high speed side collision?

Isn't the primary purpose of a roll cage to defend against a rollover? I know it's a cage, but the strength is in the hoops (and their supports), right? Unlike the front and rear of a car, the sides have almost zero deformable mass to protect the occupants. An incoming car doesn't have far to go (nor much mass to move) before intruding into the cockpit.

Does the number of bars or their arrangement matter much in this kind of crash?

Dave Patten
09-30-2008, 07:25 AM
I know the focus in the thread has been on effective side protection, but one of the areas that most road race cage designs seem to not offer is proper forward area roll protection on cars with a highly raked windshield. The rally cages pictured have a tube added into the side hoop from the top of the A pillar to the forward floor pad. This adds tremendous strength to the cage in a roll over or impact on the leading edge of the roof.

The SCCA cage design requires the side (or front) hoop follow the A pillar. Most modern cars have such a low windshield rake that it gives limited support at the A pillar/roof intersection. This added tube in the rally cage stiffens this point tremendously and is an addition that is worth considering.

DoubleXL240Z
09-30-2008, 07:50 AM
Travis, I installed the Miatacages.com kit in a customers car, the fit and design were done very well. I was afraid that it would take more work to make the kit fit than actually bending it myself but it worked perfectly. I'll look to find some pics of it installed. definitely 2 thumbs up for the do it yourselfer. I average about $1800 for a cage so its not that far off from a custom cage though.

Knestis
09-30-2008, 08:25 AM
...and i forgot to mention that when i put in my seat, I put it as far to the right as possible - gained about 3" in additional distance from danger, which might someday be very appreciated.

K

Wreckerboy
09-30-2008, 08:29 AM
http://heddev.com/miata/product_info.php?cPath=21&products_id=35&osCsid=b354913a13d93cf9668b15f21405e1d9

i'd be most interested in a critique of this cage. it's the only "cage kit" i'm considering for my next car.

Travis - I looked at that cage when I had my car done by Chris last year. I'll be the nay sayer here on the Miatacage kit, but from a space usage viewpoint only. If you are tall the placement of the main hoop on that cage (just in front of the "parcel shelf") eats up a ton of space inside the car. I'm 6'2" and could not get sufficient head and legroom in any of the cars I say in with that cage installed.

As noted above, the cost difference between that and a custom cage is so little as to be negligable.

tnord
09-30-2008, 09:10 AM
Travis - I looked at that cage when I had my car done by Chris last year. I'll be the nay sayer here on the Miatacage kit, but from a space usage viewpoint only. If you are tall the placement of the main hoop on that cage (just in front of the "parcel shelf") eats up a ton of space inside the car. I'm 6'2" and could not get sufficient head and legroom in any of the cars I say in with that cage installed.

As noted above, the cost difference between that and a custom cage is so little as to be negligable.


i wondered about that. i'm 6'3'' so i'd likely have the same problem as you, but i'd never sat in one so it was hard to say.

looks like i'll be going the custom route.

Racer Chris
09-30-2008, 09:24 AM
Chris, I don't necessarily disagree with your technical points, but you are mistaken on the history of the rules. Prior to the 2007 change there was not even a requirement for a right-side tube. Greg
...
Going back a littler further in history...
At one time a tech inspector would look at all the roll cage rules if he saw an installation exceeding the mandate for a particular car. For instance - wrt the SS side protection - any additional bars would have to conform to the GT and Production rule that a horizontal bar and a diagonal bar bisecting the space below the horizontal were required. Two fully independent bars is stronger than the simple X. Adding a couple of vertical stringers would tie the two together very effectively.

Andy Bettencourt
09-30-2008, 10:25 AM
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.



Not quite as described here...Hunter was still moving and was not off course during impact...only one car got by - and that was BARELY...but the video is proof of the intensity of the hit.

http://www.youtube.com/watch?v=eDpUjcQe92c

Jeremy Billiel
09-30-2008, 11:33 AM
What happened to the video?

Knestis
09-30-2008, 11:50 AM
Wow. Don't blink.

K

Greg Amy
09-30-2008, 12:02 PM
In all fairness to the Mee-Otter, I don't know that I would have done any better...yes, that hurt to write, but I'll be OK...

Racer Chris
09-30-2008, 12:09 PM
It looked like he had time to slow way down, so the impact was less than 50mph even.
Too bad he tried to follow the first car through instead of heading for where the spinning car had been.
IMO this certainly proves the gross inadequacy of the simple X door bar design!

RexRacer19
09-30-2008, 12:43 PM
IMO this certainly proves the gross inadequacy of the single X door bar design! When built in a single plane without any gussets added.

I had to add to that statement. As Greg stated earlier, the tubes will be put in tension if the X is formed in a single plane. They can be designed and built better. For the passenger side of the car, I honestly don't think it needs to be bomb proof. There is a lot of room between that door and the driver. If you have to add ballast to make weight...it is a good place to put it though...

After looking at that video, one has to ask. If that hit were on the driver's side, and let's say the side impact protection was two complete "parallel" bars with maybe three vertical stringers tying them together, would the driver have come out unhurt?

Racerlinn
09-30-2008, 12:49 PM
Racin deal. Zigged when he should have zagged.

tnord
09-30-2008, 02:27 PM
comments please. this would be fore a miata, with main hoop mounted on the package shelf, and the proportions aren't exactly right in my little drawing. i don't think the distance from the rearward stringer to the main hoop would be that far.

bold lines indicate attachment/welding points.

Greg Amy
09-30-2008, 02:58 PM
...a miata, with main hoop mounted on the package shelf
A good idea, leaving plenty of space for a 6-foot + driver:

http://www.kakashiracing.com/images/DSCN3703.JPG
http://www.kakashiracing.com/images/DSCN3702.JPG

http://www.kakashiracing.com/forsale/sm.html

tnord
09-30-2008, 03:07 PM
or 6'3'' driver.

any reason you chose to go in front of the dash with the a-pillar bar?

timrogers
09-30-2008, 03:21 PM
What happened to the video?
Works fine for me.

Greg Amy
09-30-2008, 03:25 PM
any reason you chose to go in front of the dash with the a-pillar bar?
Simply just for ease of build and better leg side-hit protection. Descending side bars were for ease of ingress/egress.

Wreckerboy
09-30-2008, 04:33 PM
or 6'3'' driver.

any reason you chose to go in front of the dash with the a-pillar bar?

Travis - the cage Chris put in my car attaches at the front of the car in a fashion very similar to what you describe. As you probably know, dash removal is not that difficult. (Though I freely admit I paid Chris to do that for me as well.) The advantages are increased access area - the downtubes on mine are right in line with the dead pedal on the driver's side. The only downside is that the fuse box approaches "genuinely insane" in terms of access, but it is worth it in my eyes.

Remember, not too long ago there was a debate about the forward attachment points (at least in the northeast) and whether it was legal to attach them to the brace that runs behind the dash. Ultimately this was ruled illegal - search over at the Daniels website on the subject and I think DDG may have been involved. (I know you can't post and ask over there! :happy204:)

seckerich
09-30-2008, 04:36 PM
comments please. this would be fore a miata, with main hoop mounted on the package shelf, and the proportions aren't exactly right in my little drawing. i don't think the distance from the rearward stringer to the main hoop would be that far.

bold lines indicate attachment/welding points.

A cage like yours is what started a huge debate on other sites about door bars. Cars were sent home because the door bar did not connect the main hoop and down tube. My read is that a tube that goes to the attachment point for required element is same as going to that tube. The lower tube in the door counts as a seperate attachment point unless you stretch the plate for the main hoop down the allowed 15 inches. Not something you should get grief over but it is not "technically" legal. I had a car come through with your style cage and we added a short piece of tube from the lower bar to the hoop. Rules do not say "continuous" door bar. :rolleyes:

DoubleXL240Z
10-01-2008, 08:32 AM
Travis,
I believe as well that your design would not be legal, nor would I think that would be a safer alternative. I believe the way to the strongest intrusion protection would be to have your door bars attached to the main hoop and a-pillar. As it sits now the door bar is attached to sheet metal at the rear. Think monocoque here!! I also would not do a main hoop on that parcel shelf. Drivers side impact at rear wheel and there is nothing preventing a left rear tire from being punched into your kidney etc. or the whole car coming through. Again, try to think monocoque. The high main hoop route starts protection 2 1/2 feet off the ground and your sitting under it. Where most bumpers are flying around. Honestly if you don't fit with a safe cage try a different car. I'm 6'4" so I'm in familiar situations.

tnord
10-01-2008, 09:08 AM
Travis - the cage Chris put in my car attaches at the front of the car in a fashion very similar to what you describe. As you probably know, dash removal is not that difficult. (Though I freely admit I paid Chris to do that for me as well.) The advantages are increased access area - the downtubes on mine are right in line with the dead pedal on the driver's side. The only downside is that the fuse box approaches "genuinely insane" in terms of access, but it is worth it in my eyes.


meh. i never had to get at it once in the 5 years i had my last car. i'm not too concerned about that.



Remember, not too long ago there was a debate about the forward attachment points (at least in the northeast) and whether it was legal to attach them to the brace that runs behind the dash. Ultimately this was ruled illegal - search over at the Daniels website on the subject and I think DDG may have been involved. (I know you can't post and ask over there! :happy204:)

you mean that stock tube that runs behind the dash? i wasn't planning on attaching to it, but replace it. not sure if IT and SM rules differ here, but i thought that was legal. no, i don't remember the debate, and i can't search on that site either. not that that site has much of anything useful going on anymore anyway.....

tnord
10-01-2008, 09:21 AM
A cage like yours is what started a huge debate on other sites about door bars. Cars were sent home because the door bar did not connect the main hoop and down tube. My read is that a tube that goes to the attachment point for required element is same as going to that tube. The lower tube in the door counts as a seperate attachment point unless you stretch the plate for the main hoop down the allowed 15 inches. Not something you should get grief over but it is not "technically" legal. I had a car come through with your style cage and we added a short piece of tube from the lower bar to the hoop. Rules do not say "continuous" door bar. :rolleyes:

that's a good idea steve. with the 'X' bar design i feel like it leaves a rather large "gap" down at the bottom of the door by the rocker. that straight piece of bar with the separate attachment point was just my attempt at solving that.

i'm thinking your statement about "a tube that goes to the attachment point for a required element is same as going to that tube" is in reference to the bottom of the two 'X' bars, or the middle of the three? others have interpreted the rules in the same way, as the NASCAR bars in my last car had the upper tube attached to the main hoop itself, and the lower bar was attached to the plate that the main hoop was attached to.

were either one of these drawings how you "solved" that problem?

spnkzss
10-01-2008, 09:23 AM
that's a good idea steve. with the 'X' bar design i feel like it leaves a rather large "gap" down at the bottom of the door by the rocker. that straight piece of bar with the separate attachment point was just my attempt at solving that.

i'm thinking your statement about "a tube that goes to the attachment point for a required element is same as going to that tube" is in reference to the bottom of the two 'X' bars, or the middle of the three? others have interpreted the rules in the same way, as the NASCAR bars in my last car had the upper tube attached to the main hoop itself, and the lower bar was attached to the plate that the main hoop was attached to.

were either one of these drawings how you "solved" that problem?

Just FYI. If it's strictly IT, I don't know about SM, IT allows 144 sq in now with no side longer than 15". And yes the second picture that is another attachment point, unless you can take advantage of the previously mentioned rule.

tnord
10-01-2008, 09:30 AM
Travis,
I believe as well that your design would not be legal, nor would I think that would be a safer alternative. I believe the way to the strongest intrusion protection would be to have your door bars attached to the main hoop and a-pillar. As it sits now the door bar is attached to sheet metal at the rear. Think monocoque here!! I also would not do a main hoop on that parcel shelf. Drivers side impact at rear wheel and there is nothing preventing a left rear tire from being punched into your kidney etc. or the whole car coming through. Again, try to think monocoque. The high main hoop route starts protection 2 1/2 feet off the ground and your sitting under it. Where most bumpers are flying around. Honestly if you don't fit with a safe cage try a different car. I'm 6'4" so I'm in familiar situations.

i'm no engineer, so i don't know how well i could argue that attachment at the package shelf is equally as safe as at the "rocker." all i know is that it's where my last cage was attached, where Greg's was attached, and where countless other miata cages are attached. i can't see how it's any worse than the flat plates that mount strictly to the floor pan up front (also legal).

i also know that my car suffered about the largest rearward impact you can have in a miata, with the cage attached at the parcel shelf, and faired pretty well. i think the tire was knocked into the back of the seat, but changing the location of the main hoop wouldn't have prevented it.

tnord
10-01-2008, 09:38 AM
Just FYI. If it's strictly IT, I don't know about SM, IT allows 144 sq in now with no side longer than 15". And yes the second picture that is another attachment point, unless you can take advantage of the previously mentioned rule.

thanks Rob. so something more like this?

PS - this has been a very helpful discussion for me at least. Thanks everyone.

Speed Raycer
10-01-2008, 10:05 AM
Travis... with the 144" & 15" long rule, you can get all the way down to the corner brace from the package shelf with sq.in. to spare. There's a mass of structure in that whole area.

Also, ideally you want the A pillar brace to head to the node down at the front pad... sometimes you have to depart from the ideal to make things work, but you have some room there... basically you're duplicating the down bar in tGA's Miata cage.

I don't think that eliminating the dash tube is legal at all but that's a different thread ;)

tnord
10-01-2008, 10:23 AM
you're right scott.....i guess i'd be just adding a dash bar rather than replacing one.

spnkzss
10-01-2008, 10:33 AM
thanks Rob. so something more like this?

PS - this has been a very helpful discussion for me at least. Thanks everyone.

That's better, I would just have to go back and reread the rule about door bars attaching to the rear hoop. That should meet legality, but I know it's better than the picture previously.

JIgou
10-01-2008, 10:47 AM
Having removed a package shelf-mounted cage from a Miata, I can attest to the fact that there's a whole bunch of metal in that area.

magnetic1
10-02-2008, 12:37 AM
Hopefully Richie will end up posting some pictures so we can learn from this.

A big factor also is how the X is tied into the rest of the cage.

I really wanna put in some of that Impaxx foam, but it is $$$!

http://i20.ebayimg.com/08/i/001/0f/6e/620b_3.JPG

lateapex911
10-02-2008, 08:41 AM
Trav, if there's footspace, maybe adding some triangulation might help direct and distribute forces like:

tnord
10-02-2008, 08:53 AM
there's probably not.

i guess i could take out my dead pedal and just use that bar you suggested as a resting place? i might have to talk to my cage builder about that.

spnkzss
10-02-2008, 09:36 AM
Trav, if there's footspace, maybe adding some triangulation might help direct and distribute forces like:

I find that statement interesting. Technically is it legal?


9.4.C.3 Cars competing in Improved Touring, Showroom Stock, Spec Miata, and Touring may extend one tube, from each front down tube, forward to the firewall but not penetrating the firewall.

Now I agree that is nit picking and should be allowed, but is it? :shrug:

Speed Raycer
10-02-2008, 09:40 AM
Trav, if there's footspace, maybe adding some triangulation might help direct and distribute forces like:

Read the new rules on the firewall tubes? ;) The new wording limits us to one tube. Something along the lines of may add one tube connecting the cage to the firewall. Some read it as only one tube, others read it as only 1 tube can connect to the firewall and other tubes are allowed as long as they don't connect to the firewall. IMO, goofy wording with a slight change from the AS rules right above it.

:D Spanky types faster than I do!

tnord
10-02-2008, 09:51 AM
fixed.

eprodrx7
10-02-2008, 10:47 AM
From watching the video I would have to say that this is the definition of "target fixation". Meaning that the driver was looking at the spinning car and not the clear road behind Richie's car. You can hear the driver getting out of the gas at the apex of the corner so he is aware of the trouble ahead but the mistake is that he let his instinctual action of looking at the spinning car prevent him from seeing the clear road to the left. So at reduced speed he drives off line toward the spinning car. The car will always go where you are looking. That's why the cars at the junk yard all have the telephone pole dead center on the hood ornament, That is what the driver was looking at. I applaud the driver for being aware as early as he was. In all the time that I have spent instructing, overcoming instinct is the hardest thing to do. I'm glad that everyone is OK and I think that as a cage builder and driver I have learned from the incident. It is a shame that it came at such expense. :(

RexRacer19
10-02-2008, 11:50 AM
Read the new rules on the firewall tubes? ;) The new wording limits us to one tube. Something along the lines of may add one tube connecting the cage to the firewall. Some read it as only one tube, others read it as only 1 tube can connect to the firewall and other tubes are allowed as long as they don't connect to the firewall. IMO, goofy wording with a slight change from the AS rules right above it.

:D Spanky types faster than I do!

Yes, it says only one tube...but gussets are allowed and encouraged. Gussets can be tubes.
:)

spnkzss
10-02-2008, 02:27 PM
Yes, it says only one tube...but gussets are allowed and encouraged. Gussets can be tubes.
:)

Appendix B.

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

I guess the loop hole is generally?

lateapex911
10-02-2008, 04:58 PM
Forgive me, as my GCR is in the shop, but isn't there a rule allowing tubes of other dimensions within the required tubes?

tnord
10-02-2008, 05:13 PM
Forgive me, as my GCR is in the shop, but isn't there a rule allowing tubes of other dimensions within the required tubes?

i dunno....sounds light Twilight Zone shit to me.

JoshS
10-02-2008, 06:08 PM
Forgive me, as my GCR is in the shop, but isn't there a rule allowing tubes of other dimensions within the required tubes?
Yes:


G.6. Any number of additional tube elements is permitted within the boundaries of the minimum cage structure. Such tube elements may pass through any mandatory or optional bulkhead or panel separating the driver/passenger compartment from the trunk/cargo area/fuel tank/fuel cell area provided the bulkhead is sealed around such tube elements.


Related, in the previous major section:


F.3. The required tubing elements must meet the material minimums
set forth above. Optional tubing elements may be any size.

Also note item 5:


G.5. It is recommended that gussets be used at all joints. In Improved Touring, Showroom Stock, and Spec Miata a maximum of two gussets per joint are allowed and must be no thicker than .125”.

Seems like a lot of people here are recommending an X bar with four gussets. I don't think that would be legal.

lateapex911
10-02-2008, 06:29 PM
That seems like there is considerable "room" to do a lot, as long as the attachment point rules are honored.

I'd say that an extra bar as shown in my little quick drawing would be fine, although I'd attach it to the tubes at either end to minimize debates.

Speed Raycer
10-02-2008, 06:46 PM
Seems like a lot of people here are recommending an X bar with four gussets. I don't think that would be legal.

There are 2 joints in the traditional 3 bar X. You get 2 gussets per joint

CRallo
10-02-2008, 07:09 PM
From watching the video I would have to say that this is the definition of "target fixation". Meaning that the driver was looking at the spinning car and not the clear road behind Richie's car. You can hear the driver getting out of the gas at the apex of the corner so he is aware of the trouble ahead but the mistake is that he let his instinctual action of looking at the spinning car prevent him from seeing the clear road to the left. So at reduced speed he drives off line toward the spinning car. The car will always go where you are looking. That's why the cars at the junk yard all have the telephone pole dead center on the hood ornament, That is what the driver was looking at. I applaud the driver for being aware as early as he was. In all the time that I have spent instructing, overcoming instinct is the hardest thing to do. I'm glad that everyone is OK and I think that as a cage builder and driver I have learned from the incident. It is a shame that it came at such expense. :(

based on initial reports I believed that had indeed been the issue...

after seeing the video it is VERY CLEAR that is not the case. Justin drove offline AWAY from the spinning car and the car came to him... when the spin began there was no clear road to the left and while (most likely)locked up the spun car was still moving down the track. it was not until the last second that the spun car came across the track. I respect the credit that you gave the driver but I don't think you are giving him enough... You obviously are very experienced and knowledgeable but I ask that you watch the video a couple more times. A more experienced driver may have seen the spinning car change direction sooner or better been able to anticipate it but I believe that Justin did as well as anyone could expect avoiding the spinning car.:eclipsee_steering:

rsportvolvo
10-14-2008, 10:25 PM
Has anyone looked into mounting the seat to the roll cage? This is required for FIA roll cages in the WTCC. The best way to describe it is in this picture

http://polestarclub.iweb.se/archive/dokument/bilen_1024_768.jpg

This is an illustration of the Prodrive designed roll cage for the ETCC/WTCC/STCC Volvo S60. See how the seat is attached to 2 tubes mounted laterally to a longitudinal rocker panel tube. Also note the vertical tube connecting the rocker tube to the x-brace intersection.

I believe the design intent is to created a complete tubing safety cage that the driver is enclosed in. This is the design approach I would prefer to take vs. assuming the floor pan is stiff enough to protect me. Not to mention the driver's seat will most likely shift with the side entry protection bars.

Greg Amy
10-14-2008, 10:40 PM
Has anyone looked into mounting the seat to the roll cage?
Unfortunately, it is contrary to the IT regulations (i.e., "mounting points").

GA

rsportvolvo
10-15-2008, 12:14 AM
Unfortunately, it is contrary to the IT regulations (i.e., "mounting points").

GA

So is having more than 2 gussets per joint. That doesn't mean it's in the best interest of the driver's safety. It seems that keeping costs low takes precidence over safety in the Showroom Stock based classes. Not sure how a few extra tubes and some sheet metal gussets significantly increase cost? But I digress. The regulations are the rules we have to live by until changes are deemed necessary.

trhoppe
10-15-2008, 12:51 AM
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
http://www.tomhoppe.com/misc_pics/seat_mount2.jpg

front
http://www.tomhoppe.com/misc_pics/seat_mount4.jpg

-Tom

JoshS
10-15-2008, 12:58 AM
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
10-15-2008, 01:12 PM
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
10-15-2008, 01:37 PM
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. :shrug:

Dave Patten
10-15-2008, 02:18 PM
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
10-15-2008, 02:45 PM
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.
:023:


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....:shrug:

rsportvolvo
10-15-2008, 03:38 PM
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
10-16-2008, 08:10 AM
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
10-16-2008, 08:22 AM
...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
10-16-2008, 08:52 AM
......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
10-16-2008, 09:36 AM
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
10-16-2008, 10:15 AM
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
10-16-2008, 10:24 AM
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
10-16-2008, 10:35 AM
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
10-16-2008, 11:52 AM
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
10-16-2008, 12:18 PM
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
10-16-2008, 01:08 PM
Andy, is that the 04? Everyone OK?

Andy Bettencourt
10-16-2008, 01:55 PM
No, that is the #91 rental car. Driver is fine.

RexRacer19
10-16-2008, 02:36 PM
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
10-16-2008, 03:04 PM
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.

Greg Amy
10-16-2008, 03:29 PM
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
10-16-2008, 03:41 PM
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
10-16-2008, 03:52 PM
Needs to be exorcized!

Greg Amy
10-16-2008, 03:55 PM
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
10-16-2008, 04:31 PM
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
10-16-2008, 08:00 PM
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
10-16-2008, 09:16 PM
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
10-17-2008, 09:12 AM
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
10-17-2008, 09:57 AM
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
10-17-2008, 10:12 AM
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
10-17-2008, 10:13 AM
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
http://www.tomhoppe.com/pictures/2008_03_05_Race_Car/IMG_8035.jpg

Drivers side nascar bar and in the top right of the picture, the bar running along the bottom of the passenger side X bar
http://www.tomhoppe.com/pictures/2008_03_05_Race_Car/IMG_8041.jpg

-Tom

Greg Amy
10-17-2008, 11:03 AM
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
10-17-2008, 11:28 AM
>> ...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
10-17-2008, 12:26 PM
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
10-17-2008, 01:48 PM
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
10-17-2008, 02:08 PM
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
10-17-2008, 03:10 PM
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
10-17-2008, 03:42 PM
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
10-17-2008, 03:50 PM
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
10-17-2008, 03:56 PM
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

Knestis
10-17-2008, 03:57 PM
>> Dang tube has the potential to go THROUGH the driver.

Ooooh! You could take a core sample, count the rings, and figure out how hold the driver is!

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

Take a look again at what we did. We retained enough room for the door glass on my Golf, although we have subsequently removed it under the "NASCAR door bar" allowance. We also did NOT gut the door, and we run the stock interior panels, to put more crushable stuff between the drivers and danger.

K

Speed Raycer
10-17-2008, 04:26 PM
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.

And a NASCAR style bar also has enough material to potentially to the same thing. The problem is that the impacts are exceeding the materials properties -even when installed properly (proper materials, joint prep, gap, penetration etc). Not that I'd like to see it anytime soon, but I'd like to see how a Nascar style bar would have faired given the same impacts.

Add the reinforcement plates to the X's and the potential is still there for the "Big One" BUT now two tubes will have to have to have their limits exceeded as you're still going to have the same impact force and potentially the same HAZ on the tube. I'm not entirely sure that an additional sill bar would help in the case of these types of hits as the rockers seem top be coming through pretty much unscathed.

I personally am not a big fan of the two bent bars as an X simply because there's enough material to flip inward ... I think someone mentioned like a sharks mouth earlier.. allowing the other car to enter into the cage.

From a builders perspective, if you try to offset the HAZ effect by offsetting the split bars, suddenly your labeled as a hack fabricator because you "can't build a proper X bar". Try to add the proper gusset to a 3 bar X and the customer screams about the 3 hours of labor it took to do it. Suggest an X AND a NASCAR style bar then people are concerned about too much weight as well as cost. Do a traditional "ladder" style doorbar and your back at the hack fabricator status cause you didn't do the cool X with the stamped gussets....

The wording on the rule needs to be well done so as not to limit the builders like the 7th/8th point rule has done. While you're at it, how about adding a provision to go through the B pillars ala NASA's rule so we can put an end to the S bends that are so popular in the NASCAR bars.

trhoppe
10-17-2008, 05:03 PM
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.

Correct. But the tube running along the bottom is the "2nd" tube. At least I seem to think so.

-Tom

Streetwise guy
10-17-2008, 11:09 PM
Just to chime in late in the game, My belief is the x without overlapping the two tubes is really just one tube, and should be treated as such. I have done lots of nascar bars for both roadrace cars and for our local ministock class, and I think the failure point will just move downstream, so to speak,if the doors are built sturdy enough. Our ministock rules require 3 bars drivers side, plated from sill to top bar with 12 guage, creating a very heavy, very strong assembly which is still attatched to the body of the car by two tubes welded to an assembly of 22 guage tin. I always spend almost half of the time and effort in caging a car in getting the mounting plates installed and welded to as many different planes as I can manage. I see cars in every class at every type of race I go to that have a lovely looking cage or roll bar which is not attatched to the car well enough to keep it from moving under any impact.

This has been an excellent thread, with lots of good ideas brought up. I think, though, it boils down to racers remembering, or choosing to believe, that at some point their incredible talent is going to let them down, and that cage you cheaped out on, or tried to save weight on, or figured you could do yourself with that 110v welder from Harbor Freight, is the only thing between you and a fender shoved firmly up your nether regions.:unsure:

DoubleXL240Z
10-18-2008, 08:00 AM
I've got to post again!!
First, as a cage builder I agree with both Scott and Streetwise(don't see/know your name) many drivers don't want to spend the money or weight to do it right. Nascar style bars will be stronger than an x. 3 bars will be stronger yet.
But, let me digress for a minute. Half of this thread is people trying to build the strongest cage possible. The other is drawings of door bars that are trying to cheat the "physics" at work in a crash, while being legal. and trying to put a 6foot plus driver in a 5 foot something car. Sorry Travis!
The simplest way to figure this out is too look at a car that is almost designed from the start for side impact and that is a stock car. 3 or even 4 door bars are the norm. Also starting a main hoop halfway up the drivers back is not safe. It should start at the floor, and have a cross bar as close to the floor as poss. parallel with the belt bar. Try to build as close to 360 degrees around the driver as possible.
Double door bars with a third made out of 1.50x.063 would meet the GCR and only add about 5 lbs to that side. Additional tubes do not have to meet minimum dimensions. Also a petty bar from the center of the belt bar to the base of pass. side a-pillar would "help" keep that bar from caving in on a right side impact.

rsportvolvo
10-22-2008, 09:49 PM
I recently stumbled across this. For those looking for additional ideas please see the BMW E36 Super Touring car pictures located here:

http://www.m42club.com/forums/showthread.php?t=4749

This car was designed and built at the pinnacle of Touring Car racing. The rollcage picks up every key suspension point and the load paths are such that the tubes are not in bending (as much as possible). The only addition I would possibly make is a Petty bar from the top of the main hoop above the driver's head to the bottom of the passenger side down tube (i.e. base of A-pillar tube). Volvo used this type of Petty bar on the 850 Super Tourer.

rbucchino
10-23-2008, 09:29 AM
These crashes both happened in the last two weeks. The "X" design split just like Richie's, the simple NASCAR design held! Althouth I would not recommend that simple of a design, it did it's job. There was also significant damage to the rest of the chassis, it was deemed repairable.

Speed Raycer
10-23-2008, 09:53 AM
Sorry.. apples to oranges. Same speed, angles of both cars, etc? Doesn't appear to be. I see the rocker is still intact in the Nascar bar... the rocker's demolished in the X bars exterior pic.


Althouth I would not recommend that simple of a design, it did it's job. And so did the X bar. The job of the safety cage is not to save the chassis. AGAIN material properties can be surpassed no matter what the design is and how well it was designed/installed.
http://www.improvedtouring.com/forums/attachment.php?attachmentid=379&d=1224172337

http://www.improvedtouring.com/forums/attachment.php?attachmentid=392&d=1224768500

rbucchino
10-23-2008, 10:19 AM
The impact was very similar. The lack of damage to the rocker is due to the bars absorbing most of the impact and preventing intrusion. I think this is what we all are hoping for. Check out the photo below of where the energy went, the front was similar. I am just hoping we all can learn from these examples.

This also why when designing a cage, tubes have opposing tubes, not offset like this!

Scott, I also agree about surpassing the materials strength. There are a few different DOM types to choose from, some, even though legal, I wouldn't want to use.
Further more the "X" failure seems to be equally due to design, weld heat, and high impact. The Miller website just had an article about heat and suggests that alot of welders
tend to use too much heat during MIG welding. For example when welding multiple joints on the same tube, each one should be allowed to cool before welding the next. This would definately make a difference. I would like to see what weld failure analysis shows about the properties of the material being altered due to the welding heat. My bet is that when two welds done in succession on the same tube, are causing excessive crystallization around the weld heat zone. Exactly where the break occured on the "X" design.
The BMW shown in the link had nice gussets as well as impact absorbers. Somebody should see if the four gussets would be considered legal in SCCA.
Randy

lateapex911
10-23-2008, 11:38 AM
The BMW shown in the link had nice gussets as well as impact absorbers. Somebody should see if the four gussets would be considered legal in SCCA.
Randy

I would think it would, as, IIRC, the rule limits it to two gussets per joint, and as there are two joints at an X bar, that's four gussets.

Speed Raycer
10-23-2008, 01:29 PM
The impact was very similar. The lack of damage to the rocker is due to the bars absorbing most of the impact and preventing intrusion.

For one aspect of this threads debate (X bar design vs Nascar Style), that doesn't really cut it. "Similar" doesn't help and you're assuming that the Nascar bars prevented the impact from reaching the rocker. The X bars rocker appears to mimic the contour of the failed bars meaning the NCBs rocker should be doing the same thing yet are untouched. Not the same hit to make this an apple=apple.

I'd like to see how the X bars hoop joints held up.

I really wish there was a way to sled test this. Same cars, same impacts etc. Although I'd miss all of the internet debates on either "side" Things are always learned. I think the main thing we've all learned here is to gusset the crap out of joints and hopefully to drop the coin on a little more tubing when it comes to cage time.

Heading over to the miller site :eclipsee_steering:

Grumpa
10-23-2008, 01:56 PM
Scott,
I haven't seen anyone mention a particular type of material for gusseting a cage. Gussets in my cage are nonexistant and that will be dealt with now that my season is over. My question is what gusseting is better - flat stock or round tubing? The tube is obviously more time consuming to fab correctly, but are the benefits worth the effort to triangulate with tube?

Speed Raycer
10-24-2008, 09:52 AM
Really depends on the joint access. If you're not able to get 360 deg. access- use some flat stock

You want to use at least 16 ga. with 12 ga or 1/8 as your max (whatever is closest your tubing thickness). Use some cardboard or 20/22 ga as a template to get your angles correct. Whenever possible (wrt access, time & budget), use a wrapped gusset. Same thing, use a template and then make the final version.

Might be a good time for a thread about gussets... I'll work something up after the weekend if someone else doesn't start one first. I actually get to race for the first time this year so I've got my hands full!!! :eclipsee_steering::026:

Racerlinn
11-03-2008, 03:08 PM
Looking for opinions. I like the basic structure of the X bars I have and feel that they can be effective. I don't want to take a cutter to what I already have installed, so I am considering adding an additional pair of bars to the existing cage. Pic below, the black bars are existing, the blue are what I am considering adding. I have not gutted my doors as I still have the windows (which I want to retain) in behind alumimum inner door skins. The blue bars would extend minimally into the door cavity, not as a true set of NASCAR bars as many see and do. They would have the "pup tent" tensile bend outward as described originally by tGA. The gap between the new blue bars and the X bars at their center would only be a few inches.
Thoughts?
http://img.photobucket.com/albums/v366/Racerlinn/CageleftC.jpg

spdmonkey
11-03-2008, 05:41 PM
Added weight would be an issue potentially, but otherwise if done properly It would be stronger and you would save ALOT of time grinding welds off. Ask me how I know....

db

Racerlinn
11-04-2008, 08:59 AM
Added weight would be an issue potentially, but otherwise if done properly It would be stronger and you would save ALOT of time grinding welds off. Ask me how I know....

db

Dave, I'm far from a 10/10th's build, I'm not concerned about the weight.

seckerich
11-04-2008, 10:24 AM
Steve a much easier upgrade would be to add a parallel bar top and bottom to the existing X. This would tie the bars and add side protection. 2 bars about 24" long should do to basically box the X in.

Racerlinn
11-04-2008, 12:40 PM
Steve a much easier upgrade would be to add a parallel bar top and bottom to the existing X. This would tie the bars and add side protection. 2 bars about 24" long should do to basically box the X in.

Issue there is entry and egress, especially on the drivers side. A bar along the top would make my gymnastics a lot more difficult getting in and especially out of the seat.
I also like the idea (whether it is proved out or not, I'm no engineer, nor did I sleep at a Holiday Inn last night) of the bar being in "tension", ie. pointed out towards the door. The tubes would only have a single bend, at the "apex" in front of the current X bar cross. The ends would not have bends, they would weld straight on to the front and rear main bars. Of course a side impact would have to be "perfectly" perpendicular to spread equal force to front and rear tubes, but even an offset hit would seem to initially push more energy into the main hoops before getting to the X bar.
Any one else???? Please?

On edit: I also would like the new bars to be down at Miata bumper height.......just sayin.... :-)

jimbbski
11-04-2008, 11:25 PM
I've been following this thread since the beginning and have learned a few things, just to late to incorporate them into my cage build. I had the bars bent by a pro but did the cutting, fitting, and welding myself. The holes in the gussets were put there for looks and not weight savings. Please feel free to comment as I know I'd get some if I asked for none.

Doc Bro
11-05-2008, 08:28 AM
I've been following this thread since the beginning and have learned a few things, just to late to incorporate them into my cage build. I had the bars bent by a pro but did the cutting, fitting, and welding myself. The holes in the gussets were put there for looks and not weight savings. Please feel free to comment as I know I'd get some if I asked for none.


IMO I think you need a vertical bar in the area of the steering wheel on both sides to strengthen the A pillar if you go on your lid. That span looks long and the bend angle looks steep.

R

Speed Raycer
11-05-2008, 09:56 AM
http://i225.photobucket.com/albums/dd187/IzzysCages/Cages/ITBars.jpg

Add some temple bars, the A pillar bars as suggested above, (nevermind the windshield corner gussets as I didn't notice them til just now), get rid of the knee bar and move it up into the dash, preferably above the steering column, but that's not always possible. Add a 7th point to protect your feet.

Personally, on the door gussets- good idea, but I like to keep them on the outside of the tube. Lessens the "can opener" effect. In other words, I'd have made them about .5" larger all the way around and have them on the outside of the bars pushing inwards in an impact.

Just noticed the harness bar.... looks way too low for proper harness angle... but there's no seat so it's hard to tell.

Speed Raycer
11-05-2008, 10:00 AM
Steve, Your idea is probably the best idea using both styles of bars. Alternatively, maybe something like this to retain the window and gusset the X:
http://i225.photobucket.com/albums/dd187/IzzysCages/Cages/serbars.jpg
The darker blue bar would be bent out to deal with those pesky miata's. The lighter blue would be tubes forming a box of the existing joint. You could then plate that "box"