Main Hoop Braces/Bulkhead interpretations

[Racer Chris]

Originally posted by Geo:
That car is ILLEGAL AS HELL for IT.

I mostly agree!
There's nothing wrong with using more than one piece of material to make a mounting plate but that rear plate easily adds up to more than 12" in length.
There's nothing wrong with the rear downtube terminating at the crosstube, however, I think the argument that the additional bars are legal because they all attach to the same mounting plate constitutes a strained interpretation of the rules.
The car might be legal as an ITE car because it is prepared for a BMWCCA race series.

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Chris Foley
www.tangerineracing.com

[erlrich]

Originally posted by Racer Chris:
There's nothing wrong with the rear downtube terminating at the crosstube, however, I think the argument that the additional bars are legal because they all attach to the same mounting plate constitutes a strained interpretation of the rules.

Chris, I have to respectfully disagree. Right out of the GCR: "The main hoop shall have two braces extending to the rear attaching to the frame or chassis."(emphasis added) and under the section on mounting plates: "Any number of tubes may attach to the plates or each other".

I do have one question for the rules nerds, though, directly related to the cage in question here: the GCR requires two rear braces, but where does it state that they must be one continuous piece of tubing? I realize that common sense and sound structural design need to be considered when building a cage, but strictly by the rules the only place in the GCR I see a reference to a single continuous piece of tubing is in the section on the main hoop.

Earl

[Knestis]

Hi, I'm Kirk. I'm a rules NERD and I have an illegal rollcage - if the letter of the law as it is being put forth here applies.



The horizontal piece went in first, then the downward braces were fishmouthed into the joint where that tube met the plates. The centerlines of those tubes - and the additional diagonal - all align, per engineering best practices.

To suggest that the ulta-literal interpretation of a rule that was written years ago, to define a minimum standard that most current cage structures, should trump good practice is enough for me to turn in my NERD badge and join the ranks of the cheaters.

K

[erlrich]

Kirk -

Don't resign your membership just yet. I'm not an automotive engineer (but I did sleep at a Holiday Inn Express once), or a rules nerd (they keep returning my application stamped "not in this lifetime"), but (and correct me if I'm wrong) given the unibody nature of your car aren't your downtubes technically connected to the chassis? Even if that's technically not correct, there is still that whole part in the ITCS that specifically allows the tubes to connect to the rear shock towers/suspension pickup points. I can tell you this, if yours are illegal so are mine, because I did virtually the same thing with the rear braces.

The point I was making with the GCR quote was, and I still stand by this, that it is not permitted to terminate the rear braces into another tube alone.

Isn't it funny how these ultra-literal interpretations only seem to be valid when they are supporting our side of an argument (this case being no exception).

Cheers
Earl

[This message has been edited by erlrich (edited January 07, 2005).]

[Joe Harlan]

Kirk, While I have no problem with the way you did your rear tubes I could make a case that the rear tubes are connected to a rear strut bar (which is not legal)So is this a case of a legal part doing an illegal function. We had a couple of guys do a similar deal in 240z's. Again not a big deal to me because I would rather worry about safety first.

[ryotko]

I think this is a case where the GCR contradicts itself.
18.6 - Bracing - states that rear bracing must attach to "frame or chassis"
Yet 18.8.E - Mounting Plates - specifies, "Any number of tubes may attach to the plate or each other."

The contradiction is that the bracing (or any part of the cage structure) can't attach directly to the frame or chassis but has to attach to a mounting plate. So wouldn't the mounting plate rule trump the bracing rule?

-Bob

[apr67]

Originally posted by Joe Harlan:
Kirk, While I have no problem with the way you did your rear tubes I could make a case that the rear tubes are connected to a rear strut bar (which is not legal)So is this a case of a legal part doing an illegal function.

Can't call it a strut bar when it connects shocks...

Anyway, any number of tubes may connect between your legal mounting plates, ergo that configuration is legal.

[This message has been edited by apr67 (edited January 07, 2005).]

[bldn10]

"The contradiction is that the bracing (or any part of the cage structure) can't attach directly to the frame or chassis but has to attach to a mounting plate. So wouldn't the mounting plate rule trump the bracing rule?"

It doesn't really trump it - it is inherent in it. Since the cage can ONLY be attached to the car via mounting plates, it is assumed throughout the rules that any cage attachment point is via a plate. Thus, the support braces must be mounted on a plate that is attached to the frame or chassis. And that certainly includes the shock towers on unibody cars. Kirk's is legal because it does attach to the plate, the one in qustion attaches to the horizontal tube and I do not think that is legal. This has come up before in the context of "X" support braces, where one of them obviously is cut where it crosses the other and, thus, is not attached to the frame or chassis. The notion that the horizontal tube is an illegal shock tower brace is somewhat troublesome but IMO as long as it is part of an otherwise legal cage, it is OK.


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Bill Denton
87/89 ITS RX-7
02 Audi TT225QC
95 Tahoe
Memphis

[Joe Harlan]

<font face=\"Verdana, Arial\" size=\"2\">The notion that the horizontal tube is an illegal shock tower brace is somewhat troublesome but IMO as long as it is part of an otherwise legal cage, it is OK.</font>

Again,this is not enough that I would ever push the issue but the cross brace is performaning an illegal function as far as I am concerned, It is a shock/strut brace first and a mounting point for the rear down tubes second The same thing could had been done by attaching the back braces to the plate and the cross tube up hill about 3 inches....Same effect less intent....

[ITANorm]

The "rearmost horizontal cage stiffening brace", which just so happens to do a very good job of bracing the rear strut towers, has been defined as probably technically illegal but too gray to push. I asked the question several years ago. I believe the trigger for the inquiry was a certain ITS RX-7 out of Memphis.

[Bill Miller]

I'd like someone to show me where it says that you can use a 'multi-piece' mounting plate. And while we are limited to 100 in. sq. and 12" / 2" on a side. So, you can have a plate that's 12x8.25, or one that's 8.25x12, or one that fits in the 'evnvelope' defined by those two. I don't think you can start cutting a plate apart and aligning the pieces so that they fit into that same envelope. In other words, your plate must fit in a 100 in. sq. box. If the X dimension is 12", they Y dimension cannot exceed 8.25, and vice-versa. It's doesn't matter if you actually have 100 in. sq. of material in the plate. The BMW plate in question surely will not meet this test.

As far as Kirk's cage goes, I'm not convinced that it's legal. As was said, I believe that if the down tubes attached to the plate and the cross bar attached to either the down tubes of the plate itself, there would be no question.

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MARRS #25 ITB Rabbit GTI (sold) | MARRS #25 HProd Rabbit
SCCA 279608

[Joe Harlan]

Bill, Using multi pieces if plate to build a mounting plate is the only way the job can be done right. Lets not take the rule down to a pimple on a nats ass to get the job done. If the Bimmer cage was presented to me for approval it would be bounced in IT without any further thought. Kirks cage present an interesting set of thoughts on weighing between what is proper and safe and what could be considered illegal. Again I see no real issue with Kirks cage other than it doesn't really meet the letter of the law
in that one area.?

[Greg Amy]

Legal, with the cardboard templates to prove it (plan to bring your own ruler if you don't trust mine...)

http://www.kakashiracing.com/images/rollca...ge/DCP_4724.JPG

[Greg Amy]

Technical clarifications letters, for reference:

http://www.kakashiracing.com/SCCARollcage.html

...and the reply:

http://www.kakashiracing.com/RulesReply.txt

[Knestis]

Originally posted by Joe Harlan:
... Again I see no real issue with Kirks cage other than it doesn't really meet the letter of the law in that one area.?

So what I'm hearing is that you don't think it's legal because the rear braces hit the optional lateral cage element, in addition to the plate on the shell - rather than exclusively to the plate?

K



[This message has been edited by Knestis (edited January 07, 2005).]

[Joe Harlan]

So Greg, Please show me the rule that allows the rear strut bar? I can't find it.

[Joe Harlan]

Kirk, again I am not a rules geek here. I do build cages and I would have done it different to avoid even a question. I think an argument could be made for either side but I think the argument that the cross bar creates additional chassis stiffness and that was the intended reason for its placement is pretty strong.

[Geo]

Originally posted by Joe Harlan:
So Greg, Please show me the rule that allows the rear strut bar? I can't find it.

If you're talking about Greg's car, that tube is part of the cage by virtue of being attached to the cage mounting plates. I don't see how anyone could have an issue with this since attachment points are now defined by the plates.


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George Roffe
Houston, TX
84 944 ITS car under construction
92 ITS Sentra SE-R occasionally borrowed
http://www.nissport.com

[Joe Harlan]

Geo, Again I would not make an issue but somebody might.
ITCS D5d8...No other.......reinforcement of any suspension compnent or mounting point is permitted.

ITCS d5d5... cars may add (1) stayrod, located in one of the following areas:....

Now I don't remember the exact language but it goes something like "no legal modification shall provide an illegal function. In both cases I think you could show the reason for both cross bars is to stiffen the rear shock mounts.

[Greg Amy]

Originally posted by Joe Harlan:
So Greg, Please show me the rule that allows the rear strut bar? I can't find it.

You ain't lookin' hard enough <grin>:

GCR 18.2.6: "The main roll hoop shall have two braces extending to the rear attaching to the frame or chassis." Thus, the location of my plates is legal.

GCR 18.2.8.E: "Any number of tubes may attach to the plate or each other." Thus, adding additional tubes to those plates is legal.

Note my 100sq-in plate wraps around the rear upper strut area in order to spread out the loads of compression to a maximum area. The transversly-mounted bar is there to strengthen the rear legs such that a hard rear quarter hit will not stove said legs (thus leaving me vulnerable to a main hoop collapse upon a possible subsequent rollover.)

It's all totally legal. If you disagree, as noted I carry my templates with me for someone to exercise their GCR 13.2 prerogative...

If you wish to induce the "prohibited function" clause (specifically, ITCS 17.D. "No permitted component/modification shall additionally perform a prohibited function") by claiming it also stiffens the vehicle's chassis, you should be adequately prepared to demonstrate or otherwise prove how *any* properly-designed cage CANNOT at the same time strengthen or stiffen a chassis. It is, by definition and design, a required function of a rollcage, for if the car's chassis was adequately stiff such that it could withstand the forces of a crash, there would be no need for a rollcage in the first place... GA

[This message has been edited by GregAmy (edited January 07, 2005).]