Main hoop location vs the GCR

[webhound]

I have an E30 325E 4 door, starting to consider prep for going to CR school. My first step will be to strip and cage it. Looking at the GCR, 9.4.B.1.a: "On all closed cars, the main hoop must be as close as possible to the roof and “B” pillars."

If I run the main hoop against the B pillars I will have to use a bent harness bar. I would much rather run the main hoop a few inches further back against the back of the rear of the rear passenger footwell, basically where the body goes vertical for the rear seat "platform." My reasoning for this is to keep the harness bar straight and in plane with the main hoop along it's entire length.

Question is, is it legal to run the main hoop a few inches rearward of the B pillars? I'd also shoot an email to a tech guru, if I knew who I should be emailing.

Thanks.

[Greg Amy]

Post photos of the car to describe what you want to do.

The ultimate goal is to have the main hoop as close as possible to the driver. If you're a bit behind the B-pillar with the driver sitting back, that's likely fine, and vice versa. If the main hoop is reasonably close to the driver you should not have any issues.

As a general reference, draw a line from the top of the hoop to the base of the windshield; if the driver's head is below that line you're probably OK.

Ultimately, however, a local inspector will have to review your cage design and sign it off, so it is in your best interest to contact your local tech guys and work with that person prior to cutting/bending tubing.

GA

[chuck baader]

I have an e30, and my main hoop is further back. My main is actually slightly behind the B pillar and my harness bar is straight. I suggest you mount your seat and let your cage builder go from there. Location should/must depend on seat position. CB

[GKR_17]

NASCAR style door bars are hard to deal with in this situation also.

[webhound]

GKR, very valid point that I will be sure to examine.

Thanks for the replies, gents. I will be consulting with my local tech inspector.

[CRallo]

I noticed your location... We recently built a car and our main hoop actually stands ON the rear seat hump/shelf... Our was log booked in the NE and has since seen one annual since. There has been no issue, not even a mention of it.

My co driver is damn near 6.5' tall so it helps with leg room a lot!

[Simon T.]

Here is mine I was worried about it being so far back as well but have been told it's fine.

http://i1224.photobucket.com/albums/ee368/haleymward/acr.jpg

[Greg Amy]

Here is mine I was worried about it being so far back as well but have been told it's fine.
I wouldn't "ding" you on that myself, but I'd recommend to you, as I did to the original post above, why the main hoop should be fairly close to your head.

Simply put, that thing is in there to keep you from breaking your frikken' neck. The longer the front legs, the more opportunity for leg collapse. If you sit well forward of the main hoop, were you to plant that thing on its roof and the windsheild bow/front legs collapse, that roof is a'comin' down (or "up", dependong on your perspective). Vertical forces put that main hoop in compression, versus bending forces on the legs, and compression is much stronger; the closer you keep your noggin' to that hoop, the better you're protected.

The absolute worst example I'm aware of was an SSC accident at the Road Atlanta Runoffs in 1993 (?). Through a combination of failures (not specifically the front legs, but I'm using this as a worst-case example) the main hoop failed and the roof came down on his head. He was crippled for the rest of his life. From that incident came race seats in Showroom Stock and the full-width horizontal bar (as well as some other cage standards), but it illustrates the important of maintaining the integrity of your "survival space".

As I noted, I'd rather see the main hoop closer to your noggin'. But one thing you can do to improve that "space" is to weld gussets at all four corners: between the main hoop and front legs, at the bend line of the front legs at the A-pillar, and between the door bars and the main hoop and front legs. In effect, you're creating a "box" rotated 45 degrees in the space of the door area. Also note that you can have vertical bars from the front legs that actually go all the way down TO the rocker panel with a flat plate at the bottom, touching the rocker panel; as long as that part only "touches" and is not welded to the rocker, you're IT-legal. That's effectively what we did in the Integra, putting the main hoop farther back but supporting the front legs with more verticals. I thought I had some photos online on that but can't find them now...

Be creative.

[Rabbit07]

We do lots of cages at my shop. 3 e30's this month. I can tell you that I prefer to mount the seat first and then check the drivers position and build from there. I agree with Greg that the Roll hoop should be closer to to you vs further away. That all being said my Neon's cage looks just like the one pictured. I am 6' 2", so I sit fairly far back.

[RacerBill]

One other effect of moving the horizontal/shoulder harness bar further rearward is to lengthen the shoulder harnesses. In the event of an on track incident, the longer the harness, the more it will stretch, and increase the propensity to slip.

[lateapex911]

Here is mine I was worried about it being so far back as well but have been told it's fine.

http://i1224.photobucket.com/albums/ee368/haleymward/acr.jpg
Something like this Greg?

[Greg Amy]

Something like this Greg?
Si, Senor, that's a great start. On our Integra the main hoop is about as on that Neon, but Kessler actually added in a second vertical at the b-pillar, with it going down to a "stretched" mounting plate (within the allowed rules). So I actually have two verticals by the driver: one on the main hoop and one additional forward of that next to my seat.

That also makes doing the NASCAR door bars a lot easier, it becomes part of that (with another gusset tube from there inward.

Billiel! Take some quick pics of the 'Teg cage and post, please?

GA

[tderonne]

I always interpreted the roof and B-pillar statement to mean the the main hoop must be as tall and as wide as possible. Never thought about the exact wording that does seem to say near the B-pillar in the fore aft direction.

Ahhh, intent vs. wording....

[Matt93SE]

Reasons like this are why you want the main hoop as close to your head as possible: http://www.motorgeek.com/viewtopic.php?f=6&t=16273&sid=b3e063821b5ed16f9e70fe4b1aeb17f0&start=250

[Greg Amy]

Egads. Yep, definitely a cage-build-"fale". That's why you see those tube gussets there in the main hoop-to-leg area.

I'm guessing he rolled into a tree...?

[webhound]

Thanks a bunch for the replies, everyone. Matt93SE, eye opening thread, that was an unexpected mode of cage "loading," but the worst ones always are, right?

My initial plan had me just randomly placing the main hoop at the edge of the rear seat platform, as noted in my first post. My intention was to provide as much seat room as possible for the potential of other drivers in the car for enduros, etc. But, thanks to the replies here, I'm gonna look out for #1, lol!

I did speak with one of our regional tech guys last night, not chief of tech, mind you. He had cited examples such as the Neons putting the main hoop pretty far back as examples of the validity and precedent of not having the main hoop literally at the B pillar. Just to cover myself, I will be contacting chief of tech, but I don't expect to have any issues. Now on to selecting and ordering the seat.

[Bill Miller]

Read back a page or two in that thread, he talks about what happened. Pretty scary stuff. Cliff notes: Car left the track at a high rate of speed (110-120 mph), went straight into the woods, launched up one tree, rotated, and hit a much bigger tree square on the roof. Pretty amazing that the driver survived.

[lateapex911]

Egads. Yep, definitely a cage-build-"fale". That's why you see those tube gussets there in the main hoop-to-leg area.

I'm guessing he rolled into a tree...?
LAUNCHED off a tree, and mid air roll hurtled into a tree. Slid down rolled onto roof. Crushed the cage and forced the bar between his helmet and his HANS, pinning him, and collapsing his breathing tube. Medics got him out and breathing and he was airlifted to the hospital. Wowza.

[Matt93SE]

Yeah, it was a pretty hairy wreck. All those trees near the track sure make for scenic driving, but they also make for nasty wrecks.

I don't consider failure of the cage as being bad from a design or fab standpoint. I consider that a case of a 1-in-a-million wreck where the cage was subjected to loads it wasn't designed for. nobody expects to nail a tree using the roof at that angle at 100mph.

Just imagine if that has been an open top car of any sort, whether a Spridget or Formula car. Driver wouldn't have made it given those structure designs.

I guess the big thing to take from this is that unexpected things can- and WILL- happen. The whole point in a roll cage is to protect us from the wreck that we don't ever expect to have (We're all perfect drivers and never make mistakes on track! HA!), so how can you plan the cage as safe as possible, yet still allow you do to what's needed?

converse with that, where's the line you draw on your own safety? What's "safe enough" ?

[webhound]

Well, a good point was made later in that thread that makes a great case for more support for the top of the main hoop and the halo (or it's equivalent). Gusseting between the main hoop and halo, and a straight down tube from front of halo to the mounting point of the bottom of the A pillar bar may have stopped some of that collapse, and would help in a more normal rollover.

I'm glad for this discussion.

[CRallo]

In addition to the afore mentioned gussets and such that wreck shows why the "Halo" should have a cross bar or two as well...

[DoubleXL240Z]

I believe this is way past gussets. Diagonals would be a better bet. Think of a box tilted at a 45 degree angle. Same thing that is currently being built in my ITB/STL E30. Using 1.50x.065 keeps the weight down.

[Streetwise guy]

Wowsers. I guess all that whining I was doing about the FIA spec cage roof work I had to do last month was maybe a bit premature. Tomorrow I'll try to post up some pics of the FIA spec Neon roof "Caterpillar D9 landing zone" support structure. Lotsa pipe in that one.

I shall expect critical comments, and will attempt to retain some semblance of self worth.:D

[tom91ita]

i have been looking at my cage in a new light. was thinking maybe the "A" pillar should follow the windshield further down and go through the dash instead of dropping to the floor in front of the dash.

not sure now. if i did that, i would likely drop a bar down in front of the dash to hit the door bar etc. in the about the same location where the A pillar bends by the dash.

am thinking the increased distance from the main hoop to where the bar would drop through the dash may not be as good.

but then on my crx it is not that far from the main hoop either way i guess.

[Streetwise guy]

http://www.improvedtouring.com/gallery/displayimage.php?imageid=403

http://www.improvedtouring.com/gallery/displayimage.php?imageid=404

This is the FIA requirements for the roof. Seems like lots of roof support, but not so much side intrusion. This is for a rally car, if I was doing it for race I'd add nascar bars for sure. Might help, but how much roof support becomes enough to just shove the cage out the bottom of the car? 1 3/4 095 DOM, for the main structure, 1 1/2 for the supplementary. Odd thing too- dash bar is not required.

Reading the FIA rule book is very much like reading Vogon poetry. I finally cut and pasted the current, English language portion of the book.:blink:

[DoubleXL240Z]

Jim, My 2 cents (for free)! Take it at face value!!
Looks busy up there!! I would have tried to have the diagonal from the main hoop intersect the top bar( over the drivers door) in line with the roof diagonal. Move that connection rearward approx 3-4 inches, maybe downward on the main hoop 3 or 4 inches as well.
It looks as if the "extra" bar from the base of the a-pillar is bent part way up, this defeats the main structure of that bar, "pre failing" it. If loaded from the top i.e. upside down, that bar will fold quickly, much the way a hood is designed to buckle in a head-on accident. It looks like the a-pillar/ top bar could be made a bit closer to the chassis itself, and maybe extended further forward toward the a-pillar.
Your results may vary. Not valid in Canada and Mexico. Limited time offer. Not to be used in conjunction with any other offers. Your milage may vary. Results are not indicative of actual results.

[Streetwise guy]

I'm not completly happy with the location of the roof brace rear mounting point, although it does meet the rule- it has to be within ? inches of the main hoop. I see your point about the diagonal......a bit more upright would have a nicer intersection to the roof support. Its my habit to add those at a 45, about 9 inches long. Next one of these I do I'll consider that. The extra front upright, if not bent out (again, allowed in the rule) intersects the steering wheel. Not optimal. The front bar is actually pretty close where it can be- Neons are a bit curvy throught the roof'-a pillar area, makes it a bit hard to tuck real close. The windsheild header bar is snug all along the roof, and its tight along the top of the doors.

Given the Audi in the pics, I think even without the roof diagonal this might have held up better in that extreme situation.

[DoubleXL240Z]

Given the Audi in the pics, I think even without the roof diagonal this might have held up better in that extreme situation.
Very true!! You have at least 3 more bars that would have to be bent, and 2 diagonals that would be in almost perfect compression to support that loading!!
I'll get some pics of the Neon cage I did last fall!!

[Knestis]

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

That's the logic behind the diagonal alongside the driver's head. This thread reminded me that we had to take that out when we got the newer-style Recaro. I just sent RennGruppe a note asking them to re-do that element.

EDIT for Tom - you can see in this shot how far forward Pablo's tubes run.

http://www.it2.evaluand.com/gti/images/mk3.2/newpaint1.jpg

Also, we opted to not add a dash bar because VW puts an enormous bolt-in structure across the space spanning between the left and right top door hinges.

K

[Knestis]

...and I find this one interesting to think about.

http://www.specialstage.com/classifieds/data/13/large/a31.jpg

K

[DoubleXL240Z]

Holy Mololly!!!!!!!!!!!:017::017: my head hurts thinking about that one!!!

[Bill Miller]

I was wondering when Kirk was going to post Pablo's cage. Schimmel does nice work!!!:023:

That other cage looks pretty nice as well (although not IT legal).

[lateapex911]

Wowza!
Ok, I get it. That's a lot of tubes though.

So, lets guess the car.
I'm going to say a 4 door euro or british touring car build. Unless the photo is reversed. One odd thing is the cross car tubes (which don't actually go all the way across, oddly) in the main roll bar 'plane', are at different heights.

[Streetwise guy]

I'm going to guess rally car, with the co driver set right down on the floor.

And I'm always happy when I can get one with the windsheild out. I think asking for the roof panel to be taken off might be asking a bit much.

[Chip42]

And I'm always happy when I can get one with the windsheild out. I think asking for the roof panel to be taken off might be asking a bit much.

It's actually not that hard to do. shockingly easy when I did it, actually. definitely over the top for a typical cage, but if you want to go all out I'd say it's appropriate.

btw, you owe me a keyboard for "Reading the FIA rule book is very much like reading Vogon poetry."

[Knestis]

Yup. CARS Subaru rally car built to FIA specs. The shell, in its current state, is for sale, by the way.

K

[Matt93SE]

Is there enough room to get out the doors, or do they just kick the windshield out and use an ejector seat? :)

I was going to guess WRX due to the 4 doors, hatchy-shape of the back end, and mile long roofline.

[webhound]

Ok, follow on question concerning cage building, as I'm getting close now.

I've seen past discussions about rear braces passing through the rear trunk bulkhead, and ITCS examples which support this. I'm looking at the 2011 GCR right now, and the only thing I see that pertains to rear bulkhead is in 9.4.G.6: "Any number of additional tube elements is permitted within the boundaries of the 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." This seems to pertain only to additional tube elements, not the mandatory elements of the rear bracing.

The section pertaining to the rear braces is 9.4.B.2.c: "Cars must have 2 braces extending to the rear from the main hoop and attaching to the frame or chassis. Braces
must be attached as near as possible to the top of the main hoop (not more than 6 inches below the top), and at an included angle of at least 30 degrees."

On the E30, this rule should be able to be satisfied by using the front of the rear wheel tub as a mounting (chassis) structure with some finessing of the angles. I'd prefer to pass through the rear bulkhead and mount to the rear shock tower. What gives us cover for passing through the bulkhead?

[chuck baader]

Chassis forces are transmitted by springs, not the shocks. On the e30, you want the rear down tubes to attach at the junction of the rear bulkhead, rear floor, and bottom of the shock tower. Not easy, but that is where the upper rear spring perch is located. Chuck

[Greg Amy]

...This seems to pertain only to additional tube elements, not the mandatory elements of the rear bracing.


I'd prefer to pass through the rear bulkhead and mount to the rear shock tower. What gives us cover for passing through the bulkhead?
It's inferred that you can modify any stock part that gets in the way of required cage elements (within reason).

First and foremost, you need to meet the three requirements:

- must attach to "frame" or "chassis" (your car is monocoque)
- not more than 6" from top
- no less than 30 degrees.

If that means going through a stock bulkhead, then it's allowed. No one is going to ding you for that.

GA

[webhound]

Thanks guys. Chuck, you wouldn't happen to have pics of that area of your cage, would you?

[Flyinglizard]

The cross dash bars help from pulling out the A post cage mounts, in a side impact. Not many side impacts from Ralley. just landing in trees ,upside down.