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.

[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.

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.p...17f0&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.