Rollover protection question

[wmhjr]

OK, for you chassis guys experienced with SCCA and NASA....

HPDEs running under SCCA/NASA guidelines have restrictions preventing open cars (convertibles) from participating without "rollover protection". I know there are some caveats and exceptions, like at RTTH, but in general that's the case. "Rollover protection" seems to have somewhat vague requirements when you're talking non wheel to wheel or door to door racing. I've been spending some time with a local SCCA/NASA tech inspector, and here's what I came up with as a "minimum requirement" - not saying I'm doing just the minimum.

Depending on the weight (and for this let's assume 3000lb+) the guideline seems to be that you need simply some sort of rollover protection. It is not required to be mounted to the frame - body mounting is apparently OK. If body mounted, there must be a weight distribution flange under the main hoop, but interestingly it appears there are restrictions that it cannot be too large, but none about how small it needs to be. Apparently it must be 3/16" thick steel. Crazy. Also crazy is that strictly according to the rules, for a 3000lb car, you must use .120 wall steel even if you use chromoly. Crazy, but..... The main hoop must be one continuous section of tubing with no more than 4 bends in it. "If" you use a diagonal, it must be one piece and if a cross-bar/harness bar crosses it, the cross-bar/harness bar is the one that should be sectioned. I'm also told that for "track days" and most "HPDE events", things like the wall size (.095 vs .120) are really not considered. There is no requirement for forward, or "door" bars extending forward toward the kick panels. Essentially, it appears as though you could install a 4pt of .120 DOM mild steel or .095 Chromoly, mounted on 3/16" 4x4 bases to the body, having a main hoop of one continuous section with no more than 4 bends, and it would pass muster.

My plan significantly expands on this but I'd like to know for sure.

In general, can anyone comment on whether I'm correct here or not? My tentative design exceeds these basic requirements, but I do need to understand the essential requirements just to make sure I'm not screwing up.

[Bryce]

You are correct based on teh research I have done. To add to this. The main hoop support (that extend into the trunk) need to be of the same material as the main hoop and have no bends.

Keep in mind everything you said would pass NHRA spec as long as it was 1.75" OD tube and the foot plates are 6x6.

On a side note: I think the two plates should be slightly different in dimension. Otherwise you have just created a brake form. You could also slightly offset one plate from the other.

[dontlifttoshift]

I have no answers for you but would like to know about all of your questions and about placement of the rear down bars. It seems that within 6" of the top of the bar is correct. If so is there an angle requirement? I hope this isn't highjacking but this is something I have been wondereing about for a while. And how do cobras get away with that little bar behind the seat that usually is lower than the helmet....if that would fly so I could at least drive (not race) on the track I could make something like that work.

[parsonsj]

I think the NASA rules are messed up. We (NASA tech inspector, Coast Chassis fabricator, and I) discovered the odd thing about there not being a 4130 wall thickness spec for cars over 3000 lbs. It also requires two door bars (an X shape is what is intended.. though it doesn't say that).

In the end, we gave up and built an 8s NHRA cage with an extra sill bar per side and used 1.75 x .095 tube.

jp

[NOT A TA]

WHMJR: I have no knowledge of the SCCA regs. From what I know you are correct for NASA requirements for conv's at HPDEs. I believe the reasoning for the stipulation that the floor plates not be larger than a certain size is due to the chassis stiffening effect it would have for certain types of cars and the rule was just copied from a racing class tech requirement. If I recall correctly there is also a "broomstick" requirement for Conv's to make sure your rollbar and windshield frame hits the ground before your head when the harnesses stretch on impact. You could probably find the measurement requirement in NASAs tech regs. I believe the 3/16 floor plate requirement is to prevent the hoop tubing from punching a hole through the plate in the event of a drop from the sky (so to speak) if the car flips. Diagnal and harness bar, you are correct and I've never seen wall thickness checked on cars not running in door to door classes at HPDE/track days (at NASA road course events). No door bars required for convs at HPDEs in NASA.

Bryce: Good point on the 6 X 6" minimum plates. I believe the 2 floor plate tech requirements only pertains to bolt in bars.

Ramblings:
I went through the safety equipment selection process a couple years ago. I wanted to be set for NHRA NMCA ECTA NASA SCTA/BNI and SSCC and do it once without having to modify or upgrade as I went to other sanctioning bodies events. I had a hard time finding anyone with knowledge about fullfilling the requirements of multiple sanctioning bodies because most of the tech officials are well versed with their particular sanctioning bodies regulations but not those of other sanctioning bodies. This seemed to be because normally they're dealing with owners of purpose built "race cars" prepared specifically to be competitive in a certain class (or classes) of a certain sanctioning body, not idiots like us that want it all!

I found that some sanctioning bodies I wanted to run in have their tech requiremets online and some are only available by buying them in printed form. What I finally figured out was unless you're actually going to race door to door in NASA or SCCA the requirements for other sanctioning bodies we would most likely attend would have you covered at HPDEs. If you're going to Drag Race, Open Road Race, or Land Speed Race the requirements for those events will have you more than covered for HPDEs. Sooo..... after considering the speeds or quickness you'd be able to run (in your best dreams) at those types of events you can figure out which class of which sanctioning body to prepare your safety equipment to satisfy. I found that the Land Speed Racing regulations for the speeds I hope to achieve to be the most comprehensive for my intended uses so thats what I built my cars equipment to exceed. This way I'm covered for anything else I have done/will do with the car.

[Bryce]

WHMJR:
Bryce: Good point on the 6 X 6" minimum plates. I believe the 2 floor plate tech requirements only pertains to bolt in bars.

Yes, thank you for clarifying.


The main hoop has to be no less than 2" above the drivers head with the helmet on and no more than 6" behind the drivers head.

[wmhjr]

The main hoop support (that extend into the trunk) need to be of the same material as the main hoop and have no bends. .

Bryce, are you sure about that? I don't think that is actually correct for non-door to door racing. The tech inspectors I've spoken with have not yet said this either. And in practice, think about it. Miatas, Z3s and Z4s are open cars with roll hoops that do not extend "straight into the trunk without bends". Yet, they're legal. I think part of the confusion is that the way the regs are written, there are some requirements for door to door that get mixed up with HDPE type stuff. Think about this. Frankly, if the rule were truly that the main hoop support extend straight and all the way to the trunk, no convertible could even retain it's top. From a geometry perspective, that support bar would have to go straight through the top. I'd like clarification about this one, as it is crucial even with my design which exceeds other aspects of the requirements (as I understand them). Anybody else want to jump in on this one?

Keep in mind everything you said would pass NHRA spec as long as it was 1.75" OD tube and the foot plates are 6x6.

On a side note: I think the two plates should be slightly different in dimension. Otherwise you have just created a brake form. You could also slightly offset one plate from the other.

On this one, I'm pretty sure that it still will not pass NHRA/IHRA specs for a variety of reasons. First of all, for non-wheel to wheel, SCCA and NASA only require "rollover protection" and not a 6 pt cage. NHRA/IHRA mention "roll bars" but when you actually look at their definition of a roll bar, it's actually a cage as we would consider. Specifically, it must be at least 6 point - not 4 as for SCCA/NASA. Further additional requirements are that if the car is full framed, the cage must be welded to the frame. If the car is unibody, 1/8" steel plates must be secured to the top AND the bottom of the floor.

[Bryce]

Bryce, are you sure about that? I don't think that is actually correct for non-door to door racing. The tech inspectors I've spoken with have not yet said this either. And in practice, think about it. Miatas, Z3s and Z4s are open cars with roll hoops that do not extend "straight into the trunk without bends". Yet, they're legal. I think part of the confusion is that the way the regs are written, there are some requirements for door to door that get mixed up with HDPE type stuff. Think about this. Frankly, if the rule were truly that the main hoop support extend straight and all the way to the trunk, no convertible could even retain it's top. From a geometry perspective, that support bar would have to go straight through the top. I'd like clarification about this one, as it is crucial even with my design which exceeds other aspects of the requirements (as I understand them). Anybody else want to jump in on this one?

If you read all ~150 pages of the SCCA and NASA rules, its states a few times that certain requirements are on a car to car basis. That is why the most popular car in SCCA, a miata, is allowed to compete without meeting all rules. ANd yes, door to door is different than HDPEs.

On this one, I'm pretty sure that it still will not pass NHRA/IHRA specs for a variety of reasons. First of all, for non-wheel to wheel, SCCA and NASA only require "rollover protection" and not a 6 pt cage. NHRA/IHRA mention "roll bars" but when you actually look at their definition of a roll bar, it's actually a cage as we would consider. Specifically, it must be at least 6 point - not 4 as for SCCA/NASA. Further additional requirements are that if the car is full framed, the cage must be welded to the frame. If the car is unibody, 1/8" steel plates must be secured to the top AND the bottom of the floor.

That is correct last year NHRA added a door bar on the drivers side. making it a 5 point cage. The door bar needs to pass the driver between the shoulder and elbow and extend to the toe board. The "5point cage" lets you go as quick as 10.50. I think.

A full framed car needs to have the cage attach to the frame. NASA requires unibody cars have a 3/16" think plate with a minimum square inch foot print. Both only require a plate on the top side if welded to the sheetmetal. Otherwise two plates bolted together sandwiching the stock sheetmetal with 3/8 grade 8 fasteners.

[wmhjr]

So, strictly for hpde events like motor state, Midwest challenge, and the rare track day, i should be ok if my rear bars supporting the main hoop are bent, right? I realize it may not be enough for true time trials, etc - but for this kind of stuff I should be ok? I talked to Mark at McB motorsports near here again today. He's a tech inspector for NASA as well as scca. He felt that the requirement for "rollover protection" for these kinds of events would be met by my solution. Thoughts?

I do appreciate the advice.