I have been reading about the NHRA rules today regarding roll cages and found this, just want to see if this is legit or what..

"The NHRA requires a roll bar in every convertible that is 13.49 seconds or quicker in the quarter mile. For cars that are not convertible, their cut-off time is 11.49 seconds in the quarter mile. There is an exception to this rule. If the vehicle has the stock firewall and floorboard intact, it can run the quarter mile in as little as 10 seconds. The roll bar has to be constructed with 1 3/4-inch mild steel tubing with a wall thickness of 0.118 inch. Or 1 3/4 chrome-moly tubing with a wall thickness of 0.083 can be used."

This is the first I have ever seen of this "exception", I was always under the impression that no matter what, you needed a cage after 11.49 et's. What is the actual rule about this?


If this is not true does anyone know the breakdown of ET/Trap Speed to # of point cage needed? I.E what point cage is needed when going say 9.99 to 10.50's << just an example

Also are there any limitations on bending the bar that runs behind the front seats? I am 6'6 and do not want to lose all comfort while driving the car, if bending the bar around my seat position is allowable I would be more open to the idea of having a cage in the car.

 

Also, since my car is a 4dr and I am wanting to keep the rear interior so I can run FIS at import faceoff's, is there a rule about the angle in which the bars coming off the roll bar to the trunk area? Meaning can I have them bent to run along the roof line and then down through my rear deck lid?

 

its all been covered way to many times

http://www.nhra.com/UserFiles/file/G...egulations.pdf

http://www.scroungers.net/t3388-nhra...and-cage-specs

 

Maybe you can talk about it one more time for ***** and giggles as the rule book doesn't really tell me jack **** regarding rules about bending the cross bar around my seat or if there is a certain angle that the 2 bars going to the trunk area have to be at lol.

BTW look at the PDF you linked me to and read the rules regarding exhaust..no wonder I am having such a fit trying to figure this **** out haha.

1:3 EXHAUST
All cars must be equipped with exhaust collectors, headers, or
stacks installed to direct exhaust out of car body to rear of car,
away from driver and fuel tank.

How many cars (mine included) have hood exit exhaust? I dont think that counts as a as towards the rear of the car...see why I say the book doesnt really tell you much.


The 2nd link is a little more helpful in regards to showing what they consider a roll bar.



I took that photo and added some arrows to what I have in question. The red arrows are the parts I am wondering if there is a certain angle they must be at and the blue one is the bar I am asking about bending around my seat.

 

Get the seat in a comfortable spot for you, and then figure out where to place your main hoop and harness bar. The main hoop can also lean back a bit too. no more than 15 degrees if i remember right. I think the rear bars have to be as pictured, but cannot be placed less than 30 degrees? It'd be best to contact a chassis builder that deals with this kinda stuff.

 

The rear bars can have a bend, but I believe Ryan is right on with the 30* angle, with which it meets the floor. So bend accordingly to maintain that.

You can lean the main hoop back, but the top of the hoop needs to be withing 6" of the driver's helmet. I do believe you can bend the harness bar though.

As for your quote with the exhaust being directed to the rear of the car, Im pretty sure that section with which you quoted from, pertains to a certain class, such as "Sportsman" or something similar.

 

I dont think i'll have a problem with it being close to my head no matter where I sit the main hoop lol. Again I am 6'6 so I am practically backseat driving bwahaha. I wonder what the maximum degree the rear bars can be angled. My biggest issue is the car is a 4dr and I have to keep the rear interior in order to run FIS as I previously mentioned. I dont want to cut holes in a rear seat ya know. I have a feeling this car just went from street car that my son can ride in, to full fledge track car that I will grow to hate sadly...I honestly dont see how the rear seat is going to remain functional, while staying with in NHRA spec. I wonder if I can run a straight piece of piping from the main hoop along the headliner by the rear doors and then from that bar down to the trunk.

Essentially it would look something like this (dont mind my awesome art skills folks)


Red= Main Hooop Bar
Green=Piece in question
Yellow= Bars going to trunk


BTW that quote is under the "General Regulations" part of the rule book, thats why I hate the NHRA rulebook, its so damn vague to me lol.

 

6" like so.


I dont believe you can make the rear bars 2 pieces. So no, your diagram wouldnt be legal. But you could bend the bar to follow those lines. Just keep an eye on your angles.

There is NO way you could make the car retain USABLE rear seats, and a roll cage/roll bar. I wouldnt want my kid sitting anywhere in the backseat, unless he was a little guy, in a baby seat. Otherwise, you run the risk of him hitting his head on the rear bars, harness bar, etc. That would kill him.

Also keep in mind, if youre talking about going slower than 135, and building only a roll bar, you wont have to see a chassis certification tech. So you would just have to pass tech at your local track. Most likely, they wont have a clue. As long as the bars are there, and welded completely, you would probably pass.

 

Here are my shitty MS Paint skills. The blue lines are your cage. The red line is how rear bars would normally be ran. The blue one is how yours would be bent. The white lines in the background are your axis/angles from vertical. The rear bars need to be 30* or more from vertical. I would think this bend would be just fine. Ive seen more than enough people do the same thing, to retain the rear seats (more for looks or rules, not usage), without cutting them.

Hope that helps.

 

Yeah me and the wife are sitting here talking about this actually and I dont think I really want my son in the car with a cage. He is only 19 months but in case of an accident I dont really want to see his little head smashing up against a metal bar...as I said earlier, "sadly my street car is turning into a track ***** lol". I am looking at the drawing you put up and I am wondering .

I know i'll most likely need a cage as I trapped 124 on 16lbs and a slipping clutch lol. This year im coming out on 30+, a gripping clutch and race gas..so I might as well just get this over with haha

I wonder if this kit would work in my car:
http://www.jegs.com/i/Jegster/550/949201K/10002/-1


The only thing extra I beleive I would need is the swing out door bar (my big *** is not climing over a bar to get in and out of my car damnit)

 

Yea, I feel ya. I had to start on a second car, to have a street car again. After a season of not driving my hatch anywhere but off and on the trailer, and down the track, I was getting sick of it. LOL. It sucks.

Youre gonna want a 10 point cage with the info you just pointed out. If you go over 135, that 6 point wont be enough. Then youll be redoing it. So just do the 10 point from the start.

And you would be surprised by how much easier it might be to get in and out with a door bar. Gives you something to slide in and out on, rather than the seat bolsters. Its a little harder for me to get out, but easier to get in. But either way, not hard at all.

I would do something like this. And maybe call them, and see if they will upgrade you for a little more cash, to get longer bars that you can bend around the back seat.
http://swracecars.com/store/10-Point...11-5565TD.aspx

 

6'6 285...not sliding over door bars lol. I will definitley need the swingout door bars. Also I dont plan on going faster then 10.00 so a Roll bar will be enough according to the rule book

 

That jegs kit doesnt fit the four door all that great. My buddy bought one for his. But all it takes is more cutting and coping to make it all work.

 

Not to thread jack, But running 11.3 at 120 you only need a 6pt Cage, right ?
I dont get all these regulations.

 

Roll bar rule is 11.49 or 125mph(?) And yes, i believe it is only a 6pt, but it is usually built/sold in 8pt kits.
10pt roll cage required at 9.99 or 135mph.

 

My friend is having me build a cage for his All motor car and I want to make sure we do this right. So should we just go 8pt ?

 

Roll bar at 11.49-10.00 and under 135mph. 8.50-9.99 and 135-180mph require a 10pt cage.

 

Thank you, That helped alot.

 

Can anyone find proof of the "30*" rule? I'm building two FIS cages with rear seats right now and would really like to know if there is such a rule. I called the tech line, but its been busy for a few days now.

 

Try and contact your local chassis inspector, I know I double checked stuff on my cage with the local guy since its his final call and view of the rule.

 

I will try to dig up the info. I found it when I did my cage, but its been a while.

 

if it is a all motor car and dont go fast enuff to need a 10pt i would just put a 5pt in it to save weight, the passenger side door bar is not needed only the driver side

 

"All cage structures must have in their construction a cross bar for
seat bracing and as the shoulder harness attachment point; cross
bar must be installed no more than 4 inches below, and not above,
the driver’s shoulders, or to side bar. All required rear braces must
be installed at a minimum angle of 30 degrees from vertical and
must be welded in. Side bar must pass the driver at a point midway
between the shoulder and elbow."

Taken from the 2011 Rulebook PDF
http://www.bremertonraceway.com/2011...20Rulebook.pdf

Under 4:11 Roll Cage (Section 20, Page 26)

 

I dont think anyone should be concerned with the 30* angle so much though. The way I interpret it, I dont see anyone doing less than 30* anyways. Less than 30*, and youre not really preventing the hoop from being able to fall back in the event of a roll over. I drew up another diagram just for visual assistance.



Black/Grey lines are just the main hoop and door bars to give the effect of a roll bar.

Black/Red line is 90* from vertical. Directly in the middle of vertical (0*) and 90* would be 45*. So...

Black/Blue is 45* from vertical. With the same math, directly in between vertical (0*) and 45* would be somewhere around 22-23*. Which is represented by the Black/Green line.

Black and Green is at 23* or so, so figure 30* is pretty close to that. I wouldnt even want my rear bars to be at 45* if I could help it. So achieving an angle greater than 30* isnt that crazy.

 

Hmm, wonder where I can find a local certifier...maybe call the local track? Or maybe jegs would know?