toddvw

so how should the main hoop be made then?

nonvtecallmotor

Ha mine are damn near 90*.

As long as I keep getting recerted thats all that matters....

toddvw

good to know cause i think mine are more than 30 and adding on to the cage now but was afraid i wouldn't pass

njn63

A main hoop has a crossbar for the harness that maintains it's shape. The bars to the back have no such device.

The main thing that scares me is that a 4 point cage requires those bars to keep the main hoop upright. In a rollover, there is a chance it could fold those bars and push the top of the main hoop backwards. Pair that with the fact your upper harness is attached to that main hoop and you're looking at a very dangerous scenario.

If there is anything I've learned from my involvement with the NHRA it would be to not trust anything they say regarding something being safe. They are in no way proactive and will pass something until it kills someone. I guess I have a jaded perspective though considering I was in Indy in 1996 when 2 racers died in 2 days.

sander

Exactly, exactly.

turbotypeR@SPEC

Well, the car I posted pics of only went 136mph and the current car I am running is not a street car and the bars are straight. I have started working on my 25.5 cage and I have the SFI 25.5 book in front of me. It is the same as the other rule book. it shows pistures of them straight, but never mentions anything about the bars being straight or not. However, this may be an assumed rule, at least for the 25.5 cert. I am taking the car to my NHRA cert guy next week to confirm the way i am building the 25.5 cage. Mine will remain straight, but I will get verification from him on the bars being bent or straight.

sander

Awesome, that would be interesting to know.

97VRT

Thanks Rick that's the answer i was looking for.

Sander i checked everything in the '08 rule book it doesn't mention anything wrong with it.

B16A1-EF9

I know it doesn't state anywhere that they can't be bent. But its common sense, those bars are there to hold up the main hoop from folding, it only makes sense that they do stay straight. I think if they are bent it kind of defeats the purpose. Them being bent is a cosmetic thing, might as well have bolt-on "Monkey Bars"

97VRT

Well went ahead and did it.

boostedcivicsir

my car has been done since 06 and passed cert twice. you are fine.

ahobbs

im dreeding this part that i have to do

97VRT

Those bars were so hard to make. Almost ditched the back seat thing there.

josh green

You cannot go by what HIS NHRA guy says though. You have to go with whatever YOUR NHRA guy will pass. Sounds stupid I know, but its those "assumed rules" and unclear rules that they will differ on.

97VRT, I think those bars look fine, as far as structurally I cannot see them crumpling in and pulling the hoop back in a roll over. The bend doesnt appear that it would allow the bar to crumple and pull the hoop backwards.

nonvtecallmotor, I like not being able to see the rear bars. Keeps it looking more like a street car, which it easily could be.

I want to know why NHRA doesnt enforce their own rules on productions cars that go faster than their safety requirements. A local has a brand new grand sport package vette and it runs 11.2's, why isnt he required to have a 6pt cage but our cars would be? I dont see any GTR owners with cages or getting kicked off the track. Rules are rules, they should apply to ALL no matter the year, make or model.

turbotypeR@SPEC

Yeah, but this guy is very strict and by the book. if it is going to not be allowed, it will be by this guy. Trust me when I say that if it passes cert with this guy, it will with anybody.

josh green

Are you taking it to the NHRA guy down towards or in macon? I know thats who matt has used and he is very by the book.

nonvtecallmotor

Looks good

sander

I don't personally care about the rules as I am not building an NHRA car of any kind. I am just speaking on the theory of rear bar design.

I wont agree that a rear bar with any bend however will ever be sufficient for a rear support of the main hoop.

Also, 97VRT, from a fabrication standpoint, it all looks very symmetrical and good, although are there any rules against having any bends in the main hoop not equaling greater than 180 degrees? It looks like the main hoop towards the bottom comes in towards the center of the car as opposed to being straight down?

Not criticizing anyone here, just curious on the ruling.

fukenricen

ok next question what about bar behind the driver and passenger seat, can it be bent allowing drivers seat to recline back?

nonvtecallmotor

Yes it can be bent.

97VRT

It has to be like that. My 6x6 plate is as far to the side as i could beat the floor flat till. Its just how the floor of the car is designed. Stupid VW's! lol

bigTom

It doesnt make a differance. tech guys have differant "opnions" on cages but when it comes to 25.x stuff they check each and every single bar. There is no 2 ways about it. Every single bar is referenced in the SFI specs so you really cant screw it up. Anything questionable about a spec I just call SFI themselves. NHRA accepts the SFI chassis specs.

The 25.5 spec is only concerned with the drivers compartment. Nothing fore or aft of that. If i remember correctly there was a stipulation stating if you ran 4 rear bars they could be 1.5" x .065 and if you ran 6 they could be 1.375" x .058. I like using 1.625 rear backstays in any case and play it safe. Any bars thereafter really dont make any differance as far as a certification is concerned. For what its worth the only required 6x6 plates are at the 4 outter points of the drivers structure. The rear bar does NOT need to go to a 6x6.

The newly released 25.3 spec DOES referance required rear backstays as opposed to the 25.5. The 25.3 covers tube-chassis as well as OEM frame cars 6.50 to 7.49. The 25.1 pro-stock spec doesnt even have any referances to front or rear bars! Hence why many guys run full titanium front and rear clips; its not referanced int he spec and doesn't need to be 4130. FYI; 25.3 is 4130 only; 25.5 allows mild steel.

As far as bent rear bars go; I HATE THEM! but some people want/need them. They severely weaken the structural integrity of the cage. It creats a weak point during a collision which will bend. Ever wonder why FIA requires straight rear backstays!? Just because the NHRA allows bends does not mean its safe (though it can be done safely.) Food for thought; the FIA also requires a maximum of 4 bends in the main hoop not totalling more than 180 degrees.

NHRA does not limit degrees nor the amount of bends allowed. FIA and other road racing does.

97VRT

Thanks for all the info.

I feel like the NHRA's requirements on roll bars/cages is entirely to short. Just leave so many points untouched. All i have is a 2008 copy. Is there a better reference?

This is my friend and i first time making a cage. We have all the tools and materials to do it just not the experience. I think we did pretty good for two 20 year old kids. We knocked out the whole 4 point in a weekend.

bigTom

yes... the 2010 rulebook. as of 2009 the requirements for cages changed slightly with a required rear crossmember.

Thats what will kick you in the ***! My 1st rollcage took me a month and it looked like dogsh!t! With 1 other person, I can get a 10 point nowadays done in a day from scratch; rushing it! lol

extremeracer

I am looking at doing something similar on my EG hatch with keeping the rear seats and making the bars go over them

Would it not retain the structural rigidity if you put a cross bar between the 2 bars running to the back at the point where they bend down ??