Re: Roll Cage NHRA Legality Question
[Re: mopowers]
#2985927
11/16/21 09:20 PM
11/16/21 09:20 PM
|
Joined: Dec 2003
Posts: 23,558 Here
jcc
No soup for you!!!
|
No soup for you!!!
Joined: Dec 2003
Posts: 23,558
Here
|
Not sure what is going on with OP's pictured incomplete cage.
I'm with Helmuth Hübener, and no soup is being served today.
|
|
|
Re: Roll Cage NHRA Legality Question
[Re: jcc]
#2985934
11/16/21 09:35 PM
11/16/21 09:35 PM
|
Joined: Sep 2006
Posts: 3,023 Sac, CA
mopowers
OP
master
|
OP
master
Joined: Sep 2006
Posts: 3,023
Sac, CA
|
Not sure what is going on with OP's pictured incomplete cage. Disregard the rest of the cage in the photo - it's obviously under construction. I was asking specifically about the rear braces and that was the closest photo I could find to illustrate my question. Maybe I was unclear. Can rear braces be crossed (like the X-brace in the top photo), or do they have to be straight back? That's what I was getting at. I apologize for any the confusion.
Last edited by mopowers; 11/16/21 10:04 PM.
|
|
|
Re: Roll Cage NHRA Legality Question
[Re: Cab_Burge]
#2986041
11/17/21 10:38 AM
11/17/21 10:38 AM
|
Joined: Jan 2004
Posts: 8,833 fredericksburg,va
cudaman1969
Itch Nutz
|
Itch Nutz
Joined: Jan 2004
Posts: 8,833
fredericksburg,va
|
Your question is answered in the bar size part, A-two bars @1-5/8 CM any length just like the picture. If it has to have an X then the picture NEEDS changing
Last edited by cudaman1969; 11/17/21 10:40 AM.
|
|
|
Re: Roll Cage NHRA Legality Question
[Re: cudaman1969]
#2986079
11/17/21 12:34 PM
11/17/21 12:34 PM
|
Joined: Dec 2005
Posts: 12,608 Fulton County, PA
CMcAllister
Mr. Helpful
|
Mr. Helpful
Joined: Dec 2005
Posts: 12,608
Fulton County, PA
|
Concerning the rear bars in the photo...
IF they are both 1.625 x .120 and IF they are in on the correct plates, then either the straight bars going to the back OR the X brace, as long as it exceeds 30 degrees, would satisfy the "B" bars in the cert by themselves. An inspector would only be concerned with the bars needed to satisfy the cert.
ETA...per the rule book, additional "B" bars allow you to use smaller tubing and still satisfy the cert. i.e., in the photo the four rear bars could be 1.375 diameter. Or the long bars could be 1.250, IF the X is 1.625.
The "B" bars can be straight or Xd, But by Xing the short bars, rather than having them in individually and straight back, you are gaining a lot more strength and rigidity with no increase in weight or "stuff" in the car.
Welding the long bars to the body structure at the base of the rear window will tie those bars to the body at that point, using one to support the other and further stiffening the body.
Don't forget the "D" bars. Main hoop to frame tie. A second pair at that point on the main hoop being used to support the area of the floor at the front spring box will also be beneficial, especially if using leaf springs.
Last edited by CMcAllister; 11/17/21 03:00 PM.
If the results don't match the theory, change the theory.
|
|
|
Re: Roll Cage NHRA Legality Question
[Re: CMcAllister]
#2986158
11/17/21 05:16 PM
11/17/21 05:16 PM
|
Joined: Sep 2006
Posts: 3,023 Sac, CA
mopowers
OP
master
|
OP
master
Joined: Sep 2006
Posts: 3,023
Sac, CA
|
Thanks guys. I appreciate the input I knew I shouldn't have posted that photo I found online. It's just confusing the general question I had.
I did send an email to NHRA and heard back. Excellent suggestion btw, Cab. I had no idea NHRA answered emails. Per that email response and as mentioned, If there's only two rear bars, they may be X'd, but they said the two bars must attach to the horizontal portion of the main hoop. Does anyone know where in the rulebook that is stated? I'm failing to find it.
In my 66 Dart, have four bars currently, similar to the four in the top photo. Two long 1.25" bars to the rear of the trunk (attached to the horizontal part of the main hoop), and two 1.625" X'd tubes from the outer radii of the main hoop to the side of the inner wheel tub (>30 degrees). I was just curious if I could cut out the long 1.25" bars and still be legal. Sounds like no because the two X'd bars are tied to the radius and not the horizontal portion of the main hoop.
|
|
|
Re: Roll Cage NHRA Legality Question
[Re: mopowers]
#2986191
11/17/21 06:34 PM
11/17/21 06:34 PM
|
Joined: Dec 2005
Posts: 12,608 Fulton County, PA
CMcAllister
Mr. Helpful
|
Mr. Helpful
Joined: Dec 2005
Posts: 12,608
Fulton County, PA
|
Thanks guys. I appreciate the input I knew I shouldn't have posted that photo I found online. It's just confusing the general question I had.
I did send an email to NHRA and heard back. Excellent suggestion btw, Cab. I had no idea NHRA answered emails. Per that email response and as mentioned, If there's only two rear bars, they may be X'd, but they said the two bars must attach to the horizontal portion of the main hoop. Does anyone know where in the rulebook that is stated? I'm failing to find it.
In my 66 Dart, have four bars currently, similar to the four in the top photo. Two long 1.25" bars to the rear of the trunk (attached to the horizontal part of the main hoop), and two 1.625" X'd tubes from the outer radii of the main hoop to the side of the inner wheel tub (>30 degrees). I was just curious if I could cut out the long 1.25" bars and still be legal. Sounds like no because the two X'd bars are tied to the radius and not the horizontal portion of the main hoop. It's on the screenshot of the rulebook page above. We've always put the bars out near or partially in the radius.. I believe rule of thumb is it needs to be within 5" of the top of the cage. Not way down in or below the radius. Bars in the photo are right there. A picky inspector might say something about that. If your X is 1.625, the 1.25 bars going to the trunk won't matter one way or the other. Inspector will ignore those. Why cut them out? They aren't useless. SFI spec kicks in quicker than 8.50 and/or 180MPH. Slower than that is rulebook specs.
If the results don't match the theory, change the theory.
|
|
|
Re: Roll Cage NHRA Legality Question
[Re: CMcAllister]
#2986212
11/17/21 07:47 PM
11/17/21 07:47 PM
|
Joined: Sep 2006
Posts: 3,023 Sac, CA
mopowers
OP
master
|
OP
master
Joined: Sep 2006
Posts: 3,023
Sac, CA
|
Thanks guys. I appreciate the input I knew I shouldn't have posted that photo I found online. It's just confusing the general question I had.
I did send an email to NHRA and heard back. Excellent suggestion btw, Cab. I had no idea NHRA answered emails. Per that email response and as mentioned, If there's only two rear bars, they may be X'd, but they said the two bars must attach to the horizontal portion of the main hoop. Does anyone know where in the rulebook that is stated? I'm failing to find it.
In my 66 Dart, have four bars currently, similar to the four in the top photo. Two long 1.25" bars to the rear of the trunk (attached to the horizontal part of the main hoop), and two 1.625" X'd tubes from the outer radii of the main hoop to the side of the inner wheel tub (>30 degrees). I was just curious if I could cut out the long 1.25" bars and still be legal. Sounds like no because the two X'd bars are tied to the radius and not the horizontal portion of the main hoop. It's on the screenshot of the rulebook page above. We've always put the bars out near or partially in the radius.. I believe rule of thumb is it needs to be within 5" of the top of the cage. Not way down in or below the radius. Bars in the photo are right there. A picky inspector might say something about that. If your X is 1.625, the 1.25 bars going to the trunk won't matter one way or the other. Inspector will ignore those. Why cut them out? They aren't useless. SFI spec kicks in quicker than 8.50 and/or 180MPH. Slower than that is rulebook specs. I'm not seeing where it's explicitly stated in the rulebook, which prompted my question. It says "If A (meaning 1.626"), two bars." It doesn't say they should attach to to the horizontal portion of the main hoop, though, it's probably implied by what is shown in the rulebook picture, as cudaman1969 said above. I just wish it was more clear because the photo also shows two parallel rear bars, yet the NHRA tech said X'd is fine if they're attached to the horizontal portion of the main hoop. For me, I'm considering removing the two long 1.25" bars because I've changed direction a tad on my build. I may just redo the rear braces all together by using bent rear braces, so I can run a rear seat. I appreciate the input. This has been very helpful.
|
|
|
Re: Roll Cage NHRA Legality Question
[Re: mopowers]
#2986355
11/18/21 09:53 AM
11/18/21 09:53 AM
|
Joined: Oct 2007
Posts: 4,219 New York
polyspheric
master
|
master
Joined: Oct 2007
Posts: 4,219
New York
|
Where can I read up on the engineering used to make these rules?
[/sarc]
Boffin Emeritus
|
|
|
Re: Roll Cage NHRA Legality Question
[Re: polyspheric]
#2986495
11/18/21 04:57 PM
11/18/21 04:57 PM
|
Joined: Dec 2003
Posts: 23,558 Here
jcc
No soup for you!!!
|
No soup for you!!!
Joined: Dec 2003
Posts: 23,558
Here
|
Where can I read up on the engineering used to make these rules?
[/sarc] That reminds me of a disagreement I had with a city electrical inspector about grounding when I presented the current at the time NEC code book, he said "I don't care what the NEC code book says", authored and revised many times for nearly a century by hundreds of engineers and Phd's in the field.
I'm with Helmuth Hübener, and no soup is being served today.
|
|
|
|
|