Roll Cage.

[ptc]

I understand its ultimately up to a Track Tech - "Authority having jurisdiction" which doesnt always take into consideration logic and the 'intent of a rule'.... I live and work in the spec, code, rule and legal world so I know how to dissect and interpret things.

So Vin, just for discussion purposes between logical minds lets break down the roll bar rule: Which is a "Minimum Standard" and can be added to all you want to make it better.

4:10 ROLL BAR
1. All roll bars must be within 6 inches of the rear, or side, of the driver’s head, extend in height at least 3 inches above the driver’s helmet with driver in normal driving position or be within 1 inch of the roof/headliner in the area above the driver's helmet, and be at least as wide as the driver's shoulders or within 1 inch of the driver's door.

2. Roll bar must be adequately supported or crossbraced to prevent forward or lateral collapse. Rear braces must be of the same diameter and wall thickness as the roll bar and intersect with the roll bar at a point not more than 5 inches from the top of the roll bar. Crossbar and rear braces must be welded to main hoop.

3. Sidebar must be included on driver’s side and must pass the driver at a point midway between the shoulder and elbow. Swing-out sidebar permitted.

4. All roll bars 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.

5. All vehicles with OEM frame must have roll bar welded or bolted to frame; installation of frame connectors on unibody cars does not constitute a frame; therefore it is not necessary to have the roll bar attached to the frame.

6. Unibody cars with stock floor and firewall (wheeltubs permitted) may attach roll bar with 6-inch x 6-inch x.125-inch steel plates on top and bottom of floor bolted together with at least four 3/8-inch bolts and nuts, or weld main hoop to rocker sill area with .125-inch reinforcing plates, with plates welded completely.


Section 1 dictates the specs for where the bar must be in relation to the driver.

Section 2 now tells us about the ROLL BAR and its supports, but all this rule stipulates is that a ROLL BAR must be "adequately supported to prevent forward or lateral collapse", that is the ENTIRE basis for this rule. However, nowhere in the entire rule does it state REAR BARS ARE REQUIRED. So it could be interpreted that a forward brace and a lateral brace could support the same ROLL BAR from collapsing - yes?

What the rule does say and is intended is "IF" Rear Bars are used, they must meet certain criteria to support the ROLL BAR. Most people would rather go backwards instead of forward in cars because thats where the space is to do it. The rule was not specific to TRUCKS.... But the INTENT is the SAME~!

In section 3 there IS a requirement for a sidebar at the driver side.

Section 4 covers cross bracing for seats and belts that MUST be installed

Section 5 covers welding and bolting to OEM frame... its very vague and its intention is only that the connection must be SECURE.

Section 6 covers Unibody cars MAY do this and that blah blah blah.... (are not safe at all - IMHO )

So If I presented you with a 4 point mounted Rollbar (2 in front to front cab mounts, 2 in back to rear cab mounts) and 2 more lateral bars going from rear hoop inward to a frame cross member (total of 6 points) all bolted to mirror plating beneath the cab - would you as a tech inspector accept my installation as meeting the intent of the RULE 4.10?

Thanks for reading....

[vin63]

Originally Posted by ptc

.... I live and work in the spec, code, rule and legal world so I know how to dissect and interpret things.

Then 4-10 of the NHRA General Rules should be even more straight forward for you than the rest of us. There is an illustration that cites material requirements and the one back or cross bar tubing size deviation. Let us know what you end up doing and if it passes tech inspection.

http://www.nhra.com/userfiles/file/T...A_Rulebook.pdf

[ptc]

Well the word I ended up with from NHRA was that the rear bars need to be installed at a 30 degree angle of the main hoop.... well no way that will fit inside a truck cab. (and no place they could show me that was written, but OH well).... mine is not going to be NHRA approved, but will suffice a crushed cab if a roll over were to ever happen. Thats my end result.

So heres what I got so far, still working on it.....

I welded in the cab corners with blank out plates to keep crap from going down there #1.... and #2 to make the floor flat for the plates. I match drilled the plates and mounted them to the floor top and bottom. Then I welded the interior cab Plate to the floor for both the rear hoop and front bar floor mount.

The frame plate underneath will be welded to a 2" x 3" outrigger from the frame rail when I get the cab back off. So now the cab with roll bar intact can be removed by simply unbolting the 16 plate bolts and the 4 cab bolts.

[BR3W CITY]

They pulled a number from thin air? Never heard that 30* referenced in any of the little guides I read.

[vin63]

This is what I was referring to about the ambiguity of rules for non-spec'd roll cages in trucks. You did a nice job on the main hoop. The forward lean of the A-pillar is always a source of contention for me with the door bars in a traditional roll cage. That was the other reason I did a roadster chassis in my friend's '60 C10 many years ago.

[ptc]

Originally Posted by BR3W CITY

They pulled a number from thin air? Never heard that 30* referenced in any of the little guides I read.

Yea that one threw us offsides a little bit too. But Im not gonna argue with them to try and get into their 'club'... If they dont want to grow their own membership thats fine with me.


Thanks for the kudos Vin!

Onwards and upwards!

[BR3W CITY]

Originally Posted by ptc

Onwards and upwards!

according to that ruling, its more like onwards and outwards....