Roll cage D bars
 

Looking to add the D bars to my cage-for some reason builder did not add them-but I did say 10.0s main goal. NHRA says OK to anchor to OEM driveshaft tunnel. Best to where both are almost touching at top or anywhere on the tunnel-with a plate I assume since uni body but the book just said tunnel.

Plan now is maybe in the 9s.

Best to run them to the frame or frame connector.

"1 1/4” x .058” CM (.118” MS) mandatory when main hoop is welded
to plates on floor and/or rocker/sill in lieu of frame; D-bars must be
attached to frame, subframe, subframe connectors, or OEM driveshaft
tunnel. Refer to text in this section for specific criteria."


Outer hoop mounted near frame but there is no frame or subframe connectors in the area D bars should mount.

Pretty sure the D bars can be welded to subframe connectors on an F body if you want to go through the floor. I considered it on my car but just ended up using plates on the tunnel where it meets the floor on each side. The main hoop is welded to plates at the rockers not near the frame. The cross bar in the picture is too low imo and should be at the bend point of the main hoop.

My main hoop does not look like that, that is NHRA's rule book diagram.

Your main hoop doesn't attach close to the door frame?


Mine attaches by the door frame (on plates welded to floor) and the 'D' bar attaches to the subframe connectors. (which are inboard of the door frame about 10" or so?)
The tunnel would be about 2' or more inboard?


:confused:

Here are a few pictures.
Most of the road race guys would almost tie both the D bars together in the center of the driveshaft tunnel.

One thing I would do is find a guy who knows the NHRA specs and have him decide how/where to weld the bar in?
9.99 would require a chassis certification anyway, might as well have it done correctly so it will pass.

BTW, if to the tunnel it will require plates welded (or bolted?) to tunnel and bar to that.

:confused:

Your main hoop is welded at the same place as mine. You could go to the frame connectors with the D bars or to the tunnel with plates.. Either one meets spec for a unibody.

I figured it should have plates ,but the rule book does not specify that for the D bars. I could find just all the other tubes. That was the plan when I have it done.

Part of why the goal was 10.0s in the heat was to not have the hassle of a cert and a physical-even though I am in good health.But being close to that 10.0 I want to get the cage legal so it would pass. not sure why the guy forgot those to begin with. He is the tech guy at the local track for the 10.5 tire and 275 DOT classes.

Frame connectors are about 1" below the floorboard but welded to subframe in front and rear.

D bars aren't required for 10.0 so if that's what you asked for they probably weren't forgotten but just ignored.

You have to cut the floor to weld to the frame connectors which is why going to the tunnel is seen more often. Just easier.

Yea I figured probably why they did not do them. Just want to have that cushion of legality if I decide to go faster.

Heck with a lot of test and tunes I've been too even right before COVID the tech was basically "you got all the correct safety equipment? OK !"

I just added the D bars to mine. They have to weld to a 6x6 plate. The plate has to be fully welded all the way around to the tunnel.

Thanks for the picture. What I thought.