so i'm finally getting things ready to put in a regular, 8pt nhra rollbar, but the door bar mounts have me a little confused. the frames on these cars are so far inboard that you're really not left with many options where to mount them. i know a lot of people would just weld the plate to the floor and put the bar in the corner of the plate, but to me that seems like a bad idea being so far off center from the frame.

my plan:

weld some 1x3 box (or something similar) underneath the rocker panels front to back like unibody subframe connectors (yellow), and tie it into the frame (red), cut out that top section of the rocker panel and weld the usual plate to the floor/box (purple), and stick the door bar on the edge (green).


does this sound like it would work? safety and rigidity are the main concerns here, a cage doesn't do much good in a rollover if it pokes through the floor.

 

I welded plates right next to the kick panel under the dash, have a stub that comes up about the center of the speaker in case I ever did a roof hoop. Your spot needs to be farther forward.

 

yeah, i'm just worried about being able to get in and out with it being too far forward. i'm not a fan of swing out bars, haven't really seen a design that i'd put much faith in.

 

Ok, So I know the solution to your problems, but I'm not sure on my ability to explain it. I use to build tube frame chassis for circle track cars. If only I still had auto cad on my computer. I could just draw it up for you But I'll give it a try. You need to build a front hoop that connects from the frame, up and through the dash, and to the other side of the frame. then weld your side bars to the front hoop. . run one bar low, and the top to where you want it. probably one or two cross members, between the two. what you have drawn would work really well for a rock crawler or 4x4 where it may take impact under the rocker panel.

IMO welding plates would be easyer, and plenty strong enough.

 

If you can wait for tonight i can take pictures of my roll cage, its much like trochoid said go next to the kick panel area.

 

this might help some, but if you do need my other pic let me know.

 

i'm just doing an 8pt, so no halo bar. nhra says the door bar must pass across the drivers body so that's why it's where it is.

 

That configuration leaves little support for the top of the A pillars. You will need a down support from the middle of the front down tubes to the low rocker horizontal. Then you will be connecting at a un-supported horizontal tube. You will need to tie it into the inner rocker as well.
Looks like a good start you simply need to triangulate a bit with some more tubes, strategically located.


These pictures show the proper way to build the front down tubes as well as the main hoop. Although I am not a fan of those "can opener" style gussets.
Courtesy of Izzy's Custom Cages. http://www.izzyscustomcages.com/