Roll Cage Main Hoop Question

[Jolane]

Does the main hoop have to be one piece, bent in a "U"? Can it instead be a straight horizontal upper piece with two vertical pieces notched and welded? I am thinking that this could accomplish a number of things (for me at least). If this is just too stupid of a question, please let me know. I am just thinking out of the box.

BTW...I am thinking street car here, but it would be nice to follow some sort of rules I guess. Yes, I do have the ITS rollcage article also.

Thanks,

Joshua

 

Also, would it be a bad idea to cut a slot through the map light cross bar support and stick the main hoop into that, then weld down it along both edges? This would tie the roof support into the main hoop very well, and also recess it so that head room is not a big deal (even though it is pretty much behind the drivers head). A decent interior finish should also be easier with the recessed bar. I am trying to hide a rollcage the best I can.

I want the rollcage for structural stiffness and safety, but don't want my insurance company complaining, nor additional attention from the local police...plus, I have not seen something like before (maybe for good reason).

[260DET]

Build it to competition specs whatever they are in the US, a one piece hoop seems to be universal though. For good reasons, which I'm too lazy to mention

[boodlefoof]

I've never seen one that wasn't a one piece hoop.

 

I'm not sure what kind of racing rules you might be interested in following. On my '68 Camaro I put in a bar that complies with IHRA drag racing specs... If I remember right, that requires that the hoop have a wall thickness of at least .125'' at all places... which most people read to mean .134'' because it will thin out a bit at the bends and the extra wall thickness keeps you in spec.

[johnc]

Does the main hoop have to be one piece, bent in a "U"?

 

Yes.

 

Can it instead be a straight horizontal upper piece with two vertical pieces notched and welded?

 

No.

 

Yes, I do have the ITS rollcage article also.

 

Pay attention to that article.

 

Also, would it be a bad idea to cut a slot through the map light cross bar support and stick the main hoop into that, then weld down it along both edges?

 

Probably be a bad idea because that roof support is a structural box. By cutting out one side of the box you've made it very weak. A better option would be to put the main hoop right up against the roof support and weld five tabs from the hoop to the support connecting the two.

 

Roll bars and cages are first and foremost SAEFTY items. Follow the specifications set by NHRA, SCCA, NASA, POC, PCA, etc. or you'll most likely end up with something that is not safe.

[Jolane]

Thanks Everyone! It is definitive that the main hoop will be one piece. After looking at it more, the hatch hinges would have been in the way anyways for what I was originally thinking.

I see a bunch of pictures of rollcages installed, but what do people do about interior? Just don't worry about it? Custom fiberglass panels instead? Because this is a street car, I do want an interior in it.

Did anyone see the Corvette that they built on American HotRod? The interior on that was creative, yet looked good IMO. I was hoping to do something similar where the bar is "integrated" with the body.

Thanks Again,

Joshua

[Michael]

In my car the main hoop is butted against the roof support and welded to the sheet metal in several places, essentially in the manner as Johnc described. The seat is set back quite far, and actually the back of my head is only about 2†in front of the bar. Fortunately, the seatback is tall, and hopefully prevents contact between cranium and steel (it’s a Kirkey “pro street†seat).

 

I thought about burying the hoop inside the roof support sheet metal, but one would have to weld the sheet metal “box†closed again, to retain structural integrity (otherwise it’s weak in shear, or twist). This would be impractically difficult.

 

The “solution†to the interior panel problem was simply to delete them.

[Jolane]

Thanks for the input Michael. My concern is also head clearance, as I am tall. That makes me put the seat back as well.

Maybe there is not a good solution for interior panels. I really don't want to delete them, but maybe it would be possible to cover that area similar to how the A pillars are covered, with vinyl and foam.

I do not want to put all the interior panels in first, then weld the cage in. I do want to be able to remove everything for paint...

Thanks Again,

Joshua

[Pop N Wood]

You kind of need to ask yourself what you want to accomplish. If you aren't worried about class rules and only want to stiffen the chassis, then why not form some sheetmetal and simply strengthen the unibody in the area of the roof arch? Might be more work than a simple cage, but it could be done in such a way that you retain all the stock body panels. Also won't scare your passengers or create undue interest from the local cops.

 

I would imagine the idea will be met with contempt from the majority of the people on board here, but like I said you need to ask what you want to accomplish.

[johnc]

Thanks for the input Michael. My concern is also head clearance, as I am tall. That makes me put the seat back as well.

 

You can also rebuild the seat mounts as 1.5" x 3" boxes and pick up about 2" of headroom.

[Jolane]

John,

I will be rebuilding the seats mounts. I am planning on using Corbeau CR1's, which have a thicker bottom (than the A4's), so my mounts will already be lower. When I replaced the floorpans, I left seat mounts out until I get the seats. They will also serve to form a cross member of sorts (connected underneath the car), which should help tie the frame rails into the rocker boxes.

I don't really expect to need additional room for a helmet. I am considering a roll cage for safety and chassis stiffness. I really don't want to see cracks forming in my B pillars...

Joshua