darguy

Hey Gang,

I'm getting a roll bar made up for my 99 FRC and was wondering if anyone had any photos of how they mounted the main hoop to the floor, and where the rear stays tie in to the frame. Advice, suggestions?

davidfarmer

the best way to attach the main hoop is right behind the seats, basically to the inside of the frame-rails. The rear bars then go back to the frame, adjacent to the rear shock mounts. Some bars mount on the fuel bulkhead (IOPort for instance), which is technically legal, but attaching to the frame is much better.

For a full race car, you can go down THROUGH the bulkhead to the frame, which gives you more seat/head room, but that gets really messy dealing with fuel tank and line, as well as cutting out and reassembling the bulkhead.

davidfarmer

crappy old photo showing the area I mentioned. I attached a thick piece of angle iron to the inside of the frame, and also the seat-mount and bulkhead. Then welded the tubing to that.

darguy

Thanks for the info and photos - that's kind of what we were thinking of for the main hoop. For the rears, we were going to go to the frame just in front of the stowage bins.

The car is a DD - but it's going to see some track time this year, so I need to keep things reasonably civilized inside while still building a tech-friendly bar.

davidfarmer

I don't know what your needs are, but many racing organizations do not allow the rear down tubes to extend beyond the suspension points. Basically, they want it to be for safety, not for performance gains (theoretical chassis stiffness).

96solo

Here's mine just finished. The work was done by Precision Chassis in Gilbert, AZ.


Here's the rear attachment.


Here the side finished.

fatbillybob

There are always compromises to weigh. In Dave's pic the angle iron is ok but to prevent punch through I'd have a significant surface area of Angle and box the angle in so it does not bend. Then supported nascar bars also helps support the main hoop. Going back to the frame rails is the best as Dave says for rollover but then you got to cut more car to properly design the nascar bars otherwise you have to put a squiggle in them. That weakens the nascar bar who effect works in compression vs the X bars working in tension. So where dave has his bar forward of the fuel firewall makes for having nascar bars in tension. This was my solution I stole from IIRC seth the BMW guy who built and awesome C6 racer. His design supported the rollover hoop very well and I have weldment all the way up the sill plate and b piller and furthur support the extra sill plating and rolloverhoop to the tunnel the weakest point in the design. This BMW fabricator's design is the best compromise I have seen for rolloverhoop not supported to the framerails.

Bill Dearborn

I got this info from Mike Neal who worked on the Corvette Team back in 2001. Here is a copy of an e-mail he sent to somebody I know in response to a question I had asked:


---------------------- Forwarded by xxxxxxxx/US/GM/GMC on 11/12/2001 02:57 PM ---------------------------


Michael W. Neal
11/09/2001 10:01 AM

To: xxxxxxx/US/GM/GMC@GM
cc:
Subject: Re: Rollbar for C5 (Document link not converted)

As with any rollbar installation, the attachment points are critical. The loads must be transmitted down to the main rail through significant structure. The lock pillar is significant as it carries the roof bow. However the cross car beam is not load bearing in the direction that an additional rollbar would apply loads. What we usually do is weld a gussetted plate on top of the beam and to the lock pillar for the main roll hoop to weld to. This will transfer loads from the rollbar to the lock pillar to the frame rail.


Bill