Hot Rod Forum banner

69 camaro where to mount supports for main hoop

1K views 11 replies 4 participants last post by  actmobmar 
#1 ·
These are for the main rollcage hoop, they are the short bars that go down behind the main hoop to the rear passenger floor somewhere. I've heard to weld a plate to the rear floor on either side and weld the tube to that, I've also heard I should cut the floor and weld them to the subframe connectors. I want to minimize the hacking on the car and loss of interior space, so what is the right way to do it? Thanks
 
#2 ·
If this is rearward from the B pillar / front leaf spring mount area, I don't think your connectors will go back that far. I would want the bars that go down through the rear speaker panel on a plate fastened through both the floor and unibody rail's flanges if that makes sense. I've never put a cage in myself, but thats where you could tie into the vehicle's structure back there. Bolting the plate down via holes drilled through the rail flanges, sandwiching the floor itself, seems most logical. I have no idea what NHRA standards or your local track would dictate, just shooting from the hip here.
 
#4 · (Edited)
If you're concerned about NHRA requirements, here's a partial regarding cages:

"4:11 ROLL CAGE

Full-Bodied Cars

On unibody cars with stock floor and firewall (wheel
tubs permitted), the roll cage may be bolted or welded to the
floor/rocker box via 6-inch x 6-inch x .125-inch steel plates similar
to the roll-bar attachment requirements of paragraph 4:10 in this
section. Unless attaching to OEM floor or frame, the minimum
requirements for a frame member or fully welded in place frame
connectors on unibody cars to which a roll-cage member is
attached are 1 5/8-inch x .118-inch MS or .083-inch CM round
and/or 2-inch x 2-inch x .058 MS or CM rectangular.

All cage structures 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.

All required rear braces must be installed at a minimum angle of 30 degrees from vertical and must be welded in. Side bar must pass the driver at a point
midway between the shoulder and elbow."

I had to post the text, a link would only work if you were an NHRA member.

Mine run from the top of the hoop, through the package tray area, welded to the rear frame kick-up, but it's a back half car, no rear seat, that area is filled with wheel tubs. It also required relocation of the rear deck hinges, which is tricky to make them function/swing correctly. You can see in the photos how they had to be moved in quite a bit and attached to the new rear frame rails. For some reason, they just swung in a different arc from the stock location.
 

Attachments

#5 ·
Guys, I believe he is talking about the short bracing bars that would go on a 10-15° angle inward, from the main hoop seat-back crossbar to main hoop intersection point..... down to the floor near the front of the rear leaf spring eye mounting location/subframe connector tie-in point, ....or down at about a 45° angle inward to the sides of the driveshaft tunnel.

These bars are optional, they turn a 6-point roll bar into an 8-point roll BAR,.....not to be confused with an 8-point roll CAGE. They are not required for a strip legal 6-point roll bar.

I've fitted them on a '74 Nova(basically the same floor pan per se), they go down and slightly back at a 10-12° angle from mainhoop/crossbar intersection to the floor where the subframe connector meets the original rear stamped subframe rail channels, just inboard of the front spring eye pocket. They attached to the 2"x2" .095" wall square tube frame connectors that were channeled up through the rear seat passengers footwells. If you pick your point carefully, the rear seat bottom will just fit, but it is a tight fit.

If you are just going to mount them to the floor, they should be on 6"x6"x .125" thick plates welded to the floor to be NHRA/IHRA legal. No roll bat tubing can ever be welded to just the floor itself in a uni-body car, it must have the 6"x6" reinforcement to prevent it being ripped loose in a crash.
 
#6 ·
Ericnova, u r correct, these are the bars I'm talking about. So they are not required? Car is a convertible, fastest it will ever go is 9.0. Also, if anyone has pictures that would be great. Do these bars weld to the main hoop directly below the cross bar?
 
#7 ·
A little more clarification, the rule book has 330 pages, requirements are not only dictated by speed/ET but by vehicle type, convertibles have stiffer requirements than full bodied vehicles. If you intend to run in class competition, you really need to have a rule book.

ROLL CAGE
Roll cage mandatory in cars running 10.99 (*6.99) or quicker or
any car exceeding 135 mph. In full-bodied cars, with unaltered
firewall, floor, and body (from firewall rearward, wheeltubs
permitted), running between 10.00 (*6.40) and 10.99 (*6.99), roll
bar permitted in place of roll cage. In convertibles running 10.99
or quicker or exceeding 135 mph, roll cage mandatory. Cars
running between 7.50 (*4.50) and 9.99 (*6.39) must have chassis
recertified every three years by NHRA and have a serialized
sticker affixed to cage before participation.

The rules go deeper than this, individual interpretation of the rules will vary, do your homework. I'm only providing rule book text, not advising you. I don't run NHRA and IHRA comp class racing any longer, the guys who do will chime in I'm sure.
 

Attachments

#8 ·
Is that 9.0 in the 1/8 mile, or 9.0 in the 1/4 mile??

If it is 1/4 mile, your car will require a full cage, just a 6 or 8 point roll bar will not be legal because of the convertible top.

If that is 1/8 mile, then a roll bar is legal, and the braces you are wondering about are not a requirement.

On location, I fit them to meet the same intersection as the seat back crossbar at the main hoop, so that it is welded into that crotch to both the crossbar and the main hoop tube. Where they land on the floor or subframe connector is up to you.
 
#9 ·
Thanks Eric. Here's another rule book clarification regarding eighth mile events.

DESIGNATIONS
SUPER PRO: 7.00 to 11.99
PRO: 9.00 to 13.99
SPORTSMAN: 12.00 to 19.99

Since quarter-mile elapsed times would not apply for eighth-mile
racing, a style of competition common to E.T. handicap racing,
some pertinent quarter-mile elapsed times are converted to
eighth-mile figures: 9.90 = 6.30, 10.00 = 6.40, 11.00 = 7.00,
12.00 = 7.50, and 14.00 = 8.60.
 
#10 ·
It is 1/4 mile, in a convertible. I currently have a 6 point roll bar, with swing out door bars. I bought the halo bar and pillar bars, and I'll have to add the main hoop support bars. I ran 9.75 last time out and the tech wasn't as happy as I was! So the hoop supports go to where the rear floor starts to curve up to the transmission tunnel? Also I bought 6x6x 1/8 steel plates to weld to the floor
 
#11 · (Edited)
I've seen them placed in that location, along with on the sides of the driveshaft tunnel also.

I prefer to try to tie them in to the point the rear suspension is putting it's load into the chassis, so that the load is spread into the cage structure and the car floor pan..... thus I go to the rear of the subframe connector or as near as I can get to the rear leaf spring mounting cup area on Camaro/Nova.

On something with a narrowed frame and ladder bars or a 4-link then I go to the frame at the front attachment point for the ladder bar or the 4-link brackets.

Being as a convertible has stricter regulations, it might be a good idea to talk to your local tracks' tech man or regional tech director about how they would like to see the cage built. I've called the regional guy a few times to get clarification on an El Camino cage where we didn't want to put the rear cage bars through the back window into the bed, he detailed how far we could go around the bend of the main hoop from the top of the hoop and still be legal, and how much bend we could put into those rear bars to get them to come out the sail panel area instead of through the rear glass opening,

This is one place where banned member TechInspector's input would have been nice, as he was once a track tech man.

Did your tech man say anything about needing arm restraints in a convertible??
Or about having to get the chassis certified because of a less than 9.90 ET??

You will also need to have a window net.
Did they say anything about a second net(roof net) over the driver area??

Do you run top up or top down??
 
#12 ·
I have arm restraints, and run with the top down, so I don't need window nets. I was trying to understand what he was talking about with the 1" bar running diagnally from the drivers side hoop to the passenger side halo. There is nothing I see in the rule book about it. I've looked at a bunch of pictures of cages in convertibles and don't see it. I eventually will have to get the cage certified
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top