Last night I made my first cut in the body for standoffs for the roll cage. I am welding short standoffs to the frame and they pass through the floor and give me a point where I can weld/bolt the roll bar too. It bothers me making that first cut but I did it with a die grinder and have my first standoff ready to weld tonight.
I am concerned with clearance around the standoff. I would love to fiberglass the standoff to the floor leaving no gap but I am afraid of body flex cracking the fiberglass so I am considering leaving a 1/16 to 1/8th gap and filling it with black good quality RTV.
What do you guys think???
I am also bending the first pipe, the roll bar behind the seat from 1 3/4 DOM tubing. I made a plywood templete of the interior right behind the seat and will use to to bend the first bar.
I guess the first time is always the hardest.
This is not my first cage but the first in my vet, The others have been in mustangs

 

I would think that your best solution would be a good, high quailty RTV rather than fiberglass. No matter how much the cage stiffens the frame, there is going to be some movement between it and the body, and the fiberglass isn't going to flex much. Leave that 1/16 inch gap and then seal it.

Steve

 

I agree

 

How about a grommet?

 

The race crafter company that did mine used a hole saw to punch through the body. Then as you can see he bent and pop rivited white coated aluminum sheet metal around, but not quite touching the bars to allow for body to frame flex.

I used this silver colored silicone that is used to seal heating and air conditioning ducting. Like in home construction. Then of course I took the car to a car carpet shop and had them install the aluminized fire proof thermal matting and then thin light weight flame retardent carpet.

All the fire proofing and sealing is so that when one of those Vipers is following me into a turn and my brakes are better than his and he rearends me that the fire ball from my rear exploding 25 gallon gas tank doesn't even warm my buns!

You can see the clearance of the white aluminum right next to the seat. The holes through the body were big enough to ease welding of the pipes to the frame rails

 

Norval, are you making the standoffs so that the bar is removable? I have hesitated cutting mine as well (something about whacking on an original L-68 'vert just bugs me), but I want to get on a track and that's the only way. If a bolt-on bar is legal, that's what I'll do and just buy a used hatch cover to cut up. Also, are you going to use thru bolts, or flat bolt plates on the ends of the standoff and bar?

On the opening, I'm planning on using a rubber grommet. The ones I will use are tail light "donuts" used on utility beds and large trucks. The entire round light/bulb assembly is replaced and just pops out of the rubber. the outside of the rubber ring has a slot that fits the slightly smaller hole in the truck, keeping it in place.

They come in various sizes, and as long as you slide it on the bar before you put it through the hole and weld it to the frame, you don't even need to cut it. If you have a large hole in the 'glass, you would have to make cover with the grommet in that.

 

do you think 1/16 is enough?? 1/8 with a flexible silicone sounds like a winner...

 

I'm following this build up !!!

I agree, 1/16 is kinda tight. Silicone sounds like a good way to
seal her up, and the metal flashing sounds like a good idea, too.
That way, a few pop rivets or screws and you have access to
the mount points for inspection or reinforcement.

 

When I installed my roll bar I had to cut out a fair amount around the bar to have room to weld. Instead of whipping up some fiberglass and trying to get within a short distance of the bar and siliconing the gap I used a sheet of 3/16" rubber with a hole slightly smaller than the bar (push the bar thru the hole before you weld it to the frame) and glued that to the fiberglass with weatherstrip glue and then sealed around the bar/rubber with silicone. It has lasted so far allows for whatever flex the car may encounter.

You probably know this but new fiberglass does not bond well to old (cured) fiberglass. If you go that route be sure to cut grooves and gouges in the old glass where you want the new glass to bond.

Good luck,
Chris

 

Thanks for the repies guys. I am very carefully cutting the floor for a tight fit and I will go with about 1/8th clearance for the standoffs then use the same black RTV I use for putting the intake on. It is high quality, that should take care of sealing around the standoff.
The standoffs are about 4 inches tall with a 1/4 inch plate on them. The tubes will have a matching 1/4 inch plate with 4 tapped holes so each section can be installed , alined on the standoffs and bolted down.
This is so if I have to remove the cage because I am taking the time for a tight fit around the interior and I might have to remove interior panels. I also want picture perfect welds and the only way for this is on the bench. I tac a tube, take it out and mig or tig it on the bench.
I also want to double powder coat every peice after welding for that dipped in plastic look
I am considering 2 bar on each side but not sure. One low bar that is fixed and a swing out bar higher up.
I will have one through the firewall attached just behind the front A arms for sure.
I am not trying to be legal anything. I am doing it to stengthen/stiffen the frame for better handling and hopefully offer me some protection.
It will probably be 8 or 10 point, I will work that out as my gut tells me.
From doing 3 mustangs I have a feeling for how to fit/bend bars and I know the difference in feel in the car just pulling in a driveway. The cars feel so much more rigid
So the cage will come out in sections, it will be a combination of 1 3/4 and 1 1/2 , all DOM tubing, it will be heavily black powder coated, it will hopefully fit tight to the interior and hopefully my wife won't complaint about a 5 point harness on her side and stepping over the lower bar while the upper is swung into place.
The combination of the new 18 inch Pirellie tires and the cage will make the car even more stable then it already is.
The last modification this winter will be the 14 inch brakes.
Looks like a good winter comming up.

 

Chris all my welds are going to be from the outside. All of them so I can make a good fit around the tubes. I would rather cut twice then make too big a hole and I use the die gringer to expand in the direction I want to go.
I will hopefully maintain the 1/8th gap and silicon will do.
As for old fiberglass I always clean very well with 40 grit emery for a good rough surface but hopefully unless I make a mistake I won't need to.
The machine I am using for bending is a state of the art programable tube bender that my son's company has. I use the hand bender for minor tweaking. I am paying the programmer $20 per tube for his expertice on the machine. He is happy for the extra money. I already have $800 worth of tubing ready for many errors.

 

I would use the black windshield adhesive instead of rtv, it's a good bit tougher than rtv yet dlexible enough to seal stuff. I used it to glue my firewall back on and for many other applications, great stuff. I use SikaTack but I don't think that's available over htere, have used similar stuff from DoW chemicals, it was a white can.

 

Norval, do you have the time for progress pics? I am really interested in what you are doing and how it will all turn out.

Steve

 

I welded the standoffs to the frame and then welded the bar to the standoffs.I fiberglassed completely around it to the bar,i only get a small amount of squeek.

 

I will be taking pictures. Last night I was pushed for time so I just took my time cutting the first hole and didn't go to the house for the camera.
I will post alot on this over the winter.

 

That is what I want to do but what if the body moves and it cracks the fiberglass? I am going to play it safe and go with the slight gap.

Twin turbo as far as the window sealer I know they have a new product that requires you to not drive the car for a few hours while it cures and while that is not a problem in my case I don't know about the shelf life of that product once the tube is cut open. I will have to call the window shop.
Thanks for the tip

 

Guys I would love to see pictures. So far in past posts it was mainly George who posted roll bar and cage pictures.

 

Norval email me and I will send you some pics. I have glassed in all my cage without any problems.You want the body to be as one with the chassis, still on its mounts but when you torque it the whole car moves as one.When you load the engine the whole car should lean with it, if not is when you will crack everything.

 

I wish that I could have seen how some late year C-3 vette was roll caged before I started mine. I have to make some changes now, because my first test model isn't quite right.

I did use the .134 wall 1 3/4 mild steel tubing which is overkill. It really does make for a very ridged frame. I can turn into my sloped driveway and my car is on three wheels. Like my neigbhor told me that when I back out and turn to leave that i only have one front tire on the ground.

 

Gkull I can send you pics too if you want.