Last night I didn't work on the car but I was just taking a quick look and suddenly the idea of running a side bar directly from the trailing arm pocket through the firewall behind the seat and straight into this stud appealed to me.
A bar welded to the frame just infront of the trailing arm pocket and butting to the front stud which in turn has a bar running through the firewall would put some of the force on acceleration in a staight line through this bar.
Welding to the frame at this location is not a problem, the stud is extremely strong being .140 tubing and reinforced with the tube through the firewall.
It appealed to me having this low solid bar in place.
What you do guys think?
The only problem I can see is the seat not allowing room to pass a tube.
This is the heavy duty .140 wall stud I would weld close to the top of it in line with the front tube

 

also don't the engine and trans move back when you get on it ?

 

I would be a little concerned about glassing the roll cage which is welded to the frame to the body which is not. These cars have a lot of flex both in the frame which you are stiffining and the body which to some extent floats. I think you are asking for cracking doing it the way you have it. I would glass up to the tube but use silcone to make a seal. That way any flex is not transmitted directly to be body.

Tyler

 

I certainly can see your point Tyler and all my rear mounts are siliconed in with a slight slight gap, nothing past 1/8th inch.
Some responded to another post and said they have not had a problem glassing them in.
I hope I am not making a mistake.
Time will tell.
How about the idea of a tube from the trailing arm pockets directly to this stud???

 

I have a 66 coupe and a 68 vert with roll bar and the body flex difference is noticable even with the roll bar on the 68 whereas the 66 with no bar has much less. I think the nose projection on the c3s induces a lot more body stress/flex than with the c2s, combine that with a convert and you need to be careful. Your additional bar idea will provide an increased stiffing of the chassis but not real sure you will see see any 'traction bar' effect. I think the IRS geometry reduces the advantage of this additional side load transfer.
In the picture you posted it looked like the glass was molded to the roll bar.

Tyler

 

Your already triagulated on the frame behind the swing arm pivot point with the behind the seat loop going forward to the floor mounts. I can see for side impact a bar above and parrallel to the lower frame rail would be a plus and not interfere that much with climbing in and out.

Side impact is why I have the 45 degree down tube and the Sparco racing seat that holds me on each side from just above my knees to my shoulders

 

Norval, please be careful, you are way,way over my head with this, and I think you have a great thing going, but I see a case of the "while I am at it's"' creeping up on you. Be very careful or you will end up with a roll cage with a corvette in it.

 

In the picture you posted it looked like the glass was molded to the roll bar.

Tyler it is molded to the roll bar. The 4 rear mounts are silicon around the fiberglass but not in the standoff shown nor the one running through the floor. This is another experiment to see if it cracks.

 

George I have triangulated the susension in the back but not the push of the trailing arm.
Like 72GacRZR said "while I am at it"" I am trying to run a low bar and a high bar so while I am at it why not make the low bar in line with the trailing arm to get a direct push/suport of the frame in this area???
The only thing that would stop me if the seat doesn't allow the low bar passing between it and the door panel.
I will have to install the seats and check for fit.
The idea of a fixed bar, parallel to the frame appeals to me.
There will be a high bar on the 45 degree angle also but this on is swing out with a locking pin. And yes even 8 second cars can have swing out bars with locking pins.
Saw it advertised so it must be true???

 

Norval,
Sometimes it helps to draw the structure out on a piece of paper and look at direction of the forces. Tieing into frame at (or just above) the trailing arm pivot point is a good idea if this is where most of the bending force on the frame/kickup junction is coming from. If it is coming from the differential-frame cross member pushing forward, then it might be better to tie into to the frame as close to the top of the kick-up portion of the frame (in front of your roll bar mounting points) as possible.
As far as geometry goes, triangles are generally stronger than rectangles when side loads are applied. My thought for my application (6 point bolt-in rollbar) was to run the front bars from a point low on the rollbar to the transmission crossmember/frame rail junction.
Your idea would provide a rectangle (viewed from the side of the car) with the far upper corner transmitting the force forward through your front tube to the front of the frame. Great idea! The only consideration would be the "noodling" effect of such a long structural member. Think of it as a 7'-8' long, 1 5/8" thick tube (with a mid-point support). There is a lot of opportunity for flex (in towards the passenger compartment or out towards the door panel) over that distance. Also if you have any bends in the tube over the total length, it will definitely want to flex in that direction as the tube is compressed during acceleration. A straight bar over that distance will be much stronger in compression than one with any curves in it.
Anyway, I suggest you draw it out on paper, visualize your materials of construction and the forces, then make the call. Hope this helps.
Rick

 

[QUOTE=norvalwilhelm]Last night I didn't work on the car but I was just taking a quick look and suddenly the idea of running a side bar directly from the trailing arm pocket through the firewall behind the seat and straight into this stud appealed to me.
A bar welded to the frame just infront of the trailing arm pocket and butting to the front stud which in turn has a bar running through the firewall would put some of the force on acceleration in a staight line through this bar.
Welding to the frame at this location is not a problem, the stud is extremely strong being .140 tubing and reinforced with the tube through the firewall.
It appealed to me having this low solid bar in place.
What you do guys think?
The only problem I can see is the seat not allowing room to pass a tube.
This is the heavy duty .140 wall stud I would weld close to the top of it in line with the front tube

image deleted

Your cage is looking good

Interesting Idea, It's very tight through there. Any cages that I have seen that had parallel tubes one or more in ths fashion have had the doors gutted and used that space. I ran my door bar straight from the main hoop throught the firewall to the frame by the #1 body mount. I had to bend the door bar to get clearance around the seat back. One note: If you plan to use your car in any NHRA events they do have a specific rule around the placement of the door bar in rlation to the driver.

where your tube runs forward parallel to the frame rail from the dash hoop I moved mine as far up the dash hoop as I could. Second I have run a tube from the midpoint on the door bar back down to the frame at the number 3 body mount. Continuing this forward to meet the dash hoop would make a nice X but would make it near impossible to get in and out of the car.

To seal the holes in the body to the posts I am using silicone rubber sheets of air craft engine baffling held in place with 1/4 inch aluminum rivits then using flame retardant aircraft carpet to finish off the interior

http://www.ramaircraft.com/Catalog/B...bafflespg4.htm

There are other suppliers but this one carries it in a color that is close to chevy orange

 

Norval here is a nice car that i dug out of my old pictures.

 

Nice steering

nice door bars

 

That may be a nice car George but it is a full race car. Not a car like yours and mine.
I did install the low bars directly from the trailing arm pocket straight forward to the front stud. The bar is only about 36 inches long, is only 3 or 4 inches above the door sill and ties into the bar going directly through the firewall.
I felt this was a good thing to do while I was at it. I can also preload.
I am working on the down side bars now. Hopefully by the weekend one side is totally finished.
I now have 10 attachments to the frame. 5 down each side and a number of cross bars.
The high side bars are hinged and will have to be swung open to exit/enter the car. I will use quick release pins. They are legal, not that it maters to me.

The 10 or 12 point cage is not intrusive to the interior since it hugs the roofline and the side pillars. From side impact I should be pretty good with the double bars.
I want to finish over Christmas hollidays so I can start doing other things to the car.
Nearly all of our bars are under 4 feet, I did start with a few 55 inch bars but had to cut them down once bent. I am also gusseting some of the corners with 6 inch lengths of 1 inch DO M tubing.
Thanks for the picture George. That is probably something like Twin turbo will due to mount his coilovers and A arms.

 

George the 2nd picture just came through. It is indeed a strickly race car. Look at the back wheels. There is no room for movement of the back tires. They just spring them so stiff that nothing moves. They must skip over the rough sections, making and breaking traction.

 

George, the 1st and 3rd pic don't come up.

That car has a front steer sweet rack just like what I am working on, can you send me any pics you have?

Marck

 

Hey norval...

Have you thought about running a bar across the underside of the car, to mount the seats on? I've often wondered about this... a car with a full cage, but the seats mounted to the floorboards! What kind of wreck is needed to pull the mounts through the floor? Certainly the bar is capable of a wreck worse than the seat mounts can handle!

 

The forum must be on the blink because I can look at these pictures under file manager for my home page.

 

can you email them to me?

 

ZD - your not looking at it quite right. If i hit a guard rail head on, I get thrown against the belts. The belts are attached to the roll bars not the seats.

I also put large washers, like 1 1/2 inch ones under my fiberglass seat bolts.

TT - These are the only pictures I have and I see that the forum got my pictures going after i messed with the aspect ratio of my digital pictures and resubmitted them.

Norval - Your right i was looking at this guys lack of rear suspension and could tell that it has minimal verticle movement. Lots of adjustment and very solid. This car was just over 2000 pounds and in a class above my BsP