one of the pirks of talking the chassis fab/ high performace engines class here at school (wyotech) is that we get 4-6 weeks to work on our own project. the first thing on order is to finally weld in my spohn SFC's but from then on the main focus is installing a roll cage. I plan on running a forced inducted BBC(540+ci) so i need a stought frame. depending mainly on cost i am either going to choose to use 4130 or Mild steel, both DOM. I plan on tying the cage into the engine bay up next to the strut towers and running a plate to help reinforce my coilovers when my car comes down from wheelies Anyway here is my initial design, im going to take measurements tommorow and come up calculate the tubing needed, and am going to decide between 4130 or MS.any way this i just a rough sketch, but do you guys have any comments/suggestions

 

Buy a rule book. Not all the tubes need to be 1-5/8" in a full cage. You can also buy the proper building specifications for all cages from http://www.sfifoundation.com Depending on how fast you're going to run, you may need the cage built to specific specifications. It's very common to now have a 25.1D spec cage even in a 9 second car.

The only tubes in my cage that are 1-5/8"
Main hoop
Halo bar
A-pillar bars
Both rear bars
Door bar going from main hoop down to bottom of a-pillar bar.

The rest are only 1-1/2" as per rulebook specs.
I also run a sill bar. I don't have a bar running from the a-pillar bar to the shock tower through the firewall yet but I do have one running from the front of the shock tower down to the front of the frame.

 

yeah i know all the tubing doesnt have to be 1 5/8/ we have IHRA and NHRA rule books here at school thati will follow in more detail. Right now is just a parimilary sketch. Im sure the roll cage looks like anything else you see 14 point wise, but any suggestions. I was just going to run single side bars to the front sills, but my instructor told me to x brace the doors, so that in a front impact the cage will not fold in on me. How hard is it to get into the car with the x brace, im 6' 220, so im not the smallest guy on the block.

 

he also feed me the idea of tying the cage in with the front frame, due to the frame twisting after alot of power going threw it. that makes sense to me, i was just gonna run a 10 point, but why have a supper strong passanger compartment and just a stock front frame

 

The removable steering wheel makes entry and exit much easier. I can remove the T-tops also but the halo bar still gets in the way to climb over the door braces. If you don't use an X bar system, you can still make a swing out door bar.

A third gen doesn't really have a frame. It's an entire unibody car. The front and rear subframes are really just multi-layer sheet metal. SFC help tie the front and rear together making the floor between the 2 a bit stiffer. A full cage ties everything else together.

My frame doesn't twist. My body panels are still straight. My T-tops can still be taken out. My floor is a little buckled in the rear along the tranny tunnel but that was when I was still using a stock style suspension before I switched to ladder bars and before I installed the full cage.

My picture doesn't show the full extent of my cage but you can also see gussets in the corners for more strength to the welds.

 

yeah i know, but it just doesnt make sense to me to have a super strong passanger compartment that just houses me, then have a stock engine compartment with a engine with 5 times the factory horsepower

 

holy **** i just measured the car and came out with 95' of tubing, at 4.50$ a foot for my priceing thats almost 500 dollars, it looks like im just gonna get the competition engineering kit for 350$

 

Add 1 more bar diagonal across the roof starting at the rea pass side where the halo and hoop come together and run it across and tie it into the where the halo and down bars connect on the driver side. This will aid in the event of roll over and whatever happens in that type of crash.

Use the rule books to spec out your cage to stay on course and stay legal, obviously looing at many "certified cars" and having buddies with "home built" cars that got certified, I can honestly tell you, they dont look at welds as I've seen some boogered up nasty sheeot out there.

The more points you tie it in the stronger over all it's going to be, but if your going that crazy your darn near on track for just going tube chasis since "basically" your just missing frame members. There are many Outlaws running 600+cid mountain motors into the 6's and personally I have'nt seen one that took the cage into the front area of the car, they usually come through the firewall and end at a plate welded directly behind the strut tower/inner fender.

Be sure you add the additional shipping/freight that will be needed to get that $350 cage to your door, I think you'll find it's very close to raw material cost ordered in locally, only down fall with raw stock there's alot more work involved. Here's a picture of the chasis car brother in law is building for his 8? buick regal, it's actually a kit for a 3rd gen camaro, once we set the buick body on, you could not tell any different.

 

Price of kits or bare stock is cheap. Buying a kit means you don't need to worry about buying/renting a proper tubing bender. Pipe benders won't work. They pinch the tube and don't make a proper bend. Tubing benders are available commercially but if you have time and material, you can make a simple one like this. http://www.blindchickenracing.com/to...bingbender.htm

Bending tubes at the wrong angles can make building a cage expensive when you have to run out and buy more tubing. There's a real art to laying out and bending tubes for a cage.

Another thing required is a notcher so the end of one tube can be notched against another. I did all mine with a 4" disk grinder. It took longer than if I had a proper tool. High end shops with have a notching bit on a milling machine to make a precision notch.

Having a cage installed by a chassis shop is where it gets expensive. A basic cage is normally in the $100-$150 per point. A cage system such as what's in the above picture can run a few thousand dollers to have it installed not counting the tube chassis or material.

The key to strength is triangulation. The more triangles you can make, the stronger it will be but too many bars also adds a lot of weight.

You're not going to need chrome-moly tubing. You will need to TIG it together. Mild steel can be put together with a mig welder.

 

Farming out labor is a great point about added costs involved.

Here's some other things to chew on, when it comes to a race car, it's actually cheaper in the BIG picture to buy a prebuilt car or even a turn key car, problem lies is most of us dont have that kind of coin laying around to fork out in 1 chunk. With all the labor over the years, all the parts that have been bought/installed/tested and rebought, etc...I have more in my car now running the crappy slow times it does than if I'd of had the money to buy a turn key vehicle that would actually be running ALOT faster.

The chasis car above was a kit from Chris Alston Chasis, as it sits in that picture, shipped freight from Chris Alston was $4450. At the time of that picture being taken it was 2 months of labor, who knows about electrical, tools, grinder pads/cutting wheels, welding wire, etc...but just that raw tubing in kit form, plus other steel and parts he had to buy to get it there, he's already over $5K in materials...add in all the extra stuff I listed above and it gets crystal clear in a hurry.

It does'nt seem so bad cuz that 5K was spent over a 2 month period as opposed to placing an order in 1 night.

Building cars, especially race cars is not a cheap proposition when you TRUELY add up EVERYTHING involved to get it to stage A, B, C, etc....

 

tools im not worried about, we have tubing benders, notchers, chop saws you name it we have it. I plan on TIG welding the cage in too to give it a nice appearance. I actually am going to go with the S&W 14 point kit, they are just on the other side of PA so shipping shouldnt be too much, im gonna get the official price on raw stock tommorow and make my final desicion

 

I called S&W racecars today about getting a price for their 14pt roll cage and they want 497$ shipped. Im getting a price for 100' 1 5/8 .120 wall mild steel tommorow which i am thinking is going to be around 4$ a foot. So it looks like im just gonna fab it up myself. Ill let you guys know my quote for tubing when i get it, and I will start a new thread with pictures once the fab begins

 

Here's a link to a chassis construction. You might get a few ideas.

http://jbsdragracing.com/v-web/gallery/chassis

 

damn you werent kidding. nice setup

 

Well, it actually does somewhat… the cage is in there to keep you safe… the more stuff that can crumple around it and absorb energy the less energy goes into the cage and finally you and the safer you stay.

Finally, points farther forward then your strut tower or farther back then the shock mounts on an f-body really won’t do anything useful on a drag car besides add weight. On a road race car things are a little different and it makes sense to tie in the steering box/sway bar mount areas an the PHR mount and brace areas. If you’re running a fuel cell some sanctioning bodies will require that you run members behind that also.

 

I meant to ask this in the other thread… how tall are you? Did you run the halo bar inside the t-top side trim or under them?

Since I’m roughly 6’4” and 300lb I’m not sure how to do anything with t-tops, since I barely have room without the halo bar (in a hard top car I have to lower the seat for my head to clear the roof with a helmet on, and I’ve been known to smack my head into the t-tops on big bumps in t-top cars). If it wasn’t for this I’d much prefer a t-top car and they are much easier to find (I’m looking for a new body to swap my drivetrain into).

it’s not very hard to crack the floor around the tranny tunnel on these cars. You can do it with a stock engine an a manual tranny fairly easily, but it’s also pretty easy to fix.

 

be careful there… it depends on the region and the inspector. I know that locally you can get lucky and one guy will just sorta check dates on a few things and the general layout and you’re good, and another that wants perfect welds, no signs of smoothing them, confirmation of tube thickness (drill a hole or sonic check)…

first, I don’t know that I have seen a roll cage kit that didn’t require some work, tweaking and additional bends to make it fit just right, but generally it is easier if what they supply works for what you want to end up with. As far as the price, try a local speed shop. Most of them can have the kit delivered from a local warehouse saving you shipping costs entirely.

 

I'm 5'8"

I have no interior. The halo bar is stuffed up as high as it will go. It's right up against the steel brace that runs between the t-tops. The halo bar is bent to still allow the handle to open to take out the t-tops.

My cage is a Jegs kit.

 

Well i for one would have more piece of mind knowing that if i do crash going 145mph i will not have a dashboard, crossbar, and steering wheel all coming in on me. And the strut bars just adding wieght is also not true. A high torque motor mounted solid with motor plates is gonna want to twist something for one, and since these cars have a modified mcpherson style suspension from the factory, converting to mcpherson struct design (coil-over) will focus all the weight of the front end onto the strut towers. So if I pull the wheels 2 feet off the ground and come slaming back down i just the risk of shooting the strut straight threw the tower

 

what alot of good chassis guys do with unibody cars is cut the roof off so the chassis can be fully welded and made to fit better. the guy im having do the chassis on my 3rd gen works for a top dollar chassis builder, the builder doenst really do much in the way of cutting and fitting or even welding (the grunts do all the work and the big name gets all the credit), im horse trading some fab tools for labor in my chassis. so i get the same high dollar quality and finish but at a real world price.

 

And that’s exactly what he basic cage will do… it keeps the driver’s compartement safe and solid… if you start adding assorted bars going all the way to the front and rear of the car you’re adding what will become a spear in a collision, or at least a member that transfers the force of the impact directly to the structure around you. Look at the “safety cage” design of most modern cars, in a sever collision pretty much everything forward of the firewall and rear of the seats will ball up or fall off the car, absorbing the energy of the impact.

yea, and at best you brace the strut towers to the front bars which won’t do much unless you have an X brace on the door openings that meets the front bar where the strut brace goes. Take a GOOD look at some serious race cars built by real chassis builders. In the case of a drag car those front bars are there to give some structure and mounting location but are not a strong structureal member. I’ve never seen them welded with a reinforcing plate like a main hoop gets…

 

Im not deigning my car to collapse on an impact, that is the last thing i want. I want to be able to hit a wall dead on and still have the passanger compartment look like it was never in a wreck. If i ran front bars like you said and did not x-brace the doors the windshield bar would definatly come toward me in a front inpact. And with the steering wheel mounted to the roll cage that would impale me on a serious accident. I find it funny when you say look at some serious race cars by real chassis builders. I am currently in school learning to build chassis, and everything i have said in this thread i have gone over with instructors that have been building race car chassis for 25+ years.

 

First, I never suggested running with out x braced door openings.

Second, what collapses in an impact is as important as what doesn’t. If NOTHING collapses then you might as well not have the cage or the car, at that point your body will absorb the full impact since nothing else is.

If you hit a wall at 140mph the car is gone... you want to live. With what you're planning now you won't.

 

i dont get it first you say dont x brace the doors, then you say x brace them. Do you think i should leave out the strut bars because it would make my car unsafe, If thats ture then why is a 12 point cage requirede when running a 7.50 et or better?

 

What the hell is with non readers trying to use this board lately. Where did I say don’t?

Hooked on phonics… get it.

there are a lot of downright dumb NHRA and IHRA rules. While for the most part I don’t disagree with the structure required for some of the faster cages, I do disagree with the requirement for 4130 tubing (as well as the breaks in wall thickness and tube size when using it in a slower car), some of the regs on welding… Smith’s “Engineer To Win” and Fournier’s “Metal Fabricator’s handbook” both go into detail about how stupid some of that is, and you can see that NASCAR and other sanctioning bodies have outlawed in the interest of safety some of what NHRA and IHRA have specifically mandated.

 

well you have not have said outright dont x brace the doors you hinted at it. Anyway you go back to reading your books and all go back to building chassis in real life. Its funny that you dont agree with what people have been doing for years. Just saying everything in front of the passanger compartment just adds weight proves there that you have little idea of what goes into designing/building race cars.

 

Oh and i was incorrect about haveing to have a 12 point cage under 7.50 et. But you must be right, everyone that runs one is just adding unnessisary weight

 

What’s required below 8.5 depends on the class, a 25.4 or 25.5 is usually required from 8.49-7.5, and faster then that requires a 25.1d or 25.2 (or one of the dragster standards)

As far as the rest of your comments, they're not consistent with what I've already said… I don’t know what you’re reading but it’s not what I’m typing.

 

Heh, that explains a lot… I’m betting being about 8” taller and probably at least 100lbs heavier what works for you will not work for me…