Chassis rigidity

I thought that this roll bar is a really good compromise for a street/track car.
It mounts in the engine compartment.
I like the legs that run through the rockers to the front inner fenders.
It appears that it attaches to the roof.
It was sold by Hall in his 2000 catalog from which this is scanned.
He no longer caries it. Does anyone know who made it?
I'll be you a nickle that this is a copy of the factory GT4 bar.

I had the pleasure of spending time with my Dad and his brother .. Larry Lombardo who raced for some years for Bill Jenkins. He explain some eyars ago to me when I first started fabrication of my first race car.... the methodology is " your building a bridge ".

I have the Hall 4 point cage .. I say cage because it has the square above your head in the passenger compartment. With my car I plan to weld that cage in add two rear bars going straight back to the drop to the top of the rear suspension and continue to the rear frame rails and two foward thru the fire wall and tie into the front frame to date I cannot give exact points as I have never built a cage for a pantera. The 4 points in the passenger compartment will be welded to the rocker panels and possibly plated to add rigity instead of cutting up the floors for frame connectors.

I will point out that this is for my 73 L my 79 GTS by EMBO needs nothing in the sub floors or rockers as this area on this car is already heavy .. the frame on the 79 is beefy and maybe too beefy. A couple of us have inspected this and compared and feel this car is much heavier in wieght also .. the entire rear frame is BOXED .. making it a more ridgid car. But dont forget this comes at a cost of added wieght. Another thought is to just simply reweld all the seems to add rigidity. Its done a lot is STOCKER classes where rules limit major CAGES and changes to the car. How do they accomplish this ? they weld in 8 point cages and tie them into points on the body where ever they come close. This will happen often on a Pantera since it tight.

This is definately a fabricate and feel type of job. The best way is to buy a cage for the Pantera and get some extra pipe and a bender and feel it out.

Its also definately depends on what your going to use the car for. Me 'm only 5-8 and when the cage was in my 79 I had hard time getting in and out and banged my head many times on the bolt above the driver seat. The scares on my bald head were " the badge of honor " LOL

I would love to see some pictures.

Here is my first fabrication of a Comet a raced way back ..it shows the concept.

Ron

quote:

Originally posted by PanteraDoug:
...I'll be you a nickle that this is a copy of the factory GT4 bar...

Doug, I'll bet you several nickles that is a copy of the bracing employed in Hall's purple passion Pantera, that reinforces the body well enough to allow removal of the roof altogether!. Thanks for posting that pic!

Your friend on the DTBB

Pretty cool PD!

Gary

quote:

Originally posted by george pence:

quote:

Originally posted by PanteraDoug:
...I'll be you a nickle that this is a copy of the factory GT4 bar...

Doug, I'll bet you several nickles that is a copy of the bracing employed in Hall's purple passion Pantera, that reinforces the body well enough to allow removal of the roof altogether!. Thanks for posting that pic!

Your friend on the DTBB

Do you take paypal?

Did the purple color throw you ?? LOL

Halls addresses is pretty good but still think you need some thing foward and back.

I like the rocker panel supports. do you think the slide in fromt he rear in pieces and then its welded up or do you think its an assembly replacing the stock sheetmetal ??

Ron

quote:

Originally posted by accobra:
Did the purple color throw you ?? LOL

Halls addresses is pretty good but still think you need some thing foward and back.

I like the rocker panel supports. do you think the slide in fromt he rear in pieces and then its welded up or do you think its an assembly replacing the stock sheetmetal ??

Ron

It was my understanding that you cut open the rockers from the enine compartment. The inner rocker slide in. They bolt to the front inner wheelwells.
Gary said
The bar bolts together.
I know that the picture (which isn't too clear) seems to be wekded together.
Gary said it was a bolt in. He said you need to modify the gas tank which means you gotta bend it a little with a hammer.
I think his stainless tank clears with no mods.
Considering that I had everything back in and didn't need to lay out another $3000, I bought the interior 3 point bar.
In retrospect that was a mistake.
I never picked up on the purple color. I thought he was just being goofy again like the time he wanted me to buy purple poly bushings instead of black and purple flat washers. Now if he threw in a Pantera roof maybe...

I see now that makes that Hall purple cage much more attractive ... bolt in ... and I like those lightened supports. and he dosent have any more laying around ?

Ron

Call them. Gary said no, and Tara said no. If a dozen other people call maybe he'll have some more made?
Larry Stock from the Pantera Connection has something listed in his online catalog but has no pics. For $3000 it's probably some kind of cage.

Doug,

As I said I would love to see pics .. for some ideas. Thanks. The rocker panels Hall made slide in is a great idea. the top of the roll cage tieing into the roof another. The side to side supports needs some thinking ??

Ron

quote:

Originally posted by accobra:
...Halls addresses is pretty good but still think you need some thing foward and back...

Like most cars, the Pantera chassis is trying to fold itself in half, somewhere between the front & rear axles. And power applied to the wheels twists the chassis torsionally. The bending forces are controlled in the Pantera chassis through the roof & A pillars, which are attached to the bulkheads in front of & behind the passenger compartment. The Pantera's roof & A pillars are weak and allow too much flex for racing. Additionally, the rear sub frame is not very well controlled either. The six point roll cage is one way to remedy these two problems, going over the top of the passenger compartment, and using a roll cage as a stressed member of the car as well as for roll over protection. This takes the load off the roof & A pillar. If you are installing a roll cage anyway, then why not go this route?

The other method for stiffening the chassis to resist the bending forces is to stiffen the floor pan with structural bracing such as the brace sold by Hall, in Doug's picture. This will also take the load off the roof and A pillar. However, as it is pictured, the stiffening assembly does nothing to control the rear subframe, so I agree with Ron's comment that the rear wheel houses still need to be tied into that integral roll bar to reinforce that assembly. This solution to the Panteras inherent chassis flex would seem most appropriate for somebody who is not planning to install a roll bar assembly, like a show car or touring car application.

your friend on the DTBB

I'm not going racing. I just feel safer with a roll bar.
The Mustang can use a rearward brace also. Mine is a good example with it's dimpled roof. Try that with street tires! I didn't know what the sound was until I got out of the car. Surprize, surprize.
I don't have the cracks in the roof of the Pantera near the decklid like I have seen in so many cars.
I would like to avoid that. If I tie those wheel wells with braces to the roof, if I really hook up, I'll crinkle the roof

Agreed my friend.

I hear ya Doug I buckled the quarter panels on the Comet above the wheel wells ... the car needs aftermarket frame rails.

The Pantera I have to say handled excellent at Pocono .. but I can see where a lot of that pounding over time would " LEAVE A MARK " .

I think 9138 handled this way because its a virgin car. Has never been flexed.

I'm thinking that with a tube bender someone could fabricate a nice custom add on pipes to a purchased cage. The only thing I have a problem with is going thru the rear window to the rear.

Ron

quote:

Originally posted by accobra:
...The only thing I have a problem with is going thru the rear window to the rear...

Go through the bulk head below the rear window & attach to the roll bar about 1/2 way up, instead of at the top. That was easy wasn't it?

Your friend on the DTBB

The rear section is relatively easy. The difficult part is what to run through the interior.
I'm trying to get pictures of a friends 72 Pantera where he had the forward braces run against the doors. They were hinged st the doors so you didn't need to climb over.
As far as your Embo being boxed that I am sure is the correct thing to do in the rear. The inner rear tubs being stressed members is a good design. They just need to be stronger.
I think the rear roll bar being bolted to the roof stiffens the chassis for twisting enough.
One of the old Can-Am cars used the engine as a stressed member of the chassis. Maybe I can use my 180's as chassis reinforcement? Maybe the engine should have been a stressed member originally of the chassis. It sure stresses me out enough now.

If you really want to see a car perfectly done take a look at Matt Meritts car.You can really get deep into these cars both fiancially and structually.My guy mentioned to do the car "right" he would run tubes through the rocker panels to the sides of the lower front chassis,tie the 4 pts of the cage to them, cut holes in the front forward fire wall and run tubes from the front roll cage bars through the fire wall to the front chassis.Geez do you really need that.If its a pure race car, more than likely.

In my first post I mentioned what he thought made sense fiancially and structually for what the car was to be used for.You really need to be honest with yourself in what your wants and needs are.Other wise its just over kill.

Dan

PD,

Talking of using the engine as a stressed member there's a guy I met a week or so ago on a local RTP club dyno run that fabricated all his own sway bars, chassis stiffening and suspension. It looked very well thought out and immaculate, plus this guy needed a stiff chassis as he had built his own motor that put down 505 HP at the rear wheels on the chassis dyno.

To best descibe it, he had a rear upper swaybar similar to the Hall/Byars design, but instead of the second portion dropping down and being lower he had it on the higher side (just below the decklid shock mounts) and laid back enough that it tied into the ZF bellhousing with some rubber mounts. He swore by it and especially the belhousing/motor tiwe in. He had no other rear stiffening and could even still use a rear tub if required.

He was apparently fabricating and selling a few of these at one point many years ago, in fact he went as far as to suggest that the Hall design was a spin off from his own.

Julian

Geeze guys. Why don't you just start with a huge slab of tool steel and mill out everything that doesn't look like a Pantera. That way you will have a really stiff 6000 pound Pantera that will not flex.

I seem to remember that the aluminum skins on the Cobras crack from flex also.
I would say that the Pantera does exactly what it was designed for.
If you need more then you are exceeding the desin limit.
Anyone who can weld and bend tube can come in and build a tube frame dual truss. It isn't even close to rocket science.
The trick is to do it without ruining the car. I don't want a cage in the car. I already took the three point out of the car.
I always thought that the ultimate Pantera would be a brand new factory GT4.
Although I am interested in a purple 1000hp dual everything car, I don't have much respect for it. It's just another kit car. It may as well be a Fiberfab.

You see the front tirangular trunk brace alot. Which specific problem does this address. Does it stop the top a-arms from migrating like back? Does it do the same as the underchassis re-enforcement (which wouldn't help with upper chassis).

http://www.pim.net/3222006BLKGT5S73.jpg

quote:

Originally posted by comp2:
... the front tirangular trunk brace ...Which specific problem does this address...

It addresses the vendor's ability to pay his mortgage

LOL ........

your friend onthe DTBB

George you really don't think it does anything? There is a fair amount of bent/curved metal and places where it all meats which make me wonder btu I don't know what problems poeple who drive them hard have or would have up front.

One of my goals is not so much keeping from destroying the car in ocasionall track use as much giving the paint and chassis a chance not to crack so bad. My car now was painted back in the 80's. It looks great from 10-15ft. Any closer and you say What the hell happened to the paint? That is why I think I am going to take it down to the shell right now and do what I want to do to the car.

> You see the front triangular trunk brace alot. Which specific problem does
> this address. Does it stop the top a-arms from migrating like back?
> Does it do the same as the underchassis re-enforcement (which wouldn't help
> with upper chassis).

Good question. The triangular front brace is part of the 4 piece kit sold
by Hall and the Byars Brothers (Precision Proformance). It's on my list of
things to do but I haven't got around to checking on whether or not there is
a load path from the inner fender liners to the upper suspension pick-up
points. Can anyone comment? I know the sheetmetal is thin on the sides
there. In front-engined cars, similar triangulation helps with both lateral
loads during cornering and with longitudinal flexing. The kit also comes
with a brace that bolts into the lower front frame rails.

I'm coming into this discussion late and was hoping to a detailed report
of what I've found but don't have the time so let me see if I can at least
summarize. Real race cars (that start as steel uni-body production chassis)
will be stripped to a bare shell, have everything seam welded, the suspension
pick-up points reinforced, any openings triangulated and everything tied
together with a roll cage. If you have a steel roll cage hoop in proximity
to your head, it needs to be padded or you need to be wearing a helmet. Also,
the cage has to be certified for your particular race series. A buddy had to
have his cage cut out and a new one welded in to meet similar but different
rules in another series. For most applications, the full-on approach isn't
practical so you have decide what modifications you are willing to make and
accept some compromises. I've added a variety of stiffeners to several
different cars and have always been pleased with the results.

BTW, a non-rusted Pantera has pretty decent stiffness for a production car.
Goran has the numbers and has this to say:

"I have torsion tested a number of Pantera chassis. Rusted as well as
rebuilt. A rebuilt (or new) chassis is stiff enough for hard street
use. Rusted are NEVER!."

My Pantera is non-rusted and has no flex when jacking it up. On the other
hand, I checked out a Pantera for a prospective buyer in Atlanta that flexed
terribly (and squeaked and rattled on the road). That one had serious rust
issues. Adding bracing to a rusty Pantera is a bandaid fix at best.

In my case I have drop floor pans which precludes through-the-floor-pan
subframe connectors and I'm not willing to strip the tub bare. I did do
some seam welding in the engine compartment before re-painting it and I
tied the drop floor pans together. After realizing I wasn't willing to
the testing, analysis, and modfication required to do a thorough job of it,
I simply polled a number of Pantera racers that are running the braces for
their experience. The guys running the 4 piece kit all had favorable
impressions (stress cracks that stopped growing, more predictable cornering,
fewer squeaks, etc.):

"The cracks on both cars stopped growing completely after the bracing was
installed. The only way the bracing could help any more would be if the
cracks healed up and disappeared - but that would be Twilight Zone stuff.
The chassis bracing really does take the flex out of the chassis and lets
the suspension do its job."

Dan Jones

P.S. Here's the write-up I did when I installed the kit:

I just did this. It's a four piece kit, with two braces for the front and two
for the back. The two (front and rear) lower braces are bolt-in. The rear
lower brace picks up the lower A-arm bolts and has turn buckles to adjust for
width and set the pre-load. The front lower brace is similar but has no less
tha fourteen bolt holes. You position the brace in place, use the turnbuckles
to preload it so it stays in place then drill new holes. The front lower
brace is notched to clear the steering rack mounting brace. In my case ('74
model with the factory bumpsteer spacers), it did not clear. At first, I
thought I'd need to grind away about the same thickness as the rack mount
spacers but that only caused it to hit a couple of other spots. I chose not
to grind on chassis brace because it is powdercoated and is thicker metal.
When all was said and done, I ground nearly an inch off the perimeter of the
rack mount end flanges (doesn't effect the strength of the rack mount at all)
with the upper surface of the chassis brace nearly flush with the sway bar.
You really need to get it up that high as the bottom bolt holes are close to
the bottom of the frame rails. The holes are 1/2 inch diameter but the powder
coating reduces that somewhat so you may need to clearance the holes slightly.
I didn't have time to drill the holes before heading out of town but it looks
like an angle drill might help in drilling straight holes. I'll probably go
with 1/2 inch bolts but if you holes are too close to the lower frame rail
surface, you might consider 7/16". BTW, the Byars kit did not come with any
fasteners. I chose to try stainless steel. If you do the same, use a few
mild steel bolt to align things before sliding in the stainless bolts. The
stainless steel bolts gall easily and if you try to hammer one into place it
will ruin the threads. I need to mail order some thicker stainless washers
as the ones available locally were all too thin.

The upper front brace is a triangular piece with two side mounts and one
front mount. The side mount can be bolted in place or welded but the
front must be welded in place. I chose to weld all three in place. The
front mount can be welded on the interior or exterior side. I had my
radiator out so I decided to install the front mount on the exterior side.
This moves the brace forward slightly which may help with clearance should
I ever decide to space my pedals forward. My car still had the stock
limiter valve which was in the way. I had to remove it and end the lines
out of the way and will need to replace it with a tee.

The upper rear brace is a four point design that can also be welded or
bolted in place. I chose to weld which requires repainting the engine
bay. The brace picks up the two bolt holes for the stock brace and two
new lower mounting points. The brace has upper and lower turnbuckles
so you can adjust it for width.

Do you have any photos of that Dan?

> Do you have any photos of that Dan?

I took a few last time I was in Ohio. I'll download them this weekend.

Dan

I don't picture the front being as weak as the rear with the metal and curves being closer together and the way it is all joined.

PanteraDoug sent me a note asking about the cage I used to have in my Pantera. I had a cage put into 3783 after meeting a good fabricator at the SAAC Convention in Hershey in 1977. It was only a 4-point, and no attempt was made to go through the bulkhead in the ffront or rear. My main concern at the time was to provide a little extra protection in the passenger compartment, not to stiffen the chassis (with my Pantera, I was looking UP at the doorhandles of Volkswagens).


I designed the cage to have pivoting side-impact bars that would swing out to allow easy entry/egress. Here are some pictures;

[URL= ]Cage 1[/URL]

[URL= ]Cage 2[/URL]

[URL= ]Cage 3[/URL]

regards,

cobrajeff

quote:

Originally posted by comp2:
...George you really don't think it does anything? ...

Hi Gary,

to answer your question, no I don't think the front end needs much in the way of bracing. I will certainly go along with what has already been written, that the first step in strengthening the chassis will be to weld everything up, and add a few choice gussets here and there. The front of the car is boxed in pretty good, and is compact enough that the various panels are short and stiff. Keep in mind the front end has fewer torsional forces acting upon it compared to the rear end, the forces to be concerned with are mostly bending forces.

The rear end is a different story, so readers please don't lump all braces into the same catagory.

One concept I would like pass on is that when forces acting upon a chassis cause a panel to bend, flex or twist, a significant portion of those forces are dampened by the bending/twisting action. When the bending & twisting is eliminated by stiffening that portion of the car, those forces don't disappear, they are transmitted to another area of the chassis. Which is why attaching any kind of brace to the roof without reinforcing the roof or A pillars is BAD. Which is why installing braces in a car with a rusty chassis is also just going to make things worse.

I have always played devil's advocate with friends & customers who want to buy lots of parts to bolt onto their cars & motors, I'll ask "what problem were you experiencing that motivated you to buy that part", if they can't answer that question, they really didn't need the part.

In that vein of thought, unless an owner is experiencing vague handling on the track, or cracking of the body panels, there is no reason to purchase chassis braces.

There is one other factor however, bench racing. A sexy looking brace mounted in the front trunk is worth about 10 mph, or 3 seconds, in a bench racing session. That's OK by me!

your friend on the DTBB

quote:

Originally posted by cobrajeff:
PanteraDoug sent me a note asking about the cage I used to have in my Pantera.
cobrajeff

Thanks Jeff

What exactly does this do for the front?:

http://www.pim.net/3222006BLKGT5S73.jpg

I think all it does is reduce your luggage capacity while lowering your checking account balance.

Larry

quote:

Originally posted by george pence:
I have always played devil's advocate with friends & customers who want to buy lots of parts to bolt onto their cars & motors, I'll ask "what problem were you experiencing that motivated you to buy that part", if they can't answer that question, they really didn't need the part.

In that vein of thought, unless an owner is experiencing vague handling on the track, or cracking of the body panels, there is no reason to purchase chassis braces.

There is one other factor however, bench racing. A sexy looking brace mounted in the front trunk is worth about 10 mph, or 3 seconds, in a bench racing session. That's OK by me!

your friend on the DTBB

I agree with Doctor Pence. Enthusiasm seems to have gotten the best of us. I have enough trouble getting in and out as it is.

Jeff agreed ... thats why I took out the cage .. and I'm only 5-8 and it was a struggle getting in and out. I still like gary halls cage but dont agree 100% that it remedies the problem of preventings stress cracks and adding rigidity needed for hard driving. I think it added more then enough if you removed the roof. but an excelent start to expand on.

Ron

Ron

quote:

Originally posted by accobra:
Jeff agreed ... thats why I took out the cage .. and I'm only 5-8 and it was a struggle getting in and out. I still like gary halls cage but dont agree 100% that it remedies the problem of preventings stress cracks and adding rigidity needed for hard driving. I think it added more then enough if you removed the roof. but an excelent start to expand on.

Ron

Ron

I agree also, but I think it just needs additional tubes to the rear tubs. That is not too difficult to do.

Doug,

I scoped out Georges thought on going low thru the bulk head but there is conflict with the gas tank ? It may be possible to follow the rear upper frame rails and alter the top of the tank. The other side is a breeze. So now thinking I wonder if it pays to beaf up and attach the upper frame rail to the cage in the pass comp and then attach it to the rear lower frame rail in the engine comp. Gonna scope this over the weekend.

Ron

You must be thinking of seriously racing your GTS.
If you can find pictures of Kleinpeters race car it might help and then again maybe not.
I think that eventually he wound up with a full tube chassis and front and rear flip tops like a Ford GT40.
I think it was around '96 that he was selling the car and I talked to him about it. Maybe it was '86, geeze I don't remember!
He was difficult to follow in a discussion. He would start to jump up and down like a gorilla and scream about throwing piles of $100 bills at the car all the time.
He convinced me real fast (ten seconds) that I didn't want a Pantera race car. He might have crashed and burned it just to get satisfaction, I don't know? I can't believe that anyone but an oil shiek would buy it. That's only because they wouldn't understand what he was saying and had tons of money.
I think you have to put a horizontal pipe from tub to tub and tie the tubes from the top of the roll bar tight along the engine sides to it.
That would be tough with my headers, I luv my headers, don't wanna loose them.

Comp2,if you decide to track your car, keep in mind the materials and design used.Most sanctioned events use the SCCA rule book as the holy bible for their tech inspection.They have a whole section on materials and design.For instance, if my memory serves me correct, cars over 3000lbs must use 1.75 seamless DOM steel tubing.It would suck to build something only to find out it can't meet the criteria.

Dan

Danno I have been looking into it and I am basically coming up with the same thing; 1.75" dom either .118" or .125. I'll probably just go with 1/8". Some require 6 attatchment points with one set within 6" from top and 6" mounting plates.

I think I am going to build a dual hoop main bar in the engine compartment with 2 bars back to the wheel wells. I can come just bellow the window forward into the cab if I need 6 point. I will put mounting plates attatched to the firewall so I can add them latter if need be.

At that poitn I will tie in the roof. As long as that structure exist, it will help with the roof line flex.

I will also mount an extra bar from wheel well to wheel well to help stabalize the wheel well. I may come up with a "X" attatchment on the rear bars that would be removable for hard driving. Pretty much like I drew earlier.

G

It sounds like you have a plan.Try and get the best chassis fabricator.I'm fortunate that I have a few close to me.Its amazing how hard it is to get someone to do your project in a timely professional manner.Even though your paying for it.

I look forward to your progress with this project.Perhaps you'll give updates and pics.

All the best, Dan