Shno's House of Z

[OldScoolCamaro]

Originally Posted by 2cnd chance

My Z Brothers,
Do any of you know the Camaro's rigidity torsional stiffness in ft. lbs.per degree of twist? I'm in another forum dicussing this. Thanks.

....I saw that post with the blue oval guy (smart phone Einstein LOL)....should be much information sustantiating the rigidity and superior structural quality of the Zeta chasis over their technology somewhere...

[LOWDOWN]

Originally Posted by 2cnd chance

My Z Brothers,
Do any of you know the Camaro's rigidity torsional stiffness in ft. lbs.per degree of twist? I'm in another forum dicussing this. Thanks.

TWO ways of calculating it:

RBM - Resisting Bending Moment is tensile strength, used to measure framerails etc.
HERTZ - (not the rent-a-car Co.) using soundwaves through the structure
...and I don't have the answer for either. Dazzle 'em that you know TWO ways to calculate, and b/s 'em from there!

[JusticePete]

Originally Posted by LOWDOWN

TWO ways of calculating it:

RBM - Resisting Bending Moment is tensile strength, used to measure framerails etc.
HERTZ - (not the rent-a-car Co.) using soundwaves through the structure
...and I don't have the answer for either. Dazzle 'em that you know TWO ways to calculate, and b/s 'em from there!

I don't have the numbers, but the scuttlebutt is the CTS-V and Camaro TEAMS both claimed bragging rights to having the best torsional rigidity.

[2cnd chance]

Yes that's where I'm at on this.

He's touting, "S197 [convertible] chassis torsional stiffness - 6500 lbs/ft per degree of twist - source Car & Driver, June 2005, "Mustang GT convertible road test""

My origional exchange with someone else:

Originally Posted by 8cd03gro
"I don't know why everyone thinks the gt500 is going to be so expensive. More horsepower doesn't inherently make a car more expensive. They're still on a much cheaper chassis with cheaper suspension components. The MSRP of the current gt500 reflects the fact that there is no direct competitor and Ford can essentially charge whatever premium they can sell the car for. Keep that in mind."

2cnd Chance:
"Not "everyone". Horsepower = $$$$$$. Ever heard the saying "how fast you wanna go, how much $$$$$ you got". The Mustang chassis is not cheaper it's an older design that's less rigid. Final comment not any more!!! "

FYI, I found online other cars with much higher numbers in the 20,000 and 30,000, but nothing on the forum or web for the 5Gen Camaro.

[2cnd chance]

Also, wouldn't a convertible be made more rigid because of the fact that it's a convertible necessitating the extra rigidity?

[JusticePete]

Originally Posted by 2cnd chance

Also, wouldn't a convertible be made more rigid because of the fact that it's a convertible necessitating the extra rigidity?

This may help http://www.camaro5.com/forums/showth...sh+test+videos

[LOWDOWN]

Originally Posted by 2cnd chance

Also, wouldn't a convertible be made more rigid because of the fact that it's a convertible necessitating the extra rigidity?

Keep in mind virtually ALL cars, today, are unibody...no separate perimeter frame, like a pickup has. So the "triangulation" of the "structure" is the roof, combined with the floor... Wack off the roof, and you've suddenly removed a LOT of "structure". Compensation comes in the form of chassis reinforcement. BUT...drive a convertible over railroad tracks (or belgian blocks, or a washboard road, or...) and you'll see/feel/detect some degree of flex that is NOT present in the same vehicle with a solid roof (steering column/dash/windshield header/cowl "shake"). With very few exceptions (reinforced solid-roof'd convertibles, sometimes), a soft-top convertible does NOT have the same total rigidity of its "hardtop" sibling...top UP or DOWN...

In the old days of perimeter frames, convertibles had a HD reinforced frame...often shared with Station Wagons...but put some of those old raggers on a two-point hoist, and the doors might not open...!! Flex!

[LOWDOWN]

For example:

Take a look at the rocker panel width of a current Lexus IS Sedan vs. a Lexus ISC...the ISC's rocker is almost TWICE as thick, below the doors. Solid-roof'd, the ISC's rigidity is very close to the Sedan, but NOT the same. Soft tops would likely have an even greater disparity...

[LOWDOWN]

BTW, tensile strength of HD Trucks (18-wheeler types) go well into 6 figures...

Number 3 would be a good source, perhaps, for these numbers/statistics.

[2cnd chance]

Thanks guys. I've told him here's some info with more on the way. I'm sure Number 3 will have a good bit to say.

Nice link Pete.

[Mr. Wyndham]

Originally Posted by LOWDOWN

BTW, tensile strength of HD Trucks (18-wheeler types) go well into 6 figures...

Number 3 would be a good source, perhaps, for these numbers/statistics.

Which is incredible to consider when you see the things twist under the torque of a standing start...

[Number 3]

First, I can't quote the numbers but Mustang convertible is a limp noodle compared to the Camaro convertible. The team did a truly outstanding job in getting it right.

If anyone remember the C4 Corvette Targa roof..................bolted in with a wrench in the console. You could tell a huge difference with a targa in and out let alone a convertible.

The big issue, as Lowdown points out, is "cowl shake". Going over railroad tracks in a vert is a real tell on the structure of a car. If the wheel feels solid you have a winner. But the Gen 4 Camaro was a joke in relative terms for that test.

As for stiffness, you can do a simple calculation on the stiffness of a car or truck. The two usually considered are bending and torsion. Bending is simply holding the bumpers fixed and pushing up or down in the center of the body. Torsion is simply holding one bumper fixed and twisting the other.

Torsional stiffness can be in Nm/degree or torque applied per resulting twist. This gives you the simple stiffness in twist. A good number, but not always the whole story.

A stiffer car allows for some more precise suspension tuning. For example, a car that is less stiff needs all kinds of sway bars and stiff springs to handle really well. Both of these can be counter to a car that rides well. You somewhat have to consider the loose structure as part of the suspension. But stiffen the body up and you can now use the suspension and tires more appropriately. An entire engineering class or two in that, but that is the jist of it.

Now for the other part of the story, and maybe more important for a street car, is the modal ananlysis or frequency. It isn't quite sound waves, but simply you can put an accelerometer on any beam and whack it with a hammer. From the input and the resulting output you can determine the first mode. That is the frequency where the object would go into resonance. Now if you applied the sound at that frequency you could get the beam to go into resonance. I believe this is how you get the crystal glass to break with a tuning fork or in Lexus case with an LFX exhaust.

The modes are related to the simple bending and torsional measurements for stiffness, but you will have modal targets set simply to make sure that the body structure of the car does not have a first (or second or third etc. for that matter) mode that can be excited by road inputs. If I recall correctly, and I've stated many times before that is dangerous, "most" roads will go up to about 13 Hz. So you need to make sure the first mode is higher than that so that the road input doesn't excite the body close to it's resonant frequency. Again another one or two engineering classes in that.

A car that is very high in stiffness and frequency is generally one that "feels" more solid when driving not just on smooth pavement, but as Lowdown points out, belgian blocks (a key GM road input at the proving grounds).

And overall, body stiffness goes hand in hand with chassis tuning and tire selection. A huge puzzle to solve which is why it can take so long to get you an truly outstanding Camaro (or any other great car for that matter).

There let the questioning begin.

[2cnd chance]

Yeah! So the Mustang loses!? (Eyes glazed over)

Thanks Number 3.

[Mr. Wyndham]

Originally Posted by 2cnd chance

Yeah! So the Mustang loses!? (Eyes glazed over)

Thanks Number 3.

So, 3......If this is all standard knowledge...why is it that some cars (coughmustangcough) pale in comparison to others? Is it cost? Lack of expertise? Intentional Compromises to achieve other goals?