Tunnel Brace
Safety Car
Joined: Nov 2003
Posts: 4,979
Likes: 5
From: San Diego, CA "leaf" "tee" "e"
I've copied a section out of SAE SP-1282 and held a discussion about stiffening the chassis, to include the tunnel plate, and copied the highlights into:
http://forums.corvetteforum.com/showthread.php?t=984927
If you read that and have any questions about how & why the tunnel plate works, read it again. Repeat until confusions goes away. If confusion persists after three days of continued reading, come back to the thread below and post your questions:
http://forums.corvetteforum.com/showthread.php?t=979585
Eugene
http://forums.corvetteforum.com/showthread.php?t=984927
If you read that and have any questions about how & why the tunnel plate works, read it again. Repeat until confusions goes away. If confusion persists after three days of continued reading, come back to the thread below and post your questions:
http://forums.corvetteforum.com/showthread.php?t=979585
Eugene
Burning Brakes
Joined: Jul 2000
Posts: 1,134
Likes: 1
From: Arlington Texas
Originally Posted by Fuzzy
Has anybody installed the Abs of Steel tunnel brace ? Which one SS or Alum is best ? Is it worth putting on for normal street driving,while I am changing my exhaust ?
IMHO, I am very impressed with the difference that the plate made in ride quality. I was equally impressed with this as I was with the performance of the Dynatech SuperMAXX's that I installed at the same time.
Highly recommended.
Last edited by thetorch; Jan 15, 2005 at 05:53 PM.
Le Mans Master
Joined: Jul 2002
Posts: 7,076
Likes: 26
From: Nevada and Florida
Originally Posted by George8211
I thought the C5 was engineered to operate at a given frequency (28 Mhz I think) for the over all chasis and body. Since you can't take out all the harmonics out with the tires, wheels, shocks, springs... you may let the body do some absorbing also. When you make the system stiffer, it begins to change the dynamics of how the vehicle absorbs and distributes the energy from an accident.
Those are the biggest words I know, and they are probably mis-spelled... So you'll have to figure out the rest on your own.
Those are the biggest words I know, and they are probably mis-spelled... So you'll have to figure out the rest on your own.
The C5 is NOT a radio.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
Safety Car
Joined: Nov 2003
Posts: 4,979
Likes: 5
From: San Diego, CA "leaf" "tee" "e"
28 Hz or Mhz has nothing to do with the suspension or chassis on the C5. Here are the real numbers for the C5:
Structural 1st torsional mode (twist): 23 Hz
--Suspension tramp: 16 Hz
Structural 1st bending mode: 21 Hz
--Suspension hop: 15 Hz
20 dB separation between the suspension isolation components and the attaching structure
The dashed lines are designed with a significant harmonic frequency difference between itself and the line above it. The C5 isn't really that stiff. The stiffness of the C5 is compared to a good sedan many times by the GM engineers. The C5 is very stiff for an open car, and even a coupe is still structurally an open car. The Z06 may be slightly different, but AFAIK the roof/windshield still aren't stressed structures, so it shouldn't be any stiffer than the coupe or convertible. The C6 Z06 has a stressed roof/windshield, so it'd be stiffer than other variants (if they existed).
Also, a higher frequency means the structure is stiffer, and stiffer is better. Stiffer structures transmit vibrations faster. Drop a rock into water, and the vibrations will slowly spread throughout the structure. Drop a rock onto a piece of onto a cored carbon fiber plate and the vibrations will move thru it soo quickly it'll take very good sensors to see the waves moving thru the structure....but to the eye it'd look like the unit moved as a whole.
Thanks Elite, it's still growing. I'll post another significant update in a couple weeks.
Eugene
Structural 1st torsional mode (twist): 23 Hz
--Suspension tramp: 16 Hz
Structural 1st bending mode: 21 Hz
--Suspension hop: 15 Hz
20 dB separation between the suspension isolation components and the attaching structure
The dashed lines are designed with a significant harmonic frequency difference between itself and the line above it. The C5 isn't really that stiff. The stiffness of the C5 is compared to a good sedan many times by the GM engineers. The C5 is very stiff for an open car, and even a coupe is still structurally an open car. The Z06 may be slightly different, but AFAIK the roof/windshield still aren't stressed structures, so it shouldn't be any stiffer than the coupe or convertible. The C6 Z06 has a stressed roof/windshield, so it'd be stiffer than other variants (if they existed).
Also, a higher frequency means the structure is stiffer, and stiffer is better. Stiffer structures transmit vibrations faster. Drop a rock into water, and the vibrations will slowly spread throughout the structure. Drop a rock onto a piece of onto a cored carbon fiber plate and the vibrations will move thru it soo quickly it'll take very good sensors to see the waves moving thru the structure....but to the eye it'd look like the unit moved as a whole.
Thanks Elite, it's still growing. I'll post another significant update in a couple weeks.
Eugene
Melting Slicks
Joined: Feb 2004
Posts: 3,137
Likes: 1
From: Insane Diego Kalifonya Baby
Originally Posted by 99C5Vert
Hi Jeff,
This AL vs. SS argument has been going on since the second plate came out. I order the AL plate from you, but finally felt motivated enough to think through the comparison. As a disclaimer, I am a Mechanical Engineer, but it's been years since I've looked at this stuff...
Theta = TL/JG
where
Theta is the angle of deflection, given:
T = Torque applied
L = Length of plate
J = Polar moment of inertia
G = Shear Modulus
For this discussion, L is the same, and T is the same, so the twist in the plate comparison comes down to comparison of J*G
whichever design (AL vs. Steel) has a larger product, is more stiff (results in smaller theta).
J for a rectangular section is bh^3/12 + b^3h/12 where b and h are the width and height of the plate.
Assuming a typical secion of 12"X.125" for the steel plate and 12" X .25" for AL:
12*.125^3/12 + 12^3*.125/12 = .00195+18 or roughly 18
12*.25^3/12 + 12^3*.25/12 = .015 + 36 or roughly 36
Now onto the Modulus:
Al = 3.8
Steel = 10.6
So, taking the product of our two components...
1/JG = 1/(18*10.6) = .00524 for steel
1/JG = 1/(36*3.8)= .0073 for AL
So in summary, I think the steel plate is stiffer by about 30%.
Anyone who is more current on their machine design feel free to correct me.
This AL vs. SS argument has been going on since the second plate came out. I order the AL plate from you, but finally felt motivated enough to think through the comparison. As a disclaimer, I am a Mechanical Engineer, but it's been years since I've looked at this stuff...
Theta = TL/JG
where
Theta is the angle of deflection, given:
T = Torque applied
L = Length of plate
J = Polar moment of inertia
G = Shear Modulus
For this discussion, L is the same, and T is the same, so the twist in the plate comparison comes down to comparison of J*G
whichever design (AL vs. Steel) has a larger product, is more stiff (results in smaller theta).
J for a rectangular section is bh^3/12 + b^3h/12 where b and h are the width and height of the plate.
Assuming a typical secion of 12"X.125" for the steel plate and 12" X .25" for AL:
12*.125^3/12 + 12^3*.125/12 = .00195+18 or roughly 18
12*.25^3/12 + 12^3*.25/12 = .015 + 36 or roughly 36
Now onto the Modulus:
Al = 3.8
Steel = 10.6
So, taking the product of our two components...
1/JG = 1/(18*10.6) = .00524 for steel
1/JG = 1/(36*3.8)= .0073 for AL
So in summary, I think the steel plate is stiffer by about 30%.
Anyone who is more current on their machine design feel free to correct me.
Burning Brakes
Joined: Feb 2000
Posts: 1,206
Likes: 0
From: USA USA
Cruise-In II Veteran
Nice job!!
I "thought " i was fairly intelligent. I have taken machinery handbook classes and i run cnc lathe,mill,twin turret lathe/mills,etc.,BUT
i am WAY outta my league here. 
Matt
i am WAY outta my league here.
Matt
