engineers and math geeks - vibrational cause?
Thread Starter
Drifting
Joined: Sep 2004
Posts: 1,638
Likes: 3
engineers and math geeks - vibrational cause?
Allright you engineers and wanna be's - time to make that education pay off (at least for me!)
Since putting in a fidanza flywheel and new clutch into my car (86 - with ZZ4 motor and Tremek tko500) I have a vibration that appears at 3200 RPM and gets progressively worse - first time it happened I though someone had sold me flat spotted racing slicks.
Since it is RPM specific - the first thought was flywheel - but no such luck. I think that I have found the answer - but vI don't wan't to put it all back together and find out I missed.
The pressure plate turns out to need 20 grams (about 2/3 of an ounce - think 2 quarters) to balance. That seems to me to be plenty to cause the vibration - but I just wanted an edumacated verification or denial - would 20 grams lead to a noticeable vibration at 3500 RPM?
Carl Johansson
Since putting in a fidanza flywheel and new clutch into my car (86 - with ZZ4 motor and Tremek tko500) I have a vibration that appears at 3200 RPM and gets progressively worse - first time it happened I though someone had sold me flat spotted racing slicks.
Since it is RPM specific - the first thought was flywheel - but no such luck. I think that I have found the answer - but vI don't wan't to put it all back together and find out I missed.
The pressure plate turns out to need 20 grams (about 2/3 of an ounce - think 2 quarters) to balance. That seems to me to be plenty to cause the vibration - but I just wanted an edumacated verification or denial - would 20 grams lead to a noticeable vibration at 3500 RPM?
Carl Johansson
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Your one piece seal engine is externally balanced in the rear. Ideally, the pressure plate and disk would be neutrally balanced for interchangeability and replacement purposes. The flywheel should carry the specified amount of imbalance to match your engine. IF someone has internally, and neutral, balanced your engine, it is a different ball of wax.
RACE ON!!!
RACE ON!!!
Drifting
Joined: May 2003
Posts: 1,730
Likes: 1
From: Charlotte NC
St. Jude Donor '05
Originally Posted by Carl Johansson
Allright you engineers and wanna be's - time to make that education pay off (at least for me!)
Since putting in a fidanza flywheel and new clutch into my car (86 - with ZZ4 motor and Tremek tko500) I have a vibration that appears at 3200 RPM and gets progressively worse - first time it happened I though someone had sold me flat spotted racing slicks.
Since it is RPM specific - the first thought was flywheel - but no such luck. I think that I have found the answer - but vI don't wan't to put it all back together and find out I missed.
The pressure plate turns out to need 20 grams (about 2/3 of an ounce - think 2 quarters) to balance. That seems to me to be plenty to cause the vibration - but I just wanted an edumacated verification or denial - would 20 grams lead to a noticeable vibration at 3500 RPM?
Carl Johansson
Since putting in a fidanza flywheel and new clutch into my car (86 - with ZZ4 motor and Tremek tko500) I have a vibration that appears at 3200 RPM and gets progressively worse - first time it happened I though someone had sold me flat spotted racing slicks.
Since it is RPM specific - the first thought was flywheel - but no such luck. I think that I have found the answer - but vI don't wan't to put it all back together and find out I missed.
The pressure plate turns out to need 20 grams (about 2/3 of an ounce - think 2 quarters) to balance. That seems to me to be plenty to cause the vibration - but I just wanted an edumacated verification or denial - would 20 grams lead to a noticeable vibration at 3500 RPM?
Carl Johansson
Really depends on where the extra weight sits.
heres a formula for you..
F=ma
Fbalance= mass(of imbalance)x accleration normal to the weights velocity
F due to imbalance = mass x v^2/r
F due to imbalance = mass x (omega*r)^2/r
F due to imbalance = mass x (omega*r)^2/r
v=omega*r so really
F due to imbalance = mass x r omega^2
omega * (2pi Rev per sec/ radians per second) * 60 RPM/ Rev per sec
F due to imbalance = mass x r*RPM*2pi*60
so if you got 20 grams located about 6 inches from from center at 3200 RPM you basically have
.020*.15*3200*2*pi*60= 3617.28newtons
which is around 800 lb-force at any instant.
They are probally balanced quite a bit closer to the flywheels center than that.
Drifting
Joined: May 2003
Posts: 1,730
Likes: 1
From: Charlotte NC
St. Jude Donor '05
Originally Posted by Carl Johansson
Thanks - all good information - but I really need an answer to my question - will 20 grams of inbalance cause a noticable vibration at mid RPM?
Carl Johansson
Carl Johansson
yes
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
Le Mans Master
Joined: Jan 2002
Posts: 9,036
Likes: 13
From: Edmonton AB
Originally Posted by Carl Johansson
The pressure plate turns out to need 20 grams (about 2/3 of an ounce
- think 2 quarters) to balance.
- think 2 quarters) to balance.
I gather it has seen service now with you but was it new before you
used it? I would normally expect that the PP would be neutral or
close to it.
.
Drifting
Joined: May 2003
Posts: 1,647
Likes: 28
From: Woodbridge NJ
Originally Posted by Alvin
Really depends on where the extra weight sits.
heres a formula for you..
F=ma
Fbalance= mass(of imbalance)x accleration normal to the weights velocity
F due to imbalance = mass x v^2/r
F due to imbalance = mass x (omega*r)^2/r
F due to imbalance = mass x (omega*r)^2/r
v=omega*r so really
F due to imbalance = mass x r omega^2
omega * (2pi Rev per sec/ radians per second) * 60 RPM/ Rev per sec
F due to imbalance = mass x r*RPM*2pi*60
so if you got 20 grams located about 6 inches from from center at 3200 RPM you basically have
.020*.15*3200*2*pi*60= 3617.28newtons
which is around 800 lb-force at any instant.
They are probally balanced quite a bit closer to the flywheels center than that.
heres a formula for you..
F=ma
Fbalance= mass(of imbalance)x accleration normal to the weights velocity
F due to imbalance = mass x v^2/r
F due to imbalance = mass x (omega*r)^2/r
F due to imbalance = mass x (omega*r)^2/r
v=omega*r so really
F due to imbalance = mass x r omega^2
omega * (2pi Rev per sec/ radians per second) * 60 RPM/ Rev per sec
F due to imbalance = mass x r*RPM*2pi*60
so if you got 20 grams located about 6 inches from from center at 3200 RPM you basically have
.020*.15*3200*2*pi*60= 3617.28newtons
which is around 800 lb-force at any instant.
They are probally balanced quite a bit closer to the flywheels center than that.
Yeah, Jimmy Neutron!
Thread Starter
Drifting
Joined: Sep 2004
Posts: 1,638
Likes: 3
Originally Posted by Slalom4me
What's the story on the pressure plate.
I gather it has seen service now with you but was it new before you
used it? I would normally expect that the PP would be neutral or
close to it.
.
I gather it has seen service now with you but was it new before you
used it? I would normally expect that the PP would be neutral or
close to it.
.
Thats why both Carolina and Fidanza recomend spinning the flywheel and PP together before you install em - slight flub up by my mechanic - he assumed I was getting him good parts!
Carl Johansson
Last edited by Carl Johansson; Dec 7, 2005 at 09:38 AM. Reason: add more info
Drifting
Joined: May 2003
Posts: 1,730
Likes: 1
From: Charlotte NC
St. Jude Donor '05
Originally Posted by Brimis
Yeah, Jimmy Neutron!
What?? Its just f=ma..
you can write a book on the differnt things you can solve with F=ma.. one of my favorite things is showing how the weight of a car means absoulutely nothing on how much g's you can pull with it nor does it mean anything on when it will tip over.