Roll Centers on G-Body

[stock car driver]

Still nobody explaining how they get below ground when your last lines go to the tire centerline on the opposite side at ground level.

I guess Im the only one who manually lays out things to confirm my $300 dollar program is correct.

[petermanbuilt]

Alright, I guess I will set this straight for Jeff, since no one else will.

When plotting roll centers, project a line through the control arm pivot and the ball joint pivot for each control arm.

The intersection of the lines through the left upper and left lower defines the instant center for the left side suspension.

A line is then projected from this instant center to the center of the left tire contact patch. I will call this line the "left side swing arm" for future reference.

Repeat the 2 above steps for the right side.

Finally, the Moment center is determined by the intersection of the left and right side "swing arms"

Where you are WRONG Jeff is in saying that "swing arm" line goes to the opposite side. The left instant center will always project through the left side contact patch, and the right instant center always projects through the right side contact patch.

Anytime that the instant center lies outside of the tires, the moment center will be "underground" for lack of a better term.

See this link as I have drawn it out. I exaggerated the angles to make it fit on a sheet of paper.
If that is not enough I will keep proving you wrong with multiple vehicle dynamics textbooks.

http://s823.photobucket.com/albums/zz158/petermanbuilt/Moment%20Center/?action=view&current=momentcenterbelowground.jpg

Nathan Peterman
Penn State Mechanical Engineering Alumni

Still nobody explaining how they get below ground when your last lines go to the tire centerline on the opposite side at ground level.

I guess Im the only one who manually lays out things to confirm my $300 dollar program is correct.

[stock car driver]

Your drawing is based on the upper a arm angle forcing the instant center outside the tire centerlines, is that the deciding factor that changes your next point from the opposite tire to the cl of the tire on that same side?

Maybe thats correct I dont know thats why Ive been asking.

[stock car driver]

Where you are WRONG Jeff is in saying that "swing arm" line goes to the opposite side. The left instant center will always project through the left side contact patch, and the right instant center always projects through the right side contact patch.


If that is not enough I will keep proving you wrong with multiple vehicle dynamics textbooks.

http://s823.photobucket.com/albums/zz158/petermanbuilt/Moment%20Center/?action=view&current=momentcenterbelowground.jpg

Nathan Peterman
Penn State Mechanical Engineering Alumni

Go ahead and keep proving me wrong if thats what makes you feel good about yourself. I asked this question how many times?? obviously I dont know the answer or I wouldnt be asking, I dont see how ASKING for explanation can be proven wrong but whatever floats your boat...

I read your post again and I see you say ALWAYS, I look forward to many more posts from you backing up your ALWAYS since I can post many that say it isnt ALWAYS as you have said. I believe your ALWAYS only pertains to when the instant center is OUTSIDE the wheel base.

[stock car driver]

http://i642.photobucket.com/albums/uu150/jnjfab/101_0113.jpg

So this book is wrong?

[petermanbuilt]

Your drawing is based on the upper a arm angle forcing the instant center outside the tire centerlines, is that the deciding factor that changes your next point from the opposite tire to the cl of the tire on that same side?

Maybe thats correct I dont know thats why Ive been asking.

Yes the instant should should project to the contact patch of the tire on the same side!

A metric is suspension is considered an independent type suspension, simply meaning that the actions of one wheel do not have a direct effect on the other. Because of this, the IC of the left does not correlate to right side contact patch.

In contrast, when one side of a solid axle suspension hits a bump, the opposite side is forced the opposite direction because the two wheels are connected by essentially a beam.

Check out Chapter 17 of "Race Car Vehicle Dynamics" by the Millikens. It lays it all out. This book is widely considered a "bible" for vehicle dynamics as the authors spent their entire life researching the subject before writing.

I don't want to get into a pissing match, just trying to keep you from telling everyone that they are wrong when in fact, your the one that incorrect.

[stockcar5]

peters pic of right for below ground roll centers and jeff yours is correct for the ic being inside the tire contact patch.

saying the ic is always within the wheelbase is as wrong as saying there is no way the roll center can be below ground with lowers level.

[petermanbuilt]

http://i642.photobucket.com/albums/u...b/101_0113.jpg

So this book is wrong?

Nope, that drawing is correct. The instant center on the left is drawn to the left side contact patch and visa versa

I added some color to the picture you posted to show that they too are using what i said above

http://s823.photobucket.com/albums/zz158/petermanbuilt/Moment%20Center/

[stock car driver]

Nope, that drawing is correct. The instant center on the left is drawn to the left side contact patch and visa versa

I added some color to the picture you posted to show that they too are using what i said above

http://s823.photobucket.com/albums/z...ment%20Center/

Step 10 in your color pic is the instant center going to the opposite tires centerline.. Thats what Ive said all along. I see what your saying that the instant center of the left suspension which is actaully located on the right comes back to the left tires centerline. That is the tire opposite the instant center point isnt it? lol.. just like Ive said all along.

What youve explained which nobody else explained was what to do when the instant center is outside the tire, your drawing makes sense. thanks.

It does appear you want some sort of pissing match.



Stockcar5, you might as well shut up, Ive asked you to explain how you get below ground repeatedly you had nothing to offer.. This guy explained it. Scroll back I asked point blank before how the roll center was plotted when the instant center is outside the tire.. YOU didnt know your just put the number in your program, lol..

[stockcar5]

if i explained it to you you'd piss and moan anyway like always. i drew it out back in 2003 then bought a program. you'd be retarded to try and draw one out now if you own software.
i figured we were long past explanation when you clowns started comparing stats and asking each other for pics of your wives...lol

[stock car driver]

if i explained it to you you'd piss and moan anyway like always. i drew it out back in 2003 then bought a program. you'd be retarded to try and draw one out now if you own software.
i figured we were long past explanation when you clowns started comparing stats and asking each other for pics of your wives...lol

What have I pissed and moaned about ever? I cant even think of another topic on here where I ASKED a question or for help off the top of my head.


retarded would be the geometry on that chassis of yours I just worked on two weeks ago, lol.

[stockcar5]

yea i hope you get it fixed so chad can win races in it like i did. should be bad fast. he seems like a decent guy so treat him good. he said your jackass sometimes but you know it and your trying to improve yourself. seems like hes willing to give you chances most people wont.

where is he gonna race it?

[petermanbuilt]

[QUOTE=stock car driver;1502905]Step 10 in your color pic is the instant center going to the opposite tires centerline.. Thats what Ive said all along. I see what your saying that the instant center of the left suspension which is actaully located on the right comes back to the left tires centerline. That is the tire opposite the instant center point isnt it? lol.. just like Ive said all along.

Alright, It was just a confusion of wording.

When you say that the instant center goes to the opposite tires centerline I was assuming that you meant the left suspension IC went the right side tire contact patch. If you did that the moment center would be above the ground, which you stated numerous times was the case....But its not

[stock car driver]

seems like hes willing to give you chances most people wont.

Yeah thats why Im turning people away all the time.

I could build a dozen motors and chassis a year if I wanted too, but being retired theres no sense in doing more than is fun!

2011, 37 3rd members, 11 floaters, 3 nine inches. 3 motors. I know fwd cars dont count in your book so no numbers on them.
2010, 29 3rd members, re jigged 18 floaters, sold 9 floaters, 2 nine inches.

Ive removed my floaters from my website and also stopped re jigging any floaters about the middle off 2011.

[stock car driver]

[QUOTE=petermanbuilt;1502916]

Step 10 in your color pic is the instant center going to the opposite tires centerline.. Thats what Ive said all along. I see what your saying that the instant center of the left suspension which is actaully located on the right comes back to the left tires centerline. That is the tire opposite the instant center point isnt it? lol.. just like Ive said all along.

Alright, It was just a confusion of wording.

When you say that the instant center goes to the opposite tires centerline I was assuming that you meant the left suspension IC went the right side tire contact patch. If you did that the moment center would be above the ground, which you stated numerous times was the case....But its not

Like I said thanks.

I was wondering how it was laid out the old fashioned way when the uppers angle forces the ic outside the tire as in your drawing.. my computer program doesnt explain things and nobody else seemed to know either on here. Clearly many in this thread would JUMP at the chance to TEACH me something! I had no idea how to lay that out nothing in any books I have explains when the ic is outside like that.