A-Body geometry, where is the COC geometry to compare?

[DionR]

Just so maybe someone will publish their COC suspension geometry, here are my layouts of the TB suspension in various configurations:

Stock:

Closer so you can read the numbers easier:

Performance with the following setup:

LCA flat
1 degree negative camber
6 degrees positive caster
275/35R18 +35mm wheel

Stock A-Body spindle:

F-Body Spindle:

F-Body spindle with 1" extended balljoint:

Do with it what you will, but I hope someone will finally gives us some comparable data for a COC kit.

And before anyone asks, I did not "plot" a camber curve for any of these. These are static layouts and I would have to manually move things around to get the numbers. Maybe if someone wants to plug the base numbers into an analyzer it would output them?

Also, not going to say they are accurate to the 4 decimal places the dimensions show. I did my best to get the suspension mounting point locations and I believe these numbers are close enough to tell the story even if I missed something by a 1/16"-1/8".

 

[72bluNblu]

Just so maybe someone will publish their COC suspension geometry, here are my layouts of the TB suspension in various configurations:

Stock:

Closer so you can read the numbers easier:

Performance with the following setup:

LCA flat
1 degree negative camber
6 degrees positive caster
275/35R18 +35mm wheel

Stock A-Body spindle:

F-Body Spindle:

F-Body spindle with 1" extended balljoint:

Do with it what you will, but I hope someone will finally gives us some comparable data for a COC kit.

And before anyone asks, I did not "plot" a camber curve for any of these. These are static layouts and I would have to manually move things around to get the numbers. Maybe if someone wants to plug the base numbers into an analyzer it would output them?

Also, not going to say they are accurate to the 4 decimal places the dimensions show. I did my best to get the suspension mounting point locations and I believe these numbers are close enough to tell the story even if I missed something by a 1/16"-1/8".

Where is your reference point set? Do you have a list of the measurements for each component?

I have a spreadsheet that can probably do the analysis of the curves, but its inputs are all based on the coordinates of the pivot points with regard to the center of the contact patch. Obviously I can change the reference point, but it would be easier to have a list of the measurements with reference to whatever you used to take your measurements rather than pulling them from the pictures

 

[DionR]

Where is your reference point set? Do you have a list of the measurements for each component?

I have a spreadsheet that can probably do the analysis of the curves, but its inputs are all based on the coordinates of the pivot points with regard to the center of the contact patch. Obviously I can change the reference point, but it would be easier to have a list of the measurements with reference to whatever you used to take your measurements rather than pulling them from the pictures

I used the bottom of the frame where the k-frame mounts as a datum and measured up from there to the outer edge of the bushing on both ends. The rear measurement was harder since the frame slopes away at that point so I had to try and maintain the plane. This gave me the slope of the UCA mounting points. I had to work harder to get the distance in from the outside of the flange, which was my vertical datum for the suspension mounting points.

I had a loose k-frame to grab measurements off to try and locate the inner pivot for the LCA which would be in relation to the bottom and outside planes of the flange.

In the part of each layout that shows the balljoints from the side, the vertical line is the front UCA mount at the outside of the bushing and inside the mount. I used this as the last datum to find the center of the LCA and LBJ in relation to the UCA.

The other thing to note is that it doesn't seem like the bottom of the frame is level with the ground, but the slope of the torsion bar (in my case) was the same so I assumed that the suspension would effectively be 90 degrees to that plane. But it was an assumption.

So I didn't measure up to the points, I took them from the frame. And then since I had a layout of the spindle and the pivot point of both balljoints, I just set those in using the LCA length of 13" and kept the LBJ elevation the same as the LCA pivot point. Then I set the 275/35R18 +35mm wheel on that and tipped it and the spindle all back to add 1 degree of negative camber. I didn't mess with the UCA length as it is generally adjusted to get the UBJ where it is needs to be and I assumed the SPC adjustable UCA would be used. But the length was at least close enough to make sense that it was attainable.

I did not take into account any compression on the tire, and I fudged it some to keep the bottom of the tire flat to the LCA plane. Then I measured the vertical dimensions off that plane.

Because my car is way up in the air and didn't have any wheels on it, let alone the 275/35R18 I wanted, I figured this made more sense. And since I have what I believe is an accurate layout of the spindle, all I needed was to locate that and the UCA mounts to get the points and let the wheel/tire determine the total elevations. This even made it easy to do the stock suspension as I didn't have to set mine up and take measurements, all I had to do is move the spindle around based on the setup I wanted and draw some lines and take measurements.

Note that 13" for the LCA length a bit of a swag as I didn't have a LBJ to bolt in and measure to. But I did have a loose LCA to measure off of.

Sorry, that was more book than it should have been. Just wanted to explain how I got what I got.

So, my 0,0 for the above dimensions would be center of the car at ground level. But I will re-dimension things from the center of the tire contact, easy enough for me to do. Do you want all the layouts, or just the F-Body/EBJ layout?

 

[DionR]

F-Body:

F-Body/EBJ:

A-Body:

Stock:

 

[67Dart273]

Dion you might as well be talkin about space ship design to me on this LOLOL. Thanks for your effort, tho!!!

 

[DionR]

Hmm...I see that I didn't keep this up to date. I discovered that I had made an assumption that was wrong and revised my layouts and posted them in a different thread. My mistake was that I assumed the front frame rails would be effectively horizontal, and they are not. I will have to up date this with the revised layouts.

But that's not why I am posting here. On Facebook, @Chris Bolander of Bolander Fabrication and Suspensions posted some info on his COC suspension. First I have seen anything like it from one of the COC kit manufacturers, even if I can't work out exactly what the charts mean.

Looks like they chart RC, scrub and toe changes as the cars roll? But best I can tell, it doesn't say where any of those points actually start? I am sure it is useful info, but comes at things from a different point than I have been looking at things so seems less helpful in comparing the systems? Or maybe I am just too dense.

Of note, all three charts compare a 66-72 TB suspension to a BFS kit and also a 2015 Challenger.

Bolander Fabrication and Suspensions

Good afternoon! We've gotten a lot of questions lately asking, "What makes our suspension better?" We're going to answer some of those questions. From what we've noticed, one of the biggest things...

www.facebook.com

Feels like something that showed RC location and camber at roll angles with an actual location would have been more helpful? Something like this:

Help me understand what the 3 charts from BFS mean.

 

[DionR]

Here are the revised layouts for an A-Body:

So one of the things I tripped over while trying to figure out a steering issue on my '74 was that the frame rails and torsion bars are not flat to the ground. I had assumed that they would be, but in retrospect that doesn't work because even if the factory intended them to be flat to the ground, whatever stance the car is lowered to would affect it. So, I went back and revised my layout using the slope I found on my '74. Except for the stock setup as I figure if will be steeper due to the front end being higher.

Here is the F-Body spindle with a 1" longer UBJ:

And the F-Body spindle with a standard UBJ:

A-Body spindle:

And finally, stock with manual steering:

 

[DionR]

Here is the top layout entered into VSusp:

Vehicle Suspension: Front View Online Suspension Simulator

VSusp (vehicle suspension): Front View Suspension Geometry Calculator/Simulator

vsusp.com

 

[DionR]

After musing on it some, the info from BSF feels a little like smoke and mirrors. Meant to appease the questions without really showing any useful info. Best I can tell, because all the charts converge at zero all they show is the change during roll, but don't say what the actual RC height is nor amount of scrub radius. If it starts and stays at a horrible location, so what?

But it does tell me that he has actually run his suspension through an analyzer. Guessing a chart showing his RC height and chamber gain doesn't compare well so he didn't share that?

 

[72bluNblu]

After musing on it some, the info from BSF feels a little like smoke and mirrors. Meant to appease the questions without really showing any useful info. Best I can tell, because all the charts converge at zero all they show is the change during roll, but don't say what the actual RC height is nor amount of scrub radius. If it starts and stays at a horrible location, so what?

But it does tell me that he has actually run his suspension through an analyzer. Guessing a chart showing his RC height and chamber gain doesn't compare well so he didn't share that?

He started a thread here when he first released that suspension. I think the several inch tall spacer attached to the end of the steering link should tell you what his suspension program said about the bump steer in his system.

I mean sure, he corrected it, but a tall spacer like that has its own consequences.

As far as the other numbers being tied to roll angle there’s a couple things to consider. First, like you mentioned it doesn’t actually say where the roll center starts, so, it could be awful. Second, even if it’s not, that’s not data you see presented that way so it’s pretty useless without a direct comparison. And then there’s the million dollar question, how much is the roll angle actually changing? Because if the car with his suspension rolls 5° and the torsion bar car he compares it to is only rolling 3° in the same situation, well…

The other thing is that if you look at his axis on those graphs, they’re not scaled the same. So he made pretty graphs, but what do they mean?

Well, his toe change axis goes from zero to .6” and zero to -.6” where the other is degrees from -3 to +3. Now, 3° of roll isn’t very much. But a toe change of .6” is MASSIVE. Now, that’s not the usual comparison of toe change to suspension travel, so I’d have to see different numbers to put it in context. But it seems real bad.