F355 suspension Analysis

Mentally position this figure up by 3 posts in this thread.

I tried to correctly edit the above post only to run into a stupid debilitory restriction on inserting more images into already committed posts. It is this kind of limitation, that any software upgrade to this system should address before being committed into full use.

Now, after our little todo....

I have access to a 3D modeling program especially suited to suspension analysis. Prior to gains access, I built an eXcel model of the Ferari suspension. For the pure longitudinal and pute latteral directions both models are in agreement, however the 3D model is eminently superior.

Remember those geometric coordinates of the front and rear suspensioni pivot points earlier in thsi thread? Well, we take those points and use them as the initial input to a suspension analysis program. Varius books (like those mentioned above) show the kinds of suspension changes that occur at the car moves around on its suspension.

In order that the reader can follow, I am presenting the results of this analysis in several forms. For this purpose, dive is when the suspension is compressed from longitudinal forces, rise is when the suspension is decompressed from longitudinal forces. Roll is for when the suspension is compressed due to cornering.

With this in mind: The following figure shows the dynamic camber of the F355 front suspension when set at factory ride height and factory standard static camber. This point is found at Dive=0 and Roll=0 and is -0.8.



The important thing to notice, here, is that the curves slowly change. And secondarily, that if one raises of lowers the suspension overly, bad things happen to the "shape" of the curves. More on this later.

A similar graph could be done for the Dive dimension leaving Roll in the legend. I leave this out for brevity.

An important point can be seen directly in this graph. That is look at teh static position (Dive=0, Roll=0) and notice that while that curve has a non-linear shape, it does not move around ery much over the first 2 inches of travel in either direction. That is, the front suspension does not change camber as the car dives under brakes, rises under acceleration, or rolls while cornering (the important outside tire only).

The rear suspension is analysed in a similar manner:



The avid reader will notice that the shapes are rather similar, but interestingly different. And when I got to this point durring the original investigation, these charts meant absolutely nothing to me. And I fear that simple analysis from these graphs will simply give the reader a headache. So, rather than boring you out of our minds, scientists have come up with a novel way of dealing with data of this kind. It is called 3D charting.

The reader is directed to the point where dive=0, roll=0 and the static camber setting is -2.0 degrees. Unlike the case with the front end, the rear suspension has large camber changes under braking, acceleration, and cornering. It is the interplay between the rather static front end and the rather dynamic rear end, that gives this car the vehicular dynamics that is has.

The following figure shows the F355 suspension undergoing diver and roll in a single graph. Notice that this is exatly the same data we saw before, just presented in a different way.



The following figure is the F355 Rear suspension data in 3D.



At this point, the non-scientist is wondering where is all of this going. Before signing off for tonight, I would like the reader consider the following points: A) The movement of the graph up is the same as raising the ride height of the car, wile lowering the graphs is the same as lowering the car, B) raising the front graph while lowering the rear graph is the same as changing the rake of the car, C) moving the graph to the left or to the right is the same as giving the car a list.

Do not fret, this is the subject of our next adventure in suspension analysis. Stay tuned.

{An appology:: I found (what turns out to be) a little error in the above presentation a couple of days after writing the last entry. This error caused me to go back to the original data in order to find and fix the problem. This took several days of searching for the culpret in a 35 page eXcel spreadsheet. In addition, it took me over a week in order to put the mechanics which underly the analysis back into my mind, and reason about practically everything already presented and yet to be presented. I have (just tonight) gotten back to square one and can reproduce the original data and the presentation I did for the other Ferrari forum about 4 years ago. I am terribly sorry for the delay.

Finally, I will be out of town from Thursday morning through Monday night. So, I am estimatng the next entry to be the following Wednesday night.

Once again, sorry for the delay; but I am sure that you want the highest quality data presented}

For those interested in the absolute accuracy, the Line-Chart labeled "F355 Rear Camber" is in error. The error can be fixed by subtracting 0.7 from all of the value on the chart, or (equivalently) by sliding the verticle scale upwards by the same 0.7. This will put the camber at -2.0 at Dive=0 and roll=0.

[johan355GTS]

Where did all the pictures go, any chance to get them back?