In a message dated 7/21/2006 11:18:47 A.M. Pacific Standard Time,
jcreasy@perforce.com writes:
<< i dont see how lowering the rear roll center on its own can make the car
rotate better.
that change alone will increase the CG to RC distance and acts like
softening the rear bar. for example, when i lowered my front roll
center, i calculated how much more front bar i needed to balance that
change- so i changed from a 1.25" OD, .095" wall to a .188" wall front
bar which rebalanced the car. >>
I don't remember where I read this, Fred Puhn, Carroll Smith, or ??? The
point is that the car rolls about the roll axis. A flat axis produces roll
without pitch, the steeper the roll axis, the more pitch is introduced, and
the
more weight is transferred to the outside front.
<< in the scenario you describe, was there also a stiffer rear bar added?
how much stiffer? was the geometry changed, e.g. from trailing arms to
a panhard? >>
This has worked with RX-3s, without changing from leaf springs, merely
adding a Panhard. It has worked on RX2s and RX-7s by replacing the high roll
center Watts with a low roll center Panhard, retaining the four link. ALL the
successful CP cars have lowered the rear roll center.
<< but now we are describing steady state cornering- which is tuned with
bars and springs. >>
its the possible initial effect of the roll axis before steady state
that i am interested in. ive gotten several different, but impassioned,
arguments from various experts. unfortunately there is no agreement on
what the dominant effect/s is/are. >>
When I say that rotation increases, I'm talking initial rotation. Mid
corner/steady state rotation is not a desirable thing, it's all about turn-in
to
me. Maybe that's my fwd background...
In any case, I think you want to have the rear roll center adjustable, so
you can try things out for yourself.
Charlie
|