> What I would like to know is what Doug meant by "his only flaw in
> the model is he doesn't do dynamic camber and roll center change with
> roll".Could someone(hopefully Doug)help me out as to what this means.
end of that sentance it's just plain dynamic, and is constantly changing in bump,
rebound and roll. Camber change is controlled by whats called an "instant center"
or instant swing-arm lenght, this arm swings in an arc about its center and has a
certain amount of camber gain based on that arc. GPL uses this arc as formed at
ride height and each car in the sim is different. This is formed by the
suspension point placements on the tub and the lengths of the upper and lower
a-arms (see Caroll Smith's books). This arm, on a well designed suspension, is
much longer than the actual a-arm lengths. The reason they are called "instant"
is because they only occur at the instant you are looking at them. As soon as
things start to move, that swing-arm lenght starts to change, and so does the
amount of camber gain. Further complicating it is that the front and rear
swing-arm lenghts are usually different, because the rear has different
priorities than the front.
The same thing goes for roll center heights. They constantly evolve up and down,
and left and right as the car rolls squats and lifts. This affects the roll-axis
(a line drawn between the front and back roll centers) and the torque-arms
between that axis and the CG heights (there's more than one!) that the sway bar
and springs have to resist when cornering. It's an extremely complicated
interaction between all these factors that makes it so calculation intensive. The
formulas are all there, and readily available and Keammer is well aware of them -
it's just not feesable CPU-wise ATM, to do it all. Keammer is a genius - and what
he's done here with GPL - with the tools and restrictions he's been given - is
incredibly impressive.
Once these things become possible, then a true challenge to car setup and
individual car behaviour will come about.
Also, once this is done, the possiblilty of designing our own cars from scratch
can be very realistic - this I_want_to_happen :)........................
In the end, a roll bar is for driver feel and under/oversteer adjustment. The
risidual effect is that it controlls the amount or roll and resultant camber
"loss" in roll. Your job is to match the static camber settings to the amount of
roll you imposed through the srings/rollbar settings by using tire temps. BTW, I
use the word camber "loss" because most race cars suspension systems will go
*positive* camber as the car rolls, so you need to match the final loaded state
with an intial negative setting to make up for that. Complicating that issue is
the track geometry, ie banking which requires more negative camber, the driver -
the faster you go the more G's you pull the more the car rolls the more negative
camber needed or more swaybar..............and on and on........... Confused? You
should be <g>.
No, they *will* effect camber change in GPL because there is still a camber curve
as the wheel travels up and down. As you stiffen the roll bar the loaded wheel
compresses less. However, the roll of the chassis, and the resultant roll of the
suspension points, dosen't change that curve at all - this is the dynamic part.
No, see above :)
The current model is still *extremely* realistic feeling, you just don't have the
possible bad things that the car can throw at you that would effect your setup
decision and car choice.
Once we get all these things and complicated realistic track "surfaces" , we will
have the next generation :)
--Doug
PS: I corrected the spelling of my last name in the header..........don't worry,
it happens all the time I'm used to it :)