rec.autos.simulators

by **Steve Smit** » Mon, 16 Feb 2004 22:47:16

Interesting observation. In general, wouldn't higher ride frequencies be
easier to damp (with viscous shocks, as opposed to Houdailles) than lower
Hz? And why is it the obverse in off-road cars (by which I assume you mean
dune buggies, which have something like 20/80 weight distrib., as opposed to
4WDs)?

> Springs proportional to weight is not actually realistic. Making the
> springs proportional to weight gives you equal ride frequencies front and
> rear, which in the real world would cause excessive pitch response that is
> very difficult to damp out. Normally on RWD pavement racing cars you want
> the front to have a higher ride frequency than the rear, which means the
> front is proportionally stiffer than the rear. For off road it is usually
> the opposite.

> > If you run fairly even bars/shocks and realistic springs (i.e. springs
> > that are proportional to the weight of the car) ...

by **Jan Verschuere** » Mon, 16 Feb 2004 23:14:58

Also, wouldn't this have more to do with aero concerns than anything chassis
related?

Jan.
=---

by **Haqsa** » Tue, 17 Feb 2004 00:56:55

The problem is not high ride frequencies, it is equal ride frequencies.
This will cause the car to oscillate in pitch, and because of the high
moment of inertia of the car in the pitch direction you would have to use
extremely stiff shocks to damp it out. It works much better to simply
offset the frequencies so that it can't oscillate in pitch.

For passenger cars the rear frequency is usually higher than the front, so
that the rear can catch up to the front over a bump or dip, the so-called
"level ride". Off road cars are also tuned that way, for the same reason.
Doesn't matter if it's a dune buggy or a 4WD truck, the problem is how to
keep the car under control over the big bumps and dips and the solution is
the same for both. For rwd race cars on pavement it is much more important
to have a stiff front (in order to preserve the steering geometry) and a
soft rear (for traction under power), so for those cars the front is
normally set up to have a higher ride frequency than the rear.

If you look at the setups that are included with NR2003 or F1C, or PWF's
setups or Arnao's setups, you will see the same thing in all cases, front is
proportionally stiffer than rear, meaning higher ride frequency in front.

You would also normally want the front bar to be proportionally stiffer than
the rear to help prevent roll oscillation. Stiff front, soft rear, then use
camber and roll center heights to make the car turn. That seems to be the
current standard setup practice for RWD race cars on pavement.

by **Haqsa** » Tue, 17 Feb 2004 01:01:25

Not really. Totally a question of trying to control the different modes of
oscillation that the chassis can get into. The chassis has more inertia in
pitch and roll than in bump and therefore trying to control motion in those
directions with dampers alone would lead to too much damping in bump. So
the suspension is set up in such a way as to cancel the natural frequencies
in pitch and roll. More detail in my reply to Steve. Also this is covered
pretty well in RCVD and in Carroll Smith's books.

by **Jan Verschuere** » Tue, 17 Feb 2004 01:16:34

Yes, but while you say that, nowadays the aero balance dominates the high
speed handling. If you go about applying this logic to the cars in GPL you
are going to end up with chronic understeer because there's nothing to help
you turn. You can trail the brakes heavily and "squat to go" to make up for
that in a slow turn (if you're Alison Fisher, that is), but there's only one
way to take Gresil flat and that's to boost the rear spring rate.

Sorrry to keep going on about this, but applying "current" setup ideas to
GPL is one of my pet peeves. <g>

Jan.
=---

by **Haqsa** » Tue, 17 Feb 2004 08:10:07

Well I can't claim to be a GPL expert but I find I can get the cars in GPL
to turn just fine using this setup philosophy. Typically where I end up
with a Lotus, Ferrari, or Eagle is springs around 90 front, 75 rear, bars
around 120 front, 60 rear. Shouldn't turn right? Well, I use about -1
to -1.5 degrees of camber in front and only -0.25 to -0.50 in the rear, sit
the rear end up about 1/2" higher than the front, use no more than 0.125 toe
out in front, and 85 degree on the coast side of the diff. Turns just fine.
And yes, I can take Gresil flat out in such a setup.

by **Jan Verschuere** » Tue, 17 Feb 2004 08:24:09

I see where the 1/2 inch rake comes in as the rear will squat more with the
weight transfer. I gotta see this for myself, send me a Rouen and WG setup.

Jan.
=---

by **Haqsa** » Tue, 17 Feb 2004 08:43:12

It's not just the squat, but raising the rear raises the rear roll center
which adds oversteer. It's a similar effect to raising the trackbar on a
cup car.

I'll send you a couple of Ferrari setups, I think those are the ones I have
used most recently.

by **Haqsa** » Tue, 17 Feb 2004 09:33:57

Hi Eldred. Not an expert on Mosport but I just participated in a TPTCC race
there this morning and finally got to a good comfort zone with this track.
Didn't finish too well due to some racing incidents, but during happy hour I
finally figured out how to save my tires. You have to be very careful to
not overdrive the car. For me at least it was very tempting to push really
hard between the turns. But since there aren't any real straights, if you
don't have the line exactly right then going full throttle will require you
to use too much steering input to keep the car on the track, and that will
burn up your front tires very quickly, not to mention slowing you down. I
found I could push pretty hard through 1, but the section from 2 to 3, from
3 to 4, and the final 3 turns at the end of the back straight are all tire
killers if you use too much throttle and are even a little off line. Not
that I can keep it on the line, but I found that if I got off line in any of
those sections the best thing to do was lift the throttle very slightly to
bring it back, trying not to use the wheel too much, and then squeeze it
back on smoothly. My lap times also improved when I started steering more
with the throttle and less with the wheel. Still a bit off the pace but
once I figured this out I was able to run low 1:15's consistently and still
keep the tire temps down. So it was both faster and easier on the tires to
not go to full throttle unless I was absolutely certain I had the car right
on the line. Looking at my fastest lap in Replay Analyzer I was only slow
through Moss, everywhere else I was as fast as the leaders. So smoothness
is the key, that will get you up to speed and still save your tires.

BTW what's that slayer stuff in your sig? Diablo 2? Or something else?

> >Yer right, PWF's Mosport is the Gold Standard,

> Anybody have any driving tips for this track(TPTCC)? I'm burning up the
tires
> on lap 16, and I'm nowhere NEAR the pace of the other drivers in my
league...
> :-(

> Eldred
> --
> http://www.umich.edu/~epickett
> Screamers League
> IICC League
> GPLRank -6.0 MoGPL rank +267.80
> Ch.Rank +52.58 MoC +741.71
> Hist. +82.34 MoH:na
> N2k3 rank:in progress
> Slayer Spektera lvl 65 assassin
> Slayer Hendryx lvl 30 barbarian
> US East

by **Eldre** » Tue, 17 Feb 2004 11:09:08

writes:

Now my head hurts...

Eldred
--
http://www.umich.edu/~epickett
Screamers League
IICC League
GPLRank -6.0 MoGPL rank +267.80
Ch.Rank +52.58 MoC +741.71
Hist. +82.34 MoH:na
N2k3 rank:in progress
Slayer Spektera lvl 68 assassin
Spectral_K lvl 35 Necromancer
US East

by **Eldre** » Tue, 17 Feb 2004 11:09:07

writes:

Interesting. If I slow down in the turns, I just...get slower. I don't have
RA for Nascar, so I can't compare any laps. But, it seems that I have to turn
the wheel a LOT, and the car doesn't respond very well. I think I just can't
drive the correct line.

Yep, Diablo 2. I've been playing that a lot recently, since most of my GPL
leagues folded... :-(

Eldred
--
http://www.umich.edu/~epickett
Screamers League
IICC League
GPLRank -6.0 MoGPL rank +267.80
Ch.Rank +52.58 MoC +741.71
Hist. +82.34 MoH:na
N2k3 rank:in progress
Slayer Spektera lvl 68 assassin
Spectral_K lvl 35 Necromancer
US East

by **Jason Moy** » Tue, 17 Feb 2004 12:14:50

That's pretty much my normal setup practice for GPL/F1C/N2k3/GP4.
Altho I tend to use the shocks for tweaking handling and save camber
and weight adjustments for evening out tire temps.

Generally in N2k3 I (and people much much much faster than me) tend to
use front roll couples in the 90% range, at least on road courses.
Haven't done as many oval setups as I'd like so I can't comment there.
but the few I've worked on have been loose as hell if I use any kind
of rear bar.

Jason

by **Jason Moy** » Tue, 17 Feb 2004 12:16:24

Eldred if you have TPTCC2 installed and your server is available for
practice, let me know. I'm not incredibly fast (mid 13's to mid 14's)
but I'd gladly drive around with you for awhile to work on the line.

Jason

by **Haqsa** » Tue, 17 Feb 2004 13:09:39

It's not so much a case of deliberately going slower as it is a case of
going just slow enough to stay on the line without a large amount of
steering angle. You will end up faster when you get it right. It applies
more to the short chutes than the turns at the beginning of the track, but
is also important in the three final turns since you are decelerating most
of the way through them.

Regarding the chutes, from 1 to 2, 2 to 3, and 3 to 4 you have these short
chutes that look like straights but really aren't, you are turning all the
way through them. If you get the line right (and I seldom do) you can go
full throttle through the chutes. If you don't you are better off backing
off just a hair than trying to force the car along the line with the
steering wheel. You can force the car, but after a lap or two of doing that
you won't have any front tires left.

Similarly for the final turns you can force the car through and feel like
you are going really fast once or twice, but after that your tires will be
gone. And it's not really that fast. It's actually faster and easier on
the tires to use less deceleration initially but carry the deceleration
almost all the way through. Use the throttle briefly to point the car
between turns but decelerate through them, using the forward weight shift to
keep the car balanced on the line.

Now that I think about it, that's really the key concept. Using weight
transfer to help steer the car is how you save the tires, and it usually
ends up being faster too.

by **Eldre** » Wed, 18 Feb 2004 02:48:40

We have a league race at Mosport this weekend. I'll see if I can put in 100 or
so laps of practice. If I can't get any faster in that amount of time, maybe I
should just give it up.

Eldred
--
http://www.umich.edu/~epickett
Screamers League
IICC League
GPLRank -6.0 MoGPL rank +267.80
Ch.Rank +52.58 MoC +741.71
Hist. +82.34 MoH:na
N2k3 rank:in progress
Slayer Spektera lvl 68 assassin
Spectral_K lvl 35 Necromancer
US East

rec.autos.simulators

Brands Hatch Lives!

Brands Hatch Lives!

Brands Hatch Lives!

Brands Hatch Lives!

Brands Hatch Lives!

Brands Hatch Lives!

Brands Hatch Lives!

Brands Hatch Lives!

Brands Hatch Lives!

Brands Hatch Lives!

Brands Hatch Lives!

Brands Hatch Lives!

Brands Hatch Lives!

Brands Hatch Lives!

Brands Hatch Lives!

Brands Hatch Lives!