rec.autos.simulators

Kevin Caldwell
Calgary, Canada

That is slightly clearer if it is wheel spin because I can understand that there
is a sudden point where the wheels lose grip. It is simply that at a certain
force exerted by the wheels pushing against the tarmac they reach an enery level
where the *** can skate over the surface. It may be assited by the car having
less relative downforce at speed than when moving, which would explain why it is
harder to replicate in modern F1 and Indy cars. I am guessing all this but what
I'm really looking for is the physics of the thing.  I'm a newbie when it comes
to setups and driving for that matter and I wanted to understand what was going
on why the physics - ie the stuff you learn in the classroom.

Yeah, but what are the actual figure in revolutions per second. Is it linear - ie
is this value the same for 1st to 2nd as for 4th to 5th given that you have set
evenly spaced gear ratios. Again I'm looking to understand the physics.

I've tried here but Alison doesn't have Ferrari setups for these tracks.

Thanks anyway,
Paul

It is. The usable power band of those engines was pretty narrow.
Whereas a nicely motorized road car would go like this (from idle to
max rev):
little power - more - more - MORE - less - limiter
a GPL car goes like this:
little power - a bit more - a bit more - a bit more - MUCH, MUCH MORE
- broken engine. :)

As soon as "MUCH, MUCH MORE" power hits the drivetrain, the rear
wheels will break loose and the rear of the car will step to the side.
Spinning wheels, as well as locked wheels, can't transfer lateral
forces.

Basically yes. Taking above example, you want to stay as much as
possible in the "MUCH, MUCH MORE" power part of the spectrum when
accelerating - assuming that you can transfer that power to the road,
that is. Excessively spinning wheels are of no use.

So, if you shift up early, you will drop back into the "a little more"
power section, and it will take some time to get into the full power
part again. But you know the part that comes after it: broken engine.

In reality, it's not as bad, though: given that your gears are set
properly, you will always have plenty of power when shifting one mark
prior to maximum revs as indicated on your tach.

Did you check Alison's GPL page? She has Ferrari setups by Doug Arnao
for download:
http://www.racesimcentral.net/~alison/gpl/index.htm

I have no background apps running when driving GPL. I need every bit
of available CPU power.

--
Wolfgang Preiss   \ E-mail copies of replies to this posting are welcome.

Wheel spin.  Most high performance engines produce the bulk of their power
in a narrow rpm range near the engines maximum rev limit.  Lightweight cars
with little downforce tend to "break the rear (in rear wheel drive) tires
loose" as they "come up on the cam" near the rev limit, especially in the
lower gears.  Or even the higher gears if they're cold and/or your in a
slight curve.

On thing you can do to get a baseline is to run a practice with other cars
(including the same model your driving) then after a few laps check the
replay and watch what Clark with the Lotus uses, or Gurney with the
Westlake, etc.

You can avoid that by shutting down everything (ctrl-alt-del from the
desktop) but Explorer and systray, before starting GPL.  I frees up a lot of
memory, too.

Also, I might recommend a couple of books:
How To Make Your Car Handle, by Fred Puhn, ISBN 0-912656-46-8
Secrets of Solo Racing, by Henry A. Watts, ISBN 0-9620573-1-2

Think of it as a lever.  You've just barely applied enough force to cause the
lever to begin to rotate, with the car's front end as the pivot.  Opposite lock
moves the pivot in the same direction as the rear, ending rotation, but moving
the entire lever laterally.  Push a pencil around on a desk and it's easy to
see.  That's why you always end up going wide with opp-lock.  Eventually the
tires will generate enough heat, and thus friction, to stop their slide, and
with luck, you'll still be pointed in a desirable direction with pavement under
your tires.

If you try different cars, you'll notice a change in this phenomenon.  The
Lotus and Brabham, for instance, have more torque at low revs, and will break
the wheels loose at lower rpms.  The "cammy" Ferrari, on the other hand, is
more of a high revver, as befits a V12, which depends on greater valve area and
more rpms for power.  You'll notice it "hits" higher and more suddenly.  While
it's wheelspin is more sudden, it's often more controllable because the motor
is already closer to peak revs, and has less "headroom" to send you looping
around.  Really nice the way they captured this aspect of peaky engines.

For max acceleration in a straight line, shift at peak power rpms(see the
engine data in the "player info" screens; each car varies. Some cars won't live
long at this rpm level, though, so you'll have to leave a bit of room).  You
won't always want to do this, though.  Depending on track conditions, it's
often better to short-shift to minimize traction loss, which is pretty much the
Holy Grail in GPL; how to reconcile an excess of power with a surfeit of grip.
As for gear ratios, you'll want to have your upper gears more closely spaced
than the lower ones, with gradually smaller gaps from gear to gear.  You'll
know you've got it when it takes similar time spans to run through each gear.
You should divert from that ideal spacing, though,  to avoid having too many
shifts mid-corner.  You want peak revs in top gear just at your braking point
on the fastest part of the course, and a first gear that gives you good
acceleration without too much wheelspin out of the slowest corner.  Then set
your middle gears to suit.

Cheers,

Steve B.

the reason these '67 f1 cars get so darn sideways is because the
tyres they use are fairly soft and pliant, they can flex sideways
quite a way without breaking traction.
Modern tyres have many times less sideways movement so they don't
allow cars to get very sideways at all because traction is broken,
that "edge" where you are balancing the car sideways is much much
smaller. or that's what i think so far:) hoepfully i'm not too wrong.

i like to just shift the gear when the rpm reaches a certain level
just under max rpm for that engine, for instance in the lotus i
like to shift just under the 9000 rpm mark. it gives me excellent
reliability (in 3 weeks of solid GPL play i have only blown the
engine non-deliberately once, and damaged it once, both in practice
sessions). I also gear top gear so it reaches that same rpm mark
at the fastest point on the track - that way i won't over-rev and
break the engine on long straights, and i have extra rpm for
slipstreaming.
Also, i think i can feel the acceleration rate beginning to drop
if i rev too high, which is another reason i don't like to crank
the engine up too high.
I may not rev the engine to it's max power levels, but i still put
in lap times that are quicker than 95% of gpl drivers:)

not sure if any of this helped, or just confused you ;)
Grant.

Michael.

It helped - thanksPaul

All the computer players did it, so I decided to try it.

I was struggling with everyone (Lotus, ...) beating me on the
straights, not anymore :)  This also uses up more gas than
usual, so you need to add an extra gallon or so, or else
I'm running on fumes the last lap.

--
--------
Jason Monds
(Please remove 'no extra spork' when replying)