rec.autos.simulators

GPL Opposite lock

<

GPL Opposite lock

by < » Fri, 17 Apr 1998 04:00:00

There has been some discussion regarding the possibility of maintaining
opposite steering lock through entire turns in GPL, and it has been sugested
that this does not reflect the real driving behaviour of F1 cars of the
60`s.

I will contribute with some facts and some opinions to this discussion.

FACTS:

 A stabilized, as opposed to transitory, counter steering attitude of a car
through a corner is a situation where all the forces acting upon the car are
perfectly balanced and matched. The situation ends when this balance is
broken. These forces include the much forgotten inertial polar torque, which
is the inertia of an object when it is spinning around its vertical axis. In
a car, this happens when it is spinning, or going through a turn, and it is
the reason for many crashes at the exit of slow and medium corners (like
turn 8 in Watkins Glen). The forces are usually separated in 2 groups: those
developed by the tires, thanks to their grip, and those acting upon the car
as an inertial mass. The grip forces must exceed, or, at best, balance the
others if driver control is to be mantained.

There are 3 possible cases:

1- Grip forces exceed all others: the car is under control, and the
exceeding grip is used to accelerate, brake or turn, without tire slip.

2- Grip forces balance all others, but can not exceed them: this is a
transitional situation, between situations 1 and 3.

3- Grip forces are overcome by others: this is a non-control situation,
where tire slip inevitably occurs. When it does so in a straight line, the
car is either spinning under acceleration, or locking the wheels under
braking. If it happens in a turn, the car leaves its trajectory, usually
with its center of gravity following a straight line tangential to the
trajectory at the moment of the grip loss. If that loss occurs at the front
axle, the car car will not spin; if it occurs at the rear, it spins around
its vertical inertial axis.

The point here is that situation no 2 is a transitional situation, being the
point where tire grip reaches its limit. This transition can be smooth and
progressive, as is the case with rally cars with gravel or snow tires and
suspension, or it can be sudden and brutal, as is the case with circuit cars
with modern racing tires and suspensions. This suddeness is further
increased in cars with powerful aerodinamic aids, because their effect
disappears as soon as the car leaves a straight line relative to the wind.
Generally, it can be said that cars with soft suspension settings, working
with low to medium tire grip (be it due to the surface or the tires), have
smooth transitional regimes, resulting in a behaviour easy to control at the
limit, while cars with more rigid suspension settings, working with high
tire grip, have sudden transitional regimes, making them very hard, or even
impossible, to control if the limit is reached. In most modern race cars,
this is further exacerbated by aerodinamic aids, whose effect disappears
once the car starts slipping sideways.

Furthermore, it must be said that the way a car behaves at the limit (sudden
or smooth) also depends greatly upon 2 factors: suspension geometry,
especially camber, (which, if it is negative and has a value over 1,5-2
degrees, can increase cornering ability, at the expense of controlability at
the limit, and therefore it is only used in race cars prepared for tarmac),
and the rigidness of the tire carcass, which influences directly the angle
of drift (tire carcass deformation under simultaneous vertical and
horizontal loads causes the tire patch in contact with the ground to travel
in a direction slightly different from the direction where the tire is
pointing; this difference is called drift, and it occurs without tire slip,
merely due to the deformation of the carcass)

OPINIONS:

In the 60`s, racing tire technology was much more crude than it is today.
The radial tire started life then, and it was, even in 1967, at a very early
stage of development. Tires had much less grip than modern racing tires.
Tarmac technology, often forgotten, was also far less developed, and the
circuits then had far less grippier surfaces than even modern roads, let
alone modern circuits. Finally, F1 cars had very distinct characteristics
from today`s F1`s. The closest modern equivalent, chassis-wise, are modern
Formula Ford and Formula V single-seaters, and even these have modern tires
and surfaces to work with. But they do slide around, even with higher grip
than old F1`s.

What all this amounts to is this: F1 cars in 1967 had all the
characteristics to be able to behave smootly at the limit, and therefore to
be driven at that limit, drifting around with one or both axles, depending
upon suspension settings and pilot`s preferences.Some of them did it, but
most didn`t very often because they could be faster with 4-wheel drift
techniques (which is also the fastest way with GPL; check the 1:06:96 replay
at The Apex).

All this is why I think that PAPYRUS have done an unbelievably good job in
GPL; all adjectives are insufficient. I do not know, in the strictest
scientific sense, if 1967 F1 cars behave EXACTLY like they do in GPL, but I
believe very firmly that they must have been very similar, and, if there was
some difference, it just made the game better.

Finally, a word on apples and oranges: GP2 and F1RS simulate modern F1 cars,
with their huge modern tires, modern circuit surfaces, and overwhelming
aerodinamic loads; these cars do not slide around, and they are not supposed
to. Therefore, their simulators must reflect this. GP2 and F1RS are, for
different reasons, excellent simulators, but we can`t forget what it is that
they simulate, and, especially, we cannot compare their driving model with
the one in GPL. We cannot compare apples with oranges.

If anything, GPL`s model must have been, in my opinion, much harder to
conceive than those for modern cars. Racing gamers should all be very
grateful to PAPYRUS.

Finally, I want to apologise for any mistakes; I am Portuguese, and
therefore writing in English is not without risk.

PS.:Since I have the demo, I have played nothing else. My personal best is
1:08:24. Knowledge is not talent, but I`m still trying hard. By the way, I
saw at The Apex that PAPYRUS announced that the Nordschleife is in the game!
Like someone said: PAPYRUS RULES!

Bruce Kennewel

GPL Opposite lock

by Bruce Kennewel » Fri, 17 Apr 1998 04:00:00

Good grief!
Did I wander into a university lecture by accident?!
Interesing.....very interesting but it doesn't answer the question "Will I be
able to paint my helmet in my colours?"


> There has been some discussion regarding the possibility of maintaining
> opposite steering lock through entire turns in GPL, and it has been sugested
> that this does not reflect the real driving behaviour of F1 cars of the
> 60`s.

> I will contribute with some facts and some opinions to this discussion.

> FACTS:

>  A stabilized, as opposed to transitory, counter steering attitude of a car
> through a corner is .........

(A whole lot of incredibly interesting technical stuff snipped.)-
--
Bruce.
(At home)
Brian Shor

GPL Opposite lock

by Brian Shor » Fri, 17 Apr 1998 04:00:00

Excellent post...
and BTW, your english is better than a lot of native speakers of it I've seen
here.

Brian Short


> Finally, I want to apologise for any mistakes; I am Portuguese, and
> therefore writing in English is not without risk.

Spudgu

GPL Opposite lock

by Spudgu » Fri, 17 Apr 1998 04:00:00



I think you can select a single colour for your helmet in the game, but
you can't have flashy designs. This is what I figured by looking at some
of the text files in the demo subdirectories.

--
Spudgun

Ronald Stoeh

GPL Opposite lock

by Ronald Stoeh » Sat, 18 Apr 1998 04:00:00




>      Thanks for taking the time to write up such an informative post.

Thanks for reposting the whole thing, NOT!

l8er
ronny

--
Toys'R'Us '99: "So, would you like a hand gun with that action figure,
kiddo?"

          |\      _,,,---,,_        I want to die like my Grandfather,
   ZZZzz /,`.-'`'    -.  ;-;;,_              in his sleep.
        |,4-  ) )-,_. ,\ (  `'-'     Not like the people in his car,
       '---''(_/--'  `-'\_)            screaming their heads off!

Byron Forbe

GPL Opposite lock

by Byron Forbe » Sat, 18 Apr 1998 04:00:00


> Good grief!
> Did I wander into a university lecture by accident?!
> Interesing.....very interesting but it doesn't answer the question "Will I be
> able to paint my helmet in my colours?"

  LOL. Well, that was certainly a change of pace after reading his
relevant and technically elegant post!
Byron Forbe

GPL Opposite lock

by Byron Forbe » Sat, 18 Apr 1998 04:00:00


> Furthermore, it must be said that the way a car behaves at the limit (sudden
> or smooth) also depends greatly upon 2 factors: suspension geometry,
> especially camber, (which, if it is negative and has a value over 1,5-2
> degrees, can increase cornering ability, at the expense of controlability at
> the limit, and therefore it is only used in race cars prepared for tarmac),
> and the rigidness of the tire carcass, which influences directly the angle
> of drift (tire carcass deformation under simultaneous vertical and
> horizontal loads causes the tire patch in contact with the ground to travel
> in a direction slightly different from the direction where the tire is
> pointing; this difference is called drift, and it occurs without tire slip,
> merely due to the deformation of the carcass)

   Good points here. The side walls of these tyres would probably have
been weaker and the tyre profiles greater than the average race car
today. It will be also interesting to see in the full version of GPL
what the range of tyre pressures is and what pressures are optimum at
the average circuit as compared to the 37psi (my opinion of course) of
ICR2 for example.
      Still, I don't really think you have hit the nail on the head as
far as on limit control is concerned. As you mention, a very big
difference between the cars of today and those portrayed in GPL is
downforce. Therefore this makes weight transfer a much more significant
factor in GPL than most other sims. And consequently this leads to a
situation where if the tail is starting to come out on you that you can
apply a little more throttle to load the rear end up more and you have
instantly gone from an "on or over the limit" situation to being under
control again.
     I think one of the largest differences between GPL and the rest is
that the edge of adhesion can be effected very dramaticaly by throttle
control. Whereas in F1/CART sims the downforce is usually the
pre*** factor which means that once your gone, your gone in most
cases. The window of opportunity to use weight transfer to save yourself
is certainly much smaller in comparison.
    Also, as you mention, when a high downforce car is sideways the
downforce is gone. Even when one of these cars is a little out of shape,
say 10 deg, it has a loss in downforce and if the car was at or about
it's limits to begin with then this 10deg misalignment would be enough
to snap the car around.
Byron Forbe

GPL Opposite lock

by Byron Forbe » Sat, 18 Apr 1998 04:00:00


> Excellent post...
> and BTW, your english is better than a lot of native speakers of it I've seen
> here.

   Yeah, would never have guessed till he mentioned it. I think it was
just the icing on the cake of his showing off :)
John Walla

GPL Opposite lock

by John Walla » Sat, 18 Apr 1998 04:00:00


>     *** YOU, 18er, you stupid cunt!

I'm sure that will really affect Ronny - I bet he's cacking himself
with laughter right now over how worked up you are getting.

If you're gonna hurl abuse please keep it to e-mail? I expect this
will elicit another foul-mouthed tirade but I thought it was worth
politely requesting.

Thanks,
John

Peter Gag

GPL Opposite lock

by Peter Gag » Sun, 19 Apr 1998 04:00:00

Wow, that was some post, I'm *very* impressed. remind me never to
argue with you about aerodynamics? Thanks for the very informative,
and interesting post.

8?)


> There has been some discussion regarding the possibility of
maintain
> ing
> opposite steering lock through entire turns in GPL, and it has been
> sugested
> that this does not reflect the real driving behaviour of F1 cars of
> the
> 60`s.

> I will contribute with some facts and some opinions to this
discussi
> on.

> FACTS:

>  A stabilized, as opposed to transitory, counter steering attitude
o
> f a car
> through a corner is a situation where all the forces acting upon
the
>  car are
> perfectly balanced and matched. The situation ends when this
balance
>  is
> broken. These forces include the much forgotten inertial polar
torqu
> e, which
> is the inertia of an object when it is spinning around its vertical
> axis. In
> a car, this happens when it is spinning, or going through a turn,
an
> d it is
> the reason for many crashes at the exit of slow and medium corners
(
> like
> turn 8 in Watkins Glen). The forces are usually separated in 2
group
> s: those
> developed by the tires, thanks to their grip, and those acting upon
> the car
> as an inertial mass. The grip forces must exceed, or, at best,
balan
> ce the
> others if driver control is to be mantained.

> There are 3 possible cases:

> 1- Grip forces exceed all others: the car is under control, and the
> exceeding grip is used to accelerate, brake or turn, without tire
sl
> ip.

> 2- Grip forces balance all others, but can not exceed them: this is
> a
> transitional situation, between situations 1 and 3.

> 3- Grip forces are overcome by others: this is a non-control
situati
> on,
> where tire slip inevitably occurs. When it does so in a straight
lin
> e, the
> car is either spinning under acceleration, or locking the wheels
und
> er
> braking. If it happens in a turn, the car leaves its trajectory,
usu
> ally
> with its center of gravity following a straight line tangential to
t
> he
> trajectory at the moment of the grip loss. If that loss occurs at
th
> e front
> axle, the car car will not spin; if it occurs at the rear, it spins
> around
> its vertical inertial axis.

> The point here is that situation no 2 is a transitional situation,
b
> eing the
> point where tire grip reaches its limit. This transition can be
smoo
> th and
> progressive, as is the case with rally cars with gravel or snow
tire
> s and
> suspension, or it can be sudden and brutal, as is the case with
circ
> uit cars
> with modern racing tires and suspensions. This suddeness is further
> increased in cars with powerful aerodinamic aids, because their
effe
> ct
> disappears as soon as the car leaves a straight line relative to
the
>  wind.
> Generally, it can be said that cars with soft suspension settings,
w
> orking
> with low to medium tire grip (be it due to the surface or the
tires)
> , have
> smooth transitional regimes, resulting in a behaviour easy to
contro
> l at the
> limit, while cars with more rigid suspension settings, working with
> high
> tire grip, have sudden transitional regimes, making them very hard,
> or even
> impossible, to control if the limit is reached. In most modern race
> cars,
> this is further exacerbated by aerodinamic aids, whose effect
disapp
> ears
> once the car starts slipping sideways.

> Furthermore, it must be said that the way a car behaves at the
limit
>  (sudden
> or smooth) also depends greatly upon 2 factors: suspension
geometry,
> especially camber, (which, if it is negative and has a value over
1,
> 5-2
> degrees, can increase cornering ability, at the expense of
controlab
> ility at
> the limit, and therefore it is only used in race cars prepared for
t
> armac),
> and the rigidness of the tire carcass, which influences directly
the
>  angle
> of drift (tire carcass deformation under simultaneous vertical and
> horizontal loads causes the tire patch in contact with the ground
to
>  travel
> in a direction slightly different from the direction where the tire
> is
> pointing; this difference is called drift, and it occurs without
tir
> e slip,
> merely due to the deformation of the carcass)

> OPINIONS:

> In the 60`s, racing tire technology was much more crude than it is
t
> oday.
> The radial tire started life then, and it was, even in 1967, at a
ve
> ry early
> stage of development. Tires had much less grip than modern racing
ti
> res.
> Tarmac technology, often forgotten, was also far less developed,
and
>  the
> circuits then had far less grippier surfaces than even modern
roads,
>  let
> alone modern circuits. Finally, F1 cars had very distinct
characteri
> stics
> from today`s F1`s. The closest modern equivalent, chassis-wise, are
> modern
> Formula Ford and Formula V single-seaters, and even these have
moder
> n tires
> and surfaces to work with. But they do slide around, even with
highe
> r grip
> than old F1`s.

> What all this amounts to is this: F1 cars in 1967 had all the
> characteristics to be able to behave smootly at the limit, and
there
> fore to
> be driven at that limit, drifting around with one or both axles,
dep
> ending
> upon suspension settings and pilot`s preferences.Some of them did
it
> , but
> most didn`t very often because they could be faster with 4-wheel
dri
> ft
> techniques (which is also the fastest way with GPL; check the
1:06:9
> 6 replay
> at The Apex).

> All this is why I think that PAPYRUS have done an unbelievably good
> job in
> GPL; all adjectives are insufficient. I do not know, in the
strictes
> t
> scientific sense, if 1967 F1 cars behave EXACTLY like they do in
GPL
> , but I
> believe very firmly that they must have been very similar, and, if
t
> here was
> some difference, it just made the game better.

> Finally, a word on apples and oranges: GP2 and F1RS simulate modern
> F1 cars,
> with their huge modern tires, modern circuit surfaces, and
overwhelm
> ing
> aerodinamic loads; these cars do not slide around, and they are not
> supposed
> to. Therefore, their simulators must reflect this. GP2 and F1RS
are,
>  for
> different reasons, excellent simulators, but we can`t forget what
it
>  is that
> they simulate, and, especially, we cannot compare their driving
mode
> l with
> the one in GPL. We cannot compare apples with oranges.

> If anything, GPL`s model must have been, in my opinion, much harder
> to
> conceive than those for modern cars. Racing gamers should all be
ver
> y
> grateful to PAPYRUS.

> Finally, I want to apologise for any mistakes; I am Portuguese, and
> therefore writing in English is not without risk.

> PS.:Since I have the demo, I have played nothing else. My personal
b
> est is
> 1:08:24. Knowledge is not talent, but I`m still trying hard. By the
> way, I
> saw at The Apex that PAPYRUS announced that the Nordschleife is in
t
> he game!
> Like someone said: PAPYRUS RULES!

*Peter*  8-)
<

GPL Opposite lock

by < » Mon, 20 Apr 1998 04:00:00

-----Original Message-----

Newsgroups: rec.autos.simulators
Date: Sexta-feira, 17 de Abril de 1998 13:42
Subject: Re: GPL Opposite lock

>Good points here. The side walls of these tyres would probably have
>been weaker and the tyre profiles greater than the average race car
>today. It will be also interesting to see in the full version of GPL
>what the range of tyre pressures is and what pressures are optimum at
>the average circuit as compared to the 37psi (my opinion of course) of
>ICR2 for example.
>      Still, I don't really think you have hit the nail on the head as
>far as on limit control is concerned. As you mention, a very big
>difference between the cars of today and those portrayed in GPL is
>downforce. Therefore this makes weight transfer a much more significant
>factor in GPL than most other sims. And consequently this leads to a
>situation where if the tail is starting to come out on you that you can
>apply a little more throttle to load the rear end up more and you have
>instantly gone from an "on or over the limit" situation to being under
>control again.
Thank you for your comments. There is one aspect about which I`m not sure: I
have not found any information concerning the type of tire structure that
these
cars used to run. I believe it was already radials, but I`m not sure when
did
the switch from diagonal-plies occurred. This makes a huge difference to
this
issue, since radials have sidewalls that are 5 to 10 times more flexible
than
comparable diagonal-plies, while having much stiffer rolling bands (I`m not
sure
this is the right name: I`m referring to the part that touches the ground).
Therefore, the phenomenon I described in my earlier post as drift is much
increased with radials, compared to diagonal-plies, under the same loads and
tire pressures. Another important aspect is the height of the sidewall; the
greater it is, the bigger drift becomes, for the same sidewall rigidity. Old
F1
tires had much higher flanks than most modern road tires, let alone racing
ones,
which means that, even if the type, pressure and materials were identical,
they
would still get bigger drift angles.
Although I`m not sure, I believe that F1 cars in 1967 had bigger drift than
modern race cars, even if they had diagonal-ply tires, because of their very
high sidewalls. If they had radials, this is even more likely. Most
high-tech
tires nowadays use Kevlar strands or other similarly *** materials in
their
structure, which, in conjunction with their very low profile and, in some
cases,
high pressures, givs them very little drift compared to modern road tires,
and I
suppose the same is true when comparing them with 1967 racing tires.
If the bigger drift assumption is true, this would mean that the cars were
indeed easier to control at the limit, because big drift angles smoothen the
transition between below and above the limit. It would also mean that the
effect
on weight transfer by throttle control would be somewhat dampened (at least
as
far as very small corrections are concerned), because of the non-negligible
time
the tires take to develop the deformations that cause drift. Furthermore, we
have to consider how much of the available tire grip is already being used
for
cornering when such correction is made. Assuming this happens at or very
near
the limit, the increased throttle will probably have 3 effects:
1- Weight transfer towards the rear, because of acceleration
2- More grip at the rear, because of weight transfer
3- Weight transfer from the inner side of the corner to the outer side,
because
of increased speed caused by the acceleration.
However, all these effects are not instantaneous, because the loads, in
general,
and weight in particular, is fed to the tires through the suspension, which
has
internal friction, some inertial components and therfore a (very small)
reaction
time. That is one of the reasons why compression and rebound settings on
racing
dampers has to be adjusted separately for slow and fast movements.
Assuming all of this is true, then the effects of throttle-induced weight
transfer corrections would greatly depend on suspension settings. Since I do
not
know so many parameters, I can only speculate, and wish that all of these
parameters will be included in the final game.
Again, I apologise for any mistakes. I look forward to any further comments
on
this.

Daniel Fris


JulianDat

GPL Opposite lock

by JulianDat » Mon, 20 Apr 1998 04:00:00

Hmm.. Are you refering about "radials and 'bias-ply'" tires?? I recall that they
 used "bias-ply" tires.

Radials have a much "stiffer sidewall" construction vs the "softer sidewall" in
the Bias-ply tires.

Back then, they didn't use "low profile" tires, more like "bicyle tires" as I ca
ll them.; ) The "flimsy" sidewalls was one of the reasons for the lack of ahesion
 onto the racing surfaces. Just remember, suspension, tire compound and aerodynam
ic technologies weren't also up to par, as they are now at this point.

A "flexing bias-ply sidewall" is more in likely to "slide" across the racing sur
face. As the load on the tire increase, the center point of the theoretical conta
ct patch moves, thus limiting adhesion.

later

jd

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