rec.autos.simulators

by **Nick Fly** » Tue, 23 Jun 1998 04:00:00

On Fri, 19 Jun 1998 11:37:00 GMT, Christer Andersson

>Less area is a bad thing if you want to cool something. The worst scenario is a
>sphere, cause regarding a sphere you have the worst relation between volume and
>surface area. You have to little surface area per volume. In a narrow tyre
>compared to a wide tyre this relation isn't very different, it's actually a
>little bit worse for the narrower tyre, cause it's closer to the circle shape,
>when intersected. What I'm actually is saying is that regarding heat dissipation
>through the contact surface, it's about the same no matter how wide or narrow
>the tyre is. This is of course on a tyre that is the same in any other way, but
>wider or narrower.

I think you have this about exactly wrong. On a wider tire the
contact patch is thin and wide relative to the airflow, while with a
narrower tire the contact patch is more square and thus doesn't cool
as well in the middle of the patch.

- Nick

by **Christer Andersso** » Tue, 23 Jun 1998 04:00:00

Oh no, formulas, please no formulas :o). Lets wait with the formulas until we have to
calculate something and instead concentrate on how to understand this phenomena, okay :o)?

I interpreted drag as somehing dragging the car, thus vacuum. It's of course not vacuum, but a
lower air pressure than normal (if it gets to low, their will be rain).

At the front of a moving car there is something trying to push the car backwards - air
resistance. In front of the car there is of course air and to place the car where the air is,
we have to move the air, and as we all know air has mass, so this will need some force :o). I
guess we can do this in two way, either push the air in front of us (a flat front) or push it
aside (a front formed as some kind of projectile). I wont try to understand why pushing the
air is a bad idea, but we dont want a parachute effect, I guess. So we push the air aside;
over, under and to the sides of the car.

The amount of air pushed aside must be approximately the front area of the car (take a picture
of the car from the front, and any part of the picture covered by the car is the front area)
mulitplied with the length we have travelled. This mass of air being moved is of course moved
faster the faster we go. The faster we have to move the air the greater force needed to do so,
hence this force increase with speed. To calculate the force needed could be tricky, because
the air doesn't only get moved it also compresses and the compression increases with speed.

Now what we have created is locally higher pressure of air over, under and on the sides of the
moving car, so when the now locally lower pressure (what I earlier unpedagogically called
vacuum :o) ) of air behind the car gets in contact of this locally higher pressures, well,
what I'm trying to say is that I dont think the air needs a lot of force to get down behind
the car. Have you noticed how an F1 car narrows at the rear. The lower pressure sucking down
the air behind the car is of course also pulling on the car itself. To recap, this lower
pressure behind the moving car was because we travel away from the air behind the car, thus
behind the car there will be locally lower air pressure.

I dont think the lower pressure at the rear will help to suck the air from the front to the
rear. Think of it as you're standing by the side of a track looking at the air in front of you
over the track. An F1 car passes by. When it hits the air in front of you it will push that
air upwards, when the car is straight in front of you the air above it is compressed and
shortly after, because of being compressed and the lower pressure behind the car, pushed down
behind the car.

What's turbulence?

/Christer, now out of air :o)

> > > Okay, so lets talk about aerodynamic drag...o^)

> > I know, I know, I know, I mean have some guesses :o))). When a car moves it
> > leaves the air molecules that was behind it, so these molecules must be
> > replaced, because vacuum is not acceptable within our atmosphere :o). This start
> > of a vacuum behind the car will of course also pull on the car, thus drag. The
> > principle is the same as in your vacuum cleaner, Bruce, it's as we had someone
> > chasing us with a vacuum cleaner :o).

> > With a wing it gets more complicated. Because the wing has forced the air
> > upwards with speed it makes this air harder to suck in behind the car, hence the
> > vacuum gets a little larger with a wing, and even larger with more wing :o).

> > Now correct me :o).

> Sure will! :))

> This vacumn only occurs at high speeds and is more accurately termed "eddy" (or was
> that Eddie?) or turbulance. Race cars and there wings are designed to be as
> aerodynamically efficient as possible. They will enjoy perfect slipstreaming (shearing
> effects close to the surface only) until the speed of air passing around them can no
> longer act in a perfectly slipstreamed fashion and then eddies begin to form which is less
> efficient.

> From memory, this is what this all means mathematically.

> Drag increases linearly whilst in perfect slipstreaming conditions. ie Drag =
> Coefficient of drag (C) * Speed

> the Coefficient of drag (C) in this example is related to the slipperiness of the
> surface (special paints, etc) and for the entire car would be some type of average of the
> sum of all the bits of the car ie tyres, wings, driver's helmet, body, etc, etc.

> As different bits of the car enter into non slipstreamed behavior as speed increases,
> then from this point the drag increases as the square of the speed.

> ie delta Drag = C * (delta Speed) squared (Not completely sure)

> So to use the front wing as an example, lets say it has perfect slipstreaming till
> speed "Y" and that the speed of the car is Y + Z

> Drag = [C * Y] + [C * (Z squared)] (Not completely sure)

> I am rusty on this but you get the general idea.

> What a sim developer quickly realizes here is that trying to do this to complete
> accuracy is virtually impossible since it would involve modelling every single outer part
> of the car and all their different C's and slipstream thresholds. So what could be done is
> to just give the entire car an average "C" and slipstream threshold (my guess is this is
> where most sims stand for now with only linear/overall adjustments for different wing
> settings) or take it a step or 2 further and just model the most important bits. Perhaps
> model front wheels and susp boxs as 1 piece, same for rear wheels/susp boxs, front and
> rear wings, and, of course, the body/driver/helmet. I would think we should expect the
> body/susp/tyres/driver/etc and wings to be modelled independantly in modern sims. ie
> adjusting ride height at the front and rear would increase/decrease drag/downforce and
> changing wing angles would adjust the drag/downforce for them and these 3 things should be
> calculated independantly and their sum be the overall areodynamic model of the car. Maybe
> Mike Lescault could enlighten us on any plans in this area for Cart Racing 2 and how it
> was done in ICR2 :))

by **Christer Andersso** » Tue, 23 Jun 1998 04:00:00

If you would lay down on it while it's hot you'd stick to it and have great
trouble getting up again :o). Would probably have to wait until it has cooled
down.

/Christer, in favor of the larger than 1000 ms pings multiplayer proposal, with
collision detection on :o)

> Ha ha ha. Now you have me imagining what a tire 60 inches wide will do
> Christer.

> --

> mark
> "A lot of people think racing is about going fast. But it's not. It's about
> going just slow enough to stay on the track." F1RS -
> http://www.nmia.com/~chaser/car/results.htm
> Remove us here and there to mail me.

> :o). Bare with me will you, please. If we have a tyre
> with a contact patch of one square cm and it has 100 bonds, then the
> pressure on one
> bond will be 1/100 of the pressure, right? If we increase the
> contact patch to ten
> square cm, it will have 1000 bonds. The pressure per bond will now
> only be 1/1000 of
> the pressure, or 1/10 of what it was on the smaller tyre, but you
> say the traction
> added from a bond will not have decreased with 1/10, but with less
> than 1/10, on the
> bigger tyre... Why? Not why you say it, but what causes it :o)?

by **Christer Andersso** » Tue, 23 Jun 1998 04:00:00

I totally agree with everything you said, Pat, but would like to add that with a wider tyre you
can have a softer compound and it would still last as long as the harder narrower tyre.

/Christer Andersson
M.S. Computer Science and Engineering, so I just know the basic mechanical physics :o)

> I think that the "chemical bond" or "chemical adhesion" that keeps
> getting mentioned
> is simply the "stickiness" property of *** as it heats. While I'd
> agree that this
> force is much smaller than the total friction force, it is hardly
> negligible. It is
> the difference in lap times between your first lap after coming out of
> the pits, and
> your second or third lap. A few tenths of a second gained by heating
> the tires is
> very significant. I keep telling myself this as I wildly swerve during
> my warm-up
> lap :)

> > So, what does the one from the Tribology tribe say to this? And some accurate
> > percentages would be much appreciated if you could ie the percentage ratio of the friction
> > effect compared to this bonding stuff. (Come to think of it, how could one measure this?
> > Perhaps by testing tyres of the same compound but different widths at the same
> > speed/weight and calculating the difference in grip, etc, etc.....???????)

> I don't belong to any tribe, but going back to the original question
> from Simon - the
> bulk of the difference between grooved tires and slicks can be boiled
> down to the harder
> *** compound required for grooved tires (the harder compound being
> required
> due to heat build-up caused by less contact patch surface area and
> associated
> squirm/chunking). In a static situation, slick tires vs. grooved tires
> (using the
> same *** compound) should have no difference in the maximum friction
> force they can
> generate. That would correspond to the equation for friction force,
> which ignores
> surface area.

> Further, I think that in a static situation, wider tires vs. narrower
> tires
> have no difference in the maximum friction force they can generate. At
> high speeds
> (and high temp), however, the larger contact patch of the wider tires
> will provide
> more "stickiness" adhesion, and they will be slightly faster.

> --
> Pat Dotson
> B.S. Mechanical Engineering - Purdue University
> IMPACT Motorsports

by **Pat Dotso** » Tue, 23 Jun 1998 04:00:00

> I totally agree with everything you said, Pat, but would like to add that with a wider tyre you
> can have a softer compound and it would still last as long as the harder narrower tyre.

Yep, that's true, just as it's true in the slick
vs. grooved scenario. Unfortunately, there are so
many variables involved in this discussion that
something is bound to be left out. But, assuming
that for each style of tire, you select a compound
that will yield equal tire life, then the wider
tire will have a softer compound (and more grip).

The question is, will any of this help me tonight
in my first official OSCAR Freedom Cup race? :)

--
Pat Dotson
IMPACT Motorsports

by **Christer Andersso** » Tue, 23 Jun 1998 04:00:00

If you believe it will help you, it will do so :o). Anyway, good luck, Pat :o).

/Christer

> > I totally agree with everything you said, Pat, but would like to add that with a wider tyre you
> > can have a softer compound and it would still last as long as the harder narrower tyre.

> Yep, that's true, just as it's true in the slick
> vs. grooved scenario. Unfortunately, there are so
> many variables involved in this discussion that
> something is bound to be left out. But, assuming
> that for each style of tire, you select a compound
> that will yield equal tire life, then the wider
> tire will have a softer compound (and more grip).

> The question is, will any of this help me tonight
> in my first official OSCAR Freedom Cup race? :)

> --
> Pat Dotson
> IMPACT Motorsports

by **Matthew V. Jessic** » Tue, 23 Jun 1998 04:00:00

> Oh no, formulas, please no formulas :o). Lets wait with the formulas until we have to
> calculate something and instead concentrate on how to understand this phenomena, okay :o)?

I'd advise starting with basic formulas, actually.
You can do an awful lot of vehicle dynamics/performance
analysis with them. (This is only as deep as I go working
in dynamics and performance, and I have a MS in aerodynamics.
In order to go deeper, one hires a specialist in the field ;)

Really "knowing why" some shape drags or lifts
is complicated because you have to deal with the
"boundary layer" between the car surface and the
pretty-much-smoothly-flowing air. If you don't
include these complicated effects (or cheat by throwing
in a few experimental observations) you can't even
do a theory that predicts lift or drag. ("Inviscid Flow")

The air splits and flows around the vehicle. At the car
surface, the velocity of the air is equal to the velocity
of the surface - it's drug along with the vehicle. Even more
air is drug along not-quite-so near the surface to some extent,
just not fast enough to be as fast as the vehicle.
Speeding up all this air decelerates the car somewhat
(Newton's equal and opposite reactions, and all) - call
it friction drag.

The "static pressure" of the airflow
(what would be measured by a pressure port at the surface
and what creates the force that presses onto the surface)
drops as the air molecules flow faster. They have to
flow faster or slower to make changes in direction.
Going up the windshield the molecules slow and the
static pressure is higher. Going down the back of the car
they speed up and the pressure drops. When it drops
far enough, the air very near the surface actually is
forced back forward by the static pressure gradient
(rate of change). The boundary layer "Separates" and you
get a lot of air roiling around behind the car.
The pressure here is relatively low. So we have
high pressures near the front of the car, and lower pressures
at the back. Pressure times area is force,
so the summary is we have a net force aft. Call
it "Pressure Drag" or "Form Drag".

When you use Lift to get more downforce
what you are doing is forcing a lot of air upwards
to get that downforce. The average force to
change the direction of all that air slightly
upwards has a component aft as well - call it
"Induced Drag", for drag induced by lifting.

Finally, if you get near supersonic speeds,
you will add an important drag effect from shockwaves.
"Wave Drag".

Actually, if you don't include the effect of the complicated friction
forces you are doing "Inviscid Flow" above and your theory will
eventually
find the air will part around the vehicle, the pressure will be
different around different parts of the vehicle, but the overall net
effect of all those differing pressures is zero lift, and zero drag.

This is why I suggest starting with the basic equations useful for
vehicle dynamics. You have just made a justification for why
drag is commonly estimated as proportional to the area
and also proportional to the "dynamic pressure".
Density times velocity times velocity divided by 2 (just for fun.)
(Unless you get near sonic speeds, the air can be considered
"incompressible" (just like water) so the air really
doesn't compress noticibly.)

Hehe, I just glanced at "Fundamentals of Vehicle Dynamics,"
by Gillespie, S.A.E., Warrendale, PA, 1991, ISBN 1-56091-199-9
and find these are the FIRST and SECOND equations in 30 pages
on aerodynamics ;)

In practice, you use the equation:

drag = drag_coefficient times area times dynamic_pressure

for everything, including understanding that if you make the
car twice as big, and go twice as fast then you will need
six*** times the engine power portion alloted to fighting drag.

If you want to know why the car gets less drag with the
new wing airfoil in place of the old one
("what is the drag_coefficient")
you ask your aerodynamicist ;) (Or learn enough
aerodynamics to guess yourself)

See Gilespie's aerodynamics chapter ;)

- Matt

by **Todd Hecke** » Tue, 23 Jun 1998 04:00:00

My God, what have I created???? :^)

phenomena, okay :o)?
course not vacuum, but a
the car where the air is,
will need some force :o). I
(a flat front) or push it
understand why pushing the
we push the air aside;
of the car (take a picture
car is the front area)
moved is of course moved
greater force needed to do so,
could be tricky, because
increases with speed.
under and on the sides of the
unpedagogically called
higher pressures, well,
force to get down behind
lower pressure sucking down
To recap, this lower
air behind the car, thus
from the front to the
at the air in front of you
you it will push that
it is compressed and
behind the car, pushed down

>behind the car.

>What's turbulence?

>/Christer, now out of air :o)

>> > > Okay, so lets talk about aerodynamic drag...o^)

>> > I know, I know, I know, I mean have some guesses :o))). When a
car moves it
>> > leaves the air molecules that was behind it, so these molecules
must be
>> > replaced, because vacuum is not acceptable within our atmosphere
:o). This start
>> > of a vacuum behind the car will of course also pull on the car,
thus drag. The
>> > principle is the same as in your vacuum cleaner, Bruce, it's as
we had someone
>> > chasing us with a vacuum cleaner :o).

>> > With a wing it gets more complicated. Because the wing has forced
the air
>> > upwards with speed it makes this air harder to suck in behind the
car, hence the
>> > vacuum gets a little larger with a wing, and even larger with
more wing :o).

>> > Now correct me :o).

>> Sure will! :))

>> This vacumn only occurs at high speeds and is more accurately

termed "eddy" (or was
slipstreaming (shearing
begin to form which is less
conditions. ie Drag =
the slipperiness of the
type of average of the
behavior as speed increases,

- Show quoted text -

every single outer part
So what could be done is
(my guess is this is
important bits. Perhaps
wheels/susp boxs, front and
we should expect the
these 3 things should be
model of the car. Maybe

- Show quoted text -

by **Doug Millike** » Wed, 24 Jun 1998 04:00:00

> kids and during this lull I just happened to say "I was at the start of
> the footprint (of a rolling tire, not a sliding tire)and the *** is
> actually a complex brew of various polymers - long chain molecules".

> Well! Did that put the kybosh on the conversation!! Talk about being at
> a loss for words....the others just mumbled something inconsequential
> and meandered off!

Gee Bruce, sorry to hear that you work in such a boring place <grin>. We
often start the day with a comment like that, which leads into a long
conversation...it's a wonder that we ever got that book written.

Just in case you need a comment for tomorrow, here's a thought. The
polymers that are used to make race tire "***" are quite different from
those used in street tires. For example, don't try to use normal "racing
***" when it's cold - it has very little grip, much less than street
tires at the same temperature.

Remember the Indy 500 some years back when it was cold? On just about
every re-start it seemed that someone lost it getting on the power coming
out of turn 4, before their tires came up to temperature.

-- Doug

Milliken Research Associates Inc.

by **mark jeangerar** » Wed, 24 Jun 1998 04:00:00

Great! That was fun. Thanks Matt.

--

mark
"A lot of people think racing is about going fast. But it's not. It's about going just slow enough to stay on the track."

F1RS - http://www.nmia.com/~chaser/car/results.htm
Remove us here and there to mail me.

>
> Oh no, formulas, please no formulas :o). Lets wait with the formulas until we have to
> calculate something and instead concentrate on how to understand this phenomena, okay :o)?

I'd advise starting with basic formulas, actually.
You can do an awful lot of vehicle dynamics/performance
analysis with them. <clip>

by **mark jeangerar** » Wed, 24 Jun 1998 04:00:00

Wouldn't heat play the bigger part of the role? The compound that gets softer will have more surface area due to molding itself to the pavement. This appears to be true when going from an asphalt track to a concrete track on the same tires. Even with excessive sliding the concrete track offers much less grip than the rougher track does. The difference is astounding. If I use two different compounds on the same track in the same session it seems that the grip level of either compound is very close once they are heated. The harder compound only takes longer to get there.

Also, while rocks and lizards and such will stick to the heated tire, heated tire chunks don't really stick to much else.

--

mark
Please excuse my English. I am American.

F1RS - http://www.nmia.com/~chaser/car/results.htm
Remove us here and there to mail me.

> You're right, the molecules don't know what's goin on more than a couple
> microns away. Let me try to explain. If one square cm has 100 bonds, then
> ten sq cm will have 1000 bonds. Each individual bond adds to traction and
> the number of bonds is dependent on the surface area of the contact patch.
> So bigger tires have more bonds and therefor more traction. Got it?

The bonds must be between the tyre and the pavement, of course, and not within the
tyre as I thought. These bonds are not present when the tyre is cold, but when
heated the tyre surface change to be a more glue-like surface and actually stick to
the pavement as a kind of glue and increase the grip by quite a lot I would guess.
Is this added grip proportional to the pressure on the tyre, when varying the
pressure at the same temperature, or is it constant within reasonable sizes of car
and tyre? It feels as if it is constant. Even a very light car would stick very much
to the pavement, if we only could get the tyres hot enough. The effect of course
varies with tyre temperature. Is this what you were trying to explain, Jer?

/Christer, keep grasping more and more :o)

by **Grant Reev** » Wed, 24 Jun 1998 04:00:00

> There is a summary of the basics in our book, "Race Car Vehicle
> Dynamics", available through the online bookstore at www.sae.org

ah, now there's a book i would die to get my hands on :) i'm kinda
into the physics of race cars myself and it had been recommended
to me by certain leading sim developers, but i had gone and forgotten
what the name of the book was. But when i just went and looked up
your book the price scared me half to death! i think i'll wait until
i get a good fulltime job before i can afford to buy that:)

looking forward to getting it someday!
Grant Reeve.

by **Bruce Kennewel** » Wed, 24 Jun 1998 04:00:00

Yep, remember it well, Doug.

Incidentally......just out of curiosity, is your organisation free of
buffalos or do you provide buffalos with net access at no cost?

Just curious.

--
Regards,
Bruce.
----------
The GP Legends Historic Motor Racing Club is located at:-
http://www.netspeed.com.au/brucek/legends/

by **Christer Andersso** » Wed, 24 Jun 1998 04:00:00

A monster, of course, and you should be proud of it :o))).

/Christer, not afraid to confuse :o)

> My God, what have I created???? :^)

> >Oh no, formulas, please no formulas :o). Lets wait with the formulas
> until we have to
> >calculate something and instead concentrate on how to understand this
> phenomena, okay :o)?

> >I interpreted drag as somehing dragging the car, thus vacuum. It's of
> course not vacuum, but a
> >lower air pressure than normal (if it gets to low, their will be
> rain).

> >At the front of a moving car there is something trying to push the
> car backwards - air
> >resistance. In front of the car there is of course air and to place
> the car where the air is,
> >we have to move the air, and as we all know air has mass, so this
> will need some force :o). I
> >guess we can do this in two way, either push the air in front of us
> (a flat front) or push it
> >aside (a front formed as some kind of projectile). I wont try to
> understand why pushing the
> >air is a bad idea, but we dont want a parachute effect, I guess. So
> we push the air aside;
> >over, under and to the sides of the car.

> >The amount of air pushed aside must be approximately the front area
> of the car (take a picture
> >of the car from the front, and any part of the picture covered by the
> car is the front area)
> >mulitplied with the length we have travelled. This mass of air being
> moved is of course moved
> >faster the faster we go. The faster we have to move the air the
> greater force needed to do so,
> >hence this force increase with speed. To calculate the force needed
> could be tricky, because
> >the air doesn't only get moved it also compresses and the compression
> increases with speed.

> >Now what we have created is locally higher pressure of air over,
> under and on the sides of the
> >moving car, so when the now locally lower pressure (what I earlier
> unpedagogically called
> >vacuum :o) ) of air behind the car gets in contact of this locally
> higher pressures, well,
> >what I'm trying to say is that I dont think the air needs a lot of
> force to get down behind
> >the car. Have you noticed how an F1 car narrows at the rear. The
> lower pressure sucking down
> >the air behind the car is of course also pulling on the car itself.
> To recap, this lower
> >pressure behind the moving car was because we travel away from the
> air behind the car, thus
> >behind the car there will be locally lower air pressure.

> >I dont think the lower pressure at the rear will help to suck the air
> from the front to the
> >rear. Think of it as you're standing by the side of a track looking
> at the air in front of you
> >over the track. An F1 car passes by. When it hits the air in front of
> you it will push that
> >air upwards, when the car is straight in front of you the air above
> it is compressed and
> >shortly after, because of being compressed and the lower pressure
> behind the car, pushed down
> >behind the car.

> >What's turbulence?

> >/Christer, now out of air :o)

> >> > > Okay, so lets talk about aerodynamic drag...o^)

> >> > I know, I know, I know, I mean have some guesses :o))). When a
> car moves it
> >> > leaves the air molecules that was behind it, so these molecules
> must be
> >> > replaced, because vacuum is not acceptable within our atmosphere
> :o). This start
> >> > of a vacuum behind the car will of course also pull on the car,
> thus drag. The
> >> > principle is the same as in your vacuum cleaner, Bruce, it's as
> we had someone
> >> > chasing us with a vacuum cleaner :o).

> >> > With a wing it gets more complicated. Because the wing has forced
> the air
> >> > upwards with speed it makes this air harder to suck in behind the
> car, hence the
> >> > vacuum gets a little larger with a wing, and even larger with
> more wing :o).

> >> > Now correct me :o).

> >> Sure will! :))

> >> This vacumn only occurs at high speeds and is more accurately
> termed "eddy" (or was
> >> that Eddie?) or turbulance. Race cars and there wings are designed
> to be as
> >> aerodynamically efficient as possible. They will enjoy perfect
> slipstreaming (shearing
> >> effects close to the surface only) until the speed of air passing
> around them can no
> >> longer act in a perfectly slipstreamed fashion and then eddies
> begin to form which is less
> >> efficient.

> >> From memory, this is what this all means mathematically.

> >> Drag increases linearly whilst in perfect slipstreaming
> conditions. ie Drag =
> >> Coefficient of drag (C) * Speed

> >> the Coefficient of drag (C) in this example is related to
> the slipperiness of the
> >> surface (special paints, etc) and for the entire car would be some
> type of average of the
> >> sum of all the bits of the car ie tyres, wings, driver's helmet,
> body, etc, etc.

> >> As different bits of the car enter into non slipstreamed
> behavior as speed increases,
> >> then from this point the drag increases as the square of the speed.

> >> ie delta Drag = C * (delta Speed) squared (Not
> completely sure)

> >> So to use the front wing as an example, lets say it has perfect
> slipstreaming till
> >> speed "Y" and that the speed of the car is Y + Z

> >> Drag = [C * Y] + [C * (Z squared)] (Not completely sure)

> >> I am rusty on this but you get the general idea.

> >> What a sim developer quickly realizes here is that trying to do
> this to complete
> >> accuracy is virtually impossible since it would involve modelling
> every single outer part
> >> of the car and all their different C's and slipstream thresholds.
> So what could be done is
> >> to just give the entire car an average "C" and slipstream threshold
> (my guess is this is
> >> where most sims stand for now with only linear/overall adjustments
> for different wing
> >> settings) or take it a step or 2 further and just model the most
> important bits. Perhaps
> >> model front wheels and susp boxs as 1 piece, same for rear
> wheels/susp boxs, front and
> >> rear wings, and, of course, the body/driver/helmet. I would think
> we should expect the
> >> body/susp/tyres/driver/etc and wings to be modelled independantly
> in modern sims. ie
> >> adjusting ride height at the front and rear would increase/decrease
> drag/downforce and
> >> changing wing angles would adjust the drag/downforce for them and
> these 3 things should be
> >> calculated independantly and their sum be the overall areodynamic
> model of the car. Maybe
> >> Mike Lescault could enlighten us on any plans in this area for Cart
> Racing 2 and how it
> >> was done in ICR2 :))

by **Christer Andersso** » Wed, 24 Jun 1998 04:00:00

> I'd advise starting with basic formulas, actually.

You must understand that most of us dont even understand the basic formulas, imaging what damage we
could do if we started to use them without understanding them :o).

Okay, friction drag :o).

Okay, pressure drag :o). I've just did some calculations on an F1 car at around 200 kph and got this
force, caused by the pressure drag, to around 3 kN. Am I way off here??? I at least hope it's closer
to 3 kN than 0.3 kN or 30 kN. According to my simple and very approximative calculations it seems as
this pressure drag is proportional to the speed squared, so if the speed doubles the force
quadruples.

Okay, induced drag :o).

What do you mean zero drag? No pressure drag at all? In my simple world the air in front of the car
has to be moved for the car to pass and that must take a force?

Dont we have to understand them first :o)?

Sounds as if I'm not way off on the pressure drag?

Isn't that cheating :o)?/Christer, really enjoys this NG at times like this :o)

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