rec.autos.simulators

You've been playing Stunts too often :)
Seriously, I always thought it would be a neat trick, but I don't think there
are many drivers who would want to risk a ride on their skulls if they screwed
up.
--

Stephen Ferguson

"There's a madness to my method"

I just couldn't resist throwing in my $0.02 on this thread.

        The original poster of the physics info (who did a very admirable
job) didn't seem to consider the downforce produced by an F1 car's
diffuser.  When this is added to the downforce produced by the wings, the
aggregate downforce can be measured around an aerodynamic ceneter of
pressure.  This can be thought of as the center of gravity for the
aerodynamic loads on the car.  *Speculation ON* When all is said and done,
the teams try to get the center of pressure to coincide with the center of
gravity so as to produce the most neutral handling car as possible.
*Speculation off*  One important thing to remember is that the center of
pressure moves with speed.  To what extent, I'm not sure.  But it *ALWAYS*
moves rearward.  If it didn't, the car would be completely unsafe as it
would produce increasing amounts of oversteer as speed increased.  So more
downforce at the rear isn't always a bad thing.  I think the original
poster of the physics info knew this, but refrained from it for
simplicity's sake.
        The only other thing I want to throw in for a bit of clarification
is that increased vertical load on a tire (downforce in F1) does not
"require" better brakes.  It just makes the tire capable of
handling braking accelerations of a greater magnitude.  Therefore most
automotive applications employ more braking power in these areas whenever
this advantage can be gained.

Later Folks,
--
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Bill Mette         | "People are personally responsible for keeping themselves

******************************************************************************

I believe that you can accelerate a stationary car by moving a passenger
from the back to the front if there is enough friction between the
passenger's bum and the car seat 8).

This is just an opinion.

Heru.
--
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#  Heru A Hariati                # Psychoanalysis makes quite simple      #

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

One thing that causes also the weight transfer is surely the
rotation. The simplest example is a chopper where the body
of the plane tends to rotate in the opposite direction than
the rotor. In a car, even when the centre of the mass is
in the same or lower level than the axles, the rotation
generates weight transfer. So, when accelerating an RW car,
the body of the car tends to rotate in the opposite direction
compared to the rear wheels and the front of the car gets lighter.
When braking the effect is:

    Front wheels:
        Body tends to rotate around the front axle, lifting the rear.
    Rear wheels:
        Body tends to rotate around the rear axle, pressing the front down.

So, weight is transferred to the front of the vehicle.
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: One thing that causes also the weight transfer is surely the
: rotation. The simplest example is a chopper where the body
: of the plane tends to rotate in the opposite direction than
: the rotor. In a car, even when the centre of the mass is
: in the same or lower level than the axles, the rotation
: generates weight transfer. So, when accelerating an RW car,
: the body of the car tends to rotate in the opposite direction
: compared to the rear wheels and the front of the car gets lighter.

Motorcycles provide a good example of this. When given a good shot of
the throttle, the torque from the engine will cause the front end to
lift. And keeping the acceleration high enough, the front end can stay
in the air for quite a long time. Interesting point too. I wonder how
big a part it plays in determining the weights over the front and back
of an F1 car at low speed. With 750-800hp it probably factors in there
quite a bit.

RQ
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: One important thing to remember is that the center of
: pressure moves with speed.  To what extent, I'm not sure.  But it *ALWAYS*
: moves rearward.  If it didn't, the car would be completely unsafe as it
: would produce increasing amounts of oversteer as speed increased.

Does it move? Perhaps I'm oversimplifying things here, but doesn't the
downforce of each wing (and the diffuser) depend on the velocity of
the wind over their surfaces? So, at first glance, it would seem that
the ratio of downforces produced by these elements(the wings,body and
diffuser) would remain relatively constant with speed. But maybe one
element becomes effective at a later time (higher speed) than the
others. I'm not sure. But to me it would seem that above a certain
speed (where aerodynamics start playing the major role), the center of
pressure would remain in the same position. This would be good,
because the overall balance of the car would stay the same whether you
were driving 100 or 180. This to me would be safer because the driver
could better predict how his car is going to handle in a given
situation.

:       The only other thing I want to throw in for a bit of clarification
: is that increased vertical load on a tire (downforce in F1) does not
: "require" better brakes.  It just makes the tire capable of
: handling braking accelerations of a greater magnitude.  Therefore most
: automotive applications employ more braking power in these areas whenever
: this advantage can be gained.

In racing applications, I would think that the object would be to
*not* have one end of the car lock before the other, so thats why I
put it into terms of what relative brake power is required to lock all
the tires simultaneously. By this I was meaning that at this magic
bias, (when you would have all 4 lock at a given speed), you would
effectively have all 4 tires contributing the same amount to overall
deceleration. This would seem to me to be the most stable and fastest
way to brake. But I think the ideal bias changes for every different
situation so the "ideal" setting is at best a compromise.

Also, I remember reading something from Mark Blundell last season,
where he said that the wings on his Ligier were flexing a little more
than they were supposed to at speed. So maybe theres even another
factor coming into play here. It sounds like the wings are designed to
flex a certain amount at high speed so that while their downforce
decreases a certain amount, so does their drag, leaving a higher top
speed. Then when the car slows, the wings return to their more upright
shape and provide more drag but higher downforce. So to some degree,
you have "active" aerodynamics but with the wind doing the work
instead of electronics..This would lead to a
shifting of the center of pressure, but I wonder how big the effect
is. And there must be some force wasted on bending the wings down, but
maybe it is small relative to the gains they make in top speed. There
are probably hundreds of things that these F1 engineers take into
account that we can't even pronounce! :-)

Later,

RQ
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: PS - Does anyone object to holding this conv. here?  It should probably be in
:      rec.autos.sport.

Actually, there is a more appropriate newsgroup: rec.autos.tech, where
it probably should be taken.

Later,

RQ

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: According to Carroll Smith's "Tune to Win" and a few articles from Racecar
: Engineering,

SOunds like some interesting reading. I will look for the book. How
old is it? And is Racecar Engineering a magazine? If so, where did you
get it? (Not at the local newstand I assume.)

: Re: Mark Blundell's statements about wing flex.

I'll try and dig up the article this weekend and re-read it to see
what he says..

Later,

RQ

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PS - Does anyone object to holding this conv. here?  It should probably be in
     rec.autos.sport.

--
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Bill Mette         | "People are personally responsible for keeping themselves

******************************************************************************

This just sounds a little too dangerous for my tastes (i.e. Ratzenberger's
crash).  If the flex *was* intended then the Ligier designers are
psychotic.  I'm reading through the ASM's book on composites and almost
none of them are designed to knowingly flex in a structural application.  Zero
flex is obviously not possible.  This is why I think the intent of Mark's
statement was that he was bothered by the fact that his wings were flexing
at all.  Not that they were flexing too much.

        You got that right! ;-)

--
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Bill Mette         | "People are personally responsible for keeping themselves

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A few pointers- The F=u X N equation is not entirely correct. Since the
tyres adhere to the track mechanically as well as chemically, you will
get a constant friction factor, regardless of load (ie, normal force)
or static/ dynamic friction.

Since we're talking vectors here....

OK, a nitpick- velocity is a vector, speed is a scalar. Had to get that
in there. Anyway, the forces experienced by the car, (geez, it's been
years since I took dynamics!) are, as explained before, horizontal and
normal, or into/out of the track. Friction is horizontal, and as usual,
opposes motion. Since the speed (not velocity ;) of the tyre is ZERO at
the point of contact (else it spins and smokes!) static friction AND
chemical adhesion comprise the force that pushes into the track, and
the track responds by puching the car down the road. Confused? Me, too!

As far as brake balance goes....this has little to do with the downforce.
The reason brakes are traditionally adjusted forward is simple- since the
car leans forward (front dives) there is more weight transmitted to the
front. This occurs in winged cars like a Williams, or my Saturn, or cars
that people foolishly spend money on to fund the Japanese Wehrmacht.
Ask anybody who locked up the front on a bike, or flew off a motorcycle.
The front dives. OK, so you want the fronts to lock first, since by
locking first, they can stop faster, provided more weight is applied.
The idea in perfect braking is to 'scrub' the front- lock impending,
but SLOWLY turning to scrub the *** off at an even rate. Meanwhile,
the backs also brake, but since the normal force is less (it's all in
front) they merely turn slowly, not scrubbing.

In rain, the situation is reversed- water is probably one of ***'s
best lubricants....since the chemical adhesion is minimized in the wet,
the probability of lockup is much higher, and this kills the steering.
So in rain, it's better to have the rears lock first- at least, this way
the thing will steer.

SUMMARY (Finally!!)- Set brake balance forward in the dry.
                     Set brake balance backward in the wet.
                     Don't sleep as much as I did in Statics/Dynamics
                     Watch Sunday's GP of Monte Carlo at 9:20 AM
                     (EST) on ESPN. Then tape the BBC feed.

Anybody got any questions? Hope I'm not sounding arrogant :)
Post or e-mail. Later!
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| can give me more satisfaction. I don't feel happy if I am    +---------------+
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+------------------------------------------------------------------------------+

[ stuff deleted ... ]

|> As far as brake balance goes....this has little to do with the downforce.
|> The reason brakes are traditionally adjusted forward is simple- since the
|> car leans forward (front dives) there is more weight transmitted to the
|> front. This occurs in winged cars like a Williams, or my Saturn, or cars
|> that people foolishly spend money on to fund the Japanese Wehrmacht.
|> Ask anybody who locked up the front on a bike, or flew off a motorcycle.
|> The front dives. OK, so you want the fronts to lock first, since by
|> locking first, they can stop faster, provided more weight is applied.
|> The idea in perfect braking is to 'scrub' the front- lock impending,
|> but SLOWLY turning to scrub the *** off at an even rate. Meanwhile,
|> the backs also brake, but since the normal force is less (it's all in
|> front) they merely turn slowly, not scrubbing.
|>
|> In rain, the situation is reversed- water is probably one of ***'s
|> best lubricants....since the chemical adhesion is minimized in the wet,
|> the probability of lockup is much higher, and this kills the steering.
|> So in rain, it's better to have the rears lock first- at least, this way
|> the thing will steer.

Nope.

I'm going to jump in to this.  And I'm probably not even going to use the
correct technical terms. :-)  In a race car you always want the fronts to
lock first (some racers will disagree but this is a good rule).  When the
fronts lock first you at least go in a straight line.  When the backs lock
first they also lose sideways traction so the backend comes around :-(.
The brake balance is adjusted based on how much weight is being transferred
to the front wheels.  The more weight transferred to the front wheels the
more force you can apply to the brakes without locking them.  More weight
is transferred to the fronts on dry pavement because there is more grip.
MUCH less weight is transferred to the fronts in the wet because there is
less grip.

|> SUMMARY (Finally!!)- Set brake balance forward in the dry.
|>                      Set brake balance backward in the wet.

Yes.

|>                      Don't sleep as much as I did in Statics/Dynamics

:-)

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87 VW GTI 16V         85 VW Golf (race car) #32 - Conference Production H

I disagree. This group is about simulation as well as simulators.
I, for one, find the topic interesting as it tells me something about
what I might expect of realistic simulators.

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: I disagree. This group is about simulation as well as simulators.
: I, for one, find the topic interesting as it tells me something about
: what I might expect of realistic simulators.

Good point. But there is also a lot of knowledgeable people over there
who would probably be quite good at shedding more light on the
subject. That is the only reason I suggested that group. By all means
continue it here, either way I find it very interesting.

Later,

RQ
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