Pork Pie:
I'd like to try to respond to your comments individually.
> You said...
> The traction control creates a negative effect against to go straight, this
>has
> something to do, with this, how the traction control works.
You seem to be talking about cars that have limited-slip differentials--
or
at least differentials. Most of our LSR cars have no differentials-- both drive
wheels turn at the same speed, all the time.
>
> The traction control needs a exactly base parameter - on salt, no chance -
>that
> the system can calculate from the feedback, which he get from the wheels -
>means
> grip or no grip - the right correction.
> This works on a smooth surface and with a constant contact area from the tire
>to
> the ground.
I have considered this problem-- but we typically address such data "noise"
by
using trailing averages of the sensed parameters.
> Also it's necessary that the contact area between surface and tire got a
>minimum
> of size.
> The salt is to rough, the salt stucks on the tire during the run - no constant
> contact area.
Again, it sounds like you are talking about problems that can occur due to
drive wheels turning at different speeds. For most LSR cars, can't happen.
>
you said...
> Also, to go fast, the tire needs to be very small.
I can't relate to this statement at all, unless you are talking about open
wheels. Most of our really high-horsepower teams seem to want the biggest drive
tires they can get. I would. Maybe (from your statement below) you just mean
you
think the tires need to be narrow? I think many would agree with that
(including
me).
> you continued...
> Tom Burkland said it the right way - running on salt is like running on snow.
>
> A wide tire runs on salt like on ice.
>
> At last, the speed himself.
>
> The traction control helps to eliminate slipping wheels during acceleration,
>but
> we are not on the quarter mile. we like to go fast.
>
a simple TC can minimize drive tire slip at steady speed, too. LSR cars get
tire spin at steady speed when the aero resistance plus the rolling resistance
equal
(and begin to exceed) the friction force of the drive tires. This can occur
due to
a little "dip" in the salt (typically, at the salt expansion cracks) momentarily
reducing tire grip. Concievably, it would occur for the most powerful / least
aero
cars even on a perfectly smooth salt surface.
> You said...
> The traction control can work in two ways.
>
> The easiest way. Over the brakes. That means, the traction control managment
> manipulate the grip/no grip, that he brakes this wheel which lost the grip.
> This works only by low speed - up to 100 mph. If you do this on high speed, it
> can happens, that in the moment when the brake got the "signal" to "stop" the
> wheel, this wheel needs not anymore the correction. The result, you will get
>on
> one side full grip, on the other you are losing the complete grip.
> Which roadster drive got not this expierence on the salt, when he got a
> left/right side different grip and the car tries to spin.....welcome to the
>club
> of the stiff neck.
>
Certainly I agree with this! I would not personally consider using the
brakes to limit wheelspin on a LSR car (but I would not support a rule that said
that nobody else would be allowed to try a brake-based TC. Hot rods =
Freedom.).
> You said...
> The other way, is over the motor managment.
> A high complex computerprogram controls the motor managment, which sends a
> signal to the ignition system, this reduced, with a correction, the
> torque/power.
> This sounds very simple, but is in reality a extremely complex control system.
> Also this system got his problem by high speed.
We already have this on many of our engines-- we just aren't using it
with TC
(see Dave Dahlgren's response to this thread).
> You continued...
> Now someone will say - by the formula 1 it works.
> Yes and no.
> It works, due to a very smooth surface and a extrem downforce. In other words
>-
> what they called no grip, is for us sticking on salt. The range is on a
>totally
> other level.
> >From the outside it looks, like the car goes perfect straight or around the
>
> corner. The reality is, that this system supports only the driver, and the car
> still tries to go sideways. It's only the skill and reaction/correction of the
> driver, which keeps the car straight.
> And if the system loose for one second the control, the car will go sideways
>out
> of balance and will crash.
>
> On the salt, with the small tires, with less downforce and each second,
>changing
> contact/grip conditions, the traction control system will have no chance to
>make
> the right correction to the right time.
We do not typically have significant side loads, like the F1 cars. If
you
are seeing .2g on an LSR car, you probably are having a problem with your
measurement equipment (or you are already crashing!)-- right Dave? Seems like I
remember that modern F1 cars have to deal with 4 or 5 gs in the corners-- No?
And
(again), we do not have differentials.
I would give this idea more relavence with respect to a closed-course LSR car.
I
think it has no bearing for us, since we always try to go in a straight line.
>
> It's hard enough for the driver, to get this feedback, he needs to keep the
>car
> straight. A traction control which "jumps" around, makes it only more worst.
Our TCs do not need to respond to as many different things as a road
racer.
We are going straight, and the wheelspin probably varies in a fairly regular
sinusoid (due to the fact that the expansion cracks in the salt are (in any
given
year) fairly regularly spaced. Even if they weren't, the same cure would
apply--
basing corrections on a "trailing average" of the wheelspeeds. The program can
include an algorithm to make "progressive" correction, thereby damping the
response. No need for a system that "jumps" around.
>
> You said...
>
> There are two big enemies for high speed - this is
> - not enough grip
> - (too much) downforce
>
> It's all the time a compromise between downforce and enough grip.
>
> Normally the perfects status is
> - if you call standing with the whole weight on the ground as 0%
> - and lift off from the ground as 100%
> - you has to be by 99.5%
>
> ??????????
>
> Sound strange, oh, sure.
>
> To explain. You can't reduce the resistance of the car body when you drive.
>
> This is a fix number, depense to the type of car you run, a roadster got a
> higher drag as a streamliner.
>
> But you can reduce the resistance of the tire to the ground.
>
> So less this resistance is, so faster you can go.
>
> The problem is, if you reduce this resistance, you are also loosing the grip.
>
> So you have to know how much downforce (means resistance from the wheels to
>the
> ground) and how much grip you need.
>
> The best way is, to create the downforce only with the body shape. Any kind of
> wings, carnards means - to create a air brake - and this costs speed.
> With a special kind of high speed air flows (very small wings) you will get a
> resistance (like a air brake) but with the added downforce, you also get more
> speed. It needs a lot of aerodynamic expierence to find a solution that you
>get
> at last a plus on speed.
Most of the fastest LSR cars seem to depend more on ballast than on aero
downforce. Lately I have come over to this idea (although it sounds archaic).
The
biggest factor in causing the tires of our high speed machines to spin at steady
speeds is aerodynamic resistance-- that is, the resistance of the car to going
forward (most of which is aero-- only a small fraction is tires, at 300+mph)
becomes
greater than the friction force of the drive tires. You cannot add ANY aero
downforce without increasding aero resistance, as well (whether you use the
body, or
a wing). In effect, in aerodynamics "there is no free lunch." Since aero
resistance is our biggest enemy, aero downforce can't be our best friend.
Weight, of course, hurts the accelleration. But if it is used cleverly,
that
is all it hurts; it doesn't slow the top speed. And we usually have a lot of
room
to accellerate these days (thanks to "Save the Salt").
>
> You said...
> So the question for traction, is not a question for a traction control - it's
>a
> question of the compromise of downforce and resistance.
> If you got enough power you can increase the downforce, which will eliminate
>the
> traction/grip problem.
If you do this, I think you will soon get into the realm that Tom Bryant
theorized was the cause of Earl Wooden's tire failure: you simply overload the
tires-- too much downforce + torque (see Tom Bryant's response to this thread).
I
think the first thing to do is to minimize the resistance so you don't need to
ask
the tires for so much (the True/Costella car that you worked on appears to be a
good
example of this idea).
> Thanks for your response; you are new to the list, but appear to be one who
> consistently has something intelligent to say.
Russ Mack
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