rec.autos.simulators

by **Eldre** » Wed, 12 Dec 2001 06:12:32

>>First - on many of the turns, the driver gets the car into a certain
>>'attitude', and it stays at that attitude until corner exit. How do you do
>>that? When I take a turn, the car sort of 'oscillates' in the turn.

>Eldred, having read all the other posts they all made good sense. What
>worked for me though was to get the spring rates matched with the
>weight balance of the car, as discussed by Ricardo Nunnini on his
>website. The Lotus has 38% of the weight on the front wheels, 62% on
>the rear. You set the car up with 38% total spring rate on the front,
>62% on the rear. for example, 55 on the front, 90 on the rear gives
>pretty much the right ratio.

>If I ever drive GPL without the right spring rates for the car, I find
>it oscillates all over the place. When they are set as above, it sits
>into the corner nicely and feels nice and fast.

>That said, it will still oscillate slightly, just it's much easier to
>balance and more manageable. Having read Maxx's post (eventually!),
>I'll try that to see how I go. Good luck!

I ran some league practice at Zandy, and a race at Spa yesterday. I was
conscious of the throttle during the turns. My turns were a lot more steady.
Wasn't any faster, but steady...<g>

Eldred
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by **Haqsa** » Wed, 12 Dec 2001 08:38:46

> Aren't you effectively "adjusting" the rear brake bias by using the
> throttle? You set a rear bias in the chassis setup, then reduce the
> amount of rear braking effort in a race by progressively applying
> throttle under braking, in effect moving the brake bias forward.
Quite a
> balancing act, but it makes sense to me (I couldn't do it myself
though!)

I think this is true. Looked at another way, if you don't modulate the
throttle during braking, your downshifting pattern in combination with
engine braking is changing the brake bias for you, whether you like it
or not. So it behooves you to stay on the throttle a little to prevent
that.

by **Will DeRiver** » Wed, 12 Dec 2001 09:30:40

Thank you! That will prove useful! =)
--
- Will DeRivera
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- http://www.numic.net
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by **Will DeRiver** » Wed, 12 Dec 2001 09:37:43

Holy cow! Go Maxx!

/me saves post

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- Will DeRivera
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- http://www.numic.net
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by **Eldre** » Wed, 12 Dec 2001 14:32:53

><snipped>

>Holy cow! Go Maxx!

>/me saves post

Yep, there are some VERY talented people here...<g> I saved *and* printed
Maxx's suggestions...

Eldred
--
Dale Earnhardt, Sr. R.I.P. 1951-2001
Homepage - http://www.umich.edu/~epickett
GPLRank - under construction...

Never argue with an idiot. He brings you down to his level, then beats you
with experience...
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by **Rick Boy** » Wed, 12 Dec 2001 21:29:21

Applying some throttle while braking is so counter-intuitive that it sounds
more difficult than it actually is. My guess is that you would have less
trouble learning this than you had with left foot braking. I found Barty
Mee's replays to be very illustrative and helpful.

Rick

by **Jonny Hodgso** » Wed, 12 Dec 2001 21:49:08

> Eldred, having read all the other posts they all made good sense. What
> worked for me though was to get the spring rates matched with the
> weight balance of the car, as discussed by Ricardo Nunnini on his
> website. The Lotus has 38% of the weight on the front wheels, 62% on
> the rear. You set the car up with 38% total spring rate on the front,
> 62% on the rear. for example, 55 on the front, 90 on the rear gives
> pretty much the right ratio.

Agreed, although I like to have the front *slightly*
too stiff - it helps to keep the front up during
braking and jumps. I then bring the balance back
with the 'bars.

Jonny

by **Jonny Hodgso** » Wed, 12 Dec 2001 21:47:23

> Okay I admit it has been a long time since I took control theory, and I
> believe I slept through most of it anyway, but I still have to question
> this. How can you define something that is oscillatory as stable?
> Doesn't the fact that it is oscillating mean that it can't reach or
> maintain an equilibrium point?

The oscillation is a sign that there's some sort of
effect trying to return it to centre, and is determined
by the imaginary value of the poles.

It can be stable or unstable (increasing or decreasing
amplitude) depending on the real value - positive is
unstable.

Oversteer is unstable and non-oscillatory - the car's
yaw angle starts to deviate from zero, and continues
to deviate :-) (in the absence of driver correction.)

Jonny

by **Eldre** » Thu, 13 Dec 2001 04:38:36

>Applying some throttle while braking is so counter-intuitive that it sounds
>more difficult than it actually is. My guess is that you would have less
>trouble learning this than you had with left foot braking. I found Barty
>Mee's replays to be very illustrative and helpful.

Where would I find those replays?

Eldred
--
Dale Earnhardt, Sr. R.I.P. 1951-2001
Homepage - http://www.umich.edu/~epickett
GPLRank - under construction...

Never argue with an idiot. He brings you down to his level, then beats you
with experience...
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by **Eldre** » Thu, 13 Dec 2001 04:38:37

>Perfect sense and is exactly the point I was making. You ARE braking
>just as well as them, just that you enter the corner slower, hence
>need to brake earlier.

>It means you don't have to worry about improving your braking
>technique, JUST get used to entering corners quicker :-)

That actually makes me feel a bit more confidend about it. If I can figure out
how to carry the same speeds theough the corner, I should be able to brake at
the same spots... I'm thinking the speeds are more a result of the line than I
thought. Back to the drawing board...<g>
Cool, thanks!

Eldred
--
Dale Earnhardt, Sr. R.I.P. 1951-2001
Homepage - http://www.umich.edu/~epickett
GPLRank - under construction...

Never argue with an idiot. He brings you down to his level, then beats you
with experience...
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by **Eldre** » Thu, 13 Dec 2001 04:38:37

>I noticed the same thing with mine. And I really do think it's a matter of
>"trusting" the car, it just doesn't seem like you're going to make the
>corner at speed X so you continue to slow to X-10 or something to be sure
>you're going to get through okay.

Based on the discussions, My theory is this: I try to brake at the same place
as the others. Because I release the brakes before I turn, the car is more
unstable at the same(?) speed. If I'm at the same speed, I crash. Therefore,
I need to go slower through the turns, so I start hitting the brakes earlier.
I don't know if that makes any sense, or even if I've explained it
correctly...<g>

Eldred
--
Dale Earnhardt, Sr. R.I.P. 1951-2001
Homepage - http://www.umich.edu/~epickett
GPLRank - under construction...

Never argue with an idiot. He brings you down to his level, then beats you
with experience...
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by **Eldre** » Thu, 13 Dec 2001 04:38:37

>They knew they had to turn in at the turn-in cone, they also, by
>now (usually the 5th day) had a feel for speed and grip so in a
>desperate attempt to slow down enough to make the turn they
>would hold onto the brake for longer and longer until they
>would actually be easing off at the point of turn-in.

>Thats the way I'd suggest you try and do it, you need to use
>a corner were there is a very good indictaion of your normal
>braking point.

Braking, or turn-in? If you mean braking, then how do I determine the correct
turn-in point?

I sense I'll be destroying a LOT of cars this weekend...<g>

Eldred
--
Dale Earnhardt, Sr. R.I.P. 1951-2001
Homepage - http://www.umich.edu/~epickett
GPLRank - under construction...

Never argue with an idiot. He brings you down to his level, then beats you
with experience...
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by **Pat Dotso** » Thu, 13 Dec 2001 07:54:43

> Based on the discussions, My theory is this: I try to brake at the same place
> as the others. Because I release the brakes before I turn, the car is more
> unstable at the same(?) speed. If I'm at the same speed, I crash.

Do you want to know why you are unstable when you stop
braking at higher speeds?

The answer is (surprise) throttle!!!

By "unstable", you mean loose, right?

When you release the brake you are unstable because the
engine is trying to slow down the rear wheels. The
faster you are going (higher rpm), the more the engine
creates a drag on the rear wheels. Too much drag on
the rear wheels causes the car to swap ends. It's the
same thing as having too much rear brake bias. Give it
a bit of gas, and viola, no more drag on the rear wheels.

The car becomes stable.

Note that when I say "give it gas", I don't mean start
accelerating. Just match the engine rpm to your wheel
speed so that you are neither accelerating or creating
drag.

Have you tried this technique? As long as you've been
driving GPL, there isn't any reason you shouldn't be
faster.

--
Pat Dotson

by **Eldre** » Thu, 13 Dec 2001 08:41:01

>Have you tried this technique? As long as you've been
>driving GPL, there isn't any reason you shouldn't be
>faster.

Um, no talent?<g>
Seriously, I'm trying to convince myself that applying throttle while trying to
SLOW DOWN is a correct thing to do.

Eldred
--
Dale Earnhardt, Sr. R.I.P. 1951-2001
Homepage - http://www.umich.edu/~epickett
GPLRank - under construction...

Never argue with an idiot. He brings you down to his level, then beats you
with experience...
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by **Haqsa** » Thu, 13 Dec 2001 10:08:56

From what I have read in the "Bible" (Race Car Vehicle Dynamics) that is
more typical of real world setups also - the front is set up to have
slightly less static deflection than the rear, which means slightly
higher undamped natural frequency. You and I have discussed this before
and I recall you saying that they need to be slightly different to
cancel pitch oscillations, and I would assume that it is preferable to
have the front be the stiffer one since stiffer = faster response, thus
improving steering feel.

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