From: AZ Nomad on
On Wed, 28 Apr 2010 18:01:52 -0500, Matthew Russotto <russotto(a)grace.speakeasy.net> wrote:
>In article <bbeft5hfniv2tfhknmpm1oh71jpbp3m65n(a)4ax.com>,
>Ashton Crusher <demi(a)moore.net> wrote:
>>
>>I'm not too keen on the idea of "effective" being that when the
>>pavement is wet is to go sliding out of control.

>If you lock up all four wheels, the car does not go "sliding out of
>control". It behaves in a quite predictable manner, sliding
>straight in the direction it was going when the wheels locked up if on
>a flat surface.

That is only true if the sliding friction of all wheels are identical.
That might occur on sheet of ice, but it is rare otherwise.
In real life, you are out of control if you have wheels sliding as
such as any change in friction is going to steer the vehicle instead
of the driver's input.
From: Alan Baker on
In article
<4f3fd957-83e5-4ad6-8f37-d0c92cdc3168(a)s9g2000yqa.googlegroups.com>,
Dave__67 <spamTHISbrp(a)yahoo.com> wrote:

> On Apr 27, 1:37�pm, Alan Baker <alangba...(a)telus.net> wrote:
> > In article
> > <e00930b2-999a-4467-adec-85b62b909...(a)v14g2000yqb.googlegroups.com>,
> >
> >
> >
> > �Dave__67 <spamTHIS...(a)yahoo.com> wrote:
> > > On Apr 26, 2:41�pm, Alan Baker <alangba...(a)telus.net> wrote:
> > > > In article
> > > > <9bd36917-1c4c-48ba-bb9b-7061a9d6a...(a)z7g2000yqb.googlegroups.com>,
> >
> > > > �Dave__67 <spamTHIS...(a)yahoo.com> wrote:
> > > > > On Apr 22, 9:04�pm, Ashton Crusher <d...(a)moore.net> wrote:
> > > > > > On Thu, 22 Apr 2010 05:08:07 -0700 (PDT), Dave__67
> >
> > > > > > <spamTHIS...(a)yahoo.com> wrote:
> > > > > > >On Apr 21, 11:55�pm, "Nick Naim" <orb...(a)ix.netcom.com> wrote:
> > > > > > >> I pegged her at 70 years old plus minus.
> > > > > > >> She pulled �out of a fast food on my left in a heart beat
> > > > > > >> I,m in the left lane of thru traffic.
> > > > > > >> I,m on the binders on ABS and they are working on overtime.
> > > > > > >> I come to a stop 3 feet from her right front fender.
> >
> > > > > > >If your ABS is kicking on on dry clean pavement you need better
> > > > > > >tires-
> > > > > > >you're throwing away stopping distance!
> >
> > > > > > >Dave
> >
> > > > > > How do y9ou figure that? �ABS works, wet or dry, to maximize the
> > > > > > amount of time the tire is at or near peak friction level. �
> >
> > > > > No, it does not.
> >
> > > > > ABS is designed to allow you to still steer while mindlessly whomping
> > > > > on the brakes. To do so it has to leave a little traction on the
> > > > > plate.
> >
> > > > Again, not quite. ABS will reduce the amount of force applied to the
> > > > brakes whenever conditions result in the tire starting to lock up.
> >
> > > > One of those conditions could be a change in the friction of the
> > > > surface, but one could also be that you've turned the wheel.
> >
> > > > So there is no traction "left on the plate" in the way you meant.
> >
> > > > > Anyway, on dry pavement, if you can lock up the brakes, your brakes
> > > > > are better than your tires. If you improve the grip of the tires
> > > > > you'll stop faster.
> >
> > > > Not just on dry pavement. :-)
> >
> > > > --
> > > > Alan Baker
> > > > Vancouver, British Columbia
> > > > <http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>
> >
> > > If the algorithms and sensors were perfect, and there were no control
> > > loop delay, sure.
> >
> > Sorry, but they don't have to be perfect. Just better than human. And
> > give the speed of human reactions, that's not that hard.
> >
> > --
> > Alan Baker
> > Vancouver, British Columbia
> > <http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>
>
> I'm stating clearly that ABS leaves some traction 'on the plate'
> unused. The fact that an expert using skilled braking technique on dry
> pavement can stop faster with the ABS off proves this
> incontrovertibly.

The fact that a few experts can brake better than ABS is beside the
point.

And they didn't outlaw ABS in F1 because it was going to make braking
worse...

>
> I'm not debating improvements ABS gives in most circumstances compared
> to human brake modulation

For most people -- including even most very good drivers -- ABS will
give shorter, more controlled emergency braking.

That's the fact.

--
Alan Baker
Vancouver, British Columbia
<http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>
From: Alan Baker on
In article <nreft51k6vg3gluv877sfni2jbkbsgupeh(a)4ax.com>,
Ashton Crusher <demi(a)moore.net> wrote:

> On Tue, 27 Apr 2010 21:38:43 -0500, russotto(a)grace.speakeasy.net
> (Matthew Russotto) wrote:
>
> >In article <57q9t5lr4jhb5hervqhb2q51b3poff1eig(a)4ax.com>,
> >Ashton Crusher <demi(a)moore.net> wrote:
> >>>No. ABS is very close to threshold braking, but it is not. It is a very
> >>>rapid sequence of going slightly beyond the threshold and then back to
> >>>less than the threshold.
> >>
> >>Where you are getting that definition from? It makes no sense to me
> >>and is contrary to what people have claimed in the past. What's your
> >>definition of the "threshold" point?
> >
> >Take a chart of brake pressure (at the caliper or shoe) versus braking
> >force applied to the road by that tire. It'll look basically like a
> >line going from 0 upwards fairly linearly, leveling off slightly as it nears
> >a
> >peak, followed by a sharp dropoff to a horizontal line. Perfect
> >threshold braking would be holding braking pressure right at that
> >peak.
>
> You've just described what ABS does in any practical sense. To say ABS
> is qualitatively different then threshold braking is just splitting
> hairs.

No.

ABS is constantly going over and then back under that peak.

It *is* qualitatively different, but it is not quantitatively different
except for a handful of extremely skilled drivers.

--
Alan Baker
Vancouver, British Columbia
<http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>
From: Alan Baker on
In article <slrnhthgcj.er2.aznomad.3(a)ip70-176-155-130.ph.ph.cox.net>,
AZ Nomad <aznomad.3(a)PremoveOBthisOX.COM> wrote:

> On Wed, 28 Apr 2010 18:01:52 -0500, Matthew Russotto
> <russotto(a)grace.speakeasy.net> wrote:
> >In article <bbeft5hfniv2tfhknmpm1oh71jpbp3m65n(a)4ax.com>,
> >Ashton Crusher <demi(a)moore.net> wrote:
> >>
> >>I'm not too keen on the idea of "effective" being that when the
> >>pavement is wet is to go sliding out of control.
>
> >If you lock up all four wheels, the car does not go "sliding out of
> >control". It behaves in a quite predictable manner, sliding
> >straight in the direction it was going when the wheels locked up if on
> >a flat surface.
>
> That is only true if the sliding friction of all wheels are identical.
> That might occur on sheet of ice, but it is rare otherwise.
> In real life, you are out of control if you have wheels sliding as
> such as any change in friction is going to steer the vehicle instead
> of the driver's input.

I'm sorry, but in the real world, you're wrong.

I have actually gone out and practiced this emergency maneuver. And the
car goes in a straight line without rotating.

--
Alan Baker
Vancouver, British Columbia
<http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>
From: AZ Nomad on
On Wed, 28 Apr 2010 16:24:35 -0700, Alan Baker <alangbaker(a)telus.net> wrote:
>In article <slrnhthgcj.er2.aznomad.3(a)ip70-176-155-130.ph.ph.cox.net>,
> AZ Nomad <aznomad.3(a)PremoveOBthisOX.COM> wrote:

>> On Wed, 28 Apr 2010 18:01:52 -0500, Matthew Russotto
>> <russotto(a)grace.speakeasy.net> wrote:
>> >In article <bbeft5hfniv2tfhknmpm1oh71jpbp3m65n(a)4ax.com>,
>> >Ashton Crusher <demi(a)moore.net> wrote:
>> >>
>> >>I'm not too keen on the idea of "effective" being that when the
>> >>pavement is wet is to go sliding out of control.
>>
>> >If you lock up all four wheels, the car does not go "sliding out of
>> >control". It behaves in a quite predictable manner, sliding
>> >straight in the direction it was going when the wheels locked up if on
>> >a flat surface.
>>
>> That is only true if the sliding friction of all wheels are identical.
>> That might occur on sheet of ice, but it is rare otherwise.
>> In real life, you are out of control if you have wheels sliding as
>> such as any change in friction is going to steer the vehicle instead
>> of the driver's input.

>I'm sorry, but in the real world, you're wrong.

>I have actually gone out and practiced this emergency maneuver. And the
>car goes in a straight line without rotating.

I have too. You're not driving; merely a passenger when you're
sliding like that. You also run the risk of turning sideways,
backwards, or rolling the vehicle if you encounter sudden friction
while turned sideways.