ABS brakes
in [Drive]
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From: Alan Baker on 28 Apr 2010 19:55 In article <slrnhthhs7.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 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. Incorrect. 1. If I need to steer, I can pre-turn the wheels and then release the brakes. The car then seems to "leap" in a new direction. Thus I'm not a passenger. If I could stop sliding whenever I wanted to, *then* you might be able to say that. BTW, you should go out and try this. It is a revelation. If I'd practiced it more recently, I might have been able to have avoided contact at all with the car that turned left right in front of me last summer, rather than just getting the contact down to just a clip of my front right corner with his rear right, but I did also have to worry about on-coming traffic in the lane that he had just vacated. 2. In many trials -- including some where I deliberately put one side onto the gravel that had collected by the side of the road, the car never turned any significant amount. 3. The vehicle in question was a sports car and thus pretty much impossible for it to be overturned by any amount of friction from the tires. It it were possible then it would happen when the tires are hooked up in a maximum cornering effort, but I've done that and guess what? -- Alan Baker Vancouver, British Columbia <http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>
From: Alan Baker on 28 Apr 2010 20:00 In article <83q7kmFga6U1(a)mid.individual.net>, Alexander Rogge <a_rogge(a)yahoo.com> wrote: > Ashton Crusher wrote: > > No modern ABS "guesses" at anything. > > How could the ABS program know what I want to do when I touch the brake > pedal? It knows nothing except the wheel velocity and maybe how quickly > I depressed the pedal. In the examples of a sophisticated program, it > knows the velocity of the car and the angle of steering. What it cannot > know is my immediate intent, so it attempts to guess about what I want > the car to do next. No. An ABS system simply modulates brake pressure when it sees incipient lockup of a wheel. It doesn't need to know anything about intent to do that. If you turn the wheel and that uses up any small margin of traction that remains and starts to put a wheel into lockup, the ABS will see that and reduce the braking force and continue to do so more and more if you steer mroe. > > > When you say the cars you have tried miss the "optimum", how are you > > making that assessment? > > Accelerate the car to 100, point at a mark on the track, and attempt to > stop. That's the standard for most car testing. I also attempt rapid > stops at much faster speeds. > > > Most likely you are also basing your assessments on > > braking on dry pavement. > > A dry surface was the subject under discussion. > > > Although ABS will win there, where it really > > shines is on wet pavements and on pavements that have highly variable > > friction levels transversely and/or laterally. > > The other option is to slow down so that you aren't driving too fast for > conditions. That is not a subject under discussion, but the fact remains that sometimes people do stupid things in front of you that leave you without sufficient space to do anything regardless of what particular speed you're traveling. > > > A 3 or 4 circuit ABS > > can easily handle such surfaces, a single circuit, i.e. human on the > > pedal, can't hope to handle it at anything close to what the ABS can > > do. > > Yet, we seemed to drive without much difficulty before computers and ABS > programs. Most of the traction control results from the tyres, not > everything that rests on the tyres. Considering some comparative > examples of driving on snow and ice, the car with no traction control > system, rear-wheel drive and snow tyres can win over a car with 4-wheel > drive, an electronic traction-control system, and all-season tyres. The > most important components of maintaining traction are the tyres and the > driver. Not if the drivers are equal, it can't. > > There is too much reliance on these electronic control systems that were > intended to enable the car to be driven to new extremes, that are > instead used by some drivers as a crutch for common sense and having > proper equipment. Having proper tyres and a proper speed for conditions > can eliminate the need for ABS and other traction-control systems. Those are failures of driver training, not of technology. That a new technology can be abused is not a reason to avoid it. -- Alan Baker Vancouver, British Columbia <http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>
From: Matthew Russotto on 28 Apr 2010 20:02 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. It's close enough unless you're on a very uneven surface. IME, the car generally rotates a bit and slides down the crown of the road (if any) but doesn't behave erraticly. (Driving an early Miata with with the stock tires in the rain unfortunately gave too much opportunity to learn this stuff the hard way) It's when you lock some of the wheels but not all of them that you end up with the car going out of control. That requires much less of a difference in surface or in load than actually having varying sliding friction coefficients. -- The problem with socialism is there's always someone with less ability and more need.
From: Matthew Russotto on 28 Apr 2010 20:12 In article <slrnhthhs7.er2.aznomad.3(a)ip70-176-155-130.ph.ph.cox.net>, AZ Nomad <aznomad.3(a)PremoveOBthisOX.COM> wrote: > >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. You're not a passenger when sliding with all four wheels locked; you've reached the limits of your control and will have to back off the brakes if you want to do anything else, but you're not out of control. You're not going to turn sideways unless there's a major irregularity in the road surface, or you were spinning already. And unless you drive an SUV or other high center of gravity vehicle, an untripped rollover is extremely unlikely even if you do spin. -- The problem with socialism is there's always someone with less ability and more need.
From: Dave__67 on 29 Apr 2010 07:49
On Apr 28, 7:18 pm, Alan Baker <alangba...(a)telus.net> wrote: > In article > <4f3fd957-83e5-4ad6-8f37-d0c92cdc3...(a)s9g2000yqa.googlegroups.com>, > > > > Dave__67 <spamTHIS...(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. > That's the whole point- if ABS used all available traction no expert could outbrake it. You agree that a true expert can outbrake ABS when it's straight+dry so you either must agree that ABS leaves some traction on the table, or you are one of those people that can hold two controverting ideas at the same time yet feel no dissonance. > And they didn't outlaw ABS in F1 because it was going to make braking > worse... > It was going to make braking in the turns easier, srtraight-line dry braking indeed would have suffered. > > > > 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. Why are you arguing when I'm clearly stating I agree? > > -- > Alan Baker > Vancouver, British Columbia > <http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg> Dave |