ABS brakes
in [Cars]
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From: Ashton Crusher on 4 May 2010 01:08 On Wed, 28 Apr 2010 07:49:42 +0000, 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. > The only "guess's" I've heard of them adding to ABS is braking assist where it amplifies quick brake applications so you stop shorter then you otherwise would have. Other then that it's not trying to be psychic. It's a fairly straightforward concept that really needed high speed computers to facilitate a good system that could achieve both an anti-lock capacity AND near optimum friction levels. >> 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. > And have you got instrumented tests that show the friction levels and stopping distance with the same vehicle on the same pavement with the same tires from the same initial speed with enough repeat runs to be statistically significant when you do this comparison with ABS and without ABS? >> Most likely you are also basing your assessments on >> braking on dry pavement. > >A dry surface was the subject under discussion. > As I recall it was not limited to any particular surface condition. >> 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. > Or just stay home. Or buy a horse. Was there a point to your comment? >> 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. > There were quite a few improvements in brakes over the years and it's true that today, even without ABS, most cars have darn good brakes compared to what was on cars in the 60's/70's. I don't recall anyone saying ABS was an essential item. >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. You can frame just about anything in those terms. Why bother with pneumatic tires, or radial tires, or shock absorbers, or hydraulic brakes, or 4 wheel brakes, after all, "proper speed for conditions can eliminate the need for..." all that stuff. People bother with it because it's an improvement over what came before.
From: Alan Baker on 4 May 2010 02:50 In article <rs8vt5d3522s43sircri0i60a10hndfh9p(a)4ax.com>, Ashton Crusher <demi(a)moore.net> wrote: > On Wed, 28 Apr 2010 19:12:05 -0500, russotto(a)grace.speakeasy.net > (Matthew Russotto) wrote: > > >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 are on low friction wet pavement. Nope. Because you can release the brakes whenever you need to. > > >You're not going to turn sideways > > If there is lateral differential friction, which occurs often enough > it can be an issue, you will spin anywhere from 10's of degrees to > 360+ degrees, all the while going "straight" ahead. Nope. I've made a lot of test runs, and it doesn't happen. Empirical data trumps theory every time. -- Alan Baker Vancouver, British Columbia <http://gallery.me.com/alangbaker/100008/DSCF0162/web.jpg>
From: Dave__67 on 4 May 2010 07:39 On May 3, 10:22 pm, Ashton Crusher <d...(a)moore.net> wrote: > On Wed, 28 Apr 2010 04:39:25 -0700 (PDT), 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. > > >I'm not debating improvements ABS gives in most circumstances compared > >to human brake modulation > > >Dave. > > Please post your reference to this statistically valid test that shows > that over a meaningful range of friction values an expert can > consistently beat an excellent ABS. For you? No. I refuse. Find it yourself. Dave
From: Ashton Crusher on 5 May 2010 00:58 On Tue, 4 May 2010 04:39:00 -0700 (PDT), Dave__67 <spamTHISbrp(a)yahoo.com> wrote: >On May 3, 10:22�pm, Ashton Crusher <d...(a)moore.net> wrote: >> On Wed, 28 Apr 2010 04:39:25 -0700 (PDT), 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. >> >> >I'm not debating improvements ABS gives in most circumstances compared >> >to human brake modulation >> >> >Dave. >> >> Please post your reference to this statistically valid test that shows >> that over a meaningful range of friction values an expert can >> consistently beat an excellent ABS. > >For you? > >No. > >I refuse. > >Find it yourself. > > >Dave Because it doesn't exist.
From: Ashton Crusher on 5 May 2010 01:05
On Mon, 03 May 2010 23:50:20 -0700, Alan Baker <alangbaker(a)telus.net> wrote: >In article <rs8vt5d3522s43sircri0i60a10hndfh9p(a)4ax.com>, > Ashton Crusher <demi(a)moore.net> wrote: > >> On Wed, 28 Apr 2010 19:12:05 -0500, russotto(a)grace.speakeasy.net >> (Matthew Russotto) wrote: >> >> >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 are on low friction wet pavement. > >Nope. Because you can release the brakes whenever you need to. > If the need is to stop, releasing the brakes is not "control". >> >> >You're not going to turn sideways >> >> If there is lateral differential friction, which occurs often enough >> it can be an issue, you will spin anywhere from 10's of degrees to >> 360+ degrees, all the while going "straight" ahead. > >Nope. I've made a lot of test runs, and it doesn't happen. > >Empirical data trumps theory every time. I've made hundreds of test runs on different friction levels of both wet and dry pavement including both uniform and non-uniform lateral friction and I can assure you that from real world empirical data, not theory, that the car with four locked tires will spin as I previously described. If all you've done is some runs on dry pavement or wet pavement with good uniform friction you simply have not experienced the full range of what can happen. I have also seen many people try to do these tests and who think they have locked all the wheels but they have not, including experienced "expert" accident reconstructionists. |