At 16:02 05/04/99 -0700, many of you wrote:
>Boy, we're way off topic here.
Yes, I think we are OT, exept if this (anyway interesting) discussion
started talking about the CPU that drives the ABS systems (that's BTW older
than 10 years).
Anyway here my impressions:
>Secondly, ABS is for dry or wet roads. It actually increases stopping
>distance in snow and gravel, because on those surfaces it is more
>advantageous to lock up the wheels and pile up material in front of each
>tire.
This is very true, and that's why my AUDI 90 was equipped with a switch to
disable the ABS on snow. I' ve made many trials with and w./out ABS on snow
and found that the switch had a real meaning.
>ABS - American Bull Shi...
American? Was it a Bosch patent? The only page I found was on Mercedes:
http://www.mercedes-benz.com/e/innovation/rd/forschung_nov96.htm
>
> wheel motion sensors, something like the big GE locomotives. Some
> systems used notched brake drums.
Yes, in italian "ruota fonica" that in english should be a "sound wheel"
or similar: it' the same used inside many needle printer to determine the
movement of the carriage.
>So? If the car is stopped, the wheels aren't turning. If the brakes have
>locked and the car is skidding all over the place, the wheels aren't
>turning. What's the difference?
>AFAIK, it looks for times when only some of the wheels are stopped (i.e.
>it assumes that at least one wheel still has some grip on the road). If
>all the wheels are skidding, then essentially ABS won't do a darn thing.
I've asking myself the same thing. My thinking is that that the system start
its action when it detects the wheel is stopping and it cuts the breaking
pressure to this channel so the wheel starts again moving (even on ice an
unbreaked wheel rolls), so, in general, it checks that "after cutting the
breaking pressure to a stopped wheel, the same keep rolling or not"
if yes the system wait for next locking situation,
if no the system make some additional attemps on the channels then stops.
I think that specially in recent versions the ABS is checking also different
speed
between wheels.
This improvement was necessary to develop the ASR (Acceleration Skid Control)
and the amazing ESP (Electronic Stability Program).
>Having had decades of extensive driving during the long cold winters in
>western Canada, Qebec and Ontario , I would consider myself a quite skilled
>slippery road driver. The worst thing you can do when you go into a skid is
>lock your brakes. The best is to turn into the skid and use your accellerator
>and steering to bring it back under control. I would rather have any brake
>action under my control and hope I can steer out of it without using them.
I fully agree on the dangerous use of the brakes:I' ve tried to conduct
narrow mountain curves with snow, finding wich solution would better work in
case I found myself to enter the curve with a higher speed (at last with my
front wheel drive car)
So I' ve tryed different possibilities E.g. brakes, acceleration, clutch and
brakes, a lower gear etc.
I found that the best is "clutch and pray"
In fact:
brakes or clutch and brakes = front wheel skid + worse stability
lower gear or acceleration = similarly to breaks you are forcing the wheels
to an unnatural speed (different
radius)=skid + worse stability
clutch and pray = with clutch pressed every wheels automatically
adapt to the speed forced by the radius with
lateral grip as only
job to make, (e.g. with no loose of grip
caused by de- or accelerations) and the pray
helps...stability :->
> ABS seems just damnright dangerous to me
All the above was to be considered with ABS=off
>, except perhaps for the complete novice who >would lock his brakes out of
fear and >inexperience.
No, it's like the usage of safety belts, it works better or worse according
to different situations:
personally I thank the inventor of ABS because (unfortunately) I had the
chance to verify its effectiveness when (in motorway speeding at 160 km/h) I
suddenly found a stopped car in the fast lane. The good driving procedures
said that one should break down the speed as much as possible (no steering)
and then try to avoid the obstacle by steering by its side like this
--------------------------------
[=]---->--->-->->->>>\ [X]
--------------------------------
-[=]
--------------------------------
but at that speed it's very difficult to keep the car in a straight
direction to guarantee the necessary speed/stability to make the vital last
steering.The working of ABS helped me to decrease the speed with more
efficacy and allowed the late steering (while breaking):the car that
followed me (no ABS) could'nt do the same and crashed against the stopped car.
Really it's not only question of driving skills.
Riccardo Romagnoli
<chemif_at_mbox.queen.it>
I-47100 Forl?
Received on Mon Apr 12 1999 - 22:11:16 BST