Do the math on this?
Mike T.
old man was driving a pickup truck at unspecified unsafe speed. He lost
control in a corner. The pickup slid sideways for ******* 500 ******* feet.
After that, it left the roadway and hit a tree (what size, who knows), and
that the tree was sheared off by the impact. Idiot was killed, obviously.
But I'm wondering how fast was this idiot going before he lost control?
Road conditions in the area were DRY at the time. Unfortunately, there is
no information on type of pickup or what type of tires, condition, etc.
Let's say Ford F150 with OEM tires in decent shape, how fast would that have
to go to slide sideways for 500 feet and still have enough kinetic energy to
fly through the air a bit and shear off a small tree on impact?????
Then again, would an F150 even be able to go that fast in the first place?
(I doubt it) -Dave
Larry Bud
Without knowing if the truck rolled over (it HAD to have, wouldn't it?)
it would be hard to calculate.
Then again, if I could calculate it in the first place, I'd probably be
an accident investigator!
Mike T.
Well, let's change this around a bit. Let's say Ford F150 with bald tires
on dry road, all four wheels lock. How fast do you have to be going to
slide 500 feet before you stop? That should be a pretty good estimate of
how fast the truck was travelling before it went sideways. I'm guessing
sideways it wouldn't have quite as much traction. Therefore, if it was
sliding sideways at the same starting speed, it might have enough energy
left to leave the road and shear off a tree.
Don't know if it would roll over though. It wasn't an SUV, it said pickup.
Those are top heavy, but not quite as much so. -Dave
gpsman
WOW!!! Sounds remarkable, don't it?
According to a chart from Edmunds at Autotrader.com... about 90 mph
ought to cover it. Some people ought to think about that before citing
85 mph as a "perfectly safe" velocity.
- gpsman
Mike T.
"gpsman" <gps...@driversmail.com> wrote in message
news:1139855418.4...@g14g2000cwa.googlegroups.com...
Interesting information, but it's not applicable to the situation I posted
about. The article stated that the pickup slid more than 500 feet. So the
~2 seconds reaction time had already elapsed, if the driver "reacted" at all
before the slide started. Assuming that a vehicle sliding sideways would
stop exactly as fast as a vehicle stopping in a straight line, that would
mean that the vehicle in question was going considerably faster than 90MPH,
to increase his total stopping time by about 2 seconds beyond the time it
MIGHT have taken the driver to stop from 90MPH.
PLUS, the vehicle wasn't anywhere near a complete stop after 500 feet. It
still had enough energy to leave the road and shear off a tree of unknown
size.
My best guess after careful consideration is that the pickup MUST have been
travelling well in excess of 140MPH before it started sliding sideways. WTF
kind of pickup was that . . . a Tundra V8 2WD, possibly??? -Dave
Alan Baker
"gpsman" <gps...@driversmail.com> wrote:
What makes 85 mph perfectly safe is controlled access highways where
everyone *else* is doing the same speed.
>
> http://tinyurl.com/czzqd
> -----
>
> - gpsman
--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling 4 feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect
if you sit in the bottom of that cupboard."
Alan Baker
"Mike T." <he...@howyadoin.now> wrote:
I can ballpark it for you.
If we assume 1 g deceleration -- a very generous estimate:
a = 32 ft/s^2
d = 500
v = ?
Using the forumla v(final)^2 = v(initial)^2 + 2ad, and remembering the
final velocity in this case is 0.
0 = v^2 + 2 *(32) * 500
v = (32000)^(1/2) = 179 mph.
So if deceleration equalled 1 g, the truck would have had to be going
179 mph to slide for 500 feet. Even at 0.75 g, the truck would still
have had to be going 155 mph.
Mike T.
>> been
>> travelling well in excess of 140MPH before it started sliding sideways.
>> WTF
>> kind of pickup was that . . . a Tundra V8 2WD, possibly??? -Dave
>
> I can ballpark it for you.
>
> If we assume 1 g deceleration -- a very generous estimate:
>
> a = 32 ft/s^2
>
> d = 500
>
> v = ?
>
>
> Using the forumla v(final)^2 = v(initial)^2 + 2ad, and remembering the
> final velocity in this case is 0.
>
> 0 = v^2 + 2 *(32) * 500
>
> v = (32000)^(1/2) = 179 mph.
>
> So if deceleration equalled 1 g, the truck would have had to be going
> 179 mph to slide for 500 feet. Even at 0.75 g, the truck would still
> have had to be going 155 mph.
>
> --
> Alan Baker
> Vancouver, British Columbia
Wow. I guess for a change this really was unsafe speed. 155MPH estimated,
and that doesn't take into account that it still left the road and sheared
off a tree!!! Holy sh^%, maybe closer to 200MPH. What kind of pickup was
this?
What is the fastest production pickup truck sold today in the U.S.? Any
capable of speeds well in excess of 150MPH? -Dave
Alex Rodriguez
gps...@driversmail.com says...
>WOW!!! Sounds remarkable, don't it?
>
>According to a chart from Edmunds at Autotrader.com... about 90 mph
>ought to cover it. Some people ought to think about that before citing
>85 mph as a "perfectly safe" velocity.
What does one have to do with the other? You have the case of an idiot driving
to fast for conditions and losing control of their vehicle. There are many
roads where the conditions will allow you to safely drive 85mph, and faster.
The important part is being able to recognize when the conditions allow the
higher speeds.
------------------
Alex
Alex Rodriguez
he...@howyadoin.now says...
>Assuming that a vehicle sliding sideways would
>stop exactly as fast as a vehicle stopping in a straight line, that would
>mean that the vehicle in question was going considerably faster than 90MPH,
>to increase his total stopping time by about 2 seconds beyond the time it
>MIGHT have taken the driver to stop from 90MPH.
Assuming the driver knows how to properly use their brakes, a non-slidding
stop will be much shorter than a slidding stop.
>PLUS, the vehicle wasn't anywhere near a complete stop after 500 feet. It
>still had enough energy to leave the road and shear off a tree of unknown
>size.
It had to be moving pretty quickly at 500 ft. Even small trees take a lot
of energy to topple.
>My best guess after careful consideration is that the pickup MUST have been
>travelling well in excess of 140MPH before it started sliding sideways. WTF
>kind of pickup was that . . . a Tundra V8 2WD, possibly??? -Dave
140 in a full size pickup would require a substantial amount of horsepower.
Maybe a Dodge SRT pickup with the Viper V10 motor will get up to that speed,
but not a plain F150.
--------------
Alex
John F. Carr
Alex Rodriguez <ad...@columbia.edu> wrote:
>
>140 in a full size pickup would require a substantial amount of horsepower.
Most pickups are governed to 99-110 miles per hour. If the truck
was fishtailing for part of the distance it could leave skid marks
without slowing down much.
--
John Carr (j...@mit.edu)
Garth Almgren
> 140 in a full size pickup would require a substantial amount of horsepower.
> Maybe a Dodge SRT pickup with the Viper V10 motor will get up to that speed,
> but not a plain F150.
Definitely not in a plain F150, but a Lightning with a few cheap mods
(exhaust, chip, and S/C pulley) could do it.
--
~/Garth |"I believe that it is better to tell the truth than a lie.
Almgren | I believe it is better to be free than to be a slave.
******* | And I believe it is better to know than to be ignorant."
(p...@v6stang.com for secure mail info) --H.L. Mencken (1880-1956)
gpsman
> Assuming the driver knows how to properly use their brakes, a non-slidding
> stop will be much shorter than a slidding stop.
Eh... I thinka lot of variables come to play determining which would
prove shortest. Locking the wheels would create the most initial
friction... but liquid rubber may pool in front of the tire...etc.
> >PLUS, the vehicle wasn't anywhere near a complete stop after 500 feet. It
> >still had enough energy to leave the road and shear off a tree of unknown
> >size.
I think we're victims of that process of stringing together sensational
words that passes for journalism these days. Most likely, the vehicle
"traveled" rather than "skidded" 500 ft. before hitting the tree...
which may have been a dog. The facts may have been purposely distorted
in the interest of national security, can't discount that.
-----
- gpsman
Ad absurdum per aspera
> skid marks without slowing down much.
I'm trying to envision how anybody but perhaps a Hollywood stunt driver
or a pretty sharp "drifting" competitor could get 500 feet of pure
sideways travel even on purpose, never mind without rolling (note here
that "pickup truck" covers a wide range of original and aftermarket
equipment, and what torments a tire can withstand will vary too).
I've got the same hunch you seem to have -- that the original
local-paper article was either vaguely written or based on
misinterpretation of 500 feet worth of various dramas and traumas as
being all "sideways."
These are just some of the things that one would need to get
straightened out (no pun intended and probably not much of one
achieved) before starting in with the math. And if some dirt were
involved, the math would get different and harder.
Still, we can probably conclude that he was pickin'em up and puttin' em
down when he started gettin' sideways...
--Joe
Motorhead Lawyer
>
> I can ballpark it for you.
>
> If we assume 1 g deceleration -- a very generous estimate:
>
> a = 32 ft/s^2
>
> d = 500
>
> v = ?
>
>
> Using the forumla v(final)^2 = v(initial)^2 + 2ad, and remembering the
> final velocity in this case is 0.
>
> 0 = v^2 + 2 *(32) * 500
>
> v = (32000)^(1/2) = 179 mph.
>
> So if deceleration equalled 1 g, the truck would have had to be going
> 179 mph to slide for 500 feet. Even at 0.75 g, the truck would still
> have had to be going 155 mph.
Unfortunately, that's not the right ballpark. I'd be surprised to find
a pickup pulling .75 g *while sliding*. What you've overlooked is
that, even if said pickup *could* pull 0.75 g on a skidpad, it's
pulling *less* when sliding (Sliding friction is *lower* than static
friction, remember?).
Something else everyone has apparently overlooked is that trees don't
grow in pavement. They grow in dirt or grass. Therefore, at least
some of this slide was through such a surface. Needless to say, you
can slide a *long way* on grass, especially. Even more so if it's
damp. Until you can characterize the surfaces for the entire distance
of the slide and accurately consider the sliding coefficient of
friction on *all* the surfaces, a calculation for speed is nothing more
than a very rough guess.
--
C.R. Krieger
(Been there; done that)
Alex Rodriguez
gps...@driversmail.com says...
>
>
>Alex Rodriguez wrote: <brevity snip>
>> Assuming the driver knows how to properly use their brakes, a non-slidding
>> stop will be much shorter than a slidding stop.
>
>Eh... I thinka lot of variables come to play determining which would
>prove shortest. Locking the wheels would create the most initial
>friction... but liquid rubber may pool in front of the tire...etc.
On pavement, it's pretty simple. Slidding friction is always lower than static
friction. So if you are slidding, your stopping distance will be longer than
when you are braking at the threshold of sliding. That's why ABS will give you
shorter stopping distances.
--------------
Alex
necromancer
rec.autos.driving on Mon, 13 Feb 2006 19:17:02 GMT:
> If we assume 1 g deceleration -- a very generous estimate:
>
> a = 32 ft/s^2
>
> d = 500
>
> v = ?
>
>
> Using the forumla v(final)^2 = v(initial)^2 + 2ad, and remembering the
> final velocity in this case is 0.
>
> 0 = v^2 + 2 *(32) * 500
>
> v = (32000)^(1/2) = 179 mph.
>
> So if deceleration equalled 1 g, the truck would have had to be going
> 179 mph to slide for 500 feet. Even at 0.75 g, the truck would still
> have had to be going 155 mph.
If I read the OP correctly, the truck slid the 500 feet where it made
contact with the tree, sheared off the tree and then presumablly
continued moving for an unknown distance after that. Therefore, the
velocity at the instant of contact with the tree would not (IME) be
zero.
Alan Baker
"Motorhead Lawyer" <88.5...@gmail.com> wrote:
> Alan Baker wrote:
> >
> > I can ballpark it for you.
> >
> > If we assume 1 g deceleration -- a very generous estimate:
> >
> > a = 32 ft/s^2
> >
> > d = 500
> >
> > v = ?
> >
> >
> > Using the forumla v(final)^2 = v(initial)^2 + 2ad, and remembering the
> > final velocity in this case is 0.
> >
> > 0 = v^2 + 2 *(32) * 500
> >
> > v = (32000)^(1/2) = 179 mph.
> >
> > So if deceleration equalled 1 g, the truck would have had to be going
> > 179 mph to slide for 500 feet. Even at 0.75 g, the truck would still
> > have had to be going 155 mph.
>
> Unfortunately, that's not the right ballpark. I'd be surprised to find
> a pickup pulling .75 g *while sliding*. What you've overlooked is
> that, even if said pickup *could* pull 0.75 g on a skidpad, it's
> pulling *less* when sliding (Sliding friction is *lower* than static
> friction, remember?).
Yes, but skidpad performance is different from straight line performance.
You're actually talking about something I've studied a great deal, and
moreover, it's not hard to look this stuff up:
"d. The coefficient of friction for rubber sliding on concrete is 0.8"
<URL:http://encarta.msn.com/encyclopedia_761569794/Friction.html>
So, I'd have to say that I'm very much in the right ballpark.
>
> Something else everyone has apparently overlooked is that trees don't
> grow in pavement. They grow in dirt or grass. Therefore, at least
> some of this slide was through such a surface. Needless to say, you
> can slide a *long way* on grass, especially. Even more so if it's
> damp. Until you can characterize the surfaces for the entire distance
> of the slide and accurately consider the sliding coefficient of
> friction on *all* the surfaces, a calculation for speed is nothing more
> than a very rough guess.
Or...
...one could just be able to *read*.
From the original post:
"The pickup slid sideways for ******* 500 ******* feet.
After that, it left the roadway and hit a tree"
^^^^^^^^^^
And I wasn't trying to prove the pickup was going any speed, BTW. I was
attempting to refute someone who was claiming that a stop from around 85
mph would have the vehicle sliding for 500 feet.
Alan Baker
necromancer <necro...@kretp.tmy> wrote:
So?
That would make the initial velocity higher and thus the other poster's
nonsense about how this represented a speed of about 85 mph even *more*
ludicrous.
gpsman
shortest stopping distance. ABS offers steering control under maximum
braking effort by trading stopping distance for control.
-----
- gpsman
Alan Baker
Alex Rodriguez <ad...@columbia.edu> wrote:
However:
Practically speaking, unless you have ABS and can simply slam the pedal
to the floor, it takes time to *find* the threshold. That time is spent
with the vehicle traveling at its fastest speed and thus costs a great
deal in distance traveled, while simply slamming to the pedal to the
floor gets you to a braking force (essentially instantaneously as
compared to finding the threshold) that is a lot closer to threshold
braking than most people realize (at least for dry pavement).
Alan Baker
"gpsman" <gps...@driversmail.com> wrote:
First of all: ABS only trades stopping distance for control if you
actually *do* steer. Look up "friction circle".
Second: that having been said, a very skilled driver can still stop
shorter than all but the most intelligent ABS systems, as such a driver
will get the tires to spend more of their time at the threshold of
sliding friction, where most ABS systems will be cycling from somewhere
below the threshold to somewhere above and back.
DTJ
wrote:
Except it doesn't. ABS does in some cases increase stopping
distances, and in some cases it decreases. Your statement neglected
to mention that it is sometimes inferior.
*************************
Dave
Matthew Russotto
Alan Baker <alang...@telus.net> wrote:
>
>Practically speaking, unless you have ABS and can simply slam the pedal
>to the floor, it takes time to *find* the threshold. That time is spent
>with the vehicle traveling at its fastest speed and thus costs a great
>deal in distance traveled,
You find the threshold from the other side. That is, you brake until
they lock then let up a bit.
--
There's no such thing as a free lunch, but certain accounting practices can
result in a fully-depreciated one.
Alan Baker
russ...@grace.speakeasy.net (Matthew Russotto) wrote:
> In article <alangbaker-2D758...@news.telus.net>,
> Alan Baker <alang...@telus.net> wrote:
> >
> >Practically speaking, unless you have ABS and can simply slam the pedal
> >to the floor, it takes time to *find* the threshold. That time is spent
> >with the vehicle traveling at its fastest speed and thus costs a great
> >deal in distance traveled,
>
> You find the threshold from the other side. That is, you brake until
> they lock then let up a bit.
That helps, but you still have to let up a bit, without it being too
much.
That's essentially, what some ABS systems do, and they don't all
necessarily generate the shortest stops.
gpsman
You don't know? It isn't o b v i o u s?
First of all, the "idiot" who lost control... may have run over a small
object that caused a catastrophic tire failure. You don't know... do
you?
Making judgements with such scant facts indicates you are probably a
very fast thinker... but the conclusions to which you you arrive are
likely to be incorrect and therefore you would probably not be the best
candidate for 85+ mph driving.
The problem w/85+ mph is it reduces the allowable margin of driver
error and increases the potential for injury and collateral damage.
The problem w/being able to "recognize what conditions allow for higher
speeds" is that the conditions on public highways are uncontrolled for
the most part and a very small piece of road debris can constitute an
abrupt change of conditions. A 12 inch piece of tailpipe for example,
or a discarded 6 oz. Coke bottle.
I... have been sideways at 85-100+ mph... and I'm here to tell the
overconfident you that your velocity will suddenly appear to quadruple
when you're calculating steering corrections via the view out your side
window while struggling to not inhale your seat through your ass. And
ironically, it will all appear to happen silently and in slow motion.
The application of braking at that point will not be a wise option...
and just lifting off the throttle could throw the vehicle further out
of control.
No velocity is inherently dangerous... or safe. People are killed on
the road at many velocites, including zero. The other idjit here who
feels driving 85 mph is made more safe by being surrounded by traffic
of the same velocity... is just that, an idjit. It's not safe on the
racetrack and it certainly isn't safe on a public road.
-----
- gpsman
Motorhead Lawyer
> In article <1139939880.6...@o13g2000cwo.googlegroups.com>,
> "Motorhead Lawyer" <88.5...@gmail.com> wrote:
> >
> > Unfortunately, that's not the right ballpark. I'd be surprised to find
> > a pickup pulling .75 g *while sliding*. What you've overlooked is
> > that, even if said pickup *could* pull 0.75 g on a skidpad, it's
> > pulling *less* when sliding (Sliding friction is *lower* than static
> > friction, remember?).
>
> Yes, but skidpad performance is different from straight line performance.
Huh? Maybe you'd care to tell us how; unless you're referring to the
fact that the truck was sliding in a straight line.
> You're actually talking about something I've studied a great deal, and
> moreover, it's not hard to look this stuff up:
I've studied it quite a bit as well.
> "d. The coefficient of friction for rubber sliding on concrete is 0.8"
Well, it might be; but it's not likely. The coefficient of friction of
rubber sliding on concrete is not a constant. It varies most of all
with the compound of the rubber *as well as* the surface texture of the
concrete, the temperature, and to a lesser extent, the ambient
humidity. I know that professionals such as crash investigators use a
figure right around that, but they will admit that it doesn't take into
account the other factors I've mentioned. It is a rough approximation
for average calculations.
> <URL:http://encarta.msn.com/encyclopedia_761569794/Friction.html>
>
> So, I'd have to say that I'm very much in the right ballpark.
As I will continue to disagree. You need to do more research so you
can explain why a car without ground effects can generate over 1.0 g
when its tires can only generate 0.8 g. Further, why the same car with
different tires will generate different lateral g forces.
> > Something else everyone has apparently overlooked is that trees don't
> > grow in pavement. They grow in dirt or grass. Therefore, at least
> > some of this slide was through such a surface.
>
> Or...
>
> ...one could just be able to *read*.
>
> From the original post:
>
> "The pickup slid sideways for ******* 500 ******* feet.
> After that, it left the roadway and hit a tree"
> ^^^^^^^^^^
Guess you're right. But I'm guessing both parts of this statement have
some room for imprecision.
> And I wasn't trying to prove the pickup was going any speed, BTW. I was
> attempting to refute someone who was claiming that a stop from around 85
> mph would have the vehicle sliding for 500 feet.
If I could lay hands (electrons, actually) on some G Analyst plots I
have, I could tell you what kind of cf to use, but I'm not sure where
they are at the moment and, at any rate, they're for an Audi 4000
Quattro with V-rated Contis on it. If I had to guess for the average
pickup truck sliding on significantly harder compound tires, I'd have
to say the cf might be closer to .4 or .5 g. This would also produce a
reasonably believable speed from which it started to slide, don't you
think?
--
C.R. Krieger
(Been in motorsports too long ...)
Motorhead Lawyer
>
> I... have been sideways at 85-100+ mph... and I'm here to tell the
> overconfident you that your velocity will suddenly appear to quadruple
> when you're calculating steering corrections via the view out your side
> window while struggling to not inhale your seat through your ass. And
> ironically, it will all appear to happen silently and in slow motion.
> The application of braking at that point will not be a wise option...
> and just lifting off the throttle could throw the vehicle further out
> of control.
Apparently, that was at an 'uneducated' 85-100+ mph - or you'd know the
'both feet in' rule. I, too, have been sideways at those speeds - both
riding and driving. The first time riding as an instructor, I
distinctly remember calmly saying, "Both feet in." as the concrete wall
in Road America's Kink whizzed by to the right at an ever-closer
distance. [After we hit it, we spun 180, hit the rear, and bounced
across the track). They don't teach you this stuff for nothing.
Unless your skills are developed enough to *drive out of* a high speed
skid, you want to *lock the brakes* (It'll even work with ABS if you're
sideways; they all lock at once, so no wheel speed differential is
sensed.) and *disengage* power to the drive wheels (get off the gas at
least). Then, you slide until you stop. So, ironically, both of your
inclinations are dead wrong.
> No velocity is inherently dangerous... or safe. People are killed on
> the road at many velocites, including zero. The other idjit here who
> feels driving 85 mph is made more safe by being surrounded by traffic
> of the same velocity... is just that, an idjit. It's not safe on the
> racetrack and it certainly isn't safe on a public road.
Tell that to all the people safely traveling on German autobahns every
day - or for that matter, through Chicago on the Kennedy.
Alan Baker
"Motorhead Lawyer" <88.5...@gmail.com> wrote:
> Alan Baker wrote:
> > In article <1139939880.6...@o13g2000cwo.googlegroups.com>,
> > "Motorhead Lawyer" <88.5...@gmail.com> wrote:
> > >
> > > Unfortunately, that's not the right ballpark. I'd be surprised to find
> > > a pickup pulling .75 g *while sliding*. What you've overlooked is
> > > that, even if said pickup *could* pull 0.75 g on a skidpad, it's
> > > pulling *less* when sliding (Sliding friction is *lower* than static
> > > friction, remember?).
> >
> > Yes, but skidpad performance is different from straight line performance.
>
> Huh? Maybe you'd care to tell us how; unless you're referring to the
> fact that the truck was sliding in a straight line.
I'll give you one:
Since turning the vehicle creates additional friction, you have to use
some of the available traction in the tangential direction, hence you
don't have as much for lateral acceleration.
Look up "friction circle".
>
> > You're actually talking about something I've studied a great deal, and
> > moreover, it's not hard to look this stuff up:
>
> I've studied it quite a bit as well.
Right. And you don't know any reasons why skidpad lateral acceleration
might differ from straight line acceleration (or deceleration)...
>
> > "d. The coefficient of friction for rubber sliding on concrete is 0.8"
>
> Well, it might be; but it's not likely. The coefficient of friction of
> rubber sliding on concrete is not a constant. It varies most of all
> with the compound of the rubber *as well as* the surface texture of the
> concrete, the temperature, and to a lesser extent, the ambient
> humidity. I know that professionals such as crash investigators use a
> figure right around that, but they will admit that it doesn't take into
> account the other factors I've mentioned. It is a rough approximation
> for average calculations.
So what? You said I wasn't in the "right ballpark". I'd say 0.75 is very
much in the same ballpark as 0.8, wouldn't you?
>
> > <URL:http://encarta.msn.com/encyclopedia_761569794/Friction.html>
> >
> > So, I'd have to say that I'm very much in the right ballpark.
>
> As I will continue to disagree. You need to do more research so you
> can explain why a car without ground effects can generate over 1.0 g
> when its tires can only generate 0.8 g. Further, why the same car with
> different tires will generate different lateral g forces.
Gee...
Rubbers are different.
0.8 is a *ballpark* figure for typical conditions.
>
> > > Something else everyone has apparently overlooked is that trees don't
> > > grow in pavement. They grow in dirt or grass. Therefore, at least
> > > some of this slide was through such a surface.
> >
> > Or...
> >
> > ...one could just be able to *read*.
> >
> > From the original post:
> >
> > "The pickup slid sideways for ******* 500 ******* feet.
> > After that, it left the roadway and hit a tree"
> > ^^^^^^^^^^
>
> Guess you're right. But I'm guessing both parts of this statement have
> some room for imprecision.
>
> > And I wasn't trying to prove the pickup was going any speed, BTW. I was
> > attempting to refute someone who was claiming that a stop from around 85
> > mph would have the vehicle sliding for 500 feet.
>
> If I could lay hands (electrons, actually) on some G Analyst plots I
> have, I could tell you what kind of cf to use, but I'm not sure where
> they are at the moment and, at any rate, they're for an Audi 4000
> Quattro with V-rated Contis on it. If I had to guess for the average
> pickup truck sliding on significantly harder compound tires, I'd have
> to say the cf might be closer to .4 or .5 g. This would also produce a
> reasonably believable speed from which it started to slide, don't you
> think?
Utter nonsense. Half the typical figure? Please.
> --
> C.R. Krieger
> (Been in motorsports too long ...)
--
gpsman
> gpsman wrote:
> > The application of braking at that point will not be a wise option...
> > and just lifting off the throttle could throw the vehicle further out
> > of control.
>
> Apparently, that was at an 'uneducated' 85-100+ mph - or you'd know the
> 'both feet in' rule.
"BFI" is the rule when all is hopelessly lost. "Sideways" doesn't
denote "lost" or "gone", at least that's not the meaning I intended.
Hence the reference to "steering corrections".
> > No velocity is inherently dangerous... or safe. People are killed on
> > the road at many velocites, including zero. The other idjit here who
> > feels driving 85 mph is made more safe by being surrounded by traffic
> > of the same velocity... is just that, an idjit. It's not safe on the
> > racetrack and it certainly isn't safe on a public road.
>
> Tell that to all the people safely traveling on German autobahns every
> day - or for that matter, through Chicago on the Kennedy.
I'm kinda busy... and I don't speak Stupid. Maybe you could tell them
for me?
Tell all the people who ended up not "safely traveling" too.
-----
- gpsman
Matthew Russotto
gpsman <gps...@driversmail.com> wrote:
>
>I... have been sideways at 85-100+ mph... and I'm here to tell the
>overconfident you that your velocity will suddenly appear to quadruple
>when you're calculating steering corrections via the view out your side
>window while struggling to not inhale your seat through your ass. And
>ironically, it will all appear to happen silently and in slow motion.
>The application of braking at that point will not be a wise option...
>and just lifting off the throttle could throw the vehicle further out
>of control.
Ironically? More like contradictory. Can't say I've been sideways at
speeds that high; I have been sideways (and backwards) at around 65mph, and
my velocity did not appear to quadruple, though the silent slow-motion
thing did happen. Is there a magic cutoff somewhere around 75mph
where your apparent velocity suddenly goes to 300mph?
>No velocity is inherently dangerous... or safe. People are killed on
>the road at many velocites, including zero. The other idjit here who
>feels driving 85 mph is made more safe by being surrounded by traffic
>of the same velocity... is just that, an idjit. It's not safe on the
>racetrack and it certainly isn't safe on a public road.
I'll take 85mph forward over a 65mph spin any day of the week.
Anyway, if no velocity is safe, pointing out that 85mph isn't safe
seems pretty much pointless.
Alan Baker
Tell me: how did you *get* sideways at 85-100+ mph?
>
> No velocity is inherently dangerous... or safe. People are killed on
> the road at many velocites, including zero. The other idjit here who
> feels driving 85 mph is made more safe by being surrounded by traffic
> of the same velocity... is just that, an idjit. It's not safe on the
> racetrack and it certainly isn't safe on a public road.
So why is 65 safe, but 85, not?
> -----
>
> - gpsman
gpsman
> > I... have been sideways at 85-100+ mph...
>
It isn't hard. Sometimes it was intentional, for fun... other times it
was entering or exiting corners too fast, not so fun. One time... it
was off a 30' embankment. That wasn't one of the fun ones.
> > No velocity is inherently dangerous... or safe. People are killed on
> > the road at many velocites, including zero. The other idjit here who
> > feels driving 85 mph is made more safe by being surrounded by traffic
> > of the same velocity... is just that, an idjit. It's not safe on the
> > racetrack and it certainly isn't safe on a public road.
>
> So why is 65 safe, but 85, not?
"No velocity is inherently dangerous... or safe".
It's appears to be safe to travel 650 on the Salt Flats... or escape
velocity in the Shuttle... but it's all relative. It's all relatively
safe until something goes wrong. Same with flying, skydiving, base
jumping, "free" mountain climbing and surfing. (I got my worst surfing
injury on the smallest wave I ever rode. It wasn't pretty.)
Racing cars are required to be equipped with oodles of safety
equipment, many of which will never see the high side of 100 mph. What
do those idiots know that seems to escape the savants here?
<q> The relationship between vehicle speed and crash severity is
unequivocal and based on the laws of physics. The kinetic energy of a
moving vehicle is a function of its mass and velocity squared
Kinetic energy is dissipated in a collision by friction, heat, and the
deformation of mass. Generally, the more kinetic energy to be
dissipated in a collision, the greater the potential for injury to
vehicle occupants.
Because kinetic energy is determined by the square of the vehicle's
speed, rather than by speed alone, the probability of injury, and the
severity of injuries that occur in a crash, increase exponentially with
vehicle speed. For example, a 30-percent increase in speed (e.g., from
50 to 65 mi/h [80 to 105 km/h]) results in a 69-percent increase in the
kinetic energy of a vehicle. </q>
http://www.tfhrc.gov/safety/speed/speed.htm
-----
- gpsman
Alan Baker
"gpsman" <gps...@driversmail.com> wrote:
> Alan Baker wrote:
> > > I... have been sideways at 85-100+ mph...
> >
> > Tell me: how did you *get* sideways at 85-100+ mph?
>
> It isn't hard. Sometimes it was intentional, for fun... other times it
> was entering or exiting corners too fast, not so fun.
And those times, it was *you* driving too fast for conditions, right?
> One time... it
> was off a 30' embankment. That wasn't one of the fun ones.
>
> > > No velocity is inherently dangerous... or safe. People are killed on
> > > the road at many velocites, including zero. The other idjit here who
> > > feels driving 85 mph is made more safe by being surrounded by traffic
> > > of the same velocity... is just that, an idjit. It's not safe on the
> > > racetrack and it certainly isn't safe on a public road.
> >
> > So why is 65 safe, but 85, not?
>
> "No velocity is inherently dangerous... or safe".
>
> It's appears to be safe to travel 650 on the Salt Flats... or escape
> velocity in the Shuttle... but it's all relative. It's all relatively
> safe until something goes wrong. Same with flying, skydiving, base
> jumping, "free" mountain climbing and surfing. (I got my worst surfing
> injury on the smallest wave I ever rode. It wasn't pretty.)
>
> Racing cars are required to be equipped with oodles of safety
> equipment, many of which will never see the high side of 100 mph. What
> do those idiots know that seems to escape the savants here?
That they are driving through corners at the very limits of adhesion and
we're not.
>
> <q> The relationship between vehicle speed and crash severity is
> unequivocal and based on the laws of physics. The kinetic energy of a
> moving vehicle is a function of its mass and velocity squared
But real safety comes from not crashing in the first place.
>
> Kinetic energy is dissipated in a collision by friction, heat, and the
> deformation of mass. Generally, the more kinetic energy to be
> dissipated in a collision, the greater the potential for injury to
> vehicle occupants.
And a crash at 60 already has sufficient energy to kill.
Answer: don't crash. The Autobahn shows this is possible.
>
> Because kinetic energy is determined by the square of the vehicle's
> speed, rather than by speed alone, the probability of injury, and the
> severity of injuries that occur in a crash, increase exponentially with
> vehicle speed. For example, a 30-percent increase in speed (e.g., from
> 50 to 65 mi/h [80 to 105 km/h]) results in a 69-percent increase in the
> kinetic energy of a vehicle. </q>
Your source doesn't appear to know what "exponential" means (it should
have been "geometrically")
>
> http://www.tfhrc.gov/safety/speed/speed.htm
> -----
>
> - gpsman
--
gpsman
> "gpsman" <gps...@driversmail.com> wrote:
> > > Tell me: how did you *get* sideways at 85-100+ mph?
> >
> > It isn't hard. Sometimes it was intentional, for fun... other times it
> > was entering or exiting corners too fast, not so fun.
>
> And those times, it was *you* driving too fast for conditions, right?
Are you an idiot? Putting a vehicle sideways intentionally doesn't
require driving too fast for conditions. In fact, you better be damn
sure you're not driving too fast for conditions.
> > Racing cars are required to be equipped with oodles of safety
> > equipment, many of which will never see the high side of 100 mph. What
> > do those idiots know that seems to escape the savants here?
>
> That they are driving through corners at the very limits of adhesion and
> we're not.
So... what are you saying? You -won't- find the limits of adhesion
because you're a better driver or you're not flirting with them
intentionally? Don't fret, the limits of adhesion will find you...
probably when you least expect it.
> > <q> The relationship between vehicle speed and crash severity is
> > unequivocal and based on the laws of physics. The kinetic energy of a
> > moving vehicle is a function of its mass and velocity squared
>
> But real safety comes from not crashing in the first place.
Mmmm... lemme write that down...
> > Kinetic energy is dissipated in a collision by friction, heat, and the
> > deformation of mass. Generally, the more kinetic energy to be
> > dissipated in a collision, the greater the potential for injury to
> > vehicle occupants.
>
> And a crash at 60 already has sufficient energy to kill.
>
> Answer: don't crash. The Autobahn shows this is possible.
Are you some new, special kind of idiot?
> >
> > Because kinetic energy is determined by the square of the vehicle's
> > speed, rather than by speed alone, the probability of injury, and the
> > severity of injuries that occur in a crash, increase exponentially with
> > vehicle speed. For example, a 30-percent increase in speed (e.g., from
> > 50 to 65 mi/h [80 to 105 km/h]) results in a 69-percent increase in the
> > kinetic energy of a vehicle. </q>
>
> Your source doesn't appear to know what "exponential" means (it should
> have been "geometrically")
Well... you tell 'em. I couldn't bear to see the look on their faces.
-----
- gpsman
Alan Baker
"gpsman" <gps...@driversmail.com> wrote:
> Alan Baker wrote:
> > "gpsman" <gps...@driversmail.com> wrote:
>
> > > > Tell me: how did you *get* sideways at 85-100+ mph?
> > >
> > > It isn't hard. Sometimes it was intentional, for fun... other times it
> > > was entering or exiting corners too fast, not so fun.
> >
> > And those times, it was *you* driving too fast for conditions, right?
>
> Are you an idiot? Putting a vehicle sideways intentionally doesn't
> require driving too fast for conditions. In fact, you better be damn
> sure you're not driving too fast for conditions.
"other times it was entering or exiting corners too fast"...
>
> > > Racing cars are required to be equipped with oodles of safety
> > > equipment, many of which will never see the high side of 100 mph. What
> > > do those idiots know that seems to escape the savants here?
> >
> > That they are driving through corners at the very limits of adhesion and
> > we're not.
>
> So... what are you saying? You -won't- find the limits of adhesion
> because you're a better driver or you're not flirting with them
> intentionally? Don't fret, the limits of adhesion will find you...
> probably when you least expect it.
LOL
Not on dry pavement at the speed limit or well beyond it.
>
> > > <q> The relationship between vehicle speed and crash severity is
> > > unequivocal and based on the laws of physics. The kinetic energy of a
> > > moving vehicle is a function of its mass and velocity squared
> >
> > But real safety comes from not crashing in the first place.
>
> Mmmm... lemme write that down...
You should. Really.
>
> > > Kinetic energy is dissipated in a collision by friction, heat, and the
> > > deformation of mass. Generally, the more kinetic energy to be
> > > dissipated in a collision, the greater the potential for injury to
> > > vehicle occupants.
> >
> > And a crash at 60 already has sufficient energy to kill.
> >
> > Answer: don't crash. The Autobahn shows this is possible.
>
> Are you some new, special kind of idiot?
>
> > >
> > > Because kinetic energy is determined by the square of the vehicle's
> > > speed, rather than by speed alone, the probability of injury, and the
> > > severity of injuries that occur in a crash, increase exponentially with
> > > vehicle speed. For example, a 30-percent increase in speed (e.g., from
> > > 50 to 65 mi/h [80 to 105 km/h]) results in a 69-percent increase in the
> > > kinetic energy of a vehicle. </q>
> >
> > Your source doesn't appear to know what "exponential" means (it should
> > have been "geometrically")
>
> Well... you tell 'em. I couldn't bear to see the look on their faces.
Hey, you're the one quoting them as if they understand this stuff...
Motorhead Lawyer
> In article <1140033877....@z14g2000cwz.googlegroups.com>,
> "Motorhead Lawyer" <88.5...@gmail.com> wrote:
>
> Since turning the vehicle creates additional friction, you have to use
> some of the available traction in the tangential direction, hence you
> don't have as much for lateral acceleration.
>
> Look up "friction circle".
I've *taught* "friction circle", pal.
> Right. And you don't know any reasons why skidpad lateral acceleration
> might differ from straight line acceleration (or deceleration)...
The traction limit is the same in any direction.
> Utter nonsense. Half the typical figure? Please.
Well, using half the 'typical' figure equates to about 90 mph, which I
think you'd agree is about what your average Ford pickup might manage
on a good day. Or we could use your figure for a calculated result of
179 mph ...
So who looks stupid here?
--
C.R. Krieger
(Been there; drove that)
Alan Baker
"Motorhead Lawyer" <88.5...@gmail.com> wrote:
> Alan Baker wrote:
> > In article <1140033877....@z14g2000cwz.googlegroups.com>,
> > "Motorhead Lawyer" <88.5...@gmail.com> wrote:
> >
> > Since turning the vehicle creates additional friction, you have to use
> > some of the available traction in the tangential direction, hence you
> > don't have as much for lateral acceleration.
> >
> > Look up "friction circle".
>
> I've *taught* "friction circle", pal.
>
> > Right. And you don't know any reasons why skidpad lateral acceleration
> > might differ from straight line acceleration (or deceleration)...
>
> The traction limit is the same in any direction.
And on a skid pad, the sum of forces isn't purely lateral due to the
force needed to overcome drag increasing when cornering. Hence, lateral
acceleration is lower on the skid pad than it would be in a straight
line.
And the limit *isn't* the same in every direction. Tire carcasses deform
under lateral forces in a way that reduces their traction limit compared
to fore and aft forces.
>
> > Utter nonsense. Half the typical figure? Please.
>
> Well, using half the 'typical' figure equates to about 90 mph, which I
> think you'd agree is about what your average Ford pickup might manage
> on a good day. Or we could use your figure for a calculated result of
> 179 mph ...
>
> So who looks stupid here?
I didn't do the calculation to prove that the pickup was doing 179 mph.
I did it to show that the story was probably *wrong*.
> --
> C.R. Krieger
> (Been there; drove that)
--
N8N
Motorhead Lawyer wrote:
> If I could lay hands (electrons, actually) on some G Analyst plots I
> have, I could tell you what kind of cf to use, but I'm not sure where
> they are at the moment and, at any rate, they're for an Audi 4000
> Quattro with V-rated Contis on it. If I had to guess for the average
> pickup truck sliding on significantly harder compound tires, I'd have
> to say the cf might be closer to .4 or .5 g. This would also produce a
> reasonably believable speed from which it started to slide, don't you
> think?
It's entirely possible if it's an old vehicle with old tires that the
cf might be lower than you'd think. I've been chasing my tail with a
premature rear lockup issue on my '55 Stude for a while now; I've had
the rear brake drums off a couple times and can see nothing wrong other
than that the rear shoes haven't even worn in yet. Now I have the old
tires from my Porsche on the front and some BFG T/As of unknown history
on the rear (they came with the wheels.) The tires have lots of tread
left and don't appear to be weather checked or cracked at all and yet I
am getting rear lockup at something that my ass-ometer guesstimates at
about 0.15-0.2G. (it's not as handwavy as you think; I do have some
experience doing brake tests in instrumented vehicles so I have some
vague idea of what various decels feel like, although it's been a while
since I've been in an instrumented vehicle.) I cannot 100% confirm
this without trying a new pair of tires on the rear, but I suspect that
the fault is wholly with the tires as I have rebuilt all the wheel
cylinders, replaced shoes front and rear, cleaned, inspected, and lubed
where appropriate all hardware, replaced all hoses as well as the rear
axle hard line, and replaced the master cylinder. If I had all four
tires with a similar coefficient of friction it's entirely possible
that I could slide for 500 feet without achieving "excessive" speed.
Now you might express doubts about the sanity of someone who would
knowingly drive for any appreciable distance on tires like that (it
would be difficult to do so for any length of time without being aware
of the situation) and you'd be quite right to do so, but I'd be willing
to bet that there are people out there that do such things...
nate
(and I have to buy NEW TIRES TOO? make it stop! pun not intended...)
N8N
gpsman wrote:
> Alex Rodriguez wrote:
> > In article <1139855418.4...@g14g2000cwa.googlegroups.com>,
> > gps...@driversmail.com says...
> >
> > >WOW!!! Sounds remarkable, don't it?
> > >
> > >According to a chart from Edmunds at Autotrader.com... about 90 mph
> > >ought to cover it. Some people ought to think about that before citing
> > >85 mph as a "perfectly safe" velocity.
> >
> > What does one have to do with the other? You have the case of an idiot driving
> > to fast for conditions and losing control of their vehicle. There are many
> > roads where the conditions will allow you to safely drive 85mph, and faster.
> > The important part is being able to recognize when the conditions allow the
> > higher speeds.
> -----
> What does one have to do with the other?!
>
> You don't know? It isn't o b v i o u s?
>
> First of all, the "idiot" who lost control... may have run over a small
> object that caused a catastrophic tire failure. You don't know... do
> you?
Obviously you don't have the experience necessary to make such
statements, as it would take more than a tire failure to cause complete
loss of control at 85ish. I've actually had a rear tire go down on me
at >80 MPH and it was a total non-event. Unless there was an
explosion, tread separation resulting in a "gator" or similar... not a
problem.
nate
gpsman
> gpsman wrote:
> > First of all, the "idiot" who lost control... may have run over a small
> > object that caused a catastrophic tire failure. You don't know... do
> > you?
>
> Obviously you don't have the experience necessary to make such
> statements, as it would take more than a tire failure to cause complete
> loss of control at 85ish. I've actually had a rear tire go down on me
> at >80 MPH and it was a total non-event. Unless there was an
> explosion, tread separation resulting in a "gator" or similar... not a
> problem.
-----
What is it about r.a.d. that seems to make posters "go stupid"? What a
fuckin' moron.
If I understand you correctly... a - *** C A T A S T R O P H I C ***-
tire failure is equitable to a tire gradually "going down"? A tire
failure at speed -can not- lead to a crash... because it didn't in
-your- experience?
You... obviously lack not only the experience but the common sense to
deduce that all tire failures, even one as identical as possible to
your own, will likely not lead to an identical result.
This is yet another indication that high-speed driving is probably not
best for you or your fellow motorists.
-----
- gpsman
N8N
Before you use words like "stupid" you ought to think about what you're
writing. What are the odds of a well maintained vehicle with an aware
owner having any kind of tire failure other than a simple flat? Tread
separations, violent explosions, etc. are all preceded by the
appearance of sidewall bubbles, weird pulls/wobbles,
over/underinflation, overloading, etc... nails, sidewall cuts due to
road debris, etc. generally result in simply the tire going flat, not
the "catastrophic failure" you describe. The odds of a tire failure
being anything other than a simple flat are vanishingly small.
nate
gpsman
The odds are not the question. The question was: YOU don't know if the
pickup experienced a catastrophic tire failure or not... yet you felt
justified in referring to that driver as an "idiot", IIRC. The
question is: Do you jump to conclusions with insufficient evidence? I
think you've reinforced that that premise is true.
Here, you've done it again. Sometimes there's clues, sometimes there's
not. Perhaps the subtle visual clues might become evident while "in
motion"?
Catastrophic tire failures occur E V E R Y D A Y ! That's the source
of maybe half of the gators you see on the road. Go to any sizeable
trucking company and wander on around to the tire dept. for
enlightenment if you find -those- visual clues insufficient. In the
meantime, follow trucks as closely as possible... and stop jacking me
off here.
-----
- gpsman
Motorhead Lawyer
>
> I've been chasing my tail with a
> premature rear lockup issue on my '55 Stude for a while now; I've had
> the rear brake drums off a couple times and can see nothing wrong other
> than that the rear shoes haven't even worn in yet. Now I have the old
> tires from my Porsche on the front and some BFG T/As of unknown history
> on the rear (they came with the wheels.) The tires have lots of tread
> left and don't appear to be weather checked or cracked at all and yet I
> am getting rear lockup at something that my ass-ometer guesstimates at
> about 0.15-0.2G.
Why don't you swap 'em front-to-rear, m'friend? That'll tell you
instantly if it's the tires. IME, old T/As can get as hard as rocks
after a few years. Hate to see your Stude goin' backwards without
bein' in reverse ...
--
C.R.
N8N
That's a good question, and I actually have an answer for that. The
rear tires are 245/60s and I am not sure if they would actually fit on
the front without hitting the tie rod ends, upper trunnions, or other
important suspension bits. I've got 215/60s up front right now and I
added a 1/4" spacer behind the wheels so that I could maintain a
finger's width between the sidewalls and tie rod ends.
I may just try that this weekend if I get a chance though, although I
don't know that I'd feel comfortable going fast enough to give it a
real test with the tires like that.
Yes, I know, 245s are ludicrous overkill for a 289/automatic. The
price was right, they came on good MoPar "cop car" wheels and they look
freakin' cool. If I buy new tires I will probably get 215/65 or 215/70
for the front and maybe a 235/60 for the rear to make the car a little
more balanced, rubber-wise.
nate
Motorhead Lawyer
> >
> > The traction limit is the same in any direction.
>
> And on a skid pad, the sum of forces isn't purely lateral due to the
> force needed to overcome drag increasing when cornering. Hence, lateral
> acceleration is lower on the skid pad than it would be in a straight
> line.
<Heavy sigh> You seem to have all the tools but don't seem to know
whether to use a wrench or a screwdriver. Does not the concept
'sliding friction is *lower* than static friction' mean anything to
you?
> And the limit *isn't* the same in every direction. Tire carcasses deform
> under lateral forces in a way that reduces their traction limit compared
> to fore and aft forces.
With a poor suspension, yes. With a good suspension, no. With a
suspension like a truck's and with sidewalls like a truck's and
*sliding*, no. Again, with less friction (sliding), there will be less
deflection.
> I didn't do the calculation to prove that the pickup was doing 179 mph.
> I did it to show that the story was probably *wrong*.
While I am not the only one to point out that, using realistic
assumptions about the possible speed of the truck as well as realistic
assumptions about the traction conditions, it could be perfectly
plausible. Why that bothers you so much I fail to understand.
N8N
I didn't call the guy an idiot; perhaps you should review the thread.
I was merely disagreeing with your premise that the possibility of a
catastrophic tire failure automatically caused a speed of 85 MPH to be
de facto unsafe.
> Here, you've done it again. Sometimes there's clues, sometimes there's
> not. Perhaps the subtle visual clues might become evident while "in
> motion"?
>
That's entirely possible; however it's unlikely that a sidewall bubble
would not be present before you started a journey and that you wouldn't
run out of gas before there was any danger of a catastrophic failure.
You'd probably also remember running over that big piece of angle iron
or whatever or feel that new vibration or squirm and remember to check
your tires at the next gas stop.
> Catastrophic tire failures occur E V E R Y D A Y ! That's the source
> of maybe half of the gators you see on the road. Go to any sizeable
> trucking company and wander on around to the tire dept. for
> enlightenment if you find -those- visual clues insufficient. In the
> meantime, follow trucks as closely as possible... and stop jacking me
> off here.
There's a reason that truckers don't use retreads on steering axles...
retreads are pretty good at throwing gators, as opposed to tires that
were molded together at the factory. The consequences of a retread
throwing a gator on a non-steering axle of a big rig are a lot less
severe than on a passenger car... at least for the big rig. Certainly
not "catastrophic."
nate
Alex Rodriguez
gps...@driversmail.com says...
>Alex Rodriguez wrote:
>> In article <1139855418.4...@g14g2000cwa.googlegroups.com>,
>> gps...@driversmail.com says...
>> >WOW!!! Sounds remarkable, don't it?
>> >According to a chart from Edmunds at Autotrader.com... about 90 mph
>> >ought to cover it. Some people ought to think about that before citing
>> >85 mph as a "perfectly safe" velocity.
>> What does one have to do with the other? You have the case of an idiot
>>driving
>> to fast for conditions and losing control of their vehicle. There are many
>> roads where the conditions will allow you to safely drive 85mph, and faster.
>> The important part is being able to recognize when the conditions allow the
>> higher speeds.
>-----
>What does one have to do with the other?!
>
>You don't know? It isn't o b v i o u s?
>
>First of all, the "idiot" who lost control... may have run over a small
>object that caused a catastrophic tire failure. You don't know... do
>you?
Small objects don't cause catastrophic tire failures.
>Making judgements with such scant facts indicates you are probably a
>very fast thinker... but the conclusions to which you you arrive are
>likely to be incorrect and therefore you would probably not be the best
>candidate for 85+ mph driving.
I'm not the brightest, but my little brain hasn't failed me yet when driving
at 85+. The more I practice, the better I get.
>The problem w/85+ mph is it reduces the allowable margin of driver
>error and increases the potential for injury and collateral damage.
You take actions to give you a bigger margin of error at the higher speeds.
You allow more follow distance and you pass other cars carefully. Easily
done. A little practice is all it takes.
>The problem w/being able to "recognize what conditions allow for higher
>speeds" is that the conditions on public highways are uncontrolled for
>the most part and a very small piece of road debris can constitute an
>abrupt change of conditions. A 12 inch piece of tailpipe for example,
>or a discarded 6 oz. Coke bottle.
Both items you describe can be spotted during the daytime. You should be
able to go around the items and completely avoid them. It is more important
to plan on avoiding a crash than planning on what to do when you do crash.
>I... have been sideways at 85-100+ mph... and I'm here to tell the
>overconfident you that your velocity will suddenly appear to quadruple
>when you're calculating steering corrections via the view out your side
>window while struggling to not inhale your seat through your ass. And
>ironically, it will all appear to happen silently and in slow motion.
>The application of braking at that point will not be a wise option...
>and just lifting off the throttle could throw the vehicle further out
>of control.
I've never had the pleasure at those speeds. I've been sideways at 60. Scary
yes, but I didn't panick. I tried to correct the slide, but my correctinos
didn't work on the diesel fuel covered road.
>No velocity is inherently dangerous... or safe.
Agreed.
>People are killed on
>the road at many velocites, including zero. The other idjit here who
>feels driving 85 mph is made more safe by being surrounded by traffic
>of the same velocity... is just that, an idjit. It's not safe on the
>racetrack and it certainly isn't safe on a public road.
I prefer to not be surrounded by any vehicles. I figure if there are no
vehicles around me, I don't have to worry about them, and if I do something
bad, I don't have to worry about hitting someone else. I make a concious
effort to keep a decent distance between me and other cars. This can't always
be done, but at those times speeds are lower than 85mph.
-------------
Alex
Alex Rodriguez
gps...@driversmail.com says...
><q> The relationship between vehicle speed and crash severity is
>unequivocal and based on the laws of physics. The kinetic energy of a
>moving vehicle is a function of its mass and velocity squared
>Kinetic energy is dissipated in a collision by friction, heat, and the
>deformation of mass. Generally, the more kinetic energy to be
>dissipated in a collision, the greater the potential for injury to
>vehicle occupants.
>Because kinetic energy is determined by the square of the vehicle's
>speed, rather than by speed alone, the probability of injury, and the
>severity of injuries that occur in a crash, increase exponentially with
>vehicle speed. For example, a 30-percent increase in speed (e.g., from
>50 to 65 mi/h [80 to 105 km/h]) results in a 69-percent increase in the
>kinetic energy of a vehicle. </q>
No argument there. The secret is that you need to avoid crashing. If you
spend more time trying to figure out what to do when you crash instead of
spending time trying to avoid the crash in thre first place, you probably will
crash.
-------------
Alex
Alan Baker
"Motorhead Lawyer" <88.5...@gmail.com> wrote:
> Alan Baker wrote:
> > >
> > > The traction limit is the same in any direction.
> >
> > And on a skid pad, the sum of forces isn't purely lateral due to the
> > force needed to overcome drag increasing when cornering. Hence, lateral
> > acceleration is lower on the skid pad than it would be in a straight
> > line.
>
> <Heavy sigh> You seem to have all the tools but don't seem to know
> whether to use a wrench or a screwdriver. Does not the concept
> 'sliding friction is *lower* than static friction' mean anything to
> you?
Yes. But not by that much.
>
> > And the limit *isn't* the same in every direction. Tire carcasses deform
> > under lateral forces in a way that reduces their traction limit compared
> > to fore and aft forces.
>
> With a poor suspension, yes. With a good suspension, no. With a
> suspension like a truck's and with sidewalls like a truck's and
> *sliding*, no. Again, with less friction (sliding), there will be less
> deflection.
With *every* practical suspension, yes.
>
> > I didn't do the calculation to prove that the pickup was doing 179 mph.
> > I did it to show that the story was probably *wrong*.
>
> While I am not the only one to point out that, using realistic
> assumptions about the possible speed of the truck as well as realistic
> assumptions about the traction conditions, it could be perfectly
> plausible. Why that bothers you so much I fail to understand.
It didn't bother me that much -- at least not what you assumed bothered
me. What bothered me was your instant assumption that I was in the wrong
ballpark when I was clearly in the right one.
Matthew Russotto
Motorhead Lawyer <88.5...@gmail.com> wrote:
>
>Why don't you swap 'em front-to-rear, m'friend? That'll tell you
>instantly if it's the tires. IME, old T/As can get as hard as rocks
>after a few years.
Definitely. Just replaced some on my Miata. Still had tread left;
probably could drive another 10 years without losing any more tread.
gpsman
> gpsman wrote:
> > The odds are not the question. The question was: YOU don't know if the
> > pickup experienced a catastrophic tire failure or not... yet you felt
> > justified in referring to that driver as an "idiot", IIRC. The
> > question is: Do you jump to conclusions with insufficient evidence? I
> > think you've reinforced that that premise is true.
> I didn't call the guy an idiot; perhaps you should review the thread.
> I was merely disagreeing with your premise that the possibility of a
> catastrophic tire failure automatically caused a speed of 85 MPH to be
> de facto unsafe.
FUCK! You're right, you didn't call him an idiot. No, you called me
an... No, wait... I called you an idiot... Well, it's obvious I
disagree w/you about something... whatever it was. Apologies for the
mix up and that particular "idiot"... (but not much else).
No (easily attainable) velocity is inherently dangerous... or safe.
Anybody who feels 25 mph is "safe" needs to re-think the issue or try
this simple test:
Drive through a parking lot at 5 mph with your sweetie. Without
warning, slam on the brakes as hard as you can. Ask them if it felt
"safe". If you've got the balls... ask if it's ok if you make it a
habit. If you've got real balls tell them you like that sort of thing
when you're the passenger, especially without a seatbelt, the faster
the better.
If you lack a sweetie, stand in the center of your living room,
blindfolded, and spin in place for 10 seconds. Then begin a brisk
walk. And step out, like you're late for something important.
Alternatively, just stand in place and fall backward.
Then... get back to me about what you feel are "safe" velocities.
-----
- gpsman
Alan Baker
"gpsman" <gps...@driversmail.com> wrote:
Once again, you demonstrate so well that you lack the basic
understanding of how safety while driving is achieved.
richa...@usa.com
Ok y'all that should tell you what top speeds are like for pickup
trucks today.
That one was driven was by a NASCAR driver.
Not some damn drunk idiot.
And for cars, that record is held by Mclaren at 240+.
As for the original question, keep in mind that it is still possible
for power to be applied even while in a skid.
Being drunk, the driver probably never let his foot off the pedal until
he hit the tree.
SD Dave
Also keep in mind as far as the original story, it was a news article
repeating what was probably just an officer or writer's estimation. I
bet the real distance wasn't over 500 feet, but under 400, or under
300 even.
Many people aren't good at estimating distances.
Dave
N8N
Matthew Russotto wrote:
> In article <1140118728.1...@g14g2000cwa.googlegroups.com>,
> Motorhead Lawyer <88.5...@gmail.com> wrote:
> >
> >Why don't you swap 'em front-to-rear, m'friend? That'll tell you
> >instantly if it's the tires. IME, old T/As can get as hard as rocks
> >after a few years.
>
> Definitely. Just replaced some on my Miata. Still had tread left;
> probably could drive another 10 years without losing any more tread.
Well, I didn't have a chance to drive the car again this weekend as it
spent the weekend up on the lift having a fuel line replaced (old one
was crimped almost shut) but I am pretty sure that it is the tires; I
mean, there's no prop valve or anything in this system and in fact it
uses a single master cylinder so I can't see what would cause a
front/rear imbalance.
So, let's just ASSume for the sake of argument that I need new tires.
Can anyone recommend a tire for a lightly-driven, fair-weather car that
provides decent handling but doesn't turn into a rock after a couple
years? Sizes as mentioned before will be probably 215/65 or 215/70
front, 235/60 rear, all on 15x7" rims.
nate
Motorhead Lawyer
>
> So, let's just ASSume for the sake of argument that I need new tires.
> Can anyone recommend a tire for a lightly-driven, fair-weather car that
> provides decent handling but doesn't turn into a rock after a couple
> years?
Nope. You run into exactly the same conundrum as asking for the 'best'
all-around tire. There isn't one. What makes a tire 'sticky' is
having a slightly less-cured tread compound. Unfortunately, these tend
either heat-cure or oxygen-degrade (or both) to harden up within 5
years. The stickier they are, the faster it happens. The tires that
start out 'rock-hard' (70,000-mile guarantees, etc.) remain rock-hard
almost indefinitely. It's a no-win situation.
--
C.R. Krieger
(Been there; drove those)
N8N
I figured that would be the general answer; I guess I just wanted to
know if there were any tires that were particularly bad or particularly
good in that respect.
If I do get new tires, the ones that immediately spring to mind are:
-another set of T/As
-Eagle ST or whatever the current version is
-Firestone Indy 500
those seem to be the big-name "sporty" tires that are still available
in non-rubber-band profiles (I think going to 16s or 17s would probably
be a waste with early 50's suspension geometry...)
comments? anything else I should be looking at? or just pick the
cheapest of those three?
nate
Motorhead Lawyer
>
> If I do get new tires, the ones that immediately spring to mind are:
>
> -another set of T/As
> -Eagle ST or whatever the current version is
> -Firestone Indy 500
>
> those seem to be the big-name "sporty" tires that are still available
> in non-rubber-band profiles (I think going to 16s or 17s would probably
> be a waste with early 50's suspension geometry...)
>
> comments? anything else I should be looking at? or just pick the
> cheapest of those three?
Call the guys at Tire Rack. Hit the website at www.tirerack.com and
see what's there (including your possible candidates above) and then
discuss it with someone on the phone. They're not just 'order-takers'.
They'll listen and try to help you find the ideal tire for your
purposes. And they'll do it as cheaply as anyone.
--
C.R. Krieger
(Been there; bought that)
todd_...@performancesimulations.com
>
> If we assume 1 g deceleration -- a very generous estimate:
>
> a = 32 ft/s^2
>
> d = 500
>
> v = ?
>
>
> Using the forumla v(final)^2 = v(initial)^2 + 2ad, and remembering the
> final velocity in this case is 0.
>
> 0 = v^2 + 2 *(32) * 500
>
> v = (32000)^(1/2) = 179 mph.
>
> So if deceleration equalled 1 g, the truck would have had to be going
> 179 mph to slide for 500 feet. Even at 0.75 g, the truck would still
> have had to be going 155 mph.
>
Just a late, quick correction here. I think that would really be 179
ft/sec, not mph? In that case at 1g you're looking at 122mph rather
than 179mph. 0.75g would put you at 105mph. I haven't seen any tire
data that ran as low as 0.75mu, even for a locked tire. More than
likely 0.85 would be a touch more reasonable, but in reality it's
probably somewhere in between.
0.85g would put you at 112-113mph to stop to 0 in 500 feet. What
really happened depends a lot on how the skid marks really looked.
Chances are if the guy was drunk and spun the truck or got it sideways
(I didn't read the article), the skidmarks started at a slip angle of
maybe 15-20 degrees or so, which does not equate to a very large
deceleration at all during that period (only around .25g). You'd only
be decelerating in the direction opposite travel at 0.85g for the
period of time where the truck was either sideways or all four wheels
were locked. For all times at any other slip angle the deceleration
would be lower.
If one assumed he went from 20 degrees to 90 degrees slip nice and
steady over the entire spin period before hitting the tree, the average
deceleration in the direction of the road would drop from 0.85g to
about 0.6g, putting the speed at about 95mph. If he spun past 90
degrees slip angle the speed could have been even lower than that.
Todd Wasson
http://www.PerformanceSimulations.com
todd_...@performancesimulations.com
Motorhead Lawyer wrote:
Does not the concept
> 'sliding friction is *lower* than static friction' mean anything to
> you?
>
Actually when it comes to tires this isn't true except in the case of a
locked tire after the contact patch has been frying for a brief period
of time. With rubber or viscoelastic materials there's really no such
thing as sliding vs. static friction. It's all a function of sliding
velocity, and it actually increases with that up to a point in all
rubbers. Your statement is correct though for most other materials.
> > And the limit *isn't* the same in every direction. Tire carcasses deform
> > under lateral forces in a way that reduces their traction limit compared
> > to fore and aft forces.
>
> With a poor suspension, yes. With a good suspension, no. With a
> suspension like a truck's and with sidewalls like a truck's and
> *sliding*, no. Again, with less friction (sliding), there will be less
> deflection.
>
Not necessarily... Most tires indeed produce a bit more force in one
direction than the other on a tire testing machine where camber is
controlled (which eliminates "good suspension" effects). That's a bit
irrelevant to the analysis though given the lack of information on the
event.
Todd Wasson
http://www.PerformanceSimulations.com
gpsman
I wonder about the effect weight distribution would have on braking in
a skid (spin).
A P/U traveling backward would have weight shift(ing) in that direction
but be unweighting the heavier front end to some extent.
The origial report stated: The pickup slid "sideways" for 500 feet. To
me, that seems highly unlikely by itself, ends are highly likely to
swap at least 180 degrees in my experience. Not to say that it
couldn't happen... but I'd certainly decline to be the test driver for
that manuever under the most controlled conditions.
BTW, nice site.
-----
- gpsman
SD Dave
wrote:
>... but I'd certainly decline to be the test driver for
>that manuever under the most controlled conditions.
My ranger skidded to about 60 degrees off center when the ABS failed
completely, from about 55 mph. I unfortunately don't have the
distance that I slid, since the police refused to investigate, fill
out an accident report, or do anything else useful.
But yeah, buting a crash test dummy in that situation really blows. I
still feel it in my back every morning.
Dave
todd_...@performancesimulations.com
gpsman wrote:
> todd_...@performancesimulations.com wrote:
<snip>
> >
> > If one assumed he went from 20 degrees to 90 degrees slip nice and
> > steady over the entire spin period before hitting the tree, the average
> > deceleration in the direction of the road would drop from 0.85g to
> > about 0.6g, putting the speed at about 95mph. If he spun past 90
> > degrees slip angle the speed could have been even lower than that.
> -----
> I wonder about the effect weight distribution would have on braking in
> a skid (spin).
>
> A P/U traveling backward would have weight shift(ing) in that direction
> but be unweighting the heavier front end to some extent.
>
The weight distribution effect in the context of this thread is to
lower the effective friction coefficient at the highly loaded tires and
increase it at the lightly loaded ones. This gives a net drop in
friction coefficient, which really just means the 0.85g becomes
something a little lower, like 0.8g. (This change in effective
friction coefficient is called tire load sensitivity, a funny
characteristic of rubber that most other materials don't really
exhibit).
Basically what you have is a situation where at any slip angle over a
certain point, the force the tires make is more or less constant
overall. So depending on the particular tire and loadings involved, if
you're running above 10-20 degrees or so sliding angle you're making as
much force as you're going to get. I.e., you'll be "accelerating"
(decelerating) as quickly as you're going to. If you have a lot of
weight transfer occuring than that acceleration is a little bit lower.
Still though, if it was running sideways as you described then it's
actually likely to be pulling a higher deceleration than you get on the
skidpad. Most cars on the skidpad are in a stable trim situation with
some excess grip at the rear. Once you kick the vehicle sideways you
have more force at the rear than you'd have on the skidpad, so the
lateral acceleration climbs up and you get a yaw torque on the vehicle
that generally (on a road car, not sure about a pick up) would tend to
straighten the car out.
> The origial report stated: The pickup slid "sideways" for 500 feet. To
> me, that seems highly unlikely by itself, ends are highly likely to
> swap at least 180 degrees in my experience. Not to say that it
> couldn't happen... but I'd certainly decline to be the test driver for
> that manuever under the most controlled conditions.
>
Yeah, I agree. It's probably pretty unlikely it just yawed sideways
and stayed like that for that distance. It probably spun around or at
least went backwards for awhile. Point being that if any of that
happened it reduces the speed that the truck needed to be going to skid
500 feet.
I was involved (as a dumb teenager) in an incident at well over 100mph
on a freeway where a friend of mine lost control of his '71 Firebird
after avoiding a couple of other nuts that we were <cough> racing at
the time. We spun around three full times and wound up smack in the
middle of the freeway facing the right direction (there was no traffic
within a mile or so of us aside from those other two, one of which had
cut us off, somewhat leading to our piroutte.). We laughed it off
later, but in hindsight we could have easily been killed. I wouldn't
be surprised to find we went well over 500 feet during that little
maneuver. That's about 150 feet per second at the start and we were
spinning for a long time...
> BTW, nice site.
> -----
>
Thanks :-)
> - gpsman
todd_...@performancesimulations.com
SD Dave
wrote:
I was hit by a 60-something year old woman who tried passing on the
right when she saw my brake lights come on. She was 15+ over the
speed limit, hit me while I was trying to get to the right shoulder,
and repeatedly stated, "I'm so sorry I didn't try to stop, I feel just
terrible" but I was at fault.
My photos were worthless, since CA courts apparently don't take
digital photos. No CHP officer who watched me take these photos told
me so, in fact, they encouraged me to take more photos.
Her statements didn't matter since she made them under stress. The
several CHP and San Diego Officers who showed up could direct traffic,
but not fill out, sign, or affirm any paperwork regarding the case.
They heard nothing, they saw nothings, they just waved people around
us.
My truck was beyond totalled (basically shaped like a big white
banana), and I only had liability, and the lawyer I tried got nothing
useful done. I couldn't afford another at that point. My insurance
company was nice, but hinted that I'd need my own lawyer to go after
her. They agreed to pay for reasons related to "it's cheaper to pay
than fight it."
Yeah, fuck insurance, fuck the police, fuck lawyers, to be honest. The
20-something gets screwed, and gets the bonus of back problems that
have now lasted a few years and don't seem to be going anywhere. I got
$0 for those. -$(5000) if you want to add up my financial losses
directly from the accident. How much more from having an "At Fault
(Not At Fault)" accident on my record?
Any bets on my feelings about retesting all drivers? Older ones need
it, yeah, but so do younger ones I'd say.
This whole thread makes me wonder how much of the story we've heard. I
may have slid 500 feet, counting the distance her impact accelerated
me. A newspaper may have reported this as 1000 feet. I sure as fuck
didn't slide nearly .2 miles.
For the cause:
Evans Tires "fixed" my brakes. Evans Tires fucked up my ABS system,
and delayed letting me take it in to get checked out since I'd already
paid in full for the faulty repairs. Evans Tires delayed even though
I needed to drive daily to my various clients, and tried to explain
this. "It won't be a problem, it's just a sensor that's not right,"
is what they told me.
Evans Tires denied any fault at all in my ABS failing, even though
they'd replaced "everything connected to your brakes" (what I was told
the work they were doing was when I paid for it), and even though I
complained that something wasn't right within a few days (I think 2)
of the initial repairs.
Afterwards Evans Tires denied they had done anything wrong, and since
by then I couldn't afford to properly sue, Evans Tires told me (off
the record, the employee said) to "Go Fuck Myself."
So, fuck Evans Tires also. Off the record.
Dave (I'm Over It, but Fuck Evans Tires) Hogan
N8N
It's not the tires. I discovered two things this weekend: 1) you
really can fit 245/60s on the front of a Studebaker C-K body without
any rubbing, and they actually look pretty cool, in an insane,
over-the-top way. Steering is somewhat less responsive than usual
however. 2) The Yokohama AVS ES100s that I had on the front of the car
smell worse than the BFGs when you lock 'em up, but other than that
there's no perceptible difference.
So I guess I have a brake problem, not a tire problem... which is odd,
because I don't think I cut any corners on the brakes on this car...
it's gotta be something stupid that I'm missing...
nate
(at least I don't have to buy new tires this month)
todd_...@performancesimulations.com
SD Dave wrote:
> On 27 Feb 2006 22:20:26 -0800, todd_...@performancesimulations.com
> wrote:
>
> >
> >SD Dave wrote:
> >> On 27 Feb 2006 20:36:28 -0800, "gpsman" <gps...@driversmail.com>
> >> wrote:
> >>
> >> >... but I'd certainly decline to be the test driver for
> >> >that manuever under the most controlled conditions.
> >>
> >> My ranger skidded to about 60 degrees off center when the ABS failed
> >> completely, from about 55 mph. I unfortunately don't have the
> >> distance that I slid, since the police refused to investigate, fill
> >> out an accident report, or do anything else useful.
> >>
> >> But yeah, buting a crash test dummy in that situation really blows. I
> >> still feel it in my back every morning.
> >>
> >> Dave
> >
> >Lucky. I take it you hit something?
> >
> >Todd Wasson
> >http://www.performancesimulations.com
>
> I was hit by a 60-something year old woman who tried passing on the
> right when she saw my brake lights come on. She was 15+ over the
> speed limit, hit me while I was trying to get to the right shoulder,
> and repeatedly stated, "I'm so sorry I didn't try to stop, I feel just
> terrible" but I was at fault.
Ouch...