Can acceleration be >1g?
Vlad Kozlovsky
Here is an innocent question: can acceleration (positive or negative) of
an automobile be greater than 1g? It makes sense to me that it can NOT.
So, by doing a few very simple calculation one can arrive at the lowest
possible 0 to 60 mph time for ANY vehicle (using its wheels as the only
source of propultion), no matter how powerful and light it is. The
number I got is 2.721 seconds. This number must be wrong, since there
are lower 0 to 62 mph (0 to 100 kph) times recorded in the Guiness book
of records.
So, am I not thinking clearly tonight, or do you agree that the maximum
acceleration must be 1g or less? Or maybe my 0 to 60 time calculation is
wrong, even given that the first assumption is right?
Vlad.
Ron Katona
Vlad Kozlovsky wrote:
>
> Here is an innocent question: can acceleration (positive or negative) of
> an automobile be greater than 1g? It makes sense to me that it can NOT.
I would guess that most race cars exceed 1g in all directions. Even
without downforce (slow speed corners), I've read that Indy and F1 cars
reach 1.5g laterally.
> So, by doing a few very simple calculation one can arrive at the lowest
> possible 0 to 60 mph time for ANY vehicle (using its wheels as the only
> source of propultion), no matter how powerful and light it is. The
> number I got is 2.721 seconds. This number must be wrong, since there
> are lower 0 to 62 mph (0 to 100 kph) times recorded in the Guiness book
> of records.
I agree that your number must be wrong. A top fuel dragster hits 60 mph
in .8 seconds according to Road & Track. That's about 5g.
>
> So, am I not thinking clearly tonight, or do you agree that the maximum
> acceleration must be 1g or less? Or maybe my 0 to 60 time calculation is
> wrong, even given that the first assumption is right?
>
> Vlad.
I think your calculation is correct, but the premise is wrong. Why would
there be a limit at 1g?
--
Ron Katona ro...@cris.com
88 Mustang LX 5.0
97 BMW 318ti
Dick Brewster
The Mike Scanlan of time...@laraby.tiac.net fame so eloquently
said...
> Vlad Kozlovsky <v...@p3.net> writes:
>
> >Here is an innocent question: can acceleration (positive or negative) of
> >an automobile be greater than 1g? It makes sense to me that it can NOT.
> >So, by doing a few very simple calculation one can arrive at the lowest
> >possible 0 to 60 mph time for ANY vehicle (using its wheels as the only
> >source of propultion), no matter how powerful and light it is. The
> >number I got is 2.721 seconds. This number must be wrong, since there
> >are lower 0 to 62 mph (0 to 100 kph) times recorded in the Guiness book
> >of records.
>
> You're incorrect on this one. A car can accelerate at more than 1g.
> However, it cannot corner at more than 1g...
It's a good thing that F1, Indy and a whole bunch of other cars
don't know this, or they would run off of every corner on the track.
--
Dick Brewster dbrewste@
ix.netcom.com
Suzuki GSF1200S Honda CB700SC
Larry Macleod
Vlad Kozlovsky wrote:
> Here is an innocent question: can acceleration (positive or negative) of
> an automobile be greater than 1g? It makes sense to me that it can NOT.
> So, by doing a few very simple calculation one can arrive at the lowest
> possible 0 to 60 mph time for ANY vehicle (using its wheels as the only
> source of propultion), no matter how powerful and light it is. The
> number I got is 2.721 seconds.
Yes it can be greater than one. In a virtual physics envirnment where
friction is often neglected, then, acceleration could not be greater
than 1. But with friction with the road, and downforce from airflow
across the car, the maximum g-load is significantly increased.
--
Larry Macleod
remove spam from the reply address
Chuck Tomlinson
Vlad Kozlovsky <v...@p3.net> wrote:
>Here is an innocent question: can acceleration (positive or negative) of
>an automobile be greater than 1g? It makes sense to me that it can NOT.
That is not correct. A car's acceleration can exceed 1.0g in any
horizontal direction without aerodynamic assistance.
>So, am I not thinking clearly tonight, or do you agree that the maximum
>acceleration must be 1g or less? Or maybe my 0 to 60 time calculation is
>wrong, even given that the first assumption is right?
If a car (or any other vehicle) can generate more traction force
than its weight (without flipping over), it can accelerate at more
than 1.0g.
In the case of AWD: if the car can bring all of its tires to peak
traction at the same time (at low speeds) *and* the coefficient of
friction between tires and road is greater than 1.0, then the car
can accelerate at more than 1.0g. This is easy enough to prove
mathematically... maybe later :-)
If you check any road test of the new 911 Turbo (C/D 6/95, R&T 7/95,
MT 6/95, and MT 11/96), you'll notice a 0-30 time of 1.3 sec.
That's an average acceleration of 1.05g.
I'll jump the gun a bit on the motorcycle crew: any number of
unmodified street bikes can exceed 1.0g accel.
--
__
___| |____ Chuck Tomlinson <toml...@ix.netcom.com>
/___LT-1___/ Mouse Power!
|__| '94 Vette Z07/ZF6, '89 Mustang LX5.0L/T5
Greg Martin
On Tue, 25 Feb 1997 22:54:20 -0500, Vlad Kozlovsky <v...@p3.net> wrote:
>Here is an innocent question: can acceleration (positive or negative) of
>an automobile be greater than 1g? It makes sense to me that it can NOT.
>So, by doing a few very simple calculation one can arrive at the lowest
>possible 0 to 60 mph time for ANY vehicle (using its wheels as the only
>source of propultion), no matter how powerful and light it is. The
>number I got is 2.721 seconds. This number must be wrong, since there
>are lower 0 to 62 mph (0 to 100 kph) times recorded in the Guiness book
>of records.
>
>So, am I not thinking clearly tonight, or do you agree that the maximum
>acceleration must be 1g or less? Or maybe my 0 to 60 time calculation is
>wrong, even given that the first assumption is right?
>
>Vlad.
>
Maximum acceleration can, in fact, be more than 1g. 1g is just a
measurement: 9.81 m/s^2. If a car's average acceleration is greater
than 9.81 m/s^2 then it's accelerating at more than 1g. Acceleration
as a number really isn't dependent on gravity's affect; although
gravity will affect the acceleration of an object by increasing the
friction between the object and the ground.
I believe this is correct; if not please let me know.
Timothy Goddard (Hampshire RHS 97)
In a previous article, toml...@ix.netcom.com (Chuck Tomlinson) says:
>Vlad Kozlovsky <v...@p3.net> wrote:
>>Here is an innocent question: can acceleration (positive or negative) of
>>an automobile be greater than 1g? It makes sense to me that it can NOT.
>
>That is not correct. A car's acceleration can exceed 1.0g in any
>horizontal direction without aerodynamic assistance.
>
>>So, am I not thinking clearly tonight, or do you agree that the maximum
>>acceleration must be 1g or less? Or maybe my 0 to 60 time calculation is
>>wrong, even given that the first assumption is right?
>
>If a car (or any other vehicle) can generate more traction force
>than its weight (without flipping over), it can accelerate at more
>than 1.0g.
>
>In the case of AWD: if the car can bring all of its tires to peak
>traction at the same time (at low speeds) *and* the coefficient of
>friction between tires and road is greater than 1.0, then the car
>can accelerate at more than 1.0g. This is easy enough to prove
>mathematically... maybe later :-)
>
>If you check any road test of the new 911 Turbo (C/D 6/95, R&T 7/95,
>MT 6/95, and MT 11/96), you'll notice a 0-30 time of 1.3 sec.
>That's an average acceleration of 1.05g.
>
>I'll jump the gun a bit on the motorcycle crew: any number of
>unmodified street bikes can exceed 1.0g accel.
>
>--
> __
> ___| |____ Chuck Tomlinson <toml...@ix.netcom.com>
>/___LT-1___/ Mouse Power!
> |__| '94 Vette Z07/ZF6, '89 Mustang LX5.0L/T5
>
yes thats right and to prove it mathmatically is simple.
1g = 9.8 meters a second squared. thats the acceleration. and a= Vf/change
in time.
ok so Vf =30 mph or 44.0528 kph now to change that to meters =
44052.863meters hour, now to secs=12.236 ok thats Vf and the time was 1.3s
so 12.236/ 1.3s = 9.4 meters a sec squared. so thats 9.4/9.8= .96gs
wha thats not 1g. but yes a vehicle can accelerate past 1g like top fuelers
--
few are found and fewer are ever lost
they're true friends.- (maybe somebody said it, i think i made it up)
"With eyes soft as the moonlight, she makes my mind crazy like the crashing
waves of an exotic beach."
Mike Scanlan
Vlad Kozlovsky <v...@p3.net> writes:
>Here is an innocent question: can acceleration (positive or negative) of
>an automobile be greater than 1g? It makes sense to me that it can NOT.
>So, by doing a few very simple calculation one can arrive at the lowest
>possible 0 to 60 mph time for ANY vehicle (using its wheels as the only
>source of propultion), no matter how powerful and light it is. The
>number I got is 2.721 seconds. This number must be wrong, since there
>are lower 0 to 62 mph (0 to 100 kph) times recorded in the Guiness book
>of records.
You're incorrect on this one. A car can accelerate at more than 1g.
However, it cannot corner at more than 1g...
--
---- Mike Scanlan
\ / Weymouth, Mass
\/ "19 yrs old and livin life to the fullest"
Edward Kim
Mike Scanlan (time...@laraby.tiac.net) wrote:
: You're incorrect on this one. A car can accelerate at more than 1g.
: However, it cannot corner at more than 1g...
I believe that you can corner at greater than 1g. I've seen a test on a
911 Turbo and I think that that car pulled 1.01gs laterally. Or are you
meaning something else by the word "cornering?"
--
Edward Kim
Georgia Institute of Technology, Atlanta Georgia, 30332
uucp: ...!{decvax,hplabs,ncar,purdue,rutgers}!gatech!prism!
1996 Mustang GT White/Black interior 5-speed
3.55s, subframes, K&N w/o air intake silencer
Neil Weinstock
In article <MPG.d7eb8aa9...@nntp.netcruiser>,
Dick Brewster <no....@see.sig.below> wrote:
>The Mike Scanlan of time...@laraby.tiac.net fame so eloquently
>said...
>
>>
>> >Here is an innocent question: can acceleration (positive or negative) of
>> >an automobile be greater than 1g? It makes sense to me that it can NOT.
>> You're incorrect on this one. A car can accelerate at more than 1g.
>> However, it cannot corner at more than 1g...
>
>don't know this, or they would run off of every corner on the track.
<chuckle> Folks should check out the recent article on the Skidpad Challenge
that one of the car mags runs. A number of the vehicles pull *way* over 1G
on the skidpad; some are fairly entertaining contraptions I must say.
1G is coincidentally a difficult number for a typical street vehicle to
achieve (either laterally or straight-ahead) but it is by no means any sort
of theoretical limitation.
- Neil
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Neil Weinstock @ Ariel Corporation n...@ariel.com
Chuck Tomlinson
tgod...@k12.oit.umass.edu (Timothy Goddard (Hampshire RHS 97))
wrote:
>
>yes thats right and to prove it mathmatically is simple.
>1g = 9.8 meters a second squared. thats the acceleration. and a= Vf/change
>in time.
>ok so Vf =30 mph or 44.0528 kph now to change that to meters =
Nope. 1 mile is 1.609 km, so 30 mph is 48.27 kph. Looks like a
simple typo: you used 0.681 mi/km instead of 0.621 mi/km.
>44052.863meters hour, now to secs=12.236 ok thats Vf and the time was 1.3s
>so 12.236/ 1.3s = 9.4 meters a sec squared. so thats 9.4/9.8= .96gs
>wha thats not 1g. but yes a vehicle can accelerate past 1g like top fuelers
Apart from your conversion to kph, you're on the right track.
0-30 in 1.3 sec is 1.05g. Even if you use 1.349 sec (which would
round down to 1.3 sec), that's still more than 1.01g.
--
Chuck Tomlinson
Larry Carlson
I'm sure we could produce NEGATIVE Gs in excess of 1 by driving your car
head-on into my Freightliner.
Additionally, we should be able to produce high POSITIVE numbers with a
suitable explosive charge.
It seems to me that several high-performance cars are capable of near-1G
cornering forces, if not 1+G. It's mostly in the tires. Given suitably
sticky tires, >1G acceleration should be possible.
Or, am I not thinking clearly?
RMoburg
On 27 Feb 97 04:31:03 GMT, time...@laraby.tiac.net (Mike Scanlan)
wrote:
>
>You're incorrect on this one. A car can accelerate at more than 1g.
>However, it cannot corner at more than 1g...
>
>
>
OOPS! Want to try that again?
Brad Sloan
On Tue, 25 Feb 1997, Vlad Kozlovsky wrote:
> Here is an innocent question: can acceleration (positive or negative) of
> an automobile be greater than 1g? It makes sense to me that it can NOT.
> possible 0 to 60 mph time for ANY vehicle (using its wheels as the only
> source of propultion), no matter how powerful and light it is. The
> number I got is 2.721 seconds. This number must be wrong, since there
> are lower 0 to 62 mph (0 to 100 kph) times recorded in the Guiness book
> of records.
> acceleration must be 1g or less? Or maybe my 0 to 60 time calculation is
> wrong, even given that the first assumption is right?
I think it's outstanding that you've arrived at this conclusion
through what is apparently fairly independent thought. Your basic
premise is correct: cars are motivated by a traction force, and their
acceleration is therefore limited to the amount of tractive force
available. Your only mistake is in assuming that it is impossible to
achieve a coefficient of friction greater than 1. Some super-soft street
tires achieve this - you see them often at autocrosses (BF goodrich R1's,
Yokohama A008's, etc.), picking up bits of sand and assorted small matter
from the road and flinging them about - and most all race tires exceed Cf
of 1. Therefore, acceleration rates greater than 1g are not at all
impossible. The Porsche 911 Turbo, for one, averages about 1.05 g (if I
remember right) through the first 30 or so feet of its acceleration from
zero.
Brad Sloan
Clemson University
Clemson, SC
Brad Sloan
On 27 Feb 1997, Mike Scanlan wrote:
>
> You're incorrect on this one. A car can accelerate at more than 1g.
> However, it cannot corner at more than 1g...
>
Ouch. Sorry Mike, that's not correct at all. 1g is a good bit
easier to accomplish laterally than longitudinally. F1 has experienced
lateral accelerations of about 3g's w/downforce. Formual SAE cars
routinely get 1.4 without any aero affects at all.
Michele D'AMICO
> On Tue, 25 Feb 1997 22:54:20 -0500, Vlad Kozlovsky <v...@p3.net> wrote:
>
> >Here is an innocent question: can acceleration (positive or negative) of
> >Vlad.
Then Greg Martin wrote:
> Maximum acceleration can, in fact, be more than 1g. 1g is just a
> measurement: 9.81 m/s^2.
You are correct, Greg. Accelleration can, in principle, be greater that
1 g. In fact, in powerful sporting cars DECELERATION (i.e. braking) can be
(slightly) greater than 1 g. The problem is not the engine's power; the real
problem is how to tranfer all the torque to the wheels, without slipping.
> Acceleration
> as a number really isn't dependent on gravity's affect; although
> gravity will affect the acceleration of an object by increasing the
> friction between the object and the ground.
Yes, gravity will increase vertical weight (force) for a given mass, thus increasing
adhesion (hope the word makes sense in English !) to the ground.
This vertical force can also be obtained exploting aerodynamical circulation through
spoilers, like in F1; the _apparent_ weight of the car can then be much greater than
the one due to gravity only.
--
============================================================================
Mr. Michele D'AMICO (Assistant Professor) E-Mail: dam...@elet.polimi.it
Dipart. di Elettronica - Politecnico di Milano
Piazza L. Da Vinci, 32 - Milano 20133 ITALY
Tel. (+39) 2.2399.3613 - FAX (+39)2.2399.3413 -
- If you are really motivated, you can visit my WEB page at:
http://www.elet.polimi.it/people/damico
============================================================================
Bruce Augenstein
Vlad Kozlovsky wrote:
>
> Here is an innocent question: can acceleration (positive or negative) of
> an automobile be greater than 1g?
Easily. It's a matter of power (torque, actually), gearing and traction,
if one is addressing positive acceleration, and braking power and
available traction on deceleration. Aerodynamics can also play a part
(mostly on race cars) to drive cornering and braking forces well above
one G, but even some street cars can exceed one G in terms of cornering,
given sticky enough tires. A more or less typical high performance
street tire has a coefficient of friction somewhere in the 1.10 to 1.20
range, and race rubber is *way* above that.
The current magic number appears to be four (4). That is to say, the
highest performing race cars (in various categories) appear to be able
to generate about four Gs of cornering, braking and acceleration rates.
Formula 1 and Indycars generate these levels of high speed cornering and
braking limits largely because they have down-force generating
aerodynamic aids.
Top fuel dragsters will *average* over three Gs in a standing start
quarter mile (current best figures are 4.56 seconds and 318+ mph), but
will peak at over four Gs - largely due to hot, sticky tires on a hot
sticky track. They do a "burnout", spinning and heating the tires across
the starting line, then line up in the area they've just "prepared".
These cars also have approximately 100% of their weight on the
drivewheels during a run (the front tires touch down just often enough
to (mostly) retain directional control), and they also do some sort of
magical chassis dynamic thingie off the line that defies description
(and scientific analysis, I might add), but appears to screw the
drivewheels into the track.
Bruce
Vlad Kozlovsky
Yes, I agree with this completely. The most obvious contributor to
making >1g lateral acceleration possible is downforce, which becomes a
VERY significant factor at speed, especially with race cars. The other
significant force involved is centrifugal (sp?). All this is pure high
school physics...
Vlad.
Vlad Kozlovsky
Brad Sloan wrote:
> On Tue, 25 Feb 1997, Vlad Kozlovsky wrote:
> I think it's outstanding that you've arrived at this conclusion
> through what is apparently fairly independent thought. Your basic
Well, thank you :)
> premise is correct: cars are motivated by a traction force, and their
> acceleration is therefore limited to the amount of tractive force
> available. Your only mistake is in assuming that it is impossible to
> achieve a coefficient of friction greater than 1. Some super-soft street
Hmm.. I have a really hard time comprehending this concept. After all,
how can a tire be so sticky that it actually increases the rebound force
of the Earth's surface, acting opposite to the force of gravity? It may
get very close to it, but to actually increase it? How?
> tires achieve this - you see them often at autocrosses (BF goodrich R1's,
> Yokohama A008's, etc.), picking up bits of sand and assorted small matter
> from the road and flinging them about - and most all race tires exceed Cf
Is this how? Just using dirt and sand particles? But dirt and sand on
the track tend to actually reduce the coefficient of traction...
>> of 1. Therefore, acceleration rates greater than 1g are not at all
>> impossible. The Porsche 911 Turbo, for one, averages about 1.05 g (if I
>> remember right) through the first 30 or so feet of its acceleration from
>> zero.
This sound very impressive but how is it possible without additional
downforce? Is there something I am missing? Is there another force that
gets introduced into the system, other than the force of gravity and the
opposing force of rebound? It would REALLY be nice to actually
understand how this Newtonian system works. I heard there is a book
called "Physics of Racing," does anyone have access to it?
Vlad.
Anthony Potts
On Thu, 27 Feb 1997, RMoburg wrote:
> On 27 Feb 97 04:31:03 GMT, time...@laraby.tiac.net (Mike Scanlan)
> wrote:
>
>
> >
> >You're incorrect on this one. A car can accelerate at more than 1g.
> >However, it cannot corner at more than 1g...
> >
>
> OOPS! Want to try that again?
>
Indded, the Lotus Elise can corner at about 1.2g.
Formula one cars, on unbanked corners can hit, on occasions, 4g.
There is nothing special about 1g in terms of a car's performance.
Well, any car which can perform maneovers at above 1g is pretty special,
but that's not to say that it's a limit in any way.
Anthony Potts
CERN, Geneva
Patrick T.P. Chin
Of course it can. 1g just mean 9.8 m/sec^2 which has nothing to do with the
acceleration of cars or anything. You can visulize it as the following: if
you have a pendulum hanging in a car while accelerating at 9.8m/sec^2, it will
swing back by 45 degrees. (assuming you are on a flat place near the surface
of the earth)
Patrick
Stephen Westin
> Brad Sloan wrote:
> > On Tue, 25 Feb 1997, Vlad Kozlovsky wrote:
> > I think it's outstanding that you've arrived at this conclusion
> > through what is apparently fairly independent thought. Your basic
>
> Well, thank you :)
>
> > premise is correct: cars are motivated by a traction force, and their
> > acceleration is therefore limited to the amount of tractive force
> > available. Your only mistake is in assuming that it is impossible to
> > achieve a coefficient of friction greater than 1. Some super-soft street
> Hmm.. I have a really hard time comprehending this concept. After all,
> how can a tire be so sticky that it actually increases the rebound force
> of the Earth's surface, acting opposite to the force of gravity? It may
> get very close to it, but to actually increase it? How?
Nope. The classical model of friction just says that the friction
force is proportional to the normal force (gravity here). It's routine
these days to achieve a constant of proportionality greater than
1. It's really more complicated than this; you can think of the
"constant" as being a variable that depends on things like slip rate
and normal loading. For example, doubling the load on a tire will
generally fall short of doubling its traction.
For an everyday example of this sort of thing, think of a piece of
sticky tape; it routinely resists lateral displacement, even with *no*
normal force applied.
> > tires achieve this - you see them often at autocrosses (BF goodrich R1's,
> > Yokohama A008's, etc.), picking up bits of sand and assorted small matter
> > from the road and flinging them about - and most all race tires exceed Cf
> Is this how? Just using dirt and sand particles? But dirt and sand on
> the track tend to actually reduce the coefficient of traction...
The point is this: the tire sticks to bits of pavement. If the bits
aren't attached, it does no good. If the bits are still part of the
road, it increases traction.
> >> of 1. Therefore, acceleration rates greater than 1g are not at all
> >> impossible. The Porsche 911 Turbo, for one, averages about 1.05 g (if I
> >> remember right) through the first 30 or so feet of its acceleration from
> >> zero.
> This sound very impressive but how is it possible without additional
> downforce? Is there something I am missing?
Yes. There is no fundamental law limiting the coefficient of friction
(the constant of proportionality) to 1.
<snip>
--
-Stephen H. Westin
swe...@ford.com
The information and opinions in this message are mine, not Ford's.
Stephen Westin
> Brad Sloan wrote:
> > On 27 Feb 1997, Mike Scanlan wrote:
> > > You're incorrect on this one. A car can accelerate at more than 1g.
> > > However, it cannot corner at more than 1g...
> > Ouch. Sorry Mike, that's not correct at all. 1g is a good bit
> > easier to accomplish laterally than longitudinally. F1 has experienced
> > lateral accelerations of about 3g's w/downforce. Formual SAE cars
> > routinely get 1.4 without any aero affects at all.
>
> Yes, I agree with this completely. The most obvious contributor to
> making >1g lateral acceleration possible is downforce, which becomes a
> VERY significant factor at speed, especially with race cars. The other
> significant force involved is centrifugal (sp?). All this is pure high
> school physics...
Many cars can average nearly 1g deceleration, say in a 60-0
stop. Those with sufficient tires and favorable weight distribution
(rear-engine Porsches come to mind) can comfortably exceed it. By my
calculations, a 1g deceleration is a 120ft. stop from 60 MPH, so any
stopping distance less than this indicates a deceleration greater than
1g.
Just looking at random on Edmunds, I find the Camaro Z28 coupe stops
in 118 ft. I make that out to be a mean deceleration of 32.8 ft/sec,
or about 1.02g. The Porsche Turbo come out to 1.11g mean deceleration
from 60 MPH.
Acceleration is another matter; 0-60 in 2.73 sec would be a mean of
1g. I suspect that a few production cars can manage 1g acceleration at
certain speeds; certainly some racing cars do.
dave lawson
Chuck Tomlinson wrote:
>
> Vlad Kozlovsky <v...@p3.net> wrote:
> >Here is an innocent question: can acceleration (positive or negative) of
>
> That is not correct. A car's acceleration can exceed 1.0g in any
> horizontal direction without aerodynamic assistance.
>
> >acceleration must be 1g or less? Or maybe my 0 to 60 time calculation is
> >wrong, even given that the first assumption is right?
>
> than 1.0g.
>
> In the case of AWD: if the car can bring all of its tires to peak
> traction at the same time (at low speeds) *and* the coefficient of
> can accelerate at more than 1.0g. This is easy enough to prove
> mathematically... maybe later :-)
>
> If you check any road test of the new 911 Turbo (C/D 6/95, R&T 7/95,
> MT 6/95, and MT 11/96), you'll notice a 0-30 time of 1.3 sec.
> That's an average acceleration of 1.05g.
>
> I'll jump the gun a bit on the motorcycle crew: any number of
> unmodified street bikes can exceed 1.0g accel.
>
> --
> __
> ___| |____ Chuck Tomlinson <toml...@ix.netcom.com>
> /___LT-1___/ Mouse Power!
> |__| '94 Vette Z07/ZF6, '89 Mustang LX5.0L/T5
Sorry to jump in on a reply to the post, but I didn't find the original
post.
The number of g's that a car can generate horizontally is dependant on
two fundamental things. The vertical force generated between the tires
and the road and the co-efficient of friction of the rubber compound on
the surface.
Thus, soft compounds on dry rough pavement give the greatest friction
and thus the greatest side force. Cars whos aerodynamics cause
additional down force to be generated can increase the available
friction forces. If the total friction force exceeds the weight of the
vehicle, then the g force is greater than 1.
Goemetry effects of the suspension will NOT increase the available side
force, only decrease it from the theoretical maximum. Uneven loading on
the tires, body roll, unequal slip angles on the tires, etc will all
decrease the available friction force. The average car is not designed
to generate the maximum possible side force because the required
suspension geometry and stiffness would make the car unsuitable for
typical road use. Todays 'sports cars' make the trade off between best
ride quality and best handling (not to mention ground clearance!).
Dave
Brad Sloan
On Thu, 27 Feb 1997, Vlad Kozlovsky wrote:
> > premise is correct: cars are motivated by a traction force, and their
> > acceleration is therefore limited to the amount of tractive force
> > available. Your only mistake is in assuming that it is impossible to
> > achieve a coefficient of friction greater than 1. Some super-soft street
>
> Hmm.. I have a really hard time comprehending this concept. After all,
> how can a tire be so sticky that it actually increases the rebound force
> of the Earth's surface, acting opposite to the force of gravity? It may
> get very close to it, but to actually increase it? How?
It's actually quite simple. To put it technically, in order for a
tire-road interface to have a coefficient of friction > 1, the force
required to lift the tire from the surface of the road is greater than
the weight of the tire itself. To put it simply, the tires are simply
"sticky" by the original definition of "sticky"-it sticks.
> > Yokohama A008's, etc.), picking up bits of sand and assorted small matter
> > from the road and flinging them about - and most all race tires exceed Cf
>
> Is this how? Just using dirt and sand particles? But dirt and sand on
> the track tend to actually reduce the coefficient of traction...
Yes, they do, but the context in which you are referring now is
the effective Cf between the road-tire interface. Obviously, it would be
darn near impossible to achieve a Cf of 1 where there is sand on the
track. However, if a tire can "pick up" particles such as these *where
the particles are present*, then it's a pretty good indicator that the
tires are "sticky" enough to achieve a Cf >1 where there is clean track.
In an autocross, the phenomenon of flinging particles is best
observed at a staging area or out of the "line" on the track, as the line
tends to get cleaned of those particles. Where the track is clean, there
are no flinging particles - and the Cf of a tire that would pick these
particles up *if they were there* is now >1.
> called "Physics of Racing," does anyone have access to it?
Vlad, what is you educational background? It seems you've had at
least some higher-level instruction on Newton's 2nd Law, so I think you
must have at least a sophomore-level education in Mech. Engineering or
Physics. Is that so?
Julian A F Bradbury
Edward Kim <gt7...@acmey.gatech.edu> writes
>Mike Scanlan (time...@laraby.tiac.net) wrote:
>: You're incorrect on this one. A car can accelerate at more than 1g.
>: However, it cannot corner at more than 1g...
>911 Turbo and I think that that car pulled 1.01gs laterally. Or are you
>meaning something else by the word "cornering?"
F1 cars circa 93/94 were pulling up to 3.5G in cornering, when they
began to head towards 4 drivers began to complain a little as I recall.
Accelerator lift-off pulled 1.5G before touching the brakes.
Very few road cars can break 1G cornering. 993 is one, then again if it
is the gross purple one I've seen the quicker it can run the better ;)
Others come close, the MR2 and 95 RX 3rd gen TT (0.98G) spring to mind.
--
Julian AF Bradbury http://www.ergonite.demon.co.uk
John E. Yurkon
In article <Pine.OSF.3.91.970227...@hubcap.clemson.edu> Brad Sloan <psl...@hubcap.clemson.edu> writes:
> It's actually quite simple. To put it technically, in order for a
> tire-road interface to have a coefficient of friction > 1, the force
> required to lift the tire from the surface of the road is greater than
> the weight of the tire itself. To put it simply, the tires are simply
> "sticky" by the original definition of "sticky"-it sticks.
Not really. It could be sticky, but does not need to be. Its
not related to lifting the tire. F=uN. F is the force needed to
slide the object and N is the normal force (in the case of a tire,
the weight on the tire). u is then called the kinetic coefficient of
friction. If F>N then u>1. F is normal to N so it cannot "lift"
the tire.
As an aside, as Superball has a coefficient of friction in the 1,000's
on a proper surface, such as glass. But, it is not sticky. Wouldn't
work very well on a car either since the forces needed would destory
the ball. ;)
John
Eric Parkin
Vlad Kozlovsky <v...@p3.net> wrote in article <3313B3...@p3.net>...
> Here is an innocent question: can acceleration (positive or negative) of
> an automobile be greater than 1g? It makes sense to me that it can NOT.
Yes, one example is the Stock 1996 Subaru Imprezza WRX Ra STI. It
pulls 1.01g's in accelerating from a dead stop for about the first 30ft
after launch.
> source of propultion), no matter how powerful and light it is. The
> number I got is 2.721 seconds. This number must be wrong, since there
> are lower 0 to 62 mph (0 to 100 kph) times recorded in the Guiness book
> of records.
The extinct WSC Prototype cars from the late eighties were very quick..
0-60 in roughly 1.75seconds. I seem to recall a certain motorcycle doing
it in .6 *(to 60mph)*, and 6.6 to 213.77mph. :) geez.
--
... epa...@op.net - 1986 VW Motorsports Golf GT-R #72 ....
.. 1996 SCCA NEDiv Solo I/Hillclimb Rally Class Champion ..
... ESP Motorsport's Page: http://www.op.net/~eparkin/esp ...
Paul Jones
Vlad Kozlovsky wrote:
Brad Sloan wrote:
> On Tue, 25 Feb 1997, Vlad Kozlovsky wrote:
> I think it's outstanding that you've arrived at this
conclusion
> through what is apparently fairly independent thought. Your basic
Well, thank you :)
> premise is correct: cars are motivated by a traction force, and
their
> acceleration is therefore limited to the amount of tractive force
> available. Your only mistake is in assuming that it is impossible
to
> achieve a coefficient of friction greater than 1. Some super-soft
street
Hmm.. I have a really hard time comprehending this concept. After
all,
how can a tire be so sticky that it actually increases the rebound
force
of the Earth's surface, acting opposite to the force of gravity? It
may
get very close to it, but to actually increase it? How?
> tires achieve this - you see them often at autocrosses (BF
goodrich R1's,
> Yokohama A008's, etc.), picking up bits of sand and assorted small
matter
> from the road and flinging them about - and most all race tires
exceed Cf
Is this how? Just using dirt and sand particles? But dirt and sand
on
the track tend to actually reduce the coefficient of traction...
>> of 1. Therefore, acceleration rates greater than 1g are not at
all
>> impossible. The Porsche 911 Turbo, for one, averages about 1.05
g (if I
>> remember right) through the first 30 or so feet of its
acceleration from
>> zero.
This sound very impressive but how is it possible without additional
downforce? Is there something I am missing? Is there another force
that
gets introduced into the system, other than the force of gravity and
the
opposing force of rebound? It would REALLY be nice to actually
understand how this Newtonian system works. I heard there is a book
called "Physics of Racing," does anyone have access to it?
Vlad.
The unusual properties of tire traction come from the fact that the
rubber deforms (or changes shape) as it presses against the ground. In
the perfect world of physics models, the frictional force depends ONLY
on normal force and coefficient of friction. This would mean that the
amount of surface area in the contact patch is irrelevant. We all know
this is not the case with tires touching the ground. The surface of the
pavement is not perfectly smooth, and the surface of the rubber tire
deforms to grip the irregularities of the pavement. The interaction is
far more complex than the usual "frictional force due to coef of
friction and normal force" that is studied in physics class. The
deformation of materials allows greater frictional forces than the
typical model would suggest. Of course, like others have mentioned,
downforce and weight transfer and other factors also come into play.
-Paul Jones
<pej...@dhinternet.com>
Brad Sloan
On 27 Feb 1997, John E. Yurkon wrote:
> In article <Pine.OSF.3.91.970227...@hubcap.clemson.edu> Brad Sloan <psl...@hubcap.clemson.edu> writes:
> > It's actually quite simple. To put it technically, in order for a
> > tire-road interface to have a coefficient of friction > 1, the force
> > required to lift the tire from the surface of the road is greater than
> > the weight of the tire itself. To put it simply, the tires are simply
> > "sticky" by the original definition of "sticky"-it sticks.
>
> Not really. It could be sticky, but does not need to be. Its
> not related to lifting the tire. F=uN. F is the force needed to
> slide the object and N is the normal force (in the case of a tire,
> the weight on the tire). u is then called the kinetic coefficient of
> friction. If F>N then u>1. F is normal to N so it cannot "lift"
> the tire.
If we are speaking in the context of a tire-road interface (which
I hope we are), then a tire is "sticky" if you set the tire on the road,
attempt to pick it up, and discover that the force required to pick it up
is greater than the tire's weight.
And if you're concerned about the *kinetic* coefficient of
friction, then you are not driving properly. :)
Ron Katona
Paul Jones wrote:
>
> The unusual properties of tire traction come from the fact that the
> rubber deforms (or changes shape) as it presses against the ground.
Not being a physics major, I'd ask this question: How does tire width
affect all this? Is the coefficient of friction a constant, that is
independent of tire width, or is the contact patch area included in the
cf figure?
Or, does the cf remain constant, but the larger contact patch offer more
area for this deformation to take place, therefore raising cornering
limits? Of course, we can't increase the size of the contact patch
lengthwise without making the tire ridiculously tall, so we go for added
width. What is the added width actually doing for us?
--
Ron Katona ro...@cris.com
88 Mustang LX 5.0
97 BMW 318ti
Sergey Macheret
Vlad Kozlovsky wrote:
>
> Here is an innocent question: can acceleration (positive or negative) of
> an automobile be greater than 1g? It makes sense to me that it can NOT.
> possible 0 to 60 mph time for ANY vehicle (using its wheels as the only
> number I got is 2.721 seconds. This number must be wrong, since there
> are lower 0 to 62 mph (0 to 100 kph) times recorded in the Guiness book
> of records.
>
> acceleration must be 1g or less? Or maybe my 0 to 60 time calculation is
> wrong, even given that the first assumption is right?
>
There is no law of physics that would not allow the acceleration
to exceed 1 g. In other words, acceleration/deceleration can exceed
1 g. In real world, though, this happens rarely, so your assumption
can give a reasonable (although semiempirical) estimate of minimum
acceleration time for most cars. Bear in mind, however, that some
sports/race cars can exceed 1 g (again, no physical limit!), so
your estimate would be wrong for them.
Sergey Macheret
Henri Helanto
time...@laraby.tiac.net (Mike Scanlan) writes:
>You're incorrect on this one. A car can accelerate at more than 1g.
>However, it cannot corner at more than 1g...
Now, try your very best at explaining to us WHY that is so...
...and at least I promise not to laugh. Honest. (Hehehe.. ;-)
(A hint: is the amount of friction dependent of its direction
in the first place... :)
-Henri
--
# Henri Helanto ; he...@muncca.fi ; hhel...@cc.hut.fi #
# Nissan Skyline GT-R ; Corvette Coupe 454/LS-6 ; others...#
CAUTION: Before engaging mouth make sure that the brain is in gear.
Henri Helanto
Vlad Kozlovsky <v...@p3.net> writes:
>This sound very impressive but how is it possible without additional
>downforce? Is there something I am missing?
Yep: Asphalt is by no means a flat surface where basic laws
of physics directly apply, neither is the tire.
C.R. Krieger
On Thu, 27 Feb 1997 15:59:36 GMT, Anthony Potts <po...@cms.cern.ch>
wrote:
>On Thu, 27 Feb 1997, RMoburg wrote:
>
>> On 27 Feb 97 04:31:03 GMT, time...@laraby.tiac.net (Mike Scanlan)
>> wrote:
>> >You're incorrect on this one. A car can accelerate at more than 1g.
>> >However, it cannot corner at more than 1g...
>>
>> OOPS! Want to try that again?
>Indded, the Lotus Elise can corner at about 1.2g.
>
>Formula one cars, on unbanked corners can hit, on occasions, 4g.
>
>There is nothing special about 1g in terms of a car's performance.
>
>Well, any car which can perform maneovers at above 1g is pretty special,
>but that's not to say that it's a limit in any way.
Why, THANK YOU, Anthony! My totally stock '86 Audi 4000 Quattro with
215,000 miles is now officially "pretty special"! I've pulled over 1
g both laterally and braking (stock size race tires, of course.). As
for acceleration, well ...
C.R. Krieger
"Ignore 'em, m'dear; they're beneath your dignity." - W.C. Fields
Remove "SPAM" from e-mail address.
Michael E. Mitchell
In <3313B3...@p3.net> Vlad Kozlovsky <v...@p3.net> writes:
>
>Here is an innocent question: can acceleration (positive or negative)
of
>an automobile be greater than 1g? It makes sense to me that it can
NOT.
>So, by doing a few very simple calculation one can arrive at the
lowest
>possible 0 to 60 mph time for ANY vehicle (using its wheels as the
only
>source of propultion), no matter how powerful and light it is. The
>number I got is 2.721 seconds. This number must be wrong, since there
>are lower 0 to 62 mph (0 to 100 kph) times recorded in the Guiness
book
>of records.
>
>So, am I not thinking clearly tonight, or do you agree that the
maximum
>acceleration must be 1g or less? Or maybe my 0 to 60 time calculation
is
>wrong, even given that the first assumption is right?
>
>Vlad.
>
funny car classes routinely accelerate at greater than 1g.
Michael E. Mitchell
In <3315EF...@alliedsignal.com> dave lawson
<dave....@alliedsignal.com> writes:
>
>Chuck Tomlinson wrote:
>>
>> Vlad Kozlovsky <v...@p3.net> wrote:
negative) of
>> >an automobile be greater than 1g? It makes sense to me that it can
NOT.
>>
>> horizontal direction without aerodynamic assistance.
>>
maximum
>> >acceleration must be 1g or less? Or maybe my 0 to 60 time
calculation is
>> >wrong, even given that the first assumption is right?
>>
figured all this out a long time ago... they call it NASCAR today.
The suspension geometry and unequal loading has an awful lot to do
with how quick you can put the car thru the corner. Consider the
average saturday night short track... 3/8 mile oval. The car spends
most of its time in a left turn. Weight that is placed to apply force
on the left side get transferred during the turn by centrifugal force
to the right side. Also the tire diameter has to be smaller on the
left and larger on the right. This can easily be demonstrated by
rolling a dixie cup on a table. The left front is toed out and caster
is set back and camber is positive. The right front is toed in caster
is positive and camber is negative. Ride height is lowered on the left
and softer springs are used on the left. Lots of other things are
altered in the suspension in oval track racing that are too numerous to
cover here but the one thing that doesn't change is the stopwatch. It
will take the best theory and turn it into superstition!
Anthony Potts
On Thu, 27 Feb 1997, Julian A F Bradbury wrote:
> Very few road cars can break 1G cornering. 993 is one, then again if it
> is the gross purple one I've seen the quicker it can run the better ;)
>
> Others come close, the MR2 and 95 RX 3rd gen TT (0.98G) spring to mind.
> --
Lotus elise is another one. It can apparently pull 1.2g laterally.
Anthony Potts
CERN, Geneva
David Manning
> The unusual properties of tire traction come from the fact that the
> the perfect world of physics models, the frictional force depends ONLY
> on normal force and coefficient of friction. This would mean that the
> amount of surface area in the contact patch is irrelevant. We all know
> this is not the case with tires touching the ground. The surface of the
> pavement is not perfectly smooth, and the surface of the rubber tire
> deforms to grip the irregularities of the pavement. The interaction is
> far more complex than the usual "frictional force due to coef of
> friction and normal force" that is studied in physics class. The
> deformation of materials allows greater frictional forces than the
> typical model would suggest. Of course, like others have mentioned,
> downforce and weight transfer and other factors also come into play.
>
OK, this is about what I was trying to say in my last post. Interesting
premise, though... if we could never out-grip gravity on a macroscopic
scale, we could never climb any slope of greater than 45 degrees (ie.
rock climbers, etc. almost _never_ have a normal force greater than the
component of gravity parallel to the rock face.)
David Manning
>
> This sound very impressive but how is it possible without additional
> gets introduced into the system, other than the force of gravity and the
> opposing force of rebound? It would REALLY be nice to actually
> understand how this Newtonian system works. I heard there is a book
> called "Physics of Racing," does anyone have access to it?
>
> Vlad.
It's true that the friction of the tire/road contact is a function of
the force exerted by gravity on the car; but friction is something that
happens on a molecular level; looking at the tire/road contact highly
magnified, the tire surface isn't nearly as smooth as it seems;
microscopic (and larger) pits and irregularities literally mesh with
irregularities of the road surface and pull the car along; like teeth on
gears. It's not practical, but if you were to put extended steel spikes
on your tires and drive on soft asphalt you could easily acheive enough
grip for +1g of acceleration (with the appropriate car, of course).
David Manning
>
> And if you're concerned about the *kinetic* coefficient of
> friction, then you are not driving properly. :)
>
> Brad Sloan
> Clemson University
> Clemson, SC
I suppose that depends on what you're shooting for... drag racers and
rally racers should be very interested in kinetic (sliding) friction.
John E. Yurkon
In article <Pine.OSF.3.91.970227...@hubcap.clemson.edu> Brad Sloan <psl...@hubcap.clemson.edu> writes:
> And if you're concerned about the *kinetic* coefficient of
> friction, then you are not driving properly. :)
I thought we were talking about burning rubber! ;)
John
John E. Yurkon
In article <331627...@cris.com> Ron Katona <ro...@cris.com> writes:
> Not being a physics major, I'd ask this question: How does tire width
> affect all this? Is the coefficient of friction a constant, that is
> independent of tire width, or is the contact patch area included in the
> cf figure?
>
> Or, does the cf remain constant, but the larger contact patch offer more
> area for this deformation to take place, therefore raising cornering
> limits? Of course, we can't increase the size of the contact patch
> lengthwise without making the tire ridiculously tall, so we go for added
> width. What is the added width actually doing for us?
I'm a Physicist. You should not ask one. They'll say that its
independant to first order. Wider tires have other advantages besides
traction. More stable, scrirm less etc. But, obviously drag racers
feel that wider tires (more contact area) help. And they're right.
Stress on rubber is less. If tire starts to shred like an eraser it
doesn't help traction. Also, the heat per unit area is less so
tire melts less, etc.
I just looked in table and for rubber on concrete, the coefficient
of friction is approximately 1. Obviously depends alot on
composition of rubber and condition of concrete.
John
Anthony Potts
On Tue, 25 Feb 1997, Vlad Kozlovsky wrote:
> Here is an innocent question: can acceleration (positive or negative) of
> an automobile be greater than 1g? It makes sense to me that it can NOT.
Why not?
What's stopping it being greater than 1g?
Anthony Potts
CERN, Geneva
Brad Sloan
On 28 Feb 1997, Michael E. Mitchell wrote:
> All this math and engineering! Seems like a bunch of country boys
> figured all this out a long time ago... they call it NASCAR today.
The country boys haven't "figured out" anything. It's called
empirical testing. "well, we run the car with xxxx setup last time,
and it worked purty good, so let's run it again." Empirical testing
is expensive, time consuming (especially when each team is allowed only
7 test sessions per year), and won't get you to the ultimate setup.
> cover here but the one thing that doesn't change is the stopwatch. It
> will take the best theory and turn it into superstition!
Uhhh. No.
Brad Sloan
On Fri, 28 Feb 1997, David Manning wrote:
> >
> > And if you're concerned about the *kinetic* coefficient of
> > friction, then you are not driving properly. :)
>
> rally racers should be very interested in kinetic (sliding) friction.
As for drag racers, they still use *static* friction. They do
burnouts only to heat up the tires...when they launch the car, there is
virtually no wheelspin at all. As for rallyers, they aren't very likely
to exceed 1 g on the surfaces they drive, although they are likely having
more fun that any of the rest of us. :)
Brad Sloan
On 28 Feb 1997, John E. Yurkon wrote:
> > And if you're concerned about the *kinetic* coefficient of
> > friction, then you are not driving properly. :)
> John
Nothing wrong with that, you're jsut not likely to see 1g that way.:)
Michael E. Mitchell
In <Pine.OSF.3.91.970228...@hubcap.clemson.edu> Brad
>Clemson University
>Clemson, SC
>
>
>
physical effects of the science.
Ted Heron
Alright David! - I was wondering when someone would point out that there
are other forces acting here besides friction - there is the mechanical
forces of one set of objects (thousands of small protruding parts of the
tire) pushing against another set of objects (in this case thousands of
small protruding pieces of the roadway) in much the same way (as David
points out) that a protruding set of gear teeth pushes against another
protruding set gear teeth in a vehicle's power train - nothing to do with
friction.
Ted
email: he...@austx.tandem.com
Opinions I express are my own and not my employer's.
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On Fri, 28 Feb 1997, David Manning wrote:
Lee H
The bottom line: Ask any drag racer if it is possible for an
automobile to accelerate with a force greater than 1 g. I think
you'll find the answer is definately YES.
My $0.02 (and worth every penny)
-Lee
Willy Tamm
Can an automobile achieve acceleration rates in excess of 1G?
>Vlad Kozlovsky <v...@p3.net> wrote:
>>Here is an innocent question: can acceleration (positive or negative) of
>>an automobile be greater than 1g? It makes sense to me that it can NOT.
>>So, by doing a few very simple calculation one can arrive at the lowest
>>possible 0 to 60 mph time for ANY vehicle (using its wheels as the only
>>source of propultion), no matter how powerful and light it is. The
>>number I got is 2.721 seconds. This number must be wrong, since there
>>are lower 0 to 62 mph (0 to 100 kph) times recorded in the Guiness book
>>of records.
Mike Scanlon <time...@laraby.tiac.net> replied:
>You're incorrect on this one. A car can accelerate at more than 1g.
>However, it cannot corner at more than 1g...
I'm not quite sure that I follow Mike's response but here's some food for
thought:
1. It is necessary to define the parameters of what is meant by an
"automobile". Some examples:
a. Your average Detroit (German, Japanese, Korean, Swedish, British, etc)
iron, stock, out of the showroom.
I do not believe that this category has yet touched, or exceeded, 1G.
There are some very high performance vehicles which do come very close but
without tire design/compounds which would be have to be heated up to, and
maintained at high working temperatures, together with a very narrow range of
operating parameters, pavement type, temperature, etc., I believe that we are
still dealing with the basic premise of physics which keeps cars fastened to
the earth's surface at 1G.
Advances in what are really "racing tires" defy these rules by stiction,
storing energy in deforming sidewalls, etc. Not an area which I know a lot
about, but I do know that such tires, could they be made useable for street
use are big $$$$ and have a life expectancy considerably shorter than our
average payroll cycle. :)
b. As above, with any combination of modified suspensions, tires and simple
bodywork modifications.
While somewhat of a rehash of 1a) above, let's include the "weekend racers" in
this category. While I know very little about the sport of "drag racing", it
is my understanding that acceleration figures in excess of 1G are common.
Please fill me in.
In a similar vein, the entire gamut from "showroom stock" SCCA road racing to
running on slightly banked ovals and tri-ovals should permit horizontal
and lateral accelerations in excess of 1G under certain conditions (I don't
use the term 'deceleration', it being a form of negative acceleration. Please
understand that I refer to braking as well as acceleration whenever I refer to
'acceleration'.)
c. Purpose built "open wheeled" formula racing cars which employ advanced
"aerodynamic" features, including, but not limited to some of the following.
"Inverted wing design' for the entire body wherein the air pressure below the
body is lower than above. This is a complex subject and in practice also
involves the use of both front and rear, adjustable wings to control handling
characteristics.
Given sufficient speed to develop airflow over these "upside down wings",
together with adjustable wing settings maximized for relatively twisty, lower
speed race courses, I have heard quoted both horizontal and lateral
acceleration figures approaching the realm of 4G's. In practice, G-levels
seem to run at about half of those levels, top speed being the consideration.
d. NASCAR vehicles on high banked ovals and tri-ovals must, to my way of
thinking, exceed 1G in lateral acceleration given that the high banking
figures into calculations of centrifugal force.
2. I would enjoy hearing from more learned individuals than myself but I
really cannot understand Mike Scanlon's comment that acceleration can exceed
1G, whereas cornering is limited to under 1G. Perhaps he was refering to drag
racing.
Cheers,
Willy Tamm
Marc
mik...@ix.netcom.com(Michael E. Mitchell) wrote:
>The point is IT DOESN't TAKE A ROCKET SCIENTIST to demonstrate the
>physical effects of the science.
All it takes is someone who knows how to drop something. Doesn't mean
they are doing anything intresting.....
Marc
Brad Sloan
On Fri, 28 Feb 1997, Ted Heron wrote:
> Alright David! - I was wondering when someone would point out that there
> are other forces acting here besides friction - there is the mechanical
> forces of one set of objects (thousands of small protruding parts of the
> tire) pushing against another set of objects (in this case thousands of
> small protruding pieces of the roadway) in much the same way (as David
> points out) that a protruding set of gear teeth pushes against another
> protruding set gear teeth in a vehicle's power train - nothing to do with
> friction.
On the contrary, it has everything to do with friction. Friction is
just molecules at the interface of two surfaces acting, as you said, in
similar manner to gear teeth. The concept is correct, but your
definition of friction is not.
Anthony Potts
On 27 Feb 1997, Mike Scanlan wrote:
> You're incorrect on this one. A car can accelerate at more than 1g.
> However, it cannot corner at more than 1g...
>
>
Hmm. I could go out tomorrow, and buy a car which cornered at over 1g on
the road (well, I'd have to borrow a bit money from the bank). Not even a
race car, just a sporty road car.
Anthony Potts
CERN, Geneva
Anthony Potts
On Thu, 27 Feb 1997, Vlad Kozlovsky wrote:
> > available. Your only mistake is in assuming that it is impossible to
> > achieve a coefficient of friction greater than 1. Some super-soft street
>
> Hmm.. I have a really hard time comprehending this concept. After all,
> how can a tire be so sticky that it actually increases the rebound force
> of the Earth's surface, acting opposite to the force of gravity? It may
> get very close to it, but to actually increase it? How?
What exactly are you saying here?
The poster said that you have a high mu, not a high R, but you immediately
start asking how it can increase R.
It doesn't. Mu is simply greater than one. There is no reason to assume
that mu is restricted to less than one. This is the most common
misconception we seen to find in dynamics, that a ratio is restricted to
being between zero and one.
>
> Is this how? Just using dirt and sand particles? But dirt and sand on
> the track tend to actually reduce the coefficient of traction...
They do. The fact that the tyre picks them up shows how sticky it is. It
doesn't improve its acceleration by throwing sand around.
> This sound very impressive but how is it possible without additional
> downforce? Is there something I am missing? Is there another force that
Max force is mu times the force between the tyre and the road. The
downforce can increase (if thh tyres expand, the front lifts, and so on),
but even ignoring this, simply having a large coefficient of friction
means that the forward force is greater than the downwards force.
Anthony Potts
CERN, Geneva
David Tomayko
The key element everyone is missing here, I think, is that cars do not
only use gravity to hold to the road at speeds. When a top fuel drag
car is at the end of the quarter mile at 300 miles per hour, do you
really think that the weight of the car normal to the surface of the
road is really the same as it is when the car isn't moving? I can't
remember which indy car, but I remember hearing that the downward
acceleration this particular car had due to lift (negative lift) was
more than 1g. Consequently a driver could drive the car upside down as
long as thew were driving over a certain speed.
Cars are similar to an airplane wing. There is drag and lift. Hi
performance vehicles need lift to maintain stability. This presses down
on the road more at high speed. In cornering and laterial acceleration
specs on hi perf. cars, you will see some >1g specs. Is a fighter jet
limited to 1g performance? If they were, we sure wouldn't be using them
as much.
Dave T
Dave and Rosemary
experience standing in one place on this planet.
Chuck Tomlinson
dfa...@concentric.net wrote:
>
>Isn't any acceleration gt 1 g by definition? 1 G is the gravity you
>experience standing in one place on this planet.
No. "Acceleration" pretty much means "rate of change of velocity".
If a body's velocity doesn't change, the acceleration is zero. This
is true no matter how large or small the velocity is. If you stand
in one place on the planet, and stay there, your velocity and
acceleration are both zero (relative to the planet).
Yeah, the planet is rotating, and also orbiting the sun, which AFAIK
is orbiting the center of the Milky Way. But for mundane purposes
(automotive and pedestrian), we measure "absolute" velocity and
acceleration relative to the part of the planet on which we're
standing or driving.
BTW, 1 g is how fast you would accelerate downwards if you had just
begun to fall. After a brief period of falling, aerodynamic drag
will offset some of your gravitational pull (weight), and your
acceleration will decrease. Fall long enough, and the two forces
(aero drag and weight) will balance, and you will stop accelerating.
Even though you'll be plummeting towards earth at 100 mph or more,
your acceleration will be zero. That's where a parachute helps. By
providing a lot of extra aero drag, it helps to reach a "force
balance" at much lower speed, enhancing your chances of survival.
Chuck Tomlinson
wt...@lobo.net (Willy Tamm) wrote:
>1. It is necessary to define the parameters of what is meant by an
>"automobile". Some examples:
>
>a. Your average Detroit (German, Japanese, Korean, Swedish, British, etc)
>iron, stock, out of the showroom.
>I do not believe that this category has yet touched, or exceeded, 1G.
Many high-performance production cars can brake at over 1g, a few
can corner at 1g, and at least one can accelerate at more than 1g or
the first second or so ('96+ Porsche 911 Turbo).
>I believe that we are
>still dealing with the basic premise of physics which keeps cars fastened to
>the earth's surface at 1G.
Willy, there is no such premise. The key to a car's acceleration
(in any direction) is the coefficient of friction (Cf) between the
tires and the road. The Cf is the ratio of maximum traction force
to the force pressing the tire into the road. If a car can generate
more horizontal force than it weighs, it can accelerate at more than
1.0 g. For AWD cars, this just requires a Cf of more than 1.0.
There is no physical limit that forces the Cf to be less than 1.0.
The Cf between two pieces of clean, dry nickel is 1.10. For copper,
it's 1.21 (Marks' Std Handbook for Mech. Engrs, 9th ed., Ch. 3.2).
The fact that the vast majority of materials have Cf's less than 1.0
is an unfortunate coincidence. It's like drag coefficients: many
simple shapes and almost all road vehicles have Cd's less than 1.0.
Pure coincidence. Parachutes and some winged race cars have Cd's
considerably higher than 1.0.
>2. I would enjoy hearing from more learned individuals than myself but I
>really cannot understand Mike Scanlon's comment that acceleration can exceed
>1G, whereas cornering is limited to under 1G.
Mike made a mistake.
Herbavor
In article <MPG.d7eb8aa9...@nntp.netcruiser>, no....@see.sig.below
spewed from his/her keyboard...
>The Mike Scanlan of time...@laraby.tiac.net fame so eloquently
>said...
>> Vlad Kozlovsky <v...@p3.net> writes:
-snip-
>> You're incorrect on this one. A car can accelerate at more than 1g.
>> However, it cannot corner at more than 1g...
>Indy and a whole bunch of other cars
>don't know this, or they would run off of every corner on the track.
Don't thee those cars and drivers that they can't do more than 1g. Just like
the characters in the cartoons when they forgets about gravity untill they
run off the cliff. Maybe If I forget that My car can only do .93 g's with the
tires it has now, I will improve my autoX times.
'Bavor
BobH...@misterfixit.com
Vlad Kozlovsky wrote:
>
> Here is an innocent question: can acceleration (positive or negative) of
> an automobile be greater than 1g? It makes sense to me that it can NOT.
> So, by doing a few very simple calculation one can arrive at the lowest
> possible 0 to 60 mph time for ANY vehicle (using its wheels as the only
> source of propultion), no matter how powerful and light it is. The
> number I got is 2.721 seconds. This number must be wrong, since there
> are lower 0 to 62 mph (0 to 100 kph) times recorded in the Guiness book
> of records.
>
> acceleration must be 1g or less? Or maybe my 0 to 60 time calculation is
> wrong, even given that the first assumption is right?
>
========================================================
The answer is very simple and very straightforward. If you can achieve
a coefficient of friction greater than one (1) then you can accelerate
greater than one G - in any direction, and either braking or speeding
up. So, if you put a 2000 horsepower engine in your car and want to
drive it thru the wheels in contact with the ground you better make sure
that you have paid close attention to the tires and how well they "grip"
the road.
Fuelie dragsters achieve well over 1g and they do so by spinning their
tires wildly to heat them and make them gooey - that is sort of a
"dynamic coefficient of friction" and it is much greater than one.
Of course you can achieve much better decelerations than 1g - just find
a brick wall!!
Bob
--
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(Contains) http://www.MisterFixit.com/autorepr.htm
Nasty Canasta
In article <Pine.GSO.3.95a.970301105508.28627J-100000@cms6>, Anthony Potts
<po...@cms.cern.ch> wrote:
> It doesn't. Mu is simply greater than one. There is no reason to assume
> that mu is restricted to less than one. This is the most common
> misconception we seen to find in dynamics, that a ratio is restricted to
> being between zero and one.
Holy Adhesion, Batman!
You mean that there's something going on with tires other than dry friction?!?
;{D
If I may butt in on this thread (elbow, elbow, elbow...),
I'd like to address this issue of mu being between zero, and unity.
As I recall from my days in engineering mechanics, mu(pure dry friction)
must be between zero, and unity. If mu > 1 the friction is not true dry
friction. That's not to say there is NO friction for mu >1 only that it's
not pure dry friction.
For example the of tires of top fuel dragsters were/are(?) bleached before
making a run to make them more tacky. All dragsters 'smoke' their tires
before a run to soften them. If I remember the discussion that went on
about this while I was still in college the "total friction" with tires
and pavement has three components. Towit:
dry friction,
physical engagement,
and adhesion.
So, with the dragsters tires the reason for smoking them is to soften them
it to allow the tread compound to smoosh into the grain of the pavement
(physical engagement), and the reason for bleaching them is to make them
tacky (adhesion).
I also, seem to remember some story of a physics dept. and a mechanical
engineering dept. at a major university having some roe over whether on
not mu could be greater than unity, that was based along the lines of just
what constituted true dry friction.
When physics profs. and mech engineering profs. start arguing semantics
you know it's time to take a cab!
TAXI! :{)
--
From the Catbird's seat, high atop the world's tallest concrete water tower...
"Ex Luna & Astris Scientia"
Larry Dean Luther
Luther Cybernautics
Tyler, Texas
95 deg 19 min W, 32 deg 21 min N
ldlu...@e-tex.com
_____________________________________________________________________
While it's true that two wrongs don't make a right, it is equally true that two Wrights can make an aeroplane.
_____________________________________________________________________
Jack Mott
The problem here is friction. Nobody here fully understands it.
Unfortuantely, nobody ANYWHERE fully understands it. Many people are
confused because of the frition they were taught in highschool physics,
or even intro courses in college. This friction you learned applies
only to sliding objects. That is, once you start skidding, all those
rules apply. Thats why wider tires dont always help in rain or ice or
snow. Once you are sliding, width doesnt make any difference. The
other kind of friction is static friction. When accelerating (and going
around a turn is a kind of acceleration) none of your high school
physics rules apply. Think of a guy pushing a box. The guy has his
back to a wall. Given enough muscle he can push with a billion 'G's if
he wants to. The tires are pushing on many cement protrusions. Double
the contact patch of the tire, and you double the number of protrusions
(or walls) the tires can push on. So acceleration can be as big as you
want it to even with no extra downforce.
bi...@atl.mindspring.com
ldlu...@e-tex.com (Nasty Canasta) wrote:
>In article <Pine.GSO.3.95a.970301105508.28627J-100000@cms6>, Anthony Potts
><po...@cms.cern.ch> wrote:
>> It doesn't. Mu is simply greater than one. There is no reason to assume
>> that mu is restricted to less than one.
Actually, all you gotta do is get yourself a piece of string, a ball
bearing, and a PRO-tractor.... you can make a g-force meter like the
one grade schoolers use to measure roller-coasters at the local theme
parks. You'll see that when you go backwards at a high rate of speed,
you actually not only experience negative gee forces, but go back in
time to where you once were.
"No Good Deed Goes Unpunished"
Chuck Tomlinson
ldlu...@e-tex.com (Nasty Canasta) wrote:
>Anthony Potts <po...@cms.cern.ch> wrote:
>
>> It doesn't. Mu is simply greater than one. There is no reason to assume
>> misconception we seen to find in dynamics, that a ratio is restricted to
>> being between zero and one.
>
>
>As I recall from my days in engineering mechanics, mu(pure dry friction)
>must be between zero, and unity. If mu > 1 the friction is not true dry
>friction. That's not to say there is NO friction for mu >1 only that it's
>not pure dry friction.
Hmmm... According to Marks' Standard Handbook for Mechanical
Engineers, 9th ed (1987), Chapter 3.2, the static Cf between two
smooth pieces of clean dry nickel or cast iron is 1.10. For copper
and aluminum, the static Cfs are 1.21 and 1.05, respectively.
>I also, seem to remember some story of a physics dept. and a mechanical
>engineering dept. at a major university having some roe over whether on
>not mu could be greater than unity, that was based along the lines of just
>what constituted true dry friction.
I'd love to know what fundamental "law of nature" is supposed to
prevent the Cf from being more than 1.00.
>When physics profs. and mech engineering profs. start arguing semantics
>you know it's time to take a cab!
>
>TAXI! :{)
I agree. TAXI!
Anthony Potts
On 28 Feb 1997, John E. Yurkon wrote:
> > lengthwise without making the tire ridiculously tall, so we go for added
> > width. What is the added width actually doing for us?
>
> I'm a Physicist. You should not ask one. They'll say that its
> independant to first order. Wider tires have other advantages besides
No, we tend not to be ignorant of how physical processes work.
I am amazed that even other physicists regard physicists as uninformed.
Anthony Potts
CERN, Geneva
Arnaud Tilmant
>On 27 Feb 1997, Mike Scanlan wrote:
>>
>> You're incorrect on this one. A car can accelerate at more than 1g.
>> However, it cannot corner at more than 1g...
>>
>
> Ouch. Sorry Mike, that's not correct at all. 1g is a good bit
>easier to accomplish laterally than longitudinally. F1 has experienced
>lateral accelerations of about 3g's w/downforce. Formual SAE cars
>routinely get 1.4 without any aero affects at all.
>
Right. Lateral accelerations can be upper than 1G.
A "small" Porsche 911 Turbo can get +/- 1 G
The Citroën Xantia Activa ( A simple French berlin with active
suspension) can get more than 1,2 G. It's better than the Honda
(Acura) NSX, which is a reference.
I think that a Porsche or a Venturi 400 GT can get more than 1G for
braking.
For the acceleration, it's more difficult, but the Gillet Vertigo (a
Belgian car, powered by a Ford engine, 1993 cc) was boosted (460 ch
for 712 Kg) to get the world record of acceleration (0-90 Mph : 3,266
sec), and I think such an acceleration can provide real sensation...
It must certainly be upper than 1G. ;-)
Of course, all the cars above are serial cars.
Don't use REPLY, see my .SIG (Bruce Simpson)
toml...@ix.netcom.com (Chuck Tomlinson) wrote:
>There is no physical limit that forces the Cf to be less than 1.0.
>The Cf between two pieces of clean, dry nickel is 1.10. For copper,
>it's 1.21 (Marks' Std Handbook for Mech. Engrs, 9th ed., Ch. 3.2).
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John E. Yurkon
In article <Pine.GSO.3.95a.970303183817.15221F-100000@cms2> Anthony Potts <po...@cms.cern.ch> writes:
> No, we tend not to be ignorant of how physical processes work.
>
I did not say that we were.
> I am amazed that even other physicists regard physicists as uninformed.
>
Not uninformed. We usually start with the simplist explanation, then
elaborate as necessary to make the model more accurate. It was a bit
of humor, you know? :)
John
Ted Heron
Excuuuuuse meeee...but gear teeth don't rely on friction to transmit force
to the teeth of the opposing gear - and my
Ted
email: he...@austx.tandem.com
Opinions I express are my own and not my employer's.
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On Fri, 28 Feb 1997, Brad Sloan wrote:
> On Fri, 28 Feb 1997, Ted Heron wrote:
> > Alright David! - I was wondering when someone would point out that there
> > are other forces acting here besides friction - there is the mechanical
> > forces of one set of objects (thousands of small protruding parts of the
> > tire) pushing against another set of objects (in this case thousands of
> > small protruding pieces of the roadway) in much the same way (as David
> > points out) that a protruding set of gear teeth pushes against another
> > protruding set gear teeth in a vehicle's power train - nothing to do with
> > friction.
>
> On the contrary, it has everything to do with friction. Friction is
> just molecules at the interface of two surfaces acting, as you said, in
> similar manner to gear teeth. The concept is correct, but your
> definition of friction is not.
>
>
> Brad Sloan
> Clemson University
> Clemson, SC
>
Excuuuuuse meeee...but gear teeth don't rely on friction to transmit force
to the teeth of the opposing gear, in fact much design work goes into
minimizing the amount of friction that comes into play during that process
- and the only thing that is not correct here is your comprehension of
what I said. To say it another way - if you will look again at what I
previously wrote you should note that I clearly am describing forces
*other than* friction - nowhere do I attempt to define *friction*.
Ted
Boneman
For acceleration at +1G:
Watch ESPN during a top fuel dragster race. There's your answer.
For cornering/stopping at +1G:
Watch ESPN during an Indy race. There's your answer.
And don't attribute it to downforce, either. All downforce
does is provide increased traction (at the cost of increased drag),
and traction is the key here.
I'd explain the physics in detail, but it's 1:00 in the AM and
I'm tired. Besides, actions speak louder than words, so watch ESPN.
Example: A top fuel dragster can accelerate from 0 to 300+ mph in 4 to
5 seconds. This is clearly more than 1G acceleration. But don't take
my word for it: Turn on yer tellyvision and watch a race.
-- Boneman
Chris Papademetrious
On Thu, 27 Feb 1997 11:06:24 -0500, Vlad Kozlovsky <v...@p3.net> wrote:
>Hmm.. I have a really hard time comprehending this concept. After all,
>how can a tire be so sticky that it actually increases the rebound force
>of the Earth's surface, acting opposite to the force of gravity? It may
>get very close to it, but to actually increase it? How?
Think about those trains with geared wheels that connect to teethed
rails underneath the traincar. Just sitting down on the track, given
enough power, it could pull more than 1g acceleration. Don't forget,
tires aren't just smooth idealistic objects sitting on an ideal
surface. They're organic compounds, with lots of irregularities,
sitting on an extremely irregular surface. The science of adhesion
and cohesion and traction are not *nearly* as intuitive as you think
they should be. :)
- Chris
NLW TFW NM
Dry (non-spinning) friction can also exceed 1.0. I've driven my 5100-pound
Blazer up slickrock slopes exceeding 45 degrees (a measured 49 degrees,
with some steeper sections) around Moab, because sandstone and rubber
mesh to some degree.
It was the return trip that was the real problem. You can't U-turn at 49
degrees. Had to back down (about 200 feet) in Drive, using a touch of
throttle as brakes. SPOOKY!
Mike
Never Leave Wind To Find Wind