static vs. dynamic friction of tires/road
William Martin
Can anyone suggest where to obtain data on the change of friction
between a rolling tire vs. a sliding tire on various pavement surfaces?
Thanks in advance for any info or pointers to info.
Bill Martin
-A.RIZZO
Take a tire. Put it on a road. Tie a rope and a spring scale
to it. Drag it. Record the peak force just prior to sliding.
Record the force maintained during continuous sliding. Use those
and the weight of the tire to calculate the coefficients of friction,
after you've done this little experiment, oh, a dozen times or so.
The first force will give you the coefficient of static friction,
which is what governs friction forces as a tire rolls. The second
force will give you the coefficient of dynamic friction, which
governs friction forces when you're skidding out of control with
the wheels locked.
On second thought, use two tires tied together and standing up,
so that they won't fall over and so that the tread is in
contact with the pavement.
Tony
Jim Papadopoulos
>> Can anyone suggest where to obtain data on the change of friction
>>between a rolling tire vs. a sliding tire on various pavement surfaces?
>>
>> Thanks in advance for any info or pointers to info.
>>
>>Bill Martin
>>
>
>
>Take a tire. Put it on a road. Tie a rope and a spring scale
instead of travelling to various roads in various climates,
with primitive equipment, I recommend finding
the data in technical reports. Unfortunately I don't know
exactly where to send you -- both the Department of Transportation
(Cambridge, MA) and the University of Michigan Transportation
Research Institute (UMTRI) could be good starting points.
>The first force will give you the coefficient of static friction,
>which is what governs friction forces as a tire rolls. The second
>force will give you the coefficient of dynamic friction, which
>governs friction forces when you're skidding out of control with
>the wheels locked.
a complicated frictional behaviour, especially under side
loadings. At a given forward speed, side force gives rise
to a lateral 'creeping' velocity. Plotted versus creep velocity,
side force rises to a peak and then declines. I don't
think the peak corresponds to static friction coefficient; and
while high creep velocities MIGHT correspond to dynamic friction
coefficient, in practice such velocities are never reached.
If the brakes are locked (i.e. wheels are not rotating), then
Rizzo's suggestions make sense to me. (Static friction is measured
with the car at rest...)
JP
Jim Papadopoulos
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From: cv...@cotton.vislab.olemiss.edu (Jagannath Mallela)
Subject: Re: static vs. dynamic friction of tires/road
To: bicyc...@delphi.com
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<hi4Q08d.b...@delphi.com>
In sci.engr.mech you write:
>-A.RIZZO <ri...@hogpb.ho.att.com> writes:
>
>>> Can anyone suggest where to obtain data on the change of friction
>>>between a rolling tire vs. a sliding tire on various pavement surfaces?
>>>
>>> Thanks in advance for any info or pointers to info.
>>>
>>>Bill Martin
>>>
>>
>>
>>Take a tire. Put it on a road. Tie a rope and a spring scale
In the pavement management systems employed by many highway agencies
there are ways to measure skid resistance of pavements. The instruments
used to measure this factor in principle drag a set of wheels on the
pavement surface at a preset speed. However, there are other ways of
determining the skid resistance and some use static devices. Check any
pavement book for the underlying theory. Contact any highway department
(DoT) for typical numbers.
Regards,
-jagannath
Virgilio (Dean) B. Velasco Jr.
There was an article in "The Scientific American" on this
phenomenon a few years ago. I don't recall exactly when.
All I know is that it appeared before 1991.
--
Virgilio "Dean" Velasco Jr, Department of Electrical Eng'g and Applied Physics
graduate student slave, roboticist-in-training and Q wannabe
Beam me up, Scotty. |I practice the safest form of sex| Why did the chicken
It ate my phaser. | known. It's called abstinence. | cross the Mobius strip?
-A.RIZZO
Jim Papadopoulos <bicyc...@delphi.com> wrote:
>
>Here in the late twentieth century,
>instead of travelling to various roads in various climates,
>with primitive equipment, I recommend finding
>the data in technical reports.
Hmm! Here in the 20th century we have ways of making very
pricise measurements of statistical quantities with a large
replicate standard variation. There's nothing wrong with
looking for data in the technical literature, of course.
But one should have a grain of salt on hand for those extra
few significant figures.
Rizzo
By the way, Jim, how do you like delphi? Does it cost much?
-A.RIZZO
Eric S Andersen <es_an...@pnl.gov> wrote:
>Bill,
>
>a friend of mine just got done writing an experimental lab report
>about rubber friction. Rubber does not behave like other typical
>materials. He covered topics like friction, adhesion, traction, etc.
>I believe that he started by contacting tire manufacturers. If you
>would like more info, send me an email and I will see if he is
>interested in distributing the report.
>
>ERic S. Andersen
>es_an...@pnl.gov
Is it published? Will it be published soon? How about posting
a reference for the rest of us? :-)
Tony
Olev Tammer
There is lots of research being done related to Antilock Brake Systems.
I'm sure the Society of Automotive Engineers has a number of publications
available. Contact them at 412/776-4970 (Pennsylvania).
Regards, Olev Tammer Hewlett-Packard
Internet: ol...@sdd.hp.com San Diego Technical Graphics
Eric S Andersen
Eric S Andersen
>
>Is it published? Will it be published soon? How about posting
>a reference for the rest of us? :-)
>
>Tony
The paper is not published. It was written for an experimental design
laboratory at Washington State University. I will call him and see if its
o.k. to post the report.