Neat idea I recently watch a accident investigator doing something similar.
They had a tire cut in half with a weight mounted inside attached to the
tire was a simple spring scale which the investigator pulled across the
road.
Bill
----- Original Message -----
From: "DrMayf" <drmayf@teknett.com>
To: <land-speed@autox.team.net>
Sent: Wednesday, July 02, 2003 9:37 AM
Subject: Salt-Tire Coefficient of Friction
> I am contemplating the fabrication of a doohickey that will permit me to
> measure the coefficient of friction betwen tire "rubber" and the salt.
This
> would be a small simple pull type of device. I would use a "pad around 4
> inches square with an "eye" hook to attach a cable to. The cable would be
> wound through three turning pullies so that I could pour sand into a
bucket
> as the falling pull weight. I would load the skid with sand also to some
> measure weight, hook it up, pour sand into the bucket until the static
bond
> between the tire rubber and salt is broken and it slides. Then I would
> measure the bucket and sand. I could then determine the static coefficient
> of friction, or breakaway friction. This number with the weight on a cars
> driving wheel(s) wold permit a quick calculation as to the amount of
torque
> that could be applied (force times rolling radius). This could be a gage
on
> how to apppply power as you motor down the course. However, it should be
> known that best acceleration probably comes when the tires are hazed by
> maybe 20% over the breakaway friction.
>
> As an experiment, I would perform the pull test several times, enough to
get
> a 95% confidence interval, then use the data to find the one sigma force
> values. I would repeat the experiment several times during the day to test
> the idea of water rising through the salt during the day.
>
> How could I determine the kinetic coefficient of friction?
>
> Anybody have any thoughts on this? Of any value to anyone? Off list
please,
> no need to pester everybody who does not want to read replies.
>
> mayf, the red necked ignorant desert rat in Pahrump
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