Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: Excess G forces in auto racing



Pete Lohstreter wrote:

PHYS-L@lists.nau.edu writes:
It would seem to me that the higher banking keeps the 'g-forces' more
vertical (for the drivers) which should be easier for them to handle than
the high 'gs' on flatter tracks which tend to severely stress the
neck/spine. Running INDY at 220 mph around a 9 degree bank has to be more
stressful on the body than 235 mph on a 24 degree bank. Again, as Hugh
states, we need the radius of the turns to do meaningful calculations.

Rick
A visit to the Texas Motor Speedway web-site gave the turn radius as 750
ft. (229 m). A calculation of the minimum coefficient of friction
necessary to make the 24 degree banked turn at 237 MPH (105 m/s) produced
a value of mu = 1.37.

The CRC states that the coefficient of friction for rubber on solids is
between 1 and 4.

We also determined the normal force felt by the driver to be 3.1 g's and
the centripetal force to be 4.6 g's,

That's the value of the normal acceleration I got with my assumptions
(which apparently were about right, based on Pete's data). I agree
that the sideways accelerations are more stressful on the neck and
spine, but the symptoms that the drivers were talking about were
those that one feels when the blood is drained from your brain, in
other words, the acceleration perpendicular to the road. And they
were taking about wearing g-suits in a news broadcast I heard this
afternoon. You don't get any spinal help with a g-suit. So if the
data is as stated, where did the 5 g normal accelerations come from?
Or alternatively, what is causing the symptoms of high-g acceleration?

BTW, pilots ejecting from an aircraft are typically subjected to
accelerations of 10-20 g, lasting for 1/20 to 2 seconds, depending of
the type of seat used. But that is a one time shot, and it would
appear that these drivers were being repeatedly subjected to these
accelerations for several seconds at a time. I suspect that the
repetitions are what caused the symptoms at relatively low values of
g. With a g-suit, accelerations of up to 8 g can be tolerated for
relatively long periods. Astronauts are subjected to launch
accelerations that can get up to 5-6 g, but it is relatively steady
and lasts for no more than a minute or two. But I suspect that, even
with a g-suit, the repeated cycling from high to low g would give
rise to the reported symptoms, especially the nausea reported by
several drivers.

The conclusion I come to is that the data we have is somewhat
conflicting, so either there is more that we don't know, or we're
getting information from different sources, and they haven't gotten
their stories together yet.

Hugh
--

Hugh Haskell
<mailto://haskell@ncssm.edu>
<mailto://hhaskell@mindspring.com>

(919) 467-7610

Let's face it. People use a Mac because they want to, Windows because they
have to..
******************************************************