Adriano and alpine skidpad freaks,
>Well, a properly timed skid pad would be run as follows: you have two
>circles connected at a point, basically making a figure-8. The car
starts
>at the center where the two circles meet, goes right first and goes
>around that circle twice: once to get up to speed, and the second time
>around as the actual timed measurement, then the car would go around
the
>left circle, once to settle in, and a second lap to be timed, then
leave
>the skid pad at the center, opposite where it started and it would be
>timed from the center point, where the circles meet, so again, power
>wouldn't make a difference.
You said in your post yesterday, or at least my interpretation to that
effect was, that the car will make best Gs at the raduis where the slip
angle of the tyre is at the apppropriate angle for its load.
This would mean that the two circles would have to have been
painted with prior knowledge of the correct turning radius for that
car.
In magazine road tests, the radius is gererlally specified, or at
least written in the report, and interestingly it seldom changes
from car to car to car.
While this may not yield true peak G numbers, it does appear
that it is a standard test, perfomed in some painted lot.
If the radius is to large, an underpowered car may not be able to
attain the required velocity to generate the same level of Gs
that it could have produced at a lower radius. This is especially
true of short wheelbase cars like the alpine.
The original 1961 road test had some specified skidpad radius
or diameter, which unfortunatley was not variable as should be.
The alpine didnt make enough torque to the rear wheels
in third to attain the velocity required to make peak Gs.
Second gear probably wouldnt have gotten your there
without over revving, so they condluded that a 4.22 rear
instead of thr 3.89 unit, would have gotten them the much
needed torque to pull the car at the needed higher velocity.
While I do not argue any of your technical points, I do know
that more mass means more centrifugal force, which the
tires, suspension geometry, power of the vehicle ECT must
overcome to maintain a given radius on the pad.
Centrifugal force, is the same thing as performing constant
acceleration, only the acceleration is lateral. More mass
running at a given speed means more force required to
maintain the same speed.
Your statement that weight is not a factor in attaining Gs
may hold true in a racecar where you have nearely unlimited
tire traction capabilites, and tunable suspension, but in
a production car, more mass means more roll ECT, which
means that when you put the stickiest tires you can buy,
and have given yourself about as much camber as your
suspension will give, you are at the mercy of the weight of
your car.
Shave off a few hundred pounds on the same car, and it will
make more Gs "assuming you didnt disturb the weight transfer".
Jarrid Gross
This archive was generated by hypermail 2b30 : Tue Sep 05 2000 - 10:00:35 CDT