Page 4 - Combined_57_OCR

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Performance at Dayton
Speedway

Discussion (cont’d)

particular speeds run. As a very rough estimate it appears that the
•wind effects increase the average power required by about 35 HP for
the complete lap, which would indicate that the lap speed would have
out 1.5 raph. faster with no wind.

The third factor in the power required losses is less easily
understood than the air and rolling resistance. This factor is
called the yaw tire drag for lack of a better name. This is the
power that is consumed by the tires due to cornering, It is assumed
to be equal to the total cornering force times the sine of the
average slip angle. There is some test data available that indicates
that this equation is very close to the true condition, In this case
the total cornering force is the calculated total lateral force, and
the average tire slip angle is taken as equal to the yaw angle, The
resultant poxzer consumption tire yaw drag is zero on the straight-
aways where there is no cornering force, and reaches 3 60 HP in the
number 1 turn. The values shown for tire yaw drag are both calcu-
lated and estimated, since the limited instrumentation does not give
the necessary information on the exact path of the car in the turns
and the steering and slip angles. Any reduction of the tire yaw
force would be difficult, since the total cornering force is mainly
a function of cur speed, and the tire slip angle characteristics
like the rolling resistance are a function of the tire itself that
is used on all makes of cars. Some reduction in the tire yaw drag
may be possible by varying weight distribution and roll couple dis­
tribution. It is quite likely that lowering the center of gravity
reduces this factor somewhat.

In summing up it appears that the car is performing just about
as it would be expected to. The straightaway acceleration of the
car is almost exactly what would be calculated for the known apgine
and the measured drag coefficient. The speed loss through turns 3
and 4 are what would be calculated now that good yaw data is avail­
able. The conditions in turns 1 and 2 are more effected by the wind
and therefore vary some from the calculated results, but overall the
car seems to be performing as expected. The data contained in this
letter is limited mainly by the lack of complete instrumentation,
dith the complete multi-channel tape recorder data system that has
been proposed it should be possible to find out much more easily and
throughly how the car is actually behaving on the race track, and to
find the effects of various changes on the race car.

With the data that has now been obtained on both the race car
and the race track it should now be possible to write an accurate
computer program to calculate the race car running at Daytona. Thi
will be attempted in the near future, and should provide a good
method of evaluating Daytona performance.

G.

GW/mh

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