Note: The drag figures shown are the actual drag in Newtons on the model.
The coefficient for the simulator is obtained by scaling the drag up to the expected
drag for a full size car ie. multiply by 4 then dividing by the air speed squared. The
Simulator * is the one written by Ross Perry & Ian Gardner.
CAR PERFOMANCE IMPLICATIONS:
To see in general terms how air drag influences car performance the air drag coefficient
obtained was used in the mathematical simulator. For all simulator runs the same car
parameters except for air drag coefficient were used.
The basic parameters used are those of the car PC IV (Photon Cruncher MK IV which is
fully detailed in the Design Hints) the main parameters are listed below.
Mass 2.1 kg
Solarex 10 Watt panel 88% Sun level
Engelec electronics
No Steering
AIR DRAG RACE TIME DISTANCE DIFFERENCE
COEFFICIENT SECONDS METRES
1 LAP 2 LAPS 1 LAP 2 LAPS
0.012 20.3 34.3
0.0033 18.85 30.9 10.0 23.0
- Approximate distance this car is ahead at the end of the race due only to the lower
aerodynamic drag.
NOTE: To achieve the same performance increase by weight reduction alone it would be
necessary to reduce the weight from 2.1 kg to 1.4 kg.
Calculation & Comparison of Cd:
Cd = Drag Force
!/2 x Air Density x Car Speed squared x Frontal Area
(The following data was used for calculations:
Standard air density 1.22 kg/m cubed
Standard air viscosity 1.78 by 10 to the minus 5 kg.m/sec squared)