Aerodynamic Drag

[mike tipton <mtipton@netten.net>]

Ok all you engineer types out there, see if this makes sence!
Aerodynamic drag is calculated as follows:(courtesy of SAE papers)
Aerodynamic drag = 0.5 x (air mass)x(drag coefficient)x(max vehicle 
cross section)x(road speed+head wind velocity)2
max vehicle cross section = 0.9 x track x height

                     6m x(a1-a2)
drag coefficient=    ___________
                     A x (v1squared x v2squared)

M =  vehicle mass (weight)
A =  max vehicle cross section (0.9 x track x height)
a1 = average deceleration values(high speed 60-55km/h)
a2 = average deceleration values(low speed 15-10km/h)
v1 = velocity high speed(60-55km/h)
v2 = velocity low speed(15-10km/h)
t1 = time intervals between 60-55km/h (high speed)
t2 = time interval between 15-10km/h (low speed)

Now what this all means is: 
take a car, get it up to a speed of 60km/h (va1)
allow the car to decelerate out of gear, on flat road, calm wind to
55km/h (vb1) time this interval (t1)
Repeat this at a speed of 15km/h (va2)
to 10km/h (vb2) time this interval (t2) 

now find average deceleration (a1) by subtracting (va1) from (vb2) and
divide this by (t1)

now find drag coefficient by multiplying M x (a1-a2)
divided by (A)x(v1squared-v2squared)

It helps to write it out on note paper.
                                            M