Big Gains from Aerodynamics
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This should have been the first article in this series but
better late than never. It's another excerpt from the book Inside
Slower Top Speeds but Faster Laps
Done properly, aerodynamic improvements to racing cars are
almost free performance improvements. For an open-wheeled car,
especially, the tires produce a huge amount of aerodynamic drag.
If a clever designer is able to reduce this drag by cleaning
up the flow over the bodywork and around the tires, wings, and
other downforce-producing devices can improve the car's performance
with little or no penalty. Even when added aerodynamic devices
produce some drag along with downforce, the car can turn faster
laps. The car can actually have a slower top speed due to increased
aero drag and still turn faster laps because of more downforce.
You can see a good example of how wings hurt top speeds, but
still lowered lap times, by looking back to the early '70s when
Indy car designers first began to learn about wings and downforce.
Here's a table from the book, Indy Car, by Roger Huntington,
showing the increase in speeds for the fastest two cars at the
Brickyard in 1971 and 1972. The tremendous increase in the average
lap speed came about because the United States Auto Club (USAC)
liberalized the rules for the 1972 Indy 500, allowing much bigger
wings than in 1971. Mark Donahue and Bobby Unser were the fastest
qualifiers at the 500 in those two years.
The table shows how speeds in the turns went way up due to
downforce while the drag from the wings actually lowered top
speed on the straights. Since, at Indy, the car spends a lot
of time in the turns, the overall average speed increased 17
miles an hour. In a single year!
Years earlier, when Jim Hall put a wing on the rear of his
Chaparral racecar, he made it movable and driver controllable
so it could be flattened out on the straights for less drag,
when the downforce wasn't needed. That gave him the best of both
worlds--maximum speed on the straights and downforce during braking
Another feature of Hall's design, mounting the wing directly
onto the rear suspension uprights so the aerodynamic forces go
right to the tires and not through the suspension, was simple
and direct. Unfortunately, some of these wing supports failed,
probably due to fatigue failures, causing some scary crashes.
For that reason "movable aerodynamic devices" were
immediately banned by all sanctioning bodies. From that time
on, wings and all other aerodynamic devices have been considered
a part of the body work and aerodynamic forces cannot be transmitted
directly to the wheels. .