The development of the aero package on formula one cars had for many years followed the aircraft industry. From sleek bodies, to cooling intakes and engine breather systems, the race car borrowed much of its technology from aircraft. First to realize that a car’s performance around a track could be improved by adding down-force was Jim Hall of Chaparral cars.
The First Wings
Although the Chaparral cars were sports racing cars, it wasn’t long before F1 designers realized the importance of down-force developed by wings. The wings were shaped much like those on an airplane. However, to give don-force instead of lift, the wings were inverted for race car use.
The early wings were mounted differently than today in that they bolted directly to the uprights (axle supports). By mounting the wings in this way, the pressure generated as the car moved forward was fed almost directly to the wheels/tires. Although this was a more efficient way of mounting the wings (for transmitting the down-force to the tires), the wing and its mounting structures were subject to shock loadings from bumps on the track.
Safety Concerns
After many breakages, the FIA ruled that the wings had to be mounted on the sprung mass of the cars. In addition, they (the FIA) also ruled that the wing must angle could not change as the car was being driven. This latter rule was born out of concern for the speed increase the cars were achieving. Although the ideal wing configuration is to have little or no down-force on the straights, and maximum on the corners, having adjustable wings when the car is in motion brought to the fore many safety concerns.
After the teams had experimented and to a certain extent, perfected the wing configurations – both front and rear – the designers turned to modifying the underside of the cars. It was Colin Chapman and the Lotus team that first developed devices to increase down-force from aero devices placed below the car.
Diffusing the Airflow
Chapman and his team experimented with tunnels under either side of the cars. The tunnels were shaped to have a small entry section that tapered up toward the rear of the car. This tapered shape had the effect of diffusing the air flow as it traversed the tunnels and in so doing reduced the pressure under the car in relation to that above, resulting in down-force.
Not only was the down-force increased with the introduction of side tunnels, but the engineers were excited to find that the resultant drag was not as great as expected. Although the down-force generated by the side tunnels could not be altered/adjusted (unlike the wings), the wing area could be reduced which reduced the overall drag.
Taking the side tunnel design to the next stage incorporated side fences on the tunnels and Sidepods that touched the track, creating a seal. The down-force levels increased dramatically with this design and resulted in the FIA ruling that no part of the car could touch the track, with the obvious exception of the tires.
Flat Bottom Rules
The new rules dictated that the underside of the cars must be flat from the front wheel center line to the corresponding position at the rear (commonly called the flat bottom). As a result, the engineers turned their attention to the underside of the car aft of the rear wheel center lines. Their designs followed the Sidepod/tunnel concept by having a diffuser section starting from the end of the flat bottom, to as far back as the regulations would allow.
While the flat bottom rule had reduced the effectiveness of the side tunnels, the engineers found that by running the cars with rake (the rear of the car being higher than the front), the pressure below the car could be reduced. Not only did the cars develop more overall down-force by running with rake, the front wings became more effective the closer they were positioned to the ground.
Over the years, as the rules were changed to reduce aero down-force, the engineers would find ways of improving the efficiency of the approved aerodynamic aids. The current regulation governing F1 aero devices are strictly enforced, but engineers will interpret the rules in a way that gives their team the competitive advantage. A case in point at the start of 2009 is the Brawn GP team and their rear diffuser.
Rule Changes
The F1 rules were changed considerably over the winter of 2008/9. Primarily, the FIA (in agreement with the teams) wanted to reduce the aerodynamic down-force of the cars by as much as 50%. Having achieved this with front and rear wing size and position changes, the teams looked at ways of getting the down-force back.
The Brawn GP, Williams, and Toyota teams designed rear diffusers that were legal within the regulations, but not considered to be within spirit of them. Some of the other F1 teams have protested the legality of the design and the case will be heard at the international court of appeal.
The search for improved aerodynamic efficiency within F1 is as dynamic as the air around the cars. Aerodynamics will be high on the priority list of designers for many years to come.
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