Related: Automotive Materials
Ask any truly dedicated NASCAR fan what happened on February 18, 2001, and you’ll get a quick reply noting it was the day Dale Earnhardt, Sr., was killed when his car hit the wall of turn number four at 180 mph during the last-lap of the Daytona 500. Four other NASCAR drivers had died during the previous season. But Earnhardt’s death seemed to be the proverbial straw that broke the backs of NASCAR officials, who were determined to improve safety. NASCAR’s research and development department, then headed by Gary Nelson, himself a former crew chief on the circuit, began the painstaking process of determining how to do it. “The accident investigators recommended we prioritize our work and they pointed out that 65% of our focus should be on the driver restraint system, so we made changes to the neck and head support systems. They then projected we could improve safety by 25% through better energy absorption of the track barrier systems, while the final 10% would have to come from the car itself,” says Nelson, who has left NASCAR and now runs his own racing consultancy business. While work on the restraint and barrier systems seemed simple, the complexities of reengineering the car itself turned out to be more daunting, to the point engineers had code-named the program “The Car of Tomorrow.” The goal was simple: engineer a car that was not only safer, but more cost-effective produce, while devising a set of geometric standards that must be adhered to with exact technical measurements. In other words: one car for every track.
Needless to say, long-time NASCAR fans and drivers were more than a little concerned. Nelson and his team began polling team owners and drivers in 2001 on what they wanted from the Car of Tomorrow program. While most of the teams simply wanted improved front and rear bumper strength and fire suppression systems. There was little call for more radical changes. Nelson was undaunted as he championed for more aggressive changes: “If we would have taken popular opinion instead of a total engineering approach, we would have spent a lot of time on the front bumper, but we knew we had to make a car that was fundamentally different.” Since the car itself acts as the first barrier to protect the driver, everything had to be taken into consideration. The first step was the engineer a single chassis rather than permitting teams to modify their vehicles based on track lengths and aerodynamic test results. “We have now essentially a blueprint everyone must work within”—the Car of Tomorrow is mandated for the short-track courses at present—“while the previous-generation car is more of a set of parameters where we said you could move things like the frame rails within a certain range. Now, there is no range, it’s just one place and that’s where you put it,” Nelson says. Although it might seem team owners would be delighted to have one car versus the 18 or 19 that has been the norm, that’s not the case. Nelson says teams have always used the parameters as a way to gain an edge on the track. For instance, he points out several teams have one crew member responsible for positioning the fuel cell in different areas of the car to gain better weight distribution and aero, depending on the track. The Car of Tomorrow puts that guy out of a job, since the fuel cell is now frozen in one location.
NASCAR engineers first looked at way to protect the driver from intrusion, whether through contact with a wall or another vehicle. This resulted in moving the driver’s seat 4 in. closer to the center of the car and the roll cage 3 in. toward the rear. There is a 2.5-in. increase in roof height and a 4-in. width increase to the greenhouse. Double frame rails were added to the driver’s side of the vehicle with steel plating added to cover the door bars, providing the ability to support energy-absorbing IMPAXX foam-based material developed by Dow Automotive (www.automotive.dow.com). Impact energy is managed through a series of controlled reactions within the foam. The result is a controlled release of energy, allowing forces to be better spread throughout the vehicle from the time of impact to the end of the crash sequence. Another change is encasing the drive shaft a steel tube designed to prevent it from piercing the floor pan and impaling the driver.
The fuel cell, which holds 18 gallons (a 2-gallon decrease), has a strengthened bladder, thicker container and a safer check valve, along with new energy-absorbing honeycomb material that keeps the cell intact during a collision. Should the fuel cell be compromised, the Car of Tomorrow features an advanced fire-suppression system that utilizes DuPont FE-36 extinguishant.
Although the Car of Tommorrow is highly standardized, with more than 200 defined points, this doesn’t mean automakers and team owners can’t distinguish their specific models (e.g., Chevrolet Impala, Ford Fusion, Dodge Avenger, Toyota Camry) (see sidebar). “Sure, we have standardized much of the chassis and body, but we have left some room for manufacturer identity. We have specific guidelines as to where the roll bars and the frame rails should be, but the pick-up points on the chassis are not regulated at all except for asymmetry requirements,” says NASCAR design engineer Dan Kurtz.
Aerodynamics Cause Concern
Making the car wider and taller means some sacrifices when it comes to aerodynamics, resulting in a slower average speed on the track. But according to Brett Bodine, who heads NASCAR’s cost and research operations, the addition of an adjustable front splitter and rear wing provide benefits when it comes to vehicle control. “We have added more adjustability with the rear wing and the front splitter, allowing teams to easily adjust the down force and front and rear, along with the amount of side force. To do that with the previous car you would have to build a whole new body.” The rear wing angle can be adjusted between 0-16 degrees, while the side and end plates can be adjusted to reduce side-force, resulting in better control in traffic. In an effort to improve the stability of vehicles traveling in packs, NASCAR engineers designed the wing to reduce the amount of turbulent air produced at the rear of the car. “The wing provides a more stable condition for the car following and now we’re likely to see the following car run closer. Also, the reduced side force will make the driver feel more confident throughout the corners,” Bodine says.
The molded fabric front splitter can be adjusted fore and aft 4-6-in., depending on the amount of down-force and aerodynamic balance desired. Teams can easily custom tune the splitter for each track without having to make radical changes to the body structure. “What this means is that as opposed to having different cars made for each driver, now teams can just tune the exact same car for several different drivers, which helps to keep operating costs down,” Bodine says.
As Bodine’s title indicates, NASCAR is concerned with costs. The standardized Car of Tomorrow not only helps hold down costs by eliminating the need for multiple versions of a single car, but it goes a long way towards helping teams take advantage of modern manufacturing technologies that were once elusive to the sport. Since the basic chassis and body of the car are based on NASCAR’s blueprint, automating the construction of these structures makes ideal business sense. Evernham Motorsports has already hinted at the idea of building body and chassis components for some of its competitors (see “NASCAR Gets Automated”) using robots and automated equipment. Former NASCAR R&D chief Nelson says he was conscious of the need to make Car of Tomorrow provide new insight into race car construction. “I envision the smart team owners will move towards more automation in manufacturing. I could imagine some of the teams having a welding robot working at 3 a.m. putting a chassis together,” he says. Bodine predicts Car of Tomorrow will cut the number of cars needed by each team by upwards of 50%: “I wish I could be a team owner again,” he quips.
COT From an OEM Perspective
Even though NASCAR engineers have been working on the Car of Tomorrow for more than six years, the decision to gain input from the vehicle OEMs did not take root until 2005, when both sides had to endure the grueling process of meshing mass-market vehicle design with purpose-built race car thinking. “When we first met, we asked do we really need a new car and, well, the ship had sailed on that,” says Pat Suhy, GM Racing NASCAR group manager. “We wanted to ensure that the overall platform aerodynamically would provide competitive racing, and we knew we had to get our design folks to work quickly on the cold surface.” A small team of designers inside the Chevrolet brand studio were tasked with developing a racer that would resemble the Impala SS found on the showroom floor. Needless to say, a lot of give and take was required before both Chevrolet and NASCAR came to a mutually agreeable solution. The main point of contention revolved around how far back from the top of the bumper through to the top of the headlamps could be influenced by each OEM’s design team, which required more than a year of discussions. “It was difficult keeping up with NASCAR’s changes because as we would go through the process, we would get a change just about every week in terms of the generic shape or how they would maintain various aspects of the body,” Suhy says. In the end, NASCAR decided it was in the best interest of both manufacturers and race teams to allow them to tailor their front fascia designs to meet branding requirements.
As the design team conquered their challenges, GM engineers worked to assure the chosen designs would not impede on the aerodynamics of the vehicle through the use of computation fluid dynamics simulation tools. “NASCAR was very responsive to our input based on the CFD results,” says Kevin Bayless, GM Racing oval track chassis/aero program manager. Engineers also analyzed the effectiveness of the front splitter and rear wing with CFD tools and discovered some marked improvements in the aerodynamic properties of the Car of Tomorrow when compared with the previous racer: “Where we saw the greatest gain was in the area of flow off the back of the vehicle, particularly at the base of the wing and the decklid,” Bayless says.