Article courtesy of Something About Everything Racin’
A National Association for Stock Car Auto Racing (NASCAR) car is an amazing machine that pushes the physical limitations of automotive engineering. Crafting one of these cars is a meticulous task that takes dozens of designers, engineers and mechanics who put in hundreds of hours to perfect the car before it ever rolls onto a race track.
On the track, the driver shows off his professional skills by directing this 3,400-pound machine around an oval track at speeds that would terrify most people. For many, sitting at the helm of one of these custom-made dream machines is an appealing notion. With 750 horsepower under the hood, the cars have the ability to reach speeds of more than 200 mph.
But being behind the wheel of this car as it is spinning out of control on a high-banked super-speedway at 180 mph (289 kph), heading directly into a concrete retaining wall — this is the sober reality that professional drivers must face. Certainly, the tragic death of seven-time NASCAR champion Dale Earnhardt at the 2001 Daytona 500 race increased everyone’s awareness of the dangers of professional car racing.
In an average street car equipped with air bags and seatbelts, occupants are protected during 35-mph crashes into a concrete barrier. But at 180 mph, both the car and the driver have more than 25 times more energy. All of this energy has to be absorbed in order to bring the car to a stop. This is an incredible challenge, but the cars usually handle it surprisingly well.
A NASCAR racing car is basically a skeleton of strong metal tubing covered with thin, metal sheeting. The cars are equipped with a variety of safety devices that have evolved over the years in response to accidents and crashes that have injured or killed drivers.
The key to surviving a crash is for the car to remove the energy from the driver’s body as slowly as possible. Street cars have many safety devices designed with this in mind. The structure of a street car is designed to crush and thus absorb a lot of energy, giving the other safety devices, like seat belts and airbags, more time to slow the driver’s body down.
A NASCAR race car uses some of the same techniques. The front and rear clip are built from thinner steel tubing so that they will crush when the car hits another car or a wall.
The middle section is designed to be strong enough to maintain its integrity during a crash, thereby protecting the driver. In addition to being collapsible, the front clip is designed to push the engine out of the bottom of the car — rather than into the driver’s compartment — during an accident.
In the past, several deaths occurred when drivers still in their seats were thrown from cars. To counter this, NASCAR rules now require that the seat be attached, at several points, directly to the tubular structure that forms the roll cage, which is sometimes the only part of the car left intact after a crash.
The shape of the seat is important, too. Most of the seats found in NASCAR race cars wrap around the driver’s rib cage. This provides some support during a crash, spreading the load out over the entire rib cage instead of letting it concentrate in a smaller point. Some newer seats wrap around the driver’s shoulders as well, which provides better support because the shoulders are more durable than the rib cage.
The safety belts and the seat transfer most of the driver’s energy to the car during a crash. On a street car, the seatbelts are designed to stretch during a crash, which limits the force placed on the driver and gives him or her a little more time to slow down. On a NASCAR vehicle, however, the seat belts are much stronger — they are designed to hold the driver tightly in his seat so that his body slows down with the car.
The restraint used on NASCAR race cars is a five-point harness. Two straps come down over the driver’s shoulders, two straps wrap around his waist and one comes up between his legs. The straps are made from thick, padded nylon webbing. They are much stronger than the seatbelts in a street car.
Recently, several deaths have occurred as a result of severe head and neck trauma. Hoping to prevent those types of injuries, NASCAR will be requiring the use of an approved head-and-neck restraint. In October 2001, NASCAR officials mandated the use of head-and-neck-restraint systems for all drivers racing in the Winston Cup Series, Nascar Busch Series or Nascar Craftsman Truck Series.
The window openings on the cars are covered by a mesh made from nylon webbing. This webbing helps keep the driver’s arms from flailing out of the car during a crash. The G-forces are so high during a crash — between 50 and 100 times the force of gravity — that it is impossible for the driver to control the position of his arms. This can be especially dangerous if the car rolls over and starts tumbling. The net also has a quick release so that the driver can get it out of the way without much effort.
In 1994, NASCAR introduced roof flaps — a safety device designed to keep cars from going airborne and tumbling over the track. Before this, when the cars spun out at high speeds (more than 195 mph / 324 kph), they would often fly into the air once they had rotated about 140 degrees. At this angle, the car takes on a shape that interacts with the wind very much like a wing.
 When the car has spun around 140 degrees, its shape is very similar to that of a wing. |
If the speed of the car is high enough, it will generate enough lift to pick up the car. To prevent this, NASCAR officials developed a set of flaps that are recessed into pockets on the roof of the car. Through wind-tunnel testing, NASCAR determined that the area of lowest pressure is at the back of the roof, near the rear window.
When the car reaches an angle at which it generates significant lift, the low pressure above the flaps sucks them open. The first flap to open is the one oriented at a 140-degree angle from the centerline of the car. Once this flap opens, it disrupts the airflow over the roof, killing all of the lift.
An area of high pressure forms in front of the flap. This high-pressure air blows through a tube that connects to the pocket holding the second flap, causing the second flap to deploy. The second flap, which is oriented at 180 degrees, makes sure that the car continues to kill the lift as it rotates. After the car has spun around once, it has usually slowed to the point that it no longer produces lift. The roof flaps keep the cars on the ground as they spin. This allows the skidding tires to scrub off some of the speed, hopefully allowing the driver to regain control. If not, at least the speed is reduced before the crash.
 NASCAR race-car windshields are made out of Lexan, the same polycarbonate material used to make bulletproof glass. |
The windshields on NASCAR race cars are made of Lexan, which is the same polycarbonate material used on fighter-plane canopies. This material is very strong, but also surprisingly soft. This softness is actually what gives it its strength. When an object hits the Lexan windshield, it doesn’t shatter it. Instead, the object scratches, dents or imbeds itself in the windshield.
The windshields are usually constructed from three relatively flat pieces of Lexan. Each piece is supported by a framework built into the roll cage — this gives the windshield the strength to resist large objects. The downside of a Lexan windshield is that it scratches very easily — you could scratch one with your fingernail. A bare Lexan windshield would have to be replaced after every race because of scratches from sand and other grit on the track. But instead of replacing them, the NASCAR teams apply an adhesive film to the windshields that is harder than the Lexan and as clear as glass. After each race, the film can be peeled off and replaced, leaving the Lexan unscratched. Some teams apply several layers of this film and remove them one at a time during the race.
In the 1950s, NASCAR race cars used the fuel tanks from whatever street car they were based on. There were some schemes for wood reinforcements, but leaks and fires were common. Today’s 22-gallon fuel tanks, also called fuel cells, have built-in safety features to limit the chance of them rupturing or exploding. Fuel cells have a steel outer layer and a hard, plastic inner layer. The fuel cell is located in the rear of the car and is held in place by four braces that keep it from flying loose during an accident. It is filled with foam, which reduces the slosh of the fuel and any chance of explosion by reducing the amount of air in the cell. If the cell does ignite internally, the foam absorbs the explosion. The car also has check valves that will shut off fuel if the engine is separated from the car.
One part of a NASCAR car engine that was implemented for safety reasons is now being pointed at as the cause for many of the multi-car accidents during races. Restrictor plates are used at NASCAR’s super-speedways, including Daytona and Talladega, to slow cars down. The New Hampshire International Speedway was recently added to that short list of restrictor-plate tracks following the deaths of Adam Petty and Kenny Irwin on that track within months of each other. A restrictor plate is a square aluminum plate that has four holes drilled into it. Hole size is determined by NASCAR and varies between 0.875 inches and 1 inch. Restrictor plates are placed between the carburetor and the intake manifold to reduce the flow of air and fuel into the engine’s combustion chamber, thus reducing horsepower and speed.
Restrictor plates were implemented in 1988 following Bobby Allison’s crash into a retaining fence at 210 mph, which endangered hundreds of fans. Also in 1987, Bill Elliott set the track record by running a lap around the track at 213 mph. Some believe that if restrictor plates weren’t used, NASCAR cars could race on super-speedways at speeds in excess of 225 mph due to the improved aerodynamics of the cars over the past decade.
While NASCAR officials contend that restrictor plates are needed to prevent high-speed crashes like Allison’s, many drivers complain that restrictor plates are the cause of multi-car accidents. Restrictor plates reduce speed by about 10 mph, leaving the field of more than 40 cars bunched tightly as they race around the track at 190 mph. If one of these cars crashes, it usually causes several other cars to crash along with it.
Even under normal, street-driving conditions, there is a great chance that an accident will occur, and that numerous injuries will result. NASCAR lacks many of the safety measures found in other racing series, including some type of safety committee, a medical or safety director or a consistent traveling safety team that attends every race. A heavy burden is placed on the NASCAR drivers themselves to make sure that they are as safe as possible when they step inside their cars. In stock-car racing, the chances for serious injury increase because the force at which these cars collide with other cars or walls is far greater. NASCAR race cars move faster and are heavier than conventional vehicles. Before beginning a race, a NASCAR driver dons several pieces of protective equipment that could save his life if an accident were to occur. This gear covers the driver from head to toe and would even protect him if a fire were to break out in his car.
 Most drivers wear a full-face helmet. Trickle does sometimes but usually doesn’t. |
The head is probably the most vulnerable part of the human body during an accident. While the driver’s body is strapped in very tightly, the head can jerk around uncontrollably. The helmet is designed to dissipate impact energy over the entire helmet and prevent debris from puncturing it. Every NASCAR driver is required to wear some type of helmet.
Most wear a full-face helmet, which covers the entire head and wraps around the mouth and chin. Others wear an open-face helmet, which only covers the head. drivers who wear the open-face helmet usually wear protective goggles. They claim that a full-face helmet restricts their peripheral vision.
All helmets go through some sort of testing before they are considered safe enough for high-speed racing. Snell Memorial Foundation is an independent organization that sets voluntary standards for auto-racing helmets. To test the impact resistance of a racing helmet, Snell places the helmet onto a metal head form and drops it onto various types of anvils. If the peak acceleration impacting the metal head exceeds a magnitude of force equal to 300 Gs, or 300 times the force of gravity, it is rejected. This level of impact is hard to conceptualize — a head-on impact at 30 mph into a concrete wall is measured at 80 Gs. Most impacts on a race track are between 50 and 100 Gs. A 100-G impact for a 160-pound man would feel like 16,000 pounds pressing on top of him.
Perhaps the most recognizable piece of NASCAR racing gear is the driver’s suit, which is emblazoned with patches of the team’s sponsors. These suits are almost as recognizable as the drivers themselves. While most of us think of this suit as a walking billboard, it is actually quite important for the safety of the driver. The suit is made out of either Proban or the same Nomex material that lines the inside of the driver’s helmet.
 The drivers’ trademark racing-suits protect them in case of fires. |
Nomex is a fire-retardant material that protects the driver and crew if there is a flash fire in the pits or a fire resulting from a crash. Unlike other flame-retardant materials, the flame resistance of Nomex cannot be washed out or worn away. The Nomex is woven into a material that is used to make the suit, gloves, socks and shoes worn by the driver.
One of the most common injuries in NASCAR is the driver’s feet being burned by the heat coming from the engine. These suits are given a rating to determine how long they will protect drivers from second-degree burns in a gasoline fire, which can burn at between 1,800 and 2,100 degrees Fahrenheit. Ratings are provided by the SFI Foundation, a non-profit organization that sets standards for various pieces of racing equipment. SFI ratings range between 3-2A/1 (three seconds of protection) to 3-2A/20 (40 seconds of protection).
Four NASCAR drivers have been killed on the track since May 2000 — Adam Petty, Kenny Irwin, Tony Roper and Dale Earnhardt Sr.. All of these drivers were killed when their vehicles slammed head-on into a retaining wall, causing a fracture to the base of the skull. Some believe this type of injury is due to the driver’s head being left unsecured in the car while his body is strapped securely to his seat.
The risk of severe injury, and possibly death, prompted six NASCAR drivers to try out a new device called the Head And Neck Support (HANS) system at the 2001 Daytona 500. This device was co-developed by Dr. Robert Hubbard, a professor of engineering at Michigan State University, and his brother-in-law, former IMSA car driver Jim Downing. The HANS device is designed to reduce the chance of injury caused by unrestrained movement of the head during crashes.
The HANS device is a semi-hard collar made of carbon fiber and Kevlar, and it is held onto the upper body by a harness worn by the driver. Two flexible tethers on the collar are attached to the helmet to prevent the head from snapping forward or to the side during a wreck. The device weighs approximately 1.5 pounds. Doctors have said that it is unclear if the HANS device could have saved Earnhardt, but it is believed that the device saved the life of a Championship Auto Racing Teams (CART) driver in January 2001. While practicing for an upcoming race, Bruno Junqueira spun out of control and slammed into a concrete wall at 200 mph. Junqueira, who was wearing the HANS device, walked away from the crash without injury.
In October 2001, NASCAR officials mandated the use of an approved head-and-neck-restraint system for all drivers racing in the Winston Cup Series, Nascar Busch Series or Nascar Craftsman Truck Series. NASCAR officials have said that NASCAR race cars are different from CART cars, and they are unsure if the device would be as effective for NASCAR drivers. Drivers, including Earnhardt, have complained that the device is too bulky, would restrict movements and would make it difficult for drivers to exit the car in emergencies. Hubbard/Downing Inc. said it was producing only three to four of these helmets per day just weeks before the 2001 Daytona 500, but received nearly three-dozen orders within hours after Earnhardt’s crash. Ford has offered to pay for a HANS device for any driver who wants to wear one.
