NASCAR safety, it’s an evolutionary process

By JON CULLIMORE
Trucking 2000

5/20/2008

The term NASCAR safety may seem like an oxymoron, given all the thrills, chills and spills during a typical race. But it’s rare these days, even during the most devastating crashes, that anyone gets injured or killed. That wasn’t always the case. In the sport’s early decades, it wasn’t unheard of for spectators sitting in the stands to get injured or even killed. During the mid-1950s the public’s growing concern over safety almost outlawed the sport altogether. NASCAR was instrumental in not only killing a proposed ban but also lead the industry in safety improvements.

The cars and conditions under which they race are a far cry from those early days. With 750 horsepower, the cars can reach more than 200 mph, enough to scare even the toughest. But, being behind the wheel as a car is spinning out of control toward a concrete retaining wall is the sober reality professional drivers must face.

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.

This gear includes a fire retardant suit and a helmet, which have evolved from years of testing and development, but the single most talked about piece of protective gear to be implemented in recent years is the HANS device. The accidents that spurred its development and use rocked the racing community.

Four NASCAR drivers have been killed on the track since May 2000: Adam Petty, Kenny Irwin, Tony Roper and Dale Earnhardt. Killed when their vehicles slammed head-on into a retaining wall, all of these drivers suffered a fracture at the base of the skull. Some believe this injury is caused by 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 Head And Neck Support (HANS) system at the 2001 Daytona 500. 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 device is a 1.5 pound, semi-hard collar made of carbon fiber and Kevlar. It is held onto the driver’s upper body with a harness.

Two flexible tethers on the collar are attached to the helmet that help prevent the head from snapping forward or to the side during a wreck. Doctors have said it’s unclear if the HANS device could have saved Earnhardt, but it is believed that it saved the life of a 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.

For a time NASCAR officials said their cars were different and the device would be as effective for NASCAR drivers. Drivers, including Earnhardt, complained that the HANS was too bulky, restricted movements and made it difficult for drivers to exit the car in emergencies.

Makers of the device, Hubbard-Downing Inc., said it was producing only three to four helmets per day just weeks before the 2001 Daytona 500, but received nearly three-dozen orders within hours after Earnhardt’s crash. Ford even offered to pay for a HANS device for any driver who wanted to wear one.

In October 2001, NASCAR officials mandated the use of approved head-and-neck-restraint systems for all drivers racing in the series it sanctioned. While today’s NASCAR car is no more than a basic skeleton of metal tubing covered with thin, metal sheeting, the safety devices in and around the cars have evolved similar to the HANS, over years in response to accidents and crashes that have injured or killed drivers.

The key to a driver 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. Street cars are designed to crush and absorb much of the energy of an impact, giving the other safety devices, such as seat belts and airbags, more time to slow down the driver’s body.

A race car uses some of the same principles. The front and rear are built from thinner steel tubing so they will crush on impact with another car or a wall. The engine is mounted so it can drop out of the car during frontal crashes. The middle section, which includes a roll cage, is designed to maintain its integrity during a crash and protect the driver.

The seat has several important jobs: It must keep the driver inside the roll cage, keep him from contacting anything hard during a crash, and bend to help absorb energy during the crash. The seats wrap around the driver’s rib cage to provide support. They spread pressure out over the entire rib cage instead of letting it concentrate in one point. Some newer seats wrap around the driver’s shoulders as well, to provide better support since the shoulders are more durable than the rib cage.

One of the items most directly responsible for protecting drivers is the safety harness. In addition to the seats, the safety harness absorbs most of the driver’s energy during a crash. On a street car, seatbelts are designed to stretch, which limits the force placed on the driver.

On a NASCAR vehicle, however, the restraint used is a five-point harness made from thick, padded, nylon webbing. With two straps over the driver’s shoulders, two around his waist and one between his legs, this restraint is designed to not stretch but hold the driver tightly in his seat so his body slows down with the car.

The window openings on race cars are covered by a mesh also made from nylon webbing. This net helps keep drivers’ arms from flailing out of the car. G-forces during a crash are between 50 and 100 times the force of gravity, making it impossible for drivers to control the position of their arms. In the event of an emergency, the net also has a quick release so the driver can escape without much effort.

In 1994, NASCAR introduced roof flaps to keep cars from going airborne during crashes. Before this, when cars spun out at high speeds more than 195 mph, they would often fly into the air once they had rotated about 140 degrees. At this angle, the car interacts with the wind much like a wing. If the speed of the car is great enough, it will generate the necessary lift to pick up the car. To help prevent this, flaps recessed into pockets on the roof and deploy to generate down force.

Through wind-tunnel testing, NASCAR officials determined 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, low pressure above the flaps suck them open.

The first flap to open is the one at a 140-degree angle from the centerline of the car. Once this flap opens, it disrupts airflow over the roof, killing all 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, set at 180 degrees, makes sure no lift is generated as the car continues to rotate.

While the roof flaps keep cars on the ground as they spin, skidding tires reduce the vehicle’s speed and hopefully help the driver regain control. If not, at least speed is reduced before impact.

Windshields on race cars are made of Lexan, the same polycarbonate material used on fighter-plane canopies. Usually made from three pieces of Lexan, each windshield piece is supported by a framework built into the roll cage. This gives the windshield the strength to resist large objects. While this material is very strong, it’s also surprisingly soft. When an object hits it, the material doesn’t shatter. Instead, the object scratches, dents or imbeds itself in the windshield.

A bare Lexan windshield would have to be replaced after every race, but NASCAR teams apply an adhesive film that is harder than the Lexan and as clear as glass. After each race, the film can be peeled off and replaced, leaving the windshield 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, made of a steel outer layer and a hard, plastic inner layer, are located in the rear of the car and attached with four braces that keep them from flying loose during an accident. The tanks are filled with foam that reduces the slosh of the fuel and limits air in the tank and thus the chance of explosion. If the fuel does ignite internally, the foam slows the rate at which ignition can occur. The fuel lines also have check valves that close if the engine is separated from the car.

One measure that was implemented for safety reasons is now being criticized as the cause for many multi-car accidents – restrictor plates. Mandated in 1988 after a 210-mph crash by Bobby Allison endangered hundreds of fans, they are used at NASCAR’s superspeedways, including Daytona and Talladega.

A restrictor plate is a square aluminum plate placed between the carburetor and intake manifold to reduce the flow of air and fuel into the engine and limit horsepower and speed. While NASCAR officials contend that restrictor plates are needed to prevent high-speed crashes like Allison’s, many drivers complain that the plates force the field of more than 40 cars to bunch tightly as they race around the track. If one car crashes, it usually causes several other cars to crash along with it.

While the debate continues, some believe the aerodynamics of today’s cars without restrictor plates would allow speeds in excess of 225 mph at the superspeedways. With those speeds, let’s hope safety gets put first.