NASCAR Has an Injury Problem. There are Engineering Solutions.
NASCAR auto racing is one of the safest forms of that sport—but brain injuries are still happening.
NASCAR stock-car racing has evolved from cow pasture competitions between bootleg alcohol runners into a billion-dollar national sport in the U.S. Part of its popularity is built into the nature of the sport: closed-bodied cars that allow very close racing with occasional incidental contact. That contact does produce accidents, and over the years, the governing body has added regulations to improve driver safety. The new cars used today are a major departure from the shop-built chassis of the past. They are a spec car, purchased from a single manufacturer, and use significantly higher technology than any past generation of car in the sport’s history. Safety was a factor in the design from the beginning, but concussion remains a serious risk in the sport. The cars are safer, but closed head injuries are still damaging, even ending driver careers. Why? Jim Anderton comments.
If you’re a fan of NASCAR—and even if you’re not—you’ve probably seen the spectacular highlight reel footage of what fans of the sport call “The Big One.”
The Big One is seen in its worst form at superspeedways like Daytona and Talladega. Those massive pileups are spectacular—but are also remarkable for the ability of drivers to generally climb out of the wreckage unharmed. This is an engineering achievement, created through 70 years of progressive rule changes by the governing body to make the vehicles safer.
Fatalities are rare in stock-car racing today, and this year saw the debut of what NASCAR calls the Next Gen car, a radical change in the sport’s operating principles.
In the past, individual teams either built cars in their own shops, or bought chassis and engines from other shops and prepared them for competition. Some preparers became legendary in the sport. Petty Engineering, the Wood Brothers, Holman and Moody and a few others dominated the sport, and fed parts and cars to other competitors. The Next Gen car is a fundamental change: a spec car, built by a single manufacturer and purchased by the teams as a complete chassis.
The last vestiges of production car technology, namely sheet steel bodies and five-lug wheel hubs, are gone, and the sport has moved to the high technology seen in international sports car racing. The cars are also significantly stiffer, which is great news for engineers and crew chiefs when setting up the car—but which has also added a new safety issue for drivers: concussion.
Head injuries are nothing new in NASCAR. The sport’s leading driver, Dale Earnhardt, was killed by a basal skull fracture in the 2001 Daytona 500 in a relatively minor crash, a tragedy which drove the widespread adoption of head and neck restraints in all forms of motorsports. The HANS device, combined with very strong seats that hold the driver and the driver’s head in position during a violent wreck, have helped—but today’s stiff car, even with softer racetrack walls, better helmets and custom seats, is still delivering impact decelerations that are causing serious concussions.
Alex Bowman has been eliminated from playoff contention due to five races missed after a concussion suffered in Texas. Kurt Busch has had his career essentially ended due to a concussion sustained in the new car. Careers cut short due to head injuries are not new in the sport. Ernie Irvan, Steve Park, Bobby Allison and other outstanding drivers have suffered career-ending brain injuries at the highest level of the sport.
But the Next Gen car was designed with the latest technology. What’s going on?
Well, in motorsports, a stiff chassis is a good chassis. It allows precision suspension setups with fewer variables due to unintended rates induced by bending modes in the structure. And in some types of collision, a secure roll cage does protect the driver, especially in rollovers and flips.
But encapsulating the driver and immobilizing him or her doesn’t address the fundamental problem of a very stiff structure: acceleration. Or more specifically, deceleration of the driver’s head, and the brain sloshing into the inside of the skull as a result.
There is no way to remediate that problem by strapping the driver in tighter into a stronger seat. The only solution is to decrease the G-forces of impact, and as every first-year student knows, the equations of distance, velocity, acceleration and third derivative forces (sometimes called “jerk”) are dependent on Delta V and the distance over which that velocity goes to zero.
Soft walls help, but something has to deflect to allow the driver’s head to decelerate more slowly. Either the chassis structure has to deform, as it does in production cars for this purpose, or the seat must be redesigned to yield a little, either through deformable structures, shear bolts with captive lanyards or some form of spring mounting.
I suspect that even two or three inches of seat movement may be enough to significantly reduce the G loading on drivers’ skulls. Designing seats that move inside the roll cage is completely counterintuitive to everyone from Hendrick Motorsports to guys like me with my stick welder, but the physics are irrefutable.
NASCAR designed a very strong car that can take a hit and keep on driving. That creates exciting racing, but no sport can keep ending its stars’ careers through injury. NASCAR really doesn’t have very many options here. Either make the chassis structures more deformable or allow the seats to move a little. Neither will require an extensive redesign of the Nex Gen car.
I suspect one or both of those solutions are going to be seen in the sport before next February’s Daytona 500.