The three most crucial parameters in determining the severity of a crash are:
How much kinetic energy the car carries
How long the collision takes
The angle at which the car hits
The last of these factors requires trigonometry to explain properly. You can probably intuit, however, that a shallower hit is preferable to a head-on — or rear-on — hit.
When the angle between the car and the wall is small, most of the driver’s momentum starts and remains in the direction parallel to the wall. The car experiences a small change in velocity.
The larger the angle, the larger the change in perpendicular speed and the more force experienced. NASCAR has noted that more crashes this season have had greater angles than in the past.
Busch and Bowman both had pretty large-angle hits, so we’ll skip the trig.
Energy — in pounds of TNT
A car’s kinetic energy depends on how much it weighs and how fast it’s going. But the relationship between kinetic energy and speed is not linear: It’s quadratic. That means going twice as fast gives you fourtimes more kinetic energy.
The graph shows the kinetic energies of different kinds of race cars at different speeds. To give you an idea of how much energy we’re talking about, I expressed the kinetic energy in terms of equivalent pounds of TNT.
A Next Gen car going 180 mph has the same kinetic energy as is stored in almost three pounds of TNT.
Because IndyCars are about half the weight of NASCAR’s Next Gen car, an IndyCar has about half the kinetic energy of a Next Gen car when both travel at the same speed.
At 330 mph, Top Fuel drag racers carry the equivalent of six pounds of TNT in kinetic energy.
All of a car’s kinetic energy must be transformed to other types of energy when the car slows or stops. NASCAR states that more crashes are occurring at higher closing speeds, which means more kinetic energy.
Longer collisions > shorter collisions
That seems counterintuitive, doesn’t it? Who wants to be in a crash any longer than necessary?
But the longer a collision takes, the more time there is to transform kinetic energy.
A pitting car starts slowing down well below it reaches its pit box. The car’s kinetic energy is transformed into heat energy (brakes and rotors warming), light energy (glowing rotors), and even sound energy (tires squealing).
The same amount of kinetic energy must be transformed in a collision — but much faster. In addition to heat, light and sound, energy is transformed via the car spinning and parts deforming or breaking. (This video about Michael McDowell’s 2008 Texas qualifying crash goes into more detail.)
The force a collision produces depends on how long the car takes to stop. Compare the force from your seat belt when you slow down at a stop sign to what you feel if you have to suddenly slam on the brakes.
To give you an idea of how fast collisions can be, the initial wall impact in the crash that killed Dale Earnhardt Sr. lasted only eight-hundredths (0.08) of a second.
SAFER barriers use a car’s kinetic energy to move a heavy steel wall and crush pieces of energy-absorbing foam. That extracts energy from the car, plus the barrier extends the collision time.
The disadvantage is that a car with lower kinetic energy won’t move the barrier. Then it’s just like running into a solid wall.
That’s the same problem the Next Gen car seems to have.
Chassis stiffness: A Goldilocks problem
The Next Gen chassis is a five-piece, bolt-together car skeleton, as shown below.
That graphic doesn’t show another important safety feature: the energy absorbing foam that covers the outside of the bumpers. It’s purple in the next diagram.
All cars are designed so that the strongest part of the car surrounds the occupants. Race cars are no different.
The center section of the Next Gen chassis is made from stout steel tubing and sheet metal. Components become progressively weaker as you move away from the cockpit. The bumper, for example, is made of aluminum alloy rather than steel. The goal is transforming all the kinetic energy before it reaches the driver.
Because the Next Gen car issues are with rear impacts, I’ve expanded and highlighted the last two pieces of the chassis.
The bumper and the rear clip don’t break easily enough. The rear ends of Gen-6 cars were much more damaged than the Next Gen car after similar impacts.
If your initial thought is “Just weaken the struts,” you’ve got good instincts. However, there are two challenges.
I highlighted the first one in red: the fuel cell. About the only thing worse than a hard collision is a hard collision and a fire.
The other challenge is that a chassis is a holistic structure: It’s not like each piece does one thing independent of all the other pieces. Changing one element to help soften rear collisions might make other types of collisions harder.
Chassis are so complex that engineers must use finite-element-analysis computer programs to predict their behavior. These programs are analogous to (and just as complicated as) the computational fluid dynamics programs aerodynamicists use.
Progress takes time
An under-discussed complication was noted by John Patalak, managing director of safety engineering for NASCAR. He told NBC Sports’ Dustin Long in July that he was surprised by the rear-end crash stiffness.
The Next Gen car’s crash data looked similar to that from the Gen-6 car, but the data didn’t match the drivers’ experiences. Before addressing the car, his team had to understand the disparity in the two sets of data.
They performed a real-world crash test on a new configuration Wednesday. These tests are complex and expensive: You don’t do them until you’re pretty confident what you’ve changed will make a significant difference.
But even if the test goes exactly as predicted, they aren’t done.
NASCAR Cup Series drivers race on the road for the final time this season Sunday, as the Charlotte Motor Speedway Roval course ends the playoffs’ Round of 12.
The 17-turn, 2.28-mile course incorporating the CMS oval and infield will determine the eight drivers who will advance to the next round of the playoffs. Chase Elliott won last Sunday at Talladega Superspeedway and is the only driver who has qualified for a spot in the Round of 8.
NASCAR has suspended Rodney Childers, Kevin Harvick‘s crew chief, for four races and fined him $100,000 for what the sanctioning body called modification of a part supplied by a vendor.
Harvick, who is out of the Cup Series playoffs, and the Stewart-Haas Racing No. 4 team were docked 100 points.
Harvick’s car and that of Martin Truex Jr. were taken to NASCAR’s Research and Development Center in Concord, N.C. after last Sunday’s race at Talladega Superspeedway. There were no penalties assessed to the Truex team.
Harvick’s car erupted in flames during the Southern 500 Sept. 4 at Darlington Raceway. After he climbed from the smoking car, Harvick blamed the fire on “just crappy parts on the race car like we’ve seen so many times. They haven’t fixed anything. It’s kind of like the safety stuff. We just let it keep going and keep going.
“The car started burning and as it burned the flames started coming through the dash. I ran a couple laps and then as the flame got bigger it started burning stuff up and I think right there you see all the brake fluid that was probably coming out the brakes and part of the brake line, but the fire was coming through the dash.
“What a disaster for no reason. We didn’t touch the wall. We didn’t touch a car, and here we are in the pits with a burned-up car, and we can’t finish the race during the playoffs because of crappy-ass parts.”
Unless the team appeals, Childers would miss races at Charlotte, Las Vegas, Homestead and Martinsville and would return for the season finale at Phoenix.
NASCAR president Steve Phelps told the Associated Press that officials have not targeted Harvick. “I would say that’s ridiculous,” he said. “No one has a vendetta against Kevin Harvick or Rodney or anyone at Stewart-Haas Racing.”
On Wednesday afternoon, Harvick tweeted, “Seems strange…” A Childers tweet called the penalty “Shocker…..”.
NASCAR also announced Wednesday it has suspended Young’s Motorsports crew chief Andrew Abbott indefinitely for a behavioral violation during pre-race inspection. He must undergo anger-management training to be reinstated. The team races in the Camping World Truck Series.
Elliott is the clear favorite to win a second championship. He won Sunday at Talladega to advance to the Round of 8 and can relax Sunday at Charlotte having punched his ticket. Relaxing isn’t likely, however, as Elliott will be among the favorites to win.
Last three races: 2nd at Talladega, 4th at Texas, 30th at Bristol
Past at CMS Roval: Won in 2018.
Blaney continues along a path that could result in him winning the Cup championship without winning a race. He came within an eyelash of winning Sunday at Talladega but fell victim to Chase Elliott’s last-lap charge. He should be a threat Sunday at the Roval, where he has four straight top 10s.
Larson’s last win — and his last top-four finish — came at Watkins Glen seven races ago. He is 18 points over the cutline entering Sunday’s race.
QUESTIONS TO ANSWER
Points position: 9th
Last three races: 9th at Talladega, 15th at Texas, 20th at Bristol
Past at CMS Roval: Sunday will mark his first Cup race. Has three top threes in four Xfinity starts.
Cindric hasn’t won since the season-opening Daytona 500 and is one of five drivers still in the playoffs who own only one victory this year. His ninth-place run at Talladega ended a streak of four straight finishes of 12th or worse.