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Two drivers missed the races this year after severe rear-end collisions. Kurt Busch been out since Accident in qualifying in Pocono in July. Alex Bowman Bolted firmly into a wall in Texas will Miss Sunday’s race In Charlotte Ruffal (2 p.m. ET, NBC).

Other drivers noticed it The blows they received in the next generation car are among the hardest they’ve ever felt In the car cup.

“When I crashed (in practically Auto Club Speedway), I thought the car had been wrecked, and I could barely support the bumper. I just felt Someone hit you with a hammerKevin Harvick He told NBC Sports.

The three most important factors in determining the severity of a collapse are:

  • The amount of kinetic energy carried by the car
  • How long does the collision take?
  • The angle at which the car hits


The last of these factors requires trigonometry to explain properly. You’ll likely sense that a flat hit is better than a headshot or backhand.

Graphic display of hitting less deep (low angle) and hitting deeper (high angle)
Click to see it enlarged

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 is subjected to a slight change in speed.

The larger the angle, the greater the change in vertical velocity and the greater the force. NASCAR has noticed that more crashes this season have had larger angles than in the past.

Busch and Bowman both got really big corner hits, so we’re going to skip the triangles.

Energy – pounds of TNT

The kinetic energy of a car depends on how much it weighs and its speed. But the relationship between kinetic energy and velocity is not linear: it is quadratic. This means to go twice as soon as possible four times More kinetic energy.

The graph shows the kinetic energies of different types of racing cars at different speeds. To give you an idea of ​​how much energy we’re talking about, I expressed kinetic energy in terms of equivalent pounds of TNT.

A vertical bar graph showing the kinetic energies and energies of different types of racing cars

  • A next-generation car traveling at 180 mph has the same kinetic energy stored in roughly three pounds of TNT.
  • Because IndyCars is about half weight From NASCAR’s Next-Generation Car, an IndyCar has about half the kinetic energy of a next-generation car when both travel at the same speed.
  • At 330 mph, Top Fuel racers carry the equivalent of six pounds of TNT in kinetic energy.

All kinetic energy of the car must be Transformed into other types of energy When the car slows down or stops. NASCAR states that more accidents occur at higher shutdown speeds, which means more kinetic energy.

Longer Collisions > Shorter Collisions

This seems counter-intuitive, right? Who wants to be in an accident longer than necessary?

But the longer the collision lasts, the more time there is for the transfer of kinetic energy.

A car that is swaying begins to decelerate much lower than it reaches its bore box. The vehicle’s kinetic energy is converted into thermal energy (heating of the brakes and rotors), light energy (glowing rotors), and even sound energy (tyres screeching).

The same amount of kinetic energy must be transferred in the event of a collision – but faster. In addition to heat, light, and sound, energy is converted by vehicle spinning and parts deforming or breaking. (This video is about Michael McDowell‘s 2008 Texas Playoff Crash Goes into more detail.)

The force the 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 would feel if you had to apply the brakes all of a sudden.

To give you an idea of ​​how fast the collisions are, the initial wall effect in the crash that killed Dale Earnhardt Sr. It lasted only eight hundred (0.08) of a second.

SAFER baffles use the kinetic energy of a vehicle to move a heavy steel wall and crush pieces of energy-absorbing foam. This extracts energy from the vehicle, plus the fender extends impact time.

The disadvantage is that a vehicle with low kinetic energy will not move the barrier. Then it’s like running into a solid wall.

This is the same problem as the next generation car.

Structure rigidity: moderate problem

The Next Generation chassis is a five-piece, bolt-on vehicle skeleton, shown below.

A graphic showing the five parts of the Next Generation Structure.
Image courtesy of NASCAR. Click to enlarge.
Foam around the outside of the rear bumper
Purple is an energy-absorbing foam. Image courtesy of NASCAR. Click to see it enlarged.

This graphic does not show another important safety feature: the energy-absorbing foam that covers the outside of the fenders. It’s purple in the following diagram.

All cars are designed so that the most powerful part of the car surrounds the passengers. Racing cars are no different.

The middle part of the next generation chassis is made of solid steel tubes and sheet metal. The components get progressively weaker the further away from the cockpit. The bumper, for example, is made of aluminum alloy instead of steel. The goal is to convert all the kinetic energy before it reaches the driver.

Since the problems with the next generation car are related to rear impacts, I widened and accentuated the last two pieces of the chassis.

Rear section and bumper, with fuel cell and struts shaded

The bumper and rear clip don’t break easily enough. The rear ends of the Gen-6 cars suffered far more damage than the next generation car after similar effects.

If your initial thinking is “only the weakest struts,” you have good instincts. However, there are two challenges.

The first one highlighted in red: the fuel cell. The only thing worse than a hard crash is a hard crash And the a fire.

Another challenge is that the structure is an all-encompassing structure: it’s not as if each piece does one thing independently of all the others. Changing one element to help mitigate rear-end collisions could make other types of collision more difficult.

The structure is so complex that engineers must use finite element analysis computer programs to predict their behavior. These programs are similar (and just as complex as) the computational fluid dynamics programs used by aerodynamicists.

Progress takes time

John Patalak, NASCAR’s managing director of safety engineering, noted a complexity that wasn’t discussed. Tell Dustin Long from NBC Sports in July He was surprised by the stiffness of the rear collision.

The next-generation car’s crash data looked similar to that of the Gen-6, but the data did not match the drivers’ experiences. Before talking about the car, his team had to understand the discrepancy in the two data sets.

They performed a real-world crash test on a new configuration on Wednesday. These tests are complicated and expensive: don’t do them until you are absolutely confident that what you’ve changed will make a big difference.

But even if the test goes exactly as expected, it will not take place.

Safety moving target.

And it always will be.

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