Dr. Diandra: Next Gen tech vs. Martinsville

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Martinsville Speedway is the platonic ideal of short-track racing.

We expect — we look forward to — banging, bumping and short tempers. Add in high-profile drivers yet to win a race and the result is likely to be accidents and spins.

Will the Next Gen car’s composites, brakes and suspension stand up to the task?

Last year’s two Martinsville races tied for the most cautions (15). The spring Martinsville race featured seven spins and five accidents, while the fall race had only one spin, but 11 accidents. The track’s closest competitors (Nashville, fall Darlington and fall Texas) each had 11 cautions.

Thirty-one cars spun or were involved in accidents at 2021 Martinsville races.

Cautions by race and type for the 2021 NASCAR Cup Series

Saturday night’s race will be 400 laps instead of the traditional 500. We’ll have to scale down our expectations — and the numbers of cautions, but we still have three stages. Last spring, nine of the 13 spins/accidents came in the third stage.

Next Gen car at Martinsville

Two Next Gen design changes could enhance the propensity for bumping and banging: Brakes and body.

Enlarging the wheels from 15 inches to 18 inches means more room for brakes. A driver can brake later going into a corner and thus go deeper into the corner. With more ability to dissipate heat, wearing out the brakes won’t be as much of a problem as in past Martinsville races.

“We have more braking power than we have grip,” Alex Bowman said.

“Before,” Dale Jarrett said on the NASCAR on NBC podcast, “if you took it in a little too deep, not only did you drive it further into the corner, you started wheel hopping.”

Driving the car further into the corner increases the the potential for contact.

“Not that I’m looking for wrecks,” Jarrett said. “Contact is what we look for and that’s why we love those short tracks.”

The second change – composite car bodies – first appeared in 2017 in the Xfinity Series, where they proved more resilient than steel.

Composite bodies rebound from scrapes with the wall, but their real advantage is standing up to cut tires. A tire coming apart acts like the string in a weed whacker: It can cut right through metal.

That whipsaw action can transform the minor problem of a blown tire into the major problem of a shredded quarter panel.

“The car from a door-banging side of things, rubbing, not cutting tires down, we haven’t really seen that happen yet,” Joey Logano told Dustin Long.

And that’s thanks to composites.

What is a composite?

Composite is short for composition material. Two dissimilar materials combine to make a material with properties better than either material individually.

Remember that Reese’s ad starring Kevin Harvick and IndyCar driver Tony Kanaan? They’re selling a taste composite. Peanut butter cups are good. Caramel is good. When you put them together, it tastes better – and different – than either one separately.

Structural composites, like those in the Next Gen car body, are strong but lightweight. These materials originally developed in the aerospace industry, where every pound increases the fuel bill, or even the ability to get off the ground in the first place.

Composites follow a simple formula. A matrix – a fiber or particle – combines with a binder like an epoxy or a cement.

You are more familiar with composites than you might think. Wood is a composite. Cellulose is a strong, fibrous material. Soft, gluey lignin holds the cellulose fibers together.

Your bones are also composites. Hydroxyapetite — a strong-but-brittle mineral — embeds in collagen, which is soft and cushiony.

Paper mache, concrete, asphalt, adobe, mother of pearl and plywood are all composites. Although composites are new to bodies, NASCAR already uses them in seats, dashboards and even NACA ducts.

Five Star Race Car Bodies in Twin Lakes, Wisconsin makes the Next Gen body. Although the specific materials in the Next Gen body are proprietary, the matrix includes carbon fiber and Kevlar.

The fibers are woven into fabric. Sheets of fabric are stacked, with the fiber direction varied so that the composite is equally strong in all directions.

A drawing showing a fiber for a composite, the fiber woven into cloth and the process of stacking the cloth prior to molding

There’s one more component to the composite body. It takes a lot to break carbon fiber composites, but they can break. Because they are brittle, they fracture and leave shards of material everywhere – about the last thing you want on a racetrack.

So there’s one more element to counteract the brittleness: Layers of a proprietary material sandwich the carbon fiber and help hold it together in case of accidents.

A graphic showing how fiberglass bookends the carbon fiber-Kevlar composite fabric

After loading the fabric layers into a mold, they are saturated with an epoxy-type resin. Suction pulls the fabric tightly against the mold while the composite cures.

Once cured, any holes or tabs necessary for fitting the body onto the chassis and other body pieces are drilled. Even the nuts used in flange fitting the body together are glued into place.

And there’s only one way the parts fit together, so unlike my experiences with flat-pack furniture, it’s pretty much impossible to do it wrong.

Why carbon-fiber composites instead of steel?

Carbon fiber composite is five times stronger than steel by weight. Neither chemicals nor heat damage it.

“The superior flame resistance is one of the things we’re really proud of achieving,” said Corey Schultz, vice president of sales and marketing at Five Star Race Car Bodies.

It’s also twice as stiff as steel, which means that carbon-fiber composite parts don’t deflect when a car is going 200 mph. NASCAR had to add rules for the Gen-6 car to prevent teams from making hoods and decklids that changed shape at speed and provided an aerodynamic advantage.

Another feature of the Next Gen composite is that it is repairable – but not by teams. Pieces in need of attention must be returned to Five Star for repairs.

So more bumping and banging at Martinsville?

Given bigger brakes and stronger bodies, you might expect drivers to turn the aggression knob all the way up to eleven at Martinsville.

But maybe not.

Suspension issues arose at the Clash at the L.A. Coliseum, which is the track most similar to Martinsville that’s hosted the Next Gen car. Those failures may have been due to the lack of run-off space, or just unfamiliarity with the new car. But drivers took note.

“Before, we didn’t want to hit the wall because of aero,” Chase Elliott said at Richmond last week. “Now, it’s the suspension.”

In particular, the rear toe link appears to be the weakest part of the Next Gen suspension. Toe is the angle the wheels make with the car’s centerline.A graphic explaining toe as it refers to wheelsThe toe link is the part that moves one side of the wheel in or out. It’s really nothing more than a rod with connectors at either end.

“It’s crazy,” Logano said. “You look at these cars that get out of the race because something broke on their car after a wreck and the body looks fine. … Even Daytona, we saw cars crash really hard and it’s kind of like the body pops back and it doesn’t look bad, but everything behind it is crushed.”