"Portable Inspection for Race Cars," Feature Article, May 2008

portable inspection
for race cars

Advanced technology changes the rules and helps enforce them, too.

This story was written by staff writers with the assistance of outside contributors.

When Nascar driving legend Dale Earnhardt Sr. died in a final-lap crash during the 2001 Daytona 500, it stunned his legions of fans in the auto racing world. However, it also jump-started a movement by Nascar to recast safety regulations and put racing competitors on a more level surface.

Largely as a result of that tragic occurrence, Nascar, the paramount stock car racing organization in the United States, announced on Jan. 11, 2006, the creation of a universal car it called the Car of Tomorrow.

The Car of Tomorrow, a new race car style for Nascar's Nextel Cup Series, made its debut in March 2007 with much fanfare. After years of development, Nascar's Research and Development Center conceived a race car that would improve driver safety and refine component designs to improve performance baselines and overall competition.

Located in Concord, N.C., the Nascar R&D Center is a $10 million facility where a team of experts has focused its attention and ingenuity on the overall safety of the sport without forfeiting speed or competition.

Standard procedure: To assure that everyone plays by the same rules under Nascar's new Car of Tomorrow standards, Jeff Uran uses a CMM to verify chassis dimensions in a measuring area at Nascar's R&D Center in Concord, N.C.

Every racing team pushes the envelope to win, and many go so far as to engineer and build different cars for different track conditions. As a result, cost has spiraled out of control. Well-funded teams have up to 15 cars or more. The Car of Tomorrow program has implemented measures to control product costs and reduce the practice of manufacturing track-specific cars.

The R&D team developed an adjustable rear wing and a front splitter, along with a refined body and a chassis measurement process, intended to create a level playing field for large and small teams with varying amounts of investment dollars.

Thus far, four COT body types have been approved: the Chevrolet Impala SS, Dodge Avenger, Ford Fusion, and Toyota Camry.

The COT has improved safety features over the older Nascar standard. The driver's seat has been moved four inches to the right, the roll cage has been shifted three inches to the rear, and the car is two inches taller and four inches wider. Larger crumple zones are built into the car on both sides, for more protection.

The splitter is a piece of fiber-reinforced plastic used on the bottom front of the car to produce downforce, replacing the valence. The car's exhaust runs through the body, and exits on the right side, which diverts heat away from the driver. The fuel cell is stronger, and has a smaller capacity (17¾ gallons, down from 22 gallons, which as of 2007 has become standard in all cars). All cars are required to fit the same set of templates.

Standardizing and Verifying

To ensure that race teams are adhering to the standards of the Car of Tomorrow, Nascar has introduced a chassis certification program that includes both dimensional control and metal thickness testing.

"We verify some of the dimensions implemented for safety, such as the driver compartment space and more," said Dan Kurtz, a design engineer at Nascar. "We also have standardized portions of the chassis and body, and those areas are validated, too. This approach allows the owner to lean more to the production side of the business, where they do not have to change things for every race like track-specific cars or a new trend in aerodynamics. New teams can purchase a chassis from a local maker and know they are getting just as competitive a car as the big teams. Those are the reasons the COT is here, with safety being the most important aspect."

For the data acquisition and inspection process, Nascar has acquired two GridLOK systems from Romer Inc. of Wixom, Mich., with portable coordinate measuring machine technology.

Used for in-place measurement of large parts, the solution consists of a 7-axis Romer Infinite articulating arm with standard probes, the Romer GridLOK "conical seat" flooring system, and PowerInspect software from Delcam plc of England.

The CMM arm rests on a mobile base and is moved around a chassis or car to gather data inside, behind, and underneath the measured object. The articulating arm has a measuring volume of 12 feet. It has a patented system for infinite rotation in the primary axes for ease of use.

Jerry Kaproth, safety coordinator at Nascar, said, "The Romer system comes into play every day to verify dimensional controls that were implemented for safety and cost containment. Nascar has standardized portions of the chassis and the body, and we validate all of those areas during the certification process."

According to Kurtz, "Tolerances are much tighter on the Car of Tomorrow than ever before. Our objective was to make the tolerances reasonable so that every organization could build a car and reside within the tolerance, but to make it tight enough that teams do not build track-specific cars to one side or the other of the tolerance. By locking down enough dimensions, the teams will not be significantly different. They may bring different cars to different tracks to rotate them out, but there won't be major variations in terms of aerodynamics and performance properties."

Systems Set to Go

An operator can acquire data with the same part origin while working in a 13x20-foot footprint. To do that, the system uses 5/8-in.-diameter conical seats flush mounted in a steel plate resting on the floor. Placed at three-foot intervals, each conical seat is certified with a laser tracker during installation.

The operator touches a ball probe into three different conical seats, and the CMM arm is locked to the common origin. This "locking method" doesn't interrupt software programs, and requires no use of buttons or computer keyboard selections. If the operator wishes to inspect in another area, he moves the arm, and repeats the locking procedure with the conical seats. No matter how many times the portable CMM is moved, GridLOK retains measuring accuracies because the 3-D data acquired is relative to the same part origin with no cumulative error.

Kurtz conceived and executed the new measurement procedures. When the COT design standards began to materialize, he built 3-D solid models in-house using Pro/Engineer CAD software. Engineers who worked on that project defined specific parameters for the driver's cage.

"We started off with just the center section of the car, which is the driver's compartment and the passenger's side of the car. We wanted to standardize that area, so a CAD model was created in-house," Kurtz said. "We sent the CAD file to a manufacturer in Illinois, and had CNC cut and bent tubes delivered back to us. They are tabbed and slotted to fit together in the proper position to make up the center section of the car. Our most regulated areas are the center section, the rear clip, and the location of the fuel cell. The front clip is defined by rules about the symmetry, not actual locations, and located about a centerline."

So once Nascar set the rules, it had to devise a method to enforce them. Kurtz created a dimensional verification operation guided by a customized PowerInspect inspection routine.

Mounted on the wall near each GridLOK inspection station is a large plasma screen displaying the software's interface. The software prompts for each strategic inspection point. Using the arm's mouse mode and wireless features, inspectors are able to interact with the program by using the large screen alone; no keyboard interaction is required. The macro-driven program not only ensures consistency between inspectors, but has proven to be an effective training tool as well.

Gathering Chassis Data

Kurtz inspected the first 75 chassis to prove out the concept. Then Jeff Uran, a technical inspector at Nascar, was brought in to learn the process. Uran was formerly a Nascar Nextel Cup official with a background as a pit road inspector. Assigned to the COT inspection team, he had the expertise to work closely with Kurtz to refine the program.

With 95 percent of the teams in the local area, transporting a chassis to the R&D Center for certification has been a fairly smooth process. Deliveries occur nearly every day for first-come, first-served inspection. The chassis is placed in the measuring area. Uran locks into the coordinate system, then centers the framework.

Each team essentially defines its centerline by a receiver located on the chassis, and the receiver sits on a defined fixture. The inspectors use a point-line-plane alignment system, and with a slight rotation to zero out on the y-axis, the chassis centerline and the coordinate system centerlines are rectified and ready for inspection.

Using the articulating arm and a 15 mm ball probe, Uran works his way around the chassis gathering 3-D data for tolerance analysis. With nearly 400 inspections under his belt, he averages about four inspections a day. Three other inspectors also have been trained to use the portable inspection system.

Positions of safety: Vehicles must meet tight standards under the Car of Tomorrow rules if they are to compete in Nascar events. Many of the new design features, such as the placement of the driver's seat and roll bar, and size of the fuel tank, are intended to improve the safety of drivers.

Once the inspection is complete, the PowerInspect software generates an Excel spreadsheet report and the documentation is printed. Areas that failed the inspection are highlighted for close examination. The inspector will probe the area in question a second time to determine if a surface aberration or other anomaly is the cause.

Uran said, "After we measure and confirm that each chassis meets our standards, the framework goes back to the shop where the body will be installed. If a team makes modifications or a vehicle is wrecked, the chassis must be returned to the R&D center for a complete recertification. If a car does not pass, we have a discussion about the problem areas, and the team is provided with detailed inspection documentation as to why the chassis failed."

After the dimensional inspection, Uran proceeds to the metal thickness certification, strictly enforced by the governing body. The entire chassis certification process takes 1½ to 1¾ hours. If the framework passes the certification, Nascar applies 10 RFID chips to the chassis for automatic identification. The RFID technology records the serial number and all pertinent data. When the race car appears at the actual race, all 10 chips must be in place for scanning and certification.

"When a chassis is presented to us by a COT team, a serial number is assigned to that car for its entire lifecycle," Kaproth said. "Once certified, 10 RFID chips are immediately catalogued, then applied to specific areas of the chassis. When the car arrives at the racetrack, an inspector scans the microchips and proceeds to conduct their on-site qualification. Without RFID clearance, the car will not see the track."

Sixteen races were conducted using the new race car in 2007. Then, Nascar announced it would use the Car of Tomorrow exclusively in 2008, a year earlier than planned. As the COT goes full-time, Nascar recognizes that more use will translate into more information for future design enhancements. In the first five events this year, Nascar reported an average margin of victory of 0.505 second. When compared to 1.286 seconds in the same five races last season, the group emphasizes that the COT program is on the right track.

According to Kaproth, "The Car of Tomorrow initiative allowed us to expand on the knowledge base we were accumulating on a race-by-race case. At the same time, we took the opportunity to look at other important aspects from the racing community as a whole. We wanted to make strides in safety and competitiveness, and at the same time improve the financial health of the sport. In the very first COT race at the Bristol Motor Speedway, 59 cars raced within six-tenths of a second of each other. It was extremely competitive to make the final field of 43. And it is very encouraging to see that some small and new teams have done fairly well to date."