Case Studies: NASCAR Speeds Certifications While Boosting Safety
At the competitive edge in every professional sport, the margins of victory mean tiny differences in energy efficiency, skill and physical configuration. Over time, these strivings give rise to elaborate rules governing competitors' behavior, their contests, and the unending attempts by the clever and the well-financed to create a winning edge by stretching the rules.
To deal with this in stock-car racing, NASCAR opened a research and development (R&D) facility in Concord, NC, in January 2003. In addition to staff and facilities for materials testing and aerodynamics, it is equipped with advanced dimensional measurement technology to assist in the approval and verification of vehicles and parts as submitted by the manufacturers.
The facility's dimensional measurement system is a Romer portable coordinate measuring machine (CMM) and GridLOK from Romer CimCore (Wixom, MI). The system includes PowerInspect software developed by Delcam Inc. (Windsor, Ontario) and sold by Romer. The GridLOK is installed on a 10- by 20-foot steel fabrication plate with locator holes in a 2.6-foot grid. A standard car lift straddles the GridLOK plate.
Daniel Kurtz, the operator and design engineer at NASCAR's R&D facility, sees the use of the Romer arm and PowerInspect as increasingly critical to speed up the approval of new or restyled car bodies, exterior trim and bumper fascia. Kurtz says that the portable CMM technology minimizes opportunities for disputes over measurements and for achieving greater accuracy in dimensional checks.
"We need the higher accuracy as the allowable tolerances are getting smaller, because the teams are increasingly using very precise digital technologies of their own as they seek a winning edge," Kurtz says.
The R&D effort in Concord is focused on enhancing three things: safety through various R&D initiatives; competitiveness as an increasingly long list of critical measurement ensures a level playing field for all cars and trucks; and affordability for competitors.
Gary Nelson, NASCAR's managing director of R&D, says, "The Romer arm and PowerInspect help us make sure that all the Fords, Chevys, Dodges and Pontiacs really have the same configuration as the baseline configuration submitted by the auto manufacturers and approved for competition by NASCAR. NASCAR inspectors and NASCAR competitors get very serious and pay close attention to every detail. We are dealing with some of the most competitive people in the world. Verifiable dimensional accuracy measurements will be a big boost to the sport."
During qualifying time trials and on race days, a set of 31 aluminum templates ensures that the car aerodynamically matches the cars submitted for competition by the manufacturers. Specifically, the templates check:
• The racecar's overall length and width.
• "Skin" curve profiles of hoods, roofs, windshields, deck lids (trunks), bumper facings (fascia), front fenders and rear quarter panels.
• Key dimensional relationships such as the roof's maximum height from the ground and the 10-inch roof mark, which is measured longitudinally from the centerline of the rear axle. Other critical measurements include the hood at the 10.5-inch mark, and the rear quarter panel height.
"We put the Romer GridLOK floor plate under a lift so the arm only has to be located, referenced and zeroed-in once," Kurtz says. "Then it can be used for a wide variety of measurements outside and inside the body. With the GridLOK plate, the 9-foot arm's work envelope allows us to dimension most points on the body and relate them to just about any other point on the body or in the chassis.
"With [the] car up on the lift," he continues, "the arm can dimension most points underneath, too."
According to Kurtz, no additional fixtures are needed and operators do not have "to play digital leapfrog to reach things." Key dimensions of a new car are taken in one hour by one person as opposed to the longer two-person process previously used.
The files comprise the computer-aided design (CAD) models against which PowerInspect checks the cars' surfaces. For each of hundreds of points probed with the Romer arm, PowerInspect generates coordinates in 3-D space plus tolerances and deviations from the corresponding point in the CAD model.
Aerodynamic flows over the rear spoiler and front-end create downforces that help the car stay "glued" to the pavement going into turns. Because the vortexes in aerodynamics rarely extend more than 0.0001 inch from the car's surface, drag and downforce can be varied by subtle manipulations of the car's skins. In turn, tiny variations in aerodynamic friction and downforce can have large impacts on speed, cornering, balance and handling.
For these reasons, NASCAR is serious about making sure that whatever races with an automaker's nameplate bears an extremely close resemblance to what came off the factory assembly line-a resemblance that can be digitally verified.
For each of 100-plus races every year, NASCAR has a field of up to 43 cars or trucks, every one of which must be dimensionally checked. A major role of the Romer arm and PowerInspect is to periodically requalify the templates.
With PowerInspect, the arm is used to compare curves in new templates made from the submissions. Comparing dimensions quickly and unambiguously reveals any changes that have been made on new submissions and provides precise dimensional data on which NASCAR officials base their decisions.
"The Romer [arm] is not intended just to speed up the process of approving a car. Its role is to make the templates better as the dimensional tolerances we have to work are getting progressively tighter," Kurtz says. "The templates' accuracy is very good now, but it will become crucial as race team engineers learn to use dimensional technology to wring small but crucial advantages from smaller and smaller tweaks."
• The use of the Romer arm and PowerInspect speed up the approval of new or restyled car bodies, exterior trim and bumper fascia.
• The portable CMM technology minimizes opportunities for disputes over measurements and achieves greater accuracy in dimensional checks.
• During qualifying time trials and on race days, a set of 31 aluminum templates ensures that the car aerodynamically matches the cars submitted for competition by the manufacturers.
• Key dimensions of a new car are taken in one hour by one person as opposed to the longer two-person process previously used.