IRL: Chevy's IRL chassis test procedures

shakes up IRL chassis development Chevy IRL Chassis Development: Shaken, not stirred. RICHMOND, Va., June 26, 2002 -- Like secret agent James Bond, who preferred his martinis shaken instead of stirred, Chevrolet teams are shaking things up in...

shakes up IRL chassis development

Chevy IRL Chassis Development: Shaken, not stirred.

RICHMOND, Va., June 26, 2002 -- Like secret agent James Bond, who preferred his martinis shaken instead of stirred, Chevrolet teams are shaking things up in the Indy Racing League. The shaker they use can't be found in any bartender's kit, however. They rely on an instrumented seven-post rig that accurately simulates the stresses and strains of oval-track racing in a laboratory environment. Information generated on a seven-post rig can be invaluable on a challenging track like Richmond International Raceway's tight .75-mile oval, the site of Saturday night's 250-lap SunTrust Indy Challenge.

Like wind tunnels and dynamometers, the seven-post rig is another tool in GM Racing's race car development kit. While a wind tunnel gauges aerodynamic performance and a dyno measures engine output, the seven-post rig puts the chassis and suspension to the test.

"A seven-post rig allows a racing team to recreate the vehicle's behavior on the track in a controlled environment," said Kevin Bayless, a chassis and aerodynamics consultant for GM Racing who works closely with Chevrolet IRL teams. "The device is called a 'seven-poster' because there are typically seven hydraulic actuators that work on the car."

Unlike a paint can shaker at the local hardware store, the seven-post rig's hydraulic plungers and rams are precisely controlled by a computer to reproduce the loads encountered on the track. Similar systems are used to evaluate the ride and handling of GM production vehicles.

"The race car sits on four wheel actuators that simulate a variety of road inputs," Bayless explained. "Three additional actuators simulate the aerodynamic downforce produced by the wings and ground effects, as well as the suspension loads produced on a banked oval. These actuators also provide a means to roll the vehicle to evaluate cornering performance.

"The seven-post rig allows us to analyze the effects of various suspension settings on the race car's wheels loads and ride height," Bayless continued. "It permits a team to work through a variety of spring, damper and roll bar packages quickly to develop an optimum combination."

Like any laboratory tool, the seven-post rig has limitations, however.

"After we develop a package on the seven-post rig, it still must be tested and proven on the track," Bayless noted. "Setups that look promising on the seven-poster don't always work in the real world.

"Chassis and suspension development on a seven-post rig is still in its infancy, and we're continuously learning more about the process," he explained. "The interactions between the suspension, the chassis, the aerodynamic loads and the track are extremely complex. Of course, the driver must also feel confident and comfortable with the setup, and that's something that can't be evaluated on a test rig. However, the seven-poster does allow us to identify potential gains in performance that warrant further testing."

With the introduction of sophisticated tools like the seven-post rig, there's a whole lotta shakin' goin' on in the world of Indy car chassis development.

-gm racing-

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Series Automotive , IndyCar