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NASCAR Sprint-Cup Series
CUP: SHR Puts Testing Data To Work
A seven-post rig is a critical tool for NASCAR engineers...
Tom Jensen  |  Posted March 25, 2010   Charlotte, NC
During this week’s two-day test at Charlotte Motor Speedway, Stewart-Haas Racing attached 64 devices to its cars, all of which fed back a lot of data for evaluation. (Photo: Getty Images)
Editor’s Note: This is the second story in a three-part series that goes behind the scenes to show how Stewart-Haas Racing collects and uses data gathered during NASCAR Sprint Cup testing.

Part 1: Engineering Key To Tests

There are two keys to making a NASCAR Sprint Cup test session worthwhile. The first is to gather accurate data. The second is to put that data to good use.

To use data properly requires the right tools. And one of the key tools that’s gained popularity in recent years is known as a seven-post rig, or a seven-post shaker. General Motors was the first to develop the seven-post rig, a machine that can replicate actual race track chassis and aerodynamic loads back in a team’s shop.

In the late 1990s, NASCAR teams began using these machines extensively, with Richard Childress Racing one of the first teams to purchase one in the mid-2000s. Now, virtually every top Sprint Cup team has its own seven-post machine, which can cost $1-2 million per machine.

How does it work? That’s little more complicated.

“A seven-post refers to there are seven vertical hydraulic actuators,” said Jim Kasprzak, GM Racing Chassis Engineer. “One goes under each of the wheels, so that’s four. And then we have three other actuators that attach to the frame, and that puts in the vertical input that you would see from the aero load and the vertical banking as you go around the track. We’re replicating input at the wheels and the vertical load from banking and aero all the way around, and that’s what makes up the seven-post.”

In layman’s terms, a “vertical hydraulic actuator” is a device that can either push the chassis up or pull it down. So when a race car is on the seven post, the actuators are moving it up and down, just like a race car moves up and down on the track at 180 miles per hours.

During this week’s two-day test at Charlotte Motor Speedway, Stewart-Haas Racing engineers attached 64 devices called data channels to Tony Stewart’s No. 14 Office Depot/Old Spice Chevrolet Impala SS during the test. All those data channels collected information about what the car was doing at speed from a chassis, engine and aerodynamic perspective.

“We take the data at the race track and then we go back and we create what we call a drive file, that replicates the inputs,” said Kasprzak. “Then you go back and you can work on suspension setups — springs, bars, shocks — in the laboratory or on the seven-post for the race track. And that way, you can develop not only setups for the race track, but you can develop information — basically a notebook for the race track. ‘If I put this on, it’s going to do this to ride hight. If I put this on, I’m going to get more downforce. If I change this, I’m going to get more grip.’”

“We’re looking to collect data so we can go back to our seven-post tomorrow and recreate that data with our seven-post,” said Daniel Knost, SHR’s seven-post engineer. “... We’re logging the data here (at Charlotte Motor Speedway) and we’ll take it back to the shop tomorrow and recreate that data using techniques and process that GM has set out for us. So we can make shock changes for the Charlotte race, after we’ve made that drive file.”

Why is that important? Because it gives the team a scientific basis for their car setups when they get to the track. The crew chief and the car chief have an excellent idea of what the setup needs to be instead of taking a wild swing at it.

“However the car is, you can look at your notes from the seven-post when you go out,” said Kasprzak. “‘If the car is doing this, l’m going to do this.’ And I know what it’s going to do to both the attitude of the car and the handling of the car. So I know what to do. I’m not just guessing on what to put on the car.”

The other thing the seven post gives teams is efficiency.

“A seven-post run is like a minute,” said Kasprzak. “Then you can walk out to make a (suspension) change, go back and run it again. You can make 50 or 60 runs in a day on the seven-post. It would take you days of track testing to make that many runs. A day of seven-post testing is probably equivalent to three days of track testing.”

Tomorrow: We’ll conclude the series with a look at what goes on behind the scenes at the Stewart-Haas Racing shops as they evaluate the data from the Charlotte test.

Part 1: Engineering Key To Tests

Tom Jensen is the Editor in Chief of SPEEDtv.com, Senior NASCAR Editor at RACER and a contributing Editor for TruckSeries.com. You can follow him online at twitter.com/tomjensen100 and e-mail him at Jensen is the author of “Cheating: The Bad Things Good NASCAR Nextel Cup Racers Do In Pursuit of Speed,” and has appeared on numerous television and radio shows. Jensen is the past President of the National Motorsports Press Association and an NMPA Writer of the Year.

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