Why the seven-post rig is such great shakes

Even the newest stock car fan knows that the home base for most NASCAR Nextel Cup race teams is in and around Charlotte, N.C. -- even though NASCAR was founded and has its headquarters in Daytona Beach, Fla. And some will know that the other center for U.S. auto racing is Indianapolis, where the stock car boys will invade the open wheel boys (and girls) territory this weekend to run the Allstate 400 at the Brickyard.

However, even the most die-hard racing fans probably don't know how much more interaction the two types of racing -- open wheel and stock car -- have in and around Indianapolis away from the famed Brickyard. Over the years many major racing related companies either moved to or established operations in and around Indianapolis to support the open wheel activities at IMS. Back then the open wheel boys were far more advanced in their technology than the stock car boys.

But that has gradually changed to where the current NASCAR teams are just as technologically advanced and perhaps even more innovative in many ways than the open wheel boys are today. That brings me to one of the latest buzz words in NASCAR -- the "seven-post shaker."

Everybody is talking about the seven-post shaker as if it is the latest and greatest revolutionary technology to become available to the teams in NASCAR. While it has great value to today's teams, as I will explain, the seven-post shaker has been around for many years. The difference today is the teams and their engineers and crew have finally figured out how to use the device to their benefit.

So what is a seven-post shaker and why has it become the latest rage in NASCAR?

The four-post shaker, which is the seven-post shaker's predecessor has been around for decades in the automotive industry. Auto manufacturers use the four-post shaker to test their various models for squeaks, rattles and durability, etc. in order to improve their products. However, the four-post shaker has very little value -- other than durability -- in the testing of a race car. But someone figured out almost 30 years ago that, if they added more "posts" to the system, they could test a wider spectrum of other scientific disciplines and gain more knowledge in a controlled atmosphere.

A four-post shaker simply means that each wheel sits on its own shaker post that can be moved vertically and laterally to simulate road surface conditions so engineers can see if their suspension systems are working as designed. Plus they can measure other areas such as road noise transfer into the cockpit, etc. The body and chassis of the vehicle float freely on the suspension as it is shaken so there is limited data that a race team can gain from a four-post shaker.

However, when you add more posts to the system where you can simulate the forces of lateral load, vertical load, squat and dive, etc. by controlling the body and chassis movement in concert with the suspension movement you have a different animal that can provide important and informative data to a race team trying to gain an advantage in their car's setup.

Just up the road from where the NASCAR boys will be racing at Indianapolis Motor Speedway is a technology company named Auto Research Center. ARC was started as a support arm for Reynard Racing Cars -- a leading manufacturer of open wheel Champ Cars back in the 1990s.

ARC has one of the most advanced seven-post shaker systems in the world. Primarily because it has spent many years developing the software systems that allow its engineers to better control the testing and interpret the information they are receiving from the test runs on their seven-post shaker.

It wasn't always that way, said Robert Yates of Robert Yates Racing. Yates sent one of his cars to ARC for testing in the early years of the rig's development and said, "All we learned back then was how to shake a race car to pieces.

"But, over time, we have learned how to conduct tests that provide us with relevant information that we can use to improve the cars."

So now the seven-post shaker is the latest rage in the Nextel Cup garage with many teams buying their own shakers so they can conduct extensive tests in the comfort of their own shops.

Does it really help? Well, Hendrick Motorsports has had one for more than a year, and they dominated the first half of the 2007 season in wins and top five finishes. You do the math.

If there is one thing I have learned over my many years of involvement with NASCAR, it is that race teams are like teenagers when it comes to the latest fads or gimmicks. It is the old, "If they have one then we have to have one too!" mentality that permeates NASCAR. Can we say a little superstitious and very competitive? Actually a lot superstitious and extremely competitive.

To better understand the dynamic impact the "shaker" is having in Nextel Cup consider this: If I were to tape a live squirrel to my head and then go out and win a Nextel Cup race then I will guarantee you that the garage area would look like "Frontierland" the very next race with every team member and driver having a squirrel taped to his head. If I were to win two races with a squirrel taped to my head then we would probably see live squirrel coats the next week. After all, if a little of something is good then a lot must be better! I can see it all now, "squirrel futures" would soar on the commodities market and oak trees would be stripped of their acorns to feed the burgeoning squirrel population in the Nextel Cup garage, etc. But I digress. Where was I? Oh yeah, seven-post shakers.

Therefore whenever something like the seven-post shaker comes along that actually works and makes a positive impact -- look out! I'm almost afraid to point out that the Formula One boys have 11-post shakers at their disposal! Some of the Formula One teams added three posts to the four-post shaker back in the early '80s and now have rigs with up to 11 posts, so I'm not sure where it will all end.

But I do know where it started over here. ARC was the first in the United States to have a seven-post shaker, boasted Henri Kowalczyk, ARC's vehicle dynamics manager.

So Henri, What exactly are you trying to achieve with a seven-post shaker?

"Basically everything that we simulate -- banking, lateral load transfer, braking and acceleration and downforce ends up changing the vertical loading of the tires so that is ultimately what we are looking at," Kowalczyk explained.

Well, Henri, is it true that these things are powered by a bunch of recently unemployed squirrels running on a treadmill? According to Henri the actuators or posts are operated by hydraulics, so I guess the squirrels are on their own for now.

There are two manufacturers of the shakers, Kowalczyk said. One, MTS Systems Corp., is in the United States and the other, Servotest, is in the United Kingdom.

"There is basically only one model of the seven-post shaker," Kowalczyk explained. "The improvements come by way of upgrading the control systems and the data analysis.

"You can add more posts to add more forces into the car and suspension as the Formula One teams have done. You need sensors to install on the car and computers to analyze the data, etc. When we first installed our seven-post shaker we had to learn all of that ourselves. Now we can offer a turnkey solution to customers interested in installing their own rigs."

The basic rig costs about $800,000, he said.

"Plus you have to install it on an isolated concrete pad so that the vibrations don't feed back into the building and the building noise doesn't affect the results of the test. After everything is done you will have about one and one-half million dollars invested," Kowalczyk explained.

That would pay for a lot of squirrel hats, Henri.

"You need to understand vehicle dynamics, so mechanical engineers are usually involved. Also a good understanding of vibrations and frequency domain analysis is required," Kowalczyk said. "And finally, you need to understand how it all translates to the track so a good background in setting up race cars is needed."

Kowalczyk said many of the employees at ARC have a racing background, so they understand what the teams are looking to achieve.

"The main advantage of the rig is that it is in a controlled environment and it is extremely repeatable. You don't have to worry about track conditions changing or the driver getting tired, etc. It is also more cost effective than track testing because you are not having to rent a track, incur travel expenses and put wear and tear on the engines, transmissions and tires, etc. It is also very convenient to change over to different test configurations," Kowalczyk explained.

Plus, I pointed out, you don't have to feed or clean up after it like those squirrels.

"The results can be very realistic compared to the track. It all depends on how good the data is that you have to work with," Kowalczyk said. The data he referred to is the "track mapping" and "aero mapping" that teams develop from actual tests on various tracks. Once you have good data from the track you can match it on the rig, Kowalczyk said.

"The data can come from hub accelerations, shock displacements or push rod loads if you are dealing with an open wheel race car," he said. "Also you will need good aerodynamic data that is collected in the wind tunnel to conduct realistic testing.

"There are some limitations because the rig cannot simulate the effects of roll centers or anti-dive but, as long as you understand that, it is still a valuable tool for the teams," Kowalczyk said.

You can also do fatigue testing on the rig that allows you to find the weak points in the car and develop parts (within NASCAR's specifications, of course) that are lightweight but will still survive the forces imparted on them, Kowalczyk said. ARC even has a software package that allows the teams to simulate laps on the rig and then change the parameters of their car setup -- spring stiffness, downforce drag levels and horsepower, etc. and then run additional laps that can be graphed on the computer for comparisons that are similar to the data acquisition packages (track mapping) the teams use when testing at the various tracks.

Mechanics can now swap out their wrenches for a computer keyboard.

ARC can do different types of testing on their seven-post shaker, Kowalczyk said. "We can do sine wave, random noise and full track replications," he noted. Anything that has a spring and a damper (shock) has a natural vibration, so that is what they try to define and then manage or control.

They can also do aerodynamic simulations on cars and trucks -- even semi-truck haulers! Want to know if your package will survive being shipped to your dear old aunt in Ohio? ARC even tests packaging designs to simulate shipping abuse so manufacturers can develop better methods for protecting products such as electronics during shipment. However, I still don't see any employment opportunities for all those unfortunate and recently furloughed squirrels.

Unlike my squirrel buddies, it appears the seven-post shaker is becoming a vital part of NASCAR race car technology and development and will be around for quite some time into the future. Teams who cannot afford to spend a couple of million dollars for their own shaker rigs can go to places like ARC in Indianapolis or Ohlins USA in Hendersonville, N.C., to "shake, rattle and win." Hey, buddy! Can you spare an acorn or two?

Bill Borden is a former championship winning crew chief who operated David Pearson's Racing School for many years.