Talladega pas de deux Why does a NASCAR pas de deux work only at Daytona and Talladega
Answer: because only Talladega and Daytona are smooth enough for two car Contact Push Drafting to work.
Talladega race is this weekend where you'll see more racing in the two cars in what we call Contact Push Drafting formation: two cars actually in contact; with the trailing car physically pushing the lead car.
Contact Push Drafting (CPD) only happens at two tracks on the NASCAR circuit: Talladega, and now that Daytona has been repaved, there also. Here's why. All other tracks are bumpy by comparison to Talladega and Daytona. When a car goes over a bump there's a lot going on in the suspension system. Watch the suspension system of a car while going over a bump, we can simulate this effect by dropping the front end of a car onto a table, starting with the instant before the tires hit the ground.
Then 0.10 seconds later for comparison.
Viewing the same event from the front of car shows that as the chassis dives relative to the wheels it results in a change of wheel camber (inclination or tilt of the wheels). Here is the car just at the instant of impact by the front wheels.
,….and one-tenth of a second later.
Using the graph background in the image it is possible to collect data for the camber angle as a function of how far the chassis dives.
This results in the steer angle of the wheels also changing as a result of going over a bump, an effect not surprisingly called "bump steer." Thus, driving over bumps actually makes a car follow a swerving path, like a series of very shallow S turns. Most importantly, not a straight path. In order for Contact Push Drafting to work the cars must remain lined up, pushing smoothly and along the same line; weaving back and forth relative to each other is a sure fire formula for a wreck..
Because the lead car goes over a bump first, then the trailing car a fraction of a second later it is nearly impossible to maintain a uniform push direction between the two cars.
Only when the track surface is extremely smooth, i.e., Talladega and Daytona, does the Contact Push Draft work. Since this configuration is also results in the fastest combination or formation of cars it is certain to be used extensively.
Or at any rate until the car shapes are changed. For a video version of this explanation you can also see Ten80 Student Racing Challenge: NASCAR STEM initiative on YouTube http://www.youtube.com/user/Ten80Education?blend=22&ob=5#p/a/u/0/VC4aP4bz0iI
Jeff is an engineer and an artist. His second career has been in creating STEM Challenges to help some students better prepare for careers in STEM professions and help all students learn the importance in data driven decision making.