Stock Car Science

After getting in late from Columbus, I made the mistake of listening to the radio as I attempted to sleep. Listening to the comments about the Red Bull Racing penalties got me slightly riled. NASCAR came down hard on Red Bull, including 150 driver/owner points, a $100 kilobuck fine and indefinite suspensions for the car chief and the crew chief. My preliminary thoughts about what might have happened and why turned out to be pretty close to what I’ve been hearing through the grapevine. But there are a couple big misconceptions running around from the sound of it. Let’s take a look at a few of them.

The penalties were so high because this is a safety issue. This is not a safety issue. We’re talking about twenty-five mils of steel versus twenty mils. (A mil is a thousandth of an inch.) The body is for aerodynamics, not strength. The strength of a race car comes from its roll cage. NASCAR does have a rule that you cannot race without a doorskin; however, that rule is probably outdated. In the new car, there is a 90 mil thick piece of steel in the passenger side door and a sheet of Tegris (the splitter material)in the driver’s side door. Those two components are there to prevent anything sharp from coming in between the door bars and hitting the driver. A twenty-five mil sheet of steel isn’t going to protect you from much and losing five mil from that isn’t going to make a noticeable difference.

The reason for the stiff penalty is that NASCAR is escalating penalties each time they catch someone messing with the chassis or the body. If you look at the penalties this year, they’ve steadily gotten worse. The exception is a 25-point penalty for the 12 car; however that was a height violation, not a chassis/body violation.

How could the driver not know that this was going on? Easy. With a very few exceptions, what the driver knows about the car is what the crew chief tells him. Some drivers ask a lot of questions about what springs and shocks and steering box are in the car. Few drivers spend a lot of time at the shop. They are usually so busy with appearances and such that they come from their motor home, spend a little while talking with the crew chief and get in the car.

There have to have been a lot of people who knew about this because acid dipping pieces of sheet metal isn’t easy to do. Acid etching has legitimate uses, some of which are applied to rather large parts. For example, if you want to weld or braze something, or coat a piece of metal with a decorative coating, an acid etch gives you a clean smooth surface. The words “acid dipping” conjure up a vision of a mad scientist with the vat of boiling green liquid. Solder flux is a type of acid etch. Stainless steel etch is usually a mixture of hydrofluoric and nitric acid. You could brush it on, leave sit for a little while and rinse it off pretty easily. It is, of course, possible that a lot of people knew, but the process is not a complicated enough thing to require that a lot of people be involved. We used a similar etch to clean stainless parts for a sputtering system. I remember as a graduate student leaving a couple shims in the etch for too long and coming back to find that they were totally gone - etched entirely away.

In my first post, I just used the side of the car as an example. Remember that you’re not just trying to make the car lighter - you’re trying to make it bottom heavy. The most obvious place to thin the metal would be the roof panel. If you were clever, you would thin only the center section of the roof because if you thin the edges, you might have problems in welding, and if you mess with the edges that can be seen (the bottom of the doorskin, for example), it would be easier to detect. If you estimate the roof at 4 foot by 4 foot (again, round numbers just as an easy estimate), and uniformly decrease the thickness to 20 mils, you’re saving maybe three pounds. But it is much more significant saving three pounds at the very top of the car compared to saving three pounds at the bottom of the car. The total numbers I’ve heard say that the car was somewhere around 12-16 lbs lighter. Where that 12-16 lbs was missing is very important.

How could the crew chief not know? This originally bothered me as well, but remember that the overall weight of the car is 3450 lbs. You’re talking about 0.4% of the total weight. Given everything else that can change on the car (and everything that has to be done before going to the track and at the track), I’m convinced it could be overlooked pretty easily.

Red Bull management must have known since they aren’t contesting the penalty. When something like this happens, teams usually find out pretty fast who was responsible for the infraction. You have two choices then: fire someone publicly, or do as Joe Gibbs Racing did when they were caught in the Nationwide Series. JGR simple said that they know how it happened, and that they believed the people involved deserved a second chance. It’s just not a NASCAR thing to identify some guy who works in the shop and throw out his name to the press. What the RBR statement says is that they know they were guilty.

I will write a little more about center of gravity in the future to explain why the location of the missing weight is so important.