Stock Car Science

C’mon, will Chad Knaus please push the limits of the gray area so that I can write about something other than drugs? But that’s the big news (again) this week given that someone leaked that the drug Jeremy Mayfield tested positive for was methamphetamine.

Amphetamine (C₉H₁₃N) is a psychostimulant. Methamphetamine (C₁₀H₁₅N) is an even more powerful psychostimulant. Standard tests usually test for the general class of amphetamines (which includes meth). For example, the Federal government guidelines require that companies requiring commercial class drivers licenses clear their employees for the “SAMHSA-5″ the Substance Abuse and Mental Health Services Administration. So most drug testing companies’ basic test covers:

1. Cannabinoids (marijuana, hash)
2. Cocaine (cocaine, crack, benzoylecognine)
3. Amphetamines (amphetamines, methamphetamines, speed)
4. Opiates (heroin, opium, codeine, morphine)
5. Phencyclidine (PCP)

A lot of the amphetamine molecules look very similar to neurotransmitter molecules that occur naturally in your body, like epinephrine, norepinephrine, and dopamine. Methamphetamine and amphetamine have an interesting property: They have enantiomers. Long word, but don’t panic. Put your right and left hands in front of you backs of your hands toward your face. They are mirror images of each other. There’s no way that you can rotate your hands so that they line up exactly on top of each other (meaning that both backs still face you). Meth is the same way. There are two versions of it.

l-methamphetamine (an abbreviation for levomethamphetamine) is on the right in the picture above. l-meth is the active ingredient in inhalers like Vicks. (This is why Mayfield was asked specifically if he had used Vicks. The other form dextromethamphetamine or d-methamphetamine is what we know as meth.

When methamphetamine gets to the brain,it triggers the release of of dopamine, serotonin and norepinephrine, the feel-good neurotransmitters, which is why it induces such a powerful feeling of euphoria – and why it is so highly addictive. Meth is often smoked because you get more of the feel-good molecules into your body that way (90.3% bioactive via smoking vs. 60.2% orally).

Here’s why the presence of two versions of the same molecule is important: If you take meth, it’s entirely d-methamphetamine. A number of other drugs contain molecules like pseudoephedrine, which are metabolized by the body and can produce amphetamine.

For example, famprofazone, an over-the-counter med that’s found in some pain medications, produces equal amounts of the d- and l- forms of meth and amphetamine when it is metabolized in the body. So if the meth that is detected is due to use of this drug, then there should be comparable amounts of each version of the molecule.

The use of something like Adderall or Claritin-D that could produce amphetamines in the urine as a byproduct would produce both types of molecules, which leads me to wonder whether the reason Dr. Black said that there was “no way” the combination of the two over-the-counter medicines could have produced the result they saw is because they detected only the d- version of amphetamine molecules and the over-the-counter medications would have produced both l- and d- versions. (And if you used Vick’s, you’d find only the l-version.

Needless to say, tests beyond the basic five are required to detect the enantiomers. The two molecules have the same mass - they’re just shaped differently. The shape means that they attach to other molecules differently, so you can distinguish between them by seeing how they react to other molecules. Current tests are very sensitive, allowing testers to rule out prescription drugs as the source of the positive results.

More as it develops, but I really am making a plea to Chad to come up with something really creative so that the next entry is about racecars and not this.

I’m behind the curve again, having had final exams to grade and such, but with all the talk about Jeremy Mayfield’s suspension for failing a drug test, I had to write something about drug tests and what you can reliably conclude from them. Disclaimer: I’m not a medical doctor, but even a casual perusal of the drug-testing literature suggests to me that drug testing is a lot more complicated than the black-and-white results people would have you belive. NASCAR has a drug-testing policy that allows them to test urine, blood, saliva, hair or breath if there is “reasonable suspicion". Random competitor tests are also done on a weekly basis.

What is Being Tested For?

NASCAR crews (not drivers) were given a list that includes:

• Seven different amphetamines, including methamphetamine and PMA, a synthetic psychostimulant and hallucinogen.
• Three drugs classified under ephedrine.
• 13 different narcotics, including codeine and morphine.
• Ten different benzodiazepines and barbituates.
• Marijuana, cocaine, zolpidem, nitrites, chromates and drugs that can increase specific gravity.

Amphetamines are ‘uppers’, which decrease fatigue by increasing levels of the stress hormones norepinephrine (attention and responding/fight-or-flight reactions), and the neurotransmitters serotonin (modulates anger, aggression, mood, metabolism, etc.), and dopamine (increases heart rate and blood pressure).

Ephedrines are stimulants, appetite suppressants, decongestants. The molecule Ephedrine looks very similar to amphetamine. Psuedoephedrine is like the left-handed version of ephedrine and that’s what’s in over-the-counter decongestants like Sudafed.

Narcotics is an imprecise term that usually refers to anything that deadens the senses. Codeine, morphine, heroin, etc. fall in this category.

Benzodiazepines and barbituates are downers, which do the opposite of amphetamines and decrease the action of the central nervous system.

Prohibiting marijuana, cocaine and zolpidem (a sleep aid that is in things like Ambien) is obvious, but the last part doesn’t make sense at first reading. I believe the idea is that nitrites and chromates can be used to adulterate a urine sample to try to hide drug use. “Drugs that can increase specific gravity” means the specific gravity of urine (as was pointed out by a poster on rowdy.com). One way of checking for adulterated samples is measuring the pH, temperature and specific gravity (the density of the sample relative to water). If the values are outside of a specified expected range, then the sample is suspect. So the latter part of that rule isn’t about illegal substances, it’s about things that you might take in order to hide the use of illegal substances. For example, if you drink large quantities of water (1-2 liters), most of it comes out in the urine and that dilutes anything elkse in there.

Needless to say, you don’t want anyone in a position of responsibility on one of these substances. Note that this list is for the crews. The drivers don’t have a list, but you could safely assume that all of the substances mentioned are off-limits, plus some. NASCAR reserves the right to test for anything they think could potentially impair a driver on the track.

How Do You Tell If Someone’s Used These?

A sample (usually urine) is collected and split into two parts called the ‘A’ sample and the ‘B’ sample. The A sample is tested with a chemical test called an immunoassay. Immunoassay (IA) tests, as I’ll describe in a moment, are more general tests. The B sample is stored and there are specific protocols for how the sample must be stored. If the IA test shows one or more positives, then the B sample is brought out and tested using a more sophisticated test called Gas Chromatography-Mass Spectroscopy. If the B sample tests negative, then the test is generally regarded as negative. If the B sample tests positive for one of the banned substances, then the driver is notified and disciplinary action is taken.

Immunoassays work sort of like a jigsaw puzzle. There are antibodies (detectors) and antigens (targets). The two types of molecules bind to each other.

The molecule in the upper left of the picture above is our detector molecule. The circle represents something that can be detected - a fluorescent molecule, a magnetic bead or something similar. The molecules on the right-hand side are the molecules in the sample to be analyzed. Our detector molecule has a binding site - the fork pointing to the right, and that binding site will allow it to only link to specific shapes of molecules. (In reality, the binding is chemical, not by shapes, but I find the analogy to shapes easier to understand.) Our detector will only bind to triangle shapes, but there’s a problem here in that there are blue triangles and green triangles. Immunoassays are very sensitive - they’re good at detecting things, but they are not always as specific as we might like. The green triangles might represent a banned drug, while the blue ones are harmless – but both bind to our detector molecule.

That’s OK because we have the B sample and if the A sample shows that there might be something there, we then analyze the B sample using a more specific technique. Gas chromatography is used to separate molecules by weight. The sample is run through a column so that all the molecules with the same weight as the target substance are collected. We do this in elementary school with kids and pens. The analogy we use is to make two rows of kids the same length. Two kids are chosen to be ’sample molecules’. The first kids is allowed to just walk down the row. The second kid must shake hands with everyone in the row as he walks. We start both kids at the same time and, not suprisingly, the student who has to shake hands takes a lot longer to travel the same lengths as the student who doesn’t. In GS, the sorting is done by weight, so all the molecules with the same weight as the suspicious molecule are separated.

The molecules are then heated. All molecules break into fragments in rather predictable manner when heated, so the mass spectrometer detects fragments and you can infer what the molecule was before it was broken up, and how much of it there was.

The Caveats

False Positives

A false positive is when you find that the molecule you’re testing for is there, but it isn’t really. There are A LOT of things that cause false positives. For example, buproprion (an anti-depressant) can cause a false positive for amphetamine. So can an awful lot of other things. Apparently, if a driver has a prescription for one of the conflicting substances, they just have to have their doctor contact the drug testing doctor and things are OK.

To make it more complicated, some drugs are quickly metabolized (broken up) by the body. Amphetamine passes through the body into the renal system (the urine) mostly unadulterated by the body; however, other drugs are transformed by the body and what you test for are the products of metabolizing the drug. Some drug tests are therefore very indirect.

Chain of Custody

The lab handling the analysis must follow proper procedures and be very careful to make sure that they don’t mix up samples or cross-contaminate one sample with another. While you hope that all labs are careful, there are plenty of incidences in which labs have been found to have shoddy procedures.

A problem, of course, is the time scale of the tests: urine tests can detect drug use from timescales of hours to days. NASCAR didn’t relate that there was a problem with the test for a few days, so taking another urine test after notification wasn’t a possibility. It is, however, possible to test for drug use in hair, which can reflect drug use over a period of weeks to months. NASCAR allows no appeal, which seems to me very misguided. NOTE ADDED: ESPN is reporting that Mayfield is having hair samples tested.

Conflict of Interest

The doctor that NASCAR has contracted with to conduct the drug testing also owns the lab at which the tests are done. This seems to me to be a clear conflict of interest. At the very least, NASCAR should have an independent person versed in drug testing overseeing the test. If I were NASCAR, I would have the samples tested at two different labs, preferably one lab chosen by the person being tested. This is too important an issue to leave to the possibility of a lab screw up - and the papers are full of people being let out of jail because of mess ups in testing laboratories. There are a lot of places for things to go wrong. It doesn’t sound like that’s what happened here because of Mayfield’s defense that an interaction between a prescription drug and an over-the-counter drug is responsible for the positive; however, sometimes the perception of unfairness - totally independent of the reality - is damning.

The other conflict of interest issue is whether NASCAR should make the drug for which the positive test was found public or not. One the one hand is Mayfield’s right to privacy. He may be taking antidepressants and not wish to have that revealed; however, if Mayfield waives that right, this isn’t an issue. The latest statement Mayfield issued (from an infield hospitality trailer during the All-Star Race) says that NASCAR hasn’t told him what drug he tested positive for, while NASCAR claims that he’s been told verbally on three occasions the identity of the drug. This is extremely troublesome for two reasons. First, if he’s found guilty, he ought to at least know the evidence against him. Second, how can he claim a reason for why he tested positive if he doesn’t know what he tested positive for?

Can We Make a Judgement?

No, we can’t because there simply hasn’t been enough data released to make a determination. The people who are assuming guilt or innocence are doing so based on their opinions, not on evidence. More balanced are the writers calling for greater transparency. If Mayfield follows up on his threat of legal action, the truth may come out. Until then, we are pretty much stuck in the dark, trying to make decisions based on who we deem to be most trustworthy - a pretty poor way to do science, especially when a man’s reputation is at stake here. Let’s hope that the facts are brought to light and we can all make a conclusion based on real evidence

NOTES Added: Jeremy claims he doesn’t know what substance he tested for. Dr. Black claims he’s told Jeremy personally. Jeremy says he hasn’t gotten it in writing. Dr. Black says that NASCAR issues written reports, not him. NASCAR says that they aren’t aware Jeremy wanted a written report. Come on folks. Argh!

Also see: Marc at Full Throttle has a great post on the issue - well worth reading.

“You have to understand that, like, for years, we have had wrecks like this every time we come to Talladega ever since the (restrictor) plate got here, and for years, it was celebrated. The media celebrated it, the network celebrated it, calling it the Big One, just trying to attract attention.” –Dale Earnhardt, Jr.

My least favorite part of every Talladega pre-race show used to be watching Elliott Sadler tumbling through the infield. And you know, regardless of which network is carrying the race, they’re going to show a montage of crashes. Most will also show Bobby Allison’s 1987 crash - the one that instigated restrictor plates. Did anyone else have a really sick sense of deja vu watching the 99 car of Carl Edwards go airborne and tumble along the fence?

In both crashes, the cars because airborne and, instead of hitting the wall, the cars ended up in the catchfence. In 1987, Bobby Allison’s car pulled about 100 ft of chain-link fence down and sprayed debris into the crowd. A number of fans were injured, including a woman who lost an eye.

Most of the publicity about track safety has focused on SAFER barriers; however, there are researchers improving catchfences as well and the results were evident Sunday. The 99 rolled along the fence, but if you compare the two incidents, today’s fence did a much better job. Fences have difficult tasks: They have to allow spectators to see while being strong enough to contain a flying racecar. A stock car going 190 mph into a rigid barrier would produce a peak force of about 9700 lbs. The force the catchfence experienced would be less because fences have some give, but that’s still pretty impressive for steel and wire, especially if you look at how the 1987 fence did.

Fans and pundits are calling for NASCAR to ‘fix the car’ so that it stays on the ground. If you watch closely, you’ll notice that the primary safety device that guards against cars going airborne did work. Edwards’ roof flaps deployed and, in fact, you can see the car start to lower when the flaps come all the way up. That’s when the 39 got into him and was just far enough under to send the 99 into the air.

Matt Kenseth took a nasty roll during the Nationwide series race at Talladega on Saturday. In the numerous replays of the accident, I kept looking for the roof flaps rising as the car spun sideways. As far as I can tell, the roof flaps didn’t deploy on his Nationwide car. (NOTE: As Nick points out in the comments, this wasn’t an aerodynamic issue - it was more of a mechanical issue, like a SUV rollover. Thanks to Nick for pointing this out.)

Roof flaps are the two inserts on the top of the car. One runs along a line from left to right and one is angled at 45 degrees to the first, as shown in the figure below (which comes from the original patent #5374098).

Roof flaps (the invention of which I detail in my book The Physics of NASCAR) are designed to keep cars on the ground. Faster-moving air exerts less pressure and slower-moving air exerts more pressure. A wing develops lift because the air flowing under the wing moves slower than the air going over the wing. That creates more pressure underneath the wing than over the wing, which generates a net force upward. You want that for an airplane, but you don’t want it for a race car.

A NASCAR race car is pretty stable when airflow comes from the nose to the tail. The problems start when the car turns sideways because a sideways racecar looks a little too much like a wing. Air flows over the roof of a sideways racecar very quickly. It stays attached to the car’s surface for a long time, and that creates a low pressure region on the top of the car. A little air (or another car) gets under the car and all of a sudden, the car is an airplane. This only happens when the car rotates enough, so you need a solution that only becomes active when the car is really yawed.

You want the air to detach from the car’s roof, which increases the pressure on the top of the car and decreases the lift. That’s where the roof flaps come in. As shown below, the roof flaps are flaps of metal that are normally flush with the roof. If the pressure on the roof gets low enough, the pressure differential between the underside of the flap and the top of the lap causes the roof flap to pop up. A tether keeps the flaps perpendicular to the roof surface until the car gets going the right direction.

There’s an additional bit of help as well from the cowl area - the part of the car where the windshield meets the hood which also has flaps, as shown below.

The central flap is the air intake for the engine and the two piece called out on either side are the cowl flaps. Cowl flaps work the same way as the roof flaps, opening when the pressure on top becomes much lower that the pressure underneath. The opening of the cowl flaps allows air to escape from under the car and that also decreases lift. (The patent number on that one is #5544931.)

“(Drivers) have been saying this for years: racing like this is not a whole lot of fun.” –Dale Earnhardt, Jr.

In my opinion, calls for NASCAR to improve the roof flaps or other aerodynamic components so that they can keep the cars on the ground at Dega and Daytona regardless of circumstances are wrong-headed. NASCAR needs to decrease engine horsepower at the big tracks so that restrictor plates aren’t necessary. Slowing down the cars by making the restrictor plate hole smaller isn’t going to help. Most engine programs already have a totally separate plate engine program, so they’re putting a ton of effort into motors for just those four races already. Decrease the banking a bit, or make the banking different in different corners to introduce a ‘handling aspect’ that is present at Daytona and missing at Talladega. You can’t make the drivers ‘take it easy’, or suggest that changing the yellow line rule is going to solve the problem, because all it takes is a single freak coincidence. If Newman’s car hadn’t been right there, I suspect Carl’s car would have come down and hit more of the SAFER barrier instead of the catchfence. It looks from the most recent reports that the worst injury in the crowd is a broken jaw, but it could have been much, much worse.

What makes good racing? It’s the relative speed, not the absolute speed. If two cars are going nose-to-nose for the win, it’s just as exciting at 170 mph as it is at 190 mph. Does it really matter that much to you? It does to the drivers.

“I don’t know how I’d change this racing. I know it’s a spectacle for everybody and that’s great and all – but it’s not right to ask all these guys to come out and do this. What if the car goes up in the grandstands and kills 25 people? … I don’t know if I could live with myself if I ended up in the grandstands.” –Carl Edwards

NASCAR has a long, long history of being reactive. Here’s an instance in which NASCAR must be proactive and make changes before something really serious happens.

Here’s why I’m optimistic that might actually happen. I realized only recently that NASCAR hired Tom Gideon to be Director of Safety Initiatives for the R and D Center. Tom - someone whose integrity is respected throughout motorsports - was a prime moving force in motorsports safety at GM prior to his retirement. Tom will continue the tradition Steve Peterson started and, I’m sure, bring a number of his own initiatives to the job.

NOTE ADDED 4/28/09: A couple comments on some other reports: First, Reid Spencer reports that the roof flaps popped up in the wrong order; however, that should have very minimal - if any - impact on their function. Roof flaps are designed to disturb the flow of air over the roof of the car, as described above. The faster they deploy, the faster they can do their job. Even if one of the flaps ’stuck’, it’s hard to believe that anything would have prevented the combination of the 09’s wake and the 39’s rapid approach from launching the 99.

“I would assume they just adapted their principles and the locations of the old style car to this new style car when it comes to the roof flaps and the cowl flaps and the things like that,” said Newman, who emphasized the importance of keeping the cars on the pavement.

Second, Ryan Newman has a Bachelor’s degree in vehicle dynamics. That doesn’t make him the authority on everything scientific. To Reid Spencer’s credit, he doesn’t let Newman have the last word. He cites Robin Pemberton, who notes that the roof flaps on the new car are larger to take into account the differing aerodynamics, and Bernie Marcus, Ford’s aerodynamicist, who points out that they did “at least three wind-tunnel tests” looking at differences in roof flap function on the new car. Unless Newman has some prior knowledge, it is arrogant and ignorant to suggest that NASCAR just transferred the roof flap design from the old car to the new car without testing it.

Patrick Canupp, Director of Aerodynamics at Joe Gibbs Racing, notes that he hasn’t seen the test data, but that NASCAR usually tests new car designs “at Lockheed where the yaw table can put the car at nearly any yaw angle.", which means that they were in a position to look at roof flap function over a range of orientations of the car with respect to the airflow. Patrick also points out the most important element here - something that most media coverage glosses over. Engineering is not simple. You’re looking at complex machines and interactions between multiple complex machines. You can’t predict all the possible solutions and, even if you could, “that is still just a simulation of the actual event, whose detailed surface pressure history can be quite different,” Patrick notes.