Stock Car Science

Congrats! If you’re reading this, it means that they turned on the Large Hadron Collider without creating any black holes…yet.

If there’s one question I get when I speak it is: “If they were going to design a car from scratch, is the new car really the best they could do?” My favorite phrasing of this question is “If we can put a man on the moon, why can’t NASCAR build a car that can race? (Uh, how much money did that cost, how long did it take and how many people lost their lives in that endeavor?)

At this point in the season, I think everyone recognizes the big problems with the new car:

• The center of gravity of the new car is a couple of inches higher than in the old car. That exacerbates load transfer, which means that the car has overall less grip.
• NASCAR instituted a minimum and maximum height for the splitter. The old valence only had a minimum height. The new restriction reduces the front-end travel on the car, making it harder to get the car in the aerodynamically favorable “hound dog” (nose down tail up) position. The end result: less grip.
• The total aerodynamic downforce of the new car is less than the aerodynamic downforce of the old car–again, the end result being less grip.
• NASCAR tightly legislates body shape, precluding the teams from making the body asymmetric. An asymmetric body can help the car turn better. This removed one of the main tools teams had to get ahead, as very small changes to the body can produce big changes in aerogrip.
• The new car is much more ‘finicky’ (as Chad Knaus puts it) than the old car. We’ve seen a couple of examples where teams that are usually really good got to the track and "missed the setup". Even with three practices worth of tweaking, they could never get the car handling correctly.

These points have been well documented, so let’s put a moratorium on the cranky articles that do nothing more than complain about the car, or even complain that the right people aren’t complaining about the car. My father had a policy: If you can’t suggest something better, you don’t have the right to complain.

‘Better’ implies realistic, so all the calls to go back to the old car are banned under my moratorium as well. It just ain’t gonna happen. Can you imagine the teams scrapping two years of work–and inventory–and trying to buy back all those chassis from the ARCA teams?

Besides, most of the teams will tell you that they’ve learned a lot about the new car since the beginning of the year. Few teams bring back the same car to a track because they’ve made so many changes that the car from the first race–even a car that wonthe first race–wouldn’t be competitive.

There are two big components to my solutions. The first time. Teams used to have twenty races worth of data from which to determine set ups. This year, they have at most three races worth of data. It’s not entirely surprising that teams miss the setup sometimes. Every time I talk with engineers, they tell me how much more they understand about the car. That aspect is just going to work itself out with time; however, the narrowing of the ‘grey area’ is another matter. The primary ‘grey area’ teams used to have was manipulating the body shape. They don’t have that any more, so they have to focus on other (often less familiar) areas. Some crew chiefs complain that NASCAR is getting to be too much like a spec series, where everyone gets the exact same equipment. We’re pretty far from a spec series, but the series is definitely headed more toward that direction than I think most of us would like.

For what it’s worth, here are my suggestions for what NASCAR ought to be considering as they start to write the 2009 rule book. All of my suggestions end tied with one common thread,which is purposely making the box in which teams can work bigger.

• The CG has to be lowered. Teams are searching for even small changes in the weight distribution. Some teams are replacing metal dashboard panels with carbon fiber panels to save 6-9 lbs of weight that is located fairly high on the body. (This sort of defeats the idea of decreasing cost because carbon fiber is expensive.) A smart team would contact the Tegris people (the material from which the splitter is made). Milliken (the folks who make the splitter) recently launched a molded kayak made from Tegris that is strong and lightweight. The primary use of Tegris now is as sheet goods (cutting the splitter out of a flat piece), but Milliken has some really nice molding technology. Tegris will save weight without costing as much as carbon fiber. But these are small changes. Why not just make the car another 100 lbs heavier and let the teams put all of that extra weight on the left side of the car if they want. Yes, the cars would be a little less peppy (Not even NASCAR can outlaw F=ma), but if the handling improves, you’re going to get better racing and happier drivers.
• Give everyone the same basic engine block and cylinder head, but allow them a wider range of variation in how they can modify the components. Wait, you say–isn’t that moving into a spec series? I’m arguing it’s not because, although they’ll have the same basic components, I would give them a much larger box within which to work. For example, allow variation in bore dimensions (not volume, but aspect ratio) and a wider range of intake manifold geometries. I’m tired of the whining about how one manufacturer has an advantage because of their basic engine design. You shouldn’t be at a disadvantage because your manufacturer hasn’t gotten a new engine approved yet. Give all the teams the same basic components, enlarge the box and then let the engine guys do what they can to get as much horsepower as they can. There is nothing sacred about these engines: It’s not like the manufacturers pull a few off the production line and ship them off to Charlotte.
• Instead of mandating two or three rear-end gears, give the teams a continuous (and wider) range of gears to use. That will further broaden the box for the engine while keeping a limit on the rpm range.
• The car needs more downforce, so the aerodynamic issues have to be addressed. The NASCAR R and D center has a handful of engineers. Asking this small group of people to design a brand new race car and have it work perfectly is utterly unrealistic. On a major team, about 10% of the employees are engineers, which means over the last two years, there have been probably 350-450 engineers thinking really hard about how to make the car go fast. Some of those people are very smart aerodynamicists. NASCAR needs allow each team one participant, lock them in a room with the NASCAR R and D staff, sit them down around a table and let them propose how to change the car’s aerodynamics. They’ll bring a wealth of ideas and information. Give them as their goal coming up with an aerodynamic ‘box’. It would be a fun meeting to be at because different teams have been focusing on different aspects of aerodynamics. No one will want to reveal their closest-held secrets, but I bet a consensus of common issues would emerge that would improve the aerodynamic issues such as downforce and, most importantly, the effect of sideforce on turning and passing.
• A lot of people are calling for a return of the spoiler. The problem is that the higher greenhouse doesn’t let the air hit the old spoiler as well as it did in the old car. Don’t think NASCAR isn’t concerned about the wing. Notice that the Nationwide COT (NCOT) is keeping the spoiler, but the spoiler has a different shape. Since the NCOT uses the same chassis and presumably has the same height issues, here’s a chance for NASCAR to do some experimenting with spoiler shape. My rental car in Richmond had a wing in the back and I must say that not being able to see out the rear window is really annoying.
• If they’re going to reserve a room for the aero think tank, they might as well get suspension experts together as well and ask for ideas on how much they can increase the front travel without totally obviating all the work the teams have done with bump stops and chassis stops. Again, put reps from the different teams in the same room and let them say as much as they are willing to say in front of each other. If someone bright takes all of those ideas and puts them together to find the overlaps, they should end up with a box within which the engineers have plenty of room to experiment.

I’d like to close this week by thanking all the folks at Richmond: My hosts at VCU were terrific, especially Wanda, the administrative assistant in the History department who took care of all the logistics. I had a couple good meals and enjoyed myself greatly, even if my shoes still are a little damp. The people in Richmond–as in most places in the South–are very friendly, but especially so at the track. That’s a big difference from some places, where track security seems to enjoy telling people "no". The folks at RIR kept smiles on their faces, even as the rain moved in Friday afternoon and they realized they’d have to postpone the race. As fan-friendly as the larger tracks are, I really like the smaller tracks like Bristol, Richmond and Martinsville, where getting a dent in your fender doesn’t end your day. I look forward to returning to Richmond and getting to see a race there in the future.

Just when you think things can’t get any busier, they do. It’s the end of the fiscal year at my university, which means getting buried in a mound of paperwork. We’re doing three workshops this fall for teachers on using NASCAR to get kids interested in math and science, plus I’m giving a number of talks around the country. The next talk is in Richmond VA on Thursday, September 4th at VCU. I’m really excited about a project we’ve just started with the Dallas Museum of Nature and Science that will culminate in a week of activities at the museum prior to the Texas race November 2nd. We’ve got lots of support from the track and Office Depot on that event, so I hope to see some locals there.

I am cleaning out my mailbag and realized I have a couple questions I haven’t answered, so here they are:

What are tire codes? What do they tell the driver about the tire?

They don’t actually tell the driver a whole lot, but they are very valuable to the tire specialist and the crew chief

You can find a lot of information about tires. I usually look on jayski’s race pages, but the information comes from Goodyear and is public domain, so you may find it in other places. If you look at last February’s California race, you’ll find:

Number of Tires: Left-side –1,525, Right-side–1,525

Tire Codes: Left-side– D–4146; Right-side– D–4150

Tire Circumference: Left-side–87.3 inches; Right-side–88.6 inches.

Technical Inspection Inflation: Left Front–30 psi; Left Rear–30 psi ; Right Front–48 psi; Right Rear–45 psi

Minimum Recommended Inflation: Left Front–22 psi; Left Rear–20 psi; Right Front–45 psi; Right Rear–42 psi

Estimated Pit Window: Every 40-44 laps, based on fuel mileage

Let’s see what we learn from that. First, there are a heck of a lot of tires. For comparison, they bring about 525 tires for the Nationwide Series when it runs at California. If you figure 44 teams, that’s 35 sets of tires per team. Normally, teams get six-seven sets of tires for practice and qualifying, and 10-16 sets of tires for the race. The exact number depends on the length of the race and number of practices. For example, Richmond in two weeks is an impound race and there is one practice. There will be three practices this weekend at the track I’m trying really hard not to keep calling Fontana.

The teams have their wheels delivered to Goodyear. Every wheel has the team name on it so Goodyear knows who gets the tires. Goodyear has to mount and balance all of the tires for all of the teams. In the lower left of the picture below (about 7-8 o’clock), you’ll see two silver things and lines drawn in silver Sharpie (the best thing for writing on tires with!). Those are weights that are added to balance the tires. The writing is there so that if the tire comes back without the weights, the team can tell that there was supposed to be a weight there. Some time the chatter in a tire is due to unbalanced tire.

The tire codes (D-4146 and D-4150) are Goodyear’s way of identifying specific tire recipes. Different code means different type of tire. With the exception of the road courses, you’ll always see different tire codes for the left and the right. The left-side tire is softer. Left-side tires don’t carry as much load as right side tires (because we always turn left). If you made the two sides wear equally, the lefts wouldn’t wear as much as the rights. You’ll also notice that the left and right-side tires have different circumferences, which I’ve explained elsewhere.

Tires with different tire codes can have different tire wall construction, different types of cords, and different types of rubber for the tread. Goodyear usually runs 20-30 different tires during the course of a season. Some are particular to particular tracks (i.e. Indianapolis is a special case), and others you’ll find run in a number of places (like 1.5 mile intermediate tracks).

In addition to the tire code, there is also a barcode (which you can see at about 7 o’clock in the picture). The tire code is like a zipcode. The barcode is like an address. The barcode tells the tire specialist (the full-time person at the track who does nothing but deal with tires) what mold number was used to make the tire, what day the tire was made, and what shift the tire was made on. Goodyear had experienced a strike toward the end of 2006/start of 2007 and I remember the tire specialists at Atlanta in 2007 identifying which tires were made during the strike

The tire specialist reads the barcodes and can download all of this information at the track from a Goodyear database. The tire specialist then groups the tires into like sets. He or she (and yes, there are some women tire specialists) tries to group tires according to date and time made, mold number and circumference. Making tires is an incredibly imprecise process. You’re putting something in a mold and then basically steaming it. Not all tires will shrink to exactly the same size, so they measure the circumference of each individual tire.

The crew chief then looks through the tire specialist’s group and sometimes will ask the tires to be regrouped if the crew chief thinks there is a more optimal pairing. They want each set of right-side and left-side tires to be as similar as possible. The tire sets are given numbers (1, 2, 3…) and the crew gives the tire specialist an idea of what order he’d like the tires to be on the car. If you are on pit road right before a race, look for long strips of masking tape with numbers on the back of the box. That’s the order of the tires the crew chief has dictated. You may see similar strips of tape on the front pants legs of the race engineer. I’ve seen a couple of them keep a copy of the order there for easy reference. The numbers are, of course, upside down so the engineer can read then when he’s sitting.

Two sets of pressures are given: one set is the set the tires are expected to be at during tech inspection. Note that the left sides have lower pressures because, again, the left-side tires carry less load than the right-side pressures. Goodyear mandates minimum tire pressures. The NASCAR official in each pit checks the pressure of one of the front tires to make sure it is above minimum. They don’t need to check all because you need the tires to be balanced. If you fill one tire to the right pressure and underfill the others, you’re going to have a squirrelly car. (Yes, Marc, “squirrelly” is a technical term. I know you were going to ask.)

Can drivers tell when there’s a mismatched set of tires? Some can. It usually depends how mismatched they are, or if there’s something else going on (like lug nuts not being tightened enough).

For those of you wondering, the tire in the picture is from Junior’s car in 2006 October at Lowe’s. The pink lines are meant to help the tire changer register the lugs faster. There’s an experiment waiting to be run–see if the pink on the lugs and/or the hubs actually makes a difference. I’ve seen studies about general visual accuity, but not about pit stops per se.

What kind of wave was the crowd doing at Bristol?

Physics teachers everywhere thank you for that question. That was a transverse wave. A transverse wave is when the things making up the wave (in this case, people), move in one direction, but the wave itself moves in a direction perpendicular to the direction the people move. The wave moved around the track, but the people moved up and down.

The other kind of wave is a longitudinal wave. A longitudinal wave moves along the same direction the things making up the wave move. To do a longitudinal wave, you’d stay seated and move to your left or right. Sound waves are longitudinal waves. Next spring at Bristol, I think they ought to go for the world record for the largest longitudinal wave. I think it would be easy to break because I’m not sure the Guiness people differentiate between them. But we’d know.

Why would a good team like Gibbs cheat?

I’ve been doing a series of interviews for ‘hero cards’ we’re making for the people who use math and science to make cars go fast, so I’ve gotten to ask a lot of people some very personal questions. I learned two things. First, people who work in NASCAR are competitive. I realize most people don’t associate ‘engineer’ with ‘competitive’, but the people who are are the top are definitely very competitive. Secondly, working in NASCAR, even if you have a job where you don’t go to the track, is extremely stressful. Things are very close and the stakes are large when you’re talking about holding on to sponsors, drivers, crew members, etc. I hadn’t appreciated how much pressure people who work for race teams feel. If you’re at the top, it’s the struggle to stay there, to avoid getting paranoid that other teams are starting to gain on you and that maybe you’re missing something that’s going to turn out to be really important in three or four races.

I’m not condoning cheating, especially if it’s the stupid kind (as opposed to the innovative kind where you sort of have to chuckle a bit and appreciate either the guts or the brain it took to try it). Even very honorable people sometimes do things they wouldn’t normally do if they weren’t under pressure. Either Joe or J.D. Gibbs made a comment that the folks involved were good employees. They’ve given up a lot for the team. (Ask how many people who are on the road for a race team have missed anniversaries, graduations and birthdays). Gibbs said that these employees made mistakes, but they had the confidence that they were one-time judgment lapses, not character flaws. If anything questionable happens with one of these people again, however, I wager that they are going to be out the door.

On the other hand, there is still a culture of glorification of cheating in NASCAR. We had our own scandal in physics a couple years ago, when a guy who worked at Bell Labs (The Hendrick Motorsports of NASCAR) was caught using the same graph in two different papers–with two different axes. He was no doubt a smart guy. But they ended up firing him and his university revoked his Ph.D. The community even had an interesting discussion about whether his supervisor ought to bear some of the blame for not keeping close enough track of his employee (or whether he even knew about it). It was not a shining moment for the field of condensed matter physics.

Hendrick Schon, the scientist in question, eventually got another job in science. The rumor is that the person who hired him said, “He must have something going for him because he fooled so many smart people for so long.

I keep telling my physics friends that there are lots of similarities between physics and NASCAR.

I have never seen Robin Pemberton looking so disgusted as he did during an interview replayed on NASCAR Now Monday evening. (Well, maybe not since Daytona 2007.) NASCAR did a chassis dyno test after the Michigan race on a number of NASCAR Nationwide cars. They found 1/4-inch-thick magnets underneath the accelerator pedals of the 18 and the 20 Joe Gibbs Racing cars. To their credit, JGR took responsibility, apologized and started an internal investigation to figure out who was responsible.

You may have heard some strong reactions from some of the other owners. One of the reasons for the animosity is that Toyota runs the same engine in Cup and Nationwide, whereas the other manufacturers have to maintain separate engine programs for the two series. I know that some of the companies that run both series have 90% of their engine shop dedicated to Cup engines, so there’s some resentment that Toyota only has to run one program.

The facts: The purpose of the magnetic shims was to prevent the accelerator pedal from being pushed all the way down. In a carbureted engine, pushing the accelerator pedal opens valves in the carb. The more you push the pedal, the more the valves are opened. The valves regulate how much of the air/fuel mixture enters the engine. The wider the valves are opened, the more air/fuel mixture goes into the cylinders and the more energy is produced. If you prevent the pedal from going all the way to the floor, the throttle doesn’t open all the way and you produce less horsepower.

As you probably remember, NASCAR gave Toyota a more tapered tapered spacer than the other manufacturers after engine dyno numbers showed that the Toyota engines had a 15 hp peak horsepower advantage. The cheat was an attempt to have the Gibbs Toyota engines show lower horsepower than the engine actually was capable of and (I guess) either make NASCAR feel guilty that they penalized Toyota too much, or prevent further reductions of the tapered spacer. Some thought must have gone into how thick a magnet they needed: If they had knocked the horsepower down too much, it would have looked suspicious.

Why magnetic shims? You could have accomplished the same thing with a non-magnetic shim; however, you would have had to have come up with a way to hold the shim in place, like glue or tape. NASCAR mandates the use of magnetic stainless steel in the car. A rare-earth permanent magnet will stick really really well to magnetic stainless steel. I have a couple neodymium-iron-boride magnets that you literally have to keep a piece of cardboard between becuase if they get stuck together, you’re going to have a very difficult time getting them unstuck. So all the folks who are wondering if those magnets they claim you can put around your gas line to save money actually work, forget it. They don’t. The only reason a magnet was used was because it could be put there quickly, would stay put, and could be removed quickly. They could have used plastic or non-magnetic metal and had the same effect on the throttle action; however, the high heat in the car might have softened any adhesive or tape used to stick it in place or the driver might have knocked it loose.

Every report I’ve heard says that the magnets were in place during the race. (correction) As the story has evolved, it appears now that the crew members derived a ploy about needing to retrieve a forgotten notebook to get into the car after the race, so it now appears as though the magnets were NOT in the car during the race. (correction) Given how closely the cars are watched (especially the 20, which finished 3rd), there wouldn’t be many possibilities to slip something in place (although doing so would only have taken a very few moments). At Milwaukee, where NASCAR did engine dyno tests, the cars pulled off the track and headed toward their haulers, but the NASCAR officials stopped all the cars just inside the garage gates. None of the teams seemed to know what was happening until they got the word that there were going to be engines selected for dyno testing. The only other possibility I can think of would be the driver moving the magnet into place after the race and I just can’t see Tony Stewart going for that.

What makes the decision to try this even more questionable is that this was to be a chassis dyno test, not an engine dyno test. In a chassis dyno test, the cars are rolled up onto a mobile chassis dyno, which is a platform that has a large massive drum on which the rear wheels are placed. The car is strapped onto the platform and when the throttle is pushed, the rear wheels turn the drum instead of moving the car. If I remember right, NASCAR uses a DYNO-mite dynamometer.

A chassis dyno test doesn’t test only the engine: it also reflects all the frictional losses in the drivetrain. So, for example, if your oil were thick for some reason, you might have the best engine, but you would see lower numbers on the dyno because some of your engine power was being used to overcome friction and that power wasn’t available to the rear wheels. An engine dynamometer measures only the engine. I can’t see that NASCAR would make decisions on engine policy based on a chassis dyno measurement since a chassis dyno measurement measures much more than the engine. It is tough to imagine that, based on a chassis dyno test, NASCAR would decide to make the holes in the Toyota tapered spacer larger again. Just for the record, NASCAR used an engine dyno when they tested NNS cars in Milwaukee and Chicagoland and a chassis dyno in Atlanta earlier in the season.

So what was really the point of this? You make yourself less competitive (unless there was some way that the magnets got put into the cars after the race) and you chance a huge fine. I’m working on a novel and this seems like a perfect revenge scheme for a disgruntled employee, doesn’t it? You compromise the performance of the car AND you create a scandal that could result in long-term suspensions for crew chiefs and car chiefs. Or it could just be someone doing something amazingly ignorant.

The penalties are likely to be major. I’m sure NASCAR has the same feeling I get when I catch a student cheating in a really stupid way. You’re incensed because they’re cheating and then you’re more incensed because they think you’re so stupid that you wouldn’t catch it. When there was a major cheating scandal in F1, they made the guilty company ineligible for the equivalent of the manufacturer’s championship. That’s a punishment for the offenders, but it also puts an asterisk next to the manufacturer that does win the championship.

The arguments that it was justified for JGR to cheat because NASCAR unfairly took away 15 hp from Toyota when they were within the engine rules is just plain bogus and I bet that most of the folks at JGR would tell you the same thing. The people who work there that I’ve met are simply too good to resort to doing something like this.

UPDATE 8/20/08 Dave Moody has a really good summary of the penalties, announced Wednesday, so I won’t type in my own attempt to explain because I think he covered just about everything. I personally was expecting car and crew chief suspensions for the rest of the season, so the indefinite suspension came as quite a surprise.

UPDATE 8/20/08 Lee Spencer has a nice article with a rational description of the incident, the penalties and why this is all such a big deal.

UPDATE 8/23/2008: Mike Mulhern has a great column in which he sheds a little more light on the deception. Apparently the crew members involved had thought enough about this that they had a cover story. Great, except the cover story was that (as one of the comments below suggested) they were arguing that the magnets were stops to prevent the throttle cable from being overextended. They used a magnet in the car because then the driver could kick it out of the way if they wanted to. Sounds perfectly reasonable. Except they forgot to let the drivers in on the story, so it was obvious to the Nationwide officials when they asked the drivers that the driver had no clue what was going on.