Stock Car Science

Enough about the Car of Tomorrow already. Let’s talk about the Driver of Tomorrow and the Race Team of Tomorrow.

Are drivers still important or is the new car really a remote control toy for the engineers? A number of drivers have complained they don’t think they play a very important role anymore, especially in testing. Testing is different because teams are allowed to us telemetry (things like transducers that measure the forces pushing the wheel into the track, or provide the engineer a trace of when the driver is on the gas and when he’s on the brake). Teams are prohivited from using telemetry during race weekends. So why do you even need a star driver for testing if you can read the data directly from the car?

Kyle Busch understands:

"I think (at tests) the important thing is the feedback I can give him (the crew chief)…At these tests, we can utilize telemetry on the cars, and it’s important for my feedback to match up with what they’re seeing on the computers with the engineers. Once we get into the season, and we can’t use the telemetry, that communication is important into getting the right setups and the right changes from practice to qualifying to the race."

Testing helps the crew chief calibrate the driver so he can tell the difference between ‘loose’ and ‘crazy loose’. The Driver of Tomorrow has to communicate much more clearly with the crew. An experienced crew chief with the old car could watch lap times and how the car runs around the track to get an idea of what needed fixing. Things are different with the new car. The driver’s ability to describe precisely and correctly how the car is handling is the only hope the team has for making the car handle better. This is what mathematicians call a ‘necessary, but not sufficient condition’. A person who is a great communicator won’t necessarily be a good driver; however, a very good driver will be less successful if he can’t come up more detailed feedback than "this car has zero grip". Kasey Kahne attributes in part his rebound from a pretty disappointing 2007/early 2008 to improved communication.

"I’m doing a much better job communicating with Kenny Francis (Team Director, No. 9 Dodge Charger) and Chad (Johnston), our engineer, giving them the information that they need to make the car better and I think that’s been helpful as well.”

Wouldn’t you like to find out exactly what happened to change how Kasey provides feedback? This is something beyond just hitting on the right combination of springs and shocks. The importance of communicating is why some teams have sent their drivers and crew chiefs for the NASCAR equivalent of couples therapy and why a driver can turn around a season by switching crew chiefs. The onus for this communication falls on the crew chief, primarily because an owner is much more likely to replace a crew chief than a driver.

Over the last ten or so years, the crew chief’s role has gotten so complex that you always see a minimum of two crew members sitting on the front bench of the pit box: The crew chief and the race engineer. Kasey commented not just on communicating with Kenny Francis, the crew chief, but also with Chad Johnston, the race engineer. Different teams have different ways of dividing the duties, mostly according to the personalities of the two people. Sometimes (like the No. 9 this year and the No. 19 for part of last year), the crew chief and the race engineer are degreed engineers. Other times, such as the current configurations of the 19, 20 and 48 cars, the crew chief’s qualifications come from experience rather than college.

I spent last Saturday in Milwaukee with the GEM No. 9 Nationwide car as part of my follow-up for the paperback version of The Physics of NASCAR, in which I’ll update all the interesting things that have happend with the new car this year. (I hope to be able to report a happier ending for Elliott’s team than the hardcover version has.) I was with the Nationwide team because Kirk Almquist, the current crew chief (Team Director in GEM-talk) was Elliott Sadler’s car chief (Car Director) last year. Ramon Zambrano and Chris Miko from the No. 19 are also now with the No. 9 Nationwide car.

Kirk has a degree from a two-year technical institute, while his race engineer, Tom Gray, has a mechanical engineering degree from from Purdue. Tom was at Purdue about the same time Ryan Newman was there and neatly sidestepped my question about whether Ryan was a good student by noting that Ryan spent a lot of time in his room playing video racing games. (It seems to have worked for Ryan). I watched the No. 19 last year with two engineers communicating with a non-engineer driver. Watching Tom and Kirk communicate with each other and their driver was fascinating. Both Tom and Kirk mentioned that they have to constantly negotiate differences between "this is what the book says should happen"and "this is what I know from experience is going to happen".

If you’ve never been to a standalone Nationwide event, I highly recommend it. Things are a little more laid back, even though the entire event is crammed into a single day. Two practices between nine and noon, with a half-hour break in-between, qualifying about 4:30 p.m., and the race at 7:30 p.m. Nationwide teams only get five sets of tires (six for rookies), so interpreting their practice data is more complicated than the Cup teams because they may hit on a good setup late in practice when they are on worn tires, so their times are slower than the folks who unloaded in good form, even though the car might be better. Kirk is the first crew chief I’ve seen actually working on the car. Both Kirk and Tom have driving experience, so their communication with their driver was aided by the fact that they share a common language in terms of appreciating what it means, for example, when the driver says the front is chattering.

Kirk and Tom have an additional challenge. Chase Miller, Kasey, Elliott and Patrick Carpentier share the driving duties, with Kasey and Chase doing the majority of the driving. That means they have to take into account four different driving styles and four different communication styles. Chase was driving in Milwaukee and again, it was interesting to watch as the team worked through the problem solving exercise that is a NASCAR race.

The other important member with whom the driver has to communicate is the spotter. If you’ve listened to Cup races, you’ve probably noticed that either the spotter or the crew chief takes on a mentor/coach role.

Ray Evernham called a number of races for Elliott last year and his management style during the race is unique. Elliott gets frustrated pretty quickly when the car doesn’t handle the way he thinks it should. Ray was a reassuring voice on the radio, repeatedly telling his driver not to worry, and that were going to (not going to try to, mind you, but going to) fix the car. Elliott’s spotter takes on that role many times.

Tommy Wheeler (a physics grad from Davidson College) is GEM’s engineering services director. In Milwaukee, he was subbing as spotter for driver Chase Austin since Chase’s regular spotter was out in Sonoma. (You need two spotters for road courses.) Tommy was well qualified, having spotted for Jeff Gordon and Terry Labonte, but what really brought home the importance of managing the driver was listening to Tommy giving Chase encouragement and suggestions before and throughout the race, especially while Kirk and Tom Gray were wrapped up planning strategy. Tommy would tell Chase what lines the leaders were using, and compare how he was doing in turns 1 and 2 compared to turns 3 and 4. Chase, for his part, is more mature in terms of driving and communicating than the average 21-year old (not to mention a couple 30-ish Cup drivers).

Last weekend reinforced how important it is for the car to turn well. Last year with Elliott, almost every race seemed to be about the car not turning. Milwaukee was more of the same problems: Not enough grip to get on the gas coming out of the turns. The biggest turn the car made, however, wasn’t initiated by Chase. The result is shown in the post-race picture below.

I got to spend a bit of time with Chase’s Mom and Dad, who drove all the way from Georgia to watch him race. They are delightful people and it was wonderful to watch Chase be genuinely complimented when people asked for his autograph with his Mom and Dad beaming nearby.

The new car is here in the Cup Series and on its way to the Nationwide series. NASCAR has made it clear that the new car is here to stay. The teams that are successful will be the ones that figure out how to develop the driver (and crew) of tomorrow.

Some drivers have stumbled out of their cars and asked reporters for a few moments to hydrate and catch their breath before giving interviews the last few weeks. At Pocono, Denny Hamlin and Dale Earnhardt, Jr., in particular, looked flushed and tired.

Drivers say the new car is too hot. The unleaded fuel does burn hotter. Kyle Petty mentioned that the exhaust was 40-50°F hotter, and John Darby conceded that this might translate to 10°F-20°F temperature rise in the car. But the unleaded fuel was used last year and heat in the car wasn’t an issue. In the new car, however, airflow underneath the car is decreased by the splitter, which lessens the under-car cooling (which is where the exhaust pipes are). In addition, the exhaust pipes are located in a different place than in the old car.

One obvious solution was advanced by Cup Series director John Darby, who suggested that some drivers are not availing themselves of existing driver cooling technologies. Hamlin admitted that his team was one of those; however, Greg Biffle didn’t have any complaints about the heat, even after his cooling device shut off during the Pocono race.

The disorientation, tiredness and flushing might be heat, but– as NASCAR has already recognized–it might also be a result of carbon monoxide.

Carbon monoxide (CO) is an odorless, colorless, invisible gas that prevents oxygen from being taken from your lungs to your brain, heart and anywhere else. Carbon monoxide is generated when combustion doesn’t go according to plan, which means furnaces, wood fires, portable generators and, yes, stock cars, can all produce CO.

The amount of CO in a typical passenger car’s exhaust is small (about 2%). The exhaust passes through a catalytic converter, where each CO molecule picks up an oxygen atom and is converted into a relatively harmless carbon dioxide (CO₂) molecule. Carbon dioxide isn’t poisonous, but it is a greenhouse gas.

Stock cars don’t have catalytic converters. Making a lot of engine power depends on getting the combustion reactants (gas and air) and products (exhaust) into and out of the engine quickly. A catalytic converter would slow the exhaust getting out of the engine and limit engine power. There are no catalytic converters (or mufflers, for that matter) on stock cars.

Carbon monoxide poisoning can be chronic or acute. Acute means a high dose in a short time (which can be deadly). Chronic means that effects build up from repeated small exposures, which is the main hazard to drivers. In 2002, driver Rick Mast retired because he had become so sensitive to carbon monoxide that he couldn’t bear to mow the lawn or ride in a convertible.

The symptoms of mild CO poisoning include confusion, failure to answer questions, and ignoring instructions. (Of course, that describes a couple of drivers on a good day.) The best indication is a change in the driver’s attitude over time, as Ray Evernham noted back in 1997 when he was Jeff Gordon’s crew chief.

“I can tell immediately, by the way Jeff answers me on the radio, when the carbon monoxide is getting to him,” says Evernham. “He becomes a smart-ass. When I started working with him, I thought he was a smart-ass. But the more I got to know him, and the more I learned about carbon monoxide, the more I realized what was happening. How many races are won or lost in the last 50 miles?”

The problem came to a head when the cars became more airtight to gain aerodynamic advantage. When Tony Stewart complained about how bad he felt at Martinsville in 2002, NASCAR and a number of teams (notably Hendrick Motorsports, Penske Racing, and Joe Gibbs Racing) developed catalysts to clean the driver’s air.

A catalyst is a material that makes a chemical reaction happen, but doesn’t take part in the reaction. The platinum in your car’s catalytic converter is a catalyst. CO doesn’t convert into CO₂ spontaneously: The platinum provides a little incentive for the CO to make the change. The problem is that the platinum has to be a few hundred degrees Fahrenheit to make this work.

The solution, which I detailed in The Physics of NASCAR, is a catalyst NASA originally developed to convert the carbon monoxide generated by space-based lasers back to carbon dioxide so it could be used again. Space is cold, which is why they needed to develop a special catalyst that would work at low temperatures. And if it will work in space, it ought to work just fine in a race car.

Small beads or honeycomb supports coated with the catalyst provide a large surface area and thus a high rate of converting CO to CO₂. Air is brought into the cockpit by NACA ducts and flows through the catalyst (and usually a battery-run air cooler), then is directed through a hose to the top of the driver’s helmet.

A car is a holistic system: Changing one thing can have ramifications in areas you might not expect. You might change running shoes and your hips start hurting. You don’t wear the shoes on your hips, but your hips are affected by different shoes.

The indication that there is more than one factor active is the lack of direct correlation between who was complaining and who wasn’t. Carl Edwards was fine, but Denny Hamlin wasn’t. Both have personal trainers who keep them in shape. Jeff Burton complained about a hot steering wheel, but not about feeling bad personally.

Where does carbon monoxide come into play? Heat can exacerbate the effect of CO. When you get hot, your heart beats faster and you need more oxygen. Even though there might be no more CO in the cockpit than before, the combination of the heat and the CO can have a disproportionate effect on the drivers. (See Walker, et al, Comparative Biochemistry and Physiology Part A, 128, 709 (2001).) Also, a driver is more likely to be exposed to CO when the car has body damage because a breach in the sheet metal can let more exhaust fumes into the cockpit. I seem to recall that, at Pocono, Denny Hamlin had some damage relatively early in the race and that might have exacerbated the issue. (I also recall that the very first COT races last year had some problems with CO that were attributed to using too-thin sheet metal in the exhaust system.)

There isn’t a simple way to make the drivers feel better in the car. Each car is set up slightly differently (different cooling devices, for example), and multiple effects make finding the cause much more complicated. The first step, before calling for NASCAR to change the car, is for individual teams to make sure they are doing everything they can to minimize the heat and the carbon monoxide the driver is exposed to.

Side note: If you didn’t check your CO and smoke alarms when we switched to daylight savings time, please take a moment and make sure they are functioning correctly. Race fans, remember to take all the appropriate safety precautions with generators when you’re camping out at the track. The June Speedway Illustrated has a story on disaster narrowly averted at the Short Track Nationals in Little Rock that everyone who uses a generator should read carefully.

UPDATE: ESPN reports that none of the drivers monitored for CO showed a ‘dangerous level’, and that the temperatures in the car vary depending on how much the teams do in terms of things like insulating the floorboards and the exhaust pipes. One can understand NASCAR’s frustration with drivers complaining about the new car being hot when their teams haven’t implemented even the simple things already in existence and known to mitigate the situation.

Yaw makes the new car easier to drive. So why did NASCAR make a rule limiting the amount of yaw allowed in the car?

Initially, NASCAR was steadfast that they weren’t going to make a rule about yaw.

They [complain] when we’ve got too many rules and then they want us to create more." –John Darby

Last week, NASCAR made two rules that allow a limited amount of yaw. One degree of toe is allowed in the rear wheels, and the displacement between the front of the rear tire and the back of the rear tire must be no greater than 5/8". There are two rules because there is more than one way of angling the rear tires. Toe is the slant of the tires when you’re looking at them from above, as shown below.

Toe usually refers to the front tires, but in this case, teams are angling the rear tires so that the rear end of the car is displaced relative to the front end of the car, thus putting the car in yaw. (And yaw helps the car turn.) The second way you can get the tires at an angle is to offset the axles. The 5/8″ rule accounts for both toe and offsetting the axes

One concern expressed by a couple crew chiefs (notably Mike Ford, crew chief for the No. 11 car) is how NASCAR is going to measure the one degree accurately, because the toe of the rear housing should be measured relative to the rear ring gear and you can’t do that without disassembling the rear end. I understand that NASCAR will measure the 5/8″ rule and then if there is a question that the car isn’t in compliance, they’ll do the more careful measurement after the race. They’ll also probably randomly measure some cars as well. The desire to take a chance with getting away with something is likely going to be tempered by the precedent set last week when NASCAR assesed the Haas CNC cars a 150-point penalty and suspended not only the crew chiefs, but also the car chiefs.

I did a calculation to see how much offset one degree of toe in the tire would give you. It comes out to about a half inch. Two degrees of toe would give you about an inch difference between the front and the back of the tire.

That’s the what of the rule. What about the why? Why did NASCAR feel compelled to tighten even further the box the teams have in which to maneuver? Eliminate the black helicopter arguments: (NASCAR wants Jeff Gordon/Hendrick Motorsports/Dale Earnhardt, Jr. to win; NASCAR just wants to take all the fun out of racing) and what do you have left?

One argument advanced is that the cars look "look silly" dog tracking down the straightaway, and that the NASCAR rule change is due to pressure from journalists and fans. If commentators hadn’t pointed it out, I think the yaw escalation would have gotten much further along before the average fan started noticing. Few fans see the cars struggling to make it up the scales.

Marc from Full Throttle pointed out that the Nationwide cars are pretty yawed out, but NASCAR hasn’t made any rules restricting yaw there. There’s a slight difference in the origin of the yaw: Nationwide cars are twisted because of changes to the body, while Cup cars are yawed due to changes to the rear housing.

Why does that make a difference? When you start changing the rear housing geometry, you’re changing how things mechanically interact with each other. When you change the body shape, you’re changing how air flows over the car. Changing the mechanical working of the car has potentially more serious consequences. For example, the rear housing has the rear-end gear and all the gears in the differential. Most of these gears mesh at 90-degree angles to each other. Try offsetting pinion gears by a couple degrees and see how well they work. I talked to people from two different teams (neither of which was having great success with the yawed out setup) and both said they saw major problems with gears binding, gears getting chewed up, or excessive heating when they ran extreme yaw setups on chassis dynos. One engineer mentioned that he suspected the Penske cars had to machine significant modifications into the rear differential to allow the gears to work properly at those high offset angles, and to offset the increase drag you would generate due to the additional friction between the mismatched gears. I believe it was at Martinsville that the 00 had its rear end housing catch on fire (there was a spectacular photo in NASCAR Scene) and I wonder whether that might have been related to rear-end housing experiments.

The situation is, in some ways, similar to the coil-binding issue. In the old car, teams limited the car’s travel (how far the car moves up and down) by setting up the front springs so that the coils of the spring actually touched. When the coils ‘bound’ (as shown below), the car couldn’t sink any lower into the track.

The problem with coil binding is that cars are designed to run on springs. When you coil bind, the car depends entirely on the tire to absorb any bumps and shocks, and tires (in which 1 psi corresponds roughly to 60 lbs/inch of spring rate) aren’t designed to do this. The transition from having a spring to not having a spring is quick and some drivers had a very difficult time coping with the unexpected things the car might do.

There are some similar issues with the yawed out cars. Some teams caught onto it much faster than others, and some drivers adapted to driving a yawed out car faster than others. Just as the coil binding set up caused the tires to take on a task they weren’t engineered to handle, moving the rear axle at an angle other than the one it was designed for can create stresses the axles weren’t designed to deal with.

The Young’s Modulus characterizes the stiffness of a material. Your bones are much stiffer longitudinally (along their length) than they are laterally (perpendicular to their length.). Your bones are usually supporting the weight of your body when you are standing (i.e. the bones are being stressed along their length). Most breaks are due to stress perpendicular to the bone. All structures are designed for a particular use: When you use them in ways other than they were designed to be used, you are likely to find that they don’t perform quite right.

NASCAR also noted that cost was a concern. John Darby said that,even though the curved rear-end housing used by Penske was legal (actually, the words he used were “not illegal"), the idea that everyone was going to get rid of their existing rear end housings and replace them was a bad idea. The crew chief of the 77 car, Chris Carrier (from a very nice NASCAR Scene article by Jeff Gluck that unfortunately doesn’t appear to be available on the web), swears that the parts they used were off the shelf.

“It’s not something that was made in Moscow in the basement of some retired scientist who was under the influence. We bought them.”

Chris, by the way, is quickly becoming my candidate for most quotable crew chief. When you click the link, search for ‘rocket’.

Jeff Gordon publicly commented about the yaw issue, as he did about the coil binding. There tend to be two groups of people in NASCAR: Those who think the spirit of the law should be enforced and those who think the letter of the law should be enforced. Chris Carrier’s comments are an example of the former. Denny Hamlin gives an example of the latter when he said (As quoted from the same NASCAR Scene article by Jeff Gluck),

“It is good that NASCAR is not letting it get too out of hand because these cars were made to drive straight…They (NASCAR) wanted to set a level playing field and all the cars to look the same around the race track, and I think that’s the way of getting them back in their hands.”

I used to let my physics students use a crib sheet for tests: one page, anything they wanted written on it. Creating the crib sheet forces students to winnow out the main ideas of the unit because they can’t write down everything. Or so I thought.

This worked really well for quite a while, until some students used a reducing photocopier to get much more information on the page than they could if they had to write it out themselves. This didn’t bother me much, and the students who were doing this weren’t scoring any better (or worse) on average than the students who didn’t.

The reduction process escalated until students were bringing in essentially every word of the class notes. They had so much in front of them that they couldn’t find anything during the test. There was an inverse relationship between the amount of material on the crib sheet and the grade: The more material a student had on their crib sheet, the lower their grade. More significantly (to me), students were skipping the most important step: Identifying the main ideas of the unit . I finally had to make a rule that the crib sheets had to be written in pencil or pen - no mechanical copying allowed. And some students complained about it just as much as some crew chiefs are complaining about this rule.

That’s where I think NASCAR is with yaw. They came up with the new car and new rules to address issues they felt had gotten out of hand. There are always some innovators who find ways to make things better or easier. Those are the folks who thought of offsetting the rear axle to increase yaw. There are also always the people who take things as far as they can get with them, which forces the teacher (or the sanctioning body) to make additional rules. NASCAR clearly recognizes that a little yaw is a good thing, otherwise they would have outlawed yaw entirely.