Memories of Martinsville

 Martinsville  No Responses »
Apr 062013
 

Martinsville is my favorite track and it has absolutely nothing to do with the hot dogs.  It’s a short, flat track out in the middle of nowhere.  It doesn’t have the high speeds and pack racing of Daytona and Talladega.  It’s not located near a major metro area like Las Vegas or Chicago where there’s plenty to do outside the track.  But it holds a special place for me.

When I was writing The Physics of NASCAR, I arrived about 6am, before the Sun was up, to make sure I wouldn’t hit traffic and miss the opening of the garage.  I sat in my rental car and read through my notes from the last day… and scanned the weather forecast because there was likely going to be rain.

There weren’t a lot of cars there in the parking lot just off the midway.  Three generations of a family were setting up their breakfast opposite me.  The kids were a little sluggish — apparently not used to getting up quite this early on a Sunday.  Before long there was a grill running and the smell of food that was much better than the McDonald’s I’d picked up along the way.  I enjoy the quiet of the early morning because it’s the perfect time to think – to get yourself oriented for the day.

At first, it was just the low buzz of the people across the way cooking and drinking the first cups of coffee of the day.  And then, off somewhere in the darkness, a low voice started singing a hymn.  Other voices joined in and the sound quietly made its way across the parking lot.  A religious service was being held near the 31 souvenir trailer and the hollers of Martinsville made the perfect acoustics for a church.  A preacher started talking – not a revival-type sermon, but a low, quiet reflection about the importance of thinking about what you do in life and how you treat other people.  About the fact that each of us has the power each day to make someone else’s life better — or worse — and that we need to keep that in mind before we act.  There was more singing, more people joining in as the Sun started to rise and light spread over the parking lots.  I’m not an organized religion person.  The year my grandmother took me to get my throat blessed, I got the mumps.  But sitting there in my car listening to the singing was a truly spiritual moment and a reminder to take a few moments each morning and think about what you can and should do during the rest of the day.

There is a lot I remember about that weekend.  I actually never ate a hot dog.  I was too busy running around trying to keep up with everything.  I do remember the thrill of  standing in the qualifying line on pit road with the car already on the track whizzing by us fifteen feet away.  You know how Kenny Wallace always talks about ‘Kenny Wallace the race car driver’ not being anything like Kenny the television guy?  It’s 100% true.  Wallace started out joking with everyone and as the car crept up to the front of the qualifying line, he got quieter and quieter, focusing only on the qualifying effort.  Walking pit road with Josh, Elliott Sadler’s crew chief at the time, as he gestured with a cup of coffee (the 19 team had the best coffee!) at cracks in the pit stall that might cause a pit crew member to slip during a stop.  Watching Kirk, Elliott’s crew chief, crawl over the little half wall that forms one side of the garage stall and stand a few feet from the track trying to see how the car was transferring weight as it came out of the corner for as long as he could before a NASCAR official told him to move back.  Learning that the best place for me to stand so I’d be out of the way was inevitably wherever the trash can was.   The best National Anthems of any track.  The quiet competence of the head engineer, Chad Johnston — who is now Martin Truex, Jr.’s crew chief — instructing the crew to get a canopy up over the tires when it became clear it would rain.  How nice everyone on that team was to me while I was following them around asking annoying questions.  Watching how hard a disappointing finish affects the driver and the crew.  Seeing how much sheer love of the sport and competitiveness everyone associated with NASCAR has.

Martinsville may not have fancy suites and garages, the best toilets in the series, or the poshest hotels — but if anyone asks me what tracks they ought to make sure they get to, Martinsville is right up there in my top three.

Degrees of Difference: How is Martinsville like Fontana?

 Auto Club Speedway of California, Martinsville, math, Talladega, Texas Motor Speedway, Trigonometry  1 Response »
Oct 252012
 
DLPTXTrackBanking

I love getting questions from readers because I always worry that the geeky stuff I find interesting is only interesting to me.  I love it even more when they not only give me a question, they also supply part of the answer!  This one has to do with the degrees of difference between Martinsville and Fontana.

Michael J. Clark asked a really good question about Martinsville and Fontana:

Why does Fontana (banking in the turns is 14 degrees) seem to have such higher banking than Martinsville (banking in the turns is 12 degrees)?  I would think the 2 degrees more that Fontana has wouldn’t look so dramatically different than Martinsville, but it really does.  I’m guessing it has to do with the fact that Fontana’s turns are about 10 car-widths wide (my estimate) compared to the turns at Martinsville, which seem to be about four car-widths wide.

Great question and another example (like race cars seemingly speeding up when spinning into the grass) of how our perceptions are often subjective.

We always talk about Martinsville being a “flat track”, which is sort of unfair.  It’s flat compared to Talladega and Daytona, but there are still twelve degrees of banking in the turns.  Nothing like a little trigonometry at the racetrack – what does twelve degrees look like?  Let’s start with some definitions so we’re all talking about the same things.

Track width is measured across the track surface and forms the hypotenuse of a right triangle.

Any right triangle can be described by the lengths of any two sides, or the length of one side and one angle.  Remember SOHCAHTOA? You can (finally!!) use your trig to reverse engineer the racetrack.

One degree isn’t really all that large.  A banking angle of one degree means that in order to get a rise of one foot, you need to have a run of about 57 feet.  One degree isn’t very much, as shown in my figure below.

The top picture shows what a banking angle of one degree would look like, with the rise of 1 foot and the run of 57 feet.

The bottom picture is a scale drawing of Martinsville Speedway, which has a track width of about 55 feet (although I think it is a little narrower in the corners).  The banking angle is variously given as 11 degrees or 12 degrees.  I’m using 12 degrees here because that’s what the official NASCAR site says.  Given the hypotenuse (track width) and the banking angle, I can back calculate to show that the rise is about 11.4 feet and the run is about 54 feet.

Now to Michael’s question.  The diagram below shows scale drawings of the banking at Martinsville and California and (just for comparison) Talladega.  I’m using the best numbers I can find on the web.  If someone has more accurate numbers, please let me know.  Kudos, by the way, to Talladega for having one of the best webpages of track data.

Michael has great instincts – the track at Fontana is two-to-three car lengths wider than Martinsville.  This means that the rise is seven feet (one Brad Daugherty) higher than Martinsville at the edge of the track. That increase in rise makes the banking look steeper because you’re looking up a greater distance.

(You always hear that Talladega is five stories tall.  I’m not sure what they’re counting in that calculation because I get 26 feet, which is pretty far short of five stories unless you have very short stories.)

In addition to the greater width, you also have to remember that there’s a huge difference in overall scale.  Martinsville was the second track I visited while writing The Physics of NASCAR – the first was Atlanta.  Martinsville was the track that made me love short tracks.  You get up close to the action and even though they’re not going 200 mph, when you’re that close to them going 100 mph, it seems really fast.  Short tracks are a great challenge to the crew chief (and the driver) because suspension movement is so much more important than aerodynamics.  And, of course, tempers seem to be proportional to the track length of the track:  at Martinsville, they are both really short.

But you have to realize just how much smaller Martinsville is than the California track.  The straights at Martinsville are 800 feet, while the backstretch at Fontana is 2500 feet.  Martinsville is .524 miles, which is 2777 feet.  If you unrolled the Martinsville track, you could just about fit the entire thing on Fontana’s backstretch.  The picture below is my attempt to make a to-scale drawing of the two tracks.  The banking at Fontana looks huge compared to the banking at Martinsville not only because the track is wider at Fontana, but also because the track is simply bigger.  When you look out into the turns, you simply see a lot more asphalt.

Side note:  The featured picture in the post at the top shows me trying to stand up on the 24-degree banking at Texas Motor Speedway, just to give you an idea of how steep 24 degrees actually is.  This was while we were shooting the Science of Speed video series.

So that’s the difference between the tracks at Martinsville and Fontana.  I’m told there is absolutely no comparison between their hot dogs.

Thanks for the question, Michael!  Questions (and suggestions for the Sirius radio “NASCAR Mythbusters” segment) are always welcome.  Click on the ‘contact’ tab above to send me an email.

I’m heading out to Joliet, IL to give my  Science of Speed talk at Joliet Junior College Friday October 26th at 7:00 p.m.  More information on how to get there can be found on my appearances page.  My talk is aimed at the average NASCAR fan and focuses on why it’s a lot harder to drive fast than most of us think.  Most people leave the talk with even more respect for what professional racecar drivers do.  I promise no pop quizzes, so please come on out and meet me!

 

 

Dover: Why Concrete Races Differently than Asphalt

 Asphalt, Bristol Motor Speedway, Dover International Speedway, Mark Martin, Martinsville, Materials, Tracks  6 Responses »
Sep 282012
 

One of the questions you’ll hear drivers and crew chiefs asked a lot this weekend at Dover is how the concrete track affects the racing.  Here’s how:

Asphalt vs. Concrete

Concrete and asphalt are father and son.  They have in common what you and would call it “rocks”, but professionals call it “aggregate”.  Aggregate comes in a huge variety of types, depending on the materials from which the rocks are made, the quality of the material, the size of the rocks and the distribution of sizes of the rocks.

Concrete is an technically any mixture of rocks aggregate stuck together with a binder.  The type of binder determines the properties of the concrete and even the color.

Concrete is the oldest engineered construction material, dating back to the Roman Empire.   The reason only parts of the Roman Colosseum and the Pantheon are missing have more to do with humans than the failure of the materials.  Today’s concrete is more than ten times stronger than the version the Romans developed.

The most common binder in the concrete used in roads, parking lots and sidewalks is Portland cement.  Portland cement (and its close relatives) are mixtures of  limestone and clay, which are crushed to a powder and heated to over 2700 degrees Fahrenheit.  This is the form you buy it in.  To use is, you reconstitute the dry powder with water, and the individual grains form calcium-silicate-hydrate (C-S-H) bonds that make a very strong glue.

Asphalt is a type of concrete, that uses bitumen — tarry black stuff — to hold it all together.   A typical composition for asphalt is 80% aggregate, 15% binder and 5% air voids.  Bitumen comes from the heaviest components of crude oil, and has the consistency of molasses (which is why it has to be heated before being used).   Because bitumen derives from oil, the price of asphalt changes with the price of oil.

 

But Which is Better?

As with most “which is better”, the answer depends on what you what to use it for.  The primary difference between asphalt and concrete is the rigidity of the two materials and how they distribute the load over the base on which they are laid.   The more rigid the pavement, the more the load is distributed over the surface when something like a car move over it.

Asphalt, which is more flexible (relative to concrete), transmits higher, more concentrated loads to the base, as shown below.  I’ve drawn the stress distributions in red.  The concrete spreads out the stress over a larger area, while the asphalt transmits stress to a narrows area.  The narrower area and the same load means that the stress is more concentrated.

Because concrete is stronger, asphalt has to be thicker to get the same rigidity.  Asphalt does have an advantage, however, in that its flexibility allows it to expand and contract with temperature changes with less cracking.  Even so, concrete lasts 10-15 years longer than asphalt.

Asphalt is the traditional material for paved racing surfaces.  Only three Sprint Cup tracks feature concrete:  Dover, Martinsville and Bristol.  They have in common that they are all tracks of one mile or less with significant banking.  (OK – you may not view the 12 degree banking at Martinsville as ‘significant’, but those 12 degrees are the reason the corners are concrete while the rest of the track is asphalt.  The stress on the pavement in the corners necessitated replacing the original asphalt with concrete.)

Dover is one mile with 24-degree banking and Bristol is a little more than a half mile with 24-28 degree banking.  The steep banking and the tight curves make keeping asphalt in good racing condition a challenge.  Having concrete also gives a track a unique character – as well as the opportunity to have a really cool monster statue outside.

How Concrete Changes Racing

 

Grip Level

The grip level can be very different between asphalt and concrete, depending on a lot of factors.   Concrete is inherently more grainy, and its surface can be patterned to create more grip.  Drivers talk about bumps in asphalt as being large and wavy, while bumps in concrete they describe as  more vibrational.  Concrete usually has to be laid down in sections, which means you can have those bumps like you find between slabs on a sidewalk.  The picture at left shows the Google Earth view of Dover’s surface and you can see the individual slabs.

The grip on an asphalt  track depends  on the type of aggregate used, the degree of wear and the character of the bitumen.

For example, Atlanta has a very rough surface because its bitumen wears faster than the aggregate, as I’ve shown at right.   When an asphalt track is first laid down, the surface is very level.  As the bitumen wears away, the tops of the uppermost layer of aggregate are exposed.  The sharp edges of the aggregate are worn down by the tires rubbing against the rocks, but the aggregate sticking out provides a lot of grip.  Eventually, enough bitumen wears away that the aggregate starts coming out, which weakens how well the track holds together and necessitates a re-pave.

Concrete doesn’t wear as fast as asphalt and thus the grip level doesn’t change as much over long periods of time.

Light and Heat

Would you believe that the color of the track makes a big difference in how the track races?

Light comes in a range of wavelengths from smaller than billionths of a meter to larger than billions of meters long.  Our eyes detect a very, very small fraction of that electromagnetic radiation in the nanometer (billionth of a meter) range.  From red to violet, the wavelength ranges from about 800 nanometers to 400 nanometers.  The light from the Sun contains a wide range of wavelengths, including ultraviolet light (UV) (which is smaller wavelength than visibile light), all the colors of the rainbow, and lots of infrared  (IR) radiation.

Our eyes don’t detect the UV or IR light – we see the mixture of all the different colors of light together, which makes white.  Artificial light (like fluorescent) generates a different mixture of wavelengths, which is why it looks different than sunlight.

You see the colors of objects because all materials absorb some wavelengths (colors) of light and reflect others.  When light hits a red object, as I’ve shown at left, all colors except red are absorbed and what comes to your eyes is just the red light.

White surfaces reflect a wide spectrum of wavelengths and absorb very little of the spectrum.  The light that is incident on a white surface is reflected back to our eyes and the broad spectrum of wavelengths we see as ‘white’.  Black is the opposite:  black absorbs a lot of different wavelengths, so very little reflects back to our eyes and we get black.

 

In addition to the visible light, the spectrum from the sun includes the aforementioned ultraviolet  and infrared waves.  Infrared radiation has longer wavelengths than red light.  We don’t see it – we sense it as heat.  You’ll notice that the lamps they use to keep food warm always have a red glow:  they output some visible light, but they mostly output heat .  You will never see food being kept warm by blue light.

How is all this relevant to a racecar?

Put a piece of black paper and a piece of white paper in the Sun and feel their surfaces after a few hours.   The black paper absorbs a lot of the radiation from the Sun and gets very warm.  The white paper doesn’t absorb as much of the Sun’s energy (although it does absorb some), so it stays relatively cooler.  If you measure the temperature of a track over the course of a race, it can change by tens of degrees depending on the weather.

One effect of the changing temperature is how hot the tires get.  If the track is 60 degrees vs. 120 degrees Fahrenheit, that generates a very noticeable level of change in the grip.  But even more importantly, bitumen (the binder in asphalt) is a petroleum product.  As the temperature rises, oils in the bitumen get warmer and make the track more slippery.   Portland cement is crushed-up rocks which (when dry) are not slippery at all.

The end result is that, a concrete track doesn’t change over the course of a race nearly as much as an asphalt track.  Crew chiefs say that the track at Dover is easier to ‘keep up with’ because changes in temperature over the course of the race don’t change the racing surface as much with concrete as they do with asphalt tracks.

The Nature of Friction

There are two types of friction .  The first, called abrasive friction, is the one you learned about in school.  This is the type of friction between sandpaper on a wood block.  The second kind (which I never know about until I wrote The Physics of NASCAR) is adhesive friction, which is the molecular-level stickiness of the track combining with the molecular-level stickiness of the tires.  The heat generated by the tires makes the topmost layer of the track gooey.  The outermost layer of the tire also becomes gooey, resulting in an effect very much like chewing gum stuck on your shoe on a hot sidewalk.  The gooeyness of the track  bonds with the gooeyness of the tires for microseconds and resists forward motion.  That’s grip.

The nature of adhesive friction on asphalt is very different than on concrete because the two materials are so very different.  Concrete has much less adhesive friction.  This doesn’t change the grip level so much (because the abrasive frictions are different) – however, it does make a big difference in what happens when you lose grip. Think about sticking a weight to a piece of wood with gum.  The asphalt surface would be really sticky gum and the concrete surface would be dried up, not-very-sticky gum.  If you turn the wood so that the surface is vertical, the stickier gum is going to hold better.

In terms of a racecar, Mark Martin pointed out:

“… when you lose grip on a concrete surface, you feel like you just got cut loose from a rope. It’s amazing. It’s like losing half of your grip, rather than about 20 or 30 percent that you lose on asphalt.”

All the drivers’ intuitions that are developed on asphalt – which comprise the vast majority of NASCAR tracks – are thus challenged when they drive on concrete.

So there you have it – not necessarily better or worse, just different.

For those of you who have noticed the blog has been quiet the last two weeks, it’s because my older cat, Chaos, was very ill and finally passed away last Sunday. She was my race-watching buddy, although I have to admit that she usually fell asleep somewhere around lap 25 and woke up just in time to see the last 30 laps or so.

I miss her all the time, but I will especially miss her on raceday when she liked to compete with my computer for lap space.

The Reason for Decreasing Cautions

 Bristol Motor Speedway, Cautions, Consipracies, Martinsville, math, Texas Motor Speedway, Uncategorized  4 Responses »
May 262012
 

This was the first year that most people noticed a decrease in the number of cautions, but (as I’ve pointed out), 2012 is merely the latest in a six-year trend of decreasing cautions.  The same downward trend is evident in the Nationwide Series.  This year is perhaps notable for it being so extreme.

I’ve plotted the cautions per 100 miles (the best way I’ve found to compare changing race lengths and different tracks) for Cup races so far this year at right.  The plot shows the minimum and maximum values for each track, with the average shown by an open square.  The red square shows the cautions for 2012.  At California, Bristol, Martinsville, Texas, Kansas, Talladega and Darlington, the 2012 value is the lowest value in the last six years.

The data clearly shows the trend:  The question, of  course, is why?

Given that it’s happening in both Nationwide and Cup, that sort of eliminates issues like the introduction of new cars (either COT or the new Nationwide car), the Chase Format, etc.  What was left to investigate?  How about the drivers?  A number of commentators has suggested that drivers were just “better” now.  But how do you test this?

I started by deciding that experience and quality could be indicated by number of races run and number of races won, respectively.  I decided to compare 2005 (which had the highest number of cautions) with 2011.

My criteria for including drivers was that the driver had to have run more than 15 races during the season.  That kept the focus on the full-time drivers.  I totaled two quantities for the drivers that made the cut:  the total number of career laps they had run in the Cup Series (including the season in question) and the total number of career races they had won in the Cup Series.

Year 2005 2011
Races run 11109 12180
Races won 485 485

The drivers who spent the most time on track in 2011 had about a thousand (1071 to be precise) more races worth of experience:  with roughly 25 drivers included that’s an average experience level of 40 races, or almost a full season per driver. The number of wins was exactly the same.

I looked into the details as to what had really changed between 2005 and 2011.  We lost a lot of experienced drivers from active competition:  Dale Jarrett, Ricky Rudd, Rusty Wallace, Sterling Marlin, Kyle Petty, Michael Waltrip, and Ken Schrader for starters.  Their places were taken by drivers just starting out:  From 2005 to 2011, Kasey Kahne went from 72 races run and 1 win to 288 races run and 12 wins.  Kyle Busch went from 42 races and 2 wins in 2005 to 257 races and 23 wins in 2011.  Jamie McMurray didn’t make the active list in 2005, but in 2011 had 230 races and 6 wins.  Even the folks we think of as veterans, look at Tony Stewart: from 248/24 to 464/44, and Carl Edwards: 49/4 to 265/19.

Even drivers who haven’t won races have run a lot more races and gained a lot more experience:  Dave Blaney (200 races by 2005 vs. 397 races by 2011).

So I started thinking about the average experience of the drivers.  I made histograms of the number of drivers who had run some number of races, as shown at right and below.  They are plotted on the same vertical scale for easy comparison.

In 2005, 10 drivers had under 100 races worth of experience.  In 2011, only 5 drivers had 100 races or less on their resumes.  (One of those five was the 2011 Daytona 500 winner.)  In 2005, 27% of the drivers had fewer than 100 races under their belts, while in 2011, the figure was only 12%.  Yes, we lost a lot of really experienced driver with more than 600 races under their belts, but the younger, newer drivers also gained a lot of experience over those five years.

I’m not sure you learn as much from the races won.  There were 12 drivers with no wins in 2005 and 11 in 2006.  But there was only one driver who had won one race in 2005 and eight who had won one race in 2011.

There were plenty of people making the aggrandized claim that the reason cautions are decreasing is “these are the best race car drivers in the world”.  I’d make a slightly less aggressive conclusion and say that NASCAR has much more experienced drivers now than they had in 2005 and that’s why the number of cautions has decreased.

There are (as always) caveats.  Having watched the Nationwide race at Charlotte and poor Travis Pastrana causing multiple cautions, it would be interesting to go back and look at whether the drivers I didn’t count in this survey had more wrecks than the regular drivers.

 

Why You Can’t Predict Anything Based on the First 10 Races

 Martinsville, math, New Hampshire, Richmond, Talladega, Texas Motor Speedway  1 Response »
Apr 202012
 

The plot below shows the cumulative number of cautions per mile since 2007.  I’m using number of cautions per100 miles to 1) make up for races that were not run to completion; 2) compensate for green-white-checkered finishes; 3) compensate for tracks that have shortened races; and 4) compensated for changing order in which tracks are visited.

Cautions per 100 miles can be thought of as follows:  If the cautions per 100 miles is 1.6, then the number of cautions for a 500 mile race would average (1.5*500/100) = 6.

The results are sort of interesting:

Things to notice:

1)  All of the final values for cautions per 100 miles end up between 1.8 and 2.4, even though the values at the start of the year ranged from 1.4 to 3.1.

2)  The data for the first 10 races changes wildly with each race.  The data don’t start to converge toward their final values until at least 15 races into the season.  I suspect that if you plotted a drivers’ standing in the points as a function of number of races, you would see the same behavior.  Why?  As the total number of miles run increases, the number of cautions in a race is increasingly small compared with the total number of  miles run.

3)  Despite the decreasing fluctuations, there are still quite a few noticeable jumps upward.  When I saw them, I immediately thought:  Ah – there’s Bristol.  But closer inspection showed me wrong.  The big troublemakers are Richmond and Martinsville, which together account for the largest number of upward jumps.

4)  There seems to be a significant difference in caution rates from 2008/2009 to 2010/2011.  Anyone want to venture guess as to what is responsible?

 

Are Cautions Really Going Down?

 Atlanta Motor Speedway, Cautions, Martinsville, math, New Hampshire, News, Talladega, Texas Motor Speedway  No Responses »
Apr 182012
 

I honestly cannot help it – scientists are naturally skeptical.  If you make an assertion, I will have to question you on what data you have that supports it.  This is second nature to the people I work with, but I realize it is damned irritating to non-scientists (aka “normal”) people.

So when I started reading everywhere that “cautions were down 35%”, I had to go look into it.  This is a preliminary post – more detailed analysis will follow as soon as I’ve read my students’ final projects and gotten comments back to them.

First, let’s talk statistics.  Reliable statistics require large numbers.  It drives me nuts when people extrapolate from the first few races of the year.  You can’t claim much on the basis of five data points.  Even the top quark required seven (if I remember right – they did get more after they announced they’d found it).

The stock market fluctuates up and down.  Everyone except people who are thinking about retiring ignore the short-term fluctuations and focus on the long-term trends.  What do the data say about cautions in NASCAR?

I picked five tracks to analyze in this first round:  Martinsville, Texas, Talladega, New Hampshire and Atlanta.  The first four represent a range of track types, while the last was chosen to see whether the cautions were “cookie cutter-like”.  I first plotted the number of cautions as a function of year for all the tracks together.  If cautions are decreasing, we should see a general trend downward.  Here’s what I got:

Not much of a clear trend, huh?  If anything, it looks like the overall trend (since 1950) is going up.

Thinking it might be unfair to use really old data, I decided to focus on 1997-2012.  I plotted all five tracks on their own graph for just those years.  I’m sorry for the color – those are the defaults on Origin.  I will change them when I do a full post.

What do you think?  I might buy a downward trend for Texas, but it’s hard to make that argument for the other tracks. Martinsville went from 18 in the last race of 2011 to 7 this year – that’s a 61% drop right there — but if you compare it to the Spring race (and an argument can be made for comparing Spring to Spring and Fall to Fall), that race had only 11 cautions.  That’s a drop of 36.3%.  there is a wide gap between those two figures.

Just for fun, I took the historical data for the three tracks with long records.  Here they are:

As I said, I’ll follow this up with more extensive analysis, but I wanted to get the data out there ASAP.