Keeping Racecars on the Racetrack

 Aerodynamics, Downforce, Drag, Lift-Off Speed, Roof Flaps, Ryan Newman, Talladega, Yaw  1 Response »
May 102013
 

Ryan Newman escaped NASCAR sanctions for his comments immediately after being discharged from the infield care center at Talladega.

“They can build safer racecars, they can build safer walls, but they can’t get their heads out of their asses far enough to keep them on the race track and that’s pretty disappointing, and I wanted to make sure I get that point across,” he said. “You all can figure out who ‘they’ is.”

You’ll hear people talk about aerogrip and mechanical grip.  Aerogrip comes from air pushing the car into the track, while mechanical grip is due to the weight of the car pushing the car into the track.  What pushes down can also push up, so it’s not surprising that the same two factors contribute to cars becoming airborne.

Aerodynamic Takeoff

When a car rotates (so that its side or its back is leading instead of its front), it looks an awful lot like an airplane wing — a shape that is optimized to generate lift.  The faster air flows over a surface, the lower the pressure.  In the figure below, the longer and greener the arrow is, the faster the air flows over the car.  This shows airflow from the front of the car, but the same areas where air flows quickly when the car is going straight are the same areas where air flows quickly when the car is yawed.

BernoulliCar

NASCAR race cars have roof flaps and hood flaps that are located where – surprise – the green arrows are in the figure above.  (Figure Credit: USA Today) .  In the Gen-6 car, the roof flaps are much larger and the previous “cowl flaps” were moved onto the hood proper.  The hood now extends up to the windshield and there is no cowl anymore.

Gen6_RoofandHoodFlaps

A roof flap or hood flap slows down the air passing over the car, thus forcing it to exert more pressure downward, which pushes the car back down to the ground.

Mechanical Take-Off

The other way a car’s wheels can leave the ground is due to mechanical forces that cause the car to roll over.  Torque is the application of a force that causes rotation.  If you look at some of the classic rolling accidents from Talladega, a number of them are caused by a car moving from the pavement to the grass or vice-versa.  There is almost always a step up or down at the transition from one surface to another and that step creates a torque that causes the car to roll.   In the diagram below, the car is skidding sideways, then hits a bump.  The torque created by the bump causes the car to rotate.

CG_Torques

A torque can be applied anywhere and could be caused by anything on the track — including another car.

Talladega

The incident last weekend at Talladega was combination of these factors.  The video shows that the 36 hits Busch (78) at the right rear quarter panel, turning the 78.  As the car rotates, one roof flap deploys, indicating that the pressure above the car became less than that inside the car; however, the critical factor looks to be the 36 getting under the right rear quarter panel and creating a torque that rolls the 78.  If you look back to the first diagram, you’ll see that these cars have a rake in the back. The upswing helps air move out from under the car and decreases lift; however, it’s also a place where the nose of one car can launch the other.  As the 78 is rolling, the 39 drives right under him and the 78 lands on the 38.

The Fix(es)

1.  Eliminate abrupt steps between the racing surface and the infield in the triovals.  Remove the grass in the infield of the trioval area so that there isn’t a transition.  You can paint asphalt as well as you can paint grass.  Having a continuous surface, with a very smooth transition from banking to flat (the abrupt change from banked to flat can also create a torque that flips cars) would eliminate a lot of problems.

2.  Decrease speed.  The ability of cars to take off when they rotate is dependent on the yaw angle and the speed they are traveling.  You can’t do anything to prevent the cars from rotating, so the only option is to decrease the speed of the cars.  You could do this by making the restrictor plate smaller (see below why that probably won’t help) or giving the cars much more drag so that they can’t go as fast.

3.  Stop Pack Racing.  The Big One happens because there are so many cars so close to each other traveling at high speed.  200 mph is a football field per second.  You literally have no time to react.  This is a direct consequence of restrictor plate racing, where the drivers are at full throttle all the time.  Many fans like pack racing; however, if you want pack racing, you’re going to have to accept that we’re going to have accidents like the ones we’ve seen this year during the Nationwide race in Daytona (in which fans were injured) and like we saw last weekend at Talladega.

4.  Have the drivers get their heads out of their @**$* and drive better.  The Talladega accident happened because drivers tried to make their cars do things the cars weren’t capable of doing.  Simple as that.  NASCAR cannot fabricate an idiot-proof car.  As long as drivers push their cars past their limits, there will be accidents.

About Newman’s Comments

It’s really easy to criticize abstract entities like “NASCAR” because you’re not really criticizing a person — it’s a faceless corporate entity.  When you know the people who are being criticized, you take the criticism differently.  I know a number of the people responsible for safety in NASCAR.  They have dedicated their lives to making racing safer and not just for  ‘stars’ like Mr. Newman.  Think about how many lives these folks have saved.  It is unfair  to characterize them the way Mr. Newman did.  I understand being mad, but it’s disappointing that Mr. Newman lacks the grace to express his frustration some way other than name calling.

I’m also disappointed by NASCAR’s stand on the issue, either.  I’m OK with not fining Mr. Newman for his comments.  They were made in the heat of the moment and I’d be pretty steamed if a car landed on me, too.   It seems to me that there’s a very fine line between criticizing officiating and criticizing people’s integrity.  The statement NASCAR put out, however, seems to imply that it’s OK to attack the integrity of people as long as you’re not attacking the “racing product”.  Seems to me there’s something wrong when you put product before people.

I’ve said it before, but it beats repeating:  there is no way to make racing 100% safe.  NASCAR has made enormous strides in safety, but there is — and always will be — the potential for serious injury and death.  If human beings never made mistakes, racing would be significantly safer than it is; however, the fact is that the human element of racing is perhaps the most important and that brings with it the likelihood of mistakes.

If you’re not willing to accept that, you should consider another line of work

Here’s an older video about aerodynamics and lift:

Why You Don’t Mess With Fuel Cell Foam

 Explosions, Fines, Fuel Cells, Johnny Sauter, Kansas, Rules, ThorSport  1 Response »
Apr 262013
 

We’d been hearing rumors of penalties stemming from Kansas and everyone expected them to be announced Tuesday.  Since penalties usually have some scientific component, I was sort of hoping for some new material.  Tuesday came and went.  Nothing.  Wednesday, all heck broke loose as penalties were announced for the No 20 JGR car (engine issues) and the No 98 ThorSport truck.

The JGR issue isn’t that complicated — or interesting.  Someone screwed up and connecting rod that was too light got into an engine.  It’s beyond surprising that Toyota said that they don’t have the personnel to check all the engine parts – given that everyone knows that penalties for engine violations are huge, why would you risk something like this happening?  The penalty was pretty severe and NASCAR has to crack down.  I get taking away points, leveling fines and such — but the tradition of holding the crew chief responsible for the engine when the engine comes from a supplier who doesn’t let the team touch it is out-of-touch with the realities of NASCAR today.  That was a valid punishment when everything came from the team, but there is no reason Jason  Ratliff should be suspended over an issue that was entirely JGR.  I have no problems with the other penalties, but that one is pretty unfair in my opinion.

The more interesting — and less discussed — penalty is the ThorSport/Johnny Sauter one.  (It was a tough week for Wisconsin drivers).  The team was docked 25 points, which is pretty huge for the Truck Series and the crew chief fined $10,000.  (I realize that seems small when compared to the Sprint Cup Series penalties, but the Truck Series has correspondingly lower purses and salaries.)  Here’s the official NASCAR statement.

“The No. 98 truck was found to have violated Sections 12-1 (actions detrimental to stock car racing); 12-4K (if in the judgment of NASCAR Officials, race equipment that has been previously verified or previously approved and/or sealed by NASCAR for use in an event, pursuant to sub-section 8-6 and/or 8-12, has been altered, modified, repaired, or changed in any manner); 20B-16 (once a fuel cell or fuel cell components have been certified, modifications of any kind will not be permitted to the fuel cell or fuel cell components); and 20B-16.1B (standard black, safety foam with minimum free-standing height of eight (8) inches, acceptable to NASCAR Officials, and used as provided by an approved fuel cell manufacturer, must be used: Fuel cell safety foam modification.”

A fuel cell is slightly different than a fuel tank.  A fuel tank is pretty much an empty container, which leaves open the possibility of raging fires and/or explosions.  Fuel cells, which provide additional levels of safety, became standard after the death of Fireball Roberts from burns received during a car fire at Charlotte in 1964.

Engines_FuelCell_FuelSafeAs shown below, a fuel cell is a metal can (minimum thickness of 18 gage, which is 0.047″) fitted with a flexible bladder shaped to fit the can.  The bladder contains the fuel, but it’s not just a bag of fuel in a metal case.

The most important part of the fuel cell is the item labeled ’1′ in the picture above – the safety foam baffling.  In the picture below, the black thing on the left is the bladder and the yellow stuff is the foam.  The foam is a cross between a nerf ball and the white styrofoam you use to make models of the solar system in elementary school.  That is to say that the foam is sort of coarse, like the white styrofoam, but it’s not rigid – it gives a little when you squish it.  It’s also gasoline resistant.

http://i2.wp.com/www.fuelsafe.com/store/media/catalog/product/cache/1/image/9df78eab33525d08d6e5fb8d27136e95/R/B/RB215_1_1.jpg?resize=410%2C274

Foam is mostly air.  There are even special foams called aerogels, in which 99 percent of the volume of the foam is air.  (Those foams are fragile and would be destroyed by gasoline.)  The foam takes up a small volume of the fuel cell, so it doesn’t change the capacity of the fuel cell by very much; however, it plays two very important roles.

The function most people know is that the foam keeps fuel from sloshing around in the turns.  A full tank of fuel weights about  120 pounds.  When a car corners, everything that isn’t rigidly attached to the wheels feels a force to the right.  The grip you have depends on how much weight is pushing down on each tire.  When weight shifts to the right side of the car, you lose grip on the left side tires.  There’s only so much you can do to keep the body from rolling in the turns – you don’t need the gasoline moving to the right as well.

More importantly, the foam prevents explosions.   If you tossed a match into a container of gasoline (warning: do not attempt this at  or anywhere else), the explosion would happen before the match actually hit the gasoline.  When you have a cup of water, it looks like there is water in the bottom and air on top.  In reality, there are water molecules from the liquid escaping into the air (and water molecules from the air condensing back into the liquid) all the time.  When you microwave that water until it boils, you force more molecules from the liquid phase into the gas phase.  The hotter the water is, the more water molecules in the air immediately above the liquid water.

In order to smell something, the molecules from the thing you’re smelling have to make their way into your nose.  You don’t smell liquids – the molecules from the liquid vaporize and make their way into your nose.

Slide1Gasoline is volatile.  In fact, any liquid that you can smell is volatile, which simply means that the molecules can very easily move from liquid to vapor.  If you look at a traditional fuel tank that is only partially full, it isn’t a layer of gasoline and a layer of air.  It’s a layer of gasoline and a layer of gasoline vapor mixed with air.

When gasoline is purposely combusted in an engine, it has to be sprayed as a very fine mist.  The finer the mist, the more efficiently it combusts.  The top layer in the fuel tank – the gasoline vapor – is highly flammable.  A spark will combust the fuel vapor molecules nearest to it.  That combustion compresses the rest of the fuel vapor, leading to a chain reaction and an eventual explosion.

Foam in a fuel cell prevents a concentration of the fuel vapor plus air mixture, which significantly reduces the probability that the fuel cell will explode in case of a fire. Reducing the amount of foam in a fuel cell, either by not putting it in to the eight-inch mandated height, or by carving out hollows in the interior of the foam, creates a very highly flammable pocket of fuel vapor and a major safety hazard.

While manipulating the foam might give you an advantage in terms of being able to fit more fuel into the tank, it creates a major, major safety hazard by making the fuel cell more likely to explode in case of an accident.  While people talk about messing with the fuel being a major no-no, the big thing here is really the safety aspects.

 

Notes on Respect and Fines

 Denny Hamlin, Fines, Gen-6, NASCAR, public relations, Rules  7 Responses »
Mar 112013
 

A short note on Denny Hamlin’s comments on the Gen-6 car and subsequent fine.

I’ve talked to a lot of the people in the trenches involved in designing and creating the Gen-6 car.  That includes people from manufacturers and teams.  All of them have said that the development of the Gen-6 car is a major sea change for NASCAR.  This is the most collaborative that NASCAR has been with introducing a new car in some time.  Manufacturers and teams were consulted and they all feel that their opinions mattered and were taken into consideration.   This was a very, very different process than the COT introduction, which was designed by NASCAR and plans delivered to teams.

So when a driver talks trash about the Gen-6 car, they aren’t just talking trash about NASCAR – they’re insulting the people on their own team and their manufacturer, all of whom have been working collaboratively to make the best car possible.   NASCAR deserves some major accolades for opening up the process.  One team principal even declared it “a new business model where we are partners with NASCAR”.

Is the car perfect?

Heck, no.

But when did you ever do something and get it perfect the first time out?  I’ve said already that we’re going to have revisions throughout the year as we learn more about the car.  No one expected it would come out and be exactly right the first couple of weeks.

If drivers want to help with the tweaking, then they need to make constructive specific comments (like where and under what conditions they’re having problems passing) rather than blanket condemnation of the car and the process.

Having said that, I also disagree with NASCAR fining Hamlin.   I can see their point of view.  Changing corporate culture is a very, very hard thing to do.  NASCAR met the teams more than halfway.  They did a lot of the things people behind the scenes have been asking them to do for some time.   And then a driver comes out and slams the car in the most general, broad way possible.

I suspect it’s like parents who tell their kid he can come in a 9pm instead of 8pm and then the kid stays out till 10 pm.  For heavens’ sake — they were trying to do something nice and they got slapped in the face.  NASCAR is rightfully aggravated.

But I think most fans listened to his comments and thought the same thing as one caller to SiriusXM Speedway, who said

“Of course he’s complaining about the car.  He lost!”

We know drivers are frustrated when they get out of the car and often for some time afterward.  We know they say things that are not always tactful and are sometimes rather wrong-headed.  You don’t have to fine a driver to let us know that you think he or she was out of line.   Hamlin’s fine shifted the focus from racing to public relations.  And that’s not why most of us watch.

From the Lab Notebook: Las Vegas and the Mysteriously Missing Oil Tank Cover

 Aerodynamics, Downforce, Drag, Edwards Carl, Jack Roush, Las Vegas Motor Speedway, Rules  No Responses »
Mar 062013
 

As we head for Las Vegas this weekend, I thought I’d repost on of my most popular posts from stockcarscience.com on 3/5/2008  since the redirects for the old stockcarscience.com site don’t work reliably.  The post is about Carl Edwards’ 2008 win at Las Vegas when the team was subsequently fined for having their oil tank cover lid askew at the end of the race.  I have edited the post extensively, adding some new information and better graphics.

Danny LaDue asks: Can you explain the location of a NASCAR oil tank reservoir and how the lack of one could improve aerodynamics?

Thanks for the question, Danny.

NPR got this one wrong.  Frank DeFord in his usual Wednesday commentary made a comment that was essentially — look, the lid was still in the car, it didn’t give him a weight advantage, so NASCAR was wrong to penalize the team.  Don’t these folks known anything?

That’s the problem with aerodynamics — you can’t see it happening.

Unlike your car, the oil in a NASCAR car isn’t stored in the engine (called a wet sump system).  NASCAR uses a dry sump system, in which oil is

stored in an oil  reservoir. The oil reservoir is located behind the driver’s seat and is surrounded on the sides and top by sheet metal, which forms the oil tank.   The sheet metal minimizes heat radiating into the car, traps fumes from the hot oil, and serves as an additional firewall.  This function is so important that NASCAR doesn’t allow the top of the tank to be attached using quick connect fasteners. Some teams duct tape the lid on. The picture to the right shows the location of the oil tank with respect to the chassis. It doesn’t show the cover, which would sit on top of the tank.  The oil reservoir itself is closed and pressurized.

So if the oil tank cover plays such an important role, why would you leave it loose, much less leave it off?   The answer is aerodynamics.  The air exerts forces on the car in different directions.   Drag is the force air creates along the length of the car.  Air creates drag when it hits the front of the car,  but it also creates drag when it gets inside the car because there is no way for it to get out.   Drag always acts opposite the direction the car is trying to move, so you want to eliminate as much drag as possible.

Downforce and lift are the names for the forces pushing straight down or up on the car. Downforce pushes the tires harder into the track and provide grip, while lift pulls up on the car.  These two forces are in direct opposition to each other.  The bigger force wins.  You want to maximize downforce and minimize lift.

Downforce_oilTank1The oil tank is open to the bottom of the car. Air under the car creates lift.  Even though you try to keep the splitter close to the ground, there is always some air that gets under the car.  If the oil tank lid isn’t firmly tightened down, it creates a path for air to get out of the car, which reduces lift.

When the amount of lift decreases because of the loose oil tank cover, then the net downforce is larger because there is less air pushing upward. More downforce translates directly into more speed, as shown in the figure below.  Remember learning about ‘net force’ in physics?  Yep – it is actually useful.  The loose oil tank cover likely provided a little extra downforce — in a sport where races are won by thousandths of seconds, even “a little” advantage is important.

Downforce_oilTank2

One of Rusty Wallace’s cars originally penalized in the Nationwide series won its appeal on the basis that all of the bolts on the oil tank cover were engaged fully and the design of the oil reservoir was such that it led to the apparent opening. I can imagine (especially having seen graduate students overtighten bolts) that if you screwed down really hard on the bolts and the oil tank lid were on the thin side, you might be able to warp the cover on the oil tank lid a little and get some air escape.  The problem with this argument is that you can only use a ‘bad design’ argument once because NASCAR will make you redesign it.

The case of the No. 99 car’s oil reservoir lid is a little different, though, because the reports have been that the lid was entirely missing. In fords, the oil tank cover is held on by a single bolt.  Carl Edwards said on NASCAR This Week that a “bolt backed out”.  Jack Roush made the argument that the vibrations in the car caused vibration harmonics that caused the bolt to unscrew itself.  Even if that’s true (and I have to admit I’m a little skeptical about it), should you really have a safety feature held in place by a single bolt?

NASCAR fined the driver and the owner 100 points (old points scheme!), fined crew chief Bob Osborne (B.S. in Mechanical Engineering from Penn State) $100,000, 100 points and suspended him for six weeks.

Did Danica Get the Daytona 500 Pole Because of Her Weight Advantage?

 Center of Gravity, Danica Patrick, Daytona, Inspection, Poles  5 Responses »
Feb 202013
 

Note – this was revised 2/20/13 because new information became available.  It is amazing how hard it is to get a straight answer to things sometimes!

Did Danica Patrick win the Daytona 500 pole because she has a weight advantage?

Chuck Tolsma asked via Facebook:

Evidently weight is added for lighter drivers. How is it distributed in the car? Did Danica win the pole because she has a weight advantage? What is the effect of weight on downforce and is it really as significant as alleged by a couple of media people?

Minimum Weight Rule

Let’s start with the facts: NASCAR requires all cars meet a minimum weight requirement. (Car weight is measured with all the fluids and a full tank of fuel. The way the rule is phrased in the NASCAR rulebook is sort of confusing because they specify the minimum car weight without driver, but then the minimum car weight changes depending on the weight of the driver. So if the driver is 180 lbs and above, the car must weigh at least 3300 lbs. If the driver is 170-179 pounds, the car must weight at least 3310 lbs. The list keeps going, in increments of 10 pounds, all the way down to 140-149 lbs.

From That’s Racin’, the NASCAR rulebook says:

DRIVER WEIGHT MINIMUM OVERALL CAR WEIGHT
180 lbs. – Above 3,300 lbs.
170 lbs. – 179 lbs. 3,310 lbs.
160 lbs. – 169 lbs. 3,320 lbs.
150 lbs. – 159 lbs. 3,330 lbs.
1400 lbs. – 149 lbs. 3,340 lbs.

@bobpockrass clarified this rule earlier today on twitter:  The max ballast anyone is allowed to put on their car, regardless of weight, is 40 lbs.

Drivers are weighed with all their gear on — helmet, firesuit, gloves, sunglasses, sharpies… This can add another 15-20 lbs of weight to a driver.  So although Danica weighs about 100 lbs, with her gear, we’re actually talking 115-120 lbs.  Same goes for the other drivers as well.

This would imply that Danica’s car is 3340 lbs.  Add in her and her gear and the total weight is 3340+120 = 3460 lbs, which is 20 lbs below the 3480 lb absolute minimum weight that any other drivers could get down to.

Why doesn’t NASCAR do things the way many other series do?  Just weight the driver and the car together and it has to meet a minimum weight.  My guess is that NASCAR drivers spend so much time doing publicity for their sponsors and fans that it would be tough to schedule.  This way, you only need the driver once (or twice) a year.

The question that remains (now that we actually have a reliable answer to the weight question) is:  Does that 20 lbs make a difference?

Weight Distribution

Total weight is not as important as where the weight is located.  NASCAR has a bunch of rules on where ballast (additional weight used to bring the car to minimum weight) can be located.  They also mandate a right-side weight of (I believe) 1,620 lbs minimum.

Why does NASCAR mandate how much weight is on the different sides of the car? Because weight distribution determines mechanical grip. The mechanical downforce on each tire — the grip — depends on much weight is pushing down on that tire. More weight on the tire means more grip.

When you turn left, the body leans from the left side of the car to the right side of the car. So when you turn left, you decrease the force pushing down on the left wheels and thus you lose grip (i.e. mechanical downforce) on the left side of the car.

How much weight shifts depends on the center of gravity of the car. The higher up the weight is, the higher the center of gravity of the car becomes. The higher the center of gravity of the car, the more weight shifts when you turn. Think about taking a corner in an SUV with a high center of gravity vs. a sports car with a low center of gravity. The higher center of gravity makes the car lean more in the turn.

For these two reasons, anytime you have a choice where to put weight, you choose left and low. Left because you want to keep as much grip on those left tires while turning and low because it decreases the center of gravity. The center of gravity is why teams have been making carbon fiber dashboards – it decreases weight relatively high in the car and allows them to compensate by putting the weight where it will decrease the center of gravity.

It’s pretty straightforward to compare the CG of a car given the driver weight, the ballast weight and the car weight. So my friend Josh Browne (one of Elliott Sadler’s former crew chiefs and now a Ph.D. student at Columbia) and I plugged some numbers to see if this made much of a difference.  I went through a bunch of possible scenarios this morning once I got confirmation on the weight.

Based on these estimates — which don’t take into account a lot of other factors — if their put the entire 40 pounds on the left hand side, Danica’s car might have a lower CG by maybe a tenth of an inch — or two.  That’s simply not enough advantage to matter, especially since you have (as pointed out by @keselowski) other factors.  The one Brad pointed out was that the car height is measured with the driver in the car – a lighter driver doesn’t bring the car down as much.  I’m still trying to find how much lattitude teams have with rear springs at Daytona to figure out whether the set up could compensate for that.

Regardless, remember that the center of gravity and the overall weight is one of a bunch of factors, all of which could be a plus or a minus.

The calculations also explain why you don’t keep letting them add ballast — at some point, you get too big of an advantage if the ballast amount gets large enough and that more than overcomes having the weights equal.  Weight distribution is way, way more important than total weight.

But Wait! Don’t Women Have a Lower CG than Men?

Yeah. About an inch lower. Even taking that into account, the numbers don’t change much. The advantage she’d have is in the noise because you have so many other variables, like seat weights and placements, dashboard weight, etc. that could change. Women have a lower of center of gravity because (in general) we have wider hips and narrower waists, whereas men are more uniform.

Remember — we’re talking about 3300 pounds+ of car and 100-200 lbs of driver and ballast.  The driver and ballast is such a small part of the center of gravity, that you’d have a really hard time significantly manipulating the CG that way.

Conclusion

In talking to engineers on race teams, I’ve heard the same thing over and over: she won because Hendrik gave her good equipment and the fastest engine. They had nothing to lose. Being on the pole at Daytona doesn’t mean very much in terms of winning the race, but look at the huge publicity boost. It was on the nightly network news. How often do we get on the mainstream news for anything other than crashes and fights?

The folks in the garage are pretty quick to raise a ruckus if they think something sneaky or unfair is going on.  Have you heard scores of drivers complaining about the 10 having an unfair advantage?  If none of them think there’s anything suspicious about Danica’s pole, why do we?

Want to know stuff about the Gen-6 Car? Tweet your questions to @drdiandra or find me on facebook. I’ll find the answers for you.  And hopefully they won’t be as hard to figure out as this one was!

Other Relevant Posts

Gen 6 Car

Superspeedway Science

Buy my book! The Physics of NASCAR

Secrets of the Gen-6 Car: Superstrength Windshields

 Car Parts, Greg Biffle, Lexan, Robin Pemberton, Tom Gideon, Windshields  5 Responses »
Feb 152013
 

A number of drivers have sounded a common refrain:  the CoT was engineered to be safe … and that’s why it was… well… sort of ugly and not very racy.  The Gen-6 car is a much better looking vehicle and (once the teams get a handle on the engineering) it should also give us a better show.  But don’t let its looks fool you:  NASCAR did not forgot safety in the Gen-6 car.

During a recent visit to the NASCAR R&D Center, Tom Gideon — NASCAR’s Safety Czar — gave me a tour through some of the changes you might not notice… unless something bad happens.  The drivers were briefed on these changes during Daytona testing last month and the reactions have been uniformly positive.

There is a line of Diet Coke cans sitting on the front edge of Tom’s desk.  They aren’t for drinking:  they’re there to become high-speed projectiles.

Why Diet Coke?

Because, Tom explained, if you splat regular Coke onto a car, you’ll spend the rest of the afternoon cleaning up the gooey, nasty mess produced by all that high-sucrose corn syrup.

The soda cans (actually, their less-fortunate cousins) were projected at car windshields.  NASCAR windshield are, of course, not made of glass.  They are made of a plastic called polycarbonate, which is better known by the trade name Lexan.   Lexan is clear, like glass, but it gives more easily and thus can take higher impacts without breaking.  In fact, the shark fins on the Gen-6 cars are made of Lexan, which makes them virtually invisible when the cars are on the track.

Lexan is also more expensive than glass, which is why most passenger cars still use glass in their windshields and windows.  Windshields are made from laminated safety glass.  Laminated means stacking up a bunch of layers of something and compressing them to make a single unit.   Plywood is a laminate of wood, which you can see if you look at the end grain.

Laminated autoglass sandwiches a very thin polymer film (polyvinyl butyral, a.k.a.  PVB) between two layers of glass. The layers are heated under pressure, chemically bonding the glass and the film.  The polymer film (in contrast to glass) is elastic – that’s the layer that allows the glass to absorb energy when something hits it.  This is the same idea as padding your dashboard – the padding extends the time of your collision and thus decreases the overall force.  The polymer film insert in your car’s windshield also absorbs UV rays from the sun, protecting the fabric, leather and plastic inside the car.  Most importantly, if laminated glass breaks, the polymer film holds the pieces together.  The side windows in your car are made from  a different kind of glass that is designed to shatter into a zillion tiny — and rounded — pieces if it breaks.  This allows a person to climb out a broken side window without restriction (or cuts).

NASCAR_brokenThe Diet Coke cans on Tom Gideon’s desk were representative of the types of projectiles that might land on a track.  If you think something as seemingly innocent as a soda can  can’t do any real damage, look at this blog I wrote awhile back when a Dallas TV station contacted me to verify the story of a woman who claimed a styrofoam drink cup thrown from a passing car had punched a hole through her windshield.  The hole is shown at right and, yes, a styrofoam drink cup traveling at high speed can break a windshield.

A Lexan windshield wouldn’t have broken, but the windshields in NASCAR racecars have to stand up to much more than soda cans.  They have to survive impacts of things like like wayward car parts.  Last year in Charlotte, a piece of brake rotor hit Greg Biffle’s windshield.  The brake rotor didn’t go through the windshield, but the impact did blow out the interior window braces so that they were hanging over the steering wheel and impeding Biffle’s ability to steer.

Five years ago, NASCAR was in reactive mode when it came to safety.  They weren’t anticipating problems, they were rushing to develop solutions when something happened on the track.  Things have changed:  NASCAR is sufficiently ahead of the game that they aren’t waiting for a catastrophe to happen before they start innovating.

One of the R&D Center’s new toys pieces of scientific equipment is a pneumatic cannon.  It uses compressed gas (just like a potato gun) to propel a projectile toward a windshield at about 50 mph.  In addition to the soda cans, NASCAR used solid metal cylinders to test the Gen-5 windshield using the new pneumatic cannon.  The old windshield wasn’t unsafe, but the R&D Center realized they could do better.

NASCAR_Gen6WindshieldLamination improves the strength and energy-absorbing ability of glass, and it does the same thing for Lexan. The Gen-5 windshield (shown at top left) was a little less than a quarter-inch thick.

The new window uses two pieces of Lexan, each half the thickness of the old window, with a 30 mil (that’s 30 one-thousandths of an inch) polymer film between them.  A really good-quality heavy duty trash bag is 4 mil thick, so the film in the new windshield is about seven or eight trash bags thick.  After heating and pressure treatment, you have a perfectly clear, superstrong windshield that is only thirty thousandths of an inch thicker than the old window.  Robin Pemberton told the media that the new windshield could withstand the equivalent of a connecting rod going 200 mph without breaking.

The pneumatic cannon resulted in some additional developments that I’ll detail in my next post.  Questions and comments are always welcome.

 

Will the Gen-6 Car Affect the Number of Cautions?

 Cautions, Edwards Carl, math, Racing, Tony Stewart  4 Responses »
Jan 252013
 

I love the Gen-6 car.  Not as much as I love the Nationwide cars (but that’s got more to do with what I drive than it does the cars).  The big question is whether the decrease in cautions is going to be changed because of the new car.Let’s start (as we usually do) with the new car.

Graph4Let’s start (as we usually do here) with the data.  I’ve tabulated the data for cautions for the last twelve seasons and found that cautions have been decreasing since 2005, as shown,  for both the Nationwide and the Sprint Cup series.

In order to compare the two series and to compare between seasons within a single series, I’ve plotted the number of cautions per 100 miles.

In 2012, the Sprint Cup series had 1.57377 cautions per 100 miles.  They drove 13725 miles total, so that was 216 cautions total.

In 2012, the Nationwide series had 2.23969 cautions per 100 miles.  They drove 8240 miles, with comes out to 189 cautions — essentially the same number of cautions per mile they had last year.

Conclusion #1.  If the Nationwide drivers had driven the same number of miles as the Sprint Cup drivers, they would have had 307 cautions.

You’ll notice that I’ve drawn lines through each set of data.  They aren’t just a best fit by eye – I actually did a non-linear least-squares fit that determines the line that goes closest to all the points.  The data are decidedly linear and, more importantly, there aren’t any bumps or jump in, say, 2008, when the COT (which I guess is now the Gen-5 car) was introduced, or in 2011 when the Nationwide car was changed.  The data remained pretty consistent.

Conclusion #2.  Cautions are not affected much by the car that’s being driven.  Sure, I expect there to be some driver errors when a car doesn’t handle the way the driver expects it to behave; however, these guys catch on really quickly, so that’s going to be maybe 5 cautions.  Five out of 216 is like 2.3 percent, which is well within the error in the fit parameters.

Why are the cautions decreasing?  I’ve gone into this before, but I believe it is essentially because the drivers have a lot more experience now than they did in previous years.  There are a lot of veteran drivers in the Cup series right now, and I calculated that if you add up all the races run by the current crop of drivers, they have run a total of about 1000 more races in 2011 than they did in 2005.  That’s a whole lot of experience, and it’s distributed amongst the drivers.   Compare just two drivers:  Tony Stewart had run 248 races in  2005 and at the end of 2012, had run 500.  Carl Edwards had only run 49 races in 2005 – compare that to the 301 races he’d run as of today.  (I am only counting points paying races.  If you could somehow quantify the number of practice laps, time testing, etc., I think that would only make my argument stronger.)

So, in short, I don’t expect there will be any significant change in cautions because of the new car — up or down.  What do you think?

 

Is There Really a Second-Place Curse?

 Clint Bowyer, Dale Earnhardt Jr., Denny Hamlin, Edwards Carl, Jeff Gordon, Jimmie Johnson, Kasey Kahne, Keselowski Brad, Kyle Busch, Mark Martin, Martin Truex Jr, math, Tony Stewart  No Responses »
Dec 072012
 

One of the commentators after the final race in Homestead mentioned that Jimmie Johnson should be happy he finished in third because it allows him to avoid the “dreaded second-place curse”.
Anytime someone says something like that, it makes me wonder whether there really is a curse, or whether that person had just been talking to Carl Edwards.  So I analyzed a little data and guess what… there really IS a second place curse.

I used data from the last twelve years — from racing-reference.info, bless them!  After trying a couple of different approaches to making the data easy to visualize, I ended up with something a little more complicated than I would have liked.

Bear with me – it’s not as yucky as it looks.  I have plotted on the horizontal axis the place in which a driver finished in the first year listed, which we’ll call “X”.  I then calculated the change in positions of the same driver the next year (X+1) and plotted that on the vertical scale.  So the first set of data has X = 2000 and X+1=2001.

  • A positive number on the vertical axis means that the driver finished better by that many places in the following year. For example, +5 means that the driver finished five places better the next year than they finished the year before.
  • A negative number on the vertical axis means they finished worse the next year. A -5 means they moved down five spots in the final standings.

I went through and removed any special cases — like Mark Martin running full time one year, but not the next, Busch brothers missing races (that’s a different kinds of curse), people retiring, etc.  The graph below summarizes the top 16 finishing places and the change in final standing over the last twelve years.

There’s an obvious statistical implication:  If you finish second, for example, you have only one place to move up and forty one places to move down.  You’re either going to win the championship next year, become second again, or move down.  The probability is that you’re going to finish worse than second.

To look at the data in a slightly different way, I plotted it the same way they plot the daily activity of the the stock market:  the symbol shows you the average.  One line extends up to the maximum increase in position and one line extends down to the largest drop in position.

 

The first-place curse

In fact, if we’re going to call dropping in the standings a “curse”, then there is clearly a first-place curse that affects everyone except Jimmie Johnson.  Mose drivers who win the championship one year inevitably finish worse the next year.  When I say ‘drop in points’, it’s not a huge drop:  nine places was the most anyone who finished first dropped.

The average first time finisher fell almost five positions.  That’s including four consecutive ’0′s due to Jimmie Johnson.  If we exclude Jimmie just because what he did was really unprecedented (and unlikely to be duplicated), the average first-place finisher falls almost seven positions the next year – about the the same as the second-place driver.

The second-place curse

Second place shows a very similar story, only worse.  There is only one case in twelve years in which the second place finisher one year won the championship the next year.  That was Jimmie Johnson.  Whoops – Rick pointed out my mistake.  It was 2001 -2o02 and the driver was Tony Stewart!  On average (including Jimmie), the second place finisher finishes about seven positions lower the next year.

The three biggest drops in point standings (-15, -13, -11, -9 and -7) are due to Martin, Edwards, Biffle, Edwards and Hamlin.  There are no extenuating circumstances like crew chief changes, owner changes, etc. on which to blame the drops.  Four out of five of those drivers were all driving for Roush at the time… maybe there’s a Roush curse?

The bad news for Jimmie Johnson… and everyone else who made the chase

Here’s the bad news for Jimmie:  Yes, he avoided the second-place curse; however, no third-place driver has gone on to finish first or second the next year.  The best they’ve done was to match their third-place finish.

Yep, perhaps there’s a third-place curse as well, as third-place drivers finish an average of three places lower the following year.

In fact, you don’t find a finishing position in which there is an average probability of bettering your finish until 7th place.  On the graph above, you can see that the majority of finishes were improvements, although without one -11 change, it would be a much more positive number.  After that, it’s an oscillation between slightly better and slightly worse.

A caveat of this data analysis is that the Chase sort of messed things up going out past 10 because a driver in the Chase can’t finish lower than 10th, even if he misses races or otherwise would have fallen much lower without the Chase format.

 

NASCAR Concussions II: A Screening Test to Avoid Relying Entirely on the Driver

 Concussion, Dale Earnhardt Jr., NASCAR, Opinion, Talladega  No Responses »
Oct 152012
 

I was lucky enough to speak with Dr. Mark Lovell, an innovator in neurocognitive testing inbetween talks at a conference he was attending.  (Neurocognitive, incidentally, describes those thinking functions that are closely linked to particular areas of the brain.  We’re talking about things like attention, memory, speaking and understanding language, solving problems, and making decisions.)  Dr. Lovell was the founding director of the University of Pittsburgh’s Medical Center’s Sports Medicine Concussion Program and has published over a hundred journal articles and authored or co-authored nine textbooks about sports-related concussions.

Dr. Lovell came to my attention as the developer of the ImPACT (Immediate Post-Concussion Assessment Testing) test, which was one of the tools used to evaluate Dale Earnhardt, Jr.’s concussion.  Given that he is right up the road in Pittsburgh, I thought I’d spend a little time looking into exactly what the test is and whether it’s a viable alternative for NASCAR to use in screening drivers for concussion.

As I mentioned in my last post, physical damage to the brain can be detected by techniques like magnetic resonance imaging; however, even if the physical structure is intact, the brain works primarily on electrical and chemical signals – and we don’t have a way to simply look into a person’s head and verify that all the neurons are sending and receiving signals correctly.

Lovell wanted to make clear that concussions are a rapidly evolving field of research, noting that “90 percent of everything we know about concussion has been learned in the last ten years”.   Ten years ago, no one thought a concussion was a big deal.  Getting your “bell rung” was part of sports like football, hockey and boxing.  We’re learning now — especially from long-term studies of football and hockey players) that even a “mild” concussion in which you don’t lose consciousness can have short- and long-term results.

Here’s what the ImPACT test looks like:  You sit in front of a computer terminal for about twenty minutes and respond to a series of fast-moving activities.   For example, you’re given twelve target words to memorize – you get to see the words for 750 milliseconds each — and you get to see each word twice.  You are then presented with twenty four words, twelve of which are the ones you saw already and twelve of which are similar in some way to the words you saw.  For example, you might be shown the word “ice” as one of the ones to remember and “snow” as a non-target word.    A box comes up and asks “was pencil one of the words displayed?” and you click yes or no.  There are similar exercises using abstract designs, letters, colors, and symbols.  Each exercise tests one (or more) neurocognitive function.

It’s not easy.  In fact, when you’re done, you feel a little like someone has been throwing things at your brain.  The test requires you to multi-task and if you took the time to try to think about how to cheat, it would be obvious that you weren’t giving it your best try.

Lovell emphasizes that a complete evaluation for concussion requires many parts:  The process requires collecting demographic information and a health history survey, including any history of previous concussions.  If you’ve had mental health issues or are taking medications, that has to be factored in as well.  A full description of the injury also is usually included.  Assuming NASCAR adapted this as a standard test, this would all be on file or easily available.

The ImPACT test looks at six distinct elements:

  • Verbal memory (your ability to pay attention, learning and memory relating to verbal things like words, symbols and letters)
  • Visual memory (visual attention and scanning, learning and memory related to visual processes)
  • Visual motor speed (visual processing, learning and memory, and visual-motor response speed)
  • Reaction time (how fast you can respond to something)
  • Impulse control (this is actually a way of measuring the uncertainties inherent in the testing)
  • Symptom score (this measures the presence and severity of 22 symptoms, ranging from sleeping to balance to irritability to fogginess).  This is really the only area of the test in which a driver could try to hide evidence of a concussion.

Dr. Lovell recommends that athletes do a “baseline test” prior to engaging in their sport.  For NASCAR, that would be at the start of every season.  Although the test is still useful without a baseline, having the pre-test allows you to compare a driver’s current state with his previous state and reduces uncertainties that might be caused by things specific to an individual.   Over many years of testing athletes at all levels, the ImPACT people have collected scores for people in different age groups, genders and populations (i.e. athletes vs. us couch potatoes), so even without a baseline, a doctor would have some reference point for how well you ought to score by comparing your score with a typical score of someone similar to you.

One of the challenges of concussion is that it’s a type of injury in which the patient may try to hide the symptoms from the doctor.  Dr. Lovell designed the ImPACT test to help diagnose concussion, even when the subject is reluctant to admit that he or she is exhibiting symptoms.  Trying to purposely score poorly on the test works against the athlete (a bad score makes it more likely you’ll be sat down), so the athlete is motivated to do their best.

Anyone developing a test (whether it be for education or medicine) has to worry about people who try to get around the test’s purpose.  What was most impressive to me in reading the research papers about the ImPACT test is that the developers have come up with ways to tell when people are trying to outwit the test.  Dr. Lovell laughed when he told me that some athletes “sandbag” during their baseline testing, thinking that if they have a lower baseline score, they can get hurt and it won’t be detected.  The test developers have found ways to measure whether someone was trying, for example, to be more accurate by taking the test more slowly, or to complete the test quickly without worrying about being correct.  The test is not only measuring neurocognitive function, it’s measuring whether you’re taking the test to the best of your ability.

Your score on the ImPACT test isn’t a yes/no measure of whether you have a concussion.  Concussion is a subtle enough injury that you still need evaluation by an experienced professional; however, Dr. Lovell believes that the ImPACT test is a good way to screen athletes to determine whether additional medical evaluation is necessary.

Your score on the ImPACT test also gives the diagnosing doctor some help in predicting time to recovery.  The team has developed a cut-off score that broadly predicts whether recovery time will be less than or more than two weeks.  It’s not exact, of course.  Dr. Lovell emphasizes that one of the challenges understanding and treating concussions is that every individual is different.  Most will fall into a “normal” range, but there are always exceptions at both ends of that range.  Repeat testing helps the doctor measure how well the patient is progressing because there can still be neurocognitive impairment well after the obvious symptoms have gone away.

ImPACT is a twenty-minute test administered on a computer.  A system for administering the test could be brought to any race (it’s much more portable than an engine dyno!) and, given that it takes just 20 minutes to complete, seems like a very easy to implement screening tool after any hard impact.  Again, Dr. Lovell would be the first to emphasize that you don’t just take the test and know that you do/don’t have a concussion; however, NASCAR could easily require any driver involved in a crash to do a quick assessment to determine whether they should be seen by a doctor for further followup.

Concussions – What Are They and Why Stop Racing?

 Concussion, Dale Earnhardt Jr.  Comments Off
Oct 112012
 

We all know that concussions are caused by hits to the head, but what actually IS a concussion and why is one forcing Dale Earnhardt, Jr. to step out of the car and effectively take himself out of the running for a championship?

How Do You Know You’ve Got One?

A concussion is a type of traumatic brain injury (TBI).  The Centers for Disease Control estimate that 1.7 million people suffer a traumatic brain injury every year.  A concussion is a mild type of TBI, but it is not (as we used to think) negligible.  Symptoms of concussion generally fall into four categories:  problems thinking and/or remembering and concentrating; physical signs like headaches, nausea, or balance problems; emotional distress like irritability, sadness or nervousness, and sleep changes.  Symptoms don’t always appear right away after a concussion – it may take days to notice them.  The concept of ‘concussion’ isn’t really well agreed upon by the experts. Most limit concussion to a state in which there is no physical brain damage.  There is even disagreement as to whether you have to lose consciousness to have an official concussion.

Dale Jr.’s doctor mentioned that he had a ‘special’ MRI (magnetic resonance imaging) scan.  I suspect it was a functional MRI scan – you can read more about that and its utility in sports here.

What is a Concussion?

If you were to open up a head, the first thing you would notice is the cerebrospinal fluid.  Your brain is not rigidly held in place in your head.  The cerebrospinal fluid surrounds your brain and gives it a cushion so that it doesn’t bang against the skull when you move your head suddenly.  It’s sort of like an internal helmet for your brain.  In a concussion, the motion of the head is so sharp that the cerebrospinal fluid isn’t able to provide adequate cushioning.  Interestingly, some researchers believe that it’s the rotation of the brain and not the straight-line  motion that is responsible for the damage.  In fact – Dale, Jr. noted during his press conference this morning that the Talladega crash was “only” 20 g, but he also said that he was spinning at Talladega.  Once the damage happens, it can persist for days to weeks — or longer.  We’re still figuring that out.

What we know is that a concussion changes the biochemical functioning of the cells in the brain.  A brain relies on two types of cells:  glial cells (which are like the brain’s pit crew, providing structural and metabolic support) and neurons.  The neurons (shown at right) are responsible for transmitting information.  The axon sends out information and the soma and dendrites receive information.  The information starts as an electrical pulse and then is converted into a chemical signal at the junctions between neurons.  In order for this to work, everything has to function correctly:  encoding the signal by the axon, the chemical processes that move the signal from neuron to neuron, and the decoding process by the soma and dendrites.  If any of these is impaired, the message is compromised.  You can think of a concussion as being like a cell phone in an area of poor reception.  Your cell phone, the person to whom your talking’s cell phone, and the transmission towers all have to work.  If they don’t, some things get through, but other things are jumbled and you can’t understand the message.

Your brain is one giant chemistry set.  When the electrical signals in your brain aren’t converted to chemicals appropriately, you end up with an imbalance of chemicals within the brain.  This means that your brain slows down – the cells slow down the process of dividing and become less active.  There can be a reduction in blood flow to the brain, and less energy is sent to the cells than they expect.  It’s very much like what happens when you get a cold – everything slows down in your body so that the immune system can focus on fighting off the cold.  In this case, however, it’s your brain that slows down.

The primary treatment for a concussion is rest – physical and mental.  A concussion impacts the functioning of the brain, so someone suffering a concussion needs to go easy on the thinking and external stimulus, as well as physically rest. The most important factor, thought, is that the brain is much more susceptible to long-term damage while it is recuperating.  If Dale Earnhardt, Jr. were in another crash this week, he could suffer more damage and it could be more severe.  We know that repeated concussions, like those sustained by football players or boxers, have the potential to cause long-term debilitating neurological diseases like Parkinsons or Alzheimers.  That’s why it is important for him to step out of the car this week.  I can’t imagine it was an easy decision for him to make; however, it was the right decision for him to make.

Questions

Q:  Why wasn’t Dale Earnhardt, Jr. diagnosed until now?

A:  Symptoms sometimes don’t show up for days — or weeks.  Also, many symptoms are possible to have without having a concussion – it’s the combination of symptoms that makes it a concussion.

As Dale, Jr. mentioned in his press conference, he didn’t tell anyone he had symptoms.  A more serious concussion could produce noticeable dizziness, lack of balance and coordination, vomiting or other symptoms, but the list of symptoms includes things like persistent headaches that aren’t apparent to doctors unless the patient says something.

Q:  Why sitting out two weeks?

A:  We don’t know how long it takes for the brain to heal.  It’s still healing, even after the immediate symptoms disappear.  Given the increased danger of possibly permanent damage if he were in another crash, this seems like a good decision.  Having two concussions within a few weeks of each other makes the situation worse.

Q:  If Dale, Jr. feels better in time for Kansas, could he race?

A:  Probably not.  Even when the symptoms lessen, there is still the increased risk for injury.  The patient feeling better is not a reliable indication that he is able to race.  Since they announced two weeks already, I’d be surprised if he’s at Kansas.

Q:  What is the “impact” test?

A:  ImPACT stands for Immediate Post-Concussion Assessment and Cognitive Testing.  It is a computerized test that takes about 20 minutes to complete and provides doctors with a way of assessing if there has been damage to the brain.    It’s a neurocognitive test – meaning that it tests how your brain is working.  Things like X-Rays and standard MRIs look at the physical condition of the brain – this looks at the functionality.  The test measures verbal and visual memory, how long it takes you to process information, and reaction time.  It consists of things like a series of three letters that you are asked to remember and reproduce, matching colors and shapes, etc.

Here’s the catch:  everyone is going to score differently on a test like this.  You can’t compare Dale Jr. and another driver and tell anything about Dale Jr.’s concussion.  If you don’t have a baseline measurement – a measurement prior to any concussions – you don’t have a way to tell whether there was brain damage or whether the subject just happens to have a slow reaction time.   You can re-administer the test after the brain has had time to heal and look for improvement, but you can’t compare it to the pre-concussion condition without a baseline measurement.  Seems to me that every driver ought to have a routine test done at the start of every season.  You can read more about ImPACT at their website.  They do caution that their test is ONE component in making a diagnosis and determining treatment.  NOTE:  read Dustin Long’s story on baselines and their importance.

 

 

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