Aug 212015

A lot of drivers cite Bristol as one of their favorite tracks. It’s a great exhibit for the argument that racing is more than just pure speed. High banks (which we know mean speed!) and a short track, which means tight racing. But a lot of drivers will tell you that Bristol is one of the most exhausting, physically demanding tracks on the circuit. Add to that the inherent stress of short-track racing, where 43 cars are operating in a limited (half-mile) track.

Regular readers know that the force it takes to turn a race car is given by:


So it is harder to turn (i.e. you need more force)

  • when you have a heavy car
  • when you’re going fast
  • when you’re trying to make a tight turn

So when you compare a thousand foot turn radius like at a superspeedway with the 250-foot turn radius of Bristol, it’s four times easier to turn at Daytona  — if you’re turning at the same speed.

Turning Force

Using a typical weight for a Gen-6 car (3300 lbs of car and 180 lbs of driver), we can figure out how much force it takes to make a car turn.  (Disclaimer: Parts of this table are from a previous blog.)

Track Turn radius
Turning Force
Talladega 1000 33 180 6,848 1.97
200 8,456 2.43
Daytona 1000 31 180 7,532 2.16
Bristol 242 24-28 130 16,235 4.67
100 9,606 2.76

Newton’s First Law says that a car going straight down the frontstretch at Bristol will keep going straight (and into the wall) unless a force acts on it and causes it to turn.

Consider a soccer ball rolling past you. You want to change its direction, so you kick it at a right angle to the direction it’s headed. The faster it’s moving, the harder you have to kick it to change its direction. The direction it goes is a combination (a physicist would say “a vector sum”) of the direction it had been heading and the direction of the force (the kick) you applied to it.

Putting Turning Force in Perspective…

Just to put these numbers in perspective, let’s look at one of the largest land animals, the elephant. My father always made a big deal of knowing the difference between an African and an Asian elephant. The African elephant is larger (up to 13 feet tall) than the Asian (“only” 12 feet). You tell them apart because the African elephant has much larger ears, has two ‘fingers’ on its trunk, and has much more wrinkly skin. The Asian elephant has smaller ears, only one ‘finger’ on its trunk, and smoother skin on the head and face.


What does this have to do with anything? An adult male African Elephant weighs, on average, 15,400 pounds.

Turning a NASCAR race car at Bristol at 130 mph requires a force slightly greater than the weight of an African Elephant.

I’ve graphed the force needed to turn as a function of speed below. (Note that the turn radii at Bristol are different for turns 1/2 and 3/4. Turns 1/2 have a turn radius of 242 ft, while 3/4 have a turn radius of 256 ft.)



Compare this to Daytona, which has higher speeds, but also larger turns.


So it’s actually easier to turn at Daytona, even though the speeds are a higher, you’ve got four times more turn radius.


We can also look at this in terms of the g’s the drivers pull while traveling around Bristol.


Just for reference, most amusement park rides top out at about 3G; however, some roller coasters go up to 4G (SheiKra Rollercoaster at Tampa) or 4.5G (e.g. the Titan Rollercoaster in Texas).

Although the “G” is the acceleration due to the Earth’s gravity (which always points to the center of the Earth), we use G to measure acceleration in any direction: up or down, back or forth, or sideways.  Drag racers experience accelerations of about 5G backward at take off.  When you’re turning at constant speed, the acceleration is sideways (which engineers call ‘lateral’).

The green line is on there because around 5-6 G’s, drivers start to be impaired because the forces actually change the ability of the blood to circulate through the body. Drivers may experience greyout, which is a loss of color vision, tunnel vision (loss of peripheral vision), blackout (complete loss of vision, but still conscious) and finally G-LOC (which is loss of consciousness because of gravitational forces) .

Now, if you’re paying close attention, you will notice that the graph of ‘G’s and the graph of forces look very similar. In fact, they are the same trend because you get the g’s by dividing the turning force by the mass of the car and the acceleration due to gravity (32.2 ft/sec/sec).

The Effect of Banking: Inside Line or Outside Line

One of the most interesting things about Bristol is that it now has graduated banking – from 24 degrees to 28 degrees. As we’ve discussed before, the higher the banking, the more the track helps the car turn. But here’s the twist: If you go up high to take advantage of the higher banking, you actually have to travel a longer distance.  The racing surface width is 40 feet. Now, one of the problems with the way track measurements are specified is that you don’t actually know where they measured the track length.

BSPEED_Bristol_TrackConfigLet’s assume for the purposes of argument that the 0.533 width was measured at the apron – which means that the end of the track at the outside wall is 40 feet further out. The distance down the front and back stretches are the same, so all we’re worried about is the difference in the turns.

If you take the outside line rather than the inside line, you’re going about 125 feet more distance than your competitor who takes the inside line. So you have to find out, given your car’s setup, whether the additional banking helps you turn faster.

If you take the outer line then at 130 mph, you need 13,910 lbs of force, compared to the 16, 235 lbs you need at the inside. You pull 4.00 gs instead of 4.67 gs on the inside. At 130 mph, you’re covering 190 feet per second, so the time it takes you to traverse the extra 125 feet is a little more than half a second. Not much, right?

Except lap times run around 15 seconds.

At the April race, final practice times ranged from 15.043 seconds (Kurt Busch, in first place) to 15.818 seconds (Alex Kennedy in 43rd place).  Half a second takes you from first to 40th place. So you darned well better be faster if you’re traversing the outside.

Now, I don’t know where the 242.45 feet for the turn 1/2 radius was measured. If it was measured at the midpoint of the track, then the differential is smaller, but I figure I’d take the most extreme case to make the point.

Related Posts:

Racing Without Friction

Why Turning is Hard

Aug 072015

Analog vs. Digital

VinylRecordAlbumThe big difference between analog and digital is continuous vs. discrete. An analog signal is a continuous signal in which something like a pointer moves the same way as something else. For example, an analog multimeter has a dial that moves in proportion to the voltage it is measuring.

Those of you of a certain age may remember these odd looking flat black vinyl things called ‘records’. Records are analog devices. A groove is cut into the vinyl. A stylus rides along the groove and translates the wiggles in the groove into an electrical signal, which is then transmitted to a speaker, which turns it into a vibration (which, when pleasant, we call “music”.)

Digital files (your mp3s, for example; everything on your iPod) encode music in 0s and 1s. Instead of a continuous, physical groove, it’s a bunch of data. There are a lot of advantages to digital. It doesn’t degrade with repeated playings, it’s much less fragile, and you can include a lot more information compared to a record player.

On the other hand, digital music can loose some of the ‘character’ of analog music and you cannot substitute a mp3 file for a frisbee.

Like music, the gauges on a car may also be analog or digital. Up until now, NASCAR hasn’t allowed digital gauges. Here’s examples of all three:


On the left is an analog gauge. This is the usual dial gauge that many cars still have. Like the record and the needle, physical components move in response to the car’s speed. (How Stuff Works has a nice explanation of how speedometers work.)

In the middle is an analog gauge that’s been supplemented with LED lights. This was the big deal change a few years ago. The driver didn’t have to squint and try to read the divisions of the gauge. The mechanics would pre-set the gauge so that a few lights would display when the car reaches a particular rpm. The really fancy gauges even had different colored LEDs so that the driver not only had the lights turning on, but the colors to warn them.

A Brief Digression about LEDs

The LED-modified gauge didn’t work its way into racing until the last five to seven years. There’s a good reason why. LEDs are a pretty new innovation. Yes, now you can buy LED lights that change colors and change their colors using your phone.

The principle behind Light Emitting Diodes (LEDs) was discovered in the 1920s, but the first practical LEDs didn’t show up until the 1960s. The first LEDs (circa 1962) were red and so low brightness they were difficult to see. Remember the first calculators?


They had to add plastic, prismatic lenses to make them easier to read because they were hard to read by themselves. They just weren’t bright enough. It wasn’t until the 1970s that high-brightness, affordable LEDs were being made and the spectrum of colors ranged from red to… orange-yellow.

As you move through the rainbow, the wavelength of the light changes. Red is somewhere around 700 nanometers and violet around 400 nanometers. We figured out how to make longer-wavelength LEDs first from a semiconductor material called Gallium Arsenide Phosphide. High-brightness blue LEDs were not invented until 1994 and utilized a different semiconductor called Indium Gallium Nitride. This led to the development of white-light LEDs (you use phosphors to convert blue to red. yellow and green). White light is the combination of all colors and that’s why you can now go and buy a LED lightbulb. The reason we didn’t have LED gauges until recently is that the LEDs needed to be bright and robust enough to survive being a racecar. But those gauges are about to become history. NASCAR will allow digital gauges.

Back to the Digital Tachometer

A digital tachometer gives you numbers directly.  No more trying to read the tiny little divisions on an analog gauge to see how close you can get to your pit road cut off without going over. Whereas an analog tach may tell you you’re somewhere between 4000 rpm and 4100 rpm, the digital tach will tell you you’re at 4036 rpm. Most of the time, that type of precision isn’t good for anything — but when you’re on pit road and trying to stick below the pit road speed limit, you want to know EXACTLY how fast the engine is going.

Actually, you want to know how fast the car is going. Any gauge can be digital – oil pressure, speed, fuel pressure… pretty much any gauge can be made digital.

A digital gauge MAY include a graphical display of some type – sometimes, even ones that look like the familiar analog dials.

The Glass Cockpit

Brian France mentioned the idea of the “glass cockpit” back in July 2012. There’s a continuing fight within NASCAR about how much information drivers and crews should have – and how much of that information ought to be accessible to fans. It seems sort of silly that people are losing races because they got a pit road penalty for speeding. It’s frustrating for everyone involved.

Moving to fuel injection necessitated adding a number of sensors to the cars and integrating them into a single . Digital dashboards were tested back in April at Kentucky, but we’ve heard very little about them since them.

The term “glass cockpit” comes to us from aviation. By the 1970s, the average plane had over 100 gauges and dials. If you need a piece of information – the status of a wing flap, or your fuel level – you don’t want to have to search for it. It needs to be right there, at hand. A racecar isn’t as complicated as an airplane, but the amount of information the driver has access to is getting larger and larger.

Here’s an example of an early-2000’s era dashboard.


Recently, we’ve added a trackbar adjustment knob, too. It’s a lot to look at when you’re going 180 mph.

Here’s a helmet-cam picture from Kevin Harvick’s car. I included it because you’ll notice that the driver is looking through the steering wheel. If you go to the original video (, you can see that the gauges on the sides disappear from view when turning.


Not only can you not see all the information that’s there…  there’s a lot of information that’s not there. There’s no speedometer (I’ve explained that a tachometer is actually more accurate than a speedometer, but when you go to digital, that’s out the window.) There’s no lap time displayed, or cockpit temperature or fuel gauge or tire pressure or…

As NASCAR moves more and more toward technology, the drivers (and crews) will have more and more information available. This is good… up to a point.

How many times have you fumbled around all the menus on a piece of software looking for that command you know is there, but you never remember where it is?

When I’m coming down Pit Road for a pit stop, I don’t care about my lap time or my oil pressure or my fuel pressure. I care about one thing: Don’t speed. And this is one of the big reasons for the digital dash.

Information can be grouped into pages, displaying only the information that is relevant to the driver at that time.

Jamie McMurray tweeted a couple pictures of the digital dashboard during a tire test in Kentucky.

NASCAR_DigitalDash_McMurray2 NASCAR_DigitalDash_McMurray

Important note – it’s the same display in both pictures, just different pages.

A couple interesting things to note:

You can display information in different formats. Your driver is used to gauges? Sure. Note that in the upper picture, there is a red line, a green line and a yellow line right on the tach. A visual indicator for the driver when he or she is getting close to pit road speed or the engine speed at which the engine designers start to get nervous.

The lower display shows lap times! Right now, the driver depends on the spotter or crew chief for that information. And, of course, if you have a driver who doesn’t want to know, you just don’t put that piece of information on the screen.

It looks like the McLaren PCU-500N Digital Dash Display will be the only one allowed for competition. McLaren already makes a display unit (the PCU-8D) for F1. You can get an idea of the types of information they display in the video below.


Optional Now… Mandatory for 2016

ChadKnausAccording to the NASCAR Sprint Cup Series rule book, digital dashboard display

“may be used at all Events after August 5, 2015. Digital dash display use will not be permitted before August 5, 2015. Effective January 1, 2016, a digital dash display must be used at all Events.”

Why August 5th?  Some of the conspiracy theorists over on Reddit suggest that the significance of the date is that it’s Chad Knaus’ birthday.

It’s also Alan Gustafson’s birthday, but Gustafson won’t be using the dashboard in Jeff Gordon’s car this weekend. Why?

As Gustafson said on SiriusXM Radio’s The Morning Drive, the digital dash is about 5 pounds heavier than the analog dash they’re using now. The advantages of the digital dash don’t outweigh (literally) its weight penalty. Five pounds located up high in the car, is a pretty stout competitive disadvantage – until 2016, when everyone is required to run the new dashes.

Aug 052015

Well, it finally happened.

They made it so easy to make an infographic, even I — the least design-savvy person in the entire world — can do it.

It’s not perfect – the tool I used doesn’t seem to like fractions, so I couldn’t get it to give me any lines between 0 and 1 on the chart of how much fuel you need to complete a lap at different tracks – but hopefully the bars give you an idea.

Fuel Mileage Races Infographic

Jul 242015

Aerodynamics is complicated. Let’s just get that out of the way. But it’s not so complicated that we can’t understand what’s going on with just a little patience.

Why 3D?

Every wonder why they call it three dimensions? The reason it’s three is because I (or you) can denote any point in space with only three numbers. For example: a latitude, a longitude and an altitude. Since we’re dealing with much more limited spaces, a simple Cartesian Coordinate system, like this one, usually suffices.


The line that goes out to the point P is a three-dimensional vector. It’s got parts going in the x, y and z directions. By specifying that there is so much in the x-direction, so much in the y-direction and so much in the z-direction, I’ve told you everything you need to reconstruct that vector.

Forces in 3D

A force (a push or a pull) can act in any direction, but in order to understand the effect of that force, it’s easier if we break it down into its components – how much of the force acts in the x-direction, how much acts in the y-direction, etc.

When we do this on a race car, we give the different directions their own fancy names – just to make us seem extra clever. Basically, any force that acts in the opposite direction the car is going is called drag. Any force that pushes the car into the track is called downforce.

When the force acts up instead of down, it’s called lift. Yes, I know it should be called ‘upforce’, but the people who study aeroplanes named it.

Not shown in the picture below is side force, which would be in or out of the page.


Spoiler Alert!

Let’s think about the air acting on the spoiler. Because the spoiler is at an angle, the force on the spoiler is at the same angle (it’s perpendicular to the surface). So some of the force on the spoiler points down and some of the force points horizontally.

Which means some of the air hitting the spoiler creates downforce, and some of the air hitting the spoiler creates drag.


The more area there is for the air molecules to hit, the larger the force. A tall spoiler creates  more force than a short spoiler – but because of what I said up above, the angle of the spoiler is absolutely critical.

The more upright the spoiler, the more of the force is drag and the less of the force is downforce.  If the spoiler were horizontal, you’d get all downforce. If the spoiler were perfectly upright (vertical), all the force would be drag.

Why a Different Package for Indy vs. Kentucky?

In Kentucky, NASCAR went with a shorter spoiler to reduce the downforce. Passing has been a persistent problem at 1.5 mile tracks and the idea was that if the cars weren’t quite so dependent on aerodynamic forces, then the loss of those forces when you get close to another car wouldn’t have such a great impact.

And that strategy seems to have paid off well.

But Indianapolis and Michigan are very different kinds of tracks. At 2.5 miles and 2 miles respectively, they  are closer to superspeedways than they are to 1.5 mile tracks. At Indy and Michigan, the cars get going very fast down the straightaways, which lets the leading car get away from its pursuers. And it’s pretty tough to pass a car if you’re two lengths behind it going into the corner.

So the goal at these almost-superspeedway tracks is to slow down the maximum speeds along the straightaways so that a car can’t get away so easily. This is a little different than the goal at the intermediate tracks.

There’s a couple of ways to slow down a car: the two most obvious are

  • Decreasing horsepower
  • Increasing drag.

Decreasing horsepower introduces its own challenges, as we know from restrictor plate racing, so NASCAR is using the increased drag approach at Indy. And they’re doing that by setting the spoiler height at a pretty astounding 9 inches tall. At Kentucky, the spoiler had been reduced to 3.25 inches.

The best way to understand how much of a difference this is comes from a tweet from JGR Racing, which actually shows you the difference. Extra points for having gotten the product placement in there!


That’s a pretty big honking spoiler, eh?

But, you’re thinking (at least I hope you’re thinking) wait a moment… If they increase the spoiler height to increase the drag, aren’t they also increasing the downforce?

Yep. They are. It would be lovely to have a knob that you could turn and independently change the amount of front and rear downforce, and the amount of drag. But real life isn’t that simple.

Those Poor Engineers… NOT

The spoiler isn’t the only thing that’s changed. The changes in toto are…

  • 9″ spoiler
  • 1″ wickerbill (aka Gurney flap)
  • 2″ splitter
  • 43″ radiator pan width
  • speedway extension on the quarterpanels and rear bumper – the same ones run at the superspeedways.

So you’re thinking – my goodness, pity the engineers. All these changes.

Lemme tell you – the engineers are not upset. They love the opportunity to get ahead of the other teams by being smarter and figuring stuff out before someone else does. This is a chance for a team to get a win simply by understanding the set ups better than anyone else.

And something else to think about. In my column about Kentucky, I showed the changes in the spoiler and radiator pan sizes as a function of time. Well, I’ve updated those.

BSPEED_2015RulesChangesbyTrack_Spoiler BSPEED_2015RulesChangesbyTrack_RadiatorPan

The radiator pan is the exact same size at Indy as it was in 2014. The spoiler is only one inch taller than it was in 2014. And the teams have plenty of experience with the rear aerodynamic extensions from years of racing at Talladega and Daytona.

Yes, it does mean that they have to put those disparate elements together – which they haven’t done before – but the teams with the strongest technical staffs will be in the best position to take advantage of these just-in-time adjustments.

Personally, I’m psyched about track-specific packages. It gives the teams much more of a box to work in, which means they have that much more room to be creative. Looking forward to Indy!


Jul 132015

Someone asked in the comments how much kinetic energy Austin Dillon had when he hit the catchfence at Daytona. I don’t know exactly how fast he was going  (probably was somewhere around 180 to 200 mph), so I figured I’d just make a graph and include a couple reference points in terms of kinetic energy scales.

The left axis is labeled in MegaJoules (MJ), which are millions of Joules. To give you an idea

  • 0.009 MJ = energy contained in a AA alkaline battery
  • 0.038 MJ = energy contained in one gram of fat
  • 0.04-0.05 MJ = energy contained in one gram of gasoline
  • 8.4 MJ =  daily recommended energy intake for a typical active woman  (2000 calories)
  • 110 MJ = energy expended by a typical rider in the Tour de France
  • 122 MJ = energy contained in a gallon of gasoline
  • 1000 MJ = energy of a typical lightening bolt

So without further comment, here’s the kinetic energy of Austin Dillon, where I used his NASCAR official weight of 185 lb and minimum car weight of 3300 lbs. Black cowboy hat not included.


Jul 072015

As some of you know, I was in New York for the weekend celebrating my anniversary, so I’m just now catching up on the weekend’s accident at Daytona. Note: Some basic information about catchfences is modified (and updated) from a blog originally posted on 11/14/11.

And I bet there are some typos, still.

A Brief History of Barriers

Track barriers originally were erected to keep cars separated from spectators.  In addition to concrete walls to prevent the cars from driving off track, debris-spewing accidents necessitated fencing to contain airborne objects.

ChainlinkFenceCatchfences should have the same properties as walls, but they can’t block the view.  Chain link fence is a good compromise: It’s cheap, plentiful, easy to put up and surprisingly strong given its high visibility.

Chain-link fabric is an elastic metal mesh. It can give in two ways: gentle forces cause the mesh to deform.  The diamonds stretch out of shape, but when the force is removed, the fabric springs back to its original shape. The fence can also deform by stretching the wires that make up the mesh. A large-enough force will break the wire entirely.

The mesh must must supported, usually by poles and cables. How much the mesh can stretch depends on how it is supported.  If the frame is too big – meaning that there’s a very large area of mesh between supports — the mesh can stretch too much. How the poles are attached to the mesh is critical, because the attachments allow the load to be shared between the fabric and the poles.  The larger the forces, the more robust the links between the poles and the mesh must be.
Catchfence_Daytona2Race track fencing is stouter in just about every way.  The mesh is made of larger-diameter wire with higher tensile strength.  The links between the poles and the fabric are stronger:  In the picture at right (Daytona), steel cables run horizontally through the mesh and are fixed to the vertical poles using some massive turnbuckle-like fixtures.

Different tracks have different installations.  Some have metal tubing running horizontally as reinforcement. Catchfence improvements have primarily been via stronger mesh, stronger or a greater number of poles, or better links between the poles and the mesh.  But it’s basically the same fundamental design.

The chain-link fence is a motorsports institution, with different sanctioning bodies requiring different standards for debris fencing.  In the FIA test, a 760-kg  (1675 lb) test mass is shot into a fence at a speed of 65 km/h (40 mph) at heights of 1.6 m and 2.5 m (5.25 and 8.2 feet respectively).  While 40 mph seems very slow, they’re taking just about the entire mass of an Indy car and concentrating it in a relatively small sphere.  A real car would impact over a much larger area and spread out the force.


The photo at left shows a Geobrugg fence being tested:  The mesh deforms (a lot!) – but it does not break. Load is transferred to the poles, with the poles nearest the impact bending, but not breaking.  The emphasis, however, is pretty strictly on containment.

Geobrugg, one of the primary catchfence providers for motorsports (and many other things) made the video below that shows a car going into a standard vs. going into one of their fences.

The advances in catchfencing that have been made are huge; however, you are always going to have issues. As long as the fence is permeable, small pieces (and fluids) are going to get through the fence. Some of the people injured in the Carl Edwards crash in Talladega were burned by oil. Unless you use a solid fence, this is a hazard you will never eliminate.

Is Speed a Factor?

We’ve been hearing calls for slowing things down at Daytona. Is speed the issue? It is certainly true that speeds have been increasing.


Here’s the pole speeds at Daytona over its entire history. You have to be a little careful. The idea of group qualifying is very recent, and we know single car speeds are lower than those of cars in a pack, so it’s not quite fair to compare these one one one. But the pack qualifying pole speeds are a good 4mph below the peak single-car pole speed, which means we’re still probably 8-10 mph slower than the highest speeds that have been raced at Daytona.

So maybe it would be helpful to compare speeds at different tracks this year, since single-car speeds aren’t really all that different than race speeds at non-plate tracks.


I put triangles above the plate tracks. You’ll notice that speeds there aren’t that much higher than many of the other tracks – and Michigan was faster than either Talladega or Daytona.

Which led me to wonder about whether this year was just an anomaly. So here’s this year and last year.


Michigan is consistently faster than either Daytona or Talladega. I also wanted to look at the speeds for the Sprint Cup versus the XFINITY series, because the last big accident we had at Daytona was Kyle Larson running in the then-Nationwide series.


You can see that the lower-level series runs at significantly lower speeds (10-15 mph) – and still they’re getting in the air.

So I have a hard time believing that simple reducing speed is going to have a lot of effect on these types of crashes.

Pack Racing

So what’s the big different between Michigan – the fastest track – and Daytona/Talladega? It’s the restrictor plates. Restrictor plates produce a very different type of racing. If you watch the throttle/brake indicators during non-restrictor plate races, you’ll see the drivers easing off the throttle going into the turns, or even braking. The pole speed is an average speed, which means they’re generally traveling faster down the straightaways and slower in the turns.

Not at a plate track. The throttle is full open at all times. The cars are maxed out in terms of their engines.

Remember that, at 204 mph, a car goes a football field a second. Think about that. You’ve seen cars scatter to avoid accidents on other tracks. You can’t do that on a plate track because there is nowhere to go. You’re blocked in on all side.

An accident on a plate track is more likely to involve multiple cars. The last line here is the total number of cars involved in accidents

Michigan 2014 Daytona 2015 July Daytona 2015 Feb Las Vegas 2015 Atlanta 2015
6 1-car accidents
1 9-car accident
5 1-car accidents
1 7-car accident
1 9-car accident
1 11-car accident
2 1-car accidents
2 2-car accidents
2 7-car accidents
3 1-car accidents 2 1-car accidents
1 4-car accidents
1 6-car accidents
15 32* 20 3 12

* didn’t mention how many were involved in the end-of-race crash because it wasn’t technically a caution, so the number is much larger.

The numbers are small, so it’s hard to prove this, but my intuition, based on observations and the data we do have, is that more cars involved in an accident at close quarters mean

  • more likelihood of a car spinning (and cars are more likely to become airborne if they are not going straight)
  • more likelihood of a car launching off another car and getting airborne

When all this happens in conjunction with high speeds, you have all the elements for a catastrophic accident.

I am not suggesting we remove restrictor plates – that would be just plain stupid for both the drivers and the fans.

So Let’s Just Make Pack Racing Safer!

Everyone seems to assume that NASCAR will come up with a solution that will allow pack racing to continue the way we’re used to it happening. They’ve done an admirable job of dealing with past issues…


There are limits. I mean, if we could do anything, we’d have cured cancer and found a way to make sure everyone in the world has access to clean drinking water.


If there were an obvious solution to make pack racing safer, NASCAR would have already done it. It is possible that there isn’t a solution and that pack racing will always be inherently more dangerous than other types of racing.

Cars travel just as fast at other tracks and they don’t leave the ground nearly as often as they do at Talladega and Daytona.  Putting on a smaller restrictor plate to decrease speeds will not help. It’s not the speed. It’s the combination of the speed and the pack racing.

Perhaps the best that can be done is to protect spectators and let drivers take their chances. (If you’re wondering whether a Lexan ‘hockey-type wall’ would work, I addressed that elsewhere. (TL;DR: expensive and difficult, especially since you not only have to stop the car and parts from getting into the stands, you have to make sure that you don’t make it more dangerous for the drivers.)

Perhaps you have to make a radical change to the engine so that the drivers have to brake and accelerate around the track and you don’t get pack racing. This would make a lot of fans upset. There is nothing as breathtaking as standing in the infield watching the entire field take the turn.

There is also nothing as breathtaking as that gasp of fear, your heart skipping a beat and the feeling in the pit of your stomach as you whisper a prayer that the driver in the crunched up shell of a car just coming to a stop will climb out and wave and live to race another day.

Jul 032015

Daytona is an enormous, sweeping track. Two-and-a-half miles, 31-degree banking and corner radii of a thousand feet. The infield by itself is 180 acres. If you’ve ever been there (or Talladega), it really does take your breath away when you first enter. Now, bigger tracks (or rather, tracks with bigger turns) automatically mean higher speeds.

There’s a formula for this that tells you how much force you need to make a car turn under specific conditions.


The way to think about this is that it is harder to turn (i.e. you need more force)

  • when you have a heavy car
  • when you’re going fast
  • when you’re trying to make a tight turn

So when you compare a thousand foot turn radius like at a superspeedway with the 250-foot turn radius of Bristol, it’s four times easier to turn at Daytona if all other things are held equal.

The equation above is the equation for centripetal force, which is the force that makes a car turn. The centripetal force tends to confuse people because of its direction. The centripetal force points toward the center if the car is moving in a circle. The way I think of it is if you swing a tennis ball around on a string in a horizontal circle over your head, the thing that keeps it going in a circle is the string – producing a force toward the center.

Well, it’s the exact same thing for a car, except instead of a string, you have tires. The force needed to turn a NASCAR stock car at 130 mph at Bristol is about six tons. Yep, tons.


Because Daytona is so much larger, you need about four times less force to turn at the same speed.

But why stop at 130 mph?

When Daytona was being planned in the fifties, Bill France knew he wanted high banks. Why?


That’s right, banking equals speed, too. Here’s why. Look at the car on a flat track first. I’ve drawn it so the car is moving away from you and it’s turning left (of course).



The force the track exerts on the car is always perpendicular to the track surface. So none of the force of the track on the car is in the direction that helps the car turn. All of the turning force has to come from the interaction between the tires and the track. If you don’t have enough friction, then you’re going to slide out toward the wall.

Banking helps us turn. Let’s give our track a little banking and see why.



Two things change. First, the friction between the tires and the track have also tilted. That means you’re not getting the full force from the tires that you did before; however, the force of the track on the car has also shifted direction.

Now the track is helping the car turn. The higher the banking, the more help the car gets from the track.

If you’ve never been on a track, it’s almost hard to appreciate banking. Here’s me filming for our Science of Speed webvideo series at Texas Motor Speedway. I had this great pair of boots I had planned to wear for this shoot, but it turns out you really can’t wear heels on 24 degrees of banking.

And no, the car is not moving. I am adventurous, but I am not (usually) stupid.



Turning on Ice

So one of the questions I sometimes get asks how important friction is in turning corners. So let’s play Einstein here…

Einstein thought up all kinds of very strange and mathematically intense ideas about how the universe – space and time, specifically, work. He couldn’t actually do experiments to test all of his ideas. (Plus, he was a theorist and it’s usually best not to trust them with anything more potentially dangerous than a sharp pencil.)

So he did what are called gedanken experiments. Gedanken is the German verb for ‘to think’. These are thought experiments – but they sound much more impressive if you call them gedanken experiments.

We’re going to imagine that a highly localized ice storm hits Daytona. So localized, in fact, that it just hits turns 3 and 4 of the Daytona International Speedway. It covers them with ice. What happens to the car hurtling in there?

There’s an equation – and if you’re the kind of person who breaks into a cold sweat at the sight of a radical (that’s a square root), then just grab your chair tight for a moment. (If you want to see the details, I suggest the wonderful Hyperphysics site.)



All this says is that it is possible to bank a track highly enough that you can take the turn without ANY FRICTION AT ALL.

So if we plug in the numbers for Daytona… we find that, in the absence of friction, you could go 139 mph around the turn.This shouldn’t be all that surprising – after all, Daytona could be viewed as an overgrown luge or bobsled track, right? Those tracks have very high banks because there’s a minimal amount of steering going on.

Being the mathematically OCD person I am, I graphed the maximum speed as a function of banking degree.


Remember that we not only have friction, we have lots of it from the tires interacting with the track – that’s why the cars go much faster than in our frictionless case here.

Interestingly, if a car doesn’t go fast enough around a banked turn, it will actually slide down the track.

This presents a major problem when you’re repaving a very banked track because, as a rule, heavy machinery doesn’t move very quickly. The video below shows the 2010 Daytona repaving (pictures, but mostly video).

You’ll see that the paving trucks are actually being held in place by other equipment because otherwise, they would slide (or worse, tumble), right down the track. And that would make for some pretty sloppy surfaces to race on.

Jun 192015

Last Tuesday, NASCAR announced aerodynamic modifications to be implemented for the Kentucky Speedway Sprint Cup race on July 11th. While the changes are (right now) only for that race, there’s every expectation that if they help reduce the dreaded ‘aero push’ problem, they may be extended (or modified) for other 1.5 mile tracks.

The changes are fairly straightforward to make, which is why NASCAR can mandate them without much lead notice. All the parts are bolt-ons, as opposed to changes in the body panels, for example. Here they are:

  1. The rear spoiler will be shortened from 6 inches to 3.5 inches
  2. The front splitter will be shortened by 1-3/4 inches
  3. The radiator panel will be narrowed from 38 inches to 25 inches.

These changes continue in the vein of the changes made at the beginning of the 2015 season. At the start of the season, the spoiler was decreased from 7-1/4 to 6 inches and the radiator pan was narrowed down to 38 inches. So the changes are designed for the same goal: decrease the dependence of the car on aerodynamic forces so that passing isn’t quite as hard as it is now. This translates to decreasing the downforce on the car – depending less on aerodynamic grip than on mechanical grip.

The question I’ve heard the most this week is some variation on being concerned that taking downforce away from the car might lead to the cars being more likely to become airborne. I’ve discussed how cars can take to the air. Let’s look at how aerodynamic forces are generated so we can understand how big a problem this is — or isn’t.

We need to start with Bernoulli’s Principle. It’s a rather complicated principle, but we only need one part of it to apply it to a race car.


Here’s how I remember which way it goes. The roof flaps on the car are there because, when the car goes fast, the air moves quickly over the roof of the car and the pressure on the roof decreases. If the car spins, the roof flaps open. That slows down the air, and increases the pressure, keeping the car on the ground. (I’ve also done a pretty complete discussion of roof flaps in a previous blog.)

MWR_AerodynamicsAt right is a computational fluid dynamics diagram generated by Michael Waltrip Racing shown at right. Their color scheme is that the slowest moving air (the highest pressure) is red and the fastest moving (lowest pressure) air is in blue. (It’s a rainbow, except without indigo and violet.)

If you look at the front of the car, you’ll notice that the splitter area is a place where the air slams up against the car and slows way down. And, in fact, that’s why the splitter is there. The splitter generates front downforce. If we looked at the rear of the car, you’d see another area of higher pressure by the spoiler, which is responsible for rear downforce. This diagram also shows you the low-pressure area at the top of the car.

Net Force: Lift vs. Downforce

The classic example of how Bernoulli’s law is harnessed in vehicles is the airplane wing. The wing is shaped such that air moves faster over the top of the wing than under the wing. This means that the force pushing up is greater than the force pushing down, and that creates a net lift. (And if you want to see something really cool, take a look at this new NASA plane that changes wing shape in real time.)



If you want downforce instead of lift, you shape the wing differently.

 Splitting Airs

The splitter is so named because it literally splits the air coming at the car into two parts: air that goes over the top or around the car and air that goes under the car. A splitter is a much more tunable device than the old air dam, which provided a vertical surface to direct air around the car, but had no horizontal component.


The air running into the car is slowed down, which creates downforce and the faster moving air gets underneath and creates lift.

The splitter is designed so that you can vary how much of it juts out from the car. This is important because the force you get from any surface is the pressure times the (perpendicular) area of the surface. Having less splitter exposed means less area, which translates into less downforce. But it also means less lift, because the same air stream is creating both the up and the down forces.

At the same time, they’ve made the radiator pan (which is poorly named, because it has nothing whatsoever to do with the radiator) smaller. If the underside of the car is nice and smooth, air flows quickly under the car. The radiator pan is really just a flat panel that covers the pipes, ducting and other complicated shapes and presents the air with a smooth surface.

The larger the radiator pan, the more of a ‘sucking effect’ you get, where the lower pressure actually acts like a vacuum, pulling the car down to the track. NASCAR made the pan even narrower than before, which slows down the air.

I would be very surprised if there were any greater incidence of vehicles going airborne – especially given the lower horsepower we have now relative to 2014. Remember that aerodynamic forces go like the speed squared, so if you’re going slower, you’re not making as much lift or downforce.

Radiator Pan

RadiatorPanThe radiator pan is really just a flat piece of metal that (on a stock car) has nothing to do with the radiator except that it’s located in the general area in which the radiator is located. Its sole purpose is smoothing out the surface underneath the car.

The picture is from a NBC NASCAR America video in which Steve Letarte summarizes the 2015 rules changes. It’s the best overview of the changes and the one I use for reference all the time.

The underside of a race car is sort of a mess. Pipes, tubes, ductwork all snake their way through. Aerodynamically, that rough surface, with all its dips and peaks, slows the air down as it moves under the car.  Putting a smooth sheet of metal on the underside of the car decreases the drag and allows the air to flow more smoothly (which means faster) under the car.

And since faster means less pressure, a smooth undercar surface tends to ‘suck’ the car down to the track, giving you more downforce. There’s another effect, however. If a car does start to get airborne, a huge flat plate provides a really nice surface to generate lift off. Decreasing the size of the plate makes the underside of the car much rougher and would decrease lift in case a car does get airborne.

RadiatorPanChange_2015KentuckyThe plate was narrowed by 10% from 2014 to 2015 and now it’s being narrowed again from 38 inches to 25 inches. If the last change was 10%, then the reduction was by about 5 inches. This makes the radiator pan about 58% the width it was in 2014.


Moving to the  rear of the car, the spoiler is going to be a mere 3.5 inches tall. As in the front of the car, the larger the area, the larger the force. A smaller spoiler doesn’t let as many air molecules bang down on the car, so you get less rear downforce. But there’s more to it than that. The spoiler also produces a stream of ‘dirty air’ at the rear of the car. That turbulent flow is part of what makes it so hard for the trailing car to get close enough to the leading car to pass it. Lowering the spoiler decreases the wake behind the car, which should (in principle) help passing.


Even without the benefits of cleaning up the car’s wake, they pretty much have to adjust the rear of the car if they’re going to adjust the front. If they decrease front downforce and don’t do anything to the back, you’ve got a car that is going to be tight no matter what you do to it. The rear wheels will stick better that the front, so the car moves forward, just not necessarily in the direction you wanted it to go. It’s really all a matter of balance.

There’s another consequence of shortening the spoiler, and that’s decreasing the drag. While the spoiler supplies rear downforce, it also presents an impediment to the air molecules, creating a force opposite the direction the car is moving

Where Do We Go From Here?

It’s been a bit flip floppy around here, right? First NASCAR said they might use 2016 rules for the All-Star race. Then they decided not only not to try that experiment, but maybe there wouldn’t be any aerodynamics changes. Then we get an announcement that we’re changing the rules for one race in two weeks.

It seems like short notice, but the race teams had pretty good indication of what was coming long before we did. NASCAR did make the point that they didn’t want to give the teams six weeks to camp out at wind tunnels researching the changes. NASCAR has enough experience with the Gen-6 car that they’re pretty certain that the changes they’re making won’t be a disaster (plus, they’ve told the teams they need to be ready to revert back to the ‘old’ package at any time during the Kentucky weekend. If any problems crop up, they’ve got a good fallback.)

NASCAR made a big point that “this is a race, not an experiment”. They have to be cautious about what they say because people tend to jump on things and give disproportionate weight to them. Then if NASCAR changes something, they’re accused of not being honest or trying to mess with fans.

One of the hypotheses going around is that NASCAR would have different aerodynamic specifications for each track. This would reverse the trend toward trying to use the same car at every track, but it would give NASCAR a much better way of keeping the racing exciting by minimizing aeropush. And for those people who think it would be terribly confusing for the teams, trust me. These are really smart people. They’re good at keeping track of things.

You know what I’d like to see? I’d like them to run this same experiment at some of the other 1.5 mile tracks, and then come up with an intermediate track “box” – a range of values for splitter and spoiler so that the teams can have a little play in splitter and spoiler configurations. This would let them tune the car for different drivers much better than they can now – and it’s no secret that some drivers have not had an easy time adapting to the current configuration.

The one unknown in all this, however, is going to be tires. Goodyear already tailors tires to different tracks, so it’s not asking them to do a lot more, but it does mean that they have another round of development to do as rules shift.






Jun 052015 at the Dover race were unseasonably high. Kurt Busch’s Stewart-Haas 41 team was told by NASCAR officials to remove “heat shields” from their fuel cans. The cans (shown at right) have an 11-gallon capacity. Not shown in the pictures is a tube that connects the nozzle at the top with the vertical part coming straight up from the can. This attachment recovers overflow fuel – remember when we used to have a ‘catch can man’?

Apparently, Busch’s team was using some type of heat shield on the cans to keep them cool. All of the things I’ve read about NASCAR’s response seem to mention safety. This is an important consideration, especially given the incident we had at Richmond where three people were burned seriously enough by a fuel fire to have to go to the hospital.

What hasn’t been mentioned is whether this is actually a performance issue.


As you probably know from middle school, “dense” means “thick”. But we’re going to use it in its precise scientific meaning.



Density has units like grams per liter or pounds per cubic foot.

Simplifying Assumptions

OK – let’s make some simplifications for the purposes of discussion.

1.  Gasoline is made up of a mix of molecules, so there’s really no such things as “a gasoline molecule”. In reality, gasoline contains a bunch of hydrocarbons with four to twelve carbons atoms per molecule.  For you specialists, it’s a mix of alkanes, cycloalkanes and alkenes. For the sake of discussion, I’m going to talking about “a gasoline molecule”.

2. Molecules are absurdly small. and talking about their mass becomes unwieldy.  Octane (one of the hydrocarbons in gasoline) has a molecular weight of 114.22852, which means that if you put Avogadro’s number of octane molecules (which would be 6.023×1023 molecules) on a scale, the scale would read 114.22852 grams.

This means that a single octane molecule weighs 1.897 x 10-22 g. That is  0.00000000000000000000001897 g.  You get the point: they’re very small. So we’re going to talk about density in terms of number of molecules more than their mass. The two are related, of course (mass = number of molecules x mass of one molecule), but I think it’s easier to visualize with number.

3. Finally, there ought to be a couple billion billion billion molecules in the drawings, but I just don’t have the patience to draw them. So we’re using simpler numbers like “10” and “20”.

Density of Gasoline and Temperature

The density of typical gasoline is 6.073 lb/gal at 60°F. Whenever you list a density, you must list the temperature at which the density if measured, because density changes with temperature. If you blow up a balloon, then put it in a freezer, the volume of the balloon shrinks -that’s because molecules slow down when it gets cold (like most of us do).

Most things in an automobile that deal with gasses or liquids work on volume. A fuel injector, for example, is set to let a particular volume of gasoline into the combustion chamber. So let’s think about what the change in density with temperature means in terms of a constant volume.

Most liquids become less dense at the temperature gets warmer. So if you get a gallon of gasoline at a higher temperature, the molecules are spaced out more, which means you get fewer molecules when it’s warm than you do when it’s cold.


How the density of gasoline changes with temperature is pretty well known and shown below. Let’s check the axes here to see the magnitude we’re talking about.  I’ve plotted a 126 degree change in temperature, over which the density changes by about 8 percent. If you’re looking at a ten degree change, say from 60°F to 70°F, you’re talking about a little more than a half a percent change in density.


Combustion works on the basis of a precise chemical equation. Each fuel molecule needs a particular number of oxygen molecules to combust. If there are too few oxygen molecules, then some of the gasoline molecules do not combust. If there are too many oxygen molecules, then some of the oxygen molecules just hang around. Either way, you’re limited by whichever component of the combustion process is smaller.

At high altitudes, or high moisture in the air, you get less power from the engine because there are fewer oxygen molecules in the air coming into the engine.

This is the idea behind turbochargers. Turbochargers compress the air going into the engine, so in a fixed volume of air, you get more oxygen molecules. More oxygen molecules means you can inject a larger volume of gasoline and make more power with each combustion.

The same idea can be used on the fuel side. There are systems on the market you can buy that use compressed gasses to cool the fuel – essentially they’re an air conditional, but for the gasoline. That lets you pack as many fuel molecules as possible into each charge that goes into the cylinder. You can let in more air, and – voila – more power. Of course, you reach a point of diminishing returns. The fuel has to be heated to combust and if the fuel is too cold, it won’t heat fast enough and some of those molecules won’t combust and won’t produce any power.

Is It a Performance Advantage?

Did having heat shields on the fuel cans help Kurt Busch? If we’re just talking mechanical heat shields – metal that reflects heat and keeps it from being absorbed by the can – I don’t see how they could’ve gotten more than a five to (maybe) ten degree decrease in temperature. That’s less than one percent change in density, which is pretty small. But also remember that over a 400-mile race, a typical NASCAR race car will use 100 gallons of gasoline, so you’re getting a 1% advantage over the entire course of the race. And races are determined on very small margins, so it’s not impossible that it’s a performance advantage – but it’s not a huge one.

Is This a Safety Issue?

No. The auto-ignition temperature of gasoline (the temperature at which gasoline will spontaneously ignite) is around 500°F. Cooling the gasoline on pit road will have pretty much zero effect on safety aspects.

What about my car? Do I get cheated when I fill up when it’s hot?

There’s an urban legend that you should always fill up your car in the morning instead of in the evening because you get fewer gas molecules for the price when you’re dispensing warmer gasoline. Maybe on those rare days when you have a 40°F temperature change, but on most days… it’s not going to make a heck of a lot of difference. Consumer Reports actually did the experiment.

But the winter/summer change and the sheer amount of gasoline we use does have an effect. The Today Show had a report a couple years ago (2012) on this very phenomenon. If gas pumps are calibrated in cool weather, then you’re actually getting less gasoline for the dollar when you fill the tank in hot weather.  They cite a 2007 Congressional report that says Americans paid an estimated $1.5 billion extra for gas that summer. That sounds like a really big number, but remember there are 300 million people in the U.S. and we use a lot of gas. If each person in the country gets $1 (edit  – I should never do math in my head…)  less gasoline in the summer, there’s 300 million dollars right there.

A group called for a mandate for gas stations to use equipment that measures the temperature and takes that into account when calculating gas prices. After all, they do it in Canada and have been doing it for a couple decades now.  The problem is that most cost-effectiveness studies show that if the government mandates temperature compensating pumps, the cost for installing and maintaining them gets passed along to the consumer. In the short term, no one would save any money.

Plus, there are a lot more important things to be worrying about in the world, don’t you think?




May 152015

The All Star Race, let’s face it, is a series of gimmicks strung together in the cause of entertainment.

Not that there’s anything wrong with doing that. It’s what every sport does. People like home runs? Then let’s have an ‘event’ in which people just try to hit home runs. People want to feel like they play a role? Then let’s make a ballot and let people pick who they want to see.

It’s all O.K. because (as Drew Carey said “What’s My Line”) the points don’t count.

NASCAR had an interesting thought last year. What if we use the All-Star race to test out the proposed 2016 rules package? They’ve since backed off on the idea. It’s asking the teams to do a lot of work for a race with no points, and a public test has few benefits. If the rules don’t work, it’s embarrassing. Even if they do work, getting data from instrumented cars (as could happen at a real “test”) offers a much more controlled way in which to evaluate the new package. (Bob Pockrass has a nice summary of this.)

Not to worry, though, because NASCAR fans are full of ideas about how to spice up the All-Star Race. Let’s move the venue. Let’s have no rules at all and let the teams bring anything they want. Let’s race the haulers instead of the cars. Let’s have everyone bring back a favorite old-time paint scheme.

Let’s run the race backward.

That seems like a pretty simple modification


Handedness-ChiralityYour scientific word for today is chirality.

Chirality is a type of asymmetry. Put your hands out in front of you, palms down. Keeping your palms facing down, try to move them in such a way that they exactly match up with each other.

I’ll save you some time. It can’t be done.

Your hands are chiral. Don’t be going getting a big head about it, though. Everyone’s are. So are your feet. But you can toss that you’re chiral into conversation and (some) people will be impressed.

If you look at the way a spiral twists, we say that it is either left-handed or right-handed, as shown in the picture at right.  Your fingers on the appropriate hand curl in the same direction as the spiral.

Not only are your hands and feet chiral, so is you DNA. Imaging taking a long ladder and twisting it into a spiral – that’s what you DNA looks like. It’s commonly described as a twisted helix

Interestingly, it only twists one way. DNA (shown below) is right-handed.


So is NASCAR. Well, if you leave out the road courses. For all but two out of the 26 races in a year, we turn left. (And yes, that makes the trace track right-handed.)

NASCAR is Chiral

Why turn left? If you try to track down the answer, you’ll find a lot of interesting theories about this. The one I see most often is that turning left is safer. Since you’re more likely to spin out and hit an outside wall, you should put the driver so that he or she sits on the side of the car away from the outside wall.

Okay, except for the face that most forms of non-stock car racing have the driver sitting in the center of the car.

So let’s look back at racing’s DNA by considering non-automotive competitions. Most race track designers adopted the conventions used by the closest form of non-car racing: horse racing.

In the U.S., horse races turn left. The USA track and field organization tells us that in 1912, the international governing body of track and field made an arbitrary decision that runners would run counterclockwise and it’s been that way ever since.

But I like this theory better. The Thoroughbred Racing Association says American racetracks were designed to be counterclockwise in 1780 because American breeders were still angry at the British because 1776.

British horses turn right. So in true American tradition, we did the opposite.

Left, Right… Does It Really Matter?

Impact_PitRoadWallEndIn a word, yes.

Tracks are designed to be run in particular direction, which means everything is optimized for that direction. There are some minor issues, like sightlines, pitting from the “wrong” side of the car, etc., but there is one very good reason for not running a track in the opposite direction.

I’ve mentioned before that the most dangerous place a car can hit is the end of a wall. If a car hits broadside (leftmost picture at right), the entire side of the car is taking the force of the impact.

If the car hits the end of the pit road, you’re concentrating all that force over a much smaller area. You’re much more likely to rupture the car that way and allow the wall (or parts of the car) to hit the driver.

Mark Martin experienced such a crash involving the pit road wall in Michigan in 2012. He noted it was a freak accident, but that class of hits remains the most serious type of impact a driver can experience.

Ideally, you’d just get rid of breaks in the walls, right? Problem is that it is impossible to make a continuous wall around the inside of the track. Cars have to get in and out of the garage and (more importantly) emergency vehicles have to have ready and immediate access to the track. So there are gaps in the wall in various places.

Let’s think about how we might do this. Simplest idea first. Just put a break in the wall,as shown below. The emergency vehicles can sit just beyond the opening and, if they’re needed, they can be out on the track in a matter of seconds.


Here’s the problem. You’ve now got cars headed toward an unprotected wall end. The cars move from left to right in the picture. Given the momentum toward the right, it’s far more probable that the car would hit something in front of it than behind it.



So if you look carefully the next time you’re at the track, look for the fishscales.

No, not the rap album.

Most tracks have them, so if you know what you’re looking for, they’re pretty easy to find examples of. Thanks to Google Earth, I’m able to show you one from Charlotte Motor Speedway at right. I highlighted the feature of interest.

They’re called fish scales because they overlap and the overlap provides protection while still allowing for motion – the same way the scales on a fish protect the fish, but still allow it to move.

It’s a little easier to see if we change the opening I designed up above to something more like this:


We’ve put the facing end of the wall pretty much out of reach of the car by overlapping the walls as shown. Now if there’s a hit, it’s on a curved portion of the wall, not an end.

But Wait…

You’re thinking – but the other end of the opening hasn’t changed. It’s still a concrete wall sticking out there.

True, but the probability of a driver hitting it is very small.

Except if you’re running the track in the direction opposite for which it was designed.

I know, you’re thinking this isn’t a big deal. But it was to Gary Terry.

Terry worked for a company that offered driving experiences in ‘exotic’ cars – Lamborghinis and the like at the Walt Disney World track. Terry was riding in the right seat (as a passenger) on April 12th of this year when the car hit the end of a wall. The driver was not seriously injured.

Terry was killed.

A heartfelt post by Jon Miller entitled “Please Stop Killing My Friends” on Jalopnik points out that the car was driving the course backward.


The green arrow shows the direction the track designer intended when he laid it out. The orange arrow shows the direction they were going.

The campaign to pay for funeral and related expenses, and for a college trust fund for Terry’s daughter Taylor. If you have a few dollars for a good cause, please donate:

And tell everyone who suggests running a race backward that there’s a really good reason for not doing so.

Another example where something seemingly simple turns out to have much more behind it.

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