Are SAFER Barriers Everywhere the Solution?

TL;DR:  No.

As the extent of Kyle Busch’s injury Saturday evening at Daytona became evident, Twitter erupted in angry calls for SAFER barriers to be put up on every wall at every track. An interesting division of sides appeared. A small number of people cautioned that simply plastering every track with SAFER barriers was likely to not only not prevent driver injuries, but might actually introduce new problems. Other people accused this group of being insensitive and “stupid”.

Interestingly, the small number of cautionary voices were people like the folks who write Racecar Engineering magazine, people who have been involved with motorsports safety research and people with advanced engineering degrees.

So let’s be really clear here. While I appreciate the passion with which people responded to the accident, opinion has absolutely no place in science and engineering. We work with facts, realizing that oftentimes, we don’t have all the facts we need. In an ideal world, we would have data from collisions at every track in the world, from every angle, with every type of racecar. But we don’t.

It’s fine for fans (and especially for drivers and their teams) to raise their voices and demand more attention to safety, but the average fan (or the average driver) has zero business specifying what those safety measures ought to be. The average NASCAR executive or track administrator doesn’t, either.  Motorsports safety is a constantly evolving research field and luckily, NASCAR recognizes that and works with the top people in the field.

Daytona

Let’s start with the obvious. A bare concrete wall at a track where speeds reach 200 mph is indefensible. To their credit, NASCAR and the Daytona folks promised to rectify that right away. Tire barriers – which are not ideal, but are definitely better than nothing – were up for the next day’s race.

Racetracks originally put up concrete walls to contain the cars and protect the fans. They weren’t there for driver safety. People don’t question the status quo.  It wasn’t until a number of serious accidents in both IndyCar and NASCAR prompted an effort to develop a better wall. I detail the origin and development of the SAFER barriers in my book, The Physics of NASCAR, based on my interviews with the barrier developers. The effort was initiated by IndyCar, but gained momentum when NASCAR threw their support (and money) behind it.

Once the technology was developed and proven, NASCAR mandated SAFER barriers on the outside walls of all tracks. It was a long road to development because it was a brand new (and frankly, counterintuitive) idea and everyone wanted to make sure it would work under as many conditions as possible.

How SAFER Barriers Work

For an overview of NASCAR safety, check out this video I made with the National Science Foundation. Here’s the brief version.

BSPEED_SAFERBarrier_Schematic

The SAFER barrier works by extending the time of impact. It’s much more comfortable to fall on a mattress than a floor because the mattress gives. The mattress absorbs and dissipates energy, so that the energy isn’t dissipated through you.

BSPEED_SAFERBarrier_HitA NASCAR stock car going 180 mph has approximately the same kinetic energy as stored in 2 pounds of T.N.T. When the car comes to a stop, all that energy has to go somewhere. Energy can be dissipated by skidding (friction between wheels and asphalt), light and sound (it takes energy to make that screeching noise and to produce sparks), spinning (energy is used to rotate the car) and deformation (energy is used to crunch or break things).  The key is that you want to dissipate energy any way except through your driver.

A mattress won’t make much difference to a speeding stock car. You need something much stiffer, and that’s the purpose of the SAFER barriers. They’re like mattresses for race cars. They use the energy of the car to deform the barriers and spread out the impact over a longer time. This directs energy away from the driver.

Why SAFER Barriers Aren’t the Only Answer

SAFER barriers save lives and this analysis is meant in no way to diminish their importance. But the inventors of the SAFER barriers would be the first folks to remind us that it takes multiple safety devices, working in unison, to protect the drivers (and the crowds). HANS or hybrid devices, helmets, restraints and the car itself are all part of the equation. You can’t address any one of those elements without considering the others. So here, briefly, are some things to think about.

Kinetic Energy Ranges

SAFER barriers work best in a specific kinetic energy range. I was surprised when interviewing drivers for my book to find that more than one mentioned that hitting a SAFER barrier at low speed actually hurt worse than hitting a concrete wall. But it’s true. The wall works by giving. If you don’t hit it hard enough, it doesn’t give and then it is just like hitting a concrete wall. This is relevant for a couple reasons.
1.  Most tracks host more than one kind of racing series. The kinetic energy scales of those series can vary widely. Any solution has to make the track safer for everyone who races there, not just stock cars.
2. Different tracks have different speeds, so even just within a single racing series, this means different kinetic energies. Compare Martinsville and Daytona, where the maximum speeds are a factor of 1.5-2 different. That means the kinetic energy scales differ by a factor of 2.25-4. That’s a big range. The response of the SAFER barriers can be tuned by using different strength foams and different types of steel tubing – but again, it has to work for all series racing there, not just NASCAR.

Get Off Your Grass

Get rid of the grass. Grass has no business being anywhere in a racetrack that cars could possible end up in.

a. Remember how I mentioned that you can dissipate energy by friction between the tires and the ground? The higher the coefficient of friction between the two materials, the more energy you dissipate. You know what the coefficient of friction is between grass and rubber? Very small. It’s even smaller when the grass is wet. This is why road courses have gravel traps. Huge friction that slows down the cars and hopefully stops them before they hit. (Gravel traps have their problems, notably that it’s near impossible to get out of one once you get in one, and that flying gravel is dangerous and difficult to clean up.)

b. Second, there is a drop off between the asphalt and the grass – a lip on which the car can catch, creating a torque. Check out Elliott Sadler’s crash at Talladega.

When he comes from the grass back onto the track, the roof of the car catches on that lip and starts the car rolling again. If I were a driver or an owner, I would be after every track to get rid of any grass near the track.

The Car Itself

NASCAR has done an amazing job engineering a much safer car than we had fifteen years ago. But the job isn’t done. There hasn’t been a career-ending injury (including death) during a race in any of NASCAR’s three major series since 2001. (Note added. It was pointed out to me that Jerry Nadeau‘s career ended after a very hard hit in 2003 during practice for a race at Richmond.) The injuries we have seen have all been below the knee. Dario Franchitti broke an ankle at Talladega. Brad Keselowski hit a wall testing at Road Atlanta and broke an ankle. Kyle Busch’s injuries from the Daytona crash were to his left foot and right lower leg.

The pedal box and the front of the car need some attention. Can the idea of collapsible steering columns be worked into the pedals? The front of the car is designed to crush (thus dissipating energy) in a crash, but maybe there is a way to refine how the crushing happens and reinforce the driver’s cockpit near the legs. I’m sure the folks at the NASCAR R&D Center are already thinking about this side of the problem.

Perhaps there are driver safety devices than could be developed as well, similar to the HANS device that prevents the head from slamming forward in  a wreck. Maybe there’s a carbon fiber leg brace or similar piece that could provide some extra protection for the driver’s legs in a crash. Of course, anything developed can’t interfere with the driver’s ability to control the car after a crash.

The Fallacy of Safe Racing

Motorsports is dangerous. People are killed participating in motorsports – especially at the lower levels, where the safety requirements are much lower than in the high-dollar, high-visibility series. But even in NASCAR, even in F1, even in Indy, there will be serious injuries and – I’m sorry to say – we haven’t lost our last driver to an on-track incident. All you need is that one in a thousand, one in ten-thousand confluence of events.

What Should Fans and Drivers Be Demanding?

Don’t tell NASCAR and the tracks that they should cover every conceivable wall with SAFER barriers and then sit back and congratulate yourself for a job well done.

Consider for a moment the ratio of people whose job it is to make cars fast to people whose job it is to make racing safer.

NASCAR has become so much more proactive about safety in the last years. If I were a driver, I would be lobbying NASCAR to hire more people at their R&D Center focused on safety, and to support more motorsports safety research at universities and industry.

The FIA has an Institute for Motorsports Safety.  It’s a non-profit foundation that centralizes safety initiatives and testing and works to get safety innovations on the track quickly.

Maybe it’s time for NASCAR to team up with IndyCar and the Tudor United Sports Car series and form something similar in the U.S. This isn’t an issue that should come up only after a serious wreck. It’s an issue that needs long-term, on-going commitment and attention. As a fan, I’d pay an extra buck or two on top of a race ticket if that ‘tax’ were earmarked for safety research.

For More:

 

Does Daytona Qualifying Really Matter?

Okay, it obviously does if you’re one of the cars that fails to make the race. But beyond that- given the huge amount of attention that’s been given to the ’embarrassment’ that was this year’s qualifying – does where you start make any different as to where you finish?

To investigate, I plotted the starting positions against the finishing positions for each race at Daytona. I wanted to do both the July and the February race to see if there was any difference given the different formats of the qualifying (regular qualifying+ duels vs. regular qualifying).

If there were a trend, you would expect a pattern to emerge on the graph. For example, starting position tends to be very important at mile-and-a-half tracks. Although there’s some scatter in the data, there’s a pretty clear trend that the people who start toward the front tend to finish toward the front. Same for the folks who start in the back.

BSPEED_StartingPositionDaytona500

It’s always interesting to look at the points that don’t follow the trend. For example, the point in the upper right circled in red is a car that had engine problems and didn’t finish the race.

The point that is the furthest from the line (furthest defined as the perpendicular distance between the point and the line) is the one circled in crimson and labeled “Harvick”. Despite leading 23 laps, Harvick had axle/hub trouble and spent 30 laps in the garage. His 41st place finish didn’t reflect how good his car was – at least until it broke.

Similarly, the other crimson-circled data points represent cars that ran more than 3 laps down due to problems in the pits, mechanical difficulties, or accidents that didn’t result in the car leaving the race, but did enough damage to require time in the garage or pits fixing the car.

Here’s similar data for Phoenix – it shows the trend even more strongly. If you started well and your name wasn’t Kurt Busch (engine failure), you finished pretty well. If you started in the back, that’s pretty much where you stayed.

BSPEED_StartingPositionDaytona500_2014Phoenix

So if this post is about Daytona, why am I going on and on about Las Vegas and Phoenix?  Well…

I wanted to show you what you were looking for first. And the analogous plot for Daytona is a mess. You might not realize that it means there isn’t a trend if you hadn’t seen data where there was a trend first. So here’s last year’s Daytona 500.

BSPEED_StartingPositionDaytona500_2014Daytona500

 

Again, plotting starting spot on the horizontal axis and finishing position on the vertical axis. I got clever this time – the red shading represents finishing positions that were six laps or more down relative to the winner. The red circles represent DNFs, due either to engine problems or crashes. (Just for comparison – at Las Vegas in 2014, only the last nine positions were six or more laps down.

There’s no discernible trend in this plot. Now you see why I showed you the other one first, right?

But maybe it’s one of those anomalous years, right? Let’s look at the data for the last three Daytona 500s.

BSPEED_StartingPositionDaytona500_CumDaytona

<sarcasm> Oh, yeah. Much clearer.</sarcasm>.

The trend (or rather, the lack of a trend) holds for the last three Daytona 500s and, in fact, for the July races as well.

Drivers and media types tend to talk about Daytona being a ‘crap shoot’. That’s reflected by the fact that where you finish has very little to do with where you start when you’re talking Daytona.

Why? Well, one big factor is that the close proximity of the racing means that you are much more affected by everyone else on the track. You can be the perfect driver, but it you happen to be behind Donny Dangerous and he spins, you have little chance of avoiding being caught up in it yourself. Remember at 190mph, you’re talking traveling a football field in the blink of an eye.

 

 

 

 

Engine Rules Changes for 2015

There’s a lot of talk about all the rules changes for 2015. The limiting of the horsepower has been a hot topic of discussion, with people suggesting that NASCAR is basically mandating spec engines.  Here’s a couple of things to think about in terms of engines as we get closer to Daytona.

“750 hp Engine” Doesn’t Tell the Whole Story

When someone says they have a 900-horsepower engine, the only thing that tells you is that the maximum power it outputs is 900 hp.  Importantly, power output changes with revolutions per minute (rpm), as shown graphically below.

Engine_Powervsrpm_TwoCars

The power curves for these two cars have the same maximum horsepower, but the range over which they have that horsepower is different.  Let’s say the gearing is such that you’re running most of the race in the 8000-rpm range. Car 1 would have an advantage because (in that rpm range), it has higher horsepower. Car 2’s curve, however, is broader, which means it has a higher horsepower over a broader range.

Tapered Spacers

The big impetus for engine rule changes is NASCAR’s desire to lower speeds (which, it is theorized, will improve racing by lessening the effect of aerodynamics making it hard to pass when cars get close to each other).

There are lots of ways to decrease engine horsepower, but remember that teams have put untold amounts of money into designing and refining the current engines. Designing entirely new engines is a major undertaking, and a risk to mandate without pretty high confidence that lower horsepower will indeed help the quality of racing.

For 2015 NASCAR has gone with the simplest solution: a 1.170 tapered spacer that they expect will reduce power by about 125 hp.

Combustion is the chemical reaction whereby fuel mixes with oxygen and releases energy. It’s very similar to another chemical process called respiration, which is how your body converts food to energy.  In this case, you mix two fuel molecules (C8H18 is octane, one of the hydrocarbons in fuel) and 25 oxygen molecules.

EQ_CombustionBig

 

Remember your chemistry teaching talking about stoichiometry? Stoichiometry is the ratio of molecules, because they only combine in particular ways. If you’ve got four octane molecules, you need 50 oxygen molecules, etc. Combustion demands that exact ratio. The amount of fuel you put in a cylinder depends on how much air you can get in.

That’s how tapered spacers and restrictor plates work – they limit how much air gets into the cylinder, which limits how much fuel you can put into the cylinder, which in turn limits how much energy is produced.

taperedspacer_CUP

A couple people have asked if this is going to have the the same effect as a restrictor plate. No! Fluids (and air is a fluid) travels differently through an orifice (the technical word for a hole) and through a nozzle (which is what the tapered space is).  Don’t believe me?  Here’s proof:

The tapered spacer does change how the air goes into the cylinder and that is something the teams are studying using Computational Fluid Dynamics — and figuring out how to use to their advantage.

ICE_CFD

The Rules Don’t Say “Your Engine Must Be 770 hp”

NASCAR engine rules address the physical properties of the engine – things like cylinder height and bore, compression ratio, and which materials can be used.  This has always been the case. They control things like rpms and horsepower indirectly via things like gear rules.

So teams actually have a fair number of variables with which to experiment.  The big emphasis is energy efficiency. There are two major energy transformations in the engines: combustion, which converts the potential energy in the fuel to the linear motion of the pistons, and then the linear motion of the pistons is converted to rotational motion.

The conversion processes aren’t perfect. If the air-fuel mixture isn’t right, you don’t get all the energy out of the fuel. This is addressed by specific geometry issues (which controls how the air gets into the cylinder), and EFI mapping.

The other main culprit in energy losses is friction.  In a conventional road car, only about 14% of the energy you put into it actually gets to the wheels. The rest is lost (or used by the air conditioning, power windows, radio, etc.).  Most of the energy losses are in the engine. In a conventional car, 60-70% of the energy loss is in the engine.

Surprisingly, NASCAR (and most race car) engines are more efficient than passenger car engines, due in large part to the use of advanced coatings on engine parts. A typical valve has at least three different coatings – A hard coating on the tip to protect against valve lash wear, low-friction coatings on the stem, and hard coatings on the dome to protect against valve seat recession.

MetTech_ValveFailureThese coatings are often very thin – a hair’s width or two or three. Materials used include Titanium Nitride (that’s what those gold-colored drill bits are coated with) and diamond-like carbon (DLC). DLC has a much smaller coefficient of friction against steel than steel (0.7) or titanium nitride (0.3). DLC has a coefficient of friction on steel of 0.2.

There are companies in the Charlotte area that offer detailed failure analysis of engine parts, like the valve below. They use scanning electron microscopy to examine the parts. The culprit is often the coatings coming off.

Remember back in 2008, when Hendrick Motorsports had a baffling sweep of engine failures? The culprit was the coatings on the cam and/or lifters. They delaminated (i.e. came off) and the small flakes got into other parts of the engine. The clearances between moving parts in a race engine are much smaller and the tiny flakes of coating jammed up the engines, leading to failure.

Teams keep such detailed records of which parts go in which cars that Hendrik was able to track down the batch of parts that failed and ensure they weren’t being used in any other cars.

So if these coatings make engines more efficient, why aren’t they in all our cars?  The usual answer – cost. Coated parts are more expensive and people don’t want to pay extra money for a small improvement in performance/duration. Race teams, on the other hand will spend whatever they can to shave a few more seconds off their time.

So there it is. We’re still nowhere near spec engines, even with the new rules.  I suspect at some point, there will be an engine design initiative, but NASCAR has been fairly respectful for not throwing a zillion changes at the teams at one time.

And don’t forget, we won’t even see the tapered spacer until after Daytona because Daytona and Talladega are still using restrictor plates.