Exotic Materials in NASCAR Engines?

I was at a panel discussion some years ago at a motorsports engineering meeting about materials allowed on the car by different racing series. They had the tech people for IMSA, F1, Indy and NASCAR up there answering questions from the audience.

NASCAR gets a lot of ribbing because compared to, say, F1, we are sort of in the dark ages. See, NASCAR (in attempts to keep cost reasonable) frowns on “exotic materials”. Tubes in the chassis are steel, not titanium or titanium alloys. Exotic is usually a code word for “expensive”.

Someone asked the panel what exactly was meant by “exotic materials”. Robin Pemberton replied

“If you have to ask, it’s exotic.”

Lots of people think that NASCAR requires that all engine blocks be made of cast iron.  That’s actually not written anywhere.  The engine blocks have to be from the manufacturer’s original castings. There is an explicit rule that the engine blocks can’t be aluminum.

Why would you want aluminum?  Aluminum is much lighter. Newton’s Law says that the force the engine provides is equal to the product of mass times acceleration (F=ma). Don’t let people tell you NASCAR is about speed. It’s really about acceleration.

Newton’s law says that if you want a big acceleration, you need a big force and/or a small mass. So anything you can do to lighten up the engine (which sits relatively high in the car) will help your acceleration and your handling.

Ford’s new F-150, for example, replaces steel with aluminum to save weight and thus improve gas mileage. Aluminum has it’s challenges, but since NASCAR doesn’t allow it to be used in the engine block, let’s look at what you might do.

Crystal Structure

Get yourself a pencil and a diamond.  I’ll wait.

The pencil lead is grey, opaque and soft. The diamond is clear, shiny and very hard. But they’re both nothing more than Carbon atoms, with the atoms arranged differently.

800px-Graphite-layers-side-3D-balls

This is graphite (pencil lead). Ignore the colors, they’re just there to show you that graphite is sheets upon sheets of carbon atoms arranged in a hexagonal pattern.  Every ball there represents a carbon atom.

Diamond is a little more complicated. Exact same atoms, but different arrangement (below).

Diamond_cubic_animation

 

Two big differences here to notice. First, each carbon atom in graphite is connected to three other carbon atoms, but in diamond, each carbon atom is connected to four other carbon atoms. This is the reason for the second thing to notice:  Graphite is made of planes of atoms with no connection between those planes. That means that it’s easy to shear (slide off) entire planes of atoms. That’s what happens when you write. The diamond planes are interconnected, which makes it much harder to remove one layer.

Yeah, But What’s That Got to Do with Engines?

NASCAR engine blocks are indeed made from cast iron, but not the cast iron you’re probably used to. A brief lesson on how you make cast iron. You start with iron, which is a very malleable (meaning easily deformed) material. Through millions of years of experimentation, people realized that you could change the properties of cast iron depending on what you added.

In face, if you put small amounts of Carbon in with the iron and heat treat it in a very specific way, the Carbon freezes in graphite flakes, like the picture on the left below. The flakes give the iron a lot of strength, but they also make it brittle. The sharp points on those graphite flakes are very high-stress points, which means it’s easier to start a crack there. If you’ve ever cracked an engine block or a frying pan, you know how that works. Once the crack starts, it keeps cracking. So gray iron, which is what this type is called, is strong, but brittle.

Then some enterprising soul figured out that if you add some magnesium, the Carbon doesn’t form flakes, it forms globs. (Yes, globs is the technical term.) Since there are no sharp points, there’s less stress and less cracking, which is why this type of cast iron is called ductile iron. Ductile being the opposite of brittle. This solves the problem of cracking, but ductile iron is nowhere near as strong as gray iron.

CastIronTypes

Sometime in the 1960’s, someone Baby Bear’ed cast iron. They found that if you added Mg anywhere from 0.007% to 0.015%, you get something spectacular, which is shown in the bottom-most picture. (Credit for the pictures: http://www.atlasfdry.com/graphite-iron.htm)

To set the scale, the bar shown is 50 micrometers. Micro just means millionth. Most human hairs are between 50 and 100 micrometers in diameter. The picture you’re looking at is three or four hair-widths wide.

If I had found this, I would have called it “micro-coral”. You get some of the flat flakes of gray iron, which provides the strength, but the edges of the flakes are round (like ductile iron). This cast iron is just right. It’s not as strong as gray iron, but it also doesn’t crack as easily as ductile iron.

This is called Compacted Graphitic Iron or, if you’re German, Gusseisen mit Vermiculargraphit.  I’ll abbreviate it CGI.

And CGI is the “exotic material” NASCAR teams use for engine blocks. You can have a comparable strength with less weight. CGI engine blocks are especially useful in V-shaped engines because that area between the two cylinder banks (the two edges of the ‘V’) has to take a lot of stress.

You may wonder why, if we knew about this material in the 1960’s, it’s taken so long to use it for engines. The reason is because of the very fine control over the amount of Magnesium added. It has to be controlled to within a few thousandths of a percent. A change of just one one-hundredth of a percent can drop the tensile strength by 25%. A person in a lab can exert this much control, but if you’re going to make this in a production facility, you need computers and computerized manufacturing.

This Week’s Semi-Gratuitous Colorful Picture for Moody

The pictures I’m showing you are Scanning Electron Micrographs. Instead of using light waves, we use electrons to make the image. Light can be thought of as a particle or a wave. So can things like electrons, protons, neutrons, etc.

Electrons have a much smaller wavelength than visible light, which means electrons can “see” things our eyes have no chance of seeing. Color doesn’t really mean anything when you’re talking electrons because color refers to a range of wavelengths that our eyes are capable of seeing.

But, of course, that doesn’t stop scientists from artificially coloring their images to make them clearer to explain or, sometimes, just because you can. So here, from The Telegraph, is an artificially colored scanning electron micrograph of a flea done by a gentleman named Steve Gschmeissner. He’s got everything from cells to bugs to plants.

SEM_Flea

And yes, there are a lot of scientists who buy images like this to frame and put on their walls. I have x-ray images of calla lilies and eucalyptus in my living room.

But no bugs.

 

 

2015 Rules and Lug Nuts

Welcome back from the holiday shut down. December in the U.S. is like August in Europe. Everyone you need something from is gone. I’m happy to be back to the regular grind.

Forty-three days till the Daytona 500. The shops are buzzing with activity as everyone adjusts to another new rules package. The engine folks are working overtime dealing with the changes there. The only thing that’s slowed down is planning for on-track independent testing, since that’s been eliminated this year. But more time in the wind tunnel, on the seven-post machine, at the computers.

Pit crews have a number of new issues to deal with this year and they stem from NASCAR’s decision to eliminate the tradition of having one official in each pit box during pit stops. Starting this year, they’ll rely on cameras to provide information about any infractions and calls will be made from a central location where all the camera feeds are monitored.

This change necessitates some compromises. Some rules will be easier to enforce via the cameras, while others will be more difficult. As the NASCAR Insiders point out, one of the less-enforced rules is that teams can’t be on the ground in their own pit stall until their enters the pit box immediately behind theirs.   The Insiders note that when NASCAR tested the system in 2014, they found that this rule was routinely violated, but called by officials only when the violation was blatant.

funny gifs

The gif above come from:  http://www.gifbin.com/988955 and it’s there to illustrate that one of the violations that will be more difficult to enforce with the video system is whether all the lugnuts are on tightly or not. Here’s the verbiage from the 2014 rule book.

Where tire(s)/wheel(s) are replaced, all lug nuts must be installed before the car leaves the assigned pit box area. When a NASCAR Official detects a violation, the car must return to its assigned pit box for inspection.

200610Lowes_TireCloseUpIf a lugnut ends up on the ground instead of on a wheel, that’s pretty obvious and officials would require the team to bring the car back in. (No one ever ‘inspected’ the tire – they just put a lug nut on the lug.)

NASCAR uses a five-stud configuration for their tires. Some sports cars and open-wheel cars using a single, central stud, but NASCAR likes to stick with things that look more like what we have on our cars.

As a side note, one of the disadvantages of the five-lug system is that when a lug nut gets away from the pneumatic air wrench (which spins it pretty quickly), it behaves very much like a bullet when it goes flying. Most people who have spent time on Pit Road have been hit by a flying lug nut. It hurts. Without proper head and eye protection, a flying lug nut could do some real damage.

Teams do everything they can to make getting tires on and off the car as fast and fail-proof as possible.

NASCAR_lugs

Notice that you see hardly any thread once the lugs are on. The rules require that the first thread must be visible when the lug nut is installed. The remainder of the lugs are smooth and the outmost portion rounded to enable the wheels to slide on quickly and the lugs to tighten fast. Teams are experimenting with different types of air guns to try to speed up their pit stops.

The lugs are mandated to be solid, one-piece heavy duty 5/8 inch diameter with 18 threads per inch. The lugnut itself is required to be one inch (OD) and a minimum of 0.650 inches thick.  So, if there’s 18 threads per inch and the width of the lug nut is 0.650 inches, then there are (18 x 0.65 = 11.7) just about 12 threads in play.

Yes, teams have been caught boring our the lug nuts so that there are fewer threads that have to catch, which means they go on faster.

The obvious question is: “How many lug nuts do you actually need to hold the wheel on?”  I asked a former tire changer. He gave me a big grin. His answer?

Two. But they have to be the right two.

The two next to each other won’t work very well. Two approximately across from each other would be better. Three would be even better. Two lug nuts aren’t ideal, but five is probably overkill.

Which brings us to the people questioning whether this is a really bad idea on NASCAR’s part because it encourages the teams to do something unsafe – possibly to skimp on making sure that every last lug nut is one-hundred-percent, absolutely positively tight as it can be. Teams will cheat a little now that they’re not being watched, which means we’re likely to have safety issues with wheels coming off.

It’s true that teams may not be as paranoid about making sure they don’t do something they could get called for. But the penalties have been called primarily for missing lugnuts, not those that aren’t completely tightened because that’s very difficult to see – camera or in person.

Plus, it’s in the team’s interest not to leave the lugs loose. If one is noticeably loose, you’re likely to develop a vibration in the wheel and that causes not only a potential problem with the wheel, it can totally freak out a driver into thinking he’s about to have a flat.

We’ve seen tire changers signals to the crew chief that they are afraid they missed a lug — even when the official didn’t see it or call it. A crew chief may call a driver back to check, just because a crash could knock you completely out of a race while checking will only set you back a lap or maybe two.

The rule I’m far more concerned about in terms of safety is that NASCAR will not allow one team to help the team in the next box from over the wall. The origin of the rule is to prevent one team (say a team in the Chase) from getting essentially an extra pit crew member, or allowing their pit crew to go faster because they’re got a safety net in the form of someone else corralling their stray tires.

But, the danger of a tire rolling out of a pit box and being punted by a car is significant. Tire plus wheel is seventy plus pounds. A flying tire can literally kill someone one. NASCAR is going to be more rigorous about ensuring that pit crew members  stay in control of the tires until they are more than half way back to the wall (where, in theory, they wouldn’t roll out into the path of an oncoming car), but I would really hate to see a case in which someone hesitated to stop a tire that ended up posing a threat to the people on Pit Road.

The NASCAR Insiders suggest that there are likely to be a plague of penalties in the first couple of races as the teams adjust to the new enforcement criteria. As usual, they’ll adapt quickly, but keep an eye on Pit Road for the first couple races of 2015.

In only 43 days!

And since I know Moody will be disappointed at the lack of colorful graphics, I’ll leave you with a New Year’s present. When you were toasting in the start of 2015, you probably weren’t paying a lot of attention to the bubbles in your bubbly. Well, a couple fluid dynamicists in France have made a career of studying bubbles and they provided some neat diagrams showing how fluid dynamics works in champagne.

ChampagneFluidDynamics

I, of course, will have to procure a couple bottles of champagne so I can check this out myself…