Stock Car Science

There’s a wonderful gadget called wordle that analyzes text and picks out the words that are used with greatest frequency. So I had it analyze the blog and this is what it came up with.

Maybe it’s because they counted tire and tires as two separate words, but I sure feel like we’ve been talking about nothing but tires lately. I guess wordle could be used as a kind of blogger Rorschach test. According to it, I clearly have an engine fixation.

We’re talking about tires anyway. It took them a week, but Goodyear outlined their plan for making sure that what happened at Indy won’t happen again. They expressed the plan in corpo-speak, that unique permutation of the English language spoken only by PR types, upper-level managers and university administrators. Personally, when I hear “stakeholder", I think vampire. I’ve included a bit of translation and exposition beneath each point. Goodyear says their plan includes:

• Completing the extensive post-race analysis in process that includes all internal aspects of tire design and manufacturing and discussions with key external stakeholders, including representatives from NASCAR, team owners, crew chiefs and drivers to gain insight to information that will provide clarity to the final analysis.

Translation: We didn’t create this problem and we can’t fix it by ourselves.

• Engaging research scientists and engineers, including available assets and modeling capabilities from the Sandia National Laboratories, to develop a range of potential short-term solutions.

Translation: We need to do something really quick and we’re calling in outside experts to make sure we’ve got something by next July.

Comment: Metals are usually pretty well behaved. Rubber is made of intertangled polymer chains with a lot of other stuff added in. The polymer chains stretch and squish and the other stuff in the mix affects how they stretch and squish. That’s what happens on an atomic level. Then you make the rubber part of a macroscopic item like a tire, into which you have to build belts, cords and other structures. This is not a simple problem.

The folks at Sandia National Laboratory have great expertise in computer modeling. ‘Modeling’ is producing something in the computer and then testing it in the computer. Modeling is to tire testing sort of like computational fluid dynamics is to taking a car to the wind tunnel. You can test a lot of ideas on the computer at fairly low cost and then take the most promising of those to try in the real world. The danger is that the output of computer models is only as good as what goes into the models. Sometimes you get surprised when you find that your model doesn’t agree with reality and you have to go back and tweak the model. Sandia scientists use computers to model things like surface water in Iraq, biobatteries that can be implated to power things like artifical retinas, and combustion. Sandia has expertise in non-linear responses, which is when a small change in an input can produce large changes in the output. Think of a really touchy volume knob that blares if you touch it just the wrong way. Tires exhibit bigtime nonlinearity, so if you’re going to pick minds, Sandia is a good group of minds to pick.

• Scheduling a fall track test at Indianapolis with multiple participants to test solutions to full fuel stop capabilities and test again in the spring of 2009 to fine-tune the specific race setup.

Translation: If we have problems again next year, no one is going to be able to complain that they didn’t get to have some input. We’re leaving the Spring test with everyone there saying that we’ve got a good tire, so if something does go wrong, we’re going to remind everyone that we brought what they were happy with.

"Full fuel stop capabilities" is a fancy way of saying that we need tires that will last as long as a tank of gas. Goodyear counted on the track rubbering up the same way it had in the past. They had how many years of coming to the track, having tire problems in the first practice, and then having the track rubber in. They need additional track time to see exactly what is happening. You can do all the computer modeling you want, but the ultimate test is on the track.

• Accelerating discussions with appropriate NASCAR representatives, team owners, drivers, crew chiefs and track management on any future tire. Among elements already being considered are larger overall diameters, wider section widths, and larger bead diameters.

Translation: We didn’t create this problem and we can’t solve it by ourselves. We’re tired of everyone blaming us. If we have another disaster, we’re not going down by ourselves. More about the possible changes below.

• Developing future tires as a long term solution, looking proactively at the vehicle, tire, setup and track combinations for a complete package to assure only the highest level of performance for NASCAR’s racing fans.

Translation: We know fans were unhappy. Don’t look for anything radical in the near term. Our first goal is to fix the problem for next year, but the long-term solution is probably not going to be making a minor change to the existing tire. NASCAR is going to have to give us the flexibility to do something very different in the long term because we’ve learned that adapting the old tire may not work everywhere. Teams are going to have to help us out by giving us set-ups so that if they’re going aggressive with the suspension, we’re testing aggressive.

I don’t mean to sound anti-Goodyear, (except for my general dislike of people who make up words when there are perfectly fine words that say the same thing.)

The big long-term changes are wholesale modifications to the tire size, construction, bead size, etc. What does a bigger tire do?

A wider tire will do a better job dissipating the heat induced in the tire by friction between the tire and the track. If the volume of the tire increases, there are more gas molecules inside the tire. The heat generated by friction is spread out over a larger number of molecules. The pressure won’t increase as much when the temperature increases (and you thought you’d never use the ideal gas law!) The larger number of rubber molecules will also help dissipate the heat better, which will also keep the tires cooler. But if there is a larger area of tire rubbing on the track won’t that create more heat? Remember back to high school physics: The size of the frictional force (which is what creates heat) is independent of the area of the two objects that are rubbing together.

If you have a wider time, there is more rubber, so more rubber should be available to rub off on the track (provided, of course, that the rubber sticks to the track.)

There are some stress issues as well. The wider the tire, the better force is distributed across the tire. If you have 1800 lbs of force on a tire, it makes a big difference if the force is being supported by 36 square inches or 42 square inches. Each square inch of the tire will support less force becuase there is more total area. If you don’t believe me, go put on a pair of stilletto heels and walk around for a half hour, then do the same thing in your flip flops.

A wider tire WILL provide more grip, but not because it creates more friction. (You can look in the book for the ‘why’ of that one.)

There are a lot of benefits to a wider tire; however, the teams are going to have to develop new suspension setups. Look for engineers scratching their heads during practice the first couple of races with the new tire when the setups that were working wonderfully last year are failing miserably with the wider tire.

The other tire issue this week was at the Montreal Nationwide race, where they raced (for the first time ever as ESPN reminded us again and again) in the rain. Rain tires have grooves instead of the entirely flat surface of the slicks they normally race. Why? Treads aren’t for grip: the recesses allow water to get out from under the tires, giving the tire a better shot at gripping the track. Slicks allow hydroplaning: Water gets between the tires and the track. The problem with water (as with any liquid) is that the molecules aren’t connected very well to each other, so when you push on water, it doesn’t push back. That makes it really hard to get any traction between the tires and the track.

One of the teams almost put the rain slicks on the wrong wheels. This is significant because the treads are directional: They are angled to channel the water away from the car. If you put them on backward, the water gets directed under the car, which is not so good.

The most important thing they learned from Saturday’s experiment is that you can race when the track is wet, but maybe not when it’s actually raining. The windshield wipers are not exactly state of the art, and I wonder if some teams didn’t believe NASCAR would make them go out in the rain since a couple cars opted not to use wipers, One of them was Carl Edwards (loved him trying to squeegee the outside of the window under caution). You know that money isn’t the reason they didn’t have windshield wipers. There were two major crashes under caution because it rained so hard the drivers couldn’t see. So maybe rain tires are a solution to very long track-drying times, but it remains a fact of motorsports that the driver has to be able to see where he’s going.