Air Titan: It Sucks and Blows

Water is critical to the existence of human life.  Why do you think we spend so much time looking for it on other planets?

It is, however, less than desirable on a racetrack.  Water gets between the tires and the track, which decreases friction.  Decreased friction means lower speeds and higher probability of crashing.

Before you read any more, head over and read why it takes so long to dry racetracks.

OK.  Welcome back.

The traditional way of removing water from a race track was to evaporate it using jet engines.  Evaporation is the process of turning a liquid into a vapor.  In the case of the jet dryer, this is done by heating the water until it evaporates.   The exhaust from a jet engine is somewhere in the 1000 F -1300 F temperature range.

The problem is that evaporation is a slow procedure, even when abetted by jet engine temperatures.  Only the molecules on the surface of the water can evaporate, so you have to evaporate the water layer by layer.  This is why it takes a couple of hours to dry an intermediate-size track.

The new system (Air Titan) relies on a little different approach.  The majority of the water will be blown off the track, leaving a thin residual layer that can then be evaporated by the jet dryers.

The leading edge of the system is a series of pickup trucks towing trailers and attached to another vehicle by giant hoses.  The trailers contain the equipment that pushes the water off the track.  There’s a really great picture of the water sheeting off in the New York Times article.

This is trickier to design than it sounds. Air has to be compressed to very high pressure, then blown onto the track in a controlled way.  If you just blow air on the track, the water will spatter in every direction and the net drying effect will be negligible. If you have jets of air that focus on discrete spots, the water in the area you miss is going to spread out and re-wet the track.  You have to have a continuous sheet of air, angled to push water exactly where you want it to go.  The compressors are huge – as you can see from the diagram above.  Three compressors are being towed on a semi truck on the apron, as the center of gravity of the semi is too high for it to be on the banking.

A series of pickup trucks will circle the track in a synchronized way:  the truck closest to the outside wall will blow the water there down to the next groove.  A pickup following behind in the that groove will push it down further and so on.  (One might imagine a blower powerful enough to blow air down the track from the outside groove to the apron.  But I bet you’d have a really hard time finding someone to volunteer to be the driver of the truck on the apron.)  There’s a nice animation of the process on YouTube.

NASCAR_AirTitanDiagramBlowing the water off the track is only the first part of the process.  A vacuum truck on the apron will suck up the water pushed down by the air jets.   The process finishes off with the traditional jet dryers – which now only have to evaporate the very thin layer of water that remains on the surface.

The system isn’t Juan Pablo-proof, but because of the hoses and the water sheeting down the track, racecars won’t be allowed on the track while the dryers are out there.  Reports are that it’s costing NASCAR mid-to-upper six figures to develop the system — which is probably a small price compared to losing valuable airtime or being shunted to a less-widely distributed cable station due to delays.

The idea is to be able to dry a big track like Talladega in less than an hour, but even Air Titan doesn’t solve all the problems.  The rain has to stop before the drying system can be used, so rain delays may be minimized… but they won’t be a thing of the past.

Not until NASCAR figures out how to control the weather.


Plate Racing Rules: Getting Ready for Talladega

Most of the issues we were talking about at the start of the year regarding the measures NASCAR has taken to eliminate or reduce the two-car draft are still in play, so I thought I’d put the most important in one place as you start getting ready for Talladega this weekend.

One of the major changes is the radiator: The water capacity was decreased, which means that it can’t cool as effectively as it could with a larger volume of water. That limits how long cars can draft together in close formation, where the trailing car’s radiator is blocked and doesn’t get as much air circulating.

A related issue is the small, but extremely important limiter on the radiator called a pop-off valve This is one of the easiest last-minute changes NASCAR can make to adapt to changing temperatures — and new innovations teams have made to get around the current rules.

Finally, it seems as though bump drafting has gotten harder to do correctly. It’s all a matter of preventing cars from getting torqued. Literally.

What’s a Pop-Off Valve — and Why You Need to Know for the Daytona 500

Note added 14:14 2/22/12:  OK, I did predict that this was likely to change.  You can look at the chart on the video and see that the temperature at 28 psi is about 271 F.

One thing you will hear a lot as soon as coverage of practice starts Wednesday will be speculation about possible changes to the pop-off valve on the radiator.  What is a pop-off valve and how will it affect the Daytona 500?  Here’s the answer:

One of the reasons for the focus on the pop-off valve is that it’s one of the most easily adjustable pieces of the strategy to prevent tandem drafting.  If the temperatures are warmer, NASCAR can raise the pop-off valve pressure if they think there might be a need for more cooling.  EFI makes changing restrictor plate sizes a bigger deal than it used to be – so if there are changes, this (and the size of the grill opening) are the most likely places for them to happen.