Firewalls and Aerodynamics

My friend at the Milwaukee Journal Sentinal, Dave Kallmann (whose online column should be a regular read for race fans) asked about the confiscated firewalls from the Number 11 car at Indy.  That reminded me of the  first NASCAR race I was supposed to attend as research for my book The Physics of NASCAR. That was California in 2007. I was to follow around the number 19 car, at that time driven by Elliott Sadler and crew chiefed by Josh Browne.

Then Josh and three other crew chiefs got themselves suspended at Daytona for using bolts in the spoilers that had tiny holes drilled all the way through the shanks. I know what these are (and where to find a picture) because we used to use them in the lab in our vacuum systems.  If you put a bolt into a hole, you trap air in the hole. We’re trying to leave on about 1 in every 1,000,000,000,000 molecules in the vacuum chamber, so it’s absolute critical that we can pull them all out.

The reason the team used… excuse me, I mean allegedly used… the bolts is because it gave the air trapped in the trunk of the car a way out and that should decrease drag and thus increase speed. So my first research race turned out to be Atlanta.

During Indy post-race inspection, some rear firewalls from the number 11 car were confiscated. A firewall is a piece of sheet metal that puts a barrier between the driver and anything you don’t want the driver exposed to, which may include fire, hot oil and other fluids, carbon monoxide, smoke, etc.  I’ve indicated the front firewalls on the picture because I couldn’t find a good picture of rear firewalls.

Apparently the firewalls, or their positioning, was suspicious to the NASCAR inspectors. It’s possible there was just an error in the way the parts were installed (the teams manufacture a lot of cars and sometimes there are mistakes). But there is also the possibility that moving the rear firewalls around does pretty much the same thing that the vented bolts did: they provide a path for air to get out of the car and thus reduce drag and increase speed.

Seems like a pretty minor thing to move a few pieces of sheet metal around just a little; however, the positions of the sheet metal are specified pretty precisely. Modifying the arrangement can compromise drive safety in terms of an opening allowing smoke or fire into the cockpit.

We’ll see this afternoon whether NACSAR comes down hard on the team because this is a safety-associated issue. It may just have been a mistake; however, NASCAR doesn’t consider intention in determining the severity of a penalty.

Incidentally, Dave does an online race chat on Wednesdays at 1 pm Central. It’s not limited to NASCAR, so if you have a chance, join in the chat.

And can you believe it? I’m finally getting back to Milwaukee and it ends up being a week when the Brewers are out of town the entire week.  I’m going to have to just break down and go see them when they come to town and play the Nats.  At least Karl Ratzsch’s is still there.  And the Zoo.