If you really want to learn about downforce in NASCAR racing - and we suspect that since you're reading this article,
They do -- a logical place to go would be NASCAR itself.
In fact, NASCAR has put together a pretty handy glossary of common racing terms, including one for downforce. It essentially states that air pressure moving across the various surfaces of a race car creates "downforce" or increased weight. And while downforce increases tire grip and cornering speeds, there's a significant tradeoff — more downforce also increases drag, which reduces speed right off the bat [source:NASCAR.com].
In the past, NASCAR teams could drive completely different vehicles. As a matter of fact; Each participating manufacturer had their own, somewhat unique and recognizable look and feel. In recent years, however, NASCAR has attempted to level the playing field by standardizing the body shape that racing teams are allowed to bring to competition. As a result, the body of all NASCAR Sprint Cup racers, regardless of manufacturer, is identical – with the exception of the paintwork, of course.
Tomorrow's NASCAR car is the current design used exclusively in NASCAR Sprint Cup races. The design increases driver safety as cars go faster and faster every year. But with increasing speeds, the downforce must also increase to be on the safe side. The extra downforce increases drag, which slows the car down.
Does this seem like an endless battle of physics? Well it is. On the next page we take a look at these forces as they relate to a NASCAR race car.
- NASCAR-Rennphysik 101
- Maximum downforce
Much like geometry and billiards are closely related, there is a lot of physics involved in NASCAR racing - or really any form of auto racing. If you want a simple way to remember some of the key factors in NASCAR, just remember the three Ds - downforce, drag and draft.
Downforce is created by air flowing over the top of the car, forcing it down toward the road surface. Downforce increases drag. Drag is the drag force experienced by the vehicle from air pushing against it and the extra weight the downforce creates. Riders can reduce the drag they experience on the racetrack by slipstreaming. Drafting is when Driver B slides his car's nose almost under the rear bumper of Driver A's car to improve airflow over both cars. Sometimes you'll hear this maneuver called "running nose-to-tail."
When it comes to keeping the tires on the track through corners, downforce is definitely the most important of the three D's. But on the long, straight sections of road that immediately follow the corners, downforce isn't quite as important. Here the driver would like a little less downforce and therefore a little less drag. It really is a delicate balance. A lack - or even a significant reduction - of downforce could cause the car to lift off the track surface, much like an airplane taking off. So how does a NASCAR's design prevent this from happening?
The front bumper of a NASCAR race car is very low and also wide. It's really more of an air dam than a bumper. It directs the moving air over the roof of the car and not under it. This creates a low pressure area under the car and a high pressure area above the car. This is called negative lift and is exactly the opposite of how an airplane works. Where air pushes up on an airplane wing, it pushes down on a racing car.
The idea is to have most of the air flow over the top of the car to maximize downforce. This is where the front fairing comes into play. The nose of the car is as low as possible and the front fenders are flared wide to force air up and over the car.
The problem, as you may have figured out by now, is that low nose with flared fenders gives plenty of frontal area to push through the air. As you can imagine, this creates a lot of drag. If you want a firsthand demonstration of what drag is, next time you're on the freeway, try sticking your hand out of the car window, palm forward. This is what drag feels like. Next, tilt your hand 90 degrees so your palm is facing the road. You will immediately feel the difference. With less surface area facing the wind, the air can slip around your hand, making it much easier to slice through the air. You can also vary the angle of your hand to create lift (raising your hand) or down (lowering your hand). So drag is easy to fine-tune by hand, but what about fine-tuning an entire race car? Especially one that runs at speeds of 322 km/h (200 mph) on different track surfaces and in different weather conditions.
Balancing downforce and drag within the confines of NASCAR-sanctioned bodywork is a trick that teams simply must master as best they can. One way teams make the most of these forces on the track is to bring the third D into the mix – drawing. Next, let's take a closer look at drafting.
Drivers always say they want more downforce in the corners. What that really means is they want maximum stickiness in the corners and minimum drag on the straights. That's difficult—especially when the customization teams allowed to make the NASCAR Sprint Cup body are so small.
However, there are some fine-tuning that teams can do, such as: B. adjusting the angle of the rear spoiler. The steeper the rear wing, the more downforce it can generate at the rear of the car. This keeps the rear tires firmly planted on the pavement. At the front end, a part called a "splitter" serves a similar role to keep the front wheels grounded. The splitter is the component you see on the leading edge of a NASCAR race car. It runs the full width of the car, is adjustable, and often looks like it's low enough to scratch thatSpurSurface.
There are times when teams choose to get as much downforce as possible. For example, on street circuits with lots of curves and very few long straight sections. Minor modifications to the rear wing and front splitter maximize downforce and increase the car's cornering grip.
But the majority of races in theNASCAR scheduleare on high-speed oval tracks. This brings us back to our question of how to balance downforce and drag. An elaboration can help. Dragging on the track allows the vehicle following the leading car to reduce its drag. The air flowing over the front car also flows over the windshield and roof of the second car. That's great for the second car and any car that happens to be behind it, but what's the lead car got in all of this? The lead car of a winding pair also has some of the maneuver. The second car reduces the pressure resistance of the car in front. You can think of the pressure drag as a low-pressure wave left behind by the car as it speeds down the track. However, this type of caster actually pulls the vehicle backwards. By eliminating the pressure drag on the lead car, the two character cars can gain an advantage of up to 5 mph over a car doing laps alone [source:Schirber].
Once the little tweaks are made for the right downforce, the driver has a good feel for the race car (and track) and maybe even practiced their drawing skills, there really is only one way to take full advantage of aerodynamics during the race : Do not fall. That's logical advice, isn't it? When every NASCAR Sprint Cup team has made the tiniest adjustments to the vehicle's aerodynamics to give themselves an advantage of just a few hundredths of a second per lap, something as small as a crumpled front corner can dashed their hopes of winning that day.
Too much benefit
In the late 1960s and early 1970s, before body standardization in the NASCAR series, the Plymouth Superbird maximized downforce and minimized drag with a long, pointed nose and an almost comically massive rear wing. The aerodynamic advantage of the Superbird design proved valuable as track speeds increased. However, NASCAR officials were quick to put severe restrictions on these cars, which soon led to their decline in the sport and also in production. The Superbird had such an odd appearance that Plymouth dealers couldn't find anyone to buy it, so they often sat in car lots - unintentionally. Today, original Plymouth Superbirds are considered extremely collectible - with correspondingly high price tags!
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- ESPN.com. "downforce." July 23, 2008. (December 8, 2008) http://sports.espn.go.com/rpm/nascar/icons/news/story?id=3430034
- Jim's garage. "Aerodynamics, downforce, ground effects." 18 August 2007. (8 December 2008) http://jimsgarage.wordpress.com/2007/08/18/aerodynamics-downforce-ground-effects/
- NASCAR.com. "NASCAR Glossary." (8 December 2008) http://www.nascar.com/kyn/101/glossary/index_all.html
- Schirmer, Michael. "The Daytona 500: Flying without leaving the ground." live science. February 15, 2007. (December 8, 2008) http://www.livescience.com/technology/070215_nascar_aero.html
- Yager, Bryan. "Aerodynamics in Auto Racing." NASA. 27 August 2001. (8 December 2008) http://www.nas.nasa.gov/About/Education/Racecar/aerodynamics.htm