NASCAR has had to step in and carefully regulate the aerodynamic features of each vehicle in competition to keep a level playing field. A rear spoiler design that stands off the rear deck lid will increase downforce, reducing lift at high speeds while incurring a drag penalty. F But how do you know how much grip a racetrack has? After reviewing ride height data from early tests and determining where the drivers felt comfortable after the car was adjusted, it was easy to identify that it correlated with a downforce distribution of approximately 30 per cent front. Because of the enormous time demands of three manufacturers wind tunnel testing in the same period, three clones of the submission vehicle were produced for the OEMs to use in their private testing efforts. Lift -- colloquially called a skyward force -- is usually present to one degree or another in a moving object. Covering much of the rear deck with a new sloped piece of glass and significantly shortening the decklid was a quick, cost-effective solution that lowered the drag coefficient from 0.375 to 0.365 in wind tunnel testing. Flaps recessed into the car's roof, another safety feature, begin to rise if air pressure suddenly drops above the car, blocking air flow [Source: Leslie-Pelecky]. Aerodynamic drag is the force of air along the length of the traveling car, opposing the car's force. NASCAR has to do this in a slightly more advanced way: Theyre interested in the grip all the way around the track, so they map the coefficient of friction values and collect them on a computer with a GPS index. Comment with your thoughts below! The main results are compared to a wind tunnel experiment conducted with 1/18 replica of a Nascar. The front bumper is the first part of the vehicle that the air must flow around. Because speed is, obviously, the main factor in NASCAR races, aerodynamics is a crucial element in stock car design. The objective is to create a low-pressure area, or partial vacuum, underneath the nose [source: Circle 304]. The F1 cars are still faster than most other race cars because they weigh very little, their their center of mass is very low, and they make huge downforce with their wings and bodywork. [18], Air curtains divert air flow from slots in the body and guide it towards the outside edges of the wheel wells. Plus free access to the digital archive over 100 back issues! It keeps the pressure underneath the car down, preventing lift. Reported drag areas range from the 1999 Honda Insight at 5.1sqft (0.47m2) to the 2003 Hummer H2 at 26.5sqft (2.46m2). Stories have floated around Formula 1 paddocks of trusting CFD analysis on front and rear wings only for them to completely defy aerodynamic logic during a race weekend. PJ1 Trackbite is a sticky, water-resistant substance that increases grip. Many racing authorities have banned side skirts, but they remain a flashy feature of certain passenger cars [Source: BMW]. A passenger car driving on the highway spends an estimated 60 percent of its energy overcoming air drag, a far greater percentage than tire friction and the energy needs of the drive train itself [source: Beauchamp]. Thats as bad as What kind of underwear does a mermaid wear? A well-prepared student entering a world of possibility and excitement, with a proud group of invested parents standing behind it, wishing it every success. {\displaystyle F={\tfrac {1}{2}}\times {\text{air density}}\times \mathbf {\text{drag area}} \times {\text{speed}}^{2}} If you're curious about aerodynamics, do further research on the Internet or at your local library. On the contrary, some drag force is very much needed to keep all four wheels firmly stuck on the tarmac in a controllable manner, and of course you want to make sure some airflow is slapping up against the radiators and other heat exchangers that your vehicle may have to maximise cooling. [1] There are many different ways to reduce the drag of a vehicle. This design reduces drag; however, it may cause the brakes to heat up more quickly because the covers prevent airflow around the brake system. Aerodynamics remains a vibrant and young field of engineering, with many innovations still to come down the road. Spoilers, front air dams and wings produce this effect. Do you know of any cars that have particularly low drag coefficients? The Next Gen features the passively deployed bonnet (hood), and roof flaps NASCAR uses in all its vehicles, but the diffuser presented a new opportunity to add another safety device a diffuser flap. Automotive designers and NASCAR teams rely on aerodynamic principles to create improvements in the power and handling of vehicles at high speeds. This article will demystify NASCAR lingo, starting with the phenomenon of aero push. This is commonly seen in vehicles such as the first generation Honda Insight. If you restrict the competition to solid objects, still the half sphere wins with a drag coefficient of 1.17. Coastdown testing is a proven method for determining the drag coefficients for road cars whilst the vehicle is in its normal operating environment. Optimizing that is up to the teams. However, with the poor aerodynamics of their standard bodies they were drag limited to roughly 150 mph (or a bit more) with the right gearing. Another was at the rear of the car, where the production wheel tubs further closed off the rear of the boot (trunk) area, sealing in hot air from the transaxle cooler. The value of drag coefficient for a something of the general dimensions of a car lies around the 0.3-0.4 mark. The grille in most production vehicles is generally designed to maximize air flow through the radiator where it exits into the engine compartment. You can do the same coefficient of friction measurement if you have a spring scale. u0001 Some sports cars have a surprisingly high drag coefficient (such as the Ariel Atom at 0.40), but this is to compensate for the amount of lift the vehicle generates, while others use aerodynamics to their advantage to gain speed and as a result have much lower drag coefficients. Another factor in moving toward a symmetric body was the evolution of the NASCAR racing calendar. The trailing vehicle, if it tailgates at a certain proximity, can take advantage of the lead car's aerodynamic force. This effect is more pronounced in the incremental drag data in Fig. (Accessed 12/14/08) http://www.circletrack.com/techarticles/0304_aerodynamics_tech_definitions/index.html, Cislunar Aerospace. But, of course, Goodyear engineers cant just make the stickiest tire possible, because soft tires wear out faster. This is aero push, also called a "tight" condition, requiring the trailing driver to ease off the accelerator to regain traction [source: ESPN]. Terms & Conditions | A much more common option is to replace the windshield wipers with lower profile wipers, or to only remove the windshield wiper on the passenger side of the vehicle, and even to fabricate a deflector to deflect the air up and over the wipers.[16]. "BMW Side Skirts." PRO NOTE: There are three components to the coefficient of friction when dealing with soft, stretchy materials like rubber: adhesion ( molecular interaction between tire and road); hysteresis (due to deformation of the tires) and cohesion (due to wear and tear). "ESPN Will Show the Unseen of NASCAR." The deletion of parts on a vehicle is an easy way for designers and vehicle owners to reduce parasitic and frontal drag of the vehicle with little cost and effort. This can reduce drag as well but a boattail would reduce the vehicles drag more. You hear number for stock-car tire coefficients of friction around 1.0 to 1.5. The obvious element in the physics of NASCAR is the aerodynamic design required by these cars in order to achieve top speeds of near 200 mph with the minimum drag coefficient. "Aerodynamics and Race Cars. With these elements settled, the OEM aero teams and design studios went to work on what would become their 2022 challengers. Could NASCAR use more complex techniques to make this measurement? Since most coefficients of friction are less than 1 (even tires wouldnt be more than 1.5), you need a scale that goes to 1.5 times the weight of the object. Aerodynamic drag increases with the square of speed; therefore it becomes critically important at higher speeds. What is the drag coefficient of a Nascar? Overall, the Next Gen car has been a once-in-a-lifetime project for most of those involved, who may never see another project quite as revolutionary to an ecosystem as this. On a track like Daytona, with its long straightaways and banked, sharp corners, the designs tend toward keeping drag to a minimum. -3.80. This is done to direct airflow around and over the vehicle rather than allowing air to travel under it. Right-side tires must deal with more force, so they are harder and dont wear as quickly. This offset generates rear side force, resulting in a restorative, positive yawing moment to the car. But the advantage of the way theyre doing it is that they can make measurements quickly enough to determine whether they need to apply more PJ1 Trackbite before a race. A coefficient of friction above one would be like trying to push your file cabinet along a really hot asphalt road if the bottom of the file cabinet is made of chewing gum. [22][pageneeded], The underside of a vehicle often traps air in various places and adds turbulence around the vehicle. Minimizing variables is always a good thing. On the one hand, many drivers can remain competitive in a close race by piggybacking on the lead vehicle, taking advantage of the increased force and decreased engine strain. This pushed the initial outer tunnel ramp forward and outward. Stay safe. 2 After eight years of racing, though, it was time to update the look of NASCARs top series to more closely resemble their roadgoing counterparts, which too had evolved over that stretch. [17], When air flows around the wheel wells it gets disturbed by the rims of the vehicles and forms an area of turbulence around the wheel. Several safety innovations are installed on NASCAR vehicles for such emergencies, such as a recessed right-side window. "Going With the Flow." Flat spoilers, possibly angled slightly downward may reduce turbulence and thereby reduce the coefficient of drag. Drag is the major obstacle to acceleration and racing speed. 28 January 2009. speed Passenger cars have become more shapely over the years as manufacturers discovered how streamlining can increase fuel efficiency, allowing a car to travel at the same speed using less horsepower. In ESPN's NASCAR coverage, a special-effects gimmick called Draft Track shows viewers how aero push works in real time, representing air currents via animated green puffs on the screen [source: Hiestand]. Goodyear produces different tire compounds for different tracks, as well as different left- and right-side tires. But how do they know when they need it? Perhaps the best place to start is at the nose of the vehicle. Its a blunt instrument, but a historical element that completes the stock racecar look. The average modern automobile achieves a drag coefficient of between 0.25 and 0.3. (Accessed 12/17/08 via Google Books) http://books.google.com/books?id=OAK3yFlHoTAC, Tierney, John. It also allows the car to correct itself when the driver oversteps the bounds of traction at the rear. Where the drag coefficient and reference area have been collapsed into the drag area term. Introducing a symmetric body eliminated the majority of these issues and presented a car that is a near spitting image of its street counterpart. This equation is simply a rearrangement of the drag equation where we solve for the drag coefficient in terms of the other variables. As the car cuts a path through the air, some air molecules collide with the front bumper, producing resistance. A front air dam is often used which extends from the very front of the vehicle down to the lowest part of the vehicle. drag coefficient Theyre probably also reading the temperature of the track at each spot. The coefficient C D is called the drag coefficient, a dimensionless number that is a property of the object. Although both methods can be accurate, nothing in the engineering world beats physical testing, where the true real world effects of the air passing over the car can be recorded to influence any design tweaks needed to the bodywork. "Aerodynamics - Stock Car Aero Defined." As a result, this modification is more commonly seen in high efficiency vehicles rather than sports cars or racing vehicles. The wide slicks used for racing are designed to maximize the coefficient of friction between the tire and the racetrack. Even casual fans are constantly exposed to the terminology of automotive aerodynamics. So how does NASCAR test for coefficient of friction? For the men and women of NASCAR R&D, Dallara, and the industry involved in making the new car a reality, the start of the regular season in Daytona will be not so much the birth of a new era, but more like a college graduation. A properly angled nosepiece, placed low to the ground, directs the majority of the air upward over the top of the car. In 2003, Car and Driver magazine adopted this metric as a more intuitive way to compare the aerodynamic efficiency of various automobiles. Add in the fact that the ability of the rear of a car to generate downforce is hampered by the mass in front means, basically, that the front of any car has the first choice on making downforce. Im guessing an airplane tire satisfies the bill without a lot of extra fiddling about. The highly concentrated vortex core suggests a stable vortex flow. In all cases, the reference area is the cross section orthogonal to the flow direction. To provide a reference for drag coefficients given to certain cars, heres a quick run-down of some values that may surprise you: Car manufacturers have been including drag coefficients within their cars stats much more in the last decade, coinciding with the transition towards eco-friendly motoring. During a high-speed spin, air can move rapidly enough over the roof and hood to produce a powerful lift force. Racecar Engineering is the worlds leading motorsport technology magazine. Youve measured the coefficient of friction. While such application may be useful for racing, for most road vehicles this would produce minimal improvement in overall drag reduction. Drag is a force that acts parallel to and in the same direction as the airflow. Development of the underwing was done in parallel with common elements development on the body. The advent of a new vehicle allowed NASCAR and the OEM aero teams to further refine an already tight Gen 6 submission process. The other factor how the tires interact with the track depends on the specific of the tires and the track. Therefore: Did you notice that all the real-world numbers above are less than one? Teams use tire pressure and small differences in circumference to further fine-tune grip. (When making spherical-cow jokes, and only when making spherical-cow jokes, you may read it as moo.). This downforce is the key to maintaining traction through the tight and constant turns of a short-track race. The coefficient of friction between the metal cabinet and the shag rug is 75/100 = 0.75. But lift doesn't necessarily mean an upward force countering gravity. tells you how easy or hard it is to slide one material on another. The behavior of the Drag Coefficient was further investigated by analyzing how it varies with velocity. MEW really? Aerodynamic force results from differences in pressure on the sides of the moving object. Another alternative is to equip the vehicle with a single wiper placed in the centre of the windshield, allowing it to cover both sides of the windshield. "NASCAR's Screech and Slam? Extremes are created by such machines as the eco-friendly solar powered vehicles. Some of this was attributable to inadequate insulation and material changes in production, but a great deal was due to the ingestion of hot radiator air into the cockpit and inadequate evacuation of air from the cockpit. This concept is not new to vehicles in general but, for all previous NASCAR designs, the radiator simply emptied into the under-bonnet (hood) region like a production car. Side skirts -- long horizontal pieces running low along the side of a vehicle -- were developed in car racing as a way to reduce air pressure underneath and gain downforce. For larger vehicles such as trucks, mud flaps are still important for their control of spray, and in 2001 a new version of the mud flap was introduced that has been shown to create significantly less aerodynamic drag than standard mud flaps.[6][7][8]. This is called drafting. It first really dove into this experiment with the current S- and C-Class, getting these standard internal combustion sedans as low as a coefficient of drag number of 0.24. 2), suggesting an induced drag (vortex drag) contribution (Jones [1990]). 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