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Above: Canadian race car driver Jacques Villeneuve waits at the wheel of a McLaren F1 GTR racing car, in pit road at Circuit Mont-Tremblant during the 2010 Legends of Motorsport meeting. Source: Wikimedia Commons.
Across the world, high performance race cars speed their way to glory and prize money for their drivers. Every driver wants his/her car to make it to the finish line sooner than other drivers. That often means going further on a tank of fuel – what we know as fuel efficiency. Non-race car drivers also want to go as far as possible on the fuel in their cars, which is why many of the cars we see on the road today have fuel-saving technologies that were first developed for race cars.
Smooth and Sleek
Figure 1: How air moves around an airfoil, a sphere and a flat plate. Image source: Let’s Talk Science.
Race cars don’t have sleek bodies just to make them look cool - their shape has a lot to do with how they use fuel. As a car moves, it pushes through the air in front of it. The air, which is made up of molecules, pushes back against the car. This pushing force caused by the air is called drag or air resistance. Drag is what counteracts the forward force of thrust from a car’s engine and slows down its forward motion. There are two main types of drag that affect cars - Form Drag and Surface Friction Drag.
Form drag is drag that is caused by the shape of an object travelling through a fluid material, such as air. Some shapes move fairly smoothly through air while others do not. Shapes that are tapered front to back, like an airfoil (see top of Figure 1), move through air without creating a lot of turbulence (disturbed air) behind them. However, shapes like the sphere and the flat plate (see Figure 1) create a lot of turbulence behind them. This turbulence creates drag which slows down an object’s forward movement. In the case of a car, energy is used and fuel is consumed not only to move the car itself, but also to push through the air. With streamlined shapes less energy and fuel is used in the moving of air, so more will go into moving the car.
Race car designers were the first to realize that cars with a streamlined shape, similar to an airfoil, would be able to move faster and use less fuel than cars that did not have this shape (see Figure 2). They were also the first to use wind tunnels to test car designs. Today, both race cars and production cars have body shapes that reduce the effects of form drag (see Figure 3).
Figure 3: 2012 Ford Focus at the 2010 Canadian International Auto Show. Image source: Wikimedia Commons
Figure 2: Fernand Gabriel driving a Mors in Paris-Madrid 1903. Image source: Wikimedia Commons
The other type of drag is known as Surface Friction Drag. This type of drag occurs as a result of the roughness of the surface moving through air. To reduce surface friction drag, race cars are designed to be as smooth as possible. That is why racing cars look so smooth and glossy! Many production cars have adopted this smoothness in their designs as well (see Figure 3).
Light and Fast
It takes more energy (and fuel) to move a heavy car than it does to move a lighter car. We can show this using Newton’s second law (F = ma). For a given acceleration (a), you need a greater force (F) to move a greater mass (m). Knowing this, race car designers have looked for ways to produce cars with less mass, while still being strong and safe.
Car frames, body panels and many engine parts are typically made from steel, a metal which is strong and relatively inexpensive. Steel is also dense and heavy for the structural strength it provides, so race car designers were some of the first to explore replacing steel with other lighter materials, such as aluminum and titanium. Aluminum parts are much lighter than steel parts (1 kg of aluminium can replace up to 2 kg of steel). They also do not corrode easily, so parts made from aluminum could stand up to weather better than steel ones. Aluminum is currently being used for car parts such as car bodies, drive shafts, bumpers, wheels, etc. and its use in cars, both on the track and off, is growing.
Like aluminum, other materials such as titanium and carbon fibres have been tested on race cars. Connecting rods (rods which connect the piston to the crankshaft) made of a titanium alloy, first used in Formula One cars, can now be found in some of Honda’s sports cars. Titanium makes the rods lighter and stronger than steel connecting rods.
Figure 4: Carbon fibre reinforced plastic on an Alfa Romeo 4C Image source: Wikimedia Commons
Carbon fibres (see Figure 4) are long strings of carbon atoms which are bundled together to form a thread-like fibre which can be used by itself or woven into a fabric. The carbon fibres are extremely strong and light and are resistant to high temperatures, which make them highly desirable for race cars. Carbon fibres have begun to be used on production cars, but only on high-end sports cars because they are currently very expensive.
Race car designers continue to find creative ways to make race cars more fuel efficient due to new racing standards and public demand. In the long run, we all benefit from these fuel efficient innovations.