Forged Magnesium Wheels: For Racing Applications

Formula E:  Energized, Inspired, All-electric!

Formula E’s first groundbreaking season ran in 10 of the world’s top cities, starting in Beijing in September 2014 and ending in London in June 2015.

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The championship showcases 10 two-driver teams, racing on temporary city-centre circuits for an “electrifyingly” exciting competition for motorsport fans.  Starting this December (2017), the FIA Formula E championship  heads into its fourth season with a total of 14 races on the schedule.1502089886_vg

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The FIA (Federation Internationale De L’Automobile) is the governing body for Formula E, along with other championship motorsports.  A key FIA objective is to encourage and implement the adoption of common regulations for all forms of motorsports and series across the world.                                                                                

The FIA specifies competition standards for everything from mandatory pit stops to number and types of wheels and tires, and as restrictions are lifted or modified, and regulations continue to evolve from season to season,  many Formula E teams may opt for lighter and stronger forged wheels (versus cast wheels of various metals, including aluminum), particularly forged magnesium wheels–a decision that would lead to major safety and performance improvements along with further reduction of emissions. When discussing Formula E vehicles and other alternative racing series championships, we often focus on battery specifications and powertrain details but tend to underestimate the significance of wheels, a component having quite a pronounced effect.

 

Why Magnesium?

Magnesium is one-third lighter than aluminum and can provide meaningful weight reduction where applied. In the case of both passenger cars and high-performance racing vehicles the impact is especially important because wheels, along with the brake system, comprise unsprung weight. The ratio of sprung to unsprung weight is essential since the force exerted by the unsprung components on the car directed upward must be offset by the sprung weight–otherwise the car loses its grip with the asphalt making it harder to steer, especially at cornering.  Reducing unsprung rotating weight can help improve the dynamics of a vehicle, since the heavier the wheels, the more energy and time are required to alter their speed of rotation. Lightweight wheels help achieve faster acceleration and may reduce stopping distance. The aggregate effect on a vehicle when replacing typical wheels with forged magnesium versions can reach 5% and more. According to comparative testing conducted between the standard Porsche 918 Spyder configuration and the Weissach upgrade package consisting of forged magnesium wheels and light sports belts, the vehicle fitted with forged magnesium wheels accelerated from 0 to 300 km/h in 19.9 seconds, which is > 2 seconds faster than with the original aluminum wheels. Braking distance reduction was not measured as part of the study.

And magnesium has still more to offer. These alloys have greater capacity for heat dissipation, which helps prevent brakes from overheating.  “Notably,” adds Mark Lisnansky of SMW Wheels, “magnesium is known for its extraordinarily high damping factor, enabling wheels to absorb road vibrations. This ensures that tires maintain tighter grip with the road while reducing the amplitude of vertical movement, thus decreasing misplaced kinetic energy. Plus, due to its much lower density, and considering its elastic modulus, the specific stiffness of well-designed magnesium wheels is superior to aluminum counterparts.”

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Forging Technology

After selecting the alloy, the actual forging process is of vital importance. The benefits magnesium brings are compounded with best-in-class forging technology. Most professionals know that forged wheels are stronger and more ductile than their cast counterparts–but not all forgings are created equal. The closed-die hydraulic forging process eliminates non-directional crystal microstructure of the metal and reduces the wall thickness by about 20 percent. The resulting structure is fibrous and fine grained, radiating from the centre of the hub along the spokes toward the rim. The grain is arranged transversely at the rim. The hot metal flows into the die tooling cavities and assumes the required net shape in accordance with the precise die tooling design.

Depending on the complexity of the wheel configuration, the forging process may be performed in one or several steps before a forged part assumes the actual final shape, with about 3 mm of extra metal all around, plus a bit more metal between spokes. The more precisely the die configuration follows the contour of the finished exemplars, the higher the quality of the completed wheel, and the less machining is required. The pattern of the grain is arranged along the direction of the load, thereby maximally strengthening the wheel (up to double the strength).

All wheels are subjected to special heat treatment to further increase their strength. Combining these processes enhances the wheel’s ability to withstand extreme loads. Producing wheels by the hot closed-die forging process is a costly proposition, so relatively few manufacturers can afford to invest building a press having 15,000 tons of force, plus acquiring the know-how and technological expertise for this type of manufacturing. Still, professional drivers (pilots) demand the advantage of the forged wheel’s superior characteristics. For this reason, many companies purchase forgings (semi-finished wheels) from large manufacturers.There are very few truly capable forged blanks manufacturers worldwide. As a result, a number of alternative processes, such as flow forming (spinning) and liquid forming have emerged. These are typically of higher quality than cast wheels and come at a lower cost. Manufacturers often call the end product “forged wheels,” but they tend to have inferior properties compared to true-forged wheels.

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CO2 Emissions

“Formula E aims to represent a vision for the future of the motor industry, serving as a framework for R&D around the electric vehicle, accelerating general interest in these cars and promoting clean energy and sustainability.” e-racing.net

Reducing negative environmental impact while improving vehicle performance are paramount considerations and motivators for the Alternative Racing category. So this represents a potentially optimal testing ground for forged magnesium wheels to be put to work–allowing for the accumulation of analytical data on fuel consumption, tire and brake wear, carbon dioxide emissions, braking/stopping distance and other measurements. This compiled intelligence places Alternative Racing at the forefront of innovation, which ultimately serves the development of street-legal, zero emission cars that go the distance in a better and safer way. The case for forged magnesium wheels in this competitive environment is quite compelling.

Precisely manufactured to be the lightest wheels in the industry, SMW forged magnesium wheels are made to win races.

Discover the world of forged magnesium wheels at smwwheels.com.

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