Technical Report The Construction of Alloy Wheels :: Design and Technology

Technical Report The Construction of Alloy Wheels Introduction Aluminium alloy wheels are now used in all branches of Motor Racing, ranging from Touring cars and Rally cars to Formula One cars. The Alloy wheels offer far superior mechanical properties than the conventional steel wheels formerly used. These benefits include reduced un-sprung weight, i.e. not held by the suspension, providing more precise steering input and improved responsiveness. Alloy wheels also improve acceleration and braking due to the reduction of weight. The added strength of a quality alloy wheel can significantly reduce wheel/tire deflection in cornering. This is particularly critical with a vehicle equipped with high performance tires where lateral forces may approach 1.0g. The metals in alloy wheels are excellent conductors of heat - improving heat dissipation from the brakes - reducing risk of brake fade under demanding conditions. Additionally, alloy wheels can be designed to allow more air to flow over the brakes, this can help cooling. The alloy used in the finest road wheels today is a blend of aluminium and other elements. The term "mag wheel" is sometimes incorrectly used to describe alloy wheels. Magnesium is generally considered to be an unsuitable alloy for road usage due to its brittle nature and susceptibility to corrosion. Nowadays, there are basically three ways in which alloy automotive wheels are constructed. The three types can be referred to simply by cast, billet and forged. Casting is a relatively inexpensive way to produce a high-quality, fairly strong alloy wheel; many aftermarket alloy wheels designed for street use are made this way. Billet wheels are machined from a solid chunk of material and forging uses intense heat and pressure to transform a slug of alloy material into the final shape of a wheel. This report will focus mainly on the casting processes used. Casting Processes The most common process of constructing alloy wheels is One-Piece Casting, there are a number of methods to do this, and the most basic is Die Casting, this process is used world wide throughout the casting industry and is not exclusive to alloy wheels. The Die Casting process uses a permanent mould usually made of metal, which generally means that there is high tooling costs compared to other methods of casting, but this high tooling cost is combined with low production costs. This means that die casting is suitable for products with a large production number. There are four main processes in the die casting family, these are: Gravity Die Casting Pressure Die Casting Low Pressure Die Casting Squeeze Casting Gravity Die Casting This process is the most simple of the four, the mould or die, which is generally made in two halves, is filled with molten metal, in the