Development of a Lightweight One-Piece Aluminum Casting Swingarms

Fuel-efficient motorcycles are essential for energy conservation and environmental load reduction. To achieve low fuel consumption, reducing the weight of the body parts of the motorcycle is important. This study focuses on reducing the weight of the swingarms, a relatively heavy body part. However, reducing the weight of swingarms is challenging owing to the low flexibility in their shape because swingarms are conventionally made of multiple pipes and casting parts welded together. Therefore, we utilized the integral casting technology and examined a new light weight shape. However, creating a new shape manually is difficult. Thus, we examined a new shape using the shape optimization technology, which has been recently used in additive manufacturing. The shapes fabricated using this technology are generally complex and difficult to manufacture by casting. Therefore, we adjusted optimization condition with casting. We derived a new shape which can not only be casted but also has good balance between weight and rigidity. After studying the casting design using casting simulation, a prototype was fabricated by sand mold casting. We achieved a weight reduction of 7.3% compared to the conventional welded structure. The prototype passed the onboard durability test, and the running evaluation test was completed without any problems.