End Carriage for Overhead Cranes – Design, Performance, and Reliability

The end carriage, also known as the end truck or end beam, is a fundamental structural component of an overhead traveling crane. It is located at both ends of the crane bridge and serves as the connection between the main girders and the traveling mechanism. The end carriage not only supports the weight of the crane and its lifted load, but also ensures stable and precise movement of the entire crane along the runway rails.

Structurally, the end carriage is typically fabricated from high-strength steel plates, formed into a box-section or channel-section beam to provide excellent rigidity and torsional resistance. The design must account for complex loading conditions, including vertical bending, horizontal sway, and torsional stresses during crane operation. The wheel assemblies, including driving and driven wheels, are mounted directly onto the end carriage, and the wheel flanges are precisely machined to ensure correct alignment with the rail gauge. The wheel treads are heat-treated to achieve a surface hardness of HB300–350, with a hardened depth of no less than 20 mm, to resist wear and prolong service life.

The end carriage also houses the traveling drive units, which usually consist of a motor, gearbox, brake, and drive shafts. In modern European-style cranes, integrated gearmotors are frequently used to directly drive the wheel sets without intermediate couplings, significantly improving transmission efficiency and reliability. The wheel axles are manufactured from high-strength alloy steel such as 40CrMo, and are accurately machined to guarantee a precise interference fit with the wheel discs. The bearing housings are made from cast steel (e.g., 25–30 grade) and are bolted to the end carriage structure. The use of high-quality bearings, such as NSK or SKF, ensures smooth rotation and long maintenance intervals.

During manufacturing, the end carriage requires strict quality control in welding and machining. After welding, stress-relieving heat treatment is applied to minimize distortion. The mounting surfaces for wheel bearings and gearboxes are machined using boring processes to maintain high assembly precision. Horizontal wheel skew is one of the most critical technical parameters—excessive skew can cause rail biting, increased resistance, vibration, and accelerated wear, severely reducing crane service life. Therefore, manufacturers strictly limit wheel skew values in accordance with international standards.

Modern end carriages are designed for modularity, allowing easy adaptation to various span widths and load capacities. With continuous technological development, lightweight designs using high-strength materials and finite element analysis (FEA) have become common, improving performance while reducing dead weight and energy consumption.

In summary, the end carriage is not merely a supporting structure, but a precision-engineered component that directly influences the safety, stability, and operational efficiency of the crane.