Ordinary bridge cranes generally consist of a crane trolley, a bridge traveling mechanism, and a bridge metal structure. The crane trolley is composed of three parts: a lifting mechanism, a trolley traveling mechanism, and a trolley frame. The lifting mechanism includes a motor, a brake, a reducer, a drum, and a pulley block. The motor drives the drum to rotate through the reducer, causing the wire rope to wind onto or off the drum to lift or lower the load. The trolley frame is a frame that supports and mounts components such as the lifting mechanism and the trolley traveling mechanism, and is usually a welded structure. The drive methods of the crane traveling mechanism can be divided into two categories: one is centralized drive, which uses a motor to drive the active wheels on both sides through a long transmission shaft; the other is separate drive, which uses a motor to drive each active wheel on both sides. Small and medium-sized bridge cranes mostly use a "three-in-one" drive method in which the brake, reducer, and motor are combined into one unit. For large-capacity ordinary bridge cranes, the drive device often uses a universal joint for easy installation and adjustment. The crane traveling mechanism generally only uses four active and passive wheels. If the load is very large, the wheel pressure is usually reduced by increasing the number of wheels. When the number of wheels exceeds four, a hinged balanced frame device must be used to distribute the load of the crane evenly among the wheels. The metal structure of the bridge frame consists of main beams and end beams, and is divided into two types: single main beam bridge frames and double beam bridge frames. A single main beam bridge frame consists of a single main beam and end beams located on both sides of the span, while a double beam bridge frame consists of two main beams and end beams. The main beams and end beams are rigidly connected, and wheels are installed at both ends of the end beams to support the bridge frame running on the overhead track. Rails are welded onto the main beams for the crane trolley to run on. There are many types of bridge frame main beam structures, with typical ones including box structures, four-truss structures, and hollow truss structures. Box structures can be further divided into several types, such as regular track box-shaped double beams, offset track box-shaped double beams, and offset track box-shaped single main beams. The regular track box-shaped double beam is a widely used basic form, consisting of upper and lower flange plates and vertical side plates. The crane rail is located on the center line of the upper flange plate. It has a simple structure, is easy to manufacture, and is suitable for mass production, but it is relatively heavy. The cross-sections of offset track box-shaped double beams and offset track box-shaped single main beams are both composed of upper and lower flange plates and unequal thickness main and auxiliary webs. The crane rail is located above the main web, and the short stiffeners inside the box can be omitted. The offset track box-shaped single main beam replaces two main beams with one wide-flange box-shaped main beam, resulting in a lighter weight but more complex manufacturing process. The four-truss structure is composed of four planar trusses to form a closed spatial structure. A walkway plate is generally laid on the surface of the upper horizontal truss. It is lightweight, has high rigidity, but compared to other structures, it has large external dimensions, complex manufacturing, and low fatigue strength, and is rarely produced. The hollow truss structure is similar to the offset track box-shaped main beam, consisting of four steel plates to form a closed structure. Except for the main web being a solid web I-beam, the other three steel plates are cut into many windows according to design requirements, forming a hollow truss without diagonal braces. Walkway plates are laid on the upper and lower horizontal trusses, and the crane traveling mechanism and electrical equipment are installed inside the bridge frame. It is lightweight, has high overall rigidity, and is a widely used type in China. Ordinary bridge cranes mainly use electric drive and are generally operated from a driver's cab, but remote control is also available. The lifting capacity can reach 500 tons, and the span can reach 60 meters. Simple beam bridge cranes, also known as beam cranes, have a similar structure to ordinary bridge cranes, but with smaller lifting capacity, span, and operating speed. The bridge frame main beam is a simple section beam composed of I-beams or other steel sections and plate steel. A hand chain hoist or electric hoist is equipped with a simple trolley to serve as the crane trolley. The trolley generally runs on the lower flange of the I-beam. The bridge frame can run along the track on the overhead track or along the track suspended under the overhead track. This type of crane is called a suspended beam crane.