What is a trolley on a crane?

In crane operations, the trolley¹ plays a pivotal role in moving loads across the crane’s bridge. It is an essential component of many cranes, especially overhead and tower cranes, facilitating the movement of heavy materials² and improving operational efficiency. Understanding the function and design of the trolley is key to appreciating how cranes function in construction and industrial settings.

The trolley on a crane moves loads along the bridge, making it a crucial part of the crane’s lifting and positioning system.

Now, let’s dive deeper into the role of the trolley and how it compares to other crane components, like the bridge.

What is the difference between a crane bridge³ and a trolley?

A crane bridge and a trolley work together, but they serve different purposes. The crane bridge is the horizontal structure that spans the work area, while the trolley moves along the bridge, carrying the load across the span.

The crane bridge is the stationary horizontal structure, while the trolley moves along it to transport loads.

The crane bridge is essentially the main framework of the crane. It is the part of the crane that spans the area where the lifting occurs, and it supports the trolley as it moves back and forth. The trolley, on the other hand, is a movable carriage attached to the bridge. It holds the lifting hook or other load-bearing devices and travels along the bridge to position the load where it is needed. I remember working on a project where the crane bridge had to span a large factory floor, while the trolley allowed us to position steel beams exactly where they were required. Without the trolley’s mobility, we would have had a much more difficult time maneuvering the materials across such a large area.

Key differences between a crane bridge and a trolley:

What is the pulley on a crane called?

The pulley on a crane is typically called a "sheave." Sheaves are the wheels or grooved rollers that guide the crane’s ropes or cables, facilitating the lifting and lowering of loads.

A crane’s pulley is known as a sheave, and it is responsible for guiding cables to lift and lower loads.

The sheave is an integral part of the crane’s hoisting system. It helps guide the rope or cable over the correct path, reducing friction and ensuring smooth lifting operations. These pulleys can be found at various points along the crane’s lifting mechanism, including the hook block and the top of the crane’s tower. I’ve often seen how important a well-maintained sheave⁴ is in keeping crane operations smooth, especially in heavy lifting tasks. If the sheave gets worn down or damaged, it can lead to a breakdown in the crane’s functionality, making maintenance a key part of crane safety.

Functions of sheaves on a crane:

What are the safety devices in a tower crane⁵?

Tower cranes are equipped with several safety devices to protect both the crane operator and the surrounding workers. These safety devices include limit switches, load moment indicators, anti-collision systems, and more.

Tower cranes are equipped with safety devices like load moment indicators and limit switches to ensure safe operation.

Safety devices are critical for tower cranes, which operate at great heights and carry heavy loads. A key safety device is the load moment indicator (LMI)⁶, which warns the operator when the crane is approaching its lifting capacity. Other devices include anti-collision systems⁷ that prevent the crane from colliding with other cranes or structures and limit switches⁸ that restrict the crane’s movement to safe ranges. I recall a time when a load moment indicator went off during a lift, preventing an overload. These devices not only ensure the safety of crane operators but also protect the entire construction site from accidents.

Common safety devices in tower cranes:

What is the purpose of a trolley?

The purpose of a trolley on a crane is to move the load horizontally across the crane’s bridge. This movement allows the crane to lift materials and place them in specific locations, often with great precision.

The trolley’s purpose is to move the load horizontally along the crane bridge, facilitating accurate material placement.

The trolley is integral to the crane’s ability to place materials precisely where they are needed. By moving along the crane bridge, it allows the operator to lift materials and position them with accuracy across large work areas. Whether it’s placing beams in a building’s frame or positioning materials on a factory floor, the trolley is the component that enables horizontal movement. During a recent construction project, I saw how the trolley enabled operators to position the components of a steel structure, ensuring everything was aligned perfectly without manual labor.

Functions of a trolley:

What is a stack trolley?

A stack trolleys⁹ is a type of trolley used specifically to lift and stack materials, often in a warehouse or industrial setting. It’s designed to stack materials neatly and safely, sometimes even vertically.

A stack trolley is designed to lift and stack materials, commonly used in warehouses or industrial environments.

Stack trolleys are a specialized type of trolley that are used to move materials in a stacking formation. These are commonly found in industries where the organization of materials is crucial, such as in warehouses or factories. A stack trolley’s design allows for lifting and arranging items into neat stacks, helping with organization and space management. I’ve seen stack trolleys used in large storage areas, where they help place heavy materials on top of each other, keeping them secure and easy to access.

Features of a stack trolley:

Conclusion

The trolley on a crane is essential for moving loads across the crane bridge, and it is designed for precision and efficiency. Different types of trolleys, like stack trolleys, offer specialized functions depending on the needs of the construction or industrial site.