The three basic units for an overhead crane are the bridge, hoist, and which?

• A. Carrier
• B. Runway
• C. Trolley
• D. Girder

Answer: (C)

An overhead crane is built from three main functional units: the bridge, the hoist, and the trolley. The trolley is the moving carriage that runs along the bridge and carries the hoist, allowing the load to be positioned anywhere along the length of the bridge. The hoist provides the vertical lift, while the bridge spans the workspace and moves along the runway. The runway is the fixed track system that guides the bridge, and a girder is a structural part of the bridge itself, not a separate unit. So the trolley is the essential third unit because it enables the horizontal movement of the hoist along the bridge to reach different load points.