The distance from the crane's hook to the center of rotation is commonly called what?

• A. Operating radius
• B. Radius of gyration
• C. Boom length
• D. Load center distance

Answer: (A)

Operating radius is the distance from the crane’s hook to the center of rotation, which is the radius of the hook’s circular path as the crane turns. This distance is crucial because the load moment equals the weight times the operating radius, so lifting with a larger radius reduces capacity and affects stability.

Radius of gyration is a concept from rotational dynamics about how mass is distributed in a body, not a measurement of the crane’s geometry. Boom length is the straight-line reach from the rotation point to the hook in a given configuration, but the distance in question is specifically the hook’s distance to the rotation center regardless of the boom angle or configuration. Load center distance relates to how far the load’s center of gravity is from the rotation center, which influences moment calculations but is not the hook-to-center distance itself. Therefore, the hook-to-center-of-rotation distance is called the operating radius.