Abstract: Means for extending and retracting the telescoping boom assembly of a rotatable mobile crane wherein the boom assembly comprises a plurality of telescoping parts, slidably received one into the other. The boom extension and retraction means is operable at any angular displacement of the boom assembly, the operating angle of the boom assembly being maintained during the extension or retraction thereof. Means for extending and retracting the boom assembly include a single fluid driven linear motor or hydraulic cylinder suitably attached at one end portion of the motor to a base portion of the boom assembly. An opposite end portion of the linear motor is selectively securable to the telescoping sections of the boom assembly to permit extension thereof. A cylinder guide is mounted on the fluid driven linear motor, both the cylinder guide and motor contained within the boom assembly, the cylinder guide providing support for the linear motor and maintaining the alignment of the extension and retraction means.

Abstract: A system and method are disclosed whereby a crane boom assembly of relatively long length and large load carrying capacity may be automatically stowed and carried on the superstructure of a crane assembly. With the boom assembly in the stowed position, the boom and superstructure combination may be carried on a single truck and trailer combination for highway transport. Power driven means are provided for unstowing and stowing the boom assembly with respect to the superstructure. To unstow the boom assembly, first power driven means are provided to translate the boom forwardly with respect to the superstructure. Foot pins located at the rear of the boom assembly are mountable in the main pivot means on the superstructure of the crane when the boom assembly is fully extended forwardly of the superstructure to an intermediate unstowed position.