A crane including a main boom having a first end portion and a second end portion, and being supported by a support structure via a hinged connection whereby the main boom is pivotable in a vertical plane. A pivoting assembly is arranged below the main boom, wherein the pivoting assembly includes an electric motor-and-winch assembly, a sheave assembly, and one or more drive wires extending between the motor-and-winch assembly and the sheave assembly.

A portable crane formed of composite members. A composite mast is coupled to a composite boom. A boom end housing removably couples at a top of the mast and includes an enclosure. A first end of the boom couples within the boom end housing. A boom pivot couples to the boom end housing and couples the boom to the mast. An angle adjuster releasably secures the boom at a desired angle relative to the mast. In implementations an end cap is included at a second end of the boom, coupled to a sheave with a pin, the end cap covering a terminal end of a second end of the boom and extending along both sides of a slot in an upper surface of the second end and along a portion of a first side of the second end and along a portion of a second side of the second end.

A slew bearing that includes an inner ring. The slew bearing also includes a first outer ring positioned about a first portion of the inner ring. The slew bearing also includes a second outer ring operably engaged with the first outer ring, wherein the second outer ring is positioned about a second portion of the inner ring opposite to the first outer ring. The slew bearing also includes at least one set of ball operably engaged with the inner ring and one or both of the first outer ring and the second outer ring. The inner ring of the slew bearing is configured to rotate about the first outer ring and the second outer ring.

A heavy-lift rotating kingpin slewing crane is disclosed having an upper bearing for a rotating kingpost crane which achieves equalized radial loading on all boom-side bearing rollers arranged in tandem on approximately a 120 degree arc segment of an upper radial bearing assembly when reacting the crane's operating load-moment couple-forces transferred from the rotating kingpost structure into the stationary kingpost housing at the upper bearing outer race surface. The bearing system comprises a concentrically nested set of load spreader bodies interconnected by pins and arranged to transfer the horizontal couple-forces from each side of the kingpost structure via a linkage to centrally located, largest spreader bodies which progressively reduce and transfer the load radially into smaller spreader bodies until an equal set of radial loads arrive on a set of bearing rollers.