Crane, crane assembly method and disassembly method

A crane comprising:

• a crane body;
• a boom having a boom proximal end attached to the crane body rotatably about a boom rotation axis extending in a right-left direction of the crane body relatively to the crane body and a boom distal end opposite to the boom proximal end, the boom being capable of derricking with the boom proximal end as a fulcrum;
• a jib having a jib proximal end attached to the boom distal end rotatably about a jib rotation axis parallel to the boom rotation axis and a jib distal end opposite to the jib proximal end;
• and
• a jib posture retention device that retains the jib in a predetermined frontward tilt posture with respect to the boom when the boom has uprisen, wherein:
• the boom has a rope connection place at a position separate from the boom distal end toward the boom proximal end;
• the jib posture retention device includes:
• a jib-side support rope having one end connected to the jib distal end and the other end opposite to the one end;
• a boom-side support rope having one end connected to the rope connection place of the boom and the other end opposite to the one end;
• a rope connection part to which the other end of the jib-side support rope and the other end of the boom-side support rope are separably directly connected;
• and a jib mast that supports the jib in a predetermined frontward tilt posture in cooperation with the jib-side support rope and the boom-side support rope on a back side of the jib, by holding the rope connection part at a tensioning position while the jib mast is attached to an attachment object that is one of the boom distal end and the jib proximal end, when the jib is in the predetermined frontward tilt posture, the tensioning position being a position at which the rope connection part is separated from the jib proximal end and the boom distal end backward of the jib proximal end and the boom distal end to an extent that the jib-side support rope is linearly tensioned between the rope connection part and the jib distal end and the boom-side support rope is linearly tensioned between the rope connection part and the rope connection place of the boom;
• and
• the jib mast is configured to be shiftable between a tension form of holding the rope connection part at the tensioning position in an uprise posture in which the jib mast extends from the attachment object backward of the attachment object and a looseness allowing form of locating the rope connection part at a looseness allowing position, which is a position closer to the boom distal end than the tensioning position and closer to the jib proximal end than the tensioning position to allow the jib-side support rope and the boom-side support rope to be loosened, while keeping the rope connection part along with the jib-side support rope and the boom-side support rope, attached to the jib mast.