Abstract: A tower crane with a counterweighted luffing boom has its counterweight lines and pulleys so arranged that, in normal operating positions of the boom, the counterweights and lines tend to swing the boom upwardly, but when the boom angle is steep, beyond about 70.degree. from the horizontal, the counterweights and lines then pull on the boom in the opposite direction, tending to retard further upward travel. The boom and supporting structure are thereby protected against overbooming by wind forces when the boom is inclined at a very steep angle facing into the wind.

Abstract: A method and apparatus for lifting a tower crane, and for supporting the tower crane when lifted, utilizes the existing structure of the tower's mast sections for connection of lifting and supporting apparatus. Hydraulic jacks lift threaded lifting rods, which extend down to a pair of lifting yokes by means of adjustable nuts positioned to engage lifting surfaces of the jacks from above. At the top of the stroke of the jack, a second set of nuts are spun down the threaded rods to a position engaging a stationary support surface from above, so that the jacks can then be lowered and the first set of nuts can be spun down and returned to their original position. A third set of nuts is positioned near the bottoms of the rods to provide a means for supporting the lifting yokes.