Lift enhancing beam attachment with movable counterweights

An attachment for increasing the lifting capacity of a crane having a mobile lower works with an upper works including a rear portion rotatably mounted on the lower works and having a pivotally mounted boom and an upwardly and rearwardly projecting mast carried on the upper works with means for lifting a load from the top of the boom and rigging means interconnecting the top of the boom and the top of the mast, comprising in combination, means interconnecting the top of the mast and the rear portion of the upper works for opposing a load lifted from the top of the boom, a counterweight support beam detachably connected to the crane upper works and extending rearwardly from the rear portion of the upper works, a counterweight assembly including a movable carrier mounted on the support beam for movement along the length thereof, means for selectively moving the counterweight carrier fore and aft along the beam, leg means for normally supporting the trailing end of the beam on the ground, and means interconnecting the trailing end of the beam and the top of the mast for raising the leg means from the ground incident to lifting a heavy load from the boom.