A crane assembly which, in heavy lifting configuration, has a platform with boom carrier and counterweight support rotatably mounted on a ring with the mounting including a king pin removably secured to the ring. For portability, the king pin and sections of the ring are removed and a transporter run within the ring and beneath the platform. The platform will easily accept a variety of hoisting machinery. Not only are the boom, mast and ring suitable for other crane configurations, but also the counterweight support and boom carrier are standard subcombinations held rigid with the platform through links defining triangular frames.