Abstract: Wheel assemblies for attachment to a carriage or a vehicle. The wheel assemblies can be configured for four wheel steering, locked in predetermined directions, or free pivoting. The wheel assemblies further include an apparatus for retracting and extending the wheels of the carriage to support the carriage on fixed length supports.

Abstract: A compact mobile crane for lifting or lowering a load to or from a roof or other location of a building, and for raising, lowering, and supporting a load along the sides of a building. Elements of the mobile crane can be folded to allow the mobile crane to be moved into, and transported by, a standard size building elevator. Wheel assemblies on the carriage of the mobile crane can be configured for four wheel steering, locked in predetermined directions, or free pivoting. The wheel assemblies further include a wheel retraction apparatus for retracting the wheels of the mobile crane to support the crane on fixed length supports. The carriage frame members include rows of holes spaced at equal distances from each other, providing a system for easily fastening numerous elements to the mobile crane.