Would anyone be interested in the "Photography Game" here?

[doctorwayne]

....can you explain how the crane fits together?

Well, there would be more parts to a real crane of this type, but the two long sections represent what's called the "bridge". In my earlier photo of the Erie Nothshore's yard crane, these are the members which stretch between the rails of the crane's runway, spanning the yard below. The sections shown on the first and last flatcars are the bridge end-members - they're bolted (or rivetted or welded) to the ends of the bridge members, and are the portion containing the double-flanged wheels on which the bridge assembly runs. The load on the flatcar between the two bridge member loads represents part of the trolley, which rides atop rails (installed on site) on the main bridge members. These are the wheeled members, and they'd be tied together by other sections not modelled.
Also not modelled are the electrical cabinets for the bridge and trolley, drive motors, gear boxes, drive shafts and pillow blocks for the wheels, collector rails and shoes, walkways, railings, an operator's cab, hoist drum(s), etc., etc. Some of those things would be fabricated on site, while others could be shipped crated, either on open cars or in boxcars.

The crane parts load and the yard crane are both based on cranes at the steel plant where I worked, although not modelled after a specific prototype crane.
There were also cantilever-type cranes used to unload coal and ore from lakeboats, but they were of a much larger type - their span required truss-type construction and the runway rails were at (or near) ground level, the crane supported on built-up wheeled towers.

Wayne