My favorite dockside machine is the Hulett ore unloader. Sadly, they are no longer in existence, and I have no photos of my own of them (they were a familiar sight to me as I grew up in Cleveland, Ohio), so I will have to draw upon a photo from the Internet (sadly I do not even know how to credit it):
Hulett ore unloader, Cleveland, Ohio (fairly recent times)
These stupendous machines were used to extract iron ore (taconite) from the holds of the gigantic vessels (always called "boats", never "ships", despite their size) that transported the iron ore from the mines near the upper great lakes to the steel manufacturing towns on the south shore of Lake Erie (prominently Cleveland but also several other towns).
The machines had a large scoop bucket at the bottom of a vertical "leg", which was supported by a counterweighted parallel-arm arrangement (so the leg could be raised and powered while remaining vertical) that was in turn mounted on a large wheeled carriage so it could move from left to right (as we see it in the photo) on an even larger carriage. This larger carriage could move parallel to the railroad tracks beneath.
The machine operator was in a cab in the leg just above the bucket (we can see him in the near machine, about halfway between the center of the bucket assembly and the large sprocket wheel).
The leg could also be rotated so as to rotate the bucket.
The bucket opened and closed not only in that its two members could swing open but also in that they separated by horizontal motion, thus given them an enormous "bite". The capacity of the bucket ranged from 15 to 20 tons of ore, depending on the version of the machine.
The operator would lower the bucket into the hold, close it to get a "bite" of ore, raise it, and then move the supporting carriage to our right until the bucket was just "on shore" (the position for the nearest machine in the photo). Then the bucket would open, dumping the ore into a hopper that could travel on rails to our right. It would be moved to just over the destination rail car and its bottom would open, allowing the ore to go into the car.
By the use of this intermediate hopper, the actual bucket and its gigantic carriage did not have to travel far enough to directly discharge into the rail car, and in any case the size of the bucket was such that it could not dump into the relatively-small rail car.
The hopper can in fact travel beyond the rail tracks to dump the ore into a storage area (to our far right), when appropriate.
We see a very narrow electric locomotive running on narrow-gauge rails between the third and fourth rail tracks (there is another set of such rails between the first and second main tracks). This "pusher" engine was used to position individual rail cars so they would in the proper position to receive the ore from the hopper, I believe by pushing them with a pole that ran between a pocket on the engine and a pocket on the car (all rail cars have these "pole pockets" to allow a similar maneuver, perhaps with a full-width engine, in marshaling yards). (I don't know nearly enough about the pusher engines.)
In my youth, the sight of dozens of these behemoths operating at the Cleveland ore docks was wondrous indeed. In fact, a popular form of weekend entertainment for my family in that era was to drive to near the docks so the Huletts could be watched fairly close-up.
The"modern" buildings seen in the distance suggest that this was a fairly recent photo (not sure just what that means), likely not long before the use of the Hulett unloaders was discontinued (about 1992). (In modern times, "self-unloading" ore boats came into use.)
There are many further fascinating aspects of Hulett unloader operation, but I need to go to breakfast now.
Best regards,
Doug