Hulett
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- For other uses, see Hulett (disambiguation).
The Hulett automatic ore unloader was invented by George Hulett of Ohio in the late 1800s; he received a patent for his invention in 1898. The first working machine was built the following year at Conneaut Harbor in Conneaut, Ohio. It was successful, and many more were built along the Great Lakes, especially the southern shore of Lake Erie to unload boats full of taconite from the mines near Lake Superior.
Hulett-bucket.jpg
A Hulett unloader runs on two sets of parallel tracks along the face of the docks, one near the edge and one further back, with normally enough distance for four sets of railroad tracks in between. Steel towers, riding on wheeled trucks, support girders that run from front to back, perpendicular to the dock face.
Along these girders runs a carriage which can move toward or away from the dock face. This in turn carries a large walking beam which can be raised or lowered; at the dock end of this is a vertical column with a large scoop bucket on the end. A parallel beam is mounted half-way down this column to keep the column vertical as it is raised or lowered. The scoop bucket is thus lowered into the ship's hold, closed to capture a quantity (10 tons approx.) of ore, raised, and moved back toward the dock.
To reduce the required motion of the carriage, a moving receiving hopper runs between the main girders. It is moved to the front for the main bucket to discharge its load, and then moves back to dump it into a waiting railroad car, or out onto a cantilever frame at the back to dump the load on a stockpile.
Hulett-discharging.jpg
The Hulett can move along the dock to line up with the various holds on an ore boat. Once the hold is mostly empty, the Hulett cannot easily finish the job itself. Early on, workmen would descend into the hold and shovel the remaining ore into the Hulett's bucket; later on, a wheeled excavator would be carried aboard inside the Hulett's bucket to fill the Hulett.
The Hulett machine revolutionised iron ore shipment on the Great Lakes. Previous methods of unloading lake freighters, involving hoists and buckets and much hand labor, cost approximately 18¢/ton. Unloading with a set of Huletts cost only 5¢/ton. Furthermore, unloading only took 5-10 hours, as opposed to days for previous methods. Lake boats changed to accommodate the Hulett unloader, and became much larger; doubling in length and quadrupling in capacity.
By 1913, 54 Hulett machines were in service; two were built at Lake Superior (unloading coal) and five at Gary, Indiana, but the vast majority were along the shores of Lake Erie. The additional unloading capacity they brought helped permit a greater than doubling of the ore traffic in the 1900–1912 period. A total of approximately 75 Huletts were built. One was installed in New York City to unload garbage. They were unsuited to salt-water environments because they could not adjust for rising and falling tides, and few were so used.
The lake's Huletts were used until about 1992, when self-unloading boats were introduced. Most have since been scrapped, but some remain in Cleveland, Ohio and elsewhere.
References
- Miller, Carol Poh. (1979). Historic American Engineering Record OH-18: The Pennsylvania Railway Ore Dock. National Park Service, Washington DC. Available at the Library of Congress web site http://www.loc.gov/.
External links
- Hulett Automatic Ore Unloaders Home Page (http://web.ulib.csuohio.edu/SpecColl/glihc/hulett/) at the Great Lakes Industrial History Center.
- Designation as Historical Mechanical Engineering Landmark (http://www.asme.org/history/brochures/H199.pdf) (PDF) by the American Society of Mechanical Engineers (ASME)