Whereas the portal crane can revolve and move along its 20 foot wide tracks, masting sheers are not much more than two wooden or metal poles attached at the top in the shape of an 'A.' Incredibly strong, sheers are fixed in position instead of being able to move to a job, a job had to be moved to the sheers.ĭuring the Age of Sail, this was not a problem.
Naval History and Heritage Command Photographs, NH 42479 Masting SheerĪs the Charlestown Navy Yard’s last remaining cranes, the portal cranes bear little resemblance to the Yard’s earliest permanent cranes: the masting sheers. Paddle steamer USS WABASH, seen here at the Charlestown Navy Yard’s Sheer Warf in 1876, points out one major downside to the sheer design: sheers were strong but immobile.Ĭourtesy of the Naval Historical Foundation.
#NAVY PORTAL INSTALL#
Prior to the development of modern cranes, navy yard workers used sheer legs to install masts and other ship components. These cranes played a pivotal role in the building and repairing of ships at the Yard starting from their introduction in the 1940s until the Yard’s closure in 1974. The combination of its open portal, revolving top, and ability to move made the portal crane remarkably flexible and well-suited to its work at the Navy Yard.
They were so prevalent on docks that they were also sometimes called "dockside cranes." Another nickname, "whirley crane," points to an additional design feature: the top can be revolved-or whirled-around by the operator. The "portal crane" design proved very popular in industrial areas where space was at a premium, and the Charlestown Navy Yard was no different. Conversely, operators could move the cranes along railroad tracks, driving them over blockages and repositioning them where needed.
Crane 62, seen in the background, remains at the Charlestown Navy Yard today.īoston National Historical Park, BOSTS 10894-1423 A Portal Crane by any other nameįrom underneath, it is easy to see why the two large cranes still found at the Charlestown Navy Yard-Crane 62 and Crane 65-are called "portal cranes." The open space, or portal, between the metal legs allowed workers and machines to move through the crane rather than having to go around. Note the 20-foot-wide rails embedded in the pier along which the cranes could be moved by crews. Navy Yard crews used portal cranes 69 and 62 in tandem to move a load too heavy to move with a single crane.
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