Saturday, March 15, 2008

History of the Carroll Street Retractile Bridge

Retractile Mechanism and Carroll Street Garden 1912
The bridge slides open to a perpendicular angle in the middle of the Gowanus Canal until shipping has passed and it slides back again to close
(Brooklyn Collection, Brooklyn Public Library)

Retractile Bridges date back to drawbridges. Although never a very popular design, they were used in the mid-19th century for narrow crossings where maximum horizontal clearance was required. One clear drawback of this model was that a significant amount of land had to be reserved on the bank of the waterway to "park" the structure when it was in the open position. At the turn of the century, New York City boasted five retractile bridges.

The Carroll Street Bridge is a simple, largely utilitarian structure that consists of two steel-plate girders that support the deck, two wooden, cantilevered sidewalks, and a central latticework frame supporting long stays that fan out to connect to both sides of the bridge. The stays support the structure when the Bridge is in operation. Swinging gates close the roadway and outside pedestrian walkways when the bridge is open.

The genius of the retractile bridge is not immediately evident. Under the wooden deck, the girders are supported on a set of wheels that rest on steel rails. Much like a cable car, the bridge is drawn in and out by a cable that runs into the operating house located on the western side of the Canal. The steam engine that originally operated the bridge was converted to an electrical motor in 1908.

In large part, the Carroll Street Bridge had remained unchanged over its first hundred years. In addition to the conversion from steam to electricity, alterations have included the replacement of the rails, wheels, axles, and the elegant iron hand railings was replaced with cruder angle irons in the late 40’s.

No comments: