Tuesday, November 14, 2017

Cortland Street (Clybourn Place) Bridge

The official name is Clybourn Place Bridge.

20141212 7523, a view of the east side
Below is a photo dump of the pictures I took as I walked across the south side of the bridge.
The visible racks (the three round "toothed" steel members) are a signiture of the first generation of the "Chicago" type drawbridges.
Significance: Designated a landmark by the American Society of Civil Engineers, the Cortland Street Bridge is a double-leaf bascule span that became in the early twentieth century the standard for movable bridges designed by the city engineer of Chicago. The Cortland Street bridge was the first of this type and featured electric motors that drove pinion gears which engaged a rack attached to the end of each truss. Counterweights on the shore sides of the bridge counterbalanced the roadway and superstructure that spanned the river and thus little power was required to raise or lower the bridge. When raised, each leaf assumed a nearly vertical position providing a wide clearance for vessels plying the river. City engineers designed the machinery so that the bridge could open within one minute during calm weather and under three minutes during windy conditions. [HAER IL-138]
As one would expect for such an historic bridge, Historic Bridges has an extensive writeup about this bridge.
Digitized by Google

Digitized by Google

Cortland Street Bridge in 1902 looking east from the Public Works Annual Report.
[Note the street car tracks without any electric wires above them. Electricity was still relatively new in 1902 so the streetcars are probably still being pulled by horses. I spent some time trying to find the Google copy of the 1902 report, but I was not successful.]
Photo from HAER ILL, 16-CHIG, 136--6 from Library of Congress
[This is one of the three "inside" photos in the LoC report. I was not able to find the electric motor in any of them. On the left is the pinion gear that is engaged with the rack that goes up through the street.]
This bascule bridge replaced a swing bridge, and it was the fifth one built at this site.
Digitized by Google
The previous bridge at this location was also the first documented bridge at this location. It was a hand-turned iron/wood combination bridge built in 1873 by Fox and Howard. It was 140 feet long and 32 feet wide. [Historic Bridges]

Now for the promised photo dump.
Note the plaque in the crossmember truss was custom fit to the opening.

The city has refurbished this bridge a few times, and they have been careful about saving the historic details.

Note the I-beam that has locked
the two leaves together. 
I did spot at least two barges upstream of this bridge. In the Chicago area, the tugboats have pilot houses that can be lowered to go under the bridges because all of the bridges on the Chicago Sanitary and Ship Canal are now fixed.

Historic Bridges believes the railing on the approach is of the original design. 

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