Northern Avenue Bridge

 

Northern Ave 2

Overview

This bridge is a Truss Moveable Swing Bridge.  It was built in 1908 and was originally used for traffic.  Today the bridge is pedestrian only and you can see remnants of past uses (the railroad tracks cracking the pavement in the center of the bridge).  This bridge is a truss bridge that swings out to allow ships by.

How it Works

Truss bridges have members (pieces) in tension (pulling) or compression (pushing).  The center of the bridge swings out by a gear system.  It used to be operated by a person releasing pressurized air to move gears but today the person is now using control that operate motors which turn the gears.

droppedImage

Things to Notice

The entire bridge uses rivets not bolts.  In the time the bridge was built construction included heating up metal pins then hitting them with a cup to form the rivets.

A bridge keeper stays on the bridge to operate it, as boats need passage.  A federal law states that boat traffic has the right of way over any other traffic passing over the bridge.

Facts

The old gear can be seen as you walk past the Barking Crab.  Note the spots where teeth are chipped or have been welded back on.  The forces in this gear are extremely high to get the bridge moving.

 

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