Drawbridge

From Free net encyclopedia

Image:Magerebrug.jpg Image:Vincent Willem van Gogh 070.jpg A drawbridge is a type of movable bridge typically associated with the entrance of a castle, but the term is often used to describe all different types of movable bridges, like bascule bridges and lift bridges.

The most common type of drawbridge consists of a wooden platform with one fixed side (normally with a hinge), and the other side attached to the wall it is raised against by rope or chains. Pulling on the chain raises the bridge. These chains were usually operated from a floor higher than the drawbridge.

In the Middle Ages, drawbridges were often used to allow or deny access across a moat or ditch. They could be let down to allow people across, or pulled up to deny entry into the castle.

Now, with cars and trains in need of crossing small waterways without blocking boats from passing, drawbridges have a more peaceful reason for their existence.

In Queensland, diamond crossings between narrow gauge cane tramways and main lines are being replaced by drawbridges, so that the rails of the main line are completely unbroken by gaps or weak spots. This also allows the main line speeds to be raised.

Accidents

Occasionally, large ships will collide with bridge piers or pylons. Historically, there appears to be no significant difference whether the bridge is of the fixed and opening kind.

Trains, which by the time they see the drawbridge open, cannot stop in time, sometimes run over open drawbridges. Such accident include

• 1853 – Norwalk, Connecticut - locomotive and four and a half cars ran through the open drawbridge and plunged into the Norwalk River. 46 passengers were crushed to death or drowned and approximately 30 were severely injured.
• 1950s ? – Bayonne, NJ, killing 53.
• List of rail accidents for more details.

See also

• Movable bridge for a list of other movable bridge types

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