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Drawbridge

 
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A drawbridge is a type of movable bridge typically associated with the entrance of a castle
Castle

A castle is a defensive structure seen as one of the main symbols of the Middle Ages. The term has a history of scholarly debate surrounding its exact meaning, but it is usually regarded as being distinct from the general terms fort or fortress in that it describes a residence of a monarch or noble and commands a specific defensive territor...
. The term is often used to describe all different types of movable bridges, like bascule bridge
Bascule bridge

A bascule bridge is a moveable bridge with a counterweight that continuously balances the span, or "leaf," throughout the entire upward swing in providing clearance for boat traffic....
s and lift bridge
Lift bridge

A vertical lift bridge or lift bridge is a type of movable bridge in which a span rises vertically while remaining parallel with the deck....
s.

le drawbridges may be found in short canal crossings, where the lifting mechanism is a pair of overhead beams with counterweight
Counterweight

A counterweight is an equivalent counterbalancing weight that balances a load....
s that are not a part of the bridge's load bearing structure. The most common type of drawbridge consists of a wood
Wood

Wood is an organic material; in the strict sense wood is produced as secondary xylem in the stems of woody plants, notably trees but also shrubs, etc....
en platform
Deck (bridge)

A bridge deck or roadbed is the roadway, or the pedestrian walkway, surface of a bridge. It is not to be confused with any Deck #Common names for decks of a ship....
 with one fixed side (normally with a hinge
Hinge

A hinge is a type of Bearing that connects two solid objects, typically allowing only a limited angle of rotation between them. Two objects connected by an ideal hinge rotate relative to each other about a fixed axis of rotation ....
), and the other side attached to the wall from a floor higher than the drawbridge.

In the Middle Ages, drawbridges were often used to allow or deny access across a moat
Moat

A moat is deep, broad trench, usually filled with water, that surrounds a structure, installation, or town, normally to provide it with a preliminary line of Defense ....
 or ditch.






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Encyclopedia


A drawbridge is a type of movable bridge typically associated with the entrance of a castle
Castle

A castle is a defensive structure seen as one of the main symbols of the Middle Ages. The term has a history of scholarly debate surrounding its exact meaning, but it is usually regarded as being distinct from the general terms fort or fortress in that it describes a residence of a monarch or noble and commands a specific defensive territor...
. The term is often used to describe all different types of movable bridges, like bascule bridge
Bascule bridge

A bascule bridge is a moveable bridge with a counterweight that continuously balances the span, or "leaf," throughout the entire upward swing in providing clearance for boat traffic....
s and lift bridge
Lift bridge

A vertical lift bridge or lift bridge is a type of movable bridge in which a span rises vertically while remaining parallel with the deck....
s.

Overview

Simple drawbridges may be found in short canal crossings, where the lifting mechanism is a pair of overhead beams with counterweight
Counterweight

A counterweight is an equivalent counterbalancing weight that balances a load....
s that are not a part of the bridge's load bearing structure. The most common type of drawbridge consists of a wood
Wood

Wood is an organic material; in the strict sense wood is produced as secondary xylem in the stems of woody plants, notably trees but also shrubs, etc....
en platform
Deck (bridge)

A bridge deck or roadbed is the roadway, or the pedestrian walkway, surface of a bridge. It is not to be confused with any Deck #Common names for decks of a ship....
 with one fixed side (normally with a hinge
Hinge

A hinge is a type of Bearing that connects two solid objects, typically allowing only a limited angle of rotation between them. Two objects connected by an ideal hinge rotate relative to each other about a fixed axis of rotation ....
), and the other side attached to the wall from a floor higher than the drawbridge.

In the Middle Ages, drawbridges were often used to allow or deny access across a moat
Moat

A moat is deep, broad trench, usually filled with water, that surrounds a structure, installation, or town, normally to provide it with a preliminary line of Defense ....
 or ditch. They could be let down to allow people across, or pulled up to deny entry into the castle.

There are also drawbridges where the cars will stop and the bridge will open to allow large vessels to go through because they are to big to go under and they can't go around.

Road and rail


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
Queensland

Queensland is a States and territories of Australia of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory to the west, South Australia to the south-west and New South Wales to the south....
, 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.

Another rail use of drawbridges was on the Listowel and Ballybunion
Lartigue Monorail

The Lartigue Monorail system was invented by the France engineer Charles Lartigue . The most famous Lartigue rail tracks was the Listowel and Ballybunion Railway....
 railway in Ireland. This was a sort of monorail, where trains hung on either side of a fence-like track. Road crossings were either a gate-like Stuart section of track or twin drawbridges,that allowed crossing at rail level.

Accidents


April 23, 1853 – Rancocas Creek
Rancocas Creek

Rancocas Creek is a tributary of the Delaware River, approximately 30 mi long, in southwestern New Jersey in United States. It drains a rural agricultural and forested area on the eastern edge of the New Jersey Pine Barrens north and northeast of Camden, New Jersey and the New Jersey suburbs of Philadelphia, Pennsylvania....
, New Jersey: Engineer of Camden & Amboy's 2 p.m. train out of Philadelphia, Pennsylvania misses stop signals (SPAD) and runs his train off of an open drawspan at Rancocas Creek. Fortunately, there are no fatalities.

See also


  • List of rail accidents
    List of rail accidents

    This is a list of rail accidents from 2000 to the present. The list includes some Improvised explosive device.See also:*List of rail accidents ...


Gallery



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