Drawbridge

Article

November 30, 2021

A drawbridge is a type of defensive movable bridge that lowers and rises to open or close the passage over a ditch encircling a fortified structure.

Function

The drawbridge is traditionally associated with medieval castles, some of which had such a bridge over their moat or dry moat. The lifting of the bridge then made it possible to block the entrance in the event of an attack. Usually, for added security, a castle drawbridge precedes a portcullis. The entrances to the fortifications of the Séré de Rivières system are also equipped with various types of drawbridges. There were several types of drawbridges. Overhead crane Chain and arrow drawbridge Chain drawbridge without boom Drawbridge without boom tilting up Constant counterweight drawbridge Rigid transmission drawbridge Flexible transmission drawbridge Movable bridge without counterweight Simple movable weighbridge Modern overhead crane

Types

Overhead crane

The overhead crane is not strictly speaking a drawbridge, but it is nevertheless one of its predecessors. The traveling crane is the direct successor of the ancient movable bridges. The system will remain in force, more particularly in the south of France until the end of the Middle Ages. Examples: Overhead cranes: Forts de Lévis (Canada), Fort de Loncin (Belgium) Side-erasing bridges: Fort du Parmont (France), Fort d'Arches (France), Fort de Bron (France) Longitudinal erasure bridges: Fort de Feyzin (France).

Drawbridge with arrows and chains

Apart from a few appearances in the 13th century, it was not until the 14th century to see this process commonly used. At the beginning of the 14th century, at the entrance of bridges thrown over the ditches in front of the doors, wooden drawbridges attached to the barriers, or advanced masonry works were established. By the middle of the 14th century, drawbridges were applied to the gates themselves. Despite serious drawbacks (great height of its arrows therefore visible from a great distance and therefore vulnerable, deep grooves made on the facade of the door to receive them), they will remain in use until the modern period. The drawbridge of the castle of Lassay (France) is an example of this type, with a retractable ramp. It is also found at the Château de Pierrefonds (France). This type of drawbridge was more particularly used for supplies and was used to pull goods.

Chain drawbridge without arrow

This type of drawbridge is a variation of the chain and arrow drawbridge. The counterweights are suspended behind the deck beams, making it easier to raise the deck when operating the winch. Examples: Porte de Sens in Villeneuve-sur-Yonne (France), Chateau de Bonaguil (France).

Drawbridge without tilting boom when rising

Drawbridge without tilting boom by raising from the front

It is the simplest and undoubtedly the best process [ref. necessary] of a movable bridge because it avoids arrows or chains that the besieger can destroy with artillery (powder or its ancestor without powder). The mobile apron, also called flight, is balanced by a false apron, or cubée, which descends into a vat when the flight is raised like a balance. This medieval system found all its advantages in reaction to powder artillery and remained in use unchanged until the beginning of the 18th century. However, the system required a fairly deep pit, 4 meters minimum, where the humidity was harmful for the false apron. However, this embankment had an advantage: if the assailant succeeded in destroying the bridge, the embankment could serve as a second ditch (forming a pit-obstacle called haha) which slowed down the assailant even more. A TR

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