Featured image of Castle Drawbridge

Castle Drawbridge

As the term suggests, a drawbridge is a bridge pulled back completely or at times from the middle. Usually, a castle drawbridge is found at the entrance of a castle or tower surrounded by a moat (a water body surrounding any fortification). Drawbridge is often referred to as ‘bascule bridge’, which means ‘balance-scale’ in French. Castles in the middle ages were usually defended by a moat, upon which was constructed a wooden bridge. 

Purpose of Castle Drawbridge

Hammond Castle Drawbridge
Hammond Castle – Drawbridge”, by Brian Herzog, is licensed under CC BY-NC-SA 2.0

Medieval castle drawbridges usually served the purpose of letting ships going from under the bridge pass conveniently. These also sometimes served the purpose of defence, for such bridges were often pulled back to prevent the entry of certain people. These often were used as a guard to sustain as many attacks as possible before the peril reached the royal household or fortification. Since these operate quickly and need relatively less effort, drawbridges were abundantly used to clear the marine traffic quickly and smoothly.

Design of Castle Drawbridge

Bunratty Castle - Drawbridge Mechanism
Bunratty Castle – Drawbridge Mechanism”, by Joseph Mischyshyn, is licensed under CC BY-SA 2.0

Castle drawbridges would be lifted or taken down with the help of chains attached above the gate-passage. The attached chains could themselves be constructed with counterweights to provide weight- which is seen in the case of Alnwick Castle. These counterweights would be set up against the roof of the gate-passage when the drawbridge was down. These would also close against the gate-arch when the bridge was raised.

There exist three kinds of designs for castle drawbridges, the counterweights for which can be located above or below the deck.

The first kind of drawbridge has a fixed trunnion at the top, which is instrumental in its movement. The trunnion rotates on a large axle. It is also usually called the Chicago bascule (the name being derived from Chicago for its common use there). Further improvements in such drawbridges were made by Joseph Strauss.

The second type is the Scherzer rolling lift trunnion, which raises the span by rotating on a path similar to a rocking-chair base. Its improvement was patented in 1893 by William Donald Scherzer, an American engineer.

The third type is found rarely and is called the Rall kind. This combines rotating lifts on trunnions when being opened. These bridges were patented in 1901 by Theodor Rall. 

History of Castle Drawbridge

Cawdor castle, drawbridge
Cawdor castle, drawbridge”, by John Mason, is licensed under CC BY 2.0

It is believed that the Egyptians first used structures like drawbridges sometime around 2000 BCE. These drawbridges were quite simple and required a very minimal workforce to lift them when required.

However, the use of steam power in the 1850s brought a significant change in the amount the bridges were used since now they could not be operated quickly enough in practicality.

Drawbridges, however, also proved to be a disadvantage to the royal armies in medieval times. This was so, because going by the structure of the drawbridge, it would be one of the first parts of the castle to be attacked. The artillery would harm the wooden segment during a blockade, and this would, further on, be quite a grind when being repaired.

Castles with drawbridges are also found at a number of places in France, including in the Château du Plessis-Bourré. In England, two working drawbridges are even presently used at Helmingham Hall, constructed in the early sixteenth century. The most famous drawbridge, however, is the Tower Bridge in London that spans over the River Thames. One of the oldest drawbridges is found at the Buhen fortress, built around 1860 BCE.

From ancient times to later eras, when they used to be of significant use, castle drawbridges surely were to the fortifications of a strong shield to a soldier. Some more beautiful castles with drawbridges are Château de Bonaguil and Conwy Castle, which are definitely worth a visit.

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