Ravelin

As Ravelin ( German: Wall plate) is referred to in the fortress being an independent work, whose job it is to the curtain, so to protect the wall between two bastions, - hence its German name Wall Shield - and simultaneously back up their Facen.

For the historical development of ravelins

The Ravelin is the oldest and most important outwork of bastionären fastening system. It arose from small outworks, which should cover the bridge leading over the moat to the city or fortress gates, in front of a direct attack. From this original function of protecting the gate bridge, dates and its original Italian name " Rivellino " ( ie small banks or work with the usual German term for it: bridgehead ). Therefore, the Ravelin was at first only a small work that would only complicate the access to the bridge in front of the fortress gates. When they then realized in the 16th century, so that in general, the curtain had better protection, they began to build a Ravelin and to gradually increase before other curtains. However, only the German military architect Daniel Hamstead realized (1536-1589), the principal significance of ravelins (which he still referred to as " unmarried military " or " Revelin "). He called to make them as large as possible so that they fully covered the curtain and the flanks of the bastions and put a flanking fire in front of the bastion tips. In the following period, ravelins found in virtually all forts that were built after the bastionären fastening system.

In order to design

In bastionären system of fortifications, the Ravelin has (almost) always a triangular in plan and is thus about as either Flesche ( a plant with two Facen ) or as Lunette created ( a plant with two Facen and two edges). It was always constructed in the moat of the curtain wall, with its ramparts were always lower than those of the underlying main walls and the adjacent bastion walls. Since the 17th century, its base was always at least as wide that it completely covered the curtain behind it. Usually (but not always ) was located in front of the Ravelin another ditch as an approximation obstacle.

Preserved ravelins

The oldest surviving Wall Shield is located in the Italian town of Sarzanello and was built in 1497. Originally it was like the Peter Ravelin protect the citadel Petersberg (Erfurt ) the gates of a fortress, which were connected with them over a bridge or embankment. Towards the end of the 16th century, went on to build extra wide ravelins before scoreless Wall sections as the Ravelin Anselm of Petersberg Citadel in Erfurt, one of which could be fired from the grave entire section in front of the bastions. First, we built the ravelins entirely of masonry, since the late 16th century was mainly in Northern Europe to about aufzuschütten the banks of earth, as these are the cast-iron cannonballs of siege artillery better absorbed than pure masonry.

One of the oldest preserved ravelins represents one of the bastion castle Homburg (Saarland) dar. He was in the last quarter of the 16th century, built for the extension of the medieval Homburg into a bastion castle.

In the wake of the Thirty Years' War, the Council of Zurich decided to fix the city 's most modern large scale according to the findings. After lengthy evaluation of various fortification systems, the project of Johann Georg Werdmüller 1642 was not built as a raised circular wall, but after bastionären mounting system, and thus took the design ( Vauban ) by Sébastien Le Prestre de Vauban ( 1633-1707 ) partially anticipated ( → main article fortification Zurich ). The existing fortifications of Lake Zurich in 1657 were extended to include the pentagonal Ravelin scratch in the Limmat river. With the opposite scratch quarters respectively the production site of the Bauhaus, the city sided open bulwark was connected by a bridge with a drawbridge.

Pictures

Kehl side of the fortress Ravelin Hulst (Netherlands) seen from the main wall of the early 17th century

Ravelin Anselm of Petersberg Citadel (built 1681-1700 )

Ravelin Peter the Petersberg Citadel (built 1708)

The former Ravelin scratch ( Bauschänzli ) in Zurich, view from Stadthausquai

Ravelin at Valença fortress, Portugal