Catenary rosette

Catenary rosette of the Hamburg tram

A catenary Rosette - also home rosette , wall escutcheon , wall anchors , wall iron , catenary hook or in Austria Wall Rosette called - is a special form of the contact wire suspension for trams and trolleybuses , more rarely, railways . The rosettes, usually made of cast iron , are used to anchor or brace the overhead contact line on the buildings of the streets through which they pass. They are always used when catenary masts can not be erected for spatial reasons (for example narrow streets) or for aesthetic reasons . Costs also play a role: Rosettes are significantly cheaper to build than masts.

principle

Functionally, such a rosette consists of a base plate that is screwed to the building wall through - usually four - round holes near the edge, and two cast-on bearing blocks that accept a vertical bolt. This usually holds a rotatable drum with several radial bores into which the forks for holding the guy ropes are screwed, holds at the top with a head and is secured at the bottom with a split pin. In Hamburg in particular, rotatable metal tongues were also used instead of drums (see picture).

Four screws offer - compared to at least three geometrically required - a certain redundancy against breakage of screws or plate and a larger minimum lever of the contact surface. Today, anchoring anchors are more service-friendly, mostly by using two stainless steel eyebolts placed close to each other and a short fork in the anchoring, with three connections by shackles .

history

The age of the electric tram began at the end of the 19th century, and the electric tram, the Lichterfelde – Kadettenanstalt in Berlin, opened in 1881, is considered the first electrified route . In quick succession, other companies were electrified, but the optical effects of the overhead lines were often perceived as annoying and unaesthetic at the time. In order to compensate for this, the fortifications in the early years of the "electric" were carried out particularly artfully. This is especially true for the period around the turn of the century . For this reason, particularly artfully executed catenary rosettes are typically found on buildings built in the Art Nouveau style .

When designing the suspensions, design elements from ornamentation and rosette art in architecture were used . It was these bonds that ultimately gave the catenary rosettes their name. In later years, however, the catenary rosettes became increasingly simple and over the years they were replaced by simple wall hooks without any decoration (not to be confused with the similar-looking wall hooks for fastening street lighting ). Compared to the simple hooks of the street lighting, the catenary rosettes are much more massive, they must also be able to withstand the vibrations of the catenary caused by the spring pressure of the pantograph .

Even if the rosettes were technically the same, they show recognizable differences in the ornamental detail. In Hamburg, for example, there are five different forms analogous to the tram companies of the time and their different partners in electrification.

Catenary rosettes are or were found less often on railways, as a rule this is the case with electrically operated small railways or local railways , provided that these also drive or run through built-up streets. Examples of such cases are the Strausberg Railway , the former Klingenthal – Sachsenberg-Georgenthal narrow-gauge railway or the Münster – Cannstatt industrial railway , which has also been closed . In Austria you can also find these along the route of the discontinued Innsbruck – Hall in Tirol local train and the Stubaitalbahn .

On the Lviv tram in the Ukraine, the individual rosettes used to be numbered to make them easier to locate.

Contact line rosette in Erfurt
Contact line rosette on a half-timbered building
Preserved rosette of the Graz tram
Rose window on the Ravensburg – Baienfurt tram
A relic of the Palatinate Oberland Railway
Collection in the Transport Museum Frankfurt am Main

present

When the tram networks are still in operation, the contact wire is in many cases still attached to the original catenary rosettes on the house walls. Often these rosettes are "camouflaged" insofar as they were painted over in the same color when the facades were occasionally renovated.

Often, however, such rosettes are the only relics today that are reminiscent of long-abandoned tram lines or completely closed tram operations . In Hamburg, for example, around 600 of these relics still keep the memory of the former tram alive, although the last line was closed in 1978. Occasionally, rosettes are still hanging on houses in front of which tram traffic was stopped in 1943 (in Hamburg e.g. in Waterloostraße / Eimsbüttel) or even earlier (in extreme cases in 1923 - in Hamburg Arnoldstraße 22 / Ottensen) - in some cases by the house owners as a technical monument deliberately shown on its facade as a special feature.

Nevertheless, these catenary rosettes are still being used in some cases today. The cross-section of the street is not restricted by additional masts, the waiver usually benefits the usable width of the sidewalk. Simple shapes and corrosion-resistant material are typical for new rosettes, and simple wall hooks are also typical for sufficiently solid building structures. For example, as part of the 2007 changeover of tram line 15 to tram operation , the Stuttgart trams had some wall rosettes reproduced based on historical models. These have been used in the Alexanderstraße in Stuttgart .