Bow collector

A bow collector is one of the three main devices used on tramcars to transfer electric current from the wires above to the tram below. While once very common in continental Europe, it was replaced by the pantograph or the trolley pole, itself often later replaced by the pantograph.

When the bow collector was first conceived by German inventor Ernst Werner von Siemens in the late 1880s, American inventor Frank J. Sprague of Virginia had just patented his trolley pole system of current collection from an overhead wire. To avoid contravening this patent, the Siemens company was forced to design its own, unique form of current collection, namely the bow collector. The bow collector was first used by the Siemens electric company in its early electric tramcars in either the late 1880s or early 1890s. The Hobart electric tramway system - the first of its kind in the Southern Hemisphere, opened in 1893 - used Siemens cars with very early bow collectors. Many other continental European and some British tramway systems, including Leeds and Glasgow, also used this method.

The bow collector is one of the simplest and most reliable methods of current collection used on tramways. The very earliest versions were simply very heavy-gauge wire or steel bars bent into a rectangular shape and mounted long-side-down on the tramcar roof. The height of the collector was such that its top edge would scrape along the wire above. The top section is made of a 1 inch broad (or thereabouts) steel rod, machined to have a bow-shaped cross section, hence the name. This bow shaped rod is referred to as the 'collector plate', and in later models may be up to several inches wide. Unlike many trolley poles, the bow collector does not normally have a revolving base (one exception was in Rome, where the entire assembly could be revolved), but is rather fixed centrally to the tramcar roof.

...
Wikipedia