pantographs

A pantograph is a mechanical linkage used to copy or scale a drawing, map, or other motion. The term derives from Greek roots meaning “all” and “to write,” reflecting its ability to reproduce a shape at a different size. Today, pantographs are best known for their role in electric traction systems on trains and trams, where they function as current collectors.

In form, a pantograph typically consists of a parallelogram-shaped linkage with several bars that maintain a rigid, mirrored relationship between two points. One end is connected to the vehicle frame and the other carries a contact element, such as a carbon shoe or metal contact strip, which slides along an overhead conductor. The linkage is designed to preserve the orientation of the contact element relative to the line, while a spring or pneumatic system applies light force to maintain consistent contact. The arrangement allows the contact to follow uneven or dynamic surfaces and to adapt to changes in line height and geometry.

uses and applications have evolved over time. In drawing and drafting, pantographs enabled scaling copies of diagrams and maps with relatively simple mechanisms. In rail and tram systems, they provide a reliable method of collecting electrical power from overhead wires, enabling propulsion while reducing wear on the overhead line. Modern pantographs emphasize electrical reliability, reduced wear, and aerodynamic profiles, and they may incorporate sensors to detect arcing, loss of contact, or other faults.

See also: overhead line, catenary, trolley pole, electric traction.