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Concept
Wigwag (railroad)
Résumé
Wigwag is a nickname for a type of railroad grade crossing signal once common in North America, referring to its pendulum-like motion that signaled the approach of a train. The device is generally credited to Albert Hunt, a mechanical engineer at Southern California's Pacific Electric (PE) interurban streetcar railroad, who invented it in 1909 for safer railroad grade crossings. The term should not be confused with its usage in Britain, where "wigwag" generally refers to alternate flashing lights, such as those found at modern level crossings.
Soon after the advent of the automobile, travel speeds were increasing and the popularity of enclosed cars made the concept of "stop, look, and listen" at railroad crossings difficult. Fatalities at crossings were increasing. Though the idea of automatic grade crossing protection was not new, no one had invented a fail-safe, universally recognized system. In those days, many crossings were protected by a watchman who warned of an oncoming train by swinging a red lantern in a side-to-side arc, used universally in the U.S. to signify "stop". This motion is still used today by railroad workers to indicate stop per the General Code of Operating Rules (GCOR) Rule 5.3.1. It was presumed that a mechanical device that mimicked that movement would get the attention of approaching motorists and give an unmistakable warning.
The earliest wigwags used by Pacific Electric, built in the railroad's shops, were gear-driven, but proved difficult to maintain. The final design, first installed in 1914 at a busy crossing near Long Beach, California, utilized alternating electromagnets pulling on an iron armature. A red steel target disc, slightly less than in diameter was attached, which served as a pendulum. There was a red light in the center of the target, and with each swing of the target a mechanical gong sounded.
The new model, combining sight, motion and sound, was dubbed the magnetic flagman, and was manufactured by the Magnetic Signal Company of Los Angeles, California, though it is unclear exactly when production began.
Source officielle
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