Теміржол кесіміндегі ескерту сигналдары: "Вигваг" туралы

Railroad grade crossing signal

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 a train's approach. 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 United States 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 2 feet (1 m) 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. After the distinctive signals were installed, train and car collisions decreased at PE grade crossings. The signs became so common throughout the area that they were near icons of Southern California motoring. Their popularity led to Magnetic Signal wigwags appearing at railroad crossings across the United States—including on Alaska's Copper River and Northwestern Railway and on several Hawaiian railroads—and across Canada, Mexico, and as far away as Australia. There are also photographs of the Magnetic Flagman in use in Europe. Three mechanically identical versions were produced. The upper quadrant model was mounted directly atop a steel pole and waved the target above the motor box. It was intended for use where space was limited. Since the target could not serve as the pendulum, a cast iron counterweight opposite the target was used. Accurate computer generated animation of that type of signal can be seen in the 2006 movie, Cars. The lower quadrant version waved the target below the motor box and was intended to be cantilevered from a pole, over road traffic. Some railroads, especially in the north western US, mounted their lower quadrant versions directly on top of a tall steel pole similar to the upper quadrant signal. They were placed on one side of the road, or on an island in the center of the road, and often had crossbucks fastened on top of the motor box. A lower quadrant signal of that kind is seen in the 2004 film Lemony Snicket's A Series of Unfortunate Events. Though Magnetic Signal manufactured a steel pole and cast iron base for the purpose (which served as a cabinet for backup batteries and relays), PE often mounted the cantilevers on the wooden poles that also supported the overhead catenary providing power for streetcars. That rendered batteries unnecessary, since any failure of PE's generators resulted in a shutdown of the railway. It also permitted the relays to be housed in a separate, inexpensive cabinet, reducing the cost of the installation. The third and least common version was a pole mounted lower quadrant signal, with the motor box fixed to the top of an octagonal steel frame that surrounded the target, presumably to protect both banner and motor box from being damaged by road vehicles. Dubbed the "peach basket" because of the protective framework, the apparatus was crowned by another visual warning, the traditional X shaped "RAILROAD CROSSING" sign, or crossbucks. The majority of peach baskets were used by the Union Pacific Railroad. One version of the signal had the lower stripe on the banner replaced with the word stop that was lighted. When the signal was at rest, the words were hidden behind a screen that was painted to look like the missing stripe. They were either mounted on an island in the center of the road or on the side of the road. The Magnetic Flagman wigwag waves its target using large, black electromagnets pulling against an iron armature. Sliding contacts switch the current from one magnet to the other. Each Magnetic Flagman includes a builder's plate (bottom center) detailing patent dates and power requirements. There were a few other models that were either manufactured by Magnetic Signal or customized by the different railroads. Some examples included two signals on the same pole for different traffic approaches, a circular upper quadrant signal in which the target swung in a circular frame, and three position signals where the target was hidden behind a sign when the signal was inactive. The Norfolk and Western Railway decided to make a change in which the motion limiting bumpers were placed on the front of the signal instead of inside at the rear, so that the torque on the armature was reduced. They also had unique lights on their banners. Any version could be ordered to operate using the railroad signal standard of 8 volts DC (VDC) current, or the 600 VDC used to power streetcars and electric locomotives, with little more than a change in the electromagnets. Most, if not all, of the 600 VDC units were used by PE. With the conversion to diesel power after PE sold its passenger operations in 1953, those 600 VDC wigwags were gradually converted to 8 VDC units. There were also some 110 volt AC models of Magnetic Flagman used on several railroads, including Norfolk and Western, Winston Salem Southbound, and the Milwaukee Road. Since AC power did not generate good torque, a coil cutoff device was installed that utilized all four magnets until full motion of the banner was obtained, then two of the magnets went off line and movement was maintained by the remaining two magnets. Various options were available. One was a round, counterbalancing "sail" for use in windy areas and which was sometimes painted in the same scheme as the main target. A warning light with adjustable housing was offered, as was an "OUT OF ORDER" warning sign that dropped into view if power to the signal was interrupted. There was a rare adjustable turret style mount for properly aiming the signal if space did not allow the cantilever to fully extend over the roadway. The last known example of the turret mounted wigwag was removed from service in Gardena, California in 2000, while the versions with the warning signs were mostly shipped to Australia. One surviving example is on display at the Newport Railway Museum in Melbourne, Victoria, and one has been restored and now operates on the Puffing Billy Railway. An example or two of each signal still survive with collectors. A ruling by the United States Interstate Commerce Commission mandated a change in the target in the early 1930s. It required a change in the paint scheme from solid red to a black cross and border on a white background, but there was no other change until a ruling that required the alternating red lights in use today. That, along with other rules about grade crossing signaling that the wigwags were unable to meet due to their power requirements, rendered them obsolete for new installations after 1949, but grandfathering laws allowed them to remain until the crossings they protected were upgraded. The Magnetic Signal Company was sold to the Griswold Signal Company of Minneapolis shortly after World War II. Production of new signals continued until 1949, and replacement parts until 1960. The symbol of a black cross on a white background was adopted in the US as the traffic sign warning drivers about an unprotected grade crossing and was incorporated into the corporate logo of the Santa Fe Railroad. It remains in use today, although with a yellow background and the cross rotated 45 degrees into an "X". Some railroads, among them the Louisville and Nashville Railroad, used a concentric black circle on a white background, resembling a bullseye, but that scheme was rare, partly because the L&N used few wigwags.