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Early toy trains used two metal rail tracks like most real trains. However, manufacturers quickly found that using a center rail for electric power and the two outer rails for common or ground made the track less prone to electrical short circuits. Thus most scales and gauges that predate HO scale use three rails for operation.
A key advantage for three-rail track is reverse loops, where a train enters a loop through a turnout and then exits through the same turnout in order to change the train's direction. With two-rail track, when the track reverses on itself, this causes a short circuit. With three-rail track, because the center rail remains constant and the outer rails are electrically identical, this causes no problems.
The third rail has also been used to automate and animateThis animation moves at 10 frames per second. This animation moves at 2 frames per second. At this rate, the individual frames should be discernable. Animation refers to the process in which each frame of a film or movie is produced individually, whether layoutLayout in publishing, is the process of arranging editorial content, advertising, graphics and other information in a manner that creates an effective presentation. Keyboard layout in civil engineering it can mean a map or a drawing of a construction sites. An accessory, such as a railway signalA Signal is a mechanical or electrical device that indicates to train drivers information about the state of the line ahead, and therefore whether they must stop or may start, or instructions on what speed they may drive their train. Network Rail two-aspe, can be wired to a section of track that has had one of its outer rails insulatedInsulators are materials which prevent the flow of heat (thermal insulators) or electrical current (electrical insulators). The opposite of electrical insulators are conductors and semiconductors, which permit the flow of current (Note: a semiconductor is, either at the factory or by a hobbyThis article is about pastimes. For the bird species, see hobby (bird). For the horse species, see hobby (horse). For the airport, see Hobby Airport. A hobby is a spare-time recreational pursuit. In the Middle Ages, falconry was a very popular pastime (whist. A passing train then activates the insulated rail, completing the circuit and causing the accessory to operate.
Insulated rails (or rail sections) can also be used to control turnouts, causing the turnout to switch to the position needed by an oncoming train.
Because of this feature, railroad carA railroad car (or, more briefly, car , also known as an item of rolling stock in British parlance, is a vehicle on a railroad or railway that is not a locomotive one that provides another purpose than purely haulage, although some types of car are poweres intended for three-rail operation will not work on two-rail track unless their wheels are first insulated from each other. Cars intended for two-rail track will operate on three-rail track, but they will not activate controls wired to an insulated rail. Conversion of three-rail cars for two-rail operation, or vice-versa, is thus a common practice among hobbyists. It requires either replacing the bogieA bogie (UK) or wheel truck (US) is a structure underneath a train to which wheel axles (and, hence, wheels) are attached. If they are used there are two for each carriage, wagon and locomotive, or alternatively, they are at the connections between the cas (wheel assemblies) on the car, or replacing metal axles with axles made of a non-conductive material.
The main disadvantage of three-rail track is its lack of realism. While some real-world trains do use a third rail, the prototypes for the majority of model railroad operations do not. LionelLionel, LLC is a designer and importer of toy trains and model railroads, based in Chesterfield, Michigan and currently in bankruptcy. Its roots lie in the 1969 purchase of the Lionel product line by cereal conglomerate General Mills. Although Lionel, LLC tried to improve this situation in the late 1950s with its Super O track, which blackened the middle rail and made it thinner in order to make it less visible. Other O scale manufacturers use similar techniques today.
Although most three-rail systems ties the two outer rails together electrically, some manufacturers wire all three rails independently. GarGraves is a North American manufacturer of O gauge three-rail track with all of its rails insulated. Trix Express is a European manufacturer of three-rail track who insulates all three rails.
On a simple, non computerised layout only one train can run independently on a either a two or three-rail system (two trains if combined with overhead lines). On the insulated three-rail type, two trains can run independently (three trains if combined with overhead lines).
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