Collectors
Most electric railway systems take the power from an external generator. This means the electricity has to be collected while the locomotive is on the move. In this context a locomotive refers to any electric vehicle on a guided track system. Other than railways the other most common system of electrically powered guided transport is a tramway system.
Generally electric locomotives collect power through a third rail or an overhead wire. The full circuit is completed by track rails. For main line railways with their protected lines overhead lines and third rails are not a problem. Tramways operate in cities. This means that the third rail system is not really practical. It has been used, protection being offered to other road users by placing it in a central groove. Even so the ingress of dirt and water can cause problems.
An alternative solution is to use studs. All the systems have a switch in the stud and a means to switch on the stud only while it is covered by the moving vehicle. As at least one stud must be covered by the collector at all times a long collector is used. The length has to be slightly greater than the maximum distance between any two studs. This collector is known as a skate or ski collector. This type of electrical power collector needs to move in the vertical plane to allow for natural differences in the height of the power supply studs.
It is used on some full size tramway systems where there is a need for overhead wires not to be used, usually in areas of scenic value. It is also used on model railway systems as the center line of studs is less obtrusive than a single central rail. For outdoor model railway systems the use of a stud supply system with a skate/ski collector has certain practical advantages. The system is inherently self-cleaning. While the track may not be perfect, with both rails acting as the return part of the system in parallel electrical pick up problems are substantially reduced.
While the obvious use is on railway power collection, the system also has applications wherever electrical energy needs to be transferred from a static source to moving user, or vice versa.
Read more about this topic: Stud Contact System