Three Rail Model Railways were the earliest electric model railways using an external power source. It was much easier to provide an insulated central third rail than it was to make insulated two rail track and wheel insulated models. The concept of two rail model railways was known early on in model rail history. Practicalities meant that three rail was more popular.
Tinplate track could be easily made with an extra insulated third rail. In fact Hornby and others made all their track suitable for electrification. Kits became available to convert two rail tin plate track to three rail electric tin plate track.
However, three rail model train systems are still with us. However, those made today tend to be scale 0 and above where the emphasis is on the quality of the rolling stock rather than the overall layout. It also permits modern and genuinely vintage trains to run on the same track.
There are some practical reasons why three rail might want to be used. Three rail systems do not have problems with reversing loops. Also it is possible to create a simple automatic running system using a three rail system where the running tracks are insulated from each other.
A variation of the the third rail is the stud system. Rather than a rail down the centre of the track there is a line of studs. On the locomotive the collector is longer than for a three rail system. At all times the collector, or skate, must be in contact with one stud. The idea is to have a three rail system that is less obvious than a centre third rail. Only one manufacturer used this system in quantity. However, many garden rail enthusiasts use it as the skate and studs tend to self clean, so ensuring better continuity than a three or two rail system.
Of course, the 'third rail' can be an overhead wire. Alternatively it can emulate a full scale side rail system. Such systems can operate as three rail systems with the advantages it offers, but need make no concessions from reality.
Tinplate track could be easily made with an extra insulated third rail. In fact Hornby and others made all their track suitable for electrification. Kits became available to convert two rail tin plate track to three rail electric tin plate track.
However, three rail model train systems are still with us. However, those made today tend to be scale 0 and above where the emphasis is on the quality of the rolling stock rather than the overall layout. It also permits modern and genuinely vintage trains to run on the same track.
There are some practical reasons why three rail might want to be used. Three rail systems do not have problems with reversing loops. Also it is possible to create a simple automatic running system using a three rail system where the running tracks are insulated from each other.
A variation of the the third rail is the stud system. Rather than a rail down the centre of the track there is a line of studs. On the locomotive the collector is longer than for a three rail system. At all times the collector, or skate, must be in contact with one stud. The idea is to have a three rail system that is less obvious than a centre third rail. Only one manufacturer used this system in quantity. However, many garden rail enthusiasts use it as the skate and studs tend to self clean, so ensuring better continuity than a three or two rail system.
Of course, the 'third rail' can be an overhead wire. Alternatively it can emulate a full scale side rail system. Such systems can operate as three rail systems with the advantages it offers, but need make no concessions from reality.