Construction of out SM32 lines began during the 1990's. Some members had tried running Mamod live steam locos on the O gauge. This was not entirely successful as the loco's looked out of scale on the O gauge track, and also had a tendency to melt sections of it when they were being steamed up.
It was decided to convert the single track branch line which ran between Lympsham and Darlington to SM32 track so that these locos could be used away from the main line. The original line had a very steep gradient coming out of Darlington to get over the main line. The opportunity was taken to change this arrangement to a Ffestiniog Railway style spiral. It was soon realised that simply replacing the end to end branchline would not provide a very long run for the live steam locos. In order to rectify this significant extensions were made to allow a continuous run. This involved creating another two bridges under the path near Lympsham.
This line soon proved popular with members and visitors. The next stage was to provide a better steaming up area than Darlington and Lympsham as on Open Days these stations were often busy enough with O gauge operations. Spurs were built off the loop near Darlington, bridging over the O gauge track, and on to a new SM32 station.
Since this line was constructed at approximately the time of the club's 40th anniversary it came to be known as the Ruby line. After a few years operation it was time to extend again. Another loop was constructed, this time outside the O gauge circuit. The new loop was joined to the Ruby line with four connections so that the two loops could be operated as a longer combined loop of figure of eight. Another new station and passing loop were incorporated on the new tracks. This new line was christened the Millenium Line as its construction was started in 2000.
Most of the track base is constructed from concrete blocks. The blocks are cemented onto a foundation of hard-core. Once the cement base has set the voids between the blocks are filled in with mortar. The track is then nailed onto the concrete blocks. PECO track is used. Most of the points are also PECO, with a few Tenmille units also used.
The club owns a small amount of rolling stock and a couple of battery powered locos. Most locomotives are owned by members. Both battery powered and live-steam locomotives are in use. Some of the live steam locos are fitted with radio control. The Ruby line has some severe gradients and provides a particular challenge for live steam locos.