Engine No3 "Wyddfa" was one of the original purposed built engines purchased for £1525
The Snowdon Mountain Railway - Rheilffordd yr Wyddfa is a narrow gauge rack and pinion mountain railway in North Wales. It is a tourist railway that travels the 4.7 miles from Llanberis to the summit of Snowdon.
The railway is the only public rack and pinion railway in the United Kingdom, and after more than 100 years of operation it remains a popular tourist attraction. The railway is operated in some of the harshest weather conditions in Britain, with services curtailed from reaching the summit in bad weather and remaining closed during the winter from November to mid-March. Single carriage trains are pushed up the mountain by either steam locomotives or diesel locomotives.
To ensure the trains were able to embark upon the steep and continual gradients of Snowdon safely, the newly formed Snowdon Mountain Tramroad and Hotels Co. Ltd went to Switzerland to find the best mountain railway technology. A German engineer, Dr. Roman Abt, had patented a rack and pinion system that was being used reliably in the Swiss Alps. Whilst in Switzerland the company purchased three steam locomotives and they arrived in Llanberis in 1895 to help with the construction, a further two trains arrived in 1896 when the railway opened.
Smooth and constant operation when tackling the steep gradients is achieved by a double racked rail used with a rotating toothed pinion. The pinion is mounted underneath the locomotive and guarantees the locomotive does not lose grip on the mountain. The pinion is the only source of traction for the locomotive with the wheels supporting the weight of the engine. Unique to rack railways, the locomotive always pushes the carriage up the mountain and, for safety reasons, is never coupled to the train. The carriage has its own set of brakes that bring the carriage to a standstill if it disengages from the locomotive.