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Tyler's Curve is the sharpest curve on the line, where up trains change direction from North-East to North-West around the hanging valley of Llyn Mair. Passengers on the valley side have a good view of Maentwrog village and the Vale of Ffestiniog. Having a radius of only 2.4 chains, it is the tightest on the operational railway. It is named after Captain Tyler, the Inspecting Officer appointed by the Board of Trade who recommended approval of the FR's application to open the line to public passenger traffic. This whole section of line would have been by-passed by tunnels if the 1869 double tracking had gone ahead.
The superelevation or cant of the track here in later days of the Old Company was three and a half inches on a two foot gauge track. There were special 'high-heeled' chairs (Will Jones' description) giving a three-inch rise on the outer rail. This had been done because the wheels - especially of the slate waggons - had worn so much that their cones had disappeared, so to throw their weight inwards, the cant was raised. It should be possible, given this cant and the moments of inertia of the train, to calculate the intended speed. Stories of 40 mph are whispered in dark corners, but there are few reliable records of those days. In restoration days, the line speed was reduced to 20 mph and the high-heeled chairs became a thing of the past.
The curvature was one and three-quarter chains (116ft, 35m) in olden times, but by meticulous geometry this was eased to 2.4 chains.
The stone retaining wall supporting the line was rock bolted and pressure grouted in December 1999, by scaffolding out below the line. Supplies and the workforce were brought down from Tan y Bwlch by Moel Hebog and train.
Just above the curve is Plas Halt.
Please note it is dangerous to lean out of the window. A 6'10" train barely fits in a cutting little more than 7' wide.