Template:Moelwyn Tunnels Old & New

Tunnels and Loading Gauge, etc.

Comparison of Tunnels, etc.

N	Year	Link	Gradient	Length	Curvature	Tracks	Ventilation	Width $	Height $	Sides	Roof	Lining	Engineer	Remarks	Notes
101	1842* 1863+	Old Moelwyn Tunnel * Horse Power + Steam power	1 in 80? x	730yd	Straight	1	3	8' 0"	9' 6"	Straight	roughly Semi-circle	Stone portals; unlined within	J. Spooner	Replaced 1836 inclines	* No Problems + Nasty, confined, wet
106	1977	New Moelwyn Tunnel	1 in 80? x	275yd	Straight	1	None	11' (+/- 3")	12' (+/- 6")	Straight	Low arc	Shot Concrete (Shotcrete)	M.A. Schumann; the Three Miners	Deviation avoids flooding	Comfortable
201	1851	Garnedd Tunnel	1 in 80; dips under portals	60yd	Slightly curved	1	No	8' 0"	ca.10'	roughly straight	Semi-circle, stone portals	Mostly unlined; brick piers in places	J. Spooner	Deviation of 1836 route
701	1836	FR Structure gauge						8' 0" various cuttings, now less; was ca.7' at Cemetery 1963	8' 6" (to 1956) but 9' 8"(since 1963) Rhiw Plas			Smallest bridge or tunnel			GS
705	1836	FR Loading gauge						6' 2" plus in-swing at carriage centres	9ft +/- 3ins			Largest rolling stock			GL

• Notes: N/A = Not Available.
• x Notes: Ruling Grade about 1 in 80.
• + Notes: At ruling gradient.
• $ Notes: Structure gauge and loading gauge are not simple rectangles.

Gallery

• 
  Tunnel profile Old Moelwyn Tunnel
  An unpleasant tunnel in steam days.
• 
  New tunnel (right) looks much wider
  than the old tunnel (left).
• 
  Tunnel profile New Moelwyn Tunnel
• 
  Garnedd Tunnel west portal

Rathole

A rathole tunnel is so-called when a combination of factors make it difficult, unpleasant, and even dangerous to operate, including

• gradient too close to the ruling gradient.
• length longer than the "momentum distance".
• wet rails from steam and/or water seepage.
• unhelpful wind direction.
• train load too close to full load.
• loading gauge too close to the structure gauge.
• awkward stop at bottom of tunnel.
• insufficient time between trains for smoke to clear.
• single line rather than double line.
• lack of escape route for crew in case of stall.
• even great engineers made mistakes and rathole tunnels.

There is a standing instruction to enginemen on the FR that in the event of the engine coming to a stand in a tunnel, the train must run back by gravity outside the tunnel before any effort is made to blow up steam.