GWR Route: Banbury to Wolverhampton

GWR Route: North Warwickshire Line

Birmingham Snow Hill Station: gwrbsh1672

One of the Siemens electrically powered point machines installed on one of the facing switches (lever 46) of the relief line scissors crossover at the north end of Birmingham Snow Hill. The cast iron cover of the point machine has been hinged open to reveal the internal workings. The point machine contains an electrical motor to drive a geared wheel, which is coupled at high level to a rod operating a rocking shaft. This rocking shaft travels under the rail and lifts or lowers the plunger bolt and operates the locking bar. Also connected to the geared wheel at a lower level is the rodding linked to the point tongues, which operate the point movement. This is mechanically interlocked, such that it can only operate once the plunger bolt and locking bar have been disengaged by the high level operating mechanism and this mechanism also re-engages the plunger bolt and locking bar following the operation. A smaller second box attached to one of the sleepers behind the point machine, contains the electric detector circuitry which identifies that the point tongues are correctly positioned and that the plunger bolt is fully home.

Robert Ferris

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