Point rodding
Point rodding is used to mechanically operate points from a signal box or ground frame. On the F&WHR this is mainly associated with mechanical ground frames at sidings or train operated trailable points. The automatic stations and the Harbour Station signal box use point motors so do not require long rodding runs.
The rods are typically made of iron pipes of about 25mm diameter, or upside-down "U" channel of similar dimensions.
The rods are supported by rollers at intervals of about 2 metres.
Cranks can be installed to change direction by say 90 degrees such as when crossing tracks.
Because rods expand and shrink with temperature increases and decreases, compensating cranks are provided so that half of the rodding pushes while the other half pulls, thus cancelling out temperature changes. Sunlit and shaded sections of rodding need to be compensated separately.
Due to friction, there is a limit on the distance between points and signal box.
Gallery[edit]
- Point Rodding
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Point rodding at Dduallt. -
Point rodding at Dduallt (zoom)
( yellow arrow)
Compensating Cranks (red)
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