South approach viaduct - detail of the change from conventional rails (top) to the special Forth Bridge rails (fixed directly by coach screws onto wooden pads on the deck).

Description South approach viaduct - detail of the change from conventional rails (top) to the special Forth Bridge rails (fixed directly by coach screws onto wooden pads on the deck).

Date 29/8/1988

Collection Records of the Royal Commission on the Ancient and Historical Monuments of Scotland (RCAHMS), Edinbu

Catalogue Number B 3151

Category Photographs and Off-line Digital Images

Copies SC 728334

Scope and Content Joint between conventional rails and 'Forth Bridge Rails' on south approach viaduct, Forth Bridge, Edinburgh and Fife The Forth Bridge was built between 1883 and 1890 to designs by engineers Sir John Fowler (1817-98) and Sir Benjamin Baker (1840-1907) with Sir William Arrol (1839-1913) and Joseph Phillips as contractors. This massive steel railway viaduct features three double cantilevers connected by girders with a total span of 2.5 km. This shows the point in the railway track where the rails change from standard rails (top) to special 'Forth Bridge Rails' on the approach viaduct. Forth Bridge rails are bolted directly onto timber logs within a trough, whereas standard rails are secured with metal clips to sleepers set in ballast (gravel). The Forth Bridge expands and contracts due to climate changes, sometimes varying up to 0.6m in length between summer and winter. To cope with these variations expansion joints (rails cut at an angle so they can slide backwards and forwards) in the rails move with the bridge to ensure the safety of trains. Source: RCAHMS contribution to SCRAN.

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